Environmental Protection
Agency
Emergency end
Remedial Response
March 1983
Superfund
Record of Decision:
Commencement Bay/
Tacoma Well 12A Site,
WA
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA/ROD/R10-83/001
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
SUPERFUND RECORD OF DECISION:
Commencement Bay/Tacoma Well 12A Site, WA
5. REPORT DATE
03/01/83
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final ROD Report
14. SPONSORING AGENCY CODE
800/00
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The South Tacoma Channel, Well 12A is in the City of Tacoma, WA, and lies within
the Commencement Bay drainage area. In Sept. 1981, Well 12A was voluntarily removed
from service by the city when chlorinated organic solvents were detected. During
1982, volatile organics were discovered in nearby Well 9A which was also closed. A
ground water study confirmed that should the contaminated wells closest to the
source remain shut down, pumping of the other production wells would draw the con-
taminated plume throughout the well field.
The cost-effective Initial Remedial Measure (IRM) is to pump and treat water
from Well 12A. Pumping of the well will assist in confining contaminant movement
within the aquifer. Air stripping will occasionally allow the city to use the water
when its quality is acceptable. The cost of the project is estimated to be
$1,200,000. Operation, maintenance, and monitoring costs are estimated to be
$60,000 annually.
Key Words: Cost Effective Alternative, Ground Water Contamination, Hydraulic
Barrier, Contaminant Source Location, Cleanup Goals, Dilution,
Water Quality Criteria, Air Pollution, Noise Pollution, Selected
Alternative
7.
KEY WORDS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Croup
Record of Decision
Commencement Bay/Tacoma Well 12A Site, WA
Contaminated media: gw
Key contaminants: solvents, VOCs, TCE, DCE
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21. NO. OF PAGES
56
20. SECURITY CLASS (This page I
None
22. PRICE
EPA Form 2220.1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
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EPA Form 2220-1 (R«v. 4-77)
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ROD ISSUES ABSTRACT
Site; Tacoma Well 12A, Washington
Region; X
AA, OSWER
Briefing Date; March 18, 1983
SITE DESCRIPTION
The South Tacoma Channel, Well 12A is in the City of Tacoma,
Washington and lies within the Commencement Bay drainage area. In
September 1981, Well 12A was voluntarily removed from service by the
city when chlorinated organic solvents were detected. During 1982,
volatile organics were discovered in nearby Well 9A which was also
closed. A ground water study confirmed that should the contaminated
wells closest to the source remain shut down, pumping of the other
production wells would draw the contaminated plume throughout the well
field.
SELECTED ALTERNATIVE
The cost-effective Initial Remedial Measure (IRM) is to pump and
treat water from Well 12A. Pumping of the well will assist in
confining contaminant movement within the aquifer. Air stripping wil^i
occasionally allow the city to use the water when its quality is
acceptable. The cost of the project is estimated to be $1,200,000.
Operation, maintenance and monitoring costs are estimated to be $60,000
annually.
ISSUES AND RESOLUTIONS KEY WORDS
1. Pumping and treatment of one well in a field . Cost Effective
of multiple wells to provide a hydraulic Alternative
barrier to future contaminant migration . Ground Water
into the field and into other wells may be Contamination
considered an appropriate remedial action. . Hydraulic
Barrier
2. Investigation to locate a contaminant . Contaminant Source
source should continue even when treatment Location
of a contaminated area has been approved as
a remedial response. The source, when
identified, should also be treated by an
appropriate remedial action. The pumping of
Well 12A will prevent migration of the
contaminants to other wells in the field,
but does not eliminate the source of
contamination. Work on locating the source
is continuing.
-1-
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Tacoma Well 12A, Washington
March 18, 1983
Continued
ISSUES AND RESOLUTIONS KEY WORDS
3. Establishing the goal for cleanup involved . Cleanup Goals
adjusting the water quality criteria to . Dilution
reflect periodic use and dilution. . Water Quality
Criteria
4. When selecting a remedial action it is . Air Pollution
important to evaluate air and noise . Noise Pollution
pollution which may result from the . Selected
implementation of the remedy. Alternative
-2-
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RECORD OF DECISION
REMEDIAL ACTION SELECTION
SITE: Tacoma Well 12A
Commencement Bay/South Tacoma Channel
Tacoma, Washington
Documents Reviewed
V
I have reviewed the following documents describing the need for and
analysis of the feasibility and cost-effectiveness of remedial alternatives
for Well 12A in the South Tacoma Channel:
Study Titled: Remedial Investigation, Well 12A
Tacoma, Washington, 2/10/83 (Draft)
Study Titled: Tacoma Well 12A, Remedial Action
Feasibility Study, February 1983 (Draft)
Executive and Narrative Summaries
Record of Decision Summary Sheet
Public Participation Responsiveness Summary
Staff Recommendations
Declarations
Consistent with the Comprehensive Environmental Response, Compensation
and Liability Act of 1980, and the National Oil and Hazardous Substances
Contingency Plan, I have determined that the pumping and treatment of
Well 12A is a necessary and timely remedial action to protect public
health and the environment, is a feasible and cost-effective remedy, and
1s a necessary component of any final remedy that will effectively and
reliably mitigate and minimize damage to, and provide adequate protection
of public health, welfare and the environment. I have also determined
that the action 1s appropriate when balanced against the need to use
Trust Fund money at other sites.
:ting Assistant Administrator
Office of Solid Waste and Emergency Response
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WELL 12A REMEDIAL ACTION
EXECUTIVE SUMMARY
In conjunction with several State and local agencies, EPA 1s proposing a
remedial.action to allow treatment of. water from the contaminated drinking
water Well 12A. EPA Is working In close conjunction with the State Depart-
ments of Ecology and Social and Health Services, the City of Tacoma Water
Division and the Tacora Pierce County Health Department.
The well was discovered to be contaminated with volatile organic solvents
about September 1981. At the advice of the Department of Social and Health
Services, the City voluntarily removed the water well from service. In
April 1982, U.S. Environmental Protection Agency began an Investigation of
the extent and nature of the contamination found 1n Well 12A. At the same
time, the Tacoma Pierce County Health Department began an Investigation as
to possible sources of the contaminants. The results of the former Investi-
gation demonstrate that there 1s a contaminated plume with organic solvents
In concentrations of parts per million to the northeast of City Well 12A.
The ultimate sources of this plume have not yet been Identified.
During 1982, Well 12A was out of service but other wells within the well-
field continued to pump. The contaminant plume moved Into the wellfleld and
volatile organlcs were discovered 1n nearby Well 9A. This well 1s now
closed. Results of the groundwater Investigation Indicate that contamina-
tion will continue to move Into the wellfleld as pumping continues unless
remedial action 1s pursued. Without action, the contamination will effec-
tively eliminate Tacoma's source of water for meeting the higher summer
demand.
The proposed action 1s a treatment system 1n Well 12A which will remove the
contamination through aeration. Pumping of Well 12A will provide a barrier
to future contaminant migration Into the wellfleld. Treatment will provide
the City with water of acceptable quality for consumption. It Is possible
that the system will be overloaded by the contaminant levels. In the case
that effluent quality falls, the system will discharge to Commencement Bay
but at a level sufficient to protect aquatic life.
Several alternatives were examined before selecting this system. The pro-
posal of 5 aeration towers 1s the most cost-effective of any of the systems
evaluated. Cost of the project 1s about $1.2 million.
Additional work 1s being done to locate the source of contamination. If
this can be accomplished, further measures will be taken to mitigate contam-
ination of the aquifer.
More detailed Information can be obtained from the Remedial Action Feasibil-
ity Study and by contacting EPA Region 10.
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NARRATIVE SUMMARY
HISTORY
Tacoma Well 12A 1s within the South Tacoma Channel Commencement Bay
Superfund designation. This area of Tacoma, Washington 1s a commercial
Industrial zone with a long history of development.
In September 1981, volatile organic contaminants were found 1n the
well. At the advice of the State Department of Social and Health Ser-
vices, the well was removed from service by the City. At that time, the
concentration was several hundred parts per billion, Including tetra-
chloroethane, trlchloroethylene and dlchloroethylene.
In October, Commencement Bay was listed-on the Interim Priority List. A
remedial groundwater Investigation was Initiated to determine the extent
of contamination and potentially locate a source. Concurrently, surface
Investigations looked at business types to Identify those which may have
contributed to the problem.
To date, no source has been Identified. However, a plume of contamina-
tion has been located giving a general direction, northeast, to the
primary source. Concentration within the plume 1s several parts per
million.
During 1982, Well 12A was out of service. All of the other wells were
1n operation during the summer pumping season. Analysis of these other
wells showed that an additional well had become contaminated. This well
was the closest to 12A, Immediately southwest. The groundwater study
confirmed that should the contaminated wells closest to the source
remain shut down, pumping of the other production wells would draw
contaminants closer and evidently all the wells would be tainted.
With two wells contaminated and to be held out of service, the City of
Tacoma 1s placed 1n a situation of water shortages during the summer.
Further, 1f contamination 1s permitted to move Into the wellfleld, 30*
of the total, water system capacity would be lost.
CURRENT STATUS
The remedial action feasibility study addresses the options for mitiga-
tion. They are generally 1) no action and abandonment of the contami-
nated wells, 2) alternative water supply, and 3) treatment.
No action 1s an unacceptable option as 1t does nothing to protect the
drinking water supply and quality for the City of Tacoma. Without some
mitigation, contamination would move within the aquifer to other wells.
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No alternative sources of water exist for the City 1n the short term.
The wellfield is essential to the City's future drinking water planning.
Pumping and treatment of Well 12A 1s the only alternative capable of
protecting the ground water aquifer and alleviating drinking water
shortages. Pumping of the well will provide an effective hydraulic
barrier to contaminant movement within the aquifer. Treatment of
the water will allow the City to use the water as Its quality permits
or to discharge the water to Commencement Bay at a quality sufficient
to protect marine life.
Treatment at Well 12A 1s an interim measure. As a source or sources
can be identified, actions for local control at the source may be
more effective 1n mitigating contamination 1n the aquifer.
PUBLIC INPUT
On March 10, 1983, a public meeting was held regarding the proposed
action. Concurrently, public comment was solicited from information
made available. A responsiveness summary 1s attached in this package.
STATE INPUT
The State of Washington, through Its Departments of Ecology and Social
and Health Services, along with the City of Tacoma and the Tacoma/
Pierce County Health Department, have cooperated with Region 10 and
have supported this project. The State/EPA contract is attached in
the package.
RECOMMENDED ALTERNATIVE
Section 300.68(e)(1) of the NCP authorizes Initial remedial measures
that are necessary to limit exposure or threat of exposure to a
significant health or environmental hazard. The current contamination
of Well 12A and the potential for serious additional contamination of
the aquifer absent action to pump and treat Well 12A warrants
Implementation of the proposed remedial action as an Initial remedial
measure. Our evaluation of the cost-effectiveness of each of the
proposed alternatives, the comments received from the public,
Information from the Remedial Investigation and Feasibility Study
Reports, and Information from the State, support a decision that
the proposed project of treatment of the contaminated drinking
water well by aeration, utilizing the pumping as a hydraulic barrier,
1s the appropriate remedy.
Section 300.68(j) of the NCP also states that the_appropr1ate extent
of remedy shall be determined by the lead agency's selection of the
remedial alternative which the agency determines 1s cost-effective
(I.e., the lowest cost alternative that 1s technologically feasible
and reliable and which effectively mitigates and minimizes damage
to and provides adequate protection of public health, welfare, or
the environment. The above information supports a finding that
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this proposed action would be Tirecessary component of any final
remedy that will effectively mltfgate damage to and provide adequate
protection of public health, welfare, and the environment.
Approval of this project 1s requested along with approval of an
allocation for $1.2 million for Its Implementation as needed above,
the State of Washington" has endorsed the project and has assumed a
10% cost share.
SCHEDULE
This project 1s based upon a hydraulic barrier being developed prior
to heavy usage of the well field. This would dictate project start
up 1n July 1983. Immediate authority 1s required to complete design
and construction by this deadline.
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\CSW-OI
S. 35 fh ST I
/27/82»l4
MONITORING W£LL
CONCENTRATION (ug/L)
EXISTING CITY WATER WELL
CONCENTRATION (ug/L)
— ESTIMATED EQUIVALENT
CONCENTRATION LEVELS
11 SL 33th ST.
j
SCALE IN rr*T
AREAL DISTRIBUTION OF 1,1,2,2 TETRACHLOROETHANE
FROM OCTOBER 27, 1982 TO NOVEMBER 30, 1982
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AREA EXTENDS
TO THE'NORTH
AND TO THE EAST
ceo
LEfigND
• MONITORING WELL
O EXISTING CITY WATER WELL
j CCMCTERY j
PROBABLE PRIMARY SOURCE AREA
REMEDIAL INVESTIGATION
TACOMA WELL I2A
TACOMA. WASHINGTON
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