&EPA
                 United States
                 Environmental Protection
                 Agency
Region 10
1200 Sixth Avenue, Suite 900
Seattle WA 98101
                 March 2013
                                                          EPA910-R-13-003
                      SUPPORT DOCUMENT FOR SOLE
                   SOURCE AQUIFER DESIGNATION OF
                   THE BAINBRIDGE ISLAND AQUIFER
                                           SYSTEM
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            SUPPORT DOCUMENT
  FOR SOLE SOURCE AQUIFER DESIGNATION
OF THE BAINBRIDGE ISLAND AQUIFER SYSTEM
                   Prepared by

      U.S. Environmental Protection Agency, Region 10
         Office of Environmental Assessment for:
               Drinking Water Unit,
              Seattle, Washington 98101
                   March 2013

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                          TABLE OF CONTENTS

INTRODUCTION	5
  Purpose	5
  Sole Source Aquifer Program	5
  Petition	6
  Community Involvement	6
GEOGRAPHY	7
  Climate	7
HYDROGEOLOGY	7
BOUNDARIES	10
GROUND WATER QUALITY	10
POTENTIAL FOR CONTAMINATION	11
POPULATION AND DRINKING WATER CONSUMPTION	11
ALTERNATIVE DRINKING WATER SOURCES	12
CONCLUSION	12
REFERENCES	15
                                FIGURES
Figure 1. Petitioned Bainbridge Island and surrounding area
Figure 2. Surficial geology of Bainbridge Island

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    FINAL SUPPORT DOCUMENT FOR SOLE SOURCE
 AQUIFER DESIGNATION OF THE BAINBRIDGE ISLAND
                      AQUIFER SYSTEM
                         INTRODUCTION
Purpose

      This document summarizes readily available information and
describes the technical and legal basis for the proposed U.S.
Environmental Protection Agency (EPA) designation of the Bainbridge
Island aquifer system as a sole source aquifer.  All technical information
presented in the document is referenced from the petition submitted to
EPA.

Sole Source Aquifer Program

      The Sole Source Aquifer Program is authorized by the Safe Drinking
Water Act of 1 974 (Safe Drinking Water Act, Public Law 93-523 42 U.S.C.
300 et.seq).  Section 1424(e) of the Safe Drinking Water 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 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."

      EPA defines  a sole or principal  source aquifer as an aquifer or
aquifer system which supplies at least 50 percent of the drinking water
consumed in the area overlying the aquifer, and for which there is no
alternative source  or combination of  alternative drinking water sources
which could  physically, legally and economically supply those dependent
upon the aquifer (U. S. EPA, 1 987). For convenience, all EPA designated

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sole or principal source aquifers or aquifer systems are often referred to
simply as "sole  source aquifers".

      Although EPA has authority to initiate sole source aquifer
designations, the agency has a longstanding history of only responding
to petitions. Until 1 987, EPA accepted sole or principal source aquifer
petitions which contained a minimum amount of information. This
practice changed when EPA released the Sole Source Aquifer Petitioner
Guidance document in February of 1 987.  The guidance clarifies the
definition and acceptable delineation of a sole or principal source aquifer,
and describes how to petition EPA.

Petition

      The EPA Region 10  Drinking Water Unit in the Office of Water and
Watersheds received a draft sole source aquifer petition dated August 5,
2009 from Melanie Keenan and Malcolm Gander, individuals and
residents of Bainbridge Island.

      Additional information was requested by EPA from the petitioners
and was  submitted to EPA postdated July 9, 2010.  On August 12, 2010
the petitioners were informed by EPA that their submittal  was complete
and the technical review could begin. In January 201 2 comments by the
petitioners were incorporated into this draft technical support document
and received by Rl 0 Drinking Water Unit in the Office of Water and
Watersheds.

Community Involvement

      In  February 201 2, EPA began developing the community outreach
plan for this potential designation. The Agency designed a
communication strategy.  This guided our efforts to ensure that the
community and interested stakeholders were informed of EPA's actions
and had the opportunity to be meaningfully involved.

      A public comment period of forty-five days from April 20 through
June 4, 201 2 was announced in the Bainbridge Islander local newspaper
and announced via mailings and email. The mailings and emails also
included  a Fact Sheet that discussed the project and where to review the
project documents.  On April 20 the Draft Technical Support Document
and the original petition were posted on a dedicated web  site
(http://go.usa.gov/PzJ).  Hard copies of the above referenced  project
documents were also available for public review at the Bainbridge Island
Library Reference desk and at the  Bainbridge Island City Hall.

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      EPA received a total of seven comments. Two of the comments
were from the petitioners.  Of the five remaining comments four were in
support of the designation and one had questions.
                           GEOGRAPHY

      The petitioned area is Bainbridge Island (Figure 1). The Island's
hydrogeologic characteristics are similar to the following Puget Sound
islands whose aquifers have already been designated as sole source
aquifers by EPA:  Camano, Whidbey, Marrowstone, Guemes, and Vashon-
Maury. The island has a total of 53 miles of seawater shoreline. Interior
plateaus reach maximum elevations of 300 to 400 feet above mean sea
level.  The island can be  divided into 12 drainage basins and is primarily
a mixture of developed land and variably forested areas. The Olympic
Mountains are located  40 miles northwest and the Cascade Mountains are
50 miles to the east (Keenan and Gander, 2009).

Climate

      Bainbridge Island has a mid-latitude, wet-coast marine climate with
relatively cool, dry summers and mild, rainy winters.  Summer
temperatures average in  the 70s during the day and 50s at night, winter
temperatures are generally in the 40s during the day and 30s at night.
Rainfall ranges from 34 to 36 inches per year (Keenan  and Gander, 2009).
                          HYDROGEOLOGY

Geology

      The following information was extracted from the petition (Keenan
and Gander, 2009).

      At least six advances and retreats of Pleistocene continental
glaciers over the last 300,000 years has shaped the present-day
landscape and underlying hydrostratigraphy of the Island  (Easterbrook
1 994). This resulted in the deposition of large volumes of
unconsolidated glacial and interglacial material  (mixtures  of sand, silt,
clay and gravels), which are host to the aquifers of the Island.  Other
geologic units are present on the Island and have  less importance from a
hydrologic standpoint.  These units include surficial Quaternary alluvial
deposits, and Tertiary sedimentary rocks, which are exposed at the
southern end of the Island on the up-thrown side of a major east-west

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trending fault that transects the Island. Figure 2 presents a surficial
geologic map of the Island.

      The Quaternary alluvium unit includes recent stream,  lake,
floodplain, beach,  and peat deposits. These are generally thin and
discontinuous surficial deposits that cover less than one percent of the
study area.

      The Vashon  deposits are the youngest glacial deposits on the
Island (Easterbrook 1 968;  Easterbrook 1 994). They consist  of poorly
sorted sand and gravel of the Vashon recessional outwash (Qvr). Below
the Qvr is the much more extensive Vashon till (Qvt), which  comprises the
majority of the Island's surficial exposures. The Qvt is a mixture of
unstratified clay through boulder size detritus. Below the Qvt  is the
Vashon advance outwash (Qva), composed of sand and silty sand with
lesser amounts of  gravel and occasional lenses of silt.  Locally, the
Lawton Clay (Qvl) lies below the Qva and consists of clay and silt
deposited in lakes  that formed ahead of the advancing Vashon glacier.

      Below the Vashon  deposits are alternating groups of nonglacial and
glacial unconsolidated sedimentary deposits, which have been variably
named by several earlier workers. This early glacial period's deposits are
not as  evident as the Vashon, but are present above sea level.
Delineation of the  glacial units is further complicated by yet another
earlier interglacial  and then glacial episode that are present  in some
outcrops above sea level.  Older glacial/interglacial episodes are evident
in well logs and do not outcrop.

   The aforementioned east-west fault at the south end of the Island
juxtaposes unconsolidated Pleistocene sediments to the north with
Tertiary sedimentary bedrock in the  south.  The Tertiary bedrock, which
is mantled by Vashon glacial deposits, is the oldest material on the
Island.  The bedrock  consists of shale, sandstone, and conglomerate
deposited in a marine environment, and have been assigned to either the
Blakely Formation  or the Blakely Harbor Formation.

Aquifer System

   The following information was extracted from the petition (Keenan
and Gander, 2009).

   Large volumes of  unconsolidated glacial and interglacial  materials are
host to the aquifers on Bainbridge Island.  Six principal aquifers have
been identified on  the Island:

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   1)  Perched Aquifer System (PA) - This aquifer occurs in Vashon
      advance glacial outwash, which consists of fine to medium-grained
      silty sand with interspersed gravelly units. About 4 percent of the
      wells on the island are reportedly completed in this unit, and the
      producing zone is generally > 200 feet (ft) above mean sea level
      MSL.

   2)  Semi-Perched  Aquifer (SPA) - This aquifer occurs in  a mixture of
      non-glacial and glacially-derived sands and gravels. About 25
      percent of the wells on the island are  completed in this unit, and
      the producing zone is generally between 100 and -20 ft MSL.

   3)  Sea Level Aquifer (SLA) - This aquifer  has been tentatively  assigned
      to glacial deposits referred to as the Salmon Springs Drift.  It is the
      most widely used aquifer with 53 percent  of the wells completed in
      this unit,  and  the producing zone is 40 to -230 ft MSL.

   4)  Glaciomarine  Aquifer System (GMA) -  This aquifer ranges in
      composition from clay, silt, and silt-rich sand,  to sand and gravel.
      It also contains interspersed zones of organic  material, which
      indicates a non-glacial origin for this unit. About 2  percent of the
      island wells are completed in this unit. Several of the island's deep
      production wells are screened in the top of this aquifer, and the
      producing zone is typically -400 to -76- ft MSL.

   5)  Fletcher Bay Aquifer System (FBA) - This is the deepest of the six
      main aquifers encountered on the island.  It is composed of sand
      and gravel with subordinate amounts  of silt and silty sand. Wells  in
      this unit are typically screened between
      -690 to -1,010 ft MSL.  Although less than 1  percent of the island's
      wells are  completed in this unit, the metered Kitsap Public Utility
      District (KPUD) and City of Bainbridge Island Fletcher Bay Aquifer
      (GOBI FBA) wells provide approximately 30 percent of the estimated
      total water production on the island.

   6)  Bedrock Aquifer System (BAS) - This aquifer  is a minor source of
      groundwater on the island.  Less than one percent of the wells are
      completed in  this unit. The wells are  screened in sedimentary
      rocks of the Blakely Harbor and Blakely Formations, and are located
      on the south end of the island.

   On-lsland precipitation is the only source of aquifer recharge  in the
SSA. Approximately thirty-four to thirty-eight inches of rain falls annually
on Bainbridge Island, with the majority of that occurring in the winter

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months.  All of the water from the aquifers, as well as lakes, ponds, and
streams,  originates from precipitation on the island.

   The ability of the Island to meet water demands in the future depends
largely on production from the Fletcher Bay Aquifer System, which
currently produces the most for the City of Bainbridge Island.  The
Fletcher Bay Aquifer System has been correlated with deep aquifers on
Kitsap Peninsula; however, there is no evidence that the two are
hydraulically connected. The Fletcher Bay Aquifer System is not an
unlimited source,  and its recharge area and recharge rates are poorly
understood.

   Another important source of groundwater resources on the Island is
the Sea Level Aquifer System.  Future increases in production have been
recommended to be taken from this  System, particularly in the north and
central portions of the Island.  The Sea Level Aquifer system is not an
unlimited source,  and its recharge area and recharge rates are unknown.
                           BOUNDARIES

The petitioned aquifer is presented in Fig. 1.  The Bainbridge Island Sole
Source Aquifer boundaries are representative of an aquifer system that
encompasses the entire Bainbridge Island area. The aquifer area is
bounded on all sides by Puget Sound. The vertical extent of the aquifer
system at depth  includes all potable water-bearing geologic units
underlying the island.

      The Bainbridge Island Sole Source Aquifer boundaries were
determined by following aquifer definitions from EPA Guidance (EPA,
1 987). The Guidance states that petitioners may request designation for
part of an aquifer, an entire aquifer, or an aquifer system.  A petitioner
can request designation for part of an aquifer if that portion is
hydrogeologically separated from the rest of the aquifer. A petitioner can
also request designation for an aquifer system to the extent that all
aquifers in the system are hydrogeologically connected.
                    GROUND WATER QUALITY

      A comprehensive study of the drinking water quality on Bainbridge
Island has never been completed due to lack of funding. In general,
groundwater quality on the Island is good.  Iron and manganese are the
most common analytes found to exceed the Federal Maximum
Contaminant Level (MCL).  High iron and manganese can cause a
10

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somewhat objectionable odor, taste, or color, but generally are not
considered a health problem.
                POTENTIAL FOR CONTAMINATION

      The aquifer system is vulnerable to contamination due to potential
seawater intrusion, accidental spills, petroleum products, small
hazardous waste generators, household  hazardous waste disposal,
leachate from the closed Island landfill, leachate from the incompletely
remediated Wyckoff Superfund site in Eagle Harbor, or leachate from
Washington Department of Ecology listed Hazardous Sites such as the
former Unocal Station on Winslow Way (WDOE 201 la), the Strawberry
Plant site on Weaver Road (WDOE 2011 b), and the Winslow Way West &
Madison Avenue North site (WDOE 2011 b), failing septic systems,
fertilizers, pesticides and herbicides, improperly abandoned wells, and
the impact of population growth. The aquifer system is also vulnerable to
contamination from open ground water situations such as sand and
gravel mining operations.
      POPULATION AND DRINKING WATER CONSUMPTION

      The population of Bainbridge Island is approximately 23,290.  It is
estimated the population will increase to 25,474 by 2020, and 28,1 95 by
2030. One hundred percent of the current population on the island
obtain their drinking water from the petitioned aquifer.  The sole source
aquifer system on the Island underlies the entire Island. Actual usage
was calculated by multiplying population by an estimated per capita
consumption rate, which includes municipal, domestic, commercial,
irrigation, fish  propagation, and stock watering uses, and also includes
an estimate of water use from claims and users of wells that are exempt
from water rights. The  1 990 population number of 1 5,736 was
multiplied by an average use  of per capita value of 1 32 gallons per day
which yielded an annual continuous consumption total of 1,442 gpm.
The projected 2014 annual continuous consumption total was calculated
to be  2,067 gpm.  This  may represent approximately 1 8 percent of the
estimated total groundwater resource; however, the actual groundwater
resource is unknown based on a lack of data (Keenan and Gander, 2009).
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           ALTERNATIVE DRINKING WATER SOURCES

      EPA guidance requires that petitioners demonstrate not only that
an aquifer supply 50 percent or more of the drinking water for the area,
but also that there are no alternative sources or combination of sources
which could physically, legally, and economically supply all those who
depend upon the aquifer system for drinking water (EPA, 1 987).  The
petitioners for the Bainbridge Island Aquifer System have adequately
demonstrated that there are no additional sources of drinking water that
are economically available.

      Each of the potential alternative sources that the petitioner
evaluated has  limitations on quantity or quality of an economically
feasible alternative water source and/or the feasibility of development.
There are no potential surface water bodies as a source for drinking
water and the two alternatives scenarios of piping water across Agate
Pass Bridge to the Island or installation of a desalination plant are both
considered cost-prohibitive at this time, and as such are not considered
alternative sources of drinking water.  Therefore none of the potential
alternative sources qualify as Alternative Drinking Water Sources as
defined in the EPA Petitioners Guidance.
                           CONCLUSION

      A sole source aquifer system must supply at least 50 percent of the
drinking water consumed within the natural boundaries of the aquifer
system, and there can be no economically or legally available alternative
source that could supply the entire population living in the area. The
Bainbridge Island Aquifer System supplies all of the drinking water to
people living in the petitioned area, and there are no economical and
legally available alternative sources of water.  Given these conditions, the
Bainbridge Island Aquifer System meets the criteria of EPA designation  as
a sole or principle source aquifer under Section  1424(e) of the Safe
Drinking Water Act.
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    122°50
                                                               122*30'
122°20'
47°50' -
47'40'
47"30' —
EXPLANATION
  Location subsequent figure:
                           WASHINGTON



                             Figure location
     Base from U.S. Geological Survey digital data, 1:24.000, 1988
     Universal Transverse Mercator projection, rone 11
     North American Datum of 1983
                                                                                               10 MILES
                                                                                      8     10 KILOMETERS
     Figure 1.  Map of the proposed Bainbridge Island sole source aquifer, USGS
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                                                                         FIGURE 3.3
                                                               GEOLOGIC SURFACE MAP
                                                            MODIFIED FROM DEETER. 1979
                                                    BAIWRDGE ISLAND LEVEL II BASIN ASSESSMENT
Figure 2.  Geology of Bainbridge Island, City of Bainbridge Island, 2000.
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                          REFERENCES

City of Bainbridge Island, 2008, City of Bainbridqe Island Stop Work
Order, Triangle Sand Pit, Fletcher Bay Road and Lynwood Center Drive,
Bainbridqe Island Washington, July.

City of Bainbridge Island, 2000, City of Bainbridqe Island Level II
Assessment. An Element of the Water Resources Study. 70 pages.

Keenan, Melanie and Gander, Malcolm, 2009, Bainbridqe Island Sole
Source Aquifer Designation Petition, 65 pages.

U.S. Environmental Protection Agency, 1987, Sole Source Aquifer
Designation  Petitioner Guidance, 30 pages.

U.S. Geological Survey, 2011, Conceptual Model and Numerical
Simulation of the Groundwater-Flow system of Bainbridqe Island,
Washington, Scientific Investigations Report 2011-5021, 96 pages.

Washington Department of Ecology, 2011 a, Confirmed & Suspected
Contaminated Sites List, Bainbridge Island City Strawberry Plant Site,
August 1 6.

Washington Department of Ecology, 2011 b, Hazardous Sites List. Unocal
Station 4388, August 31.
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