Appendix H: 

Geology and Soils

Discipline Report

Point Defiance Bypass 

Project 

Soils and Geology 

Discipline Report 

September 2012 

Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page i 

Table of Contents 

Summary ........................................................................................................................................... 1

Affected Environment and Effects ................................................................................................ 1

Recommended Minimization ........................................................................................................ 2

Chapter 1 – Project Description ........................................................................................................ 5

Introduction................................................................................................................................... 5

Purpose and Need ....................................................................................................................... 5

What alternatives are being considered for the Point Defiance Bypass Project? ......................... 6

What’s happening in the bypass corridor today? .......................................................................... 7

What would happen if the Project were not built? ......................................................................... 7

What are the proposed improvements and related activities of the Point Defiance Bypass 

Project? ........................................................................................................................................ 7

What are the proposed operational changes that would result from the Point Defiance Bypass 

Project? ........................................................................................................................................ 8

Chapter 2 – Methodology ................................................................................................................ 10

What was the methodology for this analysis? ............................................................................. 10

Chapter 3 – Affected Environment .................................................................................................. 13

What is the study area? .............................................................................................................. 13

What are the existing conditions in the study area? ................................................................... 13

Chapter 4 – Project Effects ............................................................................................................. 26

What are the potential effects of the No Build Alternative? ........................................................ 26

What are the potential effects of the Build Alternative? .............................................................. 28

Chapter 5 – Recommended Minimization Measures ....................................................................... 36

What minimization is required for the No Build Alternative? ....................................................... 36

What minimization is required for the Build Alternative? ............................................................ 36

References ...................................................................................................................................... 42

Table of Exhibits 

Exhibit 1. Build Alternative Components ........................................................................................... 9

Exhibit 2. Surficial Geology in the Study Area ................................................................................. 15

Exhibit 3. Fault Map ........................................................................................................................ 21

Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 1 

Summary 

Affected Environment and Effects 

The Project lies within the southern Puget Sound Lowland, an elongated 

topographic and structural depression filled with a complex sequence of 

sediments deposited by glacial processes and non-glacial geologic 

processes similar to those of the present day. Soil originating from the 

Vashon Stade of the Fraser Glaciation is present across most of the project 

alignment. This soil is relatively dense and typically has high strength. 

Since the retreat of the Vashon glacial ice, fluvial and lacustrine sediments 

have been deposited along rivers and streams and in closed topographic 

depressions. The fluvial and lacustrine deposits are less dense and have 

lower strength than the glacial deposits and are considered to be 

susceptible to liquefaction. 

No Build Alternative 

No construction effects are anticipated for the No Build Alternative. 

Operational effects of the No Build Alternative include continued 

instability of steep slopes along the existing rail alignment and effects 

related to earthquake activity. Liquefiable soil is present along the existing 

rail alignment from TR Junction near the Puyallup River to about Old 

Town Tacoma and in scattered areas along the BNSF alignment along 

Puget Sound. Soil liquefaction can result in settlement and lateral 

deformation of the tracks in areas where liquefiable soil is present. 

Liquefaction occurs when vibrations within a soil mass cause the soil 

particles to temporarily lose contact with one another. As a result, the soil 

behaves like a liquid, has an inability to support weight, and can flow 

down slopes (lateral spreading). Damage as a result of earthquake activity 

would likely result in temporary discontinuation of train traffic until 

repairs can be made. Soil and organic debris from steep slopes along the 

tracks could potentially block drainage ditches, resulting in erosion and 

possibly contributing to continued landsliding along the No Build 

Alternative alignment, which may also disrupt train operations. 

Build Alternative 

Potential construction effects as a result of the Project include increased 

wind and water erosion from land clearing operations and from cuts into 

existing slopes; sloughing and shallow landsliding on overly steep 
September 2012 Point Defiance Bypass Project 

Page 2 Soils and Geology Discipline Report 

temporary excavation slopes; poor drainage control, which could affect 

temporary excavation slopes and adjacent properties; and damage to 

pavements as a result of heavy construction traffic. 

Potential physical effects as a result of the Project include changes to the 

topography and landscape along the alignment. 

Potential operational effects as a result of the Project include damage to 

the tracks and structures as a result of soil liquefaction and lateral 

spreading. Areas of concern include: 

 The vicinity of I-705 (Rail MP 2.1 to Rail MP 2.2); 

 Between about Tacoma Avenue South (Rail MP 2.7) and 

South “M” Street (Rail MP 3.2); and 

 The portion of the alignment east of East “G” Street (Rail MP 1.8) 

Liquefaction can result in significant settlement and lateral deformation of 

the tracks in areas where liquefiable soil is present. Embankment failure, 

especially east of Freighthouse Square, may also occur due to a loss of 

underlying soil strength and lateral spreading displacement of the soil 

toward the Puyallup River. Damage as a result of earthquake activity 

would likely result in temporary discontinuation of train traffic until 

repairs can be made. 

The track sections between Pacific Avenue (Rail MP 2.3) to about East 

“M” Street (Rail MP 3.2) and the steep hillside traversed by the BNSF 

main line south of I-5 (Rail MP 20.0) are located in landslide hazard areas. 

In these sections, landsliding could result in blocked drainage ditches and 

possibly temporarily block the tracks with debris, disrupting train 

operations. 

Recommended Minimization 

No Build Alternative 

No minimization is proposed for the No Build Alternative. 

Build Alternative 

Potential effects as a result of the Project are generally minor in nature and 

most can be easily addressed using proper construction means and 

methods and employing Best Management Practices (BMPs) during 

construction. 

To address the potential construction effects of the Project , a Temporary 

Erosion and Sediment Control Plan will be prepared for approval in 

accordance with BMPs included in WSDOT’s Highway Runoff Manual
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 3 

(WSDOT 2010a) and procedures in the National Pollutant Discharge 

Elimination System (NPDES) guidelines administered by the Washington 

State Department of Ecology (Ecology website, 2011). Other controls that 

may be implemented include restriction of work activities to the dry 

season and limiting access to the site. Areas disturbed during construction 

would be paved or permanently restored as soon as possible. Trucks 

hauling soil would be covered to prevent material from being deposited 

onto roadways. 

Temporary excavation slopes would be evaluated and designed by 

experienced structural and geotechnical engineers and sloped accordingly 

to prevent surface sloughing and shallow landsliding. Proper erosion 

control and surface water runoff BMPs would be implemented to prevent 

sedimentation and destabilizing temporary excavation slopes. Permanent 

cut slopes would be no steeper than two horizontal feet to one vertical foot 

(2H:1V) and vegetated as soon as possible. Properly designed retaining 

walls would be used where permanent cut slopes cannot be constructed at 

2H:1V or flatter. 

All fill and pavement areas would be sloped to drain away from 

construction areas and prevent ponding of water and softening of subgrade soils. Drainage water from construction areas would be directed into 

suitable drainage features in accordance with BMPs. No water would be 

allowed to drain out over existing slopes, into excavations, or onto subgrade areas. 

Damage to pavement would be minimized by choosing construction traffic 

routes that avoid areas of potential soft sub-grade and/or inadequate 

pavement thickness. If no alternative exists, portions of existing roadways 

with pavement sections inadequate for handling construction traffic may 

be removed and replaced with pavement sections of appropriate thickness. 

Alternatively, pavement damage caused by construction traffic could be 

mitigated by replacing the damaged pavement following completion of 

construction. New pavement would be designed by a qualified civil or 

geotechnical engineer in accordance with American Association of State 

Highway and Transportation Officials (AASHTO) guidelines. 

Potential operational effects of the Project related to the soil conditions 

along the project alignment would be mitigated by proper design of 

Project elements. The Project would be designed considering the 

seismicity of the site and the design guidelines presented in WSDOT’s 

Highway Runoff Manual (WSDOT 2010a), Design Manual (WSDOT, 

2010b), and Bridge Design Manual (WSDOT, 2011), AASHTO’s Load 

and Resistance Factor Design Bridge Design Specifications (AASHTO, 

2010), the AREMA Manual for Railway Engineering (AREMA, 2011), 

and the International Building Code (ICC, 2009). 
September 2012 Point Defiance Bypass Project 

Page 4 Soils and Geology Discipline Report 

Permanent drainage facilities for slopes, walls, or fills would be designed 

for anticipated water flows. All permanent drainage systems would be 

installed so that water does not overflow and is not directed onto slopes or 

other areas that may be sensitive to erosion or landsliding. The Project 

includes drainage features, such as ditches, that are not currently present 

or are inadequate along the existing rail. Such features would likely reduce 

the effects of uncontrolled or undesirable surface water runoff. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 5 

Chapter 1 – Project Description 

Introduction 

Under the High-Speed Intercity Passenger Rail (HSIPR) Program and 

pursuant to a programmatic Tier I Environmental Assessment (EA) the 

Federal Railroad Administration (FRA) has approved an application from 

the Washington State Department of Transportation (WSDOT) to improve 

the Pacific Northwest Rail Corridor (PNWRC), a federally designated 

high-speed rail corridor. One project included in the PNWRC application 

is the Point Defiance Bypass Project (the Project), which would respond to 

deficiencies in the existing rail operations around Point Defiance. This 

Discipline Report has been prepared in support of the project-specific EA 

for the Point Defiance Bypass project. 

The Project is located in Pierce County along an existing approximately 

20-mile rail corridor between Tacoma and Nisqually.1 The Project would 

provide for the re-routing of Amtrak passenger trains from the BNSF rail 

line that runs along the southern Puget Sound shoreline (Puget Sound 

route) to the Point Defiance Bypass route, an existing rail corridor that 

runs along the west side of I-5. The Project would consist of railroad track 

and support facility improvements, and relocation of the Tacoma Amtrak 

Station to Freighthouse Square in Tacoma. 

Purpose and Need

As described above, the Point Defiance Bypass route is part of the larger 

PNWRC. Within Washington State, the vision for the PNWRC is to 

“...improve intercity passenger rail service by reducing travel times and 

achieving greater schedule reliability in order to accommodate growing 

intercity travel demand...”2. 

The purpose of the Project is to provide more frequent and reliable highspeed intercity passenger rail service along the PNWRC between Tacoma 

and Nisqually. In conformity with the decisions under the Tier 1 

Programmatic EA, the PNWRC Improvement Program has reduced the 

overall environmental effects of providing improved passenger rail service 

 

1

 The three owners of the project corridor are Sound Transit, Tacoma Rail, and BNSF. 2 WSDOT 2009
September 2012 Point Defiance Bypass Project 

Page 6 Soils and Geology Discipline Report 

with the use of an existing transportation corridor and associated 

infrastructure, rather than creating a new corridor. 

The Project is needed to address the deficiencies in the existing rail 

alignment around Point Defiance. The existing alignment (Puget Sound 

route), shared by freight and passenger rail traffic, is near capacity and is 

therefore unable to accommodate additional high-speed intercity 

passenger rail service without substantial improvements. In addition, the 

existing alignment has physical and operational constraints that adversely 

affect both passenger train scheduling and reliability. 

Improving intercity passenger rail service in the project area and meeting 

the Project needs would be accomplished by: 

 Enhanced Frequency: Increasing Amtrak Cascades round-trips from four 

to six by 2017 to meet projected service demands. 

 Improved Reliability: Reducing scheduling conflicts with freight trains 

that often result in delays, and by minimizing or avoiding operational 

delays (e.g., drawbridge openings) and weather-related delays (e.g., 

mudslides), and improving on-time performance from 68 percent to 88 

percent. 

 Enhanced Efficiency: Enhancing the efficient movement of people by 

decreasing trip times by 10 minutes, and reducing the amount of time 

passenger trains spend yielding to freight movements. 

 Improved Safety: Constructing at-grade crossings with upgraded safety 

features, including wayside horns, median barriers, advance warning 

signals, and traffic signal improvements.

What alternatives are being considered for the Point 

Defiance Bypass Project? 

FRA and WSDOT conducted an evaluation of three build alternatives: the 

Point Defiance Bypass Alternative, the Shoreline Alternative, and the 

Greenfield Alternative. Two of the alternatives (the Shoreline Alternative, 

and the Greenfield Alternative) were eliminated from further study. 

Although both alternatives could meet the Project’s purpose and need, 

they were determined to be impracticable and unfeasible due to technical 

constraints, high construction costs, and significant environmental effects. 

Grade separations were also evaluated for further consideration. FRA and 

WSDOT’s preliminary analysis revealed that current and projected future 

traffic volumes do not warrant the construction of new grade-separated 

crossings. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 7 

What’s happening in the bypass corridor today? 

The rail line between TR Junction and East “D” Street in Tacoma hosts 

both freight and commuter trains, including freight operators Tacoma Rail 

and BNSF, and Sound Transit’s Sounder commuter rail service. Freight 

train traffic between TR Junction and East “D” Street averages under two 

trains per day, while Sound Transit currently operates 18 trains per day 

between Freighthouse Square and Seattle each weekday, and also offers 

occasional special event trains, usually on weekends, to serve sporting and 

other events in Seattle. Sounder service to Lakewood begins in late 2012. 

What would happen if the Project were not built? 

If the Project were not built (the No Build Alternative), Amtrak’s 

Cascades and Coast Starlight passenger train service would continue to 

use the existing Puget Sound route. The No Build Alternative includes 

only the minor maintenance and repair activities necessary to keep the 

existing Puget Sound route operational. With the No Build Alternative, it 

would be expected that as freight traffic increases, congestion would 

adversely affect Amtrak service reliability, and the travel time for Amtrak 

trains between Seattle and Portland would increase. 

Along the Point Defiance Bypass route, the Tacoma Rail and BNSF 

freight services would continue. The at-grade crossings at Clover Creek 

Drive Southwest, North Thorne Lane Southwest, Berkeley Street 

Southwest, 41st Division Drive, and Barksdale Avenue Southwest would 

not be upgraded. 

Sound Transit’s Sounder commuter passenger trains will become 

operational in late 2012 between the Tacoma Dome Station at 

Freighthouse Square in Tacoma and Sound Transit’s Lakewood Station 

(on the Point Defiance Bypass route) with as many as 18 Sounder trains 

per day. 

What are the proposed improvements and related activities 

of the Point Defiance Bypass Project? 

The Project consists of railroad track and support facility improvements, 

and the relocation of Amtrak’s Tacoma Station. Exhibit 1 shows the 

components of the Build Alternative. The following details specific 

components of the Build Alternative. 

 Construct New Track Adjacent to the Existing Main Line – A new 

3.5-mile track adjacent to the existing main line would be constructed 

from South 66th Street (Rail MP 6.9) in Tacoma to between Bridgeport 
September 2012 Point Defiance Bypass Project 

Page 8 Soils and Geology Discipline Report 

Way SW (Rail MP 10.4) and Clover Creek Drive SW (Rail MP 10.9) in 

Lakewood. 

 Reconstruct and Rehabilitate the Existing Main Line – Starting just 

southwest of Bridgeport Way Southwest (Rail MP 10.4) in Lakewood, the 

existing track would be reconstructed to a location southeast of the I5/Mounts Road Southwest interchange (Rail MP 19.8) at Nisqually 

Junction. 

 Improvements at at-Grade Crossings – Several grade crossings would 

be improved with wayside horns, gates, traffic signals and signage, 

sidewalks, median separators, and warning devices. These crossings 

include Clover Creek Drive Southwest, North Thorne Lane Southwest, 

Berkeley Street Southwest, 41st Division Drive and Barksdale Avenue. 

 Tacoma Amtrak Station Relocation – The existing Tacoma Amtrak 

Station would be relocated from its Puyallup Avenue location to the 

Tacoma Dome Station at Freighthouse Square, at 430 E. 25th Street in 

Tacoma. 

What are the proposed operational changes that would 

result from the Point Defiance Bypass Project? 

Amtrak’s existing Cascades and Coast Starlight passenger train service 

would be rerouted from the Puget Sound route along the Puget Sound 

shoreline to the Point Defiance Bypass route. The Project would also 

provide for additional Amtrak Cascades service by increasing the number 

of round trips provided from 4 to 6, or a total of 12 Cascades service train 

trips. Amtrak Coast Starlight would also travel on the Point Defiance 

Bypass route for a total of two Coast Starlight service train trips. The 

speed of these passenger trains would be up to 79 mph. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 9 

Exhibit 1. Build Alternative Components 
September 2012 Point Defiance Bypass Project 

Page 10 Soils and Geology Discipline Report 

Chapter 2 – Methodology 

The purpose of this Soils and Geology Discipline Report is to identify soil 

and geologic conditions and associated potential hazards, assess the 

potential effects of the Project with respect to soils and geology, and if 

found appropriate, identify measures to mitigate potential adverse effects. 

What was the methodology for this analysis? 

Geologic and soil conditions were reviewed because the Project would 

involve the movement and alteration of soil and rock materials. Geologic 

information of the study area was obtained by collecting and reviewing 

existing data, and conducting geologic and geotechnical reconnaissance to 

assess surface conditions, geologic hazards, and likely subsurface 

conditions. Understanding the geology and soils in the study area is 

necessary to understand and limit potential environmental effects. 

Information was collected from Pierce County Critical Areas Mapping, 

City of Tacoma Critical Areas Mapping, Pierce County Soil Survey 

(NRCS, 1979), US Geological Survey (USGS) Geology Maps, 

Washington Department of Natural Resources Geology Maps, and 

previous geotechnical reports. 

Project files and archives from several sources were reviewed to obtain 

site-specific geotechnical subsurface information along the Project 

corridor. These efforts were concentrated on sources where large amounts 

of information were already stored and easily accessed. Data, primarily 

consisting of boring logs, were collected from the following sources: 

 Consultant project files 

 WSDOT 

 City of Lakewood 

 Sound Transit 

Sources of existing subsurface information are listed in the Reference 

section of this report. In addition, information contained in the previous 

Soils and Geology Discipline Report (WSDOT, 2007) was incorporated 

into this report as appropriate. 

In addition, between November 2006 and May 2011, Project teams 

conducted field visits to the study area to assess surface conditions, 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 11 

geologic hazards, and likely subsurface conditions. The site 

reconnaissance completed in May 2011 was restricted to public rights of 

way between 100th Street Southwest (Rail MP 9.1) and Gravelly Lake 

Drive (Rail MP 11.7) and between North Thorne Lane Southwest (Rail 

MP 12.8) and Berkeley Street Southwest (Rail MP 13.7). No subsurface 

information investigations were conducted as part of this study. 

Based on the information obtained from the studies above, both the Build 

and the No Build alternatives were evaluated with respect to their potential 

geologic effects. Preliminary evaluations were made related to geologic 

hazards, earthquakes, and other geologic issues. The evaluations were 

made based on experience with similar projects and similar soil 

conditions, and conceptual engineering analyses. Potential operational 

effects were identified including seismic hazards, steep slope hazards, 

erosion, and ground vibrations. Potential construction effects were 

identified including erosion, excavation, and fill stability; groundwater 

effects; settlement; and ground vibration. Potential secondary and 

cumulative effects were also identified. 

If the potential for effects to these resources was found, recommended 

BMPs were developed for each effect identified. The recommended BMPs 

were selected based on experience with similar projects and accepted 

industry standard engineering practices. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 13 

Chapter 3 – Affected Environment 

What is the study area? 

For the purposes of this report, the study area is defined as the corridor 

that lies within 1,000 feet both left and right of the centerline of the 

Project, including relocating the Tacoma Amtrak Station to the Tacoma 

Dome Station at Freighthouse Square. 

What are the existing conditions in the study area? 

Geologic Setting 

The study area lies in the southern portion of the Puget Lowland, an 

elongated topographic and structural depression filled with a complex 

sequence of unconsolidated sediments deposited during the Pleistocene 

(from approximately 2 million to 12,000 years ago). These sediments were 

deposited by glacial processes associated with the incursion of large, 

glacial ice sheets into the Puget Lowland and by non-glacial geologic 

processes similar to those of the present day. These unconsolidated 

deposits overlie bedrock, which lies approximately 1,000-1,700 feet below 

the ground surface in the study area (Jones, 1996). 

The Puget Lowland was glaciated six or more times during the 

Pleistocene. The last glaciation, known as the Vashon Stade of the Fraser 

Glaciation, receded from the area about 13,500 years ago. This ice sheet is 

estimated to have been about 3,000 feet thick in the vicinity of the study 

area. Since retreat of the Vashon glacial ice, fluvial and lacustrine 

sediments have been deposited along rivers and streams and in closed 

topographic depressions. 

Topography 

From TR Junction (Rail MP 1.0) to East “G” Street (Rail MP 1.8), the 

topography along the rail line is of low relief and lies along the southern 

side of the Puyallup River Valley between approximately elevation 10-30 

feet above sea level. From East “G” Street, the topography begins to rise 

upward from the Puyallup River Valley to a broad upland plateau with 

relatively low relief that lies between approximate elevations of 200-400 

feet to the I-5 crossing (Rail MP 20.0) then decreases to about elevation 70 

feet at the southern terminus of the study area. 
September 2012 Point Defiance Bypass Project 

Page 14 Soils and Geology Discipline Report 

Most of the rail line is situated on the broad upland plateau. Coastal bluffs 

that descend to waters of Puget Sound bound the west side of the upland 

plateau. Steep bluffs that descend to the lowland floodplains of the 

Puyallup and Nisqually rivers bound the northeast and southwest sides of 

the upland plateau, respectively. The east side of the plateau is bounded by 

the Cascade foothills. 

The upland surface comprises numerous north-trending ridges and swales 

and numerous large topographic channels that trend westerly, which 

control the orientation of many of the upland stream channels. The upland 

is also occupied by numerous closed depressions, some of which are 

occupied by small lakes and poorly drained areas. 

The portion of the rail line along the Puyallup River to about East “G” 

Street (Rail MP 1.8) lies within a low-relief alluvial plain. The orientation 

of surface features is generally controlled by the Puyallup River. 

The existing rail line extends westward from the Puyallup River Valley to 

about Pacific Avenue (Rail MP 2.3), then climbs upward to the Nalley 

Valley at South “M” Street (Rail MP 3.2), then turns southward and 

traverses across the upland plateau to the southern edge of the plateau 

along the Nisqually River Valley. With the exception of the portion of the 

rail line between Pacific Avenue and South “M” Street, most of the study 

area is flat, with a few moderately sloped depressions. Hillside slopes 

along the portion of the rail line between Pacific Avenue and South “M” 

Street are moderate to very steep. Hillside slopes at the southern end of the 

study area, south of the I-5 crossing (Rail MP 20.0), are also moderate to 

very steep. 

Study Area Geology 

Geologic mapping in the vicinity of the study area includes work by Smith 

(1972, 1976) and Walsh (1987). The geology in the vicinity of most of the 

study area has been recently remapped by Troost (in review), Troost et al. 

(in review) and Walsh et al. (2003). 

The generalized geology in the vicinity of the study area is depicted in 

Attachment A, Figures A-1 through A-10, which is adapted from Troost 

(in review), Troost et al. (in review), Walsh (1987), and Walsh et al. 

(2003). Descriptions of the geologic units used in the geologic map are 

presented in Exhibit 2 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 15 

Exhibit 2. Surficial Geology in the Study Area 

Unit 

Designation 

Geologic 

Unit Description 

af Fill and Modified 

Land 

Clay, silt, sand, gravel, organic matter, riprap, and debris or 

a mixture of. Includes engineered and non-engineered fills. 

Mapped only where fill placement is extensive, sufficiently 

thick to be of geotechnical significance, and readily 

verifiable. 

Qal Alluvium River or creek deposits, normally associated with historical 

streams, including overbank deposits. Sand; silty sand; 

gravelly sand; very loose to medium dense. 

Qmw Colluvium and 

Alluvial Fan 

Deposits 

Loose soil and glacial sand and gravel deposited by soil 

creep and shallow raveling on hill slopes and alluvial fan 

deposition, some of which occurred during the waning 

stages of the Vashon Stade of the Fraser Glaciation. 

Qp Peat Depression fillings of organic materials. Peat; peaty silt; 

very soft to medium stiff. 

Qgof, Qvr Recessional 

Glacial 

Outwash 

Recessional Outwash – Recessional Lacustrine (Qgof) and 

Glaciofluvial sediment (Qvr) deposited as glacial ice 

retreated. Lacustrine deposits of clayey and sandy silt 

associated with glacial Lake Russell and other lakes of 

Vashon glacial recession; soft to medium stiff. Glaciofluvial 

deposits include Steilacoom gravel; sand, gravelly sand or 

sandy gravel; medium dense to dense. 

Qvi Ice Contact 

Deposits 

Heterogeneous soils deposited against or adjacent to ice 

during the wasting of glacial ice; commonly reworked; 

stratified to irregular bodies of gravel, sand and silt; loose 

to dense. 

Qvie Eskers Sinuous, steep-walled mounds of loose gravel and sand 

deposited in ice-confined channels by glacial meltwater. 

Qvt Glacial Till Lodgment till laid down along the base of the glacial ice. 

Gravelly, silty sand or gravelly, sandy silt; very dense; 

"hardpan;" boulders and cobbles common. 

Qva Advance 

Outwash 

Glaciofluvial sediment deposited as glacial ice advanced, 

sand, gravelly sand, or sandy gravel; dense to very dense. 

Qpogc Pre-Olympia Coarse-grained pre-Olympia glacial deposits. 

The topography and near-surface geology of the study area is largely the 

product of the last glaciation (Vashon). The Vashon glaciation left a 

prominent pattern of north-trending ridges and swales as the glacial ice 

crossed the upland plateau, and left deposits of sand and gravels that 

mantle the upland surface. The Vashon and older deposits in the Tacoma 

area form a sequence of permeable sand and gravel layers separated by 

finer-grained layers of clay and silt or other low permeable soils, which 

are exposed in places along the steep slopes that border the upland plateau. 

The Vashon and older deposits comprise several aquifers (a geologic 

formation that contains sufficient saturated permeable material to yield 

water to wells and springs) and aquitards (geologic formations that may 

contain groundwater but are incapable of transferring that water to a well 

or spring) within the subsurface, which control subsurface water 

movement from the upland to the lowland as well as the locations of 

streams and creeks that occupy former outwash channels (Jones et al., 

1999). 
September 2012 Point Defiance Bypass Project 

Page 16 Soils and Geology Discipline Report 

On the hillside areas on both sides of the alignment corridor, a complex 

series of glacially overridden soils (soils that were compacted by the 

weight of overriding glacial ice) layers are present. These soils were 

deposited during glacial events and during interglacial periods (periods 

where no glaciers were present) that were similar to the present‐day 

environment. 

In general, most of the alignment crosses the low relief, upland surface, 

where most existing cuts into the subsurface along this portion of the 

current alignment are relatively small. The portion of the track section 

from TR Junction (Rail MP 1.0) to the upland area is generally at grade, 

with the exception of the portion from East “K” Street (Rail MP 1.5) to 

Freighthouse Square, which is elevated on a trestle. No adjustments to the 

track or changes in operational speed are planned as part of the Project. As 

such, only near-surface geologic materials are pertinent to an 

understanding of potential effects to the environment from the Project. 

The predominant geologic unit along the rail line corridor is mapped as 

Vashon-age recessional outwash, which was deposited as the glaciers 

retreated. Ice contact deposits, advance outwash, pre-Fraser deposits, 

alluvium, and fill are mapped east of about South “M” Street (Rail MP 

3.2). Ice contact deposits are mapped near DuPont and advance outwash is 

mapped along the rail line south of the I-5 overpass (Rail MP 20.0). 

Recessional outwash rivers scoured channels in the landscape and 

deposited sand and gravel. The most significant recessional event was that 

relating to the Steilacoom gravel, a geologic formation of coarse gravel 

deposited in south- and west-trending channels carved by torrential 

floodwaters released from a former proglacial lake that occupied the 

Puyallup River Valley. The proglacial lake was created by a stagnant ice 

sheet. 

Along the rail line corridor, Steilacoom gravel is commonly about 20 feet 

thick but locally can be much thicker. In the study area, this deposit 

chiefly consists of openwork gravel with abundant cobbles. Openwork 

gravel is coarse gravel deposited in high-energy streams and rivers, 

resulting in the removal and subsequent absence of fine-grained particles 

from the void spaces between the gravel particles. Steilacoom gravel was 

not overridden by glacial ice, so it is generally medium dense. These 

highly permeable deposits at or near the ground surface are significant 

aquifer recharge areas and are highly susceptible to environmental 

contamination of groundwater. 

Glacial till from the Vashon glaciation mantles much of the upland area to 

the east and generally underlies the recessional deposits along the rail line, 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 17 

with the exception of the portion of the rail line through the Nalley Valley. 

The torrential floodwaters released from the former proglacial lake that 

occupied the Puyallup River Valley scoured through the glacial till and 

into the advance outwash, exposing glacial till and advance outwash on 

the Nalley Valley sides. Glacial till is an unstratified and unsorted mixture 

of sand, gravel, silt, and clay deposited at the base of a glacier and 

subsequently overridden by the ice and compacted to a very dense state by 

the weight of the overriding ice. Glacial till has very low permeability and 

typically acts as an aquitard, restricting the downward flow of 

groundwater and reducing recharge of deeper aquifers. Till occurs at or 

near the ground surface within the study area and makes up the core of 

low hills that are present in the vicinity of the alignment. Where till is 

exposed at the ground surface, runoff is likely to be rapid, with very little 

infiltration of precipitation. 

Glacial till is commonly covered by a relatively thin layer of sediments 

that were deposited during retreat of the ice sheet. These recessional 

deposits include ablation till, ice contact deposits, glacial outwash, and 

recessional lacustrine (lake environment) deposits. These materials were 

deposited away from the ice by meltwater streams that flowed from the 

retreating glacier or deposited in place as the stagnant ice melted. 

Post-glacial deposits in the vicinity of the study area include alluvium, 

depression fillings, and fill. Alluvium is sediment deposited by water 

flowing in streams. Alluvium is likely to be present along present-day 

streams and rivers, such as Murray Creek (Rail MP 13.9), Clover Creek 

(Rail MP 10.8), and the Puyallup and Nisqually rivers. Where 

encountered, alluvium is likely to consist of loose sand and gravelly sand 

to silt and sandy silt. A thick accumulation of alluvium is present along the 

Puyallup River east of TR Junction (Rail MP 1.0) and along the Nisqually 

River, west of the existing rail line, as shown in Attachment A, Figures A1 and A-10. 

Depressions in the ground surface following retreat of the Vashon 

glaciation became lakes and ponds that slowly filled with fine-grained (silt 

and clay) soil. Organic material and peat also accumulated as these lakes 

turned into bogs and marshes. These organic deposits are commonly 

associated with existing wetlands or a previous marsh environment. These 

deposits are present on either side of the Tacoma/Lakewood city boundary 

line. Localized deposits too small to have been mapped may be crossed by 

the alignment. 

Fill is mapped along the project alignment between TR Junction (Rail MP 

1.0) and East “G” Street (Rail MP 1.8) and is present along numerous 

other places along the alignment. Fill is soil placed by humans, and it can 
September 2012 Point Defiance Bypass Project 

Page 18 Soils and Geology Discipline Report 

have widely varying properties, depending on the material used as fill and 

whether the fill was placed in an engineered or non-engineered fashion. 

Fill is present along portions of the existing rail alignment. The fill was 

placed during construction of the existing Sound Transit-owned rail line 

and the BNSF main line to provide a uniform grade. Such areas of fill are 

likely to be of limited depth and extent. 

The embankment fill that supports the rail line at about Rail MP 20.3 

appears to be unstable. Based on field observations (Shannon & Wilson, 

2009a), an approximately 300-foot-long section of the embankment has 

moved slightly downward. This movement may reflect settlement or 

failure of the fill or of the relatively soft or loose soils inferred to underlie 

portions of the embankment. 

At the Freighthouse Square station location, the surficial geology has been 

mapped (Troost in review) as generally consisting of ice contact deposits, 

Vashon glacial till, and pre-Fraser deposits. Though not shown on the 

geologic map of the area, surficial fill is present at the site. The mapped 

geology in the study area is generally consistent with conditions observed 

in the borings completed in the vicinity of the site (Landau Associates, 

2008a), though glacial till was not encountered in the borings. 

There are no unique or protected geologic resources, or geologic resources 

of specific local interest, identified in the study area. 

Soils 

According to the US Department of Agriculture Soil Conservation Service 

Soil Survey of Pierce County Area, Washington, the predominant soils in 

the study area are Spanaway gravelly sandy loam (NRCS, 1979). The soil 

survey does not map soils within cities or military reservations; therefore, 

soils along portions of the alignment within the Tacoma city limits and 

JBLM have not been mapped. Spanaway gravelly sandy loam soils are 

formed in glacial outwash on uplands and are described as somewhat 

excessively drained with moderately rapid permeability. In areas underlain 

by these soils, runoff is slow and there is little erosional hazard. These 

soils are generally a good source of sand and gravel for construction 

purposes. 

Within the broad area of mapped Spanaway soils, localized depressions in 

the upland area are mapped as being underlain by DuPont muck. The only 

area of these soft soils within or very near the study area is south of 

84th Street S (Rail MP 8.0). Infiltration is slow in these soils. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 19 

The slopes that border the plateau in the northern and southern portion of 

the study area are not included in the soil survey because of their location 

within the City of Tacoma and within JBLM, respectively. 

Extrapolating from the closest adjacent areas that were mapped, Puyallup 

fine sandy loam soil is likely present in the area along the Puyallup River 

to about East “G” Street (Rail MP 1.8). Puyallup fine sandy loam is 

derived from sandy alluvium, infiltration is moderate to rapid, and there is 

only a slight erosion hazard. West of about East “G” Street to the upland 

area west of South Chandler Street (Rail MP 3.4), the soils are likely of 

the Alderwood and Kitsap Series. Alderwood gravelly sandy loam is 

derived from glacial till and permeability is very slow. The erosion hazard 

varies from slight for gentle slopes to moderate to severe for steeper 

slopes. Kitsap silt loam is derived from fine-grained, glacial lacustrine 

deposits and permeability is very slow. The erosion hazard varies from 

slight for gentle slopes to severe to very severe for steeper slopes. On 

steep slopes, these soils are susceptible to landsliding. 

Extrapolating from the closest adjacent areas that were mapped, Spanaway 

gravelly sandy loam, Nisqually loamy sand, and Kitsap silt loam soils are 

likely present in the southern portion of the study area within JBLM. 

Nisqually loamy sand is derived from sandy glacial outwash and has a 

high permeability. In areas underlain by these soils, infiltration is rapid 

and there is only a slight erosion hazard. Kitsap silt loam is derived from 

fine-grained, glacial lacustrine deposits and permeability is very slow. In 

areas underlain by these soils, the erosion hazard is moderate. These soils 

are susceptible to landsliding. 

There are no unique or protected geologic resources, or geologic resources 

of specific local interest, identified in the study area. 

Surface Water and Groundwater 

Surface water and groundwater over most of the rail alignment are 

controlled primarily by soil conditions and topography. In the northern 

portion of the rail alignment, groundwater is controlled primarily by the 

Puyallup River. The topography across the upland portion of the study 

area is generally flat and the soils are coarse-grained and permeable. 

Rather than flowing overland and forming streams, most of the 

precipitation falling in the vicinity of the study area infiltrates directly into 

the highly pervious soils (Steilacoom gravel). The only streams within the 

study area are Murray Creek (Rail MP 13.9) and Clover Creek (Rail 

MP 10.8). Flett Creek lies just outside of the study area. 

Water that infiltrates into the ground migrates laterally through the 

shallow groundwater system. The groundwater table over most of the 

upland area is approximately 10-40 feet below the ground surface. The 
September 2012 Point Defiance Bypass Project 

Page 20 Soils and Geology Discipline Report 

water table commonly intersects larger depressions in the upland surface 

resulting in standing bodies of water in these depressions, such as 

American Lake and Gravelly Lake. Because of rapid infiltration and the 

shallow groundwater system, the aquifer formed by Steilacoom gravel is 

highly susceptible to contamination. From TR Junction (Rail MP 1.0) to 

Freighthouse Square, groundwater is generally shallow and is highly 

susceptible to contamination. 

Geologic Hazards 

Washington State’s Growth Management Act (Chapter 36.70A RCW) 

requires all cities and counties to identify critical areas within their 

jurisdictions and to formulate development regulations for their protection. 

Among the critical areas designated by the Growth Management Act are 

geologically hazardous areas, defined as such because of their potential 

susceptibility to erosion, sliding, earthquake, or other geologic events, or 

because of their past use (e.g., landfill). These areas may not be suitable 

for development consistent with public health and safety concerns without 

conducting specific studies during the design and permitting process. 

Potential geologic hazards that may affect the study area are discussed 

below. Some of these hazards are identified as regulated critical areas of 

Pierce County (PALS, 2011), which also includes the City of Lakewood, 

and the City of Tacoma (2010), and are discussed in a separate section. 

Geologic hazards and critical areas may be regulated differently within 

different jurisdictions within the study area. 

Seismicity 

The study area is located in a moderately active tectonic province that has 

been subjected to numerous earthquakes of low to moderate strength and 

occasionally to strong shocks during the brief 170-year record in the 

Pacific Northwest. Some of the largest historical earthquakes in the Puget 

Lowland include the magnitude 7.1 Olympia earthquake of April 13, 

1949; the magnitude 6.5 Seattle-Tacoma earthquake of April 29, 1965; 

and the recent magnitude 6.8 Nisqually earthquake that occurred on 

February 28, 2001. Geologic evidence indicates that a magnitude 9 

earthquake on the Cascadia Subduction Zone occurred approximately 300 

years before present. 

Faulting 

The nearest potentially active fault to the study area is the Tacoma Fault, 

which lies approximately 5 miles north of the northern end of the Project 

(Exhibit 3). This northwest-trending fault zone consists of several fault 

splays in an area as wide as 7 miles (Brocher et al, 2001). The locations of 

the fault splays are largely determined from overwater seismic reflection 

profiles within Puget Sound; the location of the fault splays on land have 

been extrapolated and are not precisely known. Recent studies indicate 

late Holocene movement on this fault (Sherrod et al, 2004). 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 21 

Exhibit 3. Fault Map 
September 2012 Point Defiance Bypass Project 

Page 22 Soils and Geology Discipline Report 

Liquefaction and Lateral Spreading 

Soil liquefaction is a phenomenon in which pore water pressure in loose, 

saturated, granular soil increases during ground shaking to a level near the 

initial effective stress, thus resulting in a reduction of shear strength of the 

soil (a quicksand-like condition). As a result of this reduction in shear 

strength during liquefaction, lateral spreading (ground movement on very 

gentle slopes) and landsliding may occur. Because of the reduced soil 

strengths, vertical and lateral foundation restraint may also be significantly 

reduced. 

Lateral spreading is a phenomenon where lateral ground displacements 

occur as a result of soil liquefaction. Lateral spreading is typically 

observed on very gently sloping ground or on virtually level ground 

adjacent to slopes. Lateral spreading tends to break the upper soil layers 

into blocks that progressively move downslope during an earthquake. 

Large fissures at the head of the lateral spread are common, as is 

compressed or buckled soil at the toe of the soil mass. Lateral spreading 

displacements can range from a few centimeters to meters, depending on 

the magnitude and duration of the seismic event (Kramer, 1996). From 

accounts of recent large earthquakes, including the relatively recent Kobe 

earthquake, lateral spreading at waterfront facilities typically appears to be 

more prevalent in upland areas within about 300 feet of the shoreline; 

however, case histories have documented lateral spreading occurring up to 

about 1,200 feet from the free-face of the soil mass. 

Soils susceptible to liquefaction and lateral spreading include 

non-engineered fills and loose Holocene alluvium below the groundwater 

table, such as present in the Puyallup River Valley (east of Rail MP 1.8) 

and the Nisqually River Valley (located northwest of Rail MP 21.0). 

Alluvium deposited along small streams such as Clover Creek (Rail 

MP 10.8) and Murray Creek (Rail MP 13.9) may also be susceptible to 

liquefaction. 

Several localized areas of potentially liquefiable soil were identified in the 

project corridor (Shannon & Wilson, 2006; Shannon & Wilson, 2009b). 

These areas include just west and east of Interstate 705 (I-705) (Rail MP 

2.1 to MP 2.2) and between about Tacoma Avenue S (Rail MP 2.7) and 

South “M” Street (Rail MP 3.2). 

Slope Stability 

Areas of potential slope instability within the study area comprise 

localized steep slopes (slopes greater than 40 percent) along the track 

section between Pacific Avenue (Rail MP 2.3) and about South “M” Street 

(Rail MP 3.2) and immediately north of the I-5 overcrossing (Rail 

MP 20.0) and a broad area of steep slopes south of the I-5 overcrossing. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 23 

Slopes that have been identified as having a relatively high risk of 

instability by Pierce County and the City of Tacoma are shown in 

Attachment A, Figures A-11 through A-20. Most of these slopes are 

relatively stable under static conditions, but some areas may be susceptible 

to failure. Slopes identified as having a relatively high risk of slope 

instability under static conditions are more likely to fail during a large 

earthquake. 

Two areas of instability were reported in the area (Shannon & Wilson, 

2009b) within the study area. Both of these areas are south of the I-5 

overcrossing at Rail MP 20.0. One area of past landsliding is just north of 

the junction between the Lakeview Subdivision and the BNSF main line at 

about Rail MP 20.9. At this location, slopes as steep as 65 degrees are 

located close to the track along the uphill (east) side. The soils at this 

location consist of fine-grained silt and clay. Blocks of soil at the top of 

the slope have slumped downward, with some soil falling onto flat ground 

adjacent to the track. Shannon & Wilson (2009b) indicates that shallow 

failures have also occurred on the slope below the rail line, south of Rail 

MP 21.0. 

The other area of observed instability is a side hill embankment where the 

rail line is not constructed on a full bench cut (approximately Rail 

MP 20.3). At this location, the rails of the track were reported (Shannon & 

Wilson, 2009b) to be displaced slightly toward the downhill (west) side of 

the embankment. The embankment soils adjacent to the track appear to be 

slightly lower than adjacent areas of the embankment to the north and 

south. This section of the line likely would require ongoing, periodic 

maintenance to keep the rails aligned. The movement of these 

embankment soils may be the result of failure of the embankment itself or 

of a bearing capacity failure of underlying soft, weak sediments. Poor 

drainage conditions were reportedly observed along this portion of the 

track (Shannon & Wilson, 2009b). 

Critical Areas 

Many areas along the rail line are designated as environmentally critical 

by Pierce County (PALS, 2011) and the City of Tacoma (2010). 

Ordinances pertaining to these environmentally critical areas regulate 

development within or adjacent to such areas to protect the environment 

and proposed development. The soils-related critical areas comprise 

seismic, volcanic, landslide, erosion, and aquifer recharge hazard areas. 

Pierce County, including City of Lakewood and City of Tacoma hazard 

areas in the vicinity of the Project are shown in Attachment A, Figures A11 through A-20. 
September 2012 Point Defiance Bypass Project 

Page 24 Soils and Geology Discipline Report 

Seismic Hazards Areas 

Seismic hazard areas are those areas that are subject to severe risk of 

damage as a result of seismic-induced settlement, shaking, lateral 

spreading, surface faulting, slope failure, or soil liquefaction. These 

conditions occur in areas underlain by non-cohesive soils of low density, 

usually in association with a shallow groundwater table. 

The floodplains of the Nisqually River and Puyallup River are designated 

potential seismic hazard areas (Attachment A, Figures A-11 and A-20) 

because of the susceptibility of the soil to undergo liquefaction during an 

earthquake. The track section between TR Junction (Rail MP 1.0) and 

about East “G” Street (Rail MP 1.8) crosses through a designated seismic 

hazard area. The track located adjacent to the Nisqually River Valley (Rail 

MP 20.7 to MP 21.0) is located outside of the designated seismic hazard 

area. 

Volcanic Hazard Areas 

The City of Tacoma and Pierce County define volcanic hazard areas as 

those areas subject to pyroclastic flows, lava flows, and inundation by 

lahars, debris flows, or related flooding resulting from geologic and 

volcanic events on Mount Rainier. The Puyallup River Valley is mapped 

as a volcanic hazard area (Attachment A, Figure A-5). The track is located 

within this mapped volcanic hazard area from TR Junction (Rail MP 1.0) 

to about East “G” Street (Rail MP 1.8). The Nisqually River Valley is also 

mapped as a volcanic hazard area (Attachment A, Figure A-20). In this 

portion of the alignment, the track is located outside of the volcanic hazard 

area. Pierce County hazard maps show volcanic hazard areas along the 

Puyallup and Nisqually rivers as high as elevation 80 feet. 

Landslide Hazard Areas 

The City of Tacoma and Pierce County define landslide hazard areas as 

those areas potentially subject to mass movement due to a combination of 

geologic, seismic, topographic, hydrologic, or man-made factors. 

Landslide hazard areas in the study area are shown in Attachment A, 

Figures A-11 through A-20. Numerous areas designated by Pierce County 

as landslide hazard areas are present within the City of Lakewood. These 

steep slope areas are generally associated with cut or fill slopes at freeway 

interchange ramps, bridges across I-5, or grade-separated crossings of the 

existing rail line. Most other designated landslide hazard areas are 

localized steep slopes that are not much more than 20 feet high. 

The most extensive landslide hazard areas designated by the City of 

Tacoma in the study area are along the track section between about Pacific 

Avenue (Rail MP 2.3) and South “M” Street (Rail MP 3.2). 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 25 

The steep hillside traversed by the BNSF main line south of the I-5 

overcrossing (Rail MP 20.0) has not been mapped as a steep slope hazard 

area because of its location within JBLM. Other steep slopes may be 

present within JBLM. These hillside slopes are potentially prone to 

instability and are subject to regulation under Pierce County’s critical 

areas ordinance. 

Erosion Hazard Areas 

Erosion hazard areas are those areas where the combination of slope and 

soil type makes the area susceptible to erosion by water flow, either by 

wave action, channel migration, or surface runoff. Mapped erosion hazard 

areas are present within the study area but not immediately adjacent to the 

proposed improvements (Attachment A). The mapped erosion hazard 

areas in the study area are primarily associated with potential erosion from 

channel migration of rivers or streams. Soil susceptible to erosion is 

present along the railroad corridor when cleared of vegetation or exposed 

on cut or fill slopes. 

Aquifer Recharge Areas 

The Steilacoom gravel together with the deeper Vashon advance outwash 

composes what is known as the upper aquifer. This aquifer is a highly 

used source of groundwater, and is tapped by public and private wells as a 

source of drinking water. Because of rapid infiltration and the shallow 

groundwater system, the aquifer formed by the Steilacoom gravel is highly 

susceptible to contamination. To protect this critical resource, these highly 

permeable surficial deposits along with wellhead protection areas are 

designated as aquifer recharge areas by the City of Tacoma and Pierce 

County. The study area from north of the I-5 DuPont Interchange (Rail 

MP 18.5) to Yakima Street (Rail MP 2.8) is mapped as an aquifer recharge 

area by Pierce County and the City of Tacoma. Regulations associated 

with these aquifer recharge areas provide standards to protect critical 

groundwater resources. 

The portion of this aquifer recharge area that lies within the City of 

Tacoma is also regulated by the South Tacoma Groundwater Protection 

District. The South Tacoma Groundwater Protection District is an overlay 

land use control district designed to prevent the degradation of 

groundwater in this aquifer system by controlling the use and handling of 

hazardous materials. 

Timber and Mineral Resources 

There are no timber or mineral resources present within the study area. 
September 2012 Point Defiance Bypass Project 

Page 26 Soils and Geology Discipline Report 

Chapter 4 – Potential Project Effects 

This chapter discusses possible direct effects that could result from the No 

Build Alternative, and the direct and indirect effects that could result from 

the Build Alternative, to the geology- and soils -related aspects of the 

environment. 

The Build Alternative effects would be related to the operation and 

construction of new or rehabilitated structures in the Project alternative on 

the existing features in the study area. Potential effects to geology and 

soils have been differentiated as construction effects, permanent physical 

effects, and operational effects, using the geology and soils identified in 

the existing conditions section. 

Construction effects, usually temporary, are those that are resolved or 

mitigated by the end of construction activity. Permanent physical effects 

are those permanent topographic changes to the landscape caused by 

construction of a project. Operational effects are those caused by changes 

in railroad operations—not only the logistics of train travel, but also the 

daily activities on, and maintenance of, railroad facilities. 

The Project alternatives consist of a No Build Alternative and a Build 

Alternative. The No Build Alternative assumes that Amtrak trains would 

remain on the Puget Sound route and would not be shifted to the project 

corridor, the Point Defiance Bypass. The tracks on the Tacoma 

Rail/BNSF- and Sound Transit-owned corridor would remain in their 

current condition and have the same or similar train usage as they 

currently do. 

Sound Transit Sounder service would be in place between Tacoma and 

Lakewood, an existing condition for this analysis. 

What are the potential effects of the No Build Alternative? 

The No Build Alternative would not require any construction, such as that 

being considered under the Build Alternative. However, existing 

conditions under the No Build Alternative would persist and have the 

following effects. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 27 

Construction Effects 

With the No Build Alternative, there would be no construction effects. 

Physical/Operational Effects 

There is a history of landsliding and unstable slopes between about North 

36th Street (approximately Rail MP 33.1 on the Point Defiance Bypass 

Route line) in Tacoma to Nisqually Junction (approximately Rail MP 24.7 

on the Point Defiance Bypass route). Unless slope inclinations are reduced 

or other measures employed, soil and organic debris from failures of steep 

slopes along the tracks are expected to continue, which would affect 

regular train schedules and speeds and occasionally result in the potential 

to block train traffic. The existing embankment at Rail MP 20.3 on the 

BNSF main line appears to be moving or has moved in the past. The 

embankment could continue to move if it is not stabilized. If not 

stabilized, slope failure could occur and as a result, train traffic could be 

blocked, and sediment could be delivered to adjacent drainages and 

streams. 

If a seismic event occurs, the stability of existing structures, slopes, and 

fill embankments along the No Build Alternative rail alignment could be 

affected. Liquefiable soil is present along the existing rail alignment from 

TR Junction to about Old Town Tacoma and in scattered areas along the 

BNSF alignment along Puget Sound. Liquefaction can result in 

widespread damage to the tracks. Damage would be expected to consist of 

settlement and lateral deformation of the tracks in areas where liquefiable 

soil is present. Embankment failure may also occur due to a loss of 

underlying soil strength and the lateral displacement of soils toward the 

Puyallup River and Puget Sound. The magnitude of settlement, soil 

movement, and loss of strength is a function of the soil thickness, soil 

quality, groundwater level, location and magnitude of the seismic event, 

and the specific foundation system of the structure. 

Soil liquefaction, should it occur, would likely lead to consolidation of 

loose, saturated soil deposits, resulting in some surface settlement at the 

site. Since subsurface conditions vary, overall settlement would vary, 

leading to differential settlements along the track alignment. The track 

section between the Puyallup River to TR Junction (Rail MP 1.0) is within 

the zone of potential lateral spreading as a result of soil liquefaction. 

Damage as a result of soil liquefaction and lateral spreading would likely 

result in temporary discontinuation of train traffic. 
September 2012 Point Defiance Bypass Project 

Page 28 Soils and Geology Discipline Report 

The No Build Alternative would not result in any indirect or cumulative 

effects because the Point Defiance Bypass Project would not be 

constructed. 

What are the potential effects of the Build Alternative? 

Following are the geology- and soils-related effects of the Build 

Alternative. 

Construction Effects 

No construction is planned for the track section between TR Junction (Rail 

MP 1.0) and the new station at Freighthouse Square (Rail MP 2.0). The 

existing track would be used in its current condition. Therefore, no 

construction effects are expected for this track section. 

The track section between Freighthouse Square to about 225 feet east of 

South Chandler Street (Rail MP 3.4) is being prepared for Sounder service 

by Sound Transit and would be finished before commencement of the 

Project. This new commuter service is considered an existing condition, 

and no construction effects would be attributed to the Project for this track 

section. 

The track section between 225 feet east of South Chandler Street (Rail 

MP 3.4) to South 66th Street (Rail MP 6.9) has been constructed and no 

alterations to the track section are planned, although upgrades to the 

warning systems are planned at several crossings. No construction effects 

are anticipated from upgrading the crossing warning systems. 

Sub-grade preparation and placement of the track sub-ballast has been 

completed for the track section between South 66th Street (Rail MP 6.9) to 

about 700 feet beyond the Lakewood Station (Rail MP 10.1). Anticipated 

construction activities for this track section include placement of the track 

ballast material and the rail. 

The track section between about 700 feet beyond the Lakewood Station 

(Rail MP 10.1) to the southern terminus of the Project would be 

reconstructed. The anticipated construction activities for the Project for the 

track section would include: 

 Clearing and grubbing the existing ground of vegetation when new 

fill would be placed for the improved track sections 

 Cutting into existing slopes to allow for track structure widening 

 Excavating ditches to allow for drainage of surface water 

 Placing fill for new embankments, and widening existing 

embankments 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 29 

 Placing track sub-ballast and ballast material 

 Hauling away and disposing of excavated material. 

Additional construction activities along the rail line include possibly 

extending the bridge abutment wing walls with retaining structures for the 

two bridges crossing I-5 near Rail MP 20.0. For the track section in the 

vicinity of the Mounts Road overpass (Rail MP 19.8), additional 

construction activities may include regrading slopes to flatten inclines 

where needed and building new retaining structures to accommodate track 

widening. South of I-5 (Rail MP 20.0), additional construction activities 

may include protecting the track from upslope debris and removal of 

existing loose fill. 

Construction activities for the new station in the vicinity of Freighthouse 

Square would include: 

 Clearing and grubbing the existing ground of vegetation 

 Removing existing improvements such as underground utilities, 

pavement, and buildings 

 Removing unsuitable soils for the site 

 Placing and compacting fill to establish final site grades 

 Paving. 

The construction activities for the Build Alternative would result in shortterm geology- and soils-related effects to the study area. Construction of 

the Build Alternative would not affect unique or protected soil or geologic 

resources because none are present in the study area. The construction 

effects are discussed in the following paragraphs. 

Erosion and Sediment Control 

Reconstruction of the existing track and construction of new track requires 

land clearing, removal of soil and ballast, and other site preparation work. 

Because the study area would be located within an existing railroad 

corridor (except for portions of the study area required to accommodate 

the Tacoma Amtrak Station relocation to Freighthouse Square), 

construction in these areas would temporarily disturb soils. Relocating the 

Tacoma Amtrak Station to Freighthouse Square may also require land 

clearing, removal of soil, and other site preparation work. 

In areas of proposed new construction, soil beneath proposed fills and 

structures would be cleared and grubbed of all vegetation and debris, and 

stripped of all organic topsoil. In areas where the existing track is to be 

reconstructed, the sub-grade would be graded to meet the design roadbed 

elevation, width, and slopes. Minor grading work would be required in 

areas where the track would be rehabilitated. 
September 2012 Point Defiance Bypass Project 

Page 30 Soils and Geology Discipline Report 

The high permeability of the coarse granular soils that dominate along the 

study area, particularly north of the I-5 overcrossing (Rail MP 20.0), 

indicates that the likelihood of erosion is small. However, soil exposed in 

sloped excavations or fills may be susceptible to erosion locally until 

vegetation is established. The soil at the new Freighthouse Square Station 

is susceptible to erosion. Any areas that are disturbed during construction 

would be subject to increased erosion if proper erosion control measures 

are not incorporated in the design. Surface water flow across exposed soil 

would remove sediment and deposit it in downslope areas. If the exposed 

soil is allowed to dry out, the soil can also be susceptible to wind erosion. 

The amount of erosion and sedimentation would depend on the amount of 

soil exposed and/or disturbed, weather conditions, groundwater 

conditions, and the erosion control measures implemented. The eroded 

soils could be carried into stormwater drains, existing culverts, adjacent 

streets, or adjacent properties. During construction, the tires of 

construction vehicles could also carry soil onto roadways when leaving 

construction areas, which could then be carried into ditches or stormwater 

drains. However, through the use of Best Management Practices (BMPs) 

and minimization measures these effects would be minimized or avoided. 

Cuts into Existing Slopes 

Construction may require temporary and permanent cuts into existing 

slopes to allow for widening of embankments and construction of drainage 

ditches. During construction, soils exposed in slope excavations may be 

susceptible to erosion until vegetation is established. Cuts into slopes for 

track and culvert construction could result in shallow landslides and 

sloughing. The higher the cut slope, the more prone the slope is to erosion 

and slope failure, and the greater the potential effect. Failure of higher 

slopes could result in greater volumes of failed material, which could 

block drainages or be eroded and conveyed to streams. 

Construction of new abutment wing walls for the I-5 crossing (Rail 

MP 20.0) may require high cuts into existing slopes. These temporary cuts 

are likely to be steep and prone to failure until permanent wing walls have 

been constructed. Failure of these slopes could result in sediment being 

conveyed in the ditches along I-5 to the Nisqually River. However, 

through the use of BMPs and minimization measures these effects would 

be minimized or avoided. 

Fill Embankments 

South of South 66th Street (Rail MP 6.9), the project alignment is 

underlain by outwash sand and gravel or very dense or hard soils. 

Localized zones of soft or weak foundation soils may be present in 

portions of this section of the alignment. Soil at the new Freighthouse 

Square station is also anticipated to consist of very dense soil. Settlement 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 31 

caused by construction of fill embankments in these areas is anticipated to 

be minor and would occur as the fill is being placed. 

Fill slopes could fail, particularly if constructed too steep or if the 

underlying foundation soil is loose or soft. The likelihood of failure would 

increase as the height of the fill increases. Fill slopes constructed on 

existing slopes are prone to failure if the previous fill surface is not 

properly benched prior to new fill placement. 

The sand and gravel deposits that dominate along the project alignment 

south of South 66th Street (Rail MP 6.9) are likely to be suitable for use as 

fill during construction unless they locally contain a relatively high 

percentage of silt and clay or organic material. 

The use of BMPs and minimization measures would result in minimizing 

and avoiding effects to fill embankments. 

Drainage in Construction Areas 

During construction, poor surface water control practices could result in 

drainage of surface water onto unstable slopes. This could result in 

landslides or erosion, or affect adjacent properties. Between the I-5 

overpass (Rail MP 20.0) and South 66th Street (Rail MP 6.9), surface 

water should infiltrate into the pervious soils with little runoff. Therefore, 

it is unlikely that poor drainage practices would result in landsliding or 

significant erosion onto adjacent properties. The portion of the project 

alignment most prone to instability from poor drainage practices is located 

south of the I-5 overpass where the slopes are steeper and underlain in 

places by relatively loose, colluvial soils. 

Pavements 

Soil from cuts into slopes, and soil and ballast removed from the existing 

track would need to be hauled off site. New soil and ballast would need to 

be imported to rehabilitate and reconstruct the track. Dump trucks would 

use the existing access roads as haul roads. In places, this could include 

city or county streets, but would be limited to streets that are rated for 

truck traffic. 

Economic Resources 

Earthwork that would generate appreciable economic resources (soil that 

can be used as fill material) is expected to be primarily limited to the 

portion of the alignment where the existing main line would be 

reconstructed [i.e., between Bridgeport Way Southwest (Rail MP 10.4) 

and Clover Creek Drive Southwest (Rail MP 10.9) to just southeast of the 

I-5/Mounts Road Southwest interchange (Rail MP 19.8)]. Soil generated 
September 2012 Point Defiance Bypass Project 

Page 32 Soils and Geology Discipline Report 

during soil cutting is anticipated to consist primarily of topsoil and sand 

and gravel. The topsoil would not be suitable for use as structural fill on 

the Project and should be disposed of at an approved off-site location. 

Sand and gravel generated during cutting would likely meet WSDOT’s 

criteria for Common Borrow, and is likely suitable for use as fill during 

construction unless it locally contains a relatively high percentage of silt 

and clay or organic material. Soil generated during cutting would not be 

suitable for use on the Project for other purposes without significant 

processing. 

Physical Effects 

Cuts and fills would be required to construct the Project. These cuts and 

fills would temporarily disturb soils and other geologic features in the 

study area. The heights of anticipated cuts into slopes and fills would vary 

along the project corridor. In areas where there is an insufficient space to 

accommodate large cuts or fills, retaining walls would be constructed. 

Operational Effects 

Long-term geology- and soils-related effects could occur during normal 

operations of the proposed tracks, depending on design. The Project would 

be designed based on the available subsurface information, design 

procedures and criteria approved by WSDOT, and existing site conditions. 

If subsurface conditions at the site are different from those discovered 

during field explorations, or site conditions change during the life of the 

Project, future effects to the site could occur. There would be no long-term 

operational effects to unique or protected soil or geologic resources 

because none are present in the study area. Long-term operational effects 

are discussed below. 

Seismic Considerations 

If a seismic event occurs during the life of the Project, the stability of 

structures, permanent cut slopes, and fill embankments could be affected. 

West of East “G” Street in Tacoma (Rail MP 1.8), the project alignment is 

generally underlain by sandy gravel and gravelly sand, which are not 

generally susceptible to liquefaction. Localized zones of potentially 

liquefiable soil are potentially present in the vicinity of I-705 (Rail MP 2.1 

to MP 2.2) and between about Tacoma Avenue S (Rail MP 2.7) and South 

“M” Street (Rail MP 3.2). The portion of the alignment located east of 

East “G” Street (Rail MP 1.8) is mapped as being within a high 

liquefaction hazard area (see Attachment A). 

Liquefaction can result in widespread damage to the tracks if not properly 

mitigated. Damage would be expected to consist of settlement and lateral 

deformation of the tracks in areas where liquefiable soil is present. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 33 

Embankment failure may also occur due to a loss of underlying soil 

strength and the lateral displacement of soils toward the Puyallup River. 

The magnitude of settlement, soil movement, and loss of strength is a 

function of the soil thickness, soil quality, groundwater level, location and 

magnitude of the seismic event, and the specific foundation system of the 

structure. 

Soil liquefaction, should it occur, would likely lead to consolidation of 

loose, saturated soil deposits, resulting in some surface settlement at the 

site. Since subsurface conditions vary, overall settlement would vary, 

leading to differential settlements along the track alignment. The track 

section between the Puyallup River and TR Junction (Rail MP 1.0) is 

within the zone of potential lateral spreading as a result of soil 

liquefaction. 

In areas adjacent to steep slopes or in mapped potential landslide areas 

(see Attachment A), cut slopes could experience shallow landsliding as a 

result of seismic shaking, which could deposit material onto the tracks. 

Steep Slopes 

The track sections between Pacific Avenue (Rail MP 2.3) to about East 

“M” Street (Rail MP 3.2) and the steep hillside traversed by the BNSF 

main line south of I-5 (Rail MP 20.0) are located in landslide hazard areas. 

In these sections, landsliding could result in blocked drainage ditches and 

possibly temporarily block the tracks with debris. 

Cuts into Existing Slopes 

Cuts into existing slopes, to allow for reconstruction and rehabilitation of 

the existing tracks and construction of new tracks, may experience erosion 

and surface sloughing over the lifetime of the Project. The degree of 

erosion would depend on near-surface soils, weather conditions, potential 

seismic events, establishment of vegetation, surface drainage, and other 

factors. Surface slumps or landslides occurring in the future may result in 

the deposit of material onto the tracks. Erosion could result in sediment 

reaching drainage ditches along the tracks. 

New Fill 

Reconstruction and rehabilitation of the existing tracks or construction of 

new tracks would require placement of structural fill and ballast along the 

project corridor. Long-term settlement of the new fill could occur. Based 

on available subsurface data, the portion of the Project located west of 

East “G” Street in Tacoma (Rail MP 1.8) is underlain by sand and gravel 

or other very dense or hard soils. Settlement in these soils would be small 

and occur immediately after the fill is placed. Since site grades are not 

being changed between TR Junction (Rail MP 1.0) and East “G” Street, 

settlement in this portion of the alignment is not anticipated. 
September 2012 Point Defiance Bypass Project 

Page 34 Soils and Geology Discipline Report 

Permanent Drainage 

Permanent drainage facilities for slopes, walls, or fills could result in 

increased water flow to existing culverts or drainage ditches. Additional 

sediment load from slope erosion may result in buildup in ditches, 

culverts, swales, and other drainage features. Water that overflows or is 

incorrectly directed could result in drainage onto adjacent slopes and 

properties. This could cause erosion or landsliding, and affect adjacent 

properties. However, through the use of BMPs and minimization measures 

these effects would be minimized or avoided. 

Ground Vibration Amplification 

West of East “G” Street (Rail MP 1.8), the near-surface soil is mapped as 

consisting of outwash sands and gravel or very dense or hard soils. These 

soil types do not typically transmit or amplify ground vibrations. 

A geologic reconnaissance of the portions of the corridor between 100th

Street Southwest (Rail MP 9.1) and Berkeley Street Southwest (Rail MP 

13.7) was completed on May 16, 2011 to determine if any soil possibly 

susceptible to amplifying ground vibration (i.e., soft clay or peat layers 

greater than about 20 feet thick) are present. During the geologic 

reconnaissance, no deposits of soft clay or peat were observed in the 

immediate vicinity of the rail line. Consequently, it is unlikely that 

amplification of ground vibration would occur along this portion of the 

alignment. 

The soil mapped between TR Junction (Rail MP 1.0) and East “G” Street 

(Rail MP 1.8) consists of fill and alluvial deposits. These soils can 

transmit and amplify ground vibrations. 

Indirect Effects 

The Project is located within an existing rail corridor and urbanized area. 

The only potential indirect effect tied to the Project is that it may 

indirectly influence redevelopment near the relocated Amtrak Station at 

Freighthouse Square (see Land Use Discipline Report3

). Such 

redevelopment would be consistent with local zoning and approved by 

state and local agencies and would take place in previously disturbed areas 

and would have no effect on geologic or soils resources. Thus, no indirect 

effects to geologic or soils resources are expected. 

 3 WSDOT 2012
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 35 

Cumulative Effects 

The Project would have no direct or indirect effect on geologic resources 

or high value soils. Thus, the Project would not contribute to a cumulative 

effect on these resources. 
September 2012 Point Defiance Bypass Project 

Page 36 Soils and Geology Discipline Report 

Chapter 5 – Recommended 

Minimization Measures 

As noted previously, no significant effects to geology and soils are 

anticipated. This chapter provides Best Management Practices (BMPs) 

that could be applied during construction and operation to minimize the 

Project’s effects. 

What minimization is required for the No Build Alternative? 

No minimization is proposed under the No Build Alternative. Some 

minimization measures will likely be implemented by the corridor owners 

in the future if landsliding or embankment failure were to occur along the 

existing rail alignment. 

What minimization is required for the Build Alternative? 

The following minimization measures for the Build Alternative 

predominantly focus on minimization of potential construction effects. 

Construction Effects 

The Project will be constructed in accordance with WSDOT guidelines. 

The following sections address the minimization for each of the potential 

construction effects. 

Erosion and Sediment Control 

Best Management Practices (BMPs), such as construction staging, barrier 

berms, filter fabric fences, temporary sediment detention basins, and use 

of slope coverings to contain sediment on site, will be effective in 

protecting water resources and reducing erosion from areas with cuts, fills, 

or excavations. Erosion control measures suitable to the site conditions 

will be included as part of the Project design. Temporary erosion and 

sediment control plans will be prepared for approval in accordance with 

BMPs included in WSDOT’s Highway Runoff Manual (WSDOT, 2010a). 

Erosion control measures will include vegetative and structural controls. 

Other controls that could be implemented include restriction of work 

activities to the dry season and limiting access to the site. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 37 

Areas disturbed during construction that will not be paved or permanently 

covered will be revegetated to minimize erosion as soon as possible. 

Revegetation methods will include covering cleared areas, graded areas, 

excavation slopes, and embankments. These areas will be covered with 

netting, mulching, or hydroseeding as appropriate to minimize erosion and 

encourage revegetation. The exposed soil will be moistened with a water 

truck in order to control dust and wind erosion in addition to the erosion 

control measures specified above. 

Structural controls are artificial means of preventing sediment from 

leaving the construction area. Parking and staging areas for vehicles and 

equipment could be covered with a gravel work pad where appropriate to 

prevent the disturbance and erosion of the underlying soil. Silt fences will 

be placed around disturbed areas to filter sediment from unconcentrated 

surface water runoff. Straw bales will be placed in paths of concentrated 

runoff to filter sediment. Temporary ditches, berms, and sedimentation 

ponds will be constructed to collect runoff so that entrained sediment 

could settle out of the water prior to being released into drainages, 

streams, or wetlands. Cleaning tires and tracks of heavy equipment before 

they leave the site will also assist in retaining sediment on site. In addition, 

truck loads will be covered to prevent sediment deposit onto roadways. 

Proposed minimization measures will comply with temporary stormwater 

design and treatment procedures based on WSDOT’s Highway Runoff 

Manual (WSDOT, 2010a). Such procedures follow the National Pollutant 

Discharge Elimination System (NPDES) guidelines administered by the 

Washington State Department of Ecology (Ecology website, 2011). 

WSDOT guidelines require approval of a Stormwater Site Plan and a

Temporary Erosion and Sediment Control Plan prior to construction, 

which will be prepared as part of Project construction documents. The 

erosion and sediment control measures will be in place before any 

demolition, clearing, grading, or construction occurs. 

Cuts into Existing Slopes 

Temporary excavation slopes would typically be no steeper than 

1.5 horizontal feet to one vertical foot (1.5H:1V). According to 

construction drawings (HDR 2010a,b), permanent cut slopes are expected 

to be no steeper than 2H:1V. Retaining walls such as mechanically 

stabilized earth (MSE) walls, cast-in-place (CIP) concrete retaining walls, 

soldier pile, or soil nail walls will be used where cut slopes cannot be 

constructed at 2H:1V or flatter. Because of the nature of the soils that 

underlie the study area and the geometry of proposed cuts and fills, the 

risk of slope instability is relatively small. The risk of slope instability is 

slightly higher south of the I-5 overpass (Rail MP 20.0) because of higher 

proposed cut slopes and the potential presence of groundwater perched on 

top of fine-grained soils that “daylight” on the existing slope faces. 
September 2012 Point Defiance Bypass Project 

Page 38 Soils and Geology Discipline Report 

The potential for slope instability and erosion on cut slopes during 

construction will be reduced by using BMPs. Cut slopes and cut walls will 

be evaluated and designed by experienced structural and geotechnical 

engineers. Potential landsliding and erosion could also be reduced by 

intercepting surface water runoff and conveying it through a tightline to 

the bottom of the slope. This interception could consist of covering the 

slope with plastic sheeting, installing drains, and/or restricting 

construction to dry weather. As soon as possible during or after 

construction, vegetative controls will be installed. This will include 

covering the slopes with netting, mulching, or hydroseeding, as 

appropriate, to minimize erosion and encourage revegetation on the 

slopes. 

Fill Embankments 

According to the design drawings (HDR, 2010a,b), fills will be 

constructed with side slopes of 2H:1V, which should be stable for the soils 

present along the Project. Retaining walls such as MSE or CIP concrete 

retaining walls will be used where fill slopes cannot be constructed at 

2H:1V or flatter. Fill slopes and fill walls will be evaluated and designed 

by experienced structural and geotechnical engineers. Because of the 

relatively dense nature of the near-surface soils mapped along the 

alignment, significant settlement of fill embankments is not anticipated 

and no minimization is required. 

As soon as possible during or after construction, vegetative controls will 

be installed on all fill embankments. This will include covering the slopes 

with netting, mulching, or hydroseeding, as appropriate, to minimize 

erosion and encourage revegetation of the slopes. 

Drainage in Construction Areas 

All fill and pavement areas will be sloped to drain away from construction 

areas and prevent ponding of water and softening of sub-grade soils. 

Drainage water from construction areas will be directed into suitable 

drainage features in accordance with BMPs. No water will be allowed to 

drain out over existing slopes, into excavations, or onto sub-grade areas. 

Pavements 

Pavement damaged by construction traffic could be replaced following 

completion of the proposed improvements. New pavement will be 

designed by a qualified civil or geotechnical engineer in accordance with 

American Association of State Highway and Transportation Officials 

(AASHTO) guidelines. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 39 

Physical Effects 

Cuts, fills, and retaining walls will be required to construct the Project. 

Cuts, fills, and retaining walls are generally kept to the minimum 

necessary to construct the Project using appropriate design based on the 

site conditions. No minimization of permanent physical effects is required 

or proposed. 

Operational Effects 

Minimization measures for the direct operational effects of the Project are 

based on the site information and standard design and construction 

procedures. As part of the final design, the geology- and soils-related 

features may be evaluated by an experienced geotechnical engineer who 

will provide appropriate design recommendations. These 

recommendations will be based on the subsurface conditions in the study 

area, as indicated by field explorations. The design recommendations will 

take into account the direct operational effects of the Project alternatives 

and provide for adequate minimization for these effects. 

The Project will be designed based on WSDOT design procedures and 

criteria, American Railway Engineering and Maintenance-of-Way 

Association (AREMA) design procedures, the International Building 

Code, and existing site conditions. To adequately define subsurface 

conditions for design of the features included in the Project, additional 

subsurface data may be collected. In general, a geotechnical investigation 

will be completed to support final Project design. Adequate subsurface 

information will allow improved evaluation of foundation capacities, 

estimated settlements, and liquefaction potential. 

Seismic Considerations 

The Project elements will be designed considering the seismicity of the 

site and the design guidelines presented in WSDOT’s Design Manual

(WSDOT, 2010b) and Bridge Design Manual (WSDOT, 2011), 

AASHTO’s Load and Resistance Factor Design Bridge Design 

Specifications (AASHTO, 2010), the AREMA Manual for Railway 

Engineering (AREMA, 2011), and the International Building Code (ICC, 

2009). 

In the areas west of East “G” Street (Rail MP 1.8), shallow landsliding 

may occur adjacent to steep slopes or in areas identified as landslide 

hazard areas (see Attachment A) during a major earthquake. Cut retaining 

walls such as soldier pile or soil nail walls could be used to stabilize the 

slopes. Alternatively, a catchment wall could be constructed at the base of 

the slope to catch any landslide debris. The soldier pile, soil nail, or 
September 2012 Point Defiance Bypass Project 

Page 40 Soils and Geology Discipline Report 

catchment wall requirements will be evaluated and designed by 

experienced structural and geotechnical engineers. 

Potential liquefaction of loose or soft alluvium and/or fill soil located east 

of East “G” Street (Rail MP 1.8), in the vicinity of I-705 (Rail MP 2.1 to 

Rail MP 2.2), and between about Tacoma Avenue S (Rail MP 2.7) and 

South “M” Street (Rail MP 3.2) is possible during an earthquake. Most 

railroad agencies consider track distress from seismic events 

(e.g., liquefaction) to be a maintenance issue and ground improvement 

below at-grade tracks is typically not performed. 

If liquefaction-induced distortion is intolerable, liquefaction could be 

mitigated by designing the proposed improvements to tolerate the vertical 

and horizontal movements caused by liquefaction and lateral spreading or 

implementing ground improvement measures. Ground improvement 

measures could include stone columns, vibro-compaction, 

vibro-replacement, deep soil mixing, compaction grouting, and others. 

Lateral spreading could be reduced by stabilizing the soil adjacent to the 

Puyallup River by using ground improvement or installing retaining 

structures at appropriate depths and locations. Selection of the 

minimization techniques depend upon a number of issues including the 

soil type, level of improvement required, area and depth to be improved, 

proximity of existing structures, presence of contaminated soil and 

groundwater, and cost. The specific method of ground improvement will 

be determined as part of the design and permit approval process by a 

qualified geotechnical engineer. 

Cuts into Existing Slopes 

Minimization for the proposed cuts includes performing proper design, 

defining the location and extent of unstable soils, and using proper 

construction procedures. To mitigate slope instability in cut areas, slope 

angles and retaining walls will be designed based on the characteristics of 

the soils in the cut. The cut wall will be evaluated and designed by 

experienced structural and geotechnical engineers. 

Some of the slopes that are currently prone to instability will be flattened 

to more stable inclinations. Vegetation will be installed on the slopes to 

mitigate surface erosion and sloughing. For surficial slides that may occur 

along the slopes, a catchment area or catchment wall can be constructed at 

the base of the slope. 

New Fill 

Based on the mapped geology, extensive deposits of loose/soft soil are not 

present in areas where appreciable fill will be placed. If loose/soft soil is 

encountered during construction or during site-specific design, settlement 

due to compression of loose/soft soils could be mitigated by removing and 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 41 

replacing the unsuitable soils or by placing the fill and allowing it to settle 

prior to construction. Existing utilities near the new fill will be relocated if 

loads and settlements will cause damage. 

Permanent Drainage 

Permanent drainage facilities for slopes, walls, or fills, will be designed 

for the anticipated water flows. All permanent drainage systems will be 

installed so that water does not overflow and is not directed onto slopes or 

other areas that may be sensitive to erosion or landsliding. The Project 

includes drainage features, such as ditches, that are not currently present 

or are inadequate along the existing rail. Such features will likely reduce 

the effects of uncontrolled or undesirable surface water runoff. 

Ground Vibration 

It is unlikely that significant ground vibration would occur as a result of 

increased passenger rail service; therefore, no minimization is required. 
September 2012 Point Defiance Bypass Project 

Page 42 Soils and Geology Discipline Report 

References 

AASHTO. 2010. AASHTO LRFD Bridge Design Specifications, 

American Association of State Highway and Transportation 

Officials, 5th edition. 

AMEC Earth & Environmental. 2008. Geotechnical Engineering Report, 

American Lake Gardens & Tillicum Sewer Extension, Lakewood, 

Washington, prepared for Parametrix, October 9. 

AREMA. 2011. Manual for Railway Engineering, American Railway 

Engineering and Maintenance-of-Way Association. 

Borden, R.K. and K.G. Troost. 2001. Late Pleistocene Stratigraphy in the 

South-Central Puget Lowland, Pierce County, Washington, 

Washington Division of Geology and Earth Resources Report of 

Investigations 33, December. 

Brocher, T.M., T. Parsons, N.I. Blakely, et al. 2001. Upper Crustal 

Structure in Puget Lowland, Washington: Results from the 1998 

Seismic Hazards Investigation in Puget Sound, Journal of 

Geophysical Research, v. 106, pp. 13,541-13564. 

CH2M Hill. 1996. SR 5/Exit 119 Interim Modifications, Draft 

Geotechnical Technical Memorandum, prepared for Washington 

State Department of Transportation, January 4. 

City of Tacoma. 2010. Tacoma Municipal Code, Title 13, Land Use 

Regulatory Code. 

DNR. 2005. A.C. Tarr, USGS, scanned and vectorized DGER Open File 

Report 87-3. T.J. Walsh, DGER, converted the original geologic 

unit symbology to DGER statewide 1:100,000 geologic unit 

symbology. T.T. Young and J.E. Schuster, DGER, moved Tarr’s 

GIS data into the DGER data structure and added attributes. T.J. 

Walsh compiled the geology of the north half of the quadrangle, 

and J.E. Schuster digitized and attributed the geologic data for the 

north half of the quadrangle. Washington Department of Natural 

Resources. 

Dragovich, J.D., R.L. Logan, H.W. Schasse, T.J. Walsh, W.S. Lingley, Jr., 

D.K. Norman, W.J. Gerstel, T.J. Lapen, J.E. Schuster, and K.D. 

Meyers. 2002. Geologic Map of Washington – Northwest 

Quadrant: Washington Division of Geology and Earth Resources 

Geologic Map GM-50, Scale 1:250,000. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 43 

Ecology website. 2011. Resources and Guidance for the Construction 

Stormwater General Permit,

http://www.ecy.wa.gov/programs/wq/stormwater/ 

construction/resourcesguidance.html.

EES, Carr/Associates, and Adolfson & Associates. 1993. South Tacoma 

Wellhead Project Program, Vol. 2 – Technical Appendices, 

Monitoring Well Logs 92.1, 92.3, and 92.5. 

Hart Crowser. 1996. Technical Memorandum, Cleanup Action Plan, South 

Dupont Interchange Easement Property, Fort Lewis Landfill No. 9, 

Pierce County, Washington, prepared for Washington State 

Department of Transportation, January 24. 

HDR. 2010a. Point Defiance Bypass Project. 100% Submittal 

Construction Drawings, Station 28+00 to 616+56, February 24. 

HDR. 2010b. Point Defiance Bypass Project, 100% Submittal 

Construction Drawings, Track Cross Sections, Station 26+00 to 

542+00, February 24. 

ICC. 2009. 2009 International Building Code, International Code Council. 

Jones, M.A. 1996. Thickness of Unconsolidated Deposits in the Puget 

Sound Lowland, Washington and British Columbia, US Geological 

Survey, Water Resources Investigation Report 94-4133. 

Jones, M.A., L.A. Orr, J.C. Ebbert, and S.S. Sumioka. 1999. GroundWater Hydrology of the Tacoma-Puyallup Area, Pierce County, 

Washington, U.S. Geological Survey Water-Resources 

Investigations Report 99-4013. 

Kramer, S.L. 1996. Geotechnical Earthquake Engineering, Prentice Hall, 

Inc, Upper Saddle River, New Jersey. 

Landau Associates. 2006. Geotechnical Report, Leach Creek Force Main, 

City of Tacoma, Tacoma, Washington, prepared for the City of 

Tacoma, February 7. 

Landau Associates. 2008a. Geotechnical Report, East 26th Street South 

Parking Garage, Tacoma, Washington, prepared for the City of 

Tacoma, October 21. 

Landau Associates. 2008b. Geotechnical Report, Cline Avenue Southwest 

Water Main Improvement Project, Lakewood, Washington, 

prepared for HCWL, August 7. 

Landau Associates. 2010. Environmental Services Report, South Cedar 

Street Sanitary Sewer, Main Replacement, Tacoma, Washington, 

prepared for the City of Tacoma, November 1. 

Landau Associates. 2011. Geotechnical Report, South Tacoma Way 

Sanitary Sewer Reroute, South 66th Street to South 72nd Street, 
September 2012 Point Defiance Bypass Project 

Page 44 Soils and Geology Discipline Report 

Tacoma, Washington, prepared for the City of Tacoma, February 

14. 

NRCS. 1979. Soil Survey of Pierce County Area, Washington, Spokane, 

Washington, Natural Resources Conservation Service, Washington 

State Office. 

PALS. 2011. Hazard Data Compiled by PALS and Electronically 

Downloaded from the Internet by Landau Associates, GIS 

Department, Pierce County Planning and Land Services, May. 

Pierce County. 2010. Pierce County Code, Title 18E, Development 

Regulations – Critical Areas. 

Shannon & Wilson. 2006. Final Geotechnical Report, Final Design, 

Sounder Commuter Rail, Tacoma to Lakewood Track and Signal 

Improvements, Pierce County, Washington, prepared for HDR 

Engineering, Inc., February 10. 

Shannon & Wilson. 2009a. Final Geotechnical Report, Final Design, Point 

Defiance Bypass Project, Pierce County, Washington, prepared for 

HDR Engineering, Inc., June 26. 

Shannon & Wilson. 2009b. Geotechnical Report, D to M Streets Track 

and Signal Project, Sounder Commuter Rail, Tacoma, Washington, 

prepared for Parsons Brinkerhoff, October 30. 

Sherrod, B.L., T.M. Brocher, C.S. Weaver, R.C. Bucknam et al. 2004. 

Holocene Fault Scarps near Tacoma, Washington, USA: Geology, 

v. 32, pp. 9-12. 

Sinclair, K.A. 2001. Assessment of Surface Water and Groundwater 

Interchange Within the Muck Creek Watershed, Pierce County, 

Washington, Environmental Assessment Program, Washington 

State Department of Ecology, Publication No. 01-03-037. 

Smith M. 1972. Stratigraphy and Chronology of the Tacoma Area, 

Washington, unpublished M.S. thesis, Western Washington 

University. 

Smith, M. 1976. Surficial Geology of Northeast Tacoma, Pierce County, 

Washington, Washington Division of Geology and Earth 

Resources Open-File Report 76-9, 1 sheet, Scale 1:24,000. 

Troost, K.G., in review, Geologic Map of the Tacoma South 7.5-Minute 

Quadrangle, Washington, U.S. Geological Survey Miscellaneous 

Field Investigation, MF_, Scale 1:24,000. 

Troost, K.G., D.B. Booth, and R.K. Borden, in review, Geologic Map of 

the Steilacoom 7.5-Minute Quadrangle, Washington: US 

Geological Survey Miscellaneous Field Investigation, MF_, Scale 

1:24,000. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report Page 45 

USGS. 1999. Ground-Water Hydrology of the Tacoma-Puyallup Area, 

Pierce County, Washington, U.S. Geological Survey Water 

Resources Investigation Report 99-4013. 

Walsh, T.J. 1987. Geologic Map of the South Half of the Tacoma 

Quadrangle, Washington, Washington Division of Geology and 

Earth Resources, Open File Report 87-3, Scale 1:100,000. 

Walsh, T.J., R.L. Logan, M. Polenz, and H.W. Schasse. 2003. Geologic 

Map of the Nisqually 7.5-Minute Quadrangle Thurston and Pierce 

Counties, Washington, Washington Division of Geology and Earth 

Resources Open File Report 2003-10, Scale 1:24,000. 

Walters, K.L. and G.E. Kimmell. 1968. Ground-Water Occurrences and 

Stratigraphy of Unconsolidated Deposits, Central Pierce County, 

Washington, Washington Department of Water Resources Water 

Supply Bulletin 22. 

WSDOT. 1964a. C.S. 2701, PSH#1 (SR-5), L-1048, Olympia to Fort 

Lewis, N.P. Ry. Fort Lewis Branch Foundation Investigation, 

Washington State Department of Transportation, October 19. 

WSDOT. 1964b. C.S. 2701, PSH#1 (SR-5), L-1048, Olympia to Fort 

Lewis, N.P. Ry., Point Defiance Line U’Xing and Retaining Wall 

Foundation Investigation, Washington State Department of 

Transportation, October 20. 

WSDOT. 1966. Plan Sheets, SR-5, Northern Pacific Railroad 

Undercrossing, Washington State Department of Transportation, 

August. 

WSDOT. 1968a. CS 2702, SR-5, L-3151, Old Nisqually Road to North 

Fort Lewis, Lewis Dr. O’Xing (widening) Sta 678 Foundation 

Investigation, Washington State Department of Transportation, 

June 18. 

WSDOT. 1968b. CS 2701, SR-5, L-3151, Old Nisqually Road to North 

Fort Lewis, Laundry Spur O’Xing (widening) Sta. 623+65 

Foundation Investigation, Washington State Department of 

Transportation, June 18. 

WSDOT. 1968c. CS 2701 and 2702, SR-5, 35164BA, Old Nisqually Road 

to North Fort Lewis, North Fort Lewis Interchange and Weight 

Station No. 2, Washington State Department of Transportation, 

October 23. 

WSDOT. 1979. C.S. 3402/2701, SR-5, L-6182, Nisqually River Bridge 

Modifications, Sta. LR 1596, Washington State Department of 

Transportation, January 2. 

WSDOT. 1996. Geotechnical Report SR-5, South DuPont Interchange, 

Washington State Department of Transportation. 
September 2012 Point Defiance Bypass Project 

Page 46 Soils and Geology Discipline Report 

WSDOT. 2005. SR-5, MP 131.17 to 133.64, C-6958, South 48th Street To 

Pacific Avenue Underground Stormwater Detention Tank – 

Preliminary Geotechnical Recommendations, October 4. 

WSDOT. 2007. Point Defiance Bypass Project, Soils and Geology 

Discipline Report, August. 

WSDOT. 2009. Pacific Northwest Rail Corridor Tier 1 Environmental 

Assessment. Available at: 

http://wadot.wa.gov/Freight/publications/PNWRCReports.htm 

WSDOT. 2010a. Highway Runoff Manual, Washington State Department 

of Transportation Report M 31-16, 1 v, revised May 16. 

WSDOT. 2010b. Design Manual, Washington State Department of 

Transportation Report M 22-01.07, v. revised July. 

WSDOT. 2011. Bridge Design Manual, Washington State Department of 

Transportation Report M 23-50, 1 v, revised May. 

WSDOT. 2012. Point Defiance Bypass Project, Land Use Discipline 

Report, September. 
Point Defiance Bypass Project September 2012 

Soils and Geology Discipline Report 

Attachment A 
Tacoma Eastern Gu

Roosevelt

Ditc h

Puyallup

River

Northern Limit

TR Junction

Amtrak

Station

Freighthouse

Square

§ ̈¦5

§ ̈¦507

UV7

UV7

Qvt

Qva Qva

Qpogc

m

Qva Qva m

Qpogc

Qob

af

Qvt

Qva

Qpfc

Qvi

Qvt

Qvt

Qal

Qvr

Qal

RM 3.0

RM 2.0

RM 1.0

Pt. Defiance Rail Bypass

Attachment 1: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 1 Nov 7, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
§ ̈¦5

UV16

Qvt

Qvr

Qvt

Qvr

af

Qvt

Qva

Qvt Qvt

Qvr

Qvt

Qva

Qvt

m

m

Qvt

Qvr

Qva Qpogc

Qvi

RM 5.0

RM 4.0

RM 3.0

Pt. Defiance Rail Bypass

Attachment 2: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 2 Nov 7, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
F el tt Creek

Qvr

Qvt

Qva

Qvt

Qvr

Qvt

Qvr

RM 7.0

RM 6.0

RM 5.0

Pt. Defiance Rail Bypass

Attachment 3: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 3 Nov 7, 2011

N

# 0 0.25 0.5 Miles

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
Flett Creek

F el tt Cree

Flett

Creek

Holding

Basin

Qvt

Qvt

Qvr

Qvi

RM 9.0

RM 8.0

RM 7.0

Pt. Defiance Rail Bypass

Attachment 4: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 4 Nov 7, 2011

N

# 0 0.25 0.5 Miles

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
Clover 

Clover Creek

Seeley

Lake

Sound Transit

Lakewood Station

§ ̈¦5

§ ̈¦5

Joint Base

Lewis-McChord

RM 11.0

RM 10.0

RM 9.0

Qvt

Qvi

Qvr

Qvi

Qvi

Pt. Defiance Rail Bypass

Attachment 5: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 5 Nov 7, 2011

N

#

0 0.25 0.5 Miles

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
American

Lake

Gravelly

Lake

Emerson

Lake

Carter

Lake

Gravelly

Lake

§ ̈¦5

Qvt

Qvt

Qvt

Qvr

Qvi

Qvi

RM 13.0

RM 12.0

RM 11.0

Pt. Defiance Rail Bypass

Attachment 6: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 6 Nov 7, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
Murray Creek

American

Lake

American Lake

§ ̈¦5

Qvi

Qvi

Qvi

Qvr

Qvt

RM 15.0

RM 14.0

RM 13.0

Pt. Defiance Rail Bypass

Attachment 7: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 7 Nov 7, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
Sequali tchew Creek

Sequalitchew

Creek

Sequalitchew

Lake

American

Lake

§ ̈¦5

Qvi

Qvr

Qvr

Qvi

Qvi

RM 17.0

RM 16.0

RM 15.0

Pt. Defiance Rail Bypass

Attachment 8: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 8 Nov 7, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
Hodge

Lake

Grant

Lake

Strickland

Lake

Pond

Lake

Sellers

Lake

§ ̈¦5

Qvt

Qvr

Qvr

Qvt Qvt

Qvr

RM 19.0

RM 18.0

RM 17.0

Pt. Defiance Rail Bypass

Attachment 9: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 9 Nov 7, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
Red

Sa

ml on Creek

Southern Limit

Nisqually Junction

§ ̈¦5

§ ̈¦5

Qmw

Qvt

Qvt

Qal

Qvr

Qvt

Qva Qva

Qvr

Qvr Qmw

Qvr

af

af

af

Qmw

af

Qvie

Qvie

Qvt

Qva

Qvt

Qvt

Qgt

Qga

Qmw

Qva

af

Qmw

Qmw

af

Qmw

Qpf

Qal

af

af

af

Qvr

Red Salm o n Creek

Nisqually River

RM 21.0

RM 20.0

Pt. Defiance Rail Bypass

Attachment 10: Geology

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 10 Nov 7, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map

Note: See Text for

Explanation of Geologic Units
§ ̈¦5

§ ̈¦507

UV7

UV7

RM 3.0

RM 2.0

RM 1.0

Pt. Defiance Rail Bypass

Attachment 11: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 1 Nov 3, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map
§ ̈¦5

UV16

RM 5.0

RM 4.0

RM 3.0

Pt. Defiance Rail Bypass

Attachment 12: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 2 Nov 3, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map
RM 7.0

RM 6.0

RM 5.0

Pt. Defiance Rail Bypass

Attachment 13: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 3 Nov 3, 2011

N 0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map
RM 9.0

RM 8.0

RM 7.0

Pt. Defiance Rail Bypass

Attachment 14: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 4 Nov 3, 2011

N

# 0 0.25 0.5 Miles

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map
§ ̈¦5

§ ̈¦5

Joint Base

Lewis-McChord

RM 11.0

RM 10.0

RM 9.0

Pt. Defiance Rail Bypass

Attachment 15: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 5 Nov 3, 2011

N

#

0 0.25 0.5 Miles

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map
§ ̈¦5

RM 13.0

RM 12.0

RM 11.0

Pt. Defiance Rail Bypass

Attachment 16: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 6 Nov 3, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map
§ ̈¦5

RM 15.0

RM 14.0

RM 13.0

Pt. Defiance Rail Bypass

Attachment 17: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 7 Nov 3, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map
§ ̈¦5

RM 17.0

RM 16.0

RM 15.0

Pt. Defiance Rail Bypass

Attachment 18: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 8 Nov 3, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map
§ ̈¦5

RM 19.0

RM 18.0

RM 17.0

Pt. Defiance Rail Bypass

Attachment 19: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 9 Nov 3, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map
§ ̈¦5

§ ̈¦5

Text

Red Salm o n Creek

Nisqually River

Nisqually River

RM 21.0

RM 20.0

Pt. Defiance Rail Bypass

Attachment 20: Geologic Hazard Areas

Geologic Hazard Areas

Moderate to High

Liquefaction Hazard Potential

High Liquefaction

Hazard Potential

Potential Erosion Hazards

Potential Volcanic Hazards

Potential Landslide Hazards

Steep Slope Critical Areas

25% - 40% Slope

> 40% Slope

1o»1⁄4 Railroad Crossing Grade

")RM Rail Milepost

Pierce Co Railroads

Project Corridor

Airports

Panel 10 Nov 3, 2011

N

0 0.25 0.5 Miles #

Tacoma

Lakewood

Fife

DuPont

Gig Harbor

University Place

Fircrest

Steilacoom

Ruston

1 2

3

4

5

6

7

8

9

10

Data Sources: Pierce County; TANA Dynamap Transportation; US Census Bureau; US Environmental Protection Agency;

WA Dept. of Ecology; WA Dept. of Health; WA Dept. of Natural Resources; WA Dept. of Transportation

N

#

Location Map