United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Re*pc-iae
EPA/ROD/R10-85<006
September 1985
Superfund
Record of Decision
Ponders Corner, WA
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TECHNICAL REPORT DATA
fPlease ftttl Inunctions on the revene before completing)
1. REPORT NO.
EPA/ROD/R10-85/006
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
SUPERFUND RECORD OF DECISION
Ponders Corner, WA
(Second Remedial Action)
6. REPORT DATE
September 30, 1985
6. PERFORMING ORGANIZATION CODE
7. AUTMOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
B. 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
IS. SUPPLEMENTARY NOTES
16. ABSTRACT
Ponders Corner, or the Lakewood site as it is identified in the National Priorities
List, is located in Pierce County, Washington, south of the city of Tacoma. In July
1981, EPA sampled drinking water wells in the Tacoma, WA area for contamination with
purgeable halocarbons. The sampling showed that Lakewood Hells HI and H2 were contami-
nated with 1,2-dichloroethylene (1,2 DCE), trichloroethylene (TCE), and tetrachloro-
ethylene. In mid-August 1981 Lakewood water district took wells HI and Hi out of pro-
duction. ,
It was determined that the septic tanks and the ground disposal area of a commercial
cleaners were the probable source of well water contamination. Solvents used in the
dry cleaning process were disposed in the septic tank and liquid wastes consisting of
solvent-contaminated sludges and water draw-off were disposed on the ground outside the
cleaners. Initial Remedial Measures (IRMs) implemented in June 1984 at the site in-
cluded the construction of air stripping towers for wells HI and H2. The recommended
alternative for this second remedial action includes: operation of the H1-H2 treatment
system to continue cleanup of the aquifer; installation of variable-frequency con-
trollers on the well pump motors; changing fan drives to reduce treatment tower air flow
installation of additional monitoring wells, upgrading existing wells, and continuing
routine sampling and analysis of the aquifer; placement of administrative/institutional
(see spearate sheet) ____^___^__^____^__^___________^^_^^____________
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Record of Decision
Ponders Corner, WA (Second Remedial Action)
Contaminated Media: gw, soil
Key contaminants: 1,2-dichloroethylene (1,2
DCE), trichloroethylene (TCE), tetrachloro-
ethylene, solvents
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (Tins Report/
None
21. NO. OF PAGES
69
20. SECURITY CLASS (TMspagtl
None
22. PRICE
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TITLE AND SUBTITLE
Tille should indica Ie dC3~ly an~ brien~ the subjeO:I 0:0ver3~ u.1" Ihe report., 3nd be "is,'13Y~'" "rol11in~'nlly. S.'I ,uhlill~', il"us.''', 111 s11131i.'r
type or olherwlse subordlnale 1110 main ulle. When a rcportls "repared In mon° Ih3n ono: mlulII". n'/,,';lI Ih., "ril113ry lill~'. 3d.. Yolanw
number and include subtille for Ihe speciOc lille.
4.
I.
REPORT DATE
Each reporl shaU carry a dale indic:alinlalleast monlh'and year. Indkate Ihe hasis un whkh il was ...'le"I.'" (q:.. Jatc' "limll'. Jilt., "J"
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PERFORMING ORGANIZATION CODE
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7.
AUTHORISI
Give namtlsl in o:onvcntional order (John R. lJoto, J. Robt,,, !Joe', ('IC'.). List ;lulhur's ;lftili;atiun il" it ,Iin,'rs frOI11 Ih,' l",rl""'l11inj: .,rj:ani.
ulion.
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t.
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. 10. PROGRAM ELEMENT NUMBER
Use the program elemenl number under whio:h Ihe report W;lS prepared. Subor"inil'" numbllr, III")' be indll,I,',IIIII'a"'n'h~'"",
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11. SUPPLEMENTARY NOTES
Enter information nol included elsewhere but useful, such liS:
To be published in, Supersedes. Supplements. ctc.
Prcpllfed in o;uoperillion with. Translilliun ..I", l're""III~'d ii' "UII"'''''',,' "r.
11. ABSTRACT
Include a brief (200 WOTds or IfIS) factual summary of the most silmili,'lInl informillion o;onliline,1 ill .h,' "'11(111. " Ih,' "',,,,,. "'111';1111' iI
sipific:ant bibliography or literalure survey, men lion it here.
17. KEY WORDS AND DOCUMENT ANALYSIS
(a) DESCRIPTORS - Selecl flom Ihe Thesaurus of i::nlinccrinl! ilnd ~i"nlilk Terllls the proper ilulhuri/,,'11 "',,"' Ihill uJenllt"y Ih., lIIa)III
concept of Ihe research and arc sufficienlly specific and precise 10 be used ilS index enlries I"or l.:alilluj:II1j:.
(b) IDENTIFIERS AND OPEN-ENDED TERMS - Use identifiers for projecl nill111.:5. code nllmcs. ~'tlu1pmenl IIc'lj:nillurs. clc. Use "I'en.
ended lerms written in descriplor form for those subjects for which no descriplor e)(isls.
(c) COSA TI HELD GROUP. Field IInd group IIssignmenl5 ,lie to be Iilk"n ftom Ihe 1965 ('OS,\ 1'1 Suhiecl ('iI'",wry Ust. Sinn' Ihe mil'
jorily of documents are multidisciplinary in nature. the Plimary /'ield/Group ilssignmel\llsI will bII 'I,,:dfi~' "isn"line, iln'iI III' human
endeavor, or type of physical object. The applicationls) will be cruss-refclcnced with scrumlary I id,//l illlll\, ~"Ij:nllwlIl' Ihat will 1,,11111,
the primary poslingls).
18. DISTRIBUTION STATEMENT
Denote releasabilil)" 10 Ihe public or limitation for reasons olher Ih..n security for eJ\ilm"le "ReI"a'" (;lIh"'II~'''.'' ('ile any a~ail;ohlhl)" I"
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22. PRICE
Insertlhe price sel by the National fechnicallnformalion S,'rvice ur Ihc Governmenll'rinting OITil.:e. if knuwn.
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SUPERFUND RECORD OF DECISION
Ponders Corner, WA
(Second Remedial Action)
Abstract - continued
restrictions ~n the installation and use of wells; excavation and removal of the
septic tanks and drainfield piping on the cleaners property, and placement of
administrative restrictions on excavation into the contaminated soils to reduce
the risks associated with uncontrolled excavation. Total capital cost for the
selected remedial action is estimated to be $334,970 with O&M costs approximately
$85,700 per year. The aquifer cleanup level will be addressed in a later decision,
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Record of Decision
Remedial Alternative Selection
SITE
Ponders Corner, Washington
DOCUMENTS REVIEWED
I am basing my decision primarily on the fOllowing documents describing
the analysis of the cost and effectiveness of the remedial alternatives for
the Ponders Corner Site.
Public Comment Remedial Investigation Report Appendices, Ponders
Corner, Washington.
Public Comment Feasibility Study Ponders Corner, Washington
Summary of Remedial Alternatives Selection
Responsiveness Summary
DESCRIPTION OF SELECTED REMEDY
Continue operation of the Hl-HZ treatment system to continue
cleanup of the aquifer. The aquifer cleanup level will be
addressed in a later decision, based on data gathered during this
operation.
Install variable-frequency controllers on the well pump motors to
reduce energy requirements and thereby reduce costs. .
Change fan drives to reduce treatment tower air flow to reduce
energy requirements and thereby reduce costs.
Install additional monitoring wells, upgrade existing wells, and
continue rou.tine sampling and analysis of the aquifer to monitor
the progress of its cleanup and to provide an early warning of
potential n,w aquifer contaminants.
Place administrative restrictions on the installation and use of
wells to minimize the potential for use of contaminated
groundwater.
Excavate and remove the septic tanks and drain field piping on the
Plaza Cleaners property to reduce the risks associated with
uncontrolled excavation by removing the most contaminated soil,
and comply with other environmental la'~s.
Place administrative restrictions on excavation into the
contaminated soils to reduce the risks associated with
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DECLARATIONS
Consistent witn the Comprehensive Environmental Response. Compensation. and
Liability Act of 1980 (CERCLA). and the National Contingency Plan (40 CFR
Part 300). I have determined that the above Description vf Selected Remedy
at the Ponders CQrner site is a cost-effective remedy and provides adequate
protection of public health. welfare. and the environment. The State of
Washington has been consulted. and is presently reviewing the approved
remedy. .
I have also determined that the action being taken is appropriate when
balanced against the availability of Trust Fund monies for use at other
sites. In addition. the continued operation of the Hl - H2 treatment system
. modified with variable frequency controllers and reduced fan speed. and
excavation of the septic tanks and drain fields for off-site transport.
treatment. and secure disposal are more cost-effective than other remedial
actions. and are necessary to protect public health. welfare. or the
environment. All off-site disposal shall be in compliance with the policies
stated in Jack W. McGraw. Acting Assistant Administrator. Office of Solid
Waste and Emergency Response's r4ay 6. 1985. memorandum entitled Procedures
for Planning and Implementing Off-site Response Actions.
Tne remedial action includes the maintenance of institutional controls with
which to prohiDit withdrawals of groundwater from the area of the plume of
contamination. and the selection of the endpoint of groundwater and soil
treatment at the source area.
Selection will take into account the site specific and regional
characteristics and will be protective of the public health and the
environment. The endpoint levels of treatment are to be evaluated by the
Regional Administrator after two years from the execution of this document.
The Regional Administrator shall have the authority to approve modifications
to the choice and operation of certain aspects of the remedy as discussed in
the Summary of Remedial Alternatives Selection insofar as those
modifications are equivatent in effectiveness and cost or are necessary for
. the protection of health or the environment.
In addition. the action may require future operation and maintenance (0 & M)
activities. not including the 0 & M for the stripping towers. to ensure the
continued effectiveness of the remedY. These activities will be cons1dered
. part of the approved action and eligible for Trust Fund monies until such
time that the Regional Administrator makes the decision regarding the
endpoint level of treatment for soils and groundwater. At the time when the
levels are set. the Regional Administrator will also decide on the future
status and funding of 0 I M.
If additional remedial actions are determined to be necessary. a Record of
Decision will be prepared for approval of the future remedial action.
CS~5 'SO ~Cjt~
Date
~~~ 7\ ~~
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SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
Ponders Corner, Washington
SITE LOCATION AND DESCRIPTION
Ponders Corner, or the Lakewood site as it is identified in the
National Priorities List, is located in Pierce County, Washington, south of
the citY of Tacoma and adjacent to Interstate Highway 5 (Figure 1).
The Ponders Corner site includes the property upon which a business
known as Plaza Cleaners has operated for several years on South Tacoma Way
just north of the interstate, and the regional aquifer within about a
2,OOO-foot radius of Plaza Cleaners (Figure 2).
This area is predominantly residential to the north of the Burlington
Northern Railroad tracks, and commercial and light industrial alon9 Pacific
Highway. Lakewood Water District has two of its production wells (Hl and
H2) on a fenced sit~ immediately south of Interstate 5 and east of New York
Avenue. Residential property lies to the east of the well site, a~d McChord
Air Force Base is south of the wells bordering on New York Avenue. The
Lakewood wells are the location of the recently completed EPA Ponders Corner
Initial Remedial Action (IRM), consisting of two air stripping towers, a
pumphouse, a clear well, and associated piping and equipment.
SITE HISTORY
Groundwater Contamination Discovery
In July 1981, EPA sampled drinking water wells in the Tacoma,
Washington, area for contamination with purgeable halocarbons. The sampling
showed that Lakewood Wells Hl and H2 were contaminated with
l,2-dichloroethylene (1,2 DCE), trichlorethylene (TCE), and
tetrachloroethylene, oft~n called perchloroethylene (PERC). The chemicals
. tetrachloroethylene, trichloroethylene and 1,2 (trans.) dichloroethylene,
which were released into the environment at the site are "hazardous
substances" pursuant to 42 U.S.C. 9601(14). In mid-August 1981 Lakewood
Water district took wells Hl and H2 out of production, notified its
customers of the well contamination, and requested that a water conservation
plan be followed.
Wells Hl and H2 make up the Ponders Corner well field. Both wells are
approximately 110 feet deep and together can supply up to 2,600 gallons per
minute (gpm). Before the wells were taken out of production because of
contamination, they supplied water to the Ponders Corner/~anza P~rk area,
provided over 10 percent of the district's needs, and were a critical
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2
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TACOMA
. Pond8n Comer
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2
.
.
.
10
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- - -
SCALE IN MILES
FIGURE 1
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WASHINGTON
LOCATION OF PONDERS CORNER
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PLAZA
CLEANERS
McatORD AF8
UGINO
. MONITORING WILL
. TEST OR PRODUCTION WILL
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PONDERS CORNER
STUDY AREA
ICM.I.'",
FI GURE 2
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Source History
During August 1981, t~~ Washington Department of Ecology (WDOE)
inspected several businesses near the Ponders well field for potential
sources of contamination. Plaza Cleaners, across the freeway and about 800
feet away from the production wells, was the only business identified as a
major potential source of contamination. In the past, Plaza Cleaners
operated a dry cleaning and laundry business with three drycleaning
machines, two reclaimers (dryers), and five commercial washing machines.
Some solvent used in the dr,ycleaning process was discharged into the
cleaner's septic tank system. Other wastes containing solvent were
deposited on the ground outside the building.
Supplemental Investigations
. In October 1981, EPA drilled 10 shallow observation wells within 50
feet of wells Hl and H2 ~o investigate the potential contamination of a
shallow perched aquifer. It was hypothesized that contamination traveled
from the shallow aquifer to the production aquifer through the unsealed
gravel pack around well H2. The investigation showed that the shallow
aquifer above well H2 was not contaminating the production aquifer. USEPA
released a report for this first-phase investigation in January 1982.
In March 1982 a deep monitoring well (MW 11) was completed near wells
Hl and H2 to determine the depth of greatest contamination. The highest
concentrations.were found at depths of 85 to 95 feet. Between June 1982 and
January 1983, 13 additional deep monitoring wells were completed to further
explore and define the extent of contamination.
In February and March 1983 all the monitoring wells and wells Hl and H2
were sampled. The greatest contamination was found in MW 20, located
approximately 50 feet from Plaza Cleaners. Two deep monitoring wells (MW 12
and MW 14) located southeast of wells Hl and H2 were found to be
. contaminated by methylene chloride, suggesting a second potential source of
contamination from McChord Air Force Base.
In late March 1983, WDOE, EPA, and the Tacoma-Pierce County Health
Oepartment inspected Plaza Cleaners and sampled its septic tanks. The
analysis of septic tank sludge test yielded results as high as 483 ppm of
tetrachloroethylene. On April 1, 1983, WDOE issued Plaza Cleaners an
enforcement order to cease dumping solvent-containing material and to submit
and implement plans for investigating and eliminating the contamination
problem.
On April 11, 1983, the contents of the three septic tanks at ~laza
Cleaners were removed, salnpled, and placed in temporary storage pending
their classification. WDOE staff noted in their inspection report that the
septic tanks at Plaza Cleaners may not have impermeable bottoms. In early
May 1983, WDOE supervised the excavation and sampling of soils at Plaza
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to eliminate all discharges to the ground and groundwater by July 1, 1983.
On September 7,.1983, WDOE and ~he present and former owners of Plaza
Cleaners signed an agreement before the State Pollution Control Hearings
Board stipulating thJt Plaza Cleaners would cease discharging laundry and
dry cleaning wastes onsite, would remove contaminated soils, and would
cooperate with WDOE to protect the aquifer from contaminants released at the
site.
Plaza Cleaners has since stopped disposal of solvents to the ground and
septic tanks, and some of the surrounding soil has been replaced with
noncontaminated soil. Plaza Cleaners is no longer using their septic system
as they are currently connected to Lakewood's sewage system. It is not
known, however, whether all sources of contamination have been removed.
Ponders Corner FFS/IRM
In March 1984, EPA authorized a Focused Feasibility Study (FFS) of
treatment alternatives that could be implemented by mid-1984 on wells Hl and
H2 to restrict the spread of the contaminants in the aquifer and restore
normal water service in the surrounding area. An air stripping system was
recommended and designed. Construction was authorized in July 1984, and the
system started up in late September. Well water contamination was in the
range of 100 to 500 micrograms per liter (ug/L) of tetrachloroethylene at
startup, decreased rapidly after several days pumping, and has continued to
decrease.
Contamination levels in early March 1985, were about 50 and 10 ug/L of
tetrachloroethylene in wells Hl and H2", respectively. Treated water
concentrations of the contaminants have been well below the established
discharge limits since startup and are also consistently below the
laboratory detection limits.
Remedial Investigation/Feasibility Study
.
A Remedial Investigation (RI) was initiated to better identify the
extent and source of contamination. Field work began in December of 1984
and was completed in February of 1985. The results of the RI are presented
in the Public Comment Remedial Investigation, Ponders Corner, Washington,
Report. GroundWater elevation and water qualitY sampling continued during
March, April, and May 1985.
The Feasibility Study was initiated to develop and evaluate
alternatives which would remediate the contamination at this site. defined
by the Remedial Investigation. The Public Comment Feasibility Study,
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6
CURRENT SITE STATUS
Remedial Investigation Activities and Objectives
The purpose of the Remedial Investigation (RI) was to obtain sufficient
data in the area of Ponders Corner to determine the extent and source of the
contamination so that the need or the effectiveness of remedial measures
could be quantitatively evaluated during the Feasibility Study (FS). The
majority of the field work for the RI was completed in December 1984,
through February 1985. The field work completed included the following work
elements:
~investigation of site conditions by installing nine deep and three
shallow monitor wells to provide a comprehensive picture of the
groundwater regime (e.g., flow patterns, hydraulic connections between
l~ers), and to determine the nature and extent of groundwater
cont6mination and confirm the sources of contamination;
-excavation of the waste line at Plaza Cleaners and drilling of seven
soil borings to determine the extent and character of remaining sources
of contamination at Plaza Cleaners, and to determine if other sources
are contributing to the problem; and
-collection of samples for field and laboratory analysis to determine
the extent and concentration of contamination in the soil and aquifers
in the study area.
~drogeo10gy
Ponders Corner is situated on an upland drift plain that slopes gently
to the northwest, terminating at Puget Sound. The area around Ponders.
Corner has a maritime climate with cool, wet winters and warm, dry summers.
. Average annual precipitation is 40 inches, 85 percent of which falls during
the months of September through April. Mean lake evaporation is about 23
inches per year. Most of the evaporation occurs during the months with
lowest precipitation, indicating a strong seasonal trend for groundwater
recharge and surface runoff.
Local annual recharge for the open area immediately behind Plaza
Cleaners is estimated to be about 11 inches, or about 40 percent of the
total precipitation. Recharge in areas adjacent to Plaza Cleaners will be
less because much of the area is paved and drained to storm sewers. A
visual inspection of these areas found that about 50 percent are paved or
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The four hydrogeological units of interest which underlie the Ponders
Corner area are as follows:
-The permeable sands and gravels of the recessional outwash deposits,
known as the Steilacoom gravels
-The semiconfining silt and clay-rich Vashon till that contains lenses
of clean gravel in places
-The highly stratified. yet permeable. advance outwash deposits that
form the primary aquifer .
-The generally less permeable Colvos sand that grades to a clayey sand
or blue clay at its base. .
Figure 3 is a north-south cross section connecting the Plaza Cleaners
property with the Lakewood wells Hl and H2. This figure shows typical
groundwater elevations and directions of gl JUndwater movement under pumping
conditions.
The Steilacoom gravels vary in thickness from 1 to 58 feet in the
Ponders Corner area. The gravels are typically unsaturated. except in an
area east of Plaza Cleaners and near wells Hl and H2. In these areas
perched. saturated zones several feet thick can exist. These zones are
capable of yielding several tens of gallons per minute. Limited water level
data from monitoring wells screened in the gravels indicate that the
direction of flow is to the south near Plaza Cleaners and to the northwest
near wells Hl and H2.
The underlying Vashon till is highlY variable in thickness and moisture
content. Over the study area. the till can range from 8 to 92 feet in
thickness. It is thickest to the north and west of Plaza Cleaners and
becomes quite thin. and possibly discontinuous. southeast of wells Hl and
H2. While the upper portion of the till is generally unsaturated. saturated
. zones can be found elsewhere. particularly near the bottom of the till and
in gravel lenses foun~ in this zone.
One of these lenses appears to be large in lateral extent. covering an
. area including Plaza Cleaners property. This lens is saturated and appears
to be hydraulically interconnected with the Steilacoom gravels. Drawdowns
in shallow monitoring wells screened in the Steilacoam gravel unit were
observed during a 72-hour aquifer test of well H2. The rate and direction
of water movement in the till are difficult to estimate.
The surface contact between the till and the underlying advance outwash
is found at a depth of 25 to 84 feet. In the immediate vicinity of Plaza
Cleaners and to the north. the outwash is relatively thin (on the order of
20 feet). South of Plaza Cleaners and near wells Hl and H2 the outwash
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NORTH
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PLAZA CLEANERS
. SOUTH
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...1 ...2
1M
22
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200
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TYPICAL GROUNDWATER ELEVATIONS
UNOER PUMPING CONDITIONS
DIRECTION OF GROUNDWATER MOVEMENT
UNDER PUMPING CONDITIONS
NORTH-SOUTH CROSS-SECTION
BEtWEEN PLAZA CLEANERS
AND H1 AND H2
FIGURE 3
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Under nonpumping conditions (that is. when wells Hl and H2 are not
operating) the.general direction of flow in the advance out.~sh.is to the
northwest. The average gradient across the ponders Corner area is 0.0035
foot per foot. or about 18 feet of vertical drop per mile (Figure 4).
Under pumping conditions. a zone of capture forms around wells Hl and
H2. Wells Hl and H2 had been pumping a total of approximately 2.000 gpm
continuously since September 26. 1984. The approximate location of the zone
of capture formed by these two wells is shown in Figure 5. Theoretically.
groundwater within the zone of capture will ultimately be extracted by the
wells. Groundwater outside the zone of capture will continue to move toward
Gravelly Lake.
Local recharge to the advance outwash is mainly from precipitation that
percolates down through the Steilacoom gravel and Vashon till zones. The
primary point of local discharge is Gravelly Lake. The lake has no surface
inlet or outlet.
Groundwater Contamination Migration
Contamination of the site and groundwater resulted from effluent
discharges from septic tanks behind Plaza Cleaners and sludge disposal on
the land surface. Between 15.000 and 20.000 gallons of effluent were
discharged on a daily basis. Data on contamination levels in the effluent
are limited; however. sampling by the WDOE found that supernatant in the dry
cleaner's septic tank system contained 550 ug/L tetrachloroethylene and 29
ug/L trichloroethylene. At a flow rate of 20.000 gallons per day (gpd) and
assuming the supernatant contamination levels are indicative of the levels
discharged to the drain field. loading of PERC and TCE may have been as high
as 0.09 and 0.005 pound per day. during the years of the operation of the
cleaners. .
Effluent discharge from the drain field provided a significant driving
force for contaminant migration. The flow rate cited above is about 40
times greater than the estimated recharge rate of 17 inches per year for the
area immediately behind Plaza Cleaners. Based on the available soils and
geologic data. it appears that the effluent migrated vertically through the
Steilacoom gravels. Upon reaching the surface of the Vashon till. it may
have migrated laterally along the surface of the till until it reached a
conduit into the till (Figure 6). Possible conduits through the till
include the gravel lenses known to exist in the vicinity of Plaza Cleaners.
discontinuities in the till where it thins to the southeast. or the
suspected but never substantiated presence of dry well(s). The
contamination then worked its way vertically and laterally through the till
into the advance outwash. Once in the advance outwash. the contamination
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UGUID
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. MONITORING WELL
. TUT OR PRODUCTION WELL
- WATER LEVEL-CONTOUR, SOUD
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WHERE INFERRED. ELEVATION
IN FEET ABOVE MEAN SEA LEVEL.
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ICALE IN FEET
RE 4
WATER-LEVEL CONTOUR
MAP OF THE ADVANCE
OUtWASH AQUIFER,
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IN FEET AIOYE MEAN SEA LEVEL,
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ZONE OF CAPTURE
FOR WELLS H1 AND H2
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DIRECTION OF CONTAMINANT
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12
PLAZA CLIANIRI
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PLAN VIEW OF CONTAMINANT
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II
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ow ADVANCI OUTWAIM
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~ DIRECTION OF CONTAMINANT
MIGRATION
ow GRAVIL. WILL GRADED
GP PAVIL. POORLY GRADED
GM IlL TV GRAVEL
GC CLAYEY GRAVEL
IW lAND. WILL GRADeD
1M' lAND. POORLY GRADED
1M SILTY lAND
ML liLT. LOW LIQUID LIMIT
CROSS.SECTION VIEW OF
CONTAMINANT MIGRATION
-------
14
During the time when wells Hl and H2 were taken out of service,
contaminant migration in the advance outwash was mainly to the northwest in
response to the regional flow gradient. During this time some contamination
appears to have mi grated beyond the zone of capture for wells Hl" and H2.
The rate of contaminant migration in the 5teilacoom gravels and Vashon
till has probably decreased substantially following the cessation of
discharges from the Plaza Cleaners septic tanks in July of 1983.
Contaminant migration in these zones is now controlled by local natural
recharge.
Units of Contamination
The two relatively distinct units of contamination at Ponders Corner
are the near-surface soils and the aquifer.
50ils Unit
The near-surface soils on the Plaza Clearners property were
characterized with seven soil borings and six shallow test pits. 50il
samples from each boring and test pit showed PERC contamination in the upper
12 to 13 feet of soil in the immediate vicinity of the dry cleaner1s septic
tanks and drain field known to have received solvent-contaminated
wastewater. Smaller pockets of contamination were found to a depth of 25
feet near borings 582 and 5B7.
Figure 8 shows the inferred PERC distribution in the upper 5 feet of
soil. The highest concentrations are near the back entrance to Plaza
Cleaners where solvent-contaminated wastes were diposed on the ground
surface.
Figure 9 shows the tnferred PERC distribution along the main axis of
. the drain field. Except for several small pockets of contamination, most of
the PERC 15 located i.n the upper 12 to 13 feet of so11.
Based on the inferred lateral and vertical extent of soil
contamination, about 83,000 cubic feet (3,100 cubic yards) of soil are
contaminated with approximately 5 pounds of PERC. This equates to an
average soil concentration of 500 ug/kg. Where it was detected, PERC
concentrations range from 11 to 3,880 ug/kg.
Given an estimated recharge rate of 17 inches per year over the area of
soil contamination (approximately 9,000 square feet), the current.rate of
PERC leaching from the soils unit is 0.001 pound per day. This calculation
assumes an average soil concentration of 500 ug/kg and a soil-water
-------
..
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PLAZA CLEANERS
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- ELECT'UC
f'OWEALINE
CONCENTRATION DISTRIBUTION OF PERC
IN THE 0.0 TO 6.o.FT DEPTH INTERVAL
-------
NW IE
- "' :8 35 58-1 S8-8
------- ]
5OCr' -
-=-... = =- FILL
GW-GM
210 -- - =---......... ]
... - --:-- - ~ - STEILACOOM GRAVEL
0 QM 1
T.D. 28'
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GW,
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ow GRAVE~WELLGRADED
GMI' GRAVE~ POORLY GRADED
OM SILTY QltAVEL
GC CLAYEYQRAVEL
SW SAND. WELL GRADED
ilL SILT. LOll LIQUID LIMIT
CONCENTRATION DISTRIBUTION OF
PERC ALONG MAIN AXIS OF DRAINFIELD
-------
..
17
This rate of leaching will decrease over time as soil contamination
levels decrease. Assuming PERC is lost from the soil unit only through
natural leaching. it will take about 20 years for soil concentrations to
decrease below a detectioli limit of 20 ug/kg. .
Aquifer Unit
Contamination in the groundwater unit is actually a composite of the
contamination in the saturated portions of the Steilacoom gravels. Vashon
till. and advance outwash.
The magnitude and lateral extent of contamination in the Steilacoom
gravel and Vashon till zones are difficult to estimate because data are so
limited. particularly in the immediate vicinity of Plaza Cleaners.
In adaition to the limited number of wells which were screened in these
zones. sampling of MW 288. MW34 and MW36 has yielded little or no water
since being installed. Water was initially encountered in all three wells
during drilling and well construction. The lack of water in the Steilacoom
gravel can be attributed to the limited precipitation during the winter of
1985. and the cessation of discharges to the Plaza Cleaners septic tanks and
drain field. In addition. sanitary and storm sewer systems for the area
around Plaza Cleaners were recently completed.
The magnitude of contamination in the Steilacoom gravel zone in shown
in Table 1 in tenns of both average. minimum. and maximum groundwater
concentrations. These results were obtained by combining the concentrations
measured in MW 34 and MW 36. Although both wells are screened in the
Steilacoom gravel and Vashon till. most of the water in the wells comes from
the Steilacoom gravel unit.
The magnitude of contamination in the Vashon till zone is shown in
Table 1 in terms of average. maximum and minimum concentrations. Only the
concentrations measured at MW 208 were used because it is the only well in
. the till where contamination has been detected.
The magnitude and lateral extent of contamination in the advance
outwash zone are better defined and continue to change with time in response
to the extraction of groundwater at Hl and H2. Table 1 lists the average
and maximum and minimum concentrations based on water quality data collected
during February. March. and May of 1985. OVer these 4 months. average PERC
concentrations decreased from 33 ug/L in February to 13 ug/L in May. TCE
concentrations have also decreased. As of May 1985. TCE was detected only
at low levels in MW 16A. 1.2-0CE was detected in July 1984. Since that
-------
18
,>
TABLE 1
ESTIMATED QUANTITIES OF CONTAMINATION IN EACH ZONE
OF THE GROUNDWATER UNIT
SteU8C0C8 Gr..el VubOft 1111 AcSvanC8 Outwub
1.~ DC! !CI PEIIC 1.~ DCI !CE PDC 1.~ DC! !CE ~
A.en..
CClDC8DtI'aUOD (\I,lL) NO .~ 110 lID 58 ~,5oo lID 3 16
II&IIbU of (l)MrnUou 1 2 2 3 5 ~8
II1DI88/IIU188
CoDc8Dtl'at1oD hllllL) 83-139 12-103 570-. ,866 1.5-6.3 0.5-110
Total Vol.. of
CODtu1Date4 5 5 5 2.0.10' 2.0.10' 2.0&10' 7 7 7
II8CU8 (w ft) 7.5810 7.5x10 7.5810 ..5x10 ..5alO ..SalO
ApproIIS88te ....
of CoDt.81DaUOD
(11)>) . 20 14 1,300 l' 180
lID . DOt dIIt8Ctac1.
1,2 DC! . 1,2-cS1Cbloroetb,lene.
!CE . tl'1Cbloroetbfl.e.
PDC . tetl'aCbloroethJl...
\I,lL. ucrovr'" per Utero
-------
..
19
TaDle 1 also shows the volume of aquifer contaminated as of February
1985 and the approximate mass of each contaminant present in the zone. This
volume estimate is based on a lateral extent of contamination of 900,000
square feet for PERC and an average saturated thickness of 50 feet. The
lateral extent of contamination continues to decrease, particularly at the
higher concentration levels. Figures 10, 11 and 12 show the concentration
distribution for PERC in February, March, and May of 1985. Similar figures
were not constructed for TCE because it was detected only in MW 16A.
IRM (Hl, H2) Performance
Influent PERC and TCE concentrations from the advance outwash at Hl and
H2 have steadily decreased over the operating period of the stripping
towers. As of March 5, 1985, PERe concentrations at H1 and H2 were 9.7 and
52 ug/L, respectively. TeE concentrations were 0.45 and 1.7 ug/L in Hl and
H2, respectively, on the same date. Average performance characteristics of
the treatment system from January to March 1985 are shown in the table below.
Table 2
Hl-H2 PERFORMANCE
JANUARY 10 MARCH 1985
H1 Well H2 Well Two Towers Treated Water Stack Llischarge
Flow 800 gpm 1,200 gpm 2,000 gpm 2,000 gpm 60,000 cfm total
PERe 8.54 ug/L 71 ug/L 46 ug/L 0.12 ug/L
1.04 lb/day 0.003 1 b/day 1. 1 01 1 b/day
TCE 0.43 ug/L .2.1 ug/L 1.43 ug/L 0.07 ug/L
0.034 lb/day 0.002 lb/day 0.032 lb/day
TOTALS 1.1381b/day 0.005 1b/day 1.1331b/day
210 ug/m3
Groundwater Contamination Outside of the Zone of Capture for H1 and H2
As shown on Figures 11 and 12, a portion of the contaminant plume has
migrated beyond the estimated zone of capture for H1 and H2. Bec~use
concentrations at MW 30 have decreased since February 1985 and no
contamination has been detected at MW 31, it appears that the contamination
at MW 32 is an isolated portion of the plume that migrated beyond MW 30
-------
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CONTOURS fOR PERC.
MAY ,1185
ICALE III flIT
[ 12
-------
-
23
Measured concentrations at MW 32 during March, April, and May 1985 were
4.3, 5.0, ~nd 6.9 ug/L, respectively. As this contamination migrates beyond
MW 32 to Gravelly Lake, the concentration will decrease due to dispersion,
dilution by recharge, adsorption, and possibly degradation. Groundwater
contaminated at a level of about 7 ug/L at MW 32 is estimated to be at a
level of about 1 ug/L at the edge of Gravelly Lake.
PUBLIC HEALTH EVALUATION
Health Effects
The three chemicals of concern at this site are tetrachloroethylene
(PERe), trichloroethylene (TeE), and 1,2 dichloroethylene (1,2 DeE).
Members of the chloroethylene series, including PERe, TeE, and 1,2-DeE, are
central nervous system depressants. Acute exposure to these chemicals
results in lassitude and mental fogginess. There have been reports of mild
irritation, light-headedness, and mild headaches caused by exposure to these
chemicals.
The long-term, low-dose effects on the central nervous system have not
been well documented in the scientific literature. Acute exposure can,
however, produce damage to liver and kidneys.
Although few studies have been performed, these three chlorinated
ethylenes have not been found to be teratogenic in laboratory animals
tested. All chemicals appear to require metabolic activation for any
mutagenic effect. There is generally insufficient evidence on the
mutagenicity of these chlorinated ethy1enes. Both TeE and PERe have been
shown to be liver carcinogens in at least one strain of mice, and EPA
considers them to be suspected carcinogens. DeE is not believed to be
carcinogenic. The International Agency for Research on Cancer (IARe)
believes that there is inadequate evidence for classifying PERe and TeE as
human carcinogens. .
. To date, there are no known reports of illness in the Ponders Corner
study area attributed to the presence of PERe, TeE, or 1,2-DeE.
Exposure
All exposure and risk assessments were designed under the assumption
that the stripping towers at Hl and H2 would continue to operate and provide
a safe drinking water supply to the Lakewood Water District residents.
The potential routes for exposure from the contaminants at the Ponders
Corner site include use of the untreated groundwater in the uncaptured
-------
24
excavation at the Plaza Cleaners property, use of treated well water, and
exposure to surh,;e waters. The latter two routes were detennined not to be
significant exposure routes for the contamination at this site. Exposure to
surficial soils on the Plaza Cleaners property was also not considered as a
significant route of exposure, while the initial removal actions on site,
and the remedial investigation, removed or aereated the most contaminated
surface soils. Clean fill and gravel were used to recover the area.
Subsequently, only if excavating occurs on site will there by significant
potential for exposure to the contaminated soil. .
The maximum and mean concentrations found in the soil and groundwater
units are listed in the table below.
Table 3
MAJOR VOLATILE ORGANICS IN PONDERS CORNER STUDY AREA
1 984-1 985
Chemical
Detected Concentrations
Soils Groundwater
(ug/kg)a ~
Max. Mean ~
Tetrachloroethylene (PERC) 3,880 500 922 16
TrfchloroethYlene (TCE) 5 3 57 3
l,2-(cis)dichloroet~lene (DCE) 4 3 85
a Based on sof 1 wet weight.
The three chemicals of concern are highly volatile and easily escape
from contaminated materiah upon exposure to air. This feature, especfal1y
where .air concentrations can be diluted by winds, greatly reduces the
-------
,
25
In general, only PERC is considered as a major contaminant of the soil,
and only PERC and TCE are considered as rajor contaminants of the
grour.1water. .
Laboratory analyses of contaminants in the soils of the study area were
conducted on soil borings and test pit samples. Where detected,
concentrations of PERC ranged from 11 to 3,880 ug/kg and averaged 500
ug/kg. Small amounts of both DCE and TCE were detected. Concentrations
found were 1 to 4 ug/kg of DCE and 1 to 5 ug/kg of TCE. All concentrations
were based on wet weight of. soils.
Exposure to contaminated soil can occur by ingestion~ inhalation, and
dermal contact. The evaluation of workers at an excavation site indicated
that they would not receive significant exposure by directly ingesting the
soil. Methodologies for estimating dermal exposure to contaminated soil are
under development, and were therefore unavailable to quantify this exposure
route. However, compared to the poteutfal inhalation exposure, the amount
of potential dermal exposure would be relatively small. The exposure route
of concern in the soils unit was determined to be the potential for
inhalation of entrained dust and vapors during excavation at the Plaza
Cleaners site.
The absolute and realistic worst-case airborne concentrations of PERC
associated with different soil contamination concentrations during
excavation of a 4-foot deep by 4-foot wide by 120-foot-long trench across
the property, were calculated. The absolute worst-case scenario is for
excavation to occur under stagnant air conditions. For the realistic
worst-case scenario wind speed would be 0.25 mph.
Under absolute worst-case conditions, that is, during stagnant air
conditions, American Conference of Governmental-Industrial ~gienists
(ACGIH) Threshold Limit Value-Time Weighted Average (TLV-TWA) criteria would
be exceeded if excavation occurred in any area where the soil concentrations
. of PERC were in excess' Qf about 150 ug/kg. Under similar absolute
worst-case conditions, immediately dangerous to life or health (IDLH)
criteria would be exceeded only in areas where PERC soil concentrations were
above 1,500 ug/kg. Because the average subsurface soil concentration of
PERC is 500 ug/kg in the study area, it is likely that, under stagnant air
-------
v
26
The following table shows the probable PERC concentrations and exposure
limits for. inhalation during trench excavation.
Table 4 .
PROBABLE PERC CONCENTRATION AND EXPOSURE
LIMITS FOR INHALATION DURING TRENCH EXCAVATIONa
Absolute Reali stic
Worst-Case Worst-Case
Airborne Airborne ACGIHc
Sol1 Levels Levels Maximum Recommended Air Levels
Concentration of vap~rsb of vap~rsb TLV-TwAd IDLHe
(ug/kg) (mg/~l (mg/~l mg/~ (ppm) mg/~ (ppm )
3,880 8,600 2 335 (50) 3,400 (500)
1,500 3,300 0.9 335 (50) 3,400 (500)
1,000 2,200 0.6 335 (50) 3,400 (500)
500 1,100 0.3 335 (50) . 3,400 (500)
50 110 0.03 335 (50) 3,400 (500)
Of 40 0.01 335 (50) 3,400 (500)
aAssumes a trench 4 feet deep by 4 feet wide by 120 feet long.
bAssumes stagnant air conditions for absolute worst-case scenario and a
wind speed of 0.25 mph for realistic worst-case scenario; average speed for
Sea-Tac Airport is 9.1 mph.
cAmerican conference of Governmental-Industrial Hygienists.
dThresho1d limit value-time weighted a~erage (8 hours); OSHA values are
twice these amounts, that is, 670 mg/m (100 ppm).
;Immediate1y dangerous to life or health.
. Approximate detection limit is 20 ug/kg.
The above calculations are evaluating exposures to the
workers in the trench only. Due to dilution factors, there is no presumed
exposure to the public. The airborne concentrations of PERC as a function
of wind speed in the hypothetical trench are presented in the following
-------
. .
27
Table 5
AIRBORNE DERC CONCENTRATIONS FOR COMPLETE
SURFACE SOIL REMOVAL AND TRENCH EXCAVATION AS A
FUNCTION OF WIND SPEED
PERC Soil Perc Air Levels (mg/m3) for Wind Speed
Concentration . (mph)
Scenario (ug/kg) 0.25 1.0 5.0 9. 1
Trench Excavationa 500 0.3 0.07 0.01 0.008
Trench Excavationa 3.800 2 0.5' O. 1 O. 1
Surface Soil Removalb 500 0.04 0.009 0.0025 0.001
aAssumes a trench 4 feet deep by 4 feet wide by 120 feet long.
bAssumes the upper 4 to 6 inches of clean soil were removed instantaneously.
Note: ACGIH TLV-TWA is 335 mg/m3.
The average wind speed for the study area is 9.1 mph. Using a
conservative scenario of a 0.25 mph wind speed and the most contaminated soil
(3.880 ug/kg) the airborne concentrations of PERC would be two orders of
magnitude below the ACGIH TLV-TWA criteria. and therefore constitute a safe
working environment.
There is no significant exposure associated with inhalation of windborne
dust from the Plaza Cleaners property because the top 4 to 6 inches of surface
. ground materials have been replaced with new. clean materials.
The exposure route of untreated groundwater from the uncaptured portion of
the contaminant plume assumed the installation of a new well. There are
currently no known private well users in. or downgradient of the plume.
The exposure from any contamination in the water treated by the stripping
towers at Hl and H2 has been carefully monitored. The pumping and treating of
this contaminated aquifer. had. by January 1985. reduced the July 1984.
concentrations of the contaminants of concern in the groundwater. as measured
at Hl and H2 (Figure 13). PERC declined from 922 to 100 ug/L. TCE from 57 to
30 ug/L. and DCE from 85 ug/L to nondetectable levels. The currently
operating aeration tower system for these two wells achieves average removal
-------
.
-~
\ ,I
i ,
---------
---------
--------
- f: f: -r------
t ..... J
....
L-
--...-------
---------
---------
I WELLHI I
I IlOl' I
"'"'''' I ONUIID ~
"".. I
.
-
,
1I8QtI..CIIOEIM IIEIIGII CONCEII1'IUIIIO
1 - - -----------
~ DEllGNCONCEIIIIIA1ION
--------- ----------
---
N
0>
II
55
J8
.- ..e. .---.-.-.-........-.. --------.-.---.-.-... __e.
.
. - - ,. US '20'25
.. .. . 24""'"
.
.
. I
--..
. .
71 . .
tI Dee ..
.
-,. .
.....
.....
11 . 25
-.ocM4
.
-- AIIIr'"
WB.L",~cPBQ
......... WB.L",~(ICEI
- - - WB.LIII~(IIIRC)
......... WB.LIII~(ICEI
CONCENTRATION OFTCE AND PERC
IN WELLS H1 AND H2. SEPTEMBER
1984 TO JANUARV 1985
-------
29
concentrat~ons in the drinking water of PERC and TCE are calculated to average
0.2 and 0.9 ug/l, respectively. They are nondetectable by laboratory
analyses, as shown in the following table. .
Table 6
CONCENTRATION OF VOLATILE ORGANICS IN GROUNDWATER
FROM WELLS Hl AND H2 BEFORE AND AFTER AIR STRIPPING
JANUARY 1985
Raw Treated
Well Water Detection Limit Well Water
Chemical (ug/l) {ug/l} {ug/l}
PERC 100 0.4 ND
TCE 30 1.5 ND
l,2-DCE ND 0.3 ND
ND-Nondetectable.
. The treated groundwater does not present a significant exposure route.
No significant potential environmental impacts to .gravelly lake, Clover
Creek, and the immediate' area around Plaza Cleaners were identified.
Risk Criteria
The EPA Office of Drinking Water, Criteria, and Standards Division and
Tacoma-Pierce County Health Department have established health advisories for
-------
30
TABLE 7
CRITERIA ASSOCIATED WITH DRINKING WATER ONLY CONTAMINANTSa
. (ug/L).
Excess Lifetime Tacoma I s Considered
c~er Risk ~ 5d Acceptable Acceptable for. Human Usec
Chemical 1 - l~ ~ Criteriab 1 Day 1 0 Day s
Chronic - - -
PERC 0.088 0.88 8.8 0.8
TCE 0.28 2.8 28 2.7
l,2-DCE 27 4,000 400
aAssumes consumption of 2 liters of drinking water per day over a 70-year period
~EPA, 1980).
Suppl1 ed by Tacome-Pi erce County Heal th Department.
cMemorandum from William N. Hedeman, Jr., Director, Office of Emergency and
Remedial Response, to Lee M. Thomas, Acting Assistant Administrator, Office of
Solid Waste and Emergency Response, dated May 2, 1983.
dThese factors represent the incremental increase of cancer risks over the 70
year lifetime, from this exposure.
The recommended occupational air levels for volatile organics for the three
chemicals of concern are presented in the following table.
Table 8
MAXIMUM RECOr~ENDED OCCUPATIONAL A!R LEVELS
. FOR VOLATILE ORGANICS (mg/m )
OSHA ACGIH
8-hr 8-hr
Chemical TLV-TWA Ce11ing IDLH TLV-TWA STEL
PERC 670(335) 1,340(670) 3,400 335 1,340
TCE 540 1,080(810) 5,400 270 1 . 080
l,2-DCE 790 990 1 6 ,000 790 1 ,1>00
TLV-TWA: Threshold limit value--time weighted average.
Ceiling: Maximum short-term exposure limit (15 minutes).
STEL: Short-term exposure limit (ranges from 5 to 15 minutes).
IDHL: Immediately dangerous to life or health.
Note:
Assumes daily volume of inhaled air for an adult is 21 to 23 m3.
-------
31
The risk assessments evaluated the potential of exposure from four
exposure routes, even though actual exposure from three of these routes
had been d~termined to be insignificant. The four routes evaluated were:
exposure from treated water from Hl and H2, untreated water from private
wells, contact, ingestion or inhalation of contamination at the Plaza
Cleaners site, and contact with surface waters downgradient from the Plaza
Cleaners.
Excess lifetime cancer risks for drinking water, surface exposure, and
inhalation related to the contaminants present in the Ponders Corner study
area are summarized in Table 9.
Conclusions
The 10-6 risk level, which is the action level established by the
Tacoma-Pierce County Health Department, is not being exceeded by the
existing source-pathway-receptor system (treated drinking water). ACGIH
TLV-TWA criteria would be exceeded for workers if subsurface excavation
occurred, where PERC soil concentrations are in excess of about 50 ug/kg,
during absolutely stagnant air conditions. The Plaza Cleaners site is not
expected to contribute to increases in contamination levels of groundwater
above present levels. While the dry cleaners is no longer discharging any
additional contamination onto the Plaza Cleaners property, and the air
stripping towers are in operation, future levels of contaminants in the
groundwater are expected to continue to decrease. .
ENFORCEMENT AND NEGOTIATIONS
Only the owners of the property at 12509 Pacific Highway S.W. and the
operators of the Plaza Cleaners operating at that location have been
identified as potentially responsible parties. Additional monitoring
completed during the remedial investigation did not turn up any additional
potential sources of the'groundwater contamination. On September 30,
. 1983, EPA issued CERCLA.notice letters to the property owner and the
individual who was then the operator of the cleaners. WDOE then issued an
administrative order and signed a stipulated agreement with these
parties. When additional action was deemed necessary, EPA Region 10 and
EPA Headquarters, in consultation with WDOE, determined that SUperfund
money would be used for the completion of the Remedial
Investigation/Feasibility Study (RI/FS). When it was time to begin the
field work for the Remedial Investigation, EPA and its contractors were
denied access to the site by the property owner. The owner/operator of
the drycleaning business had previously sold his interest to a new owner.
The new owner/operator of the dry cleaners allowed EPA to complet~ any
on-site work required, as long as permission had been obtained from the
property owner. EPA applied for, and obtained a warrant in Federal
District Court to have site access for the Remedial Investigation on
December 18, 1984. The majority of the field work was completed from
December 18, 1984, to January 20, 1985, the time period specified in the
-------
32
c'
TABLE 9
SORMARY OF PONDERS CORNER HEALTH EFFECTS.
IDcnue4
EInxInn PatJnray Ri8k aa.azok
Actual V8. of 'l'nated 11811 Mater frea 11-112 7xl0-e
~1IIk1D9 ad oook1D9 Jlec8Dt _uuncJ CODC8IItraUou
au.8 frea 8tr1pp1D9 toIr.n lIS Dl1uted b1 atllo8pben
Gue8 frc8 baWDV .atel' b10!9
DuMl apo8Uft to baWDv .atel'
Jlgt8Dt1a1 V.. of VDtnated 11811 ..tel'
IIHI' II 12 9Jl10"
~1IIk1D9 8DG CDOk1D9 7 UV/L JIDC, 11811 '52
au.8 frea bath1D9 wat.1' 9Jl10!l 11811 below 'ltV-ftA 1...18 .. .
DanaI aponr. to bath1D9 water 7 UV/L PIX, 11811 12
Jlgt8Dt1al IIpo8un to &011 at Plua
Cl88D8n Site
IDP8UOB of aurface 8011 lIS ...., cleaD 8011
IDp8t1OD of nbaurface 8011 6&10 -9 ~ 500 UV/q to I,. UV1k9 PIX
..10
IDbalat10D of 8Ul'face dust lIS ...., cleaD 8011
Derul C»Dtact to nrface 8011 NS Nev, deaD 8011
Derul CODtact to nb8Ul'face 8011 ~ No _tbodolOU
IDbalaUOD of 9...8 dur1D; ucavat10D 26 t1M8 ...1... 8011 COIIC8DtraUOD of
ACGIH 'ltV-'l'IfA 3,180 UV/k9 PDC, ab801utelf
2.5 t1M8 8Ull 811'
IDLH
0.006 t188 "'1-. 8011 COIIC8DtraUOB of
ACGII 'ltV-'l'IfA 1,880 UV/k9 1'111:, 0.25 -
.1Dd 8pe8d
IIpo8un to Surface ..ten Sa10 -7 ~
1.8UOD 0.. UV/L for Gr...ll, Lak. OBlf
1xl0
Gue8 frea bath1D9 . 11811 below 'ltV-'l'IfA 1...18
Derul coatact Sal0 -, ~ 0.. \AIL for Gravell, Lak. OBlf
1xl0
e .
CoD8il!8raUou u. pr18arl1, for PDC aD!! 'I'C! 1D pouD4ntu aD!! for
PDC 1D 80118. DeE.u DOt a ..~or C»DtD1DaDt 1D tbe 8tu4J 8I'H.
lIS . DOt nb8t8Dt1al.
-------
"
"
33
on site was required. Upon request, the property owner signed a consent
for access to property statement on January 29, 1985, allowing EPA to
continue the Remedial Investigation. On June 17, 1985, upon completion of
the draft RIfFS, CERCLA notice letters were once again issued to the
property owner and the former operator of the Plaza Cleaners. These
letters encouraged the recipients to undertake the next phase of the
corrective measures needed at the site. Neither recipient responded
within 14 calendar days, nor has there been a"y correspondence subsequent
to this ~ime period.
ALTERNATIVES EVALUATION
Objectives
The objectives of the proposed remedial action are to:
1.
Evaluate the potential health risks associated with the no-action
alternative which assumes the status quo of stripping towers
operation continued.
Reduce potential health risks associated with on-site excavation
and use of contaminated groundwater below those for the no-action
alternative.
2.
3.
4.
Meet requirements of other environmental regulations.
Increase the efficiency of the existing IRM, to reduce energy
requirements and thereby reduce costs.
Alternative Screening Process
Alternatives were screened separately for the soils and aquifer
. units. .-Criteria consioered in the screening included technical
feasibility. effectiveness, institutional requirements, costs, and other
site and technology-related considerations. Table 10 lists the
alternatives that were. considered and whether or not they were considered
for more detailed evaluation. Despite its high costs, soil excavation
passed the screening process because it would reduce risks and provide an
alternative for the soils unit that would satisfy Resource Conservation
Recovery Act (RCRA), and exceed public health and environmental criteria.
Vertical and horizontal barriers failed because they would provide no
improvement in public health protection. Lack of technical feasibilitY
was the primary reason that flooding failed. Finally, the alternative
water supply was dropped because of the lack of known sources, high costs,
and long implementation times.
Cost and noncost criteria were used to evaluate in detail each
alternative that passed the screening step. Noncost criteria included
technical feasibility, environmental impacts, institutional requirements.
and public health impacts. Table 11 provides a description of each
alternative, considered in detail, along with the EPA evaluation category
that each alternative satifies. Tables 12 and 13 summarize the results of
-------
Unit
5011
Landfill
Aquifer
34
"
TABLE 10
ALTERNATIVES THAT PASSED SCREENING
Alternat1ve
Excavate or treat
Cap
Vertical barrier
Horizontal barrier
Flooding'
Administrat1ve restrictions
!n-place treatment
No act10n
Extract10n & treatment
Modify Hl-H2 system
Monitor
Alternative water supply
No act10n
Sceeninq Result
Pass
Pass
Fail
Fail
Fail
Pass
Pass
{conditionally}
Fail
Pass
Pass
Pass
Fail
-------
Unit.
Soil
~uifer
,
TABLE 11
DESCRIPTION OF REMEDIAL ALTERNATIVES CONSIDERED IN DETAILED EVALUATION
alternati.e De.eription
61 - Exca.ation of 2'.200 Cy to reduce PERe to
nondeteetion Ii-it
62 - Excavation of 1.500 CI ~n .one of 8O.t
pr~ble future excavation to PERe nondetec-
tion Ii-it "
83 - Exea.ation of J.100 CI i. 80ne of 8O.t pro-
bable future e.eavation to reduce PERC to
500 119/t9
64 - Sxea.aUon of I. no CI in 80ne of 8O.t pro-
bable future exea.atlon to reduce PERC to
1,000 119/t9
55 - Cap
56 - Ad8lnl.trati.e re.trlctlon. on on.ite excava-
tion and well In.tallatlon
81 - Vapor ..tractlon
81 - 110 action
S' - Exea.atlon of '00 CY and re.o.al of septic
tank. and 8088 drain plpln9
At - additional 9roandwat.r .xtractlon near"" 32
to"r88OV. uncaptured portion of plu88
VulaUon
SIA - DI.po..l in off.lte aclA landfill
518 - DI.po.al by off.lt. ac'A
InclneraUon
SIC - DI.posal In on.lte .car. landfill
SID - onslte treat88nt in kiln
S2A - DI.po.al In off.lt. RCJA landfill
528 - On.lte treat88nt in kiln
S3A - Di.po.al in off.lt. aclA landfill
s3i - On81te treat88nt in tiln
64A - Di.po..1 in off.lt. aclA landfill
845 - on8lt. treat..nt in kiln
S5A - Clay/...brane cap
S5B - Clay cap
SSC - A8phalt cap
AlA - Di.po.al In .tOr8 sewer
AI8 - Yreat88nt by air .trlpplh9 at new
...11
Ale - Yreat8ent by air .trlpplft9 at
II/H2
EPA EvatuaUon
Cateqory
I
I
2
. 3
4
4
4
4
4 w
U1
4
3
2
4
5
4
5
4
3
]
-------
Unit
se9971FFP2
TABLE 11
(continued)
Alt.~natlv. Description
A2 -.Bxt~actioa froa till unit
AJ - 11-12 change ~o ~educe costs
At - ~reat~nt sy.~e. chaRges to reduee costs
AS - Monitor!n, to track cleanup and detect eon-
taaination froa other potential eoure.s
A6 - No action
Variation
A2A - Disposal in Stora Sewer
A2B - Shipaent by tanker to ha..~doue
waste dispoe.l facility
AJA - Puap chaRges
AJB - Va~i.bl. f~equ.ncy cont~oll.rs
AtA - Wate~ flow inere.s.
AtB - Fan speed reduction
EPA Evaluation
Cateqory
4
4
5
5
.
S
S
S
S
W
-------
TABLE 12
SUMMARY OF DE'T~ILED EVALUATION FOR SOIL UNIT ALTERNATIVES
8nnco.t Crlte~1. Co8t c~it.ri.
Enyh-t.l ....UtuU_l
1leMd1.1 alternathe Yec:hnlcel r...1bility ....ct. .equ1~_..t. PubUc ...ltla .1IP8Ct. Cap1t.l-$ !!!!!:!.. '~...nt _~th-S
51 Deep hC.".Uon
51A--orf.1t. Landr111 r...1bl.. ..r.t, th~.t Ml..1.1 C08lPU.. with V1~t..ll, .lbalaet.. '7. S40.ooo . '7.!t40.ooo
dllrilllJ .ac.".UOII requ1~_t. .ac.".Uon ri.'
SI8--orr.u. r...1bl.. ..f.t, th~..t . M1nl.1 C08IPU.. w1th V1~tU8ll, elba1aet.. 'JO.8J!t.000 'J0.8)!t.000
Inc1...~.Uon dud.. .8C.".U~ ~equh_..t. ..C.".UOII ~1.'
Slc--on.1te Landfill re..1ble. ..fet, th~.t M1nl.1 Acceptebl. V1~tual1, .11.1nat.. J.16!t.000 24.000 1.200.ooob
dudlllJ ..c.".UOII..OIM dhpo..l .ac.".UOII ri.' no ,..nl
requ1~_..t. techn1que.
fo~ 80St
"..t..
SID--on.lt. Tr..t..nt ft..t88nt technolO9f Ml..I.I. Subject to Virtual I, .11.1aete. J.l".ooo J.148.ooo
deY81a.-..t.l eacept .t .1te-apec1fic .ac.".Uon ri.1I
t~e.tae..t re,,1-
.1t.
S2 p.~t1.1 Iac.".t1011 tl W
PERe Detect10n L1.1t "'-J
S2A--Off.ite re..1ble. ..f.t, th~.t Ml..'-l Vl~tuall, .I..l.-t.. 2.140.000 2.J40.ooo
Landfill du~ ll11J .ac.". tlOll. 0lIl .ac.".Uon riall
~equ1~...nt.. t~..t88nt
technolO9f dewela.-8t.1
S28--on.lt. Tr..t..nt r...1bl.. ..f.t, thr..t Mln1..1. Ma, _t _t V1~tuall, .1balaete. 1.!t91.ooo I. !t91.ooo
durilllJ ..C...UOII. 0lIl .acept .t IICM o~... ..c.".Uon ~1.11
~equl~.....t.. t~..t8eDt tr..taent cI......,
technolO9f develCJ1881't.l .ite 1...18
SJ P.rU.I bC.".Uon to
sou 119/11, pac
SJA--orr.lt. Landfill r...lbl.. ..r.t, thr..t Mlnl..l Ma, _t _t ~. ..c.".Uon 1.16.000 1.126.000
dudll9 .ac.".Uon. 0lIl IICItA or'" ~1.'
requ1~...nt.. t~.taent cl..n..,
technolO9f dewelCJ1881'tal 1...1.
SJ8--on.lt. fte.t88nt r...lbl.. ..f.t, thr..t MI..1..1. Ma, _t _t .educe. .aca".Uon 8!tJ.000 8!tJ.000
du~11I9 ..c...Uon. 0lIl e.c.pt .t IICM O~ IID08 ~1.11
~equ1~...nt.. t~..t88nt tr..taent c.e.nup
t.chnolO9f de..1CJ1881'tal .Ite .e..l.
.Oetection li.1t .ppro.l..t.I, 20 ~9/119 '£Re.
-------
TABLE 12
(continued)
Moncoat Criteria Coat C..ileda
Envir_ntal InaUtuU-l
...-dlal Alternati.. 7echnlcal re~albil1ty IlIIp8cta .equir_nta Public Healtll ItlllKta Capital-S !!!!!:L '..eHnt tIo..th-$
.4 'artlal ..ea..tion to
1 .000 .....,., .ue:
84A--offalte Landfill r...ibl.. ..fet, threat Mln"'l ..., not _t .educe eaca.atlon 479.000 479.000
durl", .aca.aUnn. 0611 IleIlA or IIDOB rl8k
requl..-.ent.. treat8ent cleanup
technolO9Y ~..lop8ental level a
848--onalte 7reat8ent r..albl.. ..let, thr.at MIn"'l. May not 8eet Ieduce eaca.aUon 508.000 508.000
durt", .ac:a.aUon~ 0611 eacept at IleIlA or IIDOB r18k
requlr...nta. treat8ent trcat8ent cleanup
teehnolO9Y devellJl88llUI aUe lev.la
8S Cappl...
8SA--Cla,/888brane r..albl.. 06N requlr_nta lIone C08PUe. witll 1Ieduc:. potential for 7)..00 8.340c 152.000 \
requir_nt. Inadv8rtent UO "eanl
eacavatlon w
0)
SS8--Clay F...lbl.. 0IIII requir_nt. Mone C08PUe. with ~ potenUal for 60.000 6.900c 125.000
requir_nt. lRadvert.nt UO ,eaul
.aca.atlon
S5C--A8flha1t r.aalbl.. 0611 requir_nt. Mon. C08PIi.. wltll IIeduc:e potenU.I for 28.400 I.oooc 37.000
nqulre8eRta &n8cIvertent UO ,ea...1
cl..ca.atlon
86 Ad8lnl.traU.. reaalble Mone Me" oot _t IIeduc:e riP of .ac:a-
.eaulcUon IleM or IIDOB .ation without worker
cleanup protecUon
1...1a
87 vapor r..trectlon 'r..l.lnt. deve lop8eRt al All' Ma, not _t Virtual I, .ll.1nate. 38.SOO 38.500
dl8cllarlJ8 IICM or IIDOB .aca.aUon rhk
d...up
1...1.
88 110 AcUon IIone "a" not _t PotenUal eaca"atlon
IICM or tIDOB dak
d...up
l..ela
89 'arUal ..cavation. F..albl.. ..ret, thr.at . "i"I_1 .educe eaca.atlon 2J1.2oo 2)1.200
of'alt. landfill durl", .aca.atlnt. GIlt r1ak
.hpo..l requlr...nt.. t..eat88nt
tec:llnolO9Y daY8lopaental
-------
"
TABLE 13
SUMMARY OF DETAILED ANALYSIS FOR AQUIFER UNI~
~t Crlterl. ,... CCI8t Crlterl.
--I-t.l luUtuU_1
1leMd1.1 Altel'ft8th. Tedmleal P888lbIlU, 18PKt. IleqUI..-nt. Publle ..alth l8P8Ct. CepU.1 -!!!!L ~re_t WOrth
AI htraeUon ".r .. U
AIA--StOr8 ~r ,...Ibl., 5- to '-ye.r 110M. el18l- Water quilt, IIecIuc:e 9roundwat.r ,. ,000 8,500 U!', JOG
DI8p0881 .1.... elaan.. tI- nate PElle .tandard. will UM rlak 8. yearal
.19raUon to be applied
Gra-II, La"a
AI8--Alr StrlpplftfJ r.a.lble, 5- to '-year 110M. ,,1181- CCl8pUe. with lIeduce 9roundwat.r 412,000 9,500 445,000
.1.1- daan.. U..., 0611 nat. PElle requlr-nt. UM rlak 8. yeu.I
raqub-t. .lqraUon to
Gravell, La,.
AIC--Tr.at at HI-HZ r.a.lbl., 5- to '-ye.r 110M. el1.l- CCl8pUa. with -..- 9roundwatar Z46,ooo 14,500 )19,000
.In'" daan.. U-, 0611 nate PEIIC requlr_nt. UM rlak 16 ,aaral
requb-nt. .lqraUon to
Gravall, La'e
AZ btraeUon rr- Till to.
\0
A2A--St0r8 ~r HIfJIh prabebillt, of failure 110M "ater quality PoteaUal ,roundIMt.r 2,000 1,500 n,ooo
0"110..1 .tandard. wUl u.. rlak no yeu.'
be appl led
A28--Tanker Truek HIfJIh prab8blllt, of fallura !lone CCl8pUa. with Potential ,raandwater 16,000 '1,000 462,000
Oiapoul requb-nU UM dak no ,.anl
A1 HI-8Z MOdification
AJA--"'" Cba18CJ8 re..lble, 10- to IZ-year Hone CCl8pUe. wltlll Poteatlel ,roundIMter 18,000 2J ,000 187,000
.Inl- el"an.. tl- requb-at. UM dak no ,.anl
A18--vart_l- rea.lble, 10- to 12-yeer !lone CGllPUe. with Potential ,roundIMter 58 ,000 18,500 162,000
Prequaner .lnl808 elean.. tl- requb_nt. UM d... (10 ,eanl
Controller
.. Treat88llt S,.t-
MOdU IcaUon
A..----tar Plaw r.a.Ible, 8- to "year ......, reduce CallPUe. wi till . Potential ,~ter 0 a U5,.OOlb
Incre... 81.1- dean.. U- PBM: .Iqre- requb_nt. UM d ak 88 ,.anl
tl- to Cra.-
elly ""a
A.8--Pen 8peecJ r...lbl., 10- to 12-year 110M CGllPII.. wltll Potantl.1 ,roundweter Z,OOO 15, JOG 219,000
l18d8c:t 1- .Inl... eleanup tl- requl_nU . UM d.' 110 ,ear.1
.~ chanqe for 8 ,ear.. 1Ied8c.. de.nup Une b, J year.;
-------
""'1.1 Al~.rnatl..
AS
IIonltod...,
A6
110 acU-
Yechnlcal Fea.lbility
r...lbl., OMI ~...h--tI
r...lbl., 10- to 12-year
.ini- cI.anup. t"', 0."
requh_nt..
TABlE 13
Ccont1nued)
~.t Criteria
Enwh-ntal
I....ct.
lion.
IIone
In.UtuU-l
lequlr_nt.
llay not _t
IICItA ..... IIDOC
cleanup 1...1.
May not ~
IIC.. and IIDOC
c:eanup 1...1.
COlt Cdteda
PotenUal 9r~a~.r
U88 r hk
Public ..aith 11IP8Ct. Capital
22,000
PotenUal 9~~~.r
u.. ~i.k
J2.OOO
-!!!!!.... Pre_~ IIorth
219.000
'10 reant
~
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. '
41
Soil Unit Alternatives
The major concern associated with the no-action alternative was that,
under stagnant air conditions, PERC concentrations in portions of the soil
unit would be high enough to generate airborne concentrations in excess of
the TLY-TWA, if these portions of the soil were exposed through excavation.
The public health evaluation also concluded that, under conditions of
minimal air movement, airborne PERC concentrations in an excavation would
be well below the TLV-TWA. Thus, the soil unit alternatives should be
compared in terms of their costs and ability to reduce the risks
associated with potential onsite excavation. Impacts that each
alternative have on reducing PERC leaching to groundwater are not
considered important because leaching under the no-action alternative
represents only an equivalent concentration of 0.04 ug/L at wells Hl and
H2.
Each of the $1(1 excavation alternatives provides some degree of risk
reduction. Alternative Sl--Deep Excavation provides for almost complete
risk reduction at a very high cost. Total costs range from $71 million to
$3 million, depending upon whether the soils are treated and disposed
offsite or onsite. The lowest cost variation for Alternative Sl is onsite
treatment (Alternative SID). Onsite treatment in a kiln, however, is a
developmental technology, and could result in impacts to the environment
during stockpiling and treating of the soil. The magnitude of the
environmental impacts would depend upon the characteristics of the site
chosen for the treatment plant. Disposal in an onsite RCRA landfill
(Alternative SlC) is similar in total cost to onsite treatment. .
One disadvantage to all the excavation alternatives is the potential
worker hazard associated with removing contaminated soils from beneath the
building. Breathing apparatus would likely be required because airborne
PERC concentrations may exceed worker limits.
Partial excavation to remove the most highly contaminated soils can
provide a range of ri~k reduction depending upon the maximum soil
concentration limit that is selected. Alternatives 52, S3, and 54
represent those possibilities in that the maximum PERC concentration in
soil following implementation ~f each action would be the detection limit
(i.e., 20 ug/kg), 500 ug/kg and 1,000 ug/kg, respectively. Figure 14
gives the approximate cost of partial excavation as a function of the PERC
concentration in air that would occur under absolute worst-case conditions
(stagnant air in a trench). Avproximate cost curves are given for both
-------
42
'0.
o.
..
....
..-
.
. ....\:---"
\ --...,
........ .
1-
J -
.
I
,
I
\ "
\ ,
\ ..)~
\~& \=
\ \
,
,
......... \
\
'.
.
'0
.
.
.
"
,
...
..
OA
u
at
..
,..
,.. ..
018 ...
nv.,.&
1.0
...
RISK REDUCTION VS. COST
FOR PARTIAL EVALUATION
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. .
43
Only Alternative S2, Partial Excavation to the Detection Limit, would
reduce potential worst-case airborne concentrations below the TLV-TWA.
This alternative provides the same .evel of risk reduction as Alternative
Sl for about $0.8M to $1.6M less because detectable contamination would be
removed from the zone of future probable excavation. Thus, Alternative S2
is more cost-effective that Alternative Sl.
Both Alternative S3, Partial Excavation to 500 ug/kg, and Alternative
54, Partial Excavation to 1,000 ug/kg, could result in concentrations
above the limit. The approximate cost to reduce potential, absolute
worst-case concentrations to the TLV-TWA would be approximately $1 million
if onsite treatment is used or $1.8 million if offsite disposal is used.
The above comparisons are valid only for absolute worst-case
conditions. Under the more realistic conditions of minimal air movement,
PERC concentrations would likely be at least three orders of magnitude
lower. Minimal air movement would produce concentrations well below the
TLV-TWA even given the maximum known PERC concentration in the soil unit
(i.e., 3,880 ug/kg). Thus, if one assumes absolute worst-case conditions
have a low probability of occurrence, there is little incentive to
implement any of the partial excavation alternatives as discussed above.
Subsequent to the development and evaluation of the soil excavation
alternatives, which are based on achieving target cleanup levels, another
partial excavation alternative was introduced for consideration.
Alternative S9 consists of excavating and removing the septic tanks,
drainfield piping, and directly associated soils. Excavation under the
building would not be done. Excavated soil and construction materials
would be disposed in a licensed landfill.
Although the contents of the tanks were previously pumped, some
question remains whether the tanks have bottoms or not, and whether all
the contents were removed. In other words, it is suspected that sludges
may exist in the tank~, drainfield, and adjacent soils, and that this
. material- may have higher levels of contamination than were measured in the
RI soil sampling.
The performance, reliability, implementability, and safety of
Alternative S9 would be the same as those for the other partial soil
excavation alternatives discussed earlier, except that the worker hazard
for excavating under the building would be eliminated.
This alternative would consist of excavating approximately 900 cubic
yards to remove the tanks and drainfield piping to a depth of about 10
feet. Some building shoring would be required (Figure 15).
-------
. .
UGIIIID
t '.
.
\"'I..~ 28 .1:.:'.1;
.
:.:; :. :.
~ DRAIN"II.D L.INII
o
IOIL.IORINGI
IXCAVAnD VOLUME. tOO ~
o
~ .. ~'
Ci
S~ ~ .
o
44
PI.AtA \;L[Af\;tH~
.
...
IHORING
..
DE"" 1 10 FT.
REMOVE TANKS
. DIWNFIILD
~~., j. ..
:'
SE' .,
~
....
\ ~ : . .
~ :. ".; ;
10
@
TANK AND DRAINFIELD
EXCAVATION
ALTERNATIVE 58
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45
TABLE 14
ALTERNATIVE S9--TANK EXCAVATION
Construction
Excavate 900 cubic yards
Remove tanks and drainpipe
Haul and dispose-Arlington'
Building shoring-70 1 ft
Backfill
Costs ($)
$ 5,070
400
125,000
48,200
11,430
$190,100
9,800
5,600
1,200
24,500
$231 ,200
Construction Subtotal
Health and Safety 15S of site costs
Mobilization and temporary facilities,
7.5~ of above onsite
Bonds and insurance, 1.5S of above onsite
Contingency, 3bs of above onsite
Estimated Construction Total
Engineering and Design
Table 4-8
Services During Construction
Table 4-11
$ 12,750
9,500
Subtotal, Initial Cost
Annua 1 O&M
$ 253,450
-0-
. Project PW
$ 253,450
The public health result of the alternative would be to reduce the
risks associated with potential future excavation in this area. This
reduction in risk would result from the removal of soils previously
characterized as containing about 3,800 ug/L PERC and from the removal of
the tanks and drain piping, which may have contaminated sludges.
The excavation would not remove contaminated soil to a predetermined
level, as with the other soils removal alternatives, and would leave some
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. .
46
However. it would remove the most contaminated soil from the area around
the buried utility lines. which would be a likely area for future
excavation~ The resulting nealth risk would be equivalent to tba~ of
Alternative S2.
The institutional issues for Alternative S9 are the same as those for
Alternative S4 . discussed in Chapter 4.
Alternative SS--Capping provides a relatively low cost means of
addressing potential risks posed by onsite excavation. While this
alternative does not eliminate the source. it does provide a physical
barrier that would reduce the potential for inadvertent excavation.
Alternative SS is three to nine times less costly than the least expensive
partial excavation alternative.
The most cost-effective alternative is Alternative S6--Administrative
Restrictions. This alternative provides for the notification that a
potential hazard exists in onsite soils and that appropriate ~recautions
should be taken during excavation. Such a noti.'ication would reduce risk
at essentially no cost. The one disadvantage of this alternative is that
it provides no risk reduction for inadvertent excavation.
The least costly combination of alternatives that would provide some
level of risk reduction would be Alternatives SSC and S6. Alternative S6
would provide notification to most individuals who would conduct onsite
excavation. while Alternative SSC would limit the possibility for
inadvertent excavation. A potential health threat would still exist.
however. because the contamination would remain in place. This threat
could be reduced only through excavation and removal or treatment. The
most cost-effective excavation alternative would involve partial removal
of the most highly contaminated soils. septic tanks. and drainf~eld
followed by disposal in a landfill. Alternative S9. Inplace treatment by
vapor extraction is a promising but developmental process that may
effectively remove the. volatiles at a lower cost than excavation.
Aquifer Unit Alternatives Analyses
The major concerns associated with the no-action alternative is that
there are potential health risks posed by using contaminated groundwater
not being captured by wells Hl and H2. and that the stripping towers and
wells Hl and H2 were not treating the water under the most cost-effective
operation parameters. The latter is of concern because the minimum
operating time for the entire treatment system will be on the order of 8
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47
Alternative Al, Extraction Well Near MW 32, would eventually reduce
the potential health risk posed by that portion of the plume not currently
being captured by wells Hl and H2. . Based on the water quality samples
collected to date, PERC concentrations vary between 4.3 and 6.9 ug/l.
Concentrations in this range fall between the 10-5 (8.8 ug/l) and 10-6
(0.88 ug/l) excess lifetime cancer risk levels for PERC. The lowest cost
variation (Alternative AlA) for this alternative would involve disposal to
a storm sewer. The present-worth cost of this action is about $125,000.
Cleanup of the escaping plume would take about 5 to 7 years. Cleanup time
for the entire aquifer would not be affected, however, because of the
continuing input to the aquifer from the till. Disposal to a storm sewer
would require interagency coordination with WDOE and the local storm sewer
agency.
Based on a 1984 survey of private wells in the stu~ area, there is
currently no use of groundwater in the vicinity of the uncaptured portion
of the plume. Thus, there is currently no one at risk. Alternative Al
would only protect unknown, future users of the groundwater. In addition,
the installation of an extraction well near MW 32 would not reduce the
potential risk immediately. Complete cleanup would take an estimated 5-7
yea rs .
Alternative A2, Extraction Well in the till, would not be
cost-effective. It is highly likely that the extent of cleanup would be
localized because of the limited water-yielding capacity of the till and
potential discontinuities in the gravel lens. Alternative A2 would have a
minimal impact on reducing the mass of contamination in the till zone,
estimated at about 0.9 pound per year removed, out of 1,300 total in the
till. .
Alternative.A3, Hl-H2 Pump Changes, would address only the issue of
operattng costs. Of the two variations, the alternative involving the
installation of variable-frequency controllers (Alternative A3B) would be
most cost-effective. Jhe controllers would result in an annual saving of
. about $12,700 a year.
Reduced operating'costs would also be realized by implementing
Alternative A4--Treatment System Changes. In particular, the variation
involving changes to the air supply fans would be the most
cost-effective. Tnis variation would produce an annual saving of $8,500.
If both A3B, Variable Frequency Controllers and A4B, Fan Speed Reduction,
are implemented, and annual cost saving of about $21,000 would result, as
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. .
v
48
TABLE 15
COMPARISON OF COSTS FOR NO CHANGE WITH
ALTERNATIVES A38 AND A48 ON Hl-H2 TREATI4ENT SYSTEM
Initial Annual Annua 1
Cost OIM Savings PW-10 YR
No Change
Treatment system $43.800
We 11 pump power 31.200
Total $75.000 $460.800
Pump and Fan Changes
Treatment system with
fan speed reduction 1.600 35.325 8.475
Well pump power with
variable frequency
controllers $57.780 $18.527 12.673
$59.380 $53.852 $21.148 $390,250
Only Alternative A4A. Increasing the Well 'Pumping Rate. would address
potential health risks. Increasing the zone of capture would produce a small
decrease in the size of the uncaptured portion of the plume. This decrease
would not be instantaneous. however. and would not preclude someone from
. installi~g a private drinking water well.
Alternative A5-00Monitoring. does not directly address either cleanup and
detects the presence of contamination from known. potential. upgradient
sources.
The administrative restrictions under Alternative S6 would include a
limitation on the installation of new drinking water wells in the area. This
alternative is highly cost-effective because it provides for a substantial
reduction in potential health risks at essentially no cost.
Assuming continued operation of the Hl-H2 treatment system (tne no-action
alternative). Alternatives A38 and A48 would provide substantial cost savings
over the projected aquifer cleanup time frame of 10 to 12 years.
Implementation of Alternative S6 would substantially reduce the potential
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49
SUMMARY OF RECOMMENDED INITIAL REMEDIAL ACTION
Aquifer Unit
The following actions are recommended as the most cost-effective,
techni cally sound a lternathes and will protect pub 11 c health and the
environment (Table 16):
Continue operation of the Hl-H2 treatment system to continue cleanup
of the aquifer (Alternative A6). The aquifer cleanup level will be
addressed in a later decision.
Install variable-frequency controllers on the well pump motors to
reduce energy requirements and thereby reduce costs (Alternative
A38 ) .
Change fan drives to reduce treatment tower air flow to reduce
energy requirements and thereby reduce costs (Alternative A48).
Install additional monitoring wells. upgrade existing wells. and
continue routine sampling and analysis of the aquifer to monitor the
progress of its cleanup and to provide an early warning of potential
new aquifer contaminants (Alternative AS).
Place administrative restrictions on the installation and use of
wells to minimize the potential for use of contaminated groundwater
(Alternathe 56).
Installation of an extraction well to remove the contamination that is
escaping the zone of capture of wells Hl-H2 is considered unnecessary to
protect public health. and not cost-effective. It is not proposed because
there is no one at risk from this source. and the administrative restriction
on new wells will prec]ude future well use. Increasing the flow rate at Hl-H2
. will increase the zone of capture and the rate of aquifer cleanup but will not
affect the ultimate cleanup time. The longer term contamination input from
the till is not affected by the pumping rate. This action would not capture
all of the small separate plume that has escaped the existing zone of
influence.
The appropriate final groundwater treatment level will be determined as
additional information is gained through the operation of the systems
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,
,
TABLE 16 ,
StJMMARY OF RECOMMENDED REMEDIAL AC'l'IOH
CID8U
alte.....~l.. D8ecdpU- 88peCted ...1 t. 78.- l..ltl.1 .....1 0&11 ......11.
.. ClDftU- tna-t .t Aqulf.~ cleanup. 10 to U ,..~. $0 ..11.. CUn.nt 0&11 coat.
.1-112. $11.200
Yre.1ed wet... qual It, ..II
below l1.it. fo~ ~......t. CUI'II'..t 0i,II coat.
conU8IUDt.. $41.800
$7S.0II0 bl.U...,. "UI
.......t88nt 0611.
aJI 1...1811 ..d_Ie- II8duc8 -I'CJY ~equb-t. 10 to U ,.u. $S1. 710 "'. 500 ...... $U. 100 pe~
f~equency C08~ll.~.. 8l1li ..11 pilip pow~ coat. ,..~ on 0611 coat..
~ effect on t~.at88nt
'8J~t- o~ flow.
A" ~ fan epeed. 118duc:. -~9J ..equb-nt 10 to U ,.al'. $1.600 $15. JOG 68... $8.500 pel' '..1'
end t..eataent .,.t- co.t on 0611 coat..
with ...11.1ble .ffect Oft '5J.1OO ...n/'l'~.at88nt 0611 In
t~eataent. .....I.lone AJI end A4B
A5 Monltorl.. ..II.. Monitor equlf.r cleanup. 10 to U '..1'. 522.140 '11.900
-..pll.... aad ....1,.1. Ie"', wernl... of new U1
_I'ce.. 0
56 Ad8!n1.tr.tl.. ....trlc- ...trlct uncontrolled a.. &011.. to $0
ti- - ..n. end of cont..IRlted aquifer pe.........t
.aca..tl_. end .apaean to c:ont_l-
...ted _11. ...U..
10 to 12 ".I'a
89 bca.at. end ..- ..p- lleduce WIDder eapoau... 11 ...........t 125),450 $0
tic tenII. aad dr.ln fl.ld uncontrolled .acavation
.t .1..a CI._ra. OCCU~..
,))4.910 $l5.100 'rapo88d action
'I'ot.18 with S9
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51
Soils Unit
The following actions are recommended for the soils unit as the most
cost-effective. technically sound alternatives which will protect pUblic
health and the environment (Table 16):
Excavate and remove the septic tanks and drain field piping on the
Plaza Cleaners property to reduce the risks associated with
uncontrolled excavation by removing the most contaminated soil and
comply with other environmental laws (Alternative 59).
Place administrative restrictions on excavation into the
contaminated soils to reduce the risks associated with uncontrolled
excavation (Alternative 56).
Other. more extensive soil excavation at the Plaza Cleaners property than
that proposed is considered unnecessary to protect public health and not
cost-effective because the soil contamination presents a potential threat to
public health only if it is excavated. which can be adequately controlled by
low-cost admi~istrative restrictions.
Excavation and removal of the septic tank. drain field piping. and
administrative restrictions are proposed as the means to reduce the
possibility for uncontrolled excavation into the contaminated soil on Plaza
..Cleaners property and to reduce the worker risk in the event that uncontrolle~
excavation does occur. The lower cost alternative of an asphalt cap and
administrative restriction would provide a degree of worker protection. in
that the cap would be a physical barrier to uncontrolled excavation. However.
as the contamination remains in place. if excavation for whatever reason were
to occur in this area. this alternative would not change the workers exposure.
The Regional Administrator shall have the authority to approve changes or
additions to the trea~nt of on-site soils with other methods. including soil
. aeration. which are found to be equivalent in cost and effectiveness of the
method. The feasibil,ty of other treatment methods may be evaluated during
the design of the initial remedial action.
CONSISTENCY WITH OTHER ENVIRONMENTAL LAWS
All facets of the proposed action will be consistent with the technical
requirements of other environmental laws. The off-site transportation and
disposal of contaminated soils will be in accordance with appropriate RCRA
regulations. including manifesting of wastes and shipment to a RCRA approved
facility. Operation of aeration towers for the treatment of contaminated
groundwater will be conducted consistent with the appropriate Clean Air Act
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~
52
Safe Drinking Water Act--There are drinking water health advisories
established by the EPA Office of Drinking Water, Criteria and Standards
Division, and the Tacoma-Pierce County Health Department for the contaminants
~resent at wells Hl and H2. Groundwater from wells Hl and H2, intended to be
used as drinking water, will continue to use these advisories to treat the
water to the 10-6 risk level for the contaminants present.
Clean Air Act--The Puget Sound Air Pollution Control Agency (PSAPCA)
controls air discharges. A pennit has been issued for the Hl and H2 treatment
facilities. PSAPCA must be notified of any changes to the facility or
operating conditions that would increase the discharge. The air stripping
towers at the extraction well (at the source) will meet all technical
requirements for an air discharge.
RCRA--The decisions regarding closure of the site and the level of
groundwater quality to be achieved are deferred. In order to be consistent
with 40 CFR 264 Subpart F of the regulations, groundwater corrective action is
required until the c~ncentration of hazardous constituents at the point of
compliance for a site achieves one of the following: Maximum Concentration'
Limits (MCL), where designated for particular substances; and Alternate
Concentration Limit (ACL), which would provide adequate protection of public
health and the environment; or background levels.
EPA is not prepared at this time to determine the appropriate level of
groundwater corrective action at this site. Operation of the groundwater
treatment system has substantially reduced the amount of contaminants in the
outwash aquifer. Using data and infonnation which will be continually
collected during the stripping towers. operation period, EPA will make a
detennination as to the level of cleanup which would adequately protect health
and the environment. Under CERCLA, the groundwater treatment system would be
operated until this level of treatment is achieved, unless that level proved
technically infeasible or placed an unreasonable burden upon the Fund.
Where RCRA closure regulations are applicable, they would require that
. all hazardous wastes at.a site be removed, treated on site, or capped in such
a way as to minimize the migration of contaminants from the site. At this
site, contaminated soils would be evaluated at the Plaza Cleaners property to
determine to what degree the remedial action on the soils unit had impacted
the soils at Plaza Cleaners.
In conjunction with the establishment of a groundwater treatment level,
EPA would evaluate the level of contaminants which could be left in the soil
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53
OPERATIONS AND MAINTENANCE (OIM)
ACtivities Required for One Year After Initial Remedial Action
Well s Hl and H2
As of October 15, 1985, the Lakewood Water District will assume all the
OM4 cost associated with the stripping towers at wells Hl and H2. This
includes weekly inlet/outlet water sampling and analysis for the contaminants
of concern, pump maintenance and inspection, general equipment observations,
and maintaining data records.
Monitoring Wells
Approximately monthly sampling and analysis for the contaminants of
concern, will be conducted. Well levels and other physical parameters will
also be measured.
Soil Unit
.
As presently proposed, there will be no O&M required on this alternative.
Reporting
Bi-monthly reporting on the consolidated data from the aquifer unit will
be required.
Future Actions
Stripping towers at Hl and H2 will need to be operated for approximately
10 to 12 years.
Monitoring wells will need to be operated for the time period coinciding
with operation of the treatment system.
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,,-"
'"
Approve Initial Remedial Action
Sign ROD
Design Initiated by EPA
Sign State Superfund Contract
Construction Procurement by EPA
Construction Initiatea by EPA
qui red.
54
SCHEDULE
9/85
9/85
10/85
11/85
4186
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. .
"
COMMUNITY RELATIONS RESPONSIVENESS S~~Y
Ponders Corner (Lakewood)
Lakewood, Washington
Introduction
The public comment period on the Remedial Investigation/Feasibility
Study occurred between July 10, 1985, and August 12, 1985. A pUblic meeting
was held on July 23, 1985, at the Lakewood Branch of the Pierce County
Library. The meeting was attended by 10 persons, including representatives
from the State of Washington Department of Ecology and the Tacoma-Pierce
Coun~ Health Department. In addition, the Department of Ecology submitted
written comments. EPAls response to these comments is attached.
This document describes the concerns raised and ;omments made on EPAls
study.
Previous Activity at Site
In 1984, EPA and the State of Washington constructed a water treatment
system at this site which started operation in the fall of that year. The
result has been resumption of service by the two wells affected by the
. contamination. The water currently being provided by the wells meets the
criteria set by the Tacoma-Pierce County Health District and EPAls drinking
water standards. Concerns raised during the treatment planning and
construction phase were addressed in a previous Responsiveness Summary
accompanying the Record of Decision for the treatment system.
Concerns Raised Durin~ ~I/FS Process
Very little public' interest was noticed during the RI/FS process. EPA
issued press releases prior to any,major activity, as well as sending out
fact sheets to the mailing list periodically. In late June, a fact sheet
announcing the availabili~ of the RI Report and the FS, the public comment
period, and the date of the pUblic Meeting, was sent.
Only a few people attended the meeting. Questions raised generally
requested specifics of the investigation. The major questions rafsed were:
1.
How does EPA know the contamination comes fro~ the dry cleaning
establishment and not other sources? -
A.
EPAls monitoring well system has traced the contamination to
the area occupied ~y the cleaners. This has been confirmed
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c
~
~
2
2.
What would happen to soil excavated from the site?
~ contaminated soil or septic tank would go to a permitted
hazardous waste disposal facility.
What is happening at the cleaners now?
A.
3.
The cleaners has installed a recycling system and is
capturing solvents. Water from the washing operations is
discharged to the area's newly installed sewer system.
How long were people drinking contaminated water?
A.
4.
5.
That information is unknown. The contamination was
discovered during a national survey corducted by EPA in
.1981. The cleaners had been in operation for a number of
years, so theoretically, the wells could have been
contaminated for some time.
Is EPA sure the problem is not related to the American Lake
Gardens site (another Superfund site located about a mile away)?
A.
A.
Yes. Analysis of monitoring well samples indicates that the
two problems are unrelated.
Summary
Essentially all of the public comments received were in favor of EPAls
recommended action.
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"
FEASIBILITY STUDY
1.
The estimated nature and extent of contamination for
the uncaptured portion of the plume was questioned be-
cause of the limited available data near MW-32. While
the exact nature and extent ~annot be established with
the existing monitoring well network, sufficient data
are available to develop an estimate. Given the direc-
tion of regional groundwater movement and associated
contaminant migration to the northwest, the south-
western extent of the un captured plume must be limited
because contamination has never been detected in MW-31.
The northwestern boundary is also limited because no
PERC was detected in MW-32 in February 1985 and PERC
concentrations increased through May 1985 indicating
recent migration of the leading edge of the plume past
MW-32. The southeastern boundary is controlled by the
limits of the zone of capture. The location of the
northeastern boundary was estimated based on the north-
eastern extent of contamination in the main plume and
the direc~ion of regional groundwater movement. The
above provides the basis for the estimated extent of
contam1nation shown in Figures 1-16 and 1-17.
Since'monitoring was initiated, PERC concentrations
have increased to 6.9 ~g/L. Given that MW-30 is
approx1mately upgradient of MW-32 under nonpumping con-
ditions, it is unlikely that the maximum PERC concen-
trations at MW-32 would ever exceed the maximum of
38 ~g/L measured at MW-30. This concentration is
roughly five times greater than the 7 ~g/L concen-
tration used to analyze the potential impacts of the
uncaptured portion of the pl~me. This plume will ulti-
mately migrate to Gravell~ Lake. A more exact defini-
tion of the nature and extent of contamination would
require the installation of additional monitoring
wells. .
2.
The feasibility study states that 1,2-DCE has not been
detected in soil or the aquifer since July 1984. This
refers only to data collected during the remedial in-
vestigation. The cis isomer of 1,2-DCE was detected on
two occasions in well water from HI and H2. Well water
samplinq was conducted to monitor the performance of
the air stripping towers.
3.
A question was raised as to whether any action had been
taken to assure that private wells in the vicinity of
the plume will not be used in the future. A 198~ sur-
vey of pr1vate wells in the area found that none of the
wells in the immediate vicinity of the plume were in
use. To date, no action has been taken to assure these
wells will not be used. Future restrictions on well
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Q
~
p
b
4.
-
installation and use would occur through the implemen-
tation of Alternative S6, Administrative Restrictions.
These restrictions would likely be implemented and en-
forced by the Washington Department of Ecology and/or
Washington Department of Social and Health Services.
A question was raised as to how Alternative S7~ Vapor
Extraction System would be designed and tested. It was
envisioned that the design of the system would be
phased. Phase 1 would involve the 1nstallation of a
pair of vacuum extraction wells. A vacuum pump at-
tached to one of the wells would be used to estimate
the radius of influence, approximate vapor concen-
trations and potential removal efficiency that could be
expected. Data collected during Phase 1 would be used
to determine the exact number of extraction wells and
to size the vacuum pump and dilution fan. Phase 2
would involve the installation and operation of the
system. The costs given in the feasibility study were
based on this type of design procedure and the quan-
tities given in the feasibility study.
5.
The feasibility study provides a recommendation for
general, rather than specific, locations of additional
monitoring wells under Alternative AS, Monitoring. The
specific location of each additional well will be con-
trolled by the availability of property suitable for
well installation and permission of property owners.
Recommended locations for wells will be included in the
predesiqn report that EPA will prepare subsequent to
the responsiveness summary and record of decision
(ROD).
6.
A question was raised as to what impact continued input
of contamination from the till and soil unit would have
on the minimum operational time of the air stripping
system, and how different alternatives. would affect
this time. Based on the available information, it ap-
pears that leaching of contamination from the till is
the main factor controlling the minimum operational
time. Appendix E provides an analysis that shows that
the till may contribute PERC to Wells HI and H2 in ex-
cess of the drinking water standard for a period of
approximately 10 years. At the end of 10 years, the
average PERC concentration in the till is estimated to
be about 500 ~g/kg. This time frame is equivalent to
the time required to capture the existing plume under
current pumping conditions. Because the till will con-
tinue to contribute contamination regardless of how
fast the plume is captured, the operational time will
not be reduced by those alternatives involving in-
creased pumping (i.e., Alternative AI, Extraction Near
MW-32 and Alternative A4A, Treatment System Changes,
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9.
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Water Flow Increaser. The operational time is also not
affected by any of the soil unit alternatives. As the
results in Appendix C show, the potential contribution
of contamination from the'soil under current conditions
is negligible. After 10 years, the average PERC con-
c~ntration in soil would decrease by five times. Al-
ternatives dire~ted at soil excavation would reduce the
already negligible contribution, as would capping the
site. As the results in Appendix C indicate, PERC con-
centrations in soil would decrease only slightly after
10 years if a cap was installed. The only alternative
that would theoretically shorten the operational time
is Alternative A2, Extraction from the Till. This al-
ternative does not appear to be feasible given the low,
water-yielding capacity of the till.
A related question was raised concerning what impact
the length of operation time would have on the cost-
effectiveness of different alternatives. Basically,
increasing the length of the operational time would
increase the O&M costs of each alternative, but would
not significan~ly affect their relative
cost-effectiveness.
It is important to note the actual operation time will
be more accurately evaluated by the results of ongoing
monitoring of the aquifer unit, including the till
zone, if Alternative AS, Monitoring is implemented.
7.
A question was raised regarding the use of a depth, of
13 feet to define the vertical extent of contamination
in the soil unit. Both the remedial investigation and
feasibility study recognize that there are pockets of
soil contamination below this depth. These pockets are
small in volume and contain soil with low PERC concen-
trations. Compared to the mass of PERC contained in
the upper 13 feet of soil, the mass of contamination
below 13 fee~ is small.
8.
A question ~as raised regarding the possibility of
locating and plugging the dry well(s) that may have
been installed in the vicinity of the drainfield. Both
EPA and the Washington Department of Ecology conducted
extensive excavation programs behind Plaza Cleaners to
locate the septic tanks, drainfield, and dry well(s).
Neither was able to locate or confirm the presence of a
dry well or wells. For this reason, locating the dry
well(s) was considered to be impractical.
The feasibility study discusses potential concerns as-
sociated with contamination detected in three McChord
Air Force Base monitoring wells: AZ01, AZ02, and AZ03.
Well construction infor!"'D.tion for these monitoring
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11.
wells indicates-that AZOI and AZ02 are screened in the
Steilacoom Gravel and Vashon Till units. AZ03 is
screened in the Vashon Till and Colvos Sand units; ap-
parently, the Advance Outwash is absent in this lo-
cation. Because the wells are screened over intervals
r~nging from 60 to 80 feet in thickness, it is diffi-
cult to determine ~hich aquifer (i.e., perched aquifer
in the Steilacoom Gravel or the underlying semiconfined
aquifer), if any, is being monitored. Work conducted
to date by the Air Force suggests that the Vashon Till
may provide a barrier to the horizontal and vertical
migration of contaminants detected in the vicinity of
these wells. The Air Force is currently conducting
additional site characterization studies.
It is difficult to estimate when, if at all, a plume
from McChord would reach Wells HI and H2. Alterna-
tive AS, Monitoring, would involve the installation of
two new monitoring wells and continued monitoring of
selected existing wells to provide for early detection
of any plume migrating from McChord.
10.
The use of historical measurements of decreasing con-
tamination levels at Wells HI and H2 to estimate an
aquifer cleanup time was suggested. Appendix L, in the
feasibility study, discusses such an analysis. Cleanup
times were estimated based on the 6 months of available
data. The estimated times were found to be unrealis-
tically short and, at best, can only be used as abso-
lute minimum cleanup times.
A question was raised regarding the approach used in
Appendix E to calculate the total mass ot each contami-
nant in the aquifer unit. It was suggested that masses
be calculated as follows:
Total mass contamination = mass in solution +
mass adsorbed.
= Cw.V.ns + CS.V.Pb(l-ns)
While the first term on the right-hand side is correct,
the second term is not. The units for this term are
inconsistent given the following:
Cs . mass of contaminant/mass of. solids, \.Ig /gm
3
V = total volume, cm 3
Ph = mass of solids/total volume, gm/cm 3 3
(~-n ) c volume of solids/total volume, cm fcm
s
P would have to be defined as the mass of solids per
vBlume of solids for the units to be consistent; this
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14.
15.
"
is not the correct definition of the bulk density. The
equations in Appendix E, and the associated derivation,
are correct.
12.
A question was raised about the risk associated with
inh~lation of the strippinq tower exhaust and suqqested
that the Cancer Assessment Group (CAG) method .should be
used. CAG data for PERC are not available at this
time. Therefore, the comparison to occupational stan-
dards was included to provide a perspective on the
risk. Note that the3stack discharqe concentration
should be 0.175 mq/m and that this would be about
0.05 percent of the ACGIH threshold limit.
13.
Comments were received to the effect that carbon ad-
sorption should be evaluated for the stack discharqe
from the soil vapor extraction alternative and for the
stack discharqe of the air strippinq alternative on the
uncaptured portion of the plume. In both of these sit-
uations, the total amount of contamination is a few
.p,:,unds at most (estimated at 5 pounds in the soils unit
subject to Alternative 57 and at about 6 pounds in the
plume around MW-32 subject to Alternative A1). These
amounts are smallenouqh to present essentially no risk
to the public even if released in as short a time as a
sinqle day. The release times for these alternatives
would actually be much lonqer and the solvent concen-
tration would be reduced by dilut10n and dispersion.
For ~omparison, the PSAPCA permit for the Tacoma
Well 12A system allows 40 pounds per day to be dis-
charqed to the air. At Ponders Corner, the permit is
based on 17 pounds per day combined PERC and TCE. This
latter value is reported to be about the weight of vol-
atile material lost by evaporation each day at a qas
station. Carbon adsorption was therefore considered to
provide no needed health protection and would be costly.
A question was asked as to what was envisioned for a
horizontal barrier in the chapter on screeninq tech-
noloqies. ~ horizontal qrout layer, installed throuqh
multiple wells was envisioned. This technoloqy was
considered to be impractical in this case to assure a
continuous, tight barrier under the variable soil con-
ditions found in the till.
Questions were asked as to why a treatment option was
not considered for Alternative A2, Collection from the
Till, and why additional wells were not considered
rather than using just MW-20B. The water produc1nq
capability of the till is very low. Each of the four
wells installed in the till have been difficult, and at
times impossible to s~~ple because of a lack of water.
Extraction would therf~ore not be practical and the
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selection of treatment or disposal options is immaterial.
16.
Feasibility Study,_gage 1-13, Figure 1-6 units, should
be GPD/FT x 1 x 10 .
17.
Feasibility Study, page 1-45, ~able 1-6. The last
three columns should reference footnote "c".
18.
Feasibility Study, page 4-25, Table 4-5. The water
flow is the total for both towers; the air flow is the
flow rate per tower.
19.
Feasibili3Y Study, page 1-49, f~rst paragraph.
1.75 mg/m should be 0.175 mg/m and 0.5 percent should
be 0.05 percent.
20.
According to staff at the United States Geological Sur-
vey, Clover Creek does not flow continuously in the
vicinity of Ponders Corner. Regardless, as the fea-
sibility study states, the level of potential con-
tamination in Clover Creek would be well below
freshwater aquatic life criteria.
REMEDIAL INVESTIGATION
2.
3.
4.
1.
The 30-foot isopach contours in Figure 4.8 should be
connected to form a saddle just west. of monitoring
Wells MW-11 and MW-24.
The contact between the Advance Outwash and Colvos Sand
units, shown in Figure 4.13, should occur at a higher
elevation around MW-20. According to Table 4.1, the
contact occurs at elevation 172.5, or at the bottom of
the screened interval. The elevation of the contact is
correct in Figures 4.14, 4.15, and 4.16.
The labeling 9f different geologic units in Figures 4.3
and 4.4 is intended to provide their approximate thick-
"ness and approximate elevation of individual contacts.
As Figure 4'.2 shows, the elevation of the contact be-
tween the Steilacoom Gravel and Vashon Till varies
across the site.
Appendix C of the remedial investigation identifies
several questions related to the quality assurance/
quality control (QA/QC) procedures that were used. At
the time the remedial investigation report was being
prepared, certain QA/OC information had not been pro-
vided by the CLP. In addition, certain backup informa-
tion for non-CLP analyses had not been provided to the
contractor that prepared the remedial investigation.
All of this information is now on file with either the
EPA or the responsible non-CLP laboratories. The
-------
following provides responses to Bpecific questions that
were raised.
7.
8.
se88l7/002/7
C.2
C.6
p.
C.lO a.
b.
5.
a.
The method for soil analysis is available
from the EPA Manchester laboratory. Results
of calibration, duplicate analysis, laboratory
blanks, and matrix spikes have been provided
to the EPA from Manchester following this
report date. All QC is within a range that
would not alter the results of this report.
Calibration data can be provided, but it is
within acceptable limits of the EPA.
b.
c.
The analytical methods used can be provided
as well as data evaluation material. This
material would not affect the results of this
report.
a.
A memorandum dated April 9, 1985 from Ecology
& Environment, Inc., reports QA of Radian's
analytical data was found acceptable. .
The semivolatile compounds identified at low
concentrations have no effect on this study.
EPA QC data have been provided to the EPA
from Manchester and is within acceptable
limits.
All analyses were completed within allowed
holding times. Dates are on file.
An explanation was requested for the detection of
chloroform in MW-32 in February 1985 (see Ta-
ble 3.2 in the remedial investigation). The com-
pound wa~ only detected in one well at a concen-
tratio~ approaching the detection limit of 1 ~g/L.
Since no' other samples detected chloroform, it is
concluded that this identification is an anomaly.
6.
Several comments on the RI report were related to
the estimated mass of PERC in the soil unit.
(p 3-8, Table 3.4.) The calculations were revised
and corrected as indicated in the attached letter
and revised pages 3-8 and 3-9.
RI, page 1-12, Figure 1.5. The legend should in-
dicate ~ Concentration isopleth in ppb. .
RI, page 1-16. The paragraph on Section 6 should
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se8817/002/8
concern for public health and the environment re-
sulting from the contamination found."
9.
Section C.5 of Appendix C states that a very high
concentration of chloroform was detected in tap
water on January 11, 1985. The reported concen-
tration was 2,501 ~g/L. The source ~f the tap
water is uncertai;. Sources of decontamination
water included the drill rig, apartment complex
next to Plaza Cleaners, and Plaza Cleaners itself.
The latter two probably obtain their water from
the Lakewood Water District. Other analysis of
decontamination water did not detect unusual con-
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Pr(JI'.-ct ..,.'n..,.~(..,,,,'1' [,<\, -'"'1
(hi".. el' H.I/'Ifdl'",- '~\.. 1.
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RH hldnd \\.t ~hl~":II:" p.;',:
(509) 943-9847
August 8, 1985
Mr. Robert Schilling
CH2M HILL
1500 114th Avenue, S.E.
Bellevue, Washington 98004-2050
Dear Bob:
PONDER'S CORNER RI REPORT
Megan White; of the Washington State Department of Ecology, called me on
August 6, 1985. She said that she was unable to duplicate the values for
the mass of PERC, which are shown in Table 3.4, page 3-8 of the Ponder's
Corner RI report. I traced the documentation back to the original work
sheets. The formula used to obtain the values for mass in grams is
correct, but all the values in the hand-written Table 3.4 were calculate/"'
based on an average PERC concentration of 442 ug/Kg for all contol
intervals at all depths. Table 3.4 and the narrative on the next page hav~
been revised to reflect the use of average concentrations for each
interval. Average concentrations used for the 0-100, 100-500, 500-1,000.
and more than 1,000 ug/Kg intervals are 50, 250, 750, and 1,500 ug/Kg.
respectively. .
Because this table was not used in the FS report for calculating health
impacts or evaluating'remedial alternatives. it will have no impact on the
decision-making process. However, the revised table and page should be
se~t to all copy holders as an addendum to the RI report.
Very truly yours,
~y~~
Ronald Schalla
Project Manager
RS:np
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Table 3.3. Es~mated Volume of Contaminated Soil in
Layers-Under Plaza Cleaners, in cu ft
Volume (cu ft) of Contaminated Soil
Depth with PERC Concentrations ~ of
jnterval (ft). jO-lOOr(lOO-SOOr1,000>:
0.0- 5.0 14,200 21,900 3,820 6,120
5.0- 7.0 2,910 4,390 3,160 950
7.0- 8.5 2,240 2,370 2,280 740
8.5-11.5 7,190 4,060 2,550 476
11.5-12.5 2,000 1,290 29 0
Total Volume
of Soil
in Interval
46,040
11,410
7,630
14,276
3,319
Total Volume of Contaminated
50il Under Plaza Cleaners
82,675 cu ft
Table 3.4.
Estimated Mass of Chlorinated Hydrocarbons in
Unsaturated Layers Under Plaza Cleaners,
in grams .
Depth
Interva 1 li1l
0.0- 5.0 40.2 310 162
5.0- 7.0 8.2 62.0 134
7.0- 8.5 6.3. 33.5 96.8
8.5-11.5 20.3 57.4 108
11. 5-12.5 5.7 18.2 1.2
Total Mass of PERC Under Plaza Cleaners
Total Weight
.of Contaminant
519 1,031
80.7 285
62.8 199
40.4 226
o ~
1,766 grams
*Assumes the average PERC concentrations for each interval are 50, 250, 750,
and 1,500 ug/Kg, respectively.
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~.....;_.
.
the areal extent of the plume ~ each depth interval evaluated and the
thickness of each interval. Contaminant concentrations were further div"ided
into four ranges: 0-100 ug/Kg. 100-500 ug/Kg. 500-1.000 ug/Kg. and 1.000
ug/Kg. to determine the quantity of contaminated soil for areas of low.
moderate. high. and very high concentration within the plume.
The weight of contaminants for each depth interval and each range of
concentrations is the product of the average contaminant concentration of
each interval. the volume of contaminated soil. and the soil density. A
value of 2.000 Kg/m3 was used for soil density. This value is typical of
gravelly soils such as those found on the Plaza Cleaners site.
The results of the laboratory analyses of soil samples from soil borings
and test pits are shown in Tables 3.5 and 3.6. Only PERC was considered as a
contaminant in the soil. Where detected. concentrations of PERC ranged from
11 to 1.400 ug/Kg in the soil borings. Measurable concentrations were found
in five of the seven so11 borings. No 1.2-DCE or TCE were found in any of
the soil borings. PERC'was detected in all six of the test pits. ranging in
concentration from 29 to 3.880 ug/Kg. Minor amounts of both 1.2-DCE and TCE
were detected in one of the test pits. Quantities found were 1 to 4 ug/Kg of
1.2-DCE and 1 to 5 ug/Kg of TCE. Because these compounds were detected in
so11 that was also contami nated with PERC. thei r extent was not evaluated
separately.
The depth intervals evaluated were chosen for several reasons. The top
5 ft were-evaluated together because no surface samples were obtained. Only
one test pit was sampled in this interval . "however. most of the soil borings
were sampled at 2.5 and 5.0 ft. Locations of "the test pits and test pit
longitudinal sections are. s~own in Figure 3.2. PERC concentrations in the
test pits are shown in Figure 3.3. PERC concentrations in the 0.0- to 5.0-ft
interval, based on test pit and so11 boring data, are shown in Figure 3.4.
Few of the so11 borings were sampled in the next interval, 5 to 7 ft.
However, this interval was sampled in several of the test pits and represents
the area just above the upper drainfie1d at the Plaza Cleaners site. PERC
concentrations in the 5.0- to 7.0-ft interval appear in Figure 3.5. The 7.0-
to 8.5-ft interval includes most of the upper drainfield and was sampled in-
four of the seven soil borings and several of the test pits. Concentrations
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