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 H1-H2 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
operati on.
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 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.
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 laws.
Place administrative restrictions on excavation into the
contaminated soils to reduce the risks associated with
uncontrolled excavation.
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DECLARATIONS
Consistent with 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 of Selected Remedy
at the Ponders Corner 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 HI - 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 May 6, 1985, memorandum entitled Procedures
for Planning and Implementing Off-site Response Actions.
The remedial action includes the maintenance of institutional controls with
which to prohibit 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 equivalent 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 considered
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 & M.
If additional remedial actions are determined to be necessary, a Record of
Decision will be prepared for approval of the future remedial action.
sept so i"itC
Date
Regional Administrator
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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
2,000-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 along Pacific
Highway. Lakewood Water District has two of its production wells (HI and
H2) on a fenced site immediately south of Interstate 5 and east of New York
Avenue. Residential property lies to the east of the well site, and 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 HI and H2 were contaminated with
1,2-dichloroethylene (1,2 DCE), trichlorethylene (TCE), and
tetrachloroethylene, often 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 HI and H2 out of production, notified its
customers of the well contamination, and requested that a water conservation
plan be followed.
Wells HI 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/Nyanza Park area,
provided over 10 percent of the district's needs, and were a critical
service for fire protection.
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2
FIGURE 1
LOCATION OF PONDERS CORNER
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LEGEND
MONITORING WELL
TEST OB PRODUCTION WELL
PONDERSCORNER
STUDY AREA
KM.K INPUT
FIGURE 2
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4
Source History
During August 1981, the 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 drycleaning 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 HI and H2 to 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
HI 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 HI 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 HI 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
Department inspected Plaza Cleaners and sampled its septic tanks. The
analysis of septic tank sludge test yielded results as high as 483 ppm of
tetrachljjjroethylene. 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 Plaza
Cleaners were removed, sampled, 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
Cleaners. On June 17, 1983, WDOE issued Plaza Cleaners an enforcement order
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5
to eliminate all discharges to the ground and groundwater by July 1, 1983.
On September 7, 1983, WDOE and the present and former owners of Plaza
Cleaners signed an agreement before the State.Pollution Control Hearings
Board stipulating that 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 HI 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 HI 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 wouljlj-emediate the contamination at this site, defined
by the Remedial Investigation. The Public Comment Feasibility Study,
Ponders Corner, Washington, report contains the results of this evaluation.
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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
layers), and to determine the nature and extent of groundwater
contamination 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.
Hydrogeology
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 17 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
drain to a sewer.
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7
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 semi confining 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 HI and H2. This figure shows typical
groundwater elevations and directions of groundwater 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 HI 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 HI 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 HI 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 found 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 Steilacoom 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 HI and H2 the outwash
thickness increases to over 90 feet.
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NORTH
PLAZA CLEANERS
SOUTH
T
600
DISTANCE (FT)
800
V
•v
TYPICAL GROUNDWATER ELEVATIONS
UNDER PUMPING CONDITIONS
DIRECTION OF GROUNDWATER MOVEMENT
UNDER PUMPING CONDITIONS
1000
NORTH SOUTH CROSS SECTION
BETWEEN PLAZA CLEANERS
AND HI AND H2
00
FIGURE 3
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9
Under nonpumping conditions (that is, when wells HI and H2 are not
operating) the general direction of flow in the advance outwash 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 HI and
H2. Wells HI 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 WD0E 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
moved laterally towards well HI and H2 (Figure 7).
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LEGEND
• MONITORING WELL
¦ TEST OR PRODUCTION WELL
WATER LEVEL-CONTOUR. SOLID
- — WHERE APPROXIMATE, DASHEO
WHERE INFERRED. ELEVATION
IN FEET ABOVE MEAN SEA LEVEL.
—»• GROUNDWATER FLOW DIRECTION
BOO
SCALE IN FEET
FIGURE 4
WATER-LEVEL CONTOUR
MAP OF THE ADVANCE
1000 OUTWASH AQUIFER,
JULY 23,1984
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LEGEND
• MONITORING WELL
It TEST OR PRODUCTION WELL
WATER LEVEL-CONTOUR. SOLID
WHERE APPROXIMATE. DASHED
WHERE INFERRED. ELEVATION
IN FEET ABOVE MEAN SEA LEVEL.
M GROUNDWATER FLOW DIRECTION
¦ Ml APPROXIMATE LIMITS OF
ZONE OF CAPTURE
BOO
SCALE IN FEET
FIGURE 5
1000
ZONE OF CAPTURE
FOR WELLS H1 AND H2
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12
WELL28A&B
PLAZA CLEANERS
O
SB B
WELL 20
O
SB 4
SB 7 O Septic
Tanks
o J 34
SB 3 V
f
f
.886
'well:
~
LEGEND
DRAINFIELD LINES
SOIL BORINGS
DIRECTION OF CONTAMINANT
MIGRATION
PLAN VIEW OF CONTAMINANT
MIGRATION
FIGURE 6
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13
NW
280
260 -•
240 "
220 ¦¦
200 -¦
180
160 ¦¦
SE
FILL
£7^ 71
SM to SM-ML —
— — ^: __Gp-GW J STEILACOOM GRAVEL
VASHON TILL
ADVANCE OUTWASH
COLVOS SAND
20
40
60
FMt
DIRECTION OF CONTAMINANT
MIGRATION
GW GRAVEL. WELL GRADED
GP GRAVEL. POORLY GRADED
GM SILTY GRAVEL
GC CLAYEY GRAVEL
SW SAND. WELL GRADED
SMP SAND. POORLY GRADED
SM SILTYSAND
ML SILT. LOW LIQUID LIMIT
CROSS-SECTION VIEW OF
CONTAMINANT MIGRATION
FIGURE 7
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14
During the time when wells HI 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 migrated beyond the zone of capture for wells HI and H2.
The rate of contaminant migration in the Steilacoom 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.
Soils Unit
The near-surface soils on the Plaza CI earners property were
characterized with seven soil borings and six shallow test pits. Soil
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 cleaner's 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 SB2 and SB7.
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 inferred PERC distribution along the main axis of
the drain field. Except for several small pockets of contamination, most of
the PERC is located in the upper 12 to 13 feet of soil.
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
partition coefficient of 0.45 mL/gm.
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15
WEI-L28 A&B
PLAZA CLEANERS
WELL 20
GAS LINE
ELECTRIC
POWERLINE
SS 6
® WBLL3io
LEGEND
V//////A ORAINRELD LINES
0 SOIL BORINGS
l«optathi in ug/Kg
CONCENTRATION DISTRIBUTION OF PERC
IN THE 0.0 TO 5.0-FT DEPTH INTERVAL
FIGURE 8
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NW
SE
280
260
240 ••
SB-7
35 SB-1
SB-6
SMtoSM-ML
FILL
STEILACOOM GRAVEL
VASHON FILL
20
40
>0
Foel
Itopfeths in ug/Kg
GW GRAVEL, WELL GRADED
GMP GRAVEL. POORLY GRADED
GM SILTY GRAVEL
GC CLAYEY GRAVEL
SW SAND. WELL GRADED
ML SILT, LOW LIQUID LIMIT
CONCENTRATION DISTRIBUTION OF
PERC ALONG MAIN AXIS OF DRAIN FIELD
FIGURE 9
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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 detection 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 addition to the limited number of wells which were screened in these
zones, sampling of MW 28B, 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 terms 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 20B 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 HI 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-DCE was detected in July 1984. Since that
time no 1,2-DCE has been detected in the advance outwash.
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18
TABLE 1
ESTIMATED QUANTITIES OF CONTAMINATION IN EACH ZONE
OF THE GROUNDWATER UNIT
Stellacooa Gravel Vashon Till Advance Outvash
1,2 PCI TCE PERC 1.2 DCE TCE PE3C 1,2 DCE TCE PERC
Average
Concentration (yg/L) HD 42 110 MD 58 2,500 HD 3 16
Number of Observations — 1 2 — 2 3 — 5 28
Mln liium/Maxlmum
Concentration (yg/L) — — 83-139
Total Volume of
Contaminated
Media (cu ft) 7.5x10 7.5x10 7.5x10
Approximate Mass
of Contamination
(lb) -- 4 20
12-103 570-4,866 — 1,5-6.3 0.5-110
.OxlO6 2.0x10® 2.0x10® 4.SX107 4.5xl0? 4.5xl0?
14 1,300 — 16 180
ND » not detected.
1,2 DCE = 1,2-dlchloroetbylene.
TCE = trichloroetliylene.
PERC = tetrachloroetbylene.
Ug/L ¦ micrograms per liter.
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19
Table 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 (HI, H2) Performance
Influent PERC and TCE concentrations from the advance outwash at HI and
H2 have steadily decreased over the operating period of the stripping
towers. As of March 5, 1985, PERC concentrations at HI and H2 were 9.7 and
52 ug/L, respectively. TCE concentrations were 0.45 and 1.7 ug/L in HI 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
H1-H2 PERFORMANCE
JANUARY TO MARCH 1985
HI Well
H2 Well
Two Towers
Treated Water
Stack Discharge
Flow
800 gpm
1,200 gpm
2,000 gpm
2,000 gpm
60,000 cfm total
PERC
8.54 ug/L
71 ug/L
46 ug/L
1.04 lb/day
0.12 ug/L
0.003 lb/day
1.101 lb/day
TCE
0.43 ug/L
2.1 ug/L
1.43 ug/L
0.034 lb/day
0.07 ug/L
0.002 lb/day
0.032 lb/day
TOTALS
—
—
1.138 lb/day
0.005 lb/day
1.133 1b/day
210 ug/m
Groundwater Contamination Outside of the Zone of Capture for HI and H2
As shown on Figures 11 and 12, a portion of the contaminant plume has
migrated beyond the estimated zone of capture for HI and H2. Because
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
during the period of time HI and H2 were shut down.
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LEGEND
• MONITORING WELL
¦ TEST OR PRODUCTION WELL
— — CONCENTRATION ISOPLETH IN ppb
. . _ APPROXIMATE LIMITS OF
ZONE OF CAPTURE
600
SCALE IN FEET
1000
CONCENTRATION
CONTOURS FOR PERC,
FEBRUARY 1985
r\3
o
FIGURE 10
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' r"E. S V- i w AT ION 13*
LEGEND
^^•10-^CONCENTRATION. #Jg/L
• MONITORING WELL
W TEST OR PRODUCTION WELL
— • — APPROXIMATE LIMITS OF
ZONE OF CAPTURE
600
SCALE IN FEET
,ooo CONCENTRATION CONTOURS
FOR PERC,
MARCH 1985
FIGURE 11
-------
LEGEND
m(*»10-«'>CONCENTRATION. HalL
• MONITORING WELL
¦ TEST OR PRODUCTION WELL
• — APPROXIMATE LIMITS OF
ZONE OF CAPTURE
BOO
SCALE IN FEET
FIGURE 12
1000
CONCENTRATION
CONTOURS FOR PERC.
MAY 1985
-------
23
Measured concentrations at MW 32 during March, April, and May 1985 were
4.3, 5.0, and 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
(PERC), trichloroethylene (TCE), and 1,2 dichloroethylene (1,2 DCE).
Members of the chloroethylene series, including PERC, TCE, and 1,2-DCE, 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 ethylenes. Both TCE and PERC have been
shown to be liver carcinogens in at least one strain of mice, and EPA
considers them to be suspected carcinogens. DCE is not believed to be
carcinogenic. The International Agency for Research on Cancer (IARC)
believes that there is inadequate evidence for classifying PERC and TCE as
human carcinogens.
To date, there are no known reports of illness in the Ponders Corner
study area attributed to the presence of PERC, TCE, or 1,2-DCE.
Exposure
All exposure and risk assessments were designed under the assumption
that the stripping towers at HI 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
portion of the plume, exposure to contaminated soils and vapors during any
-------
24
excavation at the Plaza Cleaners property, use of treated well water, and
exposure to surface waters. The latter two routes were determined 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 ORGAN ICS IN PONDERS CORNER STUDY AREA
1984-1985
Detected Concentrations
Chemical
Soi 1 s
(ug/kg)
a
Groundwater
(ua/L)
Max.
Mean
Max. Mean
Tetrachloroethylene (PERC)
3,880
500
922 16
Trichloroethylene (TCE)
5
3
57 3
1,2-(cis)dichloroethylene (DCE)
4
3
85
a Based on soil wet weight.
The three chemicals of concern are highly volatile and easily escape
from contaminated materials upon exposure to air. This feature, especially
where air concentrations can be diluted by winds, greatly reduces the
potential vapor exposure of these chemicals.
-------
25
In general, only PERC is considered as a major contaminant of the soil,
and only PERC and TCE are considered as major contaminants of the
groundwater.
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 potential 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 Hygienists
(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 of 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
conditions, ACGIH TLV-TWA, but not IDLH, criteria would be violated.
-------
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 EXCAVATION3
Soil
Concentration
(ug/kg)
Absolute
Worst-Case
Ai rborne
Levels
of Vapors^
(mg/mi)
Realistic
Worst-Case
Ai rborne
Levels
of Vapors^
(mg/ml)
ACGI Hc
Maximum Recommended Air Levels
TLV-TWAd IDLH5
mg/ml (ppm)
mg/mj. (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)
0f
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.
^Threshold limit value-time weighted average (8 hours); OSHA values are
twice these amounts, that is, 670 mg/nr (100 ppm).
^Immediately dangerous to life or health,
fApproximate 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
table.
-------
Table 5
AIRBORNE PERC CONCENTRATIONS FOR COMPLETE
SURFACE SOIL REMOVAL AND TRENCH EXCAVATION AS A
FUNCTION OF WIND SPEED
PERC Soil
Concentration
Perc Air Levels (mg/m3) for Wind Speed
(mph)
Scenario
(ug/kg)
0.25
1.0
5.0
d.i
Trench Excavation3
500
0.3
0.07
0.01
0.008
Trench Excavation3
3,800
2
0.5
0.1
0.1
Surface Soil Removalb
500
0.04
0.009
0.0025
0.001
3Assumes 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
1 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 HI 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 HI 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
rates of 99.8 percent for PERC and 97 percent for TCE. The resulting
-------
50
40
500
300
200
100
'V,
TRICHLOROETHYLE
NE DESIGN CONCENTRA
HON
~ r " ~
i
/•.i
fV n
r
A/1-'
\ " 1
\ ,
TETRACHLOROETHYLE
1
4E DESIGN CONCENTR/
TION
1 ** • \
1-1
f>.v
~ 1 •
:*'•»
sj
X| WELLH2
1 not
| OPERATED
X 1 _
/
/
/
\
>
—. —— -—-
• 4 1
•• «
•• i
•
i 1
".I
¦ / \
1 / \
rrr/i i
; \X. /\
\ v. /. A
•. V •!•/»,' Vr""«
* • ** A
i i' i **»¦«
— J
•—' i" • ¦
1
r\3
CO
0 5
M-Sep-84
10 15 20 25
16-Oct-M
30
35 40 45
05-Nov-84
50
55 60 65
25-Nov-64
Day* After Start
70 75 80 85 90 95 100 105 110 115 120 125
15-Dec-84 04-Jan-SS 24-Jan-85
WELL H1 TETRACHLOROETHYLENE (PERC)
WELL H1 TRICHLOROETHYLENE (TCE)
WELL H2 TETRACHLOROETHYLENE (PERC)
WELL H2 TRICHLOROETHYLENE (TCE)
CONCENTRATION OF TCE AND PERC
IN WELLS HI AND H2. SEPTEMBER
1984 TO JANUARY 1985
FIGURE 13
-------
29
concentrations 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 HI 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
1,2-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
PERC, TCE, and 1,2-DCE, as shown in the following table.
-------
30
TABLE 7
CRITERIA ASSOCIATED WITH DRINKING WATER ONLY CONTAMINANTS®
(ug/L)
Excess Lifetime Tacoma's Considered
Cancer Risk (EPA) Acceptable Acceptable for Human Usec
Chemical lQlZ 101° TOcjfo Criteriab 1 Day 10 Days
Chronic
PERC 0.088 0.88 8.8 0.8
TCE 0.28 2.8 28 2.7 -
1,2-DCE - 27 4,000 400
aAssumes consumption of 2 liters of drinking water per day over a 70-year period
X EPA, 1980).
"Supplied by Tacome-Pierce County Health Department.
Memorandum 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 RECOMMENDED OCCUPATIONAL AIR LEVELS
FOR VOLATILE ORGANICS (mg/m3)
OSHA
ACGIH
Chemical
8-hr
TLV-TWA
Ceiling
IDLH
8-hr
TLV-TWA
STEL
PERC
670(335)
1,340(670)
3,400
335
1,340
TCE
540
1 ,080(810)
5,400
270
1.080
1,2-DCE
790
990
16,000
790
1,000
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.
Values in parentheses are NIOSH recommendations.
-------
31
The risk assessments evaluated the potential of exposure from four
exposure routes, even though actual exposure from three of these routes
had been determined to be insignificant. The four routes evaluated were:
exposure from treated water from HI 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"® 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 complete 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
warrant. However, additional sampling of the monitoring wells placed
-------
32
TABLE 9
SUHMARY OF PONDERS CORNER HEALTH EFFECTS'
Exposure Pathway
Increased
Risk
Remark
Actual Use of Treated Nell Hater from H1-H2
Drinking and cooking 7x10
Gases from stripping towers
Gases from bathing water
Dermal exposure to bathing water 1x10
-8
I
NS
*9
Recent measured concentrations
Diluted by atmosphere
Potential Use of Untreated Nell Nater
Near MH 32
Drinking and cooking
Gases from bathing water
Dermal exposure to bathing water
9xl0~ 7 yg/L PERC, Nell 32
NS Nell below TLV-THA levels
9x10 7 yg/L PERC, Nell 32
Potential Exposure to Soil at Plaza
Cleaners Site
Ingestion of surface soil
Ingestion of subsurface soil
Inhalation of surface dust
Dermal contact to surface soil
Dermal contact to subsurface soil
Inhalation of gases during excavation
NS
6x10 to
4xl0~
NS
NS
NQ
26 times
ACGIH TLV-TNA
2.5 times
IDLH
New, clean soil
500 yg/kg to 3,880 yg/kg PERC
New, clean soil
New, clean soil
No methodology
Maximum soil concentration of
3,880 yg/kg PERC; absolutely
still air
0.006 times Maximum soil concentration of
ACGIH TLV-TNA 3,880 yg/kg PERC, 0.25 mph
wind speed
Exposure to Surface Haters
Ingestion
Gases from bathing
Dermal contact
5x10" to
lxio"
NS
5xl0-7 to
1x10
0.4 yg/L for Gravelly Lake only
Hell below TLV-THA levels
0.4 y/L for Gravelly Lake only
Considerations are primarily for PERC and TCE in groundwater and for
PERC in soils. DCE was not a major contaminant in the study area.
NS = not substantial.
NQ - not quantifiable.
-------
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 RI/FS, 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 any correspondence subsequent
to this time 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.
2. Reduce potential health risks associated with on-site excavation
and use of contaminated groundwater below those for the no-action
alternative.
3. Meet requirements of other environmental regulations.
4. 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 considered 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
the detailed evaluation.
-------
34
TABLE 10
ALTERNATIVES THAT PASSED SCREENING
Unit Alternative Sceening Result
Soil Excavate or treat Pass
Landfill Cap Pass
Vertical barrier Fail
Horizontal barrier Fail
Flooding Fail
Administrative restrictions Pass
m-place treatment Pass
(conditionally)
No action Fail
Aquifer Extraction & treatment Pass
Modify H1-H2 system Pass
Monitor Pass
Alternative water supply Fail
No action Fail
-------
TABLE 11
DESCRIPTION OF REMEDIAL ALTERNATIVES CONSIDERED IN DETAILED EVALUATION
Unit
Soil
Alternative Deacription
SI - Excavation of 29,200 CY to reduce PERC to
nondetection limit
Variation
SlA - Disposal in offsite RCRA landfill
SlB - Disposal by offsite RCRA
incineration
SIC - Disposal in onsite RCRA landfill
SlD - Onsite treatment in kiln
EPA Evaluation
Category
S2 - Excavation of 7,500 CY in zone of
most
S2A
-
Disposal in offsite
RCRA
landfill
4
probable future excavation to PERC nondetec-
tion limit
S2B
-
Onsite treatment in
kiln
4
S3 - Excavation of 3,700 CY in zone of
most
pro-
S3A
_
Disposal in offsite
RCRA
landfill
4
bable future excavation to reduce
PERC
to
500 pg/kg
S3B
-
Onsite treatment in
kiln
4
S4 - Excavation of 1,420 CY in zone of
most
pro-
S4A
-
Disposal in offsite
RCRA
landfill
4
bable future excavation to reduce
PERC
to
1,000 ug/kg
S45
-
Onsite treatment in
kiln
4
S5 - Cap
S5A
-
Clay/membrane cap
3
S5B
-
Clay cap
2
S5C
-
Asphalt cap
4
56 - Administrative restrictions on onsite excava-
tion and well installation
57 - Vapor extraction
58 - No action
59 - Excavation of 900 CY and removal of septic
tanks and some drain piping
Aquifer A1 - Additional groundwater extraction near MW 32
to remove uncaptured portion of plume
A1A - Disposal in storm sewer
A1B - Treatment by air stripping at new
well
A1C - Treatment by air stripping at
H1/H2
CO
en
-------
Unit
Alternative Description
TABLE 11
(continued)
A2 - Extraction from till unit A2A
A2B
A3 - H1-H2 change to reduce costs A3A
A3B
A4 - Treatment system changes to reduce costs A4A
A4B
A5 - Monitoring to track cleanup and detect con-
tamination from other potential sources •-
A6 - No action
se9971FFF2
Variation
EPA Evaluation
Category
Disposal in Storm Sewer
Shipment by tanker to hazardous
waste disposal facility
Pump changes
Variable frequency controllers
Water flow increase
Fan speed reduction
4
4
5
5
5
5
5
5
CO
ot
-------
TABLE 12
SUMMARY OF DETAILED EVALUATION FOR SOIL UNIT ALTERNATIVES
Noncost Criteria
Cost Criteria
Remedial Alternative
SI Deep Excavation
S1A—Offsite Landfill
SIB—Offsite
Incineration
SIC—Onsite Landfill
Technical Feasibility
Feasible, safety threat
during excavation
Feasible, safety threat
during excavation
Feasible, safety threat
during excavation, O&M
requirements
Environmental Institutional
Impacts Requirements Public Health Impacts Capltal-$ OtM-$ Present Worth-$
Minimal
Minimal
Minimal
Complies with Virtually eliminates 7,540,000
requirements excavation risk
Complies with Virtually eliminates 70,035,000
requirements excavation risk
Acceptable
disposal
techniques
for most
wastes
Virtually eliminates
excavation risk
3,165,000 24,000
7,540,000
70,835,000
I
3,200,000
(30 years)
SID—Onsite Treatment
Treatment technology
developmental
Minima],
except at
treatment
site
Subject to Virtually eliminates
site-specific excavation risk
review
3,148,000
3,148,000
S2
Partial Excavation to
PERC Detection Limit3
GO
—I
S2A—Offsite
Landfill
S2B-'-Onsite Treatment
Feasible, safety threat
during excavation, OtH
requirements, treatment
technology developmental
Feasible, safety threat
during excavation, OCM
requirements, treatment
technology developmental
Minimal
Minimal,
except at
treatment
site
Virtually eliminates 2,340,000
excavation risk
May not meet virtually eliminates 1,591,000
RCRA or WDOE excavation risk
cleanup
levels
2,340,000
1,591,000
S3 Partial Excavation to
500 pg/kg PERC
S3A—Offsite Landfill
S3B—Onsite Treatment
Feasible, safety threat
during excavation, OtM
requirements, treatment
technology developmental
Feasible, safety threat
during excavation, O&M
requirements, treatment
technology developmental
Minimal
Minimal,
except at
treatment
site
May not meet
RCRA or WDOE
cleanup
levels
May not meet
RCRA or WDOE
cleanup
levels
Reduces excavation
risk
Reduces excavation
risk
1,16,000
853,000
1,126,000
853,000
"Detection limit approximately 20 |ig/kg PERC.
''Term used for PK calculation.
-------
TABLE 12
(continued)
Honcost Criteria
Cost Criteria
Remedial Alternative
S4 Partial Excavation to
1,000 yg/kg PEBC
S4A--Offsite Landfill
S48—Onsite Treatment
S5 Capping
S 5 A—C la y /membr a ne
S5B—Clay
Technical Feasibility
Feasible, safety threat
during excavation, OtM
requirements, treatment
technology developmental
Feasible, safety threat
during excavation, OSM
requirements, treatment
technology developmental
Environmental Institutional
Impacts Requirements Public Health Impacts Capital-S OSM-S Present Worth-$
Minimal
Minimal,
except at
treatment
site
Feasible, OSM requirements None
Feasible, OSM requirements None
May not meet
RCRA or WDOE
cleanup
levels
May not meet
RCRA or WDOE
cleanup
levels
Complies with
requirements
Complies with
requirements
Reduce excavation
risk
Reduce excavation
risk
Reduce potential for
inadvertent
excavation
Reduce potential for
inadvertent
excavation
479,000
508,000
73,400 8,340
60,000 6,900
479,000
508,000
152,000
(30 years)
125,000
<30 years)
CO
CO
S5C—Asphalt
Feasible, OSM requirements Hone
Complies with
requirements
Reduce potential for
inadvertent
excavation
28,400 1,000
37,000
(30 years)
S6 Administrative
Restriction
Feasible
None
Hay not meet
RCRA or WDOE
cleanup
levels
Reduce risk of exca-
vation without worker
protection
S7 Vapor Extraction
Promising, developmental
Air
discharge
May not meet
RCRA or WDOE
cleanup
levels
Virtually eliminates
excavation risk
38,500
38,500
SB Ho Action
S9 Partial excavation,
of fsite landfill
disposal
Feasible, safety threat
during excavating, 0*M
requirements, treatment
technology developmental
None
Minimal
May not meet
RCRA or WDOE
cleanup
levels
Potential excavation
risk
Reduce excavation
risk
231,200
231,200
cAverage annual OSM.
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TABLE 13
SUMMARY OF DETAILED ANALYSIS FOR AQUIFER UNIT
Remedial Alternative
A1 Extraction Near MH 32
Noncost Criteria
Cost Criteria
Technical Feasibility
Environmental
Impacts
Institutional
Requirements
Public Health Impacts Capital OtH Present worth
A1A—Storm Sewer
Disposal
feasible, 5- to 7-year
minimum cleanup time
None; elimi-
nate PERC
migration to
Gravelly Lake
Water quality
standards will
be applied
Reduce groundwater
use risk
76,000 8,500 125,300
(6 years)
A1B—Air Stripping
Feasible, 5- to 7-year
minimum cleanup time, OsM
requirements
Nonei elimi-
nate PERC
migration to
Gravelly Lake
Complies with
requirements
Reduce groundwater
use risk
412,000 9,500
445,000
(6 years)
A1C—Treat at H1-H2
Feasible, 5- to 7-year
minimum cleanup time, O&M
requirements
Nonet elimi-
nate PERC
migration to
Gravelly Lake
Complies with
requirements
Reduce groundwater
use risk
246,000 14,500
319,000
(6 years)
A2 Extraction From Till
A2A—Storm Sewer
Disposal
High probability of failure None
Water quality
standards will
be applied
Potential groundwater 2,000
use risk
3,500 23,000
(10 years)
CO
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TABLE 13
(continued)
Noncost Criteria
Cost Criteria
Remedial Alternative
AS Monitoring
A6 No Action
Technical Feasibility
Feasible, O&M requirements
Feasible, 10- to 12-year
minimum cleanup time, 06M
requirements
Environmental
Impacts
None
None
Institutional
Requirements
May not meet
RCRA and MDOE
cleanup levels
May not meet
RCRA and WDOE
cleanup levels
Public Health Impacts Capital
Potential groundwater 22,000
use risk
Potential groundwater
use risk
O&M
32,000
Present Worth
219,000
(10 years)
O
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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 TLV-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 HI and
H2.
Each of the soil excavation alternatives provides some degree of risk
reduction. Alternative SI--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 SI 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 SIC) 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 risk reduction depending upon the maximum soil
concentration limit that is selected. Alternatives S2, S3, and S4
represent those possibilities in that the maximum PERC concentration in
soil following implementation of 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). Approximate cost curves are given for both
off-site disposal in a RCRA landfill and onsite treatment.
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42
10.000-
1.000 -
•.000-
4,000-
24300-
1,000-
S9
• ••
AltemedwSA
\ N
\ +m_ AltMiatfttU
\ V
\ \
\ \ tlv-twa
—\ \——-
\OrvSit» A Off-tit*
TnihiMnl ^ Onpocaf
\
100 ™
80-
60-
40-
\
A
\
i
%
• AlUfiMllw >3
\
\
V
1 -
as
0.6
0.2-
Ahemetife 14
S9
\ it^AttimitkraSl
\ V
T V ~»**¦
On-Sto \ OH-«lt»V
I \ Tmumm \
.
0.8 1.0 1.5 2.0 IS 3.0
Com (SMI
RISK REDUCTION VS. COST
FOR PARTIAL EVALUATION
FIGURE 14
-------
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 level of risk reduction as Alternative
SI 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 SI.
Both Alternative S3, Partial Excavation to 500 ug/kg, and Alternative
S4, 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 tanks, 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).
Costs for this alternative are estimated in the following table.
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44
tLL ?'.» Q
SB ^
LEGEND
[ ''''.'V.. ' j DRAINFIELD LINES
0 SOIL BORINGS
EXCAVATED VOLUME - 900 cy
TANK AND DRAINFIELD
EXCAVATION
ALTERNATIVE S9
FIGURE 15
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45
TABLE 14
ALTERNATIVE S9—TANK EXCAVATION
Construct*on Costs ($)
Excavate 900 cubic yards $ 5,070
Remove tanks and drainpipe 400
Haul and dispose-Arlington 125,000
Building shoring-70 1 ft 48,200
Backfill 11,430
Construction Subtotal $190,100
Health and Safety 151 of site costs 9,800
Mobilization and temporary facilities,
7.5% of above onsite 5,600
Bonds and insurance, 1.51 of above onsite 1,200
Contingency, 30% of above onsite 24,500
Estimated Construction Total $231,200
Engineering and Design
Table 4-8 $ 12,750
Services During Construction
Table 4-11 9,500
Subtotal, Initial Cost $ 253,450
Annual O&M -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
contaminated soil with PERC concentrations of approximately 1,000 ug/L.
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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 health risk would be equivalent to that of
Alternative S2.
The institutional issues for Alternative S9 are the same as those for
Alternative S4 , discussed in Chapter 4.
Alternative S5--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 S5 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 precautions
should be taken during excavation. Such a notification 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 S5C and S6. Alternative S6
would provide notification to most individuals who would conduct onsite
excavation, while Alternative S5C 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 drainfield
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 HI and H2, and that the stripping towers and
wells HI 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
to 12 years.
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47
Alternative A1, 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 HI 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 A1A) 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 study 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 A1
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
years.
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, H1-H2 Pump Changes, would address only the issue of
operating costs. Of the two variations, the alternative involving the
installation of variable-frequency controllers (Alternative A3B) would be
most cost-effective. The 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. This 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
shown in the following table.
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TABLE 15
COMPARISON OF COSTS FOR NO CHANGE WITH
ALTERNATIVES A3B AND A4B ON H1-H2 TREATMENT SYSTEM
No Change
Initial Annual Annual
Cost O&M Savings PW-10 YR
Treatment system — $43,800
Well 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
installing a private drinking water well.
Alternative A5—Monitoring, 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 H1-H2 treatment system (the. no-action
alternative), Alternatives A3B and A4B 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
health risk and the need to clean up the uncaptured portion of the plume.
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49
SUMMARY OF RECOMMENDED INITIAL REMEDIAL ACTION
Aquifer Unit
The following actions are recommended as the most cost-effective,
technically sound alternatives and will protect public health and the
environment {Table 16):
Continue operation of the H1-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
A3B).
Change fan drives to reduce treatment tower air flow to reduce
energy requirements and thereby reduce costs (Alternative A4B).
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 A5).
Place administrative restrictions on the installation and use of
wells to minimize the potential for use of contaminated groundwater
(Alternative S6).
Installation of an extraction well to remove the contamination that is
escaping the zone of capture of wells H1-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 preclude future well use. Increasing the flow rate at H1-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
stripping tower and the groundwater monitoring network.
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TABLE 16
SUMMARY OF RECOMMENDED REMEDIAL ACTION
Alternative
A6
Description
A3B
A4B
AS
S6
S9
Continue treatment at
H1-H2.
Install variable-
frequency controllers.
Reduce fan speed.
Monitoring wells,
sampling, and analysis
Administrative restric-
tions on wells and
excavation.
Excavate and remove sep-
tic tanks and drain field
at Plaza Cleaners.
Expected Results
Aquifer cleanup.
Treated water quality well
below limits for
contaminants.
Reduce energy requirements
and well pump power cost.
No effect on treatment
system or flow.
Reduce energy requirement
and treatment system cost
with negligible effect on
treatment.
Monitor aquifer cleanup.
Early warning of new
sources.
Restrict uncontrolled use
of contaminated aquifer
and exposure to contami-
nated soil.
Reduce worker exposure if
uncontrolled excavation
occurs.
Costs
Term
10 to 12 years
10 to 12 years
Soils:
permanent
Wellsi
10 to 12 years
Permanent
Initial
50
557,780
10 to 12 years 51,600
10 to 12 years 522,140
50
$253,450
Annual OtH
Hells:
531,200
Treatment¦
543,600
575,000
518,500
535,300
553,800
Remarks
531,900
50
50
Current OsM cost.
Current OiM cost.
Existing Hell/
Treatment 04M.
I
Saves 512,700 per
year on OfcM costs.
Saves 58,500 per year
on out costs.
Hell/Treatment O&H in
revisions A3B and A4B
ui
o
5334,970 585,700 Proposed Action
Totals with S9
excavation alternative
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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 S9).
Place administrative restrictions on excavation into the
contaminated soils to reduce the risks associated with uncontrolled
excavation (Alternative S6).
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 administrative 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 uncontrolled
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 treatment of on-site soils with other methods, including soil
aeration, which are found to be equivalent in cost and effectiveness of the
method. The feasibility 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
regulations for emissions of volatile organics into the air.
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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
present at wells HI and H2. Groundwater from wells HI 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 permit has been issued for the HI 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 concentration 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 information which will be continually
collected during the stripping towers' operation period, EPA will make a
determination 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
without the necessity of a cap at the site.
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53
OPERATIONS AND MAINTENANCE (04M)
Activities Required for One Year After Initial Remedial Action
Wells HI and H2
As of October 15, 1985, the Lakewood Water District will assume all the
O&M cost associated with the stripping towers at wells HI 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 HI 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.
If additional soil unit work is implemented it may require O&M.
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i
j 54
i
SCHEDULE
Approve Initial Remedial Action 9/85
Sign ROD 9/85
Design Initiated by EPA 10/85
Sign State Superfund Contract 11/85
Construction Procurement by EPA 4/86
Construction Initiated by EPA 6/86
quired.
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