WORKING PAPER NO. 21
COLUMBIA RIVER BASIN PROJECT
For Water Supply and Water Quality Management
PRELIMINARY INVESTIGATION OF MUNICIPAL AND INDUSTRIAL
WATER SUPPLY AND STREAM QUALITY CONTROL REQUIREMENTS
AND BENEFITS ASSOCIATED WITH MULTIPLE-PURPOSE STUDIES
OF THE PROPOSED SCOGGINS RESERVOIR, TUALATIN PROJECT,
WASHINGTON COUNTY, OREGON
DATE: March 1962
Prepared by
Reviewed by
Approved by
DISTRIBUTION
Project Staff
Cooperating Agencies
General
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Region IX
Division of Water Supply and Pollution Control
Room 570 Pittock Block
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This working paper contains preliminary data and information
primarily intended for internal use by the Columbia River
Basin Project staff and cooperating agencies. The material
presented in this paper has not been fully evaluated and
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REPORT ON TUALATIN RIVER BASIN STUDIES
Preliminary Investigation of Municipal and Industrial
Water Supply and Stream Quality Control Requirements
and Benefits Associated with Multiple-Purpose Studies
of the Proposed Scoggins Reservoir, Tualatin Project,
Washington County, Oregon
Prepared at the Request of and
in Cooperation with the Area Engineer,
Lower Columbia Development Office,
Bureau of Reclamation, Salem, Oregon
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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ACKNOWLEDGEMENTS
This investigation and study was aided materially by officials of the
cities of Forest Grove, Hillsboro, Beaverton, Tigard, and Oswego;
the Aloha-Huber Water District; the Oregon State Board of Health and
Oregon State Sanitary Authority; and the Salem Area Office, Bureau
of Reclamation. Information furnished in the references listed below
is also acknowledged.
1. U. S. Geological Survey, Water Supply Papers, Part 14
2. U. S. Geological Survey and State Engineer of Oregon, Preliminary
Report on the Ground Water Resources of the Tualatin Valley, Oregon,
January 1956
3. U. S. Weather Bureau, Clixnatological Data, Annual Summary Sheets
4. U. S. Department of Agriculture, County Soil Survey Reports
5. U. S. Department of Agriculture, Columbia Basin Agricultural
Program Report, 1954
6. L. P. Hintze, Geologic Map of the State of Oregon, Compilation
7. U. S. Bureau o£ Reclamation, Tualatin Project, Oregon, Proposed
Report, November 1956
8. U. 8. Census o£ Agriculture, 1959
9. U. S. Census of Population, 1950
10. U. S. Census of Population, 1960
11. U. S. Census of Business, 1958
12. Oregon State Department of Employment, Oregon Covered Employment
and Payrolls. 2nd Quarter, 1960
13. Oregon State Department of Employment, Area Occupational Index
for Washington County, March-July 1959
14. Portland Metropolitan Planning Commission, Population Prospect,
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IS* Oregon State Department of Planning and Development, 1961 Registry
of Oregon Manufacturers
16. Oregon State Water Resources Board, Gaging Station Compilations
17. Stevens and Thompson, Municipal Water Supply from Coast Range
Reservoirs for the Cities of Forest Grove and Hillsboro. Oregon. 1961
18. 8tevens and Thompson, Municipal Water Supply from Scogflin9 Reservoir.
Washington County. Oregon. 1957
19. Stevens and Thompson, A Tri-County Master Plan of Sewerage for
Metropolitan Areas of Clackamas. Multnomah and Washington Counties.
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TABLE OP CONTENTS
Pane
INTRODUCTION . 1
SUMMARY 3
CONCLUSIONS 6
TUALATIN RIVER WATERSHED 8
LOCATION AND SIZE 8
PHYSIOGRAPHY 9
GEOLOGY AND SOILS 10
COVER VEGETATION II
CLIMATE 12
HYDROLOGY 13
PROPOSED PROJECT 17
STUDY OBJECTIVES AND PROCEDURES 18
PRELIMINARY ECONOMIC REPORT AND ESTIMATE
OF GROWTH. 1960-2010 21
INTRODUCTION , 21
Purpose of This Analysis 21
Definition of the Area ..................... 21
8tudy Period 21
Limitations of This Analysis 21
PRESENT ECONOMIC BASE 22
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TABLE OF CONTENTS (CONTINUED)
Zifi£
Land Use 23
Water Uses 24
Population . 24
The Present Industrial Pattern 26
ESTIMATED GROWTH. 1960-2010 ..... 28
Factors Influencing Future Growth . 28
Future Population 30
Future Land Use 33
Potential Water Uses . 35
PRESENT WATER SUPPLY .... ..... 37
GENERAL . . . . 37
GROUND WATER - MUNICIPAL AND INDUSTRIAL . . . , . 38
SURFACE WATER - MUNICIPAL AND INDUSTRIAL 38
PORTLAND BULL RUN SUPPLY 39
FUTURE WATER SUPPLY 40
PRESENT WASTE SOURCES 42
FUTURE WASTE SOURCES 45
WATER QUALITY 46
QUALITY CONTROL . . . . . * . 48
DISCUSSION ....... 49
GENERAL ........... . ..... 49
WATER SUPPLY 51
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INTRODUCTION
This report represents a preliminary examination of present and future
municipal and industrial water supply and stream quality control needs
in the Tualatin River Basin with particular reference to the feasibility
of providing storage and/or flow regulation to serve these needs in
the Bureau of Reclamati6n's proposed Scoggins Reservoir of the Tualatin
River Project, Washington County, Oregon.
Request for the investigation and report was made by the U. S, Depart-
ment of the Interior, Bureau of Reclamation, Lower Columbia Development
Office, Salem, Oregon by letter dated August 14, 1961 asking for
assistance in carrying out provisions set forth in the Water Supply
Act of 1958 (Title III, P.L. 500, 85th Congress) for implementation
of water supply programs and for an evaluation of needs, release
requirement and benefits applicable to flow regulation for control of
stream quality as provided in the Federal Water Pollution Control Act
Amendments of 1961.
The report Identifies uses and sources of water in the Tualatin Valley
area and describes sources of waste, waste treatment practices and
the effect of waste effluents and other materials on the quality of
specific reaches of the Tualatin River.
Included also is a preliminary economic evaluation of the area, the
findings of which have formed the basis for the projected municipal
and industrial water demands and waste and land use effects on stream
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2
Sinqe this investigation has been made in advance of study schedules
planned for establishment of a Comprehensive Water Supply and Water
Quality Control Program for the Columbia River Basin, certain materials
presented must necessarily await later confirmation.
1C is believed, however, that the needs for municipal and industrial
water supply storage as described, the low flow releases for quality
control indicated, and the basis for benefit computations as defined,
possess a degree of finality suitable for preliminary project planning
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SUMMARY
1. The population o£ the Tualatin Basin is expected to increase from
92,000 in 1960 to 207,000 and 500,000 by the years 1980 and 2010,
respectively.
2. It is expected that most of the future growth in the Tualatin
Basin will take place westward of the "urbanized" development extending
out from Portland.
3. "Urbanized" development by the year 1980 is expected to extend to
a line roughly connecting Tualatin, Bull Mountain, Orenco, and North
Plains and by the year 2010 is expected to extend to a line roughly
defined by North Scholls, Farmington, Hillsboro and North Plains.
4. Industrial development Is expected to consist of electronics-
scientific and food-processing type industries.
5. It is estimated that, by the years 1980 and 2010, respectively,
145,000 and 350,000 persons will be served by waters taken from
Tualatin Basin sources and that 62,000 and 150,000 persons will be
served by the Portland Bull Run supply.
6. Surface water sources within the Tualatin Basin are expected to
serve approximately 60,000 and 160,000 persons by the years 1980 and
2010, respectively.
7. The annual demand for municipal and industrial water supply from
surface sources within the basin is expected to be approximately 14,000
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8. It is reported that surface supplies in the Hillsboro-Forest Grove
area have experienced difficulties in availability of supply in recent
years.
9. It is estimated that, by the years 1980 and 2010, respectively, a
total of 407,000 and 770,000 population equivalents of domestic, muni-
cipal, and industrial wastes will be produced in the Tualatin River Basin.
10. Assuming that 75 percent of the population within the basin will
be served by sewage collection systems by the year 1980 and 90 percent
by the year 2010 and that municipal and industrial waste treatment
will accomplish 85 percent removal of the biochemical oxygen demand,
approximately 53,000 and 107,000 population equivalents of residual
waste, respectively, will be received in Tualatin Basin water courses.
11. Sufficient natural stream flows are not continuously available
to adequately assimilate and dilute future residual waste materials
expected to be received in the Tualatin River.
12. Minimum stream flow requirements to achieve water quality objec-
tives for recreation and protection of land values from the Scoggins
site to river mile 38 (below the mouth of Rock Creek) of the Tualatin
River for the year 1980 range from a winter flow of 93 cfs to a summer
flow of 130 cfs and for the year 2010 from a winter flow of 194 x:fs
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5
13. Minimum stream flow requirements to achieve quality objectives
for recreation and protection of land values between river mile 38
and the mouth of the Tualatin River for the year 1980 range from a
winter flow of 57 cfs to a summer flow of 80 cfs and for the year
2010 from a winter flow of 126 cfs to a summer flow of 175 cfs as
shown in Figure 5 of the report.
14. Flow regulation in the Tualatin Basin, in addition to assisting
in the control of stream quality within the basin, would be expected
to provide improvements in downstream reaches of the Willamette River
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CONCLUSIONS
1. At the rate of growth anticipated and with the additional demand
for municipal and industrial water supply expected, it is apparent
that early development of additional sources of supply is needed in
the Tualatin Basin.
2. The future municipal and industrial water supply requirements to
be satisfied by surface waters will involve provisions for storage
to supplement various municipal and industrial water rights being
exercised at the present time as well as to supplement the shortages
in natural yields that are expected to occur.
3. The annual benefit assignable to the inclusion of future municipal
and industrial water supply as one of the multiple functions of the
Tualatin Project would be equivalent to the annual cost of developing,
on a local level and in the absence of the project, the most likely
sources of surface supply available.
4. Benefits assignable to the proposed Scoggins Reservoir for quality
control by low flow augmentation would be equivalent to construction,
operation, and maintenance costs involved in providing similar regula-
tion by single-purpose means as, for example, from the Gaston, McKay,
Gales, or Scoggins Creek sites, whichever would be the cheapest.
5. Flow requirements for quality control between the Scoggins site and
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municipal and industrial return flows and releases from storage.
Benefit would apply to all atorago which make tip the required flows
for water quality control.
6. Inasmuch ae waste effluents would have been received in upper
reaches of the Tualatin River» diversions may be made downstream front
the mouth of Bock Creek without loss to the control of quality providing
the loner rate of flow required downstream ia maintained.
7. In event that, upon allocation of storage for the various project
purposes* any part of the requirements for municipal end industrial
water supply or quality control cannot be net with the Scoggins Reser-
voir, Tualatin Project, it is assumed that these will be incorporated
in future development planning or will be satisfied by local or other
means*
8. Comments on factors associated with the final formulation of the
project will be made at the time of formal interagency review.
9. In view of the multiplicity of beneficiaries and extent of local
participation included in the achievement of water quality goals in
this region, benefits attributable to provisions for water quality
control as & project function atre believed to be of public interest
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8
TUALATIN RIVER WATERSHED
LOCATION AND SIZE
The Tualatin River Sub-basin occupies the northwestern part of the
Willamette Basin in Washington County, Oregon, and has a total area
of 710 square miles. The Tualatin empties into the Willamette by
two- routes - one a diversion via Lake Oswego with an outlet about
seven miles above the center of the city of Portland, the other by
its natural channel seven miles further above Portland at the town
of West Linn southwest of Oregon City.
Rising in the southwest corner of Washington County in the Coast Range,
the Tualatin flows east about eight miles to Cherry Grove, where
Roaring Creek enters. Some six miles further east it leaves the
foothills and enters its broad valley at Gaston, where Wapato Creek
enters, and turns north. A mile downstream, Scoggins Creek enters,
and about three miles beyond, Gales Creek. Meandering eastward in the
flat valley, it is joined by its major tributary, Dairy Creek, near
Hillsboro. Four or five miles further, it is joined by Rock Creek,
and turns south for about eight miles to Scholls. Then it turns east
into a narrower valley through the hills south of Portland some twenty-
three miles to its confluence with the Willamette. The Lake Oswego
Canal diversion is about six miles above the mouth of the Tualatin.
The basin is roughly triangular in shape. It drains the basalt hills
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side of the Coast Range with its sedimentary and metamorphic rocks,
the old valley fill in the center of the basin, and the basalt hills
along the Willamette River southwest of Portland.
PHYSIOGRAPHY
Northwest of Portland the basin boundary lies at elevations—^of 2,000
feet or more, reaching 2,215 feet atop Green Mountain in the northern-
most corner. To the southwest along the western rim of the basin in
the Coast Range, elevations range from 2,000 feet to the high point
of 3,461 feet atop Saddle Mountain. In the Chehalem Mountains on the
south side of the basin, elevations at the rim range from 800 to 1,600
feet. At the confluence of the Tualatin with the Willamette, the
elevation is only a little over 50 feet. The broad valley in the center
of the basin occupies elevations of 150 to 200 feet.
Topography around the rim is fairly rough. Valley walls are steep in
the mountain areas, with slopes up to 40 percent common. Sunday Creek
and the main Tualatin in the headwaters drop 400 feet in two and a half
miles, and another 400 feet in the next four miles. Below Gaston, the
channel gradient is very flat, dropping only about 50 feet in twelve
miles. Through the 50 miles of its course in the flat valley below
Gaston, the Tualatin has numerous meanders and oxbow loops.
Along the north side of the basin the hills trend from southeast to
northwest, rising highest at the northernmost point. On the west side,
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the Coast Range trends north to south, with the highest elevations
about in the center. Dairy Creek and its tributaries, McKay, East
Dairy, West Dairy, Cedar, and Council Creeks drain the north and
northwest parts of the basin. Rock Creek and Fanno Creek drain the
Portland suburban area in the northeastern part of the basin. Gales
Creek, Scoggins Creek, and the upper Tualatin drain the western part.
Wapato Creek enters from the south at Gaston, and McFee, Chicken,
and Rock Creeks drain the low Chehalero Mountains across the southern
side of the basin.
GEOLOGY AND SOILS
Along the northeastern edge of the basin the geologic formations are
made up of Pliocene and Miocene volcanic rocks, principally basalt.
These formations support medium to heavy-textured soils generally of
a reddish color. Subsoils are often clayey and show a tendency to
slump and slide. Similar geology and soils are found in the eastern
Chehalem hills and south of Portland around the lower course of the
Tualatin River.
The lower hills on the western side of the basin are also in the Miocene
volcanics, but the main body of the Coast Range is made up of Eocene
and Oligocene marine sedimentary rocks. These are primarily fine-
grained sandstones with occasional interbedded shales. Soils are
heavy in texture, red to brown in color, and classified generally as
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The central flat portion o£ the basin, the Tualatin Valley, is made
up of old glacial debris and alluvium. Soils are deep and medium to
heavy-textured. Soil color is brown or black where swampy conditions
have led to development of peaty soils high in organic matter.
The U. S. Department of Agriculture Land Use Capability Classification^
shows the uppermost third of the basin land - the hill and mountain
areas - as suitable primarily for forestry. The valley floor, on flat
to gentle slopes, is shown suitable for agriculture with few or no
limitations Buch as erosion hazard. The lower hill areas in inter-
mediate position around the edge of the valley are suitable&r orchard
or grazing use with proper soil management because of a high erosion
hazard. Present land use follows the capability classification fairly
well. However, a large portion of the northeastern part of the basia
is being converted to suburban residential area.
COVER VEGETATION
The upper elevations of the Tualatin Basin, about a third of the area,
support a forest cover in which Douglas-fir is the dominant species.
Associated species include western hemlock and western red cedar.
Practically all of the old growth forest has been cut and most of the
forest area now supports vigorous stands of young second-growth
Douglas-fir. However, there are scattered patches of hardwood brush
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here and there where for one reason or another regeneration of the
conifers has not been successful.
In low-lying swampy areas and along streams the hardwoods are dominant.
These include red alder, Oregon ash, bigleaf maple, Cottonwood, and
willows. Some of the drier sites on the lower hills (as in the Chehalem
Mountains) support occasional stands of Oregon white oak.
Most of the lower hills are cultivated, some areas to orchards, some
to grain and hay crops. Other parts of the hilly fringe of the valley
have been, cleared for pasture. All of the main valley is cultivated
or is in the process of suburban development.
CLIMATE
The climate is moderate, strongly influenced by nearness of the Pacific
Ocean sixty miles to the west across the relatively low Coast Range.
Winters are wet and summers dry. Prevailing winds are westerly, from
the ocean. Surface winds are usually light to moderate.
Temperatures recorded at Forest Grove, a long-term station near the
center of the Tualatin Basin, range from a maximum of 106°F to a minimum
of -15°F. Such extremes are rare; average July temperature is 66°F,
and average January temperature 37°F. The frost-free growing season
ranges from 160 to 200 days. Both summer hot periods and winter cold
periods are of short duration.
Rainfall in the Coast Range headwaters of the Tualatin River reaches
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floor which gets from 35 to 50 Inches annually depending on aspect and
local topography. Days with measurable rain amount to about 160 per
year. Climatologic averages!/for Forest Grove are as follows:
Month
Item JFMAMJJASOND Annl.
Precip.,in. 7.4 6.1 4.8 2.7 1.5 1.3 0.4 0.5 1.7 3.3 7.5 8.3 43.9
Snowfall,in. 8.7 4.0 0.6 0 0 0 0 0 0 0 0.3 2.5 16.1
Temp., °F 37.1 40.6 44.8 49.6 55.5 60.9 65.9 66.5 60.2 52.2 44.2 38.9 51.4
Max., °F 43.5 48.4 55.0 61.6 68.4 74.8 82.3 83.2 73.8 64.0 52.2 44.9 62.7
Min., OF 30.7 32.6 34.8 37.8 42.7 47.0 49.6 49.8 46.1 40.3 36.2 32.9 40.0
Humidity is fairly high in winter, moderate in summer. Extreme low
humidity accompanies the occasional east winds in fall and winter. Sun-
shine averages about half the total possible. Night and morning fogs
are fairly common in late fall and winter. Evaporation rates are moderate,
averaging about 25 inches for the six-month growing season, and trans-
piration is moderate except during the hot dry months of July and
August when drafts on ground water are heavy.
HYDROLOGY
The stream flow regime of the Tualatin River follows that of the rain-
fall, high in winter, low in summer. Snow storage rarely builds up to
three feet and is not great enough in the Coast Range headwaters to
carry over significant amounts of water from winter to spring.
The Tualatin itself is gaged at several places, and the tributaries
Scoggins, Gales, Dairy, and McKay Creeks are or have been gaged. The
major diversion to the Lake Oswego Canal is also gaged.
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AVERAGE STREAM FLOwl^ CFS, TUALATIN BASIN
Stream, Station
Drainage Area
0 N
M A M J J A S Annual
E. Fk. Dairy Crk.,
Mountaindale,
43 sq. mi.
McKay Creek,
North Plains,
29 sq. mi.
Scoggins Creek,
Gaston,
44 sq. mi.
Gales Creek
Forest Grove,
66 sq. mi.
Tualatin River,
Gaston,
51 sq. mi.
Tualatin River,
Dilley,
133 sq. mi.
Tualatin River,
Farmington,
568 sq. mi.
Oswego Canal
Tualatin River,
Willamette,
710 sq. mi.
23 103 206 219 304 191 110 63 32 20 13 13 107
10 76 177 176 198 114 57 24 12 5 3 3 71
33 158 315 327 361 242 141 68 32 14 8 8 141
55 273 508 547 589 388 208 100 48 25 16 16 230
64 267 452 449 481 330 200 95 45 21 13 14 201
91 436 903 913 1077 680 401 185 79 31 18 21 400
212 1074 2929 3400 3942 2473 1358 565
59 49 124 91 93 78 64 50
243 98 50 62 1356
53 55 54 58 69
172 1093 3023 3772 3751 2751 1658 641 277 94 32 43 1433
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Two stations one on Gales Creek and one on West Fork Dairy Creek,
•were not included because of their short periods of record.
Recorded maximum and minimum flows are as follows, according to State
Water jiesources Board compilations:
Maximum Minimum
Station
cfs
Date
cfs
Date
E.Fk.Dairy Crk., Mtndale
1,420
Feb.'49
7
1944
MclCay Crk., N. Plains
2,100
Feb. '49
0.4
1951
Scoggins Crk., Gaston
5,320
Dec.'55
0
46-47
Gales Crk., Forest Grove
6,410
Feb. *49
3.1
1952
Tualatin R., Gaston
8,170
Dec. '55
0.2
51-52-f 3
Tualatin R., Dilley
13,200
Dec. '55
0.4
1951
Tualatin R., Willamette
23,300
Dec.«33l/
3
1929V
1/ Dec.*37 and Dec.f55 within 10 percent of this total, also.
2/ This is the only 30-year record station; others are only 11 to 19 yeare.
Nineteen of twenty peak flows occurred in December or January or February,
and one in April. The dates of greatest peak flows coincide with the
dates of major floods, as might be expected. December 1933, December 1937,
February 1949s December 1955 and December 1960 all marked major flood
occurrences. Some cropland areas are Inundated nearly rwry year bccausr
of inadequate channel capacity through the flat valley floor.
Extreme minimum flows are unfortunately far more common. Irrigation anH
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low flow. For the Tualatin near its mouth, including diversion Lo
Lake Oswego monthly flows have been below 100 cfs 20 percent of the
time in July, 90 percent in August, 80 percent in September, and
30 percent in October.
The valley fill, largely clay and silt, extends to 900 feet in depth
below the valley plain. It contains some sand strata, but very few
gravel beds. The essentially horizontal sand strata are aquifers, and
are found at depths of 40, 100, 200 and 300 feet. The Columbia basalts
underlying the basin also are aquifers. Springs flow from the base of
this and other lava formations in the basin. The water table stands
at elevations close to 200 feet in most of the basin, not far below
the surface of the valley plains. Present rates of pumping have not
caused any general decline in the water table, and recharge from
precipitation and from cross-valley streams is sufficient to compensate
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PROPOSED PROJECT
The project area comprises an estimated 17,000 irrigable acres in the
Tualatin River Basin, the center of which is located about 15 miles
west of the Portland city limits. Water for irrigation would be
provided from storage in the Scoggins Reservoir together with natural
stream flow.
In addition to provisions for irrigation, project studies involve
storage for flood control, fish and wildlife, municipal and industrial
water Bupply, quality control by flow regulation and recreation.
The site of the proposed Scoggins Dam is about five miles upstream
from the mouth of Scoggins Creek which enters the Tualatin River
approximately five miles south of Forest Grove and ten miles south-
west of Hillsboro, Washington County, Oregon. Approximately 61,000
acre-feet of water would be stored in this area to serve the various
anticipated purposes.
The municipalities of Forest Grove, Hillsboro and Beaverton have
indicated support of the project for municipal and industrial water
supplies. The Tigard Water District has expressed interest in an
additional source of water supply and the Lake Oswego Corporation is
desirous of obtaining releases from storage to maintain sanitary
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STUDY OBJECTIVES AND PROCEDURES
18
The objective of this study and report is to establish, by use of
existing and projected data, preliminary conclusions on the feasibility
of providing in the Scoggins Reservoir, storage space for municipal
and Industrial water supply and storage and/or flow regulation for
stream quality control and to enumerate where practicable the benefits
that would accrue to the project with these purposes included.
Existing sources of municipal and industrial water supply are examined
and with projected demand data, the adequacy or suitability of these
sources in meeting future demands is estimated. Where warranted, alter-
nate supplies to either replace or supplement the developed sources
are identified and explanations are given on procedures to be followed
for determining whether use of the Federal project, in lieu of other
development possibilities, would be feasible or justified and if so,
on what basis benefits may be derived.
Flow regulation requirements relate to the control of specific quality
parameters and achievement of specific objectives as governed by the
beneficial uses enumerated and the particular quality required to
satisfy these uses. Whereas flow regulation for quality control is
regarded as a supplement to waste treatment or other measures of control
at the source, computations involving needs for additional waste assim-
ilation capacity and dilution in the stream reflect provisions for ^euch
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te suspected of contributing significantly to reduced stream quality,
i.e., nutrient or mineral enrichment (excessive slime and algal growth),
toxicity, turbidity, bio-chemical oxygen demand, etc., a statement to
this effect is included with an explanation of the intent of the Public
Health Service to conduct studies and surveys at a later date on which
to base recommendation for possible further means of control.
Inasmuch as flow regulation requirements for quality control include
allowances for reasonable degrees of waste treatment, the alternate
method and hence, the benefit assignable to the storage associated with
such regulation is considered equivalent to const truetion, operation
and maintenance costs involved in the development of the least costly
single-purpose alternate impoundment structure so designed as to
provide the recommended regulation. Although, for example, such alter-
nates as waste distillation or underground disposal would accomplish
similar control, these methods are not at this time considered to be
feasible or equivalent alternates. Annual benefits assignable to flow
regulation for quality control, therefore, may be based on amortized
costs plus annual operation and maintenance expenses involved in
achieving similar regulation by the single-purpose impoundment and
release method.
As it may not always be possible in a given multiple-purpose project
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recommended quality objectives, a range of stream flows showing relative
degrees of control are prepared from which a selection of benefits
based on the extent of shortages and the relative protection afforded
the stream use or values may be determined. Unless for reasons of
practicality or physical limitations any portion of the recommended
objectives cannot be achieved by a given project, It is generally assumed
that such deficiencies would be incorporated In the planning of future
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PRELIMINARY ECONOMIC REPORT AND
ESTIMATE OF GROWTH, 1960-2010
INTRODUCTION
Purpose of This Analysis
This analysis is intended to provide a preliminary estimate of the
economic potentials and a broad guide to the anticipated growth of
the subject area.
Definition of the Area
The Tualatin River drainage basin conforms approximately to the
boundaries of Washington County, and for purposes of this analysis,
the county has been used as the unit of study. In terms of area,
the small departures of the physical basin boundary fropi the political
county boundary are roughly offsetting. In terms of population, a
small but urbanized area in southwestern Multnomah County which is
part of the Tualatin Basin is excluded by using the Washington County
boundary. The mouth of the Tualatin River also lies outside Washington
County. However, the convenience and accuracy of using available
statistics and existing forecasts, all on a county basis, and the
impracticality of attempting estimates for such small fringe areas,
make use of the county boundary advisable.
Study Period
The study period is the 50-year period 1960-2010 with an interim point
at 1980.
Limitations of This Analysis
Two limitations apply to this study. The first is that it is intended
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growth. Subsequently, in connection with the Columbia River Basin
Project for Water Supply and Water Quality Management, an analysis will
be made on an industry-by-industry basis of the growth potential in
the various sub-basins. At that time, this preliminary estimate will
be reviewed, and revised if necessary.
The second limitation is that this study is intended for use particu-
larly in assessing future water needs. Emphasis has been placed on
the analysis of those industries which make heavy demands upon the
water resource. Other industries have been considered only insofar
as they may have a significant effect on future population. For this
reason, this study is not submitted as a detailed industrial forecast.
PRESENT ECONOMIC BASE
Geography of the Study Area
The Tualatin River Basin, which, for purposes of this analysis, is
equivalent to Washington County, is located in the northwest corner
of the Willamette Valley. It consists of a broad, fertile valley
floor almost entirely surrounded by ranges of hills and mountains.
The county is about 35 miles from east to west and about 30 miles from
north to south.
Rainfall is about 35 to 50 inches in most of the Tualatin River Basin.
At Forest Grove, average January temperature is 37 degrees and average
July temperature 66 degrees. The growing season in the Basin, the
time between the last occurrence of 32-degree temperature in spring
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23
The valley floor supports a mixed agricultural economy, including
dairying, grains and vegetables, and the hillsides are used for orchards.
Land Use
According to a 1959 survey by the Oregon State Conservationist of the
U. S. Department of Agriculture, the area of Washington County was
distributed among the following uses:
Acres,
Land Use
Thousands
Forest and wooded
249
Farms and cropland
146
Urban and built-up
44
Pasture and range
6
Federal land
12
Water
1
Total Acreage in County
458
The "urban and built-up" classification includes roads, airportB,
parks, and commercial, industrial and residential uses. The bulk of
this is in the eastern portion of the county.
More than 11,000 of the 12,000 acres of federal land is U. S. Bureau
of Land Management timber land.
At the time of the 1959 Census of Agriculture, there were 106,000 acres
of harvested cropland in the county. This was a decline from 113,000
in 1954. Irrigated acreage declined from 17,000 in 1954 to 15,000 in
1959. The number of farms declined from 3700 in 1954 to 2800 in 1959,
and the average size of farm increased from 64 to 76 acres . Nearly half
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24
Water Uses
At present, the principal non-consumptive use of water associated with
the Tualatin River is at Oswego Lake, which draws its water supply
from the Tualatin. This is an important recreational facility, not
only for the residents of Oswego, but also for the Portland Metropolitan
Area. Almost the entire shoreline of Oswego Lake is developed resi-
dentislly; 480 homes have lake frontage. Over 700 boats are licensed
to use the lake. Many other residences not on the lake have lotce-use
privileges. In addition, there is a public swimming concession which
is used by hundreds of persons on summer days.
Recreational uses along the Tualatin River itself are limited, due
to the poor quality of the water, the low flow during the summer, and
the eroded shoreline resulting from extreme variation in flow during
the year. Despite these handicaps, there are a number of public
picnicking, swimming and boating facilities along the river, testifying
to the need and demand for such facilities in the Portland Metropolitan
Area. On some summer days, several thousand persons use these public
facilities.
In addition to the public facilities, the lower reaches of the river
have over 200 residences directly on the river's shore, with private
boating and swimming facilities.
Population
Population of Washington County as of April 1, 1960 was 92,237. This
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<2?
the second highest among the state's 36 counties and exceeded only
by Multnomah's 1233 persons per square mile.
Despite its high average density, the fact that a large part of the
county's population 1b concentrated along its eastern fringe means
that most of the county area retains a predominantly rural character.
This can be seen by separating the 1960 population into the following
four parts:
Portland "Urbanized" Area population, portion in Washington County,
36,889. This was defined by the federal census to Include the con-
tiguously built-up area extending out from Portland. Beaverton,
population 5,937, is Included in this portion. This population
equalled 40 percent of the county total, though the area involved
represented less than 3% of the county's total 458,000 acres. The
density in this "urbanized" area was about 3 persons per acre in 1960.
Other Urban population, 13,860. "Urban" population is defined by the
census to include incorporated areas of 2500 or more population. Aside
from Beaverton, included in the "urbanized" portion, there are only
two other cities in this class: Forest Grove, 5628j and Hillsboro, 8232.
This population equalled 15 percent of the county total.
Email incorporated places, total population 2852. The five smaij. com-
munities included in this total equalled 3 percent of the county total.
The communities and their 1960 population are: Gaston, 320; Cornelius,
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20
Rural population. 38,636. These persons, living on farms or outside
any organized community, comprised 42 percent of the county's total
population.
The concentration of population in the eastern fringe of the county is
a result of two economic factors: (1) the function of the area as a
bedroom satellite for persons employed in Portland; and (2) the loca-
tion in the area of the large oscilloscope firm which provides over
half of total manufacturing jobs in the county.
The other two principal population concentrations (Hillsboro and
Forest Grove) contain some food products and lumber-wood products
manufacturing and provide retail service functions for the surrounding
farm population.
The Present Industrial Pattern
The economy-of Washington County differs from that of the rest of the
state in several important respects. Washington County is part of the
Portland Metropolitan Area, and many of its service functions are
performed in the core area, so that employment in service industries
is relatively low in Washington County. Manufacturing employment, on
the other hand, is significantly higher in Washington County than in
the state as a whole. Among the manufacturing industries, lumber and
wood products, so dominant in other parts of the state, provide a rela-
tively small share of employment. Specialization has developed in
electronics, with one oscilloscope firm providing more than half of all
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27
Table 1 shows how the distribution of non-agricultural employment in
Washington County compared, as of April 1960, with the distribution
in the state as a whole. The data are for '"covered employment" only
(that is, employees covered by the state unemployment compensation law)
and exclude self-employed persons.
Table 1
Covered Employment in Non-Agricultural Industries
Actual Employment by Industry in Washington County, April 1960
and Percentage Distribution in Washington County and in Oregon
Industry
Mining
Construction
Manufacturing, total
Lumber, wood prod.,
furn. & fixtures
Metal, prim. & fabr.
Machinery, non-elec.
Electr. machinery
Prof.,Scient.equip.
Transport, equip.
Food and kindred
Paper and allied
Print., publ.
Chemicals, allied
Stone, clay, glass
Apparel, textiles
All other mfr.
Trans., Comm., Util.
Wholesale Trade
Retail Trade
Fin., Ins., R.E.
All other services (x)
Government
TOTAL
Number of
Employees,
Washington
County
43
1024
5256
754
59
23
2995
284
68
511
180
110
46
68
24
134
623
347
2175
311
1002
229
Percentage Distribution
Washington State of
County Oregon
11010
.39
9.30
47.75
6.85
.54
.21
27.21
2.58
.62
4.64
1.63
1.00
.42
.62
.22
1.22
5.66
3.15
19.75
2.82
9.10
2.08
100.00
.27
5.82
34.27
18.12
2.57
1.32
1.00
.27
.99
4.12
1.76
1.25
.37
.69
1.31
.50
7.78
7.43
19.29
4.74
9.72
10.68
100.00
(x) Includes business and repair services, entertainment and recreation,
and professional services.
Source: Oregon Dept. of Employment, Covered Employment and Payrolls,
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28
ESTIMATED GROWTH. 1960-2010
Factors Influencing Future Growth
Three major factors are expected to provide the economic base for the
large population increase anticipated for Washington County. The
principal factor will be the continued development of the "bedroom
satellite" function of eastern Washington County, in relation to
Portland.
A second growth factor is expected to be the further expansion of the
electronics-scientific instrument industries which are already the
primary manufacturing activities In the county. The electronics and
scientific instrument industries got an early start in Washington
Cfcunty, and it is expected that the existing nucleus of manufacturing
facilities and skilled labor force will attract other such firms to
the area. The establishment of the Oregon Regional Primate Research
Center near Orenco will also help to attract other supporting scientific
activities. In addition to the power of attraction of existing firms,
other assets seem likely to bring new industries to Washington County.
Among these assets are the availability of large industrial sites
with room for expansion, desirable living conditions, convenient trans-
portation, industrial zoning, and a growing regional market.
A third factor which can help support the future economic base, though
it will be less important than the previous two, is the potential
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29
grows, with increasing population, it is expected that there will be
a gradual shift from grain acreage to specialty crops, suitable for
canning or freezing. The Scoggins Creek project, under consideration
by the Bureau of Reclamation, would more than double the existing
irrigated acreage in the county. This would provide additional crops
to support some expansion of the food-processing industries. This
expansion in irrigated acreage will be partially offset by the gradual
withdrawal of some agricultural land from production as urban uses
displace farming. However, in this connection, the establishment in
1962 of a "farm zone" by the Washington County Planning Commission is
expected to help sustain the agricultural base of the county. The
County Planning Commission staff believes that food processing industries
will be more willing to come into the county if land zoned for "farming"
cannot freely be converted to other uses.
The distribution of agricultural production, in terms of the value of
product, in Washington County in 1958 was as follows:
Product
of Total County .
Agricultural Products—'
Fruits and nuts
Dairy products
Eggs and poultry
Grain and hay
Vegetables
Livestock
Forage crop seeds
Miscellaneous
31
22
14
12
7
5
4
5
100
1/ Source: State of Oregon Department of Employment, Area Occupational
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30
Lumber and wood products manufacturing is less important in the county
than elsewhere in the state and is expected to remain so. Table 1
shows that, at present, lumber and wood products manufacturing provides
about 14 percent of total manufacturing employment. While significant
to the economy, this proportion is far below the state average. Present
employment in this category is not expected to increase significantly
in the future. Factors operating against any increase in employment are
the gradual decline in forest acreage as other land uses expand, the
continuing trend of increasing productivity per worker, and the fact
that most logs now processed in the county are brought in from forests
outside the county. Competition for logs is likely to result in con-
solidation of some of the small sawmills, possibly resulting in the logs
going to larger plants outside this Basin. Factors which could increase
employment are the trend toward secondary manufacturing and the develop-
ment of new products based on the timber resource, and the fact that
more than half of the total foreBt area in the county has been reforested
and is now growing a new timber crop. On balance, it appears that
employment in lumber and wood products manufacturing in this Basin is not
likely to increase significantly in the future. Establishment of an addi-
tional pulp or paper manufacturing plant in the Basin is considered
unlikely.
Future Population
It is expected that the growth rate in population of Washington County
during the Btudy period will be one of the highest in the state. Its
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Ufrwf
Pacific Northwest Watsr LaborstMl
200 South c!5th Street
Corvatlis. Oregon 97330
average and the forces that caused that rapid growth are likely to
continue to operate in the period ahead.
Projections bv the U. S. Bureau of Census for future Oregon population
indicate an accelerated growth during the period 1960-80 due to in-
migration. During the period 1980-2010, the state growth rate is
expected to decline, although it will still remain above the national
average. The Portland Metropolitan Area (which includes Multnomah,
Clackamas and Washington Counties) is expected to receive a larger
than proportionate share of the increase in state population. Growth
in the metropolitan area will result from its role as the trade and
service center for the region, from the fact that it is the only diver-
sified manufacturing economy in the region, and from the presence in
the metropolitan area of specialized transportation functions not found
in other parts of the region.
Beginning about 1940, population growth in relatively densely built-up
Multnomah County began to spill over into Washington County. At the
present time, the contiguously built-up area of greater Portland extends
farther to the east and south than it does to the west into Washington
County. Growth into Washington County was held below what it would
otherwise have been by problems of sewage disposal, by a lack of water
utilities, and by relatively less convenient access to downtown Portland.
Where these problems have been solved, growth has been rapid. Develop-
ments now planned will further overcome these handicaps, and it is ex-
pected that Washington County will represent an increasing proportion
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32
Table 2 shows projected population for Washington County, and growth
rates for the county compared with other areas.
Table 2
Projected Population and Growth Rates
for Washington County Compared with Other Areas
1920-2010
1920 1930 1940 1950 1960 1980 2010
Washington County, .
population, to nearest 26 30 39 61 92 207— 500
thousand
Percentage increase
compound annual rate,
during period ending
in year shown
Washington County
1.4
2.6
4.6
4.2
4.1-/
3.0
Oregon
2.0
1.3
3.4
1.5
2.0
1.7
U. S.
1.5
0.7
1.4
1.7
1.6
1.4
a/ A population projection for Washington County to 1975 was made In 1960
by the Portland Metropolitan Planning Commission. That projection included
high, medium and low estimates. If the growth rates in that study for
1960-75 were extended to 1980, its medium estimate would be about 6 percent
below the 1980 figure in Table 2, or about 194,000. In view of the
methodology in the two projections, it is considered that the two projec-
tions are compatible.
While it is impossible to pinpoint exactly the future location of this
increased population In the county, it is expected that most of it will
represent a further extension westward of the "urbanized" development
extending out from Portland. It is probable that the growth of the rural
population and Of the small incorporated places will be very much less
than the county average. Hillsboro and Forest Grove, on the other hand,
are likely to grow somewhat more rapidly than the area surrounding them,
as the trend toward urbanization continues. Of the total county popula-
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33
18,000 would accrue to Hillsboro and Forest Grove if their growth
rate were 4.1 percent per year, that is, equal to the county average.
These assumptions would mean that, during the period 1960-1980, about
90,000 persons would be added to the "urbanized" area along the eastern
edge of the county.
On the basis of the previous assumptions, Table 3 shows estimates of
the future distribution of population in Washington County.
Table 3
Estimates of Future Population
Distribution in Washington County
(Population figures in thousands)
1960-80
Rate of
1980-2010
Rate of
1960
Increase,
1980
Increase,
2010
Area
Pop.
%/vear
I2£i
%/vear
P°P-
Total County
92
4.1
207
3.0
500
Portion of Portland
Urbanized Area
37
6.4
127
3.6
362
Hillsboro +
Forest Grove
14
4.1
31
3.0
76
Hillsboro
8
4.5
20
3.2
51
Forest Grove
6
3.4
11
2.8
25
Five Small Incor-
porated Places
3
2.0
5
2.0
8
Rural
38
.7
44
.7
54
Future Land Use
On the basis of the population growth projected in the preceding
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34
The exact location and extent of growth in urban acreage is difficult
to predict because of possible variations in the density of develop-
ment. Depending upon a number of factors, such as subdivision regula-
tions, zoning, water and sewer utility availability, and convenience
of access, "built-up" development may range from one family per acre
to four or more families per acre. In the "urbanized" portion of
Washington County, the average density in 1960 was one family pec acre.
Some of the increase in population foreseen for Washington County will
be absorbed in the present urban and urbanized areas, increasing their
density. The rest of the population increase will result in a westward
expansion of the built-up area. It seems likely that, within the
growth framework assumed above, the "urbanized" area, which Included
about 12,000 acres at the eastern edge of the county in I960, will at
least double by 1980. Much of this increase In urban acreage may come
out of land which is at present In agricultural uses, although the
"farm zone" will tend to resist encroachment upon agricultural land.
Some decline in agricultural land will occur, although this can be
partially offset by converting to crops numerous scattered wooded areas.
It is anticipated that "urbanized" development by 1980 will have
extended to a line roughly connecting Tualatin, Bull Mountain, Orenco
and North Plains.
For the period 1980-2010, a continuation of the trends anticipated for
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35
the Tualatin River from North Scholls to Hillsboro. It is not expected
that this large area will be uniformly built-up, however, since contem-
porary trends in local planning and zoning favor a heterogeneous mixture
of agricultural, residential, recreational, and controlled industrial
uses.
On the basis of the preceding assumptions and for the purpose of this
preliminary analysis, the pattern of land use in 1980 and 2010 is esti-
mated to be as shown in Table 4. The changes assumed in Table 4 for
the period 1960-80 are generally consistent with the rate of change for
the period 1960-75 forecast by the Oregon State Conservationist of the
U. S. Department of Agriculture.
Table 4
Assumed Future Land Use
Washington County
(Areas in thousands of acres)
Land Use
1960
1980
2010
Forest and wooded
249
243
224
Farms and cropland
146
138
127
Urban and built-up
44
60
90
Pasture and range
6
4
4
Federal land (mostly forest)
12
12
12
Water surface
1
1
1
Total County, thousands of acres
458
458
458
Potential Water Uses
Because of the large future population projected for the Portland"
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36
riparian recreations along the Tualatin River will increase many fold
within the study period. Recreational demand is increasing even more
rapidly than population, because of greater leisure and higher incomes.
The potential demand for tecreational uses and facilities on the Tualatin
River will be particularly great because of the limited number of com-
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37
PRESENT WATER SUPPLY
GENERAL
Developed surface and ground water sources throughout the Tualatin
River Basin serve rural, municipal, industrial and irrigation needs
amounting to approximately 16,100 acre feet annually (excludes water
delivered to the area from the Portland Bull Run cupply). Surface
sources provide 11,900 acre feet of this supply with ground water
Bourcea providing the remainder (4,200 acre feet).
Surface and ground water produced within the Tualatin Basin serve
about 65,000 persons, eight self^supplied industries and neatly 10,000
acreB of itrigated land. Land irtigation constitutes the latgest
single use of Wdtet in the basin (10,J00 acre»feet annually). Table 5
summarizes these uses and sources.
Table 5
Tualatin River Basin
Water Uses and Sources
Ground Water
Rural domestic
Municipal
Industrial (self*
supplied)
Irtigation
Surface Water
Municipal
Industrial
Irrigation
Pop., (^Plants, (2)
Acres(3)
25,000(})
17,000'*'
8 (2)
14125(3)
20,50oW
5(2)
6,640^)
Annual
Sources Ac .Ft >
5000-6000 wells 700
17 wells - 2 spra, 1200
Wells 150
Wells, aprs. 1700
Tualatin & Tribs. 2200
Municipal systems 775
Tualatin & Tribs > 8600
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38
GROUND WATER - MUNICIPAL AND INDUSTRIAL
Developed municipal and industrial ground water supplies exist mainly
in the middle to lower portion of the Tualatin Basin. Major communities
using ground water in these areas are: Beaverton, Tigard, Sherwood,
Tualatin, Oswego and the Lake Grove Water District. Municipal ground
water supplies in upper basin areas exist only at Banks and North
Plains with the Aloha-Huber area being served only partially by ground
water. Beaverton and Oswego have water main connections with the
Portland Bull Run supply from which water is drawn continuously at
maximum capacity of the line and the Wolf Creek Water District supply
from Bull Run is supplemented by water from Johnson Spring.
According to ground water records compiled by the U. S. Geological
Survey, no appreciable decline in the ground water levels has occurred
in the major areas of municipal and industrial ground water use.
SURFACE WATER - MUNICIPAL AND INDUSTRIAL
Uses of surface water from Tualatin Basin sources occur in the following
upper basin area: Forest Grove, Hillsboro, Cornelius, Gaston, Cherry
Grove and the Aloha-Huber Water District. Hillsboro obtains its
supply from the Tualatin River and Seine Creek and Forest Grove obtains
its supply from Clear Creek and Gales Creek. Gaston, Cherry Grove,
Cornelius and the Aloha-Ruber Water District each obtains water from
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39
Table 6 lists the areas, purposes and uses of surface water as supplied
from Tualatin Basin sources.
Table 6
Tualatin River Basin
Municipal and Industrial Surface Water Supplies
Population
Use Area Served Annual Ac.ft.
Hillsboro-Cornelius
Municipal 11,000 1,480
Industrial - 450
Forest Grove
Municipal 6,000 700
Industrial - 325
Gaston, Cherry Grove 500 85
Aloha-Huber 3,000 250
Totals 20,500 3,290
It is estimated that about 45 percent of the total annual demand
shown in Table 6 occurs during the period July-October when stream
flows at the intakes become most critical. It is understood, for
example, that supply difficulties were experienced in these areas
during the dry summers of 1952 and 1956.
PORTLAND BULL RUN SUPPLY
A large portion of the suburban area along the eastern section of
the basin use the Portland Bull Run supply as serviced by the West
Slope, Metzger and Wolf Creek Highway Water Districts. Partial
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40
FUTURE WATER SUPPLY
It is estimated that, of the 92,000 persons residing in Washington
County in 1960, 70 percent were supplied by waters taken from sources
developed within the Tualatin River Basin. Assuming this percentage
to remain constant and based on projected populations previously
presented, an additional 80,000 persons will be served by these sources
by the year 1980 and an additional 285,000 persons by the year 2010.
Table 7 lists the future populations, by residence category, expected
to utilize basin sources for future water supply.
Table 7
Future Populations Expected to
Utilize Tualatin Basin Water Supply Sources
Populations
Residency 1980 2010
Rural and Rural non-farm 30,500 37,500
Urban 110,000 304,500
Small Incorporations 4,500 8,000
Totals 145,000 350,000
In event that future surface and ground water supplies are developed
in proportion to the existing populations served by each, the total
populations to be served by ground water by the years 1900 and 2010
would be 85,000 and 189,875 person^ respectively,and by surface water,
60,000 and 160,125 persons, respectively.
By virtue of the nature of industrial activity in the Tualatin Basin
water use by self-supplied industries constitutes only a relatively
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41
For purposes of computing total water requirements, therefore, the
self-supplied and municipally supplied industrial water requirements
are combined in single rates representing future municipal and indus-
trial (M&I) supply demands. Table 8 lists estimates of 1980 and 2010
reauirements by use category and supply sources for the basin.
Table 8
Future Water Supply Requirements
by Uses and Sources Within
the Tualatin River Basin
1980
Avg>1J
Avg
Annual
Annual
Use Category and Source
Pop.
gped
MGD
MG
Ac.Ft.
Rural & rural non-farm
Private walls (ground)
27,500
37
1.02
372
1,140
Urban - M&I (ground)
54,000
118
6.4
2,300
7,050
Urban - M&I (surface)
56,000
202
11.3
4,130
12,700
Small inc. and assoc*
non-farm (ground)
3,500
118
0.41
150
460
Small Inc. and assoc.
non-farm (surface)
4.000
160
0.64
235
720
Totals
145,000
19.77
7,187
22,070
2010
Rural & rural non-farm
Private wells (ground)
34,250
52
1.78
650
2,000
Urban - M&I (grotmd)
151,000
168
25.3
9,250
28,400
Urban - M&I (surface)
154,500
287
44.0
16,000
49,000
Small inc. and assoc.
non-farm (ground)
4,625
168
0.78
285
880
Small inc. and assoc.
non-farm (surface)
5,625
225
1.26
460
1,410
Totals
350,000
83.12
26,645
81,690
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42
PRESENT WASTE SOURCES
Wastes produced within the Tualatin River Basin consist of domestic
sewage, cannery wastes, slaughtering and meat packing wastes, paper-
board plant wastes, tannery wastes, milk products waste and miscella-
neous wastes such as those produced in the processing of potato chips
and dog food. In terms of five-day bio—chemical oxygen demand (B0D5)^^
it is estimated that raw domestic, municipal and industrial wastes
produced within the Tualatin Basin on an annual basis average approxi-
mately 240,000 population equivalents (PE'sJ. Wastes produced by
industrial sources contribute the greater portion of this amount.
Because of the particular nature of some of the industries in the
Tualatin Basin, seasonal variability occurs in volumes and strengths
of wastes produced. It is estimated, for example, that raw industrial
(1) BOD of sewage, sewage treatment plant effluents, industrial wastes,
or polluted waters is a measure of the oxygen i'equj to stabilize
decomposable organic matter by aerobic bacterial action. Complete
stabilization requires more than 100 days at 20°C, but such long
periods of incubation are impractical. Consequently, a much shorter
period of incubation is used. Incubation for 5 days at 20°C (BOD5) is
the recommended standard procedure. Measurements of daily BOD in time
series (long term BOD) when plotted produce a logarithmic curve from
which deoxygenation velocity constants can be computed. Use of these
values is made in computing critical dissolved oxygen concentrations
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43
wastes produced in the winter months average 124,000 population
equivalents per day and during the summer months, 172,000 population
equivalents. It is known, also, that, on a day-to-day basis, even
greater extremes can occur.
A variety of waste treatment methods and disposal practices exist
throughout the Tualatin River Basin. Septic tanks with sub-surface
disposal are employed in many areas not yet served by collection
systems. Conventional waste treatment facilities designed for the
removal of solids, reduction of biochemical oxygen demand and other
waste constituents are in existence in localities where municipalities
and sanitary districts have provided collection systems. Industrial
wastes are in some instances treated in combination with municipal
waste and in other instances industrial waste treatment is accomplished
by lagooning and/or by land disposal and crop irrigation. Not all
wastes, particularly those produced by certain industries, are treated.
Constant improvements in systems, facilities and practices, however,
are taking place generally throughout the Tualatin River Basin area.
On a basin-wide basis, it is estimated that waste treatment together
with other disposal practices accomplish removal of about 75 percent
of the biochemical oxygen demand or population equivalents produced.
Table 9 summarizes estimates of population equivalents produced and
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Table 9
Wastes Produced and Loadings
Received in Tualatin Basin Streams
Sources
Raw Waste
PE'a/day
Disposed Waste
PB'a/day
Domestic (unsewered)
48,400
... U>
Municipal and Sanitary
District (sewered)
43,600
6,100
Industrial
Summer
Winter
Avg. Annual
171,500
1*3,500
147,500
8,300
110,800
60,000
(1) Sub-surface disposal
On an average annual basis, it is estimated that, of the population
equivalents disposed to basin water courses, 86 percent are received
in streams above and including McKay Creek; 11 percent are received
in the drainage system between Fanno Creek and McKay Creek; and
3 percent are received above the mouth of the Tualatin River to and
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45
FUTURE WASTE SOURCES
It is estimated that by the years 1980 and 2010 a total of 407,000
and 770,000 population equivalents of waste per day will be produced
in the Tualatin River Basin. Assuming 75 percent of the populations
to be served by sewage collection systems by the year 1980 and 90 per-
cent served by the year 2010 and that 85 percent treatment (BOD5
reduction) of municipal and industrial wastes were achieved through-
out the basin for these years, approximately 53,000 and 107,000
population equivalents, respectively, would be received In basin water
courses.
Whereas the raw industrial wastes presently produced in the basin
exceed municipal and domestic population equivalents by approximately
3.5 times, this factor Is expected to reduce to approximately 1.3 by
the year 1980 and to 0.6 by the year 2010 as a result of rapid popula-
tion growth and trends toward dry process type industries. Table 10
summarises by reaches and river miles, the future waste loadings
expected to be received in Tualatin River Basin streams.
Table 10
Future Waste Loadings
Tualatin River
Mileage - PB's
Year 62 - 46 45 - 10 9-0
1960
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WATER QUALITY
46
According to stream sampling data collected by the Oregon State Sani-
tary Authority in July and August of 1960, four distinct depressions
in the dissolved oxygen resource of the Tualatin River were noted as
a result of the exertion of bio-chemical oxygen demanding substances
in the stream. Figure 1 shows the profiles of these effects. At the
time of sampling in July the stream flows at miles 65 and 60 were in
the order of 7 and 16 cfs, respectively, and at miles 8 and 4 were in
the order of 80 and 40 cfs, respectively (mi. 4 downstream from Oswego
diversion). Stream flows during the AugU9t sampling at miles 65 and
60 were in the order of 5 and 7 cfs, respectively, and at miles 8 and
4 were in the order of 32 and 16 cfs, respectively.
The stream conditions as described above could be expected to persist
for extended periods and at times be even more pronounced. For example,
it is found by examination of gaging records for the Tualatin River
that stream flows similar to those encountered during the sampling
can occur for more than a month's time on an average of once in ten
years. Much lower rates than those encountered during the sampling
can also occur. Table 11 lists the durations and frequency of minimum
stream flows that can be encountered in the Tualatin River.
Table 11
Duration and Frequency of Minimum
Stream Flows in the Tualatin River
Days in 10 Years
River Mile - cfs
65 35 8
30
21
14
7
1
2.0
0.8
0.5
0.5
0.2
8.0
6.0
4.0
3.0
0
22
19
18
15
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[ti
!
1
I
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47
It is appatent from the foregoing that sufficient stream flow is not
continuously available to adequately assimilate and dilute waste
materials entering the Tualatin River system. It is also apparent
that with the waste loadings expected for the future, critical stream
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48
QUALITY CONTROL
In view of the particular characteristics of waste effluents produced
in the Tualatin River Basin and the types of uses made of the stream,
flow regulation for the control of the dissolved oxygen resource of the
stream is chosen as the governing control parameter. Without knowledge
at this time of such things as the nutrient enrichment effects of
return irrigation flows on the stimulation of nuisance algae and slime
growths, regulation or recommendations for the specific control of these
effects cannot at this time be made. Studies on the effects of irrigation
return flows and possibilities for control are planned for conduct at
later date. It should be understood, however, that the extent of regu-
lation required to maintain suitable dissolved oxygen levels would
provide, by means of dilution and increased assimilative capacity,
significant control of the effects of land drainage as well as control
of the effects of residual materials not removed from wastes by known
conventional treatment means.
Figures 2 and 3 show the estimated rates of stream flow required to
achieve various levels of dissolved oxygen from the Scoggins site to
river mile 38 (Rock Creek) and from Rock Creek to the mouth of the
Tualatin River, respectively, during periods of critical loading and
maximum stream temperature for the years 1980 and 2010. Figures 4 and
5 are annual hydrographs of minimum flows recommended for maximum
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I
y
%
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:n:*. |Akc>!i?Li ji-i
'¦li 'IF iMD -Wi ¦ ]ti
'Ml &JL> JS£ iiii! ILli 1_L iikfe
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DISCUSSION
49
GENERAL
The protection of public health through the provision of a safe water
supply has long been a matter of primary concern to the public health
profession and has been a significant contributing factor to the high
health standards of the Nation. However, the problem of providing
adequate amounts of safe potable water has become increasingly difficult
due to the pyramiding water demands of a rapidly expanding population.
Furthermore, the resulting increase in waste flows has caused a gradual
degradation in the quality of the Nation's waters. While improved
methods of treatment and disinfection of both wastes and water have
served to maintain the quality within tolerable limits, the p'rogress
in pollution abatement and water treatment has not kept pace with this
population growth and industrial expansion.
The familiar problems of pollution by bacteria, organic matter, and
chemicals of known toxicity and behavior have been further intensified
and complicated by problems of mineral enrichment due to water reuse
and by new types of contaminants associated with our chemical and atomic
age. The effects of these newer contaminants on water treatment
processes and on the human consumer are largely unknown. The defi-
ciencies in knowledge and the prospect of even greater quantities of
yet more complex pollutional materials reaching our surface waters
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50
It is recognized that water for human consumption holds the highest
priority of all water useB. The increased demands on quantity by an
increasing variety of uses has also brought about many conflicts which
can be solved only by intelligent and long-range management practices.
Unfortunately, practically every water use results in some degradation
of quality. As the supply becomes more critical and conflicts in use
Increase, water quality is assuming increasing importance.
Where alternate sources are available it is desirable to reserve the
highest quality water available for domestic use and to satisfy other
lower priority demands with waters of lesser quality. In areas of
limited supply the ultimate water requirements can be met only by
water re-use. Thus, dependence must be placed upon improved and more
effective methods of water and waste treatment and other control
methods in order to maintain the highest possible standards of quality
for human consumption and other uses. However, in such instances
every effort should still be made to reserve a sufficient quantity
of high quality natural waters for domestic use before they flow on
to supply other less critical demands.
It is sound planning to utilize highest quality water for highest
priority uses, and the protection of this quality against irreversible
and potentially hazardous degradation must be practiced to the fullest
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51
Inasmuch as maintenance of a high level of water quality for all uses
is basic to public health and the general well-being of the populations
and economy, planning for future water demand and uses requires the
utmost of care with application of a reasonable degree of optimism.
This is especially true when planning for needs many years in advance
as is the objective of this evaluation.
WATER SUPPLY
As indicated in an earlier chapter, the developed surface supplies in
the Tualatin Basin have experienced difficulties in supply in recent
years. At the rate of growth anticipated and with the additional
demands for municipal and industrial supply that are expected to accom-
pany this growth, it is apparent that early development of additional
sources of supply is needed. For example, by the year 1980 the four
month (July-October) demand for surface water (6,350 ac.ft.) would be
approximately equal to the minimum four month natural or unregulated
yield returning once in twenty years for the entire basin, and by the
year 2010 the four month summer demand for surface water (24,000 ac.ft.)
would exceed the minimum four month natural yield returning once in
five years for the entire basin by more than 14,000 acre feet. Since
much of this yield is not distributed evenly in relation to areas of
demand, it is apparent that source development by impoundment will be
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52
The future municipal and industrial water supply requirements to be
satisfied by surface waters will involve provisions for storage to
serve new development areas to supplement various municipal and indus-
trial rights being exercised at the present time as well as to supple-
ment the shortages in natural yields that would be expected to occur.
For example, the 1980 annual demand for surface water in the Tualatin
Basin is expected to be about 14,000 acre-feet with approximately
45 percent of this demand occurring throughout the months of April
through October when yields are at a minimum. The active storage
required to meet this demand, therefore, would be equal to 6,325 acre-
feet minus existing rights in acre-feet for this period of time plus
any deficit or apportioned shortage of rights that would occur upon
return of critical historical low stream flows.
The annual benefits assignable to the inclusion of future municipal
and industrial water supply as one of the multiple functions of the
Tualatin Project would be equivalent to the annual cost of developing
the most likely alternative source in the absence of the project.
For example, the alternatives that are available to supply the futiire
municipal and industrial requirement to be satisfied from surface
sources In the basin would be development of storage within the Tualatin
Basin and development of storage in the Wilson River or Trask River
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53
Inasmuch as benefits assignable to project storage for municipal and
industrial purposes apply only to waters made available at the outlet
of the dam, such a determination involves estimates of costs to store,
pump, transport and treat waters from the alternative site and costs
to pump, transport and treat waters (each to common point of use) from
the project. Ineyent that the cost of the most likely alternative
plan is greater than costs to pump, transport and treat waters from
the project, the difference between the two total costs may be
regarded as the benefit assignable to project storage for M&I supply.
It may be assumed for benefit computation purposes that the cost to
treat waters stored in the project or at any alternate site would be
essentially the same.
QUALITY CONTROL
In view of the importance of the water resource to the economy of
the Tualatin River Basin and surrounding region, it is imperative
that every effort be made to preserve and protect this valuable
resource. Any possible means of maintaining control of water quality,
whether it be to protect health, property or aesthetic values, would
possess particular value to the region.
Municipal and industrial waste treatment and disposal practices in
the Tualatin Basin, although generally quite adequate in relation
to present conventional standards, provide only limited protection
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54
end frequency of low stream flows that occur In the Tualatin Rivor
sad with increasing populations and Industrial activity expacted
la the region, stream quality will become more and more critical*
Such values as the aquatic environment and natural soIf-purification
properties of the stream would become increasingly affected, and
nuisance conditions that could arise would become more frequent and
severe.
It ia for the above reasons and those stated in earlior chapters
that the loinlmusi stress* flows sho\m in Figures 4 and S are recommended.
As these stream flows in combination with waste treatment offer tho
only presently known nieans of ucliieving the prescribed quality objec-
tives, (distillation possible but ciore expensive and underground
disposal would not be acceptable) benefits assignable to the Scoggins
reservoir for quality control by low flow augmentation would bo equlva*
lent to construction, operation and maintenance costs involved in
providing similar regulation by single-purpose mean3# as for example,
from tho GasLon, McKay, Galea or Scoggins Creek sites, whichever
would be the cheapest.
Whereas the flow requirements shown In Figures A and 5 refer to total
stream flows required, it is understood that these may bo composed of
natural inflow, return irrigation flows, municipal and industrial
return flows and releases front storage. Benefits would apply to all
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35
It should bo noted, also, that diversions downstream from Hock Crack
of no greater than the difference between tha flows required in the
Scoggins to river milo 3B ranch and the reach from river mile 38 to
the mouth of tha Tualatin River could occur with no loss to tho control
of quality*
Flow regulation in tho Tualatin Dasin, in addition to assisting in
tho control of stream quality within the basin would be expected to
provide improvements fin downstroam roaches of the Willamette River
and Portland Harbor*
In event that upon allocation of storage for the various project
purposes any part of the requirements for municipal and industrial
water supply or quality control as given within tho study period
cannot be met with the Scoggln3 Reservoir, Tualatin Project, it La
assumed that theso will be incorporated in future development planning
or will be satisfied by local or other means.
Comments on these factors and any other details associated with tho
final formulation of the project will be rande at the timn of formal
inter-agency review.
The quality objectives and related flow requirements recommended In
tills report are designed for achievement of the following purposes!
1. Prevent development of nuisance conditional
2* enhance the aesthetic and hanlth values of tho atroaoi and
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56
3. Provido an environment suitable for propagation of resident
and anadronous fish life;
4. Protect and enhance the natural self-purification capabilities
and assets of the stream waters;
3. Reduce and neutralise the effect of residual fertilizer®,
uaedicides, And insecticides.
The beneficiaries of water quality maintenance and values resulting
from achievement of the abovo purposes are:
1. Land values--protection and enhancementj
2. Resident populations—health, social and economic improvement;
3. Livestock'-health and well-being;
A# Natural resources—
a. Fish and wildlife precorvation;
b. Preservation of the natural eelf-purifleation asBetc of
the water resource;
5. Recrea lion—protection and enhancement;
6. Waste disposal—aooimilutivo capacity (supplemental waste
treatment)*
By virtue of the multiplicity of values (tangible and intangible) that
are derived through maintenance of atresia quality, tho bensfits attrib-
utable to provisions specifically designed for such maintenance may bo
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57
Inasmuch ao Clio water quality control program sot forth In thla report
involves a reasonable decree ol local participation in achieving the
stated goals, It Is believed oi interest to the public that low flow
augmentation ep ono of tha requisites in achieving fulfillment of this
goal bo provi-ded. BeAofits attributable to provisions for water quality
control where shown to bo Justified aa a project function, therefore*
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