Foreword 

This soil survey contains information that can be used in land-planning 

programs in Skamania County Area. It contains predictions of soil behavior for 

selected land uses. The survey also highlights limitations and hazards inherent 

in the soil, improvements needed to overcome the limitations, and the impact of 

selected land uses on the environment. 

This soil survey is designed for many different users. Farmers, foresters, and 

agronomists can use it to evaluate the potential of the soil and the management 

needed for maximum food and fiber production. Planners, community officials, 

engineers, developers, builders, and home buyers can use the survey to plan land 

use, select sites for construction, and identify special practices needed to ensure 

proper performance. Conservationists, teachers, students, and specialists in 

recreation, wildlife management, waste disposal, and pollution control can use the 

survey to help them understand, protect, and enhance the environment. 

Great differences in soil properties can occur within short distances. Some soils 

are seasonally wet or subject to flooding. Some are shallow to bedrock. Some are 

too unstable to be used as a foundation for buildings or roads. Clayey or wet soils 

are poorly suited to use as septic tank absorption fields. A high water table makes a 

soil poorly suited to basements or underground installations. 

These and many other soil properties that affect land use are described in this 

soil survey. Broad areas of soils are shown on the general soil map. The location 

of each soil is shown on the detailed soil maps. Each soil in the survey area is 

described. Information on specific uses is given for each soil. Help in using this 

publication and additional information are available at the local office of the Soil 

Conservation Service or the Cooperative Extension Service. 

Lynn A. Brown 

State Conservationist 

Soil Conservation Service 

This is a scanned version of the text of the original Soil Survey report of Skamania County Area, Washington issued October 1990. Original tables 

and maps were deleted. There may be references in the text that refer to a table that is not in this document. 

Updated tables were generated from the NRCS National Soil Information System (NASIS) and are available as a separate document. The soil map 

data has been digitized and may include some updated information. This is available for use on this website or as a downloadable data set for use in 

specialized programs. 

Please contact the Oregon State Soil Scientist, Natural Resources Conservation Service (formerly Soil Conservation Service) for additional 

information.
Location of Skamania County area in Washington. 
Soil Survey of 

Skamania County Area, Washington 

By Edward Haagen, Soil Conservation Service 

Fieldwork by Edward Haagen, Terry L. Aho, Alan Goldin, and Thomas Fait, Soil 

Conservation Service; and Robert Evans, Ronald H. Kurtz, Jeffrey A. Sherwood, and 

Philip J. Schoeneberger, Washington State Department of Natural Resources 

United States Department of Agriculture, Soil Conservation Service In 

cooperation with 

Washington State Department of Natural Resources and Washington State University 

Agriculture Research Center 

SKAMANIA COUNTY AREA is in the southwestern 

part of Washington. It has an area of 1,070,080 acres, or 

about 1,672 square miles. Stevenson, the county seat, is 

in the southeastern part of the survey area, along the 

Columbia River. The population of Skamania County in 

1980 was 7,914, which was essentially the same as that 

of the survey area. The Gifford Pinchot National Forest 

was not included in the survey area, except for 187 

square miles that has some private land holdings within it.

The survey area is in a region that has high, deeply 

dissected mountains. The southern part along the 

Columbia River has some nearly level terraces but 

mountains predominate. The west-central part is mainly 

mountainous and has a few terraces and terrace 

escarpments. The northern part is mainly mourtainous but 

has foothills forming at the base of Mount St. Helens. 

Streams generally flow westward. Timber production is 

the main economic enterprise in the county. Some areas 

are suited to apple and pear orchards. 

Soil scientists determined that there are about 65 

different kinds of soil in the survey area. The soils have a 

wide range in texture, parent material, and other 

properties. 

The present survey updates an earlier survey of 

Skamania County published in 1956 (13) and provides 

additional information and larger scale maps that show 

the soils in more detail. This survey is also an update of a 

part of a soil survey made by the Weyerhaeuser Company 

in 1971 (3). 

The survey area of Skamania County Area borders the 

survey in Clark County (17). Descriptions and names of 

soils in this survey do not fully correspond with those 

listed on soil maps for Clark County. Differences between 

this survey and older surveys should be expected as more 

is learned about soils over time and concepts about soils 

are adjusted to fit new knowledge. 

Climate 

Climatic data for this section were especially prepared for the Soil 

Conservation Service by the National Climatic Data Center, Asheville, 

North Carolina. 

The Coast Range shields the survey area from the 

severe winter storms moving inland from the ocean, and 

the Cascade Range protects the area from the high 

summer and low winter temperatures of eastern 

Washington. The Columbia River Gorge moderates the 

blocking effect of the Cascade Range somewhat by 

allowing air exchange between the inland and coastal 

areas of the state. Winds in the gorge usually blow from 

west to east in summer and from east to west in winter. 

Gale force winds through the gorge are common, 

especially in winter. Severe ice storms, locally called 
silver thaws, are another phenomenon of the part of the 

gorge that is west of the Cascade Divide. Precipitation 

and temperature vary with elevation, proximity to 

mountainous areas, position on leeward or windward 

slopes, and the season. 

Table 1 gives data on temperature and precipitation at 

Bonneville, Oregon, and at Wind River and Cougar, 

Washington, for the period 1951 to 1978. Table 2 shows 

the probable dates of the first freeze in fall and the last 

freeze in spring. Table 3 provides data on length of the 

growing season. 

In winter, the average temperature at Bonneville, Wind 

River, and Cougar are 39, 38, and 34 degrees F, 

respectively. The average daily minimum temperature is 33 

to 34 degrees at Bonneville and Cougar and 28 degrees 

at Wind River. The lowest recorded temperature, which 

occurred at Wind River on January 26, 1957, was -12 

degrees. In summer, the average temperature is 63 

degrees at Wind River and Cougar and 65 degrees at 

Bonneville. The average daily maximum temperature is 

about 76 degrees. The highest recorded temperature, 

which occurred at Wind River on July 31, 1971, and at 

Cougar on July 31, 1965, is 105 degrees. 

Growing degree days, shown in table 1, are equivalent 

to heat units. During the month, growing degree days 

accumulate by the amount that the average temperature 

each day exceeds a base temperature (40 degrees). The 

normal monthly accumulation is used to schedule single 

or successive plantings of a crop between the last 

freeze in spring and the first freeze in fall. 

The total annual precipitation is 77 inches at Bonneville, 

102 inches at Wind River, and 118 inches at Cougar. Of 

this, 20 percent usually falls in April through September, 

which includes the growing season for most crops. The 

heaviest 1-day rainfall during the period of record was 6.5 

inches at Wind River on January 15, 1974. Thunderstorms 

occur on about 7 days each year, and most occur in 

summer. 

Average seasonal snowfall is 13 inches at 

Bonneville, 109 inches at Wind River, and 29 inches at 

Cougar. The greatest snow depth at any one time during 

the period of record was 80 inches. Tie number of days 

with at least 1 inch of snow on the ground is, on the 

average, 4 days at Bonneville, 18 days at Wind River, 

and 10 days at Cougar. The number of such days varies 

greatly from year to year. 

 The average relative humidity in midafternoon is 

about 60 percent. Humidity is higher at night and the 

average at dawn is about 85 percent. The percentage 

of possible sunshine is 65 in summer and 25 in winter. 

The prevailing wind is from the northwest. Average 

windspeed is highest, 10 miles per hour, in winter. 

Physiography and Geology 

Terry L. Aho. soil scientist, Soil Conservation Service, helped to 

write this section. 

Skamania County Area is in the Cascade Range 

uplift, a region characterized by deeply dissected 

mountains. Between Cape Horn and Underwood 

Mountain, the Columbia River has cut through the 

Cascade Range to form the Columbia River Gorge, a 

deep canyon lined by precipitous slopes that have 

outcrops of basalt and andesite. 

Viewed from the higher elevations, the county has the 

appearance of a deeply dissected, sloping plateau. The 

physiographic features are rugged mountainous areas, 

river flood plains, and low terraces. Elevation ranges from 

near sea level on the Columbia River to about 3,000 feet 

on the mountain crests in the southern part of the county. In 

the northern part of the county, elevation ranges from about 

1,000 feet at Swift Creek Reservoir to 8,365 feet at Mount 

St. Helens. 

The Cascade Range in Skamania County is of 

particular interest because it contains the most complete 

stratigraphic section of Tertiary and Quaternary volcanic 

rocks in the state. In the Wind River area are extensive 

deposits of Cenozoic lava and volcanic debris. These 

rocks are divided into four units: Ohanapecosh 

Formation, Eagle Creek Formation, Yakima Basalt, and 

Quaternary basalt flows (13). 

The oldest unit, Eocene to early Oligocene in age, is 

the Ohanapecosh Formation of the Mount Rainier region. 

It is nearly 19,000 feet thick. The lower two-thirds of this unit 

is composed mostly of andesitic pyroclastic debris in tuff 

breccia. The upper 6,000 feet of the formation, which was 

deposited during the Oligocene Epoch, is composed of 

about equal amounts of conglomerate and sandstone, 

tuff, and pyroclastic breccia. 

Following folding and uplift, the top of the Ohanapecosh 

Formation was deeply weathered. Andesitic gravel and 

sand of the Eagle Creek Formation were then deposited 

over the Ohanapecosh Formation during the early 

Miocene. The Eagle Creek Formation was then eroded, 

and the resulting topography was inundated by Yakima 

Basalt from the east during the late Miocene. Deposits of 

the Eagle Creek Formation in the survey area were 

about 1,300 feet thick. Yakima Basalt flows in the area 

are as much as 2,000 feet thick. Aschoff, Skoly, and 

Zygore soils formed in residuum and colluvium derived 

from these formations. 
Gentle folding accompanied by eruptions from 

several andesitic and basaltic volcanoes took place 

during the Pliocene. This was followed by erosion that 

stripped away the lava flows, leaving only scattered 

plugs of diorite and diabase. Beacon Rock and Wind 

Mountain are remnants of these plugs. Some granodiorite 

is exposed in the southwestern part of the survey area. 

Dougan soils formed in residuum and colluvium derived 

from these intrusive formations. 

 Quaternary volcanism has been limited to the 

extrusion of basalt flows from at least ten different vents. 

The lavas can be grouped into olivine, platy olivine, and 

low-alumina basalt. These include slows from the Red 

Mountain and Trout Creek Hill volcanoes and flows of the 

Big Lava Bed north of Willard. Some of the accompanying 

volcanic ash and pumice accumulated on terraces in the 

upper Wind River area. The Stabler soils formed in this 

material, whereas the Chemawa soils formed in alluvium 

derived from volcanic ash and basalt. 

Local landslides, some taking place as recently as 

200 years ago, have occurred in several areas along the 

Columbia River. The large Bonneville landslide, between 

the cities of North Bonneville and Stevenson, exposed the 

Red Bluffs. Steever soils formed in material from this 

landslide. The landslide, which consists chiefly of the 

Eagle Creek Formation and Yakima Basalt. blocked the 

Columbia River for a short period. Another landslide 

between Wind Mountain and Dog Mountain consists 

chiefly of material from the Ohanapecosh Formation. This 

landslide is still active. It moves 40 to 50 feet a year at the 

upper end of the slide and 5 to 10 feet a year at the toe. A 

phase of the St. Martin series is mapped in this area. 

Mount St. Helens, a volcano of late Quaternary age, is 

situated near the west margin of the Cascade Range, in the 

northwestern part of the survey area. The cone consists 

of lava flows of olivine basalt and pyroxene andesite that 

surround a summit plug of dacite. Valley fill adjacent to the 

volcano includes pyroclastic flow material, lahar, and 

alluvium, which are locally interbedded with tephra and 

glacial drift (24). Shoestring, Forsyth. Polepatch. and St. 

Helens soils formed in these materials. Shoestring and 

St. Helens soils have a mantle of volcanic ash 20 to 35 

inches thick, whereas Forsyth and Polepatch soils have 

little or no mantle of ash. 

Mount St. Helens has been an intermittent source of 

tephra for more than 35,000 years (25) (fig. 1) The 

sequence and thickness of the tephra layers depend on 

the direction of the prevailing winds at the time of eruption 

(fig. 2). Tephra layer Y is one of the eldest 

layers in the upper 60 inches of the soils in northern 

Skamania County. Layer Y is present in Cattcreek and 

Tradedollar soils, which are north of Mount St. Helens. 

Moving clockwise, northeast of Mount St. Helens the 

thickness of layers T and W increases to more than 60 

inches. Minniepeak and Sinnice soils formed in layers T 

and W, with layer W extending to a depth of more than 

60 inches. 

East of Mount St. Helens, layer T is absent or very 

thin and layer W decreases to 15 to 25 inches in 

thickness. Bandid and Pelee soils formed in this area, 

with layer W overlying tephra subset B. The decrease in 

the thickness of tephra layers T and W indicates the major 

tephra fall was on an axis northeast of Mount St. Helens. 

Moving further in a clockwise direction, the thickness of 

tephra layer W decreases rapidly. Southeast of Mount St. 

Helens, tephra layer W in the Bannel soils is 5 to 6 inches 

thick over tephra subset B, set P, and in a few areas, 

layer Y. 

South and southwest of Mount St. Helens, a discrete 

layer W is absent; however, some pumice of tephra layer 

W is incorporated into the surface layer of the soils. 

Cinnamon, Lonestar, and Yalelake soils formed in tephra 

subset B and set P in this area. 

South of the Swift Creek Reservoir and in an area 

west of Mount St. Helens, the tephra fall is less than 40 

inches thick. This has resulted in soils that developed in 

a mantle of ash and in residuum and colluvium derived 

from the underlying basalt and andesite. Hatchet, Swift, 

and Vanson soils formed in these materials. 

The general soil map in the back of this survey shows 

the extent of the area that was affected by the eruption. 

The map does not cover the entire blast area, because it 

extends beyond the boundaries of Skamania County. 

Landscapes that were changed by avalanche debris, 

mudflow, or pyroclastic flow were remapped and 

renamed. Some landforms were not changed. These 

landforms received ash or tephra deposits varying in 

depth and texture. Descriptions of the affected map units 

are included. Affected areas are delineated on 

posteruption soil maps. Soil interpretations based on the 

deposits are also included in this survey. 

Eruption of Mount St. Helens 

Mount St. Helens, dormant for 123 years, erupted on 

March 27, 1980. A small crater formed in the glacial ice 

near the summit. Minor activity continued through April. 

The formation of a bulge on the north flank of the 

mountain was detected late in April. It continued to 

grow in size until May 18. 

On Sunday morning, May 18, 1980, Mount St. 
Figure 1.-Geologic history of tephra of Mount St. Helens. 

Helens erupted with cataclysmic fury. An earthquake of a 

magnitude of 5 on the Richter scale shook the mountain, 

causing the bulge on the north side; to give way in a 

giant avalanche of rock, mud, and ice. The avalanche 

was quickly followed by both vertical and horizontal 

blasts of superheated gas, ash, and rock fragments. The 

horizontal blast covered an area 8 miles long and 15 

miles wide, killing virtually everything in its path. The 

lighter material was sent into the atmosphere 

almost 14 miles straight up, forming a large ash cloud. 

The winds moved the ash cloud in a northeasterly 

direction. The ash fell over much of Eastern Washington 

and parts of Idaho and Montana. The giant avalanche of 

rock and ice spilled into Spirit Lake and filled the valley 

of the North Fork of the Toutle River with as much as 

200 feet of debris. 

Meltwater from snow and glaciers, mixed with 

volcanic debris, created huge mudflows. These 
Figure 2.-Geographic locations and profiles of soils adjacent to Mount St. Helens. 

mudflows swept down the Pine Creek, Muddy River, and 

Smith Creek, southeast of the mountain, dumping mud 

and debris in the eastern end of Swift Reservoir. 

A huge mudflow in the North and South Forks of the 

Toutle River swept down the valley carrying with it 

thousands of logs. The mudflow destroyed lodging 

camps, roads, and bridges in its path and deposited 

mud and debris into the Cowlitz and Columbia. Rivers. 

Mount St. Helens erupted again on May 25, this time 

sending clouds of ash to the southwest and northwest. 

Portland, Oregon, and Centralia, Washington, reported 

deposits of ash. Additional eruptions were reported on 

June 12, July 22, August 7, and October 16 and 17, 

but they produced only minor amounts of ashfall. Three 

years after the initial eruption, Mount St. Helens had 

lapsed into a period of calm interrupted only by an 

occasional earthquake, along with dome building and 

venting of steam and minor amounts of ash. During the 

eruptive period in the 1800's, Mount St. Helens was 

active for more than 20 years (13). 

Deposits from the May 18, 1980, eruption of Mount 

St. Helens and subsequent eruptions can be separated 

into two basic groups. The first group is flows, including 

mudflows, avalanche debris flows, and pyroclastic 

flows. These flows range from less than 1 foot to 

several hundred feet in thickness. They are separated 

on the posteruption soil maps. The second group is 

aerial deposits of ash and pumice. The aerial deposits 

are as much as about 30 inches thick. 

Of the various flows, the deepest deposit and the 
Figure 3.-Avalanche debris flow in an area of Studebaker very gravelly loamy sand, 0 to 20 percent slopes. 

most damaging was the May 18 avalanche debris flow, 

which was triggered by the lateral explosion of the north 

flank of the mountain. The debris avalanche raced down 

the north side of Mount St. Helens seconds ahead of 

the lateral blast. The debris avalanche deposited several 

hundred feet of debris into the North Fork of the Toutle 

River and into the western end of Spirit Lake. The 

resulting displacement wave of water in Spirit Lake, 

coupled with the force of the lateral blast, partially or 

completely removed soils on south-facing slopes adjacent 

to Spirit Lake and on the ridge north of the North Fork of the 

Toutle River. During the later stages of the May 18 eruption 

and the later eruptions through the summer of 1980, 

mudflows and pyroclastic flows streamed over a part of 

the avalanche debris flow. The Studebaker series was 

mapped on the avalanche debris flow (fig. 3), and the 

Panhandle series was mapped on the pyroclastic flow 

(fig. 4). 

Mudflows off the east and southeast flanks of the 

mountain flowed down the Pine Creek, Muddy River, 

and over and through Ape Canyon. The mudflows 

scoured and eroded the soils in narrow passages and 

deposited several feet of debris in wide flat areas. The 

mudflows washed out bridges and roads and sent logs 

and debris into the eastern end of the Swift Reservoir. 

Minor mudflows, off the southwest flank of Mount St. 

Helens, covered and washed out logging roads, leaving 

deposits as much as 3 feet deep. The Obscurity and 

Wakepish soils were mapped on these mudflows. 

Aerial deposits in the survey area are as much as 30 

inches thick; however, areas that have less than 4 inches 

of ash or cinder deposition have not been remapped. 

Soils that have an ash layer 4 to 20 inches thick are 

mapped as an overblown phase of the soil series 

mapped prior to the eruption. Deposits more than 20 

inches thick were mapped as the Elkprairie series. 

Some of these soils are on toe slopes and fans and in 

bottom land areas, where material from upslope erosion 

is accumulating. The deepest aerial deposit from the 

May 18 eruption is 5 to 6 miles north of the volcano 

and includes debris from the lateral blast. Depth of 

deposits decreases in all directions from this area. 

Composition
of the aerial deposits varies with direction from the 

mountain. North and northwest of Mount St. Hens the 

surface layer is predominantly volcanic ash, while 

northeast and east the surface layer is extremely cindery. 

Erosion by water and wind has greatly affected the depth 

of these deposits; thus, variations in depth may occur 

over short distances. 

A more detailed description of the affected area is 

provided in the section ''Detailed Soil Map Units'' and in 

the soil interpretation tables. Soil descriptions and other 

data provided in this survey can be used to make 

additional interpretations. 

How This Survey Was Made 

This survey was made to provide information about the 

soils and miscellaneous areas in the survey area. The 

information includes a description of the so Is and 

miscellaneous areas and their location and a discussion 

of their suitability, limitations, and management for 

specified uses. Soil scientists observed the steepness, 

length, and shape of the slopes; the general pattern of 

drainage; the kinds of crops and native plants; and the 

kinds of bedrock. They dug many holes to study the soil 

profile, which is the sequence of natural layers, or 

horizons, in a soil. The soil profiles were examined from 

the surface to a depth of 5 feet or to bedrock or other 

consolidated material where at a depth of less than 5 

feet. 

The soils and miscellaneous areas in the survey area 

are in an orderly pattern that is related to the geology, 

landforms, relief, climate, and natural vegetation of the 

areas. Each kind of soil and miscellaneous area is 

associated with a particular kind or segment of the 

landscape. By observing the soils and miscellaneous 

areas in the survey area and relating their position to 

specific segments of the landscape, a soil scientist 

develops a concept or model of how the soils were 

formed. Thus, during mapping, this model enables the 

soil scientist to predict with considerable accuracy the 

Figure 4.-Pyroclastic flow in an area of Panhandle extremely cindery loamy sand, 0 to 20 percent slopes, on the north side of Mount St. Helens. 
kind of soil or miscellaneous area at a specific location 

on the landscape. 

Individual soils on the landscape commonly merge 

gradually into one another as their characteristics gradually 

change. To construct an accurate snap, however, soil 

scientists must determine the boundaries between the 

soils. They can observe only a limited number of soil 

profiles. Nevertheless, these observations, supplemented 

by an understanding of the soil-vegetation-landscape 

relationship, are sufficient to verify predictions of the kinds 

of soil in an area and to determine the boundaries. 

Soil scientists recorded the characteristics of the soil 

profiles they studied. They noted color, texture, size, and 

shape of soil aggregates, kind and amount of rock 

fragments, distribution of plant roots, reaction, and other 

features that enable them to identify soils. After describing 

the soils in the survey areas and determining their 

properties, the soil scientists assigned the soils to 

taxonomic classes (units). Taxonomic classes are 

concepts. Each taxonomic class has a set of soil 

characteristics with precisely defined limits. The classes 

are used as a basis for comparison to classify soils 

systematically. Soil taxonomy, the system of taxonomic 

classification used in the United States, is based mainly 

on the kind and character of soil properties and the 

arrangement of horizons within the profile. After the soil 

scientists classified and named the soils in the survey 

area, they compared the individual soils with similar soils in 

the same taxonomic class in other areas so that they could 

confirm data and assemble additional data based on 

experience and research. 

While the soil survey was in progress, samples of some 

of the soils in the area were collected for laboratory 

analyses and for engineering tests. Soil scientists 

interpreted the data from these analyses and tests as 

well as the field-observed characteristics and the soil 

properties to determine the expected behavior of the soils 

under different uses. Interpretations for all of the soils were 

field tested through observation of the soils in different 

uses and under different levels of management. Some 

interpretations were modified to fit 

local conditions, and some new interpretations were 

developed to meet local needs. Data were assembled 

from other sources, such as research information, 

production records, and field experience of specialists. 

For example, data on crop yields under defined levels of 

management were assembled from farm records and from 

field or plot experiments on the same kinds of soil. 

Predictions about soil behavior are based not only on 

soil properties but also on such variables as climate and 

biological activity. Soil conditions are predictable over 

long periods of time, but they are not predictable from year 

to year. For example, soil scientists can state with a fairly 

high degree of probability that a given soil will have a 

high water table within certain depths in most years, but 

they cannot predict that a high water table will always 

be at a specific level in the soil on a specific date. 

The fieldwork on this survey was completed in 1979, 

just prior to the eruption of Mount St. Helens. The 

eruption altered many landscapes and covered a vast 

area with pumice and volcanic ash to the point that the 

area needed to be resurveyed. Observations of the area 

after the eruption were limited by accessibility. Access to 

the blast zone was restricted by the hazard of further 

eruptions. Also, the road system was destroyed by 

washouts and clogged with fallen trees, which made 

travel extremely difficult. During the summer of 1981, 

arrangements were made to fly into the area by 

helicopter. Aerial photography of the affected area was 

studied to determine the extent of the changes made to the 

landscape. Notes and profile descriptions were taken at 

various locations within the blast area. This information, 

along with the photo interpretation and information 

obtained from the U.S. Geological Survey, was used to 

set up new map units. Landscapes that were completely 

altered and soils that were covered with more than 20 

inches of volcanic ash were renamed and reclassified. 

Landscapes that were covered with pumice or volcanic 

ash, or both, 4 to 20 inches thick were correlated as 

overblown phases of the soil series that had been 

identified and mapped prior to the eruption. 
General Soil Map Units 

The general soil map at the back of this publication is 

in two parts. The first part shows all of the survey area 

as it was in 1979. The second part shows the northern part 

of the survey area as it was in 1987, after the eruption 

of Mount St. Helens. The general soil map shows broad 

areas that have a distinctive pattern of soils, relief, and 

drainage. Each map unit on the general soil map is a 

unique natural landscape. Typically, a map unit consists 

of one or more major soils or miscellaneous areas and 

some minor soils or miscellaneous areas. It is named for 

the major soils or miscellaneous areas. The soils or 

miscellaneous areas making up one unit can occur in 

other units bit in a different pattern. 

The general soil map can be used to compare the 

suitability of large areas for general land uses. Areas of 

suitable soils or miscellaneous areas can be identified 

on the map. Likewise, areas that are not suitable can 

be identified. 

Because of its small scale, the map is not suitable for 

planning the management of a farm or field or for selecting 

a site for a road or building or other structure. The soils in 

any one map unit differ from place to place in slope, 

depth, drainage, and other characteristics that affect 

management. 

The general map units in this survey have been 

grouped into general kinds of landscape for broad 

interpretive purposes. Each of the broad groups and the 

map units in each group are described in the following 

pages. 

General Soil Map Units-Preeruption 

Soils on Flood Plains and Terrace Escarpments 

This group consists of one map unit. It makes up 

about 2 percent of the survey area. 

1. Skamania-Washougal-Pilchuck 

Very deep, well drained and somewhat excessively 

drained, nearly level to steep soils; on flood plains, 

terraces, and terrace escarpments 

This map unit is in the southwestern part of 

Skamania County, along the Columbia, Wind, and Little 

White Salmon Rivers. Slope is 0 to 50 percent. 

Vegetation is mainly mixed coniferous and hardwood 

trees with an understory of shrubs and forbs. Elevation is 

50 to 800 feet. The average annual precipitation is 60 to 

70 inches, the average annual air temperature is about 

48 to 50 degrees F, and the average frost-free season is 

110 to 200 days. 

This unit makes up about 2 percent of the survey 

area. It is about 35 percent Skamania soils, 30 percent 

Washougal soils, and 10 percent Pilchuck soils. The 

remaining 25 percent is components of minor extent. 

Skamania soils are on terraces and terrace 

escarpments. These soils are very deep and well 

drained. They formed in mixed alluvium derived from 

basalt, andesite, and volcanic ash. The surface is 

covered with a mat of decomposing needles, leaves, 

and twigs. The surface layer is very fine sandy loam. 

The subsoil is very fine sandy loam and fine sandy 

loam. The substratum to a depth of 60 inches or more 

is loamy fine sand. 

Washougal soils are on terraces and terrace 

escarpments. These soils are very deep and well 

drained. They formed in mixed alluvium derived from 

basalt, andesite, and volcanic ash. The surface is 

covered with a mat of decomposing needles, leaves, 

and twigs. The surface layer is loam. The underlying 

material to a depth of 60 inches or more is gravelly 

loam and very gravelly loam over very gravelly coarse 

sandy loam and extremely cobbly coarse sand. 

Pilchuck soils are on flood plains. These soils are very 

deep and somewhat excessively drained. They formed in 

alluvium derived from basic igneous rock. The surface 

layer is very fine sandy loam. The underlying material to 

a depth of 46 inches or more is stratified loamy fine 

sand to fine sand. Strata of fine sandy loam are below a 

depth of 40 inches. 
Of minor extent in this unit are Bonneville, Hood, and 

Skelida soils. 

This unit is used for hay, pasture, homesites, and 

woodland. In some areas the main limitation is the 

hazard of flooding. 

Soils on Mountain Slopes and Terraces 

This group consists of four map units. It makes up 

about 64 percent of the survey area. 

2. Cinnamon-Stabler-Chemawa 

Very deep, well drained, nearly level to very steep 

soils; on terraces, foot slopes, and back slopes of 

mountains 

This map unit is in the southeastern and north-central 

parts of the survey area and along the Wind River. 

Slope is 0 to 90 percent. The vegetation is mainly mixed 

coniferous trees, orchards, pasture, and hay. Elevation is 

600 to 2,800 feet. The average annual precipitation is 50 

to 125 inches, the average annual air temperature is 

about 44 to 47 degrees F, and the average frost-free 

season is 90 to 160 days. 

This unit makes up about 13 percent of the survey 

area. It is about 30 percent Cinnamon soils, 15 percent 

Stabler soils, and 15 percent Chemawa soils. The 

remaining 40 percent is components of minor extent. 

Cinnamon soils are on terraces, foot slopes, and 

back slopes of mountains. These soils are very deep and 

well drained. They formed in pyroclastic flaws of volcanic 

ash and pumice. The surface layer is covered with a mat 

of decomposing needles, leaves, and twigs. The surface 

layer is sandy loam. The subsoil is loamy sand. Below 

this to a depth of 60 inches or more is a buried subsoil 

of sandy loam. 

Stabler soils are on terraces and back slopes of 

mountains. These soils are very deep and well drained. 

They formed in pyroclastic flows of volcanic ash and 

pumice. The surface layer is covered with a mat of 

decomposing needles, leaves, and twigs. The surface 

layer and subsoil are loam. The substratum to a depth of 

60 inches or more is sandy loam. 

Chemawa soils are on terraces, foot slopes and back 

slopes of mountains. These soils are very deep and well 

drained. They formed in pyroclastic flaws consisting 

mostly of volcanic ash. The surface is covered with a 

mat of decomposing needles, leaves, and twigs. The 

surface layer and subsoil to a depth of 60 inches or more 

are loam. 

Of minor extent in this unit are Forsyth, Mossyrock, 

Mountzion, Stevenson, and Underwood soils. 

This unit is used as woodland, hayland, pastureland, 

orchards, and homesites. It has few limitations. 

Chemewa soils are suited to orchards. Pears and 

apples are the main crops. Stabler soils are used for 

pasture. A few areas are used for hay. 

3. St. Martin-Steever 

Very deep, moderately well drained and well 

drained, nearly level to very steep soils; on 

mountain slopes 

This map unit is in the south-central part of 

Skamania County, near the Columbia River. Slope is 2 

to 65 percent. The vegetation is mainly mixed coniferous 

trees, a few hardwood trees, and an understory of shrubs 

and forbs. Elevation is 50 to 2,000 feet. The average 

annual precipitation is 55 to 75 inches, the average 

annual air temperature is about 46 to 48 degrees F, and 

the average frost-free season is 100 to 160 days. 

This unit makes up about 13 percent of the survey 

area. It is about 30 percent St. Martin soils and 25 

percent Steever soils. The remaining 45 percent is 

components of minor extent. 

St. Martin soils are on back slopes, foot slopes, and 

toe slopes of mountains that have been disturbed by 

landslides. These soils are very deep and moderately 

well drained. They formed in colluvium derived from 

andesite. The surface is covered with a mat of 

decomposing needles, leaves, and twigs. The surface 

layer is gravelly silty clay loam. The subsoil to a depth of 

60 inches or more is clay and silty clay loam. 

Steever soils are on back slopes, foot slopes, and toe 

slopes of mountains. These soils are very deep and well 

drained. They formed in colluvial landslide material 

derived from basalt, andesite, and conglomerate. The 

surface is covered with a mat of decomposing needles, 

leaves, and twigs. The upper part of the surface layer is 

stony clay loam, and the lower part is gravelly clay 

loam. The subsoil is very gravelly clay loam and very 

gravelly loam. The substratum to a depth of 60 inches or 

more is very gravelly loam. 

Of minor extent in this unit are Aschoff, Mountzion, 

Skoly, Stabler, Stevenson, and Zygore soils. 

This unit is used as woodland, homesites, wildlife 

habitat, watershed, and recreation areas. A few areas 

are used as hayland and pastureland. 

The soils in this unit are predominantly unstable or 

potentially unstable if disturbed. They generally are 

suited to use as woodland. The main limitations are 

seasonal soil wetness, a hazard of erosion, and the 

presence of unstable areas. If this unit is used as 

homesites, the main limitations are steepness of slope, 

wetness, high shrink-swell potential, and potential for 

landslides. 
Figure 5.-Cross section of general soil map unit 4. 

4. McElroy-Underwood-Undusk 

Very deep, well drained, nearly level to very steep soils; 

on terraces and mountain slopes 

This map unit is in the southeastern part of Skamania 

County. Slope is 2 to 65 percent. The vegetation is 

mainly mixed coniferous and hardwood trees with an 

understory of shrubs and forbs. Elevation is 400 to 2,800 

feet. The average annual precipitation is about 50 to 55 

inches, the average annual air temperature is about 44 to 

46 degrees F, and the average frost-free season is 90 to 

150 days. 

This unit makes up about 11 percent of the survey 

area. It is about 30 percent McElroy soils, 15 percent 

Underwood soils, 15 percent Undusk soils, and 40 

percent components of minor extent (fig. 5). 

McElroy soils are on back slopes and foot slopes of 

mountains. These soils are very deep and well drained. 

They formed in colluvium derived from basalt and have 

a mantle of volcanic ash. The surface is covered with a 

mat of decomposing needles, leaves, and twigs. The 

surface layer is gravelly loam. The subsoil to a depth of 

60 inches or more is very gravelly loam and very cobbly 

loam. 

Underwood soils are on benches, back slopes, and foot 

slopes of mountains. These soils are very deep and well 

drained. They formed in residuum and colluvium derived 

from basalt and andesite and have a thin mantle of 

volcanic ash. The surface is covered with a mat of 

decomposing leaves, needles, and twigs. The surface 

layer is loam. The subsoil is clay loam and loam. The 

substratum to a depth of 60 inches or more is loam. 

Undusk soils are on back slopes of mountains. These 

soils are very deep and well drained. They formed in 

colluvium derived from basalt and have a mantle of 

volcanic ash. The surface is covered with a mat of 

decomposing needles, leaves, and twigs. The surface 
layer is gravelly loam. The subsoil to a depth of 60 

inches or more is very gravelly loam and extremely 

gravelly loam. 

Of minor extent in this unit are Chemawa and 

Timberhead soils. 

This unit is used as woodland, watershed, wildlife 

habitat, and grazable woodland. Also, a few areas are 

used for orchards and as homesites and recreation 

areas. 

This unit is suited to use as woodland. The main 

limitations are steepness of slope and seasonal soil 

wetness. Underwood soils are suited to orchards in 

areas adjacent to the Chemawa soils. McElroy and 

Underwood soils generally are suited to use as 

homesites. The main limitation is steepness of slope. 

5. Zygore-Aschoff-Swift 

Very deep, well drained, nearly level to very seep soils; 

on mountain slopes 

This map unit is in the southwestern part of 

Skamania County. south of Swift Creek Reservoir. Slope is 

2 to 90 percent. The vegetation is mainly coniferous trees 

with an understory of shrubs and forbs. Elevation is 400 to 

3,000 feet. The average annual precipitation is 85 to 115 

inches, the average annual air temperature is about 43 to 

47 degrees F, and the average frost-free season is 90 to 

120 days. 

This unit makes up about 27 percent of the survey area. 

It is about 25 percent Zygore soils, 20 percent Aschoff 

soils, and 20 percent Swift soils. The remaining 35 percent 

is components of minor extent. 

Zygore soils are on foot slopes and back slopes of 

mountains. These soils are very deep and well drained. 

They formed in colluvium derived from basalt and 

andesite mixed with volcanic ash. The surface is covered 

with a mat of decomposing needles, leaves, and twigs. 

The surface layer is very gravelly loam. The subsoil is very 

gravelly loam and very gravelly silt loam. The substratum 

to a depth of 60 inches or more is extremely gravelly silt 

loam. 

Aschoff soils are on foot slopes and back slopes of 

mountains. These soils are very deep and well drained. 

They formed in residuum and colluvium derived from 

basalt and andesite mixed with volcanic ash. The surface 

is covered with a mat of decomposing needles, leaves, 

and twigs. The surface layer is very gravelly loam. The 

subsoil is very gravelly loam and very cobbly loam. The 

substratum to a depth of 60 inches, or more is very 

gravelly loam. 

Swift soils are on the side slopes and ridgetops of 

mountains. These soils are very deep and well drained. 

They formed in colluvium derived from volcanic ash and 

basic igneous rock with a mantle of volcanic ash and 

cinders. The surface is covered with a mat of 

decomposing needles, leaves, and twigs. The surface 

layer is cindery sandy loam. The subsoil is very cindery 

loam. Below this to a depth of 60 inches or more is a 

buried subsoil that is extremely cobbly loam. 

Of minor extent in this unit are Dougan, Hesson, 

Kinney, Mountzion, and Zymer soils and areas of Rock 

outcrop. 

This unit is used mainly as woodland, wildlife habitat, 

and recreation areas. A few areas are used as homesites.

This unit is suited to timber production, except for a few 

areas at higher elevations. The main limitations are 

seasonal soil wetness and steepness of slope. A limitation 

for reforestation of burned areas is brush encroachment. 

If this unit is used as homesites, the main limitation is 

slope in the steeper areas. 

Soils on Lava Flows, Mountain Slopes, Escarpments, 

Terraces, Alluvial Fans, and Terrace Escarpments 

This group consists of three map units. It makes up 

about 34 percent of the survey area. 

6. Rock Outcrop-Rubble Land-Lithic Umbric 

Vitrandepts 

Very shallow and shallow, well drained, nearly level to 

very steep soils; on mountain slopes, escarpments, and 

lava flows 

This map unit is in the north-central part of Skamania 

County, on and near Mount St. Helens. Slope is 0 to 120 

percent. Areas of Rock outcrop and Rubble land generally 

are barren. Vegetation on the Lithic Umbric Vitrandepts is 

mixed coniferous trees with an understory of shrubs and 

forbs. Elevation is 800 to 9,671 feet, on Mount St. 

Helens. The average annual precipitation is about 130 

inches, the average annual air temperature is 35 to 48 

degrees F, and the frost-free season is 80 to 115 days. 

This unit makes up about 14 percent of the survey 

area. It is about 40 percent Rock outcrop, 10 percent 

Rubble land, and 10 percent Lithic Umbric Vitrandepts. 

The remaining 40 percent is components of minor 

extent. 

Rock outcrop and Rubble land are on mountain slopes 

and escarpments, mainly on Mount St. Helens. These 

areas are mainly rock outcroppings, lava flows, and snow 

and ice fields. Rock outcrop consists of areas in which 

more than 90 percent of the surface is exposed 

bedrock. Rubble land consists of areas in 
which more than 90 percent of the surface is rock 

fragments. Elevation is 4,000 to 9,671 feet. 

Lithic Umbric Vitrandepts are on valley bottoms in 

areas of lava flows. These soils are very shallow and 

shallow and are well drained. They formed in volcanic ash 

and pumice over lava flows of andesite. The surface is 

covered with a mat of decomposing needles, leaves, and 

twigs. The surface layer to a depth of 6 inches is sandy 

loam over very cindery loamy sand. Depth to bedrock 

ranges from 5 to 15 inches. Elevation is 800 to 4,000 

feet. 

Of minor extent in this unit are Polepatch soils, 

Shoestring soils, and Badland. 

This unit is used as recreation areas, wildlife habitat, and 

watershed. The main recreational use is as geological 

sites. The main interests on the Lithic Umbric 

Vitrandepts are the lava casts of trees and lava tubes. 

Climbing perennial snowfields and glaciers are the main 

recreational uses of the Rock outcrop and Rubble land. 

7. Polepatch-Shoestring 

Very deep, well drained and somewhat excessively 

drained, nearly level to very steep soils; on terraces, 

alluvial fans, and terrace escarpments 

This map unit is in the north-central part of Skamania 

County, near Mount St. Helens. Slope is 0 to 0 

percent. The vegetation is mainly mixed coniferous trees 

with an understory of shrubs and forbs. Elevation is 2,700 

to 4,600 feet. The average annual precipitation is 130 to 

135 inches, the average annual air temperature is about 

40 degrees F, and the average frost-free season is 70 to 

90 days. 

This unit makes up about 6 percent of the survey 

area. It is about 30 percent Polepatch soils and 30 

percent Shoestring soils. The remaining 40 percent is 

components of minor extent. 

Polepatch soils are on alluvial fans and terraces. 

These soils are very deep and somewhat excessively 

drained. They formed in lahar with a thin layer of 

volcanic ash. The surface is covered with a mat of 

organic matter. The surface layer is extremely bouldery 

loamy sand. The underlying material to a depth of 60 

inches or more is extremely cobbly sand, fine sandy 

loam, and extremely stony coarse sand. 

Shoestring soils are on terraces and terrace 

escarpments. These soils are very deep and well 

drained. They formed in aerially deposited volcanic ash 

and pumice over pyroclastic flow material and lahar. 

The surface is covered with a mat of decomposing 

needles, leaves, and twigs. The surface layer is fine 

sandy loam. The subsoil is very gravelly sand sandy 

loam, and loamy sand. The substratum to a depth of 60 

inches or more is very cobbly sand and very gravelly 

sand. 

Of minor extent in this unit are Cinnamon, Pinchot, 

and St. Helens soils and Badland. 

This unit is used as woodland, recreation areas, wildlife 

habitat, and watershed. If this unit is used as woodland, 

the main limitations are winter snowpack and steepness 

of slope. Also, boulders on the surface and low available 

water capacity are limitations on the Polepatch soils. 

8. Vanson-Sinnice-Tradedollar 

Very deep and deep, well drained, nearly level to very 

steep soils; on mountain slopes 

This map unit is in the northeastern part of Skamania 

County. Slope is 0 to 90 percent. The vegetation is 

mainly mixed coniferous trees with an understory of 

shrubs and forbs. Elevation is 2,800 to 5,400 feet. The 

average annual precipitation is 90 to 125 inches, the 

average annual air temperature is about 39 degrees F, 

and the average frost-free season is 75 to 95 days. 

This unit makes up about 14 percent of the survey 

area. It is about 25 percent Vanson soils, 25 percent 

Sinnice soils, and 20 percent Tradedollar soils. The 

remaining 30 percent is components of minor extent. 

Vanson soils are on foot slopes, back slopes, and 

ridgetops of mountains. These soils are deep and well 

drained. They formed in colluvium derived from andesite 

with a mantle of volcanic ash and pumice. The surface 

layer, where mixed, is sandy loam. The subsoil is sandy 

loam, loamy sand, and very gravelly sandy loam. Bedrock 

is at a depth of 45 inches. Depth to bedrock ranges from 

40 to 60 inches. 

Sinnice soils are on foot slopes, back slopes, and 

ridgetops of mountains. These soils are very deep and 

well drained. They formed in aerially deposited layers of 

volcanic ash and pumice. The surface is covered with a 

mat of decomposing needles, leaves, and twigs. The 

surface layer, where mixed, is extremely cindery loamy 

sand. The subsoil is fine sandy loam and loamy sand. 

The substratum to a depth of 60 inches or more is 

extremely cindery sand. 

Tradedollar soils are on back slopes and ridgetops of 

mountains. These soils are very deep and well drained. 

They formed in aerially deposited volcanic ash and 

pumice. The surface is covered with a mat of organic 

material. The surface layer is sandy loam. The subsoil is 

cindery sandy loam and extremely cindery loamy sand. 

Below this to a depth of 60 inches or more is a buried 

surface layer of cindery sandy loam over a 
buried subsoil of very gravelly sandy loam. 

Of minor extent in this unit are Colter, Cattcreek, 

Hatchet, and Pelee soils. 

This unit is used as woodland, recreation areas, 

wildlife habitat, and watershed. If this unit is used as 

woodland, the main limitations are winter snowpack, 

seedling mortality, and steepness of slope. 

General Soil Map Units-Posteruption 

Soils on Mudflows 

This group consists of one map unit. It makes up 

about 23 percent of the posteruption area and about 4 

percent of the total survey area. 

9. Wakepish-Obscurity 

Very deep, somewhat excessively drained, nearly level to 

moderately steep soils; on broad fans and low terraces 

This map unit is on the west-, north-, and east-facing 

slopes of Mount St. Helens. Slope is 0 to 30 percent. 

Vegetation is absent. Elevation is 1,600 to 5,500 feet. 

The average annual precipitation is 130 to 135 inches, 

the average annual air temperature is 40 to 42 degrees F. 

and the average frost-free season is 70 to 110 days. 

This unit makes up about 23 percent of the 

posteruption area and about 4 percent of the total survey 

area. It is about 43 percent Wakepish soils and 30 

percent Obscurity soils. The remaining 27 percent is 

components of minor extent. 

Wakepish soils are on fans and low terraces along 

drainageways. These soils are very deep and somewhat 

excessively drained. They formed in mudflow material. 

The surface layer is very gravelly sandy loam. The 

underlying material is very gravelly loamy sand. 

Obscurity soils are on broad fans and low terraces. 

These soils are very deep and somewhat excessively 

drained. They formed in mudflow material. The surface 

layer is very bouldery sand. The underlying material is 

very cobbly loamy sand. 

Of minor extent in this unit are areas of Rock outcrop, 

Rubble land, and Panhandle and Studebaker soils. 

This unit has potential for use as recreation areas 

and wildlife habitat. 

Soils on Cindery Pyroclastic Flows 

This group consists of one map unit. It makes up 

about 4 percent of the posteruption area and less than 1 

percent of the total survey area. 

10. Panhandle 

Very deep, well drained, nearly level to strongly sloping 

soils; on broad fans 

This map unit is on the north side of Mount St. 

Helens. Slope is 0 to 20 percent. Vegetation is absent. 

Elevation is 2,900 to 5,000 feet. The average annual 

precipitation is about 135 inches, the average annual air 

temperature is about 40 degrees F, and the average 

frost-free season is 75 to 90 days. 

This unit makes up about 4 percent of the 

posteruption area and less than 1 percent of the total 

survey area. It is about 70 percent Panhandle soils. The 

remaining 30 percent is components of minor extent. 

Panhandle soils are on broad fans. These soils are 

very deep and well drained. They formed in cindery 

pyroclastic flow. The surface layer is extremely cindery 

loamy sand. The underlying material is very cindery 

loamy sand. 

Of minor extent in this unit are Studebaker, 

Tradedollar, and Vanson soils. 

This unit has potential for use as recreation areas 

and wildlife habitat. 

Soils on Avalanche Debris Flows 

This group consists of one map unit. It makes up 

about 18 percent of the posteruption area and about 3 

percent of the total survey area. 

11. Studebaker 

Very deep, somewhat excessively drained, nearly level to 

strongly sloping soils; in areas of valley fill 

This map unit is on the north side of Mount St. 

Helens. Slope is 0 to 20 percent. Vegetation is absent. 

Elevation is 2,700 to 5,500 feet. The average annual 

precipitation is about 135 inches, the average annual air 

temperature is about 40 degrees F, and the average frostfree season is 70 to 90 days. 

This unit makes up about 18 percent of the 

posteruption area and about 3 percent of the total 

survey area. It is about 76 percent Studebaker soils. 

The remaining 24 percent is components of minor 

extent. 

Studebaker soils are on foot slopes and toe slopes in 

highly irregular, dissected areas of valley fill. These soils 

are very deep and somewhat excessively drained. They 

formed in avalanche debris flow material. The profile to a 

depth of 60 inches or more is very gravelly loamy sand. 
Of minor extent in this unit are Panhandle, Vanson, 

and Tradedollar soils and Rock outcrop. 

This unit has potential for use as woodland and 

wildlife habitat. 

Soils Overblown by Ash 

This group consists of two map units. It makes up 

about 23 percent of the posteruption area and about 4 

percent of the total survey area. 

12. Vanson-Tradedollar 

Ash overblown, very deep, well drained, nearly level 

to very steep, cryic soils; on mountain slopes 

This map unit is on the north side of Mount St. 

Helens. Slope is 0 to 90 percent. Vegetation is absent. 

Elevation is 2,800 to 5,400 feet. The average annual 

precipitation is about 100 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free season is 75 to 95 days. 

This unit makes up about 22 percent of the 

posteruption area and about 4 percent of the total survey 

area. It is about 42 percent Vanson soils and 36 percent 

Tradedollar soils. The remaining 22 percent is 

components of minor extent. 

Vanson soils are on back slopes, foot slopes, and 

ridgetops of mountains. These soils are very deep and 

well drained. They formed in residuum and colluvium 

derived from igneous rock and have a mantle of volcanic 

ash and pumice. The surface layer is overblown with 

loamy sand ashfall. The buried surface layer is sandy 

loam. The upper part of the subsoil is cindery sandy loam, 

the middle part is loamy sand, and the lower part to a 

depth of 60 inches or more is sandy loam. 

Tradedollar soils are on back slopes and ridgetops of 

mountains. These soils are very deep and well drained. 

They formed in aerially deposited volcanic ash and pumice. 

The surface layer is overblown with loamy sand ashfall. 

The buried surface layer is sandy loam. The upper part of 

the subsoil is cindery sandy loam, and the lower part to a 

depth of 60 inches or more is extremely cindery loamy 

sand. 

Of minor extent in this unit are Vanson, Tradedollar, 

Wakepish, Studebaker. and Sinnice soils. 

This unit has potential for use as woodland, wildlife 

habitat. and recreation areas. 

13. Swift-Cinnamon 

Ash overblown, very deep, well drained, nearly level to 

very steep soils; on mountain slopes 

This map unit is in the northern part of Skamania 

County. Slope is 2 to 90 percent. Vegetation is absent. 

Elevation is 1,200 to 2,800 feet. The average annual 

precipitation is 115 to 125 inches, the average annual air 

temperature is about 43 degrees F, and the average frostfree season is 90 to 120 days. 

This unit makes up about 1 percent of the 

posteruption area and less that 1 percent of the total 

survey area. It is about 43 percent Swift soils and 29 

percent Cinnamon soils. The remaining 27 percent is 

components of minor extent. 

Swift soils are on side slopes and ridgetops of 

mountains. These soils are very deep and well drained. 

They formed in colluvium derived from volcanic ash and 

basic igneous rock and have a mantle of ash and 

cinders. The surface layer is overblown with loamy sand 

ashfall. The buried surface layer is cindery sandy loam. 

The upper part of the subsoil is very cindery loam, and 

the lower part to a depth of 60 inches or more is 

extremely cobbly loam. 

Cinnamon soils are on terraces, foot slopes, and back 

slopes of mountains. These soils are very deep and well 

drained. They formed in volcanic ash and pumice. The 

surface layer is overblown with loamy sand ashfall. The 

buried surface layer is sandy loam. The subsoil is loamy 

sand. Below this to a depth of 60 inches or more is sandy 

loam. 

Of minor extent in this unit are Vanson, Tradedollar, 

and Bandid soils. 

This unit has potential for use as woodland, 

recreation areas, and wildlife habitat. 

Soils Overblown by Cinders 

This group consists of two map units. It makes up 

about 32 percent of the posteruption area and about 5 

percent of the total survey area. 

14. Sinnice 

Cinder overblown, very deep, well drained, gently 

sloping to very steep soils; on foot slopes, back 

slopes, and ridgetops of mountains 

This map unit is in the northeastern part of Skamania 

County. Slope is 5 to 90 percent. Vegetation is absent. 

Elevation is 2,800 to 5,000 feet. The average annual 

precipitation is about 125 inches, the average annual air 

temperature is about 39 degrees F, and the average 

frost-free season is 75 to 90 days. 

This unit makes up about 24 percent of the 
posteruption area and about 4 percent of the total 

survey area. It is about 77 percent Sinnice soils. The 

remaining 23 percent is components of minor extent. 

Sinnice soils are on foot slopes, back slopes, and 

ridgetops of mountains. These soils are very deep and well 

drained. They formed in aerially deposited layers of 

volcanic ash and pumice. The surface layer is overblown 

with extremely cindery loamy sand and gravelly sand 

cinderfall. The buried surface layer is extremely cindery 

loamy sand. The upper part of the subsoil is fine sandy 

loam, and the lower part is loamy sand. The substratum to 

a depth of 60 inches or more is extremely cindery sand. 

Of minor extent in this unit are Bandid, Vanson, 

Tradedollar, and Studebaker soils. 

This unit has potential for use as woodland, 

recreation areas, and wildlife habitat. 

15. Bandid 

Cinder overblown, very deep, well drained, gently sloping 

to very steep soils; on back slopes, foot slopes, and toe 

slopes of mountains 

This map unit is on the east side of Mount St. 

Helens. Slope is 5 to 90 percent. Vegetation is absent. 

Elevation is 1,800 to 2,800 feet. The average annual 

precipitation is about 130 inches, the average annual air 

temperature is about 44 degrees F, and the average 

frost-free season is 90 to 110 days. 

This unit makes up about 8 percent of the 

posteruption area and about 1 percent of the total 

survey area. It is about 75 percent Bandid soils. The 

remaining 25 percent is components of minor extent. 

Bandid soils are on back slopes, foot slopes, and toe 

slopes of mountains. These soils are very deep and well 

drained. They formed in stratified aerially deposited ash 

and pumice. The surface layer is overblown with 

extremely cindery loamy sand and gravelly sand cinderfall. 

The buried surface layer is cindery sandy loam, fine sandy 

loam, and loamy sand. The upper part of the subsoil is 

cindery fine sandy loam, the next part is extremely 

cindery sand, and the lower part to a depth of 60 inches or 

more is stratified cindery sandy loam and loamy sand. 

Of minor extent in this unit are Sinnice, Wakepish, 

Obscurity, Swift, and Cinnamon soils. 

This unit has potential for use as woodland, 

recreation areas, and wildlife habitat. 

Broad Land Use Considerations 

The soils in the Skamania County Area vary widely in 

their potential for major land uses. About 1 percent of the 

land in the survey area is used for orchards and as 

hayland and pastureland. A small acreage is used to 

grow grain and grapes for wine. These areas are scattered 

along the major drainageways in the southern part of the 

area and are in general soil map units 1, 3, and 4, The 

main soils are those of the Chemawa, Hesson, and 

Skamania series. The hazard of erosion is the main 

limitation for crops. Some areas in map unit 1 are 

subject to flooding. Seasonal soil wetness, a hazard of 

erosion, and unstable areas are the main limitations in 

unit 3. Unit 4 has few limitations. 

More than 98 percent of the land in the survey area 

is woodland. Most of the area is owned by timber 

companies or is publicly owned. Some small privately 

owned woodlots are along the Columbia River. The soils 

in the area are well suited to use as woodland; however, 

soils at an elevation of more than 4,000 feet are subject to 

cold temperatures and soils along the Columbia River 

Gorge are subject to cold, strong winds. Productivity is 

lower in these areas. The major woodland soils are those 

of the Aschoff, Cinnamon, McElroy, Vanson, and Zygore 

series. Management practices used in logging and in 

road construction should be designed to minimize soil 

erosion and sedimentation of streams. This is most 

important on steeply sloping soils. 

About 1 percent of the land in the survey area is 

urban or built-up land. Steepness of slope has restricted 

urban development to areas on terraces and on flood 

plains along the Columbia River and its tributaries. Soils 

on the flood plains, such as those of the McBee and 

Pilchuck series, are subject to flooding. Bonneville and 

Washougal soils on terraces have poor filter material for 

septic tank absorption fields. If the density of housing is 

moderate to high, community sewage systems are 

needed to prevent contamination of water supplies as the 

result of seepage from onsite sewage disposal systems. 

The potential for recreational use is high, especially 

around Mount St. Helens. Scenic vistas, points of 

geologic interest, and alpine lakes make this area ideal 

for hiking or horseback riding. Small areas are also 

available for use as campgrounds and picnic areas. 
Detailed Soil Map Units

The map units delineated on the detailed maps at the 

back of this survey represent the soils or miscellaneous 

areas in the survey area. The map unit descriptions in 

this section, along with the maps, can be used to determine 

the suitability and potential of a unit for specific uses. They 

also can be used to plan the management needed for 

those uses. More information on each map unit is given 

under ''Use and Management of the Soils. '' 

A map unit delineation on a map represents an area 

dominated by one or more major kinds of soil or 

miscellaneous areas. A map unit is identified and named 

according to the taxonomic classification of the dominant 

soils or miscellaneous areas. Within a taxonomic class 

there are precisely defined limits for the properties of the 

soils. On the landscape, however, the soils and 

miscellaneous areas are natural phenomena, and they 

have the characteristic variability of all natural phenomena. 

Thus, the range of some observed properties may extend 

beyond the limits defined for a taxonomic class. Areas of 

soils of a single taxonomic class rarely, if ever, can be 

mapped without including areas of other taxonomic 

classes. Consequently, every map unit is made up of the 

soils or miscellaneous areas for which it is named and 

some "included'' areas that belong to other taxonomic 

classes. 

Most included soils have properties similar to those of 

the dominant soil or soils in the map unit, and thus they 

do not affect use and management. These are called 

noncontrasting, or similar, inclusions. They may or may 

not be mentioned in the map unit description. Other 

included soils and miscellaneous areas, however, have 

properties and behavior divergent enough to affect use or 

to require different management. These are called 

contrasting, or dissimilar, inclusions. They generally are in 

small areas and could not be mapped separately because 

of the scale used. Some small areas of strongly contrasting 

soils or miscellaneous areas are identified by a special 

symbol on the maps. The included areas of contrasting 

soils or miscellaneous 

areas are mentioned in the map unit descriptions. A few 

included areas may not have been observed, and 

consequently they are not mentioned in the descriptions, 

especially where the pattern was so complex that it was 

impractical to make enough observations to identify all the 

soils and miscellaneous areas on the landscape. 

The presence of included areas in a map unit in no 

way diminishes the usefulness or accuracy of the data. The 

objective of mapping is not to delineate pure taxonomic 

classes but rather to separate the landscape into 

segments that have similar use and management 

requirements. The delineation of such landscape 

segments on the map provides sufficient information for 

the development of resource plans, but if intensive use 

of small areas is planned, onsite investigation to 

precisely define and locate the soils and miscellaneous 

areas is needed. 

An identifying symbol precedes the map unit name in 

the map unit descriptions. Each description includes 

general facts about the unit and gives the principal 

hazards and limitations to be considered in planning for 

specific uses. 

Soils that have profiles that are almost alike make up 

a soil series. Except for differences in texture of the 

surface layer or of the underlying layers, all the soils of a 

series have major horizons that are similar in 

composition, thickness, and arrangement. 

Soils of one series can differ in texture of the surface 

layer or of the underlying layers. They also can differ in 

slope, stoniness, salinity, wetness, degree of erosion, 

and other characteristics that affect their use. On the 

basis of such differences, a soil series is divided into soil 

phases. Most of the areas shown on the detailed soil 

maps are phases of soil series. The name of a soil 

phase commonly indicates a feature that affects use or 

management. For example, Skamania very fine sandy 

loam, 8 to 15 percent slopes, is one of several phases 

in the Skamania series. 

Some map units are made up of two or more major 

soils or miscellaneous areas. These are complexes. 
A complex consists of two or more soils or miscellaneous 

areas in such an intricate pattern or in such small areas 

that they cannot be shown separately on the maps. The 

pattern and proportion of the soils or miscellaneous areas 

are somewhat similar in all areas. Swift-Rock outcrop 

complex, 30 to 65 percent slopes, is an example. 

This survey includes miscellaneous areas. Such areas 

have little or no soil material and support little or no 

vegetation. Badland is an example. 

Arents and Andic Cryumbrepts are examples of 

mapping units that are not members of soil series. These 

units are made up of soils grouped together at a higher 

level in the classification system. This higher level is 

used for units that have wide variations in soil properties. 

Such units appear in the tables in alphabetical order with 

the soil series, complete with interpretations. 

Tables 4a and 4b give the acreage and proportionate 

extent of each map unit. Other tables (see "Summary of 

Tables") give properties of the soils and the limitations, 

capabilities. and potentials for many uses. The Glossary 

defines many of the terms used in describing the soils or 

miscellaneous areas. 

Detailed Map Unit Descriptions 

1-Andic Cryumbrepts, 5 to 65 percent slopes. 

These deep and very deep, well drained soils are on 

ridgetops and mountain slopes. They formed in residuum

and colluvium derived dominantly from basalt and 

andesite mixed with volcanic ash. The native vegetation is 

mainly true firs and shrubs. Elevation is 2,800 to 3,500 

feet. The average annual precipitation is 100 inches, the 

average annual air temperature is about 41 degrees F, 

and the average frost-free period is 70 to 100 days. 

No single profile is typical of Andic Cryumbrepts, but 

one commonly observed in the survey area has a surface 

covered with a mat of decomposing needles, leaves, and 

twigs 1 inch thick. The surface layer is dark brown cobbly 

loam 17 inches thick. The subsoil is dark brown cobbly 

and very cobbly loam 22 inches thick. The substratum to a 

depth of 60 inches or more is brown cobbly loam. 

Included in this unit are small areas of Dougan and 

Zygore soils. Also included are small areas of Rock outcrop, 

organic soils, and soils that are shallow to bedrock. 

Included areas make up about 7 percent of the total 

acreage. 

Permeability of these Andic Cryumbrepts is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 40 to 60 inches. Runoff is medium to 

rapid, and the hazard of water erosion is severe. 

This unit is used as woodland, wildlife habitat, 

recreation areas, and watershed. 

Western hemlock, noble fir, and Pacific silver fir are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 

105 for western hemlock. On the basis of a 50-year 

curve, the mean site index is estimated to be 75 for 

western hemlock. The culmination of the mean annual 

increment (CMAI) for western hemlock is 151 cubic feet 

per acre per year at age 60. Estimates of the site index or 

CMAI for noble fir and Pacific silver fir have not been 

made. Areas of ridgetops that are subject to strong, 

persistent winds are less productive than the other areas 

in this unit. 

The main limitations for harvesting timber are 

steepness of slope, snowpack in winter, and the hazard of 

erosion. When harvesting timber, steepness of slope 

restricts the use of wheeled and tracked equipment in 

skidding. Cable yarding systems generally are safer and 

disturb the soil less. Use of wheeled and tracked 

equipment when the soil is moist produces ruts, compacts 

the soil, and damages the roots of trees. Unsurfaced 

roads and skid trails are soft and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Snowpack hinders the use of 

equipment and limits access in winter. Establishing plant 

cover in the steeper areas that have been cut or filled 

reduces erosion. Steep yarding paths, skid trails, and 

firebreaks are subject to rilling and gullying unless plant 

cover is maintained or adequate water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir or Pacific silver fir seedlings. If seed 

trees are present, natural reforestation of cutover areas by 

western hemlock occurs periodically. Droughtiness of the 

surface layer reduces seeding survival, especially on 

south- and southwest-facing slopes. The mortality rate of 

seedlings is higher in areas on ridgetops that are subject 

to strong, persistent winds than in other areas of this unit.

Among the common forest understory plants are red 

huckleberry, common beargrass, lupine, western 

brackenfern, and vine maple. 

This map unit is in capability subclass Vle. 
2-Arents, 0 to 5 percent slopes. These very deep, 

well drained to somewhat excessively drained soils are 

on alluvial river terraces. They formed in alluvium derived 

dominantly from recent construction. The introduced 

vegetation is mainly grasses and legumes. Elevation is 

60 to 100 feet. The average annual precipitation is about 

70 inches, the average annual air temperature is about 

48 degrees F, and the average frost-free period is 125 

to 135 days. 

No single profile of Arents is typical, but one commonly 

observed in the survey area has a surface layer of dark 

brown gravelly sandy loam 24 inches thick. The underlying 

material to a depth of 60 inches or more is stratified 

gravelly or very gravelly loamy sand. In some areas the 

surface layer is nongravelly. 

Included in this unit are small areas of Bonneville 

soils on terraces and Pilchuck soils on flood plains. 

Included areas make up about 5 percent of the total 

acreage. 

Permeability of these Arents is rapid. Available water 

capacity is moderate. Effective rooting depth is 60 inches 

or more. Runoff is slow, and the hazard of water erosion is 

slight. 

This unit is used for urban development, wildlife 

habitat, and recreation. 

This unit has few limitations for urban development. 

Revegetating disturbed areas around construction sites 

as soon as possible helps to control soil blowing. Removal 

of pebbles and cobbles is needed for best results when 

landscaping, particularly for lawns. In summer, irrigation is 

needed for lawn grasses, shrubs, vines, shade trees, and 

ornamental trees. 

If the density of housing is moderate to high, 

community sewage systems are needed to prevent 

contamination of water supplies as a result of seepage 

from onsite sewage disposal systems. 

This map unit is in capability subclass IVs. 

3-Aschoff very gravelly loam, 5 to 30 percent 

slopes. This very deep, well drained soil is on foot slopes 

and ridgetops of mountains. It formed in colluvium derived 

dominantly from basalt and andesite mixed with volcanic 

ash. The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 400 to 2,100 feet. The average annual 

precipitation is about 85 inches, the average annual air 

temperature is about 50 degrees F, and the average 

frost-free period is 100 to 150 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark brown and very dark 

grayish brown very gravelly loam 12 inches thick. The 

upper 21 inches of the subsoil is dark yellowish brown 

very gravelly loam, and the lower 14 inches is dark 

yellowish brown very cobbly loam. The substratum is 

dark yellowish brown very gravelly loam to a depth of 60 

inches or more. 

Included in this unit are small areas of Mountzion 

and Skoly soils. Also included are small areas of St. 

Martin and Steever soils on old landslides, soils that are 

moderately deep over basalt, and Aschoff soils that 

have slopes of more than 30 percent. Included areas 

make up about 20 percent of the total acreage. 

Permeability of this Aschoff soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

Most areas of this unit are used as woodland, 

watershed, wildlife habitat, and recreation. Some areas 

are used as homesites. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 166 for Douglas 

fir and is estimated to be 154 for western hemlock. On the 

basis of a 50-year site curve, the mean site index is 125 

for Douglas fir and is estimated to be 110 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 177 cubic feet per acre per year 

at age 60 and 244 cubic feet for western hemlock at age 

50. Among the trees of limited extent are red alder, 

western redcedar, and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads for year-round use require 

suitable surfacing. Rock for road construction is readily 

available in this unit. Occasional snowpack hinders the 

use of equipment and limits access in winter. Establishing 

plant cover on steeper slopes that have been cut or filled 

reduces erosion. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. Droughtiness of the 

surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock. 
Among the common forest understory plants are vine 

maple. Pacific dogwood, common snowberry, creambush 

oceanspray, salal, Oregongrape, false Solomons seal, 

and western brackenfern. 

The main limitation of this unit for use as homesites is 

steepness of slope. Erosion is a hazard in the steeper 

areas. Only the part of the site that is used for construction 

should be disturbed. Topsoil can be stockpiled and used 

to reclaim areas disturbed during construction. Removal 

of pebbles and cobbles in disturbed areas is needed for 

best results when landscaping, particularly in areas used 

for lawns. Mulch, fertilizer, and irrigation are needed to 

establish lawn grasses and other small-seeded plants. 

Slope is a concern in installing septic tank absorption 

fields. Absorption lines should be installed on the 

contour. 

This map unit is in capability subclass IVe. 

4-Aschoff very gravelly loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back 

slopes of mountains. It formed in residuum and colluvium 

derived dominantly from basalt and andesite mixed with 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 400 to 2,100 feet. The 

average annual precipitation is about 85 inches, the 

average annual air temperature is about 50 degrees F, 

and the average frost-free period is 100 to 150 days. 

Typically. the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark brown and very dark 

grayish brown very gravelly loam 12 inches thick. The 

upper 21 inches of the subsoil is dark yellowish brown 

very gravelly loam, and the lower 14 inches is dark 

yellowish brown very cobbly loam. The substratum is 

dark yellowish brown very gravelly loam to a depth of 60 

inches or more. 

Included in this unit are small areas of Mountzion and 

Skoly soils. Also included are small areas of St. Martin 

and Steever soils on old landslides and Zygore and 

Aschoff soils that have slopes of less than 30 percent. 

Included areas make up about 15 percent of the total 

acreage. 

Permeability of this Aschoff soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is rapid, and the 

hazard of water erosion is severe. 

This unit is used for woodland, watershed, wildlife 

habitat, and recreation. 

 Douglas fir and western hemlock are the main woodland 

species on this unit. On the basis of a 100- 

year site curve, the mean site index is 166 for Douglas fir 

and is estimated to be 154 for western hemlock. On the 

basis of a 50-year site curve, the mean site index is 125 

for Douglas fir and is estimated to be 110 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 177 cubic feet per acre per year 

at age 60 and 244 cubic feet for western hemlock at age 

50. Among the trees of limited extent are red alder, 

western redcedar, and bigleaf maple. 

The main limitation for harvesting timber is steepness of 

slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and slippery and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Occasional 

snowpack hinders the use of equipment and limits access 

in winter. Establishing plant cover on steeper slopes that 

have been cut or filled reduces erosion. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. Droughtiness of the 

surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock. 

Among the common forest understory plants are vine 

maple. Pacific dogwood, common snowberry, creambush 

oceanspray, salal, Oregongrape, false Solomons seal, 

and western brackenfern. 

This map unit is in capability subclass VIIe. 

5-Aschoff-Rock outcrop complex, 30 to 65 percent 

slopes. This map unit is on back slopes of mountains. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 400 to 2,100 feet. The average 

annual precipitation is about 85 inches, the average 

annual air temperature is about 50 degrees F, and the 

average frost-free period is 100 to 150 days. 

This unit is about 55 percent Aschoff very gravelly loam, 

30 to 65 percent slopes; 35 percent Rock outcrop; and 

10 percent included soils. The components 
of this unit are so intricately intermingled that it was not 

practical to map them separately at the scale used. 

Included in this unit are small areas of Skoly and Kinney 

soils Also included are small areas of Steever soils on 

landslides. Aschoff soils that have slopes of less than 30 

percent or more than 65 percent, and soils that are shallow 

to bedrock. Included areas make up about 10 percent of 

the total acreage. 

The Aschoff soil is very deep and well drained. It formed 

in colluvium derived dominantly from basalt and andesite 

mixed with volcanic ash. Typically, the surface is covered 

with a mat of decomposed needles, leaves, and twigs 2 

inches thick. The surface layer is very dark grayish brown 

very gravelly loam 12 inches thick. The upper 21 inches of 

the subsoil is dark yellowish brown very gravelly loam, and 

the lower 14 inches is dark yellowish brown very cobbly 

loam. The substratum to a depth of 60 inches or more is 

dark yellowish brown very gravelly loam. 

Permeability of this Aschoff soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

Rock outcrop is dominantly basalt, andesite, and a few 

areas of dacite. Numerous escarpments are in this unit. 

Most areas of this unit are used for woodland, wildlife

habitat, recreation, or watershed. A few areas are used as 

a source of gravel. 

Douglas fir and western hemlock are the main 

woodland species on the Aschoff soil. On the basis of a 

100-year site curve, the mean site index is 166 for 

Douglas fir and is estimated to be 154 for western 

hemlock. On the basis of a 50-year site curve, the mean 

site index is 125 for Douglas fir and is estimated to be 110 

for western hemlock. The culmination of the mean 

annual increment (CMAI) is 177 cubic feet per acre per 

year for Douglas fir at age 60 and 244 cubic feet for 

western hemlock at age 50. The areas of Rock outcrop 

make up about 35 percent of this unit and reduce yields 

accordingly. Among the trees of limited extent are red 

alder, western redcedar, and bigleaf maple. 

The main limitations for harvesting timber are the areas 

of Rock outcrop and steepness of slope. Rock outcrop may 

cause breakage of timber when felled and can hinder 

yarding operations. Avoiding the areas of Rock outcrop 

forces yarding paths to converge, which increases 

compaction and erosion of the soil. When harvesting 

timber, steepness of slope restricts the use of wheeled 

and tracked equipment in skidding. Cable yarding 

systems generally are safer and disturb the soil 

less. Use of wheeled and tracked equipment when the soil 

is moist produces ruts, compacts the soil, and damages 

the roots of trees. Unsurfaced roads and skid trails are 

soft and slippery and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in this 

unit. Occasional snowpack hinders the use of equipment 

and limits access in winter. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. Droughtiness of the 

surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. The areas of Rock 

outcrop limit the even distribution of reforestation. If the 

canopy is opened, brush invades and can delay the 

establishment of Douglas fir seedlings and natural 

reforestation by western hemlock. 

Among the common forest understory plants are vine 

maple, Pacific dogwood, common snowberry, creambush 

oceanspray, salal. Oregongrape, false Solomons seal, 

and western brackenfern. 

The Aschoff soil is in capability subclass VIIe, and 

Rock outcrop is in capability subclass VIlls. 

6-Badland. This map unit consists of deep, 

somewhat excessively drained areas on very steep 

terrace escarpments adjacent to Pine Creek and the 

South Fork of the Toutle River. It formed in lahar 

material. Slope is 65 to 120 percent. It supports no 

vegetation. Elevation is 1,200 to 4,400 feet. The 

average annual precipitation is about 125 inches, the 

average annual air temperature is 39 to 44 degrees F, 

and the average frost-free season is 75 to 110 days. 

No single profile is typical of Badland, but one 

commonly observed in the survey area is very cobbly 

sand and extremely gravelly sand to a depth of 60 

inches or more. 

Included in this unit are areas that have a loamy sand 

surface layer consisting of ashfall more than 20 inches 

deep and areas that have slopes of less than 65 

percent. Included areas make up about 10 percent of the 

unit. 

Permeability of Badland is very rapid. Available water 

capacity is low to moderate. Runoff is rapid, and the 
hazard of water erosion is severe. The hazard of soil 

blowing in the included areas overlain by ashfall is high. 

In areas where vegetation was removed by the initial 

blast or buried by ash and where water flow was 

concentrated, gullies formed readily. Sediment 

production will be high until the ash has been stabilized 

by vegetation. 

This unit is used for wildlife habitat and esthetic 

value. 

This map unit is in capability subclass VIlls. 

7-Bandid loamy sand, 30 to 65 percent slopes. 

This very deep, well drained soil is on back slopes and toe 

slopes of mountains. It formed in stratified, aerially 

deposited volcanic ash and pumice. The native vegetation 

is mainly mixed conifers and shrubs. Elevation is 1,800 to 

2,800 feet. The average annual precipitation is about 

130 inches, the average annual air temperature is about 

44 degrees F, and the average frost-free period is 90 to 

110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer, where mixed to a depth of 7 inches, 

is very dark grayish brown loamy sand. The upper 8 

inches of the subsoil is very dark brown loamy sand, and 

the lower part to a depth of 60 inches or more is light 

gray extremely cindery sand. 

Included in this unit are small areas of Minniepeak, 

Pelee, and Sinnice soils. Also included are small areas 

of Bandid soils that have a cindery sandy loam surface 

layer. Included areas make up about 5 percent of the 

total acreage. 

Permeability of this Bandid soil is moderately rapid in 

the upper part of the subsoil and very rapid in the lower 

part. Available water capacity is moderate. Effective 

rooting depth is 60 inches or more. Runoff is slow, and the 

hazard of water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is estimated to 

be 110 for Douglas fir and 113 for western hemlock. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 85 for Douglas fir and 80 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 98 cubic feet per acre per year at 

age 60, and for western hemlock it is 166 cubic feet at 

age 50. Estimates of the site index or CMAI for Pacific 

silver fir have not been made. Among the trees of limited 

extent is western redcedar. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Occasional snowpack hinders the use of 

equipment and limits access in winter. Cinders slough from 

road cuts onto the road surface. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or noble fir seedlings. If seed 

trees are present, natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Logging activities can readily displace the surface 

layer. Seedlings that grow in the less fertile subsoil exhibit 

poor growth. Trees are occasionally subject to windthrow 

when winds are strong. 

Among the common forest understory plants are vine 

maple, Sitka alder, huckleberry, bunchberry dogwood, 

pearly everlasting, and common fireweed. 

This map unit is in capability subclass VIIe. 

8-Bandid loamy sand, 65 to 90 percent slopes. This 

very deep, well drained soil is on back slopes of 

mountains. It formed in aerially deposited volcanic ash 

and pumice. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 1,800 to 2,800 feet. 

The average annual precipitation is about 130 inches, 

the average annual air temperature is about 44 degrees 

F, and the average frost-free period is 90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown loamy sand 

7 inches thick. The upper 8 inches of the subsoil is very 

dark brown loamy sand, and the lower part to a depth 

of 60 inches or more is light gray extremely cindery 

sand. 

Included in this unit are small areas of Minniepeak, 

Pelee, and Sinnice soils. Also included are small areas 

of Bandid soils that have a cindery sandy loam surface 

layer and Rock outcrop. Included areas in this unit 
make up about 8 percent of the total acreage. 

Permeability of this Bandid soil is moderately rapid in 

the upper part of the subsoil and very rapid in the lower 

part. Available water capacity is moderate. Effective 

rooting depth is 60 inches or more. Runoff is medium, and 

the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 110 for Douglas fir and 113 for western hemlock. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 85 for Douglas fir and 80 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 98 cubic feet per acre per year at 

age 60, and the CMAI for western hemlock is 166 cubic 

feet at age 50. Estimates of the site index or CMAI for 

Pacific silver fir have not been made. Among the trees of 

limited extent are western redcedar. 

The main limitation for harvesting timber is steepness 

of slope in some areas. Cable yarding systems generally 

are used on this unit. Logging roads require suitable 

surfacing for year-round use. Rock for road construction is 

not readily available in this unit. Logging roads generally 

need full bench construction and require frequent 

maintenance. Occasional snowpack hinders the use of 

equipment and limits access in winter. Cinders slough from 

road cuts onto the road surface. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Following road construction and clearcutting, 

road failures and landslides can occur. Steep yarding 

paths, skid trails, and firebreaks are subject to rifling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. Harvesting systems that lift logs 

entirely off the ground reduce the disturbance of the 

protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or noble fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Logging activities can readily displace the surface 

layer. Seedlings that grow in the less fertile subsoil exhibit 

poor growth. Trees are occasionally subject to windthrow 

when winds are strong. 

Among the common forest understory plants are vine 

maple, Sitka alder, huckleberry, bunchberry dogwood, 

pearly everlasting, and common fireweed. This map 

unit is in capability subclass VIle. 

9-Bandid cindery sandy loam, 5 to 30 percent 

slopes. This very deep, well drained soil is on back 

slopes, toe slopes, and foot slopes of mountains. It 

formed in stratified, aerially deposited volcanic ash and 

pumice. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 1,800 to 2,800 feet. The 

average annual precipitation is about 130 inches, the 

average annual air temperature is about 44 degrees F, 

and the average frost-free period is 90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is very dark grayish 

brown cindery sandy loam 5 inches thick, and the lower 

part is brown fine sandy loam and black loamy sand 10 

inches thick. The upper part of the subsoil is dark gray 

extremely cindery sand 12 inches thick, and the lower 

part to a depth of 60 inches or more is stratified, dark 

gray cindery sandy loam to black loamy sand. 

Included in this unit are small areas of Bannel, 

Minniepeak, Pelee, and Sinnice soils. Also included are 

small areas of St. Helens and Yalelake soils on terraces 

and Rock outcrop. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Bandid soil is moderately rapid in 

the surface layer and is very rapid in the upper part of 

the subsoil and moderately rapid in the lower part. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is slow, and the 

hazard of water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is estimated to 

be 110 for Douglas fir and 113 for western hemlock. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 85 for Douglas fir and 80 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 98 cubic feet per acre per year 

at age 60, and the CMAI for western hemlock is 166 

cubic feet at age 50. Estimates of the site index or CMAI 

for Pacific silver fir have not been made. Among the 

trees of limited extent is western redcedar. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Logging roads require 
suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Cinders slough from road cuts 

onto the road surface. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. 

Disturbance of the protective layer of duff can be reduced 

with the careful use of wheeled and tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or noble fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south and southwest-facing slopes. 

Logging activities can readily displace the surface layer. 

Seedlings that grow in the less fertile subsoil exhibit poor 

growth. Trees, are occasionally subject to windthrow when 

winds are strong. 

Among the common forest understory plants are vine 

maple, Sitka alder, huckleberry, bunchberry dogwood, 

pearly everlasting, and common fireweed. 

This map unit is in capability subclass IVe. 

10-Bandid cindery sandy loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back 

slopes of mountains. It formed in stratified, aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 1,800 to 2,800 feet. The average annual precipitation 

is about 130 inches, the average annual air temperature 

is about 44 degrees F, and the average frost-free period 

is 90 to 100 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is very dark grayish 

brown cindery sandy loam 5 inches thick, and the lower 

part is brown fine sandy loam and black loamy sand 10 

inches thick. The upper part of the subsoil is dark gray 

extremely cindery sand 12 inches thick, and the lower 

part to a depth of 60 inches or more is stratified, dark 

gray cindery sandy loam to black loamy sand. 

Included in this unit are small areas of Bannel, 

Minniepeak, Pelee, and Sinnice soils. Also included are 

small areas of Rock outcrop. Included areas make up 

about 5 percent of the total acreage. 

Permeability of this Bandid, soil is moderately rapid in 

the surface layer and is very rapid in the upper part of 

the subsoil and moderately rapid in the lower part. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is slow, and the 

hazard of water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 110 for Douglas fir and 113 for western hemlock. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 85 for Douglas fir and 80 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 98 cubic feet per acre at age 

60, and the CMAI for western hemlock is 166 cubic feet 

at age 50. Estimates of the site index or CMAI for 

Pacific silver fir have not been made. Among the trees of 

limited extent is western redcedar. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Occasional snowpack hinders the use of 

equipment and limits access in winter. Cinders slough 

from road cuts onto the road surface. Establishing plant 

cover on steeper slopes that have been cut or filled 

reduces erosion. Steep yarding paths, skid trails, and 

firebreaks are subject to rifling and gullying unless plant 

cover is maintained or adequate water bars are provided.

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or noble fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

subsoil exhibit poor growth. Trees are occasionally 

subject to windthrow when winds are strong. 

Among the common forest understory plants are vine 

maple, Sitka alder, huckleberry, bunchberry dogwood, 

pearly everlasting, and common fireweed. 

This map unit is in capability subclass VIIe. 

11-Bandid cindery sandy loam, 65 to 90 percent 

slopes. This very deep, well drained soil is on back 
slopes of mountains. It formed in stratified, aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 1,800 to 2,800 feet. The average annual 

precipitation is about 130 inches, the average annual air 

temperature is about 44 degrees F, and the average frostfree period is 90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves. and twigs 2 inches thick. 

The upper part of the surface layer is very dark grayish 

brown cindery sandy loam 5 inches thick, and the lower 

part is brown fine sandy loam and black loamy sand 10 

inches thick. The upper part of the subsoil is dark gray 

extremely cindery sand 12 inches thick, and the lower 

part to a depth of 60 inches or more is stratified, dark 

gray cindery sandy loam to black loamy sand. 

Included in this unit are small areas of Bannel, 

Minniepeak, Pelee, and Sinnice soils. Also included are 

small areas of Rock outcrop. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Bandid soil is moderately rapid in 

the surface layer, very rapid in the upper part of the 

subsoil, and moderately rapid in the lower part of the 

subsoil. Available water capacity is moderate. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is estimated 

to be 110 for Douglas fir and 113 for western hemlock. 

On the basis of a 50-year site curve, the mean site 

index is estimated to be 85 for Douglas fir and 80 for 

western hemlock. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 98 cubic feet per acre 

per year at age 60, and the CMAI for western hemlock is 

166 cubic feet at age 50. Estimates of the site index or 

CMAI for Pacific silver fir have not been made. Among 

the trees of limited extent is western redcedar. 

The main limitation for harvesting timber is steepness 

of slope. Cable yarding systems generally are used on 

this unit. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Logging roads generally need full 

bench construction and require frequent maintenance. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Cinders slough from road cuts 

onto the road surface. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and 

firebreaks are subject to rilling and gullying unless plant 

cover is maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or noble fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by western hemlock and Pacific silver fir occurs 

periodically. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

subsoil exhibit poor growth. Trees are occasionally subject 

to windthrow when winds are strong. 

Among the common forest understory plants are vine 

maple, Sitka alder, huckleberry, bunchberry dogwood, 

pearly everlasting, and common fireweed. 

This map unit is in capability subclass VIle. 

12-Bannel cindery sandy loam, 5 to 30 percent 

slopes. This very deep, well drained soil is on back 

slopes and ridges of mountains. It formed in aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 1,500 to 2,800 feet. The average annual 

precipitation is about 125 inches, the average annual air 

temperature is about 44 degrees F, and the average 

frost-free period is 90 to 110 days. 

Typically, the surface layer is very dark grayish brown 

cindery sandy loam 4 inches thick. The upper part of the 

subsoil is light gray extremely cindery sand 6 inches 

thick, and the lower part is stratified, dark brown and 

brown fine sandy loam, cindery fine sandy loam, cindery 

loamy sand, and cindery loam 40 inches thick. The 

substratum to a depth of 60 inches or more is brownish 

yellow extremely cindery sand. 

Included in this unit are small areas of Bandid, 

Cinnamon, and Lonestar soils. Also included are small 

areas of St. Helens and Yalelake soils on terraces and 

Rock outcrop. Included areas make up about 10 percent 

of the total acreage. 

Permeability of this Bannel soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is slow, and 

the hazard of water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir 

are the main woodland species on this unit. On the 
basis of a 100-year site curve, the mean site index is 

estimated to be 125 for Douglas fir and 120 for western 

hemlock. On the basis of a 50-year site curve, the 

mean site index is estimated to be 95 for Douglas fir and 

85 for western hemlock. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 122 cubic feet 

per acre per year at age 70, and the CMAI for western 

hemlock is 180 cubic feet at age 50. Estimates of the site 

index or CMAI for Pacific silver fir have not been made. 

Among the trees of limited extent are western redcedar 

and red alder. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available 

in this unit. Occasional snowpack hinders the use of 

equipment and limits access in winter. Disturbance of 

the protective layer of duff can be reduced with the careful 

use of wheeled and tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Trees are occasionally subject to windthrow when 

winds are strong. 

Among the common forest understory plants are 

Oregongrape, salal, red huckleberry, princes pine, and 

willow. 

This map unit is in capability subclass IVe. 

13-Bannel cindery sandy loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back slopes 

of mountains. It formed in aerially deposited volcanic ash 

and pumice. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 1,500 to 2,800 feet. 

The average annual precipitation is about 125 inches, 

the average annual air temperature is about 44 degrees 

F, and the average frost-free period is 90 to 110 days. 

Typically, the surface layer is very dark grayish brown 

cindery sandy loam 4 inches thick. The upper part of the 

subsoil is light gray extremely cindery sand 6 inches 

thick, and the lower part is stratified, dark brown and 

brown fine sandy loam, cindery fine sandy loam, cindery 

loamy sand, and cindery loam 40 inches thick. The 

substratum to a depth of 60 inches or more is 

brownish yellow extremely cindery sand. 

Included in this unit are small areas of Bandid, 

Cinnamon, and Lonestar soils. Also included are small 

areas of Rock outcrop. Included areas make up about 

10 percent of the total acreage. 

Permeability of this Bannel soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 125 for Douglas fir and 120 for western hemlock. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 95 for Douglas fir and 85 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 122 cubic feet per acre per 

year at age 70, and the CMAI for western hemlock is 180 

cubic feet at age 50. Estimates of the site index or CMAI 

for Pacific silver fir have not been made. Among the trees 

of limited extent are western redcedar and red alder. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round use. Rock for road construction is 

not readily available in this unit. Occasional snowpack 

hinders the use of equipment and limits access in 

winter. Establishing plant cover on steeper slopes that 

have been cut or filled reduces erosion. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Trees are occasionally subject to windthrow when 

winds are strong. 

Common forest understory plants are Oregongrape, 

salal, red huckleberry, princes pine, and willow. 

This map unit is in capability subclass VIIe.
14-Bannel cindery sandy loam, 65 to 90 percent 

slopes. This very deep, well drained soil is on back slopes 

of mountains. It formed in aerially deposited volcanic ash 

and pumice. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 1,500 to 2,800 feet. The 

average annual precipitation is about 125 inches, the 

average annual air temperature is about 44 degrees F, 

and the average frost-free period is about 90 to 110 days.

Typically, the surface layer is very dark grayish brown 

cindery sandy loam 4 inches thick. The upper part of the 

subsoil is light gray extremely cindery sand 6 inches thick, 

and the lower part is stratified, dark brown and brown 

fine sandy loam, cindery fine sandy loam, cindery loamy 

sand, and cindery loam 40 inches thick. The substratum to 

a depth of 60 inches or more is brownish yellow 

extremely cindery sand. 

Included in this unit are small areas of Bandid, 

Cinnamon, and Lonestar soils. Also included are small 

areas of Yalelake soils on terraces and small areas of 

Rock outcrop. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Bannel soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is rapid, and 

the hazard of water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is estimated 

to be 125 for Douglas fir and 120 for western hemlock. 

On the basis of a 50-year site curve, the mean site index 

is estimated to be 95 for Douglas fir and 85 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 122 cubic feet per acre per year at 

age 70, and the CMAI for western hemlock is 180 cubic 

feet at age 50. Estimates of the site index or CMAI for 

Pacific silver fir have not been made. Among the trees of 

limited extent are western redcedar and red alder. 

The main limitation for harvesting timber is steepness of 

slope. Cable yarding systems generally are used on this 

unit. Unsurfaced roads and skid trails are soft and can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round use. Rock for road construction is 

not readily available in this unit. Logging roads generally 

need full bench construction and require frequent 

maintenance. Occasional snowpack hinders the use of 

equipment and limits access in winter. Establishing plant 

cover on steeper slopes that have been cut or filled 

reduces erosion. Following road 

construction and clearcutting, road failures and 

landslides can occur. Steep yarding paths, skid trails, 

and firebreaks are subject to rilling and gullying unless 

plant cover is maintained or adequate water bars are 

provided. Harvesting systems that lift logs entirely off the 

ground reduce the disturbance of the protective layer of 

duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Trees are occasionally subject to windthrow when 

winds are strong. 

Among the common forest understory plants are 

Oregongrape, salal, red huckleberry, princes pine, and 

willow. 

This map unit is in capability subclass VIIe. 

15-Benham very cindery sandy loam, 0 to 30 

percent slopes. This very deep, well drained soil is on 

back slopes and foot slopes of mountains. It formed in 

layers of aerially deposited volcanic ash and pumice. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 1,800 to 2,800 feet. The average 

annual precipitation is about 85 inches, the average 

annual air temperature is about 44 degrees F, and the 

average frost-free period is 90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposing leaves, needles, and twigs 1.5 inches 

thick. Where mixed to a depth of 6 inches, the surface 

layer is very dark grayish brown very cindery sandy 

loam. The upper part of the subsoil is light gray 

extremely cindery sand 22 inches thick, the next part is 

mottled, grayish brown sandy loam and fine sandy loam 

10 inches thick, and the lower part to a depth of 60 

inches or more is grayish brown and strong brown very 

cindery loamy sand and extremely cindery sand. 

Included in this unit are small areas of Colter, 

Minniepeak, and Sinnice soils. Also included are small 

areas of Rock outcrop and Benham soils that are 40 to 

60 inches deep to bedrock. Included areas make up 

about 5 percent of the total acreage. 

Permeability of this Benham soil is moderately rapid 

in the middle part of the subsoil and very rapid in the 

lower part. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. Runoff is 

slow, and the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 
Douglas fir and western hemlock are the main woodland 

species on this unit. On the basis of a 100-year site curve. 

the mean site index is estimated to be 150 for Douglas fir 

and 147 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is estimated to be 115 for 

Douglas fir and 105 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 158 

cubic feet per acre per year at age 60, and the CMAI for 

western hemlock is 232 cubic feet at age 50. Among the 

trees of limited extent are red alder,, western redcedar, and 

Pacific silver fir. 

The main limitation for harvesting timber is occasional 

snowpack. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Occasional snowpack hinders the use 

of equipment and limits access in winter. Cinders slough 

from road cuts onto the road surface. Establishing plant 

cover on steeper slopes that have been cut or filled 

reduces erosion. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Droughtiness of 

the surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. Logging activities can 

readily displace the surface layer. Seedlings that grow in 

the less fertile subsoil exhibit poor growth. Trees 

occasionally are subject to windthrow. 

Among the common forest understory plants are 

Oregongrape, salal, red huckleberry, western swordfern, 

and trailing blackberry. 

This map unit is in capability subclass IVe. 

16-Benham very cindery sandy loam, 30 to 65 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in layers of aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 1,800 to 2,800 feet. The average annual 

precipitation is about 85 inches, the average annual air 

temperature is about 44 degrees F, and the average 

frost-free period is 90 to 110 days. 

Typically. the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer, where mixed to a depth of 6 inches, 

is very dark grayish brown very cindery sandy loam. 

The upper part of the subsoil is light gray extremely 

cindery sand 22 inches thick, the next part is mottled, 

grayish brown sandy loam and fine sandy loam 10 

inches thick, and the lower part to a depth of 60 inches 

or more is grayish brown and strong brown very cindery 

loamy sand and extremely cindery sand. 

Included in this unit are small areas of Colter, 

Minniepeak, and Sinnice soils. Also included are small 

areas of Rock outcrop and Benham soils that are 40 to 

60 inches deep to bedrock. Included areas make up 

about 5 percent of the total acreage. 

Permeability of this Benham soil is moderately rapid in 

the middle part of the subsoil and very rapid in the lower 

part. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. Runoff is 

medium, and the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 

150 for Douglas fir and 147 for western hemlock. On the 

basis of a 50-year site curve, the mean site index is 

estimated to be 115 for Douglas fir and 105 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 158 cubic feet per acre per year 

at age 60, and the CMAI for western hemlock is 232 cubic 

feet at age 50. Among the trees of limited extent are red 

alder, western redcedar, and Pacific silver fir. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Cinders slough from road cuts 

onto the road surface. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Logging activities can readily displace the 

surface layer; seedlings that develop in the less fertile 
subsoil exhibit poor growth and vigor. Trees 

occasionally are subject to windthrow. 

Among the common forest understory plants are 

Oregongrape,, salal, red huckleberry, western swordfern, 

and trailing blackberry. 

This map unit is in capability subclass Vlle. 

17-Bonneville stony sandy loam. This very deep, 

somewhat excessively drained soil is on river terraces. It 

formed in alluvial sand and gravel derived dominantly 

from basalt and andesite. Slope is 0 to 5 percent. The 

native vegetation is mainly mixed conifers.. hardwoods, 

shrubs, and grasses. Elevation is 50 to 400 feet. The 

average annual precipitation is about 70 inches, the 

average annual air temperature is about 48 degrees F, 

and the average frost-free period is 185 to 230 days. 

Typically, the upper part of the surface layer is dark 

brown stony sandy loam about 6 inches thick and the 

lower part is extremely gravelly coarse sandy loam 6 

inches thick. The underlying material to a depth of 60 

inches or more is dark brown and dark yellowish brown 

extremely gravelly coarse sand. 

Included in this unit are small areas of Pilchuck, 

Skamania. and Washougal soils. Also included are small 

areas of Skoly and Steever soils on mountain slopes. 

Included areas make up about 20 percent of the total 

acreage. 

Permeability of this Bonneville soil is very rapid. 

Available water capacity is low. Effective rooting depth is 

60 inches or more. Runoff is slow, and the hazard of water 

erosion is slight. This soil is subject to brief, rare periods of 

flooding in March through May. Most areas are protected 

by dams on the Columbia River. 

This unit is used for pastureland, homesites, 

woodland, recreation, and wildlife habitat. 

This unit is poorly suited to pasture. The main 

limitations are large stones and low available water 

capacity. The use of equipment is limited by stones on the 

surface. In some years, supplemental irrigation is 

needed. 

The main limitation of this unit for use as homesites is 

that the soil is a poor filter for septic tank absorption fields. 

Topsoil can be stockpiled and used to reclaim areas 

disturbed during construction. Removal of pebbles and 

cobbles in disturbed areas is needed for best results 

when landscaping, particularly in areas used for lawns. 

In summer, irrigation is needed for lawn grasses, 

shrubs, vines, shade trees, and ornamental trees. 

Selection of adapted vegetation is critical for the 

establishment of lawns, shrubs, trees, and vegetable 

gardens. If the density of housing is moderate to high, 

community sewage systems are needed to prevent 

contamination of water supplies as a result of seepage 

from onsite sewage disposal systems. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site curve. 

the mean site index is estimated to be 117 for Douglas 

fir. On the basis of a 50-year site curve, the mean site 

index is estimated to be 90. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 110 cubic feet 

per acre per year at age 60. Estimates of the site index or 

CMAI for red alder have not been made. Strong winds 

cause breakage of tree limbs and branches and reduce 

the productivity of this unit. Among the trees of limited 

extent are bigleaf maple, Oregon white oak. and black 

cottonwood. 

This unit is well suited to year-round logging 

operations. Rounded pebbles and cobbles for road 

construction are readily available in this unit. 

Disturbance of the protective layer of duff can be 

reduced with the careful use of wheeled and tracked 

equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present. natural reforestation of cutover areas by red 

alder occurs periodically. Droughtiness of the surface 

layer reduces seedling survival. Logging activities can 

readily displace the surface layer. Seedlings that grow in 

the less fertile underlying material exhibit poor growth. 

Trees occasionally are subject to windthrow. If the canopy 

is opened, brush invades and can delay the establishment 

of seedlings unless it is controlled. 

Among the common forest understory plants are vine 

maple, trailing blackberry, western hazel, poison oak, and 

common snowberry. 

This map unit is in capability subclass IVs. 

18-Cattcreek very cindery loamy sand, 65 to 90 

percent slopes. This deep, well drained soil is on back 

slopes and in cirque basins of mountains. It formed in 

pumice and volcanic ash over colluvium derived from 

andesite. The native vegetation is mainly true firs and 

shrubs. Elevation is 3,000 to 4,000 feet. The average 

annual precipitation is about 110 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free period is 70 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 6 inches, the surface layer is 

dark grayish brown and dark yellowish brown very 

cindery loamy sand. The upper 9 inches of the subsoil is 

dark brown very cindery sand, and the lower 15 
inches is strong brown extremely cindery sand. The next 

layer is a buried subsoil of dark yellowish brown 

extremely gravelly loam 24 inches thick over bedrock. 

Depth to bedrock ranges from 40 to 60 inches. 

Included in this unit are small areas of Colter, Sinnice, 

and Tradedollar soils. Also included are small areas of 

Rock outcrop and soils that are less than 40 inches 

deep to bedrock. Included areas make up about 15 

percent of the total acreage. 

Permeability of this Cattcreek soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 40 to 60 inches. Runoff is medium, and the 

hazard of water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir 

are the main woodland species on this unit. On the 

basis of a 100-year site curve, the mean site index is 

124 for western hemlock and 117 for Douglas fir. On the 

basis of a 50-year site curve, the mean site index is 86 for 

western hemlock and 90 for Douglas fir. The culmination 

of the mean annual increment (CMAI) for western hemlock 

is 188 cubic feet per acre per year at age 50, and for 

Douglas fir it is 110 cubic feet at age 60. Estimates of 

the site index or CMAI for Pacific silver fir have not been 

made. Among the trees of limited extent are noble fir, 

western redcedar, western white pine, and Alaska cedar. 

The main limitations for harvesting timber are snowpack 

in winter and steepness of slope. Cable yarding systems 

generally are used on this unit. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Snowpack in winter limits the use 

of equipment and restricts access. Cinders slough from 

road cuts onto the road surface. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Following road construction and clearcutting, 

road failures and landslides can occur. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. Harvesting systems that lift logs 

entirely off the ground reduce the disturbance of the 

protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir or noble fir 

seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. Droughtiness of the 

surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. Logging activities 

can readily displace the surface layer. Seedlings that 

grow in the less fertile subsoil exhibit poor growth. Trees 

occasionally are subject to windthrow. 

Among the common forest understory plants are Sitka 

alder, common beargrass, Oregongrape, longtube 

twinflower, western brackenfern, and bunchberry 

dogwood. 

This map unit is in capability subclass VIIe. 

19-Cattcreek very cindery loamy sand, cold, 30 to 

65 percent slopes. This deep, well drained soil is on 

back slopes and in cirque basins of mountains. It formed 

in pumice and volcanic ash over residuum and colluvium 

derived from andesite. The native vegetation is mainly 

true firs and shrubs. Elevation is 4,000 to 5.300 feet. 

The average annual precipitation is about 110 inches, 

the average annual air temperature is about 39 degrees 

F, and the average frost-free period is 70 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 6 inches, the surface layer is 

dark grayish brown and dark yellowish brown very 

cindery loamy sand. The upper 9 inches of the subsoil is 

dark brown very cindery sand, and the lower 15 inches is 

strong brown extremely cindery sand. The next layer is a 

buried subsoil of dark yellowish brown extremely gravelly 

loam 24 inches thick over bedrock. Depth to bedrock 

ranges from 40 to 60 inches. 

Included in this unit are small areas of Colter, Sinnice, 

and Tradedollar soils. Also included are small areas of 

Rock outcrop and Cattcreek soils that have slopes of less 

than 30 percent. Included areas make up about 15 

percent of the total acreage. 

Permeability of this Cattcreek soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 40 to 60 inches. Runoff is slow, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Pacific silver fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 

84 for western hemlock. On the basis of a 50-year site 

curve, the mean site index is estimated to be 60. The 

culmination of the mean annual increment (CMAI) for 

western hemlock is 95 cubic feet per acre per year at 

age 60. Estimates of the site index or CMAI for Pacific 
silver fir have not been made. Among the trees of limited 

extent are Douglas fir, noble fir, western white pine, and 

Alaska cedar. 

The main limitations for harvesting timber are snowpack 

in winter and steepness of slope, which restricts the use of 

wheeled and tracked equipment in skidding. Cable yarding 

systems generally are safer and disturb the soil less. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in this 

unit. Snowpack in winter limits the use of equipment and 

restricts access. Cinders slough from road cuts onto the 

road surface. Establishing plant cover on steeper slopes 

that have been cut or filled reduces erosion. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Droughtiness of 

the surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. Logging activities 

can readily displace the surface layer. Seedlings that grow 

in the less fertile subsoil exhibit poor growth. Because the 

surface layer and subsoil are loose, trees occasionally are 

subject to windthrow. 

Among the common forest understory plants are Sitka 

alder, common beargrass, Oregongrape, longtube 

twinflower, western brackenfern, and bunchberry 

dogwood. 

This map unit is in capability subclass VIIe. 

20-Cattcreek very cindery loamy sand, cold, 65 to 

90 percent slopes. This deep, well drained soil is on back 

slopes and in cirque basins of mountains. It formed in 

pumice and volcanic ash over colluvium derived from 

andesite. The native vegetation is mainly true firs and 

shrubs. Elevation is 4,000 to 5,300 feet. The average 

annual precipitation is about 110 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free period is 70 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 6 inches, the surface layer is 

dark grayish brown and dark yellowish brown very cindery 

loamy sand. The upper 9 inches of the subsoil is dark 

brown very cindery sand, and the lower 15 inches is strong 

brown extremely cindery sand. The next layer is a buried 

subsoil of dark yellowish brown 

extremely gravelly loam 24 inches thick over bedrock. 

Depth to bedrock ranges from 40 to 60 inches. 

Included in this unit are small areas of Colter, Sinnice, 

and Tradedollar soils. Also included are small areas of 

Rock outcrop and soils that are less than 40 inches 

deep to bedrock. Included areas make up about 15 

percent of the total acreage. 

Permeability of this Cattcreek soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 48 to 60 inches or more. Runoff is 

medium, and the hazard of water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Pacific silver fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 

84 for western hemlock. On the basis of a 50-year site 

curve, the mean site index is estimated to be 60. The 

culmination of the mean annual increment (CMAI) for 

western hemlock is 95 cubic feet per acre per year at 

age 60. Estimates of the site index or CMAI for Pacific 

silver fir have not been made. Among the trees of limited 

extent are Douglas fir, noble fir, western white pine, and 

Alaska cedar. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. Cable 

yarding systems generally are used on this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Snowpack in winter limits the use 

of equipment and restricts access. Cinders slough from 

road cuts onto the road surface. Establishing plant 

cover on steeper slopes that have been cut or filled 

reduces erosion. Following road construction and 

clearcutting, road failures and landslides can occur. 

Steep yarding paths, skid trails, and firebreaks are 

subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Droughtiness of 

the surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. Logging activities 

can readily displace the surface layer. Seedlings that 

grow in the less fertile subsoil exhibit poor growth. Trees 

occasionally are subject to windthrow. 

Among the common forest understory plants are 
Sitka alder, common beargrass, Oregongrape, longtube 

twinflower, western brackenfern, and bunchberry 

dogwood. 

This map unit is in capability subclass VIle. 

21-Chemawa loam, 2 to 8 percent slopes. This very 

deep, well drained soil is on terraces and foot slopes. It 

formed in pyroclastic flows consisting mostly of volcanic 

ash. The vegetation in areas not cultivated is mainly mixed 

conifers and shrubs. Elevation is 800 to 1,200 feet. The 

average annual precipitation is about 50 inches, the 

average annual air temperature is about 47 degrees F, 

and the average frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 14 inches thick. 

The subsoil is dark brown and strong brown loam to a 

depth of 60 inches or more. 

Included in this unit are small areas of McElroy and 

Underwood soils. Also included are small areas of 

Chemawa soils that have slopes of more than 8 percent. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this Chemawa soil is moderate. 

Available water capacity is high. Effective rooting depth is 

60 inches or more. Runoff is slow, and the hazard of water 

erosion is slight. 

This unit is used for woodland, orchards, hayland, 

pastureland, homesites, wildlife habitat, and recreation. 

Douglas fir and grand fir are the main woodland species 

on this unit. On the basis of a 100-year site curve, the 

mean site index is 150 for Douglas fir. On the basis of a 

50-year site curve, the mean site index is 114 for Douglas 

fir and 105 for grand fir. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 158 cubic feet 

per acre per year at age 60, and for grand fir it is 163 cubic 

feet at age 86. Among the trees of limited extent are red 

alder and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Disturbance of the protective layer of 

duff can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by grand fir occurs periodically. If the canopy is opened, 

brush invades and can prevent the establishment of 

Douglas fir seedlings and can delay natural reforestation 

by grand fir unless controlled. 

Among the common forest understory plants are vine 

maple, common snowberry, false Solomons seal, western 

brackenfern, and trailing blackberry. 

If this unit is used for orchard crops, the main limitation 

is the hazard of erosion. If the soil is plowed in fall, runoff 

and erosion can be reduced by seeding to a cover crop.

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition. 

Mowing at least twice a year helps to maintain uniform 

growth and discourages selective grazing. 

This unit has few limitations as homesites. Population 

growth has resulted in increased construction of homes 

on this unit. Preserving the existing plant cover during 

construction helps to control erosion. Mulch, fertilizer, 

and irrigation are needed to establish lawn grasses and 

other small-seeded plants. The soil in this unit is limited 

for the construction of roads and streets because of the 

potential for frost action. 

This map unit is in capability subclass Ile. 

22-Chemawa loam, 8 to 15 percent slopes. This 

very deep, well drained soil is on foot slopes. It formed in 

pyroclastic flows consisting mostly of volcanic ash. The 

vegetation in areas not cultivated is mainly mixed conifers 

and shrubs. Elevation is 800 to 1,200 feet. The average 

annual precipitation is about 50 inches, the average 

annual air temperature is about 47 degrees F, and the 

average frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 14 inches thick. 

The subsoil is dark brown and strong brown loam to a 

depth of 60 inches or more. 

Included in this unit are small areas of McElroy and 

Underwood soils. Also included are small areas of 

Chemawa soils that have slopes of less than 8 percent or 

more than 15 percent. Included areas make up about 12 

percent of the total acreage. 

Permeability of this Chemawa soil is moderate. 

Available water capacity is high. Effective rooting depth is 

60 inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland, orchards, hayland, 

pastureland, homesites, wildlife habitat, and recreation.
Douglas fir and grand fir are the main woodland species 

on this unit. On the basis of a 100-year site curve, the 

mean site index is 143 for Douglas fir. On the basis of a 

50-year site curve, the mean site index is 110 for Douglas 

fir and 105 for grand fir. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 149 cubic feet 

per acre per year at age 65, and for grand fir it is 163 cubic 

feet at age 86. Among the trees of limited extent are red 

alder and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Disturbance of the protective layer of 

duff can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by grand fir occurs 

periodically. If the canopy is opened, brush invades and 

can prevent the establishment of Douglas fir seedlings and 

can delay natural reforestation by grand fir unless 

controlled. 

Among the common forest understory plants are vine 

maple, common snowberry, false Solomons seal, western 

brackenfern, and trailing blackberry. 

If this unit is used for orchard crops, the main limitation 

is the hazard of erosion. If the soil is plowed in fall, 

runoff and erosion can be reduced by seeding to a cover 

crop. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition. 

Mowing at least twice a year helps to maintain uniform 

growth and discourages selective grazing. In some years, 

supplemental irrigation is needed. 

This unit has few limitations for use as homesites. 

Population growth has resulted in increased construction 

of homes on this unit. The main limitations are 

steepness of slope and the hazard of erosion in the 

steeper areas. Only that part of the site that is used for 

construction should be disturbed. Preserving the existing 

plant cover during construction helps to control erosion. 

Mulch, fertilizer, and irrigation are needed to establish 

lawn grasses and other small-seeded plants. The soil in 

this unit is susceptible to frost action, which 

may limit construction of roads and streets. 

This map unit is in capability subclass IIIe. 

23-Chemawa loam, 15 to 30 percent slopes. This 

very deep, well drained soil is on foot slopes and back 

slopes. It formed in pyroclastic flows consisting mostly of 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 800 to 1,200 feet. The 

average annual precipitation is about 50 inches, the 

average annual air temperature is about 47 degrees F, and 

the average frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 14 inches thick. 

The subsoil to a depth of 60 inches or more is dark 

brown and strong brown loam. 

Included in this unit are small areas of McElroy, 

Underwood, and Undusk soils. Also included are small 

areas of Chemawa soils that have slopes of less than 

15 percent. Included areas make up about 15 percent of 

the total acreage. 

Permeability of this Chemawa soil is moderate. 

Available water capacity is high. Effective rooting depth is 

60 inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland, orchards, hayland, 

pastureland, homesites, wildlife habitat, and recreation.

Douglas fir and grand fir are the main woodland species 

on this unit. On the basis of a 100-year site curve, the 

mean site index is 136 for Douglas fir. On the basis of a 

50-year site curve, the mean site index is 104 for 

Douglas fir and 105 for grand fir. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 139 cubic 

feet per acre per year at age 70, and for grand fir it is 

163 cubic feet at age 86. Among the trees of limited 

extent are red alder and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is wet produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery, and they can be 

impassable when wet. Logging roads for year-round use 

need to be surfaced. Rock for road construction is not 

readily available in this unit. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Disturbance of the protective layer of duff can be 

reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir seedlings. If seed 
trees are present, natural reforestation of cutover areas by 

grand fir occurs periodically. If the canopy is opened, 

brush invades and can prevent the establishment of 

Douglas fir seedlings and can delay natural reforestation 

by grand fir unless controlled. 

Among the common forest understory plants are vine 

maple, common snowberry, false Solomons seal, western 

brackenfern, and trailing blackberry. 

If this unit is used for orchard crops, the main limitation 

is the hazard of erosion. If the soil is plowed in fall, 

runoff and erosion can be reduced by seeding to a cover 

crop. 

This unit is well suited to use as hayland and 

pastureland. The main limitations are steepness of slope 

and the hazard of erosion. Erosion can be controlled by 

growing pasture. The use of equipment is limited by 

steepness of slope. Proper stocking rates, pasture 

rotation, and restricted grazing during wet periods help 

to keep the pasture in good condition and to protect the 

soil from erosion. Mowing at least twice a year helps to 

maintain uniform growth and discourages selective 

grazing. 

The main limitations of this unit for use as homesites 

are steepness of slope and the hazard of erosion in the 

steeper areas. Only the part of the site that is used for 

construction should be disturbed. Preserving the existing 

plant cover during construction helps to control erosion. 

Plant cover can be established and maintained through 

proper fertilizing, seeding, mulching, and shaping of the 

slopes. Slope is a concern in installing septic tank 

absorption fields. Absorption lines should be installed on 

the contour. 

Access roads should be designed to provide 

adequate cut-slope grade, and drains are needed to 

control surface runoff and keep soil losses to a 

minimum. The soil in this unit is susceptible to frost 

action, which may limit construction of roads and 

streets. 

This map unit is in capability subclass lVe. 

24-Chemawa loam, 30 to 50 percent slopes. This 

very deep, well drained soil is on back slopes. It formed in 

pyroclastic flows consisting mostly of volcanic ash. The 

native vegetation is mainly mixed conifers and shrubs. 

Elevation is 800 to 1,200 feet. The average annual 

precipitation is about 50 inches, the average annual air 

temperature is about 47 degrees F, and the average frostfree period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 14 inches thick. 

The subsoil to a depth of 60 inches or more is dark 

brown and strong brown loam. 

Included in this unit are small areas of McElroy, 

Underwood, and Undusk soils. Also included are small 

areas of Chemawa soils that have slopes of less than 

30 percent. Included areas make up about 15 percent 

of the total acreage. 

Permeability of this Chemawa soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, wildlife habitat, and 

recreation. 

Douglas fir and grand fir are the main woodland 

species on this unit. On the basis of a 100-year site 

curve, the mean site index is 136 for Douglas fir. On the 

basis of a 50-year site curve, the mean site index is 104 

for Douglas fir and 105 for grand fir. The culmination of 

the mean annual increment (CMAI) for Douglas fir is 139 

cubic feet per acre per year at age 70, and for grand fir it 

is 163 cubic feet at age 86. Among the trees of limited 

extent are red alder and bigleaf maple. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and slippery and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by grand fir 

occurs periodically. If the canopy is opened, brush 

invades and can prevent the establishment of Douglas 

fir seedlings and can delay natural reforestation by 

grand fir unless controlled. 

Among the common forest understory plants are vine 

maple, common snowberry, false Solomons seal, 

western brackenfern, and trailing blackberry. 

This map unit is in capability subclass VIIe. 

25-Cinnamon sandy loam, 2 to 30 percent slopes. 

This very deep, well drained soil is on terraces, foot 
slopes, and back slopes of mountains. It formed in 

pyroclastic flows of volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 1,600 to 2,800 feet. The average annual precipitation 

is about 125 inches, the average annual air temperature is 

about 44 degrees F, and the average frost-free period is 

90 to 110 days. 

Typically. the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown sandy loam 3 

inches thick. The subsoil is dark yellowish brown and dark 

brown loamy sand 19 inches thick. Below this to a depth 

of 60 inches or more is a buried subsoil of dark yellowish 

brown sandy loam. 

 Included in this unit are small areas of Lonestar, 

Swift, and Vanson soils. Also included are small areas 

of St. Helens and Yalelake soils on terraces. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Cinnamon soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is slow, and 

the hazard of water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 145 for Douglas 

fir and 133 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is 106 for Douglas fir and 

96 for western hemlock. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 152 cubic feet 

per acre per year at age 60, and the CMAI for western 

hemlock is 205 cubic feet at age 50. Estimates of the site 

index or CMAI for Pacific silver fir have not been made. 

Among the trees of limited extent are western redcedar 

and red alder. 

The main limitation for harvesting timber is occasional 

snowpack. Unsurfaced roads and skid trails are soft and 

slippery and can be impassable when wet. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is not readily available in this unit. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Disturbance of the protective layer 

of duff can be reduced with the careful use of wheeled 

and tracked equipment. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. 

 Among the common forest understory plants are salal. 

Oregongrape, red huckleberry. thimbleberry, vine 

maple. willow, and western brackenfern. 

This map unit is in capability subclass IVe. 

26-Cinnamon sandy loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back 

slopes of mountains. It formed in pyroclastic flows of 

volcanic ash and pumice. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 1,600 to 2,800 

feet. The average annual precipitation is about 125 

inches, the average annual air temperature is about 44 

degrees F, and the average frost-free period is 90 to 110 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown sandy loam 3 

inches thick. The subsoil is dark yellowish brown and dark 

brown loamy sand 19 inches thick. Below this to a depth 

of 60 inches or more is a buried subsoil of dark yellowish 

brown sandy loam. 

Included in this unit are small areas of Lonestar, Swift, 

and Vanson soils. Also included are small areas of 

Yalelake soils on terraces. Included areas make up 

about 8 percent of the total acreage. 

Permeability of this Cinnamon soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 145 for 

Douglas fir and 133 for western hemlock. On the basis 

of a 50-year site curve, the mean site index is 106 for 

Douglas fir and 96 for western hemlock. The culmination of 

the mean annual increment (CMAI) for Douglas fir is 152 

cubic feet per acre per year at age 60, and the CMAI for 

western hemlock is 205 cubic feet at age 50. Estimates of 

the site index or CMAI for Pacific silver fir have not been 

made. Among the trees of limited extent are western 

redcedar and red alder. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for yearround use. 

Rock for road construction is not readily available in this 

unit. Occasional snowpack hinders the use of equipment 

and limits access in winter. Establishing plant cover on 

steeper slopes that have 
been cut or filled reduces erosion. Steep yarding paths, 

skid trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. 

Among the common forest understory plants are salal, 

Oregongrape, red huckleberry, thimbleberry, vine maple, 

willow, and western brackenfern. 

This map unit is in capability subclass VIIe. 

27-Cinnamon sandy loam, 65 to 90 percent 

slopes. This very deep, well drained soil is on back slopes 

of mountains. It formed in pyroclastic flows of volcanic ash 

and pumice. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 1,600 to 2,800 feet. The 

average annual precipitation is about 125 inches. the 

average annual air temperature is about 44 degrees F, 

and the average frost-free period is 90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown sandy loam 3 

inches thick. The subsoil is dark yellowish brown and dark 

brown loamy sand 19 inches thick. Below this to a depth 

of 60 inches or more is a buried subsoil of dark yellowish 

brown sandy loam. 

Included in this unit are small areas of Lonestar, Swift, 

and Vanson soils. Also included are small areas of 

Yalelake soils on terrace escarpments. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Cinnamon soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is rapid, and 

the hazard of water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 145 for Douglas 

fir and 133 for western hemlock. On the basis of a 50-

year site curve, the mean site index is 106 for Douglas fir 

and 96 for western hemlock. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 152 cubic feet 

per acre at age 60, and the CMAI for western hemlock is 

205 cubic feet at age 50. Estimates of the site index or 

CMAI for Pacific silver fir have not been made. Among the 

trees of limited extent are western redcedar and red alder. 

The main limitation for harvesting timber is steepness 

of slope. Cable yarding systems generally are used on 

this unit. Unsurfaced roads and skid trails are soft and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Occasional snowpack hinders the 

use of equipment and limits access in winter. Establishing 

plant cover on steeper slopes that have been cut or filled 

reduces erosion. Following road construction and 

clearcutting, road failures and landslides can occur. 

Steep yarding paths, skid trails, and firebreaks are 

subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. 

Among the common forest understory plants are 

salal, Oregongrape, red huckleberry, thimbleberry, vine 

maple. willow, and western brackenfern. 

This map unit is in capability subclass VIIe. 

28-Colter cindery sandy loam, 0 to 30 percent 

slopes. This very deep, well drained soil is on foot slopes 

of mountains. It formed in layers of aerially deposited 

volcanic ash and pumice. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,000 feet. The average annual precipitation is about 90 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free period is 75 to 95 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown cindery 

sandy loam 6 inches thick. The substratum is white 

extremely cindery sand about 27 inches thick. Below this 

is a buried subsoil. The upper 15 inches is very dark 

grayish brown and yellowish brown sandy loam, the 

next 6 inches is gray cindery loamy sand, and the lower 

part to a depth of 60 inches or more is strong brown 

extremely cindery sand. 

Included in this unit are small areas of Benham, 

Minniepeak, and Sinnice soils. Also included are small 

areas of Tradedollar soils. Included areas make up 

about 5 percent of the total acreage. 

Permeability of this Colter soil is very rapid in the 

substratum and is moderately rapid in the upper part of 

the buried subsoil and very rapid in the lower part. 
Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is slow, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 113 for western hemlock and 117 for Douglas fir. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 80 for western hemlock and 90 for 

Douglas fir. The culmination of the mean annual increment 

(CMAI) for western hemlock is 166 cubic feet per acre per 

year at age 50, and for Douglas fir it is 110 cubic feet at 

age 60. Estimates of the site index or CMAI for Pacific 

silver fir have not been made. Among the trees of limited 

extent are western redcedar and noble fir. 

The main limitation for harvesting timber is snowpack 

in winter. Use of wheeled and tracked equipment when 

the soil is moist produces ruts and damages the roots of 

trees. Logging roads require suitable surfacing for yearround use. Rock for road construction is not readily 

available in this unit. Snowpack in winter limits the use of 

equipment and restricts access. Cinders slough from road 

cuts onto the road surface. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Disturbance of the protective layer of duff can be 

reduced with the careful use of wheeled and tracked 

equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or noble fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Logging activities can readily displace the surface 

layer. Seedlings that grow in the less fertile substratum 

exhibit poor growth. Because the substratum is loose, 

trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

common beargrass. huckleberry, longtube twinflower, 

Indianpipe, and oneleaf foamflower. 

This map unit is in capability subclass VIIe. 

29-Cotter cindery sandy loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back slopes 

and foot slopes of mountains. It formed in layers of 

aerially deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,000 feet. The average annual 

precipitation is about 90 inches, the average annual air 

temperature is about 39 degrees F, and the average 

frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 6 inches, the surface layer 

is very dark grayish brown cindery sandy loam. The 

substratum is white extremely cindery sand about 27 

inches thick. The next layer is a buried subsoil. The 

upper 15 inches is very dark grayish brown and yellowish 

brown sandy loam, the next 6 inches is gray cindery 

loamy sand, and the lower part to a depth of 60 inches 

or more is strong brown extremely cindery sand. 

Included in this unit are small areas of Benham, 

Minniepeak, and Sinnice soils. Also included are small 

areas of Rock outcrop. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Colter soil is very rapid in the 

substratum and is moderately rapid in the upper part of 

the buried subsoil and very rapid in the lower part. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, and 

the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir 

are the main woodland species on this unit. On the 

basis of a 100-year site curve, the mean site index is 

estimated to be 113 for western hemlock and 117 for 

Douglas fir. On the basis of a 50-year site curve, the 

mean site index is estimated to be 80 for western hemlock 

and 90 for Douglas fir. The culmination of the mean 

annual increment (CMAI) for western hemlock is 166 

cubic feet per acre per year at age 50, and for Douglas fir 

it is 110 cubic feet at age 60. Estimates of the site 

index or CMAI for Pacific silver fir have not been made. 

Among the trees of limited extent are western redcedar 

and noble fir. 

The main limitations for harvesting timber are snowpack 

in winter and steepness of slope, which restricts the use of 

wheeled and tracked equipment in skidding. Cable yarding 

systems generally are safer and disturb the soil less. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Snowpack in winter limits the use of equipment 

and restricts access. Cinders slough from road cuts onto 

the road surface. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and firebreaks are subject to 

rilling and gullying unless plant cover is maintained or 

adequate 
water bars are provided. Harvesting systems that lift 

logs entirely off the ground reduce the disturbance of the 

protective layer of duff. 

Seedling mortality is the main concern in the production 

of timber. Reforestation can be accomplished by planting 

Douglas fir or noble fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Logging activities can readily displace the surface 

layer. Seedlings that grow in the less fertile substratum 

exhibit poor growth. Trees occasionally are subject to 

windthrow. 

Among the common forest understory plants are 

common beargrass, huckleberry, longtube twinflower, 

Indianpipe, and oneleaf foamflower. 

This map unit is in capability subclass Vlle. 

30-Cotter cindery sandy loam, 65 to 90 percent 

slopes. This very deep, well drained soil is on back 

slopes of mountains. It formed in layers of aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,000 feet. The average annual 

precipitation is about 90 inches, the average annual air 

temperature is about 39 degrees F, and the average 

frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 6 inches, the surface layer is 

very dark grayish brown cindery sandy loam. The 

substratum is white extremely cindery sand 27 inches 

thick. The next layer is a buried subsoil. The upper 15 

inches is very dark grayish brown and yellowish brown 

sandy loam, the next 6 inches is gray cindery loamy sand, 

and the lower part to a depth of 60 inches or more is 

strong brown extremely cindery sand. 

Included in this unit are small areas of Benham, 

Minniepeak, and Sinnice soils. Also included are small 

areas of Rock outcrop and Colter soils that are less than 

60 inches deep to bedrock. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Colter soil is very rapid in the 

substratum and is moderately rapid in the upper part of 

the buried subsoil and very rapid in the lower part. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is rapid, and 

the hazard of water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir 

are the main woodland species on this unit. On the basis 

of a 100-year site curve, the mean site index is estimated 

to be 113 for western hemlock and 117 for Douglas fir. 

On the basis of a 50-year site curve, the mean site index 

is estimated to be 80 for western hemlock and 90 for 

Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 166 cubic feet 

per acre per year at age 50, and for Douglas fir it is 110 

cubic feet at age 60. Estimates of the site index or 

CMAI for Pacific silver fir have not been made. Among 

the trees of limited extent are western redcedar and 

noble fir. 

The main limitations for harvesting timber are snowpack 

in winter and steepness of slope. Cable yarding systems 

generally are used on this unit. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Snowpack in winter limits the use 

of equipment and restricts access. Cinders slough from 

road cuts onto the road surface. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Following road construction and clearcutting, 

road failures and landslides can occur. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. Harvesting systems that lift logs 

entirely off the ground reduce the disturbance of the 

protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or noble fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Logging activities can readily displace the surface 

layer. Seedlings that grow in the less fertile substratum 

exhibit poor growth. Because the substratum is loose, 

trees occasionally are subject to windthrow. 

Among the common forest understory `plants are 

common beargrass, huckleberry, longtube twinflower, 

Indianpipe, and oneleaf foamflower. 

This map unit is in capability subclass VIIIe. 

31-Colter cindery sandy loam, cold, 0 to 30 

percent slopes. This very deep, well drained soil is on 

foot slopes of mountains. It formed in layers of aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 
Elevation is 4,000 to 5.400 feet. The average annual 

precipitation is about 90 inches. the average annual air 

temperature is about 38 degrees F, and the average 

frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles. leaves. and twigs 2 inches thick. 

Where mixed to a depth of 6 inches, the surface layer is 

very dark grayish brown cindery sandy loam. The 

substratum is white extremely cindery sand 27 inches thick. 

The next layer is a buried subsoil. The upper 15 inches is 

very dark grayish brown and yellowish brown sandy loam. 

the next 6 inches is gray cindery loamy sand. and the lower 

part to a depth of 60 inches or more is strong brown 

extremely cindery sand. 

Included in this unit are small areas of Cattcreek, 

Minniepeak. Sinnice. and Tradedollar soils. Also included 

are small areas of Colter soils that are less than 60 inches 

deep to bedrock. Included areas make up about 5 percent 

of the total acreage. 

Permeability of this Colter soil is very rapid in the 

substratum and is moderately rapid in the upper part of 

the buried subsoil and very rapid in the lower part. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is slow, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir. and noble fir are the 

main woodland species on this unit, On the basis of a 100-

year site curve. the mean site index is estimated to be 91 

for western hemlock. On the basis of a 50-year site curve. 

the mean site index is estimated to be 65 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for western hemlock is 107 cubic feet per acre per 

year at age 60. Estimates of the site index or CMAI for 

Pacific silver fir and noble fir have not been made. Among 

the trees of limited extent are subalpine fir and Douglas 

fir. Areas on ridgetops that are subject to strong, persistent 

winds are less productive than other areas of this unit. 

The main limitation for harvesting timber is snowpack in 

winter. Use of wheeled and tracked equipment when the 

soil is moist produces ruts and damages the roots of 

trees. Logging roads require suitable surfacing for yearround use. Rock for road construction is not readily 

available in this unit. Snowpack in winter limits the use of 

equipment and restricts access. Cinders slough from road 

cuts onto the road surface. Disturbance of the protective 

layer of duff can be reduced with the careful use of 

wheeled and tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas of western hemlock 

and Pacific silver fir occurs periodically. Droughtiness of 

the surface layer reduces seedling, survival, especially 

on south- and southwest-facing slopes. The mortality rate 

of seedlings is higher in areas on ridgetops that are 

subject to strong, persistent winds than in other areas of 

this unit. Logging activities can readily displace the surface 

layer. Seedlings that grow in the less fertile substratum 

exhibit poor growth. Because the substratum is loose, 

trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

Sitka alder, common beargrass, huckleberry, princes 

pine. and willow. 

This map unit is in capability subclass VIIe. 

32-Cotter cindery sandy loam, cold, 30 to 65 

percent slopes. This very deep, well drained soil is on 

back slopes and foot slopes of mountains. It formed in 

layers of aerially deposited volcanic ash and pumice. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 4,000 to 5,400 feet. The average 

annual precipitation is about 90 inches, the average 

annual air temperature is about 38 degrees F, and the 

average frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 6 inches. the surface layer is 

very dark grayish brown cindery sandy loam. The 

substratum is white extremely cindery sand 27 inches 

thick. The next layer is a buried subsoil. The upper 15 

inches is very dark grayish brown and yellowish brown 

sandy loam. the next 6 inches is gray cindery loamy 

sand, and the lower part to a depth of 60 inches or more 

is strong brown extremely cindery sand. 

Included in this unit are small areas of Cattcreek, 

Minniepeak, Sinnice, and Tradedollar soils. Also 

included are small areas of Colter soils that are less than 

60 inches deep to bedrock. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Colter soil is very rapid in the 

substratum and is moderately rapid in the upper part of 

the buried subsoil and very rapid in the lower part. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, and 

the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

 Western hemlock, Pacific silver fir, and noble fir are the 

main woodland species on this unit. On the basis of 
a 100-year site curve, the mean site index is estimated to 

be 91 for western hemlock. On the basis of a 50-year site 

curve. the mean site index is estimated to be 65 for

western hemlock. The culmination of the mean annual 

increment (CMAI) for western hemlock is 107 cubic feet per

acre per year at age 60. Estimates of the site index or CMAI 

for Pacific silver fir and noble fir have not been made. 

Among the trees of limited extent are subalpine fir and 

Douglas fir. 

The main limitations for harvesting timber are snowpack 

in winter and steepness of slope, which restricts the use of 

wheeled and tracked equipment in skidding. Cable yarding 

systems generally are safer and disturb the soil less. Use 

of wheeled and tracked equipment when the soil is moist 

produces ruts, compacts the soil, and damages the roots 

of trees. Logging roads require suitable surfacing for yearround use. Rock for road construction is not readily 

available in this unit. Snowpack in winter limits the use of 

equipment and restricts access. Cinders slough from road 

cuts onto the road surface. Establishing plant cover on 

steeper slopes that have been cut or filled reduces erosion. 

Steep yarding paths, skid trails, and firebreaks are subject 

to rifling and gullying unless plant cover is maintained or 

adequate water bars are provided. Harvesting systems 

that lift logs entirely off the ground reduce the disturbance 

of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Droughtiness of 

the surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. Logging activities can 

readily displace the surface layer. Seedlings that grow in 

the less fertile substratum exhibit poor growth. Because the 

substratum is loose, trees occasionally are subject to 

windthrow. 

Among the common forest understory plants are 

Sitka alder. common beargrass, huckleberry, princes 

pine, and willow. 

This map unit is in capability subclass VIIe. 

33-Colter cindery sandy loam, cold, 65 to 90 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in layers of aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 4,000 to 5,400 feet. The average annual precipitation 

is about 90 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 6 inches, the surface layer is 

very dark grayish brown cindery sandy loam. The 

substratum is white extremely cindery sand 27 inches 

thick, The next layer is a buried subsoil. The upper 15 

inches is very dark grayish brown and yellowish brown 

sandy loam, the next 6 inches is gray cindery loamy 

sand, and the lower part to a depth of 60 inches or 

more is strong brown extremely cindery sand. 

Included in this unit are small areas of Sinnice and 

Tradedollar soils. Also included are small areas of 

Cattcreek soils in cirque basins, Rock outcrop, and 

Colter soils that are less than 60 inches deep to 

bedrock. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this Colter soil is very rapid in the 

substratum and is moderately rapid in the upper part of 

the buried subsoil and very rapid in the lower part. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is rapid, and 

the hazard of water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat. and watershed. 

Western hemlock, Pacific silver fir, and noble fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 91 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is estimated to be 65 for 

western hemlock. The culmination of the mean annual 

increment (CMAI) for western hemlock is 107 cubic feet 

per acre per year at age 60. Estimates of the site index 

or CMAI for Pacific silver fir and noble fir have not been 

made. Among the trees of limited extent are subalpine 

fir and Douglas fir. 

The main limitations for harvesting timber are snowpack 

in winter and steepness of slope. Cable yarding systems 

generally are used on this unit. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Snowpack in winter limits the use 

of equipment and restricts access. Cinders slough from 

road cuts onto the road surface. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Following road construction and clearcutting, 

road failures and landslides can occur. Steep yarding 

paths, skid trails, and firebreaks are subject to rifling and 

gullying unless plant cover is maintained or adequate 

water bars are 
provided. Harvesting systems that lift logs entirely off 

the ground reduce the disturbance of the protective 

layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Droughtiness of 

the surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. Logging activities 

can readily displace the surface layer. Seedlings that 

grow in the less fertile substratum exhibit poor growth. 

Trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

Sitka alder, common beargrass, huckleberry, princes 

pine, and willow. 

This map unit is in capability subclass Vlle. 

34-Colter, cold-Rock outcrop complex, 30 to 65 

percent slopes. This map unit is on back slopes of 

mountains. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 4,000 to 5,400 feet. The 

average annual precipitation is about 90 inches, the 

average annual air temperature is about 39 degrees F, 

and the average frost-free period is 75 to 95 days. 

This unit is about 60 percent Colter cindery sandy 

loam, cold, and 30 percent Rock outcrop. The 

components of this unit are so intricately intermingled 

that it was not practical to map them separately at the 

scale used. 

Included in this unit are small areas of Minniepeak, 

Sinnice. and Tradedollar soils. Also included are small 

areas of Cattcreek soils in cirque basins and Colter soils 

that are less than 60 inches deep to bedrock. Included 

areas make up about 10 percent of the total acreage. 

The Colter soil is very deep and well drained. It formed in 

layers of aerially deposited volcanic ash and pumice. 

Typically, the surface is covered with a mat of decomposed 

needles, leaves, and twigs 2 inches thick. Where mixed to a 

depth of 6 inches, the surface layer is very dark grayish 

brown cindery sandy loam. The substratum is white 

extremely cindery sand 27 inches thick. The next layer is 

a buried subsoil. The upper 15 inches is very dark grayish 

brown and yellowish brown sandy loam, the next 6 inches 

is gray cindery loamy sand, and the lower part to a depth 

of 60 inches or more is strong brown extremely cindery 

sand. 

Permeability of this Colter soil is very rapid in the 

substratum and is moderately rapid in the upper part of 

the buried subsoil and very rapid in the lower part. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

Rock outcrop in this unit is dominantly andesite and 

basalt. Numerous escarpments are present in this unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and noble fir are 

the main woodland species on the Colter soil. On the 

basis of a 100-year site curve, the mean site index is 

estimated to be 91 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is estimated to 

be 65 for western hemlock. The culmination of the mean 

annual increment (CMAI) for western hemlock is 107 cubic 

feet per acre per year at age 60. The areas of Rock 

outcrop make up about 30 percent of this unit and 

reduce yield accordingly. Estimates of the site index or 

CMAI for Pacific silver fir and noble fir have not been 

made. Among the trees of limited extent are subalpine fir 

and Douglas fir. 

The main limitations for harvesting timber are the 

areas of Rock outcrop, snowpack in winter, and steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Rock outcrop may 

cause breakage of timber when felled and can hinder 

yarding operations. Avoiding areas of Rock outcrop forces 

yarding paths to converge, which increases compaction 

and erosion. Use of wheeled and tracked equipment 

when the soil is moist produces ruts,, compacts the soil, 

and damages the roots of trees. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Snowpack 

in winter limits the use of equipment and restricts access. 

Cinders slough from road cuts onto the road surface. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. Harvesting systems that lift logs entirely off 

the ground reduce the disturbance of the protective layer of 

duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Droughtiness of 

the surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. The mortality rate 

of seedlings is higher in areas on ridgetops that are 

subject to strong, 
persistent winds than in other areas of this unit. The areas 

of Rock outcrop limit the even distribution of 

reforestation. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

substratum exhibit poor growth. Because the substratum 

is loose, trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

Sitka alder, common beargrass, huckleberry, princes 

pine, and willow. 

The Colter soil is in capability subclass VIIe, and the 

Rock outcrop is in capability subclass Vllls. 

35-Cryandepts, 45 to 120 percent slopes. These 

deep and very deep, moderately well drained and well 

drained soils are on north-facing mountain slopes. They 

formed in aerially deposited volcanic ash and pumice. 

The native vegetation is mainly mixed deciduous trees 

and shrubs. Elevation is 3,000 to 4,500 feet. The average 

annual precipitation is about 130 inches, the average 

annual air temperature is about 38 degrees F, and the 

average frost-free period is 60 to 80 days. 

No single profile is typical of Cryandepts, but one 

commonly observed in the survey area has a surface layer 

that is very dark brown sandy loam in the upper 13 inches 

and dark brown cindery sandy loam in the lower 3 

inches. The upper 9 inches of the subsoil is light gray 

extremely cindery sand. and the lower 21 inches is dark 

brown sandy loam. The substratum to a depth of 60 inches 

or more is strong brown very cindery loamy sand. Depth to 

bedrock ranges from 50 to 60 inches or more. 

Included in this unit are small areas of Minniepeak, 

Pelee, and Sinnice soils on ridgetops and back slopes. 

Also included are small areas of Rock outcrop and soils 

that are less than 40 inches deep to bedrock. Included 

areas make up about 10 percent of the total acreage. 

Permeability of these Cryandepts is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is medium to rapid, 

and the hazard of water erosion is moderate to severe. 

This unit is used for wildlife habitat and watershed. 

This unit is poorly suited to the production of timber. 

Vine maple, willow, and Sitka alder are the main shrub 

species on this unit. False Solomons seal. deerfoot 

vanillaleaf, and queencup beadlily are also common on 

this unit. 

This map unit is in capability subclass VIIe. 

36-Dougan very gravelly loam, 5 to 30 percent 

slopes. This moderately deep, well drained soil is on 

ridges of mountains. It formed in colluvium derived 

dominantly from andesite and granodiorite mixed with 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 2,000 to 3,000 feet. 

The average annual precipitation is about 100 inches, 

the average annual air temperature is about 43 degrees 

F, and the average frost-free period is 90 to 130 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown very gravelly 

loam 11 inches thick. The subsoil is light olive brown 

very gravelly loam 13 inches thick. The substratum is 

light yellowish brown extremely gravelly loam 15 inches 

thick over fractured andesite. Depth to bedrock ranges 

from 30 to 40 inches. 

Included in this unit are small areas of Kinney, Skoly, 

and Zygore soils. Also included are small areas of soils 

that are shallow to bedrock and Rock outcrop. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Dougan soil is moderately rapid. 

Available water capacity is low. Effective rooting depth is 

32 to 40 inches. Runoff is medium, and the hazard of

water erosion is moderate. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir, western hemlock, and noble fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 117 for Douglas fir and 113 for western hemlock. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 90 for Douglas fir and 80 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 110 cubic feet per acre per year 

at age 60, and the CMAI for western hemlock is 166 

cubic feet at age 50. Estimates of the site index or 

CMAI for noble fir have not been made. Among the 

trees of limited extent is western redcedar. Areas on 

ridgetops that are subject to strong, persistent winds are 

less productive than other areas of this unit. 

The main limitation for harvesting timber is occasional 

snowpack. Unsurfaced roads and skid trails are soft and 

slippery and can be impassable when wet. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is readily available in this unit. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Disturbance of the protective 

layer of duff can be reduced with the careful use of 

wheeled and tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir or noble fir 

seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock 
occurs readily. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. The mortality rate of seedlings is higher in 

areas on ridgetops that are subject to strong, persistent 

winds than in other areas of this unit. Logging activities 

can readily displace the surface layer. Seedlings that 

grow in the less fertile subsoil exhibit poor growth. 

Because the rooting depth is restricted by the underlying 

bedrock, trees occasionally are subject to windthrow. 

Among the common forest understory plants are vine 

maple, red huckleberry, serviceberry, common 

beargrass, pachystima, bunchberry dogwood, Oregon 

oxalis, and creambush oceanspray. 

This map unit is in capability subclass lVe. 

37-Dougan very gravelly loam, 30 to 65 percent 

slopes. This moderately deep. well drained soil is on back 

slopes of mountains. It formed in colluvium derived 

dominantly from andesite and granodiorite mixed with 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 2,000 to 3,000 feet. 

The average annual precipitation is about 100 inches, the 

average annual air temperature is about 43 degrees F. 

and the average frost-free period is 90 to 130 days. 

Typically. the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown very gravelly 

loam 11 inches thick. The subsoil is light olive brown very 

gravelly loam 13 inches thick. The substratum is light 

yellowish brown extremely gravelly loam 15 inches thick 

over fractured andesite. Depth to bedrock ranges from 30 

to 40 inches. 

Included in this unit are small areas of Skoly and 

Zygore soils. Also included are small areas of soils that 

are shallow to bedrock, Rock outcrop. and Andic 

Cryumbrepts. Included areas make up about 8 percent of 

the total acreage. 

Permeability of this Dougan soil is moderately rapid. 

Available water capacity is low. Effective rooting depth is 

30 to 40 inches. Runoff is rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir, western hemlock, and noble fir are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is estimated to be 117 for 

Douglas fir and 113 for western hemlock. On the basis of a 

50-year site curve, the mean site index is estimated to be 

92 for Douglas fir and 80 for western hemlock. The 

culmination of the mean annual increment 

(CMAI) for Douglas fir is 110 cubic feet per acre per year 

at age 60, and the CMAI for western hemlock is 

166 cubic feet at age 50. Estimates of the site index or 

CMAI for noble fir have not been made. Among the trees 

of limited extent is western redcedar. 

The main limitation for harvesting timber is steepness 

of slope. Cable yarding systems generally are used on 

this unit. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Occasional snowpack hinders the use 

of equipment and limits access in winter. Establishing plant 

cover on steeper slopes that have been cut or filled 

reduces erosion. Steep yarding paths, skid trails, and 

firebreaks are subject to rilling and gullying unless plant 

cover is maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or noble fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by western hemlock occurs readily. Droughtiness of the 

surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. Logging activities 

can readily displace the surface layer. Seedlings that 

grow in the less fertile subsoil exhibit poor growth. 

Because the rooting depth is restricted by underlying 

bedrock, trees occasionally are subject to windthrow. 

Among the common forest understory plants are vine 

maple. red huckleberry, serviceberry, common beargrass, 

pachystima, bunchberry dogwood, Oregon oxalis, and 

creambush oceanspray. 

This map unit is in capability subclass VIIe. 

38-Forsyth cindery loamy sand, 65 to 120 percent 

slopes. This very deep, somewhat excessively drained 

soil is on terrace escarpments. It formed in pyroclastic 

flow and lahar material with a thin mantle of aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 1,800 to 2,800 feet. The average annual precipitation 

is about 130 inches, the average annual air temperature 

is about 43 degrees F, and the average frost-free period 

is 90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 8 inches, the surface layer is 

dark brown cindery loamy sand. The upper 11 inches of 

the underlying material is dark brown extremely cobbly 

sand, and the lower part to a depth of 60 inches or 
more is dark gray extremely stony sand. 

Included in this unit are small areas of Pinchot and 

Swift soils on side slopes of mountains. Also included are 

small areas of Badland and Rock outcrop. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Forsyth soil is rapid. Available water 

capacity is low. Effective rooting depth is 60 inches or 

more. Runoff is very rapid, and the hazard of water erosion 

is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and lodgepole pine are the main woodland 

species on this unit. On the basis of a 100-year site curve, 

the mean site index is estimated to be 110 for Douglas 

fir. On the basis of a 50-year site curve, the mean site 

index is estimated to be 85. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 90 cubic feet per 

acre per year at age 60. Estimates of the site index or 

CMAI for lodgepole pine have not been made. Among the 

trees of limited extent are western hemlock, western white 

pine, and Pacific silver fir. 

The main limitation for harvesting timber is steepness of 

slope. Cable yarding systems generally are used on this 

unit. Logging roads require suitable surfacing for yearround use. Rock for road construction is readily available 

in this unit. Logging roads generally need full bench 

construction and require frequent maintenance. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. 

Following road construction and clearcutting, road 

failures and landslides can occur. Steep yarding paths, 

skid trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. Harvesting systems that lift logs entirely off 

the ground reduce the disturbance of the protective layer of 

duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or lodgepole pine seedlings. If 

seed trees are present, natural reforestation of cutover 

areas by western hemlock and Pacific silver fir occurs 

periodically. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

underlying material exhibit poor growth. Because the 

underlying material is loose, trees occasionally are 

subject to windthrow. 

Among the common forest understory plants are 

Sitka alder, kinnikinnick, salal, red huckleberry, princes 

pine, and lupine. 

This map unit is in capability subclass VIIe. 

39-Forsyth cobbly loamy sand, 0 to 30 percent 

slopes. This very deep, somewhat excessively drained 

soil is on terraces and terrace escarpments. It formed in 

pyroclastic flow and lahar material with a thin mantle of 

aerially deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 1,600 to 2,800 feet. The average annual precipitation is 

about 130 inches, the average annual air temperature is 

about 43 degrees F, and the average frost-free period is 

90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 8 inches, the surface layer is 

very dark grayish brown cobbly loamy sand. The upper 

11 inches of the underlying material is dark brown 

extremely cobbly sand, and the lower part to a depth of 

60 inches or more is dark gray extremely stony sand. 

Included in this unit are small areas of Pinchot, 

Polepatch, Shoestring, and St. Helens soils. Also 

included are small areas of poorly drained soils in 

depressional areas and Forsyth soils that have stones 

on the surface. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Forsyth soil is rapid. Available 

water capacity is low. Effective rooting depth is 60 

inches or more. Runoff is slow, and the hazard of water 

erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and lodgepole pine are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 

98 for Douglas fir. On the basis of a 50-year site curve, 

the mean site index is estimated to be 75. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 81 cubic feet per acre per year at age 60. 

Estimates of the site index or CMAI for lodgepole pine 

have not been made. Among the trees of limited extent 

are western hemlock, western white pine, and Pacific 

silver fir. 

The main limitation for harvesting timber is occasional 

snowpack. Rock for road construction is readily available 

in this unit. Occasional snowpack hinders the use of 

equipment and limits access in winter. Disturbance of the 

protective layer of duff can be reduced with the careful 

use of wheeled and tracked equipment. 
Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir or lodgepole pine seedlings. If seed 

trees are present, natural reforestation of cutover areas by 

western hemlock, western white pine, and Pacific silver fir 

occurs periodically. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Trees occasionally are subject 

to windthrow. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

underlying material exhibit poor growth. Trees are 

occasionally subject to windthrow when winds are strong. 

Among the common forest understory plants are Sitka 

alder, kinnikinnick, salal, red huckleberry, princes pine, 

and lupine. 

This map unit is in capability subclass IVs. 

40-Forsyth stony loamy sand, 0 to 30 percent 

slopes. This very deep, somewhat excessively drained soil 

is on terraces and terrace escarpments. It formed in 

pyroclastic flow and lahar material with a thin mantle of 

aerially deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 1,600 to 2,800 feet. The average annual 

precipitation is about 130 inches, the average annual air 

temperature is about 43 degrees F, and the average 

frost-free period is 90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 8 inches, the surface layer is 

very dark grayish brown stony loamy sand. The upper 11 

inches of the substratum is dark brown extremely cobbly 

sand, and the lower part to a depth of 60 inches or more is 

dark gray extremely stony sand. 

Included in this unit are small areas of Pinchot, 

Polepatch, Shoestring, and St. Helens soils. Also included 

are small areas of poorly drained soils in depressional 

areas and Forsyth soils that have cobbles on the 

surface. Included areas make up about 10 percent of the 

total acreage. 

Permeability of this Forsyth soil is rapid. Available water 

capacity is low. Effective rooting depth is 60 inches or 

more. Runoff is slow, and the hazard of water erosion is 

slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and lodgepole pine are the main woodland 

species on this unit. On the basis of a 100-year site 

curve, the mean site index is estimated to be 98 for 

Douglas fir. On the basis of a 50-year site curve, 

the mean site index is estimated to be 75 for Douglas fir. 

The culmination of the mean annual increment (CMAI) 

for Douglas fir is 81 cubic feet per acre per year at age 60. 

Estimates of the site index or CMAI for lodgepole pine 

have not been made. Among the trees of limited extent 

are western hemlock, western white pine, and Pacific 

silver fir. 

The main limitation for harvesting timber is 

occasional snowpack. Rock for road construction is 

readily available in this unit. Occasional snowpack 

hinders the use of equipment and limits access in winter. 

Disturbance of the protective layer of duff can be reduced 

with the careful use of wheeled and tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir and lodgepole pine seedlings. If 

seed trees are present, natural reforestation of cutover 

areas by western hemlock, western white pine, and Pacific 

silver fir occurs periodically. Droughtiness of the surface 

layer reduces seedling survival, especially on south- and 

southwest-facing slopes. Logging activities can readily 

displace the surface layer. Seedlings that grow in the less 

fertile underlying material exhibit poor growth. Because 

the surface layer and underlying material are loose, trees 

are occasionally subject to windthrow when winds are 

strong. 

Among the common forest understory plants are Sitka 

alder, kinnikinnick, salal, red huckleberry, princes pine, 

and lupine. 

This map unit is in capability subclass Vls. 

41-Fortran cindery loamy sand, 65 to 120 percent 

slopes. This very deep, somewhat excessively drained 

soil is on terrace escarpments. It formed in pyroclastic 

flow and lahar material with a thin mantle of volcanic ash 

and pumice. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 800 to 1,800 feet. The 

average annual precipitation is about 100 inches, the 

average annual air temperature is about 52 degrees F, 

and the average frost-free period is 115 to 135 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 6 inches, the surface layer is 

dark brown cindery loamy sand. The upper 5 inches of 

the subsoil is dark yellowish brown cindery sandy loam, 

and the lower 6 inches is dark brown very gravelly 

sandy loam. The substratum to a depth of 60 inches or 

more is gray extremely gravelly loamy sand. 

Included in this unit are small areas of Yalelake soils. 

Also included are small areas of Swift soils on side 
slopes of mountains, Badland, and Rock outcrop. 

Included areas make up about 5 percent of the total 

acreage. 

Permeability of the Fortran soil is moderately rapid. 

Available water capacity is low. Effective rooting depth is 

60 inches or more. Runoff is very rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, recreation. wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 131 

for Douglas fir and 130 for western hemlock. On the 

basis of a 50-year site curve, the mean site index is 

estimated to be 100 for Douglas fir and 95 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 132 cubic feet per acre per year at 

age 70, and for western hemlock it is 200 cubic feet at age 

50. Among the trees of limited extent are western 

redcedar and red alder. 

The main limitation for harvesting timber is steepness 

of slope. Cable yarding systems generally are used on 

this unit. Logging roads generally need full bench 

construction and require frequent maintenance. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Following road construction 

and clearcutting, road failures and landslides can occur. 

Steep yarding paths, skid trails, and firebreaks are 

subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock occurs periodically. Droughtiness of the surface 

layer reduces seedling survival, especially on south- and 

southwest-facing slopes. Logging activities can readily 

displace the surface layer. Seedlings that grow in the less 

fertile subsoil exhibit poor growth. If the canopy is 

opened, brush invades and can prevent the establishment 

of Douglas fir and can delay natural reforestation of 

western hemlock unless controlled. Trees occasionally are 

subject to windthrow because of poor root development in 

the substratum. 

Among the common forest understory plants are vine 

maple, bigleaf maple, western swordfern. false Solomons 

seal, and trailing blackberry. 

This map unit is in capability subclass VIIe. 

42-Haplumbrepts, 0 to 3 percent slopes. These 

very deep, somewhat poorly drained and moderately well 

drained soils are in depressional areas on river terraces 

adjacent to steep side slopes. They formed in gravelly 

alluvium derived dominantly from basalt, andesite, and 

some volcanic ash. The native vegetation is mainly 

hardwoods and scattered conifers. Elevation is 50 to 

1,000 feet. The average annual precipitation is about 75 

inches, the average annual air temperature is about 48 

degrees F, and the average frost-free period is 120 to 

140 days. 

No single profile is typical of Haplumbrepts, but one 

commonly observed in the survey area has a surface 

layer of very dark brown gravelly loam in the upper 3 inches 

and very dark brown gravelly clay loam in the lower 5 

inches. The subsoil is mottled, very dark grayish brown 

cobbly clay loam and extremely cobbly clay loam 22 

inches thick. The substratum to a depth of 60 inches or 

more is mottled, dark brown extremely gravelly loam. 

Included in this unit are small areas of McBee soils 

and Washougal soils in well drained areas. Also 

included are small areas of poorly drained soils. Included 

areas make up about 10 percent of the total acreage. 

Permeability of these Haplumbrepts is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is limited by a seasonal high water table 

that is at a depth of as little as 0.5 foot to 3 feet from 

January to May. Runoff is slow, and the hazard of water 

erosion is slight. These soils are subject to brief periods of 

ponding after heavy winter rains. 

This unit is used as woodland, pastureland, and 

wildlife habitat. 

Red alder is the main woodland species on this unit. 

On the basis of a 50-year site curve, the mean site index 

is estimated to be 85 for red alder. The culmination of 

the mean annual increment (CMAI) for red alder is 92 

cubic feet per acre per year at age 40. Among the trees 

of limited extent are western redcedar and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Disturbance of the protective layer of duff can 

be reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment and mortality are the main
concerns in the production of timber. Wetness reduces 

root respiration, which results in a low survival rate of 

seedlings. Reforestation can be accomplished by 

planting western redcedar seedlings. If seed trees are 

present, natural reforestation of cutover areas by red 

alder occurs readily. If the canopy is open, brush 

invades and can delay the establishment of western 

redcedar seedlings unless controlled. Because the 

rooting depth is restricted by a seasonal high water 

table, trees occasionally are subject to windthrow. 

Among the common forest understory plants are vine 

maple, western swordfern, western brackenfern, salal, 

Oregongrape, trailing blackberry, and sedges. 

This unit is suited to use as hayland and pastureland. 

The main limitation is seasonal soil wetness. Wetness 

limits the choice of plants and the period of grazing and 

increases the risk of suffocation from water in the root 

zone. Grazing when the soil is moist results in 

compaction of the surface layer, poor filth, and excessive 

runoff. Excessive water on the surface can be removed 

by drainage ditches. 

This map unit is in capability subclass IIIw. 

43-Hatchet gravelly sandy loam, 30 to 65 percent 

slopes. This moderately deep, well drained soil is on back 

slopes and shoulder slopes of mountains. It formed in 

residuum and colluvium derived dominantly from basalt 

and andesite mixed with volcanic ash. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,000 feet. The average annual 

precipitation is about 105 inches, the average annual air 

temperature is about 39 degrees F, and the average frostfree period is 75 to 95 days. 

Typically. the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches 

thick. The surface layer is very dark grayish brown 

gravelly sandy loam 3 inches thick. The upper 7 inches of 

the subsoil is dark brown gravelly sandy loam and 

gravelly fine sandy loam, and the lower 10 inches is dark 

yellowish brown extremely cobbly loam. The substratum 

is yellowish brown extremely cobbly clay loam 8 inches 

thick over fractured andesite. Depth to andesite or basalt 

ranges from 20 to 40 inches. 

Included in this unit are small areas of Cattcreek, 

Lonestar, Swift, Tradedollar, and Vanson soils. Also 

included are small areas of Rock outcrop and Hatchet 

soils that are less than 20 inches deep to bedrock. 

Included areas make up about 8 percent of the total 

acreage. 

Permeability of this Hatchet soil is moderate. 

Available water capacity is very low. Effective rooting 

depth is 20 to 40 inches. Runoff is medium to rapid, 

and the hazard of water erosion is moderate to severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Western hemlock. Douglas fir, and Pacific silver fir 

are the main woodland species on this unit. On the 

 basis of a 100-year site curve, the mean site index is 

118 for western hemlock and 127 for Douglas fir. On the 

basis of a 50-year site curve, the mean site index is 81 

for western hemlock and 94 for Douglas fir. The 

culmination of the mean annual increment (CMAI) for 

western hemlock is 176 cubic feet per acre per year at 

age 50, and the CMAI for Douglas fir is 125 cubic feet 

at age 70. Estimates of the site index or CMAI for 

Pacific silver fir have not been made. Areas on ridgetops 

that are subject to strong, persistent winds are less 

productive than other areas of this unit. Among the trees 

of limited extent are noble fir and western redcedar. 

The main limitations for harvesting timber are 

steepness of slope and snowpack in winter. Steepness of 

slope restricts the use of wheeled and tracked equipment 

in skidding. Cable yarding systems generally are safer 

and disturb the soil less. Use of wheeled and tracked 

equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are slippery and can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round use. Rock for road construction 

is readily available in this unit. Snowpack in winter limits 

the use of equipment and restricts access. Establishing 

plant cover on steeper slopes that have been cut or 

filled reduces erosion. Steep yarding paths, skid trails, 

and firebreaks are subject to rilling and gullying unless 

plant cover is maintained or adequate water bars are 

provided. 

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Reforestation can be 

accomplished by planting noble fir or Douglas fir 

seedlings. If seed trees are present, natural reforestation 

of cutover areas by western hemlock and Pacific silver fir 

occurs periodically. The mortality rate of seedlings is 

higher in areas on ridgetops that are subject to strong, 

persistent winds than in other areas of this unit. Logging 

activities can readily displace the surface layer. 

Seedlings that grow in the less fertile subsoil exhibit 

poor growth. Because the rooting depth is restricted by 

underlying bedrock, trees occasionally are subject to 

windthrow. Windthrow is higher in areas on ridgetops that 

are subject to strong, persistent winds than in other 

areas of the unit. 
Among the common forest understory plants are 

common beargrass, huckleberry, Oregongrape, princes 

pine, and starflower. 

This map unit is in capability subclass VIIe. 

44-Hatchet gravelly sandy loam, 65 to 90 percent 

slopes. This moderately deep, well drained soil is on back 

slopes of mountains. It formed in residuum and colluvium 

derived dominantly from basalt and andesite mixed with 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 2,800 to 4,000 feet. The 

average annual precipitation is about 105 inches, the 

average annual air temperature is about 39 degrees F, 

and the average frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown gravelly 

sandy loam 3 inches thick. The upper 7 inches of the 

subsoil is dark brown gravelly sandy loam and gravelly fine 

sandy loam, and the lower 10 inches is dark yellowish 

brown extremely cobbly loam. The substratum is yellowish 

brown extremely cobbly clay loam 8 inches thick over 

fractured andesite. Depth to andesite or basalt ranges from 

20 to 40 inches. 

Included in this unit are small areas of Cattcreek. 

Lonestar, Swift, Tradedollar, and Vanson soils. Also 

included are small areas of Hatchet soils that are less 

than 20 inches deep to bedrock and small areas of Rock 

outcrop. Included areas make up about 10 percent of the 

total acreage. 

Permeability of this Hatchet soil is moderate. 

Available water capacity is very low. Effective rooting 

depth is 20 to 40 inches. Runoff is rapid, and the 

hazard of water erosion is severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is 118 for 

western hemlock and 127 for Douglas fir. On the basis of 

a 50-year site curve, the mean site index is 81 for western 

hemlock and 94 for Douglas fir. The culmination of the 

mean annual increment (CMAI) for western hemlock is 176 

cubic feet per acre per year at age 50. and the CMAI for 

Douglas fir is 125 cubic feet at age 70. Estimates of the 

site index or CMAI for Pacific silver fir have not been made. 

Among the trees of limited extent are noble fir and western 

redcedar. 

The main limitations for harvesting timber are 

steepness of slope and snowpack in winter. Cable 

yarding systems generally are used on this unit. 

Unsurfaced roads and skid trails are slippery and can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round use. Rock for road construction is 

readily available in this unit. Logging roads generally 

need full bench construction and require frequent 

maintenance. Snowpack in winter limits the use of 

equipment and restricts access. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Reforestation can be 

accomplished by planting noble fir or Douglas fir 

seedlings. If seed trees are present, natural reforestation 

of cutover areas by western hemlock and Pacific silver fir 

occurs periodically. Logging activities can readily 

displace the surface layer. Seedlings that grow in the 

less fertile subsoil exhibit poor growth. Because the 

rooting depth is restricted by underlying bedrock, trees 

occasionally are subject to windthrow. 

Among the common forest understory plants are 

common beargrass, huckleberry, Oregongrape, princes 

pine, and starflower. 

This map unit is in capability subclass VIIe. 

45-Hatchet gravelly sandy loam, cold, 30 to 65 

percent slopes. This moderately deep, well drained soil is 

on back slopes and shoulder slopes of mountains. It 

formed in residuum and colluvium derived dominantly 

from basalt and andesite mixed with volcanic ash. The 

native vegetation is mainly mixed conifers and shrubs. 

Elevation is 4,000 to 4,500 feet. The average annual 

precipitation is about 110 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free period is 75 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown gravelly 

sandy loam 3 inches thick. The upper 7 inches of the 

subsoil is dark brown gravelly sandy loam and gravelly 

fine sandy loam, and the lower 10 inches is dark 

yellowish brown extremely cobbly loam. The substratum 

is yellowish brown extremely cobbly clay loam 8 inches 

thick over fractured andesite. Depth to andesite or basalt 

ranges from 20 to 40 inches. 

Included in this unit are small areas of Cattcreek, 
Lonestar, Tradedollar, and Vanson soils. Also included 

are small areas of Rock outcrop and Hatchet soils that 

are less than 20 inches deep to bedrock. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Hatchet soil is moderate. Available 

water capacity is very low. Effective rooting depth is 20 

to 40 inches. Runoff is medium to rapid, and the hazard 

of water erosion is moderate to severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Western hemlock and Pacific silver fir are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 84 

for western hemlock. On the basis of a 50-year site curve, 

the mean site index is estimated to be 60 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for western hemlock is 95 cubic feet per acre per 

year at age 60. Estimates of the site index of CMAI for 

Pacific silver fir have not been made. Among the trees of 

limited extent are subalpine fir, noble fir, and Douglas fir. 

Areas on ridgetops that are subject to strong. persistent 

winds are less productive than other areas of this unit. 

The main limitations for harvesting timber are steepness

of slope and snowpack in winter. When harvesting timber. 

steepness of slope restricts the use of wheeled and 

tracked equipment in skidding. Cable yarding systems 

generally are safer and disturb the soil less. Use of 

wheeled and tracked equipment when the soil is moist 

produces ruts, compacts the soil, and damages the roots 

of trees. Unsurfaced roads and skid trails are slippery and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Snowpack in 

winter limits the use of 

equipment and restricts access. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Low soil temperature in 

summer, deep snowpack, and a short growing season 

reduce the survival rate of planted and natural seedlings 

and delay their establishment, Reforestation can be 

accomplished by planting noble fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by western hemlock, Pacific silver fir, and subalpine fir 

occurs infrequently. The mortality rate of seedlings is 

higher in areas on ridgetops that are 

subject to strong, persistent winds than in other areas of 

this unit. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

subsoil exhibit poor growth. Because the rooting depth 

is restricted by the underlying bedrock, trees 

occasionally are subject to windthrow. Windthrow is 

higher in areas on ridgetops that are subject to strong, 

persistent winds than in other areas of the unit. 

Among the common forest understory plants are 

common beargrass, huckleberry, Oregongrape, princes 

pine, and starflower. 

This map unit is in capability subclass VIIe. 

46-Hatchet gravelly sandy loam, cold, 65 to 90 

percent slopes. This moderately deep, well drained soil 

is on back slopes of mountains. It formed in residuum 

and colluvium derived dominantly from basalt and 

andesite mixed with volcanic ash. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 4,000 to 

4,500 feet. The average annual precipitation is about 105 

inches, the average annual air temperature is about 38 

degrees F, and the average frost-free period is 75 to 95 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown .gravelly 

sandy loam 3 inches thick. The upper 7 inches of the 

subsoil is dark brown gravelly sandy loam and gravelly 

fine sandy loam, and the lower 10 inches is dark yellowish 

brown extremely cobbly loam. The substratum is 

yellowish brown extremely cobbly clay loam 8 inches thick 

over fractured andesite. Depth to andesite or basalt ranges 

from 20 to 40 inches. 

Included in this unit are small areas of Cattcreek, 

Lonestar, Tradedollar, and Vanson soils. Also included 

are small areas of Rock outcrop and Hatchet soils that 

are less than 20 inches deep to bedrock. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Hatchet soil is moderate. 

Available water capacity is very low. Effective rooting 

depth is 20 to 40 inches. Runoff is rapid, and the 

hazard of water erosion is severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Western hemlock and Pacific silver fir are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 84 

for western hemlock. On the basis of a 50-year site curve, 

the mean site index is estimated to be 60 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for western hemlock is 95 cubic feet per acre per 

year at age 60. Estimates of the site index 
or CMAI for Pacific silver fir has not been made. Among 

the trees of limited extent are subalpine fir, noble fir, and 

Douglas fir. 

The main limitations for harvesting timber are 

steepness of slope and snowpack in winter. Cable yarding 

systems generally are used on this unit. Unsurfaced roads 

and skid trails are slippery and can be impassable when 

wet. Logging roads require suitable surfacing for yearround use. Rock for road construction is readily available 

in this unit. Logging roads generally need full bench 

construction and require frequent maintenance. 

Snowpack in winter limits the use of equipment and 

restricts access. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and firebreaks are subject to 

rifling and gullying unless plant cover is maintained or 

adequate water bars are provided. Harvesting systems 

that lift logs entirely off the ground reduce the disturbance 

of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival. especially on south- and 

southwest-facing slopes. Low soil temperature in 

summer, deep snowpack, and a short growing season 

reduce the survival rate of planted and natural seedlings 

and delay their establishment. Reforestation can be 

accomplished by planting noble fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock, Pacific silver fir, and subalpine fir 

occurs infrequently. Logging activities can readily 

displace the surface layer. Seedlings that grow in the 

less fertile subsoil exhibit poor growth. Because the 

rooting depth is restricted by the underlying bedrock, trees 

occasionally are subject to windthrow. 

Among the common forest understory plants are 

common beargrass, huckleberry, Oregongrape, princes 

pine. and starflower. 

This map unit is in capability subclass VIIe. 

47-Hatchet-Rock outcrop complex, 65 to 90 percent 

slopes. This map unit is on back slopes of mountains. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 2,800 to 4,000 feet. The average 

annual precipitation is about 105 inches, the average 

annual air temperature is about 39 degrees F. and the 

average frost-free period is 75 to 95 days. 

This unit is about 60 percent Hatchet gravelly sandy 

loam. 65 to 90 percent slopes, and 30 percent Rock 

outcrop. The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Cattcreek, Swift, 

Tradedollar, and Vanson soils. Also included are small 

areas of Hatchet soils that are less than 20 inches deep to 

bedrock. Included areas make up about 10 percent of 

the total acreage. 

The Hatchet soil is moderately deep and well drained. 

It formed in residuum and colluvium derived dominantly 

from basalt and andesite mixed with volcanic ash. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown gravelly sandy 

loam 3 inches thick. The upper 7 inches of the subsoil is 

dark brown gravelly sandy loam and gravelly fine sandy 

loam, and the lower 10 inches is dark yellowish brown 

extremely cobbly loam. The substratum is yellowish brown 

extremely cobbly clay loam 8 inches thick over fractured 

andesite. Depth to andesite or basalt ranges from 20 to 40 

inches. 

Permeability of this Hatchet soil is moderate. 

Available water capacity is very low. Effective rooting 

depth is 20 to 40 inches. Runoff is rapid, and the 

hazard of water erosion is severe. 

Rock outcrop consists mainly of exposed areas of 

basalt and andesite. Numerous escarpments are in this 

unit. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir 

are the main woodland species on the Hatchet soil. On the 

basis of a 100-year site curve, the mean site index is 118 

for western hemlock and 127 for Douglas fir. On the 

basis of a 50-year site curve, the mean site index is 81 

for western hemlock and 94 for Douglas fir. The 

culmination of the mean annual increment (CMAI) for 

western hemlock is 176 cubic feet per acre per year at age 

50, and the CMAI for Douglas fir is 125 cubic feet at age 

70. The areas of Rock outcrop make up about 30 

percent of this unit and reduce the yield accordingly. 

Estimates of the site index or CMAI for Pacific silver fir 

have not been made. Among the trees of limited extent 

are noble fir and western redcedar. 

The main limitations for harvesting timber are Rock 

outcrop, steepness of slope, and snowpack in winter. 

Cable yarding systems generally are used on this unit. 

Rock outcrop may cause breakage of timber when 

felled and can hinder yarding. Avoiding Rock outcrop 

forces yarding paths to converge, which increases 

compaction and erosion of the soil. Unsurfaced roads 

and skid trails are slippery and can be impassable when

wet. Logging roads require suitable surfacing for year 

round use. Rock for road construction is readily 

available in this unit. Logging roads generally need full 
bench construction and require frequent maintenance. 

Snowpack in winter limits the use of equipment and 

restricts access. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. 

Steep yarding paths, skid trails, and firebreaks are 

subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir or Douglas fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by western hemlock and Pacific silver fir occurs 

periodically. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

subsoil exhibit poor growth. The areas of Rock outcrop 

limit the even distribution of reforestation. Because the 

rooting depth is restricted by the underlying bedrock, 

trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

common beargrass, huckleberry, Oregongrape, princes 

pine, and starflower. 

The Hatchet soil is in capability subclass VIIe, and 

the Rock outcrop is in capability subclass VIIIs. 

48-Hatchet, cold-Rock outcrop complex, 30 to 65 

percent slopes. This map unit is on back slopes of 

mountains. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 4,000 to 4,500 feet. The 

average annual precipitation is about 105 inches. the 

average annual air temperature is about 38 degrees F, 

and the average frost-free period is 75 to 95 days. 

This unit is about 60 percent Hatchet gravelly sandy 

loam, cold, 30 to 65 percent slopes, and 30 percent 

Rock outcrop. The components of this unit are so 

intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are small areas of Cattcreek, 

Tradedollar, and Vanson soils. Also included are small 

areas of Hatchet soils that are less than 20 inches deep to 

bedrock. Included areas make up about 10 percent of the 

total acreage. 

The Hatchet soil is moderately deep and well drained. 

It formed in residuum and colluvium derived dominantly 

from basalt and andesite mixed with volcanic ash. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown gravelly 

sandy loam 3 inches thick. The upper 7 inches of the 

subsoil is dark brown gravelly sandy loam and 

gravelly fine sandy loam, and the lower 10 inches is 

dark yellowish brown extremely cobbly loam. The 

substratum is yellowish brown extremely cobbly clay 

loam 8 inches thick over fractured andesite. Depth to 

andesite or basalt ranges from 20 to 40 inches. 

Permeability of this Hatchet soil is moderate. 

Available water capacity is very low. Effective rooting 

depth is 20 to 40 inches. Runoff is medium to rapid, 

and the hazard of water erosion is moderate to severe. 

Rock outcrop consists of exposed areas of dominantly 

basalt and andesite. Numerous escarpments are in this 

unit. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Western hemlock and Pacific silver fir are the main 

woodland species on the Hatchet soil. On the basis of a

100-year site curve, the mean site index is estimated to 

be 84 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is estimated to be 60 for

western hemlock. The culmination of the mean annual 

increment (CMAI) for western hemlock is 95 cubic feet 

per acre per year at age 60. The areas of Rock outcrop 

make up about 30 percent of this unit and reduce yield 

accordingly. Estimates of the site index or CMAI for 

Pacific silver fir has not been made. Among the trees 

of limited extent are subalpine fir, noble fir, and Douglas 

fir. 

The main limitations for harvesting timber are the 

areas of Rock outcrop, steepness of slope, and snowpack 

in winter. When harvesting timber, steepness of slope 

restricts the use of wheeled and tracked equipment in 

skidding. Cable yarding systems generally are safer and 

disturb the soil less. Rock outcrop may cause breakage 

of timber when felled and can hinder yarding. Avoiding 

Rock outcrop forces yarding and skidding paths to 

converge, which increases compaction and erosion of 

the soil. Use of wheeled and tracked equipment when 

the soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are slippery and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in 

this unit. Snowpack in winter limits the use of 

equipment and restricts access. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 
southwest-facing slopes. Low soil temperature in 

summer, deep snowpack, and a short growing season 

reduce the survival rate of planted and natural seedlings 

and delay their establishment. Reforestation can be 

accomplished by planting noble fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock. Pacific silver fir, and subalpine fir 

occurs infrequently. Logging activities can readily 

displace the surface layer. Seedlings that grow in the 

less fertile subsoil exhibit poor growth. The areas of 

Rock outcrop limit the even distribution of reforestation. 

Because the rooting depth is restricted by underlying 

bedrock, trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

common beargrass.. huckleberry, Oregongrape, princes 

pine, and starflower. 

The Hatchet soil is in capability subclass VIle, and 

the Rock outcrop is in capability subclass Vllls. 

49-Hatchet, cold-Rock outcrop complex, 65 to 90 

percent slopes. This map unit is on back slopes of 

mountains. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 4,000 to 4,500 feet. The 

average annual precipitation is about 105 inches, the 

average annual air temperature is about 38 degrees 

F, and the average frost-free period is 75 to 95 days. 

This unit is about 60 percent Hatchet gravelly sandy 

loam, cold, 65 to 90 percent slopes, and 30 percent Rock 

outcrop. The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Cattcreek, 

Tradedollar, and Vanson soils. Also included are small 

areas of Hatchet soils that are less than 20 inches deep 

to bedrock. Included areas make up about 10 percent 

of the total acreage. 

The Hatchet soil is moderately deep and well drained. It 

formed in residuum and colluvium derived dominantly from 

basalt and andesite mixed with volcanic ash. Typically, the 

surface is covered with a mat of decomposed needles, 

leaves, and twigs 2 inches thick. The surface layer is 

very dark grayish brown gravelly sandy loam 3 inches 

thick. The upper 7 inches of the subsoil is dark brown 

gravelly sandy loam and gravelly fine sandy loam, and the 

lower 10 inches is dark yellowish brown extremely 

cobbly loam. The substratum is yellowish brown 

extremely cobbly clay loam 8 inches thick over fractured 

andesite. Depth to andesite or basalt ranges from 20 to 

40 inches. 

Permeability of this Hatchet soil is moderate. 

Available water capacity is very low. Effective 

rooting 

depth is 20 to 40 inches. Runoff is rapid, and 

the hazard of water erosion is severe. 

Rock outcrop consists of exposed areas of dominantly 

basalt and andesite. Numerous escarpments are in this 

unit. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Western hemlock and Pacific silver fir are the main 

woodland species on the Hatchet soil. On the basis of a 

100-year site curve, the mean site index is estimated to be 

84 for western hemlock. On the basis of a 50-year site 

curve, the mean site index is estimated to be 60 for 

western hemlock. The culmination of the mean annual 

increment (CMAI) for western hemlock is 95 cubic feet per 

acre per year at age 60. The areas of Rock outcrop 

make up about 30 percent of this unit and reduce 

yield accordingly. Estimates of the site index or CMAI for 

Pacific silver fir have not been made. Among the trees of 

limited extent are subalpine fir, noble fir, and Douglas fir. 

The main limitations for harvesting timber are Rock 

outcrop, steepness of slope, and snowpack in winter. 

Cable yarding systems generally are used on this unit. 

Rock outcrop may cause breakage of timber when felled 

and can hinder yarding. Avoiding Rock outcrop forces 

yarding paths to converge, which increases compaction 

and erosion of the soil. Unsurfaced roads and skid trails 

are slippery and can be impassable when wet. Logging 

roads require suitable surfacing for yearround use. Rock for 

road construction is readily available in this unit, Logging 

roads generally need full bench construction and require 

frequent maintenance. Snowpack in winter limits the 

use of equipment and restricts access. Establishing 

plant cover on steeper slopes that have been cut or filled 

reduces erosion. Steep yarding paths, skid trails, and 

firebreaks are subject to rilling and gullying unless plant 

cover is maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff.

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Low soil temperature in 

summer, deep snowpack, and a short growing season 

reduce the survival rate of planted and natural seedlings 

and delay their establishment. Reforestation can be 

accomplished by planting noble fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by western hemlock, Pacific silver fir, and subalpine fir 

occurs infrequently. Logging activities can readily 

displace the surface layer. Seedlings that grow 
in the less fertile subsoil exhibit poor growth. The areas of 

Rock outcrop limit the even distribution of reforestation. 

Because the rooting depth is restricted by the underlying 

bedrock, trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

common beargrass, huckleberry, Oregongrape, princes 

pine, and starflower. 

The Hatchet soil is in capability subclass VIIe, and 

the Rock outcrop is in capability subclass Vllls. 

50-Hesson clay loam, 5 to 15 percent slopes. This 

very deep. well drained soil is or terraces. It formed in 

mixed alluvium derived dominantly from quartzite and 

basic igneous rock. The native vegetation is mainly 

mixed conifers and grasses. Elevation is 400 to 1,000 

feet. The average annual precipitation is about 70 inches, 

the average annual air temperature is about 50 degrees F, 

and the average frost-free period is 160 to 220 days. 

Typically, the surface layer is dark brown clay loam 19 

inches thick. The upper 28 inches of the subsoil is dark 

reddish brown clay loam, and the lower part to a depth of 

60 inches or more is dark reddish brown clay. 

Included in this unit are small areas of Mossyrock soils 

on high terraces and Mountzion, Skoly, and Stevenson 

soils on foot slopes of mountains. Also included are small 

areas of Hesson soils that are less than 35 percent clay. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this Hesson soil is slow. Available water 

capacity is high. Effective rooting depth is 60 inches or 

more. Runoff is slow, and the hazard of water erosion is 

slight. 

This unit is used for hayland, pastureland, cropland, 

woodland, wildlife habitat, recreation, and homesites. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet periods 

help to keep the pasture in good condition and to protect 

the soil from erosion. Mowing at least twice a year helps to 

maintain uniform growth and discourages selective 

grazing. 

This unit is well suited to small grain. Returning all crop 

residue to the soil and using a cropping system that 

includes grasses, legumes, or grass-legume mixtures help 

to maintain fertility and tilth. Practices that can be used to 

control erosion include early fall seeding, stubble-mulch 

tillage, and construction of terraces, diversions, and 

grassed waterways. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site 

curve, the mean site index is estimated to be 160 for 

Douglas fir, and on the basis of a 50-year site curve, 

the mean site index is estimated to be 120. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 170 cubic feet per acre per year at age 

65. Estimates of the site index or CMAI for red alder 

have not been made. Among the trees of limited extent 

are bigleaf maple, western hemlock, and western 

redcedar. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and sticky. and they can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round use. Rock for road construction 

is not readily available in this unit. Disturbance of the 

protective layer of duff can be reduced with the careful use 

of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red alder 

occurs readily. If the canopy is opened, brush invades and 

can prevent the establishment of seedlings unless 

controlled. 

Among the common forest understory plants are vine 

maple, common snowberry, salal, Oregongrape, 

salmonberry, thimbleberry, Oregon oxalis, and fat false 

Solomons seal. 

This unit is well suited to homesite development. The 

main limitations are steepness of slope, the hazard of 

erosion, low soil strength, and shrink-swell potential. 

Preserving the existing plant cover during construction 

helps to control erosion. Topsoil can be stockpiled and 

used to reclaim areas disturbed during construction. 

Buildings and roads should be designed to offset the 

limited ability of the soil in this unit to support a load. 

Access roads should be designed to provide adequate 

cut-slope grade, and drains are needed to control 

surface runoff and keep soil losses to a minimum. 

If this unit is used for septic tank absorption fields, the 

limitation of restricted permeability can be overcome by 

increasing the size of the absorption field. The restricted 

permeability increases the possibility of failure of septic 

tank absorption fields. Use of sandy backfill for the trench 

and long absorption lines helps to compensate for the 

restricted permeability. Steepness of slope is a concern 

when installing septic tank absorption fields. Absorption 

lines should be installed on the contour. 

This map unit is in capability subclass IIIe. 
51-Hesson clay loam, 15 to 30 percent slopes.

This very deep, well drained soil is on terraces. It formed 

in mixed alluvium derived dominantly from quartzite and 

basic igneous rock. The native vegetation is mainly mixed 

conifers and grasses. Elevation is 400 to 1,000 feet. The 

average annual precipitation is about 70 inches. the 

average annual air temperature is about 50 degrees F, 

and the average frost-free period is 160 to 220 days. 

Typically, the surface layer is dark brown clay loam 19 

inches thick. The upper 28 inches of the subsoil is dark 

reddish brown clay loam, and the lower part to a depth of 

60 inches or more is dark reddish brown clay. 

Included in this unit are small areas of Mossyrock soils 

on high terraces and Mountzion, Skoly, and Stevenson 

soils on foot slopes and back slopes of mountains. Also 

included are small areas of Stevenson and Hesson soils 

that are less than 35 percent clay. Included areas make 

up about 10 percent of the total acreage. 

Permeability of this Hesson soil is slow. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for hayland, pastureland, woodland, 

wildlife habitat, recreation, and homesites. 

This unit is well suited to use as hayland and 

pastureland. The main limitations are steepness of slope 

and the hazard of erosion. Erosion can be controlled by 

growing pasture. The use of equipment is limited by 

steepness of slope. Proper stocking rates, pasture 

rotation, and restricted grazing during wet periods help 

to keep the pasture in good condition and to protect the 

soil from erosion. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site curve, 

the mean site index is estimated to be 160 for Douglas 

fir, and on the basis of a 50-year site curve, the mean site 

index is estimated to be 120. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 170 

cubic feet per acre per year at age 65. Estimates of the 

site index or CMAI for red alder have not been made. 

Among the trees of limited extent are bigleaf maple, 

western hemlock, and western redcedar. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and sticky and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not 

readily available in this unit. Disturbance of the 

protective layer of duff can be reduced with the careful 

use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by red alder occurs readily. If the canopy is opened, 

brush invades and can prevent the establishment of 

seedlings unless controlled. 

Among the common forest understory plants are vine

maple, common snowberry, salal, Oregongrape, 

salmonberry, thimbleberry, Oregon oxalis, and fat false 

Solomons seal. 

The main limitations of this unit for use as homesites are 

steepness of slope, low soil strength, shrink-swell 

potential, and the hazard of erosion. The hazard of 

erosion is increased if the soil is left exposed during site 

development. Preserving the existing plant cover during 

construction helps to control erosion. Topsoil can be 

stockpiled and used to reclaim areas disturbed during 

construction. Plant cover can be established and 

maintained through proper fertilizing, seeding, mulching, 

and shaping of the slopes. Buildings and roads should be 

designed to offset the limited ability of the soil in this unit 

to support a load. Access roads should be designed to 

provide adequate cut-slope grade, and drains are 

needed to control surface runoff and keep soil losses to 

a minimum. Buildings and roads should be designed to 

offset the effects of shrinking and swelling. 

If this unit is used for septic tank absorption fields, the 

limitation of restricted permeability can be overcome by 

increasing the size of the absorption field. The restricted 

permeability and steepness of slope increase the 

possibility of failure of septic tank absorption fields. Use of 

sandy backfill for the trench and long absorption lines 

helps to compensate for the restricted permeability. During 

the rainy season, effluent from onsite sewage disposal 

systems may seep at points downslope. 

This map unit is in capability subclass lVe. 

52-Hesson clay loam, 30 to 40 percent slopes. This 

very deep, well drained soil is on terrace escarpments. 

It formed in mixed alluvium derived dominantly from 

quartzite and basic igneous rock. The native vegetation 

is mainly mixed conifers and grasses. Elevation is 400 

to 1,000 feet. The average annual precipitation is about 

70 inches, the average annual air temperature is about 

50 degrees F, and the average frost-free period is 160 

to 220 days. 
Typically, the surface layer is dark brown clay loam 

19 inches thick. The upper 28 inches of the subsoil is 

dark reddish brown clay loam, and the lower part to a 

depth of 60 inches or more is dark reddish brown clay. 

Included in this unit are small areas of Mountzion, 

Skoly, and Stevenson soils on back slopes of 

mountains. Also included are small areas Hesson soils 

that are less than 35 percent clay. Included areas make 

up about 10 percent of the total acreage. 

Permeability of this Hesson soil is slow. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland, wildlife habitat, and 

recreation. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site 

curve. the mean site index is estimated to be 160 for 

Douglas fir, and on the basis of a 50-year site curve, the 

mean site index is estimated to be 120. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 170 cubic feet per acre per year at age 65. 

Estimates of the site index or CMAI for red alder have 

not been made. Among the trees of limited extent are 

bigleaf maple, western hemlock, and western redcedar. 

The main limitation for harvesting timber is steepness 

of slope. Use of wheeled and tracked equipment when 

the soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are soft and sticky and can be impassable when wet. 

Logging roads require suitable surfacing for yearround 

use. Rock for road construction is not readily available in 

this unit. Establishing plant cover on steeper slopes that 

have been cut or filled reduces erosion. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red 

alder occurs readily. If the canopy is opened, brush 

invades and can prevent the establishment of seedlings 

unless controlled. 

Among the common forest understory plants are vine 

maple, common snowberry, salal, Oregongrape, 

salmonberry, thimbleberry, Oregon oxalis. and fat false 

Solomons seal. 

This map unit is in capability subclass Vle. 

53-Histic Cryaquepts, 0 to 5 percent slopes. 

These very deep, very poorly drained and poorly drained 

soils are in depressional areas on mountains and 

terraces. They formed in aerially deposited volcanic ash 

and pumice. The native vegetation is mainly grasses, 

shrubs, and scattered conifers. Elevation is 2,500 to 

4,000 feet. The average annual precipitation is about 125 

inches, the average annual air temperature is about 38 

degrees F, and the average frost-free period is 60 to 80 

days. 

No single profile is typical of Histic Cryaquepts, but one 

commonly observed in the survey area has a mat of very 

dark brown muck 13 inches thick. The surface layer is 

very dark gray loamy sand 8 inches thick. The subsoil is 

gray sandy loam 10 inches thick. The next 4 inches is a 

buried layer of very dark brown muck. The substratum 

to a depth of 60 inches or more is very dark brown 

gravelly coarse sand. 

Included in this unit are small areas of Lonestar soils 

on ridgetops of mountains and Shoestring and St. 

Helens soils on terraces. Also included are small areas

of moderately well drained soils and ponded soils. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of these Histic Cryaquepts is moderate. 

Available water capacity is high. Effective rooting depth is 

limited by a seasonal high water table that is at a depth 

of 0 to 2 feet in November to July. Runoff is slow, and the 

hazard of water erosion is slight. 

This unit is used for wildlife habitat and recreation. Itis 

poorly suited to the production of timber. 

Common plants include rose, sedges, rushes, and 

scattered Pacific silver fir, western redcedar, willow, and 

Sitka alder. 

This map unit is in capability subclass Vlw. 

54-Hoffstadt very gravelly sandy loam, 2 to 30 

percent slopes. This deep, well drained soil is on foot 

slopes and back slopes of mountains. It formed in 

colluvium derived dominantly from basic igneous rock 

mixed with volcanic ash. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 1,800 to 2,600 

feet. The average annual precipitation is about 80 

inches, the average annual air temperature is about 43

degrees F, and the average frost-free period is 150 to 180 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches 

thick. The surface layer is dark brown very gravelly 

sandy loam 4 inches thick. The subsoil is dark brown 
very cobbly sandy loam 32 inches thick. The substratum is 

dark brown extremely stony sandy loam 19 inches thick 

over fractured basalt. Depth to bedrock ranges from 40 to 

60 inches. 

Included in this unit are small areas of Hatchet and 

Vanson soils. Also included are small areas of 

Cinnamon soils, Rock outcrop. and soils that are less 

than 35 percent rock fragments. Included areas make 

up about 15 percent of the total acreage. 

Permeability of this Hoffstadt soil is moderate. Available 

water capacity is low. Effective rooting depth is 40 to 60 

inches. Runoff is medium, and the hazard of water 

erosion is moderate. 

This unit is used for woodland, wildlife habitat, 

recreation. and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 150 for Douglas 

fir and 155 for western hemlock. On the basis of a 50-

year site curve, the mean site index is 116 for Douglas 

fir and 108 for western hemlock. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 158 

cubic feet per acre per year at age 50, and the CMAI for 

western hemlock is 246 cubic feet at age 50. Among the 

trees of limited extent are red alder, western redcedar. 

and bigleaf maple. 

The main limitation for harvesting timber is occasional 

snowpack. Unsurfaced roads and skid trails are soft and 

slippery and can be impassable when wet. Logging. 

roads require suitable surfacing for year-round use. Rock 

for road construction is readily available in this; unit. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Disturbance of the protective 

layer of duff can be reduced with the careful use of wheeled 

and tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir seedlings. If seed 

trees, are present, natural reforestation of cutover areas 

by. western hemlock occurs readily. Droughtiness of the 

surface layer reduces. seedling survival, especially on 

south-. and southwest-facing slopes. 

Among the common forest understory plants are red 

huckleberry, Oregon oxalis, western swordfern, deer 

fern, trailing blackberry, Pacific trillium, and 

Oregongrape. 

This map unit is in capability subclass IVe. 

55-Hoffstadt very gravelly sandy loam, 30 to 65 

percent slopes. This deep, well drained soil is on back 

slopes of mountains. It formed in colluvium derived 

dominantly from basic igneous rock mixed with volcanic 

ash. The native vegetation is mainly mixed conifers and

shrubs. Elevation is 1,800 to 2,600 feet. The average 

annual precipitation is about 80 inches, the average 

annual air temperature is about 43 degrees F, and the 

average frost-free period is 150 to 180 days. 

Typically, the surface is covered with a mat of 

 decomposed needles, leaves, and twigs 2 inches thick. 

 The surface layer is dark brown very gravelly sandy 

loam 4 inches thick. The subsoil is dark brown very 

 cobbly sandy loam 32 inches thick. The substratum is 

 dark brown extremely stony sandy loam 19 inches thick 

 over fractured basalt. Depth to bedrock ranges from 40 

to 60 inches. 

Included in this unit are small areas of Hatchet and 

Vanson soils. Also included are small areas of Rock 

outcrop and soils that are less than 35 percent rock 

fragments. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this Hoffstadt soil is moderate. 

Available water capacity is low. Effective rooting depth is 

40 to 60 inches. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 150 for Douglas fir 

and 155 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is 116 for Douglas fir and 

108 for western hemlock. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 158 cubic feet 

per acre per year at age 60, and the CMAI for western 

hemlock is 246 cubic feet at age 50. Among, the trees of 

limited extent are red alder, western redcedar, and, bigleaf 

maple. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and Cracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

during rainy periods. Logging roads require suitable 

surfacing. for year-round use. Rock for road construction 

is readily available in this unit. Occasional snowpack 

hinders the use of equipment and limits access in winter. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rifling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. 

Seedling mortality is the main concern in. the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed 
trees are present, natural reforestation of cutover areas 

by western hemlock occurs readily. Droughtiness of the 

surface Layer reduces seedling survival, especially on 

south- and southwest-facing slopes. 

Among the common forest understory plants are red 

huckleberry, Oregon oxalis, western swordfern, deer fern, 

trailing blackberry. Pacific trillium, and Oregongrape. 

This map unit is in capability subclass Vlle. 

56-Hood loam, 15 to 30 percent slopes. This 

very deep. well drained soil is on dissected terraces. It 

formed in lacustrine deposits. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 320 to 

560 feet: The average annual precipitation is about 43 

inches, the average annual air temperature is about 49 

degrees F, and the average frost-free period is 150 to 

180 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick, 

The surface layer is dark brown loam 8 inches thick. 

The subsoil to a depth of 60 inches or more is dark 

brown and dark yellowish brown loam. 

Included in this unit are small areas of McElroy and 

Underwood soils on foot slopes of mountains. Also 

included are small areas of somewhat poorly drained 

soils and Hood soils that have slopes of less than 15 

percent. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this Hood soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 inches 

or more. Runoff is medium, and the hazard of water 

erosion is moderate. 

Most areas of this unit are used for woodland, 

pastureland., wildlife habitat, and recreation. A few areas 

are used as homesites. 

Douglas fir is the main woodland species on this unit. 

On the basis of a 100-year site curve, the mean site 

index is 147 for Douglas fir, and on the basis of a 50-year 

site curve, the mean site index is 112. The culmination of 

the mean annual increment (CMAI) for Douglas fir is 154 

cubic feet per acre per year at age 60. Among the trees 

of limited extent are grand fir and ponderosa pine. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available 

in this unit. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by ponderosa pine 

and grand fir occurs periodically. If the canopy is 

opened, brush invades and can prevent the 

establishment of planted Douglas fir seedlings and natural 

reforestation by ponderosa pine and can delay natural 

reforestation by grand fir unless controlled. 

Among the common forest understory plants are vine 

maple, western hazel, Pacific dogwood, Oregongrape, 

common snowberry, western brackenfern, and 

creambush oceanspray. 

If this unit is used as pastureland, the main limitation 

is steepness of slope. Grazing when the soil is wet results 

in compaction of the surface layer, poor tilth, and 

excessive runoff. The use of equipment is limited by 

steepness of slope. Proper grazing practices, weed 

control, and fertilizer are needed to ensure maximum 

quality of forage. 

The main limitations of this unit for use as homesites 

are steepness of slope and the hazard of erosion in the 

steeper areas. Only the part of the site that is used for 

construction should be disturbed. Preserving the existing 

plant cover during construction helps to control erosion. 

Plant cover can be established and maintained through 

proper fertilizing, seeding, mulching, and shaping of the 

slopes. Slope is a concern in installing septic tank 

absorption fields. Absorption lines should be installed on 

the contour, 

The soil in this unit is susceptible to frost action, 

which may limit construction of roads and streets. Access 

roads should be designed to provide adequate cut-slope 

grade, and drains are needed to control surface runoff 

and keep soil losses to a minimum. 

This map unit is in capability subclass IVe. 

57-Kinney loam, 5 to 30 percent slopes. This very 

deep, well drained soil is on foot slopes and back slopes 

of mountains. It formed in residuum and colluvium 

derived dominantly from granodiorite and volcanic ash. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 600 to 2,300 feet. The average 

annual precipitation is about 90 inches, the average 

annual air temperature is about 48 degrees F, and the 

average frost-free period is 125 to 145 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 12 inches thick. 

The upper 10 inches of the subsoil is strong brown 
gravelly clay loam, and the lower 6 inches is strong 

brown clay loam. The substratum to a depth of 60 

inches or more is yellowish brown loam. 

Included in this unit are small areas of Dougan soils 

on ridgetops and Aschoff, Mountzion, and Skoly soils. 

Also included are small areas of soils that are shallow to 

bedrock and Rock outcrop. Included areas make up 

about 15 percent of the total acreage. 

Permeability of this Kinney soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland. wildlife habitat, 

recreation. and watershed. 

Douglas fir, red alder, and western hemlock are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 146 for 

Douglas fir and 147 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 117 for 

Douglas fir and 105 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 

153 cubic feet per acre per year at age 60, and the CMAI 

for western hemlock is 232 cubic feet at age 50. 

Estimates of the site index or CMAI for red alder have 

not been made. Among the trees of limited extent are 

western redcedar and noble fir. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Occasional snowpack hinders the 

use of equipment and limits access in winter. Disturbance 

of the protective layer of duff can be reduced with the 

careful use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock and red alder occurs readily. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, salal, red huckleberry, cascara buckthorn, 

Oregongrape, western hazel, trailing blackberry, Oregon 

fairybells, Oregon oxalis, Pacific trillium, western 

swordfern, and western brackenfern. 

This map unit is in capability subclass IVe. 

58-Kinney loam, 30 to 65 percent slopes. This 

very deep, well drained soil is on back slopes of 

mountains. It formed in residuum and colluvium derived 

dominantly from granodiorite and volcanic ash. The 

native vegetation is mainly mixed conifers and shrubs. 

Elevation is 600 to 2,300 feet. The average annual 

precipitation is about 90 inches, the average annual air 

temperature is about 48 degrees F, and the average 

frost-free period is 125 to 145 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 12 inches thick. 

The upper 10 inches of the subsoil is strong brown 

gravelly clay loam, and the lower 6 inches is strong 

brown clay loam. The substratum to a depth of 60 

inches or more is yellowish brown loam. 

Included in this unit are small areas of Dougan soils 

on ridgetops and Aschoff, Mountzion, and Skoly soils. 

Also included are small areas of soils that are shallow 

to bedrock, Rock outcrop, and Kinney soils that have 

slopes of less than 30 percent. Included areas make 

up about 15 percent of the total acreage. 

Permeability of this Kinney soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is rapid, and the hazard of water 

erosion is severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir, red alder, and western hemlock are the 

main woodland species on this unit. On the basis of a 

100-year site curve. the mean site index is 146 for 

Douglas fir and 147 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 117 for 

Douglas fir and 105 for western hemlock. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 153 cubic feet per acre per year at age 

60, and the CMAI for western hemlock is 232 cubic feet 

at age 50. Estimates of the site index or CMAI for red 

alder and western hemlock have not been made. 

Among the trees of limited extent are western redcedar 

and noble fir. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and slippery and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for 
road construction is not readily available in this unit. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails. and firebreaks are subject to 

rilling and gullying unless plant cover is maintained or 

adequate water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless controlled.

Among the common forest understory plants are vine 

maple, salal, red huckleberry, cascara buckthorn, 

Oregongrape, western hazel, trailing blackberry, Oregon 

fairybells, Oregon oxalis, Pacific trillium, western 

swordfern, and western brackenfern. 

This map unit is in capability subclass VIIe. 

59-Kinney loam, 30 to 65 percent east slopes. This 

very deep, well drained soil is on east-facing back slopes 

of mountains. It formed in residuum and colluvium 

derived dominantly from granodiorite and volcanic ash. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 1,000 to 2,300 feet. The average 

annual precipitation is about 90 inches, the average 

annual air temperature is about 48 degrees F, and the 

average frost-free period is 125 to 145 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 12 inches thick. 

The upper 10 inches of the subsoil is strong brown 

gravelly clay loam, and the lower 6 inches is strong brown 

clay loam. The substratum to a depth of 60 inches or more 

is yellowish brown loam. 

Included in this unit are small areas of Dougan soils on 

ridgetops and Aschoff. Mountzion, and Skoly soils. Also 

included are small areas of soils that are shallow to 

bedrock, Rock outcrop, and Kinney soils that have 

slopes of less than 30 percent. Included areas make up 

about 15 percent of the total acreage. 

Permeability of this Kinney soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more, Runoff is rapid, and the hazard of water 

erosion is severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir, western hemlock, and noble fir are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 117 for Douglas 

fir. On the basis of a 50-year site curve, the mean site 

index is 94 for Douglas fir. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 110 cubic feet 

per acre per year at age 60. Estimates of the site index or 

CMAI for western hemlock and noble fir have not been 

made. Among the trees of limited extent are red alder and 

western redcedar. Cold, easterly winter winds reduce the 

productivity of this unit. 

The main limitation for harvesting timber is steepness of 

slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and slippery 

and can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Snowpack 

hinders the use of equipment and limits access in winter. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir or Douglas fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock occurs periodically. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by noble fir and western hemlock 

unless controlled. 

Among the common forest understory plants are vine 

maple, salal, red huckleberry, cascara buckthorn, 

Oregongrape, western hazel, trailing blackberry, Oregon 

fairybells, Oregon oxalis, Pacific trillium, western swordfern, 

and western brackenfern. 

This map unit is in capability subclass VIle. 

60-Lithic Umbric Vitrandepts, 0 to 15 percent 

slopes. These very shallow and shallow, well drained soils 

are on recent lava flows. They formed in volcanic ash and 

pumice over andesite. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 800 to 4,000 

feet. The average annual precipitation is about 125 

inches. the average annual air temperature is about 45 

degrees F, and the average frost-free period is 100 to 

115 days. 

No single profile is typical of Lithic Umbric 
Vitrandepts, but one commonly observed in the survey 

area has a surface layer of very dark brown sandy loam 2 

inches thick. The subsoil is very dark grayish brown very 

cindery loamy sand 4 inches thick over andesitic lava flow. 

Depth to bedrock ranges from 5 to 15 inches. 

Included in this unit are small areas of Cinnamon soils 

on foot slopes, Polepatch soils on fans, and St. Helens 

soils on terraces. Also included are small areas of Rock 

outcrop and soils that are moderately deep. Included areas 

make up about 5 percent of the total acreage. 

Permeability of these Lithic Umbric Vitrandepts is 

moderately rapid. Available water capacity is very low. 

Effective rooting depth is 5 to 15 inches. Runoff is slow, 

and the hazard of water erosion is slight. 

This unit is used for wildlife habitat, recreation, and 

watershed. 

This unit is poorly suited to the production of timber. 

Common plants include salal. huckleberry, 

kinnikinnick, creambrush oceanspray, common 

beargrass, and scattered lodgepole pine, western 

hemlock, and Douglas fir. 

This map unit is in capability subclass VIls. 

61-Lonestar cindery sandy loam, 5 to 30 percent 

slopes. This very deep, well drained soil is on foot slopes, 

back slopes, and ridgetops of mountains. It formed in 

volcanic ash and pumice over colluvium derived from 

basic igneous rock. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 2,800 to 4,500 feet. The 

average annual precipitation is about 125 inches, the 

average annual air temperature is about 40 degrees F, and 

the average frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

very dark grayish brown cindery sandy loam. The upper 7 

inches of the subsoil is dark brown cindery sandy loam, and 

the lower 4 inches is grayish brown loamy sand. The 

substratum is yellowish brown cindery loamy sand about 

10 inches thick. The next layer is a buried subsoil of dark 

yellowish brown gravelly loam 23 inches thick. Below this to 

a depth of 60 inches or more is a buried substratum of 

reddish yellow silt loam. 

Included in this unit are small areas of Cinnamon, 

Hatchet. Swift, and Vanson soils. Also included are 

small areas of poorly drained soils in depressional areas. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this Lonestar soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is slow, and the hazard of 

water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and Douglas fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 112 for 

western hemlock and for Douglas fir. On the basis of a 

50-year site curve, the mean site index is 79 for western 

hemlock and 84 for Douglas fir. The culmination of the 

mean annual increment (CMAI) for western hemlock is 

164 cubic feet per acre per year at age 50, and the CMAI 

for Douglas fir is 101 cubic feet at age 60. Estimates of 

the site index or CMAI for Pacific silver fir have not been 

made. Among the trees of limited extent are noble fir and 

western redcedar. Areas on ridgetops that are subject to 

strong, persistent winds are less productive than other 

areas of this unit. 

The main limitation for harvesting timber is snowpack 

in winter. Use of wheeled and tracked equipment when 

the soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are soft and can be impassable when wet. Logging 

roads require suitable surfacing for year-round use. Rock 

for road construction is not readily available in this unit. 

Snowpack in winter limits the use of equipment and 

restricts access. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Reforestation can be accomplished by planting noble 

fir and Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. The mortality rate 

of seedlings is higher in areas on ridgetops that are subject 

to strong, persistent winds than in other areas of this unit. 

Among the common forest understory plants are 

huckleberry, lupine, rose, sedges, and common 

beargrass. 

This map unit is in capability subclass Vle. 

62-Lonestar cindery sandy loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back slopes 

of mountains. It formed in volcanic ash and pumice over 

colluvium derived from basic igneous rock. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 2,800 to 4,500 feet. The average annual precipitation is 

about 120 inches, the average annual air temperature is 

about 40 degrees F, and the average frost-free period is 

75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 
Where mixed to a depth of 7 inches, the surface layer is 

very dark grayish brown cindery sandy loam. The upper 7 

inches of the subsoil is dark brown cindery sandy loam. 

and the lower 4 inches is grayish brown loamy sand. The 

substratum is yellowish brown very cindery loamy sand 

about 10 inches thick. The next layer is a buried subsoil of 

dark yellowish brown gravelly loam 23 inches thick. Below 

this to a depth of 60 inches or more is a buried substratum 

of reddish yellow silt loam. 

Included in this unit are small areas of Cinnamon, 

Hatchet, Swift, and Vanson soils. Also included are 

small areas of Rock outcrop. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Lonestar soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 inches 

or more. Runoff is medium, and the hazard of water 

erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and Douglas fir 

are the main woodland species on this unit. On the 

basis of a 100-year site curve, the mean site index is 

112 for western hemlock and for Douglas fir. On the 

basis of a 50-year site curve, the mean site index is 79 for 

western hemlock and 84 for Douglas fir. The culmination of 

the mean annual increment (CMAI) for western hemlock is 

164 cubic feet per acre per year at age 50, and the CMAI 

for Douglas fir is 101 cubic feet at age 60. Estimates of 

the site index or CMAI for Pacific silver fir have not been 

made. Among the trees of limited extent are noble fir and 

western redcedar. Areas on ridgetops that are subject to 

strong, persistent winds are less productive than other 

areas of this unit. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope, which restricts 

the use of wheeled and tracked equipment in skidding. 

Cable yarding systems generally are safer and disturb the 

soil less. Use of wheeled and tracked equipment when 

the soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are soft and can be impassable when wet. Logging 

roads require suitable surfacing for year-round use. Rock 

for road construction is not readily available in this unit. 

Snowpack in winter limits the use of equipment and 

restricts access. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths. skid trails. and firebreaks are subject to 

rilling and gullying unless plant cover is maintained or 

adequate water bars are provided. 

Reforestation can be accomplished by planting noble 

fir or Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. The 

mortality rate of seedlings is higher in areas on ridgetops 

that are subject to strong, persistent winds than in other 

areas of this unit. 

Among the common forest understory plants are 

huckleberry, lupine, rose, sedges, and common 

beargrass. 

This map unit is in capability subclass VIIe. 

63-Lonestar cindery sandy loam, 65 to 90 percent 

slopes. This very deep, well drained soil is on back slopes 

of mountains. It formed in volcanic ash and pumice over 

colluvium derived from basic igneous rock. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 2,800 to 4,500 feet. The average annual precipitation 

is about 125 inches, the average annual air temperature 

is about 40 degrees F, and the average frost-free period 

is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

very dark grayish brown cindery sandy loam. The upper 7 

inches of the subsoil is dark brown cindery sandy loam, 

and the lower 4 inches is grayish brown loamy sand. The 

substratum is yellowish brown very cindery loamy sand 10 

inches thick. The next layer is a buried subsoil of dark 

yellowish brown gravelly loam 23 inches thick. Below this 

to a depth of 60 inches or more is a buried substratum of 

reddish yellow silt loam. 

Included in this unit are small areas of Cinnamon, 

Hatchet, Swift, and Vanson soils. Also included are 

small areas of Rock outcrop and Lonestar soils that are 

less than 40 inches deep to bedrock. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Lonestar soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and Douglas fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is 112 for 

western hemlock and for Douglas fir. On the basis of a 

50-year site curve, the mean site index is 79 for western 

hemlock and 84 for Douglas fir. The culmination of the 

mean annual increment (CMAI) for western hemlock is 

164 cubic feet per acre per year at age 50, and the 

CMAI for Douglas fir is 101 cubic feet at age 60. 

Estimates of the site index or CMAI for Pacific silver fir 

have not been made. Among the trees 
of limited extent are noble fir and western redcedar. Areas 

on ridgetops that are subject to strong, persistent winds 

are less productive than other areas of this unit. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. Cable yarding 

systems generally are used on this unit. Unsurfaced roads 

and skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Logging roads generally need full bench 

construction and require frequent maintenance. 

Snowpack in winter limits the use of equipment and 

restricts access. Establishing plant cover on steeper slopes 

that have been cut or filled reduces erosion. Following 

road construction and clearcutting, road failures and 

landslides can occur. Steep yarding paths, skid trails, 

and firebreaks are subject to rilling and gullying unless 

plant cover is maintained or adequate water bars are 

provided. Harvesting systems that lift logs entirely off the 

ground reduce the disturbance of the protective layer of 

duff. 

Reforestation can be accomplished by planting noble 

fir or Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. 

Among the common forest understory plants are 

huckleberry, lupine, rose, sedges, and common 

beargrass. 

This map unit is in capability subclass VIIe. 

64-McBee silt loam. This very deep, moderately well 

drained soil is on flood plains and low river terraces. It 

formed in mixed alluvium derived dominantly from basalt 

and andesite. Slope is 0 to 3 percent. The native 

vegetation is mainly grasses and scattered conifers and 

hardwoods. Elevation is 50 to 200 feet. The average 

annual precipitation is about 60 inches, the average 

annual air temperature is about 50 degrees F, and the 

average frost-free period is 160 to 180 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark brown and very dark grayish 

brown silt loam 13 inches thick. The upper 18 inches of 

the subsoil is very dark grayish brown silt loam and dark 

grayish brown silty clay loam, and the lower 12 inches is 

mottled, brown silt loam. The substratum to a depth of 60 

inches or more is mottled, brown silt loam. 

Included in this unit are small areas of Washougal 

soils on terraces and Pilchuck soils. Also included are 

small areas of somewhat poorly drained and poorly 

drained soils in depressional areas. Included areas 

make up about 15 percent of the total acreage. 

Permeability of this McBee soil is moderate. Available 

water capacity is high. Effective rooting depth 

is limited by a seasonal high water table that is at a 

depth of 3 to 4 feet from March to May. Runoff is slow, 

and the hazard of water erosion is slight. This soil is 

subject to rare periods of flooding. 

This unit is used as hayland, pastureland, woodland, 

and wildlife habitat. 

This unit is well suited to hay and pasture. The main 

limitations are seasonal soil wetness and the hazard of 

flooding. Wetness limits the choice of plants and the 

period of cutting or grazing and increases the risk of 

suffocation from water in the root zone. Proper grazing 

practices, weed control, and fertilizer are needed to 

ensure maximum quality of forage. 

Douglas fir, black cottonwood, and red alder are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 111 for Douglas fir, and on the basis of a 50-year site 

curve, the mean site index is 90. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 100 

cubic feet per acre per year at age 60. Estimates of the site 

index or CMAI for red alder and black cottonwood have 

not been made. Among the trees of limited extent are 

western redcedar and western hemlock. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available 

in this unit. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red 

alder occurs readily. If the canopy is opened, brush 

invades and can prevent the establishment of Douglas fir 

seedlings unless controlled. 

Among the common forest understory plants are 

rose, spirea, willow, blackberry, grasses, and sedges. 

This map unit is in capability subclass IIIw. 

65-McDoug silt loam. This very deep, moderately 

well drained soil is on flood plains. It formed in mixed 

alluvium derived dominantly from basic igneous rock. 

Slope is 0 to 3 percent. The native vegetation is mainly .
grasses and scattered conifers and hardwoods. 

Elevation is 800 to 1,600 feet. The average annual 

precipitation is about 50 inches, the average annual air 

temperature is about 48 degrees F, and the average 

frost-free period is 130 to 150 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown and dark 

brown silt loam 12 inches thick. The subsoil is dark 

brown and dark yellowish brown clay loam and loam 26 

inches thick. The substratum to a depth of 60 inches or 

more is mottled, dark yellowish brown clay loam. 

Included in this unit are small areas of Stabler and 

Washougal soils on terraces and Underwood soils on 

back slopes of mountains. Also included are small areas 

of Riverwash and poorly drained soils in depressional 

areas. Included areas make up about 10 percent of the 

total acreage. 

Permeability of this McDoug soil is moderate. 

Available water capacity is high. Effective rooting depth 

is limited by a seasonal high water table that is at a 

depth of 2.5 to 3.5 feet at times from March through May. 

Runoff is slow, and the hazard of water erosion is slight. 

This soil is subject to rare periods of flooding. 

This unit is used as hayland, pastureland, woodland, 

and wildlife habitat. 

This unit is well suited to use as hayland and 

pastureland. The main limitations are seasonal soil 

wetness and the hazard of flooding. Grazing when the 

soil is wet results in compaction of the surface layer, 

poor tilth, and excessive runoff. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition. 

Mowing at least twice a year helps to maintain uniform 

growth and discourages selective grazing. 

Douglas fir, red alder, and black cottonwood are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 144 for Douglas fir, and on the basis of a 50-year 

site curve. the mean site index is estimated to be 110. 

The culmination of the mean annual increment (CMAI) for 

Douglas fir is 150 cubic feet per acre per year at age 60. 

Estimates of the site index or CMAI for red alder and 

black cottonwood have not been made. Among the trees 

of limited extent are western redcedar and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available 

in this unit. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red 

alder occurs readily. If the canopy is opened, brush 

invades and can prevent the establishment of Douglas fir 

seedlings unless controlled. 

Among the common forest understory plants are vine 

maple, hawthorn, wild rose, blackberry, thimbleberry, 

and snowberry. 

This map unit is in capability subclass IIIw. 

66-McElroy gravelly loam, 5 to 15 percent 

slopes. This very deep, well drained soil is on foot slopes 

of mountains. It formed in colluvium derived dominantly 

from basalt with a mantle of volcanic ash. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 400 to 2,300 feet. The average annual 

precipitation is about 55 inches, the average annual air 

temperature is about 46 degrees F. and the average 

frost-free period is 105 to 125 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown gravelly loam 10 inches 

thick. The subsoil to a depth of 60 inches or more is 

dark brown very gravelly loam and very cobbly loam. 

Included in this unit are small areas of Chemawa, 

Timberhead, Underwood, and Undusk soils. Also 

included are small areas of Hood soils on dissected 

terraces and McElroy soils that are less than 35 percent 

rock fragments. Included areas make up about 10 percent 

of the total acreage. 

Permeability of this McElroy soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is medium, and 

the hazard of water erosion is moderate. 

This unit is used for woodland, hayland, pastureland, 

homesites, wildlife habitat, and recreation. 

Douglas fir, ponderosa pine, and grand fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 133 for 

Douglas fir, and on the basis of a 50-year site curve, the 

mean site index is 100. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 134 cubic 

feet per acre per year at age 70. Estimates of the site 

index or CMAI for ponderosa pine and grand fir have 

not been made. Among the trees of limited extent are 

Oregon white oak and bigleaf maple. 
The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Occasional snowpack hinders the 

use of equipment and limits access in winter. Disturbance 

of the protective layer of duff can be reduced with the 

careful use of wheeled and tracked equipment. 

Seedling establishment and mortality are the main 

concerns in the production of timber. Reforestation can 

be accomplished by planting Douglas fir seedlings. If 

seed trees are present, natural reforestation of cutover 

areas by ponderosa pine and grand fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. If the canopy is opened, brush invades and can 

delay establishment of Douglas fir seedlings unless 

controlled. 

Among the common forest understory plants are 

creambush oceanspray, vine maple, western hazel, 

Pacific dogwood, thimbleberry. Oregongrape, dwarf 

rose, common snowberry, and common yarrow. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition and to 

protect the soil from erosion. Mowing at least twice a year 

helps to maintain uniform growth and discourages 

selective grazing. In some years, supplemental irrigation 

is also needed. 

The main limitation of this unit for use as homesites is 

the steepness of slope. Erosion is a hazard in the 

steeper areas. Only the part of the site that is used for 

construction should be disturbed. Preserving the existing 

plant cover during construction helps to control erosion. 

Removal of pebbles and cobbles in disturbed areas is 

needed for best results when landscaping, particularly in 

areas used for lawns. Mulch, fertilizer, and irrigation are 

needed to establish lawn grasses and other smallseeded plants. 

This map unit is in capability subclass Ille. 

67-McElroy gravelly loam, 15 to 30 percent 

slopes. This very deep, well drained soil is on back 

slopes of mountains. It formed in colluvium derived 

dominantly from basalt with a mantle of volcanic ash. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 400 to 2,300 feet. The average 

annual precipitation is about 55 inches, the average 

 annual air temperature is about 46 degrees F, and the 

average frost-free period is 105 to 125 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves. and twigs 2 inches thick. 

The surface layer is dark brown gravelly loam 10 inches 

thick. The subsoil to a depth of 60 inches or more is 

dark brown very gravelly loam and very cobbly loam. 

Included in this unit are small areas of Chemawa, 

Timberhead, Underwood, and Undusk soils. Also 

included are small areas of Hood soils on dissected 

terraces and McElroy soils that have slopes of less than 

 15 percent. Included areas make up about 10 percent 

of the total acreage. 

Permeability of this McElroy soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

Most areas of this unit are used for woodland, 

pastureland, hayland, wildlife habitat, recreation, and 

watershed. A few areas are used as homesites. 

Douglas fir, ponderosa pine, and grand fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 134 for 

Douglas fir, and on the basis of a 50-year site curve, the 

mean site index is 100. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 134 cubic feet 

per acre per year at age 70. Estimates of the site index 

or CMAI for ponderosa pine and grand fir have not been 

made. Among the trees of limited extent are Oregon 

white oak and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Occasional snowpack hinders the 

use of equipment and limits access in winter. Disturbance 

of the protective layer of duff can be reduced with the 

careful use of wheeled and tracked equipment. 

Seedling establishment and mortality are the main 

concerns in the production of timber. Reforestation can 

be accomplished by planting Douglas fir seedlings. If 

seed trees are present, natural reforestation of cutover 

areas by ponderosa pine and grand fir occurs 

periodically. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. If the canopy is opened, brush invades 

and can delay establishment of Douglas fir seedlings. 
Among the common forest understory plants are 

creambush oceanspray, vine maple, western hazel, 

Pacific dogwood, thimbleberry, Oregongrape, dwarf 

rose, common snowberry, and common yarrow. 

This unit is well suited to use as hayland and 

pastureland. The main limitations are steepness of slope 

and the hazard of erosion. Erosion can be controlled by 

growing pasture. The use of equipment is limited by 

steepness of slope. Proper stocking rates.. pasture 

rotation, and restricted grazing during wet periods help to 

keep the pasture in good condition and to protect the soil 

from erosion. Mowing at least twice a year helps to 

maintain uniform growth and discourages selective 

grazing. 

The main limitation of this unit for use as homesites is 

the steepness of slope. Erosion is a hazard in the 

steeper areas. Only the part of the site that is used for 

construction should be disturbed. Preserving the existing 

plant cover during construction helps to control erosion. 

Plant cover can be established and maintained through 

proper fertilizing, seeding, mulching. and shaping of the 

slopes. Removal of pebbles and cobbles in disturbed 

areas is needed for best results when landscaping, 

particularly in areas used for lawns. Mulch, fertilizer, and 

irrigation are needed to establish lawn grasses and 

other small-seeded plants. Restricted permeability and 

steepness of slope increase the possibility of failure of 

septic tank absorption fields. Access roads should be 

designed to provide adequate cut-slope grade, and 

drains are needed to control surface runoff and keep soil 

losses to a minimum. 

This map unit is in capability subclass IVe. 

58-McElroy gravelly loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back 

slopes of mountains. It formed in colluvium derived 

dominantly from basalt with a mantle of volcanic ash. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 400 to 2,300 feet. The average 

annual precipitation is about 55 inches, the average 

annual air temperature is about 46 degrees F, and the 

average frost-free period is 105 to 125 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick, 

The surface layer is dark brown gravelly loam 10 inches 

thick. The subsoil to a depth of 60 inches or more is 

dark brown very gravelly loam and very cobbly loam. 

Included in this unit are small areas of Chemawa, 

Timberhead. Underwood, and Undusk soils. Also 

included are small areas of McElroy soils that have 

slopes of less than 30 percent. Included areas make up 

about ' 0 percent of the total acreage. 

Permeability of this McElroy soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is rapid, and the 

hazard of water erosion is severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir, ponderosa pine, and grand fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 133 for 

Douglas fir, and on the basis of a 50-year site curve, the 

mean site index is 100. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 134 cubic feet 

per acre per year at age 70. Estimates of the site index 

or CMAI for ponderosa pine and grand fir have not been 

made. Among the trees of limited extent are Oregon 

white oak and bigleaf maple. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and 

tracked equipment in skidding. Cable yarding systems 

generally are safer and disturb the soil less. Use of 

wheeled and tracked equipment when the soil is moist 

produces ruts, compacts the soil, and damages the roots 

of trees. Unsurfaced roads and skid trails are soft and 

slippery and can be impassable when wet. Logging 

roads require suitable surfacing for year-round use. Rock 

for road construction is readily available in this unit. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling establishment and mortality are the main

concerns in the production of timber. Reforestation can 

be accomplished by planting Douglas fir seedlings. If 

seed trees are present, natural reforestation of cutover 

areas by ponderosa pine and grand fir occurs 

periodically. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. If the canopy is opened, brush invades 

and can delay establishment of Douglas fir seedlings. 

Among the common forest understory plants are 

creambush oceanspray, vine maple, western hazel, 

Pacific dogwood, thimbleberry, Oregongrape, dwarf 

rose, common snowberry, and common yarrow. 

This map unit is in capability subclass VIe. 

69-McElroy very stony loam, 5 to 15 percent 

slopes. This very deep, well drained soil is on foot 

slopes of mountains. It formed in colluvium derived 

dominantly from basalt with a mantle of volcanic ash. 

The native vegetation is mainly mixed conifers and 
shrubs. Elevation is 500 to 1,200 feet. The average 

annual precipitation is about 55 inches, the average 

annual air temperature is about 46 degrees F, and the 

average frost-free period is 105 to 125 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

About 3 to 8 percent of the surface is covered with stones. 

The surface layer is very dark grayish brown very stony 

loam 10 inches thick. The subsoil is dark brown very 

cobbly loam 22 inches thick. The substratum to a depth of 

60 inches or more is dark brown very gravelly loam and 

very cobbly loam. 

Included in this unit are small areas of McElroy 

gravelly loam and Underwood soils. Also included are 

small areas of soils that do not have stones on the 

surface. Included areas make up about 7 percent of the 

total acreage. 

Permeability of this McElroy soil is moderate. 

Available water capacity is low. Effective rooting depth is 

60 inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

Most areas of this unit are used as woodland, 

pastureland, and wildlife habitat. A few areas are used 

as homesites. 

Douglas fir, ponderosa pine, and grand fir are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is 133 for Douglas fir, and 

on the basis of a 50-year site curve, the mean site index 

is 100. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 134 cubic feet per acre per year 

at age 70. Estimates of the site index or CMAI for 

ponderosa pine and grand fir have not been made. 

Among the trees of limited extent are Oregon white oak 

and bigleaf maple. 

The main limitation for harvesting timber is the very 

stony surface layer. Stones on the surface hinder 

harvesting operations and can cause breakage of timber 

when felled. Unsurfaced roads and skid trails are soft and 

slippery and can be impassable when wet. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is readily available in this unit. 

Disturbance of the protective layer of duff can be reduced 

with the careful use of wheeled and tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

ponderosa pine occurs periodically. Droughtiness of the 

surface layer reduces seedling survival. especially on 

south- and southwest-facing slopes. If the canopy is 

opened, brush invades and can delay the establishment 

of Douglas fir seedlings. 

Among the common forest understory plants are 

creambush oceanspray, vine maple, western hazel, 

Pacific dogwood, thimbleberry, Oregongrape, dwarf 

rose, common snowberry, and common yarrow. 

This unit is well suited to use as pastureland. The 

main limitation is the stones on the surface, which 

interfere with mowing, seeding, and spreading of animal 

manure. Proper stocking rates, pasture rotation, and 

restricted grazing during wet periods help to keep the 

pasture in good condition and to protect the soil from 

erosion. 

The main limitations of this unit for use as 

homesites are the stones on the surface and steepness 

of slope. Erosion is a hazard in the steeper areas. Only 

the part of the site that is used for construction should 

be disturbed. Preserving the existing plant cover during 

construction helps to control erosion. Removal of 

pebbles. cobbles, and stones in disturbed areas is 

needed for best results when landscaping, particularly in 

areas used for lawns. Mulch, fertilizer, and irrigation are 

needed to establish lawn grasses and other small-seeded 

plants. 

This map unit is in capability subclass VIs. 

70-Minniepeak cindery sandy loam, 5 to 30 percent 

slopes. This very deep, well drained soil is on back 

slopes and ridgetops of mountains. It formed in aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,500 feet. The average annual 

precipitation is about 130 inches, the average annual air 

temperature is about 41 degrees F, and the average frostfree period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is dark brown 

cindery sandy loam 3 inches thick, the next 5 inches is 

black loamy sand, and the lower part is very dark gray 

very cindery sandy loam 4 inches thick. The subsoil to 

a depth of 60 inches or more is light gray and dark 

brown extremely cindery sand and extremely cindery 

coarse sand. 

Included in this unit are small areas of Bandid, 

Pelee, and Sinnice soils. Also included are small areas of 

Rock outcrop. Included areas make up about 10 percent 

of the total acreage. 

Permeability of this Minniepeak soil is rapid. Available 

water capacity is low. Effective rooting depth is 60 

inches or more. Runoff is slow, and the hazard of 

water erosion is slight.
This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, Douglas fir, and 

noble fir are the main woodland species on this unit. On 

the basis of a 100-year site curve, the mean site index 

is estimated to be 105 for western hemlock and 104 for 

Douglas fir. On the basis of a 50-year site curve, the 

mean site index is estimated to be 75 for western 

hemlock and 80 for Douglas fir. The culmination of the 

mean annual increment (CMAI) for western hemlock is 

151 cubic feet per acre per year at age 60, and the CMAI 

for Douglas fir is 89 cubic feet at age 60. Estimates of the 

site index or CMAI for Pacific silver fir and noble fir have 

not been made. Among the trees of limited extent is 

western redcedar. Areas on ridgetops that are subject 

to strong. persistent winds are less productive than other 

areas of this unit. 

The main limitation for harvesting timber is snowpack 

in winter. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. The surface layer is loose when dry. 

which limits the use of wheeled and tracked equipment. 

Snowpack in winter limits the use of equipment and 

restricts access. Cinders slough from road cuts onto the 

road surface. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir or Douglas fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival. The mortality rate of seedlings and the hazard of 

windthrow are higher in areas on ridgetops that are 

subject to strong, persistent winds than in other areas of 

this unit. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

subsoil exhibit poor growth. Trees occasionally are 

subject to windthrow. 

Among the common forest understory plants are vine 

maple. Sitka alder, princes pine, red huckleberry, pearly 

everlasting, and willow. 

This map unit is in capability subclass VIs. 

71-Minniepeak cindery sandy loam, 30 to 65 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,500 feet. The average annual 

precipitation is about 130 inches, the average annual 

air temperature is about 41 degrees F, and the average 

frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is dark brown cindery 

sandy loam 3 inches thick, the next part is black loamy 

sand 5 inches thick, and the lower part is very dark 

gray cindery sandy loam 4 inches thick. The subsoil to a

depth of 60 inches or more is light gray and dark brown 

extremely cindery sand and extremely cindery coarse 

sand. 

Included in this unit are small areas of Bandid, Pelee, 

and Sinnice soils. Also included are small areas of Rock 

outcrop. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this Minniepeak soil is rapid. Available 

water capacity is low. Effective rooting depth is 60 

inches or more. Runoff is slow, and the hazard of water 

erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, Douglas fir, and 

noble fir are the main woodland species on this unit. On 

the basis of a 100-year site curve, the mean site index 

is estimated to be 105 for western hemlock and 104 for 

Douglas fir. On the basis of a 50-year site curve, the mean 

site index is estimated to be 75 for western hemlock and 

80 for Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 151 cubic feet 

per acre per year at age 60, and the CMAI for Douglas fir 

is 89 cubic feet at age 60. Estimates of the site index or 

CMAI for Pacific silver fir and noble fir have not been 

made. Among the trees of limited extent is western 

redcedar. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope, which 

restricts the use of wheeled and tracked equipment in 

skidding. Cable yarding systems generally are safer and 

disturb the soil less. Logging roads require suitable 

surfacing for year-round use. Rock for road construction 

is not readily available in this unit. Snowpack in winter 

limits the use of equipment and restricts access. Cinders 

slough from road cuts onto the road surface. Establishing 

plant cover on steeper slopes that have been cut or filled 

reduces erosion. Following road construction and 

clearcutting, road failures and landslides can occur. Steep 

yarding paths, skid trails, and firebreaks are subject to 

rifling and gullying unless plant cover is maintained or 

adequate water bars are provided. 

Seedling mortality is the main concern in the 
production of timber. Reforestation can be accomplished 

by planting noble fir or Douglas fir seedlings. If seed trees 

are present. natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

subsoil exhibit poor growth. Trees occasionally are subject 

to windthrow. 

Among the common forest understory plants are vine 

maple, Sitka alder, princes pine, huckleberry, pearly 

everlasting, and willow. 

This map unit is in capability subclass Vlle. 

72-Minniepeak cindery sandy loam, 65 to 90 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 2,800 to 4,500 

feet. The average annual precipitation is about 130 

inches, the average annual air temperature is about 41 

degrees F, and the average frost-free period is 75 to 95 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is dark brown cindery 

sandy loam 3 inches thick, the next part is black loamy 

sand 5 inches thick, and the lower part is brown very 

dark gray very cindery sandy loam 4 inches thick. The 

subsoil to a depth of 60 inches or more is light gray and 

dark brown extremely cindery sand and extremely 

cindery coarse sand. 

Included in this unit are small areas of Bandid, Pelee, 

and Sinnice soils. Also included are small areas of Rock 

outcrop. Included areas make up about 10 percent of the 

total acreage. 

Permeability of this Minniepeak soil is very rapid. 

Available water capacity is low. Effective rooting depth is 

60 inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, Douglas fir, and 

noble fir are the main woodland species on this unit. On 

the basis of a 100-year site curve, the mean site index is 

estimated to be 105 for western hemlock and 104 for 

Douglas fir. On the basis of a 50-year site curve, the mean 

site index is estimated to be 75 for western hemlock and 

80 for Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 151 cubic feet per 

acre per year at age 60, and the 

CMAI for Douglas fir is 89 cubic feet at age 60. Estimates 

of the site index or CMAI for Pacific silver fir and noble fir 

have not been made. Among the trees of limited extent 

is western redcedar. 

The main limitations for harvesting timber are snowpack 

in winter and steepness of slope. Cable yarding systems 

generally are used on this unit. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Snowpack in winter limits the use of 

equipment and restricts access. Cinders slough from road 

cuts onto the road surface. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Following road construction and clearcutting, 

road failures and landslides can occur. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. Harvesting systems that lift logs 

entirely off the ground reduce the disturbance of the 

protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir or Douglas fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. Logging activities can readily displace the 

surface layer. Seedlings that grow in the less fertile 

subsoil exhibit poor growth. Because the subsoil is 

loose, trees occasionally are subject to windthrow. 

Among the common forest understory plants are vine 

maple, Sitka alder, princes pine, huckleberry, pearly 

everlasting, and willow. 

This map unit is incapability subclass VIIe. 

73-Mossyrock silt loam, 2 to 5 percent slopes. 

This very deep, well drained soil is on high terraces. It 

formed in loess and alluvium derived dominantly from 

volcanic ash and basalt. The native vegetation is mainly 

grasses and scattered conifers. Elevation is 300 to 1,000 

feet. The average annual precipitation is about 70 

inches, the average annual air temperature is about 51 

degrees F, and the average frost-free period is 175 to 

195 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is very dark brown 

silt loam 6 inches thick, and the lower part is dark 
brown silt loam 24 inches thick. The subsoil to a depth 

of 60 inches or more is dark brown silt loam. 

Included in this unit are small areas of Hesson soils on 

terraces and Mountzion and Skoly soils on mountain 

slopes. Also included are small areas of Skamania and 

Mossyrock soils that have slopes of more than 5 percent. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this Mossyrock soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is slow, and the hazard of 

water erosion is slight. 

Most areas of this unit are used for hayland, 

pastureland, homesites, wildlife habitat, and recreation. 

A few areas are used as cropland and woodland. 

This unit is well suited to use as hayland and pastureland. 

It has few limitations. Proper stocking rates, pasture 

rotation, and restricted grazing during wet periods help 

to keep the pasture in good condition and to protect the 

soil from erosion. Mowing helps to maintain uniform 

growth and discourages selective grazing. 

This unit is well suited to homesite development. It 

has few limitations. Mulch, fertilizer, and irrigation are 

needed to establish lawn grasses and other smallseeded plants. Buildings and roads should be designed 

to offset limited ability of the soil on this unit to support 

a load. The soil is limited for the construction of roads 

and streets because of the potential for frost action. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site 

curve, the mean site index is estimated to be 173 for 

Douglas fir. On the basis of a 50-year site curve, the 

mean site index is estimated to be 130 for Douglas fir, 

The culmination of the mean annual increment (CMAI) 

for Douglas fir is 184 cubic feet per acre per year at 

age 65. Estimates of the site index or CMAI for red 

alder have not been made. Among the trees of limited 

extent are bigleaf maple and western redcedar. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Disturbance of the protective layer 

of duff can be reduced with the careful use of wheeled 

and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by western hemlock and red alder occurs readily. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings unless controlled. 

Among the common forest understory plants are vine 

maple, red huckleberry, salal, Oregongrape, Scotch 

broom, western swordfern, and thimbleberry. 

This unit is well suited to small grain. Returning all crop 

residue to the soil and using a cropping system that 

includes grasses, legumes, or grass-legume mixtures 

help to maintain fertility and tilth. Practices that can be 

used to control erosion include early fall seeding, 

stubble-mulch tillage, and construction of terraces, 

diversions, and grassed waterways. 

This map unit is in capability subclass IIe. 

74-Mossyrock silt loam, 5 to 15 percent slopes. 

This very deep. well drained soil is on high terraces. It 

formed in loess and alluvium derived dominantly from 

volcanic ash and basalt. The native vegetation is mainly 

grasses and scattered conifers. Elevation is 300 to 

1,000 feet. The average annual precipitation is about 70 

inches, the average annual air temperature is about 51 

degrees F, and the average frost-free period is about 175 

to 195 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is very dark brown silt 

loam 6 inches thick, and the lower part is dark brown 

silt loam 21 inches thick. The subsoil to a depth of 60 

inches or more is dark brown silt loam. 

Included in this unit are small areas of Hesson soils 

on terraces and Mountzion and Skoly soils on mountain 

slopes. Also included are small areas of Skamania and 

Mossyrock soils that have slopes of more than 15 

percent. Included areas make up about 10 percent ofthe 

total acreage. 

Permeability of this Mossyrock soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

Most areas of this unit are used for hayland, 

pastureland, homesites, wildlife habitat, and recreation. 

A few areas are used as cropland and woodland. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition and 

to protect the soil from erosion. Mowing helps to 

maintain uniform growth and discourages selective 

grazing. 

The main limitations of this unit for use as homesites 
are steepness of slope and the hazard of erosion. Erosion 

is a hazard in the steeper areas. Only the part of the site 

that is used for construction should be disturbed. 

Preserving the existing plant cover during construction 

helps to control erosion. Mulch, fertilizer, and irrigation are 

needed to establish lawn grasses and other small-seeded 

plants. Buildings and roads should be designed to offset 

the limited ability of the soil in this unit to support a load. 

The soil is susceptible to frost action, which may limit 

construction of roads and streets. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site curve. 

the mean site index is estimated to be 173 for Douglas fir, 

and on the basis of a 50-year site curve, the mean site 

index is estimated to be 130. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 184 cubic feet 

per acre per year at age 60. Estimates of the site index or 

CMAI for red alder have not been made. Among the trees 

of limited extent are bigleaf maple and western redcedar. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Disturbance of the protective layer of 

duff can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red alder 

occurs readily. If the canopy is opened, brush invades and 

can prevent the establishment of Douglas fir seedlings 

unless controlled. 

Among the common forest understory plants are vine 

maple, red huckleberry, salal, Oregongrape, Scotch 

broom, western swordfern, and thimbleberry. 

This unit is well suited to small grain. Returning all crop 

residue to the soil and using a cropping system that 

includes grasses, legumes, or grass-legume mixtures help 

to maintain fertility and tilth. Practices that can be used to 

control erosion include early fall seeding, stubble-mulch 

tillage, and construction of terraces, diversions, and 

grassed waterways. 

This map unit is in capability subclass Ille. 

75-Mountzion clay loam, 2 to 15 percent slopes. 

This very deep, well drained soil is on foot slopes of 

mountains. It formed in residuum and colluvium derived 

dominantly from basalt. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 600 to 1,500 

feet. The average annual precipitation is about 70 

inches, the average annual air temperature is about 49 

degrees F, and the average frost-free period is 130 to 

150 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown clay loam 17 inches thick. 

The upper 30 inches of the subsoil is dark reddish brown 

silty clay loam, and the lower part to a depth of 60 inches 

or more is dark brown clay loam. 

Included in this unit are small areas of Aschoff, 

Steever, Stevenson, and St. Martin soils on landslides. 

Also included are small areas of Mountzion soils that 

are more than 15 percent rock fragments. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Mountzion soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is medium, and the hazard 

of water erosion is moderate. 

This unit is used for hayland, pastureland, woodland, 

homesites, and recreation. 

Douglas fir, grand fir, red alder, and western hemlock 

are the main woodland species on this unit. On the basis 

of a 100-year site curve, the mean site index is 149 for 

Douglas fir and 148 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 116 for 

Douglas fir and 105 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 

157 cubic feet per acre per year at age 60, and the 

CMAI for western hemlock is 234 cubic feet at age 50. 

Estimates of the site index or CMAI for grand fir and red 

alder have not been made. Among the trees of limited 

extent is bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and sticky and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Disturbance of the protective layer 

of duff can be reduced with the careful use of wheeled 

and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red 

alder occurs readily and natural reforestation by grand fir 

and western hemlock occurs periodically. If the 
canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by grand fir and western hemlock 

unless controlled. 

Among the common forest understory plants are vine 

maple, Oregongrape, red huckleberry, Pacific dogwood, 

common snowberry, western hazel, thimbleberry, and 

western swordfern. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition and to 

protect the soil from erosion. Periodic mowing and 

clipping help to maintain uniform growth, discourage 

selective grazing, and reduce clumpy growth. 

The main limitations of this unit for use as homesites 

are the steepness of slope and the hazard of erosion in the 

steeper areas. Only the part of the site that is used for 

construction should be disturbed. Topsoil can be 

stockpiled and used to reclaim areas disturbed during 

construction. Mulch, fertilizer, and irrigation are needed 

to establish lawn grasses and other small-seeded plants. 

The main limitations for septic tank absorption fields 

are the slope and moderate permeability. During the 

rainy season, effluent from onsite sewage disposal 

systems seep at points downslope. Steepness of slope is 

a concern when installing septic tank absorption fields. 

Absorption lines should be installed on the contour. 

This map unit is in capability subclass IIIe. 

76-Mountzion clay loam, 15 to 30 percent slopes. 

This very deep, well drained soil is on foot slopes and 

back slopes of mountains. It formed in residuum and 

colluvium derived dominantly from basalt. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 600 to 2,200 feet. The average annual 

precipitation is about 70 inches, the average annual air 

temperature is about 49 degrees F, and the average 

frost-free period is 130 to 150 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown clay loam 17 inches 

thick. The upper 30 inches of the subsoil is dark reddish 

brown silty clay loam, and the lower part to a depth of 

60 inches or more is dark brown clay loam. 

Included in this unit are small areas of Aschoff and St. 

Martin soils on landslides. Also included are small areas 

of Mountzion soils that are more than 15 percent rock 

fragments. Included areas make up about 8 percent of 

the total acreage. 

Permeability of this Mountzion soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is medium, and the hazard 

of water erosion is moderate. 

This unit is used for woodland, hayland, pastureland, 

wildlife habitat, and recreation. 

Douglas fir, grand fir, red alder, and western hemlock 

are the main woodland species on this unit. On the basis 

of a 100-year site curve, the mean site index is 149 for 

Douglas fir and 148 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 116 for 

Douglas fir and 105 for western hemlock. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 157 cubic feet per acre per year at age 

60, and the CMAI for western hemlock is 234 cubic feet at 

age 50. Estimates of the site index or CMAI for grand fir 

and red alder have not been made. Among the trees of 

limited extent are bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and sticky and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. 

Disturbance of the protective layer of duff can be reduced 

with the careful use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red 

alder occurs readily and natural reforestation by grand fir 

and western hemlock occurs periodically. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by grand fir and western hemlock 

unless controlled. 

Among the common forest understory plants are vine 

maple, Oregongrape, common snowberry, red 

huckleberry, Pacific dogwood, western hazel, 

thimbleberry, and western swordfern. 

This unit is well suited to use as hayland and 

pastureland. The main limitation is steepness of slope. 

Erosion can be controlled by growing pasture plants. 

The use of equipment is limited by steepness of slope. 

Proper stocking rates, pasture rotation, and restricted 

grazing during wet periods help to keep the pasture in 

good condition and to protect the soil from erosion. 

Mowing at least twice a year helps to maintain uniform 
growth and discourages selective grazing. 

This map unit is in capability subclass IVe. 

77-Mountzion clay loam, 30 to 65 percent slopes. 

This very deep, well drained soil is on back slopes of 

mountains. It formed in residuum and colluvium derived 

dominantly from basalt. Elevation is 600 to 2,200 feet. 

The average annual precipitation is about 70 inches, 

the average annual air temperature is about 49 degrees 

F. and the average frost-free period is 130 to 150 days.

Typically. the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown clay loam 17 inches thick. 

The upper 30 inches of the subsoil is dark reddish brown 

silty clay loam, and the lower part to a depth of 60 

inches or more is dark brown clay loam. 

Included in this unit are small areas of Aschoff and St. 

Martin soils on landslides. Also included are small areas 

of Rock outcrop, shallow soils, and Mountzion soils that 

have slopes of less than 30 percent. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Mountzion soil is moderate. 

Available water capacity is high. Effective rooting depth is 

60 inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, wildlife habitat, and 

recreation. 

Douglas fir, grand fir, red alder, and western hemlock 

are the main woodland species on this unit. On the 

basis of a 100-year site curve, the mean site index is 149 

for Douglas fir and 148 for western hemlock. On the basis 

of a 50-year site curve, the mean site index is 116 for 

Douglas fir and 105 for western hemlock. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 159 cubic feet per acre per year at age 60, 

and the CMAI for western hemlock is 234 cubic feet at age 

50. Estimates of the site index or CMAI for grand fir and 

red alder have not been made. Among the trees of 

limited extent is bigleaf maple. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and sticky and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rifling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by red alder occurs readily and natural reforestation 

by grand fir and western hemlock occurs periodically. If 

the canopy is opened, brush invades and can prevent 

the establishment of Douglas fir seedlings and can delay 

natural reforestation by grand fir and western hemlock 

unless controlled. 

Among the common forest understory plants are vine 

maple, Oregongrape, common snowberry, red 

huckleberry, Pacific dogwood, western hazel, 

thimbleberry, and western swordfern. 

This map unit is in capability subclass Vle. 

78-Pelee sandy loam, 5 to 30 percent slopes. This 

very deep, well drained soil is on back slopes and 

ridgetops of mountains. It formed in stratified, aerially 

deposited volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,500 feet. The average annual 

precipitation is about 135 inches. the average annual air 

temperature is about 39 degrees F, and the average 

frost-free period is 75 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

very dark grayish brown sandy loam. The upper 25 

inches of the subsoil is dark gray very cindery coarse sand 

and light gray extremely cindery sand, and the lower part 

to a depth of 60 inches or more is dark brown and very 

dark grayish brown sandy loam and dark brown loamy 

sand. 

Included in this unit are small areas of Bandid, 

Minniepeak, and Sinnice soils. Also included are small 

areas of Shoestring soils on terraces and Rock outcrop. 

Included areas make up about 8 percent of the total 

acreage. 

Permeability of this Pelee soil is very rapid in the 

upper part of the subsoil and moderately rapid in the 

lower part. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. Runoff is 

slow, and the hazard of water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and Douglas fir 

are the main woodland species on this unit. On the 

basis of a 100-year site curve, the mean site index is 

estimated to be 105 for western hemlock and 104 for 
Douglas fir. On the basis of a 50-year site curve, the 

mean site index is estimated to be 75 for western hemlock 

and 80 for Douglas fir. The culmination of the mean 

annual increment (CMAI) for western hemlock is 151 

cubic feet per acre per year at age 60, and the CMAI for 

Douglas fir is 89 cubic feet at age 60. Estimates of the site 

index or CMAI for Pacific silver fir have not been made. 

Among the trees of limited extent are noble fir and 

western redcedar. Areas on ridgetops that are subject to 

strong, persistent winds are less productive than other 

areas of this unit. 

The main limitation for harvesting timber is snowpack 

in winter. Use of wheeled and tracked equipment when 

the soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Snowpack 

in winter limits the use of equipment and restricts access. 

Cinders slough from road cuts onto the road surface. 

Disturbance of the protective layer of duff can be 

reduced with the careful use of wheeled and tracked 

equipment. 

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Reforestation can be 

accomplished by planting Douglas fir or noble fir 

seedlings. If seed trees are present, natural reforestation 

of cutover areas by western hemlock and Pacific silver fir 

occurs periodically. The mortality rate of seedlings is 

higher in areas on ridgetops that are subject to strong, 

persistent winds than in other areas of this unit. Logging 

activities can readily displace the surface layer. 

Seedlings that develop in the less fertile subsoil exhibit 

poor growth. 

Among the common forest understory plants are vine 

maple, willow, red huckleberry, western brackenfern, 

and pearly everlasting. 

This map unit is in capability subclass VIs. 

79-Pelee sandy loam, 30 to 65 percent slopes. This 

very deep, well drained soil is on back slopes of 

mountains. It formed in stratified, aerially deposited 

volcanic ash and pumice. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,500 feet. The average annual precipitation is about 

135 inches, the average annual air temperature is about 

39 degrees F, and the average frost-free period is 75 to

90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

very dark grayish brown sandy loam. The upper part of 

the subsoil is dark gray very cindery coarse sand and 

light gray extremely cindery sand 25 inches thick, and 

the lower part to a depth of 60 inches or more is dark 

brown and very dark grayish brown sandy loam and dark 

brown loamy sand. 

Included in this unit are small areas of Bandid, 

Minniepeak, and Sinnice soils. Also included are small 

areas of Rock outcrop. Included areas make up about 5

percent of the total acreage. 

Permeability of this Pelee soil is very rapid in the 

upper part of the subsoil and moderately rapid in the 

lower part. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. Runoff is 

slow, and the hazard of water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and Douglas fir 

are the main woodland species on this unit. On the 

basis of a 100-year site curve, the mean site index is 

estimated to be 105 for western hemlock and 104 for 

Douglas fir. On the basis of a 50-year site curve, the 

mean site index is estimated to be 75 for western 

hemlock and 80 for Douglas fir. The culmination of the 

mean annual increment (CMAI) for western hemlock is 

151 cubic feet per acre per year at age 60, and the 

CMAI for Douglas fir is 89 cubic feet at age 60.

Estimates of the site index or CMAI for Pacific silver fir 

have not been made. Among the trees of limited extent 

are noble fir and western redcedar. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope, which 

restricts the use of wheeled and tracked equipment in 

skidding. Cable yarding systems generally are safer and 

disturb the soil less. Use of wheeled and tracked 

equipment when the soil is wet produces ruts, compacts 

the soil, and damages the roots of trees. Logging 

roads require suitable surfacing for year-round use. 

Rock for road construction is not readily available in 

this unit. Snowpack in winter limits the use of equipment 

and restricts access. Cinders slough from road cuts onto 

the road surface. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and firebreaks are subject to

rilling and gullying unless plant cover is maintained or 

adequate water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Reforestation can be 

accomplished by planting Douglas fir or noble fir 

seedlings. If seed trees are present, natural 
reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. Logging activities 

can readily displace the surface layer. Seedlings that 

grow in the less fertile subsoil exhibit poor growth. 

Among the common forest understory plants are vine 

maple, willow, red huckleberry, western brackenfern, and 

pearly everlasting. 

This map unit is in capability subclass VIIe. 

80-Pelee sandy loam, 65 to 90 percent slopes. 

This very deep, well drained soil is on back slopes of 

mountains. It formed in stratified, aerially deposited 

volcanic ash and pumice. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,500 feet. The average annual precipitation is about 135 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free period is 75 to 90 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

very dark grayish brown sandy loam, The upper 25 inches 

of the subsoil is dark gray very cindery coarse sand, light 

gray extremely cindery sand, and dark brown very cindery 

sand, and the lower part to a depth of 60 inches or more 

is dark brown and very dark grayish brown sandy loam and 

dark brown loamy sand. 

Included in this unit are small areas of Bandid, 

Minniepeak, and Sinnice soils. Also included are small 

areas of Rock outcrop. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Pelee soil is very rapid in the upper 

part of the subsoil and moderately rapid in the lower part. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and Douglas fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is estimated to 

be 105 for western hemlock and 104 for Douglas fir. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 75 for western hemlock and 80 for 

Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 151 cubic feet 

per acre per year at age 60, and the CMAI for Douglas fir 

is 89 cubic feet at age 60. Estimates of the site index or 

CMAI for Pacific silver fir have not been made. Among the 

trees of limited extent are noble fir and western 

redcedar. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. Cable yarding 

systems generally are used on this unit. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is not readily available in this unit. 

Logging roads generally need full bench construction 

and require frequent maintenance. Snowpack in winter 

limits the use of equipment and restricts access. Cinders 

slough from road cuts onto the road surface. Establishing 

plant cover on steeper slopes that have been cut or filled 

reduces erosion. Steep yarding paths, skid trails, and 

firebreaks are subject to rilling and gullying unless plant 

cover is maintained or adequate water bars are 

provided. Harvesting systems that lift logs entirely off the 

ground reduce the disturbance of the protective layer of 

duff. 

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Reforestation can be 

accomplished by planting Douglas fir and noble fir 

seedlings. If seed trees are present, natural reforestation 

of cutover areas by western hemlock and Pacific silver fir 

occurs periodically. Logging activities can readily 

displace the surface layer. Seedlings that grow in the 

less fertile subsoil exhibit poor growth. 

Among the common forest understory plants are vine 

maple, willow, red huckleberry, western brackenfern, and 

pearly everlasting. 

This map unit is in capability subclass VIIe. 

81-Pelee-Rock outcrop complex, 65 to 90 percent 

slopes. This map unit is on back slopes of mountains. 

The native vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,500 feet. The average annual 

precipitation is about 135 inches, the average annual air 

temperature is about 39 degrees F, and the average 

frost-free period is 75 to 90 days. 

This unit is about 60 percent Pelee sandy loam, 65 to 

90 percent slopes, and 30 percent Rock outcrop. The 

components of this unit are so intricately intermingled that 

it was not practical to map them separately at the scale 

used. 

Included in this unit are small areas of Bandid, 

Minniepeak, and Sinnice soils. Also included are small 

areas of Pelee soils that are more than 35 percent rock 

fragments. Included areas make up about 10 percent of 

the total acreage. 

The Pelee soil is very deep and well drained. It 

formed in stratified, aerially deposited volcanic ash and 

pumice. Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is
very dark grayish brown sandy loam. The upper 25 inches 

of the subsoil is dark gray very cindery coarse sand, and 

the lower part to a depth of 60 inches or more is dark 

brown and very dark grayish brown sandy loam and dark 

brown loamy sand. 

Permeability of this Pelee soil is very rapid in the upper 

part of the subsoil and moderately rapid in the lower part. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

Rock outcrop consists of exposed areas of dominantly 

andesite. Numerous escarpments are in this unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and Douglas fir are 

the main woodland species on the Pelee soil. On the basis 

of a 100-year site curve, the mean site index is estimated 

to be 105 for western hemlock and 104 for Douglas fir. 

On the basis of a 50-year site curve, the mean site index 

is estimated to be 75 for western hemlock and 80 for 

Douglas fir. The culmination of the mean annual increment 

(CMAI) for western hemlock is 151 cubic feet per acre per 

year at age 60, and the CMAI for Douglas fir is 89 cubic 

feet at age 60. The areas of Rock outcrop make up about 

30 percent of this unit and reduce yield accordingly. 

Estimates of the site index or CMAI for Pacific silver fir 

have not been made. Among the trees of limited extent are 

noble fir and western redcedar. 

The main limitations for harvesting timber are Rock 

outcrop, snowpack in winter, and steepness of slope. 

Cable yarding systems generally are used on this unit. 

Rock outcrop can cause breakage of timber when felled 

and can hinder yarding operations. Avoiding Rock outcrop 

forces yarding paths to converge, which increases 

compaction and erosion of the soil. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Snowpack in winter limits the use 

of equipment and restricts access. Cinders slough from 

road cuts onto the road surface. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths. skid trails, and firebreaks 

are subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Reforestation can be 

accomplished by planting Douglas fir or noble fir 

seedlings. If seed trees are present, natural reforestation 

of cutover areas by western hemlock and Pacific silver fir 

occurs periodically. The areas of Rock outcrop limit the 

even distribution of reforestation. Logging activities can 

readily displace the surface layer. Seedlings that grow in 

the less fertile subsoil exhibit poor growth. 

Among the common forest understory plants are vine 

maple, willow, huckleberry, western brackenfern, and 

pearly everlasting. 

The Pelee soil is in capability subclass VIle, and the 

Rock outcrop is in capability subclass VIlls. 

82-Pilchuck very fine sandy loam. This very deep, 

somewhat excessively drained soil is on flood plains. It 

formed in alluvium derived dominantly from basic 

igneous rock. Slope is 0 to 3 percent. The native 

vegetation is mainly mixed grasses and scattered 

hardwoods. Elevation is 50 to 200 feet. The average 

annual precipitation is about 60 inches, the average 

annual air temperature is about 50 degrees F, and the 

average frost-free period is 160 to 200 days. 

Typically, the surface layer is very dark grayish brown 

very fine sandy loam 9 inches thick. The upper 19 inches 

of the underlying material is dark brown fine sand and 

loamy fine sand, the next 18 inches is brown fine sand 

and dark grayish brown loamy fine sand, and the lower 

part to a depth of 60 inches or more is very dark grayish 

brown fine sandy loam. 

Included in this unit are small areas of McBee, 

Bonneville, and Skamania soils on terraces. Also 

included are small areas of Skoly and Steever soils on 

mountain slopes and well drained soils. Included areas 

make up about 20 percent of the total acreage. 

Permeability of this Pilchuck soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is limited by a high water table that is at a depth 

of 2 to 4 feet from November to April. Runoff is slow, 

and the hazard of water erosion is slight. This soil is 

subject to occasional, brief periods of flooding from 

November to April. 

This unit is used as pastureland (fig. 6), hayland, 

woodland, and wildlife habitat. 

This unit is suited to use as hayland and pastureland. 

The main limitation is the hazard of flooding. Proper 

stocking rates, pasture rotation, and restricted grazing 

during wet periods help to keep the pasture in good 

condition and to protect the soil from erosion. 

Douglas fir and red alder are the main woodland 
Figure 6.-Area of Pilchuck very fine sandy loam used as pastureland. 

species on this unit. On the basis of a 100-year site curve. 

the mean site index is 152 for Douglas fir. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 161 

cubic feet per acre per year at age 30. Estimates of the 

site index or CMAI for red alder have not been made. 

Among the trees of limited extent are western hemlock, 

western redcedar, bigleaf maple, and black cottonwood. 

The main limitations for harvesting timber are seasonal 

soil wetness and the hazard of flooding. Use of wheeled 

and tracked equipment when the soil is moist produces 

ruts, compacts the soil, and damages the roots of trees. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. The surface layer is loose when dry, which 

limits the use of wheeled and 

tracked equipment. The high water table and occasional, 

long periods of flooding limit the use of equipment to dry 

periods. Disturbance of the protective layer of duff can be 

reduced with careful use of wheeled and tracked 

equipment. 

Seedling establishment and mortality are the main 

concerns in the production of timber. Reforestation can 

be accomplished by planting Douglas fir seedlings. If 

seed trees are present, natural reforestation of cutover 

areas by red alder occurs readily. Occasional, long 

periods of flooding reduce root respiration, which results 

in a low survival rate of seedlings. Droughtiness of the 

surface layer reduces seedling survival. If the canopy is 

opened, brush invades and can delay the establishment 

of seedlings unless controlled. Trees occasionally are 

subject to windthrow. 
Among the common forest understory plants are vine

maple, western swordfern, salmonberry, stinging nettle,

Oregon oxalis, and western brackenfern. 

This map unit is in capability subclass IVw. 

83-Pillery fine sandy loam. This very deep, 

moderately well drained soil is on flood plains and low 

river terraces. It formed in alluvium derived dominantly 

from basic igneous rock. Slope is 0 to 3 percent. The 

native vegetation is mainly mixed grasses and scattered 

conifers and hardwoods. Elevation is 900 to 1,200 feet. 

The average annual precipitation is about 100 inches, 

the average annual air temperature is about 46 degrees F, 

and the average frost-free period is 110 to 130 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is very dark grayish 

brown fine sandy loam 9 inches thick, and the lower part 

is very dark grayish brown loam 11 inches thick. The upper 

25 inches of the underlying material is dark brown and 

brown fine sandy loam, and the lower part to a depth of 60 

inches or more is brown very gravelly loamy sand. 

Included in this unit are small areas of Stabler and 

Stabbart soils on alluvial fans. Also included are small 

areas of organic soils and poorly drained soils in 

depressional areas. Included areas make up about 15 

percent of the total acreage. 

Permeability of this Pillery soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is limited by a seasonal high water table that 

is at a depth of 3 to 4 feet from March to May. Runoff is 

slow, and the hazard of water erosion is slight. This soil is 

subject to occasional, brief periods of flooding in March to 

May. Channeling and deposition are common along 

streambanks. 

This unit is used as woodland, pastureland, and 

wildlife habitat. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site curve, 

the mean site index is estimated to be 153 for Douglas fir, 

and on the basis of a 50-year site curve, the mean site 

index is estimated to be 115. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 162 cubic 

feet per acre per year at age 60. Estimates of the site 

index or CMAI for red alder have not been made. Among 

the trees of limited extent are western redcedar, western 

hemlock, and black cottonwood. 

The main limitations for harvesting timber are 

seasonal soil wetness and the hazard of flooding. Use of 

wheeled and tracked equipment when the soil is 

moist produces ruts, compacts the soil, and damages the 

roots of trees. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. When the surface layer is dry, it can 

be displaced readily by the use of equipment. 

Disturbance of the protective layer of duff can be reduced 

with the careful use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by red alder occurs 

readily. Occasional, brief periods of flooding reduce root 

respiration, which results in a low survival rate of 

seedlings. If the canopy is opened, brush invades and can 

prevent the establishment of seedlings unless controlled. 

Among the common forest understory plants are vine 

maple, salal, Oregongrape, trailing blackberry, and 

western swordfern. 

This unit is well suited to pastureland. The main 

limitation is the hazard of flooding. Proper grazing 

practices, weed control, and fertilizer are needed to 

ensure maximum quality of forage. In some years, 

supplemental irrigation is also needed. 

This map unit is in capability subclass Illw. 

84-Pinchot cindery sandy loam, 0 to 30 percent 

slopes. This very deep, well drained soil is on terraces and 

terrace escarpments. It formed in aerially deposited 

volcanic ash and pumice over lahar and alluvial sand and 

gravel. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 1,000 to 1,600 feet. The 

average annual precipitation is about 125 inches, the 

average annual air temperature is about 50 degrees F, and 

the average frost-free period is 100 to 120 days. 

Where mixed to a depth of 6 inches, the surface layer 

typically is dark brown cindery sandy loam. The upper 5 

inches of the subsoil is very dark grayish brown fine sandy 

loam, and the lower 23 inches is dark brown cindery 

sandy loam and sandy loam. The upper 15 inches of the 

substratum is dark brown very gravelly loamy sand, and 

the lower part to a depth of 60 inches or more is brown 

very cobbly sand. 

Included in this unit are small areas of St. Helens and 

Yalelake soils. Also included are small areas of 

Cinnamon and Swift soils on mountain slopes and 

poorly drained soils in depressional areas. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Pinchot soil is moderate in the 

subsoil and rapid in the substratum. Available water 

capacity is moderately high. Effective rooting depth is 
60 inches or more. Runoff is slow, and the hazard of 

water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is estimated to be 138 for 

Douglas fir, and on the basis of a 50-year site curve, 

the mean site index is estimated to be 105. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 142 cubic feet per acre per year at age 70. 

Estimates of the site index or CMAI for western 

hemlock have not been made. Among the trees of limited 

extent are western redcedar and red alder. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Occasional 

snowpack hinders the use of equipment and limits access 

in winter, Disturbance of the protective layer of duff can 

be reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock occurs periodically. Logging activities can readily 

displace the surface layer. Seedlings that grow in the less 

fertile subsoil exhibit poor growth. If the canopy is opened, 

brush invades and can prevent the establishment of 

Douglas fir seedlings and can delay natural reforestation 

unless controlled. 

Among the common forest understory plants are salal, 

Oregongrape, princes pine, western brackenfern, 

deerfoot vanillaleaf, and red huckleberry. 

This map unit is in capability subclass lVe. 

85-Pinchot cindery sandy loam, 50 to 90 percent 

slopes. This very deep, well drained soil is on terrace 

escarpments. It formed in aerially deposited volcanic ash 

and pumice over lahar and alluvial sand and gravel. The 

native vegetation is mainly mixed conifers and shrubs. 

Elevation is 1,000 to 1,600 feet. The average annual 

precipitation is about 125 inches, the average annual air 

temperature is about 50 degrees F, and the average frostfree period is 100 to 120 days. 

Where mixed to a depth of 6 inches, the surface layer 

typically is dark brown cindery sandy loam. The upper 5 

inches of the subsoil is very dark grayish brown 

fine sandy loam, and the lower 23 inches is dark brown 

cindery sandy loam and sandy loam. The upper 15 inches 

of the substratum is dark brown very gravelly loamy sand, 

and the lower part to a depth of 60 inches or more is 

brown very cobbly sand. 

Included in this unit are small areas of Yalelake soils. 

Also included are small areas of Cinnamon and Swift soils 

on mountain slopes and small areas of Badland. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Pinchot soil is moderate in the 

subsoil and rapid in the substratum. Available water 

capacity is moderately high. Effective rooting depth is 

60 inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 138 

for Douglas fir, and on the basis of a 50-year site curve, 

the mean site index is 90. The culmination of the mean 

annual increment (CMAI) for Douglas fir is estimated to be 

142 cubic feet per acre per year at age 70. Estimates of 

the site index or CMAI for western hemlock have not been 

made. Among the trees of limited extent are western 

redcedar and red alder. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is readily available in this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Occasional snowpack hinders the 

use of equipment and limits access in winter. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. Harvesting systems that lift logs entirely off 

the ground reduce the disturbance of the protective layer 

of duff. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by western hemlock occurs periodically. Logging 

activities can readily displace the surface layer. 

Seedlings that grow in the less fertile subsoil exhibit 

poor growth. If the canopy is opened, brush invades and 

can prevent the establishment of Douglas fir 
seedlings and can delay natural reforestation unless 

controlled. Reforestation can be accomplished by 

planting Douglas fir or noble fir seedlings. 

Among the common forest understory plants are 

salal. Oregongrape, princes pine, western brackenfern, 

deerfoot vanillaleaf, and red huckleberry. 

This map unit is in capability subclass VIIe. 

86-Pinoty sandy loam, 0 to 30 percent slopes. This 

very deep, well drained soil is on terraces. It formed in 

volcanic ash and pumice over lahar material and alluvial 

sand and gravel. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 1,000 to 1,500 feet. The 

average annual precipitation is about 120 inches.. the 

average annual air temperature is about 52 degrees F. 

and the average frost-free period is 100 to 120 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 6 inches, the surface layer is 

dark brown sandy loam. The upper 15 inches of the subsoil 

is dark grayish brown sandy loam and dark grayish brown 

cindery loamy sand, and the lower 9 inches is dark 

yellowish brown sandy loam. The upper 15 inches of the 

substratum is yellowish brown sandy loam, and the lower 

part to a depth of 60 inches or more is grayish brown 

extremely gravelly loamy sand. Depth to the extremely 

gravelly part of the substratum ranges from 40 to 50 

inches. 

Included in this unit are small areas of Pinchot 

cindery sandy loam and Yalelake soils. Also included 

are small areas of poorly drained soils in depressional 

areas. Included areas make up about 5 percent of the 

total acreage. 

Permeability of this Pinoty soil is moderate in the upper 

part of the substratum and rapid in the lower part. 

Available water capacity is moderately high. Effective 

rooting depth is 40 to 50 inches. Runoff is slow, and the 

hazard of water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is estimated to be 153 for 

Douglas fir, and on the basis of a 50-year site curve. the 

mean site index is estimated to be 115 for Douglas fir. 

The culmination of the mean annual increment (CMAI) 

for Douglas fir is 162 cubic feet per acre per year at age 

60. Estimates of the site index or CMAI for western 

hemlock have not been made. Among the trees of limited 

extent are western redcedar and red alder. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet, 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in this 

unit. Disturbance of the protective layer of duff can be 

reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock occurs periodically. If the canopy is opened. 

brush invades and can prevent the establishment of 

Douglas fir seedlings and can delay natural reforestation 

unless controlled. 

Among the common forest understory plants are vine 

maple, salal, western brackenfern, western swordfern, 

Oregongrape, and Pacific dogwood. 

This map unit is in capability subclass IVe. 

87-Pits. This map unit consists of quarries and 

gravel pits larger than 3 acres in size. Areas of this 

unit are on terraces and mountain slopes. The soil 

mantle in these areas has been removed, and sand, 

gravel, or crushed rock has been excavated. Small 

pits, less than 3 acres, are designated by a spot 

symbol on the soil maps. Most Pits support little if any 

vegetation. 

This map unit is in capability subclass VIIIs. 

88-Polepatch extremely bouldery loamy sand, 0 

to 30 percent slopes. This very deep, somewhat 

excessively drained soil is on alluvial fans and terraces. It 

formed in lahar material with a mantle of volcanic ash. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 2,800 to 4,000 feet. The average 

annual precipitation is about 135 inches, the average 

annual air temperature is about 40 degrees F, and the 

average frost-free period is 70 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown extremely 

bouldery loamy sand 12 inches thick. The underlying 

material to a depth of 60 inches or more is dark gray 

extremely cobbly sand and extremely stony coarse 

sand. 

Included in this unit are small areas of Lonestar and 

Pelee soils on back slopes of mountains and Forsyth, 

Shoestring, and St. Helens soils on terraces. Also 

included are small areas of poorly drained soils in 
Figure 7.-Logged area of Polepatch extremely bouldery loamy sand, 0 to 30 percent slopes. 

depressional areas and Polepatch soils that have a 

cobbly surface layer. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Polepatch soil is rapid. Available 

water capacity is low. Effective rooting depth is 35 to 40 

inches. Runoff is slow, and the hazard of water erosion 

is slight. 

This unit is used for woodland, recreation, wildlife 

habitat. and watershed. 

Western hemlock. Pacific silver fir, Douglas fir, and 

lodgepole pine are the main woodland species on this 

unit. On the basis of a 100-year site curve, the mean 

site index is estimated to be 84 for western hemlock, and 

on the basis of a 50-year site curve, the mean site index 

is estimated to be 60. The culmination of the mean 

annual increment (CMAI) for western hemlock is 95 cubic 

feet per acre per year at age 60. Estimates of the site 

index or CMAI for Pacific silver fir, Douglas fir, and 

lodgepole pine have not been made. Among the 

trees of limited extent are noble fir and western white 

pine. 

The main limitations for harvesting timber are 

snowpack in winter and the boulders on the surface. 

Boulders on the surface may cause breakage of timber 

when felled and can hinder yarding operations (fig. 7). 

Rock for road construction is readily available in this 

unit. Snowpack in winter limits the use of equipment and 

restricts access. Disturbance of the protective layer of 

duff can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting noble fir or Douglas fir 

seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock 

occurs infrequently. Droughtiness of the surface layer 

reduces seedling survival, especially on south- and 

southwest-facing slopes. Logging activities can readily 
displace the surface layer. Seedlings that grow in the 

less fertile underlying material exhibit poor growth. 

Trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

kinnikinnick, penstemon, sedges, strawberry, and 

lupine. 

This map unit is in capability subclass Vlls. 

89-Polepatch extremely bouldery loamy sand, 

cold, 0 to 30 percent slopes. This very deep, somewhat 

excessively drained soil is on alluvial fans and terraces. It 

formed in lahar material with a mantle of volcanic ash. 

The native vegetation is mainly scattered conifers and 

shrubs. Elevation is 4,000 to 4,600 feet. The average 

annual precipitation is about 135 inches, the average 

annual air temperature is about 40 degrees F. and the 

average frost-free period is 70 to 90 days. 

Typically. the surface is covered with a mat of 

decomposed needles. Leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown extremely 

bouldery loamy sand 12 inches thick. The underlying 

material to a depth of 60 inches or more is dark gray 

extremely cobbly sand, fine sandy loam, and extremely 

stony coarse sand. 

Included in this unit are small areas of Lonestar and 

Pelee soils on back slopes of mountains and Shoestring 

soils on terraces. Also included are small areas of soils 

that are shallow or moderately deep to bedrock and 

Polepatch soils that have a cobbly surface layer. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Polepatch soil is rapid. Available 

water capacity is low. Effective rooting depth is 35 to 40 

inches. Runoff is slow, and the hazard of water erosion is 

slight. 

Most areas of this unit are used for recreation, 

wildlife habitat, and watershed. A few areas are used as 

woodland. 

This unit is poorly suited to the production of timber. 

Pacific silver fir, subalpine fir, and western hemlock are 

the main woodland species on this unit, On the basis of a 

100-year site curve, the mean site index is 71 for western 

hemlock, and on the basis of a 50-year site curve, the 

mean site index is 50. The culmination of the mean 

annual increment (CMAI) for western hemlock is 75 

cubic feet per acre per year at age 60. Estimates of the 

site index or CMAI for Pacific silver fir and subalpine fir 

have not been made. Among the trees of limited extent 

are lodgepole pine, noble fir, and Douglas fir. 

The main limitations for harvesting timber are 

snowpack in winter and boulders on the surface. 

Boulders on the surface may cause breakage of timber 

when felled and can hinder yarding operations. Rock for 

road construction is readily available in this unit. 

Snowpack in winter limits the use of equipment and 

restricts access. Disturbance of the protective layer of 

duff can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock occurs infrequently. Droughtiness of the 

surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. Low soil 

temperature in summer, deep snowpack, and a short 

growing season reduce the survival rate of planted and 

natural seedlings and delay their establishment. Logging 

activities can readily displace the surface layer. 

Seedlings that grow in the less fertile subsoil exhibit poor 

growth. Trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

kinnikinnick, penstemon, sedges, strawberry, and 

lupine. 

This map unit is in capability subclass VIIs. 

90-Riverwash. This map unit consists of very 

gravelly or sandy alluvium. It is on narrow flood plains 

adjacent to fast-moving streams and rivers. Slopes are 0 

to 5 percent. The unit commonly is barren, but some 

areas support a sparse cover of cottonwood, willows, 

and grasses. 

Included in this unit are small areas of McDoug and 

Pilchuck soils. Included areas make up about 10 

percent of the total area. 

Permeability of Riverwash is rapid or very rapid. 

Available water capacity is low. Runoff is slow, and the 

hazard of riparian erosion is severe. This unit is subject 

to frequent periods of flooding. 

This unit is used as wildlife habitat. 

This map unit is in capability subclass Vlllw. 

91-Rock outcrop-Cattcreek complex, cold, 65 to 

90 percent slopes. This map unit is on back slopes 

and in cirque basins on mountains. The native 

vegetation is mainly scattered true firs and shrubs. 

Elevation is 4,000 to 5,300 feet. The average annual 

precipitation is about 110 inches, the average annual air 

temperature is about 39 degrees F, and the average 

frost-free period is 70 to 90 days. 

This unit is about 60 percent Rock outcrop and 30 
percent Cattcreek very cindery loamy sand, cold, 65 to 

90 percent slopes. The components of this unit are so 

intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are small areas of Colter, Sinnice, 

and Tradedollar soils. Also included are small areas of 

Cattcreek soils that have slopes of less than 65 percent 

and have bedrock at a depth of 20 to 40 inches. Included 

areas make up about 10 percent of the total acreage. 

The Cattcreek soil is deep and well drained. It formed 

in pumice and volcanic ash over residuum and colluvium 

derived dominantly from andesite. Typically, the surface 

is covered with a mat of decomposed needles, leaves, 

and twigs 2 inches thick. Where mixed to a depth of 6 

inches, the surface layer is dark grayish brown and dark 

yellowish brown very cindery loamy sand. The upper 9 

inches of the subsoil is dark brown very cindery sand, and 

the lower 15 inches is strong brown extremely cindery 

sand. The next layer is a buried subsoil of dark yellowish 

brown extremely gravelly loam 24 inches thick over 

bedrock. Depth to bedrock ranges from 40 to 60 inches. 

Permeability of this Cattcreek soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 40 to 60 inches. Runoff is medium, and the 

hazard of water erosion is severe. 

Rock outcrop consists of exposed areas of dominantly 

andesite. Numerous escarpments are in this unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Pacific silver fir and western hemlock are the main 

woodland species on the Cattcreek soil. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 84 for western hemlock, and on the basis of a 50-year 

site curve, the mean site index is estimated to be 60. 

The culmination of the mean annual increment (CMAI) 

for western hemlock is 95 cubic feet per acre per year at 

age 60. The areas of Rock outcrop make up about 60 

percent of this unit and reduce yield accordingly. Estimates 

of the site index or CMAI for Pacific silver fir have not 

been made. Among the trees of limited extent are Douglas 

fir, noble fir, western white pine, and Alaska cedar. 

The main limitations for harvesting timber are Rock 

outcrop, steepness of slope, and snowpack in winter. 

Cable yarding systems generally are used on this unit. 

Rock outcrop may cause breakage of timber when felled 

and can hinder yarding operations. Avoiding Rock 

outcrop forces yarding paths to converge, which 

increases compaction and erosion of the soil. Logging 

roads require suitable surfacing for year-round use. 

Rock for road construction is readily available in this unit. 

Logging roads generally need full bench construction 

and require frequent maintenance. Snowpack in winter 

limits the use of equipment and restricts access. Cinders 

slough from road cuts onto the road surface. Establishing 

plant cover on steeper slopes that have been cut or 

filled reduces erosion. Following road construction and 

clearcutting, road failures and landslides can occur. 

Steep yarding paths, skid trails, and firebreaks are 

subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs infrequently. Droughtiness of 

the surface layer reduces seedling survival, especially 

on south- and southwest-facing slopes. Logging 

activities can readily displace the surface layer. 

Seedlings that grow in the less fertile subsoil exhibit poor 

growth. The areas of Rock outcrop limit the even 

distribution of reforestation. Trees occasionally are 

subject to windthrow. 

Among the common forest understory plants are Sitka 

alder, common beargrass, Oregongrape, longtube 

twinflower, western brackenfern, and bunchberry 

dogwood. 

The Rock outcrop is in capability subclass VIlls, and 

the Cattcreek soil is in capability subclass VIIe. 

92-Rock outcrop-Rubble land complex. This map 

unit is on mountain slopes. It is barren. Elevation is 

4,000 to 9,671 feet. The average annual precipitation is 

about 130 inches, the average annual air temperature is 

about 35 degrees F, and the average frost-free season 

is 30 to 70 days. 

This unit is about 60 percent Rock outcrop and 30 

percent Rubble land. The components of this unit are 

so intricately intermingled that it was not practical to 

map them separately at the scale used. 

Included in this unit are areas of Shoestring soils and 

snow and ice fields. Most of these areas are on Mount 

St. Helens. 

Rock outcrop consists of exposed areas of basalt 

and andesite. 

Rubble land consists of areas characterized by steep 
and very steep side slopes and avalanche tracks. It 

consists of about 90 percent fragmental rock, including 

cobbles, stones, and boulders. 

This unit is used for esthetic value. 

This map unit is in capability subclass VIIIs. 

93-Rock outcrop-Xerorthents complex, 50 to 90 

percent slopes. This map unit is on back slopes and 

escarpments of mountains. The native vegetation is mainly 

shrubs and scattered conifers. Elevation is 100 to 2,200 

feet. The average annual precipitation is about 50 inches, 

the average annual air temperature is about 53 degrees 

F. and the average frost-free period is 130 to 150 days. 

This unit is about 65 percent Rock outcrop and 25 

percent Xerorthents. The components of this unit are so 

intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are small areas of McElroy, Skoly, 

and St. Martin soils on landslides. Included areas make 

up about 10 percent of the total acreage. 

The Xerorthents are shallow to deep and are well 

drained. They formed in colluvium derived dominantly 

from basalt, andesite, and some volcanic ash. No single 

profile is typical of Xerothents, but one commonly 

observed in the survey area has a surface layer of very 

dark grayish brown gravelly loam 6 inches thick. The 

upper 13 inches of the underlying material is dark brown 

very gravelly loam, and the lower part to a depth of 31 

inches is brown extremely gravelly clay loam over bedrock. 

Depth to bedrock ranges from 10 to 60 inches. 

Permeability of the Xerorthents is moderately rapid. 

Available water capacity is low. Effective rooting depth is 

10 to 60 inches. Runoff is medium to rapid, and the 

hazard of water erosion is moderate to severe. 

Rock outcrop consists of exposed areas of dominantly 

basalt and andesite. Numerous escarpments are in this 

unit. 

This unit is used as wildlife habitat and for esthetic 

value. 

This unit is poorly suited to the production of timber. 

Scattered ponderosa pine and Oregon white oak are 

the main woodland species. 

Among the common forest understory plants are 

common snowberry, Oregongrape, rose, trailing 

blackberry, and western hazel. 

The Rock outcrop is in capability subclass Vllls, and 

the Xerorthents are in capability subclass Vlls. 

94-Shoestring fine sandy loam, 0 to 30 percent 

slopes. This very deep, well drained soil is on terraces 

and terrace escarpments. It formed in aerially deposited 

volcanic ash and pumice over pyroclastic flow and lahar 

material. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 2,700 to 4,500 feet. The 

average annual precipitation is about 130 inches, the 

average annual air temperature is about 41 degrees F, 

and the average frost-free period is 70 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 5 inches, the surface layer 

and upper part of the subsoil are very dark gray fine sandy 

loam. The next 3 inches of the subsoil is dark gray very 

gravelly sand, and the lower 16 inches is dark brown 

sandy loam and very dark brown loamy sand. The 

substratum to a depth of 60 inches or more is dark 

grayish brown very cobbly sand and dark gray very gravelly 

sand. 

Included in this unit are small areas of Lonestar and 

Pelee soils on mountain slopes and Forsyth, Polepatch, 

and St. Helens soils on terraces and terrace 

escarpments. Also included are small areas of poorly 

drained soils in depressional areas. Included areas make 

up about 10 percent of the total acreage. 

Permeability of this Shoestring soil is moderate in the 

subsoil and rapid in the substratum. Available water 

capacity is moderate. Effective rooting depth is 60 inches 

or more. Runoff is slow, and the hazard of water erosion 

is slight. 

This unit is used for woodland. recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is estimated to 

be 105 for western hemlock and 104 for Douglas fir. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 75 for western hemlock and 80 for 

Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 151 cubic feet 

per acre per year at age 60, and the CMAI for Douglas fir 

is 89 cubic feet at age 60. Estimates of the site index or 

CMAI for Pacific silver fir have not been made. Among the 

trees of limited extent are noble fir and western white pine.

The main limitation for harvesting timber is snowpack in 

winter. Use of wheeled and tracked equipment when the 

soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are slippery and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in 

this unit. Snowpack in winter limits the use of equipment 

and restricts access. Disturbance of the protective layer of 

duff can be reduced with the careful 
use of wheeled and tracked equipment. 

Reforestation can be accomplished by planting noble 

fir or Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. 

Logging activities can readily displace the surface layer. 

Seedlings that develop in the less fertile subsoil exhibit 

poor growth. 

Among the common forest understory plants are salal, 

red huckleberry, false Solomons seal, trillium, and 

bunchberry dogwood. 

This map unit is in capability subclass Vls. 

95-Shoestring fine sandy loam, 50 to 90 percent 

slopes. This very deep. well drained soil is on terrace 

escarpments. It formed in aerially deposited volcanic ash 

and pumice over pyroclastic flow and lahar material. The 

native vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,700 to 4,500 feet. The average annual 

precipitation is about 130 inches, the average annual air 

temperature is about 41 degrees F, and the average 

frost-free period is 70 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 5 inches, the surface layer 

and the upper part of the subsoil are very dark gray fine 

sandy loam. The next 3 inches of the subsoil are dark 

gray very gravelly sand, and the lower 16 inches is dark 

brown sandy loam and very dark brown loamy sand. 

The substratum to a depth of 60 inches or more is dark 

grayish brown very cobbly sand and dark gray very 

gravelly sand. 

Included in this unit are small areas of Bandid.. 

Bannel, Lonestar, and Pelee soils on mountain slopes. 

Also included are small areas of Rock outcrop and 

Badland. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this Shoestring soil is moderate in the 

subsoil and rapid in the substratum. Available water 

capacity is moderate. Effective rooting depth is 60 inches 

or more. Runoff is rapid, and the hazard of water erosion 

is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir 

are the main woodland species on this unit. On the 

basis of a 100-year site curve, the mean site index is 

estimated to be 105 for western hemlock and 110 for 

Douglas fir. On the basis of a 50-year site curve, the 

mean site index is estimated to be 75 for western 

hemlock and 80 for Douglas fir. The culmination of the 

mean annual increment (CMAI) for western hemlock is 

151 cubic feet per acre per year at age 60, and the CMAI 

for Douglas fir is 89 cubic feet at age 60. Estimates of the 

site index or CMAI for Pacific silver fir have not been 

made. Among the trees of limited extent are noble fir and 

western white pine. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. Steepness of 

slope restricts the use of wheeled and tracked equipment 

in skidding. Cable yarding systems generally are safer 

and disturb the soil less. Unsurfaced roads and skid trails 

are slippery and can be impassable when wet. Logging 

roads require suitable surfacing for year-round use. Rock 

for road construction is readily available in this unit. 

Logging roads generally need full bench construction and 

require frequent maintenance. Snowpack in winter limits 

the use of equipment and restricts access. Establishing 

plant cover on steeper slopes that have been cut or filled 

reduces erosion. Steep yarding paths, skid trails, and 

firebreaks are subject to rifling and gullying unless plant 

cover is maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Reforestation can be accomplished by planting noble 

fir and Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Logging activities 

can readily displace the surface layer. Seedlings that 

develop in the less fertile subsoil exhibit poor growth. 

Among the common forest understory plants are 

salal. huckleberry, false Solomons seal, trillium, and 

bunchberry dogwood. 

This map unit is in capability subclass VIIe. 

96-Sinnice extremely cindery loamy sand, 5 to 30 

percent slopes. This very deep, well drained soil is on 

foot slopes and ridgetops of mountains. It formed in 

aerially deposited layers of volcanic ash and pumice. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 2,800 to 4,000 feet. The average 

annual precipitation is about 125 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free period is 75 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches 

thick. Where mixed to a depth of 7 inches, the surface 

layer and upper part of the subsoil are light gray 

extremely cindery loamy sand. The upper 2 inches of 

the subsoil is dark brown fine sandy loam, and the 

lower 6 inches 
is very dark brown loamy sand. The substratum to a 

depth of 60 inches or more is light gray extremely 

cindery sand. 

Included in this unit are small areas of Colter, 

Minniepeak, and Pelee soils. Included areas make up 

about 5 percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid in 

the subsoil and very rapid in the substratum. Available 

water capacity is moderate. Effective rooting depth is 60 

inches or more. Runoff is slow, and the hazard of 

water erosion is slight. 

This unit is used for woodland, recreation. wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, Douglas fir, and 

noble fir are the main woodland species on this unit. On 

the basis of a 100-year site curve, the mean site index 

is estimated to be 113 for western hemlock and 110 for 

Douglas fir. On the basis of a 50-year site curve, the mean 

site index is estimated to be 80 for western hemlock and 

85 for Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 166 cubic feet 

per acre per year at age 50, and the CMAI for Douglas fir is 

98 cubic feet at age 60. Estimates of the site index or CMAI 

for Pacific silver fir and noble fir have not been made. 

Among the trees of limited extent is western redcedar. 

Areas on ridgetops that are subject to strong, persistent 

winds are less productive than other areas of this unit. 

The main limitation for harvesting timber is snowpack 

in winter. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. The surface layer is loose when dry, 

which limits the use of wheeled and tracked equipment. 

Snowpack in winter limits the use of equipment and 

restricts access. Cinders slough from road cuts onto the 

road surface. Establishing plant cover on steeper slopes 

that have been cut or filled reduces erosion. Disturbance 

of the protective layer of duff can be reduced with the 

careful use of wheeled and tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting noble fir and Douglas fir 

seedlings. If seed trees are present. natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. Droughtiness of the 

surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. The high 

temperature of the surface layer in summer reduces 

seedling survival. The mortality rate of seedlings and the 

hazard of windthrow are higher in areas on ridgetops that 

are subject to strong, persistent winds 

than in other areas of this unit. Logging activities can 

readily displace the surface layer. Seedlings that 

develop in the less fertile subsoil exhibit poor growth. 

Trees occasionally are subject to windthrow. 

Among the common forest understory plants are red 

huckleberry, western brackenfern, vine maple. princes 

pine, Sitka alder, and willow. 

This map unit is in capability subclass Vls. 

97-Sinnice extremely cindery loamy sand, 30 to 

65 percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in aerially deposited 

layers of volcanic ash and pumice. The native vegetation 

is mainly mixed conifers. Elevation is 2,800 to 4,000 

feet. The average annual precipitation is about 125 

inches. the average annual air temperature is about 39 

degrees F. and the average frost-free period is 75 to 90 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

light gray extremely cindery loamy sand. The upper 2 

inches of the subsoil is dark brown fine sandy loam, and 

the lower 6 inches is very dark brown loamy sand. The 

substratum to a depth of 60 inches or more is light gray 

extremely cindery sand. 

Included in this unit are small areas of Colter, 

Minniepeak, and Pelee soils. Also included are small 

areas of Sinnice soils that have more than 20 inches 

of pumice on the surface. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid in 

the subsoil and very rapid in the substratum. Available 

water capacity is moderate. Effective rooting depth is 

60 inches or more. Runoff is slow, and the hazard of 

water erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, Douglas fir, and 

noble fir are the main woodland species on this unit. On 

the basis of a 100-year site curve, the mean site index 

is estimated to be 113 for western hemlock and 110 for 

Douglas fir, On the basis of a 50-year site curve, the mean 

site index is estimated to be 80 for western hemlock and 

85 for Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 166 cubic feet 

per acre per year at age 50, and the CMAI for Douglas 

fir is 98 cubic feet at age 60. Estimates of the site index 

or CMAI for Pacific silver fir and noble fir have not been 

made. Among the trees of limited extent is western 

redcedar. 

The main limitations for harvesting timber are 
snowpack in winter and steepness of slope. When 

harvesting timber, steepness of slope restricts the use of 

wheeled and tracked equipment in skidding. Cable 

yarding systems generally are safer and disturb the soil 

less. Logging roads require suitable surfacing for yearround use. Rock for road construction is not readily 

available in this unit. Snowpack in winter limits the use of 

equipment and restricts access. Cinders slough from road 

cuts onto the road surface. Establishing plant cover on 

steeper slopes that have been cut or filled reduces erosion. 

Following road construction and clearcutting, road failures 

and landslides can occur. Steep yarding paths, skid trails, 

and firebreaks are subject to rilling and gullying unless 

plant cover is maintained or adequate water bars are 

provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir or Douglas fir seedlings. If seed trees 

are present, natural reforestation of cutover areas by 

western hemlock and Pacific silver fir occurs periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. The high temperature of the surface layer in 

summer reduces seedling survival. Logging activities can 

readily displace the surface layer. Seedlings that develop 

in the less fertile subsoil exhibit poor growth. Trees 

occasionally are subject to windthrow. 

Among the common forest understory plants are red 

huckleberry, western brackenfern, vine maple, princes 

pine, Sitka alder, and willow. 

This map unit is in capability subclass VIIe. 

98-Sinnice extremely cindery loamy sand, 65 to 90 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in aerially deposited 

layers of volcanic ash and pumice. The native vegetation 

is mainly mixed conifers. Elevation is 2,800 to 4,000 feet. 

The average annual precipitation is about 125 inches, the 

average annual air temperature is about 39 degrees F, and 

the average frost-free period is 75 to 90 days. 

Typically. the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

light gray extremely cindery loamy sand. The upper 2 

inches of the subsoil is dark brown fine sandy loam. and 

the lower 6 inches is very dark brown loamy sand. The 

substratum to a depth of 60 inches or more is light gray 

extremely cindery sand. 

 Included in this unit are small areas of Colter, 

Minniepeak, and Pelee soils. Also included are small 

areas of Rock outcrop. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid in 

the subsoil and very rapid in the substratum. Effective 

rooting depth is 60 inches or more. Runoff is medium, and 

the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, Douglas fir, and 

noble fir are the main woodland species on this unit. On 

the basis of a 100-year site curve, the mean site index 

is estimated to be 113 for western hemlock and 110 for 

Douglas fir. On the basis of a 50-year site curve, the mean 

site index is estimated to be 80 for western hemlock and 85 

for Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 166 cubic feet 

per acre per year at age 50, and the CMAI for Douglas fir 

is 98 cubic feet at age 60. Estimates of the site index or 

CMAI for Pacific silver fir and noble fir have not been 

made. Among the trees of limited extent is western 

redcedar. Areas on ridgetops that are subject to strong, 

persistent winds are less productive than other areas of 

this unit. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. Cable yarding 

systems generally are used on this unit. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is not readily available in this unit. 

Snowpack in winter limits the use of equipment and 

restricts access. Logging roads generally need full 

bench construction and require frequent maintenance. 

Cinders slough from road cuts onto the road surface. 

Establishing plant cover on steeper slopes that have 

been cut or filled reduces erosion. Following road 

construction and clearcutting, road failures and 

landslides can occur. Steep yarding paths, skid trails, 

and firebreaks are subject to rifling and gullying unless 

plant cover is maintained or adequate water bars are 

provided. Harvesting systems that lift logs entirely off the 

ground reduce the disturbance of the protective layer of 

duff. Avoiding areas of Rock outcrop forces yarding and 

skidding paths to converge, which increases compaction 

and erosion of the soil. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir or Douglas fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by western hemlock and Pacific silver fir occurs 

periodically. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. The high
temperature of the surface layer in summer reduces 

seedling survival. Logging activities can readily displace 

the surface layer. Seedlings that develop in the less fertile 

subsoil exhibit poor growth. Trees occasionally are 

subject to windthrow. 

Among the forest understory plants are red 

huckleberry, western brackenfern, vine maple, princes 

pine, Sitka alder, and willow. 

This map unit is in capability subclass Vlle. 

99-Sinnice extremely cindery loamy sand, 

cold, 5 to 30 percent slopes. This very deep, well 

drained soil is on foot slopes and ridgetops of mountains. 

It formed in aerially deposited layers of volcanic ash and 

pumice. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 4,000 to 5,000 feet. The average 

annual precipitation is about 125 inches. the average 

annual air temperature is about 38 degrees F, and the 

average frost-free period is 75 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

light gray extremely cindery loamy sand. The upper 2 

inches of the subsoil is dark brown fine sandy loam, and 

the lower 6 inches is very dark brown loamy sand. The 

substratum to a depth of 60 inches or more is light gray 

extremely cindery sand. 

Included in this unit are small areas of Colter, 

Minniepeak, and Pelee soils. Also included are small 

areas of Sinnice soils that have more than 20 inches of 

pumice on the surface. Included areas make up about 5 

percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid in 

the subsoil and very rapid in the substratum. Available 

water capacity is moderate. Effective rooting depth is 60 

inches or more. Runoff is slow, and the hazard of water 

erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and noble fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 98 for western hemlock, and on the basis of a 50-year 

site curve, the mean site index is estimated to be 70. 

The culmination of the mean annual increment (CMAI) for 

western hemlock is 118 cubic feet per acre per year at 

age 60. Estimates of the site index or CMAI for Pacific 

silver fir and noble fir have not been made. Among the 

trees of limited extent is subalpine fir. Areas on ridgetops 

that are subject to strong, persistent winds are less 

productive than other areas of this unit. 

The main limitation for harvesting timber is snowpack 

in winter. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. The surface layer is loose when 

dry, which limits the use of wheeled and tracked 

equipment. Snowpack in winter limits the use of 

equipment and restricts access. Cinders slough from 

road cuts onto the road surface. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Disturbance of the protective layer of duff can 

be reduced with the careful use of wheeled and tracked 

equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock, Pacific silver fir, and subalpine fir occurs 

infrequently. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. Low soil temperature in summer, deep 

snowpack, and a short growing season reduce the 

survival rate of planted and natural seedlings and delay 

their establishment. The mortality rate of seedlings and 

the hazard of windthrow are higher in areas on ridgetops 

that are subject to strong, persistent winds than in other 

areas of this unit. Logging activities can readily displace 

the surface layer. Seedlings that develop in the less 

fertile subsoil exhibit poor growth. Trees occasionally are 

subject to windthrow. 

Among the common forest understory plants are red 

huckleberry, western brackenfern, vine maple, princes 

pine, Sitka alder, common beargrass, and willow. 

This map unit is in capability subclass Vls. 

100-Sinnice extremely cindery loamy sand, cold, 

30 to 65 percent slopes. This very deep, well drained soil 

is on back slopes of mountains. It formed in aerially 

deposited layers of volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 4,000 to 5,000 feet. The average annual 

precipitation is about 125 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free period is 75 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

light gray extremely cindery loamy sand. The upper 2 

inches of the subsoil is dark brown fine sandy loam, and 

the lower 6 inches is very dark brown loamy sand. The 

substratum to a depth of 60 inches or more is light gray 

extremely cindery sand. 

Included in this unit are small areas of Colter, 
Minniepeak, and Pelee soils. Also included are small 

areas of Sinnice soils that have more than 20 inches of 

pumice on the surface. Included areas make up about 

10 percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid in 

the subsoil and very rapid in the substratum. Available 

water capacity is moderate. Effective rooting depth is 60 

inches or more. Runoff is slow, and the hazard of

water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat. and watershed. 

Western hemlock, Pacific silver fir, and noble fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 98 for western hemlock, and on the basis of a 50-year 

site curve, the mean site index is estimated to be 70. 

The culmination of the mean annual increment (CMAI) for 

western hemlock is 118 cubic feet per acre per year at age 

60. Estimates of the site index or CMAI for Pacific silver fir 

and noble fir have not been made. Among the trees of 

limited extent is subalpine fir. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. When 

harvesting timber, steepness of slope restricts the use of 

wheeled and tracked equipment in skidding. Cable 

yarding systems generally are safer and disturb the soil 

less. Logging roads require suitable surfacing for yearround use. Rock for road construction is not readily 

available in this unit. Snowpack in winter limits the use of 

equipment and restricts access. Cinders slough from 

road cuts onto the road surface. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Following road construction and clearcutting, 

road failures and landslides can occur. Steep yarding 

paths, skid trails, and firebreaks are subject to rifling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock, Pacific silver fir, and subalpine fir occurs 

infrequently. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. Low soil temperature in summer, deep 

snowpack, and a short growing season reduce the 

survival rate of planted and natural seedlings and delay 

their establishment. Logging activities can readily 

displace the surface layer. Seedlings that develop in the 

less fertile subsoil exhibit poor growth. Trees 

occasionally are subject to windthrow. 

Among the common forest understory plants are red 

huckleberry, western brackenfern, vine maple, princes 

pine, Sitka alder, common beargrass, and willow. 

This map unit is in capability subclass VIIe. 

101-Sinnice extremely cindery loamy sand, cold, 

65 to 90 percent slopes. This very deep, well drained soil 

is on back slopes of mountains. It formed in aerially 

deposited layers of volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 4,000 to 5,000 feet. The average annual 

precipitation is about 125 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free season is 75 to 90 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

light gray extremely cindery loamy sand. The upper 2 

inches of the subsoil is dark brown fine sandy loam, and 

the lower 6 inches is very dark brown loamy sand. The 

substratum to a depth of 60 inches or more is light gray 

extremely cindery sand. 

Included in this unit are small areas of Colter, 

Minniepeak, and Pelee soils. Also included are small 

areas of Sinnice soils that have more than 20 inches of 

pumice on the surface. Included areas make up about 

10 percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid in 

the subsoil and very rapid in the substratum. Available 

water capacity is moderate. Effective rooting depth is 

60 inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and noble fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 98 for western hemlock, and on the basis of a 50-

year site curve, the mean site index is estimated to be 

70. The culmination of the mean annual increment 

(CMAI) for western hemlock is 118 cubic feet per acre 

per year at age 60. Estimates of the site index or CMAI 

for Pacific silver fir and noble fir have not been made. 

Among the trees of limited extent is subalpine fir. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. Cable 

yarding systems generally are used on this unit. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available 

in this unit. Logging roads generally need full bench 

construction and frequent maintenance. Snowpack in 

winter limits the use of equipment and restricts access. 
Cinders slough from road cuts onto the road surface. 

Establishing plant cover on steeper slopes that have 

been cut or filled reduces erosion. Following road 

construction and clearcutting, road failures and 

landslides can occur. Steep yarding paths, skid trails, 

and firebreaks are subject to rilling and gullying unless 

plant cover is maintained or adequate water bars are 

provided. Harvesting systems that lift logs entirely off the 

ground reduce the disturbance of the protective layer of 

duff. 

Seedling mortality is the main concern in the production 

of timber. Reforestation can be accomplished by planting 

noble fir seedlings. If seed trees are present. natural 

reforestation of cutover areas by western hemlock, Pacific 

silver fir, and subalpine fir occurs infrequently. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing slopes. 

Low soil temperature in summer, deep snowpack, and a 

short growing season reduce the survival rate of planted 

and natural seedlings and delay their establishment. 

Logging activities can readily displace the surface layer. 

Seedlings that develop in the less fertile subsoil exhibit 

poor growth. Trees occasionally are subject to windthrow. 

Among the common forest understory plants are red 

huckleberry, western brackenfern, vine maple, princes 

pine, Sitka alder, common beargrass, and willow. 

This map unit is in capability subclass VIIe. 

102-Sinnice, cold-Rock outcrop complex, 65 to 90 

percent slopes. This map unit is on back slopes of 

mountains. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 4,000 to 5,000 feet. The average 

annual precipitation is about 125 inches, the average 

annual air temperature is about 38 degrees F, and the 

average frost-free period is 75 to 90 days. 

This unit is about 70 percent Sinnice extremely cindery 

loamy sand, cold, 65 to 90 percent slopes, and 20 percent 

Rock outcrop. The components of this unit are so 

intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are small areas of Colter and 

Minniepeak soils. Also included are small areas of 

Sinnice soils that are less than 40 inches deep to 

bedrock. Included areas make up about 10 percent of 

the total acreage. 

The Sinnice soil is very deep and well drained. It formed 

in aerially deposited layers of volcanic ash and pumice. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 7 inches, the surface layer is 

light gray extremely cindery loamy sand. The upper 2 

inches of the subsoil is dark brown fine sandy loam, and 

the lower 6 inches is very dark brown loamy sand. The 

substratum to a depth of 60 inches or more is light gray 

extremely cindery sand. 

Permeability of the Sinnice soil is moderately rapid in 

the subsoil and very rapid in the substratum. Available 

water capacity is moderate. Effective rooting depth is 60 

inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Rock outcrop consists mainly of exposed areas of 

andesite and basalt. Numerous escarpments are in this 

unit. 

Western hemlock, Pacific silver fir, and noble fir are the 

main woodland species on the Sinnice soil. On the basis 

of a 100-year site curve, the mean site index is 

estimated to be 98 for western hemlock, and on the basis 

of a 50-year site curve, the mean site index is estimated to 

be 70. The culmination of the mean annual increment 

(CMAI) for western hemlock is 118 cubic feet per acre per 

year at age 60. The areas of Rock outcrop make up about 

20 percent of this unit and reduce yield accordingly. 

Estimates of the site index or CMAI for Pacific silver fir and 

noble fir have not been made. Among the trees of limited 

extent is subalpine fir. Areas on ridgetops that are subject 

to strong, persistent winds are less productive than other 

areas of this unit. 

The main limitations for harvesting timber are Rock 

outcrop, snowpack in winter, and steepness of slope. 

Cable yarding systems generally are used on this unit. 

Rock outcrop may cause breakage of timber when felled 

and can hinder yarding operations. Avoiding areas of 

Rock outcrop forces yarding and skidding paths to 

converge, which increases compaction and erosion of the 

soil. Logging roads require suitable surfacing for yearround use. Rock for road construction is not readily 

available in this unit. Logging roads generally need full 

bench construction and require frequent maintenance. 

Snowpack in winter limits the use of equipment and 

restricts access. Cinders slough from road cuts onto the 

road surface. Establishing plant cover on steeper slopes 

that have been cut or filled reduces erosion. Following 

road construction and clearcutting, road failures and 

landslides may occur. Steep yarding paths, skid trails, and 

firebreaks are subject to rilling and gullying unless plant 

cover is maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 
production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock, Pacific silver fir, and subalpine fir occurs 

infrequently. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. The areas of Rock outcrop limit the even 

distribution of reforestation. Logging activities can readily 

displace the surface layer. Seedlings that develop in the 

less fertile subsoil exhibit poor growth. Trees occasionally 

are subject to windthrow. 

Among the common forest understory plants are red 

huckleberry, western brackenfern, vine maple, princes 

pine, Sitka alder, common beargrass, and willow. 

The Sinnice soil is in capability subclass Vlle, and 

the Rock outcrop is in capability subclass VIIIs. 

103-Skamania very fine sandy loam, 0 to 8 percent 

slopes. This very deep. well drained soil is on terraces. It 

formed in mixed alluvium derived dominantly from basalt. 

andesite, and some volcanic ash. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 200 to 

800 feet. The average annual precipitation is about 70 

inches, the average annual air temperature is about 48 

degrees F, and the average frost-free period is 110 to 

160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 10 inches, the surface layer 

is dark brown very fine sandy loam. The upper 17 inches 

of the subsoil is dark yellowish brown very fine sandy 

loam, and the lower 16 inches is dark brown fine sandy 

loam. The substratum to a depth of 60 inches or more is 

dark yellowish brown loamy fine sand. 

Included in this unit are small areas of Stabler and 

Washougal soils and Steever soils on mountain slopes. 

Also included are small areas of Skamania and Skoly 

soils that have slopes of more than 8 percent and are on 

mountain slopes. Included areas make up about 15 

percent of the total acreage. 

Permeability of this Skamania soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is slow, and 

the hazard of water erosion is slight. 

This unit is used for hayland, pastureland, homesites, 

woodland, wildlife habitat, and recreation. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition and to 

protect the soil from erosion. Mowing helps to 

maintain uniform growth and discourages selective 

grazing. 

This unit is well suited to homesite development. 

Revegetating disturbed areas around construction sites 

as soon as possible helps to control soil blowing. Plant 

cover can be established and maintained through proper 

fertilizing, seeding, mulching, and shaping of the slopes. 

In summer, irrigation is needed for lawn grasses, shrubs, 

vines, shade trees, and ornamental trees. The soil is 

susceptible to frost action, which may limit construction of

roads and streets. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 151 for Douglas 

fir, and on the basis of a 50-year site curve, the mean site 

index is 114. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 159 cubic feet per 

acre per year at age 60. Estimates of the site index or 

CMAI for western hemlock and red alder have not been 

made. Among the trees of limited extent are grand fir and 

bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Disturbance of the protective layer of duff can 

be reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present. natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, Pacific dogwood, creambush oceanspray, trailing 

blackberry, salal, western hazel. dwarf rose, common 

snowberry, and western swordfern. 

This map unit is in capability subclass Ile. 

104-Skamania very fine sandy loam, 8 to 15 

percent slopes. This very deep, well drained soil is on 

terraces. It formed in mixed alluvium derived dominantly 

from basalt, andesite, and some volcanic ash. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 200 to 800 feet. The average annual 
precipitation is about 70 inches, the average annual air 

temperature is about 48 degrees F, and the average 

frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves. and twigs 2 inches thick. 

Where mixed to a depth of 10 inches, the surface layer is 

very dark brown and dark brown very fine sandy loam. The 

upper 17 inches of the subsoil is dark yellowish brown 

very fine sandy loam, and the lower 16 inches is dark 

brown fine sandy loam. The substratum to a depth of 60 

inches or more is dark yellowish brown loamy fine sand. 

Included in this unit are small areas of Stabler and 

Washougal soils and Steever soils on mountain slopes. 

Also included are small areas of Skamania and Skoly 

soils that have slopes of less than 8 percent or more 

than 15 percent. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Skamania soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is slow, and the 

hazard of water erosion is moderate. 

This unit is used for hayland, pastureland, homesites, 

woodland, wildlife habitat, and recreation. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition and 

to protect the soil from erosion. Mowing helps to 

maintain uniform growth and discourages selective 

grazing. 

This unit is well suited to homesite development. The 

main limitations are steepness of slope and the hazard 

of erosion in the steeper areas. Only the part of the site 

that is used for construction should be disturbed. 

Preserving the existing plant cover during construction 

helps to control erosion. Revegetating disturbed areas 

around construction sites as soon as possible helps to 

control soil blowing. Structures to divert runoff are needed 

if buildings and roads are constructed. In summer, 

irrigation is needed for lawn grasses, shrubs, vines, 

shade trees, and ornamental trees. This soil is subject to 

frost action, which may limit construction of roads and 

streets. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 151 for 

Douglas fir, and on the basis of a 50-year site curve, the 

mean site index is 114. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 159 cubic feet 

per acre per year at age 60. Estimates of the site index or 

CMAI for western hemlock and red alder 

have not been made. Among the trees of limited extent 

are grand fir and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Disturbance of the protective layer of duff can 

be reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, Pacific dogwood, creambush oceanspray, trailing 

blackberry, salal, western hazel, dwarf rose, common 

snowberry, and western swordfern. 

This map unit is in capability subclass Ille. 

105-Skamania very fine sandy loam, 15 to 30 

percent slopes. This very deep, well drained soil is on 

terraces. It formed in mixed alluvium derived dominantly 

from basalt, andesite, and some volcanic ash. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 200 to 800 feet. The average annual 

precipitation is about 70 inches, the average annual air 

temperature is about 48 degrees F, and the average 

frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 10 inches, the surface layer 

is very dark brown and dark brown very fine sandy loam. 

The upper 17 inches of the subsoil is dark yellowish 

brown very fine sandy loam, and the lower 16 inches is 

dark brown fine sandy loam. The substratum to a depth 

of 60 inches or more is dark yellowish brown loamy fine 

sand. 

Included in this unit are small areas of Washougal 

gravelly loam and Stabler and Steever soils on mountain 

slopes. Also included are small areas of Skoly soils on 

mountain slopes and Skamania soils that have slopes of 

less than 15 percent or more than 30 percent. Included 

areas make up about 15 percent of the total acreage. 
Permeability of this Skamania soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of erosion is moderate. 

Most areas of this unit are used for pastureland, 

homesites, woodland, wildlife habitat, or recreation. 

This unit is well suited to use as pastureland. The main 

limitations are steepness of slope and the hazard of 

erosion. Erosion can be controlled by growing pasture. 

The use of equipment is limited by steepness of slope. 

Proper stocking rates, pasture rotation, and restricted 

grazing during wet periods help to keep the pasture in 

good condition and to protect the soil from erosion. 

Fertilizer is needed to ensure optimum growth of grasses 

and legumes. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 151 for Douglas fir, 

and on the basis of a 50-year site curve, the mean site 

index is 114. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 159 cubic feet per acre

per year at age 60. Estimates of the site index or CMAI 

for western hemlock and red alder have not been made. 

Among the trees of limited extent are grand fir and bigleaf 

maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Disturbance of the protective layer of duff can 

be reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock and red alder occurs readily. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple. Pacific dogwood, creambush oceanspray, trailing 

blackberry, salal, western hazel, dwarf rose, common 

snowberry, and western swordfern. 

The main limitations of this unit for use as homesites 

are the steepness of slope and the hazard of erosion. 

Only the part of the site that is used for construction 

should be disturbed. Preserving the existing plant cover

during construction helps to control erosion. Plant cover 

can be established and maintained through proper 

fertilizing, seeding, mulching, and shaping of the slopes. 

Steepness of slope is a concern in installing septic tank 

absorption fields. Access roads should be designed to 

provide adequate cut-slope grade, and cross drains are 

needed to control surface runoff and keep soil losses to 

a minimum. This soil is subject to frost action, which 

may limit construction of roads and streets. 

This map unit is in capability subclass IVe. 

106-Skamania very fine sandy loam, 30 to 40 

percent slopes. This very deep, well drained soil is on 

terrace escarpments. It formed in mixed alluvium 

derived dominantly from basalt, andesite, and some 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 200 to 400 feet. The 

average annual precipitation is about 70 inches, the 

average annual air temperature is about 48 degrees F, 

and the average frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

Where mixed to a depth of 10 inches, the surface layer is 

very dark brown and dark brown very fine sandy loam. The 

upper 17 inches of the subsoil is dark yellowish brown 

very fine sandy loam, and the lower 16 inches is dark 

brown fine sandy loam. The substratum to a depth of 60 

inches or more is dark yellowish brown loamy fine sand. 

Included in this unit are small areas of Stabler and 

Washougal soils and St. Martin soils on landslides. Also 

included are small areas of Skamania and Skoly soils 

that have slopes of less than 30 percent and are on 

mountain slopes. Included areas make up about 15 

percent of the total acreage. 

Permeability of this Skamania soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is severe. 

This unit is used for woodland, wildlife habitat, and 

recreation. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 151 for 

Douglas fir, and on the basis of a 50-year site curve, the 

mean site index is 114. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 159 cubic feet 

per acre per year at age 60. Estimates of the site index 

or CMAI for western hemlock and red alder have not 

been made. Among the trees of limited extent are grand 

fir and bigleaf maple. 

The main limitation for harvesting timber is steepness 
of slope. When harvesting timber, steepness of slope 

restricts the use of wheeled and tracked equipment in 

skidding. Cable yarding systems generally are safer and 

disturb the soil less. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rifling and gullying 

unless they are protected by plant cover or adequate 

water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple. Pacific dogwood, creambush oceanspray, trailing 

blackberry, salal, western hazel, dwarf rose, common 

snowberry, and western swordfern. 

This map unit is in capability subclass VIe. 

107-Skelida silt loam, 5 to 15 percent slopes. 

This very deep, well drained soil is on terraces. It formed in 

loess and alluvium derived dominantly from basalt and 

andesite. The vegetation in areas not cultivated is mainly 

grass and scattered conifers. Elevation is 400 to 1,000 

feet. The average annual precipitation is about 60 inches. 

the average annual air temperature is about 50 degrees 

F, and the average frost-free period is 160 to 180 days. 

Typically, the surface layer is very dark grayish brown 

silt loam 15 inches thick. The subsoil to a depth of 60 

inches or more is dark yellowish brown silt loam. 

Included in this unit are small areas of Hesson. 

Mountzion, and Skoly soils on mountain slopes. Also 

included are small areas of Skelida soils that have a clay 

loam surface layer. Included areas make up about 15 

percent of the total acreage. 

Permeability of this Skelida soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 inches 

or more. Runoff is medium, and the hazard of water 

erosion is moderate. 

This unit is used mainly as cropland, pastureland, 

and hayland. It is also used for homesites, wildlife 

habitat, recreation, and woodland. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet periods 

help to keep the pasture in good condition and to protect 

the soil from erosion. Mowing helps to maintain uniform 

growth and discourages selective grazing. 

This unit is well suited to small grain. Returning all crop 

residue to the soil and using a cropping system that 

includes grasses, legumes, or grass-legume mixtures help 

to maintain fertility and tilth. Practices that can be used to 

control erosion include early fall seeding, stubble-mulch 

tillage, and construction of terraces, diversions, and 

grassed waterways. 

The main limitations of this unit for use as homesites 

are the steepness of slope and the hazard of erosion. 

Population growth has resulted in increased construction 

of homes on this unit. Preserving the existing plant cover 

during construction helps to control erosion. Mulch, 

fertilizer, and irrigation are needed to establish lawn 

grasses and other small-seeded plants. Access roads 

should be designed to provide adequate cut-slope grade, 

and drains are needed to control surface runoff and keep 

soil losses to a minimum. Buildings and roads should be 

designed to offset the effects of shrinking and swelling. 

This soil is subject to frost action, which may limit 

construction of roads and streets. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 160 for Douglas fir, and on the basis of a 50-year site 

curve, the mean site index is estimated to be 120. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 170 cubic feet per acre per year at age 65. 

Estimates of the site index or CMAI for western hemlock 

and red alder have not been made. Among the trees of 

limited extent is bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available 

in this unit. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas 
by western hemlock and red alder occurs readily. If the 

canopy is opened. brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, Pacific dogwood, salal, western hazel, dwarf 

rose, trailing blackberry, and cascara buckthorn. 

This map unit is in capability subclass IIIe. 

108-Skelida silt loam, 15 to 30 percent slopes. 

This very deep, well drained soil is on terraces. It 

formed in loess and alluvium derived dominantly from 

basalt and andesite. The vegetation in areas not 

cultivated is mainly grass and scattered conifers. 

Elevation is 400 to 1,000 feet. The average annual 

precipitation is about 60 inches, the average annual air 

temperature is 50 degrees F, and the average frost-free 

period is 160 to 180 days. 

Typically, the surface layer is very dark grayish brown 

silt loam 15 inches thick. The subsoil to a depth of 60 

inches or more is dark yellowish brown silt loam. 

Included in this unit are small areas of Hesson, 

Mountzion, and Skoly soils on mountain slopes. Also 

included are small areas of Skelida soils that have a clay 

loam surface layer and slopes of more than 30 percent. 

Included areas make up about 15 percent of the total 

acreage. 

Permeability of this Skelida soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 inches 

or more. Runoff is medium, and the hazard of water 

erosion is moderate. 

This unit is used mainly as pastureland. It is also 

used for wildlife habitat, recreation, woodland, and 

homesites. 

This unit is suited to use as pastureland. The main 

limitations are slope and the hazard of erosion. Erosion 

can be controlled by growing pasture. The use of 

equipment is limited by steepness of slope. Proper 

stocking rates, pasture rotation, and restricted grazing 

during wet periods help to keep the pasture in good 

condition and to protect the soil from erosion. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 

160 for Douglas fir, and on the basis of a 50-year site 

curve, the mean site index is estimated to be 120 for 

Douglas fir. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 170 cubic feet per acre per year at 

age 65. Estimates of the site index or CMAI for western 

hemlock and red alder have not been 

made. Among the trees of limited extent is bigleaf 

maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available 

in this unit. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, Pacific dogwood, salal, western hazel, dwarf 

rose, trailing blackberry, and cascara buckthorn. 

The main limitations of this unit for use as homesites 

are steepness of slope and the hazard of erosion. Only 

the part of the site that is used for construction should 

be disturbed. Preserving the existing plant cover during 

construction helps to control erosion. Plant cover can 

be established and maintained through proper fertilizing, 

seeding, mulching, and shaping of the slopes. Steepness 

of slope is a concern in installing septic tank absorption 

fields. Access roads should be designed to provide 

adequate cut-slope grade, and drains are needed to 

control surface runoff and keep soil losses toa minimum. 

Buildings and roads should be designed to offset the 

effects of shrinking and swelling. This soil is subject to 

frost action, which may limit construction of roads and 

streets. 

This map unit is in capability subclass IVe. 

109-Skoly stony loam, 2 to 15 percent slopes. 

This very deep, well drained soil is on mountain slopes. 

It formed in colluvium derived dominantly from basalt. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 200 to 2,200 feet. The average 

annual precipitation is about 80 inches, the average 

annual air temperature is about 50 degrees F, and the 

average frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 
The upper 5 inches of the surface layer is dark brown 

stony loam, and the lower 12 inches is dark brown very 

cobbly loam. The subsoil is dark brown very cobbly loam 

23 inches thick. The substratum to a depth of 60 inches 

or more is dark brown very cobbly loam. 

Included in this unit are small areas of Aschoff, 

Steever, Mountzion, and Skamania soils on terraces. 

Also included are small areas of Skoly soils that are less 

than 35 percent rock fragments or have slopes of more 

than 15 percent. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Skoly soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland. hayland. pastureland. 

homesites, wildlife habitat, and recreation. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is 144 for Douglas fir and 

140 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is 111 for Douglas fir and 

100 for western hemlock. The culmination of the mean 

annual increment (CMAI) for western hemlock is 218 

cubic feet per acre per year at age 60. and the CMAI 

for Douglas fir is 150 cubic feet at age 60. Among the 

trees of limited extent are red alder, bigleaf maple, and 

western redcedar. 

The main limitations for harvesting timber are stones 

on the surface and seasonal soil wetness. Use of 

wheeled and tracked equipment when the soil is moist 

produces ruts, compacts the soil, and damages the roots 

of trees. Unsurfaced roads and skid trails are soft and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Stones on the 

surface hinder harvesting and can cause breakage of 

timber. Occasional snowpack hinders the use of 

equipment and limits access in winter. Disturbance of the 

protective layer of duff can be reduced with the careful 

use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present. natural reforestation of cutover areas by 

western hemlock and red alder occurs readily. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, red huckleberry, salal, western hazel, 

Oregongrape, trailing blackberry, western swordfern, 

Oregon oxalis, and deerfoot vanillaleaf. 

This unit is well suited to use as hayland and 

pastureland. The main limitation is large stones in and 

on the surface layer. Proper stocking rates, pasture 

rotation, and restricted grazing during wet periods help 

to keep the pasture in good condition and to protect 

the soil from erosion. Mowing helps to maintain uniform 

growth and discourages selective grazing. 

The main limitations of this unit for use as homesites 

are the steepness of slope, shrink-swell potential, 

large stones, and hazard of erosion in the steeper areas. 

Only the part of the site that is used for construction 

should be disturbed. Topsoil can be stockpiled and used 

to reclaim areas disturbed during construction. Removal 

of pebbles, cobbles, and stones in disturbed areas is 

needed for best results when landscaping, particularly in 

areas used for lawns. Mulch, fertilizer, and irrigation are 

needed to establish lawn grasses and other smallseeded plants. Buildings and roads should be designed 

to offset the effects of shrinking and swelling. 

This map unit is in capability subclass IVs. 

110-Skoly stony loam, 15 to 30 percent slopes. 

This very deep, well drained soil is on mountain slopes. It 

formed in colluvium derived dominantly from basalt. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 200 to 2,200 feet. The average 

annual precipitation is about 80 inches, the average 

annual air temperature is about 50 degrees F, and the 

average frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper 5 inches of the surface layer is dark brown 

stony loam, and the lower 12 inches is dark brown very 

cobbly loam. The subsoil is dark brown very cobbly loam 

23 inches thick. The substratum to a depth of 60 

inches or more is dark brown very cobbly loam. 

Included in this unit are small areas of Aschoff, 

Steever, Mountzion, and Skamania soils on terraces. 

Also included are small areas of Skoly soils that are less 

than 35 percent rock fragments or have slopes of more 

than 30 percent or less than 15 percent. Included areas 

make up about 12 percent of the total acreage. 

Permeability of this Skoly soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, hayland, pastureland, 

wildlife habitat, and recreation. 
Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is 144 for Douglas fir and 

140 for western hemlock. On the basis of a 50-year site 

curve, the mean site index is 111 for Douglas fir and 100 for 

western hemlock. The culmination of the mean annual 

increment (CMAI) for western hemlock is 218 cubic feet 

per acre per year at age 60, and the CMAI for Douglas fir is 

150 cubic feet at age 60. Among the trees of limited extent 

are red alder, bigleaf maple, and western redcedar. 

The main limitations for harvesting timber are stones on 

the surface and seasonal soil wetness. Use of wheeled 

and tracked equipment when the soil is moist produces 

ruts, compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round. Rock for road construction is 

readily available in this unit. Stones on the surface hinder 

harvesting and can cause breakage of timber. Occasional 

snowpack hinders the use of equipment and limits access 

in winter. Disturbance of the protective layer of duff can be 

reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, red huckleberry, salal, western hazel, 

Oregongrape, trailing blackberry, western swordfern, 

Oregon oxalis, and deerfoot vanillaleaf. 

This unit is suited to use as hayland and pastureland. 

The main limitations are steepness of slope, the hazard of 

erosion, and large stones in and on the surface layer. 

Erosion can be controlled by growing pasture. The use of 

equipment is limited by stones on the surface and 

steepness of slope. Proper stocking rates, pasture 

rotation, and restricted grazing during wet periods help to 

keep the pasture in good condition and to protect the 

soil from erosion. Mowing twice a year helps to maintain 

uniform growth and discourages selective grazing. 

This map unit is in capability subclass IVe. 

111-Skoly stony loam, 30 to 65 percent slopes. 

This very deep, well drained soil is on mountain slopes. 

It formed in colluvium derived dominantly from basalt. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 200 to 2,200 feet. The average 

annual precipitation is about 80 inches, the average 

annual air temperature is about 50 degrees F, and the 

average frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper 5 inches of the surface layer is dark brown 

stony loam, and the lower 12 inches is dark brown very 

cobbly loam. The subsoil is dark brown very cobbly loam 

23 inches thick. The substratum to a depth of 60 inches or 

more is dark brown very cobbly loam. 

Included in this unit are small areas of Aschoff, Steever, 

Zygore, and Mountzion soils. Also included are small 

areas of Skoly soils that have slopes of less than 30 

percent. Included areas make up about 10 percent of the 

total acreage. 

Permeability of this Skoly soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is rapid, and the 

hazard of water erosion is severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 144 for Douglas fir 

and 140 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is 111 for Douglas fir and 

100 for western hemlock. The culmination of the mean 

annual increment (CMAI) for western hemlock is 218 

cubic feet per acre per year at age 60, and the CMAI for 

Douglas fir is 150 cubic feet at age 60. Among the trees of 

limited extent are red alder, bigleaf maple, and western 

redcedar. 

The main limitation for harvesting timber is steepness 

of slope. When harvesting timber, steepness of slope 

restricts the use of wheeled and tracked equipment in 

skidding. Cable yarding systems generally are safer and 

disturb the soil less. Use of wheeled and tracked 

equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round use. Rock for road construction 

is readily available in this unit. Stones on the surface 

hinder harvesting and can cause breakage of timber. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and 
firebreaks are subject to rifling and gullying unless plant 

cover is maintained or adequate water bars are provided.

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock and red alder occurs readily. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple. red huckleberry, salal, western hazel. 

Oregongrape, trailing blackberry, western swordfern, 

Oregon oxalis. and deerfoot vanillaleaf. 

This map unit is in capability subclass VIIe. 

112-Skoly-Rock outcrop complex, 5 to 30 percent 

slopes. This map unit is on mountain slopes. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 600 to 2,200 feet. The average annual 

precipitation is about 80 inches, the average annual air 

temperature is about 50 degrees F, and the average 

frost-free period is 110 to 160 days. 

This unit is about 60 percent Skoly stony loam. 5 to 30 

percent slopes, and 30 percent Rock outcrop. The 

components of this unit are so intricately intermingled 

that it was not practical to map them separately at the 

scale used. 

Included in this unit are small areas of Aschoff. 

Steever, and Zygore soils. Also included are small areas 

of shallow soils and talus slopes, mainly adjacent to the 

Rock outcrop. Included areas make up about 10 

percent of the total acreage. 

The Skoly soil is very deep and well drained. It formed 

in colluvium derived dominantly from basalt. Typically, the 

surface is covered with a mat of decomposed needles. 

leaves, and twigs 2 inches thick. The upper part of the 

surface layer is dark brown stony loam 5 inches thick, 

and the lower part is very cobbly loam 12 inches thick. 

The subsoil is dark brown very cobbly loam 23 inches 

thick. The substratum to a depth of 60 inches or more is 

dark brown very cobbly loam. 

Permeability of this Skoly soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

Rock outcrop consists of exposed areas of 

dominantly basalt. Numerous escarpments are in this 

unit. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on the Skoly soil. On the basis of a 

100-year site curve, the mean site index is 144 for 

Douglas fir and 140 for western hemlock. On the basis 

of a 50-year site curve, the mean site index is 111 for 

Douglas fir and 100 for western hemlock. The 

culmination of the mean annual increment (CMAI) for 

western hemlock is 218 cubic feet per acre per year at 

age 60. and the CMAI for Douglas fir is 150 cubic feet 

at age 60. The areas of Rock outcrop make up about 30

percent of this unit and reduce yield accordingly. Among 

the trees of limited extent are red alder, bigleaf maple, 

and western redcedar. 

The main limitations for harvesting timber are the 

areas of Rock outcrop and seasonal soil wetness. Use of 

wheeled and tracked equipment when the soil is moist 

produces ruts, compacts the soil, and damages the roots 

of trees. Rock outcrop may cause breakage oftimber 

when felled and can hinder yarding operations. Avoiding 

areas of Rock outcrop forces yarding and skidding paths 

to converge, which increases compaction and erosion of 

the soil. Unsurfaced roads and skid trails are soft and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Occasional 

snowpack hinders the use of equipment and limits access 

in winter. Disturbance of the protective layer of duff can be

reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock and red alder occurs readily. The 

areas of Rock outcrop limit the even distribution of 

reforestation. If the canopy is opened, brush invades 

and can prevent the establishment of Douglas fir 

seedlings and can delay natural reforestation by western 

hemlock unless controlled. 

Among the common forest understory plants are vine 

maple, red huckleberry, salal, western hazel, 

Oregongrape, trailing blackberry, western swordfern, 

Oregon oxalis, and deerfoot vanillaleaf. 

The Skoly soil is in capability subclass IVe, and 

the Rock outcrop is in capability subclass VIIIs. 

113-Skoly-Rock outcrop complex, 30 to 65 

percent slopes. This map unit is on mountain slopes. 
The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 600 to 2,200 feet. The average 

annual precipitation is about 80 inches, the average 

annual air temperature is about 50 degrees F, and the 

average frost-free period is 110 to 160 days. 

This unit is about 50 percent Skoly stony loam, 30 to 

60 percent slopes, and 40 percent Rock outcrop. The 

components of this unit are so intricately intermingled 

that it was not practical to map them separately at the 

scale used. 

Included in this unit are small areas of Aschoff, 

Steever, and Zygore soils. Also included are small areas 

of shallow soils and talus slopes, mainly adjacent to the 

Rock outcrop. Included areas make up about 10 

percent of the total acreage. 

The Skoly soil is very deep and well drained. It formed 

in colluvium derived dominantly from basalt. Typically, 

the surface is covered with a mat of decomposed 

needles, leaves, and twigs 2 inches thick. The upper part 

of the surface layer is dark brown stony loam 5 inches 

thick, and the lower part is very cobbly loam 12 inches 

thick. The subsoil is dark brown very cobbly loam 23 

inches thick. The substratum to a depth of 60 inches or 

more is dark brown very cobbly loam. 

Permeability of this Skoly soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is rapid, and the 

hazard of water erosion is severe. 

Rock outcrop consists of exposed areas of 

dominantly basalt. Numerous escarpments are in this 

unit. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on the Skoly soil. On the basis of a 

100-year site curve. the mean site index is 144 for 

Douglas fir and 140 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 111 for 

Douglas fir and 100 for western hemlock. The 

culmination of the mean annual increment (CMAI) for 

western hemlock is 218 cubic feet per acre per year at 

age 50, and the CMAI for Douglas fir is 150 cubic feet 

at age 60. The areas of Rock outcrop make up about 

40 percent of this unit and reduce yield accordingly. 

Among the trees of limited extent are red alder, bigleaf 

maple, and western redcedar. 

The main limitations for harvesting timber are 

steepness of slope and the areas of Rock outcrop. When 

harvesting timber, steepness of slope restricts the use of 

wheeled and tracked equipment in skidding. Cable 

yarding systems generally are safer and disturb the 

soil less. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Rock outcrop may cause 

breakage of timber when felled and can hinder yarding 

operations. Avoiding areas of Rock outcrop forces 

yarding and skidding paths to converge, which increases 

compaction and erosion of the soil. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in this 

unit. Occasional snowpack hinders the use of equipment 

and limits access in winter. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. The areas of 

Rock outcrop limit the even distribution of reforestation. If 

the canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, red huckleberry, salal, western hazel, 

Oregongrape, trailing blackberry, western swordfern, 

Oregon oxalis, and deerfoot vanillaleaf. 

The Skoly soil is in capability subclass VIIe, and the 

Rock outcrop is in capability subclass VIIIs. 

114-St. Helens sandy loam, 0 to 30 percent 

slopes. This very deep, well drained soil is on terraces. It 

formed in aerially deposited volcanic ash and pumice 

over pyroclastic flow and lahar. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 1,600 

to 2,800 feet. The average annual precipitation is about 

130 inches, the average annual air temperature is about 

44 degrees F, and the average frost-free period is 90 to 

110 days. 

Where mixed to a depth of 6 inches, the surface layer 

is very dark brown sandy loam. The upper 3 inches of the 

subsoil is light brownish gray extremely cindery loamy 

sand, the next 9 inches is dark brown sandy loam, and 

the lower 10 inches is dark grayish brown sand. The 

substratum to a depth of 60 inches or more is dark 

grayish brown very gravelly coarse sand. 

Included in this unit are small areas of Forsyth, 

Pinchot, Polepatch. and Shoestring soils. Also included 

are small areas of Bannel soils on mountain slopes and 
St. Helens soils that have slopes of more than 30 

percent. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this St. Helens soil is moderate in the 

subsoil and rapid in the substratum. Available water 

capacity is moderate. Effective rooting depth is 20 to 35 

inches. Runoff is slow, and the hazard of water erosion 

is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 128 for 

Douglas fir and is estimated to be 127 for western 

hemlock. On the basis of a 50-year site curve, the mean 

site index is 102 for Douglas fir and is estimated to be 90 

for western hemlock. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 127 cubic feet per acre 

per year at age 70, and the CMAI for western hemlock is 

194 cubic feet at age 50. Estimates of the site index or 

CMAI for Pacific silver fir have not been made. Among the 

trees of limited extent are western redcedar and western 

white pine. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Occasional 

snowpack hinders the use of equipment and limits access 

in winter. Disturbance of the protective layer of duff can 

be reduced with the careful use of wheeled and tracked 

equipment. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. Logging activities 

can readily displace the surface layer. Seedlings that 

develop in the less fertile subsoil exhibit poor growth. 

Trees are occasionally subject to windthrow. 

Among the common forest understory plants are 

salal, western brackenfern, willow, trailing blackberry, 

red huckleberry, and pearly everlasting. 

This map unit is in capability subclass IVe. 

115-St. Martin gravelly silty clay loam, 2 to 15 

percent slopes. This very deep, moderately well drained 

soil is on toe slopes of mountains that have been 

disturbed by landsliding. It formed in colluvium derived 

dominantly from andesite. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 300 to 

2,000 feet. The average annual precipitation is about 

55 inches, the average annual air temperature is 

about 47 degrees F, and the average frost-free period 

is 100 to 140 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches 

thick. The surface layer is black gravelly silty clay loam 4 

inches thick. The upper 7 inches of the subsoil is very 

dark grayish brown silty clay loam, and the lower part to 

a depth of 60 inches or more is light olive brown and 

light yellowish brown clay. 

Included in this unit are small areas of Aschoff, 

McElroy, and Stevenson soils on mountain slopes. Also 

included are small areas of cold soils and soils that are 

less than 35 percent clay. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this St. Martin soil is slow. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is slow, and the hazard of water 

erosion is slight to moderate. A seasonal high water table 

is at a depth of 1 to 2 feet in December to April. 

Most areas of this unit are used as woodland and 

wildlife habitat. A few areas are used as homesites. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site 

curve, the mean site index is 154 for Douglas fir, and on 

the basis of a 50-year site curve, the mean site index is 

114. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 163 cubic feet per acre per 

year at age 60. Estimates of the site index or CMAI 

for red alder have not been made. Among the trees of 

limited extent are grand fir, western redcedar, and 

bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and sticky and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Following road construction and 

clearcutting, road failures and landslides can occur. The 

seasonal high water table limits the use of equipment to 

dry periods in summer and fall. Disturbance of the 

protective layer of duff can be reduced with the careful 

use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red 

alder occurs readily. If the canopy is opened, 
brush invades and can prevent the establishment of 

Douglas fir seedlings unless controlled. The seasonal 

high water table reduces root respiration, which results 

in a low survival rate of seedlings. Because the rooting 

depth is restricted by a high water table, trees frequently 

are subject to windthrow. 

Among the common forest understory plants are vine 

maple, salal, common snowberry, dwarf rose, western 

hazel, honeysuckle, creambush oceanspray, trailing 

blackberry, and western swordfern. 

The main limitations of this unit for use as homesites 

are the seasonal high water table, low soil strength, and 

the potential for shrinking and swelling. Preserving the 

existing plant cover during construction helps to control 

erosion. Wetness can be reduced by installing drain tile 

around footings. Excess water can be removed by using 

suitably designed drainage ditches. Buildings and roads 

should be designed to offset the limited ability of the soil 

in this unit to support a load. The effects of shrinking and 

swelling can be minimized by using proper engineering 

designs and by backfilling with material that has low 

shrink-swell potential. Septic tank absorption fields do not 

function properly during rainy periods because of wetness 

and slow permeability. Use of sandy backfill for the trench 

and long absorption lines helps to compensate for the slow 

permeability. Because of wetness, effluent from septic 

tank absorption fields can surface and create a hazard to 

health. During the rainy season, effluent from onsite 

sewage disposal systems may seep at points downslope. 

This map unit is in capability subclass IVe. 

116-St. Martin gravelly silty clay loam, 15 to 30 

percent slopes. This very deep, moderately well drained 

soil is on back slopes and toe slopes of mountains that 

have been disturbed by landslides. It formed in 

colluvium derived dominantly from andesite. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 300 to 2,000 feet. The average annual 

precipitation is about 55 inches, the average annual air 

temperature is about 47 degrees F, and the average 

frost-free period is 100 to 140 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is black gravelly silty clay loam 4 inches 

thick. The upper 7 inches of the subsoil is very dark 

grayish brown silty clay loam, and the lower part to a 

depth of 60 inches or more is light olive brown and light 

yellowish brown clay. 

Included in this unit are small areas of Aschoff, 

McElroy, and Stevenson soils on mountain slopes. Also 

included are small areas of cold soils and soils that are 

less than 35 percent clay. Included areas make up 

about 15 percent of the total acreage. 

Permeability of this St. Martin soil is slow. Available 

water capacity is high. Effective rooting depth is 60 inches 

or more. Runoff is medium, and the hazard of water 

erosion is moderate. A seasonal high water table is at a 

depth of 1 to 2 feet from December to April. 

This unit is used for woodland, wildlife habitat, and 

watershed. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site 

curve, the mean site index is 154 for Douglas fir, and 

on the basis of a 50-year site curve, the mean site index is 

114. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 163 cubic feet per acre per year 

at age 60. Estimates of the site index or CMAI for red 

alder have not been made. Among the trees of limited 

extent are grand fir, western redcedar, and bigleaf maple.

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and sticky and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Following road construction and 

clearcutting, road failures and landslides can occur. A 

seasonal high water table limits the use of equipment to 

dry periods in summer and fall. Disturbance of the 

protective layer of duff can be reduced with the careful use 

of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red 

alder occurs readily. If the canopy is opened, brush 

invades and can prevent the establishment of Douglas fir 

seedlings unless controlled. Because the rooting depth is 

restricted by the seasonal high water table, trees 

frequently are subject to windthrow. 

Among the common forest understory plants are vine 

maple, salal, common snowberry, dwarf rose, western 

hazel, honeysuckle, creambush oceanspray, trailing 

blackberry, and western swordfern. 

This map unit is in capability subclass VIc. 

117-St. Martin gravelly silty clay loam, 30 to 65 

percent slopes. This very deep, moderately well drained 

soil is on back slopes of mountains that have been 

disturbed by landslides. It formed in colluvium derived 

dominantly from andesite. The native vegetation 
is mainly mixed conifers and shrubs. Elevation is 300 to 

2,000 feet. The average annual precipitation is about 55 

inches, the average annual air temperature is about 47 

degrees F, and the average frost-free period is 100 to 140 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. The 

surface layer is black gravelly silty clay loam 4 inches thick. 

The upper 7 inches of the subsoil is very dark grayish 

brown silty clay loam, and the lower part to a depth of 60 

inches or more is light olive brown and light yellowish brown 

clay. 

Included in this unit are small areas of Aschoff, McElroy, 

Stevenson, and Timberhead soils on mountain slopes. 

Also included are small areas of cold soils, soils that are 

less than 35 percent clay, and Rock outcrop. Included areas 

make up about 20 percent of the total acreage. 

Permeability of this St. Martin soil is slow. Available water 

capacity is high. Effective rooting depth is 60 inches or 

more. Runoff is rapid, and the hazard of water erosion is 

high. A seasonal high water table is at a depth of 1 to 2 

feet from December to April. 

This unit is used for woodland, wildlife habitat, and 

watershed. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site curve, 

the mean site index is 154 for Douglas fir, and on the basis 

of a 50-year site curve, the mean site index is 114. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 163 cubic feet per acre per year at age 60. 

Estimates of the site index or CMAI for red alder have not 

been made. Among the trees of limited extent are grand 

fir, western redcedar, and bigleaf maple. 

The main limitation for harvesting timber is steepness of 

slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally are 

safer and disturb the soil less. Use of wheeled and tracked 

equipment when the soil is moist produces ruts, compacts 

the soil, and damages the roots of trees. Unsurfaced roads 

and skid trails are soft and sticky and can be impassable 

when wet. Logging roads require suitable surfacing for yearround use. Rock for road construction is not readily available 

in this unit. Establishing plant cover on steeper slopes that 

have been cut or filled reduces erosion. Following road 

construction and clearcutting, road failures and landslides 

can occur. A seasonal high water table limits the use of 

equipment to dry periods in summer and fall. Steep yarding 

paths, skid trails, and firebreaks are subject to rifling and 

gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red alder 

occurs readily. If the canopy is opened, brush invades 

and can prevent the establishment of Douglas fir 

seedlings unless controlled. The seasonal high water 

table reduces root respiration, which results in a low 

survival rate of seedlings. Because the rooting depth is 

restricted by the seasonal high water table, trees 

frequently are subject to windthrow. 

Among the common forest understory plants are vine 

maple, salal, common snowberry, dwarf rose, western 

hazel, honeysuckle, creambush oceanspray, trailing 

blackberry, and western swordfern. 

This map unit is in capability subclass Vlc. 

118-St. Martin gravelly silty clay loam, slumped, 2 

to 30 percent slopes. This very deep, moderately well 

drained soil is on foot slopes of mountains that have 

been disturbed by landslides. It formed in colluvium 

derived dominantly from andesite. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 300 to 

1,600 feet. The average annual precipitation is about 55 

inches, the average annual air temperature is about 47 

degrees F, and the average frost-free period is 100 to 

140 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is black gravelly silty clay loam 4 inches 

thick. The upper 7 inches of the subsoil is very dark 

grayish brown silty clay loam, and the lower part to a 

depth of 60 inches or more is light olive brown and light 

yellowish brown clay. 

Included in this unit are small areas of Steever and 

Stevenson soils on mountain slopes. Also included are 

small areas of poorly drained soils in depressional areas. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this St. Martin soil is slow. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. A seasonal high water table is 

at a depth of 1 to 2 feet from December to April. 

Most areas of this unit are used for wildlife habitat. A 

few areas are used as homesites and woodland. 

Douglas fir and red alder are the main woodland 

species on this unit. On the basis of a 100-year site 

curve, the mean site index is 105 for Douglas fir, and on 

the basis of a 50-year site curve, the mean site index is 

80. The culmination of the mean annual 
increment (CMAI) for Douglas fir is 91 cubic feet per acre 

per year at age 60. Estimates of the site index or CMAI 

for red alder have not been made. Among the trees of 

limited extent are grand fir, western redcedar, and bigleaf 

maple. 

The main limitations for harvesting timber are seasonal 

soil wetness and hummocky terrain. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and sticky and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Following 

road construction and clearcutting, road failures and 

landslides are common. Frequent road maintenance is 

necessary on this unit. The seasonal high water table limits 

the use of equipment to dry periods in summer and fall. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present. natural reforestation of cutover areas by red alder 

occurs readily. The wet depressional areas limit the even 

distribution of reforestation. If the canopy is opened, 

brush invades and can prevent the establishment of 

Douglas fir seedlings unless controlled. The seasonal 

high water table reduces root respiration, which results in 

a low survival rate of seedlings. Because the rooting depth 

is restricted by the seasonal high water table, trees 

frequently are subject to windthrow. 

Among the common forest understory plants are vine 

maple, salal, common snowberry, dwarf rose, western 

hazel, orange honeysuckle, creambush oceanspray, 

trailing blackberry, and western swordfern. 

The main limitations of this unit for use as homesites are 

slow permeability, steepness of slope, low soil strength, 

the seasonal high water table, the potential for shrinking 

and swelling, and the instability of the soil. Preserving the 

existing plant cover during construction helps to control 

erosion. Wetness can be reduced by installing drain tile 

around footings. Excess water can be removed by using 

suitably designed drainage ditches. Buildings and roads 

should be designed to offset the limited ability of the soil in 

this unit to support a load. Septic tank absorption fields do 

not function properly during rainy periods because of 

wetness and the slow permeability. Use of sandy backfill 

for the trench and long absorption lines helps to 

compensate for the slow permeability. Dikes and channels 

that have outlets to bypass floodwater can be used to 

protect buildings and onsite sewage disposal systems 

from 

flooding. During the rainy season, effluent from onsite 

sewage disposal systems may seep at points downslope. 

The effects of shrinking and swelling can be minimized by 

using proper engineering designs and by backfilling with 

material that has low shrink-swell potential. The soil is 

susceptible to slippage, which may damage building 

foundations and roads. 

This map unit is in capability subclass Vle. 

119-Stabbart clay loam. This very deep, somewhat 

poorly drained soil is on toe slopes and alluvial fans. It 

formed in alluvium derived dominantly from igneous rock. 

Slope is 0 to 3 percent. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 800 to 1,200 

feet. The average annual precipitation is about 95 

inches, the average annual air temperature is about 46 

degrees F, and the average frost-free period is 115 to 

135 days. 

Typically, the surface layer is dark brown clay loam 13 

inches thick. The upper 16 inches of the subsoil is dark 

brown clay loam, and the lower 8 inches is light 

yellowish brown silty clay loam. The substratum to a 

depth of 60 inches or more is light yellowish brown clay 

loam. 

Included in this unit are small areas of Stabler soils 

on terraces and St. Martin soils on landslides. Also 

included are small areas of moderately well drained and 

poorly drained soils and a few areas of soils adjacent to 

streams that are subject to flooding. Included areas make 

up about 10 percent of the total acreage. 

Permeability of this Stabbart soil is moderately slow.

Available water capacity is high. Effective rooting depth

is 60 inches or more. Runoff is slow, and the hazard of

water erosion is slight. A seasonal high water table is at a 

depth of 0.5 to 1.0 foot from January to May. 

This unit is used as woodland, homesites, and 

wildlife habitat. 

Douglas fir and grand fir are the main woodland 

species on this unit. On the basis of a 100-year site 

curve, the mean site index is 139 for Douglas fir, and 

on the basis of a 50-year site curve, the mean site index 

is 107. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 144 cubic feet per acre per year 

at age 70. Estimates of the site index or CMAI for grand 

fir have not been made. Among the trees of limited extent 

are red alder, bigleaf maple, and western redcedar. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and sticky and can be impassable
when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. The seasonal high water table limits 

the use of equipment to dry periods in summer and fall. 

Disturbance of the protective layer of duff can be 

reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red alder 

occurs readily and by grand fir, periodically. If the canopy 

is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by grand fir unless controlled. The 

seasonal high water table reduces root respiration, which 

results in a low survival rate of seedlings. Because the 

rooting depth is restricted by the seasonal high water 

table, trees frequently are subject to windthrow. 

Among the common forest understory plants are vine 

maple, orange honeysuckle, dogbane, Pacific dogwood, 

western hazel, thimbleberry, Oregongrape, and trailing 

blackberry. 

This unit is poorly suited to homesite development. The 

main limitations are low soil strength, the seasonal high 

water table, and moderately slow permeability. Buildings 

and roads should be designed to offset the limited ability of 

the soil to support a load. Wetness can be reduced by 

installing drain tile around footings. Excess water can be 

removed by using suitably designed drainage ditches. 

Selection of adapted vegetation is critical for the 

establishment of lawns, shrubs, trees, and vegetable 

gardens. Septic tank absorption fields do not function 

properly during rainy periods because of wetness and the 

moderately slow permeability. Use of sandy backfill for 

the trench and long absorption lines helps to compensate 

for the moderately slow permeability. 

This map unit is in capability subclass IVw. 

120-Stabler loam, 0 to 8 percent slopes. This very 

deep, well drained soil is on terraces. It formed in 

pyroclastic flows of volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 600 to 1,600 feet. The average annual precipitation is 

about 80 inches, the average annual air temperature is 

about 46 degrees F, and the average frost-free period is 

110 to 140 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown and dark yellowish 

brown loam 9 inches thick. The subsoil is dark yellowish 

brown loam 28 inches thick. The substratum to a depth 

of 60 inches or more is dark yellowish brown sandy loam. 

Included in this unit are small areas of Skamania soils. 

St. Martin soils on landslides, and Stevenson soils on 

mountain slopes. Also included are small areas of 

somewhat poorly drained soils and Stabler soils that 

have slopes of more than 8 percent. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Stabler soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is slow, and the hazard of water 

erosion is slight. 

This unit is used for woodland, pastureland, tree 

seedling nurseries, homesites, wildlife habitat, and 

recreation. 

Douglas fir, western hemlock, and grand fir are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 141 for Douglas fir 

and 133 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is 106 for Douglas fir and 

95 for western hemlock. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 146 cubic feet 

per acre per year at age 65, and the CMAI for western 

hemlock is 205 cubic feet at age 50. Estimates of the site 

index or CMAI for grand fir have not been made. Among 

the trees of limited extent are red alder, western 

redcedar, and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil. 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

during rainy periods. Rock for road construction is not 

readily available in this unit. Disturbance of the protective 

layer of duff can be reduced with the careful use of 

wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and grand fir occurs periodically. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation unless controlled. 

Among the common forest understory plants are vine 

maple, serviceberry, Oregongrape, Pacific dogwood, 

salal, common snowberry, red huckleberry, and trailing 

blackberry. 

This unit is well suited to use as pastureland. It has 
few limitations. Proper stocking rates, pasture rotation, 

and restricted grazing during wet periods help to keep 

the pasture in good condition and to protect the soil from 

erosion. Mowing helps to maintain uniform growth and 

discourages selective grazing. 

This unit is well suited to use as homesites. It has few 

limitations. Preserving the existing plant cover during 

construction helps to control erosion. Mulch, fertilizer, 

and irrigation are needed to establish lawn grasses and 

other small-seeded plants. The soil in this unit is subject 

to frost action, which may limit construction of roads and 

streets. 

This map unit is in capability subclass Ile. 

121-Stabler loam, 8 to 30 percent slopes. This very 

deep, well drained soil is on terraces and back slopes. It 

formed in pyroclastic flows of volcanic ash and pumice. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 600 to 1,600 feet. The average 

annual precipitation is about 80 inches, the average 

annual air temperature is about 46 degrees F, and the 

average frost-free period is 110 to 140 days. 

Typically, the surface is covered with a mat of 

decomposed needles. leaves. and twigs 2 inches thick. 

The surface layer is dark brown and dark yellowish brown 

loam 9 inches thick. The subsoil is dark yellowish brown 

loam 28 inches thick. The substratum to a depth of 60 

inches or more is dark yellowish brown sandy loam. 

Included in this unit are small areas of Aschoff and 

Stevenson soils. St. Martin soils on landslides, and 

Skamania soils on terraces. Also included are small 

areas of stony soils that are shallow to bedrock and 

Stabler soils that have slopes of less than 8 percent or 

more than 30 percent. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Stabler soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 inches 

or more. Runoff is medium, and the hazard of water 

erosion is moderate. 

This unit is used for woodland, wildlife habitat, and 

recreation. 

Douglas fir, western hemlock, and grand fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 141 for 

Douglas fir and 133 for western hemlock. On the basis of a 

50-year site curve, the mean site index is 106 for 

Douglas fir and 95 for western hemlock. The culmination of 

the mean annual increment (CMAI) for Douglas fir is 146 

cubic feet per acre per year at age 65, and the CMAI for 

western hemlock is 205 cubic feet

at age 50. Estimates of the site index or CMAI for grand fir 

have not been made. Among the trees of limited extent 

are red alder, western redcedar, and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Disturbance of the protective layer of 

duff can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock and grand fir occurs periodically. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation unless controlled. 

Among the common forest understory plants are vine 

maple, serviceberry, Oregongrape, Pacific dogwood, 

salal, common snowberry, red huckleberry, and trailing 

blackberry. 

This map unit is in capability subclass IVe. 

122-Stabler loam, 30 to 65 percent slopes. This very 

deep, well drained soil is on back slopes. It formed in 

volcanic flows of volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 1,000 to 1,600 feet. The average annual precipitation 

is about 80 inches, the average annual air temperature is

about 46 degrees F, and the average frost-free period is 

110 to 140 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown and dark yellowish 

brown loam 9 inches thick. The subsoil is dark yellowish 

brown loam 28 inches thick. The substratum to a depth 

of 60 inches or more is dark yellowish brown sandy loam. 

Included in this unit are small areas of Aschoff, 

McElroy, and St. Martin soils on landslides. Also 

included are small areas of basalt Rock outcrop and 

shallow soils. Included areas make up about 7 percent 

of the total acreage. 

Permeability of this Stabler soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is rapid, and the hazard of water 

erosion is severe. 
This unit is used for woodland. wildlife habitat, and 

recreation. 

Douglas fir, western hemlock, and grand fir are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is 141 for Douglas fir and 

133 for western hemlock. On the basis of a 50-year site 

curve, the mean site index is 106 for Douglas fir and 95 

for western hemlock. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 146 cubic feet per acre 

per year at age 65, and the CMAI for western hemlock is 

205 cubic feet at age 50. Estimates of the site index or 

CMAI for grand fir have not been made. Among the trees 

of limited extent are red alder, western redcedar, and 

bigleaf maple. 

The main limitations for harvesting timber are 

steepness of slope and the hazard of erosion. When 

harvesting timber, steepness of slope restricts the use of 

wheeled and tracked equipment in skidding. Cable 

yarding systems generally are safer and disturb the soil 

less. Use of wheeled and tracked equipment when the 

soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are soft and slippery and can be impassable when 

wet. Logging roads require suitable surfacing for yearround use. Rock for road construction is not readily 

available in this unit. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and firebreaks are subject to 

rilling and gullying unless plant cover is maintained or 

adequate water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock and grand fir occurs periodically. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation unless controlled. 

Among the common forest understory plants are vine 

maple. serviceberry, Oregongrape, Pacific dogwood, 

salal, common snowberry. red huckleberry, and trailing 

blackberry. 

This map unit is in capability subclass VIle. 

123-Steever stony clay loam, 2 to 30 percent 

slopes. This very deep, well drained soil is on toe 

slopes and foot slopes. It formed in colluvial landslide 

material derived dominantly from basalt, andesite, and 

conglomerate. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 50 to 1,500 feet. The 

average annual precipitation is about 75 inches, the 

average annual air temperature is about 48 degrees F, 

and the average frost-free period is 110 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is very dark brown 

stony clay loam 5 inches thick, and the lower part is 

dark brown gravelly clay loam 7 inches thick. The upper 8 

inches of the subsoil is dark brown very gravelly clay 

loam, and the lower 10 inches is dark brown very gravelly 

loam. The substratum to a depth of 60 inches or more is 

dark brown very gravelly loam. 

Included in this unit are small areas of Aschoff, 

Mountzion, and Stevenson soils that are more stable 

than this Steever soil and areas of Skamania soils on 

terraces. Also included are small areas of Skoly soils, 

poorly drained soils, and Steever soils that have slopes of 

more than 30 percent. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Steever soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

Most areas of this unit are used for woodland, wildlife 

habitat, recreation, and watershed. A few areas are 

used as homesites and pastureland. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 131 for Douglas fir 

and 127 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is 100 for Douglas fir and 

90 for western hemlock. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 132 cubic feet 

per acre per year at age 70, and the CMAI for western 

hemlock is 194 cubic feet at age 50. Estimates of the site 

index or CMAI for red alder have not been made. Among 

the trees of limited extent are grand fir and bigleaf maple. 

The main limitation for harvesting timber is seasonal soil 

wetness. Use of wheeled and tracked equipment when 

the soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are soft and can be impassable when wet. Logging 

roads require suitable surfacing for year-round use. Rock 

for road construction is readily available in this unit. 

Disturbance of the protective layer of duff can be reduced 

with the careful use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. If the 
canopy is opened. brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple. Oregongrape. red huckleberry, trailing 

blackberry, creambush oceanspray. western hazel, 

Pacific dogwood, common snowberry, thimbleberry, and 

dwarf rose. 

The main limitation of this unit for use as homesites is 

the steepness of slope. Erosion is a hazard in the steeper 

areas. Only the part of the site that is used for construction 

should be disturbed. Topsoil can be stockpiled and used 

to reclaim areas disturbed during construction. Removal 

of pebbles and cobbles in disturbed areas is needed for 

best results when landscaping, particularly in areas used 

for lawns. Mulch, fertilizer, and irrigation are needed to 

establish lawn grasses and other small-seeded plants. 

Steepness of slope is a concern in installing septic tank 

absorption fields. Absorption lines should be installed on 

the contour. 

This unit has few limitations for use as pastureland. 

Proper stocking rates, pasture rotation, and restricted 

grazing during wet periods help to keep the pasture in 

good condition and to protect the soil from erosion. 

Mowing helps to maintain uniform growth and 

discourages selective grazing. In some years, 

supplemental irrigation is needed. 

This map unit is in capability subclass IVe. 

124-Steever stony clay loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back 

slopes. It formed in colluvial landslide material derived 

dominantly from basalt, andesite, and 

conglomerate. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 50 to 1,500 feet. The 

average annual precipitation is about 75 inches, the 

average annual air temperature is about 48 degrees F, 

and the average frost-free period is 100 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is very dark brown 

stony clay loam 5 inches thick, and the lower part is 

dark brown gravelly clay loam 7 inches thick. The upper 8 

inches of the subsoil is dark brown very gravelly clay 

loam, and the lower 10 inches is dark brown very gravelly 

loam. The substratum to a depth of 60 inches or more is 

dark brown very gravelly loam. 

Included in this unit are small areas of Aschoff, 

Mountzion. and Stevenson soils that are more stable 

than this Steever soil and Skamania soils on terraces. 

Also included are small areas of shallow soils, Rock 

outcrop, and Steever soils that have slopes of less than 30 

percent. Included areas make up about 15 percent of the 

total acreage. 

Permeability of this Steever soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. Runoff is medium, and the hazard 

of water erosion is severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 131 for 

Douglas fir and 127 for western hemlock. On the basis 

of a 50-year site curve, the mean site index is 100 for 

Douglas fir and 90 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 

132 cubic feet per acre per year at age 70, and the 

CMAI for western hemlock is 194 cubic feet at age 50. 

Estimates of the site index or CMAI for red alder have 

not been made. Among the trees of limited extent are 

grand fir and bigleaf maple. 

The main limitation for harvesting timber is steepness of

slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round use. Rock for road construction is 

readily available in this unit. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present. natural reforestation of cutover areas by 

western hemlock and red alder occurs readily. If the 

canopy is opened., brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple. Oregongrape, red huckleberry, trailing 

blackberry, creambush oceanspray, western hazel, 

Pacific dogwood, common snowberry, thimbleberry, and 

dwarf rose. 

This map unit is in capability subclass VIIe. 
125-Steever-Rock outcrop complex, 2 to 30 

percent slopes. This map unit is on toe slopes and foot 

slopes. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 50 to 1,500 feet. The average 

annual precipitation is about 75 inches, the average 

annual air temperature is about 48 degrees F, and the 

average frost-free period is about 100 to 160 days. 

This unit is about 45 percent Steever stony clay loam, 

2 to 30 percent slopes, and 40 percent Rock outcrop. 

The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Aschoff, 

Skoly, and Stevenson soils. Also included are small areas 

of poorly drained soils, shallow soils, and Steever soils that 

have slopes of more than 30 percent. Included areas make 

up about 15 percent of the total acreage. 

The Steever soil is very deep and well drained. It 

formed in colluvial landslide material derived from 

basalt, andesite, and conglomerate. Typically, the 

surface is covered with a mat of decomposed needles, 

leaves, and twigs 2 inches thick. The upper part of the 

surface layer is very dark brown stony clay loam 5 inches 

thick, and the lower part is dark brown gravelly clay loam 

7 inches thick. The upper 8 inches of the subsoil is dark 

brown very gravelly clay loam, and the lower 10 inches is 

dark brown very gravelly loam. The substratum to a depth 

of 60 inches or more is dark brown very gravelly loam. 

Permeability of this Steever soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

Rock outcrop consists of exposed areas of 

dominantly basalt, andesite, and conglomerate. 

Numerous escarpments are in this unit. 

This unit is used for wildlife habitat, recreation, 

watershed, and woodland. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on the Steever soil. On the basis 

of a 100-year site curve, the mean site index is 131 for 

Douglas fir and 127 for western hemlock. On the basis of a 

50-year site curve, the mean site index is 100 for Douglas 

fir and 90 for western hemlock. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 132 cubic 

feet per acre per year at age 70, and the CMAI for western 

hemlock is 194 cubic feet at age 50. The areas of Rock 

outcrop make up about 40 percent of this unit and reduce 

yield accordingly. Estimates of the site index or CMAI for 

red alder have not been made. Among the trees of 

limited extent are grand fir and bigleaf maple. 

The main limitations for harvesting timber are seasonal 

soil wetness and the areas of Rock outcrop. Use of 

wheeled and tracked equipment when the soil is moist 

produces ruts, compacts the soil, and damages the roots 

of trees. Rock outcrop may cause breakage of timber when 

felled and can hinder yarding operations. Unsurfaced 

roads and skid trails are soft and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Avoiding areas of Rock outcrop 

forces yarding and skidding paths to converge, which 

increases compaction and erosion of the soil. Disturbance 

of the protective layer of duff can be reduced with the 

careful use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. The areas of Rock 

outcrop limit the even distribution of reforestation. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock. 

Among the common forest understory plants are vine 

maple, Oregongrape, red huckleberry, trailing blackberry, 

creambush oceanspray, western hazel, Pacific dogwood, 

common snowberry, thimbleberry, and dwarf rose. 

The Steever soil is in capability subclass IVe, and the 

Rock outcrop is in capability subclass Vllls. 

126-Steever-Rock outcrop complex, 30 to 65 

percent slopes. This map unit is on back slopes. The 

native vegetation is mainly mixed conifers and shrubs. 

Elevation is 50 to 1,500 feet. The average annual 

precipitation is about 75 inches, the average annual air 

temperature is about 48 degrees F, and the average 

frost-free period is 100 to 160 days. 

This unit is about 45 percent Steever stony clay loam. 

30 to 65 percent slopes, and 40 percent Rock outcrop. 

The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Aschoff, 

Skoly. and Stevenson soils. Also included are small 

areas of poorly drained soils and Steever soils that 

have slopes of less than 30 percent. Included areas 

make up about 15 percent of the total acreage. 

 The Steever soil is very deep and well drained. It 

formed in colluvial landslide material derived dominantly 
from basalt, andesite, and conglomerate. Typically, the 

surface is covered with a mat of decomposed needles, 

leaves, and twigs 2 inches thick. The upper part of the 

surface layer is very dark brown stony clay loam 5 inches 

thick, and the lower part is dark brown gravelly clay loam 

7 inches thick. The upper 8 inches of the subsoil is dark 

brown very gravelly clay loam, and the lower 10 inches is 

dark brown very gravelly loam. The substratum to a depth 

of 60 inches or more is dark brown very gravelly loam. 

Permeability of this Steever soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

Rock outcrop consists of exposed areas of mainly 

basalt, andesite, and conglomerate. Numerous 

escarpments are in this unit. 

Most areas of this unit are used for wildlife habitat, 

recreation, and watershed. A few areas are used as 

woodland. 

Douglas fir, western hemlock, and red alder are the 

main woodland species on the Steever soil. On the basis 

of a 100-year site curve, the mean site index is 131 for 

Douglas fir and 127 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 100 for 

Douglas fir and 90 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 132 

cubic feet per acre per year at age 70, and the CMAI for 

western hemlock is 194 cubic feet at age 50. The areas 

of Rock outcrop make up about 40 percent of this unit 

and reduce yield accordingly. Estimates of the site index or 

CMAI for red alder have not been made. Among the trees 

of limited extent are grand fir and bigleaf maple. 

The main limitations for harvesting timber are the 

areas of Rock outcrop and steepness of slope, which 

restricts the use of wheeled and tracked equipment in 

skidding. Cable yarding systems generally are safer and 

disturb the soil less. Rock outcrop may cause breakage 

of timber when felled and can hinder yarding operations. 

Avoiding areas of Rock outcrop forces yarding and 

skidding paths to converge, which increases compaction 

and erosion of the soil. Use of wheeled and tracked 

equipment when the soil is wet produces ruts, compacts 

the soil, and damages the roots of trees. Unsurfaced 

roads and skid trails are soft and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and firebreaks are subject to 

rifling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock and red alder occurs readily. The areas of Rock 

outcrop limit the even distribution of reforestation. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, Oregongrape, red huckleberry, trailing blackberry, 

creambush oceanspray, western hazel, Pacific dogwood, 

common snowberry, thimbleberry, and dwarf rose. 

The Steever soil is in capability subclass VIle, and 

the Rock outcrop is in capability subclass Vllls. 

127-Stevenson loam, 2 to 15 percent slopes. This 

very deep, well drained soil is on toe slopes and foot slopes 

of mountains. Areas generally are hummocky. The soil 

formed in colluvial landslide material derived dominantly 

from basalt, andesite, and conglomerate. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 100 to 1,200 feet. The average annual 

precipitation is about 80 inches, the average annual air 

temperature is about 47 degrees F, and the average 

frost-free period is 110 to 150 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 11 inches thick. 

The upper 17 inches of the subsoil is dark brown loam, 

and the lower 9 inches is dark yellowish brown loam. 

The substratum to a depth of 60 inches or more is dark 

yellowish brown loam. 

Included in this unit are small areas of St. Martin and 

Steever soils in areas of colluvial landslide material and 

Skamania and Stabler soils on terraces. Also included 

are small areas of Stevenson soils that have slopes of 

more than 15 percent and somewhat poorly drained soils 

in depressional areas. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Stevenson soil is moderate. 

Available water capacity is high. Effective rooting depth is 

60 inches or more. Runoff is slow, and the hazard of 

water erosion is slight. 

This unit is used for urban development, hayland, 

pastureland, woodland, wildlife habitat, and recreation. 

The main limitations of this unit for urban 

development are steepness of slope, the hazard of 
erosion, shrink-swell potential, and low soil strength. 

Erosion is a hazard in the steeper areas. Only the part of 

the site that is used for construction should be disturbed. 

Preserving the existing plant cover during construction 

helps to control erosion. Mulch, fertilizer, and irrigation 

are needed to establish lawn grasses and other smallseeded plants. Buildings and roads should be designed 

to offset the limited ability of the soil in this unit to support 

a load. The effects of shrinking and swelling can be 

minimized by using proper engineering designs. The 

moderate permeability and steepness of slope increase 

the possibility of failure of septic tank absorption fields. 

During the rainy season, effluent from onsite sewage 

disposal systems may seep at points downslope. 

Douglas fir, western hemlock, and grand fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 154 for 

Douglas fir and 148 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 114 for 

Douglas fir and 105 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 

163 cubic feet per acre per year at age 60, and the CMAI 

for western hemlock is 234 cubic feet at age 50. Estimates 

of the site index or CMAI for grand fir have not been made. 

Among the trees of limited extent are western redcedar, 

bigleaf maple, and red alder. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and sticky and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Disturbance of the protective layer 

of duff can be reduced with the careful use of wheeled 

and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock and grand fir occurs periodically. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation unless controlled. 

Among the common forest understory plants are vine 

maple. Pacific dogwood, honeysuckle, bitter cherry, 

common snowberry, creambush oceanspray, 

Oregongrape, dwarf rose, and western brackenfern. 

 This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking 

rates, pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition and 

to protect the soil from erosion. Mowing helps to maintain 

uniform growth and discourages selective grazing. 

This map unit is in capability subclass Ille. 

128-Stevenson loam, 15 to 30 percent slopes. 

This very deep, well drained soil is on foot slopes and 

back slopes of mountains. Areas generally are 

hummocky. The soil formed in colluvial landslide 

material derived from basalt, andesite, and 

conglomerate. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 100 to 1,200 feet. The 

average annual precipitation is about 80 inches, the 

average annual air temperature is about 47 degrees F, 

and the average frost-free period is 110 to 150 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 11 inches thick. 

The upper 17 inches of the subsoil is dark brown loam, 

and the lower 9 inches is dark yellowish brown loam. 

The substratum to a depth of 60 inches or more is dark 

yellowish brown loam. 

Included in this unit are small areas of St. Martin and 

Steever soils in areas of landslide material and 

Skamania and Stabler soils on terraces. Also included 

are small areas of Stevenson soils that have slopes of 

less than 15 percent or more than 30 percent and 

somewhat poorly drained soils in depressional areas. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this Stevenson soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is medium, and the hazard 

of water erosion is moderate. 

This unit is used for urban development, woodland, 

hayland, pastureland, wildlife habitat, and recreation. 

The main limitations for urban development are 

steepness of slope, the hazard of erosion, shrink-swell 

potential, and low soil strength. The hazard of erosion is 

increased if the soil is left exposed during site 

development. Preserving the existing plant cover during 

construction helps to control erosion. Plant cover can be 

established and maintained through proper fertilizing, 

seeding, mulching, and shaping of the slopes. Buildings 

and roads should be designed to offset the limited 

ability of the soil in this unit to support a load. The 

effects of shrinking and swelling can be minimized by 

using proper engineering designs. Slope is a concern in 

installing septic tank absorption fields. Absorption lines 

should be installed on the contour. During the rainy 
season, effluent from onsite sewage disposal systems 

may seep at points downslope. 

Douglas fir, western hemlock, and grand fir are the 

main woodland species on this unit. On the basis of a

100-year site curve, the mean site index is 154 for 

Douglas fir and 148 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 108 for 

Douglas fir and 105 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 

163 cubic feet per acre per year at age 60, and the CMAI 

for western hemlock is 234 cubic feet at age 50. Estimates 

of the site index or CMAI for grand fir have not been 

made. Among the trees of limited extent are western 

redcedar, bigleaf maple, and red alder. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and sticky and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Disturbance of the protective layer 

of duff can be reduced with the careful use of wheeled 

and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock and grand fir occurs periodically. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation unless controlled. 

Among the common forest understory plants are vine 

maple. Pacific dogwood, orange honeysuckle. bitter 

cherry, common snowberry, creambush oceanspray, 

Oregongrape, dwarf rose, and western brackenfern. 

This unit is well suited to use as hayland and 

pastureland. The main limitations are steepness of slope 

and the hazard of erosion. Erosion can be controlled by 

growing pasture. The use of equipment is limited by 

steepness of slope. Proper stocking rates, pasture 

rotation, and restricted grazing during wet periods help to 

keep the pasture in good condition and to protect the soil 

from erosion. Mowing helps to maintain uniform growth 

and discourages selective grazing. 

This map unit is in capability subclass IVe. 

 129-Stevenson loam, 30 to 50 percent slopes. This 

very deep, well drained soil is on back slopes of 

mountains. It formed in colluvial landslide material 

derived dominantly from basalt, andesite, and 

conglomerate. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 100 to 1,200 feet. The 

average annual precipitation is about 80 inches, the 

average annual air temperature is about 47 degrees F, 

and the average frost-free period is 110 to 150 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 11 inches thick. The 

upper 17 inches of the subsoil is dark brown loam, and 

the lower 9 inches is dark yellowish brown loam. The 

substratum to a depth of 60 inches or more is dark 

yellowish brown loam. 

Included in this unit are small areas of Steever and St. 

Martin soils in areas of landslide material. Also included 

are small areas of Stevenson soils that have slopes of 

less than 30 percent or more than 50 percent. Included 

areas make up about 15 percent of the total acreage. 

Permeability of this Stevenson soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is rapid, and the hazard 

of water erosion is severe. 

This unit is used for woodland, watershed, wildlife 

habitat, and recreation. 

Douglas fir, western hemlock, and grand fir are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 132 for 

Douglas fir and 127 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 100 for 

Douglas fir and 90 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 

133 cubic feet per acre per year at age 70, and the 

CMAI for western hemlock is 194 cubic feet at age 50. 

Estimates of the site index or CMAI for grand fir have not 

been made. Among the trees of limited extent are 

western redcedar, bigleaf maple, and red alder. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and sticky and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. 

Establishing plant cover on steeper slopes that have 

been cut or filled reduces erosion. Steep yarding paths, 
skid trails, and firebreaks are subject to rifling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and grand fir occurs periodically. If the canopy is opened, 

brush invades and can prevent the establishment of 

Douglas fir seedlings and can delay natural reforestation 

unless controlled. 

Among the common forest understory plants are vine 

maple, Pacific dogwood, orange honeysuckle, bitter 

cherry, common snowberry, creambush oceanspray, 

Oregongrape, dwarf rose, and western brackenfern. 

This map unit is in capability subclass VIIe. 

130-Swift cindery sandy loam, 2 to 30 percent 

slopes. This very deep, well drained soil is on side 

slopes and ridgetops of mountains. It formed in 

colluvium derived dominantly from volcanic ash and basic 

igneous rock with a mantle of volcanic ash and pumice. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 1,200 to 2,800 feet. The average 

annual precipitation is about 115 inches, the average 

annual air temperature is about 43 degrees F, and the 

average frost-free period is 100 to 120 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown cindery 

sandy loam 12 inches thick. The upper 15 inches of the 

subsoil is dark yellowish brown very cindery loam, and 

the lower part to a depth of 60 inches or more is dark 

yellowish brown extremely cobbly loam. 

Included in this unit are small areas of Cinnamon, 

Hatchet, Lonestar, and Vanson soils and St. Helens and 

Yalelake soils on terraces. Also included are small areas 

of Rock outcrop. Included areas make up about 15 

percent of the total acreage. 

Permeability of this Swift soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 inches 

or more. Runoff is slow, and the hazard of water erosion is 

slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is 129 for 

Douglas fir and 119 for western hemlock. On the basis 

of a 50-year site curve, the mean site index is 96 for 

Douglas fir and 83 for western hemlock. The culmination 

of the mean annual increment (CMAI) for 

Douglas fir is 128 cubic feet per acre per year at age 70, 

and the CMAI for western hemlock is 178 cubic feet at 

age 50. Estimates of the site index or CMAI for Pacific 

silver fir have not been made. Among the trees of limited 

extent are western redcedar and red alder. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Snowpack 

hinders the use of equipment and limits access in 

winter. Cinders slough from road cuts onto the road. 

Disturbance of the protective layer of duff can be reduced 

with the careful use of wheeled and tracked equipment. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. 

Among the common forest understory plants are vine 

maple, red huckleberry, trailing blackberry, false 

Solomons seal, deerfoot vanillaleaf, western brackenfern, 

and starflower. 

This map unit is in capability subclass IVe. 

131-Swift cindery sandy loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on side 

slopes of mountains. It formed in colluvium derived 

dominantly from volcanic ash and basic igneous rock 

with a mantle of volcanic ash and pumice. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 1,200 to 2,800 feet. The average annual 

precipitation is about 115 inches, the average annual air 

temperature is about 43 degrees F, and the average 

frost-free period is 100 to 120 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown cindery 

sandy loam 12 inches thick. The upper 15 inches of the 

subsoil is dark yellowish brown very cindery loam, and 

the lower part to a depth of 60 inches or more is dark 

yellowish brown extremely cobbly loam. 

Included in this unit are small areas of Cinnamon, 

Hatchet, Lonestar, and Vanson soils and Yalelake soils 

on terraces. Also included are small areas of Rock 

outcrop. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this Swift soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 
This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit, On the basis of 

a 100-year site curve, the mean site index is 129 for 

Douglas fir and 119 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 96 for Douglas 

fir and 83 for western hemlock. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 128 

cubic feet per acre per year at age 70, and the CMAI for 

western hemlock is 178 cubic feet at age 50. Estimates of 

the site index or CMAI for Pacific silver fir have not been 

made. Among the trees of limited extent are western 

redcedar and red alder. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in this 

unit. Occasional snowpack hinders the use of equipment 

and limits access in winter. Cinders slough from road 

cuts onto the road. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. 

Steep yarding paths, skid trails, and firebreaks are 

subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. 

Among the common forest understory plants are vine 

maple, red huckleberry, trailing blackberry, false 

Solomons seal, deerfoot vanillaleaf, western brackenfern, 

and starflower. 

This map unit is in capability subclass VIIe. 

132-Swift cindery sandy loam, 65 to 90 percent 

slopes. This very deep, well drained soil is on side 

slopes of mountains. It formed in colluvium derived from 

volcanic ash and basic igneous rock with a mantle of 

volcanic ash and pumice. The native vegetation is mainly 

mixed conifers and shrubs, Elevation is 1,200 to 2,800 

feet. The average annual precipitation is about 115 

inches, the average annual air temperature is about 43 

degrees F, and the average frost-free period is 100 to 

120 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown cindery 

sandy loam 12 inches thick. The upper 15 inches of the 

subsoil is dark yellowish brown very cindery loam, and 

the lower part to a depth of 60 inches or more is dark 

yellowish brown extremely cobbly loam. 

Included in this unit are small areas of Cinnamon, 

Hatchet, Lonestar, and Vanson soils and Yalelake soils 

on terraces. Also included are small areas of Rock 

outcrop and Swift soils that are less than 60 inches 

deep to bedrock. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Swift soil is moderately high. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is 129 for 

Douglas fir and 119 for western hemlock. On the basis 

of a 50-year site curve, the mean site index is 96 for 

Douglas fir and 83 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 

128 cubic feet per acre per year at age 70, and the 

CMAI for western hemlock is 178 cubic feet at age 50. 

Estimates of the site index or CMAI for Pacific silver fir 

have not been made. Among the trees of limited extent 

are western redcedar and red alder. 

The main limitation for harvesting timber is steepness 

of slope. Cable yarding systems generally are used on 

this unit. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Logging roads generally need full 

bench construction and require frequent maintenance. 

Construction and maintenance costs are higher for roads 

on the steeper slopes. Occasional snowpack hinders the 

use of equipment and limits access in winter. 

Establishing plant cover on steeper slopes that have 

been cut or filled reduces erosion. Following road 

construction and clearcutting, road failures and 

landslides can occur. Steep yarding paths, skid trails, 

and firebreaks are subject to rilling and gullying unless 

plant cover is maintained or adequate water bars are 

provided. Harvesting systems that lift logs entirely off the 

ground reduce the disturbance of the protective layer of 

duff. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. 

Among the common forest understory plants are vine
maple, red huckleberry, trailing blackberry, false 

Solomons seal, deerfoot vanillaleaf, western 

brackenfern, and starflower. 

This map unit is in capability subclass VIIe. 

133-Swift-Rock outcrop complex, 30 to 65 percent 

slopes. This map unit is on side slopes of mountains. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 1,200 to 2,800 feet. The average 

annual precipitation is about 115 inches, the average 

annual air temperature is about 43 degrees F, and the 

average frost-free period is 100 to 120 days. 

This unit is about 65 percent Swift cindery sandy 

loam, 30 to 65 percent slopes, and 25 percent Rock 

outcrop. The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Hatchet and 

Vanson soils. Also included are small areas of 

Cinnamon soils. Included areas make up about 10 

percent of the total acreage. 

The Swift soil is very deep and well drained. It 

formed in colluvium derived dominantly from volcanic ash 

and basic igneous rock with a mantle of volcanic ash and 

pumice. Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown cindery 

sandy loam 12 inches thick. The upper 15 inches of the 

subsoil is dark yellowish brown very cindery loam, and 

the lower part to a depth of 60 inches or more is dark 

yellowish brown extremely cobbly loam. 

Permeability of this Swift soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

Rock outcrop consists of exposed areas of dominantly 

andesite and basalt. Numerous escarpments are in this 

unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on the Swift soil. On the basis 

of a 100-year site curve, the mean site index is 129 for 

Douglas fir and 119 for western hemlock. On the basis of a 

50-year site curve, the mean site index is 96 for Douglas fir 

and 83 for western hemlock. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 128 cubic feet 

per acre per year at age 70, and the CMAI for western 

hemlock is 178 cubic feet at age 50. The areas of Rock 

outcrop make up about 25 percent of this unit and reduce 

yield accordingly. Estimates of the site index or CMAI for 

Pacific silver fir 

have not been made. Among the trees of limited extent 

are western redcedar and red alder. 

The main limitations for harvesting timber are 

steepness of slope and the areas of Rock outcrop. 

Steepness of slope restricts the use of wheeled and 

tracked equipment in skidding. Cable yarding systems 

generally are safer and disturb the soil less. Rock 

outcrop may cause breakage of timber when felled and 

can hinder yarding operations. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Avoiding areas of Rock outcrop forces yarding and 

skidding paths to converge, which increases compaction 

and erosion of the soil. Logging roads require suitable 

surfacing for year-round use. Rock for road construction 

is readily available in this unit. Occasional snowpack 

hinders the use of equipment and limits access in winter. 

Establishing plant cover on steeper slopes that have 

been cut or filled reduces erosion. Steep yarding paths, 

skid trails, and firebreaks are subject to rifling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock and 

Pacific silver fir occurs periodically. The areas of Rock 

outcrop limit the even distribution of reforestation. 

Among the common forest understory plants are vine 

maple, red huckleberry, trailing blackberry, false 

Solomons seal, deerfoot vanillaleaf, western brackenfern, 

and starflower. 

The Swift soil is in capability subclass VIIe, and the 

Rock outcrop is in capability subclass VIIIs. 

134-Swift-Rock outcrop complex, 65 to 90 

percent slopes. This map unit is on side slopes of 

mountains. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 1,200 to 2,800 feet. 

The average annual precipitation is about 115 inches, 

the average annual air temperature is about 43 degrees 

F, and the average frost-free period is 100 to 120 days. 

This unit is about 60 percent Swift cindery sandy 

loam, 65 to 90 percent slopes, and 30 percent Rock 

outcrop. The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Hatchet and 

Vanson soils. Also included are small areas of 

Cinnamon soils. Included areas make up about 10 

percent of the total acreage. 

 The Swift soil is very deep and well drained. It formed 

in colluvium derived dominantly from volcanic 
ash and basic igneous rock with a mantle of volcanic ash 

and pumice. Typically, the surface is covered with a mat 

of decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown cindery 

sandy loam 12 inches thick. The upper 15 inches of the 

subsoil is dark yellowish brown very cindery loam, and the 

lower part to a depth of 60 inches or more is dark 

yellowish brown extremely cobbly loam. 

Permeability of this Swift soil is moderately high. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is rapid, and 

the hazard of water erosion is severe. 

Rock outcrop consists of exposed areas of dominantly 

andesite and basalt. Numerous escarpments are in this 

unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir, western hemlock, and Pacific silver fir are 

the main woodland species on the Swift soil. On the basis 

of a 100-year site curve, the mean site index is 129 for 

Douglas fir and 119 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 96 for Douglas 

fir and 83 for western hemlock. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 128 

cubic feet per acre per year at age 70, and the CMAI for 

western hemlock is 178 cubic feet at age 50. The areas 

of Rock outcrop make up about 30 percent of this unit 

and reduce yield accordingly. Estimates of the site index 

or CMAI for Pacific silver fir have not been made. Among 

the trees of limited extent are western redcedar and red 

alder. 

The main limitations for harvesting timber are 

steepness of slope and the areas of Rock outcrop. Cable 

yarding systems generally are used on this unit. Rock 

outcrop may cause breakage of timber when felled and 

can hinder yarding operations. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in this 

unit. Logging roads generally need full bench 

construction and require frequent maintenance. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Following road construction and clearcutting, 

road failures and landslides can occur. Steep yarding 

paths, skid trails, and firebreaks are subject to rifling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. Harvesting systems that lift logs 

entirely off the ground reduce the disturbance of the 

protective layer of duff. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. The areas of 

Rock outcrop limit the even distribution of reforestation. 

Among the common forest understory plants are vine 

maple, red huckleberry, trailing blackberry, false 

Solomons seal, deerfoot vanillaleaf, western 

brackenfern, and starflower. 

The Swift soil is in capability subclass VIIe, and the 

Rock outcrop is in capability subclass VIIIs. 

135-Timberhead gravelly loam, 5 to 30 percent 

slopes. This very deep, well drained soil is on ridgetops 

of mountains. It formed in residuum and colluvium 

derived dominantly from basalt with a mantle of volcanic 

ash. The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 2,000 to 2,800 feet. The average 

annual precipitation is about 60 inches, the average 

annual air temperature is about 44 degrees F, and the 

average frost-free period is 95 to 115 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown gravelly loam 10 inches 

thick. The subsoil is dark brown gravelly loam 30 inches 

thick. The substratum to a depth of 60 inches or more is 

dark brown loam. 

Included in this unit are small areas of McElroy, 

Underwood, and Undusk soils. Also included are small 

areas of shallow and moderately deep soils over basalt. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this Timberhead soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

Most areas of this unit are used for woodland, 

recreation, wildlife habitat. and watershed. A few areas 

are used as grazeable woodland. 

Douglas fir, grand fir, and western hemlock are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 124 for 

Douglas fir, and on the basis of a 50-year site curve, the 

mean site index is 92. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 121 cubic feet 

per acre per year at age 70. Estimates of the site index 

or CMAI for grand fir and western hemlock have not been 

made. Among the trees of limited extent is western 

redcedar. Areas on ridgetops that are subject to strong. 

persistent winds are less productive than other areas of 

this unit. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 
when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Occasional snowpack hinders the 

use of equipment and limits access in winter. Disturbance 

of the protective layer of duff can be reduced with the 

careful use of wheeled and tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are present. 

natural reforestation of cutover areas by western hemlock 

and grand fir occurs periodically. The mortality rate of 

seedlings is higher in areas on ridgetops that are subject to 

strong, persistent winds than in other areas of this unit. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. 

Among the common forest understory plants are vine 

maple, dwarf rose, common snowberry, thimbleberry, 

western raspberry, and princes pine. 

Forage on this unit consists primarily of browse, forbs. 

and some grasses. Livestock grazing is limited by the 

density of the stand. Silvicultural practices such as 

clearcutting can result in temporary increases in available 

forage. The useful lifespan of interim forage is about 10 

years. 

This map unit is in capability subclass lVe. 

136-Timberhead gravelly loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back slopes 

of mountains. It formed in residuum and colluvium derived 

dominantly from basalt with a mantle of volcanic ash. The 

native vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,000 to 2,800 feet. The average annual 

precipitation is about 60 inches, the average annual air 

temperature is about 44 degrees F. and the average 

frost-free period is 95 to 115 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown gravelly loam 10 inches 

thick. The subsoil is dark brown gravelly loam 30 inches 

thick. The substratum to a depth of 60 inches or more is 

dark brown loam. 

Included in this unit are small areas of McElroy, 

Underwood, and Undusk soils. Also included are small 

areas of Rock outcrop and moderately deep soils over 

basalt. Included areas make up about 15 percent of the 

total acreage. 

Permeability of this Timberhead soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is rapid, and the 

hazard of water erosion is severe. 

Most areas of this unit are used for woodland, 

recreation, wildlife habitat, and watershed. A few areas 

are used as grazeable woodland. 

Douglas fir, grand fir, and western hemlock are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 124 for Douglas 

fir, and on the basis of a 50-year site curve, the mean site 

index is 92. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 121 cubic feet per 

acre per year at age 70. Estimates of the site index or CMAI 

for grand fir and western hemlock have not been made. 

Among the trees of limited extent is western redcedar. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and slippery 

and can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Occasional 

snowpack hinders the use of equipment and limits access 

in winter. Establishing plant cover on steeper slopes that 

have been cut or filled reduces erosion. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present. natural reforestation of cutover areas by western 

hemlock and grand fir occurs periodically. Droughtiness 

of the surface layer reduces seedling survival, especially 

on south- and southwest-facing slopes. 

Among the common forest understory plants are vine 

maple, dwarf rose, common snowberry, thimbleberry, 

western raspberry, and princes pine. 

Forage on this unit consists primarily of browse, forbs, 

and some grasses. Livestock grazing is limited by the 

density of the stand and steepness of slope. Silvicultural 

practices such as clearcutting can result in temporary 

increases in available forage. The useful lifespan of 

interim forage is about 10 years. 

This map unit is in capability subclass VIIe. 
137-Tradedollar sandy loam, 0 to 30 percent 

slopes. This very deep, well drained soil is on ridgetops 

of mountains. It formed in aerially deposited volcanic 

ash and pumice. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 4,000 to 5,400 feet. 

The average annual precipitation is about 100 inches, 

the average annual air temperature is about 38 degrees 

F, and the average frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown sandy loam 5 

inches thick. The upper 21 inches of the subsoil is dark 

brown cindery sandy loam, and the lower 16 inches is dark 

brown extremely cindery loamy sand and strong brown 

extremely cindery sand. Below this is a buried surface 

layer of dark grayish brown cindery sandy loam 9 inches 

thick. Below this to a depth of 60 inches or more is a 

buried subsoil of dark brown very gravelly sandy loam. 

Included in this unit are small areas of Cattcreek, 

Colter, and Sinnice soils. Also included are small areas of 

Rock outcrop. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid in the upper part of the subsoil and very rapid in the 

lower part and is moderately rapid in the buried subsoil. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is slow, and 

the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Pacific silver fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 98 

for western hemlock. and on the basis of a 50-year site 

curve, the mean site index is estimated to be 70. The 

culmination of the mean annual increment (CMAI) for 

western hemlock is 118 cubic feet per acre per year at age 

60. Estimates of the site index or CMAI for Pacific silver fir 

and noble fir have not been made. Among the trees of 

limited extent are noble fir, Douglas fir, and western white 

pine. Areas on ridgetops that are subject to strong, 

persistent winds are less productive than other areas of 

this unit. 

The main limitation for harvesting timber is snowpack in 

winter. Use of wheeled and tracked equipment when the 

soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Logging roads require suitable 

surfacing for year-round use. Rock for road construction is 

not readily available in this unit. Snowpack in winter limits 

the use of equipment and 

restricts access. Cinders slough from road cuts onto the 

road surface. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Low soil 

temperature in summer, deep snowpack, and a short 

growing season reduce the survival rate of planted and 

natural seedlings and delay their establishment. The 

mortality rate of seedlings and the hazard of windthrow 

are higher in areas on ridgetops that are subject to strong, 

persistent winds than in other areas of this unit. Logging 

activities can readily displace the surface layer. Seedlings 

that develop in the less fertile subsoil exhibit poor growth. 

Trees frequently are subject to windthrow. 

Among the common forest understory plants are 

Sitka alder, tall blue huckleberry, common beargrass, 

and violet. 

This map unit is in capability subclass Vls. 

138-Tradedollar sandy loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back slopes 

of mountains. It formed in aerially deposited volcanic ash 

and pumice. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 4,000 to 5,400 feet. The 

average annual precipitation is about 100 inches, the 

average annual air temperature is about 38 degrees F. 

and the average frost-free period is 75 to 95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown sandy loam 

5 inches thick. The upper 21 inches of the subsoil is dark 

brown cindery sandy loam, and the lower 16 inches is 

dark brown extremely cindery loamy sand and strong 

brown extremely cindery sand. The next layer is a buried 

surface layer of dark grayish brown cindery sandy loam 9 

inches thick. Below this to a depth of 60 inches or more 

is a buried subsoil of dark brown very gravelly sandy 

loam. 

Included in this unit are small areas of Cattcreek, 

Colter, and Sinnice soils. Also included are small areas 

of Rock outcrop. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid in the upper part of the subsoil and very rapid in 

the lower part and is moderately rapid in the buried 
subsoil. Effective rooting depth is 60 inches or more. 

Runoff is medium, and the hazard of water erosion is 

moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Pacific silver fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 98 

for western hemlock, and on the basis of a 50-year site 

curve, the mean site index is estimated to be 70. The 

culmination of the mean annual increment (CMAI) for 

western hemlock is 118 cubic feet per acre per year at age 

60. Estimates of the site index or CMAI for Pacific silver fir 

and noble fir have not been made. Among the trees of 

limited extent are noble fir, Douglas fir, and western white 

pine. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is wet produces ruts, 

compacts the soil, and damages the roots of trees. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Snowpack in winter limits the use of equipment 

and restricts access. Cinders slough from road cuts onto 

the road surface. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and firebreaks are subject to 

rilling and gullying unless plant cover is maintained or 

adequate water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Low soil 

temperature in summer, deep snowpack, and a short 

growing season reduce the survival rate of planted and 

natural seedlings and delay their establishment. Logging 

activities can readily displace the surface layer. Seedlings 

that develop in the less fertile subsoil exhibit poor growth. 

Trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

Sitka alder, tall blue huckleberry, common beargrass, 

and violet. 

This map unit is in capability subclass VIle. 

139-Tradedollar sandy loam, 65 to 90 percent 

slopes. This very deep, well drained soil is on back 

slopes of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 4,000 to 5,400 

feet. The average annual precipitation is about 100 

inches, the average annual air temperature is about 38 

degrees F, and the average frost-free period is 75 to 95 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown sandy loam 5 

inches thick. The upper 21 inches of the subsoil is dark 

brown cindery sandy loam, and the lower 16 inches is dark 

brown extremely cindery loamy sand and strong brown 

extremely cindery sand. Below this is a buried surface 

layer of dark grayish brown cindery sandy loam 9 inches 

thick. The next layer to a depth of 60 inches or more is a 

buried subsoil of dark brown very gravelly sandy loam. 

Included in this unit are small areas of Cattcreek, Colter. 

and Sinnice soils. Also included are small areas of Rock 

outcrop and Tradedollar soils that are less than 40 inches 

deep to bedrock. Included areas make up about 15 

percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid in the upper part of the subsoil and very rapid in the 

lower part and is moderately rapid in the buried 

subsoil. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. Runoff is 

medium, and the hazard of water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Pacific silver fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 

98 for western hemlock, and on the basis of a 50-year site 

curve, the mean site index is estimated to be 70. The 

culmination of the mean annual increment (CMAI) for 

western hemlock is 118 cubic feet per acre per year at 

age 60. Estimates of the site index or CMAI for Pacific 

silver fir and noble fir have not been made. Among the 

trees of limited extent are noble fir, Douglas fir, and 

western white pine. 

The main limitation for harvesting timber is steepness of 

slope. Cable yarding systems generally are used on this 

unit. Logging roads require suitable surfacing for yearround use. Rock for road construction is not readily 

available in this unit. Logging roads generally need full 

bench construction and require frequent maintenance. 

Snowpack in winter limits the use of equipment and 

restricts access. Cinders slough from road cuts onto the 

road surface. Establishing plant cover on steeper slopes 

that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and 
firebreaks are subject to rilling and gullying unless plant 

cover is maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present. 

natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. Low soil 

temperature in summer, deep snowpack. and a short 

growing season reduce the survival rate of planted and 

natural seedlings and delay their establishment. Logging 

activities can readily displace the surface layer. 

Seedlings that develop in the less fertile subsoil exhibit 

poor growth. Trees occasionally are subject to 

windthrow. 

Among the common forest understory plants are 

Sitka alder. tall blue huckleberry. common beargrass, 

and violet. 

This map unit is in capability subclass Vlle. 

140-Tradedollar sandy loam, warm, 0 to 30 

percent slopes. This very deep, well drained soil is on 

ridgetops of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,000 feet. The average annual precipitation is about 

100 inches, the average annual air temperature is about 

39 degrees F, and the average frost-free period is 75 to 

95 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown sandy loam 

5 inches thick. The upper 21 inches of the subsoil is dark 

brown cindery sandy loam, and the lower 16 inches is dark 

brown extremely cindery loamy sand and strong brown 

extremely cindery sand. Below this is a buried surface 

layer of dark grayish brown cindery sandy loam 9 inches 

thick. The next layer to a depth of 60 inches or more is a 

buried subsoil of dark brown very gravelly sandy loam. 

Included in this unit are small areas of Cattcreek, 

Colter, Minniepeak, and Sinnice soils. Also included are 

small areas of Rock outcrop. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid in the upper part of the subsoil and very rapid in 

the lower part and is moderately rapid in the buried 

subsoil. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. Runoff is 

slow. and the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is estimated to 

be 120 for western hemlock and 117 for Douglas fir. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 85 for western hemlock and 90 for 

Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 180 cubic feet 

per acre per year at age 50, and the CMAI for Douglas fir 

is 110 cubic feet at age 60. Estimates of the site index 

or CMAI for Pacific silver fir have not been made. 

Among the trees of limited extent are noble fir and 

western redcedar. Areas on ridgetops that are subject to 

strong, persistent winds are less productive than other 

areas of this unit. 

The main limitation for harvesting timber is snowpack 

in winter. Use of wheeled and tracked equipment when 

the soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Snowpack 

in winter limits the use of equipment and restricts access. 

Cinders slough from road cuts onto the road surface. 

Disturbance of the protective layer of duff can be 

reduced with the careful use of wheeled and tracked 

equipment. 

Reforestation can be accomplished by planting noble 

fir and Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. The 

mortality rate of seedlings is higher in areas on ridgetops 

that are subject to strong, persistent winds than in other 

areas of this unit. Logging activities can readily 

displace the surface layer. Seedlings that develop in the 

less fertile subsoil exhibit poor growth. Trees 

occasionally are subject to windthrow. 

Among the common forest understory plants are 

Sitka alder. tall blue huckleberry, red huckleberry, 

common beargrass, and violet. 

This map unit is in capability subclass Vls. 

141-Tradedollar sandy loam, warm, 30 to 65 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,000 feet. The average annual precipitation is about 

100 inches, the average annual air temperature is about 

39 degrees F, and the average frost-free period is 75 to 

95 days. 
Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown sandy 

loam 5 inches thick. The upper 21 inches of the subsoil is 

dark brown cindery sandy loam, and the lower 16 

inches is dark brown extremely cindery loamy sand and 

strong brown extremely cindery sand. Below this is a 

buried surface layer of dark grayish brown cindery sandy 

loam 9 inches thick. The next layer to a depth of 60 inches 

or more is a buried subsoil of dark brown very gravelly 

sandy loam. 

Included in this unit are small areas of Cattcreek, 

Colter, Minniepeak, and Sinnice soils. Also included are 

small areas of Rock outcrop. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid in the upper part of the subsoil and very rapid in 

the lower part and is moderately rapid in the buried 

subsoil. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. Runoff is 

medium, and the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to be 

120 for western hemlock and 117 for Douglas fir. On the 

basis of a 50-year site curve, the mean site index is 

estimated to be 85 for western hemlock and 90 for 

Douglas fir. The culmination of the mean annual 

increment (CMAI) for western hemlock is 180 cubic feet 

per acre per year at age 50, and the CMAI for Douglas fir 

is 110 cubic feet at age 60. Estimates of the site index or 

CMAI for Pacific silver fir have not been made. Among the 

trees of limited extent are noble fir and western redcedar. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. Steepness of 

slope restricts the use of wheeled and tracked equipment 

in skidding. Cable yarding systems generally are safer 

and disturb the soil less. Use of wheeled and tracked 

equipment when the soil is wet produces ruts, compacts 

the soil, and damages the roots of trees. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is not readily available in this unit. 

Snowpack in winter limits the use of equipment and 

restricts access. Cinders slough from road cuts onto the 

road surface. Establishing plant cover on steeper slopes 

that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and firebreaks are subject to 

rilling and gullying unless plant 

cover is maintained or adequate water bars are 

provided. 

Reforestation can be accomplished by planting noble 

fir or Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Logging activities 

can readily displace the surface layer. Seedlings that 

develop in the less fertile subsoil exhibit poor growth. 

Trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

Sitka alder, tall blue huckleberry, red huckleberry, 

common beargrass, and violet. 

This map unit is in capability subclass VIle. 

142-Tradedollar sandy loam, warm, 65 to 90 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 2,800 to 4,000 

feet. The average annual precipitation is about 100 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free period is 75 to 95 

days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown sandy loam 5 

inches thick. The upper 21 inches of the subsoil is dark 

brown cindery sandy loam, and the lower 16 inches is dark 

brown extremely cindery loamy sand and strong brown 

extremely cindery sand. Below this is a buried surface 

layer of dark grayish brown cindery sandy loam 9 inches 

thick. The next layer to a depth of 60 inches or more is a 

buried subsoil of dark brown very gravelly sandy loam. 

Included in this unit are small areas of Cattcreek, 

Colter, and Sinnice soils. Also included are small areas 

of Rock outcrop and Tradedollar soils that are 40 to 60 

inches deep to bedrock. Included areas make up about 

10 percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid in the upper part of the subsoil and very rapid in 

the lower part and is moderately rapid in the buried 

subsoil. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. Runoff is 

medium, and the hazard of water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir 

are the main woodland species on this unit. On the 

basis of a 100-year site curve, the mean site index is 
estimated to be 120 for western hemlock and 117 for 

Douglas fir. On the basis of a 50-year site curve, the 

mean site index is estimated to be 85 for western 

hemlock and 90 for Douglas fir. The culmination of the 

mean annual increment (CMAI) for western hemlock is 

180 cubic feet per acre per year at age 50, and the 

CMAI for Douglas fir is 110 cubic feet at age 60. 

Estimates of the site index or CMAI for Pacific silver fir 

have not been made. Among the trees of limited extent 

are noble fir and western redcedar. 

The main limitations for harvesting timber are snowpack 

in winter and steepness of slope. Cable yarding systems 

generally are used on this unit. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Snowpack in winter limits the use of 

equipment and restricts access. Cinders slough from road 

cuts onto the road surface. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Following road construction and clearcutting, 

road failures and landslides can occur. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. Harvesting systems that lift logs 

entirely off the ground reduce the disturbance of the 

protective layer of duff. 

Reforestation can be accomplished by planting noble 

fir or Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Logging activities 

can readily displace the surface layer. Seedlings that 

develop in the less fertile subsoil exhibit poor growth. 

Trees occasionally are subject to windthrow. 

Among the common forest understory plants are 

Sitka alder, tall blue huckleberry, red huckleberry, 

common beargrass. and violet. 

This map unit is in capability subclass VIIe. 

143-Typic Dystrandepts, 5 to 65 percent slopes. 

These very deep, well drained soils are on cinder cones. 

They formed in volcanic material derived dominantly 

from volcanic ash, cinders, and pumice. The native 

vegetation is mainly mixed conifers and shrubs. Elevation 

is 1,400 to 2,500 feet. The average annual precipitation 

is about 100 inches, the average annual air temperature 

is about 50 degrees F, and the average frost-free period 

is 110 to 130 days. 

No single profile of Typic Dystrandepts is typical, but 

one commonly observed in the survey area has a 

surface layer of very dark brown loam 10 inches thick. 

The subsoil is dark brown cobbly loam and very stony 

loam 31 inches thick. The substratum to a depth of 60 

inches or more is dark brown cobbly loam. 

Included in this unit are small areas of Kinney, 

Mountzion, and Skoly soils on mountain slopes. 

Included areas make up about 15 percent of the total 

acreage. 

Permeability of these Typic Dystrandepts is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium to 

rapid, and the hazard of water erosion is moderate to 

severe. 

This unit is used as woodland and wildlife habitat. 

Douglas fir and western hemlock are the main 

woodland species on this unit, On the basis of a 100-

year site curve, the mean site index is estimated to be 

144 for Douglas fir, and on the basis of a 50-year site 

curve, the mean site index is estimated to be 110. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 150 cubic feet per acre per year at age 

60. Estimates of the site index or CMAI for western 

hemlock have not been made. Among the trees of limited 

extent are grand fir and western redcedar. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and slippery 

and can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. The 

surface layer is loose when dry, which limits the use of 

wheeled and tracked equipment. Occasional snowpack 

hinders the use of equipment and limits access in winter. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. Disturbance of the protective layer of duff can 

be reduced with the careful use of wheeled and tracked 

equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir or noble fir 

seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock 

occurs readily. If the canopy is opened, brush invades 

and can prevent the establishment of Douglas fir 
seedlings and can delay reforestation by noble fir and 

western hemlock unless controlled. Droughtiness of the 

surface layer reduces seedling survival, especially on 

south- and southwest-facing slopes. 

Among the common forest understory plants are vine 

maple, red huckleberry, western hazel, Oregongrape, 

trailing blackberry, and western brackenfern. 

This map unit is in capability subclass Vle. 

144-Underwood loam, 2 to 15 percent slopes. This 

very deep, well drained soil is on benches and foot slopes 

of mountains. It formed in residuum and colluvium derived 

dominantly from basalt, andesite, and a thin mantle of 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 500 to 2,000 feet. The 

average annual precipitation is about 50 inches, the 

average annual air temperature is about 46 degrees F, 

and the average frost-free period is 100 to 150 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 5 inches thick. 

The upper 14 inches of the subsoil is dark brown loam, 

and the lower 16 inches is dark brown clay loam. The 

substratum to a depth of 60 inches or more is dark 

yellowish brown loam. 

Included in this unit are small areas of Chemawa and 

McElroy soils on terraces and foot slopes and Timberhead 

and Undusk soils on ridgetops. Also included are small 

areas of soils that are more than 35 percent clay. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Underwood soil is moderately 

slow. Available water capacity is high. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, hayland, pastureland, 

orchards, homesites, wildlife habitat, and recreation. 

Douglas fir, ponderosa pine, and grand fir are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 153 for Douglas 

fir, and on the basis of a 50-year site curve, the mean site 

index is 116. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 162 cubic feet per acre 

per year at age 60. Estimates of the site index or CMAI 

for ponderosa pine and grand fir have not been made. 

Among the trees of limited extent are Oregon white oak 

and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available 

in this unit. Occasional snowpack hinders the use of 

equipment and limits access in winter. Disturbance of 

the protective layer of duff can be reduced with the careful 

use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

ponderosa pine and grand fir occurs periodically. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir and ponderosa pine 

seedlings and can delay natural reforestation by grand fir 

unless controlled. 

Among the common forest understory plants are vine 

maple, Pacific dogwood, common snowberry, 

Oregongrape, cascara buckthorn, western brackenfern, 

and princes pine. 

If this unit is used for orchard crops, the main 

limitation is the hazard of erosion. If the ground is 

plowed in fall, runoff and erosion can be reduced by 

seeding to a cover crop. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition and to 

protect the soil from erosion. Mowing helps to maintain 

uniform growth and discourages selective grazing. In 

some years, supplemental irrigation is also needed. 

The main limitations of this unit for use as homesites 

are steepness of slope, shrink-swell potential, moderately 

slow permeability, and the hazard of erosion in the steeper 

areas. Only the part of the site that is used for construction 

should be disturbed. Preserving the existing plant cover 

during construction helps to control erosion. Plant cover 

can be established and maintained through proper 

fertilizing, seeding, mulching, and shaping of the slopes. 

In summer, irrigation is needed for lawn grasses, shrubs, 

vines, shade trees, and ornamental trees. 

Use of sandy backfill for the trench and long absorption 

lines helps to compensate for the moderately slow 

permeability of the soil. During the rainy season, effluent 

from onsite sewage disposal systems may seep at points 

downslope. If the density of housing is moderate to high, 

community sewage systems are needed to prevent 

contamination of water supplies as a result of seepage 

from onsite disposal systems. The effects of shrinking 

and swelling can be minimized by 
using proper engineering designs. Buildings and roads 

should be designed to offset the limited ability of the 

soil in this unit to support a load. 

This map unit is in capability subclass Ille. 

145-Underwood loam, 15 to 30 percent slopes. 

This very deep. well drained soil is on back slopes of 

mountains. It formed in residuum and colluvium derived 

dominantly from basalt, andesite, and a thin mantle of 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 500 to 2,000 feet. The 

average annual precipitation is about 50 inches, the 

average annual air temperature is about 46 degrees F, 

and the average frost-free period is 100 to 150 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 5 inches thick. 

The upper 14 inches of the subsoil is dark brown loam, 

and the lower 16 inches is dark brown clay loam. The 

substratum to a depth of 60 inches or more is dark 

yellowish brown loam. 

Included in this unit are small areas of Chemawa and 

McElroy soils on back slopes and Timberhead and 

Undusk soils on ridgetops. Also included are small areas 

of soils that are more than 35 percent clay. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Underwood soil is moderately 

slow. Available water capacity is high. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, hayland, pastureland, 

wildlife habitat, recreation, and watershed. 

Douglas fir, ponderosa pine, and grand fir are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 153 for Douglas 

fir, and on the basis of a 50-year site curve, the mean site 

index is 116. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 162 cubic feet per acre 

per year at age 60. Estimates of the site index or CMAI for 

ponderosa pine and grand fir have not been made. 

Among the trees of limited extent are Oregon white oak 

and bigleaf maple. 

The main limitations for harvesting timber are seasonal 

soil wetness and snowpack. Use of wheeled and tracked 

equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round use. Rock for road construction is 

not readily available in this unit. Snowpack hinders 

the use of equipment and limits access in winter. 

Establishing plant cover on steeper slopes that have 

been cut or filled reduces erosion. Disturbance of the 

protective layer of duff can be reduced with the careful 

use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

ponderosa pine and grand fir occurs periodically. If the 

canopy is opened, brush invades and can delay 

establishment of Douglas fir seedlings and natural 

reforestation unless controlled. 

Among the common forest understory plants are vine 

maple, Pacific dogwood, common snowberry, 

Oregongrape, cascara buckthorn, western brackenfern, 

and princes pine. 

This map unit is well suited to use as hayland and 

pastureland. The main limitations are steepness of slope 

and the hazard of erosion. Erosion can be controlled by 

growing pasture. The use of equipment is limited by 

steepness of slope. Proper stocking rates, pasture 

rotation, and restricted grazing during wet periods help 

to keep the pasture in good condition and to protect the 

soil from erosion. Mowing helps to maintain uniform 

growth and discourages selective grazing. 

This map unit is in capability subclass IVe. 

146-Underwood loam, 30 to 50 percent slopes. 

This very deep, well drained soil is on back slopes of 

mountains. It formed in colluvium derived dominantly 

from basalt, andesite, and a thin mantle of volcanic ash. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 500 to 2,000 feet. The average 

annual precipitation is about 50 inches, the average 

annual air temperature is about 46 degrees F, and the 

average frost-free period is 100 to 150 days. 

Typically, the surface is covered with a mat of 

decomposed needles. leaves, and twigs 2 inches thick. 

The surface layer is dark brown loam 5 inches thick. The 

upper 14 inches of the subsoil is dark brown loam, and 

the lower 16 inches is dark brown clay loam. The 

substratum to a depth of 60 inches or more is dark 

yellowish brown loam. 

Included in this unit are small areas of Chemawa, 

McElroy, Timberhead, and Undusk soils. Also included 

are small areas of soils that are more than 35 percent 

clay and small areas of Rock outcrop. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Underwood soil is moderately
slow. Available water capacity is high. Effective rooting 

depth is 60 inches or more. Runoff is rapid, and the 

hazard of water erosion is severe. 

This unit is used as woodland, wildlife habitat, 

recreation areas, and watershed. 

Douglas fir, ponderosa pine, and grand fir are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 153 for Douglas fir, 

and on the basis of a 50-year site curve, the mean site 

index is 116. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 162 cubic feet per acre 

per year at age 60. Estimates of the site index or CMAI for 

ponderosa pine and grand fir have not been made. Among 

the trees of limited extent are Oregon white oak and bigleaf 

maple. 

The main limitation for harvesting timber is steepness 

of slope. Use of wheeled and tracked equipment when 

the soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are soft and can be impassable when wet. Logging 

roads require suitable surfacing for year-round use. Rock 

for road construction is not readily available in this unit. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and firebreaks are subject to 

rilling and gullying unless plant cover is maintained or 

adequate water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

ponderosa pine and grand fir occurs periodically. If the 

canopy is opened, brush invades and can delay 

establishment of Douglas fir and ponderosa pine 

seedlings and natural reforestation by grand fir unless 

controlled. 

Among the common forest understory plants are vine 

maple, Pacific dogwood, common snowberry, 

Oregongrape, cascara buckthorn, western brackenfern, 

and princes pine. 

This map unit is in capability subclass VIIe. 

147-Undusk gravelly loam, 5 to 30 percent slopes. 

This very deep, well drained soil is on back slopes of 

mountains. It formed in residuum derived dominantly from 

basalt with a thin mantle of volcanic ash. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,000 to 2,800 feet. The average annual 

precipitation is about 55 inches, the average annual air 

temperature is about 44 degrees F, and the 

average frost-free period is 90 to 120 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown gravelly loam 15 inches 

thick. The subsoil to a depth of 60 inches or more is 

dark brown very gravelly loam and extremely gravelly 

loam. 

Included in this unit are small areas of Chemawa, 

McElroy, Timberhead, and Underwood soils on ridges 

and back slopes and St. Martin soils on landslides. Also 

included are small areas of soils that are less than 35 

percent rock fragments and soils that are shallow to 

bedrock. Included areas make up about 12 percent of the 

total acreage. 

Permeability of this Undusk soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir, grand fir, and western hemlock are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 118 for 

Douglas fir, and on the basis of a 50-year site curve, the 

mean site index is 88. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 111 cubic feet 

per acre per year at age 60. Estimates of the site index or 

CMAI for grand fir and western hemlock have not been 

made. Among the trees of limited extent are red alder 

and western redcedar. Areas on ridgetops that are subject 

to strong, persistent winds are less productive than other 

areas of this unit. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in 

this unit. Occasional snowpack hinders the use of 

equipment and limits access in winter. Establishing plant 

cover on steeper slopes that have been cut or filled 

reduces erosion. Disturbance of the protective layer of 

duff can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by grand 

fir and western hemlock occurs periodically. If the canopy 

is opened, brush invades and can delay the 

establishment of seedlings unless controlled. Logging 
activities can readily displace the surface layer. Seedlings 

that develop in the less fertile subsoil exhibit poor 

growth. 

Among the common forest understory plants are vine 

maple, western hazel, red huckleberry, western 

brackenfern, and common beargrass. 

This map unit is in capability subclass IVe. 

148-Undusk gravelly loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back slopes 

of mountains. It formed in colluvium derived dominantly 

from basalt with a thin mantle of volcanic ash. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,000 to 2,800 feet. The average annual 

precipitation is about 55 inches, the average annual air 

temperature is about 44 degrees F, and the average frostfree period is 90 to 120 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is dark brown gravelly loam 15 inches 

thick. The subsoil to a depth of 60 inches or more is 

dark brown very gravelly loam and extremely gravelly 

loam. 

Included in this unit are small areas of Chemawa, 

McElroy, Timberhead, and Underwood soils on back 

slopes and St. Martin soils on landslides. Also included 

are small areas of soils that are shallow to bedrock, Rock 

outcrop, and Undusk soils that have slopes of less than 30 

percent. Included areas make up about 15 percent of the 

total acreage. 

Permeability of this Undusk soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, wildlife habitat, and 

recreation. 

Douglas fir, grand fir, and western hemlock are the 

main woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 118 for Douglas 

fir, and on the basis of a 50-year site curve, the mean site 

index is 88. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 111 cubic feet per 

acre per year at age 60. Estimates of the site index or 

CMAI for grand fir and western hemlock have not been 

made. Among the trees of limited extent are red alder 

and western redcedar. 

The main limitation for harvesting timber is steepness of

slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and can be 

impassable when wet. Logging roads require suitable 

surfacing for year-round use. Rock for road construction is 

readily available in this unit. Occasional snowpack 

hinders the use of equipment and limits access in winter. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rifling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by grand 

fir and western hemlock occurs periodically. If the canopy 

is opened, brush invades and can delay the establishment 

of seedlings. Logging activities can readily displace the 

surface layer. Seedlings that develop in the less fertile 

subsoil exhibit poor growth. 

Among the common forest understory plants are vine 

maple, western hazel, red huckleberry, western 

brackenfern, and common beargrass. 

This map unit is in capability subclass VIIe. 

149-Vanson sandy loam, 5 to 30 percent slopes. 

This deep, well drained soil is on foot slopes and 

ridgetops of mountains. It formed in residuum and 

colluvium derived dominantly from igneous rock mixed 

with volcanic ash and pumice. The native vegetation is 

mainly mixed conifers and shrubs, Elevation is 2,800 to 

4,000 feet. The average annual precipitation is about 105 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free period is 75 to 95 

days. 

Where mixed to a depth of 9 inches, the surface layer 

typically is dark brown sandy loam. The upper 7 inches 

of the subsoil is dark yellowish brown sandy loam, the 

next 8 inches is dark brown loamy sand, and the lower 

part is dark yellowish brown very gravelly sandy loam 21 

inches thick over fractured andesite. Depth to bedrock 

ranges from 40 to 60 inches. 

included in this unit are small areas of Hatchet, 

Lonestar, and Swift soils. Also included are small areas 

of Rock outcrop and Vanson soils that are more than 60 

inches deep to bedrock. Included areas make up about 

15 percent of the total acreage. 

Permeability of this Vanson soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 40 to 60 inches. Runoff is medium, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 
Western hemlock, Douglas fir, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is 102 for 

Douglas fir and 114 for western hemlock. On the basis 

of a 50-year site curve, the mean site index is 77 for 

Douglas fir and 78 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 86 

cubic feet per acre per year at age 60. and the CMAI for 

western hemlock is 168 cubic feet at age 50. Estimates 

of the site index or CMAI for Pacific silver fir have not 

been made. Among the trees of limited extent is noble fir. 

Areas on ridgetops that are subject to strong, persistent 

winds are less productive than other areas of this unit. 

The main limitation for harvesting timber is snowpack 

in winter. Use of wheeled and tracked equipment when 

the soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are soft and can be impassable when wet. Logging 

roads require suitable surfacing for year-round use. Rock 

for road construction is readily available in this unit. 

Snowpack in winter limits the use of equipment and 

restricts access. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. 

Disturbance of the protective layer of duff can be reduced 

with the careful use of wheeled and tracked equipment. 

Reforestation can be accomplished by planting noble 

fir and Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Logging activities 

can readily displace the surface layer. Seedlings that 

develop in the less fertile subsoil exhibit poor growth. 

Among the common forest understory plants are vine 

maple, red huckleberry, common beargrass, western 

princes pine, Oregongrape, salal, and longtube 

twinflower. 

This map unit is in capability subclass Vls. 

150-Vanson sandy loam, 30 to 65 percent slopes. 

This deep, well drained soil is on back slopes of 

mountains. It formed in colluvium derived dominantly 

from igneous rock mixed with volcanic ash and pumice. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 2,800 to 4,000 feet. The average 

annual precipitation is about 105 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free period is 75 to 95 days. 

Where mixed to a depth of 9 inches, the surface layer 

typically is dark brown sandy loam. The upper 7 inches 

of the subsoil is dark yellowish brown sandy 

loam, the next 8 inches is dark brown loamy sand, 

and the lower part is dark yellowish brown very gravelly 

sandy loam 21 inches thick over fractured andesite. 

Depth to bedrock ranges from 40 to 60 inches. 

Included in this unit are small areas of Hatchet, 

Lonestar. and Swift soils. Also included are small areas 

of Rock outcrop and Vanson soils that are more than 60 

inches deep to bedrock. Included areas make up about 

15 percent of the total acreage. 

Permeability of this Vanson soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 40 to 60 inches. Runoff is medium, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is 102 for 

Douglas fir and 114 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 77 for Douglas 

fir and 78 for western hemlock. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 86 

cubic feet per acre per year at age 60, and the CMAI 

for western hemlock is 168 cubic feet at age 50. 

Estimates of the site index or CMAI for Pacific silver fir 

have not been made. Among the trees of limited extent 

is noble fir. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope, which 

restricts the use of wheeled and tracked equipment in 

skidding. Cable yarding systems generally are safer and 

disturb the soil less. Use of wheeled and tracked 

equipment when the soil is wet produces ruts, compacts 

the soil, and damages the roots of trees. Unsurfaced 

roads and skid trails are soft and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Snowpack in winter limits the use of 

equipment and restricts access. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Reforestation can be accomplished by planting noble 

fir and Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. 

Logging activities can readily displace the surface layer. 

Seedlings that develop in the less fertile subsoil 

exhibit poor growth. 

Among the common forest understory plants are vine 
maple. red huckleberry, common beargrass, western 

princes pine. Oregongrape, salal, and longtube 

twinflower. 

This map unit is in capability subclass VIIe. 

151-Vanson sandy loam, 65 to 90 percent slopes. 

This deep, well drained soil is on back slopes of 

mountains. It formed in colluvium derived dominantly 

from igneous rock mixed with volcanic ash and pumice. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 2,800 to 4,000 feet. The average 

annual precipitation is about 105 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free period is 75 to 95 days. 

Where mixed to a depth of 9 inches, the surface 

layer typically is dark brown sandy loam. The upper 7 

inches of the subsoil is dark yellowish brown sandy loam, 

the next 8 inches is dark brown loamy sand, and the 

lower part is dark yellowish brown very gravelly sandy 

loam 21 inches thick over fractured andesite. Depth to 

bedrock ranges from 40 to 60 inches. 

Included in this unit are small areas of Hatchet, 

Lonestar, and Swift soils. Also included are small areas 

of Rock outcrop and Vanson soils that are more than 60 

inches deep to bedrock. Included areas make up about 

15 percent of the total acreage. 

Permeability of this Vanson soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 40 to 60 inches. Runoff is rapid, and the 

hazard of water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir are 

the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 102 for 

Douglas fir and 114 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is 77 for Douglas 

fir and 78 for western hemlock. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 86 cubic 

feet per acre per year at age 60, and the CMAI for western 

hemlock is 168 cubic feet at age 50. Estimates of the site 

index or CMAI for Pacific silver fir have not been made. 

Among the trees of limited extent is noble fir. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. Cable yarding 

systems generally are used on this unit. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is readily available in this unit. 

Snowpack limits the use of equipment and restricts 

access. Logging roads generally need full bench 

construction and require frequent maintenance. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. Harvesting systems that lift logs entirely off 

the ground reduce the disturbance of the protective layer of 

duff. 

Reforestation can be accomplished by planting noble 

fir and Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Logging activities 

can readily displace the surface layer. Seedlings that 

develop in the less fertile subsoil exhibit poor growth. 

Low soil temperature in summer, deep snowpack, and a 

short growing season reduce the survival rate of planted 

and natural seedlings and delay their establishment. 

Among the common forest understory plants are vine 

maple, red huckleberry, common beargrass, western 

princes pine, Oregongrape, salal, and longtube 

twinflower. 

This map unit is in capability subclass VIIe. 

152-Vanson sandy loam, cold, 5 to 30 percent 

slopes. This deep, well drained soil is on foot slopes and 

ridgetops of mountains. It formed in colluvium derived 

dominantly from igneous rock mixed with volcanic ash 

and pumice. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 4,000 to 5,000 feet. 

The average annual precipitation is about 125 inches, 

the average annual air temperature is about 38 degrees 

F, and the average frost-free period is 75 to 95 days. 

Where mixed to a depth of 9 inches, the surface layer 

typically is dark brown sandy loam. The upper 7 inches of 

the subsoil is dark yellowish brown sandy loam, the next 

8 inches is dark brown loamy sand, and the lower part is 

dark yellowish brown very gravelly sandy loam 21 inches 

thick over fractured andesite. Depth to bedrock ranges 

from 40 to 60 inches. 

Included in this unit are small areas of Hatchet, 

Lonestar, and Tradedollar soils. Also included are small 

areas of Rock outcrop and Vanson soils that are more 

than 60 inches deep to bedrock. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Vanson soil is moderate. Available 

water capacity is moderate. Effective rooting depth is 40 

to 60 inches. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and noble fir are 
the main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 98 for western hemlock. On the basis of a 50-year site 

curve, the mean site index is estimated to be 70 for

western hemlock. The culmination of the mean annual

increment (CMAI) for western hemlock is 118 cubic feet per

acre per year at age 60. Estimates of the site index or CMAI 

for Pacific silver fir and noble fir have not been made.

Among the trees of limited extent are Douglas fir and 

subalpine fir. Areas on ridgetops that are subject to strong. 

persistent winds are less productive than other areas of

this unit. 

The main limitation for harvesting timber is snowpack 

in winter. Use of wheeled and tracked equipment when the 

soil is moist produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are soft and can be impassable when wet. Logging 

roads require suitable surfacing for year-round use. Rock 

for road construction is readily available in this unit. 

Snowpack in winter limits the use of equipment and restricts 

access. Disturbance of the protective layer of duff can be 

reduced with the careful use of wheeled and tracked 

equipment. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. The mortality rate 

of seedlings is higher in areas on ridgetops that are subject 

to strong, persistent winds than in other areas of this unit. 

Logging activities can readily displace the surface layer. 

Seedlings that develop in the less fertile subsoil exhibit 

poor growth. Low soil temperature in summer, deep 

snowpack, and a short growing season reduce the 

survival rate of planted and natural seedlings and delay 

their establishment. 

Among the common forest understory plants are vine 

maple, red huckleberry, common beargrass, western 

princes pine, Oregongrape, salal, and longtube 

twinflower. 

This map unit is in capability subclass VIs. 

153-Vanson sandy loam, cold, 30 to 65 percent 

slopes. This deep, well drained soil is on back slopes of 

mountains. It formed in colluvium derived dominantly from 

igneous rock mixed with volcanic ash and pumice. The 

native vegetation is mainly mixed conifers and shrubs. 

Elevation is 4,000 to 5,000 feet. The average annual 

precipitation is about 125 inches, the average annual 

air temperature is about 38 degrees F, and the average 

frost-free period is 75 to 95 days. 

Where mixed to a depth of 9 inches, the surface 

layer typically is dark brown sandy loam 9 inches thick. 

The upper 7 inches of the subsoil is dark yellowish brown 

sandy loam, the next 8 inches is dark brown loamy sand, 

and the lower part is dark yellowish brown very gravelly 

sandy loam 21 inches thick over fractured andesite. Depth 

to bedrock ranges from 40 to 60 inches. 

Included in this unit are small areas of Hatchet, 

Lonestar, and Tradedollar soils. Also included are small 

areas of Rock outcrop and Vanson soils that are more 

than 60 inches deep to bedrock. Included areas make up 

about 15 percent of the total acreage. 

Permeability of this Vanson soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 40 to 60 inches. Runoff is medium, and the 

hazard of water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and noble fir are 

the main woodland species on this unit. On the basis of 

a 100-year site curve, the mean site index is estimated 

to be 98 for western hemlock, and on the basis of a 50-

year site curve, the mean site index is estimated to be 

70. The culmination of the mean annual increment 

(CMAI) for western hemlock is 118 cubic feet per acre per 

year at age 60. Estimates of the site index or CMAI for 

Pacific silver fir and noble fir have not been made. 

Among the trees of limited extent are Douglas fir and 

subalpine fir. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. When 

harvesting timber, steepness of slope restricts the use of 

wheeled and tracked equipment in skidding. Cable 

yarding systems generally are safer and disturb the soil 

less. Use of wheeled and tracked equipment when the 

soil is wet produces ruts, compacts the soil, and 

damages the roots of trees. Unsurfaced roads and skid 

trails are soft and can be impassable when wet. Logging 

roads require suitable surfacing for year-round use. Rock 

for road construction is readily available in this unit, 

Snowpack in winter limits the use of 

equipment and restricts access. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs 
periodically. Logging activities can readily displace the 

surface layer. Seedlings that develop in the less fertile 

subsoil exhibit poor growth. Low soil temperature in 

summer. deep snowpack, and a short growing season 

reduce the survival rate of planted and natural 

seedlings and delay their establishment. 

Among the common forest understory plants are vine 

maple, red huckleberry, common beargrass, western 

princes pine, Oregongrape, salal, and longtube 

twinflower. 

This map unit is in capability subclass VIIe. 

154-Vanson-Rock outcrop complex, 30 to 65 

percent slopes. This map unit is on back slopes of 

mountains. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 2,800 to 4,000 feet. 

The average annual precipitation is about 105 inches, 

the average annual air temperature is about 39 degrees 

F, and the average frost-free period is 75 to 95 days. 

This unit is about 70 percent Vanson sandy loam, 30 to 

65 percent slopes, and 20 percent Rock outcrop. The 

components of this unit are so intricately intermingled 

that it was not practical to map them separately at the scale 

used. 

Included in this unit are small areas of Hatchet, 

Lonestar, and Swift soils. Also included are small areas 

of Vanson soils that are more than 60 inches deep to 

bedrock. Included areas make up about 10 percent of 

the total acreage. 

The Vanson soil is deep and well drained. It formed in 

colluvium derived dominantly from igneous rock mixed 

with volcanic ash and pumice. Where mixed to a depth of 9 

inches, the surface layer typically is dark brown sandy 

loam. The upper 7 inches of the subsoil is dark yellowish 

brown sandy loam, the next 8 inches is dark brown loamy 

sand, and the lower part is dark yellowish brown very 

gravelly sandy loam 21 inches thick over fractured 

andesite. Depth to bedrock ranges from 40 to 60 inches. 

Permeability of this Vanson soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 40 to 60 inches. Runoff is medium, and the 

hazard of water erosion is moderate. 

Rock outcrop consists mainly of exposed areas of 

andesite. Numerous escarpments are in this unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir 

are the main woodland species on the Vanson soil. On 

the basis of a 100-year site curve, the mean site index is 

102 for Douglas fir and 114 for western hemlock. On the 

basis of a 50-year site curve, the mean site index is 

77 for Douglas fir and 78 for western hemlock. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 86 cubic feet per acre per year at age 60, 

and the CMAI for western hemlock is 168 cubic feet at 

age 50. The areas of Rock outcrop make up about 20 

percent of this unit and reduce yield accordingly. 

Estimates of the site index or CMAI for Pacific silver fir 

have not been made. Among the trees of limited extent is 

noble fir. 

The main limitations for harvesting timber are Rock 

outcrop, steepness of slope, and snowpack in winter. 

When harvesting timber, steepness of slope restricts the 

use of wheeled and tracked equipment in skidding. 

Cable yarding systems generally are safer and disturb 

the soil less. Rock outcrop may cause breakage of timber 

when felled and can hinder yarding operations. Avoiding 

areas of Rock outcrop forces yarding and skidding paths to 

converge, which increases compaction and erosion of the 

soil. Use of wheeled and tracked equipment when the soil 

is wet produces ruts, compacts the soil, and damages the 

roots of trees. Unsurfaced roads and skid trails are soft 

and can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Snowpack in 

winter limits the use of equipment and restricts access. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. 

Reforestation can be accomplished by planting noble 

fir and Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western hemlock 

and Pacific silver fir occurs periodically. Logging activities 

can readily displace the surface layer. Seedlings that 

develop in the less fertile subsoil exhibit poor growth. 

The areas of Rock outcrop limit the even distribution of 

reforestation. 

Among the common forest understory plants are vine 

maple, red huckleberry, common beargrass, western 

princes pine, Oregongrape, salal, and longtube 

twinflower. 

The Vanson soil is in capability subclass VIIe, and 

the Rock outcrop is in capability subclass VIIIs. 

155-Vanson-Rock outcrop complex, 65 to 90 

percent slopes. This map unit is on back slopes of 

mountains. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 2,800 to 4,000 feet. 

The average annual precipitation is about 105 inches, 

the average annual air temperature is about 39 degrees 
F, and the average frost-free period is 75 to 95 days. 

This unit is about 70 percent Vanson gravelly sandy 

loam, 65 to 90 percent slopes, and 20 percent Rock 

outcrop. The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Hatchet, 

Lonestar, and Swift soils. Also included are small areas 

of Vanson soils that are more than 60 inches deep to 

bedrock. Included areas make up about 10 percent of the 

total acreage. 

The Vanson soil is deep and well drained. It formed in 

colluvium derived dominantly from igneous rock mixed 

with volcanic ash and pumice. Where mixed to a depth 

of 6 inches, the surface layer typically is very dark 

grayish brown gravelly sandy loam. The upper 7 inches 

of the subsoil is dark yellowish brown sandy loam and 

dark brown very gravelly loamy sand, and the lower part 

is dark yellowish brown very gravelly sandy loam 21 

inches thick over fractured andesite. Depth to bedrock 

ranges from 40 to 60 inches. 

Permeability of this Vanson soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 40 to 60 inches. Runoff is rapid, and the hazard 

of water erosion is severe. 

Rock outcrop consists mainly of exposed areas of 

andesite. Numerous escarpments are in this unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Douglas fir, and Pacific silver fir are 

the main woodland species on the Vanson soil. On the 

basis of a 100-year site curve, the mean site index is 102 

for Douglas fir and 114 for western hemlock. On the basis 

of a 50-year site curve, the mean site index is 77 for 

Douglas fir and 78 for western hemlock. The culmination 

of the mean annual increment (CMAI) for Douglas fir is 86 

cubic feet per acre per year at age 60, and the CMAI for 

western hemlock is 168 cubic feet at age 50. The 

areas of Rock outcrop make up about 20 percent of 

this unit and reduce yield accordingly. Estimates of the 

site index or CMAI for Pacific silver fir have not been 

made. Among the trees of limited extent is noble fir. 

The main limitations for harvesting timber are Rock 

outcrop, steepness of slope, and snowpack in winter. 

Cable yarding systems generally are used on this unit. 

Rock outcrop may cause breakage of timber when felled 

and can hinder yarding operations. Avoiding areas of 

Rock outcrop forces yarding and skidding paths to 

converge, which increases compaction and erosion of the 

soil. Logging roads require suitable surfacing for yearround use. Rock for road construction 

is readily available in this unit. Logging roads generally 

need full bench construction and require frequent 

maintenance. Snowpack in winter limits the use of 

equipment and restricts access. Establishing plant cover 

on steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Reforestation can be accomplished by planting noble 

fir and Douglas fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. Logging 

activities can readily displace the surface layer. 

Seedlings that develop in the less fertile subsoil exhibit 

poor growth. The areas of Rock outcrop limit the even 

distribution of reforestation. 

Among the common forest understory plants are vine 

maple, red huckleberry, common beargrass, western 

princes pine, Oregongrape, salal, and longtube 

twinflower. 

The Vanson soil is in capability subclass VIle, and 

the Rock outcrop is in capability subclass Vllls. 

156-Vanson, cold-Rock outcrop complex, 65 to 90 

percent slopes. This map unit is on back slopes of 

mountains. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 4,000 to 5,000 feet. The 

average annual precipitation is about 125 inches, the 

average annual air temperature is about 38 degrees F, 

and the average frost-free period is 75 to 95 days. 

This unit is about 70 percent Vanson sandy loam, 

cold, 65 to 90 percent slopes, and 20 percent Rock 

outcrop. The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Hatchet, 

Lonestar, and Tradedollar soils. Also included are small 

areas of Vanson soils that are more than 60 inches deep 

to bedrock. Included areas make up about 15 percent 

of the total acreage. 

The Vanson soil is deep and well drained. It formed in 

colluvium derived dominantly from igneous rock mixed 

with volcanic ash and pumice. Where mixed to a depth 

of 9 inches, the surface layer typically is dark brown 

sandy loam. The upper 7 inches of the subsoil is dark 

yellowish brown sandy loam, the next 8 inches is dark 

brown loamy sand, and the lower part is dark yellowish 

brown very gravelly sandy loam 21 inches thick over 

fractured andesite. Depth to bedrock ranges from 40 to 

60 inches. 
Permeability of this Vanson soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 40 to 60 inches. Runoff is rapid, and the hazard 

of water erosion is severe. 

Rock outcrop consists mainly of exposed areas of 

andesite. Numerous escarpments are in this unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Western hemlock, Pacific silver fir, and noble fir are 

the main woodland species on the Vanson soil. On the 

basis of a 100-year site curve, the mean site index is 

estimated to be 98 for western hemlock, and on the basis 

of a 50-year site curve, the mean site index is estimated 

to be 70 for western hemlock. The culmination of the 

mean annual increment (CMAI) for western hemlock is 

118 cubic feet per acre per year at age 60. The areas of 

Rock outcrop make up about 20 percent of this unit and 

reduce yield accordingly. Estimates of the site index or 

CMAI for Pacific silver fir and noble fir have not been 

made. Among the trees of limited extent are Douglas fir 

and subalpine fir. Areas on ridgetops that are subject to 

strong, persistent winds are less productive than other 

areas of this unit. 

The main limitations for harvesting timber are 

snowpack in winter and steepness of slope. Cable 

yarding systems generally are used on this unit. Rock 

outcrop may cause breakage of timber when felled and 

can hinder yarding operations. Avoiding areas of Rock 

outcrop forces yarding and skidding paths to converge, 

which increases compaction and erosion of the soil. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in 

this unit. Logging roads generally need full bench 

construction and require frequent maintenance. 

Snowpack in winter limits the use of equipment and 

restricts access. Establishing plant cover on steeper 

slopes that have been cut or filled reduces erosion. Steep 

yarding paths, skid trails, and firebreaks are subject to 

rilling and gullying unless plant cover is maintained or 

adequate water bars are provided. Harvesting systems 

that lift logs entirely off the ground reduce the 

disturbance of the protective layer of duff. 

Seedling mortality is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting noble fir seedlings. If seed trees are present, 

natural reforestation of cutover areas by western 

hemlock and Pacific silver fir occurs periodically. The 

areas of Rock outcrop limit the even distribution of 

reforestation. Logging activities can readily displace the 

surface layer. Seedlings that develop in the less fertile 

subsoil exhibit poor growth. Low soil temperature in 

summer, deep snowpack, and a 

short growing season reduce the survival rate of 

planted and natural seedlings and delay their 

establishment. 

Among the common forest understory plants are vine 

maple, red huckleberry, common beargrass, western 

princes pine, Oregongrape, salal, and longtube 

twinflower. 

The Vanson soil is in capability subclass VIIe, and 

the Rock outcrop is in capability subclass VIlls. 

157-Washougal loam, 0 to 3 percent slopes. This 

very deep, well drained soil is on terraces. It formed in 

gravelly alluvium derived dominantly from volcanic ash, 

basalt, and andesite. The native vegetation is mainly 

mixed conifers and hardwoods. Elevation is 50 to 800 

feet. The average annual precipitation is about 60 inches, 

the average annual air temperature is about 48 degrees 

F, and the average frost-free period is 120 to 180 days.

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper part of the surface layer is black loam 5 

inches thick, and the lower part is very dark brown 

gravelly loam 17 inches thick. The upper part of the 

underlying material is dark brown very gravelly loam 8 

inches thick, the next 6 inches is dark brown very gravelly 

coarse sandy loam, and the lower part to a depth of 60 

inches or more is dark brown extremely cobbly coarse 

sand. 

Included in this unit are small areas of Bonneville 

soils on river terraces, Mountzion and Skoly soils on 

mountain slopes, and Hesson soils on terraces. Also 

included are small areas of moderately well drained soils 

and soils that are less than 35 percent rock fragments. 

Included areas make up about 20 percent of the total 

acreage. 

Permeability of this Washougal soil is moderate in the 

upper part of the underlying material and very rapid in the 

lower part. Available water capacity is low. Effective 

rooting depth is 60 inches or more. Runoff is slow, and 

the hazard of water erosion is slight. This soil is subject 

to rare periods of flooding. 

This unit is used mainly as woodland and homesites. It 

is also used for hayland, pastureland, and recreation. 

Douglas fir, red alder, and western hemlock are the 

main woodland species on this unit. On the basis of a 

100-year site curve, the mean site index is 143 for 

Douglas fir, and on the basis of a 50-year site curve, the 

mean site index is 114. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 149 cubic feet 

per acre per year at age 65. Estimates of the site index or 

CMAI for red alder and western hemlock 
have not been made. Among the trees of limited extent 

are western redcedar and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit, Disturbance 

of the protective layer of duff can be reduced with the 

careful use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by red 

alder occurs readily. If the canopy is opened, brush 

invades and can prevent the establishment of seedlings 

unless controlled. 

Among the common forest understory plants are vine 

maple, salal, red huckleberry, Oregongrape, western 

hazel, trailing blackberry, and western swordfern. 

The main limitation of this unit for use as homesites is 

the hazard of flooding. Topsoil can be stockpiled and 

used to reclaim areas disturbed during construction. 

Cutbanks are unstable and are subject to slumping. 

Removal of pebbles and cobbles in disturbed areas is 

needed for best results when landscaping, particularly in 

areas used for lawns. In summer, irrigation is needed 

for lawn grasses, shrubs, vines, shade trees, and 

ornamental trees. The soil in this unit is subject to frost 

action, which may limit construction of roads and streets. 

The main limitation for septic tank absorption fields is the 

risk of contaminating ground water because of poor 

filtration. If the density of housing is moderate to high, 

community sewage systems are needed to prevent 

contamination of water supplies as a result of seepage 

from onsite sewage disposal systems. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition and 

to protect the soil from erosion. Mowing helps to maintain 

uniform growth and discourages selective grazing. In 

some years. supplemental irrigation is needed. 

This map unit is in capability subclass IIIs. 

158-Washougal gravelly loam, 2 to 8 percent 

slopes. This very deep, well drained soil is on terraces. It 

formed in mixed alluvium derived dominantly from 

basalt, andesite, and some volcanic ash. The native 

vegetation is mainly mixed conifers and shrubs. 

Elevation is 200 to 800 feet. The average annual 

precipitation is about 60 inches, the average annual air 

temperature is about 48 degrees F, and the average 

frost-free period is 120 to 180 days. 

Typically, the upper part of the surface layer is black 

gravelly loam 11 inches thick and the lower part is very 

dark brown very gravelly loam 25 inches thick. The 

subsoil is dark yellowish brown very gravelly loam 8 

inches thick. The substratum to a depth of 60 inches or 

more is dark yellowish brown very gravelly sandy loam. 

Included in this unit are small areas of Skamania 

and Stable soils and St. Martin soils on landslides. 

Also included are small areas of Washougal soils that 

have slopes of more than 8 percent. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Washougal soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is slow, and the 

hazard of water erosion is slight. 

This unit is used mainly for hayland, pastureland, 

homesites, wildlife habitat, or recreation. It is also used 

as woodland. 

This unit is well suited to use as hayland and 

pastureland. It has few limitations. Proper stocking rates, 

pasture rotation, and restricted grazing during wet 

periods help to keep the pasture in good condition and 

to protect the soil from erosion. Mowing helps to maintain 

uniform growth and discourages selective grazing. In 

some years supplemental irrigation is also needed. 

This unit is well suited to use as homesites. It has 

few limitations. Preserving the existing plant cover during 

construction helps to control erosion. Plant cover can be 

established and maintained through proper fertilizing, 

seeding, mulching, and shaping of the slopes. Removal 

of pebbles and cobbles in disturbed areas is needed for 

best results when landscaping, particularly in areas used 

for lawns. In summer, irrigation is needed for lawn 

grasses, shrubs, vines, shade trees, and ornamental 

trees. Cutbanks are unstable and are subject to 

slumping. The soil in this unit is subject to frost action, 

which may limit construction of roads and streets. 

Douglas fir, red alder, and grand fir are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 158 for Douglas 

fir, and on the basis of a 50-year site curve, the mean 

site index is 119. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 168 cubic feet per 

acre per year at age 65. Estimates of the site index or 

CMAI for red alder and grand fir have not been made. 

Among the trees of limited extent are western hemlock 

and bigleaf maple. 
The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not readily 

available in this unit. Disturbance of the protective layer of 

duff can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment and mortality are the main 

concerns in the production of timber. Reforestation can be 

accomplished by planting Douglas fir seedlings. If seed 

trees are present, natural reforestation of cutover areas 

by red alder occurs readily and by grand fir, periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. If the canopy is opened, brush invades and can 

delay the establishment of Douglas fir seedlings and 

natural reforestation by grand fir unless controlled. 

Among the common forest understory plants are vine 

maple, salal, Oregongrape, red huckleberry, and thimble 

berry. 

This map unit is in capability subclass Ills. 

159-Washougal gravelly loam, 8 to 30 percent 

slopes. This very deep, well drained soil is on terraces 

and terrace escarpments. It formed in mixed alluvium 

derived dominantly from basalt, andesite, and some 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 200 to 800 feet. The 

average annual precipitation is about 60 inches, the 

average annual air temperature is about 48 degrees F. 

and the average frost-free period is 120 to 180 days. 

Typically, the upper part of the surface layer is black 

gravelly loam 11 inches thick and the lower part is very 

dark brown very gravelly loam 25 inches thick. The subsoil 

is dark yellowish brown very gravelly loam 8 inches thick. 

The substratum to a depth of 60 inches or more is dark 

yellowish brown very gravelly sandy loam. 

Included in this unit are small areas of Skamania 

and Stabler soils and St. Martin soils on landslides. Also 

included are small areas of Washougal soils that have 

slopes of less than 8 percent or more than 30 percent. 

Included areas make up about 15 percent of the total 

acreage. 

Permeability of this Washougal soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is medium, and the 

hazard of water erosion is moderate. 

This unit is used for hayland, pastureland, homesites,

woodland, wildlife habitat, and recreation. 

This unit is suited to use as hayland and pastureland. 

The main limitations are steepness of slope and the 

hazard of erosion. Erosion can be controlled by growing 

pasture. The use of equipment is limited by steepness of 

slope. Proper stocking rates, pasture rotation, and 

restricted grazing during wet periods help to keep the 

pasture in good condition and to protect the soil from 

erosion. Mowing helps to maintain uniform growth and 

discourages selective grazing. 

The main limitations of this unit for use as homesites 

are steepness of slope and the hazard of erosion in the 

steeper areas. Only the part of the site that is used for 

construction should be disturbed. Preserving the existing 

plant cover during construction helps to control erosion. 

Plant cover can be established and maintained through 

proper fertilizing, seeding, mulching, and shaping of the 

slopes. Removal of pebbles and cobbles in disturbed 

areas is needed for best results when landscaping, 

particularly in areas used for lawns. In summer, irrigation 

is needed for lawn grasses, shrubs, vines, shade trees, 

and ornamental trees. Cutbanks are unstable and are 

subject to slumping. This soil is subject to frost action, 

which may limit construction of roads and streets. 

Steepness of slope limits installation of septic tank 

absorption fields. Absorption lines should be installed on 

the contour. 

Douglas fir, red alder, and grand fir are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 158 for Douglas 

fir, and on the basis of a 50-year site curve, the mean 

site index is 119 for Douglas fir. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 168 

cubic feet per acre per year at age 65. Estimates of the 

site index or CMAI for red alder and grand fir have not 

been made. Among the trees of limited extent are 

western hemlock and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available in 

this unit. Establishing plant cover on steeper slopes that 

have been cut or filled reduces erosion. Disturbance of 

the protective layer of duff can be reduced with the 

careful use of wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be 

accomplished by planting Douglas fir seedlings. If seed 
trees are present, natural reforestation of cutover areas 

by red alder occurs readily and by grand fir, periodically. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. If the canopy is opened, brush invades and can 

delay the establishment of Douglas fir seedlings and 

natural reforestation by grand fir unless controlled. 

Among the common forest understory plants are vine 

maple. salal, Oregongrape, red huckleberry, and thimble 

berry. 

This map unit is in capability subclass IVe. 

160-Washougal gravelly loam, 30 to 50 percent 

slopes. This very deep, well drained soil is on terrace 

escarpments. It formed in mixed alluvium derived 

dominantly from basalt, andesite, and some volcanic ash. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 200 to 800 feet. The average annual 

precipitation is about 60 inches, the average annual air 

temperature is about 48 degrees F, and the average frostfree period is 120 to 180 days. 

Typically, the upper part of the surface layer is black 

gravelly loam 11 inches thick and the lower part is very 

dark brown very gravelly loam 25 inches thick. The 

subsoil is dark yellowish brown very gravelly loam 8 

inches thick. The substratum to a depth of 60 inches or 

more is dark yellowish brown very gravelly sandy loam. 

Included in this unit are small areas of Skamania and 

Stabler soils and St. Martin soils on landslides. Also 

included are small areas of Washougal soils that have 

slopes of less than 30 percent. Included areas make up 

about 15 percent of the total acreage. 

Permeability of this Washougal soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is medium, and 

the hazard of water erosion is moderate. 

This unit is used for woodland, recreation, and 

wildlife habitat. 

Douglas fir, red alder, and grand fir are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 158 for Douglas 

fir, and on the basis of a 50-year site curve, the mean 

site index is 119. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 168 cubic feet per 

acre per year at age 65. Estimates of the site index or 

CMAI for red alder and grand fir have not been 

made. Among the trees of limited extent are western 

hemlock and bigleaf maple. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and slippery 

and can be impassable when wet. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is not readily available in this unit. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails, and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. 

Seedling establishment and mortality are the main 

concerns in the production of timber. Reforestation can 

be accomplished by planting Douglas fir seedlings. If 

seed trees are present, natural reforestation of cutover 

areas by red alder occurs readily and by grand fir, 

periodically. Droughtiness of the surface layer reduces 

seedling survival, especially on south- and southwestfacing slopes. If the canopy is opened, brush invades 

and can delay establishment of Douglas fir seedlings 

and natural reforestation by grand fir unless controlled. 

Among the common forest understory plants are vine 

maple, Oregongrape, salal, red huckleberry, 

thimbleberry, Pacific dogwood, dwarf rose, princes pine, 

and common snowberry. 

This map unit is in capability subclass VIIe. 

161-Xerorthents-Rock outcrop complex, 50 to 90 

percent slopes. This map unit is on escarpments. It 

formed in colluvium derived dominantly from basalt, 

andesite, and some volcanic ash. The native vegetation 

is mainly mixed conifers and shrubs. Elevation is 100 to 

2,200 feet. The average annual precipitation is about 

50 inches, the average annual air temperature is 

about 53 degrees F, and the average frost-free period 

is 130 to 150 days. 

This unit is about 65 percent Xerorthents and 25 

percent Rock outcrop. The components of this unit are 

so intricately intermingled that it was not practical to 

map them separately at the scale used. 

included in this unit are small areas of McElroy and 

Skoly soils on mountain slopes. Also included are small 

areas of soils that have a cemented substratum or have 

slopes of less than 50 percent or more than 90 percent. 

Included areas make up about 10 percent of the total 

acreage. The percentage varies from one area to 

another. 

The Xerorthents are shallow to deep and are well 

drained. They formed in colluvium derived dominantly 

from basalt, andesite. and some volcanic ash. No single 

profile of Xerorthents is typical, but one commonly 
observed in the survey area has a surface layer of very 

dark grayish brown gravelly loam 6 inches thick. The 

upper 17 inches of the underlying material is dark brown 

very gravelly loam, and the lower part to a depth of 31 

inches is brown extremely gravelly clay loam. Bedrock is 

at a depth of 31 inches. Depth to bedrock ranges from 10 

to 60 inches or more. 

Permeability of these Xerorthents is moderate. 

Available water capacity is low. Effective rooting depth is 

10 to 60 inches or more. Runoff is rapid, and the hazard 

of water erosion is severe. 

Rock outcrop consists mainly of exposed areas of 

basalt and andesite. Numerous escarpments are in this 

unit. 

This unit is used for recreation, wildlife habitat, and 

esthetic value. 

This unit is poorly suited to the production of timber. 

Ponderosa pine and Oregon white oak are the main 

woodland species on the Xerorthents. 

Among the common forest understory plants are 

snowberry, Oregongrape, rose, trailing blackberry, and 

western hazel. 

The Xerorthents are in capability subclass VIIe, and 

the Rock outcrop is in capability subclass Vllls. 

162-Yalelake sandy loam, 2 to 30 percent slopes. 

This very deep, well drained soil is on terraces. It 

formed in volcanic ash and pumice over pyroclastic 

deposits. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 800 to 1,800 feet. The average 

annual precipitation is about 120 inches, the average 

annual air temperature is about 50 degrees F, and the 

average frost-free period is 100 to 135 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark brown and dark brown 

sandy loam 11 inches thick. The upper 9 inches of the 

subsoil is dark grayish brown gravelly loamy sand, and 

the lower 19 inches is dark yellowish brown gravelly 

sandy loam. The substratum to a depth of 60 inches or 

more is brownish yellow sand and dark yellowish brown 

gravelly loam. 

Included in this unit are small areas of Cinnamon and 

Swift soils on mountain slopes and Forsyth and 

Pinchot soils on terraces. Also included are small areas 

of Yalelake soils that are more than 35 percent rock 

fragments. Included areas make up about 8 percent of 

the total acreage. 

Permeability of this Yalelake soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is slow, and the hazard of 

water erosion is slight. 

This unit is used as woodland, recreation areas, 

wildlife habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 164 for Douglas fir 

and 154 for western hemlock. On the basis of a 50-

year site curve, the mean site index is 120 for Douglas fir 

and 110 for western hemlock. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 174 

cubic feet per acre per year at age 60, and the CMAI for 

western hemlock is 244 cubic feet at age 50. Among the 

trees of limited extent are western redcedar and red 

alder. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and can be impassable when wet. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is not readily available 

in this unit. Disturbance of the protective layer of duff 

can be reduced with the careful use of wheeled and 

tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock occurs periodically. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, salal, western brackenfern, western swordfern, 

Oregongrape, and Pacific dogwood. 

This map unit is in capability subclass IVe. 

163-Yalelake sandy loam, 30 to 65 percent slopes. 

This very deep, well drained soil is on terrace 

escarpments. It formed in volcanic ash and pumice over 

pyroclastic deposits. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 800 to 1,800 

feet. The average annual precipitation is about 120 

inches, the average annual air temperature is about 50 

degrees F, and the average frost-free period is 100 to 

135 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark brown and dark brown 

sandy loam 11 inches thick. The upper 9 inches of the 

subsoil is dark grayish brown gravelly loamy sand, and 

the lower 19 inches is dark yellowish brown gravelly 
sandy loam. The substratum to a depth of 60 inches or

more is brownish yellow sand and dark yellowish brown 

gravelly loam. 

Included in this unit are small areas of Cinnamon and 

Swift soils on mountain slopes and Pinchot soils on 

terraces. Also included are small areas of Yalelake soils 

that are more than 35 percent rock fragments. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Yalelake soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 inches

or more. Runoff is medium, and the hazard of water 

erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-year 

site curve. the mean site index is 164 for Douglas fir and 

154 for western hemlock. On the basis of a 50-year site 

curve, the mean site index is 120 for Douglas fir and 110 

for western hemlock. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 174 cubic feet per acre 

per year at age 60, and the CMAI for western hemlock is 

244 cubic feet at age 50. Among the trees of limited extent 

are western redcedar and red alder. 

The main limitation for harvesting timber is the 

steepness of slope. which restricts the use of wheeled 

and tracked equipment in skidding. Cable yarding 

systems generally are safer and disturb the soil less. Use 

of wheeled and tracked equipment when the soil is moist 

produces ruts. compacts the soil, and damages the 

roots of trees. Unsurfaced roads and skid trails are soft 

and can be impassable when wet. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is not readily available in this unit. 

Establishing plant cover on steeper slopes that have 

been cut or filled reduces erosion. Steep yarding paths, 

skid trails, and firebreaks are subject to rilling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock occurs periodically. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, salal, western brackenfern, western swordfern, 

Oregongrape, and Pacific dogwood. 

This map unit is in capability subclass VIle. 

164-Yalelake sandy loam, 65 to 90 percent slopes. 

This very deep, well drained soil is on terrace 

escarpments. It formed in volcanic ash and pumice 

over pyroclastic deposits. The native vegetation is 

mainly mixed conifers and shrubs. Elevation is 800 to 

1,800 feet. The average annual precipitation is about 

120 inches, the average annual air temperature is about 

50 degrees F, and the average frost-free period is 100 

to 135 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 1 inch thick. 

The surface layer is very dark brown and dark brown 

sandy loam 11 inches thick. The upper 9 inches of the 

subsoil is dark grayish brown gravelly loamy sand, and 

the lower 19 inches is dark yellowish brown gravelly 

sandy loam. The substratum to a depth of 60 inches or 

more is brownish yellow sand and dark yellowish brown 

gravelly loam. 

Included in this unit are small areas of Cinnamon and 

Swift soils on mountain slopes and Pinchot soils on 

terraces. Also included are small areas of Yalelake soils 

that are more than 35 percent rock fragments and Rock 

outcrop. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this Yalelake soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 164 for Douglas fir 

and 154 for western hemlock. On the basis of a 50-year 

site curve, the mean site index is 120 for Douglas fir and 

110 for western hemlock. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 174 cubic feet 

per acre per year at age 60, and the CMAI for western 

hemlock is 244 cubic feet at age 50. Among the trees of 

limited extent are western redcedar and red alder. 

The main limitation for harvesting timber is the 

steepness of slope. Cable yarding systems generally are 

used on this unit. Unsurfaced roads and skid trails are 

soft and can be impassable when wet. Logging roads 

require suitable surfacing for year-round use. Rock for 

road construction is not readily available in this unit. 

Logging roads generally need full bench construction 

and require frequent maintenance. Establishing plant 

cover on steeper slopes that have 
been cut or filled reduces erosion. Following road 

construction and clearcutting, road failures and 

landslides can occur. Steep yarding paths, skid trails, 

and firebreaks are subject to rilling and gullying unless 

plant cover is maintained or adequate water bars are 

provided. Harvesting systems that lift logs entirely off 

the ground reduce the disturbance of the protective 

layer of duff. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock occurs periodically. If the canopy is opened, 

brush invades and can prevent the establishment of 

Douglas fir seedlings and can delay natural reforestation 

by western hemlock unless controlled. 

Among the common forest understory plants are vine 

maple. salal. western brackenfern, western swordfern, 

Oregongrape, and Pacific dogwood. 

This map unit is in capability subclass VIIe. 

165-Zygore gravelly loam, 5 to 30 percent 

slopes. This very deep, well drained soil is on foot slopes 

of mountains. It formed in colluvium derived dominantly 

from basalt and andesite mixed with volcanic ash, The 

native vegetation is mainly mixed conifers and shrubs. 

Elevation is 2,000 to 3,000 feet. The average annual 

precipitation is about 90 inches, the average annual air 

temperature is about 43 degrees F, and the average 

frost-free period is 90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark brown and very dark 

grayish brown gravelly loam 14 inches thick. The upper 

12 inches of the subsoil is dark brown very gravelly loam, 

and the lower 11 inches is dark yellowish brown very 

gravelly silt loam. The substratum to a depth of 60 inches 

or more is dark yellowish brown extremely gravelly silt 

loam. 

Included in this unit are small areas of Aschoff and 

Skoly soils and St. Martin soils on landslides. Also 

included are small areas of Rock outcrop, cool soils, and 

soils that have less than 35 percent rock fragments. 

Included areas make up about 12 percent of the total 

acreage. 

Permeability of this Zygore soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. Runoff is medium, 

and the hazard of water erosion is moderate. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is 120 for Douglas fir and 

western hemlock. On the basis of a 50-year site curve, 

the mean site index is 92 for Douglas fir and 85 for 

western hemlock. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 115 cubic feet per 

acre per year at age 60, and the CMAI for western 

hemlock is 180 cubic feet at age 50. Among the trees of 

limited extent are red alder and western redcedar. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is readily 

available in this unit. Occasional snowpack hinders the 

use of equipment and limits access in winter. 

Disturbance of the protective layer of duff can be reduced 

with the careful use of wheeled and tracked equipment. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock 

occurs readily. 

Among the common forest understory plants are vine 

maple, oceanspray, salal, red huckleberry, western 

redcedar, western brackenfern, Oregon oxalis, and 

common beargrass. 

This map unit is in capability subclass IVe. 

166-Zygore gravelly loam, 30 to 65 percent 

slopes. This very deep, well drained soil is on back 

slopes of mountains. It formed in colluvium derived 

dominantly from basalt and andesite mixed with volcanic 

ash. The native vegetation is mainly mixed conifers 

and shrubs. Elevation is 2,000 to 3,000 feet. The 

average annual precipitation is about 90 inches, the 

average annual air temperature is about 43 degrees F, 

and the average frost-free period is 90 to 110 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The surface layer is very dark brown and very dark 

grayish brown gravelly loam 14 inches thick. The upper 

12 inches of the subsoil is dark brown very gravelly 

loam, and the lower 11 inches is dark yellowish brown 

very gravelly silt loam. The substratum to a depth of 60 

inches or more is dark yellowish brown extremely 

gravelly silt loam. 

Included in this unit are small areas of Aschoff and 
Skoly soils and Andic Cryumbrepts on ridgetops. Also 

included are small areas of Rock outcrop and shallow 

soils. Included areas make up about 15 percent of the 

total acreage. 

Permeability of this Zygore soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is rapid, and the 

hazard of water erosion is severe. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is 120 for Douglas fir and 

western hemlock. On the basis of a 50-year site curve, 

the mean site index is 92 for Douglas fir and 85 for 

western hemlock. The culmination of the mean annual 

increment (CMAI) for Douglas fir is 115 cubic feet per 

acre per year at age 60, and the CMAI for western 

hemlock is 180 cubic feet at age 50. Among the trees of 

limited extent are red alder and western redcedar. 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Unsurfaced roads and skid trails are soft and slippery and 

can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Occasional 

snowpack hinders the use of equipment and limits access 

in winter. Establishing plant cover on steeper slopes that 

have been cut or filled reduces erosion. Steep yarding 

paths, skid trails, and firebreaks are subject to rilling 

and gullying unless plant cover is maintained or 

adequate water bars are provided. 

Reforestation can be accomplished by planting 

Douglas fir seedlings. If seed trees are present, natural 

reforestation of cutover areas by western hemlock 

occurs readily. 

Among the common forest understory plants are vine 

maple, creambush oceanspray, salal, red huckleberry, 

western redcedar, western brackenfern, Oregon oxalis, 

and common beargrass. 

This map unit is in capability subclass VIIe. 

167-Zygore-Rock outcrop complex, 30 to 65 

percent slopes. This map unit is on back slopes of 

mountains The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 2,000 to 3,000 feet. 

The average annual precipitation is about 90 inches, 

the average annual air temperature is about 43 degrees 

F, and the average frost-free period is 90 to 110 days.

This unit is about 60 percent Zygore gravelly loam, 

30 to 65 percent slopes, and 30 percent Rock outcrop. 

The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Aschoff, 

Dougan, and Skoly soils. Also included are small areas 

of shallow soils and Rubble land, mainly adjacent to the 

Rock outcrop. Included areas make up about 10 

percent of the total acreage. 

The Zygore soil is very deep and well drained. It 

formed in colluvium derived dominantly from basalt and 

andesite mixed with volcanic ash. Typically, the surface 

is covered with a mat of decomposed needles, leaves, 

and twigs 2 inches thick. The surface layer is very dark 

brown gravelly loam 14 inches thick. The upper 12 inches 

of the subsoil is dark brown very gravelly loam, and the 

lower 11 inches is dark yellowish brown very gravelly 

silt loam. The substratum to a depth of 60 inches or more 

is dark yellowish brown extremely gravelly silt loam. 

Permeability of the Zygore soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. Runoff is rapid, and the 

hazard of water erosion is severe. 

Rock outcrop consists of exposed areas of 

dominantly basalt, andesite, and some granodiorite. 

Numerous escarpments are in this unit. 

Most areas of this unit are used for woodland, wildlife 

habitat, recreation, and watershed. A few areas are 

used as a source of gravel. 

Douglas fir and western hemlock are the main 

woodland species on the Zygore soil. On the basis of a 

100-year site curve, the mean site index is 120 for 

Douglas fir and is estimated to be 120 for western 

hemlock. On the basis of a 50-year site curve, the mean 

site index is 92 for Douglas fir and is estimated to be 85 

for western hemlock. The culmination of the mean 

annual increment (CMAI) for Douglas fir is 115 cubic feet 

per acre per year at age 60, and the CMAI for western 

hemlock is 180 cubic feet at age 50. The areas of Rock 

outcrop make up about 30 percent of this unit and reduce 

yield accordingly. Among the trees of limited extent are 

red alder and western redcedar. 

The main limitations for harvesting timber are Rock 

outcrop and steepness of slope. When harvesting 

timber, steepness of slope restricts the use of wheeled 

and tracked equipment in skidding. Cable yarding 

systems generally are safer and disturb the soil less. 

Use of wheeled and tracked equipment when the soil is 
moist produces ruts, compacts the soil, and damages the 

roots of trees. Rock outcrop may cause breakage of 

timber and hinder yarding operations. Avoiding areas of 

Rock outcrop forces yarding and skidding paths to 

converge, which increases compaction and erosion of the 

soil. Unsurfaced roads and skid trails are soft and slippery 

and can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Occasional 

snowpack hinders the use of equipment and limits access 

in winter. Establishing plant cover on steeper slopes that 

have been cut or filled reduces erosion. Steep yarding 

paths, skid trails, and firebreaks are subject to rifling and 

gullying unless plant cover is maintained or adequate 

water bars are provided. 

Reforestation can be accomplished on the Zygor soil 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock occurs readily. The areas of Rock 

outcrop limit the even distribution of reforestation. 

Among the common forest understory plants are vine 

maple, crearnbush oceanspray, salal, red huckleberry, 

western redcedar, western brackenfern, Oregon oxalis, 

and common beargrass. 

The Zygore soil is in capability subclass VIIe, and the 

Rock outcrop is in capability subclass Vllls. 

168-Zymer sandy loam, 2 to 30 percent slopes. 

This very deep, well drained soil is on mountain slopes. 

It formed in colluvium derived dominantly from volcanic 

ash and from basic igneous rock with a mantle of 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 800 to 1,600 feet. The 

average annual precipitation is about 115 inches, the 

average annual air temperature is about 49 degrees F, 

and the average frost-free period is 110 to 130 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper 4 inches of the surface layer is dark brown 

sandy loam, and the lower 6 inches is dark brown 

loamy sand. The upper 12 inches of the subsoil is dark 

yellowish brown cindery loamy sand, and the lower 6 

inches is dark yellowish brown very gravelly loam. The 

substratum to a depth of 60 inches or more is yellowish 

brown and dark yellowish brown extremely gravelly 

loam. 

Included in this unit are small areas of Cinnamon and 

Swift soils and Yalelake soils on terraces. Also 

included are small areas of shallow soils and Rock 

outcrop. Included areas make up about 15 percent of the 

total acreage. 

Permeability of this Zymer soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is slow, and the hazard of water 

erosion is slight. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is estimated to be 167 for 

Douglas fir and 154 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is estimated 

to be 125 for Douglas fir and 110 for western hemlock. 

The culmination of the mean annual increment (CMAI) 

for Douglas fir is 178 cubic feet per acre per year at age 

60, and the CMAI for western hemlock is 244 cubic feet 

at age 50. Among the trees of limited extent are western 

redcedar and red alder. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is not readily available in this unit. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Disturbances of the protective 

layer of duff can be reduced with the careful use of 

wheeled and tracked equipment. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock occurs periodically. Droughtiness of the surface 

layer reduces seedling survival, especially on southand southwest-facing slopes. If the canopy is opened, 

brush invades and can prevent the establishment of 

seedlings and can delay natural reforestation by western 

hemlock unless controlled. 

Among the common forest understory plants are vine 

maple, trailing blackberry, thimbleberry, Oregon oxalis, 

western swordfern, and pearly everlasting. 

This map unit is in capability subclass IVe. 

169-Zymer sandy loam, 30 to 65 percent slopes. 

This very deep, well drained soil is on mountain slopes. 

It formed in colluvium derived dominantly from 

volcanic ash and from basic igneous rock with a 

mantle of volcanic ash. The native vegetation is mainly 

mixed conifers and shrubs. Elevation is 800 to 1,600 

feet. The average annual precipitation is about 115 

inches, the average annual air temperature is about 49 

degrees F, and the average frost-free period is 110 to 

130 days. 

Typically, the surface is covered with a mat of 
decomposed needles, leaves, and twigs 2 inches thick. 

The upper 4 inches of the surface layer is dark brown 

sandy loam, and the lower 6 inches is dark brown loamy 

sand. The upper 12 inches of the subsoil is dark 

yellowish brown cindery loamy sand, and the lower 6 

inches is dark yellowish brown very gravelly loam. The 

substratum to a depth of 60 inches or more is yellowish 

brown and dark yellowish brown extremely gravelly loam.

Included in this unit are small areas of Cinnamon and 

Swift soils and Yalelake soils on terrace escarpments. 

Also included are small areas of Rock outcrop. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Zymer soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-year 

site curve, the mean site index is estimated to be 167 for 

Douglas fir and 154 for western hemlock. On the basis of 

a 50-year site curve, the mean site index is estimated to 

be 125 for Douglas fir and 110 for western hemlock. The 

culmination of the mean annual increment (CMAI) for 

Douglas fir is 178 cubic feet per acre per year at age 60. 

and the CMAI for western hemlock is 244 cubic feet at age 

50. Among the trees of limited extent are western redcedar 

and red alder, 

The main limitation for harvesting timber is steepness 

of slope, which restricts the use of wheeled and tracked 

equipment in skidding. Cable yarding systems generally 

are safer and disturb the soil less. Use of wheeled and 

tracked equipment when the soil is moist produces ruts, 

compacts the soil, and damages the roots of trees. 

Logging roads require suitable surfacing for year-round 

use. Rock for road construction is readily available in this 

unit. Occasional snowpack hinders the use of equipment 

and limits access in winter. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rifling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock occurs periodically. If the canopy is 

opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

reforestation by western hemlock unless controlled. 

Among the common forest understory plants are vine 

maple, red huckleberry, trailing blackberry, thimbleberry, 

Oregon oxalis, western swordfern, and pearly 

everlasting. 

This map unit is in capability subclass VIle. 

170-Zymer sandy loam, 65 to 90 percent slopes. 

This very deep, well drained soil is on mountain slopes. 

It formed in colluvium derived dominantly from volcanic 

ash and from basic igneous rock with a mantle of 

volcanic ash. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 800 to 1,600 feet. The 

average annual precipitation is about 115 inches, the 

average annual air temperature is about 49 degrees F, 

and the average frost-free period is 110 to 130 days. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper 4 inches of the surface layer is dark brown 

sandy loam, and the lower 6 inches is dark brown 

loamy sand. The upper 12 inches of the subsoil is dark 

yellowish brown cindery loamy sand, and the lower 6 

inches is dark yellowish brown very gravelly loam. The 

substratum to a depth of 60 inches or more is yellowish 

brown and dark yellowish brown extremely gravelly loam.

Included in this unit are small areas of Cinnamon 

and Swift soils and Yalelake soils on terrace 

escarpments. Also included are small areas of Rock 

outcrop and Zymer soils that are less than 60 inches deep 

to bedrock. Included areas make up about 10 percent of 

the total acreage. 

Permeability of this Zymer soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is rapid, and the hazard of 

water erosion is severe. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is estimated to be 

167 for Douglas fir and 154 for western hemlock. On the 

basis of a 50-year site curve, the mean site index is 

estimated to be 125 for Douglas fir and 110 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 178 cubic feet per acre per 

year at age 60, and the CMAI for western hemlock is 

244 cubic feet at age 50. Among the trees of limited extent 

are western redcedar and red alder. 

The main limitation for harvesting timber is steepness 

of slope. Cable yarding systems generally are used on 

this unit. Logging roads require suitable surfacing for 
year-round use. Rock for road construction is readily 

available in this unit. Logging roads generally need full 

bench construction and require frequent maintenance. 

Following road construction and clearcutting, road failures 

and landslides can occur. Occasional snowpack hinders 

the use of equipment and limits access in winter. 

Establishing plant cover on steeper slopes that have been 

cut or filled reduces erosion. Steep yarding paths, skid 

trails. and firebreaks are subject to rilling and gullying 

unless plant cover is maintained or adequate water bars 

are provided. Harvesting systems that lift logs entirely off 

the ground reduce the disturbance of the protective layer of 

duff. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock occurs periodically. Droughtiness of the surface 

layer reduces seedling survival, especially on south- and 

southwest-facing slopes. If the canopy is opened. brush 

invades and can prevent the establishment of Douglas fir 

seedlings and can delay natural reforestation by western 

hemlock unless controlled. 

Among the common forest understory plants are vine 

maple. red huckleberry, trailing blackberry, thimbleberry, 

Oregon oxalis, western swordfern, and pearly everlasting.

This map unit is in capability subclass VIIe. 

171-Zymer-Rock outcrop complex, 30 to 65 

percent slopes. This map unit is on mountain slopes. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 1,200 to 1,600 feet. The average 

annual precipitation is about 115 inches, the average 

annual air temperature is about 49 degrees F, and the 

average frost-free period is 110 to 130 days. 

This unit is about 65 percent Zymer sandy loam, 30 to 

65 percent slopes, and about 25 percent Rock outcrop. 

The components of this unit are so intricately 

intermingled that it was not practical to map them 

separately at the scale used. 

Included in this unit are small areas of Swift soils and 

Yalelake soils on terraces. Also included are small areas 

of shallow soils. Included areas make up about 10 percent 

of the total acreage. 

The Zymer soil is very deep and well drained. It formed 

in colluvium derived dominantly from volcanic ash and 

from basic igneous rock with a mantle of volcanic ash. 

Typically, the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper 4 inches of the surface layer is dark 

brown sandy loam, and the lower 6 inches is dark 

brown loamy sand. The upper 12 inches of the subsoil is 

dark yellowish brown cindery loamy sand, and the lower 

6 inches is dark yellowish brown very gravelly loam. The 

substratum to a depth of 60 inches or more is yellowish 

brown and dark yellowish brown extremely gravelly loam.

Permeability of this Zymer soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is medium, and the hazard of 

water erosion is moderate. 

Rock outcrop consists of exposed areas of dominantly 

andesite and basalt. Numerous escarpments are in the 

unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on the Zymer soil. On the basis of a 

100-year site curve, the mean site index is estimated to be 

167 for Douglas fir and 154 for western hemlock. On the 

basis of a 50-year site curve, the mean site index is 

estimated to be 125 for Douglas fir and 110 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 178 cubic feet per acre per year at 

age 60, and the CMAI for western hemlock is 244 cubic feet 

at age 50. The areas of Rock outcrop make up about 25 

percent of this unit and reduce yield accordingly. Among 

the trees of limited extent are western redcedar and red 

alder. 

The main limitations for harvesting timber are steepness

of slope and the areas of Rock outcrop. When harvesting 

timber, steepness of slope restricts the use of wheeled 

and tracked equipment in skidding. Cable yarding systems 

generally are safer and disturb the soil less. Rock outcrop 

may cause breakage of timber when felled and can hinder 

yarding operations. Avoiding areas of Rock outcrop forces 

yarding and skidding paths to converge, which increases 

compaction and erosion of the soil. Occasional snowpack 

hinders the use of equipment and limits access in winter. 

Use of wheeled and tracked equipment when the soil Is 

wet produces ruts, compacts the soil, and damages the 

roots of trees. Unsurfaced roads and skid trails are soft 

and can be impassable when wet. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Establishing 

plant cover on steeper slopes that have been cut or filled 

reduces erosion. Steep yarding paths, skid trails, and 

firebreaks are subject to rilling and gullying unless plant 

cover is maintained or adequate water bars are provided.

Seedling establishment is the main concern in the 
production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present. natural reforestation of cutover areas by western 

hemlock occurs periodically. The areas of Rock outcrop 

limit the even distribution of reforestation. Droughtiness 

of the surface layer reduces seedling survival, 

especially on south- and southwest-facing slopes. If the 

canopy is opened, brush invades and can prevent the 

establishment of Douglas fir seedlings and can delay 

natural reforestation by western hemlock unless 

controlled. 

Among the common forest understory plants are vine 

maple, red huckleberry, trailing blackberry, thimbleberry,

Oregon oxalis, western swordfern, and pearly 

everlasting. 

The Zymer soil is in capability subclass Vlle, and the 

Rock outcrop is in capability subclass VIIIs. 

172-Zymer-Rock outcrop complex, 65 to 90 

percent slopes. This map unit is on mountain slopes. 

The native vegetation is mainly mixed conifers and 

shrubs. Elevation is 1,200 to 1,600 feet. The average 

annual precipitation is about 115 inches, the average 

annual air temperature is about 49 degrees F, and the 

average frost-free period is 110 to 130 days. 

This unit is about 60 percent Zymer sandy loam, 65 to 

90 percent slopes, and 30 percent Rock outcrop. The 

components of this unit are so intricately intermingled 

that it was not practical to map them separately at the 

scale used. 

Included in this unit are small areas of Swift soils and 

Yalelake soils on terrace escarpments. Also included 

are small areas of shallow soils. Included areas make up 

about 10 percent of the total acreage. 

The Zymer soil is very deep and well drained. It formed 

in colluvium derived dominantly from volcanic ash and 

from basic igneous rock with a mantle of volcanic ash. 

Typically. the surface is covered with a mat of 

decomposed needles, leaves, and twigs 2 inches thick. 

The upper 4 inches of the surface layer is dark brown 

sandy loam, and the lower 6 inches is dark brown loamy 

sand. The upper 12 inches of the subsoil is dark yellowish 

brown cindery loamy sand, and the lower 6 inches is dark 

yellowish brown very gravelly loam. The substratum to a 

depth of 60 inches or more is yellowish brown and dark 

yellowish brown extremely gravelly loam. 

Permeability of this Zymer soil is moderate. Available 

water capacity is high. Effective rooting depth is 60 

inches or more. Runoff is rapid, and the hazard of water 

erosion is severe. 

Rock outcrop consists mainly of exposed areas of 

andesite and basalt. Numerous escarpments are in the 

unit. 

This unit is used for woodland, recreation, wildlife 

habitat, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on the Zymer soil. On the basis of a 

100-year site curve, the mean site index is estimated to 

be 167 for Douglas fir and 154 for western hemlock. On 

the basis of a 50-year site curve, the mean site index is 

estimated to be 125 for Douglas fir and 110 for western 

hemlock. The culmination of the mean annual increment 

(CMAI) for Douglas fir is 178 cubic feet per acre per year 

at age 60, and the CMAI for western hemlock is 244 cubic 

feet at age 50. The areas of Rock outcrop make up about 

30 percent of this unit and reduce yield accordingly. 

Among the trees of limited extent are western redcedar 

and red alder. 

The main limitations for harvesting timber are 

steepness of slope and the areas of Rock outcrop. Cable 

yarding systems generally are used on this unit. Rock 

outcrop may cause breakage of timber when felled and 

can hinder yarding operations. Logging roads require 

suitable surfacing for year-round use. Rock for road 

construction is readily available in this unit. Logging 

roads generally need full bench construction and require 

frequent maintenance. Following road construction and 

clearcutting, road failures and landslides can occur. 

Occasional snowpack hinders the use of equipment and 

limits access in winter. Establishing plant cover on 

steeper slopes that have been cut or filled reduces 

erosion. Steep yarding paths, skid trails, and firebreaks 

are subject to rilling and gullying unless plant cover is 

maintained or adequate water bars are provided. 

Harvesting systems that lift logs entirely off the ground 

reduce the disturbance of the protective layer of duff. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by 

western hemlock occurs periodically. The areas of 

Rock outcrop limit the even distribution of reforestation. 

Droughtiness of the surface layer reduces seedling 

survival, especially on south- and southwest-facing 

slopes. If the canopy is opened, brush invades and 

can delay the establishment of Douglas fir seedlings and 

can delay natural reforestation by western hemlock 

unless controlled. 

Among the common forest understory plants are vine 

maple, red huckleberry, trailing blackberry, thimbleberry, 

Oregon oxalis, western swordfern, and pearly 

everlasting. 
The Zymer soil is in capability subclass VIIe, and the 

Rock outcrop is in capability subclass VIIIs. 

173-Zynbar gravelly silt loam, till substratum, 8 

to 30 percent slopes. This very deep, well drained soil 

is on foot slopes and terraces. It formed in volcanic ash 

and colluvium derived dominantly from basic igneous rock 

over glacial drift. The native vegetation is mainly mixed 

conifers and shrubs. Elevation is 1,800 to 2,400 feet. The 

average annual precipitation is about 80 inches. the 

average annual air temperature is about 44 degrees F. 

and the average frost-free period is 100 to 160 days. 

Typically, the surface is covered with a mat of 

decomposed needles. leaves, and twigs 2 inches thick. 

The surface layer is very dark grayish brown gravelly 

silt loam 6 inches thick. The upper 11 inches of the subsoil 

is dark brown silt loam, and the lower 30 inches is 

yellowish brown silt loam. The upper 10 inches of the 

substratum is dark yellowish brown extremely stony silt 

loam. and the lower part to a depth of 60 inches or 

more is gray very gravelly loam. 

Included in this unit are small areas of Hoffstadt, 

Tradedollar, and Vanson soils. Also included are small 

areas of Rock outcrop and Zynbar soils that have a till 

substratum at a depth of more than 60 inches. Included 

areas make up about 15 percent of the total acreage. 

Permeability of this Zynbar soil is moderate. Available 

water capacity is high. Effective rooting depth is 40 to 60 

inches. Runoff is slow, and the hazard of water erosion is 

slight. A seasonal high water table is at a depth of 3 to 4 

feet from December to March. 

This unit is used for woodland, wildlife habitat, 

recreation, and watershed. 

Douglas fir and western hemlock are the main 

woodland species on this unit. On the basis of a 100-

year site curve, the mean site index is 161 for Douglas fir 

and 157 for western hemlock. On the basis of a 50-

year site curve, the mean site index is 123 for Douglas fir 

and 110 for western hemlock. The culmination of the 

mean annual increment (CMAI) for Douglas fir is 171 

cubic feet per acre per year at age 65, and the CMAI for 

western hemlock is 249 cubic feet at age 50. Among the 

trees of limited extent are red alder, western redcedar, 

and bigleaf maple. 

The main limitation for harvesting timber is seasonal 

soil wetness. Use of wheeled and tracked equipment 

when the soil is moist produces ruts, compacts the soil, 

and damages the roots of trees. Unsurfaced roads and 

skid trails are soft and slippery and can be impassable 

when wet. Logging roads require suitable surfacing for 

year-round use. Rock for road construction is not 

readily available in this unit. Occasional snowpack 

hinders the use of equipment and limits access in 

winter. 

Seedling establishment is the main concern in the 

production of timber. Reforestation can be accomplished 

by planting Douglas fir seedlings. If seed trees are 

present, natural reforestation of cutover areas by western 

hemlock occurs periodically. If the canopy is opened, 

brush invades and can delay the establishment of 

seedlings and natural reforestation unless controlled. 

Among the common forest understory plants are red 

huckleberry, Oregongrape, western swordfern, trailing 

blackberry, longtube twinflower, and Oregon oxalis. 

This map unit is in capability subclass IVe. 

200-Bandid extremely cindery loamy sand, 

overblown, 5 to 30 percent slopes. This very deep, 

well drained soil is on back slopes and toe slopes of 

mountains. It formed in stratified, aerially deposited 

volcanic ash and pumice. Elevation is 2,000 to 2,800 

feet. Native vegetation before the cinderfall was mainly 

mixed conifers and shrubs. The average annual 

precipitation is about 130 inches, the average air 

temperature is about 44 degrees F, and the average 

frost-free period is 90 to 110 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand and the next 10 inches is dark gray 

very cindery sand and gravelly sand. Below this is a 

buried surface layer that is very dark grayish brown 

cindery sandy loam in the upper 3 inches and brown 

fine sandy loam and black loamy sand in the lower 6 

inches. The upper part of the subsoil is dark gray 

cindery fine sandy loam 10 inches thick, the next 11 

inches is light gray extremely cindery sand, and the lower 

part to a depth of 60 inches or more is stratified, dark 

gray cindery sandy loam to black loamy sand. 

Included in this unit are areas in which the cinderfall is 

more than 20 inches deep. Also included are small 

areas of Rock outcrop. Included areas make up about 

10 percent of the total acreage. 

Permeability of this Bandid soil is moderately rapid in 

the upper part of the subsoil, very rapid in the next 11 

inches, and moderately rapid in the lower part. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where vegetation 

was removed by the initial blast or buried by cinderfall 

and waterflow became concentrated, gullies formed 

readily. Raveling of the cinders downslope and sediment 

production will be high until the cinders become 

stabilized by vegetation.
This unit is in areas used for woodland, recreation, 

wildlife habitat, and watershed. This map unit is in 

capability subclass IVe. 

201-Bandid extremely cindery loamy sand, 

overblown, 30 to 65 percent slopes. This very deep, 

well drained soil is on back slopes and toe slopes of 

mountains. These soils formed in stratified, aerially 

deposited volcanic ash and pumice. Elevation is 

1,800 to 2,800 feet. Native vegetation before the 

cinderfall was mainly mixed conifers and shrubs. The 

average annual precipitation is about 130 inches, the 

average annual air temperature is about 44 degrees F, 

and the average frost-free period is 90 to 110 days. 

This soil is overblown by cinderfall 4 to 20 inches thick. 

Typically, the upper 4 inches is light gray extremely 

cindery loamy sand and the next 10 inches is dark gray 

very cindery sand and gravelly sand. Below this is a 

buried surface layer that is very dark grayish brown 

cindery sandy loam in the upper 3 inches and is brown 

fine sandy loam and black loamy sand in the lower 6 

inches. The upper part of the subsoil is dark gray cindery 

fine sandy loam 10 inches thick, the next 11 inches is light 

gray extremely cindery sand, and the lower part to a 

depth of 60 inches or more is stratified, dark gray cindery 

sandy loam to black loamy sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep. Also included are small 

areas of Rock outcrop. Included areas make up about 

10 percent of the total acreage. 

Permeability of this Bandid soil is moderately rapid in 

the upper part of the subsoil, very rapid in the next 11 

inches. and moderately rapid in the lower part. Available 

water capacity is moderate. Effective rooting depth is 60 

inches or more. In areas where vegetation was removed 

by the initial blast or buried by cinderfall and waterflow 

became concentrated, gullies formed readily. Raveling of 

the cinders downslope and sediment production will be 

high until the cinders become stabilized by vegetation. 

This unit is in areas used for woodland, recreation, 

wildlife habitat, and watershed. 

This map unit is in capability subclass VIIe. 

202-Bandid extremely cindery loamy sand, 

overblown, 65 to 90 percent slopes. This very deep, 

well drained soil is on back slopes of mountains. These 

soils formed in stratified, aerially deposited volcanic ash 

and pumice. Elevation is 1,800 to 2,800 feet. Native 

vegetation before the cinderfall was mainly mixed 

conifers and shrubs. The average annual precipitation is 

about 130 inches, the average annual air temperature is 

about 44 degrees F, and the average frost-free period is 

90 to 110 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray cindery 

loamy sand and the next 10 inches is dark gray very 

cindery sand and gravelly sand. Below this is a buried 

surface layer that is very dark grayish brown cindery 

sandy loam in the upper 3 inches and brown fine sandy 

loam and black loamy sand in the lower 6 inches, The 

upper part of the subsoil is dark gray gravelly fine sandy 

loam 10 inches thick, the next 11 inches is light gray 

extremely cindery sand, and the lower part to a depth of 

60 inches or more is stratified, dark gray cindery sandy 

loam to black loamy sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas where the original 

surface layer is exposed as a result of erosion. Also 

included are small areas of Rock outcrop. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Bandid soil is moderately rapid in 

the upper part of the subsoil, very rapid in the next 11 

inches, and moderately rapid in the lower part. Available 

water capacity is moderate. Effective rooting depth is 60 

inches or more. In areas where vegetation was removed 

by the initial blast or buried by cinderfall and waterflow 

became concentrated, gullies formed readily. Raveling of 

the cinders downslope and sediment production will be 

high until the cinders become stabilized by vegetation. 

This unit is in areas used for woodland, recreation, 

wildlife habitat, and watershed. 

This map unit is in capability subclass VIIe. 

203-Cattcreek loamy sand, overblown, cold, 30 to 65 

percent slopes. This very deep, well drained soil is on 

back slopes and in cirque basins on mountains. These 

soils formed in pumice and volcanic ash over colluvium 

derived from andesite. Elevation is 4,000 to 5,300 feet. 

Native vegetation before the ashfall was mainly true firs 

and shrubs. The average annual precipitation is about 

110 inches, the average annual air temperature is about 

39 degrees F, and the average frost-free period is 70 

to 90 days. 

This soil is overblown by ashfall 4 to 20 inches thick. 

Typically, the upper 15 inches is dark gray loamy sand 

over a buried surface layer that is dark grayish brown 

and dark yellowish brown very cindery loamy sand 6 

inches thick. The upper 9 inches of the subsoil is dark 

brown very cindery sand, and the lower 15 inches is 

strong brown extremely cindery sand, Below this to a 

depth of 60 inches or more is a buried subsoil of dark 

yellowish brown extremely gravelly loam. 
Included in this unit are areas in which the ashfall is 

more than 20 inches deep and areas in which bedrock is 

at a depth of 40 to 60 inches. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Cattcreek soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. The hazard of soil blowing in 

the areas of ashfall is high. In areas where vegetation 

was removed by the initial blast or buried by ash and 

waterflow became concentrated, gullies formed readily. 

Sediment production will be high until the ash becomes 

stabilized by vegetation. 

This unit is in areas used for woodland, recreation, 

wildlife habitat, and watershed. 

This map unit is in capability subclass VIle. 

204-Cattcreek loamy sand, overblown, cold, 65 to 

90 percent slopes. This very deep, well drained soil is on 

back slopes and in cirque basins on mountains. It formed 

in pumice and volcanic ash over colluvium derived from 

andesite. Elevation is 4,000 to 5,300 feet. Native 

vegetation before the ashfall was mainly true firs and 

shrubs. The average annual precipitation is about 

110 inches, the average annual air temperature is about 

39 degrees F, and the average frost-free period is 70 to 

90 days. 

This soil is overblown by ashfall 4 to 20 inches thick. 

Typically, the upper 15 inches is dark gray loamy sand 

over a buried surface layer that is dark grayish brown 

and dark yellowish brown very cindery loamy sand 6 

inches thick. The upper 9 inches of the subsoil is dark 

brown very cindery sand, and the lower 15 inches is 

strong brown extremely cindery sand. Below this to a 

depth of 60 inches or more is a buried subsoil of dark 

yellowish brown extremely gravelly loam. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep and areas where the original 

surface layer is exposed as a result of erosion. Also 

included are areas in which bedrock is at a depth of 40 to 

60 inches and small areas of Rock outcrop. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Cattcreek soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. The hazard of soil blowing in 

the areas of ashfall is high. In areas where vegetation was 

removed by the initial blast or buried by ash and 

waterflow became concentrated, gullies formed readily. 

Sediment production will be high until the ash has been 

stabilized by vegetation. 

This unit is in areas used for woodland, recreation, 

wildlife habitat, and watershed. 

This map unit is in capability subclass VIle. 

205-Cinnamon loamy sand, overblown, 2 to 30 

percent slopes. This very deep, well drained soil is on 

terraces and back slopes of mountains. It formed in 

pyroclastic flows of volcanic ash and pumice. The 

native vegetation before the ashfall was mainly mixed 

conifers and shrubs. Elevation is 2,400 to 2,500 feet. 

The average annual precipitation is about 125 inches, 

the average annual air temperature is about 44 degrees 

F, and the average frost-free period is 90 to 110 days.

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown sandy loam 3 inches thick. The subsoil is dark 

yellowish brown and dark brown loamy sand 19 inches 

thick. Below this to a depth of 60 inches or more is a 

buried subsoil of dark yellowish brown sandy loam. 

Included in this unit are areas in which the ashfall 

is more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Cinnamon soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used as wildlife habitat and 

recreation. 

This map unit is in capability subclass IVs. 

206-Colter loamy sand, overblown, 0 to 30 percent 

slopes. This very deep, well drained soil is on foot slopes 

of mountains. It formed in aerially deposited volcanic ash 

and pumice. The native vegetation before the ashfall 

was mainly mixed conifers and shrubs. Elevation is 

2,800 to 5,400 feet. The average annual precipitation is 

about 90 inches, the average annual air temperature is 

about 39 degrees F, and the average frost-free period is 

75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown cindery sandy loam 6 inches thick. The 

substratum is white extremely cindery sand 27 inches 

thick. Below this to a depth of 60 inches or more is a 

buried subsoil of very dark grayish brown and yellowish 

brown sandy loam. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Colter soil is moderately rapid. 
Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass Vle. 

207-Colter loamy sand. overblown, 30 to 65 

percent slopes. This very deep, well drained soil is on 

foot slopes and back slopes of mountains. It formed in 

aerially deposited volcanic ash and pumice. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 2,800 to 4,000 feet. The average 

annual precipitation is about 90 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray sandy 

loam over a buried surface layer that is very dark grayish 

brown cindery sandy loam 6 inches thick. The substratum 

is white extremely cindery sand 27 inches thick. Below 

this to a depth of 60 inches or more is a buried subsoil 

of very dark grayish brown and yellowish brown sandy 

loam. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Colter soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

208-Colter loamy sand, overblown, 65 to 90 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation before 

the ashfall was mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,000 feet. The average annual 

precipitation is about 90 inches, the average annual air 

temperature is about 39 degrees F, and the average 

frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown cindery sandy loam 6 inches thick. The substratum 

is white extremely cindery sand 27 inches thick. Below 

this to a depth of 60 inches or more is a buried subsoil 

of very dark grayish brown and yellowish brown sandy 

loam. 

Included in this unit are areas in which ashfall is more 

than 20 inches deep and areas where the original surface 

layer is exposed as a result of erosion. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Colter soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass Vlle. 

209-Colter loamy sand, overblown, cold, 0 to 30 

percent slopes. This very deep, well drained soil is on 

foot slopes of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation before 

the ashfall was mainly mixed conifers and shrubs. 

Elevation is 2,800 to 5,400 feet. The average annual 

precipitation is about 90 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown cindery sandy loam 6 inches thick. The 

substratum is white extremely cindery sand 27 inches 

thick. Below this to a depth of 60 inches or more is a 

buried subsoil of very dark grayish brown and yellowish 

brown sandy loam. 

Included in this unit are areas in which the ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Colter soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 
This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass Vle. 

210-Colter loamy sand, overblown, cold, 30 to 65 

percent slopes. This very deep, well drained soil is on 

foot slopes and back slopes of mountains. It formed in 

aerially deposited volcanic ash and pumice. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 4,000 to 5,400 feet. The 

average annual precipitation is about 90 inches, the 

average annual air temperature is about 38 degrees F, 

and the average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 7 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown cindery sandy loam 6 inches thick. The 

substratum is white extremely cindery sand 27 inches 

thick. The next layer to a depth of 60 inches or more is a 

buried subsoil of very dark grayish brown and yellowish 

brown sandy loam. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Colter soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

211-Colter loamy sand, overblown, cold, 65 to 90 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation before 

the ashfall was mainly mixed conifers and shrubs. 

Elevation is 4,000 to 5,400 feet. The average annual 

precipitation is about 90 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free season is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown cindery sandy loam 6 inches thick. The 

substratum is white extremely cindery sand 27 inches 

thick. Below this to a depth of 60 inches or more 

is a buried subsoil of very dark grayish brown and 

yellowish brown sandy loam. 

Included in this unit are areas where the original 

surface is exposed as a result of erosion. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Colter soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

212-Colter extremely cindery loamy sand, 

overblown, 30 to 65 percent slopes. This very deep, 

well drained soil is on foot slopes and back slopes of 

mountains. It formed in aerially deposited volcanic ash 

and pumice. The native vegetation before the cinderfall 

was mainly mixed conifers and shrubs. Elevation is 

2,800 to 4,000 feet. The average annual precipitation is

about 90 inches, the average annual air temperature is 

about 39 degrees F, and the average frost-free period is 

75 to 95 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand and the next 10 inches is dark gray 

very cindery sand and gravelly sand. Below this is a 

buried surface layer of very dark grayish brown cindery 

sandy loam 6 inches thick. The substratum is white 

extremely cindery sand 27 inches thick. Below this to a 

depth of 60 inches or more is a buried subsoil of very dark 

grayish brown and yellowish brown sandy loam. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Colter soil is moderately rapid. 

Available water capacity is moderately high Effective 

rooting depth is 60 inches or more. In areas where 

vegetation was removed by the initial blast or buried by 

cinderfall and waterflow became concentrated, gullies 

formed readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders 

become stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 
213-Colter, overblown, cold-Rock outcrop 

complex, 30 to 65 percent slopes. This map unit is 

on foot slopes and back slopes of mountains. The 

native vegetation before the ashfall was mainly mixed 

conifers and shrubs. Elevation is 4,000 to 5,400 feet. The 

average annual precipitation is about 90 inches, the 

average annual air temperature is about 38 degrees F, 

and the average frost-free period is 75 to 95 days. 

This unit is about 60 percent Colter loamy sand. 

overblown, cold, 30 to 65 percent slopes, and about 30 

percent Rock outcrop. The components of this unit are 

so intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are areas in which the ashfall is 

more than 20 inches deep and areas where the original 

surface layer is exposed as a result of erosion. Included 

areas make up about 10 percent of the total acreage. 

The Colter soil is very deep and well drained. It formed 

in aerially deposited volcanic ash and pumice. It is 

overblown by new ashfall 4 to 20 inches thick. Typically. 

the upper 15 inches is dark gray loamy sand over a buried 

surface layer that is very dark grayish brown cindery sandy 

loam 6 inches thick. The substratum is white extremely 

cindery sand 27 inches thick. Below this to a depth of 60 

inches or more is a buried subsoil of very dark grayish 

brown and yellowish brown sandy loam. 

Permeability of this Colter soil is moderately rapid. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

Rock outcrop consists of exposed areas of andesite 

and basalt. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Colter soil is in capability subclass VIle, and the 

Rock outcrop is in capability subclass Vllls. 

214-Cryandepts extremely cindery loamy sand, 

overblown, 45 to 120 percent slopes. These very deep, 

moderately well drained and well drained soils are on 

north-facing mountain slopes. They formed in aerially 

deposited volcanic ash and pumice. The native 

vegetation before the cinderfall was mainly mixed 

deciduous trees and shrubs. Elevation is 3,000 to 4,500 

feet. The average annual precipitation is about 130 

inches, the average annual air temperature is about 38 

degrees F, and the average frost-free period is 60 to 80 

days. 

No single profile is typical of these Cryandepts, but 

one commonly observed in the survey area is overblown 

by new cinderfall 4 to 20 inches thick. The upper 4 inches 

is light gray extremely cindery loamy sand, and the next 

10 inches is dark gray very cindery sand and gravelly 

sand. The next layer is a buried surface layer that is very 

dark brown in the upper 13 inches and dark brown sandy 

loam in the lower 3 inches. Below this to a depth of 60 

inches or more is a buried subsoil that is light gray 

extremely cindery sand stratified with sand and sandy 

loam. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas where the original 

surface layer is exposed as a result of erosion. Included 

areas make up about 10 percent of the total acreage. 

Permeability of these Cryandepts is moderate. 

Available water capacity is low. Effective rooting depth 

is 40 to 60 inches or more. In areas where vegetation 

was removed by the initial blast or buried by cinderfall, 

and waterflow became concentrated, gullies formed 

readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders 

become stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIlle. 

215-Elkprairie loamy sand, 5 to 30 percent 

slopes. This very deep, well drained soil is on broad 

mountaintops. It formed in volcanic ash and pumice 

over weathered volcanic ash and pumice. The native 

vegetation before the ashfall was mixed conifers and 

shrubs. Elevation is 2,600 to 4,700 feet. The average 

annual precipitation is about 130 inches, the average 

annual air temperature is about 40 degrees F, and 

the average frost-free period is 75 to 90 days. 

This soil is overblown by new ashfall 20 to 35 inches 

thick. Typically, the upper part of the surface layer is dark 

gray loamy sand 6 inches thick. The next part is dark gray 

cindery sand and cindery coarse sand 11 inches thick 

over very dark gray very cindery loamy sand 6 inches 

thick. Below this is a buried surface layer and subsoil. 

The buried surface layer and the upper part of the 

buried subsoil are very dark brown and brown fine sandy 

loam and cindery loam 13 inches thick. The lower part of 

the buried subsoil to a depth of 60 inches or more is 

yellowish brown loam. 

Included in this unit are areas where the ashfall is 

more than 35 inches thick and areas of Tradedollar and 
Vanson loamy sands, overblown, where the ashfall is 

less than 20 inches thick. Included areas make up 

about 20 percent of the total average. 

Permeability of this Elkprairie soil is moderate. 

Available water capacity is high. Effective rooting depth 

is 60 inches or more. The hazard of soil blowing in the 

areas of ashfall is high. In areas where vegetation was 

removed by the initial eruption or buried by ash and 

waterflow became concentrated, gullies formed readily. 

Sediment production will be high until the ash has been 

stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIs. 

216-Hatchet loamy sand, overblown, 65 to 90 

percent slopes. This deep, well drained soil is on 

shoulder slopes and back slopes of mountains. It formed 

in residuum and colluvium derived dominantly from 

basalt and andesite mixed with volcanic ash. The native 

vegetation before the ashfall was mixed conifers and 

shrubs. Elevation is 2,800 to 4,000 feet. The average 

annual precipitation is about 105 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer of very dark grayish 

brown gravelly sandy loam 3 inches thick. The upper 7 

inches of the subsoil is dark brown gravelly sandy loam 

and gravelly fine sandy loam, and the lower 10 inches 

is dark yellowish brown extremely cobbly loam. The 

substratum is yellowish brown extremely cobbly clay 

loam 8 inches thick. Fractured andesite is at a depth of 

43 inches. Depth to andesite or basalt ranges from 40 

to 60 inches. 

Included in this unit are areas in which bedrock is at a 

depth of less than 40 inches. Also included are areas 

where the original surface layer is exposed as a result 

of erosion. Included areas make up about 10 percent of

the total acreage. 

Permeability of this Hatchet soil is moderate. Available 

water capacity is low. Effective rooting depth is 40 to 60 

inches. The hazard of soil blowing in the areas of ashfall 

is high. In areas where vegetation was removed by the 

initial eruption or buried by ash and waterflow became 

concentrated, gullies formed readily. Sediment 

production will be high until the ash has been stabilized 

by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

217-Hatchet loamy sand, overblown, cold, 30 to 

65 percent slopes. This deep, well drained soil is on 

shoulder slopes and back slopes of mountains. It formed 

in residuum and colluvium derived dominantly from 

basalt and andesite mixed with volcanic ash. The native 

vegetation before the ashfall was mixed conifers and 

shrubs. Elevation is 4,000 to 4,500 feet. The average 

annual precipitation is about 105 inches, the average 

annual air temperature is about 38 degrees F, and the 

average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer of very dark grayish 

brown gravelly sandy loam 3 inches thick. The upper 7 

inches of the subsoil is dark brown gravelly sandy loam 

and gravelly fine sandy loam, and the lower 10 inches 

is dark yellowish brown extremely cobbly loam. The 

substratum is yellowish brown extremely cobbly clay 

loam 8 inches thick. Fractured andesite is at a depth of 43 

inches. Depth to andesite or basalt ranges from 40 to 

60 inches. 

Included in this unit are areas in which the ashfall is 

more than 20 inches deep. Also included are outcrops 

of basalt or andesite, areas in which bedrock is at a depth 

of less than 40 inches, and soils that have slopes of more 

than 65 percent. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Hatchet soil is moderate. Available 

water capacity is low. Effective rooting depth is 40 to 60 

inches. The hazard of soil blowing in the areas of ashfall 

is high. In areas where vegetation was removed by the 

initial eruption or buried by ash, and waterflow became 

concentrated, gullies formed readily. Sediment 

production will be high until the ash has been stabilized 

by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

218-Hatchet loamy sand, overblown, cold, 65 to 90 

percent slopes. This deep, well drained soil is on back 

slopes of mountains. It formed in residuum and 

colluvium derived dominantly from basalt and andesite 

mixed with volcanic ash. The native vegetation before 

the ashfall was mixed conifers and shrubs. Elevation is 

4,000 to 4,500 feet. The average annual precipitation is 

about 105 inches, the average annual air temperature 

is about 38 degrees F, and the average frost-free period 

is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer of very dark grayish 
brown gravelly sandy loam 3 inches thick. The upper 7 

inches of the subsoil is dark brown gravelly sandy loam 

and gravelly fine sandy loam, and the lower 10 inches 

is dark yellowish brown extremely cobbly loam. The 

substratum is yellowish brown extremely cobbly clay 

loam 8 inches thick. Fractured andesite is at a depth of 43 

inches. Depth to andesite or basalt ranges from 40 to 

60 inches. 

Included in this unit are areas in which the ashfall is 

more than 20 inches deep and areas where the original 

surface layer is exposed as a result of erosion. Also 

included are outcrops of basalt or andesite, areas in 

which bedrock is at a depth of less than 40 inches, and 

soils that have slopes of less than 65 percent. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Hatchet soil is moderate. Available 

water capacity is low. Effective rooting depth is 40 to 60 

inches. The hazard of soil blowing in the areas of ashfall 

is high. In areas where vegetation was removed by the 

initial eruption or buried by ash and waterflow became 

concentrated, gullies formed readily. Sediment production 

will be high until the ash has been stabilized by 

vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIle. 

219-Hatchet, overblown-Rock outcrop complex, 

65 to 90 percent slopes. This map unit is on back 

slopes of mountains. The native vegetation before the 

cinderfall was mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,000 feet. The average annual 

precipitation is about 105 inches, the average annual air 

temperature is about 39 degrees F, and the average 

frost-free period is 75 to 95 days. 

This unit is about 60 percent Hatchet extremely cindery 

loamy sand, overblown, 65 to 90 percent slopes, and 30 

percent Rock outcrop. The components of this unit are so 

intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are areas in which bedrock is at a 

depth of more than 40 inches and areas in which 

cinderfall is more than 20 inches deep. Also included are 

areas where the original surface layer is exposed as a 

result of erosion. Included areas make up about 10 

percent of the total acreage. 

The Hatchet soil is moderately deep and well 

drained. It formed in residuum and colluvium derived 

dominantly from basalt and andesite mixed with 

volcanic ash. It is overblown by new cinderfall 4 to 20 

inches thick. Typically, the upper 4 inches is light gray 

extremely cindery loamy sand. The next 10 inches is dark 

gray very cindery sandy loam and gravelly sand. Below 

this is a buried surface layer of very dark grayish brown 

gravelly sandy loam 3 inches thick. The upper 7 inches 

of the subsoil is dark brown gravelly sandy loam and 

gravelly fine sandy loam, and the lower 10 inches is 

dark yellowish brown extremely cobbly clay loam. 

Fractured andesite is at a depth of 37 inches. Depth to 

andesite or basalt ranges from 20 to 40 inches. 

Permeability of this Hatchet soil is moderate. 

Available water capacity is low. Effective rooting depth 

is 20 to 40 inches. In areas where vegetation was 

removed by the initial eruption or buried by cinderfall 

and waterflow became concentrated, gullies formed 

readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders 

become stabilized by vegetation. 

Rock outcrop consists of exposed areas of andesite 

and basalt. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Hatchet soil is in capability subclass VIIe, and 

the Rock outcrop is in capability subclass VIIs. 

220-Hatchet, overblown, cold-Rock outcrop 

complex, 30 to 65 percent slopes. This map unit is on 

shoulder slopes and back slopes of mountains. The 

native vegetation before the ashfall was mainly mixed 

conifers and shrubs. Elevation is 4,000 to 4,500 feet. 

The average annual precipitation is about 105 inches, 

the average annual air temperature is about 38 degrees 

F, and the average frost-free period is 75 to 95 days. 

This unit is about 60 percent Hatchet loamy sand, 

overblown, cold, 30 to 65 percent slopes, and 30 

percent Rock outcrop. The components of this unit are 

so intricately intermingled that it was not practical to 

map them separately at the scale used. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

The Hatchet soil is deep and well drained. It formed in 

residuum and colluvium derived dominantly from basalt 

and andesite mixed with volcanic ash. This soil is 

overblown by new ashfall 4 to 20 inches thick. Typically, 

the upper 15 inches is dark gray loamy sand over a 

buried surface layer that is very dark grayish brown 

gravelly sandy loam 3 inches thick. The upper 7 

inches of the subsoil is dark brown gravelly sandy loam 

and gravelly fine sandy loam, and the lower 10 inches 

is dark yellowish brown extremely cobbly loam. The 

substratum is yellowish brown extremely cobbly clay 
loam about 8 inches thick. Fractured andesite is at a 

depth of 43 inches. Depth to andesite or basalt ranges 

from 40 to 60 inches. 

Permeability of this Hatchet soil is moderate. Available 

water capacity is low. Effective rooting depth is 40 to 60 

inches. The hazard of soil blowing in the ashfall is high. In 

areas where vegetation was removed by the initial blast 

or buried by ash and waterflow became concentrated. 

gullies formed readily. Sediment production will be high 

until the ash has been stabilized by vegetation. 

Rock outcrop consists of exposed areas of basalt 

and andesite. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Hatchet soil is in capability subclass VIle, and 

the Rock outcrop is in capability subclass VIIIs. 

221-Hatchet, overblown cold-Rock outcrop 

complex, 65 to 90 percent slopes. This map unit is on 

back slopes of mountains. The native vegetation before 

the cinderfall was mainly mixed conifers and shrubs. 

Elevation is 4,000 to 4,500 feet. The average annual 

precipitation is about 105 inches, the average annual air 

temperature is about 38 degrees F, and the average frostfree period is 75 to 90 days. 

This unit is about 60 percent Hatchet extremely 

cindery loamy sand, overblown, cold, 65 to 90 percent 

slopes. and about 30 percent Rock outcrop. The 

components of this unit are so intricately intermingled 

that it was not practical to map them separately at the 

scale used. 

Included in this unit are areas in which bedrock is at a 

depth of more than 40 inches and areas in which cinderfall 

is more than 20 inches deep. Also included are areas in 

which the original surface layer is exposed as a result of 

erosion. Included areas make up about 10 percent of the 

total acreage. 

The Hatchet soil is moderately deep and well 

drained. It formed in residuum and colluvium derived 

dominantly from basalt and andesite mixed with volcanic 

ash. This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand and the next 10 inches is dark gray 

very cindery sandy loam and gravelly sand. Below this is a 

buried surface layer that is very dark grayish brown 

gravelly sandy loam 3 inches thick. The upper 7 inches 

of the subsoil is dark brown gravelly sandy loam and 

gravelly fine sandy loam, and the lower 10 inches is dark 

yellowish brown extremely cobbly loam. The substratum 

is yellowish brown extremely cobbly clay loam 3 inches 

thick. Fractured 

andesite is at a depth of 37 inches. Depth to andesite 

or basalt ranges from 20 to 40 inches. 

Permeability of this Hatchet soil is moderate. 

Available water capacity is low. Effective rooting depth is 

20 to 40 inches. In areas where vegetation was removed 

by the initial blast or buried by cinderfall and waterflow 

became concentrated, gullies formed readily. Raveling of 

the cinders downslope and sediment production will be 

high until the cinders become stabilized by vegetation. 

Rock outcrop consists of exposed areas of basalt 

and andesite. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Hatchet soil is in the capability subclass VIIe, 

and the Rock outcrop is in capability subclass VIlls. 

222-Histic Cryaquepts loamy sand, overblown, 0 

to 5 percent slopes. These very deep, very poorly 

drained and poorly drained soils are in depressional 

areas on mountains and terraces. They formed in 

aerially deposited volcanic ash and pumice. The native 

vegetation before the ashfall was mainly grasses, shrubs, 

and scattered conifers. Elevation is 2,500 to 4,000 feet. 

The average annual precipitation is about 125 inches, 

the average annual air temperature is about 38 degrees 

F, and the average frost-free period is 60 to 80 days. 

No single profile is typical of these Histic Cryaquepts, 

but one commonly observed in the survey area has a mat 

of decomposing needles, leaves, and twigs 1 inch thick. 

The surface layer is overblown by new ashfall 4 to 20 

inches thick. Typically, the upper 15 inches is dark gray 

loamy sand over a mat of brown muck 13 inches thick. 

Below this is a buried surface layer of very dark loamy 

sand 8 inches thick. The subsoil is gray gravelly sandy 

loam 10 inches thick. The next 4 inches is a buried 

layer of very dark brown muck. The substratum to a 

depth of 60 inches or more is very dark brown gravelly 

coarse sand. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of these Histic Cryaquepts is moderate. 

Available water capacity is high. Effective rooting depth is 

limited by a seasonal high water table that extends from 

near the surface to a depth of 2.5 feet. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash has 

been stabilized by vegetation. 
This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass Vlw. 

223-Lonestar loamy sand, overblown, 5 to 30 

percent slopes. This very deep, well drained soil is on 

back slopes and ridgetops of mountains. It formed in 

volcanic ash and pumice over colluvium derived from 

basic igneous rock. The native vegetation before the 

ashfall was mainly mixed conifers and shrubs. Elevation 

is 2,800 to 4,500 feet. The average annual precipitation 

is about 125 inches. the average annual air temperature 

is about 40 degrees F, and the average frost-free season 

is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown cindery sandy loam 2 inches thick. The upper 12 

inches of the subsoil is dark brown cindery sandy loam. 

and the lower 4 inches is grayish brown loamy sand. The 

substratum is yellowish brown cindery loamy sand 10 

inches thick. Below this to a depth of 60 inches or more is 

a buried subsoil of dark yellowish brown gravelly loam. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Lonestar soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIs. 

224-Lonestar loamy sand, overblown, 30 to 65 

percent slopes. This very deep. well drained soil is on 

foot slopes and back slopes of mountains. It formed in 

volcanic ash and pumice over colluvium derived from 

basic igneous rock. The native vegetation before the 

ashfall was mainly mixed conifers and shrubs. Elevation 

is 2,800 to 4,500 feet. The average annual precipitation 

is about 125 inches. the average annual air temperature 

is about 40 degrees F. and the average frost-free period is 

75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark 

grayish brown cindery sandy loam about 2 inches thick. 

The upper 12 inches of the subsoil is dark brown cindery 

sandy loam, and the lower 4 inches is grayish brown 

loamy sand. The substratum is yellowish brown cindery 

loamy sand 10 inches thick. Below this to a depth of 60 

inches or more is a buried subsoil of dark yellowish 

brown gravelly loam. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Lonestar soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIle. 

225-Lonestar loamy sand, overblown, 65 to 90 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in volcanic ash and 

pumice over colluvium derived from basic igneous rock. 

The native vegetation before the ashfall was mainly 

mixed conifers and shrubs. Elevation is 2,800 to 4,500 

feet. The average annual precipitation is about 125 

inches, the average annual air temperature is about 40 

degrees F, and the average frost-free period is 75 to 95 

days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown cindery sandy loam 7 inches thick. The upper 7 

inches of the subsoil is dark brown cindery sandy loam, 

and the lower 4 inches is grayish brown loamy sand. The 

substratum is yellowish brown cindery loamy sand 10 

inches thick. Below this to a depth of 60 inches or more is 

a buried subsoil of dark yellowish brown gravelly loam. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep and small areas of Rock 

outcrop. Also included are areas in which the original 

surface is exposed as a result of erosion. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Lonestar soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 
ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

226-Minnieoeak loamy sand, overblown, 5 to 30 

percent slopes. This very deep, well drained soil is on 

back slopes and ridgetops of mountains. It formed in 

aerially deposited volcanic ash and pumice. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs, Elevation is 2,800 to 4,500 feet. The 

average annual precipitation is about 130 inches, the 

average annual air temperature is about 41 degrees F, 

and the average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand. Below this is a buried surface layer. The upper 3 

inches is dark brown cindery sandy loam, the next 5 

inches is black loamy sand, and the lower 4 inches is 

very dark gray very cindery sandy loam. The subsoil to a 

depth of 60 inches or more is light gray and dark brown 

extremely cindery sand and extremely cindery coarse 

sand. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Minniepeak soil is rapid. Available 

water capacity is low. Effective rooting depth is 60 inches 

or more. The hazard of soil blowing in the areas of ashfall 

is high. In areas where vegetation was removed by the 

initial blast or buried by ash and waterflow became 

concentrated, gullies formed readily. Sediment 

production will be high until the ash has been stabilized 

by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIs. 

227-Minniepeak loamy sand, overblown, 30 to 65 

percent slopes. This very deep. well drained soil is on 

back slopes and ridgetops of mountains. It formed in 

aerially deposited volcanic ash and pumice. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 2,800 to 4,500 feet. The 

average annual precipitation is about 130 inches, the 

average annual air temperature is about 41 degrees F, 

and the average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand. Below this is a buried surface layer. The upper 3 

inches is dark brown cindery sandy loam, the next 5 

inches is black loamy sand, and the lower 4 inches is 

very dark gray very cindery sandy loam. The subsoil to a 

depth of 60 inches or more is light gray and dark brown 

extremely cindery sand and extremely cindery coarse 

sand. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Minniepeak soil is rapid. Available 

water capacity is low. Effective rooting depth is 60 inches 

or more. The hazard of soil blowing in the areas of 

ashfall is high. In areas where vegetation was removed 

by the initial blast or buried by ash and waterflow 

became concentrated, gullies formed readily. Sediment 

production will be high until the ash has been stabilized 

by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

228-Minniepeak extremely cindery loamy sand, 

overblown, 30 to 65 percent slopes. This very deep, well 

drained soil is on back slopes and ridgetops of 

mountains. It formed in aerially deposited volcanic ash 

and pumice. The native vegetation before the cinderfall 

was mainly mixed conifers and shrubs. Elevation is 2,800 

to 4,500 feet. The average annual precipitation is about 

130 inches, the average annual air temperature is about 

41 degrees F, and the average frost-free period is 75 to 

95 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand and the next 10 inches is dark gray 

very cindery sand. Below this is a buried surface layer. 

The upper 3 inches is dark brown cindery sandy loam, the 

next 5 inches is black loamy sand, and the lower 4 inches 

is very dark gray very cindery sandy loam. The subsoil to 

a depth of 60 inches or more is light gray and dark 

brown extremely cindery sand and extremely cindery 

coarse sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas in which slopes are 

less than 30 percent. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Minniepeak soil is rapid. Available 

water capacity is low. Effective rooting depth is 60 

inches or more. In areas where vegetation was removed 

by the initial blast or buried by cinderfall and waterflow 

became concentrated, gullies formed readily. 
Raveling of cinders downslope and sediment production 

will be high until the cinders become stabilized by 

vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

229-Minniepeak extremely cindery loamy sand, 

overblown, 65 to 90 percent slopes. This very deep, 

well drained soil is on back slopes and ridgetops of 

mountains. It formed in aerially deposited volcanic ash 

and pumice. The native vegetation before the cinderfall 

was mainly mixed conifers and shrubs. Elevation is 

2,800 to 4,500 feet. The average annual precipitation is 

about 130 inches, the average annual air temperature is 

about 41 degrees F. and the average frost-free period is 

75 to 95 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically. the upper 4 inches is light gray extremely 

cindery loamy sand and the next 10 inches is dark gray 

very cindery sand. Below this is a buried surface layer. The 

upper 3 inches is dark brown cindery sandy loam. the next 

5 inches is black loamy sand, and the lower 4 inches is 

very dark gray very cindery sandy loam. The subsoil to a 

depth of 60 inches or more is light gray and dark brown 

extremely cindery sand and extremely cindery coarse 

sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas in which slopes are 

less than 65 percent. Also included are areas where the 

surface layer is exposed as a result of erosion. Included 

areas make up about 10 percent of the total acreage. 

Permeability of this Minniepeak soil is rapid. Available 

water capacity is low. Effective rooting depth is 60 

inches or more. In areas where vegetation was removed 

by the initial blast or buried by cinderfall and waterflow 

became concentrated, gullies formed readily. Raveling 

of the cinders downslope and sediment production will 

be high until the cinders become stabilized by 

vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

230-Obscurity very bouldery sand, 0 to 30 percent 

slopes. This very deep, somewhat excessively drained 

soil is on broad fans and low terraces along major 

drainageways. It formed in mudflow material. The soil is 

barren. Elevation is 2,800 to 5,500 feet. The average 

annual precipitation is about 130 inches, the average 

annual air temperature is about 40 degrees F, 

and the average frost-free period is 70 to 90 days. 

Typically, the upper part of the soil is gray very 

bouldery sand 20 inches thick. Below this to a depth of 

60 inches or more is dark gray very cobbly loamy sand 

and very cobbly sand. 

Included in this unit are small areas of Forsyth and 

Shoestring soils. Also included are areas of soils that 

have a gravelly loamy sand surface layer. Included 

areas make up about 15 percent of the total acreage. 

Permeability of this Obscurity soil is moderately rapid. 

Available water capacity is low. Effective rooting depth is 

60 inches or more. Runoff is slow, and the hazard of 

water erosion is moderate to high. The soil is subject to 

rare periods of flooding. 

The unit has potential for use as woodland, 

recreation areas, and wildlife habitat. 

This unit is presently undergoing primary plant 

succession. Invading plants will slowly provide a ground 

cover that will slow runoff from rain and snowmelt, reduce 

erosion, and provide food and cover for wildlife from 

adjacent areas. Eventually, established annual and 

perennial grasses, forbs, and shrubs will provide 

sufficient organic matter buildup and soil development for 

the artificial or natural regeneration of slow-growing 

timber stands. 

This map unit is in capability subclass Vlls. 

231-Panhandle extremely cindery loamy sand, 0 to 

20 percent slopes. This very deep, well drained soil is on 

broad fans. It formed in cindery pyroclastic flow. This soil 

is characterized by numerous channels and 

depressional areas. It is barren. Elevation is 2,900 to 

5,000 feet. The average annual precipitation is about 

135 inches, the average annual air temperature is about 

40 degrees F, and the average frost-free period is 70 to 

90 days. 

Typically, the upper part of the soil is light gray 

extremely cindery loamy sand 10 inches thick. Below 

this to a depth of 60 inches or more is brown very 

cindery loamy sand. 

Included in this unit are small areas of very gravelly 

loamy sand, very stony sand, and loamy sand. Included 

areas make up about 15 percent of the total acreage. 

Permeability of this Panhandle soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. Runoff is slow to medium, 

and the hazard of water erosion is moderate to high. 

This unit has potential for use for woodland, 

recreation, and wildlife habitat. 

This unit is presently undergoing primary plant 

succession. Invading plants will slowly provide a ground 
cover that will slow runoff from rain and snowmelt, reduce 

erosion, and provide food and cover for wildlife from 

adjacent areas. Eventually, established annual and 

perennial grasses, forbs, and shrubs will provide 

sufficient organic matter buildup and soil development for 

the artificial or natural regeneration of slow-growing timber 

stands, 

This map unit is in capability subclass Vlls. 

232-Pelee extremely cindery loamy sand, 

overblown, 5 to 30 percent slopes. This very deep, well 

drained soil is on back slopes and ridgetops of mountains. 

It formed in stratified, aerially deposited volcanic ash and 

pumice. The native vegetation before the cinderfall was 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,500 feet. The average annual precipitation is about 135 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free period is 75 to 90 

days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand and the next 10 inches is dark gray 

very cindery sand. Below this is a buried surface layer that 

is very dark grayish brown sandy loam 7 inches thick. The 

upper part of the subsoil is dark gray very cindery coarse 

sand and light gray extremely cindery sand 25 inches 

thick, and the lower part to a depth of 60 inches or more is 

dark brown and very dark grayish brown sandy loam and 

dark brown loamy sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas that have slopes of 

more than 30 percent. Also included are areas of Rock 

outcrop. Included areas make up about 10 percent of the 

total acreage. 

Permeability of this Pelee soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where vegetation 

was removed by the initial blast or buried by cinderfall 

and waterflow became concentrated.. gullies formed 

readily. Raveling of the cinders downslope and sediment 

production will be high until the cinders become 

stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIs. 

233-Pelee extremely cindery loamy sand, 

overblown, 30 to 65 percent slopes. This very deep, 

well drained soil is on back slopes and ridgetops of 

mountains. It formed in stratified, aerially deposited 

volcanic ash and pumice. The native vegetation before 

the cinderfall was mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,500 feet. The average annual 

precipitation is about 135 inches, the average annual air 

temperature is about 39 degrees F, and the average frostfree period is 75 to 90 days. 

This soil is overblown by new cinderfall 4 to 20 

inches thick. Typically, the upper 4 inches is light gray 

extremely cindery loamy sand over dark gray very 

cindery sand 10 inches thick. Below this is a buried 

surface layer that is very dark grayish brown sandy loam 

7 inches thick. The upper part of the subsoil is dark gray 

very cindery coarse sand and light gray extremely 

cindery sand 25 inches thick, and the lower part to a 

depth of 60 inches or more is dark brown and very dark 

grayish brown sandy loam and dark brown loamy sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Pelee soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where vegetation 

was removed by the initial blast or buried by cinderfall 

and waterflow became concentrated, gullies formed 

readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders 

become stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

234-Pelee extremely cindery loamy sand, 

overblown, 65 to 90 percent slopes. This very deep, 

well drained soil is on back slopes of mountains. It formed 

in stratified, aerially deposited volcanic ash and pumice. 

The native vegetation before the cinderfall was mainly 

mixed conifers and shrubs. Elevation is 2,800 to 4,500 

feet. The average annual precipitation is about 135 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free period is 75 to 90 

days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray 

extremely cindery loamy sand over dark gray very 

cindery sand 10 inches thick. Below this is a buried 

surface layer that is very dark grayish brown sandy 

loam 7 inches thick. The upper part of the subsoil is dark 

gray very cindery coarse sand and light gray extremely 

cindery sand 25 inches thick, and the lower part to a 

depth of 60 inches or more is dark brown and very dark 

grayish brown sandy loam and dark brown loamy sand. 
Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas that have slopes of 

less than 65 percent. Also included are areas in which 

the surface layer is exposed as a result of erosion. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this Pelee soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where vegetation 

was removed by the initial blast or buried by cinderfall 

and waterflow became concentrated. gullies formed 

readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders 

become stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIle. 

235-Pelee, overblown-Rock outcrop complex, 65 

to 90 percent slopes. This map unit is on back slopes of 

mountains. The native vegetation before the cinderfall 

was mainly mixed conifers and shrubs. Elevation is 2,800 

to 4,500 feet. The average annual precipitation is about 

135 inches, the average annual air temperature is about 

39 degrees F, and the average frost-free period is 75 to 

90 days. 

This unit is about 60 percent Pelee extremely cindery 

loamy sand, overblown, 65 to 90 percent slopes, and 30 

percent Rock outcrop. The components of this unit are 

so intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas where the original 

surface layer is exposed as a result of erosion. Included 

areas make up about 10 percent of the total acreage. 

The Pelee soil is very deep and well drained. It formed 

in stratified, aerially deposited volcanic ash and pumice. 

It is overblown by new cinderfall 4 to 20 inches thick. 

Typically. the upper 4 inches is light gray extremely 

cindery loamy sand over dark gray very cindery sand 10 

inches. Below this is a buried surface layer that is very 

dark grayish brown sandy loam 7 inches thick. The upper 

part of the subsoil is dark gray very cindery coarse sand 

and light gray extremely cindery sand 25 inches thick, 

and the lower part to a depth of 60 inches or more is dark 

brown and very dark grayish brown sandy loam and 

dark brown loamy sand. 

Permeability of this Pelee soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where vegetation 

was removed by the initial blast or buried by cinderfall 

and waterflow became concentrated, gullies formed 

readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders 

become stabilized by vegetation. 

Rock outcrop in this unit consists of exposed areas 

of basalt and andesite. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Pelee soil is in capability subclass VIIe, and the 

Rock outcrop is in capability subclass VIIIs. 

236-Polepatch loamy sand, overblown, 0 to 30 

percent slopes. This very deep, somewhat excessively 

drained soil is on alluvial fans and terraces. It formed in 

lahar material with a mantle of volcanic ash. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 2,800 to 4,000 feet. The 

average annual precipitation is about 135 inches, the 

average annual air temperature is about 40 degrees F, 

and the average frost-free period is 70 to 90 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown extremely bouldery loamy sand 12 inches thick. 

The underlying material to a depth of 60 inches or more is 

dark gray extremely cobbly sand and extremely stony 

coarse sand. 

Included in this unit are areas in which ashfall is more 

than 20 inches deep and areas of Polepatch, cold, soils. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this Polepatch soil is rapid. Available 

water capacity is low. Effective rooting depth is 20 to 40 

inches. The hazard of soil blowing in the areas of 

ashfall is high. In areas where vegetation was removed 

by the initial blast or buried by ash and waterflow became 

concentrated, gullies formed readily. Sediment 

production will be high until the ash has been stabilized 

by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass Vls. 

237-Rock outcrop-Cattcreek, overblown, cold 

complex, 65 to 90 percent slopes. This map unit is on 

back slopes and in cirque basins on mountains. The 

native vegetation before the ashfall was mainly scattered 

true firs and shrubs. Elevation is 4,000 to 5,300 feet. The 

average annual precipitation is about 110 inches, the 

average annual air temperature is about 38 degrees F, 

and the average frost-free period is 70 to 90 days. 

This unit is about 60 percent Rock outcrop and 30 
Figure 8.-An area of Shoestring loamy sand, overblown, 0 to 30 percent slopes. Note the orientation of the trees blown down by the initial blast. 

percent Cattcreek loamy sand, overblown, cold, 65 to 90 

percent slopes. The components of this unit are so 

intricately intermingled that it was not practical to map 

them separately at the scale used. 

Rock outcrop consists of exposed areas of andesite. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

The Cattcreek soil is very deep and well drained. It 

formed in pumice and volcanic ash over residuum and 

colluvium derived from andesite. It is overblown by new 

ashfall 4 to 20 inches thick. Typically, the upper 15 inches 

is dark gray loamy sand over a buried surface layer that is 

dark grayish brown and dark yellowish brown very cindery 

loamy sand 6 inches thick. The upper 9 inches of the 

subsoil is dark brown very cindery sand. and the lower 15 

inches is strong brown extremely cindery sand. The next 

layer to a depth of 60 inches or more is a buried subsoil of 

dark yellowish brown extremely gravelly loam. 

Permeability of this Cattcreek soil is moderate. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. The hazard of soil blowing 

in the areas of ashfall is high. In areas where 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Rock outcrop is in capability subclass VIlls, and 

the Cattcreek soil is in capability subclass VIle. 

238-Shoestring loamy sand, overblown, 0 to 30 

percent slopes. This very deep, well drained soil is on 

terraces and terrace escarpments. It formed in aerially 

deposited volcanic ash and pumice over pyroclastic flow 

and lahar material. The native vegetation before the 

ashfall was mainly mixed conifers and shrubs (fig. 8). 

Elevation is 2,700 to 4,500 feet. The average annual 
precipitation is about 130 inches, the average annual air 

temperature is about 41 degrees F, and the average frostfree period is 70 to 90 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand. The next 5 inches consists of a buried surface layer 

and the upper part of the subsoil, which are very dark 

gray fine sandy loam. The next 3 inches of the subsoil is 

dark gray very gravelly sand, and the lower 16 inches is 

dark brown sandy loam and very dark brown loamy sand. 

The substratum to a depth of 60 inches or more is dark 

grayish brown very cobbly sand and dark gray very 

gravelly sand. 

Included in this unit are small areas in which ashfall 

is more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Shoestring soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where 

the vegetation was removed by the initial blast or buried 

by ash and waterflow became concentrated, gullies 

formed readily. Sediment production will be high until the 

ash has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIs. 

239-Shoestring loamy sand, overblown, 50 to 90 

percent slopes. This very deep, well drained soil is on 

terrace escarpments. It formed in aerially deposited 

volcanic ash and pumice over pyroclastic flow and lahar 

material. The native vegetation before the ashfall was 

mainly mixed conifers and shrubs. Elevation is 2,700 to 

4,500 feet. The average annual precipitation is about 

130 inches. the average annual air temperature is about 

41 degrees F, and the average frost-free period is 70 to 90 

days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand. The next 5 inches consists of a buried surface 

layer and the upper part of the subsoil, which are very 

dark gray fine sandy loam. The next 3 inches of the 

subsoil is dark gray very gravelly sand, and the lower 16 

inches is dark brown sandy loam and very dark brown 

loamy sand. The substratum to a depth of 60 inches or 

more is dark grayish brown very cobbly sand and dark 

gray very gravelly sand. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Also included are small 

areas of Rock outcrop. Badland, and areas where the 

original surface layer is exposed as a result of erosion. 

Included areas make up about 10 percent of the total 

acreage. 

Permeability of this Shoestring soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where the 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is used for wildlife habitat and recreation. 

This map unit is in capability subclass VIIe. 

240-Sinnice extremely cindery loamy sand, 

overblown, 5 to 30 percent slopes. This very deep, well 

drained soil is on foot slopes and ridgetops of mountains. 

It formed in aerially deposited layers of volcanic ash and 

pumice. The native vegetation before the cinderfall was 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,000 feet. The average annual precipitation is about 125 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free period is 75 to 90 

days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand and the next 10 inches is dark gray 

very cindery sand and gravelly sand. Below this is a 

buried layer that is light gray extremely cindery loamy 

sand 7 inches thick. The upper 2 inches of the subsoil is 

dark brown fine sandy loam, and the lower 6 inches is 

very dark brown loamy sand. The substratum to a depth 

of 60 inches or more is light gray extremely cindery sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas in which slopes 

are more than 30 percent. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where the 

vegetation was removed by the initial blast or buried by 

cinders and waterflow became concentrated, gullies 

formed readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders have 

been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIs. 

241-Sinnice extremely cindery loamy sand, 

overblown, 30 to 65 percent slopes. This very deep, 

well drained soil is on back slopes of mountains. It 
formed in layers of aerially deposited volcanic ash and 

pumice. The native vegetation before the cinderfall was 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,000 feet. The average annual precipitation is about 

125 inches. the average annual air temperature is about 

39 degrees F. and the average frost-free period is 75 to 90 

days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand over dark gray very cindery sand and 

gravelly sand 10 inches thick. Below this is a buried 

surface layer. It is light gray extremely cindery loamy 

sand 7 inches thick. The upper 2 inches of the subsoil is 

dark brown fine sandy loam, and the lower 6 inches is very 

dark brown loamy sand. The substratum to a depth of 60 

inches or more is light gray extremely cindery sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas in which slopes 

are less than 30 percent. Also included are areas of 

Minniepeak soils. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where the vegetation 

was removed by the initial blast or buried by cinders and 

waterflow became concentrated, gullies formed readily. 

Raveling of the cinders downslope and sediment 

production will be high until the cinders have been 

stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIle. 

242-Sinnice extremely cindery loamy sand, 

overblown. 65 to 90 percent slopes. This very deep. well 

drained soil is on back slopes of mountains. It formed in 

layers of aerially deposited volcanic ash and pumice. The 

native vegetation before the cinderfall was mainly mixed 

conifers and shrubs. Elevation is 2,800 to 4,000 feet. The 

average annual precipitation is about 125 inches, the 

average annual air temperature is about 39 degrees F. 

and the average frost-free period is 75 to 90 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand over dark gray very cindery sand and 

gravelly sand 10 inches thick. Below this is a buried 

surface layer that is light gray extremely cindery loamy 

sand 7 inches thick. The subsoil is dark brown fine 

sandy loam 2 inches thick over very dark brown loamy 

sand 6 inches thick. The substratum to a 

depth of 60 inches or more is light gray extremely 

cindery sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep and areas in which slopes are 

less than 65 percent. Also included are areas where the 

original surface layer is exposed as a result of erosion and 

areas of Minniepeak soils. Included areas make up about 

10 percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where the 

vegetation was removed by the initial blast or buried by 

cinders and waterflow became concentrated, gullies 

formed readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders have 

been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

243-Sinnice extremely cindery loamy sand, 

overblown, cold, 5 to 30 percent slopes. This very 

deep. well drained soil is on foot slopes and ridgetops of 

mountains. It formed in layers of aerially deposited 

volcanic ash and pumice. The native vegetation before 

the cinderfall was mainly mixed conifers and shrubs. 

Elevation is 4,000 to 5,000 feet. The average annual 

precipitation is about 125 inches, the average annual air 

temperature is about 38 degrees F, and the average frostfree period is 75 to 90 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand over dark gray very cindery sand and 

gravelly sand 10 inches thick. Below this is a buried 

surface layer that is light gray extremely cindery loamy 

sand 7 inches thick. The subsoil is dark brown fine 

sandy loam 2 inches thick over very dark brown loamy 

sand 6 inches thick. The substratum to a depth of 60 

inches or more is light gray extremely cindery sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where the 

vegetation was removed by the initial blast or buried by 

cinders and waterflow became concentrated, gullies 

formed readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders have 

been stabilized by vegetation. 
This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIs. 

244-Sinnice extremely cindery loamy sand, 

overblown, cold, 30 to 65 percent slopes. This 

very deep. well drained soil is on back slopes of 

mountains. It formed in layers of aerially deposited 

volcanic ash and pumice. The native vegetation before 

the cinderfall was mainly mixed conifers and shrubs. 

Elevation is 4,000 to 5,000 feet. The average annual 

precipitation is about 125 inches. the average annual air 

temperature is about 38 degrees F. and the average frostfree period is 75 to 90 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand over dark gray very cindery sand and 

gravelly sand 10 inches thick. Below this is a buried 

surface layer that is light gray extremely cindery loamy 

sand 7 inches thick. The subsoil is dark brown fine 

sandy loam 2 inches thick over very dark brown loamy 

sand 6 inches. The substratum to a depth of 60 inches or 

more is light gray extremely cindery sand. 

Included in this unit are areas in which cinderfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where the vegetation 

was removed by the initial blast or buried by cinders and 

waterflow became concentrated, gullies formed readily. 

Raveling of the cinders downslope and sediment 

production will be high until the cinders have been 

stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

245-Sinnice extremely cindery loamy sand, 

overblown, cold, 65 to 90 percent slopes. This very 

deep. well drained soil is on back slopes of mountains. It 

formed in layers of aerially deposited volcanic ash and 

pumice. The native vegetation before the cinderfall was 

mainly mixed conifers and shrubs. Elevation is 4,000 to 

5,000 feet. The average annual precipitation is about 

135 inches. the average annual air temperature is about 

38 degrees F, and the average frost-free period is 75 to 

90 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray 

extremely cindery loamy sand over dark gray very 

cindery sand and gravelly sand 10 inches thick. Below 

this is a buried surface layer of light gray extremely 

cindery loamy sand 7 inches thick. The subsoil is dark 

brown fine sandy loam 2 inches thick over very dark 

brown loamy sand 6 inches thick. The substratum to a 

depth of 60 inches or more is light gray extremely cindery 

sand. 

Included in this unit are areas in which slopes are less 

than 65 percent and areas where the original surface 

layer is exposed as a result of erosion. Included areas 

make up about 10 percent of the total acreage. 

Permeability of this Sinnice soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where the 

vegetation was removed by the initial blast or buried by 

cinders and waterflow became concentrated, gullies 

formed readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders have 

been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

246-Sinnice, overblown, cold-Rock outcrop 

complex, 65 to 90 percent slopes. This map unit is on 

cirque headwalls and back slopes of mountains. The 

native vegetation before cinderfall was mainly mixed 

conifers and shrubs. Elevation is 4,000 to 5,000 feet. The 

average annual precipitation is about 125 inches, the 

average annual air temperature is 38 degrees F, and 

the average frost-free period is 75 to 90 days. 

This unit is about 60 percent Sinnice extremely cindery 

loamy sand, overblown, cold, 65 to 90 percent slopes, 

and 30 percent Rock outcrop. The components of this 

unit are so intricately intermingled that it was not practical 

to map them separately at the scale used. 

Included in this unit are areas of Rubble land. Also 

included are areas where the original surface layer is 

exposed as a result of erosion. Included areas make up 

about 10 percent of the total acreage. 

The Sinnice soil is very deep and well drained. It 

formed in layers of aerially deposited volcanic ash and 

pumice. It is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray extremely 

cindery loamy sand over dark gray very cindery sand 

and gravelly sand 10 inches thick. Below this is a 

buried surface layer that is light gray extremely cindery 

loamy sand and gravelly sand 10 inches thick. The 

subsoil is dark brown fine sandy loam 2 inches thick over 

very dark brown loamy sand 6 inches thick. The 

substratum to a depth of 60 inches or more is light gray 

extremely cindery sand. 
Permeability of this Sinnice soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. In areas where the 

vegetation was removed by the initial blast or buried by 

cinders and waterflow became concentrated, gullies 

formed readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders have 

been stabilized by vegetation. 

Rock outcrop consists of exposed areas of andesite 

and basalt. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Sinnice soil is in capability subclass VIIe, and 

the Rock outcrop is in capability subclass VIlIs. 

247-Sinnice loamy sand, overblown, coldRock outcrop complex. 65 to 90 percent slopes.

This map unit is on back slopes of mountains. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 4,000 to 5,000 feet. The average 

annual precipitation is about 125 inches, the average 

annual air temperature is about 38 degrees F, and the 

average frost-free period is 75 to 90 days. 

This unit is about 60 percent Sinnice loamy sand, 

overblown, cold, 65 to 90 percent slopes. and about 30 

percent Rock outcrop. The components of this unit are 

so intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are areas where the original 

surface layer is exposed as a result of erosion. Included 

areas make up about 10 percent of the total acreage. 

The Sinnice soil is very deep and well drained. It 

formed in aerially deposited layers of volcanic ash and 

pumice. The soil is overblown by new ashfall 4 to 20 

inches thick. Typically, the upper 15 inches is dark gray 

loamy sand over a buried surface layer of light gray 

extremely cindery loamy sand 7 inches thick. The subsoil 

is dark brown fine sandy loam 2 inches thick over very 

dark brown loamy sand 6 inches thick. The substratum to 

a depth of 60 inches or more is light gray extremely 

cindery sand. 

Permeability of this Sinnice soil is moderately rapid. 

Available water capacity is moderate. Effective rooting 

depth is 60 inches or more. The hazard of soil blowing in 

the areas of ashfall is high. In areas where the 

vegetation was removed by the initial eruption or buried 

by ash and waterflow became concentrated, gullies 

formed readily. Sediment production will be high until the 

ash has been stabilized by vegetation. 

Rock outcrop consists of exposed areas of andesite 

and basalt. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Sinnice soil is in capability subclass VIIe, and 

the Rock outcrop is in capability subclass VIIIs. 

248-Studebaker very gravelly loamy sand, 0 to 20 

percent slopes. This very deep, somewhat excessively 

drained soil is on foot slopes and toe slopes in highly 

irregular, dissected areas of valley fill. It formed in 

avalanche debris flow material. Slopes are mainly 2 to 20 

percent, but in places the large areas of avalanche 

deposits can have slopes of as much as 100 percent. 

Debris consisting of logs is strewn across the landscape 

in an erratic pattern. The soil is barren. Elevation is 

2,700 to 5,500 feet. The average annual precipitation is 

about 135 inches, the average annual air temperature is 

about 40 degrees F, and the average frost-free period is 

about 70 to 90 days. 

Typically, the soil to a depth of 60 inches or more is 

dark gray very gravelly loamy sand. Color ranges from 

dusky red to very dark brown. In some areas texture 

throughout the profile is extremely gravelly loamy sand 

or extremely cobbly sand. 

Included in this unit are small areas of soils that have 

an extremely cindery surface, mounds of extremely 

cindery loamy sand, and deep deposits of very fine sandy 

loam in depressional areas. Perennial and intermittent 

streams, flood plains, and depressional areas are 

included. Included areas make up about 20 percent of 

the total acreage. 

Permeability of this soil is moderately rapid. Available 

water capacity is low. Effective rooting depth is 60 inches 

or more. Runoff is slow, and the hazard of water erosion is 

slight. 

This unit has potential for use for wildlife habitat, 

recreation, and woodland. 

This unit is undergoing primary plant succession. 

Invading plants will slowly provide a ground cover that will 

slow runoff from rain and snowmelt, reduce erosion, and 

provide food and cover for wildlife from adjacent areas. 

Eventually, established annual and perennial grasses, 

forbs, and shrubs will provide sufficient organic matter 

buildup and soil development for the artificial or natural 

regeneration of slow-growing timber stands. 

This map unit is in capability subclass VIIs. 

249-Swift loamy sand, overblown, 2 to 30 percent 

slopes. This very deep, well drained soil is on side 

slopes and ridgetops of mountains. It formed in 

colluvium derived dominantly from volcanic ash and 

basic igneous rock with a mantle of volcanic ash and 
cinders. The native vegetation before the ashfall was 

mainly mixed conifers and shrubs. Elevation is 2,500 to 

2,800 feet. The average annual precipitation is about 

115 inches, the average annual air temperature is about 

43 degrees F, and the average frost-free period is 100 

to 120 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown cindery sandy loam 12 inches thick. The upper 15 

inches of the subsoil is dark yellowish brown very 

cindery loam, and the lower part to a depth of 60 inches or 

more is dark yellowish brown extremely cobbly loam. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep and areas of Rock outcrop. 

Also included are areas in which slopes are more than 

30 percent. Included areas make up about 10 percent 

of the total acreage. 

Permeability of this Swift soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. The hazard of soil blowing 

in the areas of ashfall is high. In areas where the 

vegetation was removed by the initial blast or buried by 

ash and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the ash 

has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass IVe. 

250-Swift, overblown-Rock outcrop complex, 65 

to 90 percent slopes. This map unit is on side slopes of 

mountains. The native vegetation before the ashfall was 

mainly mixed conifers and shrubs. Elevation is 2,000 to 

2,800 feet. The average annual precipitation is about 115 

inches. the average annual air temperature is about 43 

degrees F, and the average frost-free period is 100 to 120 

days. 

This unit is about 60 percent Swift loamy sand, 

overblown. 65 to 90 percent slopes, and 30 percent 

Rock outcrop. The components of this unit ore so 

intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are small areas where the original 

surface layer is exposed as a result of erosion. Included 

areas make up about 10 percent of the total acreage. 

The Swift soil is very deep and well drained. It formed 

in colluvium derived dominantly from volcanic ash and 

basic igneous rock with a mantle of volcanic ash and 

cinders. The soil is overblown by new ashfall 4 

to 20 inches. Typically, the upper 15 inches is dark gray 

loamy sand over a buried surface layer of very dark 

grayish brown cindery sandy loam 12 inches thick. The 

upper 15 inches of the subsoil is dark yellowish brown 

very cindery loam, and the lower part to a depth of 60 

inches or more is dark yellowish brown extremely cobbly 

loam. 

Permeability of this Swift soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. The hazard of soil blowing in the 

areas of ashfall is high. In areas where the vegetation 

was removed by the initial blast or buried by ash and 

waterflow became concentrated, gullies formed readily. 

Sediment production will be high until the ash has been 

stabilized by vegetation. 

Rock outcrop consists of exposed areas of 

dominantly andesite and basalt. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Swift soil is in capability subclass VIIe, and the 

Rock outcrop is in capability subclass VIIIs. 

251-Tradedollar loamy sand, overblown, 0 to 30 

percent slopes. This very deep, well drained soil is on 

ridgetops of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation before 

the ashfall was mainly mixed conifers and shrubs. 

Elevation is 4,000 to 5,400 feet. The average annual 

precipitation is about 100 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown sandy loam 5 inches thick. The upper 21 inches of 

the subsoil is dark brown cindery sandy loam. Below this 

to a depth of 60 inches or more is dark brown extremely 

cindery loamy sand and strong brown extremely cindery 

sand. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep and areas in which slopes 

are more than 30 percent. included areas make up 

about 10 percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more, The 

hazard of soil blowing in the areas of ashfall is high. In 

areas where the vegetation was removed by the initial 

blast or buried by ash and waterflow became 

concentrated, gullies formed readily. Sediment 

production will be high until the ash has been 

stabilized by vegetation. 
This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass Vls. 

252-Tradedollar loamy sand, overblown, 30 to 65 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in aerially deposited 

volcanic ash and pumice. The native vegetation before 

the ashfall was mainly mixed conifers and shrubs. 

Elevation is 4,000 to 5,400 feet. The average annual 

precipitation is about 100 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown sandy loam 5 inches thick. The upper 21 inches of 

the subsoil is dark brown cindery sandy loam. Below this 

to a depth of 60 inches or more is dark brown extremely 

cindery loamy sand and strong brown extremely cindery 

sand. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. The hazard 

of soil blowing in the areas of ashfall is high. In areas 

where the vegetation was removed by the initial blast or 

buried by ash and waterflow became concentrated. 

gullies formed readily. Sediment production will be high 

until the ash has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

253-Tradedollar loamy sand, overblown, 65 to 90 

percent slopes. This very deep. well drained soil is on 

back slopes and ridgetops of mountains. It formed in 

aerially deposited volcanic ash and pumice. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 4,000 to 5,400 feet. The average 

annual precipitation is about 100 inches, the average 

annual air temperature is about 38 degrees F. and the 

average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically. the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown sandy loam 5 inches thick. The upper 21 inches of 

the subsoil is dark brown cindery sandy loam. Below this 

to a depth of 60 inches or more is dark 

brown extremely cindery loamy sand and strong brown 

extremely cindery sand. 

included in this unit are areas of Rock outcrop and 

areas where the original surface layer is exposed as a 

result of erosion. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. The 

hazard of soil blowing in the areas of ashfall is high. In 

areas where the vegetation was removed by the initial 

blast or buried by ash and waterflow became 

concentrated, gullies formed readily. Sediment 

production will be high until the ash has been stabilized 

by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

254-Tradedollar loamy sand, overblown, warm, 0 

to 30 percent slopes. This very deep, well drained soil is 

on back slopes of mountains. It formed in aerially 

deposited volcanic ash and pumice. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 2,800 to 4,000 feet. The 

average annual precipitation is about 100 inches, the 

average annual air temperature is about 39 degrees F, 

and the average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown sandy loam 5 inches thick. The upper 21 inches of 

the subsoil is dark brown cindery sandy loam. Below this 

to a depth of 60 inches or more is dark brown 

extremely cindery loamy sand and strong brown 

extremely cindery sand. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep and areas in which slopes 

are more than 30 percent. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. The hazard 

of soil blowing in the areas of ashfall is high. In areas 

where the vegetation was removed by the initial blast 

or buried by ash and waterflow became concentrated, 

gullies formed readily. Sediment production will be high 

until the ash has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIe.
255-Tradedollar loamy sand, overblown, warm, 

30 to 65 percent slopes. This very deep, well 

drained soil is on back slopes of mountains. It formed in 

aerially deposited volcanic ash and pumice. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 2,800 to 4,000 feet. The average 

annual precipitation is about 100 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown sandy loam 5 inches thick. The upper 21 inches of 

the subsoil is dark brown cindery sandy loam. Below this 

to a depth of 60 inches or more is dark brown extremely 

cindery loamy sand and strong brown extremely cindery 

sand. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. The hazard 

of soil blowing in the areas of ashfall is high. In areas 

where the vegetation was removed by the initial blast or 

buried by ash and waterflow became concentrated, 

gullies formed readily. Sediment production will be high 

until the ash has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass Vlle. 

256-Tradedollar loamy sand, overblown, warm, 65 

to 90 percent slopes. This very deep, well drained soil is 

on back slopes of mountains. It formed in aerially 

deposited volcanic ash and pumice. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 2,800 to 4,000 feet. The average 

annual precipitation is about 100 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is very dark grayish 

brown sandy loam 5 inches thick, The upper 21 inches of 

the subsoil is dark brown cindery sandy loam. Below this 

to a depth of 60 inches or more is dark brown extremely 

cindery loamy sand and strong brown extremely 

cindery sand. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep. Also included are areas 

where the original surface layer is exposed as a result of 

erosion. Included areas make up about 10 percent of the 

total acreage. 

Permeability of this Tradedollar soil is moderately 

rapid. Available water capacity is moderately high. 

Effective rooting depth is 60 inches or more. The hazard 

of soil blowing in the areas of ashfall is high. In areas 

where the vegetation was removed by the initial blast 

or buried by ash and waterflow became concentrated, 

gullies formed readily. Sediment production will be high 

until the ash has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

257-Vanson loamy sand, overblown, 5 to 30 

percent slopes. This very deep, well drained soil is on 

foot slopes of mountains. It formed in colluvium derived 

dominantly from igneous rock mixed with volcanic ash 

and pumice. The native vegetation before the ashfall 

was mainly mixed conifers and shrubs. Elevation is 

2,800 to 4,000 feet. The average annual precipitation is 

about 105 inches, the average annual air temperature is 

about 39 degrees F, and the average frost-free period is 

75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is dark brown 

sandy loam 9 inches thick. The upper 7 inches of the 

subsoil is dark yellowish brown sandy loam, the next 8 

inches is dark brown loamy sand, and the lower part to a 

depth of 60 inches or more is dark yellowish brown very 

gravelly sandy loam. 

Included in this unit are areas in which ashfall is more 

than 20 inches deep. Also included are small areas of 

Rock outcrop and Vanson soils that are 40 to 60 inches 

deep to bedrock. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Vanson soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. The hazard of soil blowing in the 

areas of ashfall is high. In areas where the vegetation 

was removed by the initial blast or buried by ash and 

waterflow became concentrated, gullies formed readily. 

Sediment production will be high until the ash has been 

stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIs. 
258-Vanson loamy sand, overblown, 30 to 65 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in colluvium derived 

dominantly from igneous rock mixed with volcanic ash 

and pumice. The native vegetation before the ashfall was 

mainly mixed conifers and shrubs. Elevation is 2,800 to 

4,000 feet. The average annual precipitation is about 105 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free period is 75 to 95 

days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer that is dark brown sandy 

loam 9 inches thick. The upper 7 inches of the subsoil is 

dark yellowish brown sandy loam, the next 8 inches is 

dark brown loamy sand. and the lower part to a depth of 

60 inches or more is dark yellowish brown very gravelly 

sandy loam. 

Included in this unit are areas in which ashfall is more 

than 20 inches deep and Vanson soils that are 40 to 60 

inches deep to bedrock. Included areas make up about 

10 percent of the total acreage. 

Permeability of this Vanson soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. The hazard of soil blowing in the 

areas of ashfall is high. In areas where the vegetation was 

removed by the initial blast or buried by ash and waterflow 

became concentrated, gullies formed readily. Sediment 

production will be high until the ash has been stabilized by 

vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

259-Vanson loamy sand, overblown, 65 to 90 

percent slopes. This very deep, well drained soil is on 

back slopes of mountains. It formed in colluvium derived 

dominantly from igneous rock mixed with volcanic ash 

and pumice. The native vegetation before the ashfall was 

mainly mixed conifers and shrubs. Elevation is 2.800 to 

4.000 feet. The average annual precipitation is about 105 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free period is 75 to 95 

days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer of dark brown sandy 

loam 9 inches thick. The upper 7 inches of the subsoil is 

dark yellowish brown sandy loam, the next 8 inches is 

dark brown loamy sand, and the lower part to a depth 

of 60 inches or more is dark yellowish brown very 

gravelly sandy loam. 

Included in this unit are areas in which ashfall is more 

than 20 inches deep and Vanson soils that are 40 to 60 

inches deep to bedrock. Included areas make up about 

10 percent of the total acreage. 

Permeability of this Vanson soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. The hazard of soil blowing in the 

areas of ashfall is high. In areas where the vegetation was 

removed by the initial eruption or buried by ash and 

waterflow became concentrated, gullies formed readily. 

Sediment production will be high until the ash has been 

stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

260-Vanson loamy sand, overblown, cold, 5 to 30 

percent slopes. This very deep, well drained soil is on 

foot slopes and ridgetops of mountains. It formed in 

colluvium derived dominantly from igneous rock mixed 

with volcanic ash and pumice. The native vegetation 

before the ashfall was mainly mixed conifers and shrubs. 

Elevation is 2,800 to 4,000 feet. The average annual 

precipitation is about 105 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer of dark brown sandy 

loam 9 inches thick. The upper 7 inches of the subsoil is 

dark yellowish brown sandy loam, the next 8 inches 

is dark brown loamy sand, and the lower part to a depth 

of 60 inches or more is dark yellowish brown very gravelly 

sandy loam. 

Included in this unit are areas in which ashfall is more 

than 20 inches deep and Vanson soils that are 40 to 60 

inches deep to bedrock. Also included are areas of 

Rock outcrop. Included areas make up about 10 percent 

of the total acreage. 

Permeability of this Vanson soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. The hazard of soil blowing 

in the areas of ashfall is high In areas where the 

vegetation was removed by the initial eruption or 

buried by ash and waterflow became concentrated, 

gullies formed readily. Sediment production will be high 

until the ash has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 
This map unit is in capability subclass VIs. 

261-Vanson loamy sand, overblown, cold, 30 

to 65 percent slopes. This very deep, well drained soil 

is on foot slopes and ridgetops of mountains. It formed 

in colluvium derived dominantly from igneous rock 

mixed with volcanic ash and pumice. The native 

vegetation before the ashfall was mainly mixed conifers 

and shrubs. Elevation is 4,000 to 5,000 feet. The 

average annual precipitation is about 105 inches, the 

average annual air temperature is about 38 degrees F, 

and the average frost-free period is 75 to 95 days. 

This soil is overblown by new ashfall 4 to 20 inches 

thick. Typically, the upper 15 inches is dark gray loamy 

sand over a buried surface layer of dark brown sandy 

loam 9 inches thick. The upper 7 inches of the subsoil is 

dark yellowish brown sandy loam, the next 8 inches is 

dark brown loamy sand. and the lower part to a depth of 

60 inches or more is dark yellowish brown very gravelly 

sandy loam. 

Included in this unit are areas in which ashfall is 

more than 20 inches deep and Vanson soils that are 40 to 

60 inches deep to bedrock. Included areas make up 

about 10 percent of the total acreage. 

Permeability of this Vanson soil is moderate. 

Available water capacity is moderately high. Effective 

rooting depth is 60 inches or more. The hazard of soil 

blowing in the areas of ashfall is high. In areas where the 

vegetation was removed by the initial eruption or buried 

by ash and waterflow became concentrated. gullies 

formed readily. Sediment production will be high until the 

ash has been stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

262-Vanson extremely cindery loamy sand, 

overblown, 65 to 90 percent slopes. This very deep, 

well drained soil is on foot slopes and ridgetops of 

mountains. It formed in colluvium derived dominantly 

from igneous rock mixed with volcanic ash and pumice. 

The native vegetation before the cinderfall was mainly 

mixed conifers and shrubs. Elevation is 4,000 to 5,000 

feet. The average annual precipitation is about 105 

inches. the average annual air temperature is about 38 

degrees F, and the average annual frost-free period is 

75 to 95 days. 

This soil is overblown by new cinderfall 4 to 20 inches 

thick. Typically, the upper 4 inches is light gray 

extremely cindery loamy sand over dark gray very 

cindery sand and gravelly sand 10 inches thick. Below 

this is a buried surface layer that is dark brown sandy 

loam 9 inches thick. The upper 7 inches of the subsoil is 

dark yellowish brown sandy loam, the next 8 inches 

is dark brown loamy sand, and the lower part to a depth 

of 60 inches or more is dark yellowish brown very 

gravelly sandy loam. 

Included in this unit are areas of Vanson soils that are 

40 to 60 inches deep to bedrock. Also included are 

areas where the original surface layer is exposed as a 

result of erosion. Included areas make up about 10 

percent of the total acreage. 

Permeability of this Vanson soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. In areas where the vegetation was 

removed by the initial eruption or buried by cinders and 

waterflow became concentrated, gullies formed readily. 

Raveling of the cinders downslope and sediment 

production will be high until the cinders have been 

stabilized by vegetation. 

This unit is in areas used for wildlife habitat and 

recreation. 

This map unit is in capability subclass VIIe. 

263-Vanson, overblown-Rock outcrop complex, 

30 to 65 percent slopes. This map unit is on back slopes 

of mountains. The native vegetation before the cinderfall 

was mainly mixed conifers and shrubs. Elevation is 2,800 

to 4,000 feet. The average annual precipitation is about 

105 inches, the average annual air temperature is about 

39 degrees F, and the average frost-free period is 75 to 

95 days. 

This unit is about 60 percent Vanson extremely cindery 

loamy sand, overblown, 30 to 65 percent slopes, and 30 

percent Rock outcrop. The components of this unit are 

so intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are areas of Vanson soils that 

are 40 to 60 inches deep to bedrock. 

The Vanson soil is very deep and well drained. It 

formed in colluvium derived dominantly from igneous 

rock mixed with volcanic ash and pumice. The soil is 

overblown by new cinderfall 4 to 20 inches thick. 

Typically, the upper 4 inches is light gray extremely 

cindery loamy sand over dark gray very cindery sand and 

gravelly sand 10 inches thick. Below this is a buried 

surface layer of dark brown sandy loam 9 inches thick. 

The upper 7 inches of the subsoil is dark yellowish brown 

sandy loam, the next 8 inches is dark brown loamy 

sand, and the lower part to a depth of 60 inches or 

more is dark yellowish brown very gravelly sandy loam. 

Permeability of this Vanson soil is moderate. 

Available water capacity is moderately high. Effective 
rooting depth is 60 inches or more. In areas where the 

vegetation was removed by the initial blast or buried by 

cinderfall and waterflow became concentrated, gullies 

formed readily, Raveling of the cinders downslope and 

sediment production will be high until the cinders 

become stabilized by vegetation. 

Rock outcrop consists of exposed areas of andesite 

and basalt. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Vanson soil is in capability subclass Vlle, and 

the Rock outcrop is in capability subclass VIIIs. 

264-Vanson, overblown-Rock outcrop complex, 

65 to 90 percent slopes. This map unit is on back 

slopes of mountains. The native vegetation before the 

ashfall was mainly mixed conifers and shrubs. Elevation 

is 2,800 to 4,000 feet. The average annual 

precipitation is about 105 inches, the average annual air 

temperature is about 39 degrees F, and the average 

frost-free period is 75 to 95 days. 

This unit is about 60 percent Vanson loamy sand, 

overblown. 65 to 90 percent slopes. and 30 percent 

Rock outcrop. The components of this unit are so 

intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are areas in which bedrock is at a 

depth of 40 to 60 inches. Also included are areas where 

the original surface layer is exposed as a result of erosion. 

Included areas make up about 10 percent of the total 

acreage. 

The Vanson soil is very deep and well drained. It 

formed in colluvium derived dominantly from igneous rock 

mixed with volcanic ash and pumice. This soil is 

overblown by new ashfall 4 to 20 inches thick. Typically, 

the upper 15 inches is dark gray loamy sand over a buried 

surface layer of dark brown sandy loam 9 inches thick. 

The upper 7 inches of the subsoil is dark yellowish brown 

sandy loam, the next 8 inches is dark brown loamy sand. 

and the lower part to a depth of 60 inches or more is dark 

yellowish brown very gravelly sandy loam. 

Permeability of this Vanson soil is moderate. Available 

water capacity is moderately high. Effective rooting depth 

is 60 inches or more. The hazard of soil blowing in the 

areas of ashfall is high. In areas where the vegetation 

was removed by the initial eruption or buried by ashfall 

and waterflow became concentrated, gullies formed 

readily. Sediment production will be high until the 

cinders become stabilized by vegetation. 

Rock outcrop consists of exposed areas of andesite 

and basalt. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Vanson soil is in capability subclass VIIe, and 

the Rock outcrop is in capability subclass VIIIs. 

265-Vanson, overblown, cold-Rock outcrop 

complex, 65 to 90 percent slopes. This map unit is on 

back slopes of mountains. The native vegetation before 

the cinderfall was mainly mixed conifers and shrubs. 

Elevation is 4,000 to 5,000 feet. The average annual 

precipitation is about 105 inches, the average annual air 

temperature is about 38 degrees F, and the average 

frost-free period is 75 to 95 days. 

This unit is about 60 percent Vanson extremely cindery 

loamy sand, overblown, 65 to 90 percent slopes, and 30 

percent Rock outcrop. The components of this unit are so 

intricately intermingled that it was not practical to map 

them separately at the scale used. 

Included in this unit are areas of Vanson soils that 

are 40 to 60 inches deep to bedrock and areas where 

slopes are less than 65 percent. Also included are areas 

where the original surface layer is exposed as a result of 

erosion. Included areas make up about 10 percent of 

the total acreage. 

The Vanson soil is very deep and well drained. It 

formed in colluvium derived dominantly from igneous rock 

mixed with volcanic ash and pumice. The soil is 

overblown by new cinderfall 4 to 20 inches thick. 

Typically, the upper 4 inches is light gray extremely 

cindery loamy sand over dark gray very cindery sand and 

gravelly sand 10 inches thick. Below this is a buried 

surface layer that is dark brown sandy loam 9 inches thick. 

The upper 7 inches of the subsoil is dark yellowish brown 

sandy loam, the next 8 inches is dark brown loamy sand, 

and the lower part to a depth of 60 inches or more is dark 

yellowish brown very gravelly sandy loam. 

Permeability of this Vanson soil is moderate. Available 

water capacity is moderately high. Effective rooting 

depth is 60 inches or more. In areas where the 

vegetation was removed by the initial blast or buried by 

cinderfall and waterflow became concentrated, gullies 

formed readily. Raveling of the cinders downslope and 

sediment production will be high until the cinders 

become stabilized by vegetation. 

Rock outcrop consists of exposed areas of andesite 

and basalt. 

This unit is in areas used for wildlife habitat and 

recreation. 

The Vanson soil is in capability subclass VIIe, and 

the Rock outcrop is in capability subclass VIIIs. 
266-Wakepish very gravelly sandy loam, 0 to 30 

percent slopes. This very deep, somewhat excessively 

drained soil is on fans and low terraces along 

drainageways. It formed in mudflow material. The soil is 

barren. Elevation is 1,600 to 2,800 feet. The average 

annual precipitation is about 135 inches, the average 

annual air temperature is about 42 degrees F, and the 

average frost-free period is about 90 to 110 days. 

Typically, the soil is dark gray gravelly sandy loam 30 

inches thick over dark gray very gravelly loamy sand 

and very gravelly sand that extends to a depth of 60 

inches or more. 

Included in this unit are small areas of very bouldery 

loamy sand. very gravelly loamy sand, and soils that 

have been eroded to bedrock. Included areas make up 

about 15 percent of the total acreage. 

Permeability of this Wakepish soil is moderately 

rapid. Available water capacity is low. Effective rooting 

depth is 60 inches or more. Runoff is slow, and the 

hazard of water erosion is moderate to high. This soil is 

subject to frequent, brief periods of flooding during May 

through June. 

This unit has potential for use as woodland, 

recreation, and wildlife habitat. 

This unit is presently undergoing primary plant 

succession. Invading plants will slowly provide a ground 

cover that will slow runoff from rain and snowmelt, 

reduce erosion, and provide food and cover for certain 

wildlife from adjacent areas. Eventually, established 

annual and perennial grasses, forbs, and shrubs will 

provide sufficient organic matter buildup and soil 

development for the artificial or natural regeneration of 

slow-growing timber stands. 

This map unit is in capability subclass VIls. 
Prime Farmland 

In this section, prime farmland is defined and 

discussed and the prime farmland soils in this survey 

area are listed. 

Prime farmland is of major importance in providing 

the nations short- and long-range needs for food and 

fiber. The acreage of high-quality farmland is limited, 

and the U.S. Department of Agriculture recognizes that 

government at local, state, and federal levels, as well as 

individuals. must encourage and facilitate the wise use 

of our nations prime farmland. 

Prime farmland soils, as defined by the U.S. 

Department of Agriculture. are soils that are best suited to 

producing food, seed, forage, fiber, and oilseed crops. 

Such soils have properties that are favorable for the 

economic production of sustained high yields of crops. 

The soils need only to be treated and managed using 

acceptable farming methods. Adequate moisture and a 

sufficiently long growing season are required. Prime 

farmland soils produce the highest yields with minimal 

inputs of energy and economic resources, and farming 

these soils results in the least damage to the 

environment. 

Prime farmland soils may presently be in use as 

cropland, pastureland, or woodland, or they may be in 

other uses. They either are used for producing food and 

fiber or are available for these uses. 

Prime farmland is areas where the soils are well 

drained. are more than 40 inches deep, and have a 

dependable and adequate supply of moisture from 

precipitation or irrigation. Slopes generally are less than 8 

percent. It has few or no stones and is permeable to 

water and air. Prime farmland is not excessively erodible 

or saturated with water for long periods and is not flooded 

during the growing season. It also has a favorable 

temperature and length of growing season and an 

acceptable level of acidity or alkalinity. For more detailed 

information on the criteria for prime farmland 

consult the local office of the Soil Conservation Service. 

About 11,135 acres, or 3 percent of the survey area, 

meets the soil requirements for prime farmland, Areas of 

prime farmland are on benches and terraces along the 

Columbia River, in the southern part of the area. A major 

part of the prime farmland remains in second growth 

stands of Douglas fir. Cleared areas are used for 

orchards, mainly for producing apples and pears. Other 

areas of prime farmland are used for pasture and hay 

crops. 

The loss of some prime farmland to urban uses has 

been a recent trend in land use in some parts of the 

area. This puts pressure on marginal lands, which 

generally are more erodible, are difficult to cultivate, and 

commonly are less productive. 

The soil map units that make up the prime farmland in 

this survey area are listed in this section. This list does 

not constitute a recommendation for a particular land use. 

The extent of each listed map unit is shown in tables 4a 

and 4b. The location is shown on the detailed soil map in 

the back of this publication. The soil characteristics that 

affect use and management are described in the section 

"Detailed Soil Map Units." 

The following map units meet the soil requirements 

for prime farmland. 

21 Chemawa loam, 2 to 8 percent slopes 

42 Haplumbrepts, 0 to 3 percent slopes 

64 McBee silt loam 

65 McDoug silt loam 

73 Mossyrock silt loam, 2 to 5 percent slopes 

103 Skamania very fine sandy loam, 0 to 8 percent 

slopes 

120 Stabler loam, 0 to 8 percent slopes 

157 Washougal loam, 0 to 3 percent slopes 

158 Washougal gravelly loam, 2 to 8 percent slopes 
Use and Management of the Soils 

This soil survey is an inventory and evaluation of the 

soils in the survey area. It can be used to adjust land 

uses to the limitations and potentials of natural resources 

and the environment. Also, it can help avoid soil-related 

failures in land uses. 

In preparing a soil survey, soil scientists, 

conservationists, engineers, and others collect extensive 

field data about the nature and behavioral characteristics 

of the soils. They collect data on erosion, droughtiness, 

flooding, and other factors that affect various soil uses and 

management. Field experience and collected data on soil 

properties and performance are used as a basis in 

predicting soil behavior. 

Information in this section can be used to plan the 

use and management of soils for crops and pasture; as 

woodland; as sites for buildings, sanitary facilities, 

highways and other transportation systems, and parks 

and other recreation facilities; and for wildlife habitat. It 

can be used to identify the limitations of each soil for 

specific land uses and to help prevent construction 

failures caused by unfavorable soil properties. 

Planners and others using soil survey information can 

evaluate the effect of specific land uses on productivity 

and on the environment in the survey area. The survey 

can help planners to maintain or create a land use 

pattern in harmony with the natural soil. 

Contractors can use this survey to locate sources of

sand and gravel, roadfill, and topsoil. They can use it to 

identify areas where bedrock, wetness, or very firm soil 

layers can cause difficulty in excavation. 

Health officials, highway officials, engineers, and others 

may also find this survey useful. The survey can help 

them plan the safe disposal of wastes and locate sites 

for pavements, sidewalks, campgrounds, playgrounds. 

lawns. and trees and shrubs. 

Crops and Pasture 

Steven Nissley, soil conservationist. Soil Conservation Service. helped to prepare this 

section. 

 General management needed for crops and for hay and 

pasture is suggested in this section. The system of 

land capability classification used by the Soil 

Conservation Service is explained, and the estimated 

yields of the main crops and hay and pasture plants 

commonly grown are listed for each soil. 

Agriculture in the survey area is limited by 

mountainous terrain, steepness of slope, and a short 

growing season over much of the area. Gently sloping 

terraces along the Columbia River Gorge and the lower 

valleys of the Wind and Washougal Rivers are the main 

agricultural areas. 

The total cropland in the survey area is about 3,250 

acres. Of this, about 450 acres is in orchards and about 

2,750 acres is hayland and pastureland. In addition to 

the cropland, a small acreage is used for growing small 

grain and grapes for wine. About 890 acres is used for 

unimproved pasture. 

The orchards in the survey area are mainly in the 

Underwood Hill area. Apples and pears are the main 

crops. The average annual precipitation in this area is 40 

to 45 inches. These orchards are not irrigated. Tree rows 

commonly are oriented up and down the slope. This 

allows cold air drainage down the slope, but it also allows 

unrestricted flow of water. Properly managed and 

maintained cover crops are needed to control soil 

erosion. In some areas, tree rows and farm roads 

concentrate the flow of water, which causes gully erosion.

The hayland and pastureland is along the entire 

length of the Columbia River Gorge, where the slope is 

gradual enough for cultivation. The average annual 

precipitation is 40 to 80 inches. As precipitation 

increases, so does soil acidity. Lime is needed on 

legumes for maximum production. Alfalfa, alsike clover, 

red clover, birdsfoot trefoil, and big trefoil are legumes 

that are adapted to this area. Adapted grasses include 

orchardgrass, tall fescue, timothy, smooth brome, 

meadow foxtail, and reed canarygrass. 

The main conservation problem associated with 

hayland and pastureland is soil erosion caused by 

runoff following reseeding operations and from 

concentrated flow of water in areas where the plant 

cover is inadequate. Soil erosion can be reduced by 
using no-till farming, maintaining residue on the surface, 

and properly fertilizing when reseeding. Other practices 

include installing tile drainage systems and shaping and 

seeding waterways. 

Pastureland requires proper grazing to maintain 

desirable plant species. Grazing should be deferred until 

plants are at least 8 inches tall. Plants should not be 

grazed any lower than 4 inches. The regrowth period 

should be keyed to the needs of the plants. Also, grazing 

should be avoided when the field is excessively wet or 

before a reseeded stand is fully established. Pastures 

should be clipped and dragged at least once each 

summer. 

Planners of management systems for individual fields 

or farms should consider the detailed information given 

in the description of each soil under "Detailed Soil Map 

Units.'' Specific information can be obtained from the 

local office of the Soil Conservation Service or the 

Cooperative Extension Service. 

Yields Per Acre 

The average yields per acre that can be expected of 

the principal crops under a high level of management 

are shown in table 5. In any given year, yields may be 

higher or lower than those indicated in the table because 

of variations in rainfall and other climatic factors. 

The yields are based mainly on the experience and 

records of farmers. conservationists, and extension 

agents. Available yield data from nearby counties and 

results of field trials and demonstrations are also 

considered. 

The management needed to obtain the indicated yields 

of the various crops depends on the kind of soil and the 

crop. Management can include drainage, erosion control. 

and protection from flooding; the proper planting and 

seeding rates, suitable high-yielding crop varieties; 

appropriate and timely tillage, control of weeds, plant 

diseases, and harmful insects; favorable soil reaction and 

optimum levels of nitrogen, phosphorus, potassium, and 

trace elements for each crop; effective use of crop 

residue, barnyard manure, and green-manure crops; and 

harvesting that ensures the smallest possible loss. 

The estimated yields reflect the productive capacity of 

each soil for each of the principal crops. Yields are 

likely to increase as new production technology is 

developed. The productivity of a given soil compared 

with that of other soils, however, is not likely to change. 

Crops other than those shown in table 5 are grown in 

the survey area. but estimated yields are not listed 

because the acreage of such crops is small. The local 

office of the Soil Conservation Service or of the 

Cooperative Extension Service can provide information 

about the management and productivity of the soils for 

those crops. 

Land Capability Classification 

Land capability classification shows, in a general way, 

the suitability of soils for most kinds of field crops. Crops 

that require special management are excluded. The 

soils are grouped according to their limitations for field 

crops, the risk of damage if they are used for crops, and 

the way they respond to management. The grouping 

does not take into account major and generally expensive 

landforming that would change slope, depth, or other 

characteristics of the soils, nor does it consider possible 

but unlikely major reclamation projects. Capability 

classification is not a substitute for interpretations 

designed to show suitability and limitations of groups of 

soils for rangeland, for woodland. and for engineering 

purposes. 

In the capability system, soils generally are grouped 

at three levels: capability class, subclass, and unit. Only 

class and subclass are used in this survey. These 

levels are defined in the following paragraphs. 

Capability classes, the broadest groups, are 

designated by Roman numerals I through VIII. The 

numerals indicate progressively greater limitations and 

narrower choices for practical use. The classes are 

defined as follows: 

Class I soils have few limitations that restrict their 

use. 

Class II soils have moderate limitations that reduce 

the choice of plants or that require moderate 

conservation practices. 

Class III soils have severe limitations that reduce the 

choice of plants or that require special conservation 

practices, or both. 

Class IV soils have very severe limitations that 

reduce the choice of plants or that require very careful 

management, or both. 

Class V soils are not likely to erode but have other 

limitations, impractical to remove, that limit their use. 

Class VI soils have severe limitations that make them 

generally unsuitable for cultivation. 

Class VII soils have very severe limitations that make 

them unsuitable for cultivation. 

Class VIII soils and miscellaneous areas have 

limitations that nearly preclude their use for commercial 

crop production. 

Capability subclasses are soil groups within one 
class. They are designated by adding a small letter, e, w,

s, or c, to the class numeral, for example, Ile. The letter e 

shows that the main limitation is risk of erosion unless 

close-growing plant cover is maintained; w shows that 

water in or on the soil interferes with plant growth or 

cultivation (in some soils the wetness can be partly 

corrected by artificial drainage); s shows that the soil is 

limited mainly because it is shallow, droughty, or stony; 

and c. used in only some parts of the United States. 

shows that the chief limitation is climate that is very cold 

or very dry. 

In class I there are no subclasses because the soils 

of this class have few limitations. Class V contains only 

the subclasses indicated by w, s, or c because the soils in 

class V are subject to little or no erosion. They have 

other limitations that restrict their use to pasture, 

rangeland, woodland, wildlife habitat, or recreation. The 

capability subclass is identified in the description of each 

soil map unit in the section ''Detailed Soil Map Units. '' 

Woodland Management and Productivity 

Gregory S, Fisher. forester. Soil Conservation Service, 

helped to write this section. 

Most of this survey area is forest land. All privately 

owned forest land in the county is included in the 

survey area. The survey area also includes about 

120,000 acres of intermingled state (9) and federal 

woodland in the northwestern part of the county. 

Differences in climate and topography in the survey 

area result in a number of different forest types. Douglas 

fir, ponderosa pine, grand fir, red alder, Oregon white 

oak, and bigleaf maple grow at the lower elevations, 

where the annual precipitation is lower. Western 

hemlock, western redcedar, Pacific silver fir, noble fir, 

and subalpine fir grow at the higher elevations, where the 

annual precipitation is higher. Woodland productivity 

generally is highest on the soils at the lower elevations. 

The harvesting and processing of wood products is 

important to the local economy. Products include lumber, 

poles, piling, plywood, Christmas trees, and firewood. 

Large sawmill and plywood manufacturing facilities and 

numerous small, privately owned sawmills are located in 

the area. 

Soil surveys are becoming increasingly more important 

to forest land owners as they come to realize that the 

success or failure of many management practices can be 

predicted beforehand by knowing the properties of the 

various soils on which trees grow. Each map unit 

described in the section ''Detailed Soil 

Map Units" that is suitable for producing wood crops 

contains information on potential productivity, limitations 

for harvesting timber, concerns for establishing and 

producing wood crops, and the common tree species and 

forest understory plants. The methods and procedures 

used by foresters and soil scientists to develop the 

information for each map unit description are contained 

in the Soil Conservation Service National Forestry 

Manual (20) and the State of Washington Forest Land 

Grading Procedures Handbook (9). 

Forests surrounding Mount St. Helens were severely 

impacted by the May 18, 1980, eruption. About 67,000 

acres of Federal and private land in the northern part of 

the survey area was affected directly by the lateral blast 

of the eruption. The approximate acreage of forest land 

affected by the blast is as follows: timber blowdown, 

17,900 acres; standing damaged timber, 4,160 acres; 

little if any vegetation, 41,000 acres; new lakes, 1,200 

acres; and Mount St. Helens and old Spirit Lake, 2,550 

acres (21). 

Soils on which the vegetation was completely 

destroyed and areas that had been recently clearcut 

prior to the eruption support little if any vegetation at 

present. 

Within the blast area, all vegetation was killed, blown 

down, or otherwise destroyed. The Forest Service 

estimated that the total dead and downed timber on 

federal forest land was about 1.1 billion board feet. The 

volume of affected timber in the survey area is somewhat 

less because the blast area extends outside of this soil 

survey area. No estimates for the volume of affected 

timber are available for the private land within the 

survey area. 

The impact on the vegetation outside the blast area 

varies with the amount of tephra received from the initial 

and subsequent eruptions. Trees and shrubs appear to 

have suffered little negative impact. The effects on 

forbs, grasses, and other low growing plants vary with 

the amount of tephra received and the ability of the 

plants to push up through the tephra. 

Various alternatives for salvaging timber and the 

Timing of operations for salvage were considered. 

Proposals for wilderness and interpretive areas affected 

the amount of timber that could be salvaged. The 

Forest Service estimated that 580 million board feet was 

accessible for salvage on Federal land outside of 

proposed wilderness and interpretive areas; however, 

for each year of lapsed time after the first 4 or 5 years 

following the blast, it was estimated that volume losses 

would be about 50 million board feet per year (5). No 

estimates are available for the volume or time frames of 

timber salvage on private land within the survey area.
The eruptions of Mount St. Helens changed many of 

the original soil-woodland interpretations. especially 

within the blast and mudflow areas. Some of those 

changes were predicted, and others require short- and 

long-term monitoring and observation. Trees were killed 

and left standing. blown down, or otherwise destroyed 

within the blast area. Most of the trees in the mudflow area 

were destroyed. 

No site indexes are given for the posteruption map 

units listed on table 6a; however, the site indexes for 

the areas of ashfall and cinderfall are probably still valid 

because the posteruption soils are similar to the 

preeruption soils. Short-term productivity will be 

drastically reduced where tree seedling roots cannot be 

placed in or near the underlying preeruption soils. The 

new deposits of mudflow material and tephra lack some 

nutrients, organic matter, mycorrhizal fungi, and 

structure of developed soils that are necessary for 

optimum tree growth. 

Recommendations for trees to plant and the ratings 

for equipment limitation. seedling mortality, windthrow 

hazard. and plant competition are given in tables 6a and 

6b. These ratings are for areas where the roots of tree 

seedlings can be placed partially in preeruption soil 

material. 

Natural regeneration of tree seedlings is limited by the 

proximity of seed sources from trees unaffected by the 

blast. The presence of droughty, nutrient-deficient 

tephra and its tendency to crust at the surface when dry 

adversely affects the success of natural regeneration 

even in areas where the accumulations of tephra are as 

thin as 4 inches, unless it is removed or incorporated into 

the preeruption soil material. 

Accumulations of new tephra less than 4 inches thick 

should have little effect on the survival of planted tree 

seedlings; accumulations more than 4 inches thick result 

in severe seedling mortality. 

Various methods of site preparation can be used to 

reduce seedling mortality on the overblown map units. 

One method is to use an auger 6 inches in diameter to 

bore down to preeruption soil material and mix the soil 

with the new tephra prior to planting trees. Where slopes 

are less than about 25 percent, tracked equipment with 

various types of blades can be operated across slope to 

wholly or partially remove the new tephra. Sun shades 

placed on the south side of the planted seedlings provide 

some protection from direct and reflected sunlight, 

particularly where slopes are more than 60 percent. 

Extensive tree planting programs are being 

implemented on land within the blast areas, except for 

the Mount St. Helens National Volcanic Monument. 

Douglas fir and noble fir are two of the primary species 

being planted-Douglas fir on soils at less than 3,500 

feet elevation and noble fir on soils at more than 3,500 

feet. The Douglas fir seedlings being planted are mainly 

2-0 stock with a large fibrous root system 10 to 12 inches 

long. The natural vegetation that was on the overblown 

map units prior to the eruption is given in the "Common 

trees" column in table 6b. 

Trees planted in the debris flow and mudflow 

material will be much harder to establish. Numerous 

plantings of rooted black cottonwood cuttings and 

unrooted native willow cuttings have been completed in 

mudflow areas on Federal lands to evaluate seedling 

mortality. Numerous trial plantings of various coniferous 

seedlings also have been completed in the thicker tephra 

deposits on Federal lands for the same purpose. The 

success of those plantings in the mudflow and thicker 

tephra deposits should be evaluated before large scale 

tree planting programs are developed for these areas. 

Tables 6a and 6b summarize the forestry information 

given in the map unit descriptions and can serve as a 

quick reference for important woodland interpretations. 

Following is a brief description of each of the columns 

in the tables. 

Ordination symbol.-The ordination symbol is based 

on a uniform system for labeling individual soils to 

determine the potential productivity and the principal 

soil properties in relation to any hazards or limitations of 

that soil (20). The first element of the ordination symbol is 

a number that denotes potential productivity in terms of 

cubic meters of wood per hectare per year for the indicator 

tree species. The indicator species is a tree that 

commonly grows on the particular soil and is the most 

productive one; for example, a number 1 would mean 1

cubic meter of wood per hectare per year (14.3 cubic 

feet per acre per year) and 10 would mean the soil has 

potential for producing 10 cubic meters of wood per 

hectare per year (143 cubic feet per acre per year). 

Cubic feet multiplied by 5 gives the approximate growth 

volume in Scribner board feet. The second element of 

the symbol, a letter, indicates the major kind of soil 

characteristic that limits tree growth or management. The 

letter X indicates restrictions because of stones or rocks; 

W, excessive water, either seasonally or year-round, in or 

on the soil; D, restricted rooting depth; S, sandy soils; F, 

soils with coarse fragments that are more than 0.1 inch 

and less than 10 inches in diameter; and R, relief or 

steepness of slope. The letter A indicates that there are 

few, if any, limitations for use or management as forest 

land. If a soil has more than one limitation, the letter 

denoting the most limiting 
characteristic of the soil is used. 

Each soil is also rated for a number of factors to be 

considered in management. Slight, moderate, and 

severe are used to indicate the degree of major soil 

limitations or management problems. For each moderate 

or severe rating, a sentence in the applicable soil map 

unit explains the soil factors that are the basis for that 

rating. 

Equipment limitation ratings refer to the limits on the 

use of equipment, year-round or seasonally, as a result of 

soil characteristics. A rating of slight indicates that use of 

equipment is not normally restricted in kind or time of year 

because of soil factors; moderate indicates a short 

seasonal limitation because of soil wetness, a fluctuating 

water table, or some other factor; and severe indicates a 

seasonal limitation, a need for special equipment (such 

as a cable yarding system), or a hazard in the use of 

equipment. Steepness of slope, soil wetness, and 

stoniness or rockiness are the main factors that cause 

equipment limitations. As slope gradient and length 

increase, it becomes more difficult to use wheeled 

equipment, commonly where slopes are 25 to 35 percent. 

On steeper slopes, tracked equipment must be used. 

commonly where slopes are 35 to 45 percent. On the 

steepest slopes even tracked equipment cannot be 

operated safely and more sophisticated systems must be 

used. Soil wetness, especially where the soils are fine 

textured, can severely limit the use of equipment, making 

harvesting practical only during dry summer months. 

Seedling mortality ratings refer to the probability of 

death of naturally occurring or planted tree seedlings as 

influenced by kinds of soil or topographic conditions. 

Plant competition is not considered in the ratings. The 

ratings apply to healthy, dormant live seedlings from good 

stock that are properly planted or to naturally established 

seedlings that germinate during a period of sufficient soil 

moisture. Slight indicates that no problem is expected 

under usual conditions; moderate indicates that some 

problems of mortality can be expected and that extra 

precautions are advisable; and severe indicates that 

mortality will be high and that extra precautions are 

essential for successful reforestation. Soil wetness and 

droughtiness of the surface layer, especially on south- or 

southwest-facing slopes or on ridgetops, account for 

seedling mortality. To offset these, larger than usual 

planting stock, special site preparation, surface drainage, 

or reinforcement planting may be needed. 

Windthrow hazard. Ratings of windthrow hazard 

consider the soil characteristics that affect the 

development of tree roots and the ability of the soil to 

hold trees firmly. A rating of slight indicates that trees 

are not normally blown down by wind; strong winds may 

break trees but not uproot them; moderate, that an 

occasional tree may be blown down during periods of 

excessive wetness combined with moderate or strong 

winds, and severe, that many trees can be expected to be

blown down during periods of soil wetness combined with 

moderate or strong winds. Restricted rooting depth 

because of a high water table, limited depth to bedrock, 

an impervious layer, or poor anchoring of roots because 

of a loose surface layer and subsoil are responsible for 

windthrow or tree tipover. Moderate and severe ratings 

indicate the need for more care in thinning the edges of 

woodland stands, a plan calling for periodic salvage of 

windthrown trees, and an adequate road and trail 

system to allow for salvage operations. 

Plant competition ratings refer to the likelihood of the 

invasion or growth of undesirable brushy plants when 

openings are made in the tree canopy. A slight rating 

indicates that unwanted brushy plants are not likely to 

delay natural reforestation and that planted seedlings 

have good prospects for development without undue 

competition; moderate indicates that competition will 

delay natural or planted reforestation; and severe 

indicates that competition can be expected to prevent 

natural or planted reforestation. The plant competition 

ratings in tables 6a and 6b correspond to the first tree 

species listed for each soil in the "common trees" 

column. Favorable climate and soil characteristics 

account for plant competition problems. In many 

instances, the key to predicting brush competition 

problems is the quantity and proximity of seed sources or 

the quantity of unwanted brush rootstock that will resprout 

after harvest. Moderate and severe ratings indicate the 

need for careful and thorough postharvest cleanup in 

preparation for reforestation and the possibility of 

mechanically or chemically treating brush to retard its 

growth and allow seedlings to develop. 

Common trees are listed in the general order of 

decreasing occurrence in the map unit. Listed species 

occur throughout the range of the map unit. The 

detailed map unit descriptions indicate the common 

trees that are principal species (occupying at least 10 

percent of the map unit) and minor species (occupying 

less than 10 percent). 

Site index refers to the height (in feet) of the larger 

trees (dominant and codominant) when they are 50 

years old. Generally, the higher the site index, the 

higher the production of wood fiber. A site index for a 

species on one map unit should only be compared to 

site indexes on other map units for the same tree 

species. A site index was not given to any minor 
species or. because of lack of data or a suitable site index 

publication, to certain principal species (4, 9, 10, 11, 14, 

15. 16. 24. 27). 

Trees to plant are those that are planted for 

reforestation or, if suitable conditions exist, are allowed to 

regenerate naturally. Species listed are suited to the soils 

and can produce a commercial wood crop. Desired 

product, landscape position, and personal preference are 

three factors among many that can influence the choice 

of adapted trees to use in reforestation. 

Recreation 

The survey area offers diverse recreational activity such 

as boating, swimming, and fishing on its many rivers, 

lakes, and reservoirs. Camping, hiking, mountain 

climbing, and hunting are also popular. The Wind River 

Winter Sports Area is maintained by the Forest Service and 

provides marked trails for cross-country skiing and 

snowmobiling. 

Recreational use of the area was severely affected by 

the eruption of Mount St. Helens on May 18, 1980. In 1979, 

the area provided an estimated 480,000 recreation-visitor 

days for all recreation activities (19). The loss of camping 

grounds, trails, backpacking areas, and fishing and 

hunting opportunities will be slowly recovered in the blast 

area. Recreational use of the blast area is expected to 

increase because of the visitor centers that have been 

built, volcano viewpoints, and access to unique 

geological features. 

The soils of the survey area are rated in tables 7a and 

7b according to limitations that affect their suitability for 

recreation. The ratings are based on restrictive soil 

features, such as wetness, slope, and texture of the 

surface layer. Susceptibility to flooding is considered. Not 

considered in the ratings, but important in evaluating a 

site, are the location and accessibility of the area, the size 

and shape of the area and its scenic quality, vegetation, 

access to water, potential water impoundment sites, and 

access to public sewerlines. The capacity of the soil to 

absorb septic tank effluent and the ability of the soil to 

support vegetation are also important. Soils subject to 

flooding are limited for recreation use by the duration and 

intensity of flooding and the season when flooding occurs. 

In planning recreation facilities, onsite assessment of the 

height, duration, intensity, and frequency of flooding is 

essential. 

In tables 7a and 7b, the degree of soil limitation is 

expressed as slight, moderate, or severe. Slight means 

that soil properties generally are favorable and that 

limitations are minor and easily overcome. Moderate 

means that limitations can be overcome or alleviated by 

planning, design, or special maintenance. Severe means 

that soil properties are unfavorable and that limitations can 

be offset only by costly soil reclamation, special design, 

intensive maintenance, limited use, or by a combination 

of these measures. 

The information in tables 7a and 7b can be 

supplemented by other information in this survey; for 

example, interpretations for dwellings without 

basements and for local roads and streets in tables 9a 

and 9b and interpretations for septic tank absorption 

fields in tables 10a and 10b. 

Camp areas require site preparation such as shaping 

and leveling the tent and parking areas, stabilizing roads 

and intensively used areas, and installing sanitary facilities 

and utility lines. Camp areas are subject to heavy foot 

traffic and some vehicular traffic. The best soils are gently 

sloping and are not wet or subject to flooding during the 

period of use. The surface has few or no stones or 

boulders, absorbs rainfall readily but remains firm, and is 

not dusty when dry. Strong slopes and stones or boulders 

can greatly increase the cost of constructing campsites. 

Picnic areas are subject to heavy foot traffic. Most 

vehicular traffic is confined to access roads and parking 

areas. The best soils for picnic areas are firm when wet, 

are not dusty when dry, are not subject to flooding during 

the period of use, and do not have slopes or stones or 

boulders that increase the cost of shaping sites or of 

building access roads and parking areas. 

Playgrounds require soils that can withstand intensive 

foot traffic. The best soils are almost level and are not wet 

or subject to flooding during the season of use. The 

surface is free of stones and boulders, is firm after rains, 

and is not dusty when dry. If grading is needed, the depth 

of the soil over bedrock or a hardpan should be 

considered. 

Paths and trails for hiking and horseback riding 

should require little or no cutting and filling. The best 

soils are not wet, are firm after rains, are not dusty 

when dry, and are not subject to flooding more than 

once a year during the period of use. They have moderate 

slopes and few or no stones or boulders on the surface. 

Golf fairways are subject to heavy foot traffic and some 

light vehicular traffic, Cutting or filling may be required. 

The best soils for use as golf fairways are firm when wet, 

are not dusty when dry, and are not subject to 

prolonged flooding during the period of use. They have 

moderate slopes and no stones or boulders on the 

surface. The suitability of the soil for tees or greens is 

not considered in rating the soils. 
Wildlife Habitat 

Terry L. Aho, soil scientist, Soil Conservation Service. helped 

to write this section. 

Wide variations in elevation, climate, and geological 

features in the survey area result in a diversity of plant 

communities and wildlife habitat. This diversity in turn 

supports a wide variety of fish and wildlife, providing 

recreation and a source of income. To maintain this 

valuable fish and wildlife resource, an understanding of 

wildlife habitat and a well planned conservation program 

are necessary. 

The essential elements of wildlife habitat are food, 

cover, and water. The quality, quantity, and interspersion 

of these elements directly influences both wildlife 

populations and species diversity. This section discusses 

some of the principal kinds of wildlife in the area, the 

general kinds of habitat required by these species, and the 

major soils that support these kinds of habitat. 

In this survey area, rivers and streams provide habitat 

for both migratory and resident fish. The Columbia, Wind, 

and Washougal Rivers support the major runs of salmon, 

steelhead, smelt, and shad. These streams also support 

populations of sturgeon, whitefish. bass. and trout. Many 

smaller tributaries provide spawning and rearing areas for 

salmon and steelhead. In addition, they provide habitat for 

muskrats, river otters, beavers, waterfowl, bald eagles, and 

osprey. Bald eagles arrive along the Columbia River and 

its tributaries in November, when salmon are spawning. 

They feed on spawned-out salmon and smelt, which 

arrive in spring. The osprey also fish the rivers and 

streams for their food supply. 

Reservoirs and lakes provide habitat for resident 

populations of trout, bass, sunfish, perch, and crappie. 

They provide feeding and resting areas for migratory 

waterfowl, such as snow geese, mallards. pintails. teal, 

and mergansers, and to a limited extent whistling swans, 

great blue heron, and gulls (8). 

Flood plains and river terraces provide riparian habitat 

for amphibians. reptiles., rodents, weasels, raccoon, 

muskrats, skunks, and numerous species of songbirds. 

The Pilchuck, Skamania, and Washougal soils are 

examples of soils on flood plains and river terraces. 

High terraces above the flood plains provide 

openland habitat with brushy cover. These areas 

support populations of pheasant. California quail. 

meadowlarks, owls, and various other songbirds and 

birds of prey. These areas also provide habitat for 

rabbits, rodents, opossum, coyotes, and deer. 

Examples of soils on these terraces are those of the 

Chemawa, Hesson, Mossyrock, and Stabler series. 

Chemawa soils in the southeastern part of the survey 

area, near Underwood Mountain, are used for orchards. 

Mossyrock and Hesson soils in the southwestern part of 

the county are used for small grain and Christmas tree 

plantations and as hayland and pastureland. Stabler soils 

in the Upper Wind River Valley are used as pastureland. 

The mountainous, timbered areas associated with 

forestry activities support a variety of wildlife. Big game 

species include black-tailed deer, Roosevelt elk, black 

bear, cougar, and bobcat. The Mount Margaret area 

supports a small population of mountain goats. Smaller 

species in forested habitat include coyotes, rabbits, 

squirrels, chipmunks, and mountain beaver. The bird 

population includes ruffed and blue grouse, Steller's jay, 

owls, turkey vultures, and various other species of bird. 

The Aschoff, Cattcreek, Swift, Sinnice, Tradedollar, and 

Zygore soils are examples of soils that provide areas of 

forest wildlife habitat. 

As a general rule, agricultural land can be improved 

for wildlife by providing as much cover as possible. Such 

practices as planting odd areas, hedgerows, and 

windbreaks, protecting riparian vegetation, properly 

grazing pastures, and protecting land from soil erosion 

will provide food and cover for wildlife. Fish populations 

will also benefit from increased riparian vegetation and 

reduced in-stream sedimentation. 

 Several species of wildlife are dependent on old-growth 

forest land for all or part of their life cycle; however, many 

species, including deer and elk, relish the grasses, forbs, 

and shrubs that proliferate in forest openings. Small, 

irregularly shaped clearcuts are valuable feeding areas for 

10 to 20 years following logging. Forest management 

plans should include provisions to (1) protect riparian 

vegetation and a specified number of snags; (2) prevent 

erosion and stream sedimentation; and (3) reseed all 

disturbed areas such as roads, skid trails, and landings 

with a grass and legume mixture, The May 18, 1980, 

eruption of Mount St. Helens affected both fish and 

wildlife. An estimated 67,000 acres of wildlife habitat, 

1,700 acres of lakes, and 60 miles of rivers and streams 

in the survey area were destroyed or adversely affected 

by the eruption. 

Most of the wildlife habitat was destroyed by the lateral 

blast of the eruption. An estimated 2,070 black-tailed 

deer, 900 elk, 90 black bear, and 23 mountain goats were 

killed in Skamania County as a direct result of the 

eruption. Other wildlife lost in the blast were 
numerous furbearers, small mammals, birds, reptiles, 

and amphibians. 

Lakes and streams within the blast area of Skamania 

County were severely impacted by the May 18, 1980. 

eruption. Mudflows and pyroclastic flows entered and 

completely covered the North Fork of the Toutle River. 

Mudflows also severely affected the South Fork of the 

Toutle River, Muddy River, Pine Creek, and Smith Creek. 

Mudflows and debris traveling down the Muddy River 

and Pine Creek also slightly affected the Swift 

Reservoir. 

Fish in Spirit Lake. St. Helens Lake, and the smaller 

lakes were killed by the eruption, either by suffocation, 

by extreme heat, or as a result of gill abrasion caused by 

large amounts of ash in the water. 

The recovery and rehabilitation of wildlife habitat 

affected by the eruption will take many years. About 3 

years after the eruption, natural revegetation was 

becoming established along the fringe of the blast areas. 

It includes fireweed, grasses, and small shrubby plants. 

Erosion control measures of grass seedings, cottonwood 

plantings, and reforestation efforts scattered throughout 

the blast area are also a step toward the recovery of the 

wildlife habitat. Efforts by governmental agencies and 

private industry to revegetate the blast area continue. 

Soils affect the kind and amount of vegetation that is 

available to wildlife as food and cover. They also affect 

the construction of water impoundments. The kind and 

abundance of wildlife depend largely on the amount and 

distribution of food, cover, and water. Wildlife habitat 

can be created or improved by planting appropriate 

vegetation, by maintaining the existing plant cover, or by 

promoting the natural establishment of desirable plants. 

In table 8, the preeruption soils in the survey area are 

rated according to their potential for providing habitat for 

various kinds of wildlife. This information can be used in 

planning parks, wildlife refuges, nature study areas, and 

other developments for wildlife; in selecting soils that are 

suitable for establishing, improving, or maintaining specific 

elements of wildlife habitat; and in determining the 

intensity of management needed for each element of the 

habitat. 

The potential of the soil is rated good, fair, poor, or very 

poor. A rating of good indicates that the element or kind of 

habitat is easily established. improved, or maintained. 

Few or no limitations affect management, and satisfactory 

results can be expected. A rating of fair indicates that the 

element or kind of habitat can be established, improved, 

or maintained in most places. Moderately intensive 

management is required for 

satisfactory results. A rating of poor indicates that 

limitations are severe for the designated element or kind 

of habitat. Habitat can be created, improved, or 

maintained in most places, but management is difficult 

and must be intensive. A rating of very poor indicates that 

restrictions for the element or kind of habitat are very 

severe and that unsatisfactory results can be expected. 

Creating, improving, or maintaining habitat is impractical 

or impossible. 

The elements of wildlife habitat are described in the 

following paragraphs. 

Grain and seed crops are domestic grains and seed--

producing herbaceous plants. Soil properties and 

features that affect the growth of grain and seed crops 

are depth of the root zone, texture of the surface layer, 

available water capacity, wetness, slope, surface 

stoniness, and flood hazard. Soil temperature and soil 

moisture are also considerations. Examples of grain and 

seed crops are oats and barley. 

Grasses and legumes are domestic perennial grasses 

and herbaceous legumes. Soil properties and features 

that affect the growth of grasses and legumes are depth of 

the root zone, texture of the surface layer, available 

water capacity, wetness, surface stoniness, flood hazard, 

and slope. Soil temperature and soil moisture are also 

considerations. Examples of grasses and legumes are 

fescue, orchardgrass, clover, and alfalfa. 

Wild herbaceous plants are native or naturally 

established grasses and forbs, including weeds. Soil 

properties and features that affect the growth of these 

plants are depth of the root zone, texture of the surface 

layer, available water capacity, wetness, surface 

stoniness, and flood hazard. Soil temperature and soil 

moisture are also considerations. Examples of wild 

herbaceous plants are western brackenfern, western 

swordfern, dandelion, trillium, oxalis, bedstraw, lupine, 

and thistle. 

Hardwood trees and woody understory produce nuts or 

other fruit, buds, catkins, twigs, bark, and foliage. Soil 

properties and features that affect the growth of 

hardwood trees and shrubs are depth of the root zone, 

the available water capacity, and wetness. Examples of 

these plants are oak, poplar, cherry, apple, hawthorn, 

dogwood, hickory, blackberry, and blueberry. Examples 

of fruit-producing shrubs that are suitable for planting on 

soils rated good are Russian olive, autumn olive, and 

crabapple. 

Coniferous plants furnish browse, buds, catkins, and 

seeds. Soil properties and features that affect the 

growth of coniferous trees, shrubs, and ground cover 

are depth of the root zone, available water capacity, 

and wetness. Examples of coniferous plants are 
Douglas fir. Pacific silver fir, western redcedar, western 

hemlock, and grand fir. 

Shrubs are bushy woody plants that produce fruit, buds,

twigs, bark, and foliage. Soil properties and features that 

affect the growth of shrubs are depth of the root zone, 

available water capacity, salinity, and soil moisture. 

Examples of shrubs are salmonberry, Oregon grape, 

salal, and red elderberry. 

Wetland plants are annual and perennial wild 

herbaceous plants that grow on moist or wet sites. 

Submerged or floating aquatic plants are excluded. Soil 

properties and features affecting wetland plants are 

texture of the surface layer, wetness, reaction, salinity, 

slope, and surface stoniness. Examples of wetland plants 

are cattails, rushes, sedges, and reeds. 

Shallow water areas have an average depth of less 

than 5 feet. Some are naturally wet areas. Others are 

created by dams, levees, or other water-control 

structures. Soil properties and features affecting shallow 

water areas are depth to bedrock, wetness, surface 

stoniness, slope, and permeability. Examples of shallow 

water areas are reservoir and ponds. 

The habitat for various kinds of wildlife is described in 

the following paragraphs. 

Habitat for openland wildlife consists of cropland, 

pasture, meadows, and areas that are overgrown with 

grasses, herbs, shrubs, and vines. These areas 

produce grain and seed crops, grasses and legumes, 

and wild herbaceous plants. The wildlife attracted to 

these areas include California quail, pheasant, various 

songbirds, ground squirrels, rabbits, and coyote. 

Habitat for woodland wildlife consists of areas of 

deciduous plants or coniferous plants, or both, and 

associated grasses, legumes, and wild herbaceous 

plants. Wildlife attracted to these areas include ruffed 

grouse, deer, elk, and bear. 

Habitat for wetland wildlife consists of open, marshy or 

swampy shallow water areas. Some of the wildlife attracted 

to such areas are ducks, geese, wading birds, shore birds, 

muskrat, beaver, and various amphibians. 

Engineering 

This section provides information for planning land 

uses related to urban development and to water 

management. Soils are rated for various uses, and the 

most limiting features are identified. The ratings are given 

in the following tables: Building Site Development, Sanitary 

Facilities, Construction Materials, and Water 

Management. The ratings are based on observed 

performance of the soils and on the estimated data and 

test data in the "Soil Properties" section. 

Information in this section is intended for land use 

planning, for evaluating land use alternatives, and for 

planning site investigations prior to design and 

construction. The information, however, has limitations. 

For example, estimates and other data generally 

apply only to that part of the soil within a depth of 5 

or 6 feet. Because of the map scale, small areas of 

different soils may be included within the mapped 

areas of a specific soil. 

The information is not site specific and does not 

eliminate the need for onsite investigation of the soils 

or for testing and analysis by personnel experienced in 

the design and construction of engineering works. 

Government ordinances and regulations that restrict 

certain land uses or impose specific design criteria were 

not considered in preparing the information in this 

section. Local ordinances and regulations need to be 

considered in planning, in site selection, and in design. 

Soil properties, site features, and observed 

performance were considered in determining the ratings 

in this section. During the fieldwork for this soil survey, 

determinations were made about grain-size distribution, 

liquid limit, plasticity index, soil reaction, depth to bedrock, 

hardness of bedrock within 5 to 6 feet of the surface, soil 

wetness, depth to a seasonal high water table, slope, 

likelihood of flooding, natural soil structure aggregation, 

and soil density. Data were collected about kinds of clay 

minerals, mineralogy of the sand and silt fractions, and 

the kind of adsorbed cations. Estimates were made for 

erodibility, permeability, corrosivity, shrink-swell potential, 

available water capacity, and other behavioral 

characteristics affecting engineering uses. 

This information can be used to (1) evaluate the 

potential of areas for residential, commercial, industrial, 

and recreation uses; (2) make preliminary estimates of 

construction conditions; (3) evaluate alternative routes for 

roads, streets, highways, pipelines, and underground 

cables; (4) evaluate alternative sites for sanitary landfills, 

septic tank absorption fields, and sewage lagoons; (5) plan 

detailed onsite investigations of soils and geology, (6) 

locate potential sources of gravel, sand, earthfill, and 

topsoil; (7) plan drainage systems, irrigation systems, 

ponds, terraces, and other structures for soil and water 

conservation; and (8) predict performance of proposed 

small structures and pavements by comparing the 

performance of existing similar structures on the same or 

similar soils. 

The information in the tables, along with the soil 

maps and soil descriptions, and other data provided in 

this survey can be used to make additional 

interpretations. 
Some of the terms used in this soil survey have a 

special meaning in soil science and are defined in the 

Glossary. 

Building Site Development 

Tables 9a and 9b show the degree and kind of soil 

limitations that affect shallow excavations, dwellings 

with and without basements, small commercial buildings, 

local roads and streets, and lawns and landscaping. The 

limitations are considered slight if soil properties and site 

features generally are favorable for the indicated use 

and limitations are minor and easily overcome; 

moderate if soil properties or site features are not 

favorable for the indicated use and special planning, 

design, or maintenance is needed to overcome or 

minimize the limitations; and severe if soil properties or 

site features are so unfavorable or so difficult to 

overcome that special design, significant increases in 

construction costs, and possibly increased maintenance 

are required. Special feasibility studies may be required 

where the soil limitations are severe. 

Shallow excavations are trenches or holes dug to a 

maximum depth of 5 or 6 feet for basements, graves, 

utility lines, open ditches, and other purposes. The 

ratings are based on soil properties, site features, and 

observed performance of the soils. The ease of digging, 

filling, and compacting is affected by the depth to 

bedrock, a cemented pan, or a very firm dense layer; 

stone content; soil texture; and slope. The time of the year 

that excavations can be made is affected by the depth to 

a seasonal high water table and the susceptibility of the 

soil to flooding. The resistance of the excavation walls or 

banks to sloughing or caving is affected by soil texture 

and the depth to the water table. 

Dwellings and small commercial buildings are 

structures built on shallow foundations on undisturbed 

soil. The load limit is the same as that for single-family 

dwellings no higher than three stories. Ratings are made 

for small commercial buildings without basements. for 

dwellings with basements, and for dwellings without 

basements. The ratings are based on soil properties. site 

features, and observed performance of the soils. A high 

water table, flooding, shrink-swell potential, and organic 

layers can cause the movement of footings. A high water 

table, depth to bedrock or to a cemented pan, large 

stones, and flooding affect the ease of excavation and 

construction. Landscaping and grading that require cuts 

and fills of more than 5 to 6 feet are not considered. 

Local roads and streets have an all-weather surface 

and carry automobile and light truck traffic all year. 

They have a subgrade of cut or fill soil material, a base of 

gravel, crushed rock, or stabilized soil material, and a 

flexible or rigid surface. Cuts and fills generally are limited 

to less than 6 feet. The ratings are based on soil 

properties, site features, and observed performance of 

the soils. Depth to bedrock or to a cemented pan, a high 

water table, flooding, large stones, and slope affect the 

ease of excavating and grading. Soil strength (as 

inferred from the engineering classification of the soil). 

shrink-swell potential, frost action potential, and depth to 

a high water table affect the traffic supporting capacity. 

Lawns and landscaping require soils on which turf 

and ornamental trees and shrubs can be established and 

maintained. The ratings are based on soil properties, site 

features, and observed performance of the soils. Soil 

reaction, a high water table, depth to bedrock or to a 

cemented pan, the available water capacity in the upper 

40 inches, and the content of salts, sodium, and sulfidic 

materials affect plant growth. Flooding, wetness, slope, 

stoniness, and the amount of sand, clay, or organic 

matter in the surface layer affect trafficability after 

vegetation is established. 

Sanitary Facilities 

Tables 10a and 10b show the degree and the kind of 

soil limitations that affect septic tank absorption fields, 

sewage lagoons, and sanitary landfills. The limitations are 

considered slight if soil properties and site features 

generally are favorable for the indicated use and 

limitations are minor and easily overcome; moderate if 

soil properties or site features are not favorable for the 

indicated use and special planning, design, or 

maintenance is needed to overcome or minimize the 

limitations; and severe if soil properties or site features 

are so unfavorable or so difficult to overcome that special 

design, significant increases in construction costs, and 

possibly increased maintenance are required. 

Tables 10a and 10b also show the suitability of the 

soils for use as daily cover for landfills. A rating of good 

indicates that soil properties and site features are 

favorable for the use and good performance and low 

maintenance can be expected; fair indicates that soil 

properties and site features are moderately favorable for 

the use and one or more soil properties or site features 

make the soil less desirable than the soils rated good; 

and poor indicates that one or more soil properties or site 

features are unfavorable for the use and overcoming the 

unfavorable properties requires special design, extra 

maintenance, or costly alteration. 
Septic tank absorption fields are areas in which 

effluent from a septic tank is distributed into the soil 

through subsurface tiles or perforated pipe. Only that part 

of the soil between depths of 24 and 72 inches is 

evaluated. The ratings are based on soil properties, site 

features, and observed performance of the soils. 

Permeability, a high water table, depth to bedrock or to a 

cemented pan, and flooding affect absorption of the 

effluent. Large stones and bedrock or a cemented pan 

interfere with installation. 

Unsatisfactory performance of septic tank absorption 

fields, including excessively slow absorption of effluent, 

surfacing of effluent, and hillside seepage, can affect 

public health. Ground water can be polluted if highly 

permeable sand and gravel or fractured bedrock is less 

than 4 feet below the base of the absorption field, if slope 

is excessive, or if the water table is near the surface (23). 

There must be unsaturated soil material beneath the 

absorption field to filter the effluent effectively. Many local 

ordinances require that this material be of a certain 

thickness. 

Sewage lagoons are shallow ponds constructed to hold 

sewage while aerobic bacteria decompose the solid and 

liquid wastes. Lagoons should have a nearly level floor 

surrounded by cut slopes or embankments of compacted 

soil. Lagoons generally are designed to hold the sewage 

within a depth of 2 to 5 feet. Nearly impervious soil 

material for the lagoon floor and sides is required to 

minimize seepage and contamination of ground water. 

Tables 10a and 10b give ratings for the natural soil that 

makes up the lagoon floor. The surface layer and, 

generally, 1 or 2 feet of soil material below the surface 

layer are excavated to provide material for the 

embankments. The ratings are based on soil properties, 

site features, and observed performance of the soils. 

Considered in the ratings are slope, permeability, a high 

water table, depth to bedrock or to a cemented pan, 

flooding, large stones, and content of organic matter. 

Excessive seepage because of rapid permeability of 

the soil or a water table that is high enough to raise the 

level of sewage in the lagoon causes a lagoon to 

function unsatisfactorily. Pollution results if seepage is 

excessive or if floodwater overtops the lagoon. A high 

content of organic matter is detrimental to proper 

functioning of the lagoon because it inhibits aerobic 

activity. Slope, bedrock, and cemented pans can cause 

construction problems, and large stones can hinder 

compaction of the lagoon floor. 

Sanitary landfills are areas where solid waste is 

disposed of by burying it in soil. There are two types of 

landfill-trench and area. In a trench landfill, the waste 

is placed in a trench. It is spread, compacted, and 

covered daily with a thin layer of soil excavated at the site. 

In an area landfill, the waste is placed in successive 

layers on the surface of the soil. The waste is spread, 

compacted, and covered daily with a thin layer of soil 

from a source away from the site. 

Both types of landfill must be able to bear heavy 

vehicular traffic. Both types involve a risk of ground 

water pollution. Ease of excavation and revegetation 

needs to be considered. 

The ratings in tables 10a and 10b are based on soil 

properties, site features, and observed performance of 

the soils. Permeability, depth to bedrock or to a 

cemented pan, a high water table. slope, and flooding 

affect both types of landfill. Texture, stones and 

boulders, highly organic layers, soil reaction, and 

content of salts and sodium affect trench type landfills. 

Unless otherwise stated, the ratings apply only to that 

part of the soil within a depth of about 6 feet. For deeper 

trenches, a limitation rated slight or moderate may not 

be valid. Onsite investigation is needed. 

Daily cover for landfill is the soil material that is used 

to cover compacted solid waste in an area type sanitary 

landfill. The soil material is obtained offsite, transported 

to the landfill, and spread over the waste. 

Soil texture, wetness, coarse fragments, and slope 

affect the ease of removing and spreading the material 

during wet and dry periods. Loamy or silty soils that are 

free of large stones or excess gravel are the best cover 

for a landfill. Clayey soils are sticky or cloddy and are 

difficult to spread; sandy soils are subject to wind erosion.

After soil material has been removed, the soil material 

remaining in the borrow area must be thick enough over 

bedrock, a cemented pan, or the water table to permit 

revegetation. The soil material used as final cover for a 

landfill should be suitable for plants. The surface layer 

generally has the best workability, more organic matter, 

and the best potential for plants. Material from the 

surface layer should be stockpiled for use as the final 

cover. 

Construction Materials 

Tables 11a and 11b give information about the soils as 

a source of roadfill, sand, gravel, and topsoil. The soils 

are rated good, fair, or poor as a source of roadfill and 

topsoil. They are rated as a probable or improbable 

source of sand and gravel. The ratings are based on 

soil properties and site features that affect the removal of 

the soil and its use as construction material. Normal 

compaction, minor processing, and other standard 

construction practices are assumed. Each soil is 
evaluated to a depth of 5 or 6 feet. 

Roadfill is soil material that is excavated in one place 

and used in road embankments in another place. In this 

table, the soils are rated as a source of roadfill for low 

embankments, generally less than 6 feet high and less 

exacting in design than higher embankments. 

The ratings are for the soil material below the surface 

layer to a depth of 5 or 6 feet. It is assumed that soil layers 

will be mixed during excavating and spreading. Many 

soils have layers of contrasting suitability within their 

profile. The table showing engineering index properties 

provides detailed information about each soil layer. This 

information can help determine the suitability of each 

layer for use as roadfill. The performance of soil after it is 

stabilized with lime or cement is not considered in the 

ratings. 

The ratings are based on soil properties, site features, 

and observed performance of the soils. The thickness of 

suitable material is a major consideration. The ease of 

excavation is affected by large stones, a high water 

table, and slope. How well the soil performs in place 

after it has been compacted and drained is determined 

by its strength (as inferred from the engineering 

classification of the soil) and shrink-swell potential. 

Soils rated good contain significant amounts of sand 

or gravel, or both. They have at least 5 feet of suitable 

material, low shrink-swell potential, few cobbles and 

stones, and slopes of 15 percent or less. Depth to the 

water table is more than 3 feet. Soils rated fair are more 

than 35 percent silt- and clay-sized particles and have a 

plasticity index of less than 10. They have moderate 

shrink-swell potential, slopes of 15 to 25 percent, or many 

stones. Depth to the water table is 1 to 3 feet. Soils rated 

poor have a plasticity index of more than 10, a high shrinkswell potential. many stones, or slopes of more than 25 

percent. They are wet, and the depth to the water table is 

less than 1 foot. They may have layers of suitable material,

but the material is less than 3 feet thick. 

Sand and gravel are natural aggregates suitable for 

commercial use with a minimum of processing. Sand 

and gravel are used in many kinds of construction. 

Specifications for each use vary widely. In tables 11a 

and 11b, only the probability of finding material in 

suitable quantity is evaluated. The suitability of the 

material for specific purposes is not evaluated, nor are 

factors that affect excavation of the material. 

The properties used to evaluate the soil as a source of 

sand or gravel are gradation of grain sizes (as indicated 

by the engineering classification of the soil), the 

thickness of suitable material, and the content of 

rock fragments. Kinds of rock, acidity. and stratification 

are given in the soil series descriptions. Gradation of 

grain sizes is given in the table on engineering index 

properties. 

A soil rated as a probable source has a layer of clean 

sand or gravel or a layer of sand or gravel that is as much 

as 12 percent silty fines. This material must be at least 

3 feet thick and less than 50 percent, by weight, large 

stones. All other soils are rated as an improbable 

source. Coarse fragments of soft bedrock, such as shale 

and siltstone, are not considered to be sand and gravel. 

Topsoil is used to cover an area so that vegetation 

can be established and maintained. The upper 40 

inches of a soil is evaluated for use as topsoil. Also 

evaluated is the reclamation potential of the borrow 

area. 

Plant growth is affected by toxic material and by such 

properties as soil reaction, available water capacity, and 

fertility. The ease of excavating, loading, and spreading 

is affected by rock fragments, slope, a water table, soil 

texture, and thickness of suitable material. Reclamation of 

the borrow area is affected by slope, a water table, rock 

fragments, bedrock, and toxic material. 

Soils rated good have friable loamy material to a depth 

of at least 40 inches. They are free of stones and cobbles, 

have little or no gravel, and have slopes of less than 8 

percent. They are low in content of soluble salts, are 

naturally fertile or respond well to fertilizer, and are not so 

wet that excavation is difficult. 

Soils rated fair are sandy soils, loamy soils that have 

a relatively high content of clay, soils that have only 20 to 

40 inches of suitable material, soils that have an 

appreciable amount of gravel, stones, or soluble salts, or 

soils that have slopes of 8 to 15 percent. The soils are not 

so wet that excavation is difficult. 

Soils rated poor are very sandy or clayey, have less 

than 20 inches of suitable material, have a large amount 

of gravel, stones, or soluble salts, have slopes of more 

than 15 percent, or have a seasonal water table at or 

near the surface. 

The surface layer of most soils generally is preferred 

for topsoil because of its organic matter content. Organic 

matter greatly increases the absorption and retention of 

moisture and nutrients for plant growth. 

Water Management 

Tables 12a and 12b give information on the soil 

properties and site features that affect water 

management. The degree and kind of soil limitations 

are given for pond reservoir areas; embankments, 

dikes, and levees; and aquifer-fed ponds. The 
limitations are considered slight if soil properties and site 

features generally are favorable for the indicated use and 

limitations are minor and are easily overcome; moderate if

soil properties or site features are not favorable for the 

indicated use and special planning, design, or 

maintenance is needed to overcome or minimize the 

limitations; and severe if soil properties or site features 

are so unfavorable or so difficult to overcome that special 

design, significant increase in construction costs, and 

possibly increased maintenance are required. 

These tables also give for each soil the restrictive 

features that affect drainage, irrigation, terraces and 

diversions, and grassed waterways. 

Pond reservoir areas hold water behind a dam or 

embankment. Soils best suited to this use have low 

seepage potential in the upper 60 inches. The seepage 

potential is determined by the permeability of the soil and 

the depth to fractured bedrock or other permeable 

material. Excessive slope can affect the storage capacity 

of the reservoir area. 

 Embankments, dikes, and levees are raised structures

of soil material, generally less than 20 feet high, 

constructed to impound water or to protect land against 

overflow. In these tables, the soils are rated as a source 

of material for embankment fill. The ratings apply to the 

soil material below the surface layer to a depth of about 5 

feet. It is assumed that soil layers will be uniformly mixed 

and compacted during construction. 

The ratings do not indicate the ability of the natural 

soil to support an embankment. Soil properties to a 

depth even more than the height of the embankment can 

affect performance and safety of the embankment. 

Generally, deeper onsite investigation is needed to 

determine these properties. 

Soil material in embankments must be resistant to 

seepage, piping, and erosion and have favorable 

compaction characteristics. Unfavorable features 

include less than 5 feet of suitable material and a high 

content of stones or boulders, organic matter, or salts 

or sodium. A high water table affects the amount of 

usable material. It also affects trafficability. 

Aquifer-fed excavated ponds are pits or dugouts that 

extend to a ground water aquifer or to a depth below a 

permanent water table. Excluded are ponds that are fed 

only by surface runoff and embankment ponds that 

impound water 3 feet or more above the original surface. 

Excavated ponds are affected by depth to a permanent 

water table, permeability of the aquifer, and quality of the 

water as inferred from the salinity of the soil. Depth to 

bedrock and the content of large stones affect the ease of 

excavation. 

Drainage is the removal of excess surface and 

subsurface water from the soil. How easily and effectively 

the soil is drained depends on the depth to bedrock to a 

cemented pan, or to other layers that affect the rate of 

water movement; permeability; depth to a high water 

table or depth of standing water if the soil is subject to 

ponding; slope; susceptibility to flooding; subsidence of 

organic layers; and potential frost action. Excavating and 

grading and the stability of ditchbanks are affected by 

depth to bedrock or to a cemented pan, large stones, 

slope, and the hazard of cutbanks caving. The 

productivity of the soil after drainage is adversely affected 

by extreme acidity or by toxic substances in the root zone, 

such as salts, sodium, or sulfur. Availability of drainage 

outlets is not considered in the ratings. 

Terraces and diversions are embankments or a 

combination of channels and ridges constructed across a 

slope to reduce erosion and conserve moisture by 

intercepting runoff. Slope, wetness, large stones, and 

depth to bedrock or to a cemented pan affect the 

construction of terraces and diversions. A restricted 

rooting depth, a severe hazard of wind or water erosion, 

an excessively coarse texture, and restricted permeability 

adversely affect maintenance. 

Grassed waterways are natural or constructed 

channels, generally broad and shallow, that conduct 

surface water to outlets at a nonerosive velocity. Large 

stones, wetness, slope, and depth to bedrock or to a 

cemented pan affect the construction of grassed 

waterways. A hazard of wind erosion, low available 

water capacity, restricted rooting depth, toxic 

substances such as salts or sodium, and restricted 

permeability adversely affect the growth and 

maintenance of the grass after construction. 
Soil Properties 

Data relating to soil properties are collected during 

the course of the soil survey. The data and the estimates 

of soil and water features listed in tables are explained 

on the following pages. 

Soil properties are determined by field examination of 

the soils and by laboratory index testing of some 

benchmark soils. Established standard procedures are 

followed. During the survey, many shallow borings are 

made and examined to identify and classify the soils 

and to delineate them on the soil maps. Samples are 

taken from some typical profiles and tested in the 

laboratory to determine grain-size distribution and 

plasticity. 

Estimates of soil properties are based on field 

examinations, on laboratory tests of samples from the 

survey area, and on laboratory tests of samples of similar 

soils in nearby areas. Tests verify field observations. 

verify properties that cannot be estimated accurately by 

field observation, and help to characterize key soils. 

The estimates of soil properties shown in the tables 

include the range of grain-size distribution and Atterberg 

limits, the engineering classifications, and the physical 

and chemical properties of the major layers of each soil. 

Pertinent soil and water features also are given. 

Engineering Index Properties 

Tables 13a and 13b give estimates of the 

engineering classification and of the range of index 

properties for the major layers of each soil in the survey 

area. Most soils have layers of contrasting properties 

within the upper 5 to 6 feet. 

Depth to the upper and lower boundaries of each layer 

is indicated. The range in depth and information on 

other properties of each layer are given for each soil 

series under ''Soil Series and Their Morphology." 

Texture is given in the standard terms used by the 

U.S. Department of Agriculture. These terms are defined 

according to percentages of sand, silt, and clay in the 

fraction of the soil that is less than 2 millimeters 

in diameter. "Loam," for example, is soil that is 7 to 27 

percent clay, 28 to 50 percent silt, and less than 52 

percent sand. If the content of particles coarser than sand 

is as much as 15 percent, an appropriate modifier is 

added; for example, "gravelly." Textural terms are 

defined in the Glossary. 

Classification of the soils is determined according to 

the system adopted by the American Association of 

State Highway and Transportation Officials (1) and the 

Unified soil classification system (2), 

The Unified system classifies soils according to 

properties that affect their use as construction material. 

Soils are classified according to grain-size distribution of 

the fraction less than 3 inches in diameter and according 

to plasticity index, liquid limit, and organic matter 

content. Sandy and gravelly soils are identified as GW, 

GP, GM, GC, SW, SP, SM, and SC; silty and clayey 

soils as ML, CL, OL, MH, CH, and OH; and highly 

organic soils as PT. Soils exhibiting engineering 

properties of two groups can have a dual classification; 

for example, SP-SM. 

The AASHTO system classifies soils according to 

those properties that affect roadway construction and 

maintenance. In this system, the fraction of a mineral soil 

that is less than 3 inches in diameter is classified in 

one of seven groups from A-1 through A-7 on the basis of 

grain-size distribution, liquid limit, and plasticity index. 

Soils in group A-1 are coarse grained and low in 

content of fines (silt and clay). At the other extreme, soils 

in group A-7 are fine grained. Highly organic soils are 

classified in group A-8 on the basis of visual inspection 

(6). 

Rock fragments larger than 3 inches in diameter are 

indicated as a percentage of the total soil on a dry-weight 

basis. The percentages are estimates determined 

mainly by converting volume percentage in the field to 

weight percentage. 

Percentage (of soil particles) passing designated 

sieves is the percentage of the soil fraction less than 3 

inches in diameter based on an ovendry weight. The 

sieves, numbers 4, 10, 40, and 200 (USA Standard 
Series), have openings of 4.76, 2.00, 0.420, and 0.074 

millimeters, respectively. Estimates are based on 

laboratory tests of soils sampled in the survey area and 

in nearby areas and on estimates made in the field. 

Liquid limit and plasticity index (Atterberg limits) 

indicate the plasticity characteristics of a soil. The 

estimates are based on test data from the survey area 

or from nearby areas and on field examination. 

The estimates of grain-size distribution, liquid limit, 

and plasticity index are rounded to the nearest 5 

percent. Thus, if the ranges of gradation and Atterberg 

limits extend a marginal amount (1 or 2 percentage 

points) across classification boundaries, the 

classification in the marginal zone is omitted in the 

tables. 

Physical and Chemical Properties 

Tables 14a and 14b show estimates of some 

characteristics and features that affect soil behavior. 

These estimates are given for the major layers of each 

soil in the survey area. The estimates are based on field 

observations and on test data for these and similar soils. 

Depth to the upper and lower boundaries of each layer 

is indicated. The range in depth and information on other 

properties of each layer are given for each soil series 

under "Soil Series and Their Morphology." 

Permeability refers to the ability of a soil to transmit 

water or air. The estimates indicate the rate of downward 

movement of water when the soil is saturated. They are 

based on soil characteristics observed in the field, 

particularly structure, porosity, and texture. Permeability 

is considered in the design of soil drainage systems, 

septic tank absorption fields, and construction where the 

rate of water movement under saturated conditions 

affects behavior. 

Available water capacity refers to the quantity of 

water that the soil is capable of storing for use by plants. 

The capacity for water storage is given in inches of water 

per inch of soil for each major soil layer. The capacity 

varies, depending on soil properties that affect the 

retention of water and the depth of the root zone. The 

most important properties are the content of organic 

matter, soil texture, bulk density, and soil structure. 

Available water capacity is an important factor in the 

choice of plants or crops to be grown and in the design 

and management of irrigation systems. Available water 

capacity is not an estimate of the quantity of water 

actually available to plants at any given time. 

Soil reaction is a measure of acidity or alkalinity and is 

expressed as a range in pH values. The range in pH 

of each major horizon is based on many field tests. 

For many soils, values have been verified by laboratory

analyses. Soil reaction is important in selecting crops 

and other plants, in evaluating soil amendments for 

fertility and stabilization, and in determining the risk of 

corrosion. 

Shrink-swell potential is the potential for volume 

change in a soil with a loss or gain in moisture. 

Volume change occurs mainly because of the interaction 

of clay minerals with water and varies with the amount 

and type of clay minerals in the soil. The size of the 

load on the soil and the magnitude of the change in 

soil moisture content influence the amount of swelling of 

soils in place. Laboratory measurements of swelling of 

undisturbed clods were made for many soils. For others, 

swelling was estimated on the basis of the kind and 

amount of clay minerals in the soil and on 

measurements of similar soils. 

If the shrink-swell potential is rated moderate to very 

high, shrinking and swelling can cause damage to 

buildings, roads, and other structures. Special design is 

often needed. 

Shrink-swell potential classes are based on the 

change in length of an unconfined clod as moisture 

content is increased from air-dry to field capacity. The 

change is based on the soil fraction less than 2 

millimeters in diameter. The classes are low, a change 

of less than 3 percent; moderate, 3 to 6 percent; and 

high, more than 6 percent. Very high, more than 9 

percent, is sometimes used. 

Erosion factor K indicates the susceptibility of a soil 

to sheet and rill erosion. Factor K is one of six factors 

used in the Universal Soil Loss Equation (USLE) to 

predict the average rate of soil loss by sheet and rill 

erosion in tons per acre per year. The estimates are 

based primarily on percentage of silt, very fine sand, 

sand, and organic matter (as much as 4 percent) and 

on soil structure and permeability. The estimates are 

modified by the presence of rock fragments. Values of K 

range from 0.02 to 0.69. The higher the value the more 

susceptible the soil is to sheet and rill erosion. 

Erosion factor T is an estimate of the maximum 

average rate of soil erosion by wind or water that can 

occur without affecting crop productivity over a 

sustained period. The rate is in tons per acre per year. 

Organic matter is the plant and animal residue in the 

soil at various stages of decomposition. 

In tables 14a and 14b, the estimated content of 

organic matter is expressed as a percentage, by weight, 

of the soil material that is less than 2 millimeters in 

diameter. 

The content of organic matter of a soil can be 
maintained or increased by returning crop residue to the 

soil. Organic matter affects the available water capacity. 

infiltration rate. and tilth. It is a source of nitrogen and 

other nutrients for crops. 

Soil and Water Features 

Tables 15a and 15b give estimates of various water 

features. The estimates are used in land use planning 

that involves engineering considerations. 

Hydrologic soil groups are used to estimate runoff 

from precipitation. Soils not protected by vegetation are 

assigned to one of four groups. They are grouped 

according to the intake of water when the soils are 

thoroughly wet and receive precipitation from longduration storms. 

The four hydrologic soil groups are: 

Group A. Soils having a high infiltration rate (low 

runoff potential) when thoroughly wet. These consist 

mainly of deep, well drained to excessively drained 

sand or gravelly sand. These soils have a high rate of 

water transmission. 

Group B. Soils having a moderate infiltration rate 

when thoroughly wet. These consist chiefly of 

moderately deep or deep, moderately well drained or 

well drained soils that have moderately fine texture to 

moderately coarse texture. These soils have a 

moderate rate of water transmission. 

Group C. Soils having a slow infiltration rate when 

thoroughly wet. These consist chiefly of soils having a 

layer that impedes the downward movement of water or 

soils of moderately fine texture or fine texture. These soils 

have a slow rate of water transmission. 

Group D. Soils having a very slow infiltration rate 

(high runoff potential) when thoroughly wet. These 

consist chiefly of clay that has high shrink-swell potential. 

soils that have a permanent high water table, soils that 

have a claypan or clay layer at or near the surface, and 

soils that are shallow over nearly impervious material. 

These soils have a very slow rate of water transmission. 

Flooding, the temporary covering of the soil surface by 

flowing water, is caused by overflow from streams, by 

runoff from adjacent slopes, or by inflow from high tides. 

Shallow water standing or flowing for short periods after 

rainfall or snowmelt is not considered to be flooding. 

Standing water in swamps and marshes or in closed 

depressional areas is considered to be ponding. 

Tables 15a and 15b give the frequency and duration 

of flooding and the time of year when flooding is most 

likely to occur. 

Frequency, duration, and probable period of flooding 

are estimated. Frequency is expressed as none, rare, 

occasional, and frequent. None means that flooding is 

not probable, rare that it is unlikely but is possible under 

unusual weather conditions (chance of flooding in any 

year is 0 to 5 percent), occasional that it occurs 

infrequently under normal weather conditions (chance of 

flooding in any year is 5 to 50 percent), and frequent that 

it occurs often under normal weather conditions (chance 

of flooding in any year is more than 50 percent). 

Duration is expressed as very brief (less than 2 days), 

brief (2 to 7 days), long (7 days to 1 month), and very 

long (more than 1 month). The time of year that flooding 

is most likely to occur is expressed in months. 

November-May, for example, means that flooding can 

occur during the period November through May. About 

two-thirds to three-fourths of all flooding occurs during 

the stated period. 

The information on flooding is based on evidence in 

the soil profile, namely thin strata of gravel, sand, silt, or 

clay deposited by floodwater; irregular decrease in 

organic matter content with increasing depth; and 

absence of distinctive horizons, which are characteristic 

of soils that are not subject to flooding. 

Also considered are local information about the extent 

and level of flooding and the relation of each soil on the 

landscape to historic flood. Information on the extent of 

flooding based on soil data is less specific than that 

provided by detailed engineering surveys that delineate 

flood-prone areas at specific flood frequency levels. 

High water table (seasonal) is the highest level of a 

saturated zone in the soil in most years. The depth to a 

seasonal high water table applies to undrained soils. The 

estimates are based mainly on the evidence of a 

saturated zone, namely grayish colors or mottles in the 

soil. Indicated in tables 15a and 15b are the depth to 

the seasonal high water table; the kind of water table 

that is. perched. artesian, or apparent; and the months 

of the year that the water table usually is highest. A water 

table that is seasonally high for less than 1 month is not 

indicated in the table. 

An apparent water table is a thick zone of free water in 

the soil. It is indicated by the level at which water stands 

in an uncased borehole after adequate time is allowed 

for adjustment in the surrounding soil. An artesian water 

table is under hydrostatic head, generally below an 

impermeable layer. When this layer is penetrated, the 

water level rises in an uncased borehole. A perched 

water table is water standing above an unsaturated 

zone. In places an upper, or 
perched, water table is separated from a lower water 

table by a dry zone. 

The two numbers in the column "High water table'' 

indicate the normal range in depth to a saturated zone. 

Depth is given to the nearest half foot. The first numeral in 

the range indicates the highest water level. A plus sign 

preceding the range in depth indicates that the water 

table is above the surface of the soil. "More than 6.0" 

indicates that the water table is below a depth of 6 feet or 

that it is within a depth of 6 feet for less than a month.

Tables 16a and 16b give estimates of various soil 

features. The estimates are used in land use planning 

that involves engineering classification. 

Depth to bedrock is given if bedrock is within a depth of 

5 feet. The depth is based on many soil borings and on 

observations during soil mapping. The rock is specified as 

either soft or hard. If the rock is soft or fractured. 

excavations can be made with trenching machines, 

backhoes. or small rippers. If the rock is hard or massive. 

blasting or special equipment generally is needed for 

excavation. 

Potential frost action is the likelihood of upward or 

lateral expansion of the soil caused by the formation of 

segregated ice lenses (frost heave) and the subsequent 

collapse of the soil and loss of strength on thawing. Frost 

action occurs when moisture moves into the freezing 

zone of the soil. Temperature, texture, density, 

permeability, content of organic matter, and depth to the 

water table are the most important factors considered in 

evaluating the potential for frost action. It is assumed 

that the soil is not insulated by vegetation or snow and is 

not artificially drained. Silty and highly structured clayey 

soils that have a high water table in winter are most 

susceptible to frost action. Well drained, very gravelly, or 

very sandy soils are the least susceptible. Frost heave 

and low soil strength during thawing cause damage 

mainly to pavements and other rigid structures. 

Risk of corrosion pertains to potential soil-induced 

electrochemical or chemical action that dissolves or 

weakens uncoated steel or concrete. The rate of 

corrosion of uncoated steel is related to such factors as 

soil moisture, particle-size distribution, acidity, and 

electrical conductivity of the soil. The rate of corrosion of 

concrete is based mainly on the sulfate and sodium 

content, texture, moisture content, and acidity of the soil. 

Special site examination and design may be needed if 

the combination of factors creates a severe corrosion 

environment. The steel in installations that intersect soil 

boundaries or soil layers is more susceptible to corrosion 

than steel in installations that are entirely within one kind 

of soil or within one soil layer. 

For uncoated steel, the risk of corrosion, expressed 

as low, moderate, or high, is based on soil drainage 

class, total acidity, electrical resistivity near field 

capacity, and electrical conductivity of the saturation 

extract. 

For concrete, the risk of corrosion is also expressed as 

low, moderate, or high. It is based on soil texture, 

acidity, and amount of sulfates in the saturation extract. 
Classification of the Soils

The system of soil classification used by the National 

Cooperative Soil Survey has six categories (18). 

Beginning with the broadest, these categories are the 

order, suborder, great group, subgroup, family, and 

series. Classification is based on soil properties 

observed in the field or inferred from those observations 

or from laboratory measurements. Table 17 shows the 

classification of the soils in the survey area. The 

categories are defined in the following paragraphs. 

ORDER. Ten soil orders are recognized. The 

differences among orders reflect the dominant soilforming processes and the degree of soil formation. 

Each order is identified by a word ending in sol. An 

example is Inceptisol. 

SUBORDER. Each order is divided into suborders 

primarily on the basis of properties that influence soil 

genesis and are important to plant growth or properties 

that reflect the most important variables within the orders. 

The last syllable in the name of a suborder indicates the 

order. An example is Umbrept (Umbr, meaning shade. 

plus ept, from Inceptisol). 

GREAT GROUP. Each suborder is divided into great 

groups on the basis of close similarities in kind. 

arrangement, and degree of development of pedogenic 

horizons; soil moisture and temperature regimes; and 

base status. Each great group is identified by the name 

of a suborder and by a prefix that indicates a property 

of the soil. An example is Haplumbrepts (Hapl, meaning 

minimal horizonation, plus umbrept, the suborder of the 

Inceptisols that has an umbric epidedon). 

SUBGROUP. Each great group has a typic subgroup. 

Other subgroups are intergrades or extragrades. The 

typic is the central concept of the great group; it is not 

necessarily the most extensive. Intergrades are 

transitions to other orders, suborders, or great groups. 

Extragrades have some properties that are not 

representative of the great group but do not indicate 

transitions to any other known kind of soil. Each subgroup 

is identified by one or more adjectives preceding the 

name of the great group. The adjective 

Typic identifies the subgroup that typifies the great 

group. An example is Typic Haplumbrepts. 

FAMILY. Families are established within a subgroup 

on the basis of physical and chemical properties and 

other characteristics that affect management. Mostly the 

properties are those of horizons below plow depth 

where there is much biological activity. Among the 

properties and characteristics considered are particlesize class, mineral content, temperature regime, 

thickness of the root zone, consistence, moisture 

equivalent, slope, and permanent cracks. A family name 

consists of the name of a subgroup preceded by terms 

that indicate soil properties. An example is loamyskeletal, mixed, mesic Typic Haplumbrepts. 

SERIES. The series consists of soils that have similar 

horizons in their profile. The horizons are similar in color, 

texture, structure, reaction, consistence, mineral and 

chemical composition, and arrangement in the profile. 

The texture of the surface layer or of the substratum can 

differ within a series. 

Soil Series and Their Morphology 

In this section, each soil series recognized in the 

survey area is described. The descriptions are arranged 

in alphabetic order. 

Characteristics of the soil and the material in which it 

formed are identified for each series. A pedon, a small 

three-dimensional area of soil, that is typical of the series 

in the survey area is described. The detailed 

description of each soil horizon follows standards in the 

Soil Survey Manual (12). Many of the technical terms 

used in the descriptions are defined in Soil Taxonomy 

(18). Unless otherwise stated, colors in the descriptions 

are for moist soil. Following the pedon description is the 

range of important characteristics of the soils in the 

series. 

The map units of each soil series are described in 

the section "Detailed Soil Map Units." 
Aschoff Series 

The Aschoff series consists of very deep, well drained 

soils on mountains. These soils formed in residuum and 

colluvium derived dominantly from basalt and andesite 

mixed with volcanic ash. Slope is 5 to 65 percent. 

Elevation is 400 to 2,100 feet. The average annual 

precipitation is about 85 inches, the average annual air 

temperature is 50 degrees F, and the average frost-free 

season is 100 to 200 days. 

These soils are medial-skeletal, mesic Andic 

Haplumbrepts. 

Typical pedon of Aschoff very gravelly loam, 30 to 65 

percent slopes, about 3 miles northwest of North 

Bonneville; 200 feet south and 1,200 feet east of the 

northwest corner of sec. 13. T. 2 N., R. 6 E. 

O-2 inches to 0; decomposed needles, leaves, 

and twigs. 

A1-0 to 4 inches; very dark brown (10YR 2!2) very 

gravelly loam, dark grayish brown (10YR 4/2) dry; 

moderate fine granular structure; slightly hard, 

friable, slightly sticky and slightly plastic; weakly 

smeary; many very fine roots and common fine and 

medium roots; many fine irregular pores; 55 percent 

pebbles; moderately acid; clear wavy boundary. 

A2-4 to 12 inches; very dark grayish brown (10YR 3/2) 

very gravelly loam, grayish brown (10YR 5/2) dry; 

moderate fine subangular blocky structure parting to 

weak fine granular; slightly hard, friable, slightly 

sticky and slightly plastic; weakly smeary; many very 

fine roots and common fine and medium roots; many 

fine irregular pores; 55 percent pebbles 2 to 5 

millimeters in diameter; moderately acid; clear wavy 

boundary. 

Bw-12 to 33 inches; dark yellowish brown (10YR 3/4) 

very gravelly loam, brown (10YR 5/3) dry; moderate 

fine and medium subangular blocky structure; slightly 

hard, friable, slightly sticky and slightly plastic; 

weakly smeary; many very fine, common fine, and 

few coarse roots; few fine tubular pores and common 

fine irregular pores; 40 percent pebbles and 15 

percent cobbles; strongly acid; clear smooth 

boundary. 

BC-33 to 47 inches; dark yellowish brown (10YR 4/4) 

very cobbly loam, pale brown (10YR 6/3) dry; weak 

medium subangular blocky structure; slightly hard, 

friable, slightly sticky and slightly plastic; weakly 

smeary; many very fine, common fine, and few 

coarse roots; many fine irregular pores; 20 percent 

cobbles and 30 percent pebbles; strongly acid; clear 

smooth boundary. 

C-47 to 60 inches; dark yellowish brown (10YR 4/4) very 

gravelly loam, very pale brown (10YR 7/4) dry; 

massive; slightly hard, friable, nonsticky and 

nonplastic; common fine and few medium roots; few 

fine irregular pores; 45 percent pebbles and 15 

percent cobbles; strongly acid. 

The umbric epipedon is 10 to 15 inches thick. The 

solum is 40 to 55 inches thick. Reaction is strongly acid or 

moderately acid. The content of rock fragments in the 

control section averages 35 to 55 percent. 

The A horizon has hue of 10YR or 7.5YR, value of 2 

or 3 when moist and 4 or 5 when dry, and chroma of 

2 or 3 when moist or dry. 

The B and BC horizons have hue of 10YR or 7.5YR, 

value of 3 or 4 when moist and 5 or 6 when dry, and 

chroma of 3 or 4 when moist or dry. They are very 

gravelly silt loam, very gravelly loam, or very cobbly loam 

and have 10 to 20 percent cobbles and 15 to 40 

percent pebbles. 

The C horizon has characteristics similar to those of

the B and BC horizons, but it has value of 5 to 7 when 

dry and the content of rock fragments ranges from 50 to 

80 percent, increasing with depth. 

Bandid Series 

The Bandid series consists of very deep, well drained 

soils on back slopes, foot slopes, and toe slopes of 

mountains. These soils formed in stratified, aerially 

deposited volcanic ash and pumice. Slope is 5 to 90 

percent. Elevation is 1,800 to 2,800 feet. The average 

annual precipitation is about 130 inches, the average 

annual air temperature is about 44 degrees F, and the 

average frost-free season is 90 to 110 days. 

These soils are ashy over cindery, frigid Typic 

Vitrandepts. 

Typical pedon of Bandid cindery sandy loam, 5 to 30 

percent slopes, about 1 mile west of HooHoo Lake; 1,450 

feet south and 200 feet east of the northwest corner of 

sec. 16, T. 8 N., R. 6 E. 

O1-2 inches to 0.5 inch; leaves, needles, and twigs. 

O2-0.5 inch to 0; decomposed organic material. 

A1-0 to 3 inches; very dark grayish brown (10YR 3/2) 

cindery sandy loam (volcanic ash and cinders), 

brown (10YR 5/3) dry; weak fine granular structure; 

soft, very friable, nonsticky and nonplastic; many 

very fine and fine roots; many fine irregular pores; 

20 percent pumice fragments; moderately acid; 

abrupt smooth boundary. 

A2-3 to 5 inches; brown (7.5YR 5/2) fine sandy loam 
(volcanic ash), light brownish gray (10YR 6/2) dry; 

weak fine subangular blocky structure; soft, friable, 

nonsticky and nonplastic; many very fine and fine 

roots and common medium roots; many fine 

irregular pores and common fine and medium 

tubular pores; 5 percent pumice fragments; slightly 

acid; abrupt smooth boundary. 

A3-5 to 9 inches; black (10YR 2/1) loamy sand 

(volcanic ash), very dark gray (10YR 3/1) dry; weak 

fine granular structure; soft, very friable, nonsticky 

and nonplastic; many very fine and fine, common 

medium, and few coarse roots, many fine and 

medium irregular pores and common fine and 

medium tubular pores; moderately acid; abrupt 

smooth boundary. 

2Bw1-9 to 15 inches; dark gray (10YR 4,1) gravelly 

fine sandy loam (volcanic ash and cinders), gray 

(10YR 5 1) dry; moderate medium platy structure; 

soft, friable, nonsticky and nonplastic; continuous 

moderately thick lenses of very dark gray (10YR 3/1) 

gravelly sand; many very fine and fine roots and 

common medium roots; many medium tubular pores. 

15 percent pumice fragments and 30 percent 

pebbles; moderately acid; abrupt smooth boundary.

3Bw2-15 to 27 inches; light gray (10YR 7/2) extremely 

cindery sand (cinders and volcanic ash), white 

(10YR 8/1) dry; few medium distinct yellowish brown 

(10YR 5/6) mottles; single grain; loose; common very 

fine roots; many coarse irregular pores; 75 percent 

pumice fragments and 20 percent pebbles; slightly 

acid; abrupt wavy boundary. 

4Bw3-27 to 30 inches; dark gray (10YR 4/1) gravelly 

sand (volcanic ash), gray (10YR 6/1) dry; single grain;

loose; few very fine and fine roots; many coarse 

irregular pores; 10 percent pumice fragments and 20 

percent pebbles; moderately acid; abrupt wavy 

boundary. 

4Bw4-30 to 33 inches; dark grayish brown (10YR 

4/2) sandy loam (volcanic ash), light brownish gray 

(10YR 6/2) dry; weak medium platy structure; soft, 

friable, nonsticky and nonplastic; few fine and 

medium roots; few fine irregular pores and common 

fine and medium tubular pores; 10 percent pumice 

fragments; moderately acid; abrupt smooth 

boundary. 

5Bw5-33 to 41 inches; dark brown (7.5YR 3/2) cindery 

loamy sand (volcanic ash and cinders), brown (7.5YR 

5/4) dry; weak fine subangular blocky structure; soft, 

friable, nonsticky and nonplastic; common very fine 

and fine roots and few medium and coarse roots; 

many fine, medium, and coarse irregular pores and 

few fine and medium tubular 

pores; 25 percent pumice fragments and 15 percent 

scoria; moderately acid; gradual wavy boundary. 

5Bw6-41 to 50 inches; dark gray (10YR 4/1) cindery 

sandy loam (volcanic ash and cinders), gray (10YR 

6/1) dry; common fine distinct strong brown (7.5YR 

5/6) mottles; weak fine subangular blocky structure; 

soft, friable, nonsticky and nonplastic; common fine 

and few medium roots; few fine irregular pores and 

common fine and medium tubular pores; 30 percent 

pumice fragments; slightly acid; gradual wavy 

boundary. 

5Bw7-50 to 60 inches; black (10YR 2/1) loamy sand 

(volcanic ash), dark gray (10YR 4/1) dry; common 

medium distinct strong brown (7.5YR 5/6) mottles; 

weak fine subangular blocky structure; soft, friable, 

nonsticky and nonplastic; few fine roots; many fine, 

medium, and coarse irregular pores; 40 percent soft 

scoria; slightly acid. 

The upper part of the control section is stratified sand, 

loamy fine sand, and gravelly fine sandy loam. It 

averages 5 to 20 percent pumice fragments and 10 to 

30 percent pebbles. The pumice layer is 10 to 40 

inches thick or more and averages 60 to 80 percent 

cinders and 10 to 20 percent pebbles. 

The A horizon has hue of 10YR or 7.5YR, value of 2 

to 5 when moist and 3 to 6 when dry, and chroma of 1

to 3. Where value is 3 or less when moist and 5 or less

when dry, the horizon is less than 10 inches thick. 

The Bw1 horizon is stratified gravelly fine sandy 

loam, sand, and gravelly sand in the upper part. It has 

value of 3 or 4 when moist and 5 or 6 when dry. It 

averages 10 to 30 percent pebbles. 

The 3Bw2 horizon has 60 to 80 percent pumice 

fragments and 5 to 20 percent pebbles. It has stains that 

have hue of 10YR or 7.5YR, value of 5 or 6 when moist 

and 6 to 8 when dry, and chroma of 4 to 8 when 

moist or dry. 

The 4Bw and 5Bw horizons are stratified layers of 

gravelly sand, cindery loamy sand, sandy loam, and 

loamy sand. They have value of 3 to 5 when moist 

and 5 to 7 when dry and chroma of 1 to 4 when moist 

or dry. 

Individual layers have 0 to 15 percent pumice 

fragments, 0 to 15 percent hard pebbles, and 0 to 

50 percent soft scoria. 

Bannel Series 

The Bannel series consists of very deep, well drained 

soils on back slopes and ridges of mountains. These soils 

formed in aerially deposited volcanic ash and 
pumice. Slope is 5 to 90 percent. Elevation is 1,500 to 

2,800 feet. The average annual precipitation is about 

125 inches, the average annual air temperature is about 

44 degrees F, and the average frost-free season is 90 

to 110 days. 

These soils are ashy, frigid Typic Vitrandepts. 

Typical pedon of Bannel cindery sandy loam, 30 to 

65 percent slopes, about 4 miles northeast of Marble 

Mountain; 700 feet north and 2,000 feet west of the 

southeast corner of sec. 34, T. 8 N., R. 6 E. 

0-0.5 inch to 0; leaves., needles., and twigs. 

A1-0 to 1 inch; dark grayish brown (10YR 4/2) 

fine sandy loam (volcanic ash), light gray (10YR 

7/1) dry; weak very fine granular structure; soft, 

very friable, nonsticky and nonplastic; many very 

fine and fine roots; many very fine irregular pores; 

moderately acid; abrupt wavy boundary. 

A2-1 inch to 4 inches. very dark grayish brown (10YR 

312) cindery sandy loam (volcanic ash and cinders), 

grayish brown (10YR 5/2) dry; weak fine granular 

structure; soft, very friable, nonsticky and nonplastic; 

many very fine and fine roots and common medium 

roots; many fine irregular pores; 20 percent pumice 

fragments; slightly acid; abrupt wavy boundary. 

2Bw1-4 to 10 inches; light gray (10YR 7/2) extremely 

cindery sand (cinders and volcanic ash), white (10YR 

8/2) dry; yellowish brown (10YR 5/6) iron stains; 

single grain; loose; many very fine, fine, and medium 

roots; many medium and coarse irregular pores; 70 

percent pumice fragments and 15 percent pebbles. 

slightly acid; abrupt wavy boundary. 

3Bw2-10 to 17 inches, dark brown (7.5YR 4/4) fine 

sandy loam (volcanic ash), pale brown (10YR 6/3) 

dry; weak fine subangular blocky structure; soft, very 

friable, nonsticky and nonplastic; weakly smeary; 

many very fine roots and common fine and medium 

roots; many fine irregular pores; 10 percent pumice 

fragments; slightly acid; abrupt wavy boundary. 

3Bw3-17 to 22 inches; brown (10YR 5/3) cindery 

fine sandy loam (volcanic ash and cinders), pale 

brown (10YR 6/3) dry; many fine distinct dark 

yellowish brown (10YR 3/6) stains; weak fine 

subangular blocky structure; soft, friable, nonsticky 

and nonplastic; weakly smeary; many very fine and 

fine roots; many fine irregular pores; 25 percent 

pumice fragments; neutral; abrupt wavy boundary. 

3Bw4-22 to 41 inches; brown (10YR 5/3) cindery 

loamy sand (volcanic ash and cinders), very pale 

brown (10YR 7/3) dry; many fine distinct brownish 

yellow (10YR 6/8) stains; weak fine and medium 

subangular blocky structure; soft, friable, nonsticky 

and nonplastic; many very fine and fine roots and 

common medium roots; many fine irregular pores 

and few fine tubular pores; 20 percent pumice 

fragments and 5 percent pebbles; neutral; clear 

wavy boundary. 

3BC-41 to 50 inches; dark brown (10YR 4/3) cindery 

loam (volcanic ash and cinders), pale brown (10YR 

6/3) dry; weak fine subangular blocky structure; 

slightly hard, friable, nonsticky and nonplastic; 

weakly smeary; common very fine roots; common 

fine irregular pores; 30 percent pumice fragments; 

neutral; abrupt wavy boundary. 

4C-50 to 60 inches; brownish yellow (10YR 6/8) 

extremely cindery sand (cinders and volcanic ash), 

yellow (10YR 7/8) dry; single grain; loose; many 

coarse irregular pores; 60 percent pumice fragments 

and 20 percent pebbles; slightly acid. 

The control section averages 10 to 30 percent pumice 

fragments and 0 to 15 percent rock fragments. It 

averages 60 percent or more vitric volcanic ash and 

pumice. 

The A horizon has value of 3 to 5 when moist and 

5 to 8 when dry, and it has chroma of 1 to 3 when 

moist or dry. 

The 2Bw horizon has 60 to 80 percent pumice. It 

has stains that have hue of 10YR or 7.5YR and value 

of 4 or 5 when moist. Reaction is moderately acid or 

slightly acid. 

The 3Bw horizon has hue of 10YR or 7.5YR, value of 

3 to 5 when moist and 5 or 7 when dry, and chroma of 

2 to 4 when moist or dry. It has stains that have value 

of 3 to 6 when moist and 4 to 8 when dry and chroma 

of 4 to 8 when moist or dry. The horizon has strata of fine 

sandy loam, sandy loam, and loamy sand. It averages 

10 to 30 percent pumice fragments. It has intermittent 

lenses of soft scoria and coarse sand-sized ash. 

Reaction is moderately acid to neutral. 

The 3BC horizon has hue of 7.5YR or 10YR, value 

of 3 or 4 when moist and 5 or 6 when dry. and chroma 

of 2 or 3 when moist or dry. It is cindery sandy loam 

or cindery loam. Content of pumice fragments ranges 

from 15 to 35 percent. Reaction is slightly acid or neutral.

The 4C horizon has value of 5 or 6 when moist, 

and it has chroma of 6 to 8 when moist or dry. The 

horizon is 60 to 80 percent pumice fragments and 0 to 

20 percent rock fragments. It is extremely cindery sand 

or extremely cindery loamy sand. Reaction is slightly 

acid or neutral. 
Benham Series 

The Benham series consists of very deep, well 

drained soils on back slopes and foot slopes of 

mountains. These soils formed in layers of aerially 

deposited volcanic ash and pumice. Slope is 0 to 65 

percent. Elevation is 1,800 to 2,800 feet. The average 

annual precipitation is about 85 inches. the average 

annual air temperature is about 44 degrees F, and the 

average frost-free season is 90 to 110 days. 

These soils are cindery over medial, frigid Typic 

Vitrandepts. 

Typical pedon of Benham very cindery sandy loam. 0 to 

30 percent slopes, about 3 miles north of Ryan Lake; 

1,200 feet south and 1 ,000 feet east of the northwest 

corner of sec. 4, T. 10 N., R. 6 E. 

O1-1.5 inches to 1 inch; leaves, needles, and twigs. 

O2-1 inch to 0; decomposed organic material. 

E-0 to 2 inches; dark grayish brown (10YR 4/2) very 

cindery sandy loam, light brownish gray (10YR 6/2) 

dry; single grain; loose; many very fine, fine, and 

medium roots and few coarse roots; many coarse 

irregular pores; 55 percent pumice fragments; slightly 

acid; abrupt wavy boundary. 

Bw-2 to 28 inches; light gray (10YR 7/2) extremely cindery 

sand, white (10YR 8/2) dry; many medium distinct 

stains that are yellowish brown (10YR 5/6) and 

brownish yellow (10YR 6/6) when dry; single grain. 

loose; many very fine, fine, and medium roots and 

common coarse roots; many medium and coarse 

irregular pores; 75 percent pumice fragments and 15 

percent pebbles; slightly acid; abrupt smooth 

boundary. 

2Bsb1-28 to 30 inches; very dark grayish brown 

(10YR 3/2) sandy loam, light brownish gray (10YR 

6/2) dry; weak fine subangular blocky structure; soft, 

friable, nonsticky and nonplastic; common very fine, 

fine, and medium roots and few coarse roots; 

common very fine irregular pores and few fine tubular 

pores; slightly acid; abrupt smooth boundary. 

2Bsb2-30 to 34 inches; grayish brown (10YR 5/2) 

sandy loam, light brownish gray (10YR 6/2) dry; many 

fine distinct mottles that are yellowish brown (10YR 

5/6) and brownish yellow (10YR 6/6) when dry; weak 

fine subangular blocky structure; soft, friable, 

nonsticky and nonplastic; many very fine and fine, 

common medium, and few coarse roots; common 

fine irregular and tubular pores; 5 percent 

pumice fragments; slightly acid; abrupt wavy 

boundary. 

2Bsb3-34 to 38 inches; grayish brown (10YR 5/2) fine 

sandy loam, light gray (10YR 7/2) dry; common fine 

distinct mottles that are dark yellowish brown (10YR 

4/6) and brownish yellow (10YR 6/6) when dry; 

weak fine and medium subangular blocky structure; 

soft. very friable, nonsticky and nonplastic; weakly 

smeary; many very fine roots and common fine and 

medium roots; common very fine irregular pores and 

common fine tubular pores; 10 percent pumice 

fragments; moderately acid; abrupt wavy boundary. 

3Bsb4-38 to 43 inches; grayish brown (10YR 5/2) very 

cindery loamy sand, light brownish gray (10YR 6/2) 

dry; common fine distinct mottles that are yellowish 

brown (10YR 5/6) and brownish yellow (10YR 6/6) 

when dry; weak fine subangular blocky structure; soft, 

friable, nonsticky and nonplastic; many very fine and 

common fine roots; many fine and common medium 

irregular pores; 40 percent pumice fragments; 

moderately acid; clear wavy boundary. 

3Bsb5-43 to 60 inches; strong brown (7.5YR 5/6) 

extremely cindery sand, reddish yellow (7.5YR 6/6) 

dry; single grain; loose; common very fine roots and 

few fine and medium roots; many medium and coarse 

irregular pores; 75 percent pumice fragments and 15 

percent pebbles; slightly acid. 

The depth to the buried profile ranges from 20 to 35 

inches. 

The E horizon has hue of 10YR or 2.5Y, value of 4 or 

5 when moist and 6 to 8 when dry, and chroma of 0 to 

2 when moist or dry. Content of pumice fragments 

ranges from 35 to 60 percent. 

The Bw horizon has hue of 10YR or 7.5YR, value of 

6 to 8 when moist and 7 or 8 when dry, and chroma of 

1 to 3 when moist or dry. It has fine or medium stains 

that have hue of 10YR to 5YR, value of 5 to 7 when 

moist and 6 to 8 when dry, and chroma of 4 to 8 when 

moist or dry. Content of pumice fragments ranges from 

45 to 75 percent. 

The 2Bsb horizon has hue of 10YR to 5YR, value of 4 

to 6 when moist and 6 to 8 when dry, and chroma of 1 

to 3 when moist or dry. It has fine or medium mottles 

that have hue of 10YR to 5YR, value of 3 to 6 when moist 

and 5 to 7 when dry, and chroma of 4 to 8 when moist or 

dry. Content of pumice fragments ranges from 5 to 25 

percent. 

The 3Bsb horizon has hue of 10YR to 5YR, value of 5 

to 7 when moist and 6 to 8 when dry, and chroma of 
2 to 8 when moist or dry. It is 40 to 80 percent pumice 

fragments and 0 to 20 percent hard pebbles. 

Bonneville Series 

The Bonneville series consists of very deep, 

somewhat excessively drained soils on river terraces. 

These soils formed in alluvial sand and gravel derived 

dominantly from basalt and andesite. Slope is 0 to 5 

percent. Elevation is 50 to 400 feet. The average 

annual precipitation is about 70 inches, the average 

annual air temperature is about 48 degrees F, and the 

average frost-free season is 185 to 230 days. 

These soils are sandy-skeletal, mixed, mesic Entic 

Xerumbrepts. 

Typical pedon of Bonneville stony sandy loam, about 

0.5 mile west of North Bonneville, 2,140 feet north and 

200 feet east of the southwest corner of sec. 20, T. 2 N.

R. 7 E. 

A1-0 to 6 inches; dark brown (10YR 3/3) stony sandy 

loam, brown (10YR 5/3) dry; weak fine granular 

structure; soft. very friable. slightly sticky and 

nonplastic; many very fine and fine roots and common 

medium roots; many coarse irregular pores; 20 

percent pebbles. 5 percent cobbles, and 5 percent 

stones; moderately acid; clear wavy boundary. 

A2-6 to 12 inches; dark brown (10YR 3/3) extremely 

gravelly coarse sandy loam, brown (10YR 5/3) dry; 

single grain; loose; many very fine and fine roots and 

few medium roots; many coarse irregular pores; 50 

percent pebbles. 10 percent cobbles, and 5 percent 

stones; moderately acid; clear wavy boundary. 

C1-12 to 20 inches; dark brown (10YR 4/3) extremely 

gravelly coarse sand, brown (10YR 5/3) dry; single 

grain; loose; common fine and medium roots; many 

coarse irregular pores; 55 percent pebbles, 10 

percent cobbles, and 5 percent stones; slightly acid; 

clear wavy boundary. 

C2-20 to 30 inches; dark yellowish brown (10YR 4/4) 

extremely gravelly coarse sand, yellowish brown 

(10YR 5/4) dry; single grain; loose; many very fine, 

fine, and medium roots and few coarse roots; many 

coarse irregular pores; 50 percent pebbles, 10 

percent cobbles, and 5 percent stones; slightly acid; 

clear wavy boundary. 

C3-30 to 60 inches; dark yellowish brown (10YR 4/4) 

extremely gravelly coarse sand, light yellowish brown 

(10YR 6/4) dry; single grain; loose; common very fine 

and few fine roots; common coarse 

irregular pores; 60 percent pebbles, 5 percent 

cobbles. and 15 percent stones; slightly acid. 

The umbric epipedon is 10 to 14 inches thick. The 

control section averages 60 to 80 percent rock 

fragments, including 35 to 60 percent pebbles, 5 to 10 

percent cobbles, and 5 to 15 percent stones. From 3 to 5 

percent of the surface is covered with stones. 

The A horizon has value of 2 or 3 when moist and 4 

or 5 when dry, and it has chroma of 2 or 3 when 

moist or dry. 

The C horizon has value of 4 or 5 when moist and 

5 or 6 when dry. It is extremely gravelly loamy sand, 

extremely gravelly coarse sand, or extremely cobbly 

loamy sand. Reaction is moderately acid or slightly acid. 

Cattcreek Series 

The Cattcreek series consists of deep and very deep, 

well drained soils on back slopes and in cirque basins 

on mountains. These soils formed in pumice and volcanic 

ash overlying colluvium derived from andesite. Slope is 

30 to 90 percent. Elevation is 3,000 to 5,300 feet. The 

average annual precipitation is about 110 inches, the 

average annual air temperature is about 39 degrees F, 

and the average frost-free season is 70 to 90 days. 

These soils are cindery over medial-skeletal Typic 

Cryorthods. 

Typical pedon of Cattcreek very cindery loamy sand, 

65 to 90 percent slopes, about 0.5 mile northeast of 

Mount Margaret; 2,000 feet north and 1,000 feet west of 

the southeast corner of sec. 25, T. 10 N., R. 5 E. 

O-1.5 inches to 0; decomposed organic material. 

E-0 to 2 inches; dark grayish brown (10YR 4/2) very 

cindery loamy sand, light brownish gray (10YR 6/2) 

dry; single grain; loose; many fine roots; many fine 

irregular pores; 55 percent pumice fragments; 

moderately acid; abrupt smooth boundary. 

Bs1-2 to 6 inches; dark yellowish brown (10YR 3/4) 

very cindery to ashy sand, light yellowish brown (10YR 

6/4) dry; weak medium subangular blocky structure; 

loose; many very fine, fine, and medium roots and 

common coarse roots; many fine irregular pores; 50 

percent pumice fragments; moderately acid; abrupt 

smooth boundary. 

Bs2-6 to 15 inches; dark brown (7.5YR 4/4) very 

cindery sand, light brown (7.5YR 6/4) dry; single 

grain; loose; many fine and medium roots and few 

coarse roots; many coarse irregular pores; 55 
percent pumice fragments; slightly acid;, clear wavy 

boundary. 

Bs3-15 to 30 inches; strong brown (7.5YR 5/6) 

extremely cindery sand, reddish yellow (7.5YR 7/6) 

dry; single grain; loose; common fine and medium 

roots and few coarse roots; many coarse irregular 

pores; 80 percent pumice fragments; slightly acid; 

abrupt wavy boundary. 

2Eb-30 to 32 inches; brown (7.5YR 5/2) gravelly loam, 

pinkish gray (7.5YR 6/2) dry; weak fine subangular 

blocky structure; soft, very friable, nonsticky and 

nonplastic; weakly smeary; few fine and medium 

roots; few fine and medium irregular pores; 10 

percent pumice fragments and 30 percent pebbles; 

slightly acid; abrupt irregular boundary. 

2Bsb-32 to 54 inches; dark yellowish brown (10YR 

4/4) extremely gravelly loam, light yellowish brown 

(10YR 6/4) dry; weak medium and coarse 

subangular blocky structure, soft, friable, nonsticky 

and nonplastic; weakly smeary; few fine, medium, 

and coarse roots; common fine pores; 50 percent 

pebbles and 25 percent cobbles; slightly acid; abrupt 

irregular boundary. 

3R-54 inches; fractured andesite. 

Depth to bedrock is 40 to 60 inches. Depth to the 

buried layers is 30 to 35 inches. The lower part of the 

control section is 50 to 85 percent rock fragments. 

Reaction of the profile is moderately acid or slightly acid 

throughout. 

Chemawa Series 

The Chemawa series consists of very deep, well 

drained soils on terraces, foot slopes, and back slopes. 

These soils formed in pyroclastic flows consisting 

mostly of volcanic ash. Slope is 2 to 50 percent. 

Elevation is 800 to 1,200 feet. The average annual 

precipitation is about 50 inches, the average annual air 

temperature is about 47 degrees F, and the average 

frost-free season is 110 to 160 days. 

These soils are medial, mesic Andic Xerumbrepts. 

Typical pedon of Chemawa loam, 30 to 50 percent 

slopes, about 3 miles northwest of Underwood; 1 ,100 

feet south and 600 feet west of the northeast corner of 

sec. 19,T. 3N., R. 10 E., W.M. 

O1-1.5 inches to 0.5 inch; litter of needles, 

leaves, and twigs. 

O2-0.5 inch to 0; decomposed organic material. 

Ac1-0 to 4 inches; dark brown (7.5YR 3/3) loam, 

brown (7.5YR 5/3) dry; weak medium granular 

structure; soft, very friable, nonsticky and nonplastic; 

weakly smeary; many very fine and fine roots and 

few coarse roots; many fine irregular pores; 30 

percent shotlike aggregates 2 to 4 millimeters in 

size; neutral; clear smooth boundary. 

Ac2-4 to 14 inches; dark brown (7.5YR 3/3) loam, 

brown (7.5YR 5/3) dry; weak coarse granular structure; 

soft, very friable, nonsticky and nonplastic; weakly 

smeary; many very fine and fine roots, common 

medium roots, and few coarse roots; many very fine 

and common fine irregular pores; 25 percent shotlike 

aggregates 2 to 4 millimeters in size; neutral; clear 

wavy boundary. 

Bw1-14 to 31 inches; dark brown (7.5YR 4/4) loam, 

reddish yellow (7.5YR 6/6) dry; weak fine and 

medium subangular blocky structure; slightly hard, 

friable, nonsticky and nonplastic; weakly smeary; 

common very fine and fine roots and few medium 

roots; common fine irregular pores; 10 percent 

shotlike aggregates 2 to 4 millimeters in size; 

neutral; gradual smooth boundary. 

Bw2-31 to 60 inches; strong brown (7.5YR 5/6) 

loam, reddish yellow (7.5YR 6/6) dry; weak medium 

subangular blocky structure; slightly hard, friable, 

slightly sticky and nonplastic; weakly smeary; 

common fine roots; common fine irregular pores; 5 

percent shotlike aggregates 2 to 4 millimeters in 

size; neutral. 

Content of shotlike aggregates ranges from 10 to 30 

percent in the Ac horizon and decreases with increasing 

depth. The volcanic ash influence extends to a depth 

of 60 inches or more. The umbric epipedon is 10 to 14 

inches thick. Content of rock fragments in the control 

section ranges from 0 to 5 percent. 

The Ac horizon has hue of 5YR to 10YR, value of 2 

or 3 when moist and 4 or 5 when dry, and chroma of 

2 or 3 when moist and 3 or 4 when dry. Reaction is 

slightly acid to neutral. 

The Bw horizon has hue of 5YR to 10YR, value of 

3 to 5 when moist and 5 to 7 when dry, and chroma of 

4 to 6 when moist or dry. Reaction is moderately acid to 

neutral. The horizon is loam or silt loam. 

Cinnamon Series 

The Cinnamon series consists of very deep, well 

drained soils on terraces, foot slopes, and back slopes of 

mountains. These soils formed in pyroclastic flows of 

volcanic ash. Slope is 2 to 90 percent. Elevation is 1,600 

to 2,800 feet. The average annual precipitation is about 

125 inches, the average annual air temperature is 
about 44 degrees F. and the average frost-free season 

is 90 to 110 days. 

These soils are ashy over medial, frigid Typic 

Vitrandepts. 

Typical pedon of Cinnamon sandy loam, 30 to 65 

percent slopes, on Forest Service Road N816, about 

5.5 miles northeast of Cougar; 2,000 feet south and 

2,600 feet east of the northwest corner of sec. 8, T. 7 N. 

R. 5 E. 

O1-4 to 3 inches; needles, leaves, and twigs. 

O2-3 inches to 0; decomposed organic matter. 

A-0 to 3 inches; very dark grayish brown (10YR 3/2) 

sandy loam (volcanic ash), dark brown (10YR 4/3) 

dry; weak fine granular structure; soft, very friable, 

slightly sticky and slightly plastic; many very fine and 

fine roots and few medium roots; many fine irregular 

pores; slightly acid; clear wavy boundary. 

Bw 1- 3 to 11 inches; dark yellowish brown (10YR 3i4) 

loamy sand (volcanic ash), yellowish brown (10YR 

5/4) dry; weak fine subangular blocky structure; soft. 

very friable, nonsticky and nonplastic; many very fine 

and fine roots and common medium roots; many fine 

irregular pores and common fine tubular pores; 

neutral; gradual wavy boundary. 

Bw2-11 to 22 inches; dark brown (10YR 4/3) loamy 

sand (volcanic ash), light yellowish brown (10YR 

6/4) dry; weak fine subangular blocky structure; 

soft, very friable, nonsticky and nonplastic;, many 

very fine, fine, and medium roots and few coarse 

roots; many fine irregular pores and common fine 

tubular pores; slightly acid; abrupt wavy boundary. 

2Bwb1-22 to 35 inches; dark yellowish brown (10YR 

4/4) sandy loam, light yellowish brown (10YR 6/4) 

dry; moderate medium subangular blocky structure; 

slightly hard, friable, slightly sticky and nonplastic; 

weakly smeary; many fine and medium roots; many 

fine irregular pores and few fine tubular pores; 20 

percent soft weathered pumice fragments and 5 

percent hard pebbles; moderately acid; clear wavy 

boundary. 

2Bwb2-35 to 60 inches; dark yellowish brown (10YR 

4/4) sandy loam, very pale brown (10YR 7/4) dry; 

moderate medium and coarse subangular blocky 

structure; very hard, firm, slightly sticky and 

nonplastic; weakly smeary; common fine roots; 

many fine irregular pores and few fine tubular pores; 

30 percent soft weathered pumice fragments and 10 

percent hard pebbles; slightly acid. 

The ashy mantle is 20 to 30 inches thick and 

has more than 60 percent volcanic ash and 

cinders. 

The A horizon has hue of 7.5YR or 10YR, value of 2 or 3 

when moist and 4 to 6 when dry, and chroma of 2 or 3 

when moist or dry. Reaction is slightly acid or neutral. 

The Bw horizon has value of 3 or 4 when moist 

and 5 or 6 when dry, and it has chroma of 3 or 4 

when moist or dry. Texture is loamy sand or sandy 

loam. Reaction is slightly acid or neutral. 

The 2Bwb horizon has value of 4 or 5 when moist and 

5 to 7 when dry, and it has chroma of 4 to 6 when 

moist or dry. The horizon is sandy loam or loam and 

has 5 to 15 percent andesitic pebbles and 20 to 50 

percent soft weathered pumice fragments. Reaction is 

moderately acid or slightly acid. Below a depth of 40 

inches in some pedons, the 2Bwb horizon is compacted 

or weakly cemented and is very hard or hard when 

dry. 

Colter Series 

The Colter series consists of very deep, well drained 

soils on back slopes and foot slopes of mountains. These 

soils formed in layers of aerially deposited volcanic ash 

and pumice. Slope is 0 to 90 percent. Elevation is 

2,800 to 5,400 feet. The average annual precipitation 

is about 90 inches, the average annual air temperature 

is about 39 degrees F, and the average frost-free 

season is 75 to 95 days. 

These soils are cindery over medial Entic 

Cryandepts. 

Typical pedon of Colter cindery sandy loam, 30 to 65 

percent slopes, about 1 mile west of Ryan Lake; 1,300 

feet south and 1,700 feet east of the northwest corner 

of sec. 17,T. 10N., R. 6E. 

O1-2 inches to 1 inch; leaves, twigs, and needles. 

O2-1 inch to 0; decomposed organic material. 

E-0 to 2 inches; dark grayish brown (10YR 4/2) 

sandy loam, gray (10YR 6/1) dry; weak fine 

granular structure; soft, very friable, nonsticky and 

nonplastic; many very fine roots; many very fine 

irregular pores; moderately acid; abrupt smooth 

boundary. 

Bw-2 to 6 inches; very dark grayish brown (10YR 3/2) 

cindery sandy loam, grayish brown (10YR 5/2) dry; 

few fine prominent dark brown (7.5YR 4/4) mottles; 

weak fine granular structure; soft, friable, nonsticky 

and nonplastic; many very fine and common fine 

roots; many fine irregular pores; 20 percent pumice 

fragments; moderately acid; abrupt smooth 

boundary. 

C-6 to 33 inches; white (10YR 8/1) extremely 

cindery sand, white (10YR 8/1) dry; dark yellowish 

brown 
(10YR 4/4) iron stains; single grain; loose; many very 

fine and fine roots and common medium roots; many 

coarse irregular pores; 65 percent pumice fragments 

and 15 percent pebbles; slightly acid; abrupt wavy 

boundary. 

2Bwb1-33 to 37 inches; very dark grayish brown 

(10YR 3/2) sandy loam, grayish brown (10YR 5/2) 

dry; weak fine subangular blocky structure; soft, 

very friable, nonsticky and nonplastic; weakly 

smeary; many very fine and fine roots; many fine 

irregular pores and common fine tubular pores; 

slightly acid; abrupt wavy boundary. 

2Bwb2-37 to 48 inches; yellowish brown (10YR 5/4) 

sandy loam, light yellowish brown (10YR 6,/4) dry; 

common fine distinct mottles that are gray (10YR 

6/1) and light gray (10YR 7/1) when dry; weak fine 

subangular blocky structure; soft, friable, nonsticky 

and nonplastic; weakly smeary; many very fine and 

fine roots and few medium roots; common very fine 

and fine irregular pores and few fine tubular pores; 

5 percent pumice fragments; slightly acid; gradual 

wavy boundary. 

2Bwb3-48 to 54 inches; gray (10YR 5/1) cindery loamy 

sand, light gray (10YR 7/1) dry; common medium 

distinct mottles that are brown (10YR 5/3) and pale 

brown (10YR 6/3) when dry; weak fine subangular 

blocky structure; soft, friable, nonsticky and 

nonplastic; common very fine and fine roots; many 

fine irregular pores; 30 percent pumice fragments; 

slightly acid; abrupt wavy boundary. 

3Bwb4-54 to 60 inches; strong brown (7.5YR 5/6) 

extremely cindery sand, reddish yellow (7.5YR 6/6) 

dry; single grain; loose; few fine roots; many coarse 

irregular pores; 60 percent pumice fragments and 

15 percent pebbles; slightly acid. 

The A horizon has hue of 10YR or 2.5Y, value of 4 

or 5 when moist and 6 to 8 when dry, and chroma of 

0 to 2 when moist or dry. 

The Bw horizon has hue of 10YR or 7.5YR, value of 3 

to 5 when moist and 5 to 7 when dry, and chroma of 2 

or 3 when moist or dry. 

The C horizon has hue of 10YR or 7.5YR, value of 7 or 

8 when moist or dry, and chroma of 1 to 6 when moist 

or dry. Content of pebble-sized pumice fragments ranges 

from 45 to 65 percent and content of hard pebbles ranges 

from 5 to 20 percent. 

The 2Bwb horizon has hue of 10YR to 5YR, value of 

3 to 5 when moist and 5 to 8 when dry, and chroma of 

1 to 4 when moist or dry. It has fine or medium mottles 

that have hue of 10YR to 5YR, value of 3 to 6 when 

moist and 6 or 7 when dry, and chroma of 1 to 8 

when 

moist or dry. Content of pebble-sized pumice fragments 

ranges from 0 to 30 percent. 

The 3Bwb horizon has hue of 7.5YR or 5YR, value 

of 5 to 7 when moist and 6 to 8 when dry, and chroma 

of 6 to 8 when moist or dry. Content of pumice fragments 

ranges from 60 to 80 percent, and content of pebbles 

ranges from 10 to 15 percent. 

Dougan Series 

The Dougan series consists of moderately deep, well 

drained soils on back slopes and ridges of mountains. 

These soils formed in colluvium derived from andesite 

and granodiorite mixed with volcanic ash. Slope is 5 to 

65 percent. Elevation is 2,000 to 3,000 feet. The 

average annual precipitation is about 100 inches, the 

average annual air temperature is about 43 degrees F, 

and the frost-free season is 90 to 130 days. 

These soils are medial-skeletal, frigid Andic 

Haplumbrepts. 

Typical pedon of Dougan very gravelly loam, 30 to 65 

percent slopes, about 5 miles southeast of Silver Star 

Mountain; 600 feet south and 900 feet west of the 

northeast corner of sec. 27, T. 3 N., R. 5 E. 

O-1 inch to 0; leaves, twigs, and needles. 

A-0 to 11 inches; very dark grayish brown (10YR 3/2) 

very gravelly loam, grayish brown (10YR 5/2) dry; 

weak fine granular structure; slightly hard, friable, 

nonsticky and nonplastic; weakly smeary; common 

very fine, fine, and medium roots; many fine irregular 

pores; 40 percent pebbles and 10 percent cobbles; 

strongly acid; clear wavy boundary. 

Bw-11 to 24 inches; light olive brown (2.5Y 5/3) very 

gravelly loam, light yellowish brown (2.5Y 6/3) dry; 

moderate medium subangular blocky structure; 

slightly hard, friable, slightly sticky and slightly 

plastic; few very fine and fine roots; common fine 

irregular and tubular pores; 30 percent pebbles, 10 

percent cobbles, and 10 percent saprolitic 

fragments; strongly acid; clear smooth boundary. 

C-24 to 39 inches; light yellowish brown (2.5Y 6/3) 

extremely gravelly loam, pale yellow (2.5Y 7/3) dry; 

weak fine granular structure; slightly hard, friable, 

slightly sticky and slightly plastic; few fine roots; few 

fine irregular pores; 55 percent pebbles, 15 percent 

cobbles, and 15 percent saprolitic fragments; very 

strongly acid; clear wavy boundary. 

R-39 inches; fractured andesite. 

 Depth to bedrock is 30 to 40 inches. The control section 

averages 45 to 70 percent pebbles and cobbles 
and 10 to 20 percent saprolitic fragments. The umbric 

epipedon is 10 to 12 inches thick and is influenced by 

volcanic ash. 

The A horizon has value of 2 or 3 when moist and 4 

or 5 when dry. and it has chroma of 10r 2 when moist 

and 1 to 3 when dry. The horizon has 30 to 40 percent 

pebbles and 5 to 10 percent cobbles. Reaction is strongly 

acid or moderately acid. 

The B horizon has hue of 10YR or 2.5Y, value of 4 

or 5 when moist and 5 or 6 when dry, and chroma of 3 or 

4 when moist or dry. It has 30 to 40 percent pebbles, 5 

to 20 percent cobbles, and 5 to 30 percent saprolitic 

fragments. It is very gravelly loam, very gravelly silt loam, 

very cobbly loam, or very cobbly silt loam. Reaction is 

very strongly acid or strongly acid. 

The C horizon has hue of 10YR or 2.5Y, value of 5 

or 6 when moist and 6 or 7 when dry, and chroma of 3 

to 5 when moist or dry. It has 45 to 55 percent pebbles, 

15 to 30 percent cobbles, and 5 to 15 percent saprolitic 

fragments. It is extremely gravelly loam or extremely 

cobbly loam. Reaction is very strongly acid or strongly 

acid. 

Elkprairie Series 

The Elkprairie series consists of very deep, well 

drained soils on broad mountaintops and hillsides. 

These soils formed in volcanic ash and pumice over 

weathered volcanic ash and pumice. Slope is 5 to 30 

percent. Elevation is 2,600 to 4,700 feet. The average 

annual precipitation is about 130 inches, the average 

annual air temperature is about 40 degrees F, and the 

average frost-free season is 75 to 95 days. 

These soils are ashy over medial Typic Cryorthents. 

Typical pedon of Elkprairie loamy sand, 5 to 30 percent 

slopes, about 1 mile southeast of Coldwater Lake. 700 

feet east and 300 feet north of the southwest corner of 

sec. 32. T. 10 N., R. 5 E. 

C1-0 to 6 inches; dark gray (5Y 4/1) loamy sand, 

light gray (5Y 6/1) dry; massive; soft, friable, 

nonsticky and nonplastic. very strongly acid; abrupt 

smooth boundary. 

C2-6 to 11 inches; dark gray (5Y 4/1) cindery 

sand, light gray (5Y 6/1) dry; single grain; loose; 20 

percent pumice fragments; very strongly acid; 

gradual wavy boundary. 

C3-11 to 17 inches; dark gray (5Y 4/1) cindery 

coarse sand. olive gray (5Y 5/2) dry; single grain; 20 

percent pumice fragments; very strongly acid; gradual 

wavy boundary. 

C4-17 to 23 inches; very dark gray (10YR 3/1) very 

cindery loamy sand, gray (10YR 5/1) dry; single 

grain; loose; 30 percent fine pumice fragments and 

10 percent pebbles; very strongly acid; abrupt 

smooth boundary. 

2Ab-23 to 26 inches; very dark brown (10YR 2/2) fine 

sandy loam, very dark grayish brown (10YR 3/2) dry; 

weak fine subangular blocky structure; soft, friable, 

nonsticky and nonplastic; common very fine and fine 

tubular pores; extremely acid; gradual wavy 

boundary. 

2Bwb1-26 to 29 inches; brown (10YR 4/3) cindery 

loam, yellowish brown (10YR 5/6) dry; weak fine 

subangular blocky structure; soft, friable, nonsticky 

and nonplastic; weakly smeary; common very fine 

and fine tubular pores; 20 percent pumice 

fragments; very strongly acid; gradual wavy 

boundary. 

2Bwb2-29 to 36 inches; reddish yellow (7.5YR 6/8) 

cindery loam, yellow (10YR 7/8) dry; common medium 

distinct yellowish brown (10YR 5/4) mottles, yellowish 

brown (10YR 5/6) dry; weak medium subangular 

blocky structure; soft, friable, slightly sticky and 

slightly plastic; 20 percent pumice fragments; very 

strongly acid; gradual wavy boundary. 

2Bwb3-36 to 60 inches; yellowish brown (10YR 5/8) 

loam, yellow (10YR 8/8) dry; common medium 

distinct gray (5Y 5/1) mottles, light gray (5Y 7/1) 

dry; weak medium subangular blocky structure; soft, 

friable, slightly sticky and slightly plastic; weakly 

smeary; 10 percent pumice fragments; moderately 

acid. 

Depth to the buried soil ranges from 20 to 35 inches. 

It is very strongly acid to moderately acid. Depth to 

medial material ranges from 36 to 50 inches. 

The C horizon has hue of 2.5Y or 5Y, value of 3 or 

4 when moist and 5 to 7 when dry, and chroma of 1or 

2 when moist or dry. It is loamy sand to sand and is 

10 to 30 percent pumice fragments. 

 The 2Ab horizon has value of 2 or 3 when moist 

and 3 or 4 when dry, and it has chroma of 1 or 2 

when moist or dry. It is fine sandy loam or sandy 

loam. 

The 2Bwb horizon has hue of 7.5YR or 10YR, value of 

4 to 6 when moist and 5 to 8 when dry, and chroma 

of 3 to 8 when moist or dry. Mottles are none to 

common and have hue of 10YR to 5Y, value of 5 to 7 

when moist or dry, and chroma of 1 to 6 when moist 

or dry. Content of pumice fragments ranges from 10 to 

25 percent. 
Forsyth Series 

The Forsyth series consists of very deep, somewhat 

excessively drained soils on upland terraces and terrace 

escarpments. These soils formed in pyroclastic flow and 

lahar material with a thin mantle of aerially deposited 

volcanic ash and pumice. Slope is 0 to 120 percent. 

Elevation is 1,600 to 2,800 feet. The average annual 

precipitation is about 130 inches, the average annual 

air temperature is about 43 degrees F, and the average 

frost-free season is 90 to 110 days. 

These soils are sandy-skeletal, mixed, frigid Andeptic 

Udorthents. 

Typical pedon of Forsyth cobbly loamy sand, 0 to 30 

percent slopes, about 2 miles northeast of Marble 

Mountain; 600 feet north and 1,800 feet east of the 

southwest corner of sec. 34, T. 8 N., R. 5 E. 

O-0.5 inch to 0; decomposed organic material. 

E-0 to 3 inches; very dark grayish brown (10YR 3/2) 

cobbly loamy sand, light brownish gray (10YR 6/2) 

dry; weak fine granular structure; soft, friable, 

nonsticky and nonplastic; many very fine and fine 

roots and few medium roots; many fine irregular 

pores; 10 percent pumice fragments, 5 percent 

pebbles, and 15 percent cobbles; moderately acid; 

clear wavy boundary. 

Bw-3 to 8 inches; dark yellowish brown (10YR 3/4) 

gravelly sandy loam, pale brown (10YR 6/3) dry; 

weak fine granular structure; soft, friable, nonsticky 

and nonplastic; weakly smeary; many very fine and 

fine roots and common medium roots; many fine 

irregular pores; 15 percent pumice fragments. 20 

percent pebbles, and 5 percent cobbles; slightly 

acid; abrupt wavy boundary. 

2C1-8 to 19 inches; dark brown (10YR 4/3) extremely 

cobbly sand, very pale brown (10YR 7/3) dry; 

massive; loose; many very fine and few fine roots; 

many fine and medium irregular pores; 40 percent 

pebbles and 25 percent cobbles; slightly acid; abrupt 

wavy boundary. 

2C2-19 to 60 inches; dark gray (10YR 4/1) extremely 

stony sand, light gray (10YR 7/1) dry; massive; loose; 

many medium and coarse pores; 40 percent pebbles, 

15 percent cobbles, and 20 percent stones; slightly 

acid. 

The control section has 50 to 85 percent rock 

fragments. Reaction is moderately acid to neutral 

throughout. 

The E horizon has value of 5 to 7 when dry and 

chroma of 1 or 2 when moist or dry. It has 5 to 10 

percent pebbles, 15 to 25 percent cobbles, and 0 to 

10 percent stones. 

The Bw horizon has value of 5 or 6 when dry and 

chroma of 2 to 4 when moist or dry. It has 20 to 40 

percent pebbles, 5 to 30 percent cobbles, and 0 to 15 

percent pumice fragments. 

The 2C horizon has value of 3 or 4 when moist and 

6 or 7 when dry. and it has chroma of 1 to 3 when 

moist or dry. 

Fortran Series 

The Fortran series consists of very deep, somewhat 

excessively drained soils on terrace escarpments. These 

soils formed in pyroclastic flow and lahar material with a 

thin mantle of volcanic ash and pumice. Slope is 65 to 

120 percent. Elevation is 800 to 1,800 feet. The 

average annual precipitation is about 100 inches, the 

average annual air temperature is about 52 degrees F, 

and the average frost-free season is 115 to 135 days. 

These soils are sandy-skeletal, mixed, mesic Typic 

Vitrandepts. 

Typical pedon of Fortran cindery loamy sand, 65 to 

120 percent slopes. about 0.5 mile east of Swift Creek 

Dam; 2,000 feet north and 400 feet east of the southwest 

corner of sec. 21, T. 7 N., R. 5 E. 

O1-3 inches to 1 inch; leaves, needles, and twigs. 

O2-1 inch to 0; decomposed organic material. 

A-0 to 3 inches; dark brown (10YR 3/3) cindery 

loamy sand, brown (10YR 5/3) dry; weak fine 

granular structure; soft, very friable, nonsticky and 

nonplastic; many very fine, fine, medium, and 

coarse roots; many very fine and fine irregular pores; 

15 percent pumice fragments and 5 percent 

pebbles; moderately acid; clear wavy boundary. 

Bw-3 to 11 inches; dark yellowish brown (10YR 4/4) 

cindery sandy loam. light yellowish brown (10YR 

6/4) dry; weak fine subangular blocky structure; soft. 

very friable, nonsticky and nonplastic; many very 

fine and fine roots and common medium and 

coarse roots; many fine irregular pores; 15 percent 

pumice fragments and 5 percent pebbles; 

moderately acid; clear wavy boundary. 

BC-11 to 17 inches; dark brown (10YR 4/3) very 

gravelly sandy loam, brown (10YR 5/3) dry; weak 

very fine subangular blocky structure; soft, very 

friable, nonsticky and nonplastic; common very fine, 

fine. and medium roots; many very fine irregular 
pores; 35 percent pebbles. 5 percent cobbles, and 5 

percent pumice fragments; slightly acid; abrupt wavy 

boundary. 

2C-17 to 60 inches; gray (5Y 5/1) extremely gravelly 

loamy sand, light gray (5Y 7/1) dry; massive; hard, 

firm, nonsticky and nonplastic; few fine roots; few 

fine tubular pores; 55 percent pebbles, 10 percent 

cobbles, and 5 percent stones; slightly acid. 

Depth to the 2C horizon ranges from 15 to 25 inches. 

 The A horizon has value of 2 or 3 when moist and 

4 or 5 when dry, and it has chroma of 2 or 3 when 

moist or dry. It has 15 to 25 percent pumice fragments 

and 0 to 5 percent pebbles. 

The BC horizon has value of 3 or 4 when moist and 5 

or 6 when dry, and it has chroma of 3 or 4 when moist or 

dry. 

The 2C horizon has hue of 10YR to 5Y. It has 40 to 

60 percent pebbles, 5 to 15 percent cobbles, and 0 to 

10 percent stones. 

Hatchet Series 

The Hatchet series consists of moderately deep and 

deep. well drained soils on back slopes and shoulder 

slopes of mountains. These soils formed in residuum 

and colluvium derived dominantly from basalt and 

andesite mixed with volcanic ash. Slope is 30 to 90 

percent. Elevation is 2,800 to 4,500 feet. The average 

annual precipitation is about 105 inches, the average 

annual air temperature is about 39 degrees F, and the 

average frost-free season is 75 to 95 days. 

These soils are medial-skeletal Typic Cryorthods. 

Typical pedon of Hatchet gravelly sandy loam, 65 to 

90 percent slopes, about 0.5 mile south of Hanaford 

Lake; 2,500 feet south and 1,900 feet east of the 

northwest corner of sec. 30. T. 10 N., R. 5 E. 

O-0.5 inch to 0; decomposed organic material. 

A-0 to 3 inches; very dark grayish brown (10YR 3/2) 

gravelly sandy loam, dark grayish brown (10YR 4/2) 

dry; weak very fine granular structure; soft, very 

friable, nonsticky and nonplastic; many very fine roots 

and common medium and coarse roots; many very 

fine irregular pores; 20 percent pebbles; moderately 

acid; abrupt smooth boundary. 

Bs1-3 to 6 inches; dark brown (7.5YR 3/4) gravelly 

sandy loam, brown (7.5YR 5/4) dry; weak fine 

granular structure and weak fine subangular blocky; 

soft, very friable, nonsticky and nonplastic; weakly 

smeary; many very fine roots, common fine roots, 

and few medium roots; many fine irregular pores; 

15 percent pebbles and 5 percent cobbles; 

moderately acid; clear wavy boundary. 

Bs2-6 to 10 inches; dark brown (7.5YR 3/4) gravelly 

fine sandy loam, dark brown (7.5YR 4/4) dry; weak 

fine subangular blocky structure; soft, very friable, 

nonsticky and nonplastic; weakly smeary; many very 

fine roots and few medium roots; many fine irregular 

pores; 10 percent pebbles and 5 percent cobbles; 

moderately acid; abrupt wavy boundary. 

Bs3-10 to 20 inches; dark yellowish brown (10YR 3/4) 

extremely cobbly loam, yellowish brown (10YR 5/4) 

dry; weak fine subangular blocky structure; soft, 

friable, slightly sticky and slightly plastic; weakly 

smeary; many very fine and fine roots and common 

medium roots; many fine and medium irregular pores 

and few fine tubular pores; 30 percent pebbles and 

40 percent cobbles; moderately acid; abrupt wavy 

boundary. 

C-20 to 28 inches; yellowish brown (10YR 5/4) 

extremely cobbly clay loam, light yellowish brown 

(10YR 6/4) dry; massive; slightly hard, friable, slightly 

sticky and plastic; common fine and medium roots;. 

many coarse irregular pores; 30 percent pebbles and 

45 percent cobbles; slightly acid; clear wavy 

boundary. 

R-28 inches; fractured andesite. 

Depth to the lithic contact is 20 to 40 inches. The 

control section averages 60 to 90 percent pebbles and 

cobbles. 

The A horizon has hue of 10YR or 2.5YR, value of 3 

to 4 when moist and 4 to 6 when dry, and chroma of 2 

or 3 when moist or dry. 

The Bs1 and Bs2 horizons have hue of 7.5YR or 

5YR, value of 3 or 4 when moist and 5 or 6 when dry, 

and chroma of 4 to 6 when moist or dry. They have 

10 to 20 percent pebbles and 5 to 15 percent cobbles. 

The Bs3 horizon has hue of 10YR to 5YR, value of 

4 or 5 when moist and 6 or 7 when dry, and chroma of 

4 to 6 when moist or dry. It has 20 to 30 percent 

pebbles and 40 to 50 percent cobbles. 

The C horizon has hue of 10YR or 7.5YR, value of 4 

or 5 when moist and 6 or 7 when dry, and chroma of 3 

or 4 when moist or dry. It has 30 to 45 percent 

pebbles and 40 to 45 percent cobbles. It is extremely 

cobbly sandy loam, extremely cobbly loam, or extremely 

cobbly clay loam. 

Hesson Series 

The Hesson series consists of very deep, well 

drained soils on terraces and terrace escarpments. 
These soils formed in mixed alluvium derived dominantly 

from quartzite and basic igneous rock. Slope is 5 to 40 

percent. Elevation is 400 to 1,000 feet. The average 

annual precipitation is about 70 inches, the average 

annual air temperature is about 50 degrees F, and the 

average frost-free season is 160 to 220 days. 

These soils are clayey, kaolinitic, mesic Xeric 

Palohumults. 

Typical pedon of Hesson clay loam, 5 to 15 percent 

slopes, about 3 miles east of Washougal; 100 feet south 

and 300 feet west of the northeast corner of sec. 7, T. 1 N. 

R. 5 E. 

A-0 to 8 inches; dark brown (7.5YR 3/2) clay loam. 

dark brown (7.5YR 4/2) dry; moderate medium 

granular structure; slightly hard, friable, slightly 

sticky and slightly plastic, many very fine and fine 

roots; many very fine. fine, and medium irregular 

pores; moderately acid; abrupt smooth boundary. 

AB-8 to 19 inches; dark brown (7.5YR 3/3) clay loam, 

brown (7.5YR 5'4) dry; weak fine and medium 

subangular blocky structure; slightly hard, friable, 

slightly sticky and slightly plastic, common very fine 

roots, few medium irregular pores and common very 

fine and fine irregular pores; moderately acid; clear 

wavy boundary. 

Bt1-19 to 27 inches; dark reddish brown (5YR 3/4) 

clay loam, yellowish red (5YR 5/6) dry; moderate 

fine and medium subangular blocky structure; 

slightly hard, friable, sticky and slightly plastic; few 

very fine roots; common very fine irregular pores and 

few fine tubular pores; few thin clay films on faces of 

peds and in some pores; strongly acid; clear wavy 

boundary. 

Bt2-27 to 47 inches; dark reddish brown (5YR 3/4) 

clay loam, yellowish red (5YR 5/6) dry; strong 

medium subangular blocky structure; hard, firm, 

sticky and plastic; few very fine roots; few fine 

irregular pores and common very fine and fine 

tubular pores; common moderately thick clay films 

on faces of peds and in pores; strongly acid; clear 

smooth boundary. 

Bt3-47 to 60 inches; dark reddish brown (5YR 3/4) 

clay, yellowish red (5YR 5/6) dry, strong medium 

subangular blocky structure; hard, firm, very sticky 

and plastic; few very fine roots; few fine tubular pores; 

many moderately thick clay films on faces of peds 

and in pores; strongly acid. 

The upper 20 inches of the Bt horizon is 35 to 

50 percent clay. 

The A horizon has hue of 7.5YR or 10YR, value of 2 

or 3 when moist and 4 or 5 when dry, and chroma of 

2 or 3 when moist. Reaction is strongly acid or 

moderately acid. 

The Bt horizon has hue of 5YR or 7.5YR, value of

3 or 4 when moist and 4 or 5 when dry, and chroma 

of 4 to 6 when moist or dry. It is silty clay loam, clay 

loam, or clay. 

Hoffstadt Series 

The Hoffstadt series consists of deep, well drained 

soils on back slopes and foot slopes of mountains. 

These soils formed in colluvium derived from basic 

igneous rock mixed with volcanic ash. Slope is 2 to 65 

percent. Elevation is 1,800 to 2,600 feet. The average 

annual precipitation is about 80 inches, and average 

annual air temperature is about 43 degrees F, and the 

average frost-free season is 150 to 180 days. 

These soils are medial-skeletal, frigid Andic 

Dystrochrepts. 

Typical pedon of Hoffstadt very gravelly sandy loam, 

30 to 65 percent slopes, about 2 miles north of 

Tradedollar Lake; 1,000 feet south and 2,980 feet west 

of the northeast corner of sec. 6. T. 10 N., R. 5 E. 

O-2 inches to 0; partially decomposed organic litter. 

A-0 to 4 inches; dark brown (7.5YR 3/2) very gravelly 

sandy loam, brown (7.5YR 5/2) dry; weak fine 

granular structure; soft. very friable, slightly sticky 

and nonplastic; weakly smeary; many very fine roots 

and common fine and medium roots; many fine 

irregular pores; 30 percent pebbles, 10 percent 

cobbles. and 5 percent pumice fragments; 

moderately acid; clear wavy boundary. 

Bw1-4 to 22 inches; dark brown (7.5YR 4/4) very 

cobbly sandy loam, light brown (7.5YR 6/4) dry; 

weak fine subangular blocky structure; soft, very 

friable, slightly sticky and slightly plastic; weakly 

smeary; common fine, medium, and coarse roots; 

many fine irregular pores and common fine and 

medium tubular pores; 20 percent pebbles, 15 

percent cobbles, and 5 percent pumice fragments; 

moderately acid; clear wavy boundary. 

Bw2-22 to 36 inches; dark brown (7.5YR 4/4) very 

cobbly sandy loam, light brown (7.5YR 6/4) dry; weak 

fine and medium subangular blocky structure; soft, 

friable, slightly sticky and slightly plastic; weakly 

smeary; few fine and medium roots; common fine 

irregular pores and few fine tubular pores; 20 percent 

pebbles, 25 percent cobbles, and 5 percent pumice 

fragments; slightly acid; clear wavy boundary. 
2C-36 to 55 inches; dark brown (7.5YR 4/4) extremely 

stony sandy loam, pink (7.5YR 7/4) dry; massive; soft, 

very friable, slightly sticky and slightly plastic; weakly 

smeary; few fine roots; common fine irregular pores; 

10 percent pebbles, 15 percent cobbles. 40 percent 

stones, and 5 percent pumice fragments; moderately 

acid; abrupt irregular boundary. 

R-55 inches; fractured basalt. 

Depth to bedrock ranges from 40 to 60 inches. The 

control section averages 40 to 70 percent hard rock 

fragments. Reaction is moderately acid or slightly acid 

throughout. 

The A horizon has hue of 7.5YR or 10YR, value of 

2 or 3 when moist and 4 or 5 when dry, and chroma 

of 2 or 3 when moist or dry. It has 25 to 35 percent hard 

pebbles and 10 to 15 percent cobbles. 

The Bw horizon has value of 3 or 4 when moist 

and 5 or 6 when dry, and it has chroma of 4 to 6 

when moist or dry. It is very gravelly sandy loam or very 

cobbly sandy loam. The horizon has 20 to 30 percent 

hard pebbles and 10 to 25 percent cobbles. 

The 2C horizon has hue of 7.5YR or 10YR, value of 4 

or 5 when moist and 6 or 7 when dry, and chroma of 4 

to 6 when moist or dry. It has 10 to 20 percent hard 

pebbles, 15 to 25 percent cobbles, and 40 to 50 percent 

stones. 

Hood Series 

The Hood series consists of very deep, well drained 

soils on dissected terraces. These soils formed in 

lacustrine deposits. Slope is 15 to 30 percent. Elevation 

ranges from 320 to 560 feet. The average annual 

precipitation is about 43 inches, the average annual air 

temperature is about 49 degrees F, and the average 

frost-free season is 150 to 180 days. 

These soils are fine-loamy, mixed. mesic Ultic 

Haploxeralfs. 

Typical pedon of Hood loam, 15 to 30 percent 

slopes, about 3 miles north of Underwood, 1,360 feet 

south and 200 feet west of the northeast corner of sec. 3. 

T. 3 N.. R. 10 E. 

O-1 inch to 0; needles, leaves, and twigs. 

A-0 to 8 inches; dark brown (10YR 3/3) loam, brown 

(10YR 5/3) dry; weak fine and medium granular 

structure; slightly hard, very friable, slightly sticky 

and nonplastic; many very fine and fine roots and 

common medium and coarse roots, many very fine 

and fine irregular pores and common fine tubular 

pores; slightly acid; clear wavy boundary. 

AB1-8 to 13 inches; dark brown (10YR 4/3) loam, 

yellowish brown (10YR 5/4) dry; weak fine 

subangular blocky structure; slightly hard, friable, 

slightly sticky and slightly plastic; common fine and 

medium roots and few coarse roots; common very 

fine and fine irregular pores and few fine tubular 

pores; slightly acid; clear wavy boundary. 

AB2-13 to 27 inches; dark yellowish brown (10YR 4/4) 

loam, light yellowish brown (10YR 6/4) dry; weak fine 

subangular blocky structure; slightly hard, friable, 

slightly sticky and slightly plastic; common fine and 

medium roots and few coarse roots; common fine 

and medium irregular and tubular pores; moderately 

acid; gradual wavy boundary. 

Bt-27 to 46 inches; dark brown (10YR 4/3) loam, 

brownish yellow (10YR 6/6) dry; weak fine and 

medium subangular blocky structure; hard, firm, 

slightly sticky and slightly plastic; few fine, medium, 

and coarse roots; few fine and medium irregular 

pores and common fine tubular pores; few thin clay 

films on faces of peds and in pores; moderately 

acid; gradual wavy boundary. 

BC-46 to 60 inches; dark brown (10YR 4/3) loam, 

brownish yellow (10YR 6/6) dry; weak fine and 

medium subangular blocky structure; slightly hard, 

friable, slightly sticky and slightly plastic; few fine 

and medium roots; few very fine and fine irregular 

pores and few fine tubular pores; moderately acid. 

The A horizon has value of 3 or 4 when moist and 5 

or 6 when dry, and it has chroma of 2 or 3 when moist 

or dry. 

The AB horizon has value of 5 or 6 when dry, and it 

has chroma of 3 to 6 when moist or dry. It is loam or 

silt loam. 

The Bt horizon has value of 5 or 6 when dry, and it 

has chroma of 3 to 6 when moist or dry. Reaction is 

moderately acid or slightly acid. The horizon is loam or 

silt loam and is 18 to 25 percent clay. 

Kinney Series 

The Kinney series consists of very deep, well drained 

soils on foot slopes and back slopes of mountains. These 

soils formed in residuum and colluvium derived 

dominantly from granodiorite and volcanic ash. Slope is 5 

to 65 percent. Elevation is 600 to 2,300 feet. The 

average annual precipitation is about 90 inches, the 

average annual air temperature is about 48 degrees F, 

and the average frost-free season is 125 to 145 days. 

 These soils are medial. mesic Andic Haplumbrepts. 

Typical pedon of Kinney loam, 30 to 65 percent 
slopes, about 6 miles southeast of Silver Star Mountain; 

200 feet south and 500 feet west of the northeast corner 

of sec. 4. T. 2 N., R. 5 E. 

O1-3 inches to 1 inch; leaves, twigs, and needles. 

O2-1 inch to 0; black (10YR 2/1) decomposed organic 

matter. 

A-0 to 6 inches; dark brown (7.5YR 3/3) loam, brown 

(7.5YR 5/3) dry; moderate very fine and fine granular 

structure; slightly hard, friable, slightly sticky and 

slightly plastic; weakly smeary; many fine and 

common medium roots; many fine irregular pores, 25 

percent dark red (2.5YR 3/6) pebbles that are 

dominantly cinders and are 5 to 30 millimeters in 

diameter and 5 percent saprolitic fragments; strongly 

acid; clear wavy boundary. 

AB-6 to 12 inches; dark brown (7.5YR 3/3) loam. 

brown (7.5YR 5/3) dry; weak fine subangular blocky 

structure parting to weak fine granular; slightly hard, 

friable, slightly sticky and slightly plastic; weakly 

smeary; many fine and few medium roots; many fine 

irregular pores; 15 percent pebbles, of which 10 

percent is cinders, and 3 percent saprolitic fragments; 

strongly acid; clear smooth boundary. 

Bw1-12 to 22 inches; strong brown (7.5YR 5/6) 

gravelly clay loam, reddish yellow (7.5YR 6/6) dry; 

weak fine subangular blocky structure; slightly hard, 

friable, sticky and plastic; weakly smeary; common 

fine roots; common fine irregular pores; 10 percent 

pebbles, 5 percent cobbles, and 10 percent 

saprolitic fragments; very strongly acid; clear wavy 

boundary. 

Bw2-22 to 28 inches; strong brown (7.5YR 5/6) clay 

loam, reddish yellow (7.5YR 6/6) dry; weak fine 

subangular blocky structure; slightly hard, friable, 

sticky and plastic; weakly smeary; few fine roots; 

common fine irregular pores and few fine tubular 

pores; 5 percent pebbles, 5 percent cobbles, and 40 

percent saprolitic fragments; very strongly acid; 

abrupt smooth boundary. 

C-28 to 60 inches; yellowish brown (10YR 5/4) 

loam, very pale brown (10YR 7/4) dry; massive; 

slightly hard, friable, slightly sticky and slightly 

plastic; few fine roots; common medium irregular 

pores; 10 percent pebbles and 75 percent saprolitic 

fragments; very strongly acid. 

The solum is 20 to 47 inches thick. The umbric 

epipedon is 10 to 17 inches thick. The A horizon has 15 

to 35 percent cinders. The Bw and C horizons average 

10 to 25 percent hard rock fragments and 20 to 45 

percent saprolitic fragments. 

The A and AB horizons have hue of 7.5YR or 

10YR, value of 2 or 3 when moist and 4 or 5 when dry, 

and chroma of 2 or 3 when moist. 

The Bw horizon has hue of 7.5YR or 10YR, value of 4 

or 5 when moist and 5 to 7 when dry, and chroma of 4 

to 6 when moist or dry. It is loam, clay loam, or 

gravelly clay loam. It has 5 to 10 percent pebbles, 0 to 

10 percent cobbles, 0 to 15 percent stones, and 0 to 40 

percent saprolitic fragments. Reaction is very strongly 

acid to strongly acid. 

 The C horizon has 40 to 85 percent saprolitic 

fragments and 10 to 20 percent hard pebbles. 

The Kinney soils in this survey area have fewer rock

fragments in the lower part of the control section than is 

typical for the series. This difference, however, does not

significantly affect use and management. 

Lonestar Series 

The Lonestar series consists of very deep, well drained 

soils on back slopes, foot slopes, and ridgetops of 

mountains. These soils formed in volcanic ash and 

pumice overlying colluvium derived from basic igneous 

rock. Slope is 5 to 90 percent. Elevation is 2,800 to 

4,500 feet. The average annual precipitation is about 125 

inches, the average annual air temperature is about 40 

degrees F, and the average frost-free season is 75 to 

95 days. 

These soils are ashy over medial Humic Cryorthods. 

Typical pedon of Lonestar cindery sandy loam, 5 to 

30 percent slopes, on Forest Service Road N816, about 5 

miles northeast of Cougar; 2,000 feet north and 1,500 

feet west of the southeast corner of sec. 6, T. 7 N., R. 

5 E. 

O1-3 to 2 inches; needles, twigs, and leaves. 

O2-2 inches to 0; decomposed organic material. 

A-0 to 2 inches; black (10YR 2/1) fine sandy loam 

(volcanic ash), dark gray (10YR 4/1) dry; weak fine 

granular structure; soft, friable, slightly sticky and 

slightly plastic; weakly smeary; many very fine, fine, 

and medium roots and few coarse roots; many fine 

irregular pores; moderately acid; abrupt wavy 

boundary. 

Bhs-2 to 14 inches; dark brown (7.5YR 3/4) cindery 

sandy loam (volcanic ash and cinders), light yellowish 

brown (10YR 6/4) dry; many large distinct mottles that 

are dark reddish brown (5YR 3/4) and dark brown 

(7.5YR 4/4) when dry; weak fine subangular blocky 

structure; slightly hard, friable, nonsticky and 

nonplastic; many very fine and fine roots and 

common medium and coarse roots; 
common fine irregular pores; 10 percent pebbles 

and 30 percent pumice fragments; slightly acid; 

abrupt wavy boundary. 

BC-14 to 18 inches; grayish brown (10YR 5/2) loamy 

sand (volcanic ash), very pale brown (10YR 7/3) dry; 

single grain; loose; many very fine, fine, and medium 

roots; many fine irregular pores; 10 percent pumice 

fragments; neutral; abrupt smooth boundary. 

C-18 to 28 inches; yellowish brown (10YR 5/4) 

cindery loamy sand (volcanic ash and cinders), light 

yellowish brown (10YR 6/4) dry; weak fine subangular 

blocky structure; soft, friable, nonsticky and 

nonplastic; common very fine and fine roots; many 

fine irregular pores; 20 percent pebbles and 30 

percent pumice fragments; neutral; abrupt smooth 

boundary, 

2Bwb-28 to 51 inches; dark yellowish brown (10YR 

4/4) gravelly loam, very pale brown (10YR 7/3) dry; 

weak fine and medium subangular blocky structure; 

slightly hard, friable, slightly sticky and nonplastic; 

weakly smeary; few fine and medium roots; common 

fine irregular pores; 15 percent pebbles, 5 percent 

cobbles, and 15 percent soft weathered pumice 

fragments; moderately acid; clear wavy boundary. 

3Cb-51 to 60 inches; reddish yellow (7.5YR 6/6) silt 

loam, yellow (10YR 7/6) dry; weak fine and medium 

subangular blocky structure; slightly hard, friable, 

sticky and slightly plastic; few fine roots; few fine 

irregular pores; strongly acid. 

The Bhs, BC, and C horizons average 15 to 30 

percent pumice fragments, and the 2Bwb horizon 

averages 15 to 25 percent hard rock fragments. Depth to 

the buried layers ranges from 25 to 35 inches. Content of 

organic carbon ranges from 6 to 8 percent in the Bhs 

horizon. 

The Bhs horizon has hue of 7.5YR or 10YR, value of 2 

or 3 when moist and 5 or 6 when dry, and chroma of 2 

to 4 when moist or dry. It has common to many mottles 

that have hue of 7.5YR or 5YR and chroma of 2 to 4 when 

moist. Content of pumice fragments ranges from 10 to 

35 percent. Reaction is moderately acid or slightly acid. 

The C horizon has value of 4 or 5 when moist and 

chroma of 3 or 4 when moist or dry. It is 10 to 20 

percent pebbles and 10 to 35 percent pumice 

fragments. It is cindery loamy sand, cindery sand, 

loamy sand, or sand. Reaction is slightly acid or neutral. 

The 2Bwb horizon has chroma of 3 or 4 when moist 

or dry. It has 15 to 25 percent rock fragments, 

including 10 to 20 percent pebbles and 0 to 5 percent 

cobbles. It 

is gravelly loam or gravelly sandy loam. Reaction is 

moderately acid or slightly acid. 

The 3Cb horizon has hue of 7.5YR or 10YR and 

value of 4 to 6 when moist. It is silt loam or loam 

and has 0 to 10 percent rock fragments. 

McBee Series 

The McBee series consists of very deep, moderately 

well drained soils on flood plains and low river terraces. 

These soils formed in mixed alluvium derived dominantly 

from basic igneous rock. Slope is 0 to 3 percent. 

Elevation is 50 to 200 feet. The average annual 

precipitation is about 60 inches, the average annual air 

temperature is about 50 degrees F, and the average 

frost-free season is 160 to 180 days. 

These soils are fine-silty, mixed, mesic Cumulic Ultic 

Haploxerolls. 

Typical pedon of McBee silt loam, about 2 miles 

east of Prindle; 2,000 feet south and 1,000 feet west 

of the northeast corner of sec. 6, T. 1 N., R. 6 E. 

Oi-1 inch to 0; leaves and twigs. 

A1-0 to 3 inches; very dark brown (10YR 2/2) silt 

loam, brown (10YR 5/3) dry; moderate fine 

subangular blocky structure and moderate fine 

granular; slightly hard, friable, slightly sticky and 

slightly plastic; many fine roots; many fine irregular 

pores; moderately acid; abrupt wavy boundary. 

A2-3 to 13 inches; very dark grayish brown (10YR 

3/2) silt loam, brown (10YR 5/3) dry; common fine 

distinct strong brown (7.5YR 5/6) mottles; strong fine 

subangular blocky structure; slightly hard, friable, 

slightly sticky and slightly plastic; common fine roots; 

many fine irregular pores; moderately acid; clear 

wavy boundary. 

BA-13 to 21 inches; very dark grayish brown (10YR 

3/2) silt loam, yellowish brown (10YR 5/4) dry; 

common fine prominent strong brown (7.5YR 5/6) 

and yellowish red (5YR 4/6) mottles; moderate fine 

and medium subangular blocky structure; hard, 

friable, slightly sticky and slightly plastic; common 

fine roots; common fine irregular and tubular pores; 

few thin clay films on faces of peds and in pores; 

moderately acid; gradual smooth boundary. 

Bw-21 to 31 inches; dark grayish brown (10YR 4/2) 

silty clay loam, pale brown (10YR 6/3) dry; common 

fine prominent strong brown (7.5YR 5/6) and 

yellowish red (5YR 4/6) mottles; moderate medium 

subangular blocky structure; very hard, firm, sticky 

and plastic; common fine roots; many fine tubular 

pores and common fine irregular pores; common 
thin clay films on faces of peds and few 

moderately thick clay films in pores; moderately 

acid; gradual smooth boundary. 

BC-31 to 43 inches; brown (10YR 4/3) silt loam, 

pale brown (10YR 6/3) and reddish yellow (7.5YR 

6/6) dry; many fine and medium prominent strong 

brown (7.5YR 5/6) and yellowish red (5YR 4/6) 

mottles; weak coarse prismatic structure parting to 

moderate medium subangular blocky; hard, firm, 

slightly sticky and slightly plastic; common fine and 

few medium roots; many fine tubular pores; few thin 

clay films on faces of peds and few moderately thick 

clay films in pores; moderately acid; diffuse smooth 

boundary. 

C-43 to 60 inches; brown (10YR 5/3) silt loam, 

very pale brown (10YR 7/3) and reddish yellow 

(7.5YR 6/6) dry; many medium prominent strong 

brown (7.5YR 5/6) and yellowish red (5YR 4/6) 

mottles; massive; hard, firm, slightly sticky and 

slightly plastic; few fine roots; many fine and few 

medium tubular pores; moderately acid. 

The mollic epipedon is 20 to 34 inches thick. 

The A and BA horizons have value of 2 or 3 

when moist and 4 or 5 when dry. 

The Bw and BC horizons have hue of 7.5YR or 

10YR, value of 3 or 4 when moist and 5 or 6 when 

dry, and chroma of 2 to 4 when moist or dry. Texture 

is silt loam, clay loam, or silty clay loam. 

The C horizon has common to many, medium, 

prominent mottles. 

McDoug Series 

The McDoug series consists of very deep, 

moderately well drained soils on flood plains. These 

soils formed in mixed alluvium derived dominantly from 

basic igneous rock. Slope is 0 to 3 percent. Elevation 

is 800 to 1,600 feet. The average annual 

precipitation is about 50 inches, the average annual 

air temperature is about 48 degrees F. and the 

average frost-free season is 130 to 150 days. 

These soils are fine-loamy, mixed, mesic 

Cumulic Ultic Haploxerolls. 

Typical pedon of McDoug silt loam, about 4 miles 

north of Willard, 500 feet south and 1,200 feet east 

of the northwest corner of sec. 15, T. 4 N., R. 9 E. 

Oi-1 inch to 0; leaves and twigs. 

A-0 to 6 inches; very dark grayish brown (10YR 

3/2) silt loam, dark brown (10YR 3/3) dry; weak 

fine and medium granular structure; soft, very 

friable, 

nonsticky and nonplastic; many very fine and 

fine roots; many fine irregular pores; moderately 

acid; clear wavy boundary. 

AB-6 to 12 inches; dark brown (10YR 3/3) silt loam, 

dark yellowish brown (10YR 4/4) dry; weak fine and 

medium subangular blocky structure; slightly hard, 

friable, slightly sticky and slightly plastic; many very 

fine and fine roots; many fine irregular pores and 

few fine tubular pores; moderately acid; clear wavy 

boundary. 

BA-12 to 25 inches; dark brown (10YR 3/3) clay 

loam, yellowish brown (10YR 5/4) dry; moderate 

fine and medium subangular blocky structure; 

slightly hard, friable, slightly sticky and slightly 

plastic; many very fine and fine roots; many fine 

and medium irregular pores and common fine

and medium tubular pores; slightly acid; abrupt 

wavy boundary. 

Bw-25 to 38 inches; dark yellowish brown (10YR 

4/4) loam, light yellowish brown (10YR 6/4) dry; 

weak fine and medium subangular blocky 

structure; slightly hard, friable. slightly sticky and 

nonplastic; few fine, medium, and coarse roots; 

many fine irregular pores and common medium 

and coarse tubular pores; slightly acid; clear wavy 

boundary. 

C-38 to 60 inches; dark yellowish brown (10YR 4/4) 

clay loam, light yellowish brown (10YR 6/4) dry; 

common medium distinct dark grayish brown 

(10YR 4/2) mottles; massive; slightly hard, friable, 

slightly sticky and slightly plastic; few fine roots; 

few fine and medium tubular pores; slightly acid. 

The mollic epipedon is 24 to 30 inches thick. 

Depth to grayish brown mottles is 30 to 40 inches. 

The A, AB, and BA horizons have hue of 7.5YR or 

10YR, value of 2 or 3 when moist and 3 to 5 when 

dry, and chroma of 2 to 4 when moist or dry. 

The Bw horizon has hue of 7.5YR or 10YR, value 

of 3 or 4 when moist and 5 or 6 when dry, and 

chroma of 3 or 4 when moist or dry. It is loam or 

clay loam. 

The C horizon has hue of 7.5YR or 10YR, value of

3 or 4 when moist and 5 or 6 when dry, and chroma

of 3 or 4 when moist or dry. It is clay loam or silt

loam. 

McElroy Series 

The McElroy series consists of very deep, well 

drained soils on back slopes and foot slopes of 

mountains. These soils formed in colluvium derived 

dominantly from basalt with a mantle of volcanic ash. 

Slope is 5 to 65 percent. Elevation is 400 to 2,300 

feet. The average annual precipitation is about 55 

inches, 
the average annual air temperature is about 46 degrees 

F, and the average frost-free season is 105 to 125 

days. 

These soils are medial-skeletal, mesic Andic 

Xerumbrepts. 

Typical pedon of McElroy gravelly loam, 30 to 65 

percent slopes, about 2 miles south of Willard; 2,640 feet 

south and 300 feet west of the northeast corner of sec. 

12, T. 3 N., R. 9 E. 

O1-2 inches to 0.5 inch; needles, leaves, and twigs. 

O2-0.5 inch to 0; decomposed organic material. 

A1-0 to 4 inches; dark brown (7.5YR 3/2) gravelly 

loam, brown (7.5YR 5/4) dry; weak fine granular 

structure; soft, very friable, nonsticky and nonplastic; 

weakly smeary; many very fine and fine roots; many 

fine irregular pores; 25 percent pebbles; moderately 

acid; abrupt smooth boundary. 

A2-4 to 10 inches; dark brown (7.5YR 3/3) gravelly 

loam, brown (7.5YR 5/4) dry; weak fine subangular 

blocky structure parting to weak fine granular 

structure; soft, very friable, slightly sticky and 

nonplastic; weakly smeary; many very fine and fine 

roots; many fine irregular pores, 25 percent pebbles; 

moderately acid; clear wavy boundary. 

BA-10 to 24 inches; dark brown (7.5YR 4/4) very 

gravelly loam, strong brown (7.5YR 5/6) dry; weak fine 

subangular blocky structure; slightly hard, friable, 

slightly sticky and nonplastic; many very fine and fine 

roots and few medium roots; common fine irregular 

and tubular pores; 30 percent pebbles and 10 

percent cobbles; moderately acid; gradual wavy 

boundary. 

Bw1-24 to 43 inches; dark brown (7.5YR 4/4) very 

cobbly loam, strong brown (7.5YR 5/6) dry; weak fine 

and medium subangular blocky structure; slightly 

hard, friable, slightly sticky and nonplastic; many very 

fine and fine roots and few medium and coarse roots; 

common fine irregular pores and common fine and 

medium tubular pores; 30 percent pebbles and 20 

percent cobbles; moderately acid; gradual wavy 

boundary. 

Bw2-43 to 60 inches; dark brown (7.5YR 4/4) very 

cobbly loam, strong brown (7.5YR 5/6) dry; weak fine 

subangular blocky structure; slightly hard, friable, 

slightly sticky and slightly plastic; common very fine 

and fine roots and few medium and coarse roots; 

common fine tubular pores; 30 percent pebbles, 15 

percent cobbles, and 5 percent stones; moderately 

acid. 

The control section averages 35 to 60 percent rock 

fragments and 0 to 10 percent saprolitic fragments. 

Volcanic ash is most prominent in the upper 9 to 13 

inches. The umbric epipedon is 10 to 13 inches thick. 

Reaction is moderately acid or slightly acid throughout. 

The A horizon has hue of 5YR or 7.5YR, value of 2 

or 3 when moist and 4 or 5 when dry, and chroma of 

4 or 5 when dry. It is gravelly loam or very stony 

loam. 

The BA horizon has hue of 7.5YR or 5YR, value of 

4 or 5 when dry and 2 to 4 when moist, and chroma of 

4 to 6 when moist or dry. 

The Bw horizon has hue of 5YR or 7.5YR, value of 

5 or 6 when dry, and chroma of 4 to 6 when dry. It is 

very gravelly loam, very cobbly loam, or extremely 

gravelly loam. It has 35 to 55 percent pebbles and 10 

to 20 percent cobbles and stones. 

Minniepeak Series 

The Minniepeak series consists of very deep, well 

drained soils on back slopes and ridgetops of mountains. 

These soils formed in aerially deposited volcanic ash 

and pumice. Slope is 5 to 90 percent. Elevation is 2,800 

to 4,500 feet. The average annual precipitation is about 

130 inches, the average annual air temperature is about 

41 degrees F, and the average frost-free season is 75 to 

95 days. 

These soils are cindery Entic Cryandepts. 

Typical pedon of Minniepeak cindery sandy loam, 30 

to 65 percent slopes, about 3 miles southwest of Curtis 

Lake; 900 feet south and 750 feet west of the northeast 

corner of sec. 20, T. 9 N., R. 6 E. 

O-2 inches to 0; needles, leaves, and twigs. 

A1-0 to 3 inches; dark brown (10YR 4/3) cindery 

sandy loam (volcanic ash and cinders), brown (10YR 

5/3) dry; weak fine and medium granular structure; 

soft, very friable, nonsticky and nonplastic; weakly 

smeary; many very fine and fine roots. common 

medium roots, and few coarse roots; common fine 

irregular pores; 20 percent pumice fragments; slightly 

acid; abrupt smooth boundary. 

A2-3 to 8 inches; black (10YR 2/1) loamy sand 

(volcanic ash), dark gray (10YR 4/1) dry; single 

grain; loose; common fine and medium roots and 

few coarse roots; many very fine irregular pores; 

slightly acid; abrupt smooth boundary. 

AB-8 to 12 inches; very dark gray (10YR 3/1) very 

cindery sandy loam (volcanic ash and cinders), gray 

(10YR 5/1) dry; weak fine subangular blocky structure; 

soft, very friable, nonsticky and nonplastic; weakly 

smeary; many very fine and fine roots and common 

medium roots; many very fine irregular pores and 

few fine tubular pores, 40 
percent pumice; slightly acid; abrupt smooth 

boundary. 

2Bw1-12 to 16 inches; light gray (10YR 7/1) extremely 

cindery sand (cinders and volcanic ash), white (10YR 

8/1) dry; common fine and medium stains that are 

yellowish brown (10YR 5/6) and brownish yellow 

(10YR 6/6) when dry, single grain; loose, many very 

fine and common fine roots, many coarse irregular 

pores; 75 percent pumice fragments and 15 percent 

pebbles; slightly acid; abrupt smooth boundary. 

2Bw2-16 to 21 inches, dark brown (10YR 4/3) extremely 

cindery coarse sand (cinders and volcanic ash). 

brown (10YR 5/3) dry; single grain; loose; many very 

fine and fine roots and few coarse roots; many 

medium irregular pores; 60 percent pumice fragments 

and 10 percent pebbles; slightly acid; abrupt wavy 

boundary. 

2Bw3-21 to 60 inches; light gray (10YR 7/1) extremely 

cindery sand (cinders and volcanic ash), white 

(10YR 8.1) dry; many fine and medium stains that are 

yellowish brown (10YR 5/6) and brownish yellow 

(10YR 6/6) when dry; single grain; loose; common 

very fine and few fine roots; many medium and coarse 

irregular pores; 80 percent pumice fragments and 10 

percent pebbles; slightly acid. 

The control section averages 60 to 80 percent pumice 

fragments and 5 to 20 percent pebbles. Reaction is 

moderately acid or slightly acid throughout. 

The A1 horizon has hue of 10YR or 7.5YR, value of 3 

or 4 when moist and 5 or 6 when dry, and chroma of 2 to 

4 when moist or dry. 

The A2 horizon has value of 2 or 3 when moist and 4 or 

5 when dry, and it has chroma of 1or 2 when moist or 

dry. It is loamy sand or sandy loam. Content of scoria 

ranges from 0 to 15 percent. 

The 2Bw1 horizon has 65 to 80 percent pumice 

fragments and 5 to 15 percent pebbles. It has stains 

that have hue of 10YR or 7.5YR, value of 4 or 5 when 

moist and 5 or 6 when dry, and chroma of 4 to 8 when 

moist or dry. 

The 2Bw2 horizon has value of 3 or 4 when moist and 5 

or 6 when dry, and it has chroma of 2 or 3 when moist or 

dry. It has 50 to 65 percent pumice fragments and 10 to 30 

percent pebbles that are 2 to 5 millimeters in size. The 

fine earth fraction is coarse sand, sand, or loamy sand. 

The 2Bw3 horizon has 65 to 80 percent pumice 

fragments and 5 to 15 percent pebbles. It has stains 

that have hue of 10YR or 7.5YR, value of 4 or 5 when 

moist and 5 or 6 when dry, and chroma of 4 to 8 when 

moist or dry. 

Mossyrock Series 

The Mossyrock series consists of very deep, well 

drained soils on high terraces. These soils formed in 

loess and alluvium derived dominantly from volcanic ash 

and basalt. Slope is 2 to 15 percent. Elevation is 300 to 

1,000 feet. The average annual precipitation is about 70 

inches, the average annual air temperature is about 51 

degrees F, and the average frost-free season is 175 to 

195 days. 

These soils are medial, mesic Typic Dystrandepts. 

Typical pedon of Mossyrock silt loam, 2 to 5 percent 

slopes, about 6 miles northeast of Washougal; 2,190 feet 

south of the northeast corner of sec. 29, T. 2 N., R. 5 E. 

O-1 .5 inches to 0; needles, leaves, and twigs. 

A1-0 to 6 inches; very dark brown (10YR 2/2) silt 

loam, dark brown (10YR 4/3) dry; weak coarse 

granular structure; soft. very friable, slightly sticky and 

nonplastic; weakly smeary; many very fine roots and 

common fine and medium roots; many medium 

irregular pores; moderately acid; clear wavy 

boundary. 

A2-6 to 13 inches; dark brown (7.5YR 3/2) silt loam, 

yellowish brown (10YR 5/4) dry; weak fine 

subangular blocky structure; soft, very friable, 

slightly sticky and slightly plastic; weakly smeary; 

many very fine and fine roots and few medium 

roots; many medium irregular pores; moderately 

acid; clear wavy boundary. 

AB-13 to 27 inches; dark brown (7.5YR 3/3) silt loam, 

yellowish brown (10YR 5/4) dry; weak fine subangular 

blocky structure; slightly hard, very friable, slightly 

sticky and plastic; many very fine roots and common 

fine and medium roots; many medium irregular 

pores; moderately acid; clear wavy boundary. 

Bw-27 to 60 inches; dark brown (7.5YR 4/4) silt loam, 

very pale brown (10YR 7/4) dry; weak medium 

prismatic structure; hard, firm, slightly sticky and 

slightly plastic; common fine and few very fine roots; 

many fine and common medium irregular pores; 

moderately acid. 

The umbric epipedon is 24 to 30 inches thick. 

Volcanic ash influence generally extends to a depth of 

60 inches or more. 
The A and AB horizons have hue of 10YR or 7.5YR, 

value of 2 or 3 when moist and 4 or 5 when dry. and 

chroma of 2 or 3 when moist. 

The Bw horizon has hue of 10YR or 7.5YR, value of 4 

to 6 when moist and 5 to 7 when dry, and chroma of 3 

or 4 when dry. Reaction is strongly acid or moderately 

acid. 

Mountzion Series 

The Mountzion series consists of very deep, well 

drained soils on back slopes and foot slopes of 

mountains. These soils formed in residuum and colluvium 

derived dominantly from basalt. Slope is 2 to 65 percent. 

Elevation is 600 to 2,200 feet. The average annual 

precipitation is about 70 inches, the average annual air 

temperature is about 49 degrees F, and the average frostfree season is 130 to 150 days. 

These soils are fine-loamy, mixed, mesic Typic 

Haplohumults. 

Typical pedon of Mountzion clay loam, 15 to 30 

percent slopes, about 3 miles northeast of Stevenson; 

1,300 feet south and 1,000 feet west of the northeast 

corner of sec. 24, T. 3 N., R. 7 1/2 E. 

O-1 inch to 0; needles, leaves, and twigs. 

A-0 to 5 inches; dark brown (7.5YR 3/2) clay loam, 

dark brown (7.5YR 4/4) dry; moderate fine granular 

structure; slightly hard. very friable, slightly sticky and 

slightly plastic; many very fine and fine roots and 

common medium roots; many fine irregular pores; 5 

percent concretions; moderately acid; clear wavy 

boundary. 

AB-5 to 17 inches; dark brown (7.5YR 3/3) clay loam, 

dark brown (7.5YR 4/4) dry; moderate fine and 

medium subangular blocky structure; slightly hard, 

friable, slightly sticky and slightly plastic; common 

very fine, fine, and medium roots; common fine 

tubular pores; 5 percent soft basalt pebbles; 

moderately acid; clear wavy boundary. 

Bt1-17 to 35 inches; dark reddish brown (5YR 3/4) 

silty clay loam, reddish brown (5YR 4/4) dry; 

moderate fine and medium subangular blocky 

structure; hard, friable, sticky and plastic; common 

fine and medium roots and few coarse roots; 

common very fine and fine tubular pores; common 

moderately thick clay films on faces of peds and in 

some pores; strongly acid; gradual wavy boundary. 

Bt2-35 to 47 inches; dark reddish brown (5YR 3/4) 

silty clay loam, yellowish red (5YR 4/6) dry; 

moderate fine and medium subangular blocky 

structure; hard, friable, sticky and plastic; common 

fine and medium roots; common fine tubular pores; 

many moderately thick clay films on faces of peds 

and in pores; strongly acid; gradual wavy boundary. 

Bt3-47 to 60 inches; dark brown (7.5YR 4/4) clay 

loam, strong brown (7.5YR 5/6) dry; moderate fine 

and medium subangular blocky structure; hard, 

friable, slightly sticky and slightly plastic; few fine 

and medium roots; few fine tubular pores; few thin 

clay films on faces of peds; 10 percent pebbles; 

strongly acid. 

The 17- to 37-inch particle-size control section is 28 

to 35 percent clay. Depth to bedrock is 60 inches or 

more. 

The A and AB horizons have hue of 7.5YR or 5YR, 

value of 2 or 3 when moist and 3 or 4 when dry, and 

chroma of 2 or 3 when moist and 2 to 4 when dry. 

They have 0 to 10 percent pebbles and 0 to 15 

percent concretions that are 2 to 5 millimeters in 

diameter. Reaction is strongly acid or moderately acid. 

The Bt horizon has hue of 7.5YR or 5YR, value of 3 

or 4 when moist and 4 or 5 when dry, and chroma of 4 

to 6 when dry. It has 5 to 20 percent pebbles. The horizon 

is clay loam or silty clay loam. Reaction is very strongly 

acid or strongly acid. 

Obscurity Series 

The Obscurity series consists of very deep, somewhat 

excessively drained soils on broad fans and low terraces 

along major drainageways. These soils formed in 

mudflow material. Slopes are 0 to 30 percent. Elevation 

is 2,800 to 5,500 feet. The average annual precipitation is 

about 130 inches, the average annual air temperature is 

about 40 degrees F, and the average frost-free season is 

70 to 90 days. 

These soils are sandy-skeletal, mixed Typic 

Cryorthents. 

Typical pedon of Obscurity very bouldery sand, 0 to 

30 percent slopes, about 3.5 miles southeast of Mount 

St. Helens; 2,000 feet north and 2,000 feet east of the 

southwest corner of sec. 19, T. 8 N., R. 6 E. 

C1-0 to 20 inches; gray (10YR 5/1) very bouldery 

sand, light gray (10YR 7/1) dry; single grain; loose, 

nonsticky and nonplastic; many coarse irregular 

pores; 15 percent cobbles, 30 percent pebbles, and 

3 percent boulders and stones on the soil surface; 

moderately acid; clear wavy boundary. 

C2-20 to 60 inches; dark gray (10YR 4/1) very cobbly 

loamy sand with strata of cindery sand and very 

cindery loamy sand 2 to 4 inches thick, light gray 
(10YR 6/1) dry; single grain; loose, nonsticky and 

nonplastic; many medium and coarse irregular pores;

5 percent stones, 30 percent cobbles, and 25 percent 

pebbles; 10 percent pumice fragments; moderately 

acid. 

The mean annual soil temperature ranges from 39 to 

44 degrees F. The 10- to 40-inch particle-size control 

section is weakly stratified and averages 35 to 65 percent 

coarse fragments and 15 to 50 percent volcanic glass 

and glass aggregates. It is strongly acid or moderately 

acid. Some profiles contain woody organic debris that 

consists of logs, branches, and bark. 

The C1 horizon has hue of 7.5YR to 2.5Y, value of 3 to 

7 when moist and 5 to 8 when dry, and chroma of 0 to 

2 when moist or dry. 

The C2 horizon has hue of 7.5YR to 2.5Y. value of 2 to 

5 when moist and 3 to 6 when dry, and chroma of 0 

to 2 when moist or dry. It is very cobbly loamy sand or 

very cobbly sand. 

Panhandle Series 

The Panhandle series consists of very deep, well 

drained soils on broad fans. These soils formed in 

cindery pyroclastic flow material. Slopes are 0 to 20 

percent. Elevation is 2,900 to 5,000 feet. The average 

annual precipitation is about 135 inches, the average 

annual air temperature is about 40 degrees F. and the 

average frost-free season is 70 to 90 days. 

These soils are cindery Typic Cryorthents. 

Typical pedon of Panhandle extremely cindery loamy 

sand, 0 to 20 percent slopes. about 1.5 miles southwest of 

Spirit Lake; 1,000 feet south and 1,750 feet east of the 

northwest corner of sec. 21, T. 9 N., R. 5 E. 

C1-0 to 10 inches; light gray (10YR 7/1) extremely 

cindery loamy sand, white (10YR 8/1) dry; single 

grain; loose, nonsticky and nonplastic; many 

medium and coarse irregular pores; 50 percent 

pumice fragments and 15 percent pebbles; 

moderately alkaline; clear smooth boundary, 

C2-10 to 60 inches; grayish brown (10YR 5/2) very 

cindery loamy sand, light gray (10YR 7/2) dry; single 

grain; loose, nonsticky and nonplastic; many fine. 

medium, and coarse irregular pores; 35 percent 

pumice fragments and 10 percent pebbles; 

moderately alkaline. 

The mean annual soil temperature ranges from 38 to 

43 degrees F. The 10- to 40-inch particle-size control 

section averages 35 to 70 percent pumice fragments. It 

is mildly alkaline or neutral. The soil is 60 percent or 

more vitric volcanic ash and pumice cinders. 

The C1 horizon has value of 4 to 7 when moist and 5 to 

8 when dry, and it has chroma of 1 or 2 when moist or 

dry. 

The C2 horizon has hue of 7.5YR to 10YR, value of 4 

to 6 when moist and 5 to 8 when dry, and chroma of 

0 to 2 when moist or dry. 

Pelee Series 

The Pelee series consists of very deep, well drained 

soils on back slopes and ridgetops of mountains. These 

soils formed in stratified, aerially deposited volcanic ash 

and pumice. Slope is 5 to 90 percent. Elevation is 

2,800 to 4,500 feet. The average annual precipitation is 

about 135 inches, the average annual air temperature is 

about 39 degrees F, and the average frost-free season 

is 75 to 90 days. 

These soils are cindery Entic Cryandepts. 

Typical pedon of Pelee sandy loam, 30 to 65 percent 

slopes (fig. 9), about 4.5 miles northeast of Mount St. 

Helens; 500 feet south and 1,700 feet east of the 

northwest corner of sec. 31, T. 9 N., R. 6 E. 

O1-1.5 inches to 0.5 inch; leaves, needles, and twigs.

O2-0.5 inch to 0; decomposed organic material. 

A1-0 to 2 inches; dark grayish brown (10YR 4/2) very 

fine sandy loam (volcanic ash), light gray (10YR 7/2) 

dry; moderate fine granular structure; soft, very 

friable, nonsticky and nonplastic; many very fine and 

fine roots, common medium roots, and few coarse 

roots, common fine irregular pores; slightly acid; 

abrupt wavy boundary. 

A2-2 to 7 inches; very dark grayish brown (10YR 

3/2) sandy loam (volcanic ash), grayish brown 

(10YR 5/2) dry; many medium distinct dark brown 

(7.5YR 3/5) mottles on faces of peds; moderate 

medium platy structure parting to very fine 

subangular blocky; slightly hard, firm, nonsticky and 

nonplastic; many very fine and fine roots and few 

medium and coarse roots; common fine and medium 

irregular pores and common fine tubular pores; 

slightly acid; abrupt smooth boundary. 

2BA-7 to 10 inches; dark gray (10YR 4/1) very cindery 

coarse sand (volcanic ash and cinders), gray (10YR 

5/1) dry; single grain; loose; many very fine roots; 

many fine and medium irregular pores; 40 percent 

pumice fragments; moderately acid; abrupt smooth 

boundary. 

2Bw1-10 to 15 inches; light gray (10YR 7/1) extremely 

cindery sand (cinders and volcanic ash), white 
Figure 9.-Typical pedon of Pelee sandy loam, 30 to 65 percent 

slopes. 

(10YR 8/1) dry; yellowish brown (10YR 5/6) iron 

stains; single grain; loose; many very fine roots; 

many medium and coarse irregular pores; 75 

percent pumice fragments and 15 percent pebbles; 

moderately acid; abrupt smooth boundary. 

2Bw2-15 to 20 inches; dark brown (10YR 4/3) very 

cindery sand (cinders and volcanic ash), light 

brownish gray (10YR 6/2) dry; single grain; loose; 

many very fine roots, common medium roots, and few 

coarse roots; many fine and medium irregular pores; 

55 percent pumice fragments and 20 percent 

pebbles; moderately acid; abrupt smooth boundary. 

2Bw3-20 to 32 inches; light gray (10YR 7/1) extremely 

cindery sand (cinders and volcanic ash), white 

(10YR 8/1) dry; yellowish brown (10YR 5/6) iron stains; 

single grain; loose; many very fine roots; common 

medium and many coarse irregular pores; 75 percent 

pumice fragments and 15 percent pebbles; 

moderately acid; abrupt wavy boundary. 

3Bw4-32 to 42 inches; dark brown (7.5YR 3/4) sandy 

loam, dark brown (7.5YR 4/4) dry; weak fine 

subangular blocky structure; soft, friable, nonsticky 

and nonplastic; common very fine and few medium 

roots; common very fine irregular pores; 5 percent 

pumice fragments and 15 percent scoria; moderately 

acid; abrupt wavy boundary. 

3Bw5-42 to 52 inches; very dark grayish brown (10YR 

3/2) sandy loam, grayish brown (10YR 5/2) dry; 

common fine distinct yellow (10YR 7/6) mottles; weak 

fine subangular blocky structure; soft, very friable, 

nonsticky and nonplastic; continuous lenses of 

gravel-sized pumice fragments 1 to 3 inches thick; 

few very fine and fine roots; common very fine 

irregular pores; moderately acid; abrupt wavy 

boundary. 

3Bw6-52 to 60 inches; dark brown (7.5YR 3/4) loamy 

sand, dark brown (7.5YR 4/4) dry; weak medium 

subangular blocky structure; soft, friable, nonsticky 

and nonplastic; few very fine roots; common 

medium and coarse irregular pores; 55 percent 

scoria; moderately acid. 

Depth to the lower boundary of the cindery layer is 25 to 

35 inches. The 10- to 40-inch particle-size control section 

averages 35 to 60 percent pumice fragments and 5 to 

20 percent rock fragments. The upper 25 to 35 inches of 

the profile is 60 percent or more vitric volcanic ash and 

pumice. 

The A horizon has value of 3 or 4 when moist and 5 

to 7 when dry, and it has chroma of 1or 2 when moist 

or dry. The lower part has common to many, medium, 

distinct stains that have hue mainly of 7.5YR or 5YR. 
The 2Bw horizon has 40 to 80 percent pumice 

fragments and 5 to 20 percent andesitic pebbles. It is 

loamy sand to coarse sand in the fine earth fraction. 

Iron stains on the pumice fragments have hue of 10YR 

or 7.5YR and value of 4 or 5 when moist. 

The 3Bw horizon has hue of 10YR or 7.5YR, value 

of 2 to 4 when moist and 4 to 6 when dry, and chroma 

of 2 or 4 when moist or dry. Content of soft black 

scoria averages 10 to 35 percent. The horizon is 

sandy loam to loamy sand. 

Pilchuck Series 

The Pilchuck series consists of very deep, somewhat 

excessively drained soils on flood plains. These soils 

formed in alluvium derived dominantly from basic 

igneous rock. Slope is 0 to 3 percent. Elevation is 50 to 

200 feet. The average annual precipitation is about 60 

inches, the average annual air temperature is about 50 

degrees F, and the average frost-free season is 160 to 

200 days. 

These soils are mixed, mesic Dystric 

Xeropsamments. 

Typical pedon of Pilchuck very fine sandy loam, 

about 0.5 mile east of Beacon Rock; 1,000 feet south 

and 1,000 feet west of the northeast corner of sec. 30. T. 

2 N. R. 7 E. 

Ap-0 to 9 inches; very dark grayish brown (10YR 3/2) 

very fine sandy loam, brown (10YR 5/3) dry; weak fine 

subangular blocky structure; soft, very friable. 

nonsticky and nonplastic; many very fine and fine 

roots; many fine and medium irregular pores and 

common fine and medium tubular pores; moderately 

acid; abrupt smooth boundary. 

AC-9 to 18 inches; dark brown (10YR 4/3) fine sand, 

brown (10YR 5/3) dry; single grain; loose; many very 

fine and fine roots; many fine irregular pores and 

few medium tubular pores; stratified lenses of loamy 

fine sand; moderately acid; abrupt wavy boundary. 

C1-18 to 28 inches; dark brown (10YR 4/3) loamy fine 

sand. pale brown (10YR 6/3) dry; single grain; loose; 

common very fine and fine roots; many fine irregular 

pores and few medium tubular pores; moderately 

acid; abrupt smooth boundary. 

C2-28 to 38 inches; brown (10YR 5/3) fine sand, pale 

brown (10YR 6/3) dry; single grain; loose; common 

very fine and fine roots; many fine irregular pores and 

few coarse tubular pores; moderately acid; clear 

wavy boundary. 

C3-38 to 46 inches; dark grayish brown (10YR 4/2) 

loamy fine sand, pale brown (10YR 6/3) dry; few fine 

distinct dark brown (7.5YR 4/4) mottles; single grain; 

loose; common very fine and fine roots and few 

medium roots; many fine irregular pores and few 

medium tubular pores; moderately acid; abrupt wavy 

boundary. 

C4-46 to 60 inches; very dark grayish brown 

(10YR 3/2) fine sandy loam, pale brown (10YR 

6/3) dry; common fine distinct dark brown (7.5YR 

4/4) and black (10YR 2/1) mottles; massive; soft, 

friable, nonsticky and nonplastic; common very 

fine and fine roots; many fine and medium 

irregular pores and common medium tubular 

pores; moderately acid. 

Depth to stratified lenses of fine sand and loamy 

fine sand is 9 to 30 inches. 

The A and AC horizons have value of 2 or 3 when 

moist and 4 or 5 when dry, and they have chroma of 2 

or 3 when moist or dry. 

The C1 horizon has value of 5 or 6 when dry, and it 

has chroma of 2 or 3 when moist or dry. It is fine 

sand, loamy sand, or loamy fine sand. 

The C2 horizon has value of 4 or 5 when moist, 

and it has chroma of 2 or 3 when moist or dry. It is 

fine sand or coarse sand. 

The C3 and C4 horizons have value of 3 or 4 when 

moist, and they have chroma of 2 or 3 when moist or 

dry. They are stratified lenses of loamy fine sand, sand, 

fine sandy loam, or silt loam. Mottles range from common 

to many and faint to distinct and have hue of 2.5YR, 

7.5YR, or 10YR. 

Pillery Series 

The Pillery series consists of very deep, moderately 

well drained soils on flood plains and low river terraces. 

These soils formed in mixed alluvium derived 

dominantly from basic igneous rock. Slope is 0 to 3 

percent. Elevation is 900 to 1,200 feet. The average 

annual precipitation is about 100 inches, the average 

annual air temperature is about 46 degrees F, and the 

average frost-free season is 110 to 130 days. 

These soils are coarse-loamy, mixed, nonacid, mesic 

Mollic Udifluvents. 

Typical pedon of Pillery fine sandy loam, about 3 

miles north of Willard; 2,000 feet south and 1 ,000 feet 

east of the northwest corner of sec. 23, R. 7 E., T. 4 

N. 

O-1 inch to 0; leaves, needles, and twigs. 

A1-0 to 9 inches; very dark grayish brown (10YR 

3/2) fine sandy loam, pale brown (10YR 6/3) dry; 

weak 
fine granular structure; soft, very friable, slightly sticky 

and nonplastic; many fine and very fine roots and few 

medium roots; many very fine and fine irregular pores;

5 percent pebbles and 5 percent concretions; 

moderately acid; clear wavy boundary. 

A2-9 to 20 inches; very dark grayish brown (10YR 3/2) 

loam, pale brown (10YR 6/3) dry; weak fine and 

medium subangular blocky structure; slightly hard, 

friable. slightly sticky and nonplastic; common very 

fine roots and few fire and medium roots; common 

fine irregular pores and few fine vesicular pores; 10 

percent pebbles; lenses of fine sandy loam; 

moderately acid; clear smooth boundary. 

A3-20 to 32 inches; dark brown (10YR 3/3) fine sandy 

loam, pale brown (10YR 6/3) dry; weak medium 

subangular blocky structure; slightly hard, friable, 

slightly sticky and nonplastic; few fine and common 

medium roots; common fine irregular and vesicular 

pores; 5 percent pebbles; strongly acid; clear wavy 

boundary. 

C1-32 to 45 inches; brown (10YR 4/3) fine sandy loam, 

pale brown (10YR 6/3) dry; massive; slightly hard. 

friable, slightly sticky and nonplastic; common very 

fine and medium roots; common fine irregular pores 

and common fine vesicular pores; 10 percent 

pebbles; strongly acid. clear wavy boundary. 

2C2-45 to 60 inches; brown (10YR 5/3) very gravelly loamy 

sand. very pale brown (10YR 7/3) dry; single grain; 

loose. few medium and coarse roots; many very fine, 

fine, and medium irregular pores; 40 percent 

pebbles and 10 percent cobbles; moderately acid. 

The 10- to 40-inch particle-size control section is 

stratified fine sandy loam, loam, silt loam, and loamy 

fine sand and has 5 to 15 percent clay and 15 to 40 

percent sand that is fine sand or coarser. 

The A horizon has hue of 7.5YR or 10YR, and it has 

value of 3 or 4 when moist and 5 or 6 when dry. 

The C horizon has hue of 7.5YR or 10YR and value 

of 3 or 4 when moist. Reaction is strongly acid or 

moderately acid, The horizon has 5 to 15 percent rock 

fragments. 

The 2C horizon is very gravelly loamy sand or gravelly 

sand. It has 25 to 40 percent pebbles and 0 to 10 

percent cobbles. 

Pinchot Series 

The Pinchot series consists of very deep, well 

drained soils on terraces and terrace escarpments. 

These soils formed in layers of aerially deposited 

pumice and volcanic ash over lahar material and alluvial 

sand and gravel. Slope is 0 to 90 percent. Elevation is 

1,000 to 1,600 feet. The average annual precipitation is 

about 125 inches, the average annual air temperature is 

about 50 degrees F, and the frost-free season is 100 to 

120 days. 

These soils are ashy, mesic Typic Vitrandepts. 

Typical pedon of Pinchot cindery sandy loam, 0 to 30 

percent slopes, north of Forest Service Road N-90, 

about 5 miles southeast of Marble Mountain; 1,000 feet 

south and 1,600 feet west of the northeast corner of sec. 

23. T. 7 N., R. 6 E. 

A1-0 to 2 inches; very dark brown (10YR 2/2) sandy 

loam, dark grayish brown (10YR 4/2) dry; weak fine 

granular structure; soft, very friable, nonsticky and 

nonplastic; many very fine, fine, and medium roots; 

many very fine irregular pores; moderately acid; 

abrupt wavy boundary. 

A2-2 to 4 inches; dark brown (10YR 313) cindery silt loam, 

light brownish gray (10YR 6/2) dry; weak fine 

granular structure; soft, very friable, nonsticky and 

slightly plastic; weakly smeary; many very fine and 

fine roots and common medium roots; common fine 

irregular pores; 20 percent pumice fragments; 

moderately acid; abrupt wavy boundary. 

2Bw1-4 to 6 inches; light brownish gray (10YR 6/2) 

extremely cindery coarse sand, light gray (10YR 

7/2) dry; yellowish brown (10YR 5/6) iron stains; 

single grain; loose; many very fine and fine roots 

and few medium roots; many medium and coarse 

irregular pores; 65 percent pumice fragments and 

15 percent pebbles; moderately acid; abrupt wavy 

boundary. 

3Bw2-6 to 11 inches; very dark grayish brown (10YR 

3/2) fine sandy loam, brown (10YR 5,3) dry; weak fine 

subangular blocky structure; soft, very friable, 

nonsticky and nonplastic; weakly smeary; many very 

fine and fine roots and common medium roots; 

many very fine irregular pores; 10 percent pumice 

fragments; moderately acid; abrupt wavy boundary. 

3Bw3-11 to 25 inches; dark brown (10YR 3/3) cindery 

sandy loam, brown (10YR 5/3) dry; common fine 

distinct brownish yellow (10YR 6/8) mottles; weak fine 

and medium subangular blocky structure; soft, 

friable, nonsticky and nonplastic; many very fine, 

fine, and medium roots and few coarse roots; many 

fine irregular pores and common fine tubular pores; 

25 percent pumice fragments; moderately acid; 

gradual wavy boundary. 

3Bw4-25 to 34 inches; dark brown (10YR 3/3) sandy 

loam, brown (10YR 5/3) dry; weak fine and medium 
subangular blocky structure; soft, friable, nonsticky 

and nonplastic; weakly smeary; many very fine and 

fine roots and common medium roots; many fine 

irregular pores and common fine tubular pores; 15 

percent pebbles; slightly acid; abrupt smooth 

boundary. 

4C1-34 to 49 inches; dark brown (10YR 4/3) very 

gravelly loamy sand, pale brown (10YR 6/3) dry; 

single grain; loose; many very fine and fine roots; 

many fine and common medium irregular pores; 40 

percent pebbles, 10 percent cobbles, and 5 percent 

stones; moderately acid; clear smooth boundary. 

4C2-49 to 60 inches; brown (10YR 5/3) very cobbly 

sand, pale brown (10YR 6/3) dry; massive; slightly 

hard, friable, nonsticky and nonplastic; few fine 

roots; many fine and medium irregular pores; 25 

percent hard pebbles. 20 percent saprolitic pebbles, 

15 percent cobbles, and 5 percent stones; 

moderately acid. 

The upper part of the 10- to 40-inch particle-size control 

section is 60 percent or more vitric volcanic ash and 

pumice and averages 5 to 10 percent hard rock 

fragments and 10 to 25 percent pumice fragments. 

Depth to the very gravelly or very cobbly 4C horizon is 25 

to 40 inches. The lower part of the particle-size control 

section averages 45 to 75 percent hard rock fragments. 

Reaction is moderately acid or slightly acid throughout 

the profile. 

The A horizon has value of 2 to 4 when moist and 4 

to 6 when dry, and it has chroma of 1 to 4 when moist 

or dry. It averages 5 to 15 percent pumice fragments. 

The 2Bw horizon has 60 to 75 percent pumice 

fragments and 5 to 15 percent pebbles. It has iron 

stains that have hue of 10YR or 7.5YR and value of 5 

or 6 when moist. 

The 3Bw horizon has hue of 7.5YR or 10YR, value 

of 3 or 4 when moist and 5 or 6 when dry, and chroma 

of 2 to 4 when moist or dry. It is fine sandy loam or 

sandy loam. The horizon averages 10 to 25 percent 

pumice fragments and 5 to 10 percent hard rock 

fragments. 

The 4C horizon averages 40 to 80 percent rock 

fragments, including 35 to 50 percent pebbles, 5 to 20 

percent cobbles, and 2 to 10 percent stones. It is sand 

or loamy sand. 

Pinoty Series 

The Pinoty series consists of very deep, well drained 

soils on terraces. These soils formed in volcanic ash 

and pumice over lahar material and alluvial sand and 

gravel. Slope is 0 to 30 percent. Elevation is 1,000 to 

1,500 feet. The average annual precipitation is about 

120 inches, the average annual air temperature is 52 

degrees F, and the average frost-free season is 100 to 

120 days. 

These soils are ashy over medial, mesic Typic 

Vitrandepts. 

Typical pedon of Pinoty sandy loam, 0 to 30 percent 

slopes, about 5 miles southeast of Marble Mountain; 

2,500 feet south and 400 feet west of the northeast 

corner of sec. 14, T. 7 N., R. 6 E. 

O1-2 inches to 0.5 inch; needles, leaves, and twigs. 

O2-0.5 inch to 0; decomposed organic material. 

A-0 to 3 inches; very dark brown (10YR 2/2) sandy 

loam, dark grayish brown (10YR 4/2) dry; weak fine 

granular structure; soft, very friable, nonsticky and 

nonplastic; many very fine roots and common fine 

and medium roots; many very fine irregular pores; 

slightly acid; clear wavy boundary. 

AB-3 to 4 inches; dark brown (10YR 3/3) cindery 

loamy sand, brown (10YR 5/3) dry; weak fine 

granular structure; soft, very friable, nonsticky and 

nonplastic; many very fine and fine roots and few 

coarse roots; many fine irregular pores; 20 percent 

pumice fragments; slightly acid; clear wavy 

boundary. 

Bw1-4 to 9 inches; dark grayish brown (10YR 4/2) 

sandy loam, very pale brown (10YR 7/3) dry; weak 

fine subangular blocky structure; soft, very friable, 

nonsticky and nonplastic; weakly smeary; many 

very fine roots and common fine and medium 

roots; many fine irregular pores; 5 percent pumice 

fragments; neutral; clear wavy boundary. 

Bw2-9 to 21 inches; dark grayish brown (10YR 4/2) 

cindery loamy sand, very pale brown (10YR 7/3) 

dry; weak fine subangular blocky structure; soft, 

friable, nonsticky and nonplastic; weakly smeary; 

many very fine and fine roots and common medium 

roots; many fine and medium irregular pores; 20 

percent pumice fragments; neutral; clear wavy 

boundary. 

Bw3-21 to 30 inches; dark yellowish brown (10YR 

4/4) sandy loam, light yellowish brown (10YR 6/4) 

dry; weak fine subangular blocky structure; soft, 

friable, nonsticky and nonplastic; weakly smeary; 

many very fine, fine, and medium roots; many very 

fine irregular pores; 10 percent pumice fragments; 

neutral; clear wavy boundary. 

C1-30 to 45 inches; brown (10YR 5/3) sandy loam, 

pale brown (10YR 6/3) dry; massive; soft, friable, 

nonsticky and nonplastic; common very fine and fine 

roots; common fine irregular pores and few fine 
tubular pores; neutral; abrupt smooth boundary. 

2C2-45 to 60 inches; grayish brown (10YR 5/2) 

extremely gravelly loamy sand, light brownish gray 

(10YR 6/2) dry; single grain; loose; many very fine 

and fine and common medium irregular pores; 55 

percent pebbles and 15 percent cobbles; neutral. 

Depth to the 2C2 horizon ranges from 40 to 50 

inches. Reaction is slightly acid or neutral throughout 

the profile. 

The Bw horizon has value of 3 or 4 when moist and 

5 to 7 when dry, and it has chroma of 2 to 4 when moist 

or dry. It is sandy loam. cindery sandy loam, or cindery 

loamy sand. The horizon has 0 to 20 percent pumice 

fragments. 

The 2C2 horizon has value of 5 or 6 when moist and 6 

or 7 when dry. and it has chroma of 2 or 3 when moist or 

dry. It is very gravelly sand, extremely gravelly loamy 

sand, or extremely gravelly sand. The horizon has 40 to 

60 percent pebbles and 5 to 15 percent cobbles. 

Polepatch Series 

The Polepatch series consists of very deep. somewhat 

excessively drained soils on alluvial fans and terraces. 

These soils formed in lahar material with a thin layer of 

volcanic ash on the surface. Slope is 0 to 30 percent. 

Elevation is 2,800 to 4,600 feet. The average annual 

precipitation is about 135 inches, the average annual air 

temperature is about 40 degrees F, and the average frostfree season is 70 to 90 days. 

These soils are sandy-skeletal, mixed Typic 

Cryorthents. 

Typical pedon of Polepatch extremely bouldery loamy 

sand, 0 to 30 percent slopes, near Pine Creek on Forest 

Service Road N-83; about 2,000 feet south and 800 feet 

west of the northeast corner of sec. 30, T. 8 N., R. 6 E. 

O-1 inch to 0; loose partially decomposed organic 

litter. 

A-0 to 3 inches; very dark grayish brown (10YR 3/2) 

extremely bouldery loamy sand, gray (10YR 5/1) 

dry; weak fine granular structure; soft, very friable, 

nonsticky and nonplastic; many very fine and fine 

roots and common medium roots; many fine 

irregular pores; 25 percent pebbles, 10 percent 

cobbles. and 5 percent stones; boulders on 3 

percent of surface; moderately acid; clear wavy 

boundary. 

AC-3 to 12 inches; very dark grayish brown (10YR 

 3/2) extremely cobbly loamy sand, gray (10YR 6/1) 

dry; weak fine granular structure; soft, very friable, 

nonsticky and nonplastic; many very fine and fine 

roots, common medium roots, and few coarse roots; 

many fine irregular pores; 30 percent pebbles, 25 

percent cobbles, and 10 percent stones; moderately 

acid; clear wavy boundary. 

2C1-12 to 27 inches; dark gray (10YR 4/1) extremely 

cobbly sand, light gray (10YR 7/1) dry; single grain; 

loose; many very fine and fine roots and few 

medium roots; many medium and coarse irregular 

pores; 30 percent pebbles, 25 percent cobbles, and 

10 percent stones; slightly acid; abrupt wavy 

boundary. 

2C2-27 to 35 inches; dark gray (10YR 4/1) extremely 

cobbly sand, light gray (10YR 7/1) dry; single grain; 

loose; few fine roots; many medium and coarse 

irregular pores; 40 percent pebbles, 20 percent 

cobbles, and 5 percent stones; slightly acid; abrupt 

wavy boundary. 

3C3-35 to 40 inches; dark gray (10YR 4/1) fine sandy 

loam, light brownish gray (10YR 6/2) dry; massive; 

soft, friable, nonsticky and nonplastic; few fine 

irregular pores and common fine tubular pores; 

slightly acid; abrupt wavy boundary. 

4C4-40 to 60 inches; dark gray (10YR 4/1) extremely 

stony coarse sand, light gray (10YR 7/1) dry; single 

grain; loose; many medium and coarse irregular 

pores; 35 percent pebbles, 20 percent cobbles, and 

20 percent stones; slightly acid. 

The 10- to 40-inch particle-size control section 

averages 60 to 85 percent rock fragments. Reaction is 

moderately acid or slightly acid throughout. 

The A and AC horizons have value of 2 or 3 when 

moist and 5 or 6 when dry, and they have chroma of 1or 

2 when moist or dry. They are 20 to 30 percent pebbles. 

10 to 25 percent cobbles, and 5 to 10 percent stones. 

From 3 to 5 percent of the surface is covered with 

boulders. 

The C horizon has value of 4 or 5 when moist and 6 to 

8 when dry, and it has chroma of 1or 2 when moist or 

dry. It averages 30 to 40 percent pebbles, 20 to 30 

percent cobbles, and 5 to 20 percent stones. It is 

extremely cobbly loamy sand, extremely cobbly fine 

sandy loam, extremely cobbly sand, or extremely stony 

coarse sand. 

Shoestring Series 

The Shoestring series consists of very deep, well 

drained soils on terraces and terrace escarpments. 

These soils formed in layers of aerially deposited 
volcanic ash and pumice over pyroclastic flow and lahar 

material. Slope is 0 to 90 percent. Elevation is 2,700 to 

4,500 feet. The average annual precipitation is about 

130 inches, the average annual air temperature is about 

41 degrees F, and the average frost-free season is 70 to 

90 days. 

These soils are medial over sandy or sandy-skeletal, 

mixed Typic Cryorthods. 

Typical pedon of Shoestring fine sandy loam, 0 to 30 

percent slopes. about 2 miles north of Marble Mountain; 

1,200 feet south and 1,700 feet west of the northeast 

corner of sec. 36. T. 8 N., R. 5 E. 

O1-3 to 2 inches; leaves, needles, and twigs. 

O2-2 inches to 0; decomposed organic material. 

E-0 to 3 inches; very dark gray (10YR 3/1) fine sandy 

loam (volcanic ash). gray (10YR 5 1) dry; weak fine 

granular structure; soft. very friable, nonsticky and 

nonplastic; many very fine, fine, and medium roots 

and few coarse roots; many very fine irregular pores; 

strongly acid; abrupt smooth boundary. 

Bhs-3 to 5 inches; black (10YR 2/1) fine sandy loam 

(volcanic ash). dark brown (10YR 3/3) dry; weak fine 

granular structure; soft, very friable, nonsticky and 

nonplastic; weakly smeary; many very fine, fine, and 

medium roots and few coarse roots; many very fine 

and fine irregular pores; 10 percent pebbles; 

moderately acid; abrupt smooth boundary. 

2Bs1-5 to 8 inches; dark gray (10YR 4/1) very gravelly 

sand (volcanic ash and cinders), light gray (10YR 7/1) 

dry; yellowish brown (10YR 5/6) stains; single grain; 

loose; many very fine and fine roots and common 

medium roots; many coarse irregular pores; 45 

percent pebbles and 35 percent pumice fragments; 

moderately acid; abrupt smooth boundary. 

3Bs2-8 to 18 inches; dark brown (7.5YR 3/4) sandy 

loam, brownish yellow (10YR 6/6) dry; weak fine 

subangular blocky structure; soft, friable, nonsticky 

and nonplastic; weakly smeary; common fine and 

medium roots and few coarse roots; many fine 

irregular pores and common fine tubular pores; 

moderately acid; clear wavy boundary. 

3BC-18 to 24 inches; very dark brown (10YR 2/2) 

loamy sand, dark brown (10YR 4/3) dry; massive; 

slightly hard, firm, nonsticky and nonplastic; few fine 

roots; common fine and medium irregular pores; 30 

percent soft scoria; slightly acid; clear smooth 

boundary. 

4C1-24 to 32 inches; dark grayish brown (10YR 4/2) 

very cobbly sand, brown (10YR 5/3) dry; single grain; 

loose; few fine roots; many medium and 

coarse irregular pores; 25 percent pebbles and 15 

percent cobbles; slightly acid; clear smooth 

boundary. 

4C2-32 to 60 inches; dark gray (10YR 4/1) very 

gravelly sand, gray (10YR 6/1) dry; single grain; 

loose; few fine roots; many medium and coarse 

irregular pores; 30 percent pebbles, 10 percent 

cobbles, and 5 percent stones; slightly acid. 

Depth to the 4C horizon is 20 to 35 inches. The 

upper part of the 10- to 40-inch particle-control section 

is 30 to 60 percent vitric material and has 0 to 10 

percent rock fragments. The lower part is 35 to 60 

percent rock fragments. The B and C horizons are 

moderately acid or slightly acid. 

The E horizon has value of 2 to 4 when moist and 

4 to 6 when dry, and it has chroma of 1or 2 when 

moist or dry. 

The Bhs horizon has value of 2 or 3 when moist 

and 3 or 4 when dry, and it has chroma of 1 to 3 

when moist or dry. 

The 2Bs horizon has 30 to 45 percent pebbles and 30 

to 45 percent pumice fragments. Iron stains on the 

pumice fragments have hue of 10YR or 7.5YR and 

value of 5 or 6. 

The 3Bs horizon has hue of 10YR or 7.5YR, value of 

3 or 4 when moist and 5 or 6 when dry, and chroma of 

3 to 6 when moist or dry. It is mainly sandy loam or 

loamy sand and has intermittent lenses of loam. 

The 3BC horizon has value of 2 to 4 when moist 

and 4 or 5 when dry, and it has chroma of 1 to 3 when 

moist or dry. It is loamy sand or sandy loam and has 

15 to 35 percent soft scoria that can be crushed 

easily. 

The 4C horizon has value of 4 to 6 when moist and 

5 to 8 when dry, and it has chroma of 1 to 3 when 

moist or dry. It is very gravelly sand or very cobbly sand. 

The horizon averages 35 to 60 percent rock fragments, 

including 25 to 40 percent pebbles. 5 to 20 percent 

cobbles, and 0 to 5 percent stones. 

Sinnice Series 

The Sinnice series consists of very deep, well drained 

soils on foot slopes, back slopes, and ridgetops of 

mountains. These soils formed in layers of aerially 

deposited volcanic ash and pumice. Slope is 5 to 90 

percent. Elevation is 2,800 to 5,000 feet. The average 

annual precipitation is about 125 inches, the average 

annual air temperature is about 39 degrees F. and the 

average frost-free season is 75 to 90 days. 

These soils are ashy over cindery Entic Cryandepts. 

Typical pedon of Sinnice extremely cindery loamy 
Figure 10.-Typical pedon of Sinnice extremely cindery loamy 

sand, 30 to 65 percent slopes. 

Sand, 30 to 65 percent slopes (fig. 10), on Forest Service 

Road N92H, about 1.5 miles northeast of Mount St. 

Helens; 1,250 feet south and 1,100 feet west of the 

northeast corner of sec. 19, T. 9 N., R. 6 E. 

O-0.25 inch to 0; leaves, twigs, and needles. 

A-0 to 1 inch; very dark grayish brown (10YR 3/2) 

cindery very fine sandy loam (volcanic ash and 

cinders), gray (10YR 6/1) dry; single grain; loose,, 

many very fine roots; few fine irregular and tubular 

pores; 30 percent pumice fragments; slightly acid; 

clear smooth boundary. 

BE-1 inch to 7 inches; light gray (10YR 7/1) extremely 

cindery loamy sand (cinders and volcanic ash), white 

(10YR 8/1) dry; common fine distinct stains that are 

brownish yellow (10YR 6/8) and yellow (10YR 7,;

8) 

when dry; single grain; loose; many very fine and few 

medium roots; many medium and coarse irregular 

pores; 70 percent pumice fragments and 10 percent 

pebbles; slightly acid; abrupt smooth boundary. 

2Bw1-7 to 9 inches; dark brown (10YR 3/3) fine sandy 

loam (volcanic ash), light gray (10YR 7/2) dry; weak 

very fine granular structure; soft, very friable, nonsticky 

and nonplastic; weakly smeary; many very fine and 

common medium roots; common fine irregular pores; 

slightly acid; abrupt smooth boundary. 

2Bw2-9 to 15 inches; very dark brown (10YR 2/2) 

loamy sand (volcanic ash), very dark grayish brown 

(10YR 3/2) dry; single grain; soft, very friable, 

nonsticky and nonplastic; many very fine roots, 

common medium roots, and few coarse roots; 

common fine irregular pores; slightly acid; abrupt 

smooth boundary. 

3C-15 to 60 inches; light gray (10YR 7/1) extremely 

cindery sand (cinders and volcanic ash), white (10YR 

8/1) dry; many fine and medium distinct stains that are 

brownish yellow (10YR 6/8) and yellow (10YR 7/8) 

when dry; single grain; loose; common fine and few 

coarse roots; many medium and coarse irregular 

pores; 75 percent pumice fragments and 15 percent 

pebbles 2 to 10 millimeters in diameter; slightly 

acid. 

The 10- to 40-inch particle-size control section 

averages more than 60 percent vitric volcanic ash and 

cinders. The ash layer is 8 to 12 inches thick and extends 

to a depth of 14 to 21 inches. The lower part of the 

control section averages 60 to 80 percent cinders and 5 

to 15 percent pebbles. 
The A horizon has value of 2 or 3 when moist and 

5 or 6 when dry and has chroma of 1 or 2 when moist 

or dry. 

The BE horizon has stains that have hue of 10YR or 

7.5YR and value of 5 to 7 when moist and 6 to 8 when 

dry. The horizon has chroma of 3 to 8 when moist or 

dry. 

The 2Bw horizon has value of 2 or 3 when moist 

and 3 to 7 when dry. and it has chroma of 1 to 4 when 

moist or dry. It is stratified fine sandy loam, sandy loam, 

and loamy sand and has 0 to 15 percent pumice 

fragments. 

The 3C horizon has 65 to 80 percent pumice 

fragments and 5 to 15 percent pebbles. It has stains 

that have hue of 10YR or 7.5YR and value of 5 to 7 

when moist and 6 to 8 when dry. The horizon has 

chroma of 3 to 8 when moist or dry. 

Skamania Series 

The Skamania series consists of very deep, well 

drained soils on terraces and terrace escarpments. 

These soils formed in mixed alluvium derived from 

basalt. andesite. and some volcanic ash. Slope is 0 to 

40 percent. Elevation is 200 to 800 feet. The average 

annual precipitation is about 70 inches, the average 

annual air temperature is about 48 degrees F, and the 

average frost-free season is 110 to 160 days. 

These soils are coarse-loamy, mixed, mesic Typic 

Xerumbrepts. 

Typical pedon of Skamania very fine sandy loam, 0 

to 8 percent slopes, about 1.5 miles north of Carson, 

1,600 feet south and 1,200 feet east of the northwest 

corner of sec. 17. T. 3 N., R. 8 E. 

O1-1.5 inches to 0.5 inch; litter composed of 

needles, leaves. and twigs. 

O2-0.5 inch to 0; decomposed organic material. 

A1-0 to 2 inches; very dark brown (10YR 2/2) very 

fine sandy loam, dark brown (10YR 4/3) dry; weak 

fine granular structure; soft, very friable, slightly 

sticky and nonplastic; many very fine, fine, and 

medium roots; many fine and medium and 

common coarse irregular pores; moderately acid; 

clear wavy boundary. 

A2-2 to 10 inches; dark brown (7.5YR 3/2) very fine 

sandy loam, yellowish brown (10YR 5/4) dry; weak 

fine subangular blocky structure; soft, very friable, 

slightly sticky and nonplastic; many very fine, fine, 

and medium roots and few coarse roots; many fine 

and medium and common coarse irregular pores; 5 

percent pebbles 2 to 4 millimeters in diameter; 

moderately acid; clear wavy boundary. 

Bw1-10 to 27 inches; dark yellowish brown (10YR 3/4) 

very fine sandy loam, light yellowish brown (10YR 

6/4) dry; weak fine subangular blocky structure; soft, 

very friable, slightly sticky and nonplastic; many fine 

and medium roots and few coarse roots; many fine 

and common medium irregular pores; moderately 

acid; gradual wavy boundary. 

Bw2-27 to 43 inches; dark brown (7.5YR 4/4) fine 

sandy loam, light yellowish brown (10YR 6/4) dry; 

weak fine subangular blocky structure; soft, very 

friable, nonsticky and nonplastic; many fine roots 

and common medium and coarse roots; common 

fine and medium irregular pores; slightly acid; 

abrupt wavy boundary. 

C1-43 to 51 inches; dark yellowish brown (10YR 4/4) 

loamy fine sand, light yellowish brown (10YR 6/4) dry; 

massive; soft, very friable, nonsticky and nonplastic; 

common fine, medium, and coarse roots; many fine 

and common medium irregular pores; slightly acid; 

clear wavy boundary. 

C2-51 to 60 inches; dark yellowish brown (10YR 4/4) 

loamy fine sand, light yellowish brown (10YR 6/4) dry; 

massive; soft, very friable, nonsticky and nonplastic; 

common fine and medium roots and few coarse 

roots; many medium and common coarse irregular 

pores; moderately acid. 

The umbric epipedon is 10 to 15 inches thick. The 

10- to 40-inch particle-size control section is 5 to 15 

percent clay and 15 to 35 percent sand that is coarser 

than very fine sand. Reaction is moderately acid or 

slightly acid throughout. 

The A horizon has hue of 10YR or 7.5YR, value of 2 

or 3 when moist and 4 or 5 when dry, and chroma of 2 

or 3 when moist and 3 or 4 when dry. 

The Bw horizon has hue of 10YR or 7.5YR, value of 

3 or 4 when moist and 6 or 7 when dry, and chroma of 

3 or 4 when moist and 4 or 5 when dry. It is very fine 

sandy loam, fine sandy loam, or loam. 

The C horizon has value of 3 or 4 when moist and 6 

or 7 when dry, and it has chroma of 3 or 4 when moist 

or dry. It is loamy fine sand or fine sandy loam. 

Skelida Series 

The Skelida series consists of very deep, well drained 

soils on terraces and terrace escarpments. These soils 

formed in loess and alluvium derived dominantly from 

basalt and andesite. Slope is 5 to 30 percent. 

Elevation is 400 to 1,000 feet. The average annual 

precipitation is about 60 inches, the average annual 

air temperature is about 50 degrees F, and the 
average frost-free season is 160 to 180 days. 

These soils are fine-silty, mixed, mesic Typic 

Xerumbrepts. 

Typical pedon of Skelida silt loam, 15 to 30 percent 

slopes, about 4 miles east of Washougal; 300 feet 

south and 2,640 feet west of the northeast corner of 

sec. 17,T. 1 N., R. 5 E. 

Ap-0 to 7 inches; very dark grayish brown (10YR 3/2) 

silt loam, dark brown (10YR 4/3) dry; weak fine 

granular structure; soft, very friable, slightly sticky 

and slightly plastic; many very fine and fine roots; 

many very fine and fine irregular pores; moderately 

acid; clear wavy boundary. 

A-7 to 15 inches; very dark grayish brown (10YR 3/2) 

silt loam, yellowish brown (10YR 5/4) dry; weak fine 

subangular blocky structure; soft, very friable, slightly 

sticky and slightly plastic; many very fine and fine 

roots; common fine and medium irregular pores; 

moderately acid; clear wavy boundary. 

BA-15 to 20 inches; dark yellowish brown (10YR 4/4) 

silt loam, light yellowish brown (10YR 6/4) dry; weak 

fine subangular blocky structure; slightly hard, 

friable, slightly sticky and slightly plastic; many very 

fine roots and common fine roots; common fine and 

medium irregular pores; moderately acid; abrupt 

wavy boundary. 

Bw1-20 to 43 inches; dark yellowish brown (10YR 4/4) 

silt loam, light yellowish brown (10YR 6/4) dry; weak 

fine and medium subangular blocky structure; slightly 

hard, friable, slightly sticky and slightly plastic; few 

fine roots; many very fine and fine irregular pores; 

moderately acid; clear wavy boundary. 

Bw2-43 to 60 inches; dark yellowish brown (10YR 4/4) 

silt loam, light yellowish brown (10YR 6/4) dry; weak 

fine and medium subangular blocky structure; slightly 

hard, friable, slightly sticky and slightly plastic; few 

fine roots; common fine irregular pores; moderately 

acid. 

The umbric epipedon is 10 to 16 inches thick. The 

solum is more than 60 inches thick. The control section 

is 18 to 25 percent clay. Less than 15 percent of the 

10- to 40-inch particle-size control section is sand that is 

coarser than very fine sand. 

The A horizon has value of 2 or 3 when moist and 

4 or 5 when dry, and it has chroma of 3 or 4 when 

dry. The B horizon has hue of 7.5YR or 10YR. 

Skoly Series 

The Skoly series consists of very deep, well drained

soils on mountain slopes. These soils formed in 

colluvium derived from basalt. Slope is 2 to 65 percent. 

Elevation is 200 to 2,200 feet. The average annual 

precipitation is about 80 inches, the average annual 

temperature is about 50 degrees F, and the average 

frost-free season is 110 to 160 days. 

These soils are loamy-skeletal, mixed, mesic Typic 

Haplumbrepts. 

Typical pedon of Skoly stony loam, 2 to 15 percent 

slopes, about 5 miles west of Beacon Rock State Park; 

500 feet south and 100 feet west of the northeast corner 

of sec. 30, T. 2 N., R. 6 E. 

O-3 inches to 0; leaves, needles, and twigs. 

A-0 to 5 inches; dark brown (7.5YR 3/2) stony 

loam, dark brown (7.5YR 4/2) dry; strong fine 

granular structure; slightly hard, friable, slightly 

sticky and slightly plastic; many very fine and fine 

roots and common coarse roots; many very fine, 

fine, and medium irregular pores; 15 percent 

pebbles, 10 percent cobbles, 2 percent stones, 

and 5 percent soft saprolitic pebbles; strongly acid; 

clear wavy boundary. 

AB-5 to 17 inches; dark brown (7.5YR 3/2) very 

cobbly loam, dark brown (7.5YR 4/2) dry; moderate 

fine granular structure and weak subangular blocky; 

slightly hard, friable, slightly sticky and slightly plastic; 

common very fine, fine, and medium roots and few 

coarse roots; common fine tubular pores and 

common very fine irregular pores; 10 percent 

pebbles, 35 percent cobbles, and 5 percent soft 

saprolitic pebbles; strongly acid; clear irregular 

boundary. 

Bw-17 to 40 inches; dark brown (7.5YR 3/4) very cobbly 

loam, brown (7.5YR 5/4) dry; weak medium 

subangular blocky structure; slightly hard, friable, 

slightly sticky and slightly plastic; few very fine, fine, 

and medium roots; common fine tubular pores; 10 

percent pebbles, 35 percent cobbles, and 20 

percent soft saprolitic pebbles; strongly acid; gradual 

wavy boundary. 

BC-40 to 60 inches; dark brown (7.5YR 3/4) very 

cobbly loam, brown (7.5YR 5/4) dry; weak fine 

subangular blocky structure; slightly hard, friable, 

slightly sticky and plastic; few fine roots; common 

fine tubular pores; 10 percent pebbles, 35 

percent cobbles, and 10 percent stones; strongly 

acid. 

The 10- to 40-inch particle-size control section 

averages 18 to 30 percent clay, 35 to 60 percent 

rock fragments, and 5 to 25 percent saprolitic 

fragments. 
Thickness of the umbric epipedon ranges from 14 to 20 

inches. 

The A horizon has hue of 5YR or 7.5YR, value of 2 

or 3 when moist and 3 to 5 when dry, and chroma of 2 

or 3 when moist or dry. From 2 to 10 percent of the 

surface is covered with stones. 

The Bw horizon has hue of 5YR or 7.5YR, value of 3 or 

4 when moist and 4 to 6 when dry, and chroma of 3 or 

4 when moist or dry. It is very cobbly loam, very gravelly 

clay loam, or very cobbly clay loam. 

The BC horizon has value of 3 or 4 when moist and 

5 or 6 when dry. It is very cobbly loam, very cobbly clay 

loam. or extremely cobbly loam. It has 10 to 20 percent 

pebbles and 40 to 50 percent cobbles and stones. 

St. Helens Series 

The St. Helens series consists of very deep, well 

drained soils on terraces. These soils formed in layers of 

aerially deposited pumice and volcanic ash over 

pyroclastic flow and lahar material. Slope is 0 to 30 

percent. Elevation is 1,600 to 2,800 feet. The average 

annual precipitation is about 130 inches, the average 

annual air temperature is about 44 degrees F, and the 

frost-free season is 90 to 110 days. 

These soils are ashy, frigid Typic Vitrandepts. 

Typical pedon of St. Helens sandy loam, 0 to 30 

percent slopes, near Pine Creek, 1,200 feet south and 

2,100 feet east of the northwest corner of sec. 4, T. 7 

N., R. 6 E. 

O-1 inch to 0; loose, partially decomposed 

organic litter consisting of needles, leaves, twigs, 

cones, and bark. 

E-0 to 2 inches; dark grayish brown (10YR 4/2) sandy 

loam (volcanic ash), gray (10YR 6/1) dry; weak fine 

granular structure; soft, friable, nonsticky and 

nonplastic; many very fine roots and common fine 

and medium roots; many very fine irregular pores; 

moderately acid; abrupt smooth boundary. 

Bw1-2 to 4 inches; very dark brown (10YR 2/2) sandy 

loam (volcanic ash), very dark grayish brown (10YR 

3/2) dry; weak fine granular structure; soft, friable, 

nonsticky and nonplastic; many very fine roots and 

common fine and medium roots; many very fine 

irregular pores; moderately acid; abrupt smooth 

boundary. 

Bw2-4 to 6 inches; very dark grayish brown (10YR 

3/2) loamy sand (volcanic ash), light brownish gray 

(10YR 6/2) dry; weak fine subangular blocky 

structure; soft, friable, nonsticky and nonplastic; 

many very fine roots and common fine and medium 

roots; many very fine irregular pores; 10 percent 

pumice fragments; moderately acid; abrupt smooth 

boundary. 

2Bw3-6 to 9 inches; light brownish gray (10YR 6/2) 

extremely cindery loamy sand (cinders and volcanic 

ash), light gray (10YR 7/2) dry; light yellowish brown 

(10YR 6/4) stains; single grain; loose; many very 

fine roots; many medium and coarse irregular pores; 

80 percent rounded and subangular pumice 

fragments 2 to 15 millimeters in diameter and 

5percent pebbles; slightly acid; abrupt smooth 

boundary. 

3Bw4-9 to 18 inches; dark brown (10YR 3/3) sandy 

loam (volcanic ash), pale brown (10YR 6/3) dry; 

moderate fine and medium subangular blocky 

structure; soft, friable, nonsticky and slightly plastic; 

weakly smeary; few fine roots and common medium 

roots; many very fine irregular pores; 10 percent 

angular and subangular pumice fragments 2 to 5 

millimeters in diameter; slightly acid; abrupt smooth 

boundary. 

4BC-18 to 28 inches; dark grayish brown (10YR 4/2) 

sand (volcanic ash), light brownish gray (10YR 6/2) 

dry; single grain; loose; few medium and fine roots; 

many fine and medium irregular pores; 10 percent 

angular and subangular pumice fragments 2 to 10 

millimeters in diameter; slightly acid; gradual smooth 

boundary. 

5C-28 to 60 inches; dark grayish brown (10YR 4/2) 

very gravelly coarse sand, gray (10YR 6/1) dry; 

massive; hard, firm, nonsticky and nonplastic; many 

medium and coarse irregular pores; 50 percent 

pebbles and 10 percent cobbles; slightly acid. 

Depth to the 5C horizon is 20 to 35 inches. The 

upper part of the 10- to 40-inch particle-size control 

section is more than 60 percent vitric volcanic ash and 

has 0 to 10 percent rock fragments. The lower part 

averages 35 to 65 percent rock fragments. The B and C 

horizons are moderately acid or slightly acid. 

The E horizon has value of 3 or 4 when moist and 5 

or 6 when dry, and it has chroma of 1or 2 when moist 

or dry. 

The Bw horizon has value of 2 or 3 when moist and

3 to 6 when dry, and it has chroma of 1 to 3 when 

moist or dry. It averages 5 to 15 percent pumice 

fragments. 

The 2Bw horizon has 60 to 85 percent pumice 

fragments and 5 to 15 percent pebbles. It has iron 

stains that have hue of 10YR or 7.5YR and value of 

5 or 6. 
The 3Bw horizon has hue of 10YR or 7.5YR 

and value of 3 or 4 when moist. It is sandy loam or 

fine sandy loam. 

The 4BC horizon has 5 to 15 percent pumice 

fragments. It is sand or loamy sand. 

The 5C horizon has 30 to 50 percent pebbles and 5 

to 15 percent cobbles. 

St. Martin Series 

The St. Martin series consists of very deep, 

moderately well drained soils on back slopes. foot 

slopes. and toe slopes of mountains that have been 

disturbed by landslides. These soils formed in colluvium 

derived from andesite. Slope is 2 to 65 percent. Elevation 

is 300 to 2,000 feet. The average annual precipitation is 

about 55 inches, the average annual temperature is 

about 47 degrees F, and the average frost-free season is 

100 to 140 days. 

These soils are fine, montmorillonitic, mesic Aquic 

Hapludolls. 

Typical pedon of St. Martin gravelly silty clay loam, 

15 to 30 percent slopes, about 0.25 mile northwest of 

Collins; 2,500 feet south and 900 feet west of the 

northeast corner of sec. 36, T. 3 N., R. 8 E. 

O-2 inches to 0; needles, leaves, and twigs. 

A-0 to 4 inches; black (10YR 2/1) gravelly silty clay 

loam, dark grayish brown (10YR 4/2) dry; moderate 

medium granular structure; soft, friable, slightly sticky 

and plastic; many very fine and fine roots and few 

medium roots; common fine irregular pores; 20 

percent pebbles; neutral; clear smooth boundary. 

BAt-4 to 11 inches; very dark grayish brown (10YR 

3/2) silty clay loam, grayish brown (10YR 5/2) dry; 

moderate fine subangular blocky structure; slightly 

hard, friable, sticky and plastic; common very fine, 

fine, and medium roots; many very fine irregular 

pores; 20 percent soft saprolitic andesite fragments; 

slightly acid; clear smooth boundary. 

Bt1-11 to 25 inches; light olive brown (2.5Y 5/4) clay, 

light yellowish brown (10YR 6/4) dry; few fine faint 

mottles that are dark grayish brown (2.5Y 4/2) when 

moist and light olive brown (2.5Y 5/4) when dry; 

moderate fine and medium subangular blocky 

structure; hard, friable, sticky and plastic; common 

fine and medium roots; common very fine irregular 

pores and common fine tubular pores; 35 percent soft 

saprolitic andesite fragments; slightly acid; gradual 

smooth boundary. 

Bt2-25 to 60 inches; light yellowish brown (2.5Y 6/4) 

clay, light yellowish brown (10YR 6/4) dry; few fine 

faint mottles that are dark grayish brown (2.5Y 4/2) 

when moist and light olive brown (2.5Y 5/4) when dry; 

moderate medium subangular blocky structure; hard, 

friable, sticky and plastic; few fine roots; common fine 

irregular and tubular pores; 45 percent soft saprolitic 

andesite fragments; moderately acid. 

The mollic epipedon is 10 to 17 inches thick. The 10

to 40-inch particle-size control section averages 0 to 15 

percent hard rock fragments and 10 to 35 percent soft, 

weathered rock fragments. It is 40 to 60 percent clay. 

The A horizon has hue of 10YR or 2.5Y, value of 2 

or 3 when moist and 4 or 5 when dry, and chroma of 

10r 2 when moist. It has 15 to 25 percent pebbles. 

Reaction is slightly acid or neutral. 

The BAt horizon has hue of 10YR or 2.5Y and 

chroma of 2 or 3 when dry. It is clay, silty clay loam, or 

heavy clay loam and has 0 to 15 percent pebbles and 

0 to 5 percent cobbles. Reaction is moderately acid or 

slightly acid. 

The Bt horizon has value of 4 to 6 when moist and 5 

or 6 when dry, and it has chroma of 3 or 4 when moist 

or dry. It averages 15 to 45 percent soft rock fragments. 

Reaction is moderately acid or slightly acid. 

Stabbart Series 

The Stabbart series consists of very deep, somewhat 

poorly drained soils on toe slopes and alluvial fans. 

These soils formed in alluvium derived dominantly from 

fine textured igneous rock. Slope is 0 to 3 percent. 

Elevation is 800 to 1,200 feet. The average annual 

precipitation is about 95 inches, the average annual air 

temperature is about 46 degrees F, and the average 

frost-free season is 115 to 135 days. 

These soils are fine-loamy, mixed, mesic Aquic 

Hapludolls. 

Typical pedon of Stabbart clay loam, about 2 miles 

south of Stabler; 1,100 feet south and 2,000 feet east of 

the northwest corner of sec. 35, T. 4 N., R. 7 E. 

A-0 to 13 inches; dark brown (10YR 3/3) clay loam, 

brown (10YR 5/3) dry; moderate fine granular structure 

and weak very fine subangular blocky structure; soft, 

very friable, slightly sticky and nonplastic; many very 

fine and fine roots; many very fine irregular pores; 5 

percent pebbles and 10 percent concretions; strongly 

acid; clear smooth boundary. 

BA-13 to 18 inches; dark brown (10YR 3/3) clay 

loam, pale brown (10YR 6/3) dry; few fine faint dark 

grayish brown (10YR 4/2) mottles; moderate very fine 

and fine subangular blocky structure; slightly 
hard, friable, slightly sticky and slightly plastic; many 

very fine roots. common fine roots, and few coarse 

roots; common very fine irregular pores and few fine 

tubular pores. 5 percent concretions; strongly acid; 

clear wavy boundary. 

Bt1-18 to 29 inches; dark brown (10YR 4/3) clay loam, 

pale brown (10YR 6/3) dry; few fine faint dark grayish 

brown (10YR 4/2) mottles and few fine distinct strong 

brown (7.5YR 5/8) mottles; moderate fine and medium 

subangular blocky structure; slightly hard. friable, 

slightly sticky and slightly plastic; common very fine 

and fine roots and few coarse roots; few very fine and 

fine irregular pores; few thin clay films on faces of 

peds; strongly acid; clear irregular boundary. 

Bt2-29 to 37 inches; light yellowish brown (10YR 6/4) 

silty clay loam, white (10YR 8/2) dry; common fine 

distinct gray (10YR 6/1) and strong brown (7.5YR 5/6) 

mottles; moderate fine and medium subangular blocky 

structure; slightly hard, friable, slightly sticky and 

slightly plastic; few very fine and fine roots; few very 

fine tubular pores, few moderately thick clay films on 

faces of peds; strongly acid; clear wavy boundary. 

C-37 to60 inches; light yellowish brown (10YR 6/4) clay 

loam, very pale brown (10YR 7/3) dry; common fine 

distinct gray (10YR 6/1) and strong brown (7.5YR 5/6) 

mottles; massive; slightly hard, friable, slightly sticky 

and slightly plastic; few very fine roots; common fine 

and very fine irregular pores; strongly acid. 

The mollic epipedon is mottled and is 10 to 13 inches 

thick. The 10- to 40-inch particle-size control section 

ranges from 27 to 35 percent clay. Low-chroma mottles 

are at a depth of 10 to 15 inches. An apparent water table 

is at a depth of 6 to 12 inches during January to M ay. 

The A horizon has chroma of 2 or 3 when moist or 

dry. Content of concretions ranges from 5 to 10 percent. 

The Bt horizon is mottled and has value of 3 to 6 

when moist and 5 to 8 when dry, and it has chroma of 2 

to 4 when moist or dry. It is clay loam or silty clay loam. 

The C horizon has value of 4 to 6 when moist and 

5 to 7 when dry, and it has chroma of 3 or 4 when 

moist or dry. 

Stabler Series 

The Stabler series consists of very deep, well drained 

soils on terraces and back slopes. These soils formed in 

pyroclastic flows of volcanic ash and pumice. 

Slope is 0 to 65 percent. Elevation is 600 to 1,600 feet. 

The average annual precipitation is about 80 inches, the 

average annual air temperature is about 46 degrees F, 

and the average frost-free season is 110 to 140 days. 

These soils are medial, mesic Entic Dystrandepts. 

Typical pedon of Stabler loam, 0 to 8 percent slopes, 

about 3 miles northwest of Stabler; 200 feet north and 

1,600 feet east of the southwest corner of sec. 10, T. 4 

N., R. 7 E. 

O1-1 to 0.5 inch; leaves, needles, and twigs. 

O2-0.5 inch to 0; decomposed organic material. 

Act-0 to 2 inches; dark brown (10YR 3/3) loam, 

brown (10YR 5/3) dry; weak medium granular 

structure; soft, very friable, nonsticky and nonplastic; 

weakly smeary; many very fine and fine roots; many 

fine and common medium irregular pores; 15 

percent shotlike aggregates 2 to 4 millimeters in size; 

moderately acid; clear wavy boundary. 

Ac2-2 to 9 inches; dark yellowish brown (10YR 3/4) 

loam, yellowish brown (10YR 5/4) dry; weak coarse 

granular structure; slightly hard, very friable, slightly 

sticky and nonplastic; weakly smeary; many very fine 

and common fine roots; many fine and common 

medium irregular pores; 15 percent shotlike 

aggregates 2 to 4 millimeters in size; moderately acid; 

clear wavy boundary. 

Bwc-9 to 26 inches; dark yellowish brown (10YR 

3/6) loam, light yellowish brown (10YR 6/4) dry; 

weak fine and medium subangular blocky structure; 

slightly hard, friable, slightly sticky and slightly 

plastic; weakly smeary; common fine and medium 

roots; common fine irregular pores; 10 percent 

shotlike aggregates 2 to 4 millimeters in size; 

moderately acid; clear smooth boundary. 

Bw-26 to 37 inches; dark yellowish brown (10YR 4/6) 

loam, light yellowish brown (10YR 6/4) dry; massive; 

hard, firm, slightly sticky and nonplastic; weakly 

smeary; common fine roots; many fine irregular 

pores; 10 percent shotlike aggregates 2 to 4 

millimeters in size; moderately acid; clear smooth 

boundary. 

C-37 to 60 inches; dark yellowish brown (10YR 4/6) 

sandy loam, very pale brown (10YR 7/4) dry; 

massive; hard, very firm, nonsticky and nonplastic; 

weakly smeary; few fine roots; many fine irregular 

pores; slightly acid. 

The solum is 30 to 50 inches thick. The 10- to 40-

inch particle-size control section is 0 to 2 percent coarse 

fragments and 10 to 18 percent clay. Reaction is 
moderately acid or slightly acid throughout. 

The A horizon has hue of 7.5YR or 10YR, value of 2 

or 3 when moist and 4 or 5 when dry, and chroma of 3 

or 4 when dry. It is 5 to 20 percent shotlike aggregates. 

The B horizon has hue of 7.5YR or 10YR, value of 3 

or 4 when moist and 5 to 7 when dry, and chroma of 4 

to 6 when moist or dry. It is loam or silt loam. The 

upper part of the horizon is 0 to 15 percent shotlike 

aggregates. 

The C horizon has hue of 7.5YR or 10YR, value of 4 

to 7 when moist or dry, and chroma of 4 to 6 when 

moist. It is loam or sandy loam. 

Steever Series 

The Steever series consists of very deep, well drained 

soils on back slopes, foot slopes, and toe slopes. These 

soils formed in colluvial landslide material derived from 

basalt, andesite, and conglomerate. Slope is 2 to 65 

percent. Elevation is 50 to 1,500 feet. The average 

annual precipitation is about 75 inches, the average 

annual air temperature is about 48 degrees F, and the 

average frost-free season is 100 to 160 days. 

These soils are loamy-skeletal, mixed, mesic Typic 

Haplumbrepts. 

Typical pedon of Steever stony clay loam, 2 to 30 

percent slopes, about 2 miles west of Stevenson; 1,500 

feet east and 2,000 feet south of the northwest corner 

of sec. 3, T. 2 N., R. 7 E. 

Oi-1 inch to 0; leaves, needles, and twigs. 

A-0 to 5 inches; very dark brown (10YR 2/2) stony 

clay loam, dark grayish brown (10YR 4/2) dry; 

moderate fine granular and subangular blocky 

structure; slightly hard, friable, slightly sticky and 

slightly plastic; many very fine and fine roots and 

common medium roots; many fine and medium 

irregular pores; 20 percent pebbles, 10 percent 

cobbles, and 5 percent stones; moderately acid; 

abrupt wavy boundary. 

AB-5 to 12 inches; dark brown (10YR 3/3) gravelly 

clay loam. brown (10YR 5/3) dry; moderate fine 

granular structure and weak fine subangular blocky, 

slightly hard, friable, slightly sticky and slightly plastic; 

many very fine and fine roots and common medium 

roots; many fine and medium irregular pores; 30 

percent hard pebbles, 5 percent hard cobbles, and 5 

percent soft saprolitic pebbles; strongly acid; clear 

wavy boundary. 

Bw1-12 to 20 inches; dark brown (10YR 4/3) very 

gravelly clay loam, yellowish brown (10YR 5/4) dry; 

weak fine and medium subangular blocky structure; 

slightly hard, friable, slightly sticky and slightly 

plastic; many very fine and fine roots and common 

medium roots; common fine and medium irregular 

pores; 40 percent hard pebbles and 10 percent soft 

saprolitic pebbles; strongly acid; clear wavy 

boundary. 

Bw2-20 to 30 inches; dark brown (10YR 4/3) very 

gravelly loam, yellowish brown (10YR 5/4) dry; weak 

fine and medium subangular blocky structure; slightly 

hard, friable, slightly sticky and slightly plastic; 

common very fine and fine roots and few coarse 

roots; common fine irregular pores; 40 percent hard 

pebbles and 20 percent soft saprolitic pebbles; 

strongly acid; clear smooth boundary. 

C-30 to 60 inches; dark brown (10YR 4/3) very 

gravelly loam, yellowish brown (10YR 5/4) dry; 

massive; slightly hard, friable, slightly sticky and 

slightly plastic; few fine roots; few fine irregular 

pores; 40 percent hard pebbles, 10 percent hard 

cobbles, and 40 percent soft saprolitic pebbles; 

strongly acid. 

The umbric epipedon is 10 to 13 inches thick. The 

10- to 40-inch particle-size control section is 18 to 32 

percent clay and averages 35 to 60 percent rock 

fragments and 5 to 30 percent saprolitic fragments. 

Reaction is strongly acid or moderately acid throughout. 

The A and AB horizons have hue of 10YR or 2.5Y, 

value of 2 or 3 when moist and 4 or 5 when dry, and 

chroma of 2 or 3 when moist or dry. From 2 to 10 

percent of the surface is covered with stones. 

The Bw horizon has hue of 10YR or 2.5Y, value of 4 

or 5 when moist and 5 or 6 when dry, and chroma of 3 

or 4 when moist or dry. It is very gravelly clay loam, 

very gravelly loam, or very gravelly silt loam. 

The C horizon has colors and textures similar to 

those of the B horizon. 

Stevenson Series 

The Stevenson series consists of very deep, well 

drained soils on toe slopes, foot slopes, and back 

slopes of mountains. These soils formed in colluvial 

landslide material derived from basalt, andesite, and 

conglomerate. Slope is 2 to 50 percent. Elevation is 

100 to 1,200 feet. The average annual precipitation is 

about 80 inches, the average annual air temperature is 

about 47 degrees F, and the frost-free season is 110 to 

150 days. 

These soils are fine-loamy, mixed, mesic Typic 

Haplumbrepts. 

Typical pedon of Stevenson loam, 15 to 30 percent 
slopes, about 3.5 miles north of Stevenson; 300 feet 

north and 1,750 feet west of the southeast corner of 

sec. 13,T. 3N., R. 7E. 

O-1 inch to 0; needles, leaves, and twigs. 

A1-0 to 4 inches; dark brown (7.5YR 3/2) loam, dark 

brown (7.5YR 4/4) dry; weak fine and medium 

granular structure; soft, very friable, slightly sticky 

and slightly plastic; many very fine and fine roots; 

many very fine, fine, and medium irregular pores; 5 

percent concretions; moderately acid; clear wavy 

boundary. 

A2-4 to 11 inches; dark brown (7.5YR 3/3) loam. 

brown (7.5YR 5.4) dry; weak medium granular 

structure; soft, friable, slightly sticky and slightly 

plastic; many very fine and fine roots and few 

medium roots; many very fine, fine, and medium 

irregular pores; 5 percent concretions; moderately 

acid; clear wavy boundary. 

Bw1-11 to 28 inches; dark brown (7.5YR 4/4) loam, 

brown (7.5YR 5/4) dry; weak medium subangular 

blocky structure; soft, friable, slightly sticky and 

slightly plastic; common very fine and fine roots and 

few medium and coarse roots; common fine and 

medium irregular pores; 5 percent soft saprolitic 

basalt fragments; strongly acid; clear wavy boundary.

Bw2-28 to 37 inches; dark yellowish brown (10YR 4/4) 

loam, yellowish brown (10YR 5/4) dry; weak fine and 

medium subangular blocky structure; soft. very friable. 

slightly sticky and slightly plastic; few very fine. fine. 

and medium roots; many fine and medium irregular 

pores and common medium tubular pores; 40 percent 

soft saprolitic basalt fragments; strongly acid; abrupt 

wavy boundary. 

C-37 to 60 inches; dark yellowish brown (10YR 4/6) 

loam, yellowish brown (10YR 5/6) dry; massive; 

soft, very friable, slightly sticky and slightly plastic; 

few fine roots; few fine irregular pores; 50 percent 

soft saprolitic basalt fragments; strongly acid. 

The solum is 35 to 55 inches thick. The 10- to 

40-inch particle-size control section is 20 to 35 

percent clay. It averages 0 to 15 percent hard rock 

fragments and 15 to 35 percent soft saprolitic 

fragments. 

The A horizon has hue of 7.5YR or 10YR, value of 

4 or 5 when dry, and chroma of 2 or 3 when moist 

and 2 to 4 when dry. 

The Bw horizon has hue of 7.5YR or 10YR, value of 

5 to 7 when dry, and chroma of 4 to 6 when moist or 

dry. It is clay loam, loam, or silt loam. Reaction is 

strongly acid or moderately acid. 

The C horizon has hue of 10YR or 7.5YR, value of 4 

or 5 when moist and 5 to 7 when dry, and chroma of

4 to 6 when moist or dry. It is clay loam or loam and 

is 0 to 35 percent hard rock fragments and 35 to 60 

percent soft saprolitic fragments. 

Studebaker Series 

The Studebaker series consists of very deep, 

somewhat excessively drained soils on highly irregular 

mountain foot slopes and toe slopes. These soils formed 

in avalanche debris flow material. Slopes are mostly 0 to 

20 percent, but there are very short slopes of as much 

as 100 percent. Elevation is 2,700 to 5,500 feet. The 

average annual precipitation is about 135 inches, the 

average annual air temperature is about 40 degrees F, 

and the frost-free season is 70 to 90 days. 

These soils are sandy-skeletal, mixed Typic 

Cryorthents. 

Typical pedon of Studebaker very gravelly loamy 

sand, 0 to 20 percent slopes, about 3.5 miles west of 

Spirit Lake, 2,000 feet south and 1,500 feet east of the 

northwest corner of sec. 19, T. 9 N., R. 5 E. 

C1-0 to 6 inches; dark gray (10YR 4/1) very gravelly 

loamy sand. light gray (10YR 6/1) dry; single grain; 

loose, nonsticky and nonplastic; many medium and 

coarse irregular pores; 15 percent cobbles, 40 

percent pebbles, and 15 percent pumice fragments; 

moderately acid; clear wavy boundary. 

C2-6 to 60 inches; dark gray (10YR 4/1) extremely 

gravelly loamy sand, gray (10YR 5/1) dry; single 

grain; loose, nonsticky and nonplastic; many 

medium and coarse irregular pores; 20 percent 

cobbles, 45 percent pebbles, and 15 percent 

pumice fragments; moderately acid. 

The mean annual soil temperature ranges from 38 to 

43 degrees F. The 10- to 40-inch particle-size control 

section averages 35 to 80 percent coarse fragments and 

15 to 50 percent volcanic glass and glass aggregates. 

It is very strongly acid to moderately acid. 

The C1 horizon has hue of 2.5YR to 10YR, value 

of 3 to 6 when moist and 4 to 8 when dry, and 

chroma of 1 to 4 when moist or dry. Texture ranges 

from loamy sand to extremely cindery sand. 

The C2 horizon has hue of 2.5YR to 10YR, value of 

3 to 5 when moist and 4 to 8 when dry, and chroma 

of 1 to 3 when moist. It is very gravelly loamy sand, 

extremely gravelly loamy sand, or extremely cobbly 

sand. Strata that have varying amounts of gravel are 

common. 
Swift Series 

The Swift series consists of very deep, well drained 

soils on side slopes and ridgetops of mountains. These 

soils formed in colluvium derived from volcanic ash and 

basic igneous rock with a mantle of volcanic ash and 

cinders. Slope is 2 to 90 percent. Elevation is 1,200 to 

2,800 feet. The average annual precipitation is about 

115 inches, the average annual air temperature is about 

43 degrees F, and the average frost-free season is 100 

to 120 days. 

These soils are ashy over medial-skeletal, frigid 

Typic Vitrandepts. 

Typical pedon of Swift cindery sandy loam, 2 to 30 

percent slopes, about 1 mile northwest of McClellan 

Mountain; 1,200 feet south and 400 feet west of the 

northeast corner of sec. 4, T. 6 N., R. 6 E. 

O1-2 inches to 1 inch; leaves, needles, twigs, 

and moss. 

O2-1 inch to 0; decomposed organic litter. 

A1-0 to 2 inches; very dark grayish brown (10YR 3/2) 

extremely cindery sand (cinders and volcanic ash), 

grayish brown (10YR 5/2) dry; single grain; loose; 

many very fine roots and few medium roots; many 

medium and coarse irregular pores; 70 percent 

subangular pumice fragments 2 to 10 millimeters in 

size; moderately acid; abrupt wavy boundary. 

A2-2 to 4 inches; very dark grayish brown (10YR 3/2) 

cindery sandy loam (volcanic ash and cinders), light 

brownish gray (10YR 6/2) dry; weak fine granular 

structure; soft, very friable, nonsticky and nonplastic; 

many very fine and fine roots and common medium 

roots; common fine irregular pores; 15 percent 

pumice fragments 2 to 15 millimeters in size and 5 

percent angular and subangular pebbles; slightly 

acid; clear wavy boundary, 

A3-4 to 12 inches; dark brown (10YR 3/3) cindery 

sandy loam (volcanic ash and cinders), pale brown 

(10YR 6/3) dry; weak fine granular structure; soft, very 

friable, nonsticky and nonplastic; many very fine and 

fine roots and common medium roots; common 

medium irregular pores; 15 percent pumice fragments 

2 to 15 millimeters in size and 10 percent angular and 

subangular pebbles; slightly acid; clear wavy 

boundary. 

Bw-12 to 27 inches; dark yellowish brown (10YR 4/4) 

very cindery loam (volcanic ash and cinders), very 

pale brown (10YR 7/4) dry; weak fine subangular 

blocky structure; soft, friable, nonsticky and slightly 

plastic; weakly smeary; many very fine and fine 

roots and common medium roots; many fine irregular 

pores; 30 percent pumice fragments 2 to 20 

millimeters in size and 15 percent angular and 

subangular andesite pebbles; moderately acid; clear 

wavy boundary. 

2Bwb-27 to 60 inches; dark yellowish brown (10YR 

3/4) extremely cobbly loam, very pale brown (10YR 

7/4) dry; moderate medium subangular blocky 

structure; slightly hard, friable, slightly sticky and 

slightly plastic; common fine roots and few coarse 

roots; many fine and medium irregular pores; 40 

percent pebbles, 25 percent cobbles, and 10 

percent stones; moderately acid. 

The upper part of the 10- to 40-inch particle-size 

control section averages 35 to 50 percent cinders, and 

the lower part averages 40 to 75 percent hard rock 

fragments. 

The A horizon has hue of 10YR or 7.5YR, value of 2 

or 3 when moist and 5 or 6 when dry, and chroma of 

2 or 3 when moist or dry. It is 5 to 10 percent hard 

pebbles. Reaction is moderately acid or slightly acid. 

The Bw horizon has hue of 10YR or 7.5YR, value of 4 

or 5 when moist and 5 to 7 when dry, and chroma of 3 

or 4 when moist or dry. It is very cindery loam or very 

cindery sandy loam. It is 25 to 35 percent pumice 

fragments and 10 to 20 percent hard rock fragments. 

The 2Bwb horizon has hue of 10YR or 2.5Y, value of 3 

to 5 when moist and 6 or 7 when dry, and chroma of 3 

or 4 when moist or dry. It is very gravelly, very cobbly, or 

extremely cobbly. The fine earth fraction is loam or clay 

loam. It has 20 to 40 percent hard pebbles, 15 to 25 

percent cobbles, and 5 to 10 percent stones. 

Timberhead Series 

The Timberhead series consists of very deep, well 

drained soils on back slopes and ridgetops of mountains. 

These soils formed in residuum and colluvium derived 

dominantly from basalt with a mantle of volcanic ash. 

Slope is 5 to 65 percent. Elevation is 2,000 to 2,800 feet. 

The average annual precipitation is about 60 inches, the 

average annual air temperature is 44 degrees F, and 

the average frost-free season is 95 to 115 days. 

These soils are medial, frigid Andic Xerumbrepts. 

Typical pedon of Timberhead gravelly loam, 5 to 30 

percent slopes, about 2 miles east of Willard; 500 feet 

south and 200 feet west of the northeast corner of sec. 6, 

T. 3 N., R. 10 E. 

O-1 inch to 0; needles, leaves, twigs, and cones. 
A-0 to 10 inches; dark brown (7.5YR 3/2) gravelly 

loam, dark brown (7.5YR 4/4) dry; weak very fine 

granular structure; soft, very friable, slightly sticky and 

nonplastic; weakly smeary, many very fine. fine, and 

medium roots; many very fine irregular pores; 35 

percent pebbles; moderately acid; clear wavy 

boundary. 

AB-10 to 20 inches; dark brown (7.5YR 3/4) gravelly 

loam, strong brown (7.5YR 5/6) dry; weak fine 

subangular blocky structure; soft, very friable, 

slightly sticky and slightly plastic; many very fine 

and fine roots and common medium and coarse 

roots; many fine irregular pores and common 

medium tubular pores; 25 percent pebbles; 

moderately acid; gradual wavy boundary. 

Bw-20 to 40 inches; dark brown (7.5YR 4/4) gravelly 

loam, strong brown (7.5YR 5/6) dry; weak fine 

subangular blocky structure; slightly hard, friable, 

slightly sticky and slightly plastic; many very fine, fine. 

and medium roots and few coarse roots; many fine 

irregular pores and common medium tubular pores; 

35 percent saprolitic fragments and 20 percent hard 

pebbles; strongly acid; clear wavy boundary. 

C-40 to 60 inches; dark brown (7.5YR 4/4) loam, 

strong brown (7.5YR 518) dry; massive; slightly 

hard, friable, slightly sticky and nonplastic; many 

fine and medium roots; common fine irregular 

pores; 60 percent saprolitic pebbles; strongly acid. 

Volcanic ash influences the entire profile but is most 

abundant in the upper 8 to 13 inches. The 10- to 40-

inch particle-size control section averages 20 to 35 

percent hard rock fragments and is 13 to 18 percent clay. 

Reaction of the B and C horizons is moderately acid or 

strongly acid. 

The A and AB horizons have hue of 7.5YR or 5YR, 

value of 3 or 4 when dry, and chroma of 2 or 3 when 

moist and 3 or 4 when dry. 

The Bw horizon has hue of 7.5YR or 10YR, value of 4 

or 5 when dry and 3 or 4 when moist, and chroma of 

4 to 6 when dry or moist. 

The C horizon has chroma of 6 to 8 when dry. It has 

50 to 85 percent saprolitic fragments. 

Tradedollar Series 

The Tradedollar series consists of very deep, well 

drained soils on back slopes and ridgetops of 

mountains. These soils formed in aerially deposited 

volcanic ash and pumice. Slope is 0 to 90 percent. 

Elevation is 2,800 to 5,400 feet. The average annual 

precipitation is about 100 inches, the average annual air 

temperature is about 39 degrees F, and the average frostfree season is 75 to 95 days. 

These soils are cindery Typic Cryorthods. 

Typical pedon of Tradedollar sandy loam, 65 to 90 

percent slopes, about 2 miles west of St. Helens Lake; 

400 feet north and 200 feet west of the southeast corner 

of sec. 32, T. 10 N., R. 5 E. 

O-1 inch to 0; decomposed organic material. 

A1-0 to 1 inch; very dark gray (10YR 3/1) sandy loam, 

gray (10YR 6/1) dry; weak fine granular structure; soft, 

very friable, nonsticky and nonplastic; many very fine 

and fine roots; many fine irregular pores; moderately 

acid; abrupt smooth boundary. 

A2-1 inch to 5 inches; very dark grayish brown (10YR 

3/2) sandy loam, pale brown (10YR 6/3) dry; weak fine 

granular structure; soft, very friable, nonsticky and 

nonplastic; many very fine and fine roots, common 

medium roots, and few coarse roots; many fine 

irregular pores and few fine and medium tubular 

pores; 10 percent pumice fragments; moderately acid; 

clear wavy boundary. 

Bs1-5 to 15 inches; dark brown (7.5YR 4/2) cindery 

sandy loam, brown (7.5YR 5/3) dry; weak fine 

subangular blocky structure; soft, friable, nonsticky 

and nonplastic; weakly smeary; many very fine and 

fine roots and common medium and coarse roots; 

many fine irregular pores and common fine and 

medium tubular pores; 15 percent pumice 

fragments; moderately acid; clear wavy boundary. 

Bs2-15 to 26 inches; dark brown (7.5YR 4/2) cindery 

sandy loam, pinkish gray (7.5YR 6/2) dry; weak fine 

subangular blocky structure; soft, friable, nonsticky 

and nonplastic; weakly smeary; common very fine 

and fine roots and few medium and coarse roots; 

many fine irregular pores and common medium 

tubular pores; 30 percent pumice fragments and 10 

percent pebbles; moderately acid; clear wavy 

boundary. 

Bs3-26 to 35 inches; dark brown (7.5YR 4/2) 

extremely cindery loamy sand, brown (7.5YR 5/2) dry; 

common medium distinct strong brown (7.5YR 5/6) 

stains; single grain; loose; common very fine and fine 

roots and few medium roots; many fine and medium 

irregular pores and few fine and medium tubular 

pores; 60 percent pumice fragments; moderately acid;

clear wavy boundary. 

Bs4-35 to 42 inches; strong brown (7.5YR 5/6) 

extremely cindery sand, reddish yellow (7.5YR 6/6) 

dry; single grain; loose; few medium roots; many 

coarse irregular pores; 75 percent pumice 
fragments and 15 percent cobbles; moderately acid; 

abrupt smooth boundary. 

2Eb-42 to 51 inches; dark grayish brown (10YR 4/2) 

cindery sandy loam, light brownish gray (10YR 6/2) 

dry; massive; soft, friable, nonsticky and nonplastic; 

weakly smeary; common fine roots and few medium 

roots; many fine irregular pores and few fine tubular 

pores; moderately acid; gradual wavy boundary. 

2Bwb-51 to 60 inches; dark brown (10YR 4/3) very 

gravelly sandy loam, pale brown (10YR 6/3) dry; 

massive; soft, friable, nonsticky and nonplastic; 

weakly smeary; few fine roots; many medium and 

coarse irregular pores; 30 percent pumice fragments 

and 40 percent pebbles; moderately acid. 

The 10- to 40-inch particle-size control section 

averages 35 to 55 percent pumice fragments. Depth to 

the buried profile is 40 to 50 inches or more. 

The A horizon has hue of 2.5Y, 10YR, or 7.5YR, 

value of 2 or 5 when moist and 4 to 8 when dry, and 

chroma of 0 to 3 when moist or dry. 

The Bs1 horizon has hue of 7.5YR or 5YR, value of 

3 or 4 when moist and 5 or 6 when dry, and chroma 

of 2 to 6 when moist or dry. It is 15 to 30 percent 

pebble-sized pumice fragments. 

The Bs2 horizon has hue of 7.5YR or 5YR, value of 

4 to 6 when moist and 6 to 8 when dry, and chroma of 

2 to 6 when moist or dry. It is 30 to 55 percent 

pebble-sized pumice fragments and 0 to 15 percent 

hard pebbles. 

The Bs3 and Bs4 horizons have hue of 7.5YR or 

5YR, value of 4 to 6 when moist and 5 to 8 when dry, 

and chroma of 2 to 8 when moist or dry. They are 60 

to 80 percent pumice fragments and 0 to 15 percent 

pebbles. 

The 2Eb and 2Bwb horizons are 15 to 55 

percent pebbles and 0 to 20 percent pumice 

fragments. 

Underwood Series 

The Underwood series consists of very deep, well 

drained soils on foot slopes and back slopes of 

mountains and benches. These soils formed in 

residuum and colluvium derived from basalt and 

andesite with a thin mantle of volcanic ash. Slope is 2 to 

50 percent. Elevation is 500 to 2,000 feet. The average 

annual precipitation is about 50 inches, the average 

annual air temperature is about 46 degrees F, and the 

average frost-free season is 100 to 150 days. 

These soils are fine-loamy, mixed, mesic Ultic 

Haploxeralfs. 

Typical pedon of Underwood loam, 30 to 50 percent 

slopes, about 1 mile south of Willard; 200 feet south and 

1,700 feet west of the northwest corner of sec. 11, T. 3 N., 

R. 9 E. 

O1-2 inches to 0.75 inch; needles, leaves, and twigs.

O2-0.75 inch to 0; decomposed organic material. 

Ac-0 to 5 inches; dark brown (7.5YR 3/2) loam, 

brown (7.5YR 4/4) dry; weak coarse granular 

structure; soft, very friable, slightly sticky and 

nonplastic; weakly smeary; many fine roots and 

common medium roots; many coarse irregular 

pores; 35 percent fine shotlike aggregates 2 to 4 

millimeters in size; slightly acid; clear smooth 

boundary. 

BA-5 to 19 inches; dark brown (7.5YR 3/4) loam, 

brown (7.5YR 5/4) dry; weak medium subangular 

blocky structure; slightly hard, friable, slightly sticky 

and plastic; common fine and medium roots; many 

fine irregular pores and few fine tubular pores; few 

pebbles; moderately acid; clear smooth boundary. 

Bt-19 to 35 inches; dark brown (7.5YR 3/4) clay 

loam, brown (7.5YR 5/4) dry; moderate medium 

subangular blocky structure; hard, friable, slightly 

sticky and plastic; few fine, medium, and coarse 

roots; many fine irregular pores and few fine tubular 

pores; 5 percent soft pebbles; common moderately 

thick clay films in pores and on faces of peds; 

strongly acid; clear wavy boundary. 

C-35 to 60 inches; dark yellowish brown (10YR 4/6) 

loam, brownish yellow (10YR 6/6) dry; common 

medium distinct mottles that are yellowish red (5YR 

4/6) when moist; massive; slightly hard, friable, 

slightly sticky and slightly plastic; few fine roots; 

common medium irregular and tubular pores; 15 

percent soft pebbles; strongly acid. 

Thickness of the solum is 30 to 40 inches. The 

upper 4 to 6 inches of the profile is dominated by 

volcanic ash and has 15 to 35 percent shotlike 

aggregates. The 19 to 35-inch particle-size control 

section is 25 to 35 percent clay, 5 to 25 percent soft, 

weathered rock fragments, and 0 to 15 percent hard 

pebbles and cobbles. The profile has 0 to 25 percent 

rock fragments below the control section. 

The A and AB horizons have hue of 5YR or 7.5YR, 

value of 4 or 5 when dry, and chroma of 2 to 4 when 

moist or dry. 

The Bt horizon has hue of 5YR or 7.5YR and value 

of 3 or 4 when moist. It is loam or clay loam. 

Reaction is strongly acid or moderately acid. 

The C horizon has hue of 5YR, 7.5YR, or 10YR, and 

it has value of 4 or 5 when moist and 5 or 6 when dry, 

it is loam, gravelly loam, or clay loam. Reaction is 

strongly acid or moderately acid. 
Undusk Series 

The Undusk series consists of very deep, well 

drained soils on back slopes of mountains. These soils 

formed in colluvium derived from basalt with a thin mantle 

of volcanic ash. Slope is 5 to 65 percent. Elevation is 

2,000 to 2,800 feet. The average annual precipitation is 

about 55 inches, the average annual air temperature is 

about 44 degrees F, and the average frost-free season is 

90 to 120 days. 

These soils are loamy-skeletal, mixed, frigid Typic 

Xerumbrepts. 

Typical pedon of Undusk gravelly loam, 30 to 65 

percent slopes, about 2.5 miles northwest of 

Underwood; 900 feet south and 500 feet east of the 

northwest corner of sec. 17, T. 3 N., R. 10 E. 

O-1 inch to 0; needles, leaves, and twigs. 

A1-0 to 6 inches; dark brown (7.5YR 3/3) gravelly loam, 

brown (7.5YR 5/4) dry; weak fine granular structure; 

soft, very, friable, nonsticky and nonplastic; weakly 

smeary; common very fine and fine roots; common 

fine irregular pores; 20 percent pebbles and 5 percent 

shotlike aggregates 2 to 4 millimeters in size; neutral; 

clear wavy boundary. 

A2-6 to 15 inches; dark brown (7.5YR 3/3) gravelly 

loam, strong brown (7.5YR 5/6) dry; weak coarse 

granular structure; soft, very friable, slightly sticky and 

slightly plastic; many very fine and common fine roots; 

common fine irregular pores; 20 percent pebbles; 

neutral; clear wavy boundary. 

Bw1-15 to 24 inches; dark brown (7.5YR 4/4) very 

gravelly loam, strong brown (7.5YR 5/6) dry; weak fine 

subangular blocky structure; slightly hard, friable, 

slightly sticky and slightly plastic; many very fine roots 

and common fine roots; common fine irregular pores; 

35 percent pebbles; neutral; clear smooth boundary. 

Bw2-24 to 40 inches; dark brown (7.5YR 4/4) extremely 

gravelly loam, light brown (7.5YR 6/4) dry; weak fine 

subangular blocky structure; slightly hard, friable.. 

slightly sticky and slightly plastic; common very fine 

and fine roots; common fine irregular pores; 50 

percent pebbles and 10 percent cobbles; slightly 

acid; gradual smooth boundary. 

Bw3-40 to 60 inches; dark brown (7.5YR 4/4) very 

gravelly loam, reddish yellow (7.5YR 6/6) dry; weak 

medium subangular blocky structure; slightly hard, 

friable, slightly sticky and slightly plastic; common very 

fine and fine roots; common fine irregular pores; 45 

percent pebbles and 10 percent cobbles; slightly acid.

The upper 4 to 6 inches of the profile is dominated by 

volcanic ash. The umbric epipedon is 10 to 15 inches 

thick. The 10- to 40-inch particle-size control section 

averages 35 to 60 percent rock fragments and has 18 to 

25 percent clay. Reaction is slightly acid or neutral. 

The A horizon has chroma of 2 or 3 when moist. It 

has 15 to 30 percent pebbles and 5 to 10 percent 

shotlike aggregates. 

The Bw horizon has value of 4 or 5 when moist and 5 

or 6 when dry, and it has chroma of 4 to 6 when moist 

or dry. It is 35 to 50 percent pebbles and 0 to 20 percent 

cobbles and stones. 

Vanson Series 

The Vanson series consists of deep, well drained soils 

on back slopes, foot slopes, and ridgetops of mountains. 

These soils formed in colluvium derived from igneous 

rock with a mantle of aerially deposited volcanic ash 

and pumice. Slope is 5 to 90 percent. Elevation is 2,800 to 

5,000 feet. The average annual precipitation is about 105 

inches, the average annual air temperature is about 39 

degrees F, and the average frost-free season is 75 to 95 

days. 

These soils are ashy over loamy-skeletal, mixed 

Typic Cryorthods. 

Typical pedon of Vanson sandy loam, 30 to 65 

percent slopes, about 5 miles northwest of Cougar; 

2,000 feet south and 2,000 feet east of the northwest 

corner of sec. 6, T. 7 N., R. 5 E. 

E-0 to 1 inch; very dark gray (10YR 3/1) loamy sand, 

gray (10YR 5/1) dry; weak fine granular structure; soft. 

very friable, nonsticky and nonplastic; common very 

fine, fine, and medium roots; many fine irregular pores; 

moderately acid; abrupt wavy boundary. 

Bs1-1 inch to 9 inches; dark brown (7.5YR 3/3) sandy 

loam, brown (7.5YR 5/4) dry; weak fine subangular 

blocky structure; soft, very friable, nonsticky and 

nonplastic; weakly smeary; common fine roots and 

many medium and coarse roots; many fine irregular 

pores; 5 percent pebbles and 10 percent pumice 

fragments; moderately acid; clear wavy boundary. 

2Bs2-9 to 16 inches; dark yellowish brown (10YR 3/4) 

sandy loam, pale brown (10YR 6/3) dry; weak fine 

subangular blocky structure; soft, very friable, nonsticky 

and nonplastic; common fine roots and many medium 

and coarse roots; many fine and medium irregular 

pores; 5 percent pumice fragments; slightly acid; clear 

irregular boundary. 
2Bs3-16 to 24 inches; dark brown (10YR 4/3) loamy 

sand, very pale brown (10YR 7/3) dry; many fine 

prominent strong brown (7.YR 5/8) and reddish yellow 

(7.5YR 6/8) mottles; weak fine subangular blocky 

structure; soft, very friable, nonsticky and nonplastic; 

common fine and medium roots and few coarse 

roots; many fine and medium irregular pores; 10 

percent pumice fragments; slightly acid; clear wavy 

boundary. 

3Bs4-24 to 37 inches; dark yellowish brown (10YR 

4/4) very gravelly sandy loam, light yellowish brown 

(10YR 6/4) dry; weak fine subangular blocky structure;

slightly hard, friable, slightly sticky and slightly plastic;;

weakly smeary; few fine, medium, and coarse roots; 

many fine irregular pores; 30 percent pebbles and 

10 percent cobbles; slightly acid; clear wavy 

boundary. 

3BC-37 to 45 inches; dark yellowish brown (10YR 4/4) 

very gravelly sandy loam, very pale brown (10YR 7/4) 

dry; massive; slightly hard, friable, slightly sticky and 

slightly plastic; weakly smeary; few fine, medium, and 

coarse roots; 35 percent pebbles and 15 percent 

cobbles; slightly acid; abrupt irregular boundary. 

4R-45 inches; fractured andesite. 

Depth to bedrock is 40 to 60 inches. The lower part 

of the 10- to 40-inch particle-size control section is 35 to 

70 percent rock fragments. Reaction is moderately acid 

or slightly acid throughout the profile. 

The E horizon has value of 3 or 4 when moist and 5 

to 7 when dry. It has chroma of 1or 2 when moist or 

dry. 

The 2Bs horizon has hue of 7.5YR or 10YR, value of 3 

or 4 when moist and 5 to 7 when dry, and chroma of 3 

or 4 when moist or dry. It is sandy loam or loamy sand. 

The 3Bs and 3BC horizons have value of 4 or 5 when 

moist and 6 or 7 when dry, and they have chroma of 4 or 5 

when moist or dry. They are sandy loam or loam and 

have 30 to 50 percent pebbles and 10 to 20 percent 

cobbles and stones. 

Wakepish Series 

The Wakepish series consists of very deep, somewhat 

excessively drained soils on fans and low terraces and 

along drainageways. These soils formed in mudflow 

material. Slopes are 0 to 30 percent. Elevation is 1,600 

to 2,800. The average annual precipitation is about 135 

inches, the average annual air temperature is 

about 42 degrees F, and the average frost-free season is 

90 to 110 days. 

These soils are sandy-skeletal, mixed, frigid Typic 

Udorthents. 

Typical pedon of Wakepish very gravelly sandy loam, 0 

to 30 percent slopes, about 5 miles east of Mount St. 

Helens, on Smith Creek; 2,600 feet south and 500 feet 

west of the northeast corner of sec. 5, T. 8 N., R. 6 E. 

C1-0 to 30 inches; dark gray (10YR 4/1) very gravelly 

sandy loam, light gray (10YR 7/1) dry; single grain; 

loose, nonsticky and nonplastic; many fine, medium, 

and coarse irregular pores; 15 percent cobbles, 35 

percent pebbles, and 20 percent pumice fragments; 

moderately acid; clear smooth boundary. 

C2-30 to 60 inches; dark gray (10YR 4/1) very gravelly 

loamy sand, gray (10YR 6/1) dry; single grain; loose, 

nonsticky and nonplastic; many medium and coarse 

irregular pores; 20 percent cobbles and 45 percent 

pebbles; strongly acid. 

The mean annual soil temperature ranges from 43 to 

47 degrees F. The particle-size control section averages 

15 to 50 percent volcanic glass and glass aggregates and 

is 35 to 50 percent coarse fragments. It is very strongly 

acid to moderately acid. Some profiles contain woody 

organic debris that consists of logs, branches, and bark. 

The C1 horizon has hue of 7.5YR to 2.5Y, value of 3 

to 6 when moist and 4 to 8 when dry, and chroma of 0 to 

3 when moist or dry. In some areas the surface is stony 

or bouldery. Some areas have a cindery surface layer. 

The C2 horizon has hue of 7.5YR to 2.5Y, value of 3 

to 5 when moist and 4 to 6 when dry, and chroma of 0 

to 3 when moist or dry. It is very gravelly loamy sand or 

very gravelly sand. 

Washougal Series 

The Washougal series consists of very deep, well 

drained soils on terraces and terrace escarpments. 

These soils formed in mixed alluvial ash, basalt, and 

andesite. Slope is 0 to 50 percent. Elevation is 50 to 

800 feet. The average annual precipitation is about 60 

inches, the average annual air temperature is about 48 

degrees F, and the average frost-free season is 120 to 

180 days. 

These soils are medial-skeletal, mesic Andic 

Xerumbrepts. 

 Typical pedon of Washougal loam, 0 to 3 percent 

slopes, about 600 feet northeast of the steel bridge on
Shields Skye Road; 900 feet north and 300 feet west of the 

southeast corner of sec. 31. T. 2 N., R. 5 E. 

O-1 inch to 0; leaves, needles, twigs, and grasses. 

A1-0 to 5 inches; black (10YR 2/1) loam, very dark 

grayish brown (10YR 3/2) dry; moderate very fine and 

medium granular structure; soft, very friable, nonsticky 

and slightly plastic; weakly smeary; many fine roots; 

many fine irregular pores; very strongly acid; clear 

smooth boundary. 

A2-5 to 14 inches; black (10YR 2/1) gravelly loam, 

very dark grayish brown (10YR 3/2) dry; weak fine and 

medium granular structure; soft, very friable, 

nonsticky and nonplastic; weakly smeary; common 

fine roots. common very fine and fine irregular pores; 

20 percent pebbles; strongly acid; gradual smooth 

boundary. 

A3-14 to 22 inches; very dark brown (10YR 2/2) 

gravelly loam. dark grayish brown (10YR 4/2) dry; weak 

coarse subangular blocky structure; soft, very friable, 

nonsticky and nonplastic; weakly smeary; common 

very fine roots; common medium irregular pores; 20 

percent pebbles; strongly acid; abrupt irregular 

boundary. 

AC-22 to 30 inches; dark brown (7.5YR 3/2) very 

gravelly loam, brown (7.5YR 4/2) dry; massive; soft, 

friable, nonsticky and nonplastic; common very fine 

roots and few medium roots; many fine and medium 

irregular pores and few fine tubular pores; 35 percent 

pebbles and 15 percent cobbles; strongly acid; 

abrupt irregular boundary. 

C1-30 to 36 inches; dark brown (10YR 4/3) very 

gravelly coarse sandy loam, brown (10YR 5/3) dry; 

single grain; loose; few very fine roots; common 

medium and coarse irregular pores; 40 percent 

pebbles and 20 percent cobbles; intermittent weak 

silica and manganese cementation; strongly acid; 

abrupt irregular boundary. 

2C2-36 to 60 inches; dark brown (7.5YR 3/3) 

extremely cobbly coarse sand, brown (7.5YR 5/3) 

dry; single grain; loose; many medium and coarse 

irregular pores; 35 percent pebbles, 20 percent 

cobbles, and 10 percent stones; strongly acid. 

Depth to the 2C horizon ranges from 30 to 60 inches. 

The umbric epipedon is 20 to 30 inches thick. 

The A and AC horizons have hue of 10YR or 7.5YR, 

value of 2 or 3 when moist and 3 or 4 when dry, and 

chroma of 1 to 3 when moist or dry. The A horizon has 

0 to 30 percent rock fragments, and the AC horizon has 

35 to 60 percent. 

The C horizon has hue of 10YR or 7.5YR, value of 3 

or 4 when moist and 4 to 6 when dry, and chroma of 2 

to 4 when moist or dry. It is very gravelly coarse sandy 

loam, very cobbly coarse sandy loam, extremely cobbly 

coarse sandy loam, or very gravelly loam. 

The 2C horizon has hue of 10YR or 7.5YR, value of 3 

or 4 when moist and 4 to 6 when dry, and chroma of 2 

to 4 when moist or dry. It has 20 to 50 percent pebbles. 

15 to 25 percent cobbles, and 0 to 10 percent stones. 

The fine earth fraction is sand, loamy sand, or coarse 

sand. 

Yalelake Series 

The Yalelake series consists of very deep, well drained 

soils on terraces and terrace escarpments. These soils 

formed in volcanic ash and pumice over pyroclastic 

deposits. Slope is 2 to 90 percent. Elevation is 800 to 

1,800 feet. The average annual precipitation is about 

120 inches. the average annual air temperature is about 

50 degrees F, and the average frost-free season is 100 

to 135 days. 

These soils are ashy over medial, mesic Umbric 

Vitrandepts. 

Typical pedon of Yalelake sandy loam, 2 to 30 percent 

slopes, south of Forest Service Road N90, about 1 mile 

northeast of Swift Creek Dam; 2,600 feet south and 250 

feet east of the northwest corner of sec. 22, T. 7 N., R. 5 

E. 

O1-2 inches to 0.5 inch; needles, leaves, and twigs. 

O2-0.5 inch to 0; decomposed organic material. 

A-0 to 4 inches; very dark brown (10YR 2/2) sandy 

loam (volcanic ash), dark grayish brown (10YR 4/2) 

dry; weak very fine granular structure; soft, very 

friable, nonsticky and nonplastic; many very fine 

roots and common fine and medium roots; many very 

fine irregular pores; slightly acid; clear wavy boundary.

AB-4 to 11 inches; dark brown (10YR 3/3) sandy loam 

(volcanic ash), brown (10YR 5/3) dry; weak fine 

subangular blocky structure; soft, very friable, 

nonsticky and nonplastic; many very fine and fine 

roots and few coarse roots; many fine irregular pores; 

5 percent pebbles; slightly acid; clear wavy boundary.

Bw1-11 to 20 inches; dark grayish brown (10YR 4/2) 

gravelly loamy sand (volcanic ash), very pale brown 

(10YR 7/3) dry; weak fine subangular blocky structure; 

soft, very friable, nonsticky and nonplastic; many very 

fine roots and common fine and medium roots; many 

fine irregular pores; 30 percent pebbles; neutral; clear 

wavy boundary. 
2Bw2-20 to 39 inches; dark yellowish brown (10YR 

4/4) gravelly sandy loam, light yellowish brown 

(10YR 6/4) dry; weak fine subangular blocky 

structure; soft, friable, nonsticky and nonplastic; 

weakly smeary; common very fine and fine roots 

and few medium and coarse roots; many fine and 

medium pores; 15 percent pebbles and 5 percent 

cobbles. neutral; abrupt wavy boundary. 

2C1-39 to 44 inches; brownish yellow (10YR 6/8) 

sand, yellow (10YR 7/6) dry; single grain; loose; 

weakly smeary; few fine roots; many medium pores; 

10 percent pebbles and 40 percent weathered pumice 

fragments; neutral; abrupt wavy boundary. 

2C2-44 to 60 inches; dark yellowish brown (10YR 4/4) 

gravelly loam, light yellowish brown (10YR 6/4) dry; 

massive; slightly hard, friable, slightly sticky and 

slightly plastic; weakly smeary; few fine and medium 

roots; common fine irregular pores; 20 percent 

pebbles; neutral. 

Thickness of the solum ranges from 35 to 45 inches. 

The ashy mantle is 17 to 25 inches thick and contains 

more than 60 percent volcanic ash and pumice. The 10-

to 40-inch particle-size control section averages 10 to 30 

percent rock fragments. The umbric epipedon is 10 to 13 

inches thick. 

The Bw horizon has value of 3 or 4 when moist and 

5 to 7 when dry, and it has chroma of 2 to 4 when moist 

or dry. It is gravelly loamy sand or gravelly sandy loam. 

Reaction is slightly acid or neutral. 

The 2Bw horizon has value of 4 or 5 when moist and 

6 or 7 when dry, and it has chroma of 4 to 8 when moist 

or dry. It is sandy loam, loam, or gravelly sandy loam. 

Reaction is slightly acid or neutral. 

The 2C horizon has value of 4 to 6 when moist and 6 

or 7 when dry, and it has chroma of 4 to 8 when moist 

or dry. It is sandy loam or loam with thin strata of loamy 

sand or sand. The horizon has 10 to 25 percent pebbles 

and 15 to 40 percent soft, weathered pumice fragments. 

Reaction is slightly acid or neutral. 

Zygore Series 

The Zygore series consists of very deep, well drained 

soils on foot slopes, back slopes, and shoulders of 

mountains. These soils formed in colluvium derived 

dominantly from basalt and andesite mixed with volcanic 

ash. Slope is 5 to 65 percent. Elevation is 2,000 to 3,000 

feet. The average annual precipitation is about 90 inches, 

the average annual air temperature is 43 degrees F. and 

the average frost-free season is 90 to 110 days. 

These soils are medial-skeletal, frigid Andic 

Haplumbrepts. 

Typical pedon of Zygore gravelly loam, 30 to 65 

percent slopes, about 5 miles northwest of Stevenson; 

1,000 feet south and 2,000 feet east of the northwest 

corner of sec. 10, T. 3 N., R. 7 E. 

O-1 inch to 0; needles, twigs, and cones. 

A-0 to 8 inches; very dark brown (10YR 2/2) gravelly 

loam, dark brown (10YR 4/3) dry; moderate fine 

granular structure and moderate medium subangular 

blocky; slightly hard, friable, slightly sticky and 

slightly plastic; weakly smeary; many fine roots and 

common medium roots; many fine irregular pores; 15 

percent pebbles; strongly acid; clear smooth 

boundary. 

AB-8 to 14 inches; very dark grayish brown (10YR 3/2) 

gravelly loam, brown (10YR 5/3) dry; moderate fine 

and medium subangular blocky structure; slightly 

hard, friable, slightly sticky and slightly plastic; 

weakly smeary; common fine roots and few medium 

roots; common fine irregular pores; 20 percent 

pebbles and 5 percent cobbles; moderately acid; 

clear smooth boundary. 

Bw-14 to 26 inches; dark brown (10YR 3/3) very 

gravelly loam, pale brown (10YR 6/3) dry; moderate 

medium subangular blocky structure; slightly hard, 

friable, slightly sticky and slightly plastic; many fine 

roots; few fine irregular pores; 30 percent pebbles 

and 10 percent cobbles; strongly acid; gradual 

smooth boundary. 

BC-26 to 37 inches; dark yellowish brown (10YR 3/4) 

very gravelly silt loam, light yellowish brown (10YR 

6/4) dry; weak medium subangular blocky structure; 

slightly hard, friable, slightly sticky and slightly plastic; 

common fine roots; few fine irregular pores; 40 

percent pebbles and 10 percent cobbles; strongly 

acid; gradual smooth boundary. 

C-37 to 60 inches; dark yellowish brown (10YR 3/4) 

extremely gravelly silt loam, light yellowish brown 

(10YR 6/4) dry; massive; slightly hard, friable, slightly 

sticky and slightly plastic; few fine roots; few fine 

irregular pores; 50 percent pebbles and 20 percent 

cobbles; very strongly acid. 

The umbric epipedon is 12 to 18 inches thick and is 

influenced by volcanic ash. 

The A horizon has hue of 10YR or 7.5YR, value of 2 

or 3 when moist and 4 or 5 when dry, and chroma of 2 

or 3 when moist or dry. It has 15 to 20 percent pebbles 

and 5 to 10 percent cobbles. 

The Bw and BC horizons have hue of 10YR or 
7.5YR, value of 3 or 4 when moist and 5 or 6 when dry, 

and chroma of 3 or 4 when moist or dry. The 

horizons are very gravelly loam or very gravelly silt loam. 

They have 35 to 40 percent pebbles and 5 to 10 percent 

cobbles. 

The C horizon has hue of 10YR or 7.5YR, value of 3 

or 4 when moist and 5 or 6 when dry, and chroma of 

3 or 4 when moist or dry. It is very gravelly loam, extremely 

gravelly silt loam, or very cobbly loam. 

Zymer Series 

The Zymer series consists of very deep, well drained 

soils on mountain slopes. These soils formed in 

colluvium derived from volcanic ash and basic igneous 

rock with a mantle of volcanic ash. Slope is 2 to 90 

percent. Elevation is 800 to 1,600 feet. The average 

annual precipitation is about 115 inches, the average 

annual air temperature is about 49 degrees F, and 

the average frost-free season is 110 to 130 days. 

These soils are ashy over loamy-skeletal, mesic 

Umbric Vitrandepts. 

Typical pedon of Zymer sandy loam, 30 to 65 percent 

slopes. about 2 miles southeast of Cougar; 600 feet north 

and 100 feet east of the southwest corner of sec. 31, T. 7 

N., R. 5 E. 

O-3 inches to 0; leaves, needles, twigs, and moss. 

A1-0 to 4 inches; dark brown (10YR 3/3) sandy loam 

(volcanic ash and cinders), dark brown (10YR 

4/3) dry; weak fine granular structure; soft, friable, 

nonsticky and nonplastic; many very fine and fine 

roots; many fine irregular pores; 10 percent pumice 

fragments and 5 percent pebbles; moderately acid; 

clear wavy boundary. 

A2-4 to 10 inches; dark brown (10YR 3/3) loamy sand 

(volcanic ash and cinders), brown (10YR 5/3) dry; 

weak fine granular structure; soft, friable, nonsticky 

and nonplastic; many very fine and fine roots; many 

fine irregular pores; 10 percent pumice fragments and 

5 percent pebbles; moderately acid; clear wavy 

boundary. 

Bw-10 to 22 inches; dark yellowish brown (10YR 4/4) 

cindery loamy sand (volcanic ash and cinders), very 

pale brown (10YR 7/4) dry; weak fine subangular 

blocky structure; soft, friable, nonsticky and slightly 

plastic; weakly smeary; common very fine and fine 

roots and few medium roots; many fine irregular pores; 

15 percent pumice fragments and 5 percent pebbles;; 

strongly acid; clear wavy boundary. 

2BC-22 to 28 inches; dark yellowish brown (10YR 4/6) 

very gravelly loam, light yellowish brown (10YR 6/4) 

dry; weak fine subangular blocky structure; soft, friable, 

nonsticky and slightly plastic; weakly smeary; common 

very fine and fine roots; many fine irregular pores; 5 

percent pumice fragments and 40 percent pebbles; 

strongly acid; abrupt wavy boundary. 

2C1-28 to 47 inches; yellowish brown (10YR 5/6) 

extremely gravelly loam, very pale brown (10YR 

7/4) dry; massive; soft, friable, nonsticky and slightly 

plastic; weakly smeary; few very fine roots; common fine 

irregular pores; 50 percent pebbles, 15 percent 

cobbles, and 5 percent stones; strongly acid; clear 

wavy boundary. 

2C2-47 to 60 inches; dark yellowish brown (10YR 4/6) 

extremely gravelly loam, very pale brown (10YR 

7/4) dry; massive; soft, friable, nonsticky and slightly 

plastic; weakly smeary; common fine irregular pores; 65 

percent pebbles and 10 percent cobbles; strongly acid.

The umbric epipedon is 10 to 14 inches thick. The ashy 

mantle is 16 to 30 inches thick. The upper part of the 10- 

to 40-inch particle-size control section is 5 to 25 percent 

pumice fragments and 0 to 10 percent pebbles, and the 

lower part is 35 to 80 percent rock fragments. 

The A horizon has hue of 10YR or 7.5YR, value of 2 or 

3 when moist and 4 or 5 when dry, and chroma of 2 or 3 

when moist or dry. 

The Bw horizon has hue of 10YR or 7.5YR, value of 4 

or 5 when moist and 5 to 7 when dry, and chroma of 3 or 

4 when moist or dry. 

The 2BC horizon has hue of 10YR or 7.5YR, value of 4 

or 5 when moist and 5 to 7 when dry, and chroma of 4 to 6 

when moist or dry. It is 35 to 50 percent pebbles. 

The 2C horizon has hue of 10YR or 2.5Y, value of 4 or 

5 when moist and 5 to 7 when dry, and chroma of 4 to 6 

when moist or dry. It is loam or clay loam. It is 40 to 65 

percent pebbles, 0 to 15 percent cobbles, and 0 to 5 

percent stones. 

Zynbar Series 

The Zynbar series consists of very deep, well drained 

soils on foot slopes and terraces. These soils formed in 

volcanic ash and colluvium derived from basic igneous 

rock over glacial drift. Slopes are 8 to 30 percent. Elevation 

is 1,800 to 2,400 feet. The average annual precipitation is 

about 80 inches, the average annual air temperature is 

about 44 degrees F, and the average frost-free season is 

100 to 160 days. 

These soils are medial, frigid Entic Dystrandepts. 

Typical pedon of Zynbar gravelly silt loam, till 
substratum, 8 to 30 percent slopes, about 2 miles north 

of Tradedollar Lake; 2,700 feet west of the northeast 

corner of sec. 6, T. 10 N., R. 5 E. 

O-2 inches to 0; partially decomposed organic litter. 

A-0 to 6 inches; very dark grayish brown (10YR 3/2) 

gravelly silt loam, brown (10YR 5/3) dry; weak fine 

granular structure; soft, very friable, nonsticky and 

nonplastic; weakly smeary; common very fine and fine 

roots and few medium and coarse roots; many fine 

irregular pores; 15 percent pebbles; moderately acid; 

clear wavy boundary. 

Bw1-6 to 17 inches; dark brown (7.5YR 4/4) silt loam, 

light brown (7.5YR 6/4) dry; weak fine subangular 

blocky structure; soft, friable, slightly sticky and 

slightly plastic; weakly smeary, common very fine and 

fine roots and few medium roots; many fine irregular 

pores; 5 percent pebbles; moderately acid; clear 

irregular boundary. 

Bw2-17 to 31 inches; yellowish brown (10YR 5/4) silt 

loam, very pale brown (10YR 7/4) dry; weak fine 

subangular blocky structure; soft, friable, slightly 

sticky and slightly plastic; weakly smeary; few fine 

roots; common fine irregular pores; 10 percent soft 

pumice fragments; moderately acid; clear wavy 

boundary. 

Bw3-31 to 47 inches; yellowish brown (10YR 5/6) silt 

loam, brownish yellow (10YR 6/6) dry; weak fine and 

medium subangular blocky structure; soft, friable, 

slightly sticky and slightly plastic; weakly smeary; few 

fine roots; common fine irregular pores; 

slightly acid; clear irregular boundary. 

2C1-47 to 57 inches; dark yellowish brown (10YR 4/4) 

extremely stony silt loam, light yellowish brown (10YR 

6/4) dry; massive; soft, friable, slightly sticky and 

nonplastic; weakly smeary; few fine roots; few fine 

irregular pores; 25 percent pebbles, 10 percent 

cobbles, and 30 percent stones; moderately acid; 

abrupt wavy boundary. 

2C2-57 to 60 inches; gray (10YR 5/1) very gravelly 

loam, light gray (10YR 7/1) dry; massive; slightly 

hard, firm, nonsticky and nonplastic; 40 percent 

pebbles and 20 percent cobbles; moderately acid. 

The A and B horizons are moderately acid or slightly 

acid. Depth to the glacial till ranges from 40 to 60 inches 

or more. The 10- to 40-inch particle-size control section 

is 0 to 15 percent rock fragments, and the 2C horizon is 

50 to 80 percent. 

The A horizon has value of 2 or 3 when moist and 4 

to 6 when dry, and it has chroma of 2 to 4 when moist 

or dry. 

The Bw horizon has hue of 7.5YR or 10YR, value of 

4 or 5 when moist and 5 to 7 when dry, and chroma of 

4 to 6 when moist or dry. It is 0 to 15 percent pumice 

fragments and 0 to 10 percent hard rock fragments. 

The 2C horizon has value of 4 or 5 when moist and 6 

or 7 when dry, and it has chroma of 1 to 4 when moist 

or dry. It is gravelly silt loam, very gravelly loam, or 

extremely stony silt loam. The horizon is 20 to 40 percent 

pebbles, 10 to 15 percent cobbles, and 25 to 30 percent 

stones. 
Formation of the Soils

Soil is a natural, three-dimensional body on the 

Earth's surface. Its characteristics and properties have 

been determined by physical and chemical processes 

that result from the interaction of five factors: Parent 

material, climate, living organisms, topography, and time. 

The influence of any one of these factors varies from place 

to place, but the interaction of all the factors determines the 

kind of soil that forms. Soils in the survey area display a 

wide variety of diagnostic features and horizons that 

relate directly to the unique set of soil forming factors 

that characterize this area. In this section, the soil forming 

factors are described and their influences are explained 

and illustrated. 

Parent Material 

Parent material can be identified by its geologic 

origin and mineral composition. Soils that have 

developed in the survey area are derived from three 

basic types of parent material-flow rock of basalt and 

andesite, volcanic tephra deposits of ash and pumice, 

and transported material including alluvium, mudflow, 

lahar, landslide debris, and glacial drift (22). 

The oldest deposits in the area were laid down during 

the Eocene period (40 to 55 million years ago). Vast 

amounts of pyroclastic debris, mostly andesitic and dacitic 

in composition, were deposited by volcanoes to form the 

Ohanapecosh Formation. These volcanic deposits 

accumulated to a thickness of more than 10,000 feet. 

When volcanic activity ceased, gentle warping and 

faulting uplifted much of the area to form low, rolling hills. 

During early Miocene time (7 to 27 million years ago) Eagle 

Creek conglomerates of andesitic detritus and sand were 

deposited by swiftly running streams that poured into 

what may have been a broad, nearly level valley or 

basin. A period of uplifting and erosion followed until late 

Miocene time, when Yakima Basalt flows flooded the 

eroded surface. A few volcanoes erupted through the 

Yakima Basalt, leaving small stocks, plugs (such as 

Wind Mountain and Beacon Rock), and dikes (such as 

the granodiorite near Silver Star Mountain). Extensive 

uplift and erosion took 

place before the beginning of the Pleistocene Epoch. 

This left remnants of Yakima Basalt on the tops of 

mountains such as Table Mountain, Dog Mountain, and 

Underwood Mountain, and it exposed some of the 

oldest rock formations in the Cascade Range from the 

Ohanapecosh Formation. The rock of the Yakima Basalt 

formations is the source of the parent material for the 

soils in the McElroy-Underwood-Undusk general soil 

map unit, while rock from the Ohanapecosh Formation is 

the parent material for most of the soils in the ZygoreAschoff-Swift general soil map unit. 

Quaternary volcanism has been limited to the 

extrusion of basalt flows from at least ten different vents. 

The composition of the lava can be grouped into olivine, 

platy olivine, and low-alumina basalt. These include flows 

from Red Mountain, Bobs Mountain, Trout Creek Hill, 

and the Big Lava Bed north of Willard. Volcanic ash and 

pumice from these eruptions has accumulated on 

terraces in the Wind River Valley and around the base of 

Underwood Mountain. The Stabler and Chemawa soils 

are examples. 

Mount St. Helens, a volcano of late Quaternary age, 

is near the west margin of the Cascade Range in the 

survey area. The cone consists of lava flows of olivine 

basalt and pyroxene andesite, which surround a summit 

plug of dacite. Around the mountain, the landscape is 

covered with tephra deposits of dacitic pumice and 

volcanic ash. The pumice and ash are the parent 

material for most of the soils in the Vanson-SinniceTradedollar general soil map unit. 

Areas of valley fill adjacent to the volcano include 

pyroclastic flows, lahar, and alluvium, which are 

interbedded with tephra and glacial drift. Shoestring, 

Forsyth, Polepatch, and St. Helens soils are examples 

of soils that formed in these materials. 

During the latter part of the Pleistocene period, floods 

from the Columbia Basin carried silty material down the 

Columbia River channel. When water backed up into 

side drainageways, the silty material was allowed to 

settle out as lacustrine deposits. The Hood soils are an 

example of soils that formed in this parent material. 
Local landslides, some occurring as recently as 200 years 

ago, are present in several areas along the Columbia 

River. The large Bonneville slide, between North 

Bonneville and Stevenson, covers many square miles. It is 

composed primarily of Eagle Creek Formation and 

Yakima Basalt. The headwall from this landslide, which 

can be seen above the town of Stevenson, is called the 

Red Bluffs. The Columbia River was blocked for a period of 

time when this slide occurred. The Steever soils developed 

in this material. Another landslide, between Wind 

Mountain and Dog Mountain. is composed chiefly of 

material of the Ohanapecosh Formation. This landslide is 

still active, and it moves 5 to 10 feet a year at the top of 

the slide. St. Martin gravelly silty clay loam, slumped, 2 

to 30 percent slopes, is an example of a soil that 

developed in this material. 

Climate 

The climate in the survey area has an important 

overall influence on the characteristics of the soils. 

Temperature and precipitation affect the weathering rate 

of parent material and the chemical and physical changes 

that result in the formation of soils. They also affect the rate 

at which organic matter decomposes and influence the 

kind and abundance of plant growth. 

The climate in the survey area varies greatly because of 

the influence of the Cascade Range. Winds along the 

Columbia River Gorge blow alternately from east and 

west. Winds blowing from the Pacific Ocean are mild and 

moist in winter and are cool and dry in summer, which 

has a tempering effect on the climate. Winds that are 

cold and dry in winter and hot and dry in summer come 

from the intermountain region and are responsible for 

extreme changes in the weather. 

Rainfall generally increases with the elevation west of 

the Cascade Range, and it decreases rapidly as distance 

east of the Cascade crest increases. Along the Columbia 

River, rainfall ranges from 50 inches in the southwestern 

part of the survey area to more than 75 inches near the 

crest of the Cascade Range. East of the crest, rainfall 

decreases rapidly to about 35 inches in the southeast 

corner of the survey area. In the northern part of the area, 

precipitation ranges from 110 inches along the Lewis 

River to more than 140 inches at the top of Mount St. 

Helens. Most of the precipitation is received between 

October and April in the form of rain or snow. Very little 

rain falls in summer. 

 In the survey area there are three major climatic areas 

that greatly influence soil genesis; Areas that are 

warm and dry; areas that are cool and moist; and areas 

that are cold and wet. 

At low elevations, where the average annual 

precipitation is less than 70 inches, evapotranspiration 

exceeds precipitation during the growing season. This 

has resulted in the formation of soils that have a xeric 

moisture regime, which are dry in the upper part of the 

profile for 45 days or more following the summer solstice. 

On young surfaces, the accumulation of organic matter 

and limited leaching of bases have helped to develop 

soils classified as Xerolls. The McDoug soils are an 

example. On older surfaces, where soil-forming factors 

have been active for longer periods of time, soils 

classified as Xeralfs have developed. Hood and 

Underwood soils are examples. These soils are 

sufficiently dry in summer for translocated clay to 

precipitate, orient, and accumulate on soil peds to form 

an argillic horizon. 

At slightly higher elevations, the soil temperatures are 

cooler and the soils have an udic moisture regime. The 

average annual precipitation is more than 70 inches, 

which is sufficient to keep the soils moist in the upper 

part of the profile except for periods of less than 45 

days. This condition facilitates almost continuous 

leaching. As a result, these soils are leached of 

weathered clay and have low base saturation. The 

accumulation of organic matter has been sufficient for 

the development of soils classified as Umbrepts and 

Andepts. The Aschoff, Cinnamon, Dougan, and Zygore 

soils are examples. 

At very high elevations, where the average annual 

precipitation is more than 120 inches, the soils are very 

cold most of the year. The vegetation is mainly 

subalpine fir, Pacific silver fir, and western hemlock. At 

these elevations the soils develop very slowly. Cold 

temperatures suspend biological and chemical activity; 

however, some physical weathering takes place as the 

result of freezing and thawing. The cold temperatures 

and tremendous volume of precipitation result in the 

accumulation of large amounts of organic matter and the 

translocation of organic matter and sesquioxides. This 

material is deposited as coatings on soil particles and 

forms spodic horizons necessary in the development of 

soils classified as Cryorthods. The Lonestar and 

Tradedollar soils are examples. 

Living Organisms 

Living organisms are important in the formation of 

soils. Micro-organisms, plants, and animals, especially 

man, contribute to soil development. The nature of the 
changes they bring about depends on the life processes 

peculiar to each kind of organism. When newly developed 

soils receive adequate moisture and temperature, they 

are invaded by bacteria and fungi. These microorganisms convert nutrients from the soil, air, and water to 

organic residue, which over a long period of time 

contributes to soil fertility. As the fertility increases, 

grasses. shrubs, and trees become established. In time, 

the soil is capable of supporting many types of 

vegetation. In turn, plants and the residue they produce 

provide an environment in which animals can thrive. 

Bacteria are present in the soil in vast numbers, 

especially in the surface layer, where moisture, 

temperature, and aeration are most favorable. They help 

to complete important enzymatic functions in soils and aid 

in the decomposition of organic material. Mold and fungi 

are also important in the development of soil. Mold is 

most active in the formation of humus and in the 

development of soil aggregates. Fungi break down 

organic residue and make nutrients available to plants. 

Micro-organisms called actinomycetes convert nitrogen 

from the soil and air to plant nutrients. The decay of 

organic material also produces organic acids that weather 

minerals. 

Large plants are established as the fertility of the soil 

increases. Roots penetrate the soil, contribute to the 

development of soil structure, and improve porosity. When 

roots decay, especially the fine roots of grasses, they 

provide considerable organic matter to the soil. The 

accumulation of organic matter in the surface layer is 

indicated by the presence of black or very dark brown 

colors. Plants also protect the soil from erosion. Leaves, 

needles, and twigs reduce the impact of raindrops, and 

organic litter holds raindrops where they fall, thus reducing 

runoff and erosion. 

In this survey area the soils formed under three major 

types of plant cover. In the xeric soil zone, grass was a 

prominent member of the plant community, along with a 

mixed conifer and deciduous forest of Oregon white oak 

bigleaf manly ponderosa pine and Douglas fir. The annual 

dieback of roots provides large amounts of organic 

material. The deciduous trees absorb calcium and other 

bases and return them to the soil annually, thus reducing 

the effects of leaching. Under these conditions soils 

classified as Haploxerolls and Xerumbrepts are 

developed. Chemawa, McDoug, McElroy, and Skamania 

soils are examples. 

In the udic soil zone, the proportion of grasses and 

deciduous trees decreased and the proportion of 

conifers increased. Organic matter accumulated; 

however, bases were adsorbed by the conifers and not 

returned to the soil so readily as in the xeric zone. The 

greater precipitation in the udic soil zone has resulted in 

more leaching of bases. These soils are classified as 

Haplumbrepts. Aschoff, Skoly, and Zygore soils are 

examples. 

At higher elevations, mainly in places where 

precipitation exceeds 120 inches annually, the plant 

communities are dominantly conifers such as western 

hemlock, subalpine fir, and noble fir. In these areas the 

presence of large amounts of organic matter and 

leaching of bases have produced a high hydrogen ion 

concentration and resulted in the formation of a spodic 

horizon in soils classified as Cryorthods. Lonestar, 

Shoestring, and Tradedollar soils are examples. 

Animals, particularly rodents, earthworms, and ants, 

contribute to the development of soils by helping organic 

matter to decompose. They mix the soil, which works 

organic residue deeper into the profile and moves 

unweathered soil material to the surface, where it can be 

leached of nutrients. Their actions increase the 

development of soil structure and improve aeration. 

Windthrow on forest soils also aids in the churning and 

mixing of organic matter into the surface layer. 

In this survey area conditions generally are favorable 

for most organisms to function, but most of the activity is 

in the mesic soil zone. Small animals such as gophers 

and moles are common in the lower lying, warmer areas. 

The Hesson, Mossyrock, Skamania, and Skelida soils are 

examples. 

Man has affected soil development through timber 

harvest and agricultural activities. Logging operations 

mix the duff into the surface layer and produce soils that 

have a thicker, darker colored surface layer than is 

present in undisturbed areas. Soils are compacted, 

displaced, and puddled by operation of logging 

equipment, which alters the structure, porosity, and 

permeability of the soil. In addition, man has 

constructed roads and landings, which alters normal 

drainage patterns and accelerates erosion. 

Some of the soils in the survey area have been 

cultivated for more than 75 years. The major cultivated 

soils are on terraces and flood plains near waterways 

and populated areas. The Hesson, Mossyrock, 

Skamania, and Skelida soils are examples. The 

introduction of new plants, the addition of organic 

matter, such as cover crops and manure, and the 

application of lime and fertilizer have changed the 

development of these soils. Cultivated soils have 

developed a soft, dark-colored, very friable surface 

layer that is high in fertility. Soil aeration, color, and 

texture also have been altered by artificial drainage. 

Man's activities, however, have not always been 
beneficial. Tillage can result in formation of a tillage pan 

that will alter drainage, permeability, and the amount of 

runoff. Cultivation of steeper, unprotected slopes has 

also accelerated erosion. 

Topography 

The influence of topography on soil development can 

be expressed by its effect on drainage, runoff, and 

erosion. Aspect and type of landform also impact soil 

development. 

Water runs off the surface rapidly on well drained, 

steeply sloping Hatchet, Timberhead, and Skoly soils. 

This allows less water to enter the profile, and as a result 

profiles are not well developed. On well drained, 

moderately sloping Mountzion and Underwood soils, 

more water percolates through the profile. This increased 

water weathers and moves clay and organic residue from 

the A horizon and redeposits it in the B horizon. Soils on 

nearly level terraces and toe slopes receive large 

amounts of runoff from the surrounding hillsides. These 

somewhat poorly drained and moderately well drained 

soils exhibit greater development, as is indicated by the 

movement of clay and the development of soil structure. 

Stabbart and St. Martin soils are examples. Development 

of bottom land soils is dependent on the length and 

incidence of seasonal flooding and on the ability of the 

soil to let excess water drain away. Somewhat excessively 

drained Pilchuck soils are subject only to occasional 

flooding and are not seriously affected. Minor flooding can 

be a benefit by adding nutrients to the soil. Soils 

classified as Histic Cryaquepts are poorly drained and 

formed in depressional areas. They are subject to frequent 

flooding and are waterlogged much of the year. They 

receive little air for biological activity, resulting in slow soil 

development. Vegetation on these soils includes rushes 

and sedges that accumulate as layers of muck and peat. 

Erosion of soil particles is related to the relief of the 

area. This movement of soil material results from water 

runoff, soil creep, and mass wasting. Generally, as slope 

increases, runoff becomes more rapid. Rapidly moving 

water detaches soil particles and transports them 

downslope and redeposits them on foot slopes, toe 

slopes, or alluvial fans. Consequently, many of the soils 

on ridgetops and steep mountainsides are shallow to 

bedrock or are intermingled with areas of Rock outcrop. 

Soils on steep slopes are subject to soil creep, which is 

the slow movement of soil downslope by gravity. Soil 

creep prevents colluvial soils from developing clay films 

in the B horizon and from 

weathering as rapidly as other soils in the area. Kinney 

and Skoly soils are examples. 

Mass wasting of soils along the Columbia River is 

common. Weak layers in the geologic formation and 

saturated conditions have caused development of 

unstable landforms. These areas slide downslope as a 

unit, mixing and churning the soil as it moves. Soil 

development is often interrupted by periods of movement. 

St. Martin and Steever soils are examples of soils that 

developed under conditions of mass wasting. 

As time passes and organic material is added to the 

profile, an A horizon develops. The resulting profile may 

be expressed as an A horizon over an undeveloped C 

horizon. Examples of young alluvial soils are those of the 

Bonneville, Pilchuck, and Washougal series. Examples of 

recent volcanic soils are those of the Obscurity and 

Polepatch series. These soils are all weakly developed in 

coarse textured parent material that exhibits little or no 

weathering of minerals; however, sufficient time has 

passed for the accumulation of organic material in the 

surface layer. These soils are classified as Entic 

Xerumbrepts, Xeropsamments, or Cryorthents. 

In soils that have a more strongly developed profile, a 

sufficient amount of time has passed for minerals to have 

weathered. These soils are characterized as having A, B, 

and C horizons. Many of the soils in the survey area 

have this sequence of horizons. The degree to which 

these horizons are developed is an expression of their 

age. These soils are classified as Dystrandepts. The 

Stabler soils are an example. Soils classified as 

Haplumbrepts exhibit structural development in the B 

horizon. The Steever soils are an example of soils that 

show no evidence of translocated clay; however, the older 

Hesson, Mountzion, and Underwood soils do show 

evidence of translocated clay. These soils are classified 

as Haplohumults or Haploxeralfs and have well developed 

argillic horizons. 

In the northern part of the survey area, depth of volcanic 

deposits from Mount St. Helens is directly related to aspect 

and distance from the source. The thickness and 

distribution of these deposits were greatly affected by the 

velocity and direction of the wind at the time of the 

eruption; for example, the T ash and pumice deposit 

occurred in a long thin band extending northeast from 

Mount St. Helens. This indicates that at the time of the 

eruption a strong wind was blowing from the southwest. In 

contrast, the Set W pumice is a thick deposit extending 

north to east from the mountain, indicating that more 

moderate winds were blowing from a number of different 

directions. Consequently, the sequence in which these 

layers occur in the profile 
depends largely on the geographic relationship and 

distance from the mountain. 

The predominant winds blow to the northeast, so the 

thickest deposits occur in that direction; in addition, 

slopes that face toward the volcano tend to have deeper 

deposits. Also, the depth of the tephra depends on the 

steepness of the slope on which it fell. Steeply sloping 

areas have been subject to more erosion from water 

runoff and from dry ravel of pumice fragments than have 

less sloping areas. 

Sinnice and Tradedollar are examples of soils 

composed almost entirely of tephra deposits from one 

event. Bandid, Colter, and Pelee soils are examples of 

soils composed of deposits from many events and thus 

are stratified. Other soils, such as the Swift and Vanson 

soils, are further away to the south and west. These soils 

formed in a mantle of volcanic ash and pumice over 

colluvium derived from basalt and andesite. 

In addition to the tephra deposits, Mount St. Helens has 

filled the surrounding valleys with lahar, pyroclastic flow, 

and avalanche debris. These deposits commonly are 

several hundred feet thick and are composed of coarse 

sand and gravel. The soils that formed in these deposits 

are classified as Udorthents and Cryorthents. Forsyth 

and Polepatch soils are examples. Thin tephra deposits 

cover this material in some areas. The soils in these areas 

are classified as Vitrandepts. The St. Helens soils are an 

example. 

Time 

In this survey area there is a wide range in time 

during which soil development has taken place. The 

parent material ranges in age from that of the Eocene 

period (40 to 55 million years old) to the recent tephra 

deposits from the latest eruption of Mount St. Helens. 

The time required for the formation of a soil depends 

largely on the interaction of the other soil-forming factorsparent material, climate, topography, and living 

organisms. The influence of time commonly is expressed 

by the degree of horizon development. 

Parent material in time weathers to form layers or soil 

horizons. These horizons develop properties that reflect 

the extent of the rooting of plants, the downward 

movement of water, and the temperature of the soil. As 

time passes, these horizons become more developed 

and produce layers that extend deeper into the soil profile. 

Very young soils, therefore, have no identifiable horizons 

or have only thin, weakly expressed horizons. Recent 

volcanic soils, such as the Obscurity and Studebaker soils, 

and very young alluvial soils, such as 

the Wakepish soils, do not exhibit soil development. 

These soils are described as having an unweathered C 

horizon. They are classified as Udorthents or 

Cryorthents. 

In the northern part of the survey area, Mount St. 

Helens has been an intermittent but abundant source of 

volcanic material for more than 35,000 years. The 

sequence of these deposits provides an excellent record 

of the mountain's eruptive history. These deposits were 

useful marker beds for stratographic correlation and were 

used to determine the age of many of the soils. 

The most readily identifiable layers of tephra around 

the mountain are: (1) Set Y pumice, from numerous 

eruptions that took place 3,200 to 3,500 years ago; (2) 

Subset B ash and pumice, from numerous eruptions that 

took place 420 to 3,200 years ago; (3) Set W pumice, 

deposited 400 to 420 years ago; (4) T ash and pumice, 

deposited about 180 years ago (26); and (5) ash and 

pumice from the May 1980 eruption. Tephra deposits 

older than 3,500 years occur, but in most areas the 

more recent deposits extend to a depth of 60 inches or 

more. 

The different tephra deposits can be identified not only 

by their stratographic location in the profile but also by 

their color and degree of weathering. Pumice fragments in 

the Sinnice soils are present in thick bands of Layer W 

pumice with a thin layer of T ash and pumice. These 

deposits are less than 420 years old. The pumice 

fragments are ''hard," and are single grain or loose. When 

a fragment is broken, the interior is white or nearly white, 

indicating that little or no weathering has occurred. In the 

Benham and Colter soils the Layer T and W pumice is 

dated at 3,400 or 3,500 years of age but can still be 

considered as "hard." These fragments, however, have 

coatings of translocated sesquioxides and organic matter. 

These coatings are yellow or yellowish red. The coatings 

are evidence of a high degree of weathering, and horizons 

of pumice with such coatings are designated as Bhs or Bs 

to indicate illuviation or the movement of weathered iron. 

Tradedollar and Zynbar soils are examples of soils that 

formed in very deep deposits of highly weathered tephra. 

Over time soil moisture, leaching, and frost action have 

softened and broken down the glass shards. They are 

not abrasive or hard but feel greasy and smear when 

rubbed between the thumb and index finger. The colors 

of the soil indicate that a high degree of oxidation has 

occurred. 
References

(1) American Association of State Highway and 

Transportation Officials. 1982. Standard 

specifications for highway materials and methods 

of sampling and testing. Ed. 13, 2 vol., illus. 

(2) American Society for Testing and Materials. 1985, 

Standard test method for classification of soils for 

engineering purposes. ASTM Stand. D 2487. 

(3) Ducan, S.H., and E.C. Steinbrenner. 1971. Soil 

survey of the St. Helens Tree Farm. 

Weyerhaeuser Co., 39 pp. 

(4) King, James E. 1966. Site index curves for 

Douglas-fir in the Pacific Northwest. 

Weyerhaeuser Co., For. Pap. No. 8, 49 pp. 

(5) National Geographic Magazine. 1981. Mount St. 

Helens, No. 1, vol. 159, pp. 3-65, illus. 

(6) Portland Cement Association. 1962. PCA soil 

primer. 52 pp., illus. 

(7) State of Washington. 1970. Cenozoic volcanism in 

the Cascade Mountains of southern Washington. 

Dep. Nat. Resour. Bull. No. 60, 45 pp., illus. 

(8) State of Washington. 1978. Birds of the western 

Columbia Gorge. Game Dep. Appl. Res. No. 10, 

25 pp., illus. 

(9) State of Washington. 1978. Forest land grading 

procedures handbook. Dep. Nat. Resour., 83 pp., 

illus. 

(10) State of Washington. 1980. Empirical yield tables for 

the Douglas-fir zone. Dep. Nat. Resour. Rep. No. 

41, 50 pp. 

(11) State of Washington. 1981. Empirical yield tables 

for the western hemlock zone. Dep. Nat. Resour. 

Rep. No. 43, 79 pp. 

(12) United States Department of Agriculture. 1951. Soil 

survey manual. U.S. Dep. Agric. Handb. 18, 503 

pp., illus. (Supplements replacing pp. 173-188 

issued May 1962) 

(13) United States Department of Agriculture. 1956. Soil 

survey of Skamania County, Washington. Soil 

Conserv. Serv., 92 pp., maps, illus. 

(14) United States Department of Agriculture. 1960. 

Normal yield tables for red alder. For. Serv. Pac. 

Northwest Reg. Res. Pap. 36, 3 pp., tables. 

(15) United States Department of Agriculture. 1961. The 

yield of Douglas-fir in the Pacific Northwest. U:.S. 

Dep. Agric. Tech. Bull. 201 (rev.), 74 pp. 

(16) United States Department of Agriculture. 1962. 

Yield of even-aged stands of western hemlock. 

U.S. Dep. Agric. Tech. Bull. 1273, 52 pp. 

(17) United States Department of Agriculture. 1972. 

Soil survey of Clark County, Washington. Soil 

Conserv. Serv., 113 pp., illus. 

(18) United States Department of Agriculture. 1975. 

Soil taxonomy; A basic system of soil 

classification for making and interpreting soil 

surveys. Soil Conserv. Serv., U.S. Dep. Agric. 

Handb. 436, 754 pp., illus. 

(19) United States Department of Agriculture. 1980. 

Assessment of Cowlitz River, Toutle River, and 

blast area damage-resulting from May 18, 1980, 

Mount St. Helens eruption, Washington. Soil 

Conserv. Serv., Spokane, WA. 
(20) United States Department of Agriculture. 1980. 

National forestry manual. Soil Conserv. Serv., 151 

pp., illus. 

(21) United States Department of Agriculture. 1981 . Mount 

St. Helens land management plan, Cowlitz, Lewis, 

and Skamania Counties, Washington. For. Serv. 

Pac. Northwest Reg. Environ. Impact Statement. 

(22) United States Department of Agriculture. 1983. 

Soil survey of Multnomah County, Oregon. Soil 

Conserv. Serv., 225 pp., illus. 

(23) United States Department of Health, Education, 

and Welfare. 1957. Manual of septic tank 

practices. Public Health Serv. Pub. 526, 93 pp., 

illus. 

(24) United States Department of the Interior. 1975. 

Upper Pleistocene pyroclastic flow deposit and 

lahars south of Mount St. Helens volcano, 

Washington. U.S. Geol. Surv. Bull. 1383-B, 20 

pp., illus. 

(25) United States Department of the Interior. 1975. 

Widespread late glacial and postglacial tephra 

deposits from Mount St. Helens volcano, 

Washington. U.S. Geol. Surv., J. Res., vol. 3., No. 

3, pp. 329-335, illus. 

(26) United States Department of the Interior. 1978. 

Potential hazards from future eruptions of Mount St. 

Helens volcano, Washington. U.S. Geol. Surv. 

Bull. 1383-C, 26 pp., illus. 

(27) Wiley, Kenneth. 1978. Site index tables for 

western hemlock in the Pacific Northwest. 

Weyerhaeuser Co., For. Pap. No. 17, 28 pp. 
Glossary 

Aggregate, soil. Many fine particles held in a single 

mass or cluster. Natural soil aggregates, such as 

granules, blocks, or prisms, are called peds. Clods 

are aggregates produced by tillage or logging. 

Alluvial fan. The fanlike deposit of a stream where it issues 

from a gorge upon a plain or of a tributary stream 

near or at its junction with its main stream. 

Alluvium. Material, such as sand, silt, or clay, 

deposited on land by streams. 

Area reclaim (in tables). An area difficult to reclaim after 

the removal of soil for construction and other uses. 

Revegetation and erosion control are extremely 

difficult. 

Ash (volcanic). See volcanic ash. 

Available water capacity (available moisture capacity). 

The capacity of soils to hold water available for use 

by most plants. It is commonly defined as the 

difference between the amount of soil water at field 

moisture capacity and the amount at wilting point. It 

is commonly expressed as inches of water per inch 

of soil. The capacity, in inches, in a 60-inch profile 

or to a limiting layer is expressed as 

Very low ................................................ 0 to 2.0 

Low...................................................2.0 to 3.75 

Moderate ..........................................3.75 to 5.0 

Moderately high .................................5.0 to 7.5 

High ...........................................More than 7.5 

Avalanche debris flow. A large mass of snow, ice, or 

rock that becomes detached from a mountain slope 

and slides or falls suddenly downward. 

Back slope. The geomorphic component that forms the 

steepest inclined surface and principal element of 

many hillsides. Back slopes in profile are commonly 

steep, are linear, and may or may not include cliff 

segments. 

Badland. Steep or very steep, commonly nonstony, 

barren land dissected by many intermittent 

drainage channels. Badland is most common 

where streams are entrenched in soft geologic 

material. Local relief generally ranges from 25 to 

500 feet. Runoff potential is very high, and 

geologic erosion is active. 

Basal area. The area of a cross section of a tree, generally 

referring to the section at breast height and 

measured outside the bark. It is a measure of 

stand density, commonly expressed in square feet.

Base saturation. The degree to which material having 

cation exchange properties is saturated with 

exchangeable bases (sum of Ca, Mg, Na, K), 

expressed as a percentage of the total cation 

exchange capacity. 

Bedrock. The solid rock that underlies the soil and other 

unconsolidated material or that is exposed at the 

surface. 

Bottom land. The normal flood plain of a stream, 

subject to flooding. 

Boulders. Rock fragments larger than 2 feet (60 

centimeters) in diameter. 

Breast height. An average height of 41

/2 feet above the 

ground surface; the point on a tree where diameter 

measurements are ordinarily taken. 

Breccia. A coarse grained clastic rock composed of 

angular rock fragments larger than 2 millimeters in 

size, commonly cemented together in a finer 

grained matrix of varying composition and origin. 

The consolidated equivalent of rubble. 

Cable yarding. A method of moving felled trees to a 

nearby central area for transport to a processing 

facility. Most cable yarding systems involve use of a 

drum, a pole, and wire cables in an arrangement 

similar to that of a rod and reel used for fishing. To 

reduce friction and soil disturbance, felled trees 

generally are reeled in while one end is lifted or the 

entire log is suspended. 

Cirque. Semicircular, concave, bowllike areas that have 

steep faces primarily resulting from abrasion by 

glacial ice and snow. 

Clay. As a soil separate, the mineral soil particles less 

than 0.002 millimeter, in diameter. As a soil 

textural class., soil material that is 40 percent or 
more clay. less than 45 percent sand, and less than 

40 percent silt. 

Clay film. A thin coating of oriented clay on the surface of a 

soil aggregate or lining pores or root channels. 

Synonyms; clay coating, clay skin. 

Climax plant community. The plant community on a 

given site that will be established if present 

environmental conditions continue to prevail and 

the site is properly managed. 

Coarse fragments. Mineral or rock particles larger than 2 

millimeters in diameter. 

Coarse textured soil. Sand or loamy sand. 

Cobble (or cobblestone). A rounded or partly rounded 

fragment of rock 3 to 10 inches (7.6 to 25 

centimeters) in diameter. 

Cobbly soil material. Material that is 15 to 35 percent, by 

volume, rounded or partially rounded rock fragments 

3 to 10 inches (7.5 to 25 centimeters) in diameter. 

Very cobbly soil material is 35 to 60 percent of these 

rock fragments, and extremely cobbly soil material is 

more than 60 percent. 

Colluvium. Soil material, rock fragments, or both, 

moved by creep, slide, or local wash and 

deposited at the base of steep slopes. 

Complex, soil. A map unit of two or more kinds of soil or 

miscellaneous areas in such an intricate pattern or 

so small in area that it is not practical to map them 

separately at the selected scale of mapping. The 

pattern and proportion of the soils or miscellaneous 

areas are somewhat similar in all areas. 

Compressible (in tables). Excessive decrease in 

volume of soft soil under load. 

Concretions. Grains, pellets, or nodules of various sizes, 

shapes, and colors consisting of concentrated 

compounds or cemented soil grains. The composition 

of most concretions is unlike that of the surrounding 

soil. Calcium carbonate and iron oxide are common 

compounds in concretions. 

Conglomerate. A coarse grained, clastic rock composed of 

rounded to subangular rock fragments more than 2 

millimeters in diameter, it commonly has a matrix of 

sand and finer material. Conglomerate is the 

consolidated equivalent of gravel. 

Consistence, soil. The feel of the soil and the ease with 

which a lump can be crushed by the fingers. Terms 

commonly used to describe consistence are 

Loose. -Noncoherent when dry or moist; does not 

hold together in a mass. 

Friable.-When moist, crushes easily under gentle 

pressure between thumb and forefinger and can 

be pressed together into a lump. 

Firm.-When moist, crushes under moderate 

 pressure between thumb and forefinger, but 

resistance is distinctly noticeable. 

Plastic.-Readily deformed by moderate pressure 

but can be pressed into a lump; will form a "wire" 

when rolled between thumb and forefinger. 

Sticky.-Adheres to other material and tends to 

stretch somewhat and pull apart rather than to pull 

free from other material. 

Hard.-When dry, moderately resistant to 

pressure; can be broken with difficulty between 

thumb and forefinger. 

Soft.-When dry, breaks into powder or individual 

grains under very slight pressure. 

Cemented.-Hard; little affected by moistening. 

Control section (particle-size control section). The part 

of the soil on which classification is based. The 

thickness varies among different kinds of soil, but for 

many it is that part of the soil profile between depths of 

10 inches and 40 or 80 inches. 

Corrosive. High risk of corrosion to uncoated steel or 

deterioration of concrete. 

Cover crop. A close-growing crop grown primarily to 

improve and protect the soil between periods of 

regular crop production, or a crop grown between 

trees and vines in orchards and vineyards. 

Crop residue management. Returning crop residue to the 

soil, which helps to maintain soil structure, organic 

matter content, and fertility and helps to control 

erosion. 

Cropping system. Growing crops using a planned 

system of rotation and management 

practices. 

Culmination of the mean annual increment (CMAI). The 

average annual increase per acre in the volume of a 

stand. Computed by dividing the total volume of the 

stand by its age. As the stand increases in age, the 

mean annual increment continues to increase until 

mortality begins to reduce the rate of increase. The 

point where the stand reaches its maximum annual 

rate of growth is called the culmination of the mean 

annual increment. 

Cutbanks cave (in tables). The walls of excavations 

tend to cave in or slough. 

Debris flow (mudflow). A mass movement process 

involving rapid flow of highly viscous mixtures of 

debris, water, and entrapped air. Water content is as 

much as 60 percent. A mudflow is a type of debris 

flow of clastic particles of sand size and finer. 
Depth to rock (in tables). Bedrock is too near the 

surface for the specified use. 

Detritus. Loose fragments. particles, or grains that 

have been formed by the disintegration of rock. 

Diversion (or diversion terrace). A ridge of earth, 

generally a terrace, built to protect downslope 

areas by diverting runoff from its natural course. 

Drainage class (natural). Refers to the frequency and 

duration of periods of saturation or partial 

saturation during soil formation, as opposed to 

altered drainage, which is commonly the result of 

artificial drainage or irrigation but may be caused 

by the sudden deepening of channels or the 

blocking of drainage outlets. Seven classes of 

natural soil drainage are recognized: 

Excessively drained.-These soils have very high 

and high hydraulic conductivity and low water 

holding capacity. They are not suited to crop 

production unless irrigated. 

Somewhat excessively drained.-These soils have 

high hydraulic conductivity and low water holding 

capacity. Without irrigation, only a narrow range of 

crops can be grown and yields are low. 

Well drained.-These soils have intermediate 

water holding capacity. They retain optimum 

amounts of moisture, but they are not wet close 

enough to the surface or long enough during the 

growing season to adversely affect yields. 

Moderately well drained.-These soils are wet 

close enough to the surface or long enough that 

planting or harvesting operations or yields of some 

field crops are adversely affected unless artificial 

drainage is provided. Moderately well drained soils 

commonly have a layer with low hydraulic 

conductivity, a wet layer relatively high in the 

profile, additions of water by seepage. or some 

combination of these. 

Somewhat poorly drained.-These soils are wet 

close enough to the surface or long enough that 

planting or harvesting operations or crop growth is 

markedly restricted unless artificial drainage is 

provided. Somewhat poorly drained soils commonly 

have a layer with low hydraulic conductivity, a wet 

layer high in the profile, additions of water through 

seepage, or a combination of these. 

Poorly drained.-These soils commonly are so wet 

at or near the surface during a considerable part of 

the year that field crops cannot be grown under 

natural conditions. Poorly drained conditions are 

caused by a saturated zone, a layer with low 

hydraulic conductivity, seepage, or a combination 

of these. 

Very poorly drained.-These soils are wet to the 

surface most of the time. They are wet enough to 

prevent the growth of important crops (except rice) 

unless artificially drained. 

Drainage, surface. Runoff, or surface flow of water, 

from an area. 

Duff. A term used to identify a generally firm organic 

layer on the surface of mineral soils. It consists 

of fallen plant material that is in the process of 

decomposition and includes everything from the 

litter on the surface to underlying pure humus. 

Eluviation. The movement of material in true solution or 

colloidal suspension from one place to another 

within the soil. Soil horizons that have lost 

material through eluviation are eluvial; those that 

have received material are illuvial. 

Erosion. The wearing away of the land surface by 

water, wind, ice, or other geologic agents and by 

such processes as gravitational creep. 

Escarpment. A relatively continuous and steep slope or 

cliff breaking the general continuity of more gently 

sloping land surfaces and produced by erosion or 

faulting. Synonym; scarp. 

Excess fines (in tables). Excess silt and clay in the soil. 

The soil does not provide a source of gravel or 

sand for construction purposes. 

Extrusive rock. Igneous rock derived from deep-seated 

molten matter (magma) emplaced on the earth's 

surface. 

Fast intake (in tables). The rapid movement of water 

into the soil. 

Fertility, soil. The quality that enables a soil to provide 

plant nutrients, in adequate amounts and in proper 

balance, for the growth of specified plants when 

light, moisture, temperature, tilth, and other growth 

factors are favorable. 

Field moisture capacity. The moisture content of a soil, 

expressed as a percentage of the ovendry weight, 

after the gravitational, or free, water has drained 

away; the field moisture content 2 or 3 days after a 

soaking rain; also called normal field capacity, 

normal moisture capacity, or capillary capacity. 

Fill slope. A sloping surface consisting of excavated soil 

material from a road cut. It commonly is on the 

downhill side of the road. 

Fine textured soil. Sandy clay, silty clay, and clay. 

Firebreak. Area cleared of flammable material to stop 

or help control creeping or running fires. It also 

serves as a line from which to work and to 
facilitate the movement of men and equipment in fire 

fighting. Designated roads also serve as 

firebreaks. 

Flood plain. A nearly level alluvial plain that borders a 

stream and is subject to flooding unless protected 

artificially. 

Foothill. A steeply sloping upland that has relief of as 

much as 1,000 feet (or 300 meters) and fringes a 

mountain range or high-plateau 

escarpment. 

Foot slope. The inclined surface at the base of a hill. 

Forb. Any herbaceous plant not a grass or a sedge. 

Forest cover. All trees and other woody plants 

(underbrush) covering the ground in a forest. 

Forest type. A stand of trees similar in composition and 

development because of given physical and 

biological factors by which it may be differentiated 

from other stands. 

Frost action (in tables). Freezing and thawing of soil 

moisture. Frost action can damage roads, 

buildings and other structures, and plant roots. 

Full bench construction (road building). Construction of

roads on side slopes where excavated material is not 

sidecast but is hauled away to a disposal or storage 

area. 

Genesis, soil. The mode of origin of the soil. Refers 

especially to the processes or soil-forming factors 

responsible for the formation of the solum, or true soil, 

from the unconsolidated parent material. 

Glacial drift (geology). Pulverized and other rock 

material transported by glacial ice and then 

deposited. Also the sorted and unsorted material 

deposited by streams flowing from glaciers. 

Grassed waterway. A natural or constructed waterway, 

typically broad and shallow, seeded to grass as 

protection against erosion. Conducts surface water 

away from cropland. 

Gravel. Rounded or angular fragments of rock as much as 3 

inches (2 millimeters to 7.6 centimeters) in diameter. 

An individual piece is a pebble. 

Gravelly soil material. Material that is 15 to 50 percent, 

by volume, rounded or angular rock fragments, not 

prominently flattened, as much as 3 inches (7.6 

centimeters) in diameter. 

Ground water (geology). Water filling all the unblocked 

pores of underlying material below the water table. 

Gully. A miniature valley with steep sides cut by running 

water and through which water ordinarily runs only 

after rainfall. The distinction between a gully and a rill 

is one of depth. A gully generally is an obstacle to 

farm machinery and is too deep to be obliterated by 

ordinary tillage; a rill is of lesser 

depth and can be smoothed over by ordinary 

tillage. 

Hard rock. Rock that cannot be excavated except by 

blasting or by the use of special equipment that is not 

commonly used in construction. 

Horizon, soil. A layer of soil, approximately parallel to the 

surface, having distinct characteristics produced by 

soil-forming processes. In the identification of soil 

horizons, an upper case letter represents the major 

horizons. Numbers or lower case letters that follow 

represent subdivisions of the major horizons. An 

explanation of the subdivisions is given in the Soil 

Survey Manual. The major horizons of mineral soil are 

as follows: 

O horizon.-An organic layer of fresh and decaying 

plant residue. 

A horizon.-The mineral horizon at or near the 

surface in which an accumulation of humified organic 

matter is mixed with the mineral material. Also, a 

plowed surface horizon, most of which was originally 

part of a B horizon. 

B horizon.-The mineral horizon below an A horizon. 

The B horizon is in part a layer of transition from the 

overlying A to the underlying C horizon. The B 

horizon also has distinctive characteristics such as (1) 

accumulation of clay, sesquioxides, humus, or a 

combination of these; (2) prismatic or blocky structure; 

(3) redder or browner colors than those in the A 

horizon; or (4) a combination of these. E horizon.-

The mineral horizon in which the main feature is loss 

of silicate clay, iron, aluminum, or some combination 

of these. 

C horizon.-The mineral horizon or layer, excluding 

indurated bedrock, that is little affected by soilforming processes and does not have the properties 

typical of the overlying soil material. The material of a 

C horizon may be either like or unlike that in which 

the solum formed. If the material is known to differ 

from that in the solum, the number 2 precedes the 

letter C. 

R layer.-Consolidated rock beneath the soil. The 

rock commonly underlies a C horizon, but it can be 

directly below an A or a B horizon. 

Humus. The well decomposed, more or less stable part of 

the organic matter in mineral soils. 

Hydrologic soil groups. Refers to soils grouped 

according to their runoff-producing characteristics. 

The chief consideration is the inherent capacity of soil 

bare of vegetation to permit infiltration. The slope 

and the kind of plant cover are not 
considered but are separate factors in predicting 

runoff, Soils are assigned to four groups. In group A 

are soils having a high infiltration rate when 

thoroughly wet and having a low runoff potential. 

They are mainly deep, well drained, and sandy or 

gravelly. In group D, at the other extreme, are soils 

having a very slow infiltration rate and thus a high 

runoff potential. They have a claypan or clay layer 

at or near the surface, have a permanent high water 

table, or are shallow over nearly impervious bedrock 

or other material. A soil is assigned to two hydrologic 

groups if part of the acreage is artificially drained 

and part is undrained. 

Igneous rock. Rock formed by solidification from a 

molten or partially molten state. Major varieties 

include plutonic and volcanic rock. Examples are 

andesite, basalt, and granite. 

Illuviation. The movement of soil material from one 

horizon to another in the soil profile. Generally, 

material is removed from an upper horizon and 

deposited in a lower horizon. 

Impervious soil. A soil through which water, air, or roots 

penetrate slowly or not at all. No soil is absolutely 

impervious to air and wader all the time. 

Infiltration. The downward entry of water into the 

immediate surface of soil or other material, as 

contrasted with percolation, which is movement of 

water through soil layers or material. 

Infiltration rate. The rate at which water penetrates the 

surface of the soil at any given instant, usually 

expressed in inches per hour. The rate can be 

limited by the infiltration capacity of the soil or the 

rate at which water is applied at the surface. 

Irrigation. Application of water to soils to assist in 

production of crops. Methods of irrigation areBorder.-Water is applied at the upper end of a 

strip in which the lateral flow of water is controlled by 

small earth ridges called border dikes, or borders. 

Basin.-Water is applied rapidly to nearly level 

plains surrounded by levees or dikes. 

Controlled flooding.-Water is released at intervals 

from closely spaced field ditches and distributed 

uniformly over the field. 

Corrugation.-Water is applied to small, closely 

spaced furrows or ditches in fields of closegrowing crops or in orchards so that it flows in 

only one direction. 

Drip (or trickle).-Water is applied slowly and 

under low pressure to the surface of the soil or into 

the soil through such applicators as emitters, 

porous tubing, or perforated pipe. 

Furrow.-Water is applied in small ditches 

made by cultivation implements. Furrows are 

used for tree and row crops. 

Sprinkler.-Water is sprayed over the soil surface 

through pipes or nozzles from a pressure system. 

Subirrigation.-Water is applied in open ditches or 

tile lines until the water table is raised enough to 

wet the soil. 

Wild flooding.-Water, released at high points, is 

allowed to flow onto an area without controlled 

distribution. 

Lacustrine deposit (geology). Material deposited in 

lake water and exposed when the water level is 

lowered or the elevation of the land is raised. 

Lahar. Rock debris mobilized by water and derived from a 

volcano. 

Landslide. The rapid downhill movement of a mass of 

soil and loose rock, generally when wet or 

saturated. The speed and distance of movement, 

as well as the amount of soil and rock material, 

vary greatly. 

Large stones (in tables). Rock fragments 3 inches (7.5 

centimeters) or more across. Large stones adversely 

affect the specified use of the soil. 

Lava casts. The hollow impression left when a tree has 

been engulfed by a lava flow. As the tree is 

carbonized by the heat from the surrounding molten 

rock, water escaping from the trunk cools a thin crust 

of lava, which hardens around the tree trunk. The 

trunk decomposes, leaving a lava mold in the exact 

shape of the tree. 

Lava tubes. Caves or tubes formed inside a lava flow. 

Although there are several means by which lava 

caves can be created, the most common 

explanation is that the liquid interior of a lava stream 

continues to flow after the tops and sides have 

cooled and hardened. The center of the flow then 

drains away. 

Leaching. The removal of soluble material from soil or 

other material by percolating water. 

Light textured soil. Sand and loamy sand. 

Liquid limit. The moisture content at which the soil 

passes from a plastic to a liquid state. 

Loam. Soil material that is 7 to 27 percent clay 

particles, 28 to 50 percent silt particles, and less 

than 52 percent sand particles. 

Loess. Fine grained material, dominantly of silt-sized 

particles, deposited by wind. 

Low strength. The soil is not strong enough to support 

loads. 

Mean annual increment. The average yearly volume 
growth of a stand of trees from the year of origin to the 

age under consideration. 

Medium textured soil. Very fine sandy loam, loam, silt 

loam, or silt. 

Mineral soil. Soil that is mainly mineral material and 

low in organic material. Its bulk density is more 

than that of organic soil. 

Miscellaneous area. An area that has little or no 

natural soil and supports little or no vegetation. 

Moderately coarse textured soil. Coarse sandy loam, 

sandy loam, and fine sandy loam. 

Moderately fine textured soil. Clay loam, sandy clay 

loam, and silty clay loam. 

Morphology, soil. The physical makeup of the soil, 

including the texture, structure, porosity, 

consistence, color, and other physical, 

mineral, and biological properties of the various 

horizons, and the thickness and arrangement of 

those horizons in the soil profile. 

Mottling, soil. Irregular spots of different colors that vary in 

number and size. Mottling generally indicates 

poor aeration and impeded drainage. 

Descriptive terms are as follows: abundance-few, 

common, and many; size-fine, medium, and coarse; 

and contrast-faint, distinct, and prominent. The size 

measurements are of the diameter along the greatest 

dimension. Fine indicates less than 5 millimeters 

(about 0.2 inch); medium, from 5 to 15 millimeters 

(about 0.2 to 0.6 inch); and coarse, more than 15 

millimeters (about 0.6 inch). 

Mountain. A natural elevation of the land surface, rising 

more than 1,000 feet above surrounding lowlands, 

commonly of restricted summit area (relative to a 

plateau) and generally having steep sides and 

considerable bare-rock surface. A mountain 

can occur as a single, isolated mass or in a group 

forming a chain or range. 

Munsell notation. A designation of color by degrees of the 

three simple variables-hue, value, and chroma. For 

example, a notation of 10YR 6/4 is a color in hue of 

10YR, value of 6, and chroma of 4. 

Nutrient, plant. Any element taken in by a plant 

essential to its growth. Plant nutrients are mainly 

nitrogen, phosphorus, potassium, calcium, 

magnesium, sulfur, iron, manganese, copper, 

boron, and zinc obtained from the soil and carbon, 

hydrogen, and oxygen obtained from the air and 

water. 

Organic matter. Plant and animal residue in the soil in 

various stages of decomposition. 

Parent material. The unconsolidated organic and 

mineral material in which soil forms. 

Ped. An individual natural soil aggregate, such as a 

granule, a prism, or a block. 

Pedon. The smallest volume that can be called "a soil." A

pedon is three dimensional and large enough to 

permit study of all horizons. Its area ranges from 

about 10 to 100 square feet (1 square meter to 10 

square meters), depending on the variability of the 

soil. 

Percolation. The downward movement of water through the 

soil. 

Percs slowly (in tables). The slow movement of water 

through the soil, adversely affecting the specified 

use. 

Permeability. The quality of the soil that enables water to 

move downward through the profile. Permeability is 

measured as the number of inches per hour that 

water moves downward through the saturated soil. 

Terms describing permeability are: 

Very slow .............................less than 0.06 inch 

Slow .......................................... 0.06 to 0.2 inch 

Moderately slow ......................... 0.2 to 0.6 inch 

Moderate ....................... 0.6 inch to 2.0 inches 

Moderately rapid..................... 2.0 to 6.0 inches 

Rapid ...................................... 6.0 to 20 inches 

Very rapid ......................... more than 20 inches 

Phase, soil. A subdivision of a soil series based on 

features that affect its use and management. For 

example, slope, stoniness, and thickness. 

pH value. A numerical designation of acidity and alkalinity

 in soil. (See Reaction, soil.) 

Piping (in tables). Formation of subsurface tunnels or 

pipelike cavities by water moving through the soil. 

Plasticity index. The numerical difference between the 

liquid limit and the plastic limit; the range of 

moisture content within which the soil remains plastic.

Plastic limit. The moisture content at which a soil 

changes from semisolid to plastic. 

Ponding. Standing water on soils in closed depressions. 

The water can be removed only by percolation or 

evapotranspiration. 

Poor filter (in tables). Because of rapid permeability or an 

impermeable layer near the surface, the soil may not 

adequately filter effluent from a waste disposal 

system. 

Poor outlets (in tables). Refers to areas where surface or 

subsurface drainage outlets are difficult or expensive 

to install. 

Poorly graded. Refers to a coarse grained soil or soil 

material consisting mainly of particles of nearly the 

same size. Because there is little difference in size 
of the particles, density can be increased only 

slightly by compaction. 

Productivity, soil. The capability of a soil for producing a 

specified plant or sequence of plants under specific 

management. 

Profile, soil. A vertical section of the soil extending 

through all its horizons and into the parent 

material. 

Pumice. Porous tephra fragments (more than 2 

millimeters in size) ejected during volcanic activity. 

They are light weight and commonly are light in 

color. Pumice fragments will crush under a load. 

Pyroclastic. The Greek word for "fire-broken," referring to 

fragmented volcanic rock thrown out during an 

eruption. 

Pyroclastic flow. A volcanic flow of hot gas and fragmental 

material (pyroclastic); it is composed of either 

pumice or lithic (nonvesicular) debris, or a mixture of 

both. 

Reaction, soil. A measure of acidity or alkalinity of a soil, 

expressed in pH values. A soil that tests to pH 7.0 is 

described as precisely neutral in reaction because it 

is neither acid nor alkaline. The degree of acidity or 

alkalinity is expressed as 

Extremely acid................................... Below 4.5 

Very strongly acid .............................. 4.5 to 5.0 

Strongly acid.......................................5.1 to 5.5 

Medium acid ......................................5.6 to 6.0 

Slightly acid ........................................ 6.1 to 6.5 

Neutral................................................ 6.6 to 7.3 

Mildly alkaline .....................................7.4 to 7.8 

Moderately alkaline ...........................7.9 to 8.4 

Strongly alkaline ................................. 8.5 to 9.0 

Very strongly alkaline .................9.1 and higher 

Reforestation. Tree seedlings that are planted or 

become naturally established in an area of land that 

was once forested. Also includes the physical acts 

associated with planting. 

Regolith. The unconsolidated mantle of weathered rock 

and soil material on the earths surface; the loose 

earth material above the solid rock. 

Relief. The elevations or inequalities of a land surface. 

considered collectively. 

Residuum (residual soil material). Unconsolidated, 

weathered, or partly weathered mineral material 

that accumulated as consolidated rock 

disintegrated in place. 

Rill. A steep sided channel resulting from accelerated 

erosion. A rill generally is a few inches deep and 

not wide enough to be an obstacle to farm 

machinery. 

Road cut. A sloping surface produced by mechanical 

means during road construction. It is commonly on the 

uphill side of the road. 

Rock fragments. Rock or mineral fragments having a 

diameter of 2 millimeters or more; for example, 

pebbles, cobbles, stones, and boulders. 

Root zone. The part of the soil that can be penetrated 

by plant roots. 

Rooting depth (in tables). Shallow root zone. The soil is 

shallow over a layer that greatly restricts roots. 

Runoff. The precipitation discharged into stream channels 

from an area. The water that flows off the surface of 

the land without sinking into the soil is called surface 

runoff. Water that enters the soil before reaching 

surface streams is called groundwater runoff or 

seepage flow from ground water. 

Sand. As a soil separate, individual rock or mineral 

fragments from 0.05 millimeter to 2.0 millimeters in 

diameter. Most sand grains consist of quartz. As a 

soil textural class, a soil that is 85 percent or more 

sand and not more than 10 percent clay. 

Sandstone. Sedimentary rock containing dominantly 

sand-size particles. 

Saprolite (soil science). Unconsolidated residual 

material underlying the soil and grading to hard 

bedrock below. 

Scoria. Porous tephra fragments (more than 2 millimeters 

in size) ejected during volcanic activity. They are 

lightweight and commonly are dark red or black. 

Scoria fragments can be crushed between thumb 

and finger. 

Sedimentary rock. Rock made up of particles deposited 

from suspension in water. The chief kinds of 

sedimentary rock are conglomerate, formed from 

gravel; sandstone, formed from sand; shale, formed 

from clay; and limestone, formed from soft masses 

of calcium carbonate. There are many 

intermediate types. Some wind-deposited 

sand is consolidated into sandstone. 

Seepage (in tables). The movement of water through the 

soil. Seepage adversely affects the specified use. 

Sequum. A sequence consisting of an illuvial horizon and 

the overlying eluvial horizon. (See Eluviation.) 

Series , soil. A group of soils that have profiles that are 

almost alike, except for differences in texture of the 

surface layer or of the underlying material. All the 

soils of a series have horizons that are similar in 

composition, thickness, and arrangement. 

Shale. Sedimentary rock formed by the hardening of a 

clay deposit. 

Shrink-swell (in tables). The shrinking of soil when dry 
and the swelling when wet. Shrinking and swelling 

can damage roads, dams, building foundations, 

and other structures. It can also damage plant 

roots. 

Silt. As a soil separate, individual mineral particles that 

range in diameter from the upper limit of clay (0.002 

millimeter) to the lower limit of very fine sand (0.05 

millimeter). As a soil textural class, soil that is 80 

percent or more silt and less than 12 percent 

clay. 

Site class. A grouping of site indexes into 5 to 7 

production capability levels. Each level can be 

represented by a site curve. 

Site curve (50-year). A set of related curves on a graph 

that shows the average height of dominant trees for 

the range of ages on soils that differ in productivity. 

Each level is represented by a curve. The basis of 

the curves is the height of dominant trees that are 

50 years old or are 50 years old at breast height. 

Site curve (100-year). A set of related curves on a graph 

that show the average height of dominant and 

codominant trees for a range of ages on soils that 

differ in productivity. Each level is represented by a 

curve. The basis of the curves is the height of 

dominant and codominant trees that are 100 years 

old or are 100 years old at breast height. 

Site index. A designation of the quality of a forest site 

based on the height of the dominant stand at an 

arbitrarily chosen age. For example, if the average 

height attained by dominant and codominant trees 

in a fully stocked stand at the age of 50 years is 75 

feet, the site index is 75. 

Skid trails. The paths left by the skidded logs and the 

bulldozer tractor used to pull them. 

Skidding. A method of moving felled trees to a nearby 

central area. 

Slippage (in tables). Soil mass susceptible to 

movement downslope when loaded, excavated. or 

wet. 

Slope. The inclination of the land surface from the 

horizontal. Percentage of slope is the vertical 

distance divided by horizontal distance, then 

multiplied by 100. Thus, a slope of 20 percent is a 

drop of 20 feet in 100 feet of horizontal distance. 

Slope (in tables). Slope is great enough that special 

practices are required to ensure satisfactory 

performance of the soil for a specific use. 

Slow intake (in tables). The slow movement of water 

into the soil. 

Slow refill (in tables). The slow filling of ponds, 

resulting from restricted permeability in the soil. 

Small stones (in tables). Rock fragments less than 3 

inches (7.5 centimeters) in diameter. Small stones 

adversely affect the specified use of the soil. 

Soil. A natural, three-dimensional body at the earth's 

surface. It is capable of supporting plants and has 

properties resulting from the integrated effect of 

climate and living matter acting on earthy parent 

material, as conditioned by relief over periods of 

time. 

Soil separates. Mineral particles less than 2 millimeters 

in equivalent diameter and ranging between 

specified size limits. The names and sizes, in 

millimeters, of separates recognized in the United 

States are as follows: 

Very coarse sand ............................ 2.0 to 1.0 

Coarse sand .................................... 1 .0 to 0.5 

Medium sand ..................................0.5 to 0.25 

Fine sand .....................................0.25 to 0.10 

Very fine sand ...............................0.10 to 0.05 

Silt................................................0.05 to 0.002 

Clay ........................................Less than 0.002 

Solum. The upper part of a soil profile, above the C 

horizon, in which the processes of soil formation are 

active. The solum in soil consists of the A, E, and B 

horizons. Generally, the characteristics of the 

material in these horizons are unlike those of the 

underlying material. The living roots and plant and 

animal activities are largely confined to the solum.

Stones. Rock fragments 10 to 24 inches (25 to 60 

centimeters) in diameter if rounded or 6 to 15 

inches (15 to 38 centimeters) in length if flat. 

Stony. Refers to a soil containing stones in 

numbers that interfere with or prevent tillage. 

Structure, soil. The arrangement of primary soil particles 

into compound particles or aggregates. The 

principal forms of soil structure are-platy 

(laminated), prismatic (vertical axis of aggregates 

longer than horizontal), columnar (prisms with 

rounded tops), blocky (angular or subangular), and 

granular. Structureless soils are either single grained 

(each grain by itself, as in dune sand) or massive 

(the particles adhering without any regular cleavage, 

as in many hardpans). 

Subsoil. Technically, the B horizon; roughly, the part of 

the solum below plow depth. 

Substratum. The part of the soil below the solum. 

Subsurface layer. Technically, the E horizon. Generally 

refers to a leached horizon lighter in color and lower 

in content of organic matter than the overlying 

surface layer. 

Suitable surface (logging roads). Rock of adequate 
hardness and size used to surface a road that can 

withstand repeated and long-term logging truck 

traffic. 

Surface layer. The soil ordinarily moved in tillage, or its 

equivalent in uncultivated soil, ranging in depth 

from 4 to 10 inches (10 to 25 centimeters). 

Frequently designated as the 'plow layer,'' or the 

"Ap horizon.'' 

Talus. Rock fragments of any size or shape, commonly 

coarse and angular, derived from and lying at the 

base of a cliff or very steep, rock slope. The 

accumulated mass of such loose, broken rock 

formed chiefly by falling, rolling, or sliding. 

Taxadjuncts. Soils that cannot be classified in a series 

recognized in the classification system. Such soils 

are named for a series they strongly resemble and 

are designated as taxadjuncts to that series because 

they differ in ways too small to be of consequence in 

interpreting their use and behavior. 

Tephra. Fragmental volcanic debris that is transported 

from the crater through the air. Does not denote 

properties of composition, vesicularity, or grain 

size. 

Terrace. An embankment. or ridge, constructed across 

sloping soils on the contour or at a slight angle to the 

contour. The terrace intercepts surface runoff so 

that water soaks into the soil or flows slowly to a 

prepared outlet. A terrace in a field generally is 

built so that the field can be farmed. A terrace 

intended mainly for drainage has a deep channel 

that is maintained in permanent sod. 

Terrace (geologic). An old alluvial plain, ordinarily flat or 

 undulating, bordering a river, a lake, or the sea. 

Texture, soil. The relative proportions of sand, silt, and

clay particles ir. a mass of soil. The basic textural

classes, in order of increasing proportion of fine 

particles, are sand, loamy sand, sandy loam, loam, 

silt loam, silt, sandy clay loam, clay loam, silty clay 

loam, sandy clay, silty clay, and clay. The sand, 

loamy sand, and sandy loam classes may be 

further divided by specifying "coarse," "fine," or 

"very fine." 

Thin layer (in tables). Otherwise suitable soil material 

too thin for the specified use. 

Tilth, soil. The physical condition of the soil as related to 

tillage, seedbed preparation, seedling emergence, 

and root penetration. 

Toe slope. The outermost inclined surface at the base of 

a hill; part of a foot slope. 

Topsoil. The upper part of the soil, which is the most 

favorable material for plant growth. It is ordinarily 

rich in organic matter and is used to topdress 

roadbanks, lawns, and land affected by mining. 

Trace elements. Chemical elements, for example, zinc, 

cobalt, manganese, copper, and iron, are in soils 

in extremely small amounts. They are essential to

plant growth. 

Tuff. A compacted deposit that is 50 percent or more 

volcanic ash and dust. 

Unstable fill (in tables). Risk of caving or sloughing on 

banks of fill material. 

Upland (geology). Land at a higher elevation, in 

general, than the alluvial plain or stream terrace; 

land above the lowlands along streams. 

Variant, soil. A soil having properties sufficiently different 

from those of other known soils to justify a new 

series name, but occurring in such a limited 

geographic area that creation of a new series is 

not justified. 

Volcanic ash. Tephra particles less than 2 millimeters 

in size ejected during volcanic activity. Does not 

denote properties of composition, vesicularity, or 

color. 

Water bars. Smooth, shallow ditches or depressional 

areas that are excavated at an angle across a 

sloping road. They are used to reduce the 

downward velocity of water and divert it off and away 

from the road surface. Water bars can easily be 

driven over if constructed properly. 

Weathering. All physical and chemical changes 

produced in rocks or other deposits at or near the 

earth's surface by atmospheric agents. These 

changes result in disintegration and decomposition 

of the material. 

Well graded. Refers to soil material consisting of 

coarse grained particles that are well distributed 

over a wide range in size or diameter. Such soil 

normally can be easily increased in density and 

bearing properties by compaction. Contrasts with 

poorly graded soil. 

Windthrow. The action of uprooting and tipping over 

trees by the wind. 

Yarding. A logging term meaning to move a iog from 

the area in which it was cut to a landing or loading 

area. 

Yarding paths. The paths left from cable yarded logs 

as they are pulled uphill or downhill to a nearby 

central area. 

Yield (woodland). The volume of wood fiber from 

harvested trees taken from a certain unit of area. 

Usually measured in board feet or cubic feet per 

acre.