WATER QUALITY EFFECTS
of
LOWER GRANITE DAM
SNAKE RIVER
LEWISTON, IDAHO -
CLARKSTON, WASHINGTON
U.S. DEPARTMENT OF HEALTH,EDUCATION, AND WELFARE
Public Health Service, Pacific Northwest
Region IX, Portland, Oregon

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WATER QUALITY STUDY
SNAKE AND CLEARWATER RIVERS
A Report of Present and Post-Impoundment
Water Quality Conditions Associated with
Lower Granite Dam,
Lewiston, Idaho - Clarkston, Washington
Prepared for the Corps of Engineers
U. S. Army Engineer District, Walla Walla
Walla Walla, Washington
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Water Supply and Pollution Control Program, Pacific Northwest
Region IX, Portland, Oregon

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TABLE OF CONTENTS
INTRODUCTION 		1
ACKNOWLEDGMENTS 		4
SUMMARY OF FINDINGS 		5
CONCLUSIONS 		8
RECOMMENDATIONS	11
THE RIVER SYSTEM	12
STUDY AREA	17
THE FIELD STUDY	18
WATER USES	19
Municipal Water Supply 		19
Industrial Water Supply 		19
Irrigation	20
Hydroelectric Power 		20
Recreation	21
Fish and Wildlife	21
Waste Disposal	23
Water Transportation	23
SOURCES AND CHARACTERISTICS OF WASTES	24
COLLECTION AND ANALYSIS OF STREAM SAMPLES	31
Laboratory Analyses 		32
INTERPRETATION OF LABORATORY RESULTS 		34
Dissolved Oxygen 		34
Biochemical Oxygen Demand 		36
Chemical Oxygen Demand 		40
Temperature and pH	40
Alkalinity, Hardness and Sulfates 		42
Nitrates and Phosphates 		43
Solids and Sludge Deposits 		43
Bacterial Quality 		46

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ii
Page
EFFECTS OF IMPOUNDMENT AND RESERVOIR OPERATION ON
WATER QUALITY	50
Effects of Impoundment	51
Effects of Power Operations 	 60
FUTURE WATER USES	64
BIBLIOGRAPHY 	 67

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LIST OF TABLES
No.	Page
I Summary of Waste Loads in the Lewiston-Clarkston Area . .	30
II Dissolved Oxygen Summary 	 .....	36
III Biochemical Oxygen Demand Summary 		37
IV Chemical Oxygen Demand Summary 		AO
V Temperature and pH Summary			41
VI Total Alkalinity, Hardness and Sulfates Summary 		42
VII Nitrates and Phosphates Summary 		43
VIII Total and Settleable Solids Summary 		44
IX Bacteriological Analyses Summary 		48
X Estimated Cross-Section Velocities and Travel Times for
Lower Granite Reservoir with Average Discharge =
25,000 cfs	57
XI Estimated Reaeration Rates (K2 ) for Lower Granite
Reservoir, August-September Conditions with Average
Discharge = 25,000 cfs	59
LIST OF FIGURES
1.	Survey Streamflows (Provisional) 		16
2.	Gaging and Sampling Stations 		End
3.	Waste Source Locations 		25
4.	Dissolved Oxygen, Percent Saturation 	 .....	35
5.	Sludge Bed Deposits	45
6.	Estimated Density Current Profile 		54
7.	Velocity-Discharge Relationships under Natural Channel
and Impoundment Conditions 		55
8.	Estimated Travel Times under Natural Channel and

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INTRODUCTION
This report presents information on present water quality
conditions in the Snake and Clearwater Rivers in the vicinity of
Lewiston, Idaho-Clarkston, Washington, and how changes in the streams'
characteristics resulting from the construction of the proposed Lower
Granite Lock and Dam Project by the Corps of Engineers will affect the
water quality and waste disposal problems of that area.
This dam is one of four similar structures to be constructed on
the Lower Snake River to provide slack-water navigation between McNary
pool on the Columbia River and the Lewiston-Clarkston area. These are:
Ice Harbor Lock and Dam, already existing at River Mile 10; Lower
Monumental Lock and Dam at River Mile 42; Little Goose Lock and Dam,
at River Mile 70; and Lower Granite at River Mile 107.5, 32 miles
downstream from the two cities of Lewiston-Clarkston which are located
on either side of the Snake at its junction with the Clearwater River.
The last three are all in various stages of construction. The Lower
Granite pool will extend some four and one-half miles up the Clearwater
and about seven miles up the Snake above the Clearwater junction. It
will greatly alter several factors which control the waste assimilative
capabilities of the streams.
In order to better define these effects, the Walla Walla District,
U. S. Array Corps of Engineers, after discussions with the U. S. Public
Health Service, requested the Service to conduct studies to document

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2
conditions. The study was carried out by the Columbia River Basin
Project for Water Supply and Water Quality Management, Water Supply
and Pollution Control Program, Pacific Northwest, Portland, Oregon.
The first phase of the study was initiated in March 1963 and con-
sisted of the collection and analysis of such data on water quality
and domestic and industrial wastes that were available in the files of
the State water pollution control agencies of Idaho and Washington.
Although very little data existed depicting current conditions, they
were helpful in planning a field study to obtain additional informa-
tion. This study was carried out over a three-week period in July and
August 1963, the season when the combination of waste loads, low stream-
flows, and high water temperatures exerts its most serious effects on
water quality in this stretch of the stream.
The study was designed to identify the water uses, the waste
sources, points of waste discharge, diffusion patterns, stream hydrau-
lics, deoxygenation and reaeration constants, and the physical and
sanitary quality of the receiving waters. No attempt was made to
determine the efficiencies of waste treatment facilities at the several
waste sources, as the purpose of this survey was not to establish
waste treatment requirements to meet present needs but rather to
document present conditions and to define the water pollution problems
and waste loading limitations that will exist when river characteris-

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3
is required to evaluate the impact of the proposed structure on other
water uses and to assist appropriate authorities in establishing water

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ACKNOWLEDGMENTS
Grateful acknowledgment is made to the following for the
assistance rendered:
The Idaho State Board of Health and the Washington State Pollution
Control Commission for making the results of previous studies available,
and for their counsel and assistance in planning and carrying out this
study;
The City of Lewiston for making the city sewage treatment plant
laboratory available for the use of the field chemists during the
entire study period;
The Walla Walla District, U. S. Army Corps of Engineers, for
hydrologic data on the streams, for available design and operational
data on the proposed impoundments, and for making the services of a
boat and operator available for a major portion of the survey;
Dr. W. V. Burt, Chairman, Department of Oceanography, Oregon
State University, for information obtained from personal conferences
and his studies on the dissolved oxygen and temperature characteristics
resulting from proposed impoundments in the Snake and Clearwater Rivers,
and the Bureau of Commercial Fisheries, U. S. Fish and Wildlife
Service, for making these studies available;
Other State and Federal agencies which were consulted on present
and future water uses and water quality requirements for those uses;
Potlatch Forests, Inc., for making it possible to introduce the

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SUMMARY OF FINDINGS
1.	Lower Granite Dam, now in the early stages of construction, is
one of four similar Corps of Engineers projects on the Lower Snake River
which will provide slack-water navigation between McNary Pool on the
Columbia and the Lewiston-Clarkston area. This dam will create an
impoundment extending up to and beyond the cities of Lewiston and
Clarkston and will completely change the hydrologic characteristics of
the Snake and Clearwater Rivers in this area, which are now turbulent,
swift-flowing streams. Minimum flows in the Snake River below the
Clearwater junction during the late summer months range from 18,000 to
25,000 cfs. Approximately 3,000 to 5,000 cfs of this is contributed by
the Clearwater.
2.	Additional authorized Corps of Engineers projects include
Dworshak Dam on the North Fork of the Clearwater River approximately
40 miles above its junction with the Snake at Lewiston which is scheduled
for completion in 1972 and Asotin Dam on the Snake immediately above the
Lower Granite pool for which construction funds have not yet been
appropriated. Power releases from these dams will also result in further
changes in river hydraulics in the Lower Granite pool.
3.	On the basis of studies conducted by the Public Health Service
in July and August of 1963, the total organic waste as measured by the
5-day BOD reaching the Snake and Clearwater Rivers in the Lewiston-
Clarkston vicinity was estimated to be 83,450 pounds daily. At least 86
percent of this load came from a single source; namely, the Potlatch

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6
4.	The industrial waste discharged directly to the stream carried
large quantities of suspended solids and highly colored dissolved solids.
Due to the high stream velocities under present flow conditions, the
formation of sludge banks on the stream bed was not extensive. Some
visual evidence of industrial wastes was present in the vicinity of the
pulp and paper mill and packing plant outfalls during the study period.
Since the food processing plants were not in operation during the study
period, no field observations were obtained regarding this waste source.
5.	The municipal sewage treatment plants at Clarkston and Asotin,
Washington, and Lewiston, Idaho, were operating satisfactorily and
contributing a small fraction of the total waste load discharged to the
streams. All three plants provide primary treatment with separate
sludge digestion and disinfection of the plant effluent.
6.	There was a high background BOD in the Snake River as it
entered the study area. The probable cause of this condition is the
relatively high concentration of algae in the stream as it enters the
area.
7.	The Snake and Clearwater Rivers in the study area have high
reaeration rates. Because of this, the biochemical oxygen demand of the
municipal and industrial wastes and the background organic load exert a
very minor effect on the oxygen levels in the streams.
8.	Slack water conditions in the Lower Granite pool will result
in reduced stream velocities which will favor deposition of suspended
solids and will reduce mixing of wastes. The reaeration rate of the

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7
photosynthetic-respiration effects of phytoplanktonic activity in the
reservoir will be negligible. Consequently, the oxygen resources
available for stabilizing the incoming wastes will be essentially
limited to that amount of oxygen contained in the waters entering the
pool.
9. At streamflows of 25,000 cfs, the travel time through the
impoundment will increase over twenty-fold. This increased time will
result in essentially all of the BOD of the waste load being satisfied
within the impoundment^under minimum stream reaeration conditions.
Under existing flow conditions, the reaeration rate is high and only a
very small percentage of the demand is exerted within the time of

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CONCLUSIONS
The following conclusions are based on the data collected during
this survey and on data and information obtained from other sources,
particularly from the preliminary report prepared by Dr. W. V. Burt
on the effects of impoundments on temperature characteristics of the
Snake and Clearwater Rivers. The conclusions are presented as they
relate to present and post-impoundment conditions.
Present Conditions
The quality of the Snake and Clearwater Rivers in the Lewiston-
Clarkston area was in a generally satisfactory condition from a chemical
standpoint at the time of this study. Bacterial levels below the points
of waste discharge as measured during a special bacterial study in July
of 1964 were slightly higher than recommended for water-contact sports
such as bathing and water skiing. The fecal coliform counts were quite
low indicating that chlorination of sewage treatment plant effluents is
providing a relatively high degree of bacterial removal. However, there
is a potential threat in the use of these waters for recreational
purposes involving water-contact sports.
Post-Impoundment Conditions
1.	Lower Granite Reservoir can be expected to materially alter
the hydraulic characteristics of the Snake and Clearwater Rivers and
the rate at which organic matter will be stabilized by the natural
purification processes within the stream.
2.	The impoundment will create conditions which will be more

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9
diurnal variations in dissolved oxygen, with super-saturated values
occurring during daylight hours followed by significant reductions in
dissolved oxygen during nighttime hours. Algae growths also will
degrade water quality for municipal and industrial use and may create
objectionable conditions in the Clearwater arm of the impoundment from
which the City of Lewiston derives its water supply.
3.	It is anticipated that density currents will develop in the
Lower Granite pool under summer conditions. The flow in these density
currents will receive little reaeration. These conclusions are based
on theoretical calculations and further study is essential to define
better the complex relationships that may develop with the operation of
this and other upstream and downstream reservoirs.
4.	The flow releases from the Dworshak Dam on the Clearwater River
and Asotin Dam on the Snake River will have a significant effect on the
waste assimilative capacity and water quality in the Lower Granite pool.
The highly variable flow conditions occurring under power-peaking
operations of upstream hydroelectric facilities will create minimum
flows which may permit the waste to concentrate around the waste
outfalls, since there will be little stream movement and little
opportunity for mixing. It is doubtful that longitudinal diffusion
during peak flows will disperse these pockets of waste evenly throughout
the reservoir.
5.	Future operating schedules of Asotin Reservoir on the Snake

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10
may permit water from the Snake to flow upstream in the Clearwater arm
of the Lower Granite pool. This could result in residual wastes from
existing waste outfalls, at or near the confluence of the two streams,
being carried upstream to the Lewiston water supply intake area.
6.	The creation of slack water in the Lewiston-Clarkston area will
be most favorable for greatly expanded recreational use of the area for
water-contact sports. This will require an extremely high degree of
bacterial removal in all sewage treatment plant effluents. Also, to
minimize the loss of aesthetic values which might occur as a result of
foam and color from the Potlatch Forests, Inc., operation, the waste
outfall should be designed and located to produce the maximum diffusion
and mixing of wastes with the incoming streamflow. Even with this
precaution, color and foam during minimum streamflow periods may be
objectionable to recreational uses.
7.	Additional field data on actual reservoirs having similar
characteristics are necessary to evaluate more accurately the effects
of anticipated flows from upstream hydro-power operations on the quality

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RECOMMENDATIONS
1.	The Lewiston public water supply intake should be relocated
to take water from above the existing Washington Water Power Company
dam on the Clearwater River.
2.	The point of discharge of wastes of the Lewiston Sewage
Treatment Plant, Seabrook Farms Company, Potlatch Forests, Inc., and
Bristol Packing Company, should be located a sufficient distance
downstream from the mouth of the Clearwater River to remove the
possibility of these wastes being moved upstream in the event of a
flow reversal in the Clearwater arm of the reservoir.
3.	Maximum possible degree of suspended solids removal should
be provided for all waste sources of the area.
4.	After completion of the Lower Granite Dam, additional studies
should be carried out to determine the effects of the varying flows
which may result from power plant operations on the temperature,
dissolved oxygen, density current, and diffusion characteristics within
the pool. Upstream installations should also be designed so that
discharge rates and points of withdrawal can be adjusted to minimize

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THE RIVER SYSTEM
The Snake River above the Clearwater drains an area of 93,400
square miles. The upper portion of the drainage basin, from Jackson
Lake in Wyoming to Weiser, Idaho, some 212 miles upstream from
Lewiston, has been developed extensively for irrigation, and stream-
flows are highly regulated. Downstream from Weiser, however, present
water resource developments exert little effect on the streamflow
patterns.
The Payette, Weiser, Burnt, Powder, Imnaha, Salmon, and Grande
Ronde are the principal tributaries entering the Snake in this stretch
of the main stem. The terrain of these drainage areas is mountainous,
varying in elevations from 730 feet above sea level at Lewiston to
nearly 12,000 feet in the headwaters of the Salmon River in central
Idaho.
The streamflows in the Snake River at Lewiston follow a seasonal
pattern of high flows from melting snows occurring during April, May,
and early June, followed by rapidly diminishing discharges during
June and July. Minimum flows occur from late July through September.
Spring flows often approach 200,000 cfs, while average late summer
flows usually range from 18,000 to 25,000 cfs. Average monthly flows
for April, May, and June at the Clarkston gage (period of record,
1916 to 1960) are 79,570, 123,720, and 105,240 cubic feet per second.
Average flows for the last week of July and for August and September
are 23,640, 18,630, and 18,320 cfs, respectively. The minimum flow of
record is 6,680 cfs. The flows from the Clearwater are included in

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The Clearwater River, with a drainage area of over 9,600 square
miles, drains the western slopes of the Bitterroot Mountain Range and
lies between the Clark Fork-Pend Oreille River on the north and the
Salmon River on the south. Rugged and densely forested mountains up to
9,000 feet above sea level comprise the eastern portion of the basin,
while the western portion is sparsely timbered, with hills, plateaus,
and small cultivated valleys. This stream also exhibits high spring
flows and minimum late summer flows. Corresponding flows at the
Spalding gage on the Clearwater (period of record, 1926 to 1950) are
30,892, 48,251, and 32,409 cfs for April, May and June; and 4,848,
3,224, and 2,846 cfs for the last week of July through September. The
minimum flow of record is 500 cfs.
As previously stated, the streamflows are not materially altered
by impoundments or stream diversions on the main stem of the Snake or
its tributaries between Lewiston-Clarkston and Weiser, Idaho. The only
existing main stem developments are Oxbow and Brownlee hydro-power dams
owned by Idaho Power Company. Oxbow Dam at River Mile 273, 133 miles
upstream from Lewiston, forms a pool 11.4 miles long, extending to the
tail waters of Brownlee Dam at River Mile 285. The Brownlee pool
extends another 57 miles upstream, approximately ten miles below
Weiser, Idaho.
Other developments on the main stem of the Snake are being planned,
however, and these can have significant effects on downstream flows and

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River Mile 247, for which a license to construct has been granted to
Idaho Power Company by the Federal Power Commission; High Mountain
Sheep Dam at River Mile 189, just upstream from the mouth of the Salmon,
also licensed by the Federal Power Commission to Pacific Northwest Power
Company; and Asotin Dam at River Mile 145.6, at the headwaters of the
Lower Granite pool, authorized for construction by the Corps of Engineers
The flow of the Clearwater River is now relatively uncontrolled,
the only control being the Washington Water Power Company's dam just
4.6 miles above the mouth of the stream. This installation maintains a
flow of 4,300 cfs at capacity power production and, during minimum
streamflow periods, may hold back essentially all of the streamflow
during low power demand periods for release at times of peak demands.
This development has a very minor effect on the streamflow regimen of
the Snake River.
Dworshak Dam now under construction on the North Fork and the
proposed Penny Cliffs Dam on the Middle Fork of the Clearwater are
authorized Corps of Engineers projects, with the former scheduled for
completion in 1972. Funds for construction of the Penny Cliffs project
have not yet been appropriated.
The significance of the several proposed structures as related
to the water quality problems in the Lower Granite pool will be dis-
cussed in more detail under "Effects of Impoundments and Reservoir
Operation on Water Quality."
The streamflows in the Snake and Clearwater Rivers during the

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15
Clearwater) averaged 27,060 cfs during the first half of the survey
and 23,120 cfs during the last half. The Clearwater flows were 5,465
cfs and 4,465 cfs for these same periods. These flows compare with
the mean monthly flow for August of 19,300 cfs in the Snake River and
3,340 cfs in the Clearwater River and approach the mean annual low
flows, the period when the most critical water quality conditions are

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40
35
30
co
CLARKSTON GAGE
SNAKE RIVER (Includes CLEARWATER)
o
o
220
S3
w
ANATONE GAGE
SNAKE RIVER"
SPALDING GAGE
CLEARWATER RIVER
28 29 30 31
SURVEY PERIOD
24 25 26
July
August
LOWER SNAKE AND CLEARWATER RIVER
Vicinity of Lewiston, Idaho and Clarkston, Washington
Survey Stream Flows (Provisional)
(July 23 - Augsut 7, 1963)

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STUDY AREA
The study area (illustrated in Figure 2 at the end of this
report) includes that portion of the Snake and Clearwater Rivers that
will be impounded by Lower Granite Dam and extends from the dam site
(River Mile 107.5) upstream to the Asotin dam site (River Mile 146.5)
on the Snake and to the existing Washington Water Power Company dam on
the Clearwater River, 4.6 miles above its confluence with the Snake
(River Mile 139.5).
Asotin Creek enters the Snake River at River Mile 145 just below
the community of Asotin, Washington. No other streams of significance
are within the study area.
Lewiston and Lewiston Orchards on the Idaho side of the Snake,
and Clarkston and Clarkston Heights on the Washington side, have a
total population of approximately 31,000. Asotin, Washington, five
miles to the south, has a population of 800 persons.
This urban area serves as a service and distribution center for
other communities and the rural populations of southeastern Washington
and west-central Idaho. The economy of the area is built around
lumber and forest products, agriculture, and food processing. The
principal industries are: Potlatch Forests, Inc., a manufacturer of
lumber, plywood, pulp, paper, and fuel products; Seabrook Farms
Company, a pea and potato packer; and Smith Frozen Foods, a pea
processor—all located in Lewiston; and Meats, Inc., and Bristol Packing

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THE FIELD STUDY
The intensive phase of the field study was carried out from
July 22 to August 7, 1963.
The objectives of the study were:
1.	Determination of water uses;
2.	Location and characterization of waste sources;
3.	Determination of water quality and oxygen relationships
under existing flow conditions;
4.	Determination of diffusion patterns within the stream
under existing flow conditions;
5.	Determination of the presence or absence of deposits

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WATER USES
The Snake and Clearwater Rivers in the Lewiston-Clarkston area
serve a variety of important uses. These include municipal and
industrial water supply, hydroelectric power, recreation, propagation
of fish and aquatic life and wildlife, a limited amount of irrigation,
and waste disposal. The future impoundment of these waters will add
navigation as a water use.
Municipal Water Supply
The City of Lewiston derives most of its domestic water supply
from the Clearwater River. The intake and treatment plant is located
at a point two and one-half miles above its confluence with the Snake.
This point will be in the headwaters of the Lower Granite pool. Treat-
ment consists of chemical coagulation, sedimentation, rapid sand filtra-
tion, and chlorination. Because of its excellent quality, the Clear-
water River will continue as the principal source of supply for this
city.
Ground water is the primary source of supply for Clarkston, its
fringe area, and Asotin, Washington. Clarkston makes use of Asotin
Creek as an auxiliary source of water supply which receives treat-
ment consisting of sedimentation, coagulation, rapid sand filtration,
and chlorination.
Industrial Water Supply
Potlatch Forests, Inc., uses over 40 MGD from the Clearwater

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20
at a point above the Washington Water Power Company dam. The
industry will continue to use this source which is adequate to
satisfy future industrial demands. The Clearwater is also used to
transport logs to the mill from upstream timber areas and these are
stored in the power pool of the Washington Water Power Company dam.
Irrigation
Small amounts of irrigation water are pumped from the Snake River
below Lewiston-Clarkston. Primarily, this is used for sprinkler irri-
gation of orchard and truck-farm crops grown on the narrow bottom lands
along the stream. Most of these lands will be inundated by the impound-
ment, and it is not expected that irrigation will create a major water
demand with the raising of Lower Granite pool.
Hydroelectric Power
The Washington Water Power Company operates a 10,000 kilowatt
hydroelectric facility on the Clearwater River. This power plant and
dam is located four and one-half miles above the confluence of the
Clearwater with the Snake. The Lower Granite pool will extend to the
base of this dam, but will not interfere with power production. The
proposed Lower Granite and Asotin Dams will provide power production
as one of their beneficial uses. Lower Granite Dam will have a full
power capacity of 810,000 kilowatts, half of which will be installed
initially. The Asotin project will be a 384,000-kilowatt facility,

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21
Recreation
The Snake River is presently used for a variety of recreational
activities. Both Lewiston and Clarkston maintain attractive public
bathing beaches on the Snake River within their respective city
limits. Summer usage of these is estimated to be over 400 persons
per day. Occasional swimmers and bathers are also to be found on
several attractive but undeveloped beaches below the two cities.
Water skiing and pleasure boating are popular activities.
Several boat marinas along the Lewiston-Clarkston waterfronts support
these pastimes. As many as 50 water skiers and an equal number of
boaters can be counted on the river during a typical summer weekend.
These activities, however, are pretty much restricted to two short
stretches of the river at Lewiston-Clarkston where the waters are
deep and wide. During the low summer flows, many of the remaining
sections of the river are too shallow and turbulent for these sports.
The quieter waters of the Lower Granite pool should offer increased
attraction for these water-contact sports. The area of use is likely
to extend further downstream.
Fish and Wildlife
Hunting and fishing are also important uses of the Snake and
Clearwater Rivers in this area. Annually, many thousands of man-
hours are spent in goose and duck hunting and fishing for steelhead,
salmon and resident fish.
The Snake River and its tributaries are well known as migratory

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22
the Pacific Northwest. Approximately 70 percent of the steelhead
trout and 60 percent of the chinook salmon passing McNary Dam on
the Columbia River enter and ascend the Snake River. A majority
of these fish migrate to and past Lewiston-Clarkston to spawn in the
upstream tributaries of the Snake River. During 1959-60, a record
year for steelhead trout, an estimated 97,500 ascended the Snake
River to Lewiston-Clarkston. Some 40,000 of these continued up the
Clearwater River to spawn and the remaining number migrated further
up the Snake to upstream tributaries. A record run of spring chinook
salmon occurred in 1957 when 174,000 of these fish were estimated to
have migrated to spawning grounds in the Snake River tributaries
above Lewiston-Clarkston. In 1958, a record run of 37,000 fall
chinook salmon reached the Lewiston-Clarkston area for spawning further
upstream. In this run, an additional 5,000 were estimated to have
spawned directly in the Snake River below Lewiston-Clarkston. Small
runs of sockeye (blueback) and coho (silver) salmon also migrate in
the Snake River. This stream, therefore, is of major significance
to the Columbia River and Pacific Ocean fishery industry.
The Snake River supports a diverse and well-established resident
fishery. Included in this are game-fish populations of rainbow and
Dolly Varden trout, white sturgeon, mountain whitefish, smallmouth and
largemouth bass, black and white crappies, yellow perch, sunfish,
channel catfish, and brown bullheads. Non-game fish include squawfish,
carp, suckers, chiselmouth, chubs, shiners, dace and sculpins.

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Waste Disposal
As discussed under "Sources and Characteristics of Wastes," the
Snake and Clearwater Rivers receive significant discharges of domestic
and industrial wastes from several sources at or near Lewiston-Clarkston.
These are the only waste sources in the study area. In fact on the
Snake River, no other significant sources exist for over 200 miles
upstream. On the Clearwater River, several small communities located
forty miles or more above Lewiston discharge domestic sewage treatment
plant effluents to the river and its tributaries. These wastes are of
minor significance to water quality in the Clearwater and Snake Rivers
at Lewiston-Clarkston.
Water Transportation
Presently, the Snake River is not navigable except by small boats.
Completion of the four Snake River dams between Lewiston-Clarkston and

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SOURCES AND CHARACTERISTICS OF WASTES
AIL the principal waste sources are located in the immediate
Lewiston-Clarkston area. In Idaho, the Lewiston sewage treatment
plant, the Potlatch Forests, Inc., pulp and paper mill, and the
Seabrook Farms food processing industry contribute waste to the
Clearwater and Snake Rivers. In Washington, the Clarkston sewage
treatment plant and two meat packing plants, Bristol Packing Company
and Meats, Inc., discharge wastes to the Snake. The Asotin sewage
treatment plant discharges into Asotin Creek as it joins the Snake.
The organic content of sewage and industrial wastes is expressed
as biochemical oxygen demand (BOD) and population equivalent (PE).
The BOD is a measure of the amount of dissolved oxygen consumed by
biological organisms in the biochemical stabilization of organic
matter in the stream. A common base is 0.167 pounds of five-day BOD
per capita per day, the amount of oxygen used during that period of
time to stabilize the organic matter in the wastes from one person.
PE is the calculated population which would normally contribute the
same amount of BOD per day as present in a particular waste.
The locations of these waste sources are shown in Figure 3. The
characteristics and significance of these are summarized as follows:
1. Lewiston Sewage Treatment Plant. This plant receives the
wastes from the City of Lewiston, population 12,000, and from approxi-
mately 1,000 persons living in Lewiston Orchards. Eventually, the
wastes from some 7,000 of the latter's 10,000 population will enter

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)
WASTE SOURCES
A	Lewiston Sewage Treatment Plant
B	Seabrook Farms Company
C	Potlatch Forests, Inc.
D	Bristol Packing Company
E	Clarkston Sewage Treatment Plant
F	Meats, Inc.
G	Asotin Sewage Treatment Plant
VER E
CLARKSTON
WASHINGTON
H


Lewiston Water
Supply Intake"
rn A
WASHINGTON WA TER
POWER CO. DAM

LEWISTON
LEWISTON
ORCHARDS
ASOTIN
WATER QUALITY STUDY
WASTE SOURCE LOCATIONS
SNAKE RIVER.LEWISTON.IDAHO
USDEPARTMENT OF HE ALTH.EDUCATION a WELFARE
PUBLIC HEALTH SERVICE
JfiOJON
^PORTLANDjOREGON

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26
of industrial waste tributary to the municipal system. The treatment
plant is located on the north bank of the Clearwater River 0.8 of a
mile above its mouth. It provides primary treatment--sedimentation
with separate sludge digestion—plus effluent disinfection with
chlorine gas. It is a we11-maintained and efficiently operated
facility and is designed so that secondary treatment units can be
added in the future. It was placed in operation late in 1960.
The wastes entering this plant are typical domestic sewage, with
the usual commercial wastes originating within a municipality of this
size, plus the seasonal discharge of pea cannery wastes from the Smith
Frozen Foods Company. During the cannery season, the waste load from
this source may equal or exceed that from the remainder of the city.
Primary treatment will normally effect a 35 percent reduction in
biochemical oxygen demand and essentially complete removal of settle-
able solids from the raw wastes. On this basis, it is estimated that
the organic load discharged to the Clearwater River from this source
has an average population equivalent of approximately 8,400. This
would be greater during the canning season.
2. Potlatch Forests. Inc. This company operates a lumber and
plywood plant, a 650 ton/day pulp and paperboard mill, and a recently
completed 50 ton/day tissue mill on the south bank of the Clearwater
River just downstream from the Washington Power Company dam. Essen-
tially all of the liquid wastes (40 mgd) from this operation, including

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27
is discharged through an outfall sewer to the Snake River. The wastes
enter the river through a submerged, non-diffuser type outlet near the
east shore of the stream just above its confluence with the Clearwater.
Small capacity waste retention lagoons exist but were not being used
at the time of this study.
The wastes from this operation are typical of a kraft mill, with
bleaching, and contain high concentrations of oxygen-consuming sub-
stances and suspended solids. Based upon mill reports to the State
water pollution control agency and limited sampling at the plant waste
outfall, the BOD load from this source was estimated to have a popu-
lation equivalent in excess of 400,000, with high concentrations of
wood fibers.
3. Seabrook Farms Company. This industry is a food processing
plant located on the south bank of the Clearwater adjacent to the
business district of Lewiston. The industry processes and packages
peas during a six-week campaign in June and July and processes potatoes
for nine months beginning in August. The potato processing capacity
is 150 tons per day. All wastes, including caustic peel wastes, are
discharged untreated to the Clearwater a quarter of a mile above its
junction with the Snake. At the time of this study, the pea processing
season was just terminating and the potato processing had not commenced.
Consequently, it was not possible to obtain representative analysis
of the waste flows. Based upon the production figures, however, it is

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28
equivalent of 50,000 during the vegetable processing season. These
wastes, of course, will be high in suspended matter.
4.	Clarkston Sewage Treatment Plant. This plant provides primary
treatment for the domestic wastes of the 6,100 population of Clarkston.
This plant, an older but well-maintained and operated facility, provides
primary sedimentation with separate sludge digestion and effluent
chlorination. The treated wastes are discharged directly to the Snake
River one mile below Clarkston. Lower Granite pool will partially
inundate this facility and necessitate its relocation or protection by
levees. The City of Clarkston has retained an engineering firm to
study this problem. The wastes entering this plant are principally
domestic sewage with the usual discharges from commercial establishments--
no significant industrial wastes are contributed to the system. Based
upon the average efficiency of such a plant, it is estimated that the
organic load discharged to the stream will have a population equivalent
of approximately 4,000.
5.	Bristol Packing Company. This meat processor is located in
Clarkston and kills up to 50 head of cattle or 135 hogs daily.
Screening of waste solids is practiced. Grease and paunch manure
are collected for separate land disposal. Wash water, floor drainage,
and kill-blood wastes are discharged directly to the Snake River.
Based upon the animal kill at this plant, it is estimated that the
organic load discharged to the stream has a population equivalent of

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29
which are not removed in the screening operations. This firm plans to
build a waste stabilization pond for the disposal and treatment of its
entire waste load. Such a facility would substantially reduce the
organic waste load now discharged to the stream.
6.	Meats. Inc. This plant processes an average of 55 head of
cattle daily. Liquid wastes are screened. Grease and paunch manure
are collected for land disposal. The screened liquid wastes, including
kill-floor wastes, are discharged directly to the Snake River, two and
one-half miles below Clarkston. It is estimated that the waste load
from this plant will be approximately the same as that of Bristol
Packing, namely a population equivalent of 3,000, with significant
quantities of suspended matter. Lower Granite pool will partially
inundate this plant and cause its relocation.
7.	Asotin Sewage Treatment Plant. This plant receives the
domestic wastes from the city's population of 800. Primary sedimenta-
tion and effluent chlorination are provided. Effluent is discharged to
Asotin Creek, a short distance above its confluence with the Snake
River. The population equivalent of the waste load going to the
stream is estimated at 500, with very little settleable solids. This
plant site will be partially inundated by Lower Granite pool and the
plant will have to be either relocated or provided with levee protec-
tion. The City of Asotin has retained an engineering firm to study
this problem.
The estimated organic waste load entering the Clearwater and Snake

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30
TABLE I
SUMMARY OF WASTE LOADS IN
THE LEWISTON- CLARKSTON AREA
Waste Load Per Day
Source	PE	# 5-Day BOD
Lewiston Sewage Treatment Plant 	
	 8,400
1,400
Potlatch Forests, Inc	
.... 432,000
72,000
Seabrook Farms Company 	
.... 50,000
8,300
Clarkston Sewage Treatment Plant . . . .
.... 4,000
670
Bristol Packing Company 	
.... 3,000
500
Meats, Inc	
.... 3,000
500
Asotin Sewage Treatment Plant 	
.... 500
80
Total
500.900

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COLLECTION AND ANALYSIS OF STREAM SAMPLES
Twelve stream sampling stations were established on the Snake
River and two on the Clearwater. The locations of these are shown
in Figure 1 (last page of this report). The Clearwater stations
were between the mouth of the Clearwater and the Washington Water
Power Company dam. Two of the Snake River stations were upstream
from the first waste discharge at Lewiston-Clarkston but below
Asotin Creek, which receives the Asotin sewage treatment plant
effluent. Nine stations were below the junction of the Snake and
Clearwater Rivers. A special sampling station (14) was established near
the Potlatch Forests, Inc., waste outfall at River Mile S-139.5.
It was not possible to sample all stations during each sample
run. Therefore, for the first seven days of the survey, samples
were collected at Stations 1 through 6. Only the Snake River sta-
tions were sampled during the last half of the survey and at less
frequent intervals.
Samples were collected at approximately six-hour intervals
throughout the survey. Sampling schedules were so arranged that
samples would be taken at all hours during the twenty-four hour
period at the upstream stations during the first week and at each
hour of the 6 a.m. to 6 p.m. period during the second week. All
samples were surface, grab samples and, except for dissolved
oxygen samples, were composites of from two to five samples taken
at different points across the stream. Separate dissolved oxygen

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32
A limited number of bacteriological samples were taken at the
mid-stream point at all stations except 2 and 13. Long-term BOD
samples were taken at all stream stations.
Laboratory Analyses
The laboratory analyses were performed in the Columbia River
Basin Project laboratory in Portland, Oregon, and at the Lewiston
Sewage Treatment Plant laboratory in Lewiston, Idaho. The assist-
ance of the City of Lewiston in making this excellent facility
available for the duration of the study greatly expedited the con-
duct of the field analyses. All sample handling, shipment, and
analyses were carried out in accordance with the Eleventh Edition
of "Standard Methods for the Examination of Water and Waste Water,"
1960.
The following analyses were carried out on samples collected
in the study area:
Chemical Measurements
*1. Five-day biochemical oxygen demand (BOD)
2.	Long-term biochemical oxygen demand
3.	Chemical oxygen demand (COD)
*4. Dissolved oxygen (DO)
*5. Hydrogen ion concentration (pH)
^Analyses carried out in the field; all others at the Portland

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33
6.	Sulfates (SO4)
7.	Alkalinity (as CaCC^)
8.	Hardness (as CaCOg)
9.	Soluble ortho-phosphates
10. Nitrates
Physical Measurements
*1. Settleable solids
2.	Suspended solids
3.	Total solids
*4. Temperature
Biological Measurements—^
1.	Total coliform bacteria
2.	Fecal coliform bacteria
3.	Fecal streptococci bacteria
1/ Plans called for only a limited number of these analyses.
* Analyses carried out in the field; all others at the

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INTERPRETATION OF LABORATORY RESULTS
Tables showing the individual analyses of the various water
quality parameters are presented in the Appendix. Summary tables
of the more significant water quality constituents appear as a part
of the following discussions.
Dissolved Oxygen
Table II summarizes the dissolved oxygen (DO) data collected
during the survey. It will be noted that the DO concentrations
approach or exceed saturation values throughout the study area with
only a slight depression below the waste discharges at Lewiston-
Clarkston. The data also indicate that DO conditions in the stream
are adequate for all known water uses under existing flow conditions.
The data also show diurnal variations, indicating photosynthesis
by the algae in the stream. Figure 4 depicts these patterns for the
Snake and Clearwater Rivers. The Clearwater showed less diurnal
fluctuation indicating a lower concentration of algae. This prob-
ably accounts for the lower background level of BOD in the Clearwater
as compared with the Snake River.
The Snake River under present flow conditions has a relatively
high reaeration rate; the coefficient of reaeration (K2) of the
stream under existing flow conditions was calculated to be 0.344.
The deoxygenation constants (K^) calculated from long-term BOD's

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120
115
110
/—
2 105
Upper Snake Section
Middle Snake Section
Clearwater Section
NOON
24 HOUR PERIOD
DISSOLVED OXYGEN, PERCENT SATURATION
Clearwater, Upper Snake, and Middle Snake Sections

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36
to 0.113 with an average value of 0.08. This is within the expected
range for a stream such as the Snake at this location. On the basis
of the above calculations, the stream has a high capability for
assimilating oxygen-consuming wastes without seriously depressing
the DO levels in the stream.
TABLE II
DISSOLVED OXYGEN SUMMARY
July-August 1963
Snake and Clearwater Rivers
Station River No. of	% Sat. of
No.	Mile	Samples Maximum Minimum Average Average
Clearwater River
13
CLW-2.6
17
8.6
6.7
7.2
81
12
CLW-0.8
54
9.4
8.0
8.5
94



Snake
River


1
S-141.1
60
10.4
5.0
9.3
102
2
S-139.8
60
10.3
8.4
9.4
104
3
S-139.0
150
10.0
7.9
9.0
101
4
S-136.9
120
10.0
8.1
9.1
101
5
S-135.0
116
9.9
8.0
9.1
101
6
S-132.3
116
9.9
8.0
9.0
101
7
S-128.0
48
9.8
7.8
8.7
98
8
S-123.2
48
9.6
7.8
8.7
97
9
S-119.2
48
9.5
7.9
8.6
97
10
S-115.0
48
9.5
8.0
8.7
97
11
S-110.5
48
9.4
8.0
8.7
97
Biochemical Oxygen Demand
Table III summarizes the BOD data collected during the survey.
As previously indicated, the biochemical oxygen demand is a measure
of the amount of dissolved oxygen consumed in biochemical stabiliza-

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37
oxygen exceeds the rate of oxygen replenishment, then the dissolved
oxygen concentration in the stream may be reduced to a level that is
inadequate to support desirable aquatic life or the aerobic stabiliza-
tion process itself. The BOD of an organic waste, therefore, is a
measure of its impact on the oxygen resources of a stream. Also, an
increase in BOD below a waste outfall is a measure of the amount of
wastes entering the stream.
TABLE III
BIOCHEMICAL OXYGEN DEMAND SUMMARY
July-August 1963
Snake and Clearwater Rivers
Station
River
No. of
Five-dav BOD (me/1)
No.
Mile
Samples
Maximum
Minimum
Average


Clearwater River


13
CLW-2.6
18
2.69
0.80
1.37
12
CLW-0.8
18
3.37
0.40
1.34


Snake
River


1
S-141.1
19
4.70
1.83
2.96
2
S-139.8
20
3.68
0.91
2.21
3
S-139.0
29
3.44
1.08
2.00
4
S-136.9
30
3.30
1.48
2.12
5
S-135.0
29
3.06
1.50
2.36
6
S-132.3
27
3.30
1.40
2.13
7
S-128.0
12
8.90
3.40
5.67
8
S-123.2
12
6.40
2.60
3.88
9
S-119.2
12
5.60
2.40
3.48
10
S-115.0
12
5.50
2.10
3.46
11
S-110.5
12
4.30
2.18
3.12
Practically all surface waters display some background BOD. Even
decaying vegetation carried into a wilderness stream may create a

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38
pounds of oxygen for each million gallons of water. As may be noted
in Table III, the BOD of the Clearwater is slightly in excess of
1 mg/1, indicating a relatively low level of man-made pollution.
The Snake River above the Lewiston-Clarkston area, on the other
hand, had an average BOD of approximately 2.5 mg/1. This is consid-
erably higher than would be expected in view of the fact that the
nearest major source of pollution is over 200 miles upstream and
above the Brownlee and Oxbow Dams. Although there are significant
waste sources above these impoundments, the wastes would normally
be stabilized during the time of passage through this unpolluted
stretch of stream.
It is known, however, that the significant algal blooms occur
in the stream and particularly in Brownlee Reservoir. Such growths
are probably stimulated by nutrients contained in the incoming flows.
The algae exert a demand on the dissolved oxygen as they die off,
and the products of decomposition are recycled into the flowing water
to again stimulate algae production farther downstream.
It should be pointed out that with a streamflow of 25,000 cfs
the entire waste load entering the streams in the Lewiston-Clarkston
area would exert an oxygen demand of approximately 0.5 mg/1, or only
twenty percent of the background level measured during the initial
study period. While this background BOD is not a critical factor in
DO levels of the Snake River under present flow conditions, it will
be a very important factor in maintaining desirable dissolved oxygen

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39
Seven stream samples collected over a four-day period during
July 1964 from the Snake River above all waste sources in the
Lewiston-Clarkston area showed five-day BOD values ranging from
0.86 to 2.0 mg/1, with a mean value of 1.31. This is more repre-
sentative of what might be expected at this location. The higher
values observed during the previous year cannot be discounted, how-

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40
Chemical Oxygen Demand
Chemical oxygen demand is a measure of the amount of oxidizable
organic compounds present in a given sample and is measured by a
strong chemical oxidizing agent under specified conditions. Table IV
summarizes the chemical oxygen demand data obtained during the survey.
It will be noted that the variation in COD at the different stations
closely parallels that for BOD.
TABLE IV
CHEMICAL OXYGEN DEMAND SUMMARY
July-August 1963
Snake and Clearwater Rivers
Station	River	No. of		COD (mg/1)	
No.	Mile	Samples	Maximum	Minimum Average
Clearwater River
13
CLW-2.6
13


4.9
12
CLW-0.8
12


6.7


Snake
River


1
S-141.1
15
14.3
2.4
10.6
2
S-139.8
15
12.5
3.5
8.2
3
S-139.0
25
15.0
5.9
9.7
4
S-136.9
24
12.1
4.5
9.5
5
S-135.0
23
11.8
3.4
9.4
6
S-132.3
23
10.5
4.1
9.2
7
S-128.0
12
21.9
13.0
15.5
8
S-123.2
12
21.8
8.0
13.3
9
S-119.2
12
15.4
7.2
11.5
10
S-115.0
12
17.2
6.7
11.3
11
S-110.5
12
14.4
6.7
11.0
Temperature and pH
Table V summarizes the water temperature and pH data obtained

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41
Clearwater Rivers ranged from 20.6 to 22.0 degrees Centigrade, with
maximums ranging from 22.0 to 25.4 degrees C. These maximum tempera-
ture levels are near the upper limits recommended for certain species
of fish, particularly salmon and some species of trout.
TABLE V
TEMPERATURE AND pH SUMMARY
July-August 1963
Snake and Clearwater Rivers
pH	 	Temperature
Station
River
No. of

No. of
Average
Maximum
No.
Mile
Samples
Average
Samples
°C
°C


Clearwater River


13
CLW-2.6
18
7.50
17
22.0
25.4
12
CLW-0.8
18
7.84
18
20.9
23.0



Snake River



1
S-141.1
19
8.60
20
20.7
22.5
2
S-139.8
20
8.67
20
20.6
22.0
3
S-139.0
30
8.47
30
21.1
23.5
4
S-136.9
30
8.51
30
21.0
22.5
5
S-135.0
29
8.54
29
21.0
22.5
6
S-132.3
29
8.48
29
21.0
22.5
7
S-128.0
11
8.27
12
21.5
24.0
8
S-123.2
11
8.38
12
21.5
23.5
9
S-119.2
11
8.41
12
21.5
23.5
10
S-115.0
11
8.35
12
21.5
23.5
11
S-110.5
11
8.44
12
22.0
23.5
The hydrogen-ion concentrations (pH) observed during the survey
were within the ranges that would normally be expected. The pH of
the Snake River was higher than the Clearwater, which no doubt re-
sulted from the higher alkalinity and greater algal activity in the
former stream. These pH values, however, are compatible with all
present uses of these waters, including the propagation of fish and

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42
Alkalinity. Hardness, and Sulfates
Table VI presents a summary of alkalinity, hardness, and sulfate
analyses made during the survey. It will be noted that the hardness
of the Clearwater is considerably less than that of the Snake and, as
would be expected, the Clearwater contains less alkalinity. For these
reasons, the Clearwater River is preferable to the Snake River as a
source of domestic or industrial water supply.
TABLE VI
TOTAL ALKALINITY, HARDNESS, AND SULFATES SUMMARY
July-August 1963
Snake and Clearwater Rivers


*Total Alkalinity
*Hardness
Sulfates
>ta.
River
No. of
Avg.
No. of
Avg.
No. of
Avg.
No.
Mile
Samples
ma/1
Samples
mg/1
Samples
mg/1



Clearwater River



13
CLW-2.6
14
24.0
14
19.2
13
2.6
12
CLW-0.8
14
19.2
14
15.4
13
1.1



Snake
River



1
S-141.1
16
85.2
16
87.4
15
19.3
2
S-139.8
16
85.0
16
87.5
15
18.1
3
S-139.0
15
62.3
15
62.2
24
13.5
4
S-136.9
15
72.0
15
74.6
14
14.7
5
S-135.0
15
72.5
15
73.6
14
14.8
6
S-132.3
15
70.9
15
72.4
14
14.7
7
S-128.0
--
--


10
18.6
8
S-123.2
--
--




9
S-119.2
—
--
--
--

--
10
S-115.0
--
--
--
--
10
18.9
11
S-110.5
—
--





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Nitrates and Phosphates
The summary of these data, shown in Table VII, does not point
to any abnormal water quality characteristics.
TABLE VII
NITRATES AND PHOSPHATES SUMMARY
July-August 1963
Snake and Clearwater Rivers
Station
No.
River
Mile
Nitrates
No. of
Samples
Average
me/1
43
Soluble
Ortho-phosphates
No. of Average
Samples	mg/1
Clearwater River
13
12
CIW-2.6
CUW-0.8
14
13
0.20
0.03
13
13
0.04
0.02
Snake River
1
2
3
4
5
6
7
8
9
10
11
S-141.1
S-139.8
S-139.0
S-136.9
S-135.0
S-132.3
S-128.0
S-123.2
S-119.2
S-115.0
S-110.5
15
15
14
14
14
14
1
0.04
0.04
0.04
0.04
0.04
0.04
0.00
0.00
15
15
14
14
14
14
12
12
0.04
0.04
0.05
0.04
0.05
0.05
0.06
0.06
Solids and Sludge Deposits
The summary of the total and settleable solids data from the
survey is presented in Table VIII. Here again, the lower concen-
tration of total solids in the Clearwater River indicates that this

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44
On the basis of the stream samples, the increase in settleable solids
below the Lewiston-Clarkston area is considerably less than measured in a
waste sample collected from the Potlatch Forests, Inc., outfall.—
TABLE VIII
TOTAL AND SETTLEABLE SOLIDS SUMMARY
July-August 1963
Snake and Clearwater Rivers


Total
Solids
Settleable
Solids
Station
River
No. of
Average
No. of
Average
No.
Mile
Samples
ma/1
Samples
ml/1


Clearwater River


13
CLW-2.6
14
47
4
0.06
12
CLW-0.8
13
16
5
0.03


Snake River


1
S-141.1
15
140
4
0.07
2
S-139.8
15
132
2
0.07
3
S-139.0
22
101
24
0.12
4
S-136.9
22
124
24
0.14
5
S-135.0
20
118
5
0.11
6
S-132.3
20
108
5
0.12
7
S-128.0
7
120
--
--
8
S-123.2
7
118
--
--
9
S-119.2
7
114
--
--
10
S-115.0
7
120
—
--
11
S-110.5
7
114
• •
• •
An attempt was made during the survey to determine the extent
to which the settleable solids may be accumulating on the stream bed.
Several small deposits were found at the locations shown in Figure 5,
in the back-water zone of bank-side eddies where low velocities per-
mitted their accumulation. In the high velocity waters of the main
channel, sludge deposits were absent and clean stream bottoms prevailed.
1/ The sample indicated a loading of 101.5 tons per day of volatile
suspended solids. Solids from other waste sources are negligible,

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1365
10.85
S-126.3
5.85
10.25
7.40
37.30
6.16
5000
3000
10,000
SCALE IN FEET
WATER QUALITY STUDY
\ % Volatile Solids in
J Sludge Bed Deposits
SLUDGE BED DEPOSITS
S-130.8 River Mile
SNAKE RIVER. LEWISTON. IDAHO
US DEPARTMENT OF HEALTH,EDUCATION,6WELFARE
PUBLIC HEALTH SERVICE
REGION IX
PORTLAND,OREGON

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46
These bottom samples were analyzed for volatile solids, and the
percentage of volatile matter in the respective samples is indicated
in Figure 5.
Under present flow conditions, the velocities and turbulence of
the stream are sufficient to keep most of the settleable solids load
in suspension. Only in a few of the deep pools and eddies are the
velocities reduced to an extent where deposition occurs. Even in
these areas, however, deposition no doubt occurs only during low
summer and fall flows. Sludge deposits accumulating during low flow
periods are apparently scoured out by high flows during flood stages,
a situation that will not prevail when the waters are impounded.
There was visual evidence of highly colored industrial wastes in
the vicinity of the packing plant and pulp mill outfalls. Since the
food-processing plants were not in operation during the survey, no
observations were obtained regarding the visual effects from this
waste source.
Bacterial Quality
Bacterial analyses including total coliform, fecal coliform,
and fecal streptococci were carried out on a limited number of samples,
using the membrane filter method of analyses. The initial results
were considerably higher than could be accounted for from existing
waste sources. Because of this fact, the State water pollution con-
trol agencies of Idaho and Washington and the Public Health Service

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47
similar streamflow conditions. It was also agreed that the analyses
should be carried out on the ground and under the best possible
laboratory controls in order to eliminate all possible sources of
error.
In order to approach similar streamflow conditions, it was neces-
sary to postpone this follow-up work for approximately one year. In
July of 1964 a joint bacterial study was conducted by the State water
pollution control agencies of Idaho and Washington and the Public
Health Service. Eight samples were collected over a period of five
days at sampling stations on the Clearwater and Snake Rivers above
all waste discharges in the Lewiston-Clarkston area and at three
sampling points across the Snake at River Mile 131.5, which is below
all points of waste discharge. The following tests were carried out:
1.	Coliform density, using the membrane filter technique;
2.	Coliform density, using the five-tube, most probable number
technique;
3.	Confirmation of membrane filter colonies by picking to phenol
red lactose broth and transferring all positives to brilliant green
lactose bile broth;
4.	Double confirmation of MPN positives to E. C. broth and
brilliant green lactose bile. The E. C., or elevated temperature
test, at 44.5 degrees Centigrade gives the coliform density of fecal
origin.
Table IX summarizes the bacterial analyses carried out during

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48
TABLE IX
BACTERIOLOGICAL ANALYSES SUMMARY
July 1964
Snake and Clearwater Rivers

River
Average Coliform Densities
Per 100 ml
Station
Mile
MF
5 Tube MPN 5
Tube EC
Spalding
CLW-11.6
728
1,270
315
Above
Asotin
S-147.0
130
160
10
North
S-131.5
1,378
2,604
280
Middle
S-131.5
1,230
3,734
151
South
S-131.5
796
1,431
141
The results indicate there is some bacterial contamination of
sewage origin entering the Clearwater and Snake Rivers in the Lewiston-
Clarkston area. This is much less than was found in the initial sur-
vey in 1963. The bacterial levels do not indicate a serious bacterial
pollution problem; however, there is a potential threat in the use of

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DIFFUSION STUDIES
A diffusion study was conducted as a part of this survey in
order to acquire more definitive information as to the mixing charac-
teristics of the Snake River in the Lewiston-Clarkston area under
prevailing flow conditions.
A fluorescent dye tracer (Rhodaraine B dye) was introduced into
the Potlatch Forests, Inc., pulp mill effluent to tag a given mass of
industrial waste. The dye was introduced first as a large quantity
instantaneously and, second, in small amounts continuously over a
period of an hour. A fluorometer with pump was installed in a boat
and by traveling across the stream at three different stations from
River Mile 139.0 to 135.0, the water was pumped continuously through
the instrument which measured the presence of the dye to concentrations
as low as 0.1 part per billion. The measured dye concentration was
continuously recorded, providing a permanent record of the passage
of dye at each station.
Although unforeseen operating difficulties presented some prob-
lems, the study did show that nearly complete mixing of streamflow
and waste loads from the Lewiston-Clarkston area had occurred by the

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EFFECTS OF IMPOUNDMENT AND RESERVOIR OPERATION
ON WATER QUALITY
The previous discussions document water quality conditions and
the ability of the stream to assimilate municipal and industrial
wastes under prevailing streamflow conditions. The following dis-
cussions will relate to the effects of impoundments and streamflow
regulations for hydroelectric power production upon water quality,
water uses, and waste disposal problems of the area.
The construction of Lower Granite Dam can be expected to mate-
rially alter the characteristics of the Snake and Clearwater Rivers
and the rate at which organic matter will be stabilized by the stream
self-purification processes.
Slack-water conditions of impoundment will result in reduced
stream velocities which will favor the deposition of suspended solids
and will reduce diffusion and mixing of wastes in the stream, result-
ing in reduced stream reaeration. Reduced velocities and increased
retention time in the impoundment will cause an increase in surface
temperatures which will favor the growth of algae. (The presence of
essential nutrients contained in the treated wastes will also encour-
age algal production.) This growth would degrade water quality for
municipal and industrial use and would be especially objectionable in
the Clearwater arm of the impoundment, from which the City of Lewiston

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51
The following comments present a brief analysis of some of
the probable current patterns, travel times, and reaeration rates
that are expected to prevail in the impoundment during the late
summer and fall.
Effects of Impoundment
According to studies by Yih (1958)—^, Debler (1959)—^,
Harleman (1961)-^, Duncan et al. (1962)—^, and Burt (1963)—^, a
relationship between reservoir morphometry, discharge, density,
gradients, and flow pattern can be described by empirical solu-
tions of the densiometric Froude number, F^:
Q = Turbine discharge.
W = Reservoir width at the depth, zQ, and at observation
depths.
zQ = Depth from surface to centerline of turbine intakes.
p = Density of water at zQ.
g = Gravity acceleration.
jQ = Slope of vertical density gradient at zQ.
These studies suggest that, for intermediate depth reservoirs
with characteristics similar to those proposed for the Lower Snake
River, density currents may develop under summer conditions. These
density currents will increase velocities through the affected
sections and reduce reaeration at these sections to a negligible

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52
Dr. W. V. Burt, Chairman, Department of Oceanography, Oregon
State University, has carried out preliminary studies on the tempera-
ture characteristics resulting from the construction of Ice Harbor,
Lower Monumental, Lower Granite, Asotin, China Gardens, High Mountain
Sheep, Hells Canyon, Oxbow, and Brownlee Dams on the Snake River and
Dworshak and Penny Cliffs Dams on the Clearwater. Dr. Burt cautioned,
however, that the analytical relationships evaluated in his report
have not been fully corroborated: "It should be emphasized that more
field measurements in actual reservoirs are required before these
relationships will be completely understood." On the basis of these
preliminary studies, he predicts:
1.	Some reduction in temperatures is anticipated in the Lower
Snake River after full reservoir development, assuming that low-
temperature water is available from upstream;
2.	High Mountain Sheep Dam is expected to deliver cooler than
normal water to the next downstream impoundment;
3.	Dworshak and Penny Cliffs Dams will lower the temperatures
of the Clearwater River.
From these studies and from personal conferences with Dr. Burt,
it is assumed that the probable thickness of the Lower Granite Reser-
voir density current will be about 75 percent of the total depth at
the dam site, or 105 feet, during August-September. Based on a
uniform density current thickness of 105 feet, then, the intersection
of the density current and reservoir surface will be near River Mile
120.0. A plot of the probable density current profile is shown in

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Figure 7 illustrates the probable effects of impoundment on
cross-sectional velocities in Lower Granite Reservoir. During
periods of low discharge, the increased area will reduce velocities
to about ten percent of the natural channel velocities. This rela-
tionship is not constant because the reservoir pool elevation will
be held relatively constant at elevation 738 feet MSL. Thus, at
200,000 cfs, the impounded velocities will be about 30 percent of
the natural channel velocities.
Figure 8 shows the increased travel time from about River Mile
140.0 to the Lower Granite Dam at River Mile 107.5 under impoundment
conditions compared to natural channel conditions. For an average
discharge of 25,000 cfs, total travel times are about 8.5 hours for
natural flow conditions and 8.0 days for impoundment conditions, or
approximately 23 times longer. As seen from Table IX, the travel
times through the proposed reservoir have been adjusted for reduced
cross-sectional areas below River Mile 120.0 due to development of

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DEPTH
POOL ELEV.=738 FT. MSL
Stagnant
20
40
60
80
100
120
110
115
120
125
130
135
140
RIVER MILE
ESTIMATED DENSITY CURRENT PROFILE
LOWER GRANITE RESERVOIR
August-September Conditions
Average Discharge = 25,000 C.F.S.

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10.0
5.0
4.0
3.0
co
0.15
10
20
30
200
40 50
100
300 400
DISCHARGE IN 1,000 C.F.S.
VELOCITY-DISCHARGE RELATIONSHIPS UNDER
NATURAL CHANNEL AND IMPOUNDMENT CONDITIONS
Snake River Mile 132.0
Lower Granite Reservoir

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240
220
200
NATURAL CHANNEL
140	135	130	125	120	115	110
SNAKE RIVER MILE
ESTIMATED TRAVEL TIMES UNDER NATURAL
CHANNEL AND IMPOUNDMENT CONDITIONS
Through Lower Granite Reservoir
Discharge=25.000 C.F.S.
August-September Conditions

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57
TABLE X
ESTIMATED CROSS-SECTION VELOCITIES AND TRAVEL TIMES FOR
LOWER GRANITE RESERVOIR WITH AVERAGE DISCHARGE = 25,000 cfs

Cross-
sectional
Average
Travel Time
River
Area
(sq. ft.)
Velocity
(days)

Mile
Total
Effective*
(fps)
(rai./day)
Increment
Total
139.0
62,000
62,000
0.445
7.2
0.21

137.5
51,000
51,000
0.42
6.8
0.37
0.21
135.0
71,000
71,000
0.325
5.3
0.94
0.58
130.0
83,000
83,000
0.30
4.9
1.00
1.52
125.0
83,000
83,000
0.25
4.1
1.22
2.52
120.0
125,000
125,000
0.185
3.0
1.67
3.74
115.0
167,000
145,000
0.185
3.0
1.67
5.41
110.0
167,000
128,000
0.175
2.9
0.86
7.08
107.5
218,000
164,000



7.94
^Density current cross-sectional area.
The self-purification capacity of the Lower Snake River will be
greatly reduced due to increased depths and decreased velocities.
The reaeration rates (K^ ) for Lower Granite Reservoir have been
e
worked out at an average discharge of 25,000 cfs, using relationships
developed by Churchilli^ and O'Connor and Dobbins^. These relation-
ships express the reaeration rate of a river as an exponential function

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Churchill:
K = H.6 y°-969
2e " H1.673
58
O'Connor Isotropic: K2 =
e h /
V = Velocity, fps.
H = Depth, feet.
From Table X, it is seen that the reaeration rates for Lower
Granite Reservoir will be very small in the reach above River
Mile 120.0 (Ko = 0.01, more or less). Below River Mile 120.0,
e
the development of a density current will limit reaeration to
whatever oxygen can be exchanged across the stagnant water-density
current interface. Assuming laminar flow, then, reaeration below
River Mile 120.0 will be essentially zero in the density current.
On the basis of the above calculations and with existing back-
ground levels of BOD entering the Lower Granite pool, the dissolved
oxygen concentration at the lower end of the pool, during the crit-

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59
TABLE XI
ESTIMATED REAERATION RATES (K2 ) FOR LOWER GRANITE RESERVOIR
e
AUGUST-SEPTEMBER CONDITIONS WITH AVERAGE DISCHARGE = 25,000 cfs
Average Average K2
River	Depth Velocity 	Reaeration Rate ( e)
Mile
(feet)
(fps)*
01 Connor
Churchill
Average
139.0
44
0.40
0.027
0.009
0.018
137.5
53
0.49
0.022
0.008
0.015
135.0
71
0.35
0.012
0.003
0.008
130.0
77
0.30
0.010
0.003
0.006
125.0
95
0.30
0.007
0.002
0.004
120.0
98
0.20
0.006
0.002
0.004
115.0
95
0.17
a/
a/
a/
110.0
100
0.20
a/
a/
a/
107.5
105
0.15
a/
a/
a/
*Average density current cross-section velocity.

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60
Effects of Power Operations
The streamflow characteristics that will prevail in Lower
Granite pool as a result of hydroelectric power operations have
not been fully determined. These will change as upstream develop-
ments are completed and as the complex Northwest power system is
operated to meet the changing power demands. It is reasonable to
assume that hydroelectric facilities will eventually be used pri-
marily for power-peaking purposes, thereby producing highly vari-
able flows during a 24-hour period. It has been reported that
power-peaking operations of Dworshak Dam will bring flows up to
about 10,000 to 15,000 cfs in the Clearwater River during the
period of normally low flows. Flows below the Asotin Dam on the
Snake River may be expected to reach 90,000 cfs during similar
periods. The minimum flows resulting from storage during off-peak
operations may be as low as 1,000 cfs. The flow passing through
the pool in any day will approximate the average daily flow of the
two streams. These extremes in flow, together with the frequency
and duration of such flows, are of major significance from the
standpoint of evaluating the effects of waste discharges from the
Lewiston-Clarkston area on water quality conditions in the Lower
Granite pool.
The minimum flows during low power demand periods, approximat-
ing 1,000 cfs for a period of several hours, will tend to permit the
residual wastes to accumulate in a concentrated form around the

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61
and little opportunity for mixing. It is anticipated that the
higher flows which will accompany power-peaking operations will
tend to provide some longitudinal mixing of such pockets of wastes;
however, this cannot be predicted with any degree of accuracy. For
this reason, it may be necessary to maintain minimum flows in excess
of those now contemplated. There have been instances where such
accumulations of waste have moved downstream in a more or less un-
diluted slug. If this condition should prevail in the Lower Granite
pool, it could be possible for the dissolved oxygen to be completely
depleted in these pockets of pollution.
There is also the possibility of reservoir stratification with
low dissolved oxygen concentrations in the deeper waters. If this
condition should prevail in Asotin reservoir with releases from
these depths only, there will be no opportunity for reaeration in
Lower Granite pool. Such a situation would have a very serious
effect on the waste assimilative capacity of the pool. Unless
future upstream power installations are planned to provide for the
necessary flexibility in operation to offset these potential damages
to water quality, they can seriously interfere with practically all
other anticipated water uses. Fortunately, it will be possible to
study some of these factors, especially waste diffusion and stream-
flow patterns in the Lower Granite pool at various flow rates under
natural streamflow conditions before the Asotin Dam is constructed.
Such studies should serve as a valuable guide in the design and

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62
The power-peaking operations of Lower Granite, Asotin, Dworshak,
and proposed Penny Cliffs Dam may create hydraulic conditions where
discharges from Asotin Dam may cause a backflow into the Clearwater
arm of the impoundment. As previously stated, the intake for the
Lewiston surface water supply is located at River Mile 2.6 in the
Clearwater arm of the impoundment, and reversal of flow in this
channel could carry Snake River water up to the intake. Under these
conditions, it would be possible also for the backflow to carry the
waste discharges from the Potlatch Forests, Inc., and those from the
City of Lewiston upstream to the city water intake. For these rea-
sons and because of the likelihood of objectionable algae growths
in the impoundment which could create serious taste and odor prob-
lems in the public water supply, the intake for the Lewiston city
water supply should be relocated at a point above the existing
Washington Water Power Company dam.
Furthermore, since the Clearwater arm will undoubtedly be used
extensively for recreational purposes, it would be desirable for all
waste discharged to be located far enough below the confluence of
the Clearwater and Snake Rivers to prevent highly colored pulp mill
wastes and municipal sewage treatment plant wastes from being car-
ried into this area.
As previously stated, settleable solids will settle to the bottom
of the impoundment. It is unlikely that the higher flows during power-
peaking operations will re-suspend this material and move it out of

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organic matter on the bottom of the reservoir with its attendant
detrimental effects on all water uses, it is imperative that the
highest possible degree of settleable solids removal be provided

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FUTURE WATER USES
With the advent of a slack-water pool at the doorstep of a
heavily populated area, it is a certainty that water-oriented
recreation will expand very rapidly.
Water-contact sports such as swimming, water skiing, and so
forth, demand a high quality water, both from an aesthetic and a
bacteriological standpoint. It is likely that these activities
may take place throughout the pool, including the immediate
vicinity of waste outfalls. For this reason, the maximum possible
diffusion of such wastes should be planned for. It will also be
imperative that very effective and efficient disinfection of sewage
and animal waste treatment plant effluents be accomplished.
As noted previously, the present bacterial quality of the
Snake River downstream from the waste outfalls in the area does
not meet recommended bathing water standards even though chlorina-
tion of all sewage treatment plant effluents is practiced. The
reliability of bacterial control by chlorination of primary sewage
treatment plant effluents is subject to considerable variation.
This is due largely to the rapidly changing flows and organic con-
tent of such effluents, making it extremely difficult to adjust
the chlorine dosage to meet the variable chlorine demand of the
wastes. For this reason, where continuous and effective disinfec-
tion of sewage effluents is required, it is usually considered

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65
chlorination more effective and more reliable. This added factor
of safety is especially important in this situation where high
quality water uses are located so near to sources of pollution.
For this reason the water pollution control agencies of the two
states believe that secondary treatment followed by disinfection
will undoubtedly be required to adequately protect all essential
water uses. The Public Health Service concurs in this evaluation.
There is also a possibility that the color and foam from the
pulp mill wastes may create undesirable aesthetic conditions, if
the point of discharge is in close proximity to recreational areas.
This can be minimized to some extent by accomplishing the maximum
diffusion and dilution of wastes within the reservoir.
There is a possibility that hydraulic model studies would
provide information concerning the effectiveness of outfall dif-
fusers and the degree to which longitudinal mixing may be accom-
plished under the high streamflow conditions resulting from power -
peaking operations.
With the economic development of the area, domestic and indus-
trial waste production will increase during future years. It appears
reasonable that pulp production may be expected to expand from 700
to 1,000 tons per day. Comparable increases in raw wastes may be
expected from other waste sources. Therefore, it is assumed that
within the next fifty years the raw waste loads from this area may

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66
waste loads reaching the stream since improved waste treatment
practices should result in greater removals than is the case at
this time.
It may be reasonably expected, however, that the amount of
organic matter reaching the stream as residual wastes from waste
treatment facilities may have a population equivalent of from
600,000 to 700,000. This load would have the effect of exerting
slightly less than one milligram per liter demand on the dissolved
oxygen resources of the stream at an average daily flow of 25,000
cfs.
Under existing streamflow conditions, with the accompanying
high reaeration rate, the oxygen resources will be quickly restored.
However, with the impoundment, this demand will be felt in the
lower portions of the pool and will act to further depress dissolved

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BIBLIOGRAPHY
1.	C. H. Yih, "On the Flow of a Stratified Fluid." Proceedings,
3rd National Congress of Applied Mechanics, pp. 857-861. 1958.
2.	Walter R. Debler, "Stratified Flow into a Line Sink." Journal of
the Engineering Mechanics Division, Proceedings of the American
Society of Civil Engineers, vol. 2093, pp. 51-66. July 1959.
3.	Donald R. F. Harleman, "Testimony Before the Federal Powpr
Commission, Projects 2243 and 2273." Vol. 75, pp. 14,022-14,043.
Washington, D. C., July 20, 1961.
4.	Walter Duncan, Donald R. F. Harleman, and Rex Elder, "Internal
Density Currents Created by Withdrawal from a Stratified
Reservoir." Division of Water Control Planning, Tennessee Valley
Authority, and Walla Walla District, U. S. Army Engineers, Norris,
Tennessee, February 1962. 19 pp.
5.	Wayne V. Burt, "Preliminary Study on the Predicted Water Changes
of the Lower Snake River due to the Effects of Projected Dams and
Reservoirs--Part I: Forecasting Water Temperature Changes Due to
Flow through Intermediate Depth Reservoirs." Corvallis, Oregon,
November 1963. 27 pp.
6.	M. A. Churchill, "The Prediction of Stream Reaeration Rates."
Journal of Sanitary Engineering Division, American Society of
Civil Engineers, July 1962, pp. 1-46.
7.	D. J. O'Connor and W. E. Dobbins, "The Mechanics of Reaeration
in Natural Streams." Transactions. ASCE, vol. 123, pp. 641-684.

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APPENDIX
PRESENT AND POST-IMPOUNDMENT
WATER QUALITY CONDITIONS
SNAKE AND CLEARWATER RIVERS
LEWISTON, IDAHO-CLARKSTON, WASHINGTON AREA
The tables appearing in the Appendix are a record of all analyses
carried out during this study, except the bacteriological analyses
The 1963 bacteriological data are not reported because of
unaccounted-for discrepancies. However, data collected during the
joint State-PHS study in July 1964 are reported and are considered

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