Storage of Ground Water 

Behind Subsurface Dams in 

the Columbia River Basalt 

Washington, Oregon, and 

Idaho 

By R. C. NEWCOMB 

HYDROLOGY OF VOL CAN I C-ROCK TERRANES 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 383-A 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1961 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEW ART L. UDALL, Secretary 

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington 25, D.C. 
CONTENTS 

Page 

Abstract___________________________________________ A-1 Plan for test development of barrier reservoirs of ground 

Introduction_______________________________________ 1 water ______________________________________ _ 

Environment of the barrier reservoirs of ground water___ 1 Test-well location ______________________ ---------

Occurrence of ground water in the basalt__________ 2 Suggestions as to general specifications for test wells_ 

Tectonic deformation of the basalt________________ 3 Test operation of the wells ______________________ _ 

Tilting and warping_________________________ 3 Estimated cost of a proposed test installation and 

Fault-barrier conditions_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 test procedure _______________________________ _ 

Reservoirs behind structural barriers_ _ _ _ _ _ _ _ _ _ _ _ _ _ 5 Value of the benefits derived ____________________ _ 

Structural conditions creating barrier reservoirs_ 5 References cited ________________________ -- _.:.--- --- --

Known and tested structural reservoirs________ 6 

Undeveloped structural reservoirs______ _ _ _ _ _ _ _ 6 

Sites proposed for testing for impounded. ground 

water___________________________________ 8 

ILLUSTRATIONS 

Page 

A-8 

8 

10 

12 

13 

15 

15 

Page 

FIGURE 1. Map showing the main area underlain by the Columbia River basalt__________________________________ A-2 

2. View northwest down the vall8y of the South Fork of the Walla Walla River _________ ~______________________ 3 

3. View of a fault zone exposed by a road cut in the northwest bluff of the Grande Ronde River_________________ 4 

4. Close view of figure 3, showing shearing common to fault zones in the basalt__________________________ _ _ _ _ _ _ 4 

5. Block diagrams of idealized fault barriers ______ _:_______________________________________________________ 5 

6. Map of area adjacent to The Dalles, Oreg., showing fault barriers__________________________________________ · 7 

7. Geologic map of the upper part of the Walla Walla River basin__________________________________________ 9 

8. Geologic map of the Grande Ronde River valley above La Grande________________________________________ 10 

9. Block diagram of an idealized fault-barrier reservoir____________________________________________________ 11 

10. Schematic diagram of some possible arrangements of casings and wells to tap water stored in a barrier reservoir___ 12 

11. Graphs of the average monthly discharge in two rivers where structural reservoirs of ground water are believed 

present__________________________________________________________________________________________ 14 

12. Cross section of a hypothetical ground-water withdrawal system utilizing an aquifer of a barrier reservoir________ 15 

III 

HYDROLOGY OF VOLCANIC-ROCK TERRANES 

STORAGE OF GROUND WATER BEHIND SUBSURFACE 

DAMS IN THE COLUMBIA RIVER BASALT, 

WASHINGTON, OREGON, AND IDAHO 

By R. c. NEWCOMB 

ABSTRACT 

The Columbia River basalt, a thick sequence of accordantly 

layered lava flows, forms the bedrock beneath about 50,000 

square miles in 'Vashington, Oregon, and Idaho. 

The rubbly rock at the top and bottom of some of the flows 

is permeable and transmits water laterally between the flows. 

Where the strata are displaced vertically by faults, barriers 

to movement of the water are common. Where these barriers are 

transverse to the dip of the basalt layers, ground-water reservoirs are formed. Many such reservoirs are present in mountainous areas or on the flanks of mountain uplands, and their 

water has been little used to date. 

Properly designed and constructed test wells are suggested 

as a means of determining the feasibility of withdrawing water 

from these reservoirs during the growing season and allowing 

the reservoirs to refill during the winter and spring. Benefits 

from such a practice may be especially great in stream valleys 

where water is needed in the late summer. 

INTRODUCTION 

Data gathered in studies of ground water in the 

Columbia River basalt have made it increasingly clear 

that, in places, the basalt contains replenishable bodies 

of water in virtually "dead" storage. Structural barriers, which impede the movement of ground water, 

are the cause of one type of ground-water reservoir. 

Some of these reservoirs are in upland or mountainous 

areas, where the stored water would be available for 

use during the months of low streamflow each year. 

Though the amount of water that might be withdrawn 

annually from any one reservoir may be a modest few 

hundreds or thousands of acre-feet, the total may be a 

very important addition to water resources in areas 

where water is greatly needed. 

The existence of these upland reservoirs has been 

noted in previous reports. This paper is intended 

to indicate more explicitly their mode of occurrence 

and to outline a possible method of making tests to 

determine what part of the water might be replenishable. The paper is intended also to estimate the 

costs of testing and to point out some of the benefits 

to be derived from the development of this stored water. 

Because the proposed test wells would be of the same 

type as the operational producing wells tapping these 

reservoirs, they should be constructed as though they 

were to be merely the first of the permanent producing 

wells; many features of the foreseen operational-well 

installations have been incorporated in this method for 

testing the reservoirs. 

The water to be withdrawn from such a reservoir is 

referred to as "new" water because it would otherwise 

be unavailable. Under the assumptions of this plan, 

the water taken from storage as new water during the 

months of greatest need would be replaced during the 

winter and spring '"hen runoff is in excess of needs. 

The presence of these reservoirs has been noted in 

several reports on local areas, and there have been many 

inquiries for additional information and for suggestions on suitable methods of development. This plan 

for testing and the suggested procedure for any subsequent development of these reservoirs carry no implications as to who might undertake that work. If the 

first tests show development to be feasible, many organizations may be interested in the use of such reservoirs. 

The paper was prepared ·under the Feder:tl project 

for study of the hydrology of the Colur-1bia River 

basalt. Much of the supporting information is contained in reports on areas studied in cooperation with 

the State Engineer of Oregon, the Department of Conservation of Washington, and other local agencies. 

ENVIRONMENT OF THE BARRIER RESERVOIRS OF GROUND WATER 

The Columbia River basalt is a thick sequence of 

accordantly layered lava flows of basaltic and basic 

andesitic composition. The main part underlies most 

A-1 
A-2 HYDROLOGY OF VOLCANIC-ROCK TERRANES 

123° 120° -.... ---- ----r---T---

Okanogan Highlands 

- 490 EXPLANATION 

l~' 

W A S H 

ru, 

c 

ro 

0:: 

I 

Generalized boundary of the 

Columbia River basalt 

D A H 0 

FIGURE 1.-l\Iap showing the main area underlain by the Columbia River basalt, Washington, Oregon, and Idaho. 

of the area that extends westward from the northern 

Rocky Mountains to the northern Cascade Range, and 

southward from the Okanogan Highlands to the mountains of central Oregon (fig. 1). In the central part of 

this area the basalt is kno,vn to be more than 5,000 feet 

thick in places, and it tapers to zero on the older rocks 

at its margins. The individual lava flows range in 

thickness from 5 to 150 feet and average about 50 feet. 

The average flow consists of dense, almost flintlike, 

partly fractured rock at its base; grades vertically to 

dense, massive columnar-jointed rock at its center; and 

then to vesicular-and in some places rubbly-rock at 

its top. Systems of fractures cut the rock into irregular 

columnar, cubical, and platy blocks that range from 

2 to 60 inches across; the fractures formed when the 

lava was cooling. 

OCCURRENCE OF GROUND WATER IN THE BASAL·T 

Ground water moves through the rock largely in 

the permeable zones at the top of some flows. These 

tabular zones commonly are about 3 to 10 feet thick. 

In places where 2 of these permeable interflow zones 

are separated by highly jointed lava, the total thickness of a single water-bearing stratum may be 25 feet 

or more. 

The massive centers of some flows are relatively 

impermeable, and in places thick zones of the rock consist of several successive flows which are tight and 

nonwater bearing. Above the water table, these impermeable zones cause water to be perched, and below 

that level, in places, they cause the water-bearing zones 

to have no hydraulic continuity and, therefore, to have 

different water-pressure levels. Also, where the basalt 

is tilted or where the water movement is impeded by 

barriers, the water below these impermeable zones may 

be confined under pressure. 

Exact data are lacking not only on the percentage 

of interflow zones that are permeable and on their 

average water-yielding capacities, but also on their 

average thickness and permeability. These factors 

have been partly evaluated in a computation of the 

yieid of water to an average well. A computation 

made by the writer in 1947, based on records of several 

hundred wells that penetrated 300 feet or more of the 

basalt, shows that 1 gallon of water per minute for 

each foot of well that is below the regional water 
SUBSURFACE DAMS IN COLUMBIA RIVER BASALT A- 3 

table is the approximate average yield obtained by a 

10- or 12-inch well when pumped at the common drawdown of 50 to 100 feet (Newcomb, 1959). Subsequent 

records show that this estimated average is conservative for the yields obtained from the better designed 

wells now being constructed. 

Data indicate that the average capacity of the basalt 

to transmit ground water is generally uniform to a 

depth of about 1,500 feet, where the basalt is that thick. 

Not enough wells have been drilled deeper than 1,500 

feet to warrant making estimates of the average permeability of the basalt below that depth. 

TECTONIC DEFORMATION OF THE BASALT 

TILTING AND WARPING 

The basalt was extruded, in Miocene and Pliocene(~) 

time, as nearly horizontal flows. Subsequently, it was 

warped during at least two periods of folding. In 

most places, the basalt is now tilted in broad warps 

of the earth's crust. The general pattern of the regional tilting includes gentle dips inward from the 

older rocks near the boundary mountain ranges, a 

series of anticlines and intervening synclines that extend through central Washington eastward from the 

Cascade Range, and a broad anticline-known as the 

Blue Mountain anticline-that curves northeastward 

from the mountains of central Oregon. There are also 

many local structures. (See fig. 2.) 

Because ground water, which has percolated into 

the basalt, finds the easiest path of travel in the permeable interfiow zones, it moves generally down the 

dip of inclined strata. Thus, in general, the anticlines 

cause water to transfer laterally into the downwarped 

synclines, which are gathering places for the ground 

water in the basalt. Consequently the water table, or 

the piezometric surface of the ground water, beneath 

areas of inclined basalt commonly lies at or near the 

level of the principal streams. In synclines the water 

table may lie at or near the drainage level, or the 

ground water may be confined under artesian pressure. 

Most of the highly productive wells in the basalt are 

in downwarps such as occur at Walla ·walla, Cold 

Creek, and Ephrata, Wash.; The Dalles, Umatilla, and 

Pilot Rock, Oreg.; and Lewiston, Idaho. 

FAULT-BARRIER CONDITIONS 

During the deformation of the basalt, bending did 

not relieve all the stress in the rock at some places. 

Locally, these unrelieved forces produced fractures, 

called faults, along which the rocks on opposite sides 

were displaced. These faults range from large shear 

fractures along which the rocks on opposite sides were 

displaced several thousand feet, to small ones where 

FIGURE 2.-View northwest from the Blue Mountain upland ncar Mcintyre Lookout, Oreg. , down the valley of the South Fork of the 

Walla Wa ll a River, where the downstream dip of the basalt is apparent. 
A-4 HYDROLOGY OF VOLCANIC-ROCK TERRANES 

FIGURE 3.- VIew of a fault zone exposed by a road cut in the northwest 

bluff of the Grande Ronde River above La Grande, Oreg., In sec. 31, 

T. 2 S., R. 37 E. 

little displacement occurred. Rather than a single plane 

of fracture, the larger faults consist of zones of shattered and broken rock several tens or hundreds of feet 

wide (fig. 3). Even some of the small :faults, along 

which the displacement is measured in tens of feet, are 

zones of sheared and shattered rock. 

Nearly all the :faults are of the type commonly called 

normal faults, in which the fracture plane dips toward 

the down thrown side. This type generally is considered 

to indicate that tensional strains were responsible :for 

the faulting. The most common inclination, or dip, of 

the fracture planes is between 60° and 70° below the 

horizontal. 

The water-transmission characteristics o:f the :fault 

zones differ considerably from those of the unbroken 

basalt. The :fault fracturing provides a zone of low 

permeability (fig. 3), along which small amounts of 

water can move vertically in some places. The lowest 

sags in the fault traces, where they cross stream valleys, 

FIGURE 4.-Close view of pnrt of figure 3 "howing the shearing common to fault zones In the basalt. (Pick, at lt>wer right of the center, 

Is 14 Inches long.) 

are generally marked by small seepage springs. The 

permeable interflow zones that provide the lateral, or 

generally horizontal, routes of ground-water movement 

are obliterated in the fault zones and the lateral movement of the water is virtually stopped. Thus, a :fault 

zone constitutes a barrier to the otherwise normal lateral 

movement of ground water. 

In addition to those created by faulting, barriers 

can occur also along the axis of sharp folds owing to 

disruption of the permeable zones by the interflow 

grinding as the rock stretched over sharp bends of the 

basalt. These two types of localized destruction of the 

tabular paths of lateral movement of water in the basalt 

are grouped together under the term "structural barriers" (Newcomb, 1959). Intrusive dikes can also form 

barriers. However, dikes are not. so numerous or so 

continuous as the structural barriers, and in many places 

they a.re not arranged transverse to the direction of 

ground-water movement. 
SUBSURFACE DAMS IN COLUMBIA RIVER BASALT A-5 

RESERVOIRS BEHIND STRUCTURAL BARRIERS 

STRUCTURAL CONDITIONS CRFiATING BARRIER 

RESERVOIRS 

If a fault zone is parallel to the direction of groundwater movement, it has little efiect on the lateral movement of the water. However, if the fault zone is 

transverse to the direction of movement, the percola0 

0 

'<t 

tion down the gradient may be blocked and the water 

deflected around it; or, if the fault is extensive, the 

water may be dammed and may reach the surface above 

the barrier (fig. 5A). Thus, if a fault zone crosses the 

axis of a syncline, an almost complete barrier may be 

formed (fig. 5B). Surface outlets (and inlets) commonly occur at the points where the individual water1~====:;::::;:::;::::;:::;;::::;::::=::;:::::;;::::;:::::;;:::~ 

602946 0-61-2 

A. A monoclinal dip of the basalt cut 

by a transverse fault barrier 

B. A plunging syncline cut by a transverse 

fault barrier 

EXPLANATION 

Ground-water level just downstream from a fault 

----------2a -----------Ia 

Ground-water level, near the barrier, in a well that taps an aquifer 

cropping out at point 1 or 2 

Water-bearing layer shown on the 

sides of the diagrams 

FIGURE 5.--Structural features creating barrier reservoirs, 

• 
• 

A-6 HYDROLOGY OF VOLCANIC-ROCK TERRANES 

bearing zones crop out in streambeds above the barrier. 

The outlets of some reservoirs may occur also at other 

points in the streambeds upstream from the fault zone, 

because of upward cross-strata leakage from the aquifer. 

KNOWN AND TESTED STRUCTURAL RESERVOIRS 

In the quest for water in the Columbia River basalt, 

several ground-water reservoirs of the type described 

have been tapped by wells. Some reservoirs have been 

rather thoroughly developed and their extent and mode 

of occurrence are well defined. Others have been less 

well developed, and some have been tapped by only 

a few wells or by a single well. 

Possibly the most thoroughly developed groundwater reservoir of this type is that impounded behind 

the fault or sharp fold which passes through the basalt 

bedrock north of College Place, Wash., in the Walia 

'Valla syncline. The fault or sharp fold is marked 

by a 200-foot-high ridge in the bedrock surface beneath 

the 500 feet of sedimentary deposits which underlie 

the valley floor. The ridge trends east-northeast across 

the broad slope of part of the south limb of the Walia 

Walla syncline. It marks a vertical barrier to the 

lateral movement of ground water. When the first 

wells were drilled, during the years 1900-10, the artesian 

head of the water in the deep wells tapping the uppermost 200 feet of the basalt on the upgradient side of 

this barrier was about 140 feet above the land surface 

and 200 feet above the level of the water table in the 

nearby wells tapping the same rocks on the downgradient side of the barrier (Newcomb, 1951). 

Another developed reservoir upgradient from a fault 

(or sharp fold) occurs in the Upper Cold Creek syneline east of Yakima, Wash. The main part of the 

reservoir area lies in sees. 25, 26, 27, 34, 35, and 36, T. 

13 N., R. 24 E., and sees. 30 and 31, T. 13 N., R. 25 E. 

(Hart, 1958). The lower part of this plunging syneline 

is mantled by sedimentary deposits, which continue eastward beneath the high terraces in the Hanford Reservation of the U.S. Atomie Energy Commission. The 

ground-water reservoir of artesian water terminates 

abruptly in alinement with the sharp east edge of the 

Yakima Ridges to the north and south of the syncline. 

The easternmost well, the McGee, is about a quarter of 

a mile upslope from the inferred loeation of the barrier. 

Originally, the pressure level of the ground water at 

the McGee well was 212 feet above the land surface 

and about 580 feet above the level of the ground water 

in the basalt east of the barrier. 

An area south and southwest of The Dalles, Oreg., 

has several partly known ground-water reservoirs behind fault barriers in the basalt (fig. 6). The basalt 

to the south, east, and west dips into the Dalles syncline (Piper, 1932). It is eovered in many plaees by 

several hundred feet of sedimentary beds called the 

Dalles formation. Numerous faults are known to trend 

northwestward aeross the northeastward-plunging 

syneline; other faults are believed to be present but 

have not been mapped. A fault or fold escarpment 

runs south-southeastward through the western part of 

The Dalles and between the Renken well, 704 feet deep 

and at an altitude of about 625 feet, in the NWlJ.t,NEl)t 

see. 22; and the Stark well, 536 feet deep and at an 

altitude of about 700 feet, in the NWlJ.t,SWl)t sec. 27, 

T. 1 N., R. 13 E. The Stark well, three-quarters of a 

mile upgradient from this apparent barrier, has a statie 

water level slightly above the land surface. The 

Renken well, half a mile downgradient from the apparent barrier, has a water level 520 feet below the land 

surface. The differenee of about 600 feet in the water 

level of these two wells is apparently due to the barrier 

effeets of the intervening fault or sharp fold (fig. 6). 

Other reservoirs of ground water stored behind structural barriers oeeur in the Mill Creek and upper Threemile Creek areas near The Dalles. 

Ground-water reservoirs that are believed to be due 

to structural barriers oceur in other areas underlain 

by the basalt, but most of the barriers are too imperfectly known to serve as examples at this time. 

Individual wells known to illustrate the effects of 

barriers in creating ground-water reservoirs of relatively high water-pressure levels are (1) the Marion 

Coekburn well on Pine Creek, northwest of MiltonFreewater, Oreg., (Neweomb, 1951); (2) the Bureau 

of Reclamation test hole 1 at the Harris Dam site on 

the South Fork of the Walia Walia River in the 

N'VlJ.t,SEl)t see. 12, T. 4 N., R. 37 E. (G. E. Anderson, 

written eommunieation) ; and ( 3) the flowing well of 

the city of John Day, Oreg., on the north side of the 

fault whieh follows the center of the John Day River 

valley at that plaee. 

UNDEVELOPED STRUCTURAL RESERVOIRS 

Many untested reservoirs that have been formed by 

struetural barriers should oeeur in the type conditions 

present in the mountain areas and on the flanks of 

uplands. At those places little immediate need exists 

for additional water for public supply, irrigation, industrial, or other uses, but farther downstream there 

is urgent need for additional water, especially in the 

summer and autumn when loeal supplies are inadequate. Thus, the present utilization of mueh of this 

stored ground water may require transporting it in 

streams, pipelines, or flumes to points of use. Development of these supplies might also be of use in fish 

eulture, power generation, waste disposal, recreation, 
121° 

Base map by Topographic Division 

U.S. Geological Survey, 1934 

I )' V

.,,, c· 

"' 

~ 

w 

::0 

"' f-

.,. 

APPROXIMATE MEAN 

DECLINATION, 1961 

R. 12 E. 10' R. 13 E. 

1 0 1 2 3 4 5 MILES 

CONTOUR INTERVAL 50 FEET 

DATUM IS MEAN SEA LEVEL 

FIGURE 6.-Map of area adjacent to The Dalles, Oreg., showing fault barriers, 

EXPLANATION 

Fault 

Dashed where inferred 

~ 

Direction of low-angle 7J2 dip of basalt ~ 

to 

7J2 

0 ~ 

~ 

1-:rj 

Stark > 0 

well t"j 

t::::1 

> <D ~ 7J2 

Renken ~ 

well z 

0 

0 

0 ~ 

~ 

~ 

Wicks Reservoir to 

~ 

> 

~ ~ 

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t:d 

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""--1 

~ 
A-8 HYDROLOGY OF VOLCANIC-ROCK TERRANES 

and other activities. The use of the upland reservoirs, 

as proposed in this paper, is foreseen as a future source 

of supplemental water to supply some water-short 

valleys. 

SITES PROPOSED FOR TESTING FOR IMPOUND:EJ> 

GROUND WATER 

Areas (shown on figs. 1, 6, 7, and 8) in which 

transverse faults are known to cut the basalt, where 

it dips on a wide front toward a valley or is warped 

into a syncline, are present in the valleys of the Walia 

Walla River, Grande Ronde River. Mill Creek near 

The Dalles, and John Day River. s'ome of these areas 

appear to overlie structural conditions nearly ideal for 

barirer reservoirs in the basalt. There are many other 

areas where such reservoirs may occur, but the conditions are not now sufficiently known to warrant testing 

before further geologic investigations are made. 

In the Walia Walla River basin the layered basalt 

dips generally westward from the crest of the Blue 

Mountain anticline and extends beneath the alluvial 

fill which underlies the valley plains. The South Fork, 

North Fork, Mill Creek, and lesser tributaries flow 

down the regional slope in deep canyons, and the 

basalt is cut by several faults which trend generally 

transverse to the dip of the basalt (fig. 7). The basalt 

is believed to be at least 500 feet thick beneath the 

channel bed in most of these canyons. On the basis 

of the conditions observed in areas of similar geologic 

structure and on the few well data for this area, the 

fault zones probably impound ground water in the 

basalt .. ~ Sites where drilling is consid~red desirable to 

test for reservoirs of ground water are (1) along the 

South Fork, just south of the center of sec. 7, T. 4 N., 

R. 38 E., upstream from the large fault called the 

Tom Rite fault; (2) along Mill Creek near the northeast corner of sec. 19, T. 6 N., R. 38 E., upstream frt>m 

the Kooskooskie fault; and (3) along the South Fork, 

n~ar the east line of sec. 14, T. 4 N., R. 37 E., upstream from the Elbow Bend fault. These and other 

likely sites are shown on figure 7. 

In the upper part of the Grande Ronde River basin 

(figs. 1 and 8) the basalt dips southeastward off the 

Blue Mountain anticline and northwestward from the 

Elkhorn Ridge to form an elongate synclinal sag, which 

is followed eastward by the Grande Ronde River from 

noar Starkey to the va.Iley plain at La Grande (Hampton and Brown, in press). The syncline is cut transversely by northward-trending faults (fig. 8), and 

some should impound ground water. The following 

sites considered advisable to test for potential ground-

·water reservoirs are all upstream from faults: ( 1) 

along the Grande Ronde River in the S'\Vl)t sec. 36, 

T. 3 S., R. 35 E., (2) in the NEl)t sec. 15, T. 3 S., R. 

36 E., and (3) in the SvVI4SEI)t sec. 31, T. 2 S., 

R. 37 E. 

South and west of The Dalles, Oreg., the strata of 

basalt and the overlying sedimentary rocks of the 

Dalles formation dip into a plunging syncline that 

trends northeast through The Dalles (fig. 6). The 

basalt in this syncline is broken into blocks by faults, 

many of which are imperfectly known because they 

are obscure in the softer materials of the overlying 

sedimentary rocks. Some of the barrier reservoirs in 

the basalt have been tapped and partly developed by 

present wells. A well along the South Fork of Mill 

Creek, near the N1,4 cor. sec. 33, T. 1 N., R. 12 E., 

would provide a test of ground-water-reservoir conditions above the strong fault zone that crosses the South 

Fork near the Wicks Reservoir of The Dalles City 

'Vater Department. Other possible barrier reservoirs 

may be present in that area, but their testing can be 

deferred until the fault system is known in more detail. 

PLAN FOR TEST DEVELOPMENT OF BARRIER 

RESERVOIRS OF GROUND WATER 

TEST-WELL LOCATION 

The present data for developed barrier reservoirs 

indicate that it is preferable to drill wells near enough 

to the fault zones to obtain the maximum hydrostatic 

pressure, but far enough from them to avoid drilling 

in the disturbed or shattered rock. The proposed site 

of each production well should be on the upstream side 

of the fault zone. The faults of the Walla 'Valla River 

basin (fig. 7) and the Mill Creek area (fig. 6) dip 

steeply downstream; at the Grande Ronde River sites 

(fig. 8) some faults dip steeply upstream and others 

dip steeply downstream. In drilling on the upthrown 

side of a normal fault, the well can be sited reasonably 

close to the fault (as near as 200 or 300 feet). On the 

downthrown side of a normal fault, because the fault 

plane dips toward the well, a greater distance should 

be allowed-probably at least 300 feet plus a distance 

equal to the expected depth of the well. 

It is proposed that the test wells be located near 

stream level, so as to gain full advantage of any free 

artesian flow, and still be adequately sited and equipped 

with foundations and buttresses to be protected against 

damage by floodwaters of the stream. Also, the wells 

will need to be situated to permit the access of mobile 

drilling equipment. 
T. 7 N. 

T. 5 N. 

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·- uNioN-coEXPLANATION 

~1 [ ~ }' ~~ ~ ~ Alluvium <(<( 

~ ] Unconsolidated valley-fill deposits ::) z 0 underlying valley pla-ins 0 

]~[ o- ~ }~ <( ~~ - ~ -~ Columbia River basalt 1- -~ 5:; Layered lava. flows, mostly overlain e} ~ by soils except on the steep slopes 1-

Contact 

Dashed where approximately located 

u -0------····· 

Fault 

Dashed where approximately located; 

dotted where concealed. U, upthrown side; D, downthrown side 

Anticline, showing trace of axial plane 

'<'0 

Strike and dip of beds 

EB 

Generally horizontal basalt 

'2 

Generalized dip of basalt 

FIGURE 7.-Geologic map of the upper part of the Walla Walla River basin, Washington and Oregon. (After Newcomb, 1951.) 

r:n 

q 

b:! 

r:n 

q 

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t_:l:j 

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A-10 HYDROLOGY OF VOLCANIC-ROCK TERRANES 

N 

0 2 MILES 

l 

cr: 

l{ 11§E•l r~ 1-cr: 

'if(<( 

Alluvium :::>z 

0 

J{ -

)i Fanglomerate 

~: G ~{ Columbia River basalt 

Contact 

Dashed where approximately located 

~-- D 

Fault 

Dashed wh£re approximately located. U, upthrown side; D, downthroum side 

3"*' 

Generalized dip of basalt 

FIGrRE B.-Geological map of the Grande Ronde RiYer yalle~· abo,·e La Grande, Oreg. (From Hampton and Brown, 19:19.) 

SUGGESTIONS AS TO GENERAL SPECIFICATIONS FOR 

TEST WELLS 

The dip of the layers of the basalt in most of the 

stream valleys where testing is proposed ranges from 

1° to 5° and averages 2° to 3° downstream, or an average of 200 to 300 feet per mile. This average dip, together with a stream gradient of about 50 to 75 feet per 

mile, indicates that a 300-foot well would intercept the 

permeable zones that crop out in the first mile of the 

river above the well. Because different hydrostatic 

pressures probably exist in different aquifers, those of 

greater depth generally having the higher pressures, it 

is undesirable for one well to develop water from more 

than one aquifer or from more than one group of aquifers having similar hydrostatic pressures. Neglect of 

this precaution may lead to waste of reservoir water 

through aquifers of lower pressure. Consequently, the 

pairing of wells, one approximately 300 and one 600 feet 

deep may be a desirable arrangement for the testing of 

each barrier reservoir. In places where the basalt is 

thick and the reservoir is to be fully developed, a third 

well, about 1,000 feet deep, may be needed during later 

productive operation (fig. 9). 

The proper evaluation of the effect that the use of 

a ground-water reservoir will have on the nearby stream 

necessitates gaging the stream. The cost of establishing strea.m-gaging stations and operating them will be 

lessened if several nearby wells are served by one sta-

. tion. Also, savings on other surface facilities may be 

possible by grouping the wells producing water from 

different depth zones in one barrier reservoir. However, because one well can partly establish the presence 
1500 

1000 

500 

0 

EXPLANATION 

Water-bearing layer, basalt flows 

I ~ I 

ATll 

B~ 

Ill 

abl 

c 

Producing wells; cross Observation wells in 

mark is at base of aquifers tapped by 

casing wells A, B, C 

--------- ----- ------ Piezometric level of water in aquifers 

tapped by wells A, B, C 

lf.l 

q 

O::l 

lf.l 

q 

::<:l 

~ 

> 0 

l"j 

t:::1 

~ lf.l 

~ 

z 

0 

0 

t"1 

~ O::l 

~ 

> 

::0 

~ 

<l 

l"j 

::0 

O::l 

> 

~ t-3 

:FIGURE 9.-Block diagram of an idealized fault-barrier reservoir with producing and observation wells. (The diagram is cut away along the vertical plane of the stream-valley axis.) > 

I 

~ 

~ 
A-12 HYDROLOGY OF VOLCANIC-ROCK TERRANES 

and utility of a reservoir, it is probable that the initial 

testing of reservoirs will be by means of single wells. 

To serve the intended purpose, the wells must be 

properly cased. As the geologic conditions foreseen in 

these reservoirs indicate successively greater water pressure with successively greater depth, the sealing of upper aquifers of relatively low pressure head will be 

necessary in smne wells. Some possible arrangements 

of casing are shown in figure 10. Casing should be 

equal at least to standard well casing having a miniInum ·wall thickness of 0.:33 inch. It should be sealed 

to the i1npenneable parts of the rock by grouting with 

cement. The construction and arrangement of a permanent producing well should be planned to obtain at 

least a 100-year use before recasing is necessary. 

The surface appurtenances must include proper 

valve equipment, frost-protection outlets, fireproof protective shelters, and flood-damage protection. Equipment for measuri1ig the flow of the well and the flow of 

the strean1 passing the well must be included. Facilities for recording these measurements and keeping the 

records also 1nust be provided. 

At least one observation well is necessary in each 

reservoir during the test period and after full developFEET 

0 

100 

200 

300 

400 

Well tapping the first strong aquifer 

1 Alternate to 1 

A 

8 

Center of I I II massive flow 

I ~ II---

-----1 I ---II 

-----1 I 

I 

I 

~~50 

~ 

~~ ~~~50 

~~~ ~~I ~ 

C y. y. " L-l c .... .. .. 

EXPLANATION 

D D~ 

~70 " 

Cased well 

n1ent. One 6-inch observation well located upstream 

from each producing well may be necessary during ultimate full use of a reservoir. 

TEST OPERATION OF THE WELLS 

The operation is foreseen as a flow or, if necessary, 

a pump discharge from the wells in the general period 

July 1 to November 1 of most years and a period of 

shut down to allow recovery during the remainder of 

the year. Records of the discharge of the wells, the 

temperature of the water, and the flow of the adjacent 

stream are to be taken during the 4-month period of 

use. Records of water level, or water-pressure level, 

in the wells and the discharge of the nearby stream are 

to be maintained throughout the year. The facts regarding "\vater-level recovery in the aquifers 'vill determine the an1ount of water that can be extracted from 

each barrier reservoir and also the rate and timing of 

the extraction. 

The si.ruetural reservoirs suitable for testing include 

both the type in which the aquifer crops out in the 

bed of either a permanent or an intermittent stream, and 

the type in which it does not. The draining of a barrier 

Well tapping a deep aquifer 

2 Alternate to 2 ( 

I I II 

II10 

20 

Center of massive flow 

1----

, 1 __ 

I 

I~ so I~ 

10- in. 

:,.----

Hypothetical water-bearing zone 

500 n Static pressure level of the water at the --II 

.-.:-;1 ~ 

11-- --,, ~ 

LJ surface, in pounds per square inch ~~~70 

600 

Uncased 

u 

well 

Flow layering, 

~ hypothetical 

Cement seal 

{~I~ 70 

D ~~ u.-v ~II 

I I 

{ 

_j.J.->11~ 

D~~ 

"~II 

I I ..... 

FIGURE 10.-Schematic diagram of some possible arrangements of casing and wells to tap water store(! in a ba,rrier reservoir ln b~salt. 
SUBSURFACE DAMS IN COLUMBIA RIVER BASALT A-13 

reservoir is expected· to induce some recharge as a 

diversion from any flowing stream that crosses the outcrop of the aquifers. Consequently, the withdrawal 

of water from storage will be expected to cause some 

deerease in streamflow downstream from the outcrop of 

those aquifers. However, the amount of water tapped 

from storage in the reservoir is expected to be many 

times the amount of streamflow depletion indueed 

during the period of well operation. The subsequent 

refilling of the ground-water reservoir, partly by continued seepage from the stream, would occur during the 

fall and winter runoff period when sueh diversion from 

the stream is either beneficial or non detrimental (fig. 

11). It is expected that bedload movement and channel 

scour will continue the effective infiltration of water at 

the streambed outcrop of a depleted aquifer. 

The possibility of artifieial recharge to augment 

natural infiltration is present but, for brevity, is omitted 

from this report. Presumably, artificial recharge of 

dean water could be achieved hy pumping water 

through injection wells during the period of reservoir 

recovery. 

The approximate ~amount of streamflow depletion 

during the period of well use can be calculated, for 

idealized conditions, by the use of the Theis nonequilibrium equation (Theis, 1935). The effect of the 

barrier on the lowering of the water level at both the 

pumped well and the outcrop of the aquifer is computed 

fron1 that equation and adjustments derived from the 

laws governing the drawdown of the water level in 

image wells (Ferris, 1949). 

lTnder the assumed conditions of a producing-wen 

system such as is shown in figure 12, and on the basis 

of conservative coefficients of transmissibility and storage, a withdrawal of 1,000 gpm for 120 days would 

result in a drawdown 0f about 140 feet at the producing 

well and of 50 feet at the outcrop of the aquifer. In 

these calculations the coefficient of transmissibility was 

assumed to be 25,000 gallons per day per foot and the 

coefficient of storage to be 0.0001.1 

If there is 50 feet of dra wdown at the outcrop of the 

aquifer, the ground-water surface would have a generally downstream gradient of 20 feet per mile by the 

end of 120 days. Theoretically, this drawdown at the 

outcrop should induce infiltration ranging from 10 

gpm at the beginning of the pumping season to 250 

gpm at its end. Because the calculated 140 feet of 

drawdown exceeds the 100 feet of hydrostatic pressure 

1 The col:'fficient of transmissibility is df'finf'd as the number of gallons 

of water that will pass in 1 day, under prevailing conditions, through a 

vertical strip 1. foot wide extending the height of the aquifer under a 

hydraulic gradient of 1 foot in 1 foot. The coefficient of st()rage of an 

aquifer is the volume ()f water it rPleases from or takps into storage 

Jler unit surface arPa of thP aquifer per unit change in the component 

of head normal to that surface. 

at the beginning of the test, this well would need to be 

pumped near the end of the season or the flow be reduced to a seasonal average of about 700 gpm. So many 

unknowns and assumptions based on scant data are 

included in these calculations that their only significance is that they show general quantitative agreement 

with the results estimated from a qualitative approach. 

ESTIMATED COST OF A PROPOSED TEST INSTALLATION AND TEST PROCE.DURE 

The necessary test wells should include both shallow 

and deep wells, both of which are foreseen as the ultimate outlets of water from barrier reservoirs. 

Assuming that each reservoir will ultimately be developed by at least one well 300 to 400 feet deep paired 

with a well 600 to 700 feet deep, the depth of 4 test 

wells is estimated to total 2,000 feet. When completed 

with proper casing and sealing, each of these wells, of 

14-, 12-, and 10-inch diameter, may cost about $25 per 

foot. Valves, meters, aeration trays (for absorption 

of oxygen, \vhere needed), and other appurtenances are 

estimated to cost $2,000 per well. Observation wells of 

8- to 4-inch diameter located about midway between 

producing wells and the outcrop of the aquifer should 

be planned near 2 of the 4 well sites. Each would cost 

about one-fourth as much as a producing well. 

A station for accurate gaging of the nearby stream is 

estimated to cost ai1 average of $5,000, which includes the 

cost of the installation and the first year's operation. 

Such a gaging station would serve one barrier-reservoir 

installation, whether single, twin, or triple wells are 

used, but even if only one test well is drilled at each 

barrier tested, the cost of one stream-gaging station 

will need to be included in the cost of development 

for each barrier reservoir. 

On the basis of 1959 prices, the estimated cost of 

testing four barrier reservoirs with single producing 

wells is: 

Drilling casing, and completing 4 wells, total 

length 2,000 feet, at $25 per fooL _____________ $50, 000 

Appurtenances--------------------------------- 8,000 

Observation \Yells, 4____________________________ 12, 000 

Stream-gaging station (including cost of first year 

of test), 4----------------------------------- 20,000 

Total ----------------------------------- $90,000 

Thus, the cost of testing 1 barrier reservoir on a singlewell basis would be about $22,500. 

The estimated annual operating cost at 1 test reservoir 

thereafter is about $1,000, on the assumption that the 

operation would be under the supervision of a county 

watermaster or similar official. It is assumed that most 

of the cost is that of gathering the hydraulic data, 

and at any reservoir this cost would be about the same, 
A-14 

2400 

2000 

z 

ui 1600 

<.!'0 

o::z 

<o Iu 

uw 

(/)(j) 

Cia:: 

.. 

~ 

~ 

-

-

-

-

-

-

HYDROLOGY OF VOLCANIC-ROCK TERRANES 

~ Grande Ron!. River near La Grand.! Gaging station 

2 miles northwest of La Grande, sec. 36, T. 2 S., 

R. 37 E. 

J 

I 

ww 

<.!'a.. 1200 

<(Io::w 

LLILIJ >LL. <( 

>-~ ..Jill 

I::> 

1-(.) 

z 

0 

~ 

z 

ui 

<.!'0 

o::z 

<o Iu Uw 

(/)(j) 

Cia:: 

ww 

(!'a.. 

<(Io::w 

ww >LL. <( 

>-~ ..Jill 

I::> 

1-(.) 

z 

0 

~ 

-

~ 

- 800 

-

- ~ ~ 

400 ~ 

.. \ 

V ... UN ' 

0 ~J. .. '\J . I I ... V " " .. ~. I 

400 t--------South Fork of the Walla Walla River near Milton-Freewater. - ...... ------1 

Gaging station 1 mile below Elbow Bend, NEV4NE% sec. 15, 

T.4N., R.37 E. 

300 

200 

FIGURE H.-Average monthly discharge in two rivers where structural reservoirs of ground water are believed 

presen.t for artificially augmenting the annual low flow. 
SUBSURFACE DAMS IN COLUMBIA RIVER BASALT A-15 

FEET FEET 

400 Static piezometric surface of the water in the aquifer r-----------------------~--- 400 

1 . tonetimedur~P~ping _____ _ 

1 Piez~e~ ~a~-~-

300 

200 

100 

0 

I _..- · rtace) pro·hle / Stream (su 

~------.\// 

I II 

II 

II 

II 

II 

II 

II 

=II 

~II II 

II 

II 

II 

Base tt'if 

casing 

300 

200 

100 

0 

1 MILE --------------~ 

FIGURE 12.-Cro!-ls section of a hypothetical ground-water-withdrawal system utilizing an aquifer of a barrier reservoir. 

regardless of the number of wells used. Thus, ultimate full production at each reservoir m.ay not entail 

an average operational cost of much over $1,000 per 

year. 

In these estimates the cost of pumping is omitted, 

because one objective in the location of the test sites 

would be to seeure free-flowing wells where pumping 

costs would be avoided. 

VALUE OF THE BENEFITS DERIVED 

By continuing a hypothetical average well yield of · 

1,000 gpm over 120 days and assuming that 80 percent 

is new water previously unavailable, a total of 425 

acre-feet of new water would be made available by 

each well. At $8 per acre-foot, the value of this water 

for irrigation purposes would be about $3,400 per year. 

At some sites, where a hydroelectric plant would use 

the water at 200 feet gross head, this 1.75 cubic feet per 

second of new water in 120 days of the low-flow period 

would generate 67,000 kilowatt hours of electricity, 

which, at $0.007 per kilowatt hour, would have a value 

of $470 per year. 

It is difficult to compute the value of the new water 

for fish culture, especia.lly for the improvement of 

otherwise good spawning reaches that lack an adequate 

summer flow, as does the Grande Ronde River between 

Starkey and La Grande, Oreg. The value of the new 

0 

water for such uses as recreation, public and domestic 

supply, abatement of pollution, and watering of livestock is also difficult to assess at this time. 

These conservative estimates show that the wells 

would yield new water that annually would exceed in 

value the operating costs and at least 5 to 10 percent 

of the capital investment. 

REFERENCES CITED 

Ferris, J. G., 1949, Ground water, in Wisler, C. 0., and 

Brater, E. F., Hydrology: New York, John Wiley and 

Sons, p. 198--272, figs. 62-98. 

Hampton, E. R., and Brown, S. G., 1959, Geology and g·roundwater resources of the Upper Grande Ronde River basin, 

Union County, Oreg.: U.S. Geol. Survey open-file report. 

Hart, D. H., 1958, Tests of artesian wells in the Cold Creek 

area, 'Vashington: U.S. Geol. Survey open-file report. 

Newcomb, R. C., 1951, Preliminary report on the ground-water 

resources of the Walla Walla basin, Washington-Oregon: 

U.S. Geol. Survey open-file report. 

---1959, Some preliminary notes on ground water in the 

Columbia River basalt: Northwest Sci., v. 33, no. 1, p. 1-18. 

Piper, A. M., 1932, Geology and ground-water resources of 

The Dalles region, Oregon: U.S. Geol. Survey Water-Supply Paper 659-B, p. 107-189, pls.ll-19. 

Theis, C. V., 1935, The relation between the lowering of the 

piezometric surface and the rate and duration of discharge from a well. using ground-water storage : Am. 

Geophys. Union Trans., pt. 2, p. 519-524.