United States Region 10 Alaska
Environmental Protection 1200 Sixth Avenue Idaho
Agency Seattle WA 98101 Oregon
Washington
AUG 181992
Attn Of: HW-113
MEMORANDUM
SUBJECT: Explanation of Significant Differences (ESD) for the
Lakewood Superfund Site
FROM: Ann Williamson
Superfund Site Manager
TO: Bruce Cochran
Washington Department of Ecology
Cyndy Mackey Leslie Jones
EPA ORC- Region 10 EPA OWPE- HQ
Attached for your review is a draft of the ESD for the
Lakewood Superfund site. After your review, the ESD will
processed in accordance with EPA guidance documents and policy:
* Ecology's comments will be summarized in the ESD.
* As appropriate, EPA Headquarters' comments will be
incorporated into the ESD.
* The appropriate EPA regional manager will consult with
Headquarters prior to signing the ESD.
* As required by the CERCLA, Section 117(c), a notice of
availability and a brief description of the ESD will be
published in a local newspaper, i.e., the Tacoma News
Tribune.
* As also required, the ESD will be made available to the
public in the Lakewood site file, located in the EPA
regional office. This is a pre-SARA site, consequently
no Administrative Record was established.
* The information supporting the ESD, i.e., the documents
on the list of "References for Lakewood ESD," will be
placed in the Lakewood site file, along with EPA's
response to any comments on the ESD.
* A copy of the ESD will be sent to the Office of
Emergency and Remedial Response.
I would appreciate receipt of your comments within the next
two weeks. Thank you for your assistance.
Attachment
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| UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
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EXPLANATION OF SIGNIFICANT DIFFERENCES
INTRODUCTION
Site name and location:
Lakewood/Ponders Corner (Lakewood)
Lead and support agencies:
U.S. Environmental Protection Agency (EPA)
Washington Department of Ecology (Ecology)
Statutes that require Explanation of Significant Differences
(ESD):
Comprehensive Environmental Response, Compensation, and Liability
Act (CERCLA), Section 117 (c) and National Oil and Hazardous
Substances Pollution Contingency Plan (NCP),
Section 300.435(c)(2)(i)
Need for an ESD:
On September 30, 1985, EPA signed the Record of Decision
(ROD) for the Lakewood Superfund site. Since that time, an
amended ROD addressing fotfr *major~areas affecting the original
remedial decision was signed on November 14, 1986. The changes
included a significant reduction in the amount of contaminated
soil requiring excavation and off-site disposal from the three
existing septic tanks; the construction of a soil vapor
extraction system (SVES) to treat soils in place which
substantially augments remediation associated with excavating and
disposing of contaminated soil off-site; effectuating a cost
savings by implementing the soil treatment process instead of the
soil removal and disposal remedy; and, implementing a more
environmentally acceptable remedy since SVES would permanently
treat contaminated wastes and eliminate the uncontrolled
volatilization of contaminants resulting during excavation.
There are three issues which were not addressed in either
the original ROD or the Amended ROD. This Explanation of
Significant Differences (ESD) documents the revisions needed in
order to comply with the original ROD, Amended ROD and regulatory
requirements. The three issues are: (1) establishment of site-
specific cleanup levels for contaminants in soil and groundwater;
(2) final remedial action necessary to remove the source of
contamination at the site; (3) and, elimination of the
requirement to implement institutional controls on land and
groundwater use.
Establishment of site-specific cleanup goals: Site-specific
remedial cleanup levels for both the contaminated groundwater and
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soil were not established in either the ROD or the amended ROD,
but were deferred pending evaluation of site-specific conditions
and regional characteristics. Soil and groundwater cleanup
levels are being designated as part of this ESD. These cleanup
levels will be consistent with the current federal and state
standards for the contaminants of concern. The contaminant in
soil is tetrachloroethylene (PERC). The contaminants in
groundwater are cis-1,2 dichloroethylene (cis-1,2 DCE),
tetrachloroethylene (PERC) and trichloroethylene (TCE).
Final soils unit remedial action; Cleanup of site soils
began in 1983 when the owners of Plaza Cleaners agreed to send
drummed sludge from the on-site sludge removal areas to an
approved off-site disposal facility. In 1987, EPA successfully
removed contaminated solids and any water from three, on-site
septic tanks (which were used for disposal of dry cleaning
wastes) and disposed of the contaminated material off-site. The
remainder of the contaminated soil within the septic tanks and
around the historical drain field was treated using a soil vapor
extraction system to levels protective of human health and the
environment.
Field notes from the 1987 removal indicated that some sludge
was left below one of the bottomless septic tanks when efforts
were made to excavate their contents. At the time of the
removal, rice hull ash was added in an attempt to solidify the
sludge. However, the resulting "hot spot" contained high
concentrations of PERC.
EPA recently completed final remediation of this area in
July, 1992 by excavating the contaminated sludge which is
currently stockpiled in containers on-site. The contaminated
sludge is awaiting transport to an approved off-site treatment
facility for incineration. Contaminated soil from above and
around the contaminated sludge, which was also excavated during
the final remedial action but does not require incineration prior
to land disposal, has been stockpiled on-site and will be
transported to an approved hazardous waste facility for disposal.
All contaminated waste will be removed from the site by the end
of September, 1992.
Institutional Controls:
Elimination of land use restrictions: The success of the
final soil remedial action has eliminated the need for
institutional controls (as called for in the original ROD) on
land use.
Maintenance of current groundwater use restrictions: Since
initiation of the groundwater treatment program, EPA has utilized
public outreach and education to implement administrative
restrictions on the installation and use of drinking water wells
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within the contaminated area. Homeowners who currently have or
could potentially install private drinking water wells within the
plume of contamination and well drillers were notified and will
again be reminded of potential risks associated with groundwater
use in the area.
Elimination of future groundwater use restrictions: Other
institutional control measures on groundwater use such as deed
restrictions, are considered unnecessary. The use of public
outreach and education, including written notification of current
limitations on groundwater use, are sufficiently protective of
human health and the environment. Once groundwater standards
have been achieved, these measures,will no longer be necessary.
Extraction, treatment and monitoring of contaminated
groundwater will remain the hazardous waste management approach
for the Lakewood site. The remedial action will continue to be
protective of human health and the environment, and consistent
with the NCP.
Document Availability:
The ESD will become part of EPA's site file for the Lakewood
Superfund site which serves as the Administrative Record for this
pre-SARA site. The file is available to the public at the
following location:
U.S. Environmental Protection Agency
1200 Sixth Avenue, HW-113
Seattle, Washington 98101
SITE BACKGROUND
The Lakewood site is located south of the city of Tacoma,
Washington. It includes the property upon which Plaza Cleaners
has operated a dry cleaning business for many years. The
regional aquifer is also contaminated within an approximate
2,000-foot radius downgradient of Plaza Cleaners. The Plaza
Cleaners property is bounded by Interstate 5 to the south, and
surrounded on the remaining three sides by a commercial/light
industrial area. Farther north is a predominantly residential
area. Lakewood Water District has two of its production wells
(HI and H2) on a fenced area south (downgradient) of Plaza
Cleaners, across Interstate 5. Residential property lies to the
east, and McChord Air Force Base to the southeast, of the wells.
In July 1981, EPA sampled drinking water wells in the Tacoma
area for contamination by volatile organic compounds. The tests
indicated that wells HI and H2 were contaminated with TCE, PERC
and cis-1,2 DCE. The source of the contamination was determined
to be Plaza Cleaners, a dry cleaning and laundry business,
located approximately 800 feet north (upgradient) of the Lakewood
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Water District production wells. In August 1981, HI and H2 were
temporarily taken out of service while monitoring wells were
installed and contaminated surficial soil in the source area was
excavated.
A stipulated agreement for remedial action was reached
between Ecology and Plaza Cleaners in September, 1983. Plaza
Cleaners agreed to discontinue their prior solvent disposal
practices, install a system for reclaiming cleaning solvents, and
send drummed waste water and sludge to a suitable off-site
disposal facility. Contaminated soil from the on-site sludge
removal areas was replaced with clean fill. Plaza Cleaners
successfully fulfilled the terms of the agreement.
In May 1984, EPA completed a focused feasibility study (FFS)
identifying an Interim Remedial Action (IRM) needed to address
those contaminant problems posing the most immediate threat at
the site. The objectives of the IRM were to: (1) restrict the
spread of contamination within the aquifer; (2) restore normal
water service to the area; (3) and, initiate groundwater
treatment as quickly as possible. By November 15, 1984, two air
strippers had been installed to treat wells HI and H2 and were
fully operational following implementation of the IRM.
REMEDIAL INVESTIGATION fRI) AND CONTAMINATION PROBLEMS
EPA's contractor conducted a remedial investigation from
August 1984 to July 1985 to further determine the extent of
groundwater contamination at the site, test the soil at Plaza
Cleaners for remaining contaminants, and determine whether other
sources were contributing to the groundwater problem. The field
work conducted during the RI included:
- installation of nine deep and three shallow monitoring
wells to provide a comprehensive picture of the groundwater
regime (e.g. flow patterns, hydraulic connections between
layers); determine the nature/extent of groundwater
contamination; and, identify possible sources of the
contamination.
- excavation of the waste line at Plaza Cleaners and
drilling of seven soil borings to determine the extent/
character of remaining sources of contamination at Plaza
Cleaners, and to determine if other sources besides Plaza
Cleaners exist.
- collection of samples for field and laboratory analysis to
determine the extent/concentration of soil and aquifer
contamination within the study area.
The dry cleaning operation's discharge of solvents into its
bottomless (i.e. permeable) septic system and the disposal of
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other wastes containing solvents onto the ground outside their
building were suspected of causing the soil and groundwater
contamination. It was later confirmed that contamination had
resulted from effluent discharges from septic tanks behind the
Plaza Cleaners building and sludge disposal on the ground
surface.
Ecology found that supernatant (liquid overlying material
deposited by settling or precipitation) in the dry cleaner's
septic system contained 550 parts per billion (ppb) PERC and 29
ppb TCE.
Data for the two production wells (HI and H2) ranged from
100 to 500 ppb PERC prior to initiating the groundwater
treatment. Contaminant concentrations decreased rapidly after
several days of pumping, and have continued to decrease. Maximum
and mean concentrations in other groundwater monitoring wells
within the study area prior to treatment were: PERC- 922 ppb and
16 ppb, respectively, and: TCE- 57 ppb and 3 ppb, respectively.
The only detected concentration for cis-1,2 DCE was 85 ppb in a
monitoring well upgradient of the production wells.
The RI indicated that PERC contamination in soils was
highest where solvent-contaminated wastes were intentionally
disposed on the ground surface. Except for several small pockets
of contamination, most of the PERC from the soil borings and test
pit was located in the upper 12 to 13 feet of soil in the
immediate vicinity of the dry cleaner's septic tanks and drain
field. Where it was detected, PERC concentrations ranged from 11
to 3,800 ppb. The average PERC concentration in soils was 500
ppb. Maximum TCE and cis-1,2 DCE concentrations in soil were 5
ppb and 4 ppb, respectively.
REMEDY SELECTED IN THE ROD AND AS REVISED IN THE AMENDED ROD
The Feasibility Study for the Lakewood site was published in
July 1985, and the ROD was signed shortly thereafter on September
30, 1985.
The remedy selected in the ROD consisted of the following
major elements:
* Continued operation of the H1-H2 production wells'
treatment system to cleanup the aquifer. Installation
of higher efficiency equipment or modification of
existing energy reducing equipment used in the
treatment system.
* Installation of additional monitoring wells, upgrading
of existing wells, and continuation of routine sampling
and analysis of the aquifer to monitor progress and
provide early warning of potential new contaminants.
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* Excavation and removal of contaminated septic tanks and
drain field piping to avoid the possible spread of
contamination via uncontrolled excavation (i.e. future
property development). The septic tanks were found to
be bottomless, and, therefore, they were not removed.
* Placement of administrative restrictions on the
installation and use of groundwater wells and on
excavation into the contaminated soils to minimize the
potential for use of contaminated groundwater and
reduce the risks associated with uncontrolled
excavation.
An Amended ROD was signed on November 14, 1986. All of the
selected remedies and administrative restrictions in the
September 30, 1985 ROD for the aquifer unit remained the same.
Additions or modifications to the soils unit cleanup were as
follows:
* Installation of an SVES covering the area of soil
contamination over and around the historical drain
field on-site to extract PERC from the remaining
contaminated soil.
* Reduction in the amount of septic tank contents to be
removed and treated off-site. At that time, the
capability of off-site disposal consistent with the
CERCLA off-site policy was not available within Region
10 for the proposed 900 cubic yards of soil requiring
removal, as called for in the original ROD. Therefore,
contaminated solids and any water were removed from the
septic tanks and disposed off-site. The remainder of
the contaminated soil within the septic tanks and
around the historical drain field was treated via SVES.
During implementation of the remedy in the original
ROD, the septic tanks were found to be bottomless, were
left in place, and the soils treated via SVES.
* Soil and vapor testing continued until soil treatment
was deemed complete.
Establishment of cleanup goals for contaminants of concern
were delayed in both the original ROD and Amended ROD. These
documents recommended deferring establishment of the cleanup
goals for contaminated soil and groundwater until a thorough
evaluation of data, gathered during operation of the groundwater
pump and treat system and the SVES, was conducted. EPA has
determined that sufficient information has now been obtained to
establish cleanup goals at the site for all contaminants of
concern.
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SIGNIFICANT DIFFERENCES AND BASIS FOR THEM
Excavation of remaining PERC-contaminated sludge:
Results from soil sampling conducted in October, 1990,
following completion of soil remediation activities called for in
the original ROD and Amended ROD, identified elevated
concentrations of PERC at approximately 10-12 feet below ground
surface within one of the bottomless septic tanks (ST-1) on Plaza
Cleaners property. Field notes from the 1987 removal indicated
that some sludge was left in ST-1 when efforts were made to
remove the contents of the three (3) septic tanks. At the time
of the removal, rice hull ash was added in an attempt to solidify
the sludge in ST-1. Precipitation recharge probably infiltrated
the sludge/ash material containing PERC, resulting in leachate
movement downward to the underlying till and laterally and
downward through the till to the water supply aquifer below. The
soil sampling results, coupled with measurements of PERC
concentration in the head space of the SVES wells and information
contained in field notes, indicated that the elevated levels of
PERC in soils were likely localized within and below the culpable
tank at the site.
As part of the soil remedial action, high levels of PERC in
soil in the vicinity of ST-1 needed to be reduced. An evaluation
of two possible remedial alternatives was undertaken. The two
potential remedies evaluated were: (1) SVES, and (2) excavation/
treatment/off-site disposal.
The potential use of the SVES to remove PERC from the
contaminated sludge in ST-1 was found to be dependent on the
difference in permeability between the sludge material and the
surrounding fill and native gravels. Although no value of
permeability for sludge containing the rice hull ash thickener
could be found in the literature, intuitively it is expected to
be very low since the ash was added to thicken the sludge. No
references to the use of SVES on low permeability soils could be
found either, probably due to the fact that low permeability
soils are, by definition, unsuitable for treatment via SVES.
Since the literature search did not provide permeability
values for the rice hull ash (zorbital) and ash solidified
material, extensive field testing would have been required to
test the suitability of SVES as a treatment option. If the
sludge was determined to have suitable permeability for treatment
via the SVES, the system would require some modification in order
to provide treatment at the specific location of the contaminated
sludge and to accommodate any differences between sludge
permeability and soil permeability for which the system was
originally designed. Costs associated with SVES modification and
the time required to verify the effectiveness of this technology
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on rice hull ash-thickened sludge were both potentially
significant.
The other alternative considered was excavation, treatment
where necessary, and off-site disposal of the sludge. All
contaminated soil and sludge exceeding 500 ppb would be excavated
and treated via incineration if Resource Conservation and
Recovery Act (RCRA) Toxicity Characteristic Leaching Procedure
(TCLP) levels were exceeded. Alternatively, if the contaminated
material did not fail TCLP, it would be disposed at an approved
RCRA hazardous waste facility. This alternative was considered
more viable due to its technical practicability and feasibility,
timeliness, and cost.
Implementation of the excavation alternative occurred during
the months of June-July, 1992.
Ecology concurred with the implementation of this remedial
action and participated in the review of design documents
associated with this effort.
Establishment of cleanup goals:
Neither cleanup levels nor the point of compliance for soil
and groundwater contamination were established in either the
original ROD (September 30, 1985) or the Amended ROD (November
14, 1986), but were deferred until sufficient data demonstrating
the effectiveness of the remedial actions were available.
Therefore, via this ESD, EPA is establishing cleanup levels for
contaminants of concern in both soils and groundwater in
compliance with the original ROD and Amended ROD.
SOIL
PERC is the only contaminant of concern in soils at the
Lakewood site. The Washington Model Toxics Control Act (MTCA)
Cleanup Regulation Method A levels for PERC in both residential
and industrial soils is 500 ppb.
Risk information was also factored into the selection of an
appropriate cleanup goal for PERC in soil. A summary of health
effects information from the RI for potential soil exposure
pathways at the Lakewood site appears below:
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Summary of Health Effects for Soil Exposure Pathways
Potential Exposure to Soil
Ingestion of surface soil
Ingestion of subsurface soil
Inhalation of surface dust
Dermal contact/surface soil
Dermal contact/sub. soil
Inhalation of gases during
excavation
Increased Risk
not substantial
6X10"9 to 4X10"8
not substantial
not substantial
unquantifiable
26 times
ACGIH TLV-TWA
2.5 times
IDLH
Remark
new, clean soil
500-3800ppbPERC
new, clean soil
new, clean soil
no methodology
max. soil conc.
388 Oppb PERC;
absolutely
still air
0.006 times max. soil conc.
ACGIH TLV-TWA 388Oppb PERC;
0.25mph wind
speed
(ACGIH TLV-TWA: American Conference of Governmental-Industrial
Hygienists Threshold Limit Value-Time Weighted Average
IDLH; Immediately Dangerous to Life or Health)
The risk values in the above table were based on PERC
concentrations in soil prior to implementation of any soil-
related remediation efforts.
EPA is establishing the cleanup level in unsaturated soil
above the groundwater table at 500 ppb. This level is in
compliance with state regulatory requirements, is within EPA's
acceptable risk range of 10"* to 10"6, and will be protective of
the groundwater. Site-wide, surface and subsurface soil
concentrations based on existing data and confirmational sampling
results following completion of the final soil remedial action in
June-July 1992, are well below 500 ppb. Contaminated soil below
the water table is being treated as part of the groundwater
treatment unit.
Soil Standards PERC
MTCA Method A 500 ppb
Recommended Cleanup Level 500 ppb
GROUNDWATER
PERC, TCE and 1,2-DCE are the contaminants of concern in
groundwater at Lakewood. A review of current federal and state
regulatory levels for these contaminants in groundwater yielded
the following (in parts per billion):
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Groundwater standards
PERC
TCE
It2-DCE
Federal MCLs
MTCA Method A (PERC, TCE)
MTCA Method B (cis-1,2 DCE)
Recommended Cleanup Level
5.0
5.0
5.0
5.0
5.0
5.0
70.0
80.0
70.0
(MCL=maximum contaminant level)
EPA is establishing the cleanup level for groundwater at 5.0
ppb for PERC and TCE, and 70.0 ppb 1,2-DCE consistent with the
federal MCLs. These concentrations are as (or more) stringent
than the Washington MTCA Method A and B regulatory requirements.
Compliance with these cleanup goals is required throughout the
contaminated groundwater plume.
Implementation of institutional controls:
In the original ROD and Amended ROD, provisions were
included for the placement of administrative restrictions on:
(1) the installation and use of drinking water wells to prohibit
withdrawals of groundwater from the areas within the plume thus
minimizing the potential for use of contaminated groundwater, and
(2) on excavation into the contaminated soils to prevent the
possible release of contaminants in the future, resulting from
uncontrolled excavation on-site.
Residents whose properties overlie the existing groundwater
contaminant plume currently obtain drinking water from the
Lakewood Water District. Written reminders will be sent to these
property owners, real estate offices and drilling contractors
indicating the limitations on groundwater usage until cleanup
goals in this media have been met.
Soil confirmation sampling results indicate that the final
remedial action, conducted in June-July 1992, successfully
reduced site-wide concentrations of PERC below the 500 ppb
cleanup goal established in this ESD, eliminating the need for
institutional controls on land use designed to prevent direct
contact with contaminated soil.
SUPPORT AGENCY COMMENTS
Under MTCA, Ecology would usually elect to institutionalize
the requirement not to drill into, or use untreated waters from,
the contaminated plume via deed restrictions or local ordinance,
for example. However, in this case Ecology recognizes that the
original ROD and Amended ROD precede MTCA. The area is on a
community water system of which this site is a part, and the
contaminated groundwater is being treated and controlled by
Lakewood Water District. Ecology, therefore, concurs with EPA's
provision to provide written reminders indicating the limitations
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current groundwater usage to the appropriate parties
(particularly property owners and drillers). Public outreach and
education, combined with ongoing groundwater treatment and
monitoring, are considered adequate measures for the protection
of human health and the environment.
AFFIRMATION OF STATUTORY DETERMINATIONS
Considering the new information developed during the
remedial action and the resulting changes made to the selected
remedy, EPA and Ecology believe that the remedy remains
protective of human health and the environment. The revised
remedy utilizes permanent solutions to the maximum extent
practicable for this site and is cost-effective. It complies
with the NCP and other federal and state requirements that are
applicable or relevant and appropriate to this remedial action.
PUBLIC PARTICIPATION ACTIVITIES
This ESD, supporting information, and EPA's response to any
comments from the public will be added to the Lakewood site file.
For additional information regarding this ESD, please contact the
Superfund Site Manager for the Lakewood site:
Ann Williamson
1200 6th Avenue, HW-113
Seattle, Washington 98101
(206) 553-2739 or
Toil-Free: 1-800-424-4372
Ann Williamson, Superfund Site Manager
Date
Approved by:
Superfund Branch
"Date
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