EPA 910/9-87-163
United States
Environmental Protection
Agency
Region 10
1200 Sixth Avenue
Seattle WA
April 1987
Office of Ground Water
SEPA Support Document
For the EPA Designation of the
Cross Valley Aquifer as a
Sole Source Aquifer
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Support Document for the
EPA Designation of the Cross Valley Aquifer
as a Sole Source Aquifer
Office of Ground Water
U.S. EPA Region 10
Seattle, Washington 98101
September 1984
Revised April 1987
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Support Document Proposing the EPA Designation
of the Cross Valley Sole Source Aquifer
The Safe DrinMng Hater Act
The Safe Drinking Water Act, Public Law 93-523, was signed into law on
December 16, 19741. Section 1424(e) of the Act states:
"If the Administrator determines, on his own initiative or upon petition, that
an area has an aquifer which is the sole or principal drinking water source
for the area and which, if contaminated, would create a significant hazard to
public health, he shall publish notice of that determination in the Federal
Register. After the publication of any such notice, no commitment for Federal
financial assistance (through a grant, contract, loan guarantee, or otherwise)
may be entered into for any project which the Administrator determines may
contaminate such aquifer through a recharge zone so as to create a significant
hazard to public health, but a commitment for Federal financial assistance
may, if authorized under another provision of law, be entered into to plan or
design the project to assure that it will not so contaminate the aquifer."
The Petition
On July 29, 1983, the Mount Forest Protection Agency and the Cross Valley
Water Association, Inc. submitted a petition^ requesting that the aquifer
underlying the Cross Valley Water Association Service Area be designated as
the sole drinking water source for the area.
Receipt of Petition
The Administrator published a notice of receipt of the petition and a request
for public comment in the Federal Register on September 15, 19833.
Support Document
This document has been prepared to summarize available information on the
petitioned area and its ground-water resources. This information has provided
a basis for EPA action under Section 1424(e) of the Act. The following
sections provide short descriptive summaries of each topic. For more detail
the reader is advised to consult the references listed at the end of the
report.
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GENERAL DESCRIPTION OF THE "CROSS VALLEY AQUIFER" AREA
Geographic and Physical
The "Cross Valley Aquifer" is located in the Puget Sound lowland, between
Puget Sound and the Cascade Mountains4. The area petitioned for sole source
designation is mostly within the boundaries of Snohomish County, but crosses
into King County to the south. Most of the area is an undulant drift plain
with a north-south texture that is the result of glacial sculpturing during
the latest ice advance. The Snohomish River and its extensive floodplain
border the area on the north and east^.
Climate
The area's climate is temperate with mild temperatures throughout the year.
Precipitation occurs mostly during the winter months, usually as rain; summer
months are relatively dry. The average annual precipitation at Monroe, the
closest weather station with a long period of record, is 46.8 inches^.
Population
The present total population of the proposed sole source aquifer area- is
approximately 15,200 people. This includes approximately 10,700 people using
ground water. In addition, there are approximately 4,500 people living in the
eastern and southeastern portions of the proposed sole source area. These
groups of people use surface water supplied by the Alderwood and Woodinville
water districts. Approximately 700 additional persons live immediately north
of the proposed sole source area but are using ground water from the aquifer
area supplied by the Cross Valley Water Association7.
Geologic Setting
The subsurface geology, to a depth of about 300 feet, is fairly well defined.
At the surface is a mantle, up to 75 feet thick, of glacial till. Below the
till is a region-wide deposit of outwash sand or sand and gravel with moderate
permeability. This unit has been named the Esperance Sand by the U.S.
Geological Survey**.
Below the Esperance Sand is a more complex sequence of clay and firmly
cemented gravels that form a till. Information is meager on the extent and
hydraulic characteristics of these deposits, but it is known that some
permeable zones exist in the deeper section.
Beneath the deeper glacial deposits lies bedrock composed of marine sediments
and basalts. The rock surface generally dips southwesterly from exposures in
the Cathcart area to a depth of about 1,000 feet near Bothell9.
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Occurrence of Ground Hater
Most wells in the area tap water in the Esperance Sand unit which is recharged
by direct infiltration of precipitation. The water tends to be in a
"water-table state" which means that it has no appreciable confining
pressure. The Esperance Sand is generally capable of supplying yields up to
300 gpm from properly constructed wells. There is no water of regional
importance in the bedrock1^.
The information available indicates that the ground water flows generally in a
southerly direction in the main body of the aquifer. However, around the
perimeter the flow is toward the edge of the aquifer. The ground-water table
is at an elevation of about 350 feet above mean sea level, which indicates
that, depending on the land surface elevation, the ground water might be as
deep as 200 feet below ground surface in the higher areas. In some areas the
ground water is found perched above the regional water table^.
Hater Supply
an
Water for the area is supplied by the Cross Valley Water Association, Inc.,
from six (6) wells, each about 200 feet deep, most of which are drilled into
the Experance Sand Aquifer^. Two additional wells will be completed during
1987. Presently the Association has over 2,600 service connections serving
estimated 7,300 people within the proposed sole source aquifer area and an
additional 700 people immediately to the north of the proposed area. In
addition, more than 3,300 people obtain their water from individual wells,
springs and small community wells^. The Association pumped approximately
43.5 million cubic feet of water during 1986^. Total ground water use
within the proposed sole source aquifer area during 1986 is estimated at 60.5
million cubic feet. Details are given in Table 1.
The Cross Valley Water Association service area is bounded by the Silver Lake
Water District, Alderwood Water District, City of Snohomish, City of Everett,
and the Woodinville Water District. In order to make use of water from any of
the above purveyors, if available for alternate supply, major replacement and
construction of new transmission, distribution, and treatment facilities would
be required. Cross Valley Water estimates that this cost is in the millions
of dollars and is financially unfeasible for their organization 15.
Portions of the western and southeastern ends of the proposed sole source area
are served by surface water. The Alderwood Water District, using City of
Everett surface water, serves parts of Sections 16, 17, 20, 21, 22, 27, 28,
and 29, in T27N, R5E. In this area, approximately 3300 persons used 16.1
million cubic feet of water during 1986'6. The Woodinville Water District
serves approximately 1200 people in sections 5 and 6 of T26N, R6E. These
persons used approximately 0.8 million cubic feet of water during 198617.
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Table 1:
WATER CONSUMPTION WITHIN THE PROPOSED SOLE SOURCE AQUIFER AREA—1986
1 . Ground Water
Cross Valley Water
Association3
Aqua Copia Water
System0
Wood Lane Water
System^
Lake Tuck Water
System6
Individual Wellsf
(within Cross Valley
Individual Wells9
(outside of Cross Val
Total Ground Watern
2. Surface Water Use
Alderwood Water
DistrictA
Si Iver Lake Water
Volume in
Mi 1 1 ion
Cubic Ft.
43.5
1 .4
0.8
0.6
9.8
Number of
Connections
2654
82
36
45
740
Population
Served
8000b
200
130
120
2000
Water Association service area)
4.4
ley Water Association
60.5
16.1
0.2
339
service area)
3903
945
12
915
11385
3300
30
District8
Cross Valley Water
Association^
Woodinvi1le Water
District0
0.4
0.8
33
400
90
1100
Total Surface Water Use 17.5
1390
4520
Total Water Use
78.0
Ground Water as a Percentage of Total Water Use
in the area: 77.6 per cent
Surface Water as a Percentage of Total Water Use
in the area: 22.4 per cent
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Table 1 Notes:
a. Source: Personal communication, Gary Hajek, Manager Cross Valley
Water Association, April 1987.
b. Population served includes approximately 700 persons living north of
the proposed sole source area but served by ground water drawn from
the area.
c. Sources: Personal Communication, Howard Johnson, Aqua Copia Water
System, April 1987; and Washington State Department of Social and
Health Services (DSHS) Water Facilities Inventory and Report Form
(WFIRF), dated 10/27/85.
d. Source: Washington State DSHS WFIRF, dated 8/25/86.
e Source: The number of connections were provided by J. Phillips,
Lake Tuck Water Company, personal communication, April 1987.
Population and water consumption were estimated by assuming 2.7
persons per connection and consumption of 100 gallons per person per
day. This consumption estimate is based on a comparison to
adjoining water systems (Cross Valley, Aqua Copia, and Woodlane) in
which per capita consumption ranges from 111 to 143 gallons/day.
f. Sources: Population estimates were provided by Gary Hajek, Cross
Valley Water Association, and Richard Sarver, Snohomish Health
District, personal communications, April 1987. The number of
connections is an estimate calculated by using the population
estimate and assuming 2.7 persons per connection. The volume of
water used was calculated assuming consumption of 100 gallons per
person per day. The boundaries of the Cross Valley Water
Association service area are shown in the sole source aquifer
petition.
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g. The number of individual wells was estimated by counting the number
of buildings shown on the relevant portions of topographic maps.
Specifically, there are two areas of the proposed sole source
aquifer area in which public water supplies are not available and
residents rely on individual household wells. The first area is
immediately west of the Cross Valley Water Association service area
and encompasses parts of Sections 3,4,9,and 16 of T27N, R5E. The
second area is southeast of the Water Association service area and
includes parts of Sections 3 and 4 of T26N, R6E. These areas are
shown respectively, on the U.S. Geological Survey Bothell (1981) and
Maltby (1973) 7.5 minute quadrangles. As these maps do not reflect
recent intensive development the estimated number of connections is
probably much lower than the actual number. The population was
estimated by assuming 2.7 persons per connection. The volume of
water used was calculated assuming consumption of 100 gallons per
person per day.
h. Totals reflect all uncertainties inherent in previous calculations
and can thus be considered approximate.
A. Source: Number of connections and consumption were provided by
J. Blunk, Alderwood Water District, personal communication,
April 1987. Alderwood Water District has determined that there are
approximately 3.5 persons per connection.
B. Source: The number of connections and estimates of consumption were
provided by R. Heisel, Silver Lake W.D., personal communication,
April 1987. The population was estimated by assuming 2.7 persons
per connection.
C. Source: Number of connections was provided by G. Hajek, Cross
Valley Water Association, personal communication, April 1987.
Population and consumption were estimated by assuming 2.7 persons
per connection and consumption of 100 gallons per person per day.
These customers are served by City of Everett water (surface water)
through a limited capacity intertie and are located in T28N., R5E,
Section 16. This is outside of the proposed sole source aquifer
area but within the Cross Valley Water Association service area.
D. Source: Information on numbers of connections and consumption
provided by W. Davis, Woodinville Water District, personal
communiction, April 1987. The consumption rates given are at most
one-fifth of those of surrounding districts. No explanation of this
difference was offered.
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Surface Hater
The Snoqualmie River and the Snohomish River are situated near the eastern
boundary of the "Cross Valley" Aquifer area but there are no other significant
rivers or streams over the aquifer. Several small streams originate on the
land surface above the aquifer and drain the land surface toward the edge of
the aquifer. Several small lakes, such as Little Lake, Crystal Lake, and Echo
Lake are found over the aquifer.
Ground-Hater Quality
Water in the Esperance Sand unit tends to be of satisfactory quality, but
water from the deeper wells is of poorer quality. Clay and possibly some peat
zones may contribute hydrogen sulfide gas and iron^8,19.
Potential for Contamination
Since water reaches this aquifer by downward percolation of the precipitation
on the plateau surface2^, contamination from any surface source can enter
the aquifer by the same route. Any material spilled or disposed of in unlined
sites on the surface may migrate downward, under the hydrologic conditions
prevalent in the area, until it reaches the ground water. Once the ground
water becomes contaminated, its usefulness as a source of drinking water could
be impaired or destroyed. Assuming that the technology to remove the
contaminant, or contaminants, exists and is readily available, an increased
expenditure of energy and funds could still be required to make the water
useable again. If the technology is not available, or if the expense for
decontamination is too high, the contaminated aquifer could become practically
useless as a drinking water supply and its usefulness for other purposes could
be greatly impaired.
CONCLUSION AND DISCUSSION
To be designated as sole source, an aquifer must supply 50 percent or more of
the drinking water for an area. Contamination of a sole source aquifer would
pose a significant hazard to public health. The Cross Valley Aquifer provides
77.6 per cent of drinking water used in the aquifer area and adjoining service
area, and there are no feasible alternative sources of water. Therefore, EPA
Region 10 Water Division recommends to the Regional Administrator that the
aquifer be designated as a sole source aquifer. The aquifer would be
designated as the Cross Valley Sole Source Aquifer, named after the largest
public water system using the aquifer.
The area originally petitioned for designation is not exactly the same area
that is proposed for designation for several reasons. The area petitioned is
the Association service area, but the aquifer does not underlie this entire
area. In the east, the service area extends only to where the bedrock is at
or near the surface. In the north, the service area extends into bedrock
areas and into the Snohomish River flood plain, but the designated area
extends only to where the bedrock is near the surface 21,22,23. jn the
south the service area extends into King County. Available information
indicates that the western half of the aquifer tapers off north of the County
line and the eastern half of the aquifer extends south into King County23.
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The boundary of the aquifer, which includes the recharge zone, is defined by
natural landmarks where possible, and by cultural features where no such
landmarks exist. The designated aquifer is the Esperance Sand Aquifer, of
USGS nomenclature 25t within the land-surface boundary proposed above. The
designated area is generally bounded as follows: on the east and north sides
by bedrock, which is at or near land surface, on the west by the North Creek
Valley, and on the south by the County line. (See Attachment A for legal
description). The area proposed for designation covers approximately 36
square miles, and is given in Attachment B.
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REFERENCES
1. Safe Drinking Water Act, Public Law 93-523. 42 U.S.C. §300. et. seq.
2. Sole Source Aquifer Petition from Mount Forest Protection Association and
Cross Valley Water Association to U.S. Environmental Protection Agency,
Seattle, WA, dated July 29, 1983.
3. Federal Register, Volume 48, No. 180, September 15, 1983, pp. 41508-41510.
4. Newcomb, R.C., Ground-Water Resources of Snohomish County Washington,
Water Supply Paper 1135, Government Printing Office, 1952, p. 7.
5. Noble, Hohn B., Ground-Water Study for Cross Valley Water Association.
Inc., South Service Area, unpublished report, May 1972, p. 1.
6. Noble 1972, p.3.
7. Population estimates were made based on the following sources: (1) data
given on Washington State Department of Social and Health Services 1986
Water Facilities Inventory and Report Forms for each of the relevant
water purveyors: Cross Valley Water Association, Woodlane Water System,
Aqua Copia Water System, Alderwood Water District, and Woodinville Water
District; (2) Sole Source Aquifer Petition, page 4; (3) personal
communication, Richard Sarver, Snohomish Health District, April 1987; (4)
personal communications, G. Hajek, Cross Valley Water Association; P.
Blunk, Alderwood Water District; and W. Davis, Woodinville Water
District; all April 1987.
8. Noble 1972, p. 1 .
9. Noble 1972, p. 2
10. Noble 1972, p. 2.
11. Noble, John B., Ground Water Resource Evaluation for Cross Valley Water
Association, unpublished report, July 1983, plates 1 and 2.
12. Letter from Gary Hajek, Cross Valley Water Association, Inc., to Rene'
Fuentes, U.S. EPA, Drinking Water Programs Branch, dated November 29,
1983. Cross Valley Water Association water supply wells are located in
T27N, R5E, Sections 24, 25, and 35.
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10
13. Sole Source Aquifer Petition, p. 4. Other small water systems within the
proposed sole source aquifer area and Cross Valley Water Association
service area are the Woodlane Water System, the Aqua Copia/Horse County
Estates Water System, and the Lake Tuck Water System. These systems use
wells installed in the Cross Valley Aquifer, and serve, respectively,
populations of 130, 200, and 120. Production wells are located in T27N,
R5E, Sections 14, 23, and 35 and T27N, R6E, Section 26.
14. Personal Communication, Gary Hajek, Cross Valley Water Association, Inc.,
April 1987.
15. Letter from Gary Hajek, Cross Valley Water Association, Inc., to Rene'
Fuentes, U.S. EPA, November 29, 1983.
16. Personal Communication, J. Blunk, Alderwood Water District, April 1987.
17. Personal Communication, W. Davis, Woodinville Water District, April 1987.
18. Noble 1972, p. 2.
19. Letter from Thomas J. Farrell, Snohomish County Solid Waste Division, to
Wendy Marshall, U.S. EPA, dated October 31, 1983, p. 7.
20. Newcomb, 1952, p. 41.
21. Newcomb, 1952, plate 1.
22. Noble, June 1983, "Water Well and Aquifer Summary Map."
23. Earth Consultants, Inc., "Geologic, Soil, and Foundation Investigation
Phase II," unpublished report prepared for Snohomish County, updated.
24. Noble, 1983, "Water Well and Aquifer Summary Map."
25. Newcomb, 1952,' p. 19.
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Attachment A
Cross Valley Sole Source Aquifer Area
Beginning at the N.W. corner of Section 4, T.27 N., R.5 E., Willamette
Meridian, thence east along the section line to the N.W. corner of the N.E.
1/4 of Section 2, T.27 N., R.5 E., thence southeasterly to the S.E. corner of
Section 20, T.27 N., R.6 E., thence east along the section line to the N.W.
corner of the N.E. 1/4 of Section 27, T.27 N., R.6 E., thence southeasterly to
the S.E. corner of the N.W. 1/4 of Section 26, T.27 N., R.6 E., thence south
to the S.E. corner of the S.W. 1/4 of Section 2, T.26 N., R.6 E., thence west
to the S.W. corner of Section 5, T.26 N., R.6 E., thence northwesterly to the
S.W. corner of Section 26, T.27 N., R.5 E., thence west to the S.W. corner of
R.5 E., thence northwesterly to the S.W. corner of the
T.27 N., R.5 E., thence north to the S.W.corner of the
T.27 N., R.5 E., thence northeasterly to the S.E.
Section 28, T.27 N.
S.E. 1/4 of Section 20
S.E. 1/4 of Section 17
corner of section 8, T.27 N., R.5 E., thence north along the section line to
the point of beginning; being located in Snohomish and King Counties,
Washington.
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FEDERAL FINANCIALLY ASSISTED PROJECTS LOCATED IN
THE DESIGNATED AREA MUST BE DESIGNED AND CONSTRUCTED
AS TO PROTECT THE DRINKING WATER QUALITY OF THE AQUIFER
APPLICANTS ARE HEREBY NOTIFIED THE ENVIRONMENTAL
PROTECTION AGENCY, WORKING THROUGH THE FEDERAL FUNDING
AGENCY. MUST APPROVE PROJECTS PRIOR TO COMMITMENT
OF FUNDS.
R.5.E. R.6.E.
Scale in Miles
0
1
=1
DESIGNATED UNDER THE AUTHORITY
OF SECTION 1424(6} OF THE SAFE
DRINKING WATER ACT [PL 93-523)
CROSS VALLEY AQUIFER
SOLE SOURCE AQUIFER AND RECHARGE AREA
Snohomish and King Counties, Washington
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