STREAMLINED REMEDIATION SYSTEM EVALUATION (RSE-LiTE)
FOR A GROUND WATER PUMP AND TREAT SYSTEM
ENGELHARD CORPORATION FACILITY
PLAINVILLE, MASSACHUSETTS
SUBMITTED:
AUGUST 3,200 5
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Office of Solid Waste EPA 542-R-05-026
and Emergency Response August 2005
(5102G) www.epa.gov/tio
clu-in.org/optimization
Remediation System Evaluation for a
Ground Water Pump and Treat System
Engelhard Corporation Facility
Plainville, Massachusetts
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NOTICE
This report is an independent third party analysis and represents the views of the authors. This
document is not a U.S. EPA policy, guidance or regulation. It does not create or impose any
legally binding requirements or establish U.S. EPA policy or guidance. The information is not
intended, nor can it be relied upon, to create any rights enforceable by any party in litigation with
the United States or any other party. The information provided maybe revised periodically
without public notice. Use or mention of trade names does not constitute endorsement or
recommendation for use. Standards of Ethical Conduct do not permit EPA to endorse any
private sector product or service.
The U.S. Environmental Protection Agency funded the preparation of this document by
Geotrans, Inc. under EPA Contract No. 68-C-00-181 Task Order #40 to Tetra Tech EM, Inc,
Chicago, Illinois.
For further information about this report, please contact the EPA's Office of Solid Waste, Mike
Fitzpatrick, (703) 308-8411, fitzpatrick.mike@epa.gov or the EPA's Office of Superfund
Remediation and Technology Innovation, Ellen Rubin, (703) 603-0141, rubin.ellen@epa.gov.
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EXECUTIVE SUMMARY
A Streamlined Remediation System Evaluation (RSE-Lite) involves a team of expert
hydrogeologists and engineers, independent of the site, conducting a third-party evaluation of a
ground water pump and treat system or other remedy of environmental contamination. It is a
broad evaluation that considers the goals of the remedy, site conceptual model, above-ground
and subsurface performance, and site exit strategy. The evaluation includes reviewing site
documents, communicating with the site team, and compiling a report that includes
recommendations to improve the efficiency and effectiveness of the remedy. Recommendations
with cost and cost savings are provided in the following four categories:
Improvements in remedy effectiveness
Reductions in operation and maintenance costs
Technical improvements
Gaining site closeout
The recommendations are intended to help the site team identify opportunities for improvements.
In many cases, further analysis of a recommendation, beyond that provided in this report, may be
needed prior to implementation of the recommendation. Note that the recommendations are
based on an independent evaluation by the RSE-lite team, and represent the opinions of the RSE
team. These recommendations do not constitute requirements for future action, but rather are
provided for the consideration of all site stakeholders.
The Engelhard Corporation facility ("Engelhard") is a RCRA Corrective Action facility. The site
was nominated based on its long history, type and nature of volatile organic chemical presence,
and performance of the ongoing ground water remedy.
Initial site investigation and remedial activities have been conducted at Engelhard since the mid
1980's. The ground water contaminant plume consisting of tetrachloroethene (PCE) and 1,1,1-
trichloroethane (TCA) have migrated beyond the property boundary. A Corrective Action
consent order was signed by Engelhard facility and EPA in 1993. As a result, a ground water
stabilization measure (GSM) pump and treat system consisting of six deep bedrock extraction
wells and a vertical high-density polyethylene (HDPE) barrier membrane was installed and
began operating in 1998. The objective of GSM is to contain the plume along the HDPE barrier
membrane and establish a gradient reversal to capture contamination that may be present
immediately downgradient of the GSM.
The RSE-lite team found a site team committed to improving the existing remedy through a
number of pro-active actions to comply with the consent order. The RCRA Facility
Investigation is ongoing, and the data are being used to evaluate the existing remedy and its
potential for use as a final remedy. Some increases in site-related contamination were detected
on the downgradient side of the GSM during recent years of operation, and this has triggered
concerns about the effectiveness of the remedy in its current form. Between 2003 and 2004
Engelhard conducted two separate evaluations of the GSM that included field work, and have
made recommendations to upgrade the remedy based on its findings. The RSE-lite team has
in
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reviewed the site documents, these recent reports, comments provided by EPA, and responses to
those comments from Engelhard.
Based on the document review and RSE-lite conference call, the RSE-lite team has provided
recommendations for both improving the effectiveness of the system and reducing operating
costs.
The effectiveness recommendations focus on developing figures that would improve the site
conceptual model and the evaluation of plume capture. The RSE-lite team notes that achieving
"gradient reversal" as indicated in the site objectives generally requires more pumping than is
necessary for adequate capture. Despite the recent evaluations conducted by Engelhard, the
RSE-lite team does not see conclusive evidence that supports or does not support capture. The
RSE-lite recommendations, therefore, suggest an alternative, cost-effective approach for
evaluating capture. The RSE-lite recommendations also generally support the technical
recommendations offered by Engelhard in its recent evaluations. Although EPA's comments on
the recent Engelhard reports have merit, the RSE-lite team would rather see the site team focus
on the recommendations in this RSE-lite report and upgrading the GSM rather than revisiting the
previous reports to retroactively address EPA's comments. EPA's comments, however, should
be duly noted and considered for future site efforts and reports.
The cost-reduction recommendations focus on simplifying the treatment train to reduce chemical
and materials costs as wells as potentially reduce operator labor. One recommendation suggests
considering eliminating the metals removal aspect of the treatment plant, and another
recommendation suggests eliminating the use of liquid phase granular activated carbon (GAC)
given that the air stripper provides adequate and reliable treatment of volatile organic
compounds (VOCs).
IV
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TABLE OF CONTENTS
NOTICE i
EXECUTIVE SUMMARY iii
TABLE OF CONTENTS v
1.0 INTRODUCTION 1
1.1 PURPOSE 1
1.2 RSE-LiTE PROCESS 2
1.3 PARTICIPANTS ON RSE-LiTE CONFERENCE CALL 2
1.4 DOCUMENTS REVIEWED 2
2.0 BACKGROUND 4
2.1 SITE HISTORY 4
2.2 SITE CONCEPTUAL MODEL 4
2.3 GROUND WATER REMEDIAL SYSTEM 6
2.4 REMEDY GOALS 7
2.5 COSTS 8
3.0 RSE-LITE FINDINGS 9
3.1 FINDINGS PERTAINING TO REMEDY PROTECTIVENESS 9
3.2 FINDINGS PERTAINING TO COST-EFFECTIVENESS 12
3.3 FINDINGS PERTAINING TO REMEDY PROGRESS AND SITE CLOSURE 13
4.0 RSE-LITE RECOMMENDATIONS 14
4.1 RECOMMENDATIONS TO IMPROVE SYSTEM PROTECTIVENESS 14
4.1.1 Improve Documentation and Illustration of the Site Conceptual Model 14
4.1.2 Evaluate Current Level of Capture 14
4.1.3 Increase Bedrock Extraction Rate 16
4.1.4 Reconsider Increased Overburden Extraction 16
4.1.5 Sample and Analyze for 1,4-Dioxane in Continued Source Area Investigations. 17
4.2 RECOMMENDATIONS TO REDUCE SYSTEM COST 17
4.2.1 Consider Eliminating the Metals Removal Equipment 17
4.2.2 Remove Liquid Phase GAC Units 17
4.2.3 Remove Select Monitoring Wells from Routine Sampling 18
4.3 RECOMMENDATIONS FOR TECHNICAL IMPROVEMENT 18
4.4 RECOMMENDATIONS TO SPEED SITE CLOSEOUT 18
4.4.1 Revisit MNA Criteria for the Downgradient 1,1-DCE Plume 18
4.4.2 Continue with a Source Control/Containment Remedy 18
FIGURES - PREPARED BY THE SITE CONTRACTOR AND INCLUCDED FOR REFERENCE
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1.0 INTRODUCTION
1.1 PURPOSE
In 2003 and 2004, the EPA Corrective Action program and the EPA Office of Superfund
Remediation and Technology Innovation (OSRTI) sponsored independent optimization
evaluations called Remediation System Evaluations (RSEs) at five RCRA sites with pump and
treat (P&T) systems. These RSEs involved an independent team of experts reviewing site
documents, interviewing site stakeholders, and providing recommendations for improving
remedy effectiveness, reducing costs, and gaining site closure.
A RSE involves a team of expert hydrogeologists and engineers, independent of the site,
conducting a third-party evaluation of site operations. It is a broad evaluation that considers the
goals of the remedy, site conceptual model, above-ground and subsurface performance, and site
exit strategy. The evaluation includes reviewing site documents, visiting the site for 1 to 1.5
days, and compiling a report that includes recommendations to improve the system.
Based on the positive results of these RSEs, EPA Technology Innovation Field Services Division
(OERR) and the Office of Solid Waste (OSW) have commissioned a new pilot study that
involves developing and piloting a streamlined RSE process that reduces the cost of resources
relative to a full-scale RSE based on the consideration that many sites do not require a full-scale
RSE and a streamlined RSE will provide same level of beneficial results for those sites with the
reduction of cost. This streamlined RSE or "RSE-lite" evaluation includes reviewing site
documents, conducting conference calls with the site team, and compiling a report of
recommendations.
For this new pilot study, up to five RCRA Corrective Action facilities with operating remedies
have been selected to receive RSE-lites. The site managers have been asked to provide site
documents for review by the RSE-lite team. After reviewing the documents, the RSE-lite team
has communicated with the site managers to learn more about the sites and fill in information
gaps not covered by the site documents. As part of this streamlined effort, no site visit has been
conducted.
This RSE-lite report for the Engelhard Corporation facility ("Engelhard") is one of the RSE-lites
from this new pilot study. Engelhard was nominated based on its long history and ongoing
ground water remedy. The report consists of the following elements:
A brief summary on site history, site conceptual model, ground water remedial system,
remedy goals, and costs
• Recommendations to improve remedy effectiveness and efficiency of the operating pump
and test system (an interim remedy that is only one component of the site-wide remedy)
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1.2 RSE-LiTE PROCESS
Once a site is selected, a representative of the RSE-lite team contacts the site project manager to
obtain site documents for review. The documents typically include information pertaining to site
investigations, remedy design, and remedy operations and maintenance (O&M). Upon reviewing
this information, the RSE-lite team conducts a conference call with the remedy project manager
to address questions that may have arisen as part of the document review or other information
gaps. Based on the site documents and the information from communications with the site
project manager, the RSE-lite team prepares a short report documenting recommendations for
improving efficiency and effectiveness. The text of the RSE-lite report includes a brief
background of the site, series of findings from the document review and conference call, site-
specific recommendations, and a cost summary table summarizing estimated costs and cost
savings associated with implementing each recommendation.
1.3 PARTICIPANTS ON RSE-LiTE CONFERENCE CALL
The following individuals participated in the conference call as part of RSE-lite:
Tom Brown, Engelhard Corporation
John Scaramuzzo, Tetra Tech EC (project manager of ground water P&T system)
Joe Francis, Tetra Tech EC (system operator)
Steve Graham, LFR (PM for ground water assessment)
• Rick Kuhlthau, (EPA Contractor)
• Bob Brackett, RPM, EPA Region 1
• Ellen Rubin, EPA HQ
Doug Sutton, GeoTrans, Inc.
Peter Rich, GeoTrans, Inc.
Yan Zhang, GeoTrans, Inc.
1.4 DOCUMENTS REVIEWED
The following documents were reviewed as part of this RSE-lite:
Conceptual Design Report Groundwater Treatment System, Foster Wheeler
Environmental Corporation, November 1995
• Final Design Report Groundwater Stabilization System, Foster Wheeler Environmental
Corporation, December 1996
Selected sections from Draft RCRA Facility Investigation report, September 30, 1999
Groundwater Stabilization Measure (GSM) Evaluation Report, ECS, June 2004
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Groundwater Treatment Plan Operation and Maintenance Quarterly Status Report -
->nd
No. 26 Year 7 - 2na Quarter (April 1, 2004 through June 31, 2004), Tetra Tech FW, Inc.,
November 2004
Groundwater Treatment Plan Operation and Maintenance Quarterly Status Report -
No. 27 Year 7 - 3rd Quarter (July 1, 2004 through September 30, 2004), Tetra Tech FW,
Inc., January 2005
Groundwater Stabilization Measure (GSM) Upgrade Report, ECS, February 2005
Draft comments on the 6/24/04 groundwater stabilization measure report
Draft responses to draft USEPA comments on the June 24, 2004 groundwater
stabilization measure report
Draft comments on the 7/15/04 monitored natural attenuation report
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2.0 BACKGROUND
2.1 SITE HISTORY
The Engelhard Corporation facility is located at 30 Taunton Street in Plainville, Massachusetts.
The facility, which was constructed in the late 1950's, was primarily involved in the manufacture
of various precious metal products. Environmental investigation and remedial activities have
been conducted at the site since the mid 1980's. EPA and Engelhard signed a 3008(h) Corrective
Action consent order in 1993 that, among other items, requires Engelhard: to investigate several
potential areas of concern (AOC); to assess the potential migration of constituents; to evaluate
the potential human health and ecological risks posed by the presence of these constituents in the
AOCs; and to implement certain specified stabilization measures at the site.
In addition to requiring Engelhard to conduct a RCRA Facility Investigation (RFI) and several
stabilization measures, the 1993 Consent Order required that Engelhard install a ground water
pump and treat (P&T) system as a near-term stabilization measure which would reduce off-site
migration of contaminated ground water and be compatible with, and part of, a likely final
remedy. As a result, a ground water P&T system was installed in 1997 and began full-scale
operation in January 1998.
Beginning in the Spring of 2003, Engelhard conducted a series of activities to evaluate the
efficacy of the on-site ground water contaminant system, involving review of prior data, new
field investigations and pumping tests, and further data evaluation. This evaluation was
undertaken as part of a review of operations at the five-year (1998-2002) period of performance,
and also occurred in response to an increase in volatile organic compounds (VOC)
concentrations observed in monitoring wells downgradient of the system during the 2002 annual
ground water sampling event.
2.2 SITE CONCEPTUAL MODEL
Source Area and Contaminants of Concern
Six VOCs are consistently detected in ground water: cis-l,2-dichloroethene (1,2-DCE); 1,1-
dichloroethene (1,1-DCE); 1,1-dichloroethane (1,1,-DCA); 1,1,1-trichloroethane (TCA);
trichloroethene (TCE); and tetrachloroethene (PCE). In general, 1,1,1-TCA and PCE are
detected at the highest concentrations, followed by TCE, 1,1-DCA, and 1,1-DCE. VOC
concentrations in the bedrock wells are generally higher than those observed in corresponding
overburden wells. Figures generated by the site contractor are included as an attachment to this
document to illustrate well locations and the extent of contamination in both the overburden and
bedrock.
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The highest contaminant concentrations during the January 1995 - October 2003 sampling
events are listed in the following table:
Concentration
Overburden Zone
Bedrock Zone
1,1,1-TCA
(ug/L)
5,300
43,000
PCE
(ug/L)
16,000
36,000
TCE
(ug/L)
1,100
1,700
1,1-DCA
(ug/L)
220
1,200
1,1-DCE
(ug/L)
300
1,300
Cis-l,2-DCE
(ug/L)
340
350
Hydrogeology
Two principal geologic zones underlying the facility include an unconsolidated (glacial-till)
overburden zone and a consolidated bedrock zone. The overburden zone represents Quaternary
glacial deposits, which consists of poorly sorted and poorly stratified, brown gravelly sand with
occasional lenses of gray silty sand. The overburden material is found at an average depth of
approximately 25 feet below ground surface (bgs). The thickness of this unit generally varies
from 18 feet to 36 feet. The ground water gradient in this overburden zone ranges from 0.015 to
0.04 feet/feet. The hydraulic conductivity ranges between 2.25><10"3 cm/sec and 6.90><10"3
cm/sec with an arithmetical mean value of 5.33x10"3 cm/sec.
The bedrock zone is comprised of the Rhode Island Formation, which consists of a light to dark
grey, hard, well fractured, slightly weathered to fresh, meta-sediment. The thickness of the
bedrock zone is approximately 150 feet and extends to a depth of approximately 180 feet bgs.
The bedrock is fractured media consisting of solid rock with a low porosity and hydraulic
conductivity (less than 10"7 cm/sec), and fracture zones with a higher hydraulic conductivity that
create a secondary porosity and a network for ground water and contaminant movement. The
ground water gradient in the bedrock is similar to that of the overburden and ranges between
0.015 to 0.04 feet/feet. The average hydraulic conductivity as determined from a pump test is
2.78x 10"4 cm/sec, which approximately one order of magnitude lower than that of the
overburden.
In general, the ground water flow direction in the overburden and bedrock zones is from the
southwest to northeast. Beneath the facility, the vertical hydraulic gradient in the overburden is
generally downward into the bedrock zone, due to ground water recharge from Turnpike Lake,
particularly at the facility's western boundary. The vertical hydraulic gradient generally reverses
in the low-lying area east of the site, due to upwelling of ground water to the unnamed streams
east of the facility. The presence of VOCs in surface water corresponds to this ground water
flow pattern. VOCs are not present in localized areas of surface water near the site but are
present in surface water in low-lying areas east of the site where impacted ground water
discharges to surface water.
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Potential Receptors
The primary ecological receptor is the surface water located to the east of the site where VOC
impacted ground water has been surfacing at a distance of 600 to 800 feet from Engelhard
facility property boundary.
Potential human receptors include nearby wells at private residences. North of the stream,
approximately a half mile to one mile away, there are residential bedrock wells at 50-100
residences. These residential wells were previously sampled and no site-related contamination
was found. The majority of the residences use city water. There are three municipal wells
located near Turnpike Lake, which is upgradient of the site contamination. The 1999 Draft
RCRA Facility Investigation also indicates that there is an irrigation well to the east of the
facility that is no longer active but has not been properly abandoned. There was no information
reviewed by the RSE-lite team that indicates whether or not this irrigation well has been
impacted. To date, the site team reports that sampling results indicate that no supply wells in the
area have been impacted by site-related contamination.
2.3 GROUND WATER REMEDIAL SYSTEM
The ground water remedial system was constructed between June and November 1997, with
system start-up occurring in December 1997 and full-scale operation beginning in January 1998.
A vertical barrier and an extraction system were installed to provide capture and reverse the
hydraulic gradient along the property boundary. The extracted ground water is subjected to
metal removal (via pH adjustment, coagulation, and precipitation), air stripping, filtration,
carbon adsorption, and discharged to Turnpike Lake. The ground water remedial system consists
of following components:
Six deep bedrock extraction wells and a vertical high-density polyethylene (HOPE)
barrier membrane extending to the depth of bedrock (see figures attached at the end of
this report)
Equalization tank with bubble diffuser
• Metal precipitation for iron and manganese
• Inclined tube/plate clarifier
Sludge storage tank
Low-profile NEEP air stripper
• Bag filter
• Filter press
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Two liquid phase granular activated carbon (GAC) units
Two vapor phase GAC units for off-gas treatment
Effluent tank
Discharge to surface water
The treatment system is designed to operate at a flow rate of 110 gpm. The design influent
concentrations for five primary contaminants of concern (COCs) are listed below.
Contaminants
Trichloroethene
1,1,1 -trichloroethane
1,1-dichloroethene
Tetrachloroethene
1,1-dichloroethane
Design Influent Concentration
(ug/L)
602.5
3,127.6
2.1
3,332.8
15.3
2.4 REMEDY GOALS
As required in Consent Order, the general performance standards for stabilization of ground
water include: a) designing, installing, operating, and maintaining a ground water P&T system
that utilizes pumping wells to significantly reduce migration of contaminated ground water off-
site by causing a reversal of the natural hydraulic gradient in the bedrock and overlying
unconsolidated saturated zones along an approximately 540 foot line running parallel to Route
152; and b) treating recovered ground water to the extent necessary to comply with applicable
discharge standards. The extraction wells are located approximately 50 feet to the west of Route
152 (i.e., the facility-side of Route 152 as indicated in the figures attached at the end of this
report). In addition to owning the property where the facility is located, the site team reports that
Engelhard also has partial control over property that extends approximately 200 feet east of
Route 152.
The requirements for GWTP aqueous effluent discharge to local surface water, Turnpike Lake,
are contained in the National Pollution Discharge Elimination System (NPDES) Permit
Exclusion dated July 2, 1997. The specific guidance for the discharge of vapor from the
remediation system is governed by the Massachusetts Bureau of Waste Site Cleanup (BWSC)
Policy No. WSC-94-150 "Off-Gas Treatment of Point Source Remedial Air Emissions", which
requires the destruction or removal of 95% of the VOCs in an off-gas system.
The discharge criteria for discharging treated ground water to Turnpike Lake are listed in the
following table.
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Contaminants
1,1,1 -trichloroethane
1 , 1 -dichloroethene
Tetrachloroethene
Trichloroethene
Benzene
Total BTEX
MTBE
Methylene Chloride
Cis-l,2-DCE
Trans- 1,2-DCE
1,1 -DCA
Chloroethane
Chloroform
TPH
Discharge Limit (ug/L)
200
7
5
5
1
100
70
5
70
100
100
100
100
5,000
2.5 COSTS
The 2004 budgeted costs for treatment plant O&M are listed below. This budget does not
include costs associated with ground water sampling, the ongoing investigation/evaluation
efforts, or the project management and reporting.
Cost Category
Labor (Operator and Home Office)
Chemical/Bag Filters
Lab Analysis
Maintenance, Calibration, & Repair
Parts, Tools, & Equipment
Health & Safety Supplies
Service Tech (Carbon)
Sludge
Waste Disposal
ODCs
Total
2004 Budget
$79,595
$2,500
$6,000
$13,000
$13,500
$1,500
$9,500
$7,500
$0
$7,905
$141,000
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3.0 RSE-LITE FINDINGS
The findings indicated below are not intended to suggest a deficiency in the remedy design or
operation. These findings are not intended to suggest requirements for the site. Rather, these
findings are the opinions of a third-party evaluation team and are only provided for consideration
by the site team.
3.1 FINDINGS PERTAINING TO REMEDY PROTECTIVENESS
The RCRA Facility Investigation (RFI) is ongoing and one of the recommendations is to
include 1,4-dioxane on the list of analytes. The site team reports that it sampled for 1,4-
Dioxane and found it to be non-detect during the 1995 RCRA Facility Investigation.
These results were not available for review during the RSE-lite.
The P&T system is operating continuously except for minimal downtime due to short
scheduled shutdowns for minor maintenance. The average flow rate of the system is
approximately 40 gpm to 45 gpm based on the December 2004 and February 2005 O&M
reports, which is less than the 55 gpm that the site team previously established to
maintain the ground water gradient reversal and is much less than the design flow rate of
110 gpm. It should be noted that the site team is discussing whether or not gradient
reversal is practical, or even achievable, especially below 60 feet bgs. Recent studies by
Engelhard reveal that capture provided by the GSM, particularly along its southern half
(PW-1 through PW-3), is insufficient to prevent contaminant migration.
The 2002 sampling results indicate the presence of elevated VOC concentrations
downgradient of the barrier wall. In particular, at one well downgradient of GSM, MW-
17, 1,1,1-TCA and PCE concentrations had increased from 6,500 ug/L to 35,000 ug/L
and from 4,600 ug/L to 36,000 ug/L, respectively, from 1995 to 2002. This increase in
the wells downgradient of barrier wall might have resulted from the temporary shutdown
of PW-3, and the decrease of concentrations in those wells noted during the 2003
sampling event is possibly due to resuming pumping at PW-3. The site team reports that
concentrations have continued to decline in these wells in subsequent sampling events.
The June 24, 2004 Ground water Stabilization Measure Report documents evaluations
that Engelhard conducted on the effectiveness of the GSM. Engelhard and its contractors
reviewed existing site information and conducted field work in 2003 and early 2004 with
the following objectives:
o Assess the ground water flow patterns near the facility in the absence of pumping
o Develop an updated site conceptual model of ground water flow under actual
pumping conditions
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o Identify the relative effectiveness of individual extraction wells to control ground
water flow
o Evaluate the efficiency of the GSM in terms of plume capture
The field work consisted of 10 additional piezometers in the vicinity of the GSM, pump
tests for each of the six pumping wells, and ground water sampling of bedrock
piezometers. The following conclusions were reached:
o The GSM is not effectively capturing all VOC contamination and the GSM may
be pulling contamination into the bedrock
o A fault trending west to east may be present near PW-2, providing a conduit for
preferential ground water flow and contaminant transport
o The capture zones of the extraction wells in the southern part of the GSM (PW-1
through PW-3) do not provide sufficient overlap such that the loss of one well
cannot be compensated by increased pumping from additional wells
The following recommendations were provided:
o Evaluate the condition of the existing pumping wells
o Install an overburden/shallow bedrock well screen at PW-2
o Reduce the pumping rate at PW-6
o Decommission PW-4 and/or PW-5 as extraction wells
o Potentially convert Pla and P12a into extraction wells
EPA had a number of comments on this report, including the following:
o The usage and designation of "rock quality designation" (RQD) needs to be
clarified.
o EPA raised a number of concerns regarding data quality due to how the tests were
conducted and how the data were interpreted. Concerns included the observation
of rising water levels during pumping tests, the method used for interpreting
pump test data, not allowing the aquifer to stabilize in between pump tests, using
water levels from pumping wells during pump tests rather than nearby
piezometers.
o The figures presented in the report show hydraulic influence and not hydraulic
control.
In general, Engelhard appeared to acknowledge the comments but maintained that the
information collected was semi-qualitative in nature and sufficiently accurate for moving
forward with recommending and pursuing GSM upgrades.
The RSE-lite team identified a reporting error in the June 2004 report that does not
appear to have greatly affected site decisions but should be noted. The reported
hydraulic conductivity values in the June 2004 GSM report from recent pump tests are
likely in error. The report uses the following equation for determining transmissivity
(which, in turn, is used to estimate the hydraulic conductivity).
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T =
264 xQ
As
where
Tis the transmissivity
Q is the pumping rate
As is the drawdown observed over one logic cycle of time (e.g., 50 min. to 500 min.)
This is only an appropriate equation to use when parameters are input using specific units
(gpm for the pumping rate and feet for drawdown with transmissivity calculated in
gpd/ft). However, it appears that inappropriate units were used. The following general
equation for consistent units (Driscoll, 1986) is correct:
2.3x
T =
where
Tis the transmissivity (ft2/day)
Q is the pumping rate (ft3/day)
As is the drawdown (ft) observed over one logic cycle of time (e.g., 50 min. to 500 min.)
The following table includes the hydraulic conductivity measurements reported in the
June 2004 GSM report along with the correct hydraulic conductivity measurements using
the general equation with consistent units.
Location
PW-1
PW-2
PW-3
PW-4
PW-5
PW-6
(Incorrect)
Hydraulic Conductivity Range
June 2004 GSM
(cm/sec)
3.92xlO-3-2.38xlQ-1
2.06xlO-1-5.00xl(r1
1.08xlO-2-4.89xl(r2
7.36xlO-3-1.54xl(r2
1.18xlO-2-8.97xl(r2
4.31x10°- 1.4X101
(Correct)
Hydraulic Conductivity Range
Using Consistent Units
(cm/sec)
2.72xlO-6-1.65xlO-4
1.43xlO-4-3.47xl(r4
7.5xlO-6-3.40xl(r5
5.1xlO-6-1.07xl(r5
8.19xlO-6-6.23xl(r5
2.99xlO"3-9.72xlO"3
As is evident, the hydraulic conductivity measurements using the consistent units are a
factor of 1440 lower than those reported in the June 2004 GSM report and are
comparable to (or even lower than) the measurements that were provided in the
Conceptual Design Report. The values from the Conceptual Design Report were used
for the designing the site and for consideration during the RSE-lite. As a result, the RSE-
lite team believes that the correct information has been used in making major site
decisions and that the hydrogeological analysis provided in the RSE-lite report is a
reasonable representation of the site hydrogeology.
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To address data gaps and provide useful information for upgrading the GSM, the facility
and its contractor conducted a series of evaluations including collecting water quality
samples from each of the extraction wells, hydraulic conductivity testing of upgradient
piezometers, evaluation of the extraction wells, and sampling of extraction wells for
parameters that could lead to well fouling. The data and analysis is included in the
February 2005 Ground water Stabilization Measure (GSM) Upgrade Report.
The report documents that the highest contaminant concentrations are found in the area
between PW-1 and PW-3 (the highest are at PW-2). The report suggests short-circuiting
of the GSM and cites the following reasons:
o Poor control of ground water in the overburden near PW-2 and several other
extraction wells
o Limitation in the amount of water that is extracted from PW-1 through PW-5
o Excessive extraction from PW-6
The report also provides the following recommendations:
o Installation of a well screen at PW-2
o Installation of a high capacity pump at PW-2
o Implementation of alternative discharge pipe connections
o Implementation of a well maintenance program
o Replace the PW-6 pump with a lower capacity pump
o Adjust the wells screens of PW-1 and PW-3 to increase extraction from the
overburden
o Ground water monitoring for three months to monitor changes associated with
these upgrades
3.2 FINDINGS PERTAINING TO COST-EFFECTIVENESS
The site team appears to operate a very cost-effective remedy. Based on the O&M
reports that were reviewed during the RSE-lite, the air stripper is successful at meeting
the discharge requirements and has the appropriate failsafes. The GAC polishing appears
to focus more as a redundant treatment component rather than an active aspect of VOC
removal.
The majority of costs associated with O&M are related to operator labor, which is
required at the current levels due to operations of the metals removal components.
The other significant component of costs can likely be attributed to ongoing site
investigations and evaluations of the GSM. The cost-effectiveness of the remedy will
largely rely on the site team's ability to efficiently conduct the necessary investigations
and modify the GSM to provide the necessary level of plume capture.
12
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3.3 FINDINGS PERTAINING TO REMEDY PROGRESS AND SITE CLOSURE
Sampling results at the site, both near the GSM and upgradient of the GSM, suggest the presence
of dense non-aqueous phase liquids (DNAPL), which would make it very difficult for aquifer
restoration to be achieved in a reasonable time frame (i.e., on the order of 30 years).
13
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4.0 RSE-LITE RECOMMENDATIONS
4.1 RECOMMENDATIONS TO IMPROVE SYSTEM PROTECTIVENESS
4.1.1 Improve Documentation and Illustration of the Site Conceptual Model
Cross sections showing water levels, potentiometric contours, physical features, and contaminant
concentrations would help with illustrating the site conceptual model. In addition,
potentiometric surface maps (in plan view) for both the overburden and bedrock would be
helpful. When determining potentiometric contours (in cross section or plan view) the water
level measurements from operating extraction wells should not be used because they typically
are lower than representative water levels from the aquifer (due to well losses and other factors)
and may tend to overestimate plume capture. It is likely appropriate to collect water level
measurements on a quarterly basis (rather than the current monthly basis) for eight quarters
while adjustments are made to the GSM; however, after these eight quarters, it may be
appropriate to further reduce the frequency to semi-annual.
The reduction in the frequency of measuring water levels will likely save several hours of labor
per quarter, but it is unclear if this will translate to a reduction in labor costs if the measurements
are collected by the operator. The cost of generating these figures is relatively low, particularly
since base maps have already been prepared. Including these figures in future reports may
increase annual costs by approximately $5,000 per year.
4.1.2 Evaluate Current Level of Capture
The site team should attempt to evaluate the degree of plume capture offered by the current
GSM. The RSE-lite team recognizes that the recent work has had this as one of objectives, but
the RSE-lite team does not see conclusive evidence one way or the other regarding plume
capture or the lack of plume capture.
Site documentation indicates that the remedy objective requires gradient reversal. Gradient
reversal generally requires more pumping than is necessary for adequate capture. Therefore, the
degree of capture offered by the system may be adequate for plume control although gradient
reversal may not be achieved (now or in the future). Furthermore, although a substantial data set
is available for the site, the RSE-lite team has not seen a presentation of the data that indicates
whether or not capture (or gradient reversal) is adequate.
The RSE-lite team recommends cost-effectively evaluating capture with the following
approaches:
• water budget analysis
interpretation of a capture zone with potentiometric maps and cross-sections
monitoring of contaminant concentrations in downgradient performance wells
14
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The water budget analysis compares the amount of contaminated water flowing through or past
the area of interest (in this case, the 540-foot line along the property boundary and Route 152)
and the amount of water that is extracted. Using the parameters from Section 2.2 of this report,
the amount of water flowing through the overburden is approximately 38 gpm and the amount of
water flowing through the bedrock is approximately 10 gpm. Given that the extraction rate is
close to this value suggests that pumping might be adequate for capture. However, the pumping
is heavily weighted toward PW-6, and preferential pathways are likely present in other areas
along the GSM that may prevent the other pumping wells from intercepting all of the
contaminated water. For this reason, the results of the water budget analysis are generally
confirmed with other lines of evidence such as interpretation from potentiometric surface maps
and concentration trends at downgradient wells.
The potentiometric surface maps recommended in Section 4.1.1 can be used to evaluate the
extent of capture for both the overburden and bedrock. The number of wells and piezometers
near the GSM should provide above average resolution for illustrating both horizontal and
vertical gradients. Flow lines can be drawn using these maps to indicate what areas are captured
by what wells. The potentiometric surface maps may indicate that the capture zone extends
beyond the extraction wells, which means that even though the gradient may not be reversed in
every location, capture does extend beyond the GSM and is pulling contamination toward the
wells. A review of the site plan indicates that the only two locations with sufficient data to
observe gradient reversal based on water level pairs are between P4/4a and P3/3a and between
P8/8a and P7/7a (other points appear to require water levels from operating extraction wells).
The gradients may not be reversed in these two locations, but, once again, capture may be
adequate, and the potentiometric surface maps should provide a more comprehensive indication
of that capture.
One of the better indications of capture is whether or not concentrations at downgradient wells
are decreasing to background concentrations. However, because concentration trend monitoring
takes time, this evaluation should be accompanied by the previous two approaches (a water
budget analysis and the use of potentiometric surface maps). The concentrations at monitoring
wells that are in the capture zone will not decrease and should not be used for this type of
evaluation. Therefore, wells such as MW-4, MW-14, MW-16, MW-17, etc. may not be
appropriate. A review of the potentiometric surface maps should provide an indication if these
wells are inside of the capture zone or downgradient of it. For this site, it may be most
appropriate to monitor the wells in Ring 1 (e.g., the MW-40, MW-41, MW-22, MW-30, and
MW-8 clusters). The new piezometers immediately downgradient of the GSM, along with the
MW-04 cluster and MW-25 cluster, may or may not be appropriate for monitoring concentration
trends as part of a capture zone analysis, but the MW-03 cluster is almost certainly too close to a
pumping well to be outside of its capture zone and would therefore be inappropriate for
monitoring concentration trends for the purpose of evaluating capture. The locations of existing
monitoring wells and extraction wells are indicated in the figures (developed by the site
contractors) that are attached at the end of this report.
The cost for this type of analysis should be reasonable compared with other site activities. The
water budget analysis is a set of simple analytical calculations, the potentiometric contour figures
(plan view and cross-section) were recommended in Section 4.1.1, and monitoring
15
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concentrations in monitoring wells is a typical exercise associated with P&T system O&M. The
only additional cost is for interpreting the data from these multiple lines of evidence, forming a
conclusion, and documenting the work. The above-described work could likely be done for
under $10,000 at this site.
4.1.3 Increase Bedrock Extraction Rate
The preliminary water budget analysis conducted in Section 4.1.2 suggests that the current
extraction rate is very close to the extraction rate required to provide capture. Given that the
pumping is not uniform and preferential flow paths likely exist, it is very likely that the GSM
extraction rate needs to be increased, particularly near PW-2 and PW-3. Site data suggest that
the highest concentrations both at the GSM and upgradient of the GSM are in the bedrock. As a
result, the RSE-lite team believes that the increased extraction should likely occur from the
bedrock. There should be little concern in pulling contamination down from the overburden to
the bedrock near the GSM because the contamination from the overburden (along with the
contamination that is already present in the bedrock in this area) would be removed by the GSM
once the extraction rate has been appropriately adjusted. The RSE-lite team agrees with
Engelhard's recommendations for installing a higher capacity pump in PW-2 and for
implementing a well maintenance program to reduce well fouling. If this action item does not
provide adequate extraction, additional wells between PW-2 and PW-3 would likely be
appropriate. This additional pumping should not significantly increase the O&M costs for the
treatment plant because the highest O&M cost is associated with operator labor, which should
not change with an increase in the extraction rate. If additional pumping would significantly
increase O&M costs, the site team might be able to reduce pumping from PW-6, if that reduction
does not compromise capture in the northern part of the GSM.
The RSE-lite has not provided estimated costs for addressing this recommendation. The RSE-
lite team defers to the site team and their knowledge of site-specific costs.
4.1.4 Reconsider Increased Overburden Extraction
The RSE-lite team does not believe that enhanced extraction from the overburden is as a high
priority. Concentrations at MW-14, MW-16, and MW-17 (which are bedrock and deep bedrock
wells) increased shortly after the GSM came on line. As the site team suggests, the increases in
these wells may result from the overburden ground water mounding behind the vertical
membrane and pushing water under the membrane. However, because the GSM is in place,
improving extraction in the bedrock should provide adequate capture of contaminated ground
water that is migrating from upgradient in the bedrock or migrating downward from the
overburden to the bedrock. Installing an overburden well screen at PW-2 would certainly result
in the extraction of additional water and would not be detrimental to system operation.
Therefore, although the RSE-lite team does not see this as a priority, it would not dissuade
Engelhard from following through with this action item. In contrast, the RSE-lite team sees little
benefit to extending the overburden well screens for PW-1 and PW-3 toward the high water table
mark. This may slightly increase the yield of these wells, but the increased exposure of the well
screen to air would likely increase the rate of fouling, and the concerns regarding fouling may
likely exceed the benefits of increased extraction in these locations.
16
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The RSE-lite has not provided estimated costs for addressing this recommendation. The RSE-
lite team defers to the site team and their knowledge of site-specific costs.
4.1.5 Sample and Analyze for 1,4-Dioxane in Continued Source Area Investigations
The presence of high concentrations of 1,1,1-TCA makes it a possibility that 1,4-Dioxane is
present at the site. The site team reports that it sampled for 1,4-Dioxane and found it to be non-
detect during the 1995 RCRA Facility Investigation. As the site team continues its investigation
of other source areas, it is recommended that sampling and analysis include 1,4-Dioxane,
especially in the areas with the highest concentrations of 1,1,1-TCA. The added cost for this
analysis should be negligible with respect to other site costs.
4.2 RECOMMENDATIONS TO REDUCE SYSTEM COST
4.2.1 Consider Eliminating the Metals Removal Equipment
The site team reports that there currently is no discharge limit for iron and manganese, and it
appears that the metals removal equipment is present for removing iron and manganese to
prevent fouling of downstream treatment components. The influent concentration of iron ranges
from 1 mg/L to 3 mg/L (manganese concentrations are lower), and these concentrations typically
do not present a problem for running an air stripper if a suitable maintenance program is in place.
Such a program might involve cleaning the air stripper trays with a pressure wash wand
(estimated twice per month) and periodically taking the system apart for a more thorough
cleaning (potentially quarterly rather than the current semiannual frequency). This type of
maintenance program is generally much less costly than running a metals removal system for
less than 1 pound per day of iron (2 mg/1 at 40 gpm). The elimination or bypassing of the metals
removal equipment (excluding cost reductions associated with decreased labor) should reduce
annual costs by about $20,000 based on the costs reported in Section 2.5 of this report for
chemicals, sludge disposal, maintenance, calibration, repairs, parts, etc.). As a first step, the site
team should consider bypassing the metals removal system for a period of time to test the
effectiveness of the air stripper and the cleaning program in the absence of active metals
removal. If successful, the site team could then consider permanently bypassing or eliminating
the metals removal components of the treatment system.
4.2.2 Remove Liquid Phase GAC Units
The air stripper by itself based on the quarterly report review removes VOCs to non-detectable
concentrations and based on the document review and RSE-lite conference call has appropriate
failsafes. It appears that the GAC unit is not necessary for effective operation. If the GAC units
are removed, the weekly bag filter change-outs, twice monthly GAC backwashes, and GAC
change-outs may be eliminated. Not including labor reductions the savings in GAC and bag
filter cost are estimated at approximately $2,000 per year.
17
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Discontinuing metals removal (Section 4.2.1) and the use of GAC would remove all the labor-
intensive system activities except air stripper cleaning. Even if 8 hours per week were still
assumed for operation, the labor cost reduction would be approximately $40,000 per year.
4.2.3 Remove Select Monitoring Wells from Routine Sampling
As the site team becomes comfortable with the degree of capture and how it will be interpreted, a
routine monitoring program should be established. It is unclear what wells the site team will
choose to include, but the RSE-lite team has the following suggestions that could save costs.
Because aquifer restoration will not happen for decades, the RSE-lite team recommends a well
sampling program that is geared toward evaluating plume capture and the effectiveness of
monitored natural attenuation for the downgradient plume. Wells that are within the capture
zone, immediately upgradient of the extraction system, or in the source area will remain
contaminated and will not assist with either of these two objectives. As a result, those wells
should be either eliminated from the sampling program or sampled on a relatively infrequent
basis (once every year or two years). Furthermore, changes in the downgradient portion of the
plume will likely occur over a relatively long time period, and annual monitoring may be
appropriate.
Because a routine monitoring program has not yet been established, the potential cost savings
associated with this recommendation cannot be calculated.
4.3 RECOMMENDATIONS FOR TECHNICAL IMPROVEMENT
No recommendations have been made in this category.
4.4 RECOMMENDATIONS TO SPEED SITE CLOSEOUT
4.4.1 Revisit MNA Criteria for the Downgradient 1,1-DCE Plume
Once the GSM is effectively controlling plume migration, the site team may want to revisit the
standards associated with MNA for the downgradient plume. The GW-2 standards that EPA is
apparently considering are very strict due to the 1 ug/L standard for 1,1-DCE, which are
reportedly based on risks associated with potential vapor intrusion. If there are no residences or
other structures that would be potentially impacted by vapor intrusion now or in the future, other
criteria for VOCs (especially for 1,1-DCE) that are based on more realistic exposure points, such
as use of ground water as a potential drinking water supply or discharge of ground water to
surface water.
4.4.2 Continue with a Source Control/Containment Remedy
The RSE-lite team was asked to evaluate the GSM and was not provided information pertaining
to ongoing investigations and pilot tests in the source area. In addition, subsequent to the RSE-
18
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lite conference call, the site team indicated to the RSE-lite team that DNAPL is present in the
overburden and that multi-phase extraction has been piloted. As a result, the RSE-lite team is
not providing a specific recommendation regarding the source area. Rather, the RSE-lite team
provides the following thoughts for consideration by the site team. The RSE-lite team notes that
ground water monitoring results suggest the presence of DNAPL in both the overburden and
bedrock. While source zone remediation in the overburden may prove effective at removing
contaminant mass, the RSE-lite team believes source zone remediation in the bedrock would
likely be substantially more difficult and costly. When it comes to addressing DNAPL
contamination in bedrock, the site team may want to focus on source zone containment with the
GSM rather than pursue source zone removal.
Because the source area mass removal efforts (in both the overburden and bedrock) will not
likely be sufficient reduce concentrations to the point where the GSM can be discontinued, the
RSE-lite team believes the prime focus for the site team should be on upgrading the GSM and
demonstrating that it is effectively capturing the plume. The RSE-lite team suggests
implementing the recommendations provided in this report and moving forward with GSM
upgrades rather than revisiting the already completed reports to address EPA's comments. EPA
provided useful comments on the recent reports, but the RSE-lite team suggests that the feedback
be considered for similar work that is conducted at the site in the future so as not to detract from
making the upgrades.
19
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Cost Summary Table
Recommendation
4.1.1 Improve Documentation and
Illustration of the Site Conceptual
Model
4.1.2 Evaluate Current Level of
Capture
4.1.3 Increase Bedrock Extraction
Rate
4.1.4 Reconsider Increase
Overburden Extraction
4.1.5 Review Past Data and/or
Resample for 1,4-Dioxine
4.2.1 Eliminate Metal Removal
Equipment
4.2.2 Remove Liquid Phase GAC
Units
4.2.3 Remove Select Monitoring
Wells from Routine Sampling
4.4.1 Revisit MNA Criteria for the
Downgradient 1,1-DCE Plume
4.4.2 Continue with a Source
Control/Containment Remedy
Reason
Protectiveness
Protectiveness
Protectiveness
Protectiveness
Protectiveness
Cost Reduction
Cost Reduction
Cost Reduction
Site Closeout
Site Closeout
Estimated Additional
Capital Costs
($)
$0
$10,000
Not quantified
Not quantified
$0
$0
$0
Not quantified
Not quantified
Not quantified
Estimated Change in
Annual Costs
($/yr)
$2,500
$0
Not quantified
Not quantified
$0
($20,000)
($42,000)
Not quantified
Not quantified
Not quantified
Costs in parentheses imply cost reductions.
20
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FIGURES*
* Prepared by the site contractor and included for reference
-------
CLOSE UP OF COURTYARD
CURRENT 8UJUMNG
*** \FQRMER BUILDING
.MW14
MW20A
IWW20B
QMW09
IIW51 A.-4 \
WW21
WHXS/BARR1ER WALL MW218
-MWI?
MW34
,MW35
QMW3S
MW23A
SMW39
LEGEND:
OVSR8UROB4 fc»NlfDRW8
8H180CK MOKfTOMW «Kli
DEEP BEDROCK MCMTORWG VTO.L
^M«X»IED MOMITOWNS «EU.
EXTRACTION WQJ.
«€R8UI8«N/i£DROCK PIEZOMETER PWR
£N?f VW1
BUiLCWS DEMOLISHED
FORMER BUILDINGS
REVISIONS
1 - OCTOKR 4, 2004
REV 2 - KCOil8E8 18, 2004
89? North ATtaue, Svtte 11 * TttefleliS, Mi 01001
Figure 1
Site Plan
BT: JPO WTI:
2004
A?P8«BJ W: SC
AS NOTED
FU No.: MS*0-0002.dw
-------
OVERBURDEN MNrTOKNG WELL
r A8ANDONE0 OVERBURDEN MONFTORINS WEU.
OVERBURDEN PIEZOMETER
DRY WEii
BUILDIMG DtUOLISHED
FORMER BUILDINGS
CLOSE UFVOF COURTYAID
\
19
UPPBK
l£FT
FOR CLOSE
UP OF
eommxo
PCE CONCENTRATION CONTOUR (Uf/L)
310 PCE CONCENTRATION (ug/L)
J Estimated Value
U PCE not dateeted obov« }ndloat«d dcttcfim limit
(1) Collected Aug/Sup 1997
(2) Cdlactud Now 2001
(3) CoHoeted Sep/Oct 2003
(4) Collaeted Jtm/Apr 2004
(5) Collected August 200+
1 - OCTOBER 4, 2C04
DECEMBER 16, 2004
SOT North ATB»«»» Suite 11 * WftkefleW, MA 01001
Rgure 2
Tetrochloroethene (PCE) Isoconcentration
Mop of Overburden Zone
Sftf: JDO
OATC Dtcemter 2004 SCALE AS NOTED
APPROVED BY: SS
RLE No.: MS*D-QOQZ.ti*g
-------
OVERBURDEN MONITORINC WELL
A8ANOONE0 OVERBURDEN MONITORING WELL
© OVERBURDEN PIEZOMETER
ELL
BUILDING DEMOLJSHED
FORMES BUILDINGS
EXTRACTION WELLS/BARRIER WAIL,
1.1.1-TCA CONCENTRATION COMTOUR (ug/L)
310 1.1,1-TCA CONCENTRATION (ug/l)
J Etflmoted Vdua
1.1.t~TCA not dstactBct above indleotod detactwn Bmit
(1) Coilsetsd *ag/Sef» 1397
CoNoeted Nov 2001
(3) Coitocted Sep/Qet 2003
(4) Collected Jon/Apr 2004
REVISIONS
REV 1 - OCTOBER 4, 2004
REV 2 - DECEMBER 16, 2004
SO? North Avauu, Suite 11 * Wak»fIeW, MA 01001
Figure 3
1,1,1 -Trichloroethone
Isoconcentrotion Mop of
DRMW BY: JOD DATE Dectmbef 2i
APPRfMD 8ft SS RLE
(1,1,1-TCA)
Overburden Zone
»4 sc«£ AS mm
Hu MiM>~C002.d«,
-------
SCI MW33C IQ.S u
" -SB
0,5 Tl'
EXTRACTION WEUS/BWRIER WAU,
REV 2 - 16, 2004
8Q3ROCK MONinOSING Wai
DEEP BEDROCK MONITORING WELL
ABANDONED BEDROCK MOHITORING WEU.
BEDROCK PIEZOMETER
8UIU3WS DEMOLISHED
FORMER 6U1LD1NSS
PCE CONCENTRMION CONTOUR (ug/L)
310 PCE CONCENTRATION (iig/L)
J Estimated Vofus
U PCE not detected above Indicated detection limit
(1) Colbcted Aug/Sap 1997
Cotlacted Nay 2001
(3) Collected Sep/Oct 2003
(4) Collected Jon/Apr 2004
(5) Collected August 2004
Suite li » T«i«a»W, MA 01001
SM1 ftg Wll>8l8«iSSB
Rgyre 5
Tetrachloroethene (PCE)
Isoconcentrotion Mop of Bedrock Zone
atnnK ay; JDO DATE Dectmbw 2004 SCALE; AS NOTED
-------
SttMW33CfQ.S U
BEBSOCK MONITORING WEU.
DEEP BEDROCK MONITOSIN6 WELL
ABANDONED BHJROCK MONrTORWG Wat
BEDROCK PIEZOMETER
BUILDIMG DEWOUSHED
FORMER BUILDINGS
1,1,1-TCA COMCEMTIWTION CONTOUR
1,1,1-TCA CONCENTRATOM (ugA)
J Estimatod Value
1.1,1-1** not *rt»et«i atov» indlcotiwl dtteethm IWt
(1) Colieot«i Aug/Sep
(2) ColloctBc! Nav 2001
(3) CoBoctat S*p/0ct 2003
(4) ColfsctMi Jon/Apr 2004
(S) Coilsctsd Augytt 2004
REVISIONS
<&MW408 It,300 f
5053
REV 1 - OCTOBES 4, 2004
REV 2 - DECEMBER 18, 2004
60? Karth Avenue, Suite 11 * WitltefleW. Ml otOOJ
7ii-2«~M6n
Figure 6
1,1,1 -Trichloroethane (1,1,1 -TCA)
Isoconcentration Mop of Bedrock Zone
Ml: OecsmiMf 2004 SCALE AS
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