TOTAL ENVIRONMENTAL RESTORATION CONTRACT USACE CONTRACT NO. DACW33-03-D-0006 TASK ORDER 3 SOURCE CONTROL REMEDIAL ACTION DRAFT SVE EVALUATION TECHNICAL MEMORANDUM SILRESIM SUPERFUND SITE Lowell, Massachusetts November 2004 Prepared for: Department of the Army New England District, Corps of Engineers 696 Virginia Road Concord, MA 01742-2751 Prepared by: Tetra Tech FW, Inc. 133 Federal Street Boston, MA 02110 Submitted by Tetra Tech FW, Inc. on Behalf of: Jacobs – Tetra Tech FW Joint Venture 2 Center Plaza Boston, MA 02108-1906

Revision Date Prepared By Approved By 0 11/30/04 D. McCarron J. Scaramuzzo

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TABLE OF CONTENTS

1.0 INTRODUCTION...........................................................................................................................1-1 1.1 Background......................................................................................................................1-1

1.1.1 SVE Pilot Tests ...................................................................................................1-1 1.1.2 Phase I SVE........................................................................................................1-2 1.1.3 ERH Pilot Test.....................................................................................................1-2

1.2 SVE Evaluation Objective ................................................................................................1-3 2.0 IMPLEMENTATION DESIGN CONCEPTS ..................................................................................2-1

2.1 Design Basis ....................................................................................................................2-1 2.2 Operation and Maintenance.............................................................................................2-4

3.0 IMPLEMENTATION COSTS.........................................................................................................3-1 3.1 Capital Costs....................................................................................................................3-1 3.2 Operation and Maintenance Costs ..................................................................................3-4 3.3 Total Costs .......................................................................................................................3-5

4.0 IMPLEMENTATION BENEFITS ...................................................................................................4-1 4.1 Contaminant Mass Estimate ............................................................................................4-1

4.1.1 Uncertainty in Mass Estimate .............................................................................4-2 4.2 Source Removal Benefit ..................................................................................................4-2 4.2 Management of Migration Benefit ....................................................................................4-3

5.0 SUMMARY....................................................................................................................................5-1 6.0 REFERENCES..............................................................................................................................6-1

LIST OF FIGURES Figure 2-1 SVE Implementation Scenarios .......................................................................................2-2 Figure 4-1 Total VOC Concentration vs. Depth, Silresim Property – Area of High Contamination ..4-4

LIST OF TABLES Table 3-1 Silresim SVE Cost – Scenario 1 ......................................................................................3-2 Table 3-2 Silresim SVE Cost – Scenario 2 ......................................................................................3-3

LIST OF APPENDICES Appendix A Phase I SVE Summary Report September 1998 – December 1999 (Annotations) Table A-1 SVE Subsurface Component Summary

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ACRONYMS AND ABBREVIATIONS

AHA Activity Hazard Analysis bgs below ground surface CQCP Construction Quality Control Plan CUG Clean-Up Goals EPA U.S. Environmental Protection Agency ERH Electrical Resistance Heating GAC granulated activated carbon GWTP groundwater treatment plant LEL lower explosive limit LIS Lowell Iron and Steel O&M operation and maintenance PHA Process Hazard Analysis QAPP Quality Assurance Project Plan RA remedial action RCP Regulatory Compliance Plan RI Remedial Investigation RI/FS remedial investigation/feasibility study ROD Record of Decision ROI radius of influence SSHP Site Safety and Health Plan SVE Soil Vapor Extraction TOX thermal oxidizer TtFW Tetra Tech FW, Inc. ug/L micrograms per liter USACE U.S. Army Corps of Engineers VOC volatile organic compound w.c. water column WCSDP Waste Collection, Storage and Disposal Plan

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1.0 INTRODUCTION

Tetra Tech FW, Inc. (TtFW) has prepared this Draft SVE Evaluation Technical Memorandum (Technical Memorandum) as part of the Source Control Remedial Action at the Silresim Superfund Site (the Site) in Lowell, Massachusetts. The Technical Memorandum was completed under Task Order No. 03 of the U.S. Army Corps of Engineers (USACE) Contract No. DACW33-03-D-0006. The purpose of this Technical Memorandum is to provide an evaluation of the benefits and costs of operating a Soil Vapor Extraction (SVE) system at the Site. This Technical Memorandum includes a discussion of implementation benefits including impact on estimated removal of contaminated mass during implementation, implementation design concepts and preliminary implementation cost estimate.

1.1 Background

The U.S. Environmental Protection Agency (EPA) specified a multiphase plan for the Source Control Remedy in the Record of Decision (ROD) for the Silresim Superfund Site. The ROD specified, as one phase of the remedy, that volatile organic compound (VOC) contamination is to be removed from the surficial and unsaturated soils using SVE. The surficial and unsaturated soils are defined as 0 to 1 ft below ground surface (bgs) and 1 ft bgs to the top of the water table (unsaturated zone), respectively. Additionally, an on-site groundwater treatment plant (GWTP) is currently managing contaminated groundwater at the Site.

The challenge of implementing SVE at any site depends on level of detailed knowledge regarding site-specific conditions such as soil geology, groundwater, chemical contamination and other environmental properties. This insight is typically gathered during the remedial investigation/feasibility study (RI/FS) phase of work and is continually refined and modified as the remedial action (RA) phase proceeds. For Silresim, the knowledge base from the RI was limited with respect to site-specific SVE information. However, it was known that the Site possessed formidable hydrogeologic and multi-contaminant mix conditions that would present impediments to SVE implementation. Since no fieldwork had been previously performed at the Site in regards to extraction of soil vapor, several air permeability and vapor extraction tests were performed prior to implementation of SVE.

1.1.1 SVE Pilot Tests

From July 1995 to December 1996, Air Permeability and SVE pilot tests were completed to fulfill the pilot test requirement of the ROD and to determine the effectiveness of SVE for removing the subsurface contaminants to levels established in the ROD. The Air Permeability Tests included field testing at multiple locations to collect flow versus vacuum measurements along with soil gas samples for contaminant characterization through laboratory analyses. The Pilot Test included simultaneous operation of multiple SVE techniques (heated air injection, multiphase (high vacuum) extraction, and dewatering/vapor extraction) for approximately four months across five areas of the Site.

Several significant conclusions and findings resulted from the conditions identified and data gathered from the Air Permeability and SVE Pilot Tests (Foster Wheeler, 1995a; Foster Wheeler, 1997). These included findings of extremely low permeability soils, high soil moisture, short-circuitry in the gravel layer, and the presence of relatively significant VOC contaminant mass. Overall, the SVE testing program provided an extensive foundation for understanding and implementing SVE at the Site. During the Pilot Test and associated Air Permeability Test, approximately 4,100 lbs. of VOC contaminants were removed.

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1.1.2 Phase I SVE

Following the Pilot Test, a full scale (Phase I) SVE was initiated utilizing information learned from the Pilot Test. Phase I SVE included 14 months of operations beginning in October 1998 and was completed in December 1999, resulting in significant mass removal of VOCs in the unsaturated zone soils. However, it was determined that SVE without thermal enhancements would not achieve the required soil cleanup goals and was therefore terminated as a source control measure. Limitations to the SVE technology were:

• low permeability soils; • high groundwater table; • high soil moisture contents in the unsaturated zone; and • clay cap with an underlying gravel layer causing short circuiting.

One of the major obstacles to SVE was that the shallow groundwater extraction wells were not able to sufficiently dewater the Site as was originally intended.

The Phase I SVE program was completed with minimal operational problems (approximately 94% on-line percentage), and a total contaminant removal of approximately 24,000 lbs. This total was within the range of the total mass potentially available for removal by SVE as defined in the SVE Phase I Implementation Plan. In addition, data collection yielded valuable information regarding SVE implementation and operation. Phase I SVE report recommendations are provided in Appendix A for reference.

1.1.3 ERH Pilot Test

Applied enhancements during the SVE Pilot Tests and Phase I SVE indicated some improvements, however, it became evident that a more vigorous technology improvement was necessary to try to reach the required cleanup goals. Following an evaluation of SVE thermal enhancement technologies, Electrical Resistance Heating (ERH) was selected for pilot testing. One of the main advantages of the ERH technology is that it has been proven effective in low permeability, saturated soil.

A Pilot Test was designed to evaluate ERH at the Site and determine the effectiveness of ERH for enhancing the performance of SVE in the removal of VOC contaminants to Site Clean-up levels. Installation of the ERH system commenced in August 2002. System start-up began in early October 2002. Heating operations were completed over a three-month period ending in early January 2003.

The ERH Pilot Test was located in a site area known to have high levels of VOC contamination in both soil and groundwater. The area of the one array pilot study was approximately 850 ft². The depth of treatment extended to 40 feet bgs resulting in a total treatment volume of soil and groundwater of approximately 1,250 yd³. The estimate of mass removed by ERH during the Pilot Test from both soil and groundwater was approximately 1,500 lbs. of vapor phase VOCs, with shallow groundwater VOC contamination (to 24 ft bgs) reduced by greater than 99%. Decisions on whether or not to continue with ERH as a source control remedy have not yet been finalized.

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1.2 SVE Evaluation Objective

SVE has been evaluated and implemented through a number of activities at the Site as summarized in Section 1.1, Background. All of this work has been documented in various Site Work Plans and Reports. Overall two overarching findings have been documented for implementing SVE at the Site.

1. It has been concluded that conventional SVE will not likely attain the cleanup levels established in the ROD but conventional SVE has the ability to remove a significant amount of mass as observed during Phase I SVE implementation.

2. SVE enhancements using ERH have the potential to reach ROD cleanup levels; however, implementation of ERH across the Site may be logistical and cost prohibitive.

The objective of this Technical Memorandum is to perform an evaluation of the cost/benefits of implementing a SVE system at the Site based on the recommendations presented in the Phase I SVE report (Appendix A). The evaluation is provided in three sections of this Technical Memorandum:

• Implementation Design Concepts • Implementation Costs • Implementation Benefits

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2.0 IMPLEMENTATION DESIGN CONCEPTS

This section provides design concepts and applicable design details necessary to evaluate the approach and costs of installing and operating a SVE system at the Site. Further definition of the design details as part of a Site Work Plan will be necessary following a decision to implement SVE at the Site.

2.1 Design Basis

The Phase I SVE Recommendations (Appendix A) approach for continuing SVE is used as a guide in outlining the design concepts. The Phase I approach recommended:

• Continue SVE utilizing the best performing wells at the Site; • Use on-site vapor phase granulated activated carbon (GAC) for collection of extracted VOC

vapors while investigating a long-term vapor phase treatment technology; and • Continue minimal environmental monitoring of the SVE operations.

Two scenarios are presented in this Technical Memorandum for evaluation:

• Scenario 1: implementing SVE at select existing subsurface wells to minimize capital costs.

• Scenario 2: additional installation of several new SVE wells in order to target a larger area and it’s corresponding contaminant mass.

SVE Technologies to be Implemented

Conventional SVE (i.e., SVE with no enhancements) will serve as the treatment technology and will be implemented at the identified implementation area.

SVE Duration

In order to simplify operation and maintenance (O&M) and thereby reduce costs, it is not recommended that the SVE system be operated during the winter months, December through March. Therefore, it is recommended to operate the selected SVE scenario for 8 months (April through November) prior to assessing its effectiveness for continuation.

SVE Location

The areas selected for SVE implementation are depicted in Figure 2-1 and are divided into two possible operational scenarios as described below:

Scenario 1

The locations of the best performing wells during Phase I SVE are within the areas labeled Areas 2 and 5 during Phase I SVE implementation. Existing wells in these areas that are recommended to be used for additional SVE operations are highlighted as Scenario 1 wells in Figure 2-1. These wells include: SV-2, SV-4, SV-5, SV-6, W-11, W-14, W-23, W-24, W-25, W-26, MP-2, MP-3, MP-4, MW-405B, MW-101B, MW-302B, and MW303B. Appendix A, Table A-1 provides well construction details for these wells.

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Figure 2-1 SVE Implementation Scenarios

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Scenario 2

A significant portion of the Site could be targeted by a SVE system as contaminant levels exceed the Site Clean-up Goals in most areas across the Site. For mass removal goals, however, the area of high soil contaminant concentrations is the primary selection criteria for determining a target area. Other considerations for selecting a location for a SVE system are proximity to GWTP infrastructure, a location either within the Silresim Property or on an off-site property such as Lowell Iron and Steel, subsurface infrastructure and location of highly contaminated groundwater.

The area proposed to be used for Scenario 2 is the area encompassing both Areas 2 and 5 and the area between and around these areas, inclusive of the existing wells selected in Scenario 1. Figure 2-1 depicts this area, which is approximately 15,000 ft2.

Operational Strategy and Vapor Phase Treatment

A strategy similar to that used for Phase I SVE will be used for this evaluation. The vapor treatment system using GAC is a limiting factor on the rate of contaminant removal due to the direct proportions that exist between the pounds of contaminants removed, the size of GAC units needed for treatment and the cost to regenerate a pound of GAC. It is assumed that an appropriate maximum contaminant removal rate for SVE at the Site is 100 lbs/day. Also, assumed is the use of the existing site equipment, which includes the 1,800-lb. GAC units, the vacuum blower and available piping and hoses that were used during the Phase I activities. In terms of available mass removal, Scenario 2 is conservatively expected to average at least twice as many pounds removed per day.

It is understood that the use of GAC for vapor phase treatment may not be the most cost-effective long-term treatment system for SVE at the Site. However, for the short-term operation under current consideration (one year = actual eight months of operations to avoid winter disruptions) use of the existing GAC vessels would be most cost effective. Various vapor phase treatment options have been reviewed for the Site as an alternative to GAC. In summary, thermal oxidation represents the only proven vapor phase treatment alternative. The existing GWTP currently includes a thermal oxidizer system with a wet scrubber as part of its treatment train. The concurrent use of this system for both the groundwater treatment plant and the SVE system has been conceptually considered in the past. Should an SVE system be installed with a plan to operate over multiple years, then the GWTP thermal oxidizer (TOX) or new SVE TOX should be considered.

SVE Wells

Scenario 1

No new wells required, utilizes existing most productive (as determined in Phase I operations) wells only.

Scenario 2

As a basis for meeting the above operational strategy, the factors that contribute significantly to the contaminant removal rate include the following:

• the location and number of extraction well/points utilized; • the individual well characteristics such as flow versus vacuum;

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• the radius of influence (ROI), as defined by an induced vacuum of one-half inch of water column (w.c.) or greater;

• contaminant concentration in the subsurface; and • soil above the water table that remains saturated due to infiltration and smearing.

Based on pilot test findings, the ROI for the Areas 2 and 5 was estimated to be 2 to 10 feet depending on the applied vacuum levels. Using a 15 feet well spacing (equivalent to a 7.5 feet ROI) across the target area results in approximately 60 new wells required. The design basis for the new wells for this evaluation is that the wells will be 4-inch diameter wells installed to 12 feet bgs with a 5-ft screened interval from 7 to 12 ft bgs. Exact locations and construction details of the new SVE wells would be completed in the design work plan if this scenario were to be selected for implementation.

Above Ground Equipment and Systems

The existing aboveground equipment including the GAC vessels, Phase I SVE blower, condensate equipment and available hoses and piping will be used during this SVE implementation. Any equipment or materials no longer available will need to be procured for the implementation.

The existing GAC units at the Site will be refilled with reactivated carbon to be used for treatment of contaminated vapors generated from the SVE operations.

Coordination with the GWTP

Coordination will be performed between the ongoing GWTP operations and new SVE activities.

2.2 Operation and Maintenance

As discussed previously, this technical memorandum assumes that the SVE system is operated for 8 months (April through November) during a given year.

Operational Oversight

In order to reduce O&M costs, SVE system oversight during normal operations is expected to be a part-time activity for one person, with additional support as needed. It is estimated that site visits twice a week will be required for system monitoring and sampling.

Process Monitoring and Sampling

Throughout implementation of SVE at the Site under either scenario, it will be necessary to collect sufficient data from the SVE systems to characterize process streams and evaluate system performance allowing modifications to be made for optimizing operational scenarios. The data collection typically includes flow, vacuum, lower explosive limit (LEL), and vapor VOC concentrations at various locations throughout the system.

The methods of chemical analyses will include field screening using portable instruments and analyses of process vapor performed at off-site analytical laboratories. Samples submitted to off-site laboratories will be at a frequency of approximately one per month, in order to gather sufficient data while sustaining minimal costs.

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Follow-On Phases

Follow-on phases should be considered to encompass larger volumes of the site soils within the influence of the SVE system and to enable more of the contamination in the surficial and unsaturated soils to be removed by SVE. The plan for follow-on phase(s) should be determined after completion of the initial year of operation. The review of the monitoring data will provide a basis for recommending how the SVE system may be further expanded across the Site.

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3.0 IMPLEMENTATION COSTS

3.1 Capital Costs

A cost estimate for each scenario is presented in Tables 3-1 and 3-2. It should be noted that these are preliminary costs only and a detailed cost estimate would be required prior to implementation. A summary of the capital costs is shown in the following table.

Capital Costs Comments Scenario 1 ~$72K Includes:

~ $30K to install the system Scenario 2 ~$136K Includes:

~ $33K for installation of new wells ~ $53K to install the system

Some of the major capital cost assumptions are highlighted below.

Design Documents

SVE systems deployed under this Technical Memorandum assumes that the TERC JV contract is used with TtFW the lead contractor. For cost savings, design documents will be completed at a minimum detail necessary to implement an approved Work Plan.

Planning Documents

Existing project plans will be amended to support the implementation of SVE. These proposed plans to be amended are listed below:

• Quality Assurance Project Plan (QAPP); • Site Safety and Health Plan (SSHP); • Waste Collection, Storage and Disposal Plan (WCSDP); • Regulatory Compliance Plan (RCP); and • Construction Quality Control Plan (CQCP).

The revisions to the SSHP will also include modifying existing Activity Hazard Analysis (AHAs) forms and a Process Hazard Analysis (PHA).

Installation of Subsurface Components

Scenario 1

This scenario will utilize the existing subsurface components (monitoring wells, SVE wells and the cap vent system). No new installation of subsurface components is included under this scenario.

Scenario 2

This scenario, in addition to using the existing wells as in Scenario 1, will also install an estimated 60 new SVE wells. This work will be completed similar to the existing SVE wells by a drilling subcontractor using auger drilling techniques.

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Table 3-1Silresim SVE Cost - Scenario 1

SVE total area (sf) = 2,660 depth (ft) = 12

total duration (dy) = 240 PROJECT TOTAL: 320,868$ Includes 20% contingencytreated volume (cy) = 1,182 estimated mass (lb) = 7,200 cost per treated cy = $271

cost per pound removed = $45

Capital Costs O&M Costs

Qty. Unit Unit Price Total Cost Qty. Unit Unit Price Total Cost

Contracting/Est. Task Order AdminPM/Cost Proposal 1 ea. 6,000$ 6,000$ PM 8 per mo. 2,000$ 16,000$ MIS 1 ea. 3,500$ 3,500$ MIS 8 per mo. 1,000$ 8,000$ Procurement 1 ea. 2,000$ 2,000$ Procurement 4 per mo. 1,000$ 4,000$

Subtotal: 11,500$ QC 8 per mo. 1,000$ 8,000$ Subtotal: 36,000$

DesignWorkplan 1 ea. 6,000$ 6,000$ Field StaffQAPP 1 ea. 5,000$ 5,000$ O&M 8 per mo. 8,000$ 64,000$ SSHP update 1 ea. 2,500$ 2,500$ O&M support 8 per mo. 4,000$ 32,000$ QCP update 1 ea. 2,500$ 2,500$ Subtotal: 96,000$ WCP update 1 ea. 2,500$ 2,500$ RCP update 1 ea. 2,500$ 2,500$ SOWs 2 ea. 3,500$ 7,000$ Miscellaneous

Subtotal: 28,000$ FID rental 8 per mo. 1,200$ 9,600$ Field supplies 8 per mo. 1,500$ 12,000$

Drilling & Sampling Subtotal: 21,600$ Mob. Auger Rig 0 ea. 3,750$ -$ Demob. Auger Rig 0 ea. 750$ -$ Drilling 4" casing 0 per ft. 25$ -$ During-Sample AnalysisSoil sampling 0 ea. 175$ -$ Summa TO-14 10 ea. 285$ 2,850$ well riser matl. 0 per ft. 5$ -$ Summa Methane 10 ea. 65$ 650$ well screen matl. 0 per ft. 8$ -$ Subtotal: 3,500$ Equip. decon 0 per hr. 300$ -$

Subtotal: -$ Vapor Treatment

Pre-Sample Analysis GAC usage 36,000 lbs. 0.44$ 15,840$ Soil VOCs 0 ea. 94$ -$ GAC changeout 20 ea. 1,000$ 20,000$ Soil TOC 0 ea. 55$ -$ Subtotal: 35,840$ Groundwater VOCs 20 ea. 85$ 1,700$

Subtotal: 1,700$ UtilitiesElectricity 26,000 kWh 0.10$ 2,600$

Installation Subtotal: 2,600$ Piping & appurt. 1 ea. 6,750$ 6,750$ Electric install 1 ea. 3,500$ 3,500$ Install/startup 3 per wk. 6,800$ 20,400$

Subtotal: 30,650$

Subtotal Capital Costs: 71,850$ Subtotal O&M Costs: 195,540$

Project Subtotal : 267,390$ Contingency (20%) 53,478$

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Table 3-2Silresim SVE Cost - Scenario 2

SVE total area (sf) = 15,000 depth (ft) = 12

total duration (dy) = 240 PROJECT TOTAL: 448,732$ Includes 20% contingencytreated volume (cy) = 6,667 estimated mass (lb) = 15,600 cost per treated cy = $67

cost per pound removed = $29

Capital Costs O&M Costs

Qty. Unit Unit Price Total Cost Qty. Unit Unit Price Total Cost

Contracting/Est. Task Order AdminPM/Cost Proposal 1 ea. 8,000$ 8,000$ PM 8 per mo. 2,000$ 16,000$ MIS 1 ea. 4,000$ 4,000$ MIS 8 per mo. 1,000$ 8,000$ Procurement 1 ea. 2,500$ 2,500$ Procurement 4 per mo. 1,000$ 4,000$

Subtotal: 14,500$ QC 8 per mo. 1,000$ 8,000$ Subtotal: 36,000$

DesignWorkplan 1 ea. 8,000$ 8,000$ Field StaffQAPP 1 ea. 5,000$ 5,000$ O&M 8 per mo. 8,000$ 64,000$ SSHP update 1 ea. 2,500$ 2,500$ O&M support 8 per mo. 4,000$ 32,000$ QCP update 1 ea. 2,500$ 2,500$ Subtotal: 96,000$ WCP update 1 ea. 2,500$ 2,500$ RCP update 1 ea. 2,500$ 2,500$ SOWs 3 ea. 3,500$ 10,500$ Miscellaneous

Subtotal: 33,500$ FID rental 8 per mo. 1,200$ 9,600$ Field supplies 8 per mo. 1,500$ 12,000$

Drilling & Sampling Subtotal: 21,600$ Mob. Auger Rig 1 ea. 3,750$ 3,750$ Demob. Auger Rig 1 ea. 750$ 750$ Drilling 4" casing 720 per ft. 25$ 18,000$ During-Sample AnalysisSoil sampling 20 ea. 175$ 3,500$ Summa TO-14 10 ea. 285$ 2,850$ well riser matl. 420 per ft. 5$ 2,100$ Summa Methane 10 ea. 65$ 650$ well screen matl. 300 per ft. 8$ 2,400$ Subtotal: 3,500$ Equip. decon 8 per hr. 300$ 2,400$

Subtotal: 32,900$ Vapor Treatment

Pre-Sample Analysis GAC usage 78,000 lbs. 0.44$ 34,320$ Soil VOCs 10 ea. 94$ 940$ GAC changeout 43 ea. 1,000$ 43,333$ Soil TOC 10 ea. 55$ 550$ Subtotal: 77,653$ Groundwater VOCs 20 ea. 85$ 1,700$

Subtotal: 3,190$ UtilitiesElectricity 26,000 kWh 0.10$ 2,600$

Installation Subtotal: 2,600$ Piping & appurt. 1 ea. 15,000$ 15,000$ Electric install 1 ea. 3,500$ 3,500$ Install/startup 5 per wk. 6,800$ 34,000$

Subtotal: 52,500$

Subtotal Capital Costs: 136,590$ Subtotal O&M Costs: 237,353$

Project Subtotal : 373,943$ Contingency (20%) 74,789$

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Mobilization and Installation of SVE Piping and Appurtenances

In order to reduce capital and O&M costs, an effort will be made to reuse any existing equipment and appurtenances remaining from the Phase I SVE installation. However, it will be necessary to procure and mobilize some additional equipment to complete the installation under each scenario.

Baseline Soil and Groundwater Sampling

Scenario 1

This scenario will not collect soil samples, since drilling is not involved in the installation. To provide further data for the site conceptual model and estimate of existing groundwater contaminant mass, groundwater sampling costs are estimated for collection of samples at each of the eleven identified existing SVE wells. In order to reduce additional costs, groundwater sampling could be coordinated with the GWTP sampling program currently being conducted by the GWTP contractor: Watermark Environmental, Inc.

Scenario 2

This scenario will collect limited soil samples during the installation of new wells and will provide further data for the site conceptual model and estimate of existing soil contaminant mass. Groundwater sampling at identified existing SVE wells and some of the new SVE wells is also planned under this scenario.

3.2 Operation and Maintenance Costs

O&M costs for an estimated 8-month operational year are also presented in Tables 3-1 and 3-2. A summary of the O&M costs is shown in the following table.

O&M Costs Comments Scenario 1 ~$195K Includes:

~ $96K for field staff oversight ~ $36K for vapor treatment

Scenario 2 ~$237K Includes: ~ $112K for field staff oversight ~ $78K for vapor treatment

Some of the major O&M cost assumptions are highlighted below.

O&M Labor

Labor is broken down into costs for task order administration and field staff oversight. Field oversight labor is estimated for routine operational time at two days per week plus additional time for scheduled and unscheduled maintenance. This level of effort is estimated to be slightly higher for Scenario 2 due to the additional vapor extraction wells employed.

Process Monitoring and Sampling

Process monitoring and sampling including field screening and laboratory analysis for VOCs is estimated to be the same for each scenario.

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Vapor Treatment

Vapor treatment cost using GAC is directly proportional to the contaminant mass removed. Using the assumption that at least twice as much mass will be consistently removed under Scenario 2, a contaminant mass removal rate of 30 lbs/day for Scenario 1 and 65 lbs/day for Scenario 2 is used in the cost estimate. Therefore GAC usage costs under Scenario 2 are expected to be slightly more than double the costs under Scenario 1.

Utilities

The utilities cost for each scenario is estimated to be the same. No cost is estimated for condensate disposal as it is expected that this will be transferred to the GWTP for processing and treatment, as it was during Phase I operations.

3.3 Total Costs

Total costs for the installation and operation of the two optional SVE systems are presented in Tables 3-1 and 3-2. Note that the total estimated costs for each subsection of work has been increased by 20% contingency to allow for a more practicable estimate. A summary of the developed costs is shown in the following table:

Total Costs Comments Scenario 1 $320K Includes:

~ 20% contingency Scenario 2 $450K Includes:

~ 20% contingency

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4.0 IMPLEMENTATION BENEFITS

4.1 Contaminant Mass Estimate

An estimated available mass of contamination at the Site has been calculated over the past several years using available data sets and specific assumptions for a defined area and volume of interest. As part of this Technical Memorandum, a review of previous mass estimates and a calculation of available mass estimate in support of the SVE implementation benefits have been performed. This evaluation is defined as follows:

• historical mass estimates – site wide; • current mass estimates completed recently – site wide; • mass estimates for the SVE scenarios; and • considerations of mass estimate model and unaccounted for mass.

Mass estimates for VOC contamination in soil at the Silresim site have ranged from approximately 50 (Foster Wheeler, 2000) to 60 metric tons (Foster Wheeler, 1996). These estimates were for the most part based on data for historical soils collected during the 1990 Remedial Investigation (RI), 1991 supplemental RI, 1995 Lowell Iron and Steel (LIS) investigation and 2001 Clean-Up Goals (CUG) investigation. Models were then constructed for the site based on the data available for VOC concentrations and sampling locations.

The 1996 estimate divided the site into cells with a representative sample concentration of Total VOCs in soils collected from inside each cell used for the calculations. The concentration was used for all soils contained within each cell and a mass for each cell calculated and all cell masses summed to reach a final site wide mass.

The mass estimate from 2000 was completed using the data collected during the CUG/Source delineation sampling. The estimate was produced using a 3-dimensional computer-modeling program (EVS, CTECH Corp). The modeling program uses a mathematical algorithm to interpolate the concentrations between the sampling locations at the site. This interpolation takes into account the spatial distribution of the data collected as well as the concentrations at the individual points. The model also takes into account a difference between vertical and horizontal spacing such that horizontal spacing is 1/10 the influence as vertical spacing (i.e., the influence of data points with 100 ft horizontal spacing is = 10 ft vertical spacing). It should also be noted that the 2000 model uses data collected following the 18 months of Phase I SVE operation (and associated mass removal) at the site.

The current VOC mass estimate is for soil in the unsaturated zone (above the water table) and the entire soil column. The entire soil column VOC mass is estimated at 32 metric tons. The VOC mass in the unsaturated zone (above the average water table elevation) is 16 metric tons while if using a low water table period the mass is estimated at 18 metric tons. These models are produced using the 3-dimensional EVS computer software.

Two scenarios for SVE (as described in the following sections) were evaluated by the model to determine the estimated mass for VOCs in the unsaturated soils. The first scenario is based on a set of existing SV wells at the site (Figure 2-1) and estimated the soil VOC mass inside a 15’ diameter area centered at the

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well. The mass estimate in the unsaturated zone using recent historical average water table depth is 750 lbs., with the estimate using recent historical low water table being 1,000 lbs.

The second scenario is based on an area of the site for the installation of new SVE wells plus the existing wells from the first scenario. The area for this scenario has an estimated VOC mass in the unsaturated soil of 4,500 lbs. for the average water table depth and 6,000 lbs. for the low water table period.

4.1.1 Uncertainty in Mass Estimate

It should be noted that these are estimates derived solely from modeling and as we have seen at the Site during actual field implementation (both Phase I SVE and the ERH Pilot Test) these tend to appreciably under estimate the available mass. Several possible explanations for underestimation of mass by the model are presented herein. The model mass estimates are not taking into account several sources of contamination likely to be removed by SVE. The CUG investigation found that there was a significant increase in the VOC contamination in soil at the water table. This increase can be seen in Figure 4-1. This zone of high VOC contamination is likely contributing a significant portion of the overall VOC mass at the site. The impact can be seen in the difference in the mass of the unsaturated zone for the average and low water tables.

Additionally, any mass in soil (or NAPL if present) that is at the top of the unsaturated zone is not accounted for in the mass estimates above, and VOCs present in the groundwater are not included in the mass estimates above. Sampling results have consistently shown that some of the highest groundwater contamination on the Silresim property is in the shallow groundwater. These concentrations have exceeded 1,000,000 ug/L. Both the shallow saturated soil and shallow groundwater contamination can potentially be removed to some extent by SVE through the partitioning from the saturated soil and groundwater to the pore space as soil vapor is removed from the overlying soil.

Historical experience utilizing laboratory analyses of the collected samples indicate that the extraction results are actually considerably higher than what is shown by the models. Therefore, the following section utilizes expected mass removal effort based on operational experience at the Site.

4.2 Source Removal Benefit

The benefit gained from this additional source removal would be the removal of contaminant mass from subsurface Site soils, thus reducing the overall contamination concern at the site. This additional source removal may lead to reduced leaching effects from the unsaturated to the saturated zones and may reduce the concerns associated with the contact risk component of the surface soils.

While the contaminant mass has been estimated for each of the scenario’s target area, experience at implementing Phase I SVE in 1998 and 1999 indicates that an amount of mass greater than these estimates is likely to be removed over a one year time period.

For estimating purposes the following mass per day removal rates are used in this evaluation. Year 1 is defined as 240 days (8 months - April through November) of operating time in order to avoid the increased technical issues and costs associated with operating an SVE system during winter (freezing) conditions.

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Estimated Mass

Removal Rate – Year 1 (lbs/day)

Total Mass Removed – Year 1

(lbs) Scenario 1 30 7,200 Scenario 2 65 15,600

4.2 Management of Migration Benefit

The removal of additional VOC source would also benefit the Site’s ongoing management of migration as reduced soil concentrations would eventually lead to reduced groundwater concentrations and therefore aid in the overall reduction of VOC contamination through improved natural attenuation.

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Figure 4-1 Total VOC Concentration vs. Depth

Silresim Property – Area of High Contamination

0

20

40

60

80

100

120

0 1000 2000 3000 4000 5000 6000 7000

Concentration (mg/Kg)

Depth (ft bgs)

SIL-SB-09

SIL-SB-10

SIL-SB-11

SIL-SB-17

SIL-SB-19

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5.0 SUMMARY

Ongoing SVE operations at Silresim are predicted to be very useful for increased VOC mass removal in the unsaturated zone, despite facing several technical issues that have made implementation of SVE at Silresim a significant challenge. As discussed, the primary technical challenges are trying to implement SVE at a site where very high soil moisture and low soil permeabilities greatly affect attaining soil cleanup goals in the low part per billion range. However, results from the Pilot Test and Phase I SVE implementation have shown that although SVE may not be practical in achieving the required ROD limits for the Site, it may be used as a considerable contaminant mass removal technology for the unsaturated zone.

Following the recommendations presented subsequent to the Phase I SVE implementation (Appendix A), a proposed procedure for further SVE implementation at the Site has been presented in this technical memo. Results from the Phase I SVE program performed from September 1998 to December 1999 indicated that mass removal goals were realized during the Phase I SVE program. Significant contaminant mass was removed from the subsurface, contributing to risk reduction at the Site by removing a continuing source of VOC contaminant migration to the groundwater. The SVE system was operated in as many areas as possible and substantial information was gathered to develop the basis for the next phase of SVE implementation. As outlined in this memo, considerable VOC mass may be removed, at a reasonable cost per pound of contaminants removed, through ongoing SVE operations at the Site.

6.0 REFERENCES

Foster Wheeler Environmental Corporation, 1995a, Air Permeability Testing Data Report, Silresim Superfund Site, Lowell, Massachusetts, August 1995.

Foster Wheeler, 1995b, Lowell Iron and Steel Property Soil Investigation Report, Silresim Superfund Site,

Lowell, Massachusetts, December 1995. Foster Wheeler Environmental Corporation, 1997, Soil Vapor Extraction Pilot Test Report, Silresim

Superfund Site, Lowell, Massachusetts, August 1997. Foster Wheeler Environmental Corporation, 2000, Phase I SVE Summary Report, Silresim Superfund

Site, Lowell, Massachusetts, February 2000. Foster Wheeler, 2003, Electrical Resistance Heating Pilot Test Final Report, Silresim Superfund Site,

Lowell, MA, September 2003.

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Appendix A

PHASE I SVE SUMMARY REPORT SEPTEMBER 1998 - DECEMBER 1999

(Annotations)

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PHASE I SVE SUMMARY REPORT, 2000 (Annotations) RECOMMENDATIONS The Phase I SVE program ran with minimal operational problems, removed approximately 24,000 lbs. of VOCs from the Site subsurface, and utilized GAC very efficiently, resulting in reduced project costs. However, the observations and data collected support the conclusions of the SVE Pilot Test Report, which stated that SVE has the potential to reduce the subsurface contaminant mass, but is not likely to reduce the contamination to ROD cleanup levels within the ROD cleanup period. Therefore, continued SVE at the Site depends upon a re-evaluation of the ROD cleanup goals. When revised numbers are developed, a more quantitative evaluation can be made in terms of the ability of SVE to achieve those revised cleanup goals.

The SVE system operation has currently been suspended, at the request of the USACE, pending further review and evaluation. The following approach is recommended should the decision be made for continuing the objective of implementing SVE to remove the maximum amount of contaminant mass possible as an aid to source reduction at the Site.

• Continued SVE utilizing the best performing wells across the Silresim Property; • Control of extracted VOCs by on-site GAC while investigating a long-term vapor phase treatment

technology; and • Continued minimal environmental monitoring of the SVE operations.

To minimize system maintenance and operation costs, the best producing wells would be hard-piped, heat traced, and insulated to allow for steady year-round operation. Additionally, system monitoring would be reduced to allow only that which is needed to make appropriate adjustments to increase mass removal as available mass for extraction decreases over time. Operational costs would further be reduced if an appropriate long term vapor phase treatment technology was determined to be more suitable than GAC.

Based on the information compiled during Phase I SVE, the necessary design basis parameters have been collected to allow for the expansion of the next phase of SVE at the Site.

Area-1

• Not recommended for SVE. Area-2

• Continue SVE at SV-2 and SV-4. • Add additional wells similar to SV-2 and SV-4 at 10 ft. spacing intervals; hard pipe for

permanent year-round extraction. Area-4

• Install 4-in. SV wells to below gravel layer at approximately 10 ft. spacing intervals. Area-5

• SVE at MP-2, MP-3, MP-4, SV-5, and SV-6.

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• Install additional, similar, extraction wells in this Area to extend the radial coverage, at approximately 10 ft. spacing intervals.

EV

• Continue SVE at EVs which show best results (EV-6 and EV-13), for flow dilution purposes. D/VE

• Not recommended for SVE implementation unless well screen construction (i.e., channel pack) is altered.

MW

• •

Continue SVE at previously utilized wells (MW-302B, 404B, 412B, 303B, and 101B). Hard pipe wells for year-round extraction at minimal operation and maintenance costs.

New Areas

•

•

• •

Install expansion of SVE system into area north of GWTP between Area-2 and Area-5 (dependent on overall objectives for long term cleanup at the Site). Combine installation of selected new SVE wells with any soil boring program performed at the Site.

Based on the information collected during the bench scale studies of vapor-phase treatment technologies, the investigation into the long term applicability of these technologies should continue.

Continue with review of innovative technologies. Review combined use with GWTP vapor-phase treatment requirements.

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Table A-1 Existing SVE Wells and Silresim Property Shallow Wells

Location (#) Type Date

Installed Well

Material Depth

(ft bgs)

Screened Interval (ft bgs)

Stick-Up(ft ags)

Diameter(in)

AT-1 Access Tube 9/96 SS 10.0 NA FM 2 AT-2 Access Tube 9/96 SS 10.0 NA FM 2 AT-3 Access Tube 8/96 SS 15.3 NA 1.7 2 AT-4 Access Tube 8/96 SS 14.8 NA 2.2 2 AT-5 Access Tube 8/96 SS 15.2 NA 1.8 2 AT-6 Access Tube 8/96 SS 15.0 NA 2.0 2 AT-7 Access Tube 8/96 SS 10.3 NA 2.3 2 AT-8 Access Tube 8/96 SS 10.1 NA 2.4 2 AT-9 Access Tube 8/96 SS 10.3 NA 2.3 2 AT-10 Access Tube 8/96 SS 10.0 NA 2.5 2 AT-11 Access Tube 8/96 SS 10.0 NA 2.5 2 AT-12 Access Tube 8/96 SS 10.0 NA 2.5 2 AT-13 Access Tube 8/96 SS 10.0 NA 2.5 2 EV-6 Vent Tube 1/84 CS 2.5-3.0 NA 3.8 4 G-1 Gravel Point 7/95 GS 2.5 1.5 - 2.5 2.0 2 G-2 Gravel Point 7/95 GS 2.5 1.5 - 2.5 2.0 2 G-3 Gravel Point 9/96 GS 2.6 1.6 - 2.6 1.9 2 G-4 Gravel Point 7/95 GS 2.5 1.5 - 2.5 2.0 2 G-5 Gravel Point 7/95 GS 2.5 1.5 - 2.5 2.0 2 G-6 Gravel Point 7/95 GS 2.5 1.5 - 2.5 2.0 2 G-7 Gravel Point 8/96 GS 2.5 1.5 - 2.5 2.5 2 G-8 Gravel Point 8/96 GS 2.6 1.6 - 2.6 2.4 2 G-9 Gravel Point 8/96 GS 2.7 1.7 - 2.7 2.3 2 G-10 Gravel Point 8/96 GS 2.4 1.4 - 2.4 2.6 2 G-11 Gravel Point 8/96 GS 2.5 1.5 - 2.5 2.5 2 G-12 Gravel Point 8/96 GS 2.5 1.5 - 2.5 2.5 2 G-13 Gravel Point 8/96 GS 2.6 1.6 - 2.6 2.4 2 G-14 Gravel Point 9/96 GS 2.5 1.5 - 2.5 2.0 2 G-15 Gravel Point 9/96 GS 2.7 1.7 - 2.7 1.8 2 G-16 Gravel Point 9/96 GS 2.7 1.7 - 2.7 1.8 2 G-17 Gravel Point 9/96 GS 2.6 1.6 - 2.6 1.9 2 G-18 Gravel Point 9/96 GS 2.7 1.7 - 2.7 2.3 2 G-19 Gravel Point 9/96 GS 2.5 1.5 - 2.5 2.5 2 MP-1 Multiphase Well 8/96 SS 32.3 11.3 - 32.3 1.5 4 MP-2 Multiphase Well 8/96 SS 32.0 7.0 - 32.0 3.3 4 MP-3 Multiphase Well 8/96 SS 33.3 8.3 - 33.3 2.0 4 MP-4 Multiphase Well 8/96 SS 32.3 7.3 - 32.3 3.0 4 PZ-801-6(a) Piezometer 8/96 T 3.2 2.8 - 3.2 2.0 0.5 PZ-801-6(b) Piezometer 8/96 T 7.2 6.8 - 7.2 2.0 0.5 PZ-801-6(c) Piezometer 8/96 T 10.2 9.8 - 10.2 2.0 0.5 PZ-801-6(d) Piezometer 8/96 T 13.2 12.8 - 13.2 2.0 0.5

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Location (#) Type Date

Installed Well

Material Depth

(ft bgs)

Screened Interval (ft bgs)

Stick-Up(ft ags)

Diameter(in)

PZ-801-6(e) Piezometer 8/96 T 16.2 15.8 - 16.2 2.0 0.5 PZ-801-6(f) Piezometer 8/96 T 19.2 18.8 - 19.2 2.0 0.5 SV-1 Soil Vapor Well 7/95 PVC 12.8 2.8 - 12.8 FM 4 SV-2 Soil Vapor Well 7/95 SS 13.8 3.8 - 13.8 2.0 4

SV-3 Soil Vapor Well 7/95 PVC 12.8 2.8 - 12.8 FM 4 SV-4 Soil Vapor Well 8/96 SS 12.3 7.3-12.3 2.0 4 SV-5 Soil Vapor Well 8/96 SS 32.1 7.1 - 32.1 3.2 4 SV-6 Soil Vapor Well 8/96 SS 32.6 7.6 - 32.6 2.7 4 W-1 Well Point 7/95 GS 7.8 2.8 - 7.8 FM 2 W-2 Well Point 7/95 GS 7.8 2.8 - 7.8 FM 2 W-3 Well Point 7/95 GS 7.8 2.8 - 7.8 FM 2 W-4 Well Point 7/95 GS 7.8 2.8 - 7.8 FM 2 W-5 Well Point 7/95 GS 7.8 2.8 - 7.8 FM 2 W-6 Well Point 7/95 GS 7.8 2.8 - 7.8 FM 2 W-7 Well Point 7/95 GS 7.8 2.8 - 7.8 FM 2 W-8 Well Point 7/95 GS 8.8 3.8 - 8.8 2.0 2 W-9 Well Point 7/95 GS 8.8 3.8 - 8.8 2.0 2 W-10 Well Point 7/95 GS 8.8 3.8 - 8.8 2.0 2 W-11 Well Point 7/95 GS 8.8 3.8 - 8.8 2.0 2 W-12 Well Point 7/95 GS 8.8 3.8 - 8.8 2.0 2 W-13 Well Point 7/95 GS 8.8 3.8 - 8.8 2.0 2 W-14 Well Point 7/95 GS 8.8 3.8 - 8.8 2.0 2 W-15 Well Point 11/95 GS 10.0 3.0 - 10.0 FM 2 W-16 Well Point 11/95 GS 10.0 3.0 - 10.0 FM 2 W-17 Well Point 11/95 GS 10.0 3.0 - 10.0 FM 2 W-18 Well Point 11/95 GS 10.0 3.0 - 10.0 FM 2 W-19 Well Point 11/95 GS 10.0 3.0 - 10.0 FM 2 W-20 Well Point 11/95 GS 10.0 3.0 - 10.0 FM 2 W-21 Well Point 11/95 GS 10.0 3.0 - 10.0 FM 2 W-22 Well Point 11/95 GS 10.0 3.0 - 10.0 FM 2 W-23 Well Point 8/96 GS 11.8 6.8 - 11.8 2.2 2 W-24 Well Point 8/96 GS 11.8 6.8 - 11.8 2.3 2 W-25 Well Point 8/96 GS 12.1 7.1 - 12.1 1.9 2 W-26 Well Point 8/96 GS 11.8 6.8 - 11.8 2.3 2 MW-308B Monitoring Well 4/86 PVC 15.1 5.1 - 15.1 1.7 1.5 MW-301B Monitoring Well 4/86 PVC 18.4 8.4 - 18.4 2.7 1.5 MW-302B Monitoring Well 4/86 PVC 14.0 4.0 - 14.0 2.1 1.5 MW-404B Monitoring Well 10/86 PVC 14.4 4.4 - 14.4 2.0 1.5 MW-412B Monitoring Well 10/86 PVC 15.4 5.4 - 15.4 0.0 1.5 MW-405B Monitoring Well 10/86 PVC 16.8 6.8 - 16.8 1.9 1.5 MW-406B Monitoring Well 10/86 PVC 18.5 8.5 - 18.5 4.9 1.5

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Location (#) Type Date

Installed Well

Material Depth

(ft bgs)

Screened Interval (ft bgs)

Stick-Up(ft ags)

Diameter(in)

MW-303B Monitoring Well 4/86 PVC 14.7 4.7 - 14.7 1.6 1.5 MW-101B Monitoring Well 11/81 PVC 16.3 6.3 - 16.2 1.6 1.5 MW-309B Monitoring Well 4/86 PVC 15.7 5.7 - 15.7 1.3 1.5 MW-105B Monitoring Well 11/81 PVC 16.0 11.0 - 16.0 1.8 1.5 MW-702C Monitoring Well PVC 14.2 4.2 - 14.2 FM 2 EW01 Extraction Well 4/95 CS 20.5 9.5 - 20.5 3.2 6 EW02 Extraction Well 3/95 CS 23.4 8.4 - 23.4 1.4 6 EW03 Extraction Well 3/95 CS 23.1 8.0 - 23.1 2.8 6 EW04 Extraction Well 4/95 CS 24.3 9.2 - 24.3 4.0 6 EW05 Extraction Well 3/95 CS 24.2 9.2 - 24.2 5.4 6 EW06 Extraction Well 3/95 CS 24.2 8.9 - 24.2 3.0 6 EW07 Extraction Well 4/95 CS 25.2 10.2 - 25.2 4.4 6 EW08 Extraction Well 4/95 CS 23.9 8.9 - 23.9 3.9 6 EW09 Extraction Well 5/95 CS 17.0 8.0 -17.0 1.8 6 EW10 Extraction Well 4/95 CS 24.5 9.5 - 24.5 3.8 6 EW11 Extraction Well 4/95 CS 15.2 10.2 - 25.2 3.9 6 EW12 Extraction Well 4/95 CS 26.1 11.0 - 26.1 4.2 6 EW13 Extraction Well 4/95 CS 27.7 12.6 - 27.7 6.9 6

Notes: bgs = below ground surface ags = above ground surface FM = flush mounted SS = stainless steel CS = carbon steel GS = galvanized steel T = teflon tubing

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