REMEDIATION SYSTEM EVALUATION
SlLRESIM SUPERFUND SITE
LOWELL, MASSACHUSETTS
Report of the Remediation System Evaluation,
Site Visit Conducted at the Silresim Superfund Site
August 15-16,2001
Final Report Submitted to Region 1
December 20, 2001
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NOTICE
Work described herein was performed by GeoTrans, Inc. (GeoTrans) and the United States Army Corps
of Engineers (USAGE) for the U.S. Environmental Protection Agency (U.S. EPA). Work conducted by
GeoTrans, including preparation of this report, was performed under Dynamac Contract No. 68-C-99-
256, Subcontract No. 91517. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
This document (EPA 542-R-02-008p) may be downloaded from EPA's Technology Innovation Office
website at www.epa.gov/tio or www.cluin.org/rse.
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EXECUTIVE SUMMARY
The Silresim Superfund Site is located in an industrial area of Lowell, Massachusetts. This Superfund site
addresses contamination associated with a chemical waste reclamation facility that was operated by
Silresim Chemical Corporation between 1971 and 1977. USEPA issued a ROD in 1991.
Groundwater contains very high levels of many Volatile Organic Compounds (VOCs), exceeding 500 ppm
at multiple locations, in both the shallow and deeper part of the aquifer, extending in all directions from the
Silresim property. These high concentrations in groundwater indicate the presence of non-aqueous phase
liquids (NAPL's) in the subsurface. The primary focus from a plume management perspective is the
VOC's. Groundwater is treated by a pump-and-treat system consisting of groundwater extraction, above-
ground treatment, and discharge to the City of Lowell Regional Wastewater Utility. The groundwater
treatment plant began operations in 1995. Substantial modifications to the groundwater extraction
operations, including the addition of new wells, occurred in early 2001. Soil Vapor Extraction (SVE) for
source area remediation has been pilot tested, but results led to a decision not to pursue a full-scale
implementation. Possible use of thermally enhanced SVE, such as Six Phase Heating, is being considered.
The RSE team found the site operators and managers to be interested in improving the performance of the
system, and found that many actions have previously been taken in pursuit of cost savings and/or technical
improvement. Some (but not all) of these previous improvements are summarized below:
• eliminated liquid phase carbon step by increasing the operating temperature of the air
stripper to enhance removal of methylene chloride, which also resulted in more aerobic
effluent (which eliminated an odor problem);
• reduced the operating temperature of the thermal oxidizer from 1600 degrees F to 1500
degrees F, resulting in a savings in natural gas usage without compromising effectiveness;
installed an automated blending system for polymer in the Metals Removal System,
eliminating the need for weekend staff;
• improved the autodialer system to allow for faster problem recognition and resolution;
• reduced groundwater analytical monitoring frequency and process analytical monitoring
frequency;
instituted a semi-annual preventative maintenance program to increase operating
efficiency; and
• performed bench-scale testing of polymers to provide better sludge settling rates, resulting
in less solids loading to the filters and less frequenting backwashing of the filters.
The RSE team also commends Site Managers for their realistic evaluation of the inability of the current
system to meet ROD objectives, and for implementing changes to the extraction strategy in 2001 (based on
recently-performed groundwater modeling) in an attempt to limit downward migration of contaminants due
to pumping at deep wells and to improve the extent of groundwater capture.
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A primary recommendation by the RSE team is that site managers continue to seek improvements to the
system and the remedy, as has been done in the past. Several additional recommendations are intended to
enhance system effectiveness:
A "target capture zone" for each layer in the groundwater flow model should be
established, based on plume extent and site management objectives. Estimated cost for
this activity is $5,000.
Enhanced particle tracking techniques are suggested that will allow more accurate and
three-dimensional capture zones predicted by the model to be superimposed on the "target
capture zone" for each model layer. Estimated cost for this activity is $10,000.
To increase confidence in model-predicted capture zones, the predictive accuracy of the
model should be evaluated by comparing model predicted values of drawdown to those
observed in the field. Estimated cost for this activity is $25,000.
• Periodic monitoring of sediments in East Pond and River Meadow Brook for the most
mobile constituents associated with the site (i.e., VOC's) is recommended, perhaps once
every two years. This might cost $10,000 per year.
Site managers should verify that no other basements (other than Lowell Iron and Steel) are
of concern within the footprint of plume, and verify that use of the basements on Lowell
Iron and Steel has not increased, and if it has, that proper precautions (i.e., ventilation) are
being implemented. This should be performed within existing budget.
The RSE team agrees with several existing recommendations to reduce costs (reduced site security,
cost/benefit analysis for additional drying of sludge), some of which have already been implemented.
Finally, given the high cost of this system ($1.4 million per year), and the likelihood that it will operate
indefinitely even if ROD objectives are modified, the RSE team recommends that site managers invest in an
evaluation of potential remedial alternatives on a regular basis (at least every 3-5 years) as new remedial
technologies are developed and/or improved. This type of analysis is currently being performed, and
therefore can be performed in the future within the current budget.
A summary of recommendations, including estimated costs and/or savings associated with those
recommendations, is presented in Section 7.0 of the report.
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PREFACE
This report was prepared as part of a project conducted by the United States Environmental Protection
Agency (USEPA) Technology Innovation Office (TIO) and Office of Emergency and Remedial Response
(OERR). The objective of this project is to conduct Remediation System Evaluations (RSEs) of pump-
and-treat systems at Superfund sites that are "Fund-lead" (i.e., financed by USEPA). RSEs are to be
conducted for up to two systems in each EPA Region with the exception of Regions 4 and 5, which already
had similar evaluations in a pilot project.
The following organizations are implementing this project.
Organization
Key Contact
Contact Information
USEPA Technology Innovation
Office
(USEPA TIO)
Kathy Yager
11 Technology Drive (ECA/OEME)
North Chelmsford, MA 01863
phone: 617-918-8362
fax: 617-918-8417
yager.kathleen@epa.gov
USEPA Office of Emergency and
Remedial Response
(OERR)
Paul Nadeau
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Mail Code 5201G
phone: 703-603-8794
fax:703-603-9112
nadeau.paul@epa.gov
GeoTrans, Inc.
(Contractor to USEPA TIO)
Doug Sutton
GeoTrans, Inc.
2 Paragon Way
Freehold, NJ 07728
(732) 409-0344
Fax: (732) 409-3020
dsutton@geotransinc.com
Army Corp of Engineers:
Hazardous, Toxic, and Radioactive
Waste Center of Expertise
(USAGE HTRW CX)
Dave Becker
12565 W. Center Road
Omaha, NE 68144-3869
(402) 697-2655
Fax: (402) 691-2673
dave j .becker@nwd02 .usace .army .mil
in
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The project team is grateful for the help provided by the following EPA Project Liaisons.
Region 1
Region 2
Region 3
Region 4
Region 5
Darryl Luce and Larry Brill
Diana Curt
Kathy Davies
Kay Wischkaemper
Dion Novak
Region 6
Region 7
Region 8
Region 9
Region 10
Vincent Malott
Mary Peterson
Armando Saenz and
Herb Levine
Bernie Zavala
Richard Muza
They were vital in selecting the Fund-lead pump-and-treat systems to be evaluated and facilitating
communication between the project team and the Remedial Project Managers (RPM's).
IV
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TABLE OF CONTENTS
EXECUTIVE SUMMARY i
PREFACE iii
TABLE OF CONTENTS v
1.0 INTRODUCTION 1
1.1 PURPOSE 1
1.2 TEAM COMPOSITION 1
1.3 DOCUMENTS REVIEWED 2
1.4 PERSONS CONTACTED 2
1.5 SITE LOCATION, HISTORY, AND CHARACTERISTICS 3
1.5.1 LOCATION 3
1.5.2 POTENTIAL SOURCES AND PREVIOUS ACTIONS 3
1.5.3 HYDROGEOLOGIC SETTING 3
1.5.4 DESCRIPTION OF GROUND WATER PLUME 4
2.0 SYSTEM DESCRIPTION 5
2.1 SYSTEM OVERVIEW 5
2.2 EXTRACTION SYSTEM 5
2.3 GROUNDWATER TREATMENT SYSTEM 5
2.4 MONITORING SYSTEM 6
3.0 SYSTEM OBJECTIVES, PERFORMANCE AND CLOSURE CRITERIA 7
3.1 CURRENT SYSTEM OBJECTIVES AND CLOSURE CRITERIA 7
3.2 TREATMENT PLANT OPERATION GOALS 8
3.3 ACTION LEVELS 8
4.0 FINDINGS AND OBSERVATIONS FROM THE RSE SITE VISIT 9
4.1 FINDINGS 9
4.2 SUBSURFACE PERFORMANCE AND RESPONSE 9
4.2.1 WATER LEVELS AND CAPTURE ZONES 9
4.2.2 CONTAMINANT LEVELS 9
4.2.3 NATURAL ATTENUATION POTENTIAL 10
4.2.4 SOURCE AREA REMEDIAL APPROACHES 10
4.3 COMPONENT PERFORMANCE 10
4.3.1 EXTRACTION-WELL PUMPS AND PIPING 10
4.3.2 PHASE SEPARATION 10
4.3.3 EQUALIZATION TANK 11
4.3.4 METALS REMOVAL SYSTEM 11
4.3.5 MULTI-MEDIA FILTERS 11
4.3.6 AIR STRIPPER (INCLUDING PRE-HEATING) 11
4.3.7 GRANULAR ACTIVATED CARBON SYSTEM 12
4.3.8 THERMAL OXIDIZER 12
4.3.9 EFFLUENT TANK 12
4.3.10 CONTROLS 12
4.4 COMPONENTS OR PROCESSES THAT ACCOUNT FOR MAJORITY OF COSTS 12
4.4.1 LABOR 13
4.4.2 LABORATORY ANALYSIS 13
4.4.3 SECURITY, SNOW REMOVAL, GROUNDSKEEPING 13
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4.4.4 UTILITIES 14
4.4.5 NON UTILITY CONSUMABLES 14
4.4.6 DISPOSAL COSTS 14
4.5 RECURRING PROBLEMS OR ISSUES 14
4.6 REGULATORY COMPLIANCE 14
4.7 TREATMENT PROCESS EXCURSIONS AND UPSETS, ACCIDENTAL CONTAMINANT/REAGENT
RELEASES 14
4.8 SAFETY RECORD 15
5.0 EFFECTIVENESS OF THE SYSTEM TO PROTECT HUMAN HEALTH AND THE ENVIRONMENT
16
5.1 GROUND WATER 16
5.2 SURFACE WATER 16
5.3 AIR 16
5.4 SOILS 17
5.5 WETLANDS 17
6.0 RECOMMENDATIONS 18
6.1 RECOMMENDATIONS TO ENSURE EFFECTIVENESS 19
6.1.1 AUGMENT EVALUATION OF GROUNDWATER CAPTURE 19
6.1.2 PERIODIC MONITORING OF SEDIMENTS IN EAST POND AND RIVER MEADOW BROOK
20
6.1.3 AIR MONITORING IN BASEMENTS 20
6.2 RECOMMENDATIONS TO REDUCE COSTS 20
6.2.1 REDUCE SITE SECURITY 20
6.2.2 COST/BENEFIT ANALYSIS FOR SLUDGE DRYING 20
6.2.3 CONTRACTING CONSIDERATIONS 20
6.3 TECHNICAL IMPROVEMENT 21
6.4 RECOMMENDATIONS TO GAIN SITE CLOSEOUT 21
6.4.1 CONTINUE TO CONSIDER SOURCE ALTERNATE REMEDIATION STRATEGIES 21
7.0 SUMMARY 22
List of Tables
Table 7-1. Cost summary table of individual recommendations.
List of Figures
Figure 1-1. Site location.
Figure 1-2. Site photograph from period where facility was active.
Figure 1-3. Total VOC plume (ll/00)and water table elevations (1988), shallow portion of aquifer
Figure 1-4. Total VOC plume (11/00) and water table elevations (1986), deeper portion of aquifer
VI
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1.0 INTRODUCTION
1.1 PURPOSE
In the OSWER Directive No. 9200.0-33, Transmittal of Final FYOO - FY01 Superfund Reforms Strategy,
dated July 7,2000, the Office of Solid Waste and Emergency Response outlined a commitment to optimize
Fund-lead pump-and-treat systems. To fulfill this commitment, the US Environmental Protection Agency
(USEPA) Technology Innovation Office (TIO) and Office of Emergency and Remedial Response (OERR),
through a nationwide project, is assisting the ten EPA Regions in evaluating their Fund-lead operating
pump-and-treat systems. This nationwide project is a continuation of a demonstration project in which the
Fund-lead pump-and-treat systems in Regions 4 and 5 were screened and two sites from each of the two
Regions were evaluated. It is also part of a larger effort by TIO to provide USEPA Regions with various
means for optimization, including screening tools for identifying sites likely to benefit from optimization
and computer modeling optimization tools for pump and treat systems.
This nationwide project identifies all Fund-lead pump-and-treat systems in EPA Regions 1 through 3 and 6
through 10, collects and reports baseline cost and performance data, and evaluates up to two sites per
Region. The site evaluations are conducted by EPA-TIO contractors, GeoTrans, Inc. and the United States
Army Corps of Engineers (USAGE), using a process called a Remediation System Evaluation (RSE),
which was developed by USAGE. The RSE process is meant to evaluate performance and effectiveness (as
required under the NCP, i.e., and "five-year" review), identify cost savings through changes in operation
and technology, assure clear and realistic remediation goals and exit strategy, and verify adequate
maintenance of Government-owned equipment.
The Silresim Site was chosen based on initial screening of the pump-and-treat systems managed by USEPA
Region 1 and discussions with the Project Liaison for that Region. This report provides a brief background
on the site and current operations, a summary of the observations made during a site visit, and
recommendations for changes and additional studies. The cost impacts of the recommendations are also
discussed.
A report on the overall results from the RSEs conducted at Silresim and other Fund-lead pump-and-treat
systems throughout the nation will also be prepared and will identify lessons learned and typical costs
savings.
1.2 TEAM COMPOSITION
The team conducting the RSE consisted of the following individuals:
Bill Crawford, Chemical Engineer, USAGE HTRW CX
Rob Greenwald, Hydrogeologist, GeoTrans, Inc. (EPA TIO's contractor)
Lindsey Lien, Environmental Engineer, USAGE HTRW CX
Doug Sutton, Water Resources Engineer, GeoTrans, Inc.
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1.3
DOCUMENTS REVIEWED
Author
USEPA
USAGE
Foster Wheeler
USEPA
Foster Wheeler
Foster Wheeler
Foster Wheeler
Foster Wheeler
Foster Wheeler
Foster Wheeler
ACOE
Foster Wheeler
Date
9/19/1991
11/18/1998
7/1999
9/1999
5/23/00
8/2000
9/2000
9/8/01
3/22/01
6/27/2001
8/13/2001
8/14/2001
Title/Description
Record of Decision
Operational and Functional Completion Report for
Management of Migration Remedy Operable Unit
ROD Remedy Review
Five Year Review
GW Monitoring and GW Treatment System O&M Status
Report, November 6, 1999 - February 5, 2000
Final Activity Plan for Additional Site Investigations and
Revision of the Site Cleanup Goals
Final Management of Migration and Source Removal
Strategy Work Plan
GW Monitoring and GW Treatment System O&M Status
Report, February 6, 2000 - August 5, 2000
GW Monitoring and GW Treatment System O&M Status
Report, August 6, 2000 - February 5, 2001
Groundwater Modeling Report
GWTP Cost Summary (handed out during RSE visit)
Silresim Operation Efficiency Improvements and Cost
Reduction Measures
1.4
PERSONS CONTACTED
The following individuals were present for the site visit:
Chet Janowski, USEPA Region 1 (RPM), 617-918-1324,
Janet Waldron, MADEP, 617-5 5 6-115 6, .... • -, -. • • .,.: .,.-.
Paul Battista, USAGE, 928-318-8800, , -\ • ::. i '•;: . ;.
David O'Connor, USAGE, 978-772-0148. . . .: . . •.;...-,.
John Haley, Foster Wheeler, 978-441-9888, .,;,.,,... .......:,
John Scaramuzzo, Foster Wheeler, 617-457-8297, , : ...
Rob Greenwald, GeoTrans, 732-409-0344, ; . •••,..,•..
Doug Sutton, GeoTrans, 732-409-0344, ,'.. .r..- ^ -.'
Bill Crawford, USAGE, 402-697-2579. .,,,..; - ;. ; .
Lindsey Lien, USAGE, 402-697-2580. ,, ;:.•;,,. ,
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1.5 SITE LOCATION, HISTORY, AND CHARACTERISTICS
1.5.1 LOCATION
The Silresim Superfund Site is located at 86 Tanner Street in an industrial area of Lowell, Massachusetts,
approximately one mile south of the central business district. The original facility consisted of
approximately 4.5 acres (Silresim property). However, the Superfund Site is geographically defined by the
extent of contamination, which extends beyond the Silresim property and includes approximately 16 acres
of groundwater and seven acres of soil. The Site vicinity is illustrated of Figure 1-1. The former Silresim
property is bordered by Lowell Iron and Steel Company to the north, the B&M railroad yard and tracks to
the east/northeast, an automobile salvage yard to the south, and Tanner Street to the west. Residential
areas are located to the south, east, and northeast, and the closest residences are approximately 300-500 ft
from the Silresim property boundary. River Meadow Brook is located approximately 400 ft west of the
Silresim property boundary. East Pond is located several hundred feet southeast of the Silresim property
boundary.
1.5.2 POTENTIAL SOURCES AND PREVIOUS ACTIONS
This Superfund site addresses contamination associated with a chemical waste reclamation facility that was
operated by Silresim Chemical Corporation between 1971 and 1977. Wastes were accepted at the facility
in drums, tank trucks, railroad cars, and other containers. These substances included halogenated solvents,
oily wastes, alcohols, plating wastes, metal sludges and pesticide wastes. The Record of Decision (ROD)
estimates that the facility handled approximately three million gallons of waste per year. The Silresim
Chemical Corporation filed for bankruptcy in 1977 and abandoned the property in January 1978. At that
time there were approximately 30,000 decaying drums on the property, covering virtually every open area
of the property (see Figure 1-2). Investigations revealed that the property had been poorly maintained and
revealed evidence of numerous spills, leakage of drums, discharges to city sewers, and runoff to adjacent
properties.
From 1978 to 1982 the State secured the property and minimized immediate threats to public health and the
environment by constructing a fence, hiring 24-hour security, removing drums and tanks, and constructing
berms and absorbent-filled trenches. In 1983-1984 EPA removed all structures remaining on the property,
extended the fence, and placed a clay cap over the property. Crushed stone was placed over areas of
surficial soil contamination adjacent to the cap's northern and southern borders and at the northeast corner
of the site. In 1986 EPA expanded the fence to enclose an area of surficial soil contamination at the
southeast corner of the site, and place crushed stone around the perimeter of the expanded fence line. There
have also been periods of SVE extraction (pilot test in 1995-96, and Phase 1 SVE in 1998-99) for the
purpose of source removal. This site was placed on the NPL in 1982. EPA issued an Administrative Order
by consent to the Silresim Site Trust in 1985. EPA issued a ROD in 1991.
1.5.3 HYDROGEOLOGIC SETTING
The Silresim property is underlain by glacial outwash deposits (20 to 100 ft thick) over bedrock (thin
discontinuous layers of glacial till immediately overlay the bedrock). The glacial outwash deposits, which
are silty sands and silts of lacrustine origin, average 80 ft in thickness but thin to the north because bedrock
elevation increases to the north. Localized stratigraphy has been described according to the following five
layers (one or more layers are absent at some locations), from top to bottom:
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Layer
Unconsolidated Overburden Layer (Unconfined Aquifer)
Upper Varved Clayey Silt Aquitard
Semi-Confined Silty Sand Aquifer
Lower Varved Clayey Silt Aquitard
Till/Weathered Bedrock Aquifer
Approximate
Thickness (ft)
~ 8 to 12 ft
-15 to 20 ft
-25 ft
-30ft
-15ft
Depth to groundwater is approximately 6-10 ft. In the Unconfined Aquifer, the major flow direction from
the Silresim property is north and northwest towards major sewer lines located several hundred feet north
and west of the property, with a component of flow to the south or southeast towards East Pond (see Figure
1-3). For the sewer line that is north of the property, water level maps from 1988 (pre-pumping) indicated
flow from both the north and the south, indicating that the sewer is a potential point of groundwater
discharge. In a report dated September 2000, Foster Wheeler estimated groundwater velocity in shallow
groundwater at approximately 30 ft/yr.
For the deeper semi-confined aquifer, flow appears to be towards the north-northwest, and southerly flow is
not apparent from the water levels. Foster Wheeler estimated groundwater velocity in the lower semi-
confined aquifer at approximately 10 ft/yr.
Pre-pumping vertical gradients were significantly downward. These downward gradients may be
augmented by standing water in detention areas after heavy rain or snowmelt, and also by ponded water
that sometimes results near the boundary of the current cap.
1.5.4 DESCRIPTION OF GROUND WATER PLUME
Groundwater contains very high levels of many Volatile Organic Compounds (VOC's). Plume maps have
generally been drawn for Total VOC's rather than individual compounds (see Figure 1-3 for the shallow
zone and Figure 1-4 for the deeper zone). Total VOC's exceed 500 ppm at multiple locations in both the
shallow and deeper part of the aquifer. Some individual VOC's with maximum groundwater
concentrations exceeding 100 ppm are 111-TCA, 1,2-DCA, 1,2-DCE, acetone, cis-l,2-DCE, methylene
chloride, and TCE. These high concentrations in groundwater indicate the presence of non-aqueous phase
liquids (NAPL's) in the subsurface. NAPL's have in fact been identified in some wells (during the RSE
visit, ajar of free-phase liquid collected from a previous SVE well location was passed around).
The total VOC plume in both the shallow and deeper part of the aquifer extend in all directions from the
Silresim property, consistent with groundwater flow directions that are predominantly to the
north/northwest as well as to the southeast in the shallow aquifer. The plume in each aquifer, as interpreted
by Foster Wheeler, extends beyond the sewer lines to the north and west of the property. This could be due
to flow under the sewer lines, or contaminant sources on the other side of the sewer line.
In addition to the VOC's, there are some exceedances of groundwater standards for several semivolatile
compounds (SVOC's) and metals, and some detections of pesticides/PCB's. However, the primary focus
from a plume management perspective is the VOC's.
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2.0 SYSTEM DESCRIPTION
2.1 SYSTEM OVERVIEW
Groundwater is treated by a pump-and-treat system consisting of groundwater extraction, above-ground
treatment, and discharge to the City of Lowell Regional Wastewater Utility. The groundwater treatment
plant began operations in 1995. Substantial modifications to the groundwater extraction operations,
including the addition of new wells, occurred in early 2001. Details are provided below.
2.2 EXTRACTION SYSTEM
The system originally consisted of 25 extraction wells, each separately piped to a groundwater treatment
plant. The original 25 extraction wells were screened in different vertical zones as follows:
13 shallow aquifer
2 moderate overburden
9 deeper overburden
1 bedrock
Each well was designed to pump at approximately 1 gpm. Historically, average production from each
shallow wells was approximately 0.3 gpm per well, while average production from moderate and deep
wells was approximately 1.5 gpm per well.
According to the latest O&M Report (thru February 5, 2001) six new wells were placed into service on
February 2, 2001, and the overall pumping strategy was revised in an attempt to limit the downward
migration of contaminants by focusing extraction in the shallow aquifer. There are six new wells (numbers
26-31), and these wells were to operate with 10 of the original wells (numbers 2-8 and 11-13) for a total of
16 operating wells. During the RSE visit, it was stated that Well 17 is also now operating.
All of the wells currently operating are shallow wells, with the exception of old Well 17 and new Well 31.
Well 31 is located north of the property and is screened from above the first aquitard down to bedrock.
The purpose of Well 31 is to intercept deep and shallow groundwater contamination that is already beyond
the operating shallow extraction wells. EW-17 is intended to augment the capture zone for deeper
groundwater, and is also located beyond the extent of the shallow wells. The new shallow wells are
screened somewhat deeper than the older shallow wells, to increase the potential for greater water
production.
2.3 GROUNDWATER TREATMENT SYSTEM
The treatment plant was originally designed to handle 36,000 gallons per day (25 gallons per minute) of
contaminated groundwater from the extraction wells. The original system consisted of the following:
phase separation (currently by-passed)
• equalization tank
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• metals removal
multi-media filtration
• preheat of the air stripper liquid feed
air stripping
• liquid granulated activated carbon polishing of the stripper effluent (recently eliminated)
thermal oxidation of stripper off gases
• discharge of the treated aqueous stream to the City of Lowell POTW
The phase separator has never recovered product and has been by-passed, and the liquid phase carbon
polishing step was eliminated by increasing the operating temperature of the air stripper.
With the modifications to groundwater extraction described in Section 2.2, the plant currently is operating
at about 10 gpm. The plant has recently been upgraded to 35 gpm capacity, which required upgrading to
2-inch piping, although there is no plan to operate the plant in excess of current rates (approximately 10
gpm) at this time.
2.4 MONITORING SYSTEM
Originally groundwater monitoring was performed quarterly, but that has been reduced to twice per year,
with one of the two events more comprehensive than the other. In the last comprehensive round (November
2000 to January 2001) 68 monitoring wells were sampled, in addition to most of the extraction wells
associated with the P&T system. Most wells were sampled for only VOC's, but select wells were also
sampled for SVOC's, PCB's, pesticides, and TAL metals.
Maximum flow rates at individual wells are measured weekly, to determine if performance is declining
(usually occurs within one month to one year). The thermal oxidizer efficiency is monitored once per
month, to make sure that efficiency exceeds a 95% guideline. Other parameters within the plant are
sampled "as needed" to assess treatment equipment performance.
Influent concentration to the plant is determined monthly. Effluent to the POTW was originally sampled
weekly and then monthly, but based on an agreement with the POTW (based on previous monitoring data)
that sampling is now performed quarterly.
The latest O&M report (March 22, 2001) contains an excellent summary of well locations and well
construction (Table A-4) which clearly indicates for each monitoring well and each extraction well the
aquifer zone screened, the well coordinates, the top and bottom of screen elevation, the top of casing,
ground elevation, and well depth.
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3.0 SYSTEM OBJECTIVES, PERFORMANCE AND CLOSURE
CRITERIA
3.1 CURRENT SYSTEM OBJECTIVES AND CLOSURE CRITERIA
The ROD, issued in 1991, identified a remedy that consists of two major elements:
• management of migration (MOM)
• source control
The objectives of the remedy were to achieve the following:
• prevent direct contact and incidental ingestion exposure to contaminated surficial soils
both on and off of the Silresim property
prevent future migration of contaminated groundwater to a hypothetical water supply well,
thereby reducing risks from ingestion of contaminated drinking water
• prevent contaminated groundwater discharge to surface waters, thereby reducing risks
from dermal absorption and ingestion exposures to contaminated surface water and
sediments
• prevent contaminated groundwater flow towards buildings, thereby reducing risks from
inhalation exposures
The objectives of the groundwater extraction system were to:
halt further migration of contaminated groundwater towards receptors
capture as much of the contaminant plume as possible
achieve drawdowns across the site in support of the source control remedy
Groundwater cleanup levels are MCL-based, and contaminant-specific soil cleanup goals were established
to prevent leaching and achieve MCL's in site groundwater.
In July 1999, a detailed review of ROD objectives was provided in the "ROD Remedy Review" report.
That report concluded that "a number of potentially serious limitations and deficiencies currently exist with
respect to meeting the ROD goals and objectives identified for the site." That report specifically
recommends a re-evaluation of site objectives. One major component of a potential ROD revision would
account for re-classification of the aquifer from Class 1 (source of potable water supply) to a lower
classification associated with "low use and value". Therefore, it is possible that the ROD objectives will be
modified in the near future.
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3.2 TREATMENT PLANT OPERATION GOALS
Treatment plant operation goals include the following:
• maximize the influent flow rate while maintaining a VOC influent concentration that is
within the design capacity of the treatment system
• meet discharge permit requirements, the most significant of which is 2.13 ppm TTO (sum
of detected pesticides/PCB's, semi-volatiles, and volatiles), as well as pH of effluent
between 6 and 9
Acetone has historically been elevated in plant effluent, and based on discussions with the POTW, the
current levels of acetone in plant effluent is acceptable because it is easily biodegradable within the POTW.
3.3 ACTION LEVELS
Site cleanup levels and treatment plant effluent levels are described in Sections 3.1 and 3.2.
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4.0 FINDINGS AND OBSERVATIONS FROM THE RSE SITE VISIT
4.1 FINDINGS
In general, the RSE team found the system to be well operated and maintained. The observations and
recommendations given below are not intended to imply a deficiency in the work of either the designers or
operators, but are offered as constructive suggestions in the best interest of the EPA and the public. These
recommendations obviously have the benefit of the operational data unavailable to the original designers.
The RSE team found the site operators and managers to be interested in improving the performance of the
system, and found that actions have previously been taken in pursuit of costs savings (many of which are
detailed below). The RSE team also found that considerable attention has been given by Site managers in
assessing the appropriateness of original remedial objectives (i.e., the ROD Remedy Review Report, July
1999), and Site managers are aware that the system is unlikely to achieve ROD objectives and that revised
objectives may be appropriate. Finally, considerable attention has been paid (and continues to be paid) on
evaluating alternatives that may lead to remediation of soils in the source area, such that a groundwater
remedy of infinite duration can be avoided.
4.2 SUBSURFACE PERFORMANCE AND RESPONSE
4.2.1 WATER LEVELS AND CAPTURE ZONES
Some water level maps have been constructed in the past, but they are not sufficiently detailed to evaluate
the capture zones achieved by the extraction system. Initially, areal capture zones were calculating using
analytical solutions for extractions wells in a uniform flow field. However, as stated in the ROD Remedy
Review report (i.e., with respect to the original extraction strategy), "given the site-specific variance in
aquifer parameters, the cyclic pumping nature in the shallow wells, and the low flow pumping rates relative
to saturated thickness in the deeper wells, it is likely that contaminated groundwater [was] escaping the
theoretical capture zones." The five-year review conducted in 1999 also notes that, with respect to the
original extraction strategy, "there has been extensive plume migration beyond the extraction well array."
Predicted capture zones for the modified extraction strategy (which was implemented in February 2001)
were evaluated with a MODFLOW groundwater flow model coupled with particle tracking. The RSE
team noted during the site visit that the particle tracking analysis presented in the Groundwater Modeling
Report is not really sufficient to demonstrate capture for the implemented strategy, and recommendations
for augmenting that modeling and particle tracking analysis are presented in Section 6.1.1 of this report.
4.2.2 CONTAMINANT LEVELS
Contaminant levels associated with VOC's at this site are extremely high over a large area that extends
well beyond the property boundary (see Figures 1-3 and 1-4). This provides evidence that the plume has
spread from its original source on the property. The most recent O&M report evaluates three-dimensional
plume patterns for individual contaminants, and concludes that individual contaminants have different
extent, both horizontally and vertically, such that the Silresim contamination should not be viewed as one
continuous plume.
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Influent concentrations to the plant are measured in TTO (sum of detected PCB's/Pesticides, SVOC's, and
VOC's). Typical influent is on the order of 100-200 ppm TTO, but has at times been as high as 400 ppm
TTO. During the RSE site visit, the system operator stated that influent concentrations as high as 300 ppm
TTO on a consistent basis might be a concern with respect to meeting discharge requirements.
4.2.3 NATURAL ATTENUATION POTENTIAL
Given the high concentrations in groundwater, which are indicative of the presence of NAPL's, there is no
chance that monitored natural attenuation at this site can adequately achieve ROD objectives (or potentially
modified ROD objectives) in the absence of active remediation
4.2.4 SOURCE AREA REMEDIAL APPROACHES
In 1995-1996, an SVE pilot test was conducted as per ROD requirements. The pilot test consisted of three
SVE techniques: conventional SVE, heated air injection with SVE, and high vacuum or multiphase SVE.
Approximately 2 tons of VOCs were removed during the pilot test. It was concluded that SVE would not
attain cleanup levels specified in the ROD, but that SVE might allow enhanced mass removal. Therefore, a
"Phase 1" SVE system was implemented in 1998-1999. During the 15-month implementation,
approximately 12 tons of VOCs were removed (compared to approximately 50 tons removed to date by the
groundwater treatment plant) . Although this was a large amount of mass removed, the system was
relatively hard to keep operating on a long-term basis. Some of the problems with SVE include low
permeability soils, a high water table, high soil moisture contents, and short circuiting though gravel placed
beneath the clay cap. It was decided that, since SVE was not expected to fully remediate the soil
contamination, that money would be better spent on other potential alternatives, and the system was
therefore shut down (although it still remains in place). Soil VOC concentrations exceed ROD cleanup
standards by up to four orders of magnitude. More recently, six-phase heating has been considered as a
potential source removal option, and a pilot test may be performed in Spring 2002.
4.3 COMPONENT PERFORMANCE
4.3.1 EXTRACTION-WELL PUMPS AND PIPING
Pumping rates are evaluated weekly to determine if performance is declining and maintenance is required.
Flow meter readings (Signet Flowmeters) are sometimes verified with buckets. Typically maintenance of
wells is required within one month to one year. Acetic acid is used for well rehabilitation, in conjunction
with "pigging" the 3/4-inch polypropylene pipes from the well back to the treatment plant. At one point an
iron sequestering "biocide"agent was tried, but it caused excess biological growth that clogged the air
stripper, and was therefore determined to be counter-productive. All pipes and pumps are also cleaned
during scheduled semi-annual shutdowns.
4.3.2 PHASE SEPARATION
Although the presence of NAPL's is suggested by the high VOC concentrations in groundwater and has in
fact been observed at a few locations, free product was never separated out by the phase separation
component of the system. Therefore, that part of the system is now bypassed so that extracted water goes
directly into an equalization tank.
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4.3.3 EQUALIZATION TANK
The equalization tank is 3000 gallons. Offgas from the equalization tank is directed to the thermal
oxidizer. Planned maintenance shutdowns to remove accumulated sludge in process tanks and pumping it
through the filter press has reduced the volume of waste material sent off-site.
4.3.4 METALS REMOVAL SYSTEM
The metals removal system (MRS) primarily addresses iron and manganese, and includes a pH
Adjustment/Flocculation Tank, Gravity Settler, Chemical Feed Equipment, and Sludge Pumping. This
equipment provides precipitation and removal of suspended solids and metals from the groundwater stream.
Sodium hydroxide is used to raise the pH, followed by a polymer addition. Sludge produced by the MRS
has historically been filter pressed twice per week (performed in level B). The sludge is slightly hazardous
(just above TCLP levels) due to the high concentrations of VOC's, and is shipped to a hazardous waste
facility in Canada. A modification is being considered to allow additional drying of the sludge, which will
reduce sludge volume and potentially make the sludge non-hazardous. A cost/benefit analysis is planned
for this potential modification, to see if the extra cost for sludge drying yields a greater cost reduction in
sludge handling and disposal. Sodium hypochlorite is added to the effluent to prevent fouling of the air
stripper.
An improvement already implemented at the site is an automated polymer blending system, which
eliminated the need for daily polymer preparation. This resulted in the elimination of the need for weekend
staffing at the plant. Also, bench scale tests of several different polymers resulted in better settling rates of
the sludge, which resulted in less loading of solids to the multi-media filters and less backwashing
requirements (from once per 4-6 hours to once every 10+ hours).
4.3.5 MULTI-MEDIA FILTERS AND pH ADJUSTMENT
The purpose of the filters is to remove total suspended solids. The media has only required changing once
in five years, and appears to be effective. After the filters, the pH is lowered to keep remaining solids in
solution, which prevents clogging of the heat exchanger.
4.3.6 AIR STRIPPER (INCLUDING PRE-HEATING)
VOC's and SVOC's are removed from groundwater by the air stripper, which operates at approximately
300 cfin. Groundwater is pumped to the top of the Air Stripper, and air blown into the bottom of the
stripper removes organics from the water. The water flows by gravity though the stripper packing and is
discharged to the effluent tank. Offgas from the stripper is sent to the thermal oxidizer.
A heat exchanger, located upstream of the air stripper, is used to raise the temperature of the water to
approximately 120-130 degrees F prior to the air stripper. This allows the air stripper to effectively
remove methylene chloride, which previously had passed through the air stripper and onto the carbon,
where it subsequently de-sorbed (sometimes causing effluent concentration violations). Consideration is
currently being given to augment the existing packed column air stripper with the installation of a low
profile-tray air stripper, which would eliminate the need to preheat the feedwater and therefore lower
natural gas usage while maintaining or improving removal efficiency for SVOCs.
Originally, fouled air stripper packing was discarded and disposed of off-site. On-site cleaning of the
packing with 15% hydrochloric acid was initiated, which allowed beneficial reuse of the packing and
eliminated an unnecessary waste stream.
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4.3.7 GRANULAR ACTIVATED CARBON SYSTEM (ELIMINATED)
By increasing the operating temperature of the air stripper, which improves stripping of methylene chloride,
liquid-phase GAC is no longer required to meet discharge requirements. In addition to removing the costs
of carbon, this has resulted in an additional benefit because the carbon caused anaerobic conditions in the
effluent tank, which in turn caused an odor problem that required chlorination. Now that GAC has been
removed, this step is no longer required.
4.3.8 THERMAL OXIDIZER
Air is pulled from the outlet of the air stripper by the oxidizer fan, is preheated in the heat exchanger, and
flows through the thermal oxidizer. The hot gas from the thermal oxidizer preheats the incoming air and is
further cooled in a water quench tower to 180 degrees F prior to entering the caustic (sodium hydroxide)
scrubber. Acid formed during the combustion process is removed from the air stream in the caustic
scrubber. The cooled clean gas is discharged through the scrubber stack to the atmosphere. A 95%
Destructive Rate Efficiency for the thermal oxidizer is required by the State. A temperature reduction
from 1600 degrees F to 1500 degrees F has resulted in a reduction in natural gas usage, without causing
efficiency to fall below the 95% guideline.
4.3.9 EFFLUENT TANK
The wastewater stream from the air stripper is pumped to the effluent storage tank where it is sampled and
analyzed prior to discharge to the POTW or reused as filter backwash. A permanently installed pH probe
is used to monitor pH of the final effluent.
4.3.10 CONTROLS
The system is highly automated. Autodialers were recently upgraded to increase the number of alarm
notifications to the plant operators during unstaffed hours, which allows quicker problem identification.
This translates to quicker response time and therefore less downtime. Also, the system can be remotely
monitored and restarted. Genesis software is utilized in conjunction with PC-Anywhere.
4.4 COMPONENTS OR PROCESSES THAT ACCOUNT FOR MAJORITY OF
COSTS
Foster Wheeler has been the O&M contractor, and the Army Corp of Engineers (ACOE) has been the
management contractor. The total budget for the current year (Year 6) is $ 1.42 million per year, plus
$39,000 per year for project management by ACOE. Breakdown according to task categories specified in
the site budget are as follows:
Task
01
02
03
- GWTP Operations
- Utilities & Supplies
- Sampling & Analysis
Budget For Current Year
($/yr)
$364,300
$257,500
$162,527
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Task
04 - Waste Handling & Disposal
05 - Record Keeping & Reporting
06 - Project Management (O&M Contractor)
07 - Out of Scope Upgrades/Improvements
PM Allocation (ACOE)
TOTAL
Budget For Current Year
($/yr)
$63,191
$ 65,087
$377,964
$125,000
$38,850
$1,454,419
The RSE team has separated the costs from the current "Year 6 Budget" into approximate costs by
category, as follows:
$775,000 Labor (O&M, sampling, reports, meetings, PM, MIS, H&S, etc.)
$125,000 Laboratory analysis
$ 65,000 Security, snow removal, groundskeeping
$125,000 Utilities
$140,000 Non-utility consumables (including trailer rental)
$ 60,000 Disposal costs
$ 40,000 ACOE project management
$125,000 Annual upgrades/improvements
Some breakdown of these costs are provided below.
4.4.1 LABOR
The plant is currently operated by two people 10 hours per day, 5 days per week, at a cost of
approximately $160,000 per year. Additionally, there is a technician with rotating responsibilities
(operation, sampling, etc.) and a full-time administrator in the trailer. There are also labor costs associated
with project management, monitor well sampling, reporting, semi-annual shutdowns and associated
maintenance, information management, monthly meetings, and other project support. These additional
labor requirements total nearly $615,000 per year. Thus, the combined labor requirements cost
approximately $775k/yr.
4.4.2
LABORATORY ANALYSIS
Laboratory support for process monitoring accounts for approximately $70,000 per year. Laboratory costs
for groundwater monitoring, air sampling, and waste disposal sampling are approximately $55,000 per
year.
4.4.3
SECURITY, SNOW REMOVAL, GROUNDSKEEPING
Security historically cost approximately $7,000 per month, but that cost should be reduced in the future
based on previous recommendations that 24-hour security is no longer required (the Year 6 Budget
assumed 24-hour security for only part of the year, based on that previous recommendation) . Snow
removal and groundskeeping are approximately $20,000 per year.
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4.4.4 UTILITIES
Natural gas is the largest utilities cost, at approximately $80,000 per year. This is primarily related to
operation of the thermal oxidizer and preheating the air stripper feed water. Natural gas is also used to
heat the building to 62 degrees F in winter. Electricity costs are approximately $25,000 per year (pumps,
air stripper, lighting, etc.). Telephone, water, and sewer are approximately $20,000 per year.
4.4.5 NON UTILITY CONSUMABLES
Trailer rental costs approximately $20,000 per year (this cost is also being eliminated by the purchase of a
fixed permanent trailer for the site in exchange for the two existing rental trailers). Chemicals used in the
treatment process account for approximately $20,000 per year. Parts, tools, lab equipment, and health and
safety equipment cost approximately $73,000 per year. Office supplies cost approximately $2,000 per
year.
4.4.6 DISPOSAL COSTS
The largest disposal costs are associated with disposal of sludge from the Metals Removal System (MRS),
and disposal of PPE, which combined cost approximately $40,000 per year.
4.5 RECURRING PROBLEMS OR ISSUES
In the past, there had been frequent failure (approximately every six weeks) of a pH probe and transmitter
used to measure effluent. In August 2000 the pH sensor and transmitter were changed to a Great Lakes
Instrument device, with significant improvement.
There have been problems with corrosion of the heat exchanger. A new unit was placed into service in
2001 (under warranty), and there is hope that this unit will not experience the same problems.
The site has instituted two scheduled shutdowns per year, which include preventative maintenance on many
system components. This has increased operational efficiency and reduced the number of unplanned
shutdowns.
4.6 REGULATORY COMPLIANCE
The plant regularly meets its permitted discharge requirements, and has a good working relationship with
the POTW. As previously stated, the POTW has allowed an exception to be made for high levels of
acetone in the discharge, since it is easily biodegraded within the POTW.
4.7 TREATMENT PROCESS EXCURSIONS AND UPSETS, ACCIDENTAL
CONTAMINANT/REAGENT RELEASES
None identified during the RSE site visit.
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4.8 SAFETY RECORD
The system has an excellent safety record. There has been only one minor accident since 1994, which
involved a third-party contractor lifting a heavy object.
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5.0 EFFECTIVENESS OF THE SYSTEM TO PROTECT HUMAN
HEALTH AND THE ENVIRONMENT
5.1 GROUND WATER
The five-year review conducted in 1999 notes that, with respect to the original extraction strategy, "there
has been extensive plume migration beyond the extraction well array." In addition, concerns were raised
that some of the deeper extraction wells might be drawing contaminants downward from the shallow zone.
Therefore, a new pumping strategy was implemented in early 2001 (see Section 2.2). However, it is not
clear that the current system adequately captures all groundwater that exceeds current cleanup goals.
According to the 5-year review, "the selected remedy is not likely to achieve all of the Remedial Action
Objectives set forth in the ROD...the remedy selected in the ROD is not expected to be protective of human
health and the environment. However, immediate threats have been addressed and current conditions at the
site are protective of human health and the environment."
Cleanup objectives for groundwater may be modified in the future based on updated risk assessment
methodologies and/or assumptions, including the reclassification of the aquifer with respect to the low
potential for groundwater use.
5.2 SURFACE WATER
Based on plume maps contained in previous site reports, contaminated groundwater has migrated towards
East Pond (to the southeast) and River Meadow Brook (to the west). Sampling has been performed in these
bodies of water several times, and a screening ecological field survey was conducted in 2000. The
conclusion by Foster Wheeler was that no conclusive link was established between constituents in these
water bodies and constituents at the Silresim Site. The RSE team believes that past and future migration of
site-related constituents to these surface water bodies and related sediments is a possibility, and some form
of routine monitoring (especially for sediments) should be conducted into the future.
5.3 AIR
There have been concerns raised regarding air quality risks in the basement of the operations building and
the administration building at Lowell Iron and Steel, an adjacent property. Air samples were collected in
1999 and 2000, and a risk assessment was performed. The risk assessment indicated cancer risks in the
administration building, and non-cancer risks were determined in both buildings for the conservative
"Reasonable Maximum Exposure (RME)" scenario, but not for the less conservative "Central Tendencies
Exposure (CTE)" scenario. The conclusion was that further air monitoring for VOC's in the basements,
and ventilation in the basements, should be performed if there is a need for more intensive utilization of the
basement space. The RSE team did not discuss air quality issues in detail during the RSE visit, but
generally agree that the very high concentrations of VOC's in groundwater merit concern with respect to air
quality in basements within the footprint of the plume (it was stated during the RSE site visit that these
were the only known basements "in the area", and site managers indicate they will confirm that
information).
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5.4 SOILS
Direct exposure to impacted soils has been mitigated by previous remedial actions at the site (capping,
placement of rocks, etc.). However, impacted soils remain at the site, such that long-term institutional
controls restricting contact with such soils will need to be in force for an indefinite period of time.
5.5 WETLANDS
Not considered as part of the RSE.
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6.0 RECOMMENDATIONS
As noted throughout this report, the RSE team found the site operators and managers to be interested in
improving the performance of the system, and found that many actions have previously been taken in
pursuit of cost savings and/or technical improvement. Some (but not all) of these previous improvements
are summarized below:
• eliminated liquid phase carbon step by increasing the operating temperature of the air
stripper to enhance removal of methylene chloride, which also resulted in more aerobic
effluent which eliminated an odor problem;
• reduced the operating temperature of thermal oxidizer from 1600 degrees F to 1500
degrees F, resulting in a savings in natural gas usage without compromising effectiveness;
installed an automated blending system for polymer in the Metals Removal System,
eliminating the need for weekend staff;
• improved the autodialer system to allow for faster problem recognition and resolution;
• reduced groundwater analytical monitoring frequency and process analytical monitoring
frequency;
reduced staffing from 24-hours per day , seven days per week manned operations to
current staffing levels per cooperation and negotiations with the Lowell POTW,
substantially reducing labor cost.
instituted semi-annual preventative maintenance program to increase operating efficiency;
and
• performed bench-scale testing of polymers to provide better sludge settling rates, resulting
in less solids loading to the filters and less frequenting backwashing of the filters.
The RSE team also commends Site Managers for their realistic evaluation of the inability of the current
system to meet ROD objectives, and for implementing changes to the extraction strategy in 2001 (based on
recently-performed groundwater modeling) in an attempt to limit downward migration of contaminants due
to pumping at deep wells and to improve the extent of groundwater capture.
During the RSE site visit is was mentioned that a settlement with potentially responsible parties for this site
has provided the funding for the remediation efforts. The RSE team believes that the resulting pool of
funds has caused site managers to consider life-cycle costs at this site more than at other fund-lead P&T
sites, because their goal has been to complete the remediation using those funds. This is consistent with
previous actions by site managers to reduce costs when possible, and also to invest in source remediation
options that might limit the groundwater remediation timeframe. It should be noted, however, that some of
the costs to date at this site have been allocated towards identifying and implementing source remediation
efforts, and that annual O&M costs could potentially be reduced in the future if the site remedy is
reformulated as a containment-only system (i.e., with little or no chance of source area remediation). The
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RSE team, however, is not specifically recommending a reformulation of objectives to "containment-only"
at this time.
A primary recommendation by the RSE team is that site managers continue to seek improvements to the
system and the remedy, as has been done in the past. The RSE team concurs with the investigation of Six
Phase Heating as a potential means of source removal. Several additional recommendations are provided
below. Cost estimates provided have levels of certainty comparable to those done for CERCLA Feasibility
Studies (-307+50%), and these cost estimates have been prepared in a manner consistent with EPA
540-R-00-002, A Guide to Developing and Documenting Cost Estimates During the Feasibility Study, July
2000.
6.1 RECOMMENDATIONS TO ENSURE EFFECTIVENESS
6.1.1 AUGMENT EVALUATION OF GROUNDWATER CAPTURE
Capture zones for the modified extraction strategy (which was implemented in February 2001) were
predicted prior to implementation with a MODFLOW groundwater flow model, coupled with particle
tracking. The RSE team noted during the site visit that the particle tracking analysis presented in the
Groundwater Modeling Report is not sufficient to demonstrate capture for the implemented strategy.
Furthermore, an attempt has not yet been made to validate the predictions of the groundwater flow
modeling with field measurements subsequent to implementation of the strategy. Finally, it is difficult to
interpret the extent of actual groundwater capture on the basis of measured water levels (in the form of
potentiometric surface maps). Therefore, the RSE team recommends the following:
A "target capture zone" for each layer in the groundwater flow model should be
established, based on plume extent and site management objectives, so that predicted
capture zones based on particle tracking results can be superimposed on the "target
capture zone" to evaluate the effectiveness of the specific extraction scenario being
simulated. Estimated cost for this activity is $5,000.
Particle tracking should be performed in forward tracking mode, with one particle released
in each cell of the model, in each model layer. The "endpoint" file can then be processed
to determine each initial particle location that ultimately is captured by one of the
extraction wells, in each model layer. These locations can then be plotted, one layer at a
time, superimposed on the "target capture zone" for that model layer. Estimated cost for
this activity is $10,000.
• To increase confidence in model-predicted capture, the predictive accuracy of the model
should be evaluated by comparing model predicted values of drawdown to those observed
in the field. Two different pumping strategies have been employed to date, such that good
"pre-pumping" and "post-pumping" water level measurements should exist for at least two
different pumping scenarios (if not, water levels can be taken during scheduled plant
shutdowns, and then again once pumping has been re-instated for several weeks). The
model can then be revised (parameter values, boundary conditions) to improve predictive
accuracy based on these comparisons to real data, and capture zones re-evaluated with
particle tracking after the model is revised. Estimated cost for this activity is $25,000.
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6.1.2 PERIODIC MONITORING OF SEDIMENTS IN EAST POND AND RIVER MEADOW BROOK
Because the groundwater plume has historically migrated towards these surface water bodies, and because
groundwater concentrations are extremely high, and because capture zone of the current extraction system
is not firmly established, periodic monitoring of sediments in these surface water bodies for the most mobile
constituents associated with the site (i.e., VOC's) is recommended, perhaps once every two years. This
might cost $10,000 per year.
6.1.3 AIR MONITORING IN BASEMENTS
As discussed in Section 5.3, the RSE team did not discuss air quality issues in detail during the RSE visit,
but generally agree that the very high concentrations of VOC's in groundwater merit concern regarding air
quality in basements within the footprint of the plume (it was stated during the RSE site visit that these
were the only known basements "in the area". The RSE team recommends that site managers verify that no
other basements are of concern within the footprint of plume. The RSE team also recommends that site
managers routinely verify that use of the basements on Lowell Iron and Steel has not increased, and if it
has, that proper precautions (i.e., ventilation) are being implemented. This should be performed within
existing budget.
6.2 RECOMMENDATIONS TO REDUCE COSTS
6.2.1 REDUCE SITE SECURITY
The RSE team agrees with an existing recommendation by site managers to reduce site security by
installing a monitored security system. This is projected to save approximately $90,000 per year. This
reduction has been completed as of August 31, 2001.
6.2.2 COST/BENEFIT ANALYSIS FOR SLUDGE DRYING
Sludge generated in the Metals Removal System is slightly hazardous due to the high concentrations of
VOC's (specific constituents that exceed TCLP standards were not identified during the RSE visit), and is
shipped to a hazardous waste facility in Canada. A modification is being considered to allow additional
drying of the sludge, which will reduce sludge volume and potentially make the sludge non-hazardous. A
cost/benefit analysis for this potential modification has been previously recommended by site managers, to
see if the extra cost for sludge drying yields a greater cost reduction in sludge handling and disposal. The
RSE teams agrees with this recommendation.
6.2.3 CONTRACTING CONSIDERATIONS
During the RSE visit it was suggested that in the future the O&M contract may be re-bid as a lump-sum
contract, as opposed to the current contract which is cost-reimbursable. If this occurs, the RSE team
suggests that the lump-sum contract be limited to those items that are definitely expected to be incurred
(e.g., operator labor, sampling and analysis, reporting, etc.). Other items for which costs to be incurred are
less certain (i.e., disposal costs, replacement parts, etc.) should remain cost-reimbursable, because such
costs will be included in a lump-sum bid whether or not they are actually incurred (i.e., to the disadvantage
ofUSEPA).
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Because this is a complex site with proactive site management (preventative maintenance, pilot testing of
remedial alternatives, evaluation of remedial objectives, etc.) the labor costs associated with site
management and operation is high. The RSE team does not have specific recommendations for reducing
these costs, although it is likely these labor costs could be substantially reduced in the future if an effective
"containment-only" approach is adopted (i.e., less resources would be required to evaluate and/or
implement source area remediation under that strategy).
6.3 TECHNICAL IMPROVEMENT
The system is well operated, and the RSE team has no recommendations for technical improvement.
6.4 RECOMMENDATIONS TO GAIN SITE CLOSEOUT
6.4.1 CONTINUE TO CONSIDER SOURCE ALTERNATE REMEDIATION STRATEGIES
The report titled "Final Management of Migration and Source Removal Strategy Work Plan" (September
2000) provided a comparative evaluation of potential remedial alternatives for management of plume
migration. These alternatives included reduced infiltration, modified groundwater extraction, sheet pile
installation, interceptor trench, and a funnel-and-gate wall.
In addition, six-phase heating was evaluated as a source removal alternative. Unlike SVE, which was
previously attempted, six-phase heating does not require the dewatering of the treatment area. The RSE
team recommends that source removal strategies such as six-phase heating be pilot tested (currently
planned for Spring 2002) only after specific metrics are developed to determine whether or not the pilot test
is a success (i.e., mass removed per dollar spent must exceed a certain value that should be determined
before the test, based on estimated scale-up factors for a full-scale implementation). Site managers must
also consider whether or not any source removal strategy will be effective at eliminating the groundwater
plume in the long term, even if substantial mass reductions are achieved, due to the uncertainty in removing
DNAPL's that are likely present in the subsurface.
Given the high cost of this system ($1.4 million per year), and the likelihood that it will operate indefinitely
even if ROD objectives are modified, the RSE team recommends that site managers invest in an evaluation
of potential remedial alternatives on a regular basis (at least every 3-5 years) as new remedial technologies
are developed and/or improved. This type of analysis is currently being performed, and therefore can be
performed in the future within the current budget.
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7.0 SUMMARY
The observations and recommendations given below are not intended to imply a deficiency in the work of
either the designers or operators, but are offered as constructive suggestions in the best interest of the EPA
and the public. These recommendations obviously have the benefit of the operational data unavailable to
the original designers.
The RSE process is designed to help site operators and managers improve effectiveness, reduce operation
costs, improve technical operation, and gain site closeout. In this report, several recommendations are
made with respect to system effectiveness. The RSE team also supports several previous recommendations
regarding cost reduction, and also supports continued attempts to identify remedial alternatives that have
the potential to enhance capture zones and/or source area remediation.
Tables 7-1 summarizes the costs and cost savings associated with each recommendation. Estimated cost
reductions are not calculated for cases where the RSE team supports a previously made recommendation,
since the RSE team is not responsible for those recommendations. Both capital and annual costs are
presented as well as the expected change in life-cycle costs over a 30-year period for each recommendation
both with discounting (i.e., net present value) and without it.
Table 7-1. Cost summary table for individual recommendations
Recommendation
6.1.1 Augment evaluation
of GW capture
6.1.2 Sediment monitoring
6. 1.3 Air monitoring in
basements
6.2.1 Reduce site security
6.2.2 Sludge drying
6.2.3 Contracting
considerations
6.4.1 Continue considering
alternatives
Reason
effectiveness
effectiveness
effectiveness
cost reduction
cost reduction
cost reduction
exit strategy
Estimated Change in
Capital
Costs
$40,000
$0
$0
Annual
Costs
$0
$10,000
$0
Life-cycle
Costs*
$40,000
$30,000
$0
Life-cycle
Costs **
$40,000
$16,114
$0
previously made recommendation
previously made recommendation
$0
$0
not quantified
$0
not quantified
$0
not quantified
$0
Costs in parentheses imply cost reductions.
For recommendations 6.1.3 and 6.4.1, the RSE feels these items can be performed within the current budget
* assumes 30 years of operation with a discount rate of 0% (i.e., no discount).
** assumes 30 years with a discount rate of 5% and no discounting in the first year.
22
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FIGURES
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FIGURE 1-1. SITE LOCATION.
SITE
MASSACHUSETTS
SITE LOCATION
-N-
LEGEND
PROPERTY BOUNDARY
APPROXIMATE LOCATION OE
IDENTIFIED SEWER LINE
0
300
600
SCALE IN FEET
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Figure 1-2. Site photograph from period where facility was active.
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FIGURE 1-3. TOTAL VOC PLUME (11/00) AND WATER TABLE ELEVATIONS (1988), SHALLOW PORTION OF AQUIFER.
-N-
LEGEND
PROPERTY BOUNDARY
« ORIGINAL EXTRACTION
WELL LOCATION
A NEW EXTRACTION WELL LOCATION
APPROXIMATE LOCATION OE
IDENTIFIED SEWER LINE
98 • GROUNDWATER ELEVATION
CONTOUR (Et, MSL)
10 TOTAL VOC CONTOUR (ppb)
0 250
SCALE IN FEET
500
Note: Locations of water level and concentration measurements not indicated on this figure.
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FIGURE 1-4. TOTAL VOC PLUME (11/00) AND WATER TABLE ELEVATIONS (1986), DEEPER PORTION OF AQUIFER.
-N-
LEGEND
PROPERTY BOUNDARY
9 ORIGINAL EXTRACTION
WELL LOCATION
A NEW EXTRACTION WELL LOCATION
APPROXIMATE LOCATION OF
IDENTIFIED SEWER LINE
98 GROUNDWATER ELEVATION
CONTOUR (Ft, MSL)
10 TOTAL VOC CONTOUR (ppb)
0 250
SCALE IN FEET
500
Note: Locations of water level and concentration measurements not indicated on this figure.
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Solid Waste and
Emergency Response
(5102G)
542-R-02-008p
October 2002
vwwv.clu-in.org/rse
www.epa.gov/tio
U.S. EPA National Service Center
for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242-2419
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