PRELIMINARY INTERPRETATION OF VOC, ARSENIC, AND URANIUM 2009 DATA IN RESIDENTIAL AND MONITORING WELLS MOTTOLO SUPERFUND SITE RAYMOND, NEW HAMPSHIRE NHDES NO. 198704094 Consisting Of – VOLUME I: TEXT AND APPENDIX A - TABLES VOLUME II: APPENDIX B - FIGURES VOLUME III: APPENDIX C THROUGH APPENDIX R

PREPARED FOR: New Hampshire Department of Environmental Services Hazardous Waste Remediation Bureau Concord, New Hampshire and United States Environmental Protection Agency Region I - New England Office of Site Remediation and Restoration Boston, Massachusetts PREPARED BY: GZA GeoEnvironmental, Inc. Manchester, New Hampshire March 2010 File No. 04.0024466.27 Copyright 2010 GZA GeoEnvironmental, Inc.

SDMS DocID 466855*466855*

TABLE OF CONTENTS Page

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ACKNOWLEDGEMENTS i

I. EXECUTIVE SUMMARY I

II. REPORT INTRODUCTION AND BRIEF SITE BACKGROUND 1

III. SUMMARY OF 2009 / EARLY 2010 SITE INVESTIGATIONS 3

IV. SUMMER 2009 SITE MONITORING ROUND 4

V. SITE NEW WELL INSTALLATIONS AND SAMPLING 5

VI. NHDES RESIDENTIAL WELL SAMPLING 6

VII. GEOPHYSICAL WELL INVESTIGATIONS 6

VIII. EPA GEO-PROBE SOIL INVESTIGATION 8

IX. DATA ANALYSIS 9 IX.1 ON-SITE 2009 DATA ANALYSIS 9 IX.2 AREA 2009 DATA ANALYSIS 11

X. CONCEPTUAL SITE MODEL AND GEOLOGICAL SETTING 14 X.1 ENVIRONMENTAL SETTING 14 X.2 NATURE AND EXTENT OF SOURCE AREA CONTAMINATION 16 X.3 VOLATILE ORGANIC CHEMICAL DISTRIBUTION 17 X.4 VARIATIONS OF GROUNDWATER CONTAMINATION MIGRATION 20 X.5 ELEVATED ARSENIC AND URANIUM IN SITE GROUNDWATER 20

XI. FINDINGS 22

XII. LIMITATIONS 24

XIII. REFERENCES 24

VOLUME I : APPENDIX A - TABLES

Table 1 On-Site Groundwater Data (Including trend graphs)

Table 1A On-Site Surface Water Data

Table 1B On-Site Sediment Data

Table 2 Geo-Probe Soil Data

Table 3 On-Site New Well Groundwater Data

Table 4 Well Redox Process Type Data

Table 5 Residential Well Chemical Data

Table 6 Interval Sampling At 31-33 Blueberry Hill Road Residential Well

Table 7 Residential Well Water Chemistry Type

Table 8 Quadrant Comparison Boxes

TABLE OF CONTENTS (continued)

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Figure 2 December 2009 Residential Water Quality Parameters

Figure 3 Topographic Map Of Mottolo Area

Figure 4 Well Cross Section A-A’ And B-B’ Lines

Figure 5 Well Cross Sections A-A’ And B-B’

Figure 6 Oxidation Reduction Potential, On-Site Overburden Wells

Figure 7 On-Site EPA Geo-Probe Locations

Figure 8 Historical Residential TCE Concentrations

Figure 9 Depth To Bedrock Map

Figure 10 On-Site Groundwater Elevation Contours In Overburden, August 2009

Figure 11 On-Site Groundwater Elevation Contours In Shallow Bedrock, August 2009

Figure 12 On-Site TCE Concentration Contours

Figure 13 On-Site Arsenic Concentration Contours

Figure 14 Oxidation Reduction Potential, On-Site Shallow Bedrock Wells

Figure 15 Residential Water Groups And Deep Bedrock Well Locations Map

Figure 16 TCE Concentrations Summary For All 2009 Sampling Events

Figure 17 Arsenic Concentrations Summary For All 2009 Sampling Events

Figure 18 Regional Groundwater Elevation Contours

Figure 19 Regional Bedrock Surface Elevation Contours

Figure 20 Residential Water Redox Process

Figure 21

Figure 22

Residential Water Type By Piper Diagrams

Conceptual Hydrogeologic Model of Site and Vicinity

VOLUME II : APPENDIX B - FIGURES

TABLE OF CONTENTS (continued)

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VOLUME III:

APPENDIX C THROUGH APPENDIX R

APPENDIX C NEW SITE WELL LOGS

APPENDIX D USGS FACT SHEET 051-03, JULY 1003, ARSENIC CONCENTRATIONS IN PRIVATE BEDROCK WELLS IN SOUTHEASTERN NEW HAMPSHIRE

APPENDIX E EPA GEO-PROBE INVESTIGATION DATA

APPENDIX F HAGER-RICHTER GEOPHYSICAL REPORT

APPENDIX G NHDES RESIDENTIAL WELL ANALYTICAL DATA

APPENDIX H NHDES ANALYTICAL DATA FOR NEW ON-SITE BEDROCK AND OVERBURDEN WELLS

APPENDIX I NHDES ANALYTICAL REPORT FOR 31-33 BLUEBERRY HILL ROAD WELL DEPTH INTERVAL SAMPLING

APPENDIX J NHDES ANALYTICAL REPORTS FOR SUMMER 2009 SITE MONITORING EVENT

APPENDIX K MICROSEEPS ANALYTICAL REPORTS FOR SUMMER 2009 SITE MONITORING EVENT

APPENDIX L MICROSEEPS ANALYTICAL REPORTS FOR NEW ON-SITE BEDROCK AND OVERBURDEN WELLS

APPENDIX M APPENDIX N APPENDIX O APPENDIX P APPENDIX Q APPENDIX R

GROUNDWATER PIPER PLOTS SAMPLING EQUIPMENT CERTIFICATIONS FIELD DATA MEASUREMENT FORMS COPY OF FIELD LOG BOOKS QUALITY ASSURANCE / QUALITY CONTROL EVALUATION SUPPLEMENTAL ARSENIC WATER QUALITY DISCUSSION

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LIST OF ACRONYMS USED IN REPORT

1,1 DCA 1,1 dichloroethane 1,2 DCE [total] 1,2 dichloroethene As [III] arsenite As [V] +5 arsenate ATV Acoustic Televiewer COC contaminant of concern DCE dichloroethene DNAPL dense non aqueous phase liquid DO dissolved oxygen EPA Environmental Protection Agency, Region I GZA GZA GeoEnvironmental, Inc. HACH 2100P Hach 2100 P Turbidity Meter Hager-Richter Hager-Richter GeoScience, Inc. HPFM MDL

Heat Pulse Flow Meter Method Reporting Limit

mg/L milligrams per liter Microseeps Microseeps, Inc. NA Natural attenuation NHB New Hampshire Boring, Inc. NHDES New Hampshire Department of Environmental Services ORP oxidation / reduction potential OTV Optical Televiewer ppb parts per billion ppm parts per million QA/QC quality assurance/quality control QED MP-20 RDL

QED MicroPurge Model MP20 multi parameter sonde Reporting Detection Limit

RI/FS Remedial Investigation/Feasibility Study RPD relative percent difference SAP Sampling and Analysis Plan TCA 1,1,1-trichlorethane TCE trichloroethene THF tetrahydrofuran TOC total organic carbon TSAs Technical System Audits U(VI) oxidized hexavalent form of uranium USGS United States Geological Survey VC vinyl chloride VOCs volatile organic compounds WSAs Work Scope Approvals

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ACKNOWLEDGEMENTS Special t hanks i s given t o t he r esidents of R aymond, N ew Hampshire who a ssisted t he site investigation a ctivities p erformed b y giving the New H ampshire D epartment o f Envi ronmental Services and G ZA G eoEnvironmental, I nc. access to their residential w ells / homes f or either drinking water sampl ing, geophysical logging, gr oundwater sampling, o r for m easuring t he groundwater level in their wells. Their pa rticipation in these ac tivities gre atly enhan ced the environmental knowledge acquired from the site investigation activities. Special t hanks are also gi ven to t he following organi zations who w orked w ith G ZA GeoEnvironmental, I nc. to hel p dev elop t he site investigation app roach and t o ass ist i n t he interpretation of the environmental data collected: US Environmental Protection Agency, Region I; New Hampshire Department of Environmental Services; United States Geological Survey; and New Hampshire Geological Survey.

I. EXECUTIVE SUMMARY

This supplemental data collection study of the Mottolo Superfund Site in Raymond, New Hampshire was funded by the Environmental Protection Agency, Region I (EPA) and by the New Hampshire Department of Environmental Services (NHDES). GZA GeoEnvironmental, Inc. (GZA) was contracted by NHDES to perform data collection activities to investigate off-site transport of trichloroethene (TCE) and mobilization of arsenic in fractured bedrock towards certain residential wells. The primary objective of GZA’s assignment was to manage specifically agreed upon data collection activities directed toward generating data for evaluating the migration of site related contaminants in the fractured bedrock toward certain impacted residential water supply wells. Activities performed include the installation of deep bedrock monitoring wells, geophysical logging of the new deep bedrock wells, sampling of residential wells, performing geophysical logging of a residential well, depth interval sampling of a contaminated residential well, measuring deep bedrock groundwater levels in site and residential wells, sampling groundwater of the site deep bedrock wells, and evaluating the collected data. The following summarizes the current findings of the investigative team’s work based on the work performed: Tricholorethene (TCE) / dichloroethene (DCE) contamination has migrated into the deep

bedrock groundwater in the area of the former drum disposal area on site;

Overburden and shallow bedrock TCE groundwater concentrations near the former disposal area and former piggery operation area are currently below detection limits (less than 2 parts per billion [ppb]). In addition, TCE concentrations detected in all other on-site overburden and shallow bedrock groundwater monitoring wells in August 2009 have decreased since the remedial investigation was performed indicating that past TCE source mass removal activities were successful in significantly decreasing contaminant mass beneath the site. It is anticipated that TCE concentrations in groundwater will continue to decrease over time;

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Overburden and shallow bedrock arsenic groundwater concentrations near the former disposal area and former piggery operation area are below detection limits (less than 1 ppb). In addition, the August 2009 data for all other overburden and shallow bedrock on-site monitoring wells shows a continuing general decreasing concentration trend for arsenic in groundwater. It is anticipated that arsenic concentrations in groundwater will continue to decrease over time;

The direction of groundwater flow in deep bedrock beneath the site is controlled by a complex network of fractures driven by natural hydraulic head gradients and likely influenced by pumping of area residential wells. Residential wells with detectable concentrations of site-related volatile organic compounds (VOCs) likely have water bearing fractures that are directly or indirectly connected to the Mottolo site bedrock fractures;

Soil testing indicates that the previous EPA remedy was successful in removing / treating the majority of VOC-contaminated soils in the former disposal area above the bedrock;

It is likely that residual contaminant mass persists proximate to the source area in overburden/shallow bedrock or deep bedrock and that this is the source of the low concentrations of VOCs that have been detected in bedrock water supplies;

Elevated arsenic concentrations in groundwater samples collected from certain residential wells on Windmere Drive and the down-gradient portions of Blueberry Hill Road is likely associated with Site related changes in groundwater geochemistry. This change is likely causing increased mobilization of arsenic above background levels that would otherwise not occur under natural conditions based on lines of evidence including the presence of the Site contaminant TCE in some of the wells and elevated pH levels. The Site related geochemistry groundwater conditions and along with elevated pH levels enhance the release of arsenic into the groundwater and result in greater concentrations of arsenic than would normally occur;

Historic disposal practices at the site that included chemicals, petroleum products and piggery wastes, created a reduced groundwater condition (i.e., low dissolved oxygen levels and low oxidation / reduction potential) that persists proximate to the source area and extends an unknown distance down gradient from the Site;

Elevated uranium concentrations detected in certain residential wells are likely associated with the presence of naturally occurring uranium in the granitic bedrock in the area (or could possibly be contained in the Berwick formation), and not related to the Site. This is based on the current body of evidence that includes no discernable link to Site-related contaminants in groundwater. Because the uranium is not related to the Site, it would not be a Superfund issue;

Residential well pumping adjacent to the western and southern site boundaries likely influences the direction of groundwater flow in certain fractures in the area;

Based on the declining trend of TCE concentrations in groundwater samples collected proximate to the source area, the residual organic material identified by the geoprobe soil investigation of the former disposal area is judged to have insufficient mass to have a significant impact on groundwater quality. Natural attenuation processes will continue to remediate this area; and

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The current arsenic groundwater concentrations in the Strawberry Lane area are currently similar to naturally occurring distributions of arsenic that are typical of southeastern New Hampshire. However, since TCE has been previously observed at 6 and 10 Strawberry Lane, it is possible that the geochemistry of the groundwater may have been and continues to be altered.

Further site characterization activities may be undertaken to further develop an understanding of the contaminant migration and arsenic dissolution processes in fractured bedrock beneath the site.

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II. REPORT INTRODUCTION AND BRIEF SITE BACKGROUND

Off-site groundwater contamination has been found in residential wells near the Mottolo Superfund Site. This report summarizes the results of an investigation to determine whether the contamination is related to the Site. This report presents a summary of the data results for the site investigation activities that were conducted during the period of March 2009 through January 2010 by NHDES, EPA and GZA at the Mottolo Superfund Site in Raymond, New Hampshire (Site). Authorization to proceed on this project was granted by NHDES in accordance with our proposed Work Scope and Budget Estimates dated July 8, 2009, October 26, 2009, and January 6, 2010 and NHDES’ Work Scope Approvals (WSAs) dated June 18, 2009 (WSA #1), July 9, 2009 (WSA #2), October 28, 2009 (WSA #3), and January 7, 2010 (WSA #4), respectively. The work was performed in general accordance with our Phase II NHDES Contract for Site Investigation - Remediation Design – Remedial Action Implementation contract. This report presents GZA's field observations, results, and opinions. This report is subject to modification if GZA or any other party obtains subsequent information. This report is subject to the Limitations presented in Section XII at the end of this report. The Site is located off Blueberry Hill Road in Raymond, New Hampshire (Figure 1 ). The Site, formerly used as a pig farm, is approximately 3 miles south of the Town of Raymond’s center and is surrounded by rural residential property, in various stages of development. The Mottolo property includes approximately 50 acres of primarily undeveloped, wooded land, divided roughly in half by a brook (Brook A), which originates beyond the southern property boundary and flows north through the property, eventually discharging to the Exeter River. Approximately 2 acres in the southwest portion of the property remain cleared near the former piggery and former disposal area. Site structures in and near the cleared area include two concrete pads for the former piggery buildings, a shed housing a boiler and former dug well which is mostly filled in currently. The Site is surrounded by private residences serviced by individual water supply wells. The Site was initially a pig farm (Balsam Environmental Consultants, Inc., 1990). From 1975 through 1979, over 1,600 drums and pails of chemical manufacturing wastes from two companies were disposed in a one quarter-acre depression referred to as the former disposal area. According to the Remedial Investigation/Feasibility Study (RI/FS) report, at least one tanker of liquid waste was known to be emptied in the same area.

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Evidence of leaking drums was reported to the State in 1979, and it was concluded that soil and groundwater beneath the Site were contaminated with primarily VOCs and aromatics, and that the contaminants were seeping into a brook that discharges to the Exeter River, located approximately one half mile to the north. Arsenic was also found to be present in groundwater and is the primary inorganic contaminant of concern (COC) at the Site. Between November 1980 and January 1982, the EPA performed a removal action including excavation, staging, testing, on-site storage, and off-site disposal of 1,600 containers of waste, and an estimated 160 tons of contaminated soil from the former disposal area located in the southern boundary area of the property. The Site was subsequently added to the National Priorities List in July 1987. A RI/FS was completed in March 1991. The COCs identified in the RI included the following: Groundwater: arsenic, 1,1 dichloroethane (1,1 DCA), 1,2 dichloroethene (1,2 DCE

[total]), ethylbenzene, tetrahydrofuran (THF), 1,1,1-trichlorethane (TCA), toluene, trichloroethylene (TCE), and vinyl chloride (VC);

Surface Water: 1,1 DCA and 1,2 DCE [total];

Sediment: 1,1 DCA and TCA; and

Soil: ethylbenzene, toluene, and xylene.

The RI found that exposure to on-site soils, air, sediments, and surface waters did not pose an unacceptable environmental or human health risk. However, the health risk from drinking on-site groundwater was determined to be above acceptable risk levels. Based on the removal action and RI/FS, the components of the remedy selected by EPA (and concurred in by NHDES), as described in the Record of Decision (March 1991), include the following: Institutional controls, including land use restrictions to limit site access and future

groundwater use/exposure;

Installation of a groundwater interceptor trench to dewater the former disposal area soils, two temporary soil caps over the former disposal area in the southern boundary area, and installation of a soil-vapor extraction system to remove VOC contaminants from the soils;

Natural attenuation (NA) of groundwater and surface water; and

Long-term sampling and evaluation of groundwater and surface water to assess compliance with cleanup levels through NA.

An in-situ vacuum extraction system (VES) was designed and built in 1993 to treat soil contamination within the former disposal area. After three years of operation, the VES system was shut down in the fall of 1996, and the soil cleanup deemed complete by EPA. In the spring of 1997, the VES cap was removed and the area was graded and seeded. The final VES closeout report was completed in 1997 and the Remedial Action was considered complete by EPA on June 28, 1998.

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In 2000, EPA decommissioned a number of wells, removed the chain link fence surrounding the Site, installed a new entry gate and modified the remaining wells. In the fall of 2001, the final components of the vacuum extraction system were removed, including the vacuum extraction wells and groundwater interceptor trench. Natural attenuation sampling began in 1993. Between 1993 and 1998 sampling varied from quarterly, to three times a year, and then to semi-annual monitoring events. Annual Sampling began in 1999 and consisted of sampling groundwater from the network of on-site monitoring wells (refer to the attached Figure 6). The residential well sampling program in 2003 was prompted by the development ongoing on Strawberry Lane at the time which coincided with the EPA 2003 5-year Superfund review. The expanded residential well sampling program in 2009 was a recommendation by EPA in 2008 (third 5-year Superfund review). The spring 2009 expanded residential well sampling performed in response to issues raised in EPA’s third 5-year review identified TCE contamination and elevated arsenic levels offsite in a number of residential wells located on Windmere Drive and Blueberry Hill Road on the west side of the Site. After the residential well sampling in March 2009, NHDES requested Cooperative Agreement funding from EPA to evaluate the potential off-site migration issues and to determine if modifications to the Site remedy are required to assure that the Site remedy will be protective of human health and the environment. To address the complex issues associated with the observed off-site migration, NHDES formed an inter-agency team of environmental experts (NHDES, EPA Region I, United States Geological Survey (USGS), and the New Hampshire Geological Survey), plus contracted with GZA to perform the investigations and analyze the collected data. The inter-agency team met periodically to discuss progress of the site investigation activities and to evaluate the data being collected. The Quality Control / Quality Assurance evaluation discussion is located in Appendix Q.

III. SUMMARY OF 2009 / EARLY 2010 SITE INVESTIGATIONS

Site-related investigations performed included the following activities and are discussed in this report: Site groundwater sampling event in August 2009 to sample the overburden and shallow

bedrock groundwater;

Installation of three deep bedrock wells on site to investigate potential migration direction of site contaminants;

Installation of one overburden well to investigate the potential for chlorinated chemical (TCE / DCE) vapor intrusion to occur downgradient in the homes on Windmere Drive and Blueberry Hill Road;

Sampling of the groundwater in the new deep bedrock wells and the new overburden well;

Quarterly NHDES residential drinking water sampling of homes surrounding the Site;

One round of residential well groundwater levels to calculate hydraulic head and estimate the direction of groundwater flow in the areas surrounding the Site;

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Geophysical logging of the three new deep bedrock wells installed on site;

Geophysical logging of the residential well at 31-33 Blueberry Hill Road in Raymond;

Vertical depth sampling of the residential well at 31-33 Blueberry Hill Road in Raymond; and

EPA Geo-Probe investigation for residual soil contamination in the former piggery building area and the former disposal area.

IV. SUMMER 2009 SITE MONITORING ROUND

In August 2009 GZA performed on-site field sampling activities in accordance with the August 6, 2009 approved Sampling and Analysis Plan (SAP). Multi-media sampling at the Site included sampling of Site overburden and shallow bedrock (less than 45-foot depth) groundwater, surface water and sediment in the brook that flows south to north through the property. The brook is referred to as ―Brook A‖. Prior to sampling, GZA conducted a comprehensive round of groundwater level measurements from on-site overburden and shallow bedrock monitoring wells to assess groundwater flow direction. Figure 6 shows the monitoring locations in the Site area. Prior to 2010, there were eleven overburden wells and twelve shallow bedrock wells (ten overburden wells are on site; one overburden well is on 4 Strawberry Lane property; ten shallow bedrock wells are on site; and two shallow bedrock wells are on 6 Strawberry Lane property). The groundwater samples were analyzed for VOCs, 1,4-Dioxane, arsenic, iron, ammonia, alkalinity, chloride, sulfate, TOC, carbon dioxide, methane, ethane, ethane, volatile fatty acids, ferrous iron, and nitrate. The brook surface water samples were analyzed for VOCs, arsenic, hardness and iron. The brook sediment samples were analyzed for arsenic and iron. Groundwater and surface water quality parameters turbidity, pH, DO, temperature, specific conductance, and oxidation / reduction potential were measured in the field. The collected multi-media samples were analyzed by NHDES’ laboratory with the exception of aqueous carbon dioxide, methane/ethane/ethene, and volatile fatty acids, ferrous iron and nitrate. Analysis of carbon dioxide, methane/ethane/ethene and volatile fatty acids was subcontracted by GZA to Microseeps, Inc. (Microseeps). The ferrous iron and nitrate were analyzed in the field using field test kits. The groundwater monitoring wells were purged and sampled using dedicated polyethylene tubing, and low flow methodology in accordance with the approved low flow sampling method using a peristaltic pump. The brook surface water was sampled using a peristaltic pump with the pump intake located at the mid-point of the stream depth. The brook sediment samples were taken using a ponar dredge device at the SW-2 and SW-3 brook locations. The brook bottom was too rocky for ponar dredge sediment sampling at the SW-1 brook location, so a stainless steel spoon was used to collect a brook sediment sample.

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V. SITE NEW WELL INSTALLATIONS AND SAMPLING

Three deep bedrock wells and one overburden well were installed on site. Figure 2 (December 2009 Res idential Water Quality Parameters) shows the locations of the four wells. The three deep bedrock wells are identified as MOT_MW-100D; MOT_MW-101D; and MOT_MW-102D. The overburden well MOT_MW-101S was originally located across from Windmere Drive; however, it was relocated across from 31-33 Blueberry Hill Road since no overburden groundwater was encountered across from Windmere Drive. The wells were installed by New Hampshire Boring, Inc. (NHB). The deep bedrock wells are 4-inch open boreholes. They were drilled by using an air rotary drill rig. A 5-inch-diameter steel casing was advanced from ground surface to bedrock surface. NHB then drilled a 5-inch-diameter borehole though the 5-inch casing approximately 5 feet to 20 feet into the bedrock (penetration into bedrock was determined based on competency of the bedrock). A 4-inch-diameter casing was advanced within the 5-inch casing approximately 5 feet to 20 feet into the bedrock surface. The 4-inch casing was grouted into place and the 5-inch casing was removed, allowing the grout to set up overnight at a minimum. Once the grout cured, drilling continued to advance the bedrock borehole with a 3 15/16 inch or smaller air rotary/air hammer bit to the target termination depth. The grouting was designed to limit cross contamination concerns from the overburden to the bedrock. A washtub was used to separate soil and rock cuttings from the water produced by the borehole. Drilling soil / rock cuttings were containerized in 55-gallon drums. All the drums were placed on the smaller concrete pad located in the former piggery operation area and will be stored until Spring 2010. The EPA mobile laboratory was on site for the drilling of deep bedrock wells MOT_MW-100D and MOT_MW-102D and performed laboratory screening for the VOC level in the water produced during drilling. When a high VOC level (52 ppb of TCE) was detected in the drilling water for MOT_MW-102D, drilling was stopped. A high VOC level was not detected in the drilling water for MOT_MW-100D. When well MOT_MW-101D was drilled, the drilling water was field screened for VOCs with a flame ionization detector targeting an action level of sustained readings of 5 parts per million (ppm) or greater. A high VOC level was not detected in the drilling water for MOT_MW-101D. The drilling water was discharged to the ground surface for all three deep bedrock wells. The overburden well MOT_MW-101S is a 2-inch groundwater monitoring well. It was drilled to the bedrock surface and a 10-foot well screen was installed. The well development water for all four wells was treated by carbon on site prior to release to the ground surface. The well depths for the four new drilled wells from ground surface are: Bedrock well MOT_MW-100D – 350 feet; Bedrock well MOT_MW-101D – 352.5 feet; Bedrock well MOT_MW-102D – 222.5 feet; and Overburden well MOT_MW-101S – 10.7 feet.

The installation well logs for the four new on-site wells are located in Appendix C.

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Each of the three deep bedrock wells were developed using a submersible pump removing a minimum of three well volumes of water from the well and allowed to recharge at least 80 percent of the pre-purge water level volume between purges. The purge water was treated by passing through activated carbon filters prior to discharge to the ground surface. The deep bedrock wells were sampled using a bladder pump immediately after the well was developed [and water level recovery reached ninety percent of the groundwater static level] so that the groundwater sampled was representative of the water in the bedrock formation. The intake of the bladder pump was placed at the mid-point of the water column and samples taken for VOCs, 1,4- Dioxane, total arsenic, arsenic III, iron, K, Mg, Na, Ca, U, Mn, dissolved arsenic, dissolved arsenic III, Bromide, ammonia, alkalinity (HCO3/CO3), chloride, sulfate, TOC, carbon dioxide, methane, ethane, ethane, volatile fatty acids, ferrous iron, and nitrate. Groundwater quality parameters turbidity, pH, DO, temperature, specific conductance, and ORP were measured in the field. The overburden well MOT_MW-101S was sampled using the low flow peristaltic pump method. The well was sampled for VOCs, total arsenic, and arsenic III. Groundwater quality parameters turbidity, pH, DO, temperature, specific conductance, and ORP were measured in the field.

VI. NHDES RESIDENTIAL WELL SAMPLING

NHDES conducted four residential well sampling events which were performed in March, June/July, September, and December 2009. See Table 5 (Residential Well Chemical Data) in Appendix A for a summary of which residential drinking water supplies were sampled and analytical results. In March, June/July, and September 2009, the selected residential drinking water supplies were sampled for VOCs and total arsenic. In the December 2009 sampling round, NHDES expanded the laboratory analysis list to VOCs, total arsenic, arsenic III, uranium, specific conductance, DO, pH, ferrous iron, ORP, alkalinity, calcium, TOC, chloride, total iron, manganese, magnesium, Bromide, nitrate, nitrite, potassium, sodium, and sulfate. These additional analyses were performed in December 2009 to characterize the chemistry of the groundwater and to facilitate the assessment of water chemistry issues enhancing the dissolving of arsenic from the bedrock into the groundwater. Consequently, Table 5 only lists the analytical results for those constituents historically analyzed. Chemistry-related data will be presented and discussed separately.

VII. GEOPHYSICAL WELL INVESTIGATIONS

Hager-Richter GeoScience, Inc. (Hager-Richter) performed geophysical logging of the three new on-site deep bedrock wells (MOT_MW-100D, MOT_MW-101D, and MOT_MW-102D) and the residential well at 31-33 Blueberry Hill Road. The geophysical logging consisted of 3-arm caliper, fluid temperature, fluid resistivity, OTV, ATV, and HPFM under ambient and stressed conditions. Hager-Richter used the following logging sequence and data acquisition parameters: LOGGING SEQUENCE AND DATA ACQUISITION PARAMETERS Log – Fluid Temperature; Fluid Resistivity, Fluid Conductivity

Sampling Interval - 0.05 feet Logging Rate - 7 - 10 feet/minute

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Logging Direction - Down and Repeat Up Log - 3-Arm Caliper to detect and measure fractures

Sampling Interval - 0.05 feet Logging Rate- 10 feet/minute Logging Direction - Up and Use Acoustic Caliper Data for quality assurance/quality control (QA/QC)

Log – Optical Televiewer (OTV) Sampling Interval - 0.01 feet Logging Rate - 6 feet/minute Logging Direction - Down and Use ATV Data for QA/QC

Log – Acoustic Televiewer (ATV) Sampling Interval - 0.01 feet Logging Rate - 6 - 8 feet/minute Logging Direction - Up and Repeat Down

Log – Heat Pulse Flow Meter (HPFM) - HPFM data was acquired at discrete depths for ambient and stressed conditions. The HPFM data provides information regarding the vertical flow rate and direction in the borehole at discrete depths in order to determine the depths where water is entering and leaving the borehole under ambient and stressed (pumping) conditions.

All of the above borehole logging was performed on wells MOT_MW-100D, MOT_MW-102D, and the residential well at 31-33 Blueberry Hill Road. All the borehole logging methods were performed on well MOT_MW-101D except for the HPFM logging. The HPFM was not performed on well MOT_MW-101D since it had a very low recharge rate (0.5 gallons per minute). The objectives of the Hager-Richter geophysical logging included collecting data regarding bedrock fracture characteristics encountered in the borehole including depth, dip azimuth, dip angle, strike, attitude, and relative water yielding characteristics. Collectively, the data would be used to further the development of the conceptual hydrogeologic model of groundwater flow and contaminant transport in the fractured bedrock beneath the site and vicinity, and to design future multi-level monitoring well installations within the open bedrock boreholes. The Hager-Richter geophysical logging results from the Site deep bedrock wells and the residential well at 31-33 Blueberry Hill Road are similar to the USGS geophysical logging results obtained from the six Strawberry Lane residential wells. The Hager-Richter report is included in Appendix F. The Hager-Richter report provides details on the geophysical data collected. These data were reviewed to provide insight to identification of the primary water bearing fracture zones within each borehole. GZA reviewed the data and developed our estimates of the primary water bearing fractures based upon fracture characteristics as evidenced by the caliper data, the azimuth and dip of fractures, and the HPFM information on water flow within the borehole. In general, the Hager-Richter data of fracture characteristics indicated a strong dip azimuth of northwesterly which is consistent with the primary fracture pattern of the area of having a northeasterly strike. This is expected and would also be consistent with a fracture pattern similar to the northeasterly trending Flint-Hill fault. Fractures were found to be relatively moderately dipping with a grouping for the most frequently observed dip angle between 30 and 75 degrees.

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Collectively, these data were used to identify which fractures are the primary water bearing fractures to each well to understand groundwater flow and contaminant migration characteristics in the study area. The following identify the primary water bearing fracture zones within each borehole tested.

No. Depth(feet) Dip Azimuth (degrees MN) Dip Angle (degrees) Strike

31-33 Blueberry Hill Rd 1 270 307 to 317 28 to 36 NE 2 285 79 to 90 27 to 29 N 3 292 93 24 N

100D 1 64 to 70 170 to 350 10 to 80 N to NE 2 274 to 279 multi multi Multi 101D 1 316 108 16 NE

102D 1 151 to 153 0 to 45 25 to 30 NW 2 196 282 to 307 10 to 30 N 3 208 299 30 N

The 31-33 Blueberry Hill Road residential well included fractures with a strong northwesterly dip azimuth with the majority of fractures dipping between 45 and 75 degrees. As indicated above, the primary water bearing fractures had a strike of northerly to northeasterly. Well MOT_MW-100D included fractures with a strong northwesterly dip azimuth with a bimodal dip distribution with a group of shallow dipping fractures and a group of steeply dipping fractures. The water-bearing fractures identified from the data for this well were consistent with these general trends. Well MOT_MW-101D included fractures with a strong northwesterly dip azimuth that are generally steeply dipping. This well did not include the HPFM testing so the estimate of the water bearing zone for this well was based on the collective evaluation of the other geophysical data and is not considered as confident as the other wells tested. Well MOT_MW-102D included a strong northwesterly dip azimuth with generally more scatter of the dip azimuth orientation compared to the other wells tested. There was also a broad range of dip angles ranging with the most frequent observations ranging from 15 to 75 degrees. The borehole geophysical data collected by Hager-Richter during this study was compared to previously collected borehole geophysical data by USGS for six residential wells along Strawberry Lane in 2004 (USGS report dated January 26, 2004 ―Borehole-geophysical logging Strawberry Lane, Raymond, New Hampshire‖). The USGS report identifies the primary water bearing fractures of the six wells evaluated. The dip azimuth of the water bearing fractures were identified as generally consistent with a northeasterly or north westerly fracture strike which is consistent with the general conceptual model of fracture fabric for the site vicinity. The USGS data also appears similar to the Hager-Richter data collected during this current study by identifying generally few discrete water bearing fractures in each well with dip azimuth orientations consistent with the regional fracture fabric.

VIII. EPA GEO-PROBE SOIL INVESTIGATION

In October 2009 EPA Remedial Response Group conducted a Geo-Probe soil sampling effort to investigate the potential for residual soil contamination in the former disposal area, in the former piggery operation area, and in the sloped downhill area near the larger concrete pad. Figure 7 (Geo-Probe Sampling Locations) in Appendix B shows the sampling locations. EPA utilized its mobile screening laboratory to provide real-time field screening results which were used to guide

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a phased sampling approach to determine subsequent sampling locations. The analytical data shown in Table 2 (Geo-Probe Soil Data) is EPA laboratory results for duplicate samples selected based on the analytical results obtained by the EPA mobile screening laboratory. Soil samples were analyzed for VOCs, aluminum, antimony, arsenic, barium, beryllium, cadmium, calcium, chromium, cobalt, total iron, lead, magnesium, manganese, nickel, vanadium, and zinc. The Geo-Probe used to collect soil cores at the Mottolo Site was a track-mounted 5400DT Geo-Probe capable of sampling to depths of 70 feet or more depending upon site conditions. The Geo-Probe uses a hydraulic hammer to push the tooling equipment into the ground. MC5 core tooling was used to collect the samples at continuous depths until refusal.

IX. DATA ANALYSIS

IX.1 ON-SITE 2009 DATA ANALYSIS

The ORP is a measurement of the potential to oxidize contaminants. Healthy surface water aquatic environments generally are 300 to 390 mV ORP. However, in wetland environments the ORP can naturally be depressed below 200 mV as generally wetlands contain a significant amount of organic matter which can use up a significant portion of the available oxygen. The presence of contaminants which can degrade under aerobic conditions can lower the ORP further. Lower ORP values and higher pH values indicate a more reduced environment which can facilitate the release of arsenic from the soils or bedrock if it is present. Figure 6 (Oxidation Reduction Potential, On-Site Overburden Wells) and Figure 14 (Oxidation Reduction Potential, On-Site Shallow Bedrock Wells) summarize the ORP measurements recorded during the August 2009 on-site sampling event. The ORP measurements in the overburden groundwater and the shallow bedrock groundwater have been similar with ORP reading between minus 216 mV and 164 mV. The ORP measurements indicate the overburden and shallow bedrock groundwater (maximum 45 feet deep) detected in site monitoring wells have a reductive water chemistry, as will be further illustrated in Section X, Conceptual Site Model And Geological Setting. The ORP readings of the deep bedrock wells located on Site indicate generally reducing conditions and the presence of the TCE breakdown product 1,2-Dichloroethene (161 ppb, Table 3 – On-Site New Well G roundwater D ata) in the on-site MOT_MW-102D deep bedrock well is evidence of reductive dechlorination of the contaminant TCE. 1,2-Dichloroethene is also present in a number of off-site residential wells but at significantly reduced concentration levels (0.6 – 3.3 ppb, Table 5). Figure 10 (On-Site Groundwater Elevation C ontours i n O verburden, August 2009 ) and Figure 11 (On-Site Groundwater Elevation Contours in Shallow Bedrock, August 2009) indicate that both the overburden groundwater and the shallow bedrock groundwater flows to the northeast to Brook A and then flows in a more northerly direction following the flow of Brook A. These data suggests that the overburden and shallow bedrock groundwater appear hydrologically connected and with similar flow directions. Figure 12 (On-Site TCE C oncentration Contours) shows the TCE overburden and shallow bedrock groundwater concentrations detected above 0.5 ppb in the August 2009 sampling event. TCE groundwater concentrations near the former disposal area and former piggery operation area are below detection (less than 2 parts ppb). The August 2009 data for the on-site wells shows a continuing general decreasing concentration trend. Well MOT_MW-21D which is just across from the site on the property of 6 Strawberry Lane has decreased from 440 ppb in September

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1992 to less than 2 ppb in August 2009. Well MOT_MW-8S located near the smaller concrete pad has decreased from a high of 210 ppb in July 1994 to less than 2 ppb in August 2009. TCE concentrations in the overburden / shallow bedrock groundwater that were detected in August 2009 are downgradient in the area just prior to Brook A. Detected concentrations vary between 5 and 119 ppb. Although well MOT_OW-2DR had 119 ppb of TCE in August 2009, it represents a decrease from its high TCE concentration of 280 ppb in April 2000. Historical TCE concentration data in groundwater are shown in Table 1 (On-Site Groundwater Data). Table 1A (On-Site Surface Water Data) and Table 1B (One-Site Sediment Data) contain the on-site surface water and sediment data, respectively. Historically, the TCE concentrations in on-site groundwater are significantly decreasing indicating that the contamination source mass has been significantly reduced. This decreasing concentration trend is shown on the TCE concentration trend graph contained the report section for Table 1. The reducing conditions present in the Site groundwater favor the degradation of TCE to cis-DCE and to trans-DCE. The cis-DCE can potentially further degrade in aerobic conditions further increasing the reducing conditions of the groundwater. No contamination was detected in samples collected from the on-site surface water or sediment. Figure 13 (On-Site Arsenic Concentration C ontours) shows the arsenic concentration in overburden and shallow bedrock groundwater from the August 2009 sampling event. Arsenic groundwater concentrations near the former disposal area and former piggery operation area are below detection (less than 1 ppb). The August 2009 data for the on-site wells shows a continuing general decreasing concentration trend. Well MOT_OW-4SR located downgradient of the concrete pads has decreased from a high of 33 ppb in July 1994 to 1 ppb in August 2009. Arsenic concentrations in the overburden / shallow bedrock groundwater that were detected in August 2009 are downgradient of the former disposal area just prior to Brook A (in the same area as the detected TCE concentrations). Historical arsenic groundwater concentration data are shown in Table 1. The elevated levels of arsenic in the on-site overburden / shallow bedrock groundwater occur in the same monitoring wells where elevated levels of TCE are present (see Figures 12 and 13). This may indicate that the contaminated groundwater chemistry is enhancing the release of arsenic from the ground soils / bedrock. Table 2 summarizes the chemical concentrations measured during the October 2009 Geo-Probe soil investigation. Figure 7 shows the on-site Geo-Probe sampling locations. Soil samples were collected in the former disposal area, in the concrete pad area, in the access road area, and in the slope area behind the concrete pads. The only area where VOCs were detected was sampling location number SB 16 in the former disposal area where a thin organic soil layer was encountered. A more focused sampling grid was established in the elevated VOC concentration area, see insert shown in Figure 7 . The elevated VOC concentration area was estimated to be approximately 6 feet wide and 10 feet long (and was located at a depth of approximately 5 to 6 feet below the surface of the ground). TCA was detected at a concentration of 20,000 ppb at one sample location in the thin organic layer (NHDES Soil Remediation Standard is 78,000 ppb). TCE was detected at 5 sampling locations in the organic layer with concentrations ranging from 150 to less than 13,000 ppb (NHDES Soil Remediation Standard is 800 ppb). Cis-1,2-Dichloroethene was detected at 5 sampling locations in the organic layer with concentrations ranging from less than 38 to less than 13,000 ppb (NHDES Soil Remediation Standard is 2,000 ppb). Other organic chemicals detected in the thin organic layer were petroleum-related chemicals (1,2,4-Trimethylbenzene, Ethylbenzene, m/p-xylene, o-xylene, and toluene). Arsenic was detected in 7 of the 37 Geo-Probe soil samples from the former disposal area from 6.8 to 83 ppm (NHDES Soil Remediation Standard is 11 ppm). Lead was detected above standard at 2 of the 37 samples from the former disposal area ranging from 420 to 530 ppm (NHDES Soil Remediation Standard is 400 ppm). The only other metal detected above standard was Beryllium

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and it was detected in1 of the 37 samples from the former disposal area ranging at 1.4 ppm (NHDES Soil Remediation Standard is 1 ppm). IX.2 AREA 2009 DATA ANALYSIS

Figure 1 5 (Residential W ater G roups) in Appendix B provides a color coding of areas surrounding the Site which facilitates data analysis. Within each group, the residential well water has similar characteristics as to whether the presence of arsenic or uranium appears to be prevalent or not. The grouping simplifies the discussion of the residential well sampling performed by NHDES. There are four groupings of residential wells plus the Site. The Western Group consists of the residential wells in Windmere Drive and Blueberry Hill Road areas. The Northern Group consists of residential wells north of the Site. The Eastern Group is comprised of wells east and south of the Site which had similar water chemistry. The Southern Group consists of the residential wells south of the Site on Blueberry Hill Road and Strawberry Lane which had similar water chemistry. Figure 2 (December 2009 Resi dential W ater Q uality Parameters) located in Appendix B summarizes the water quality information of the residential and deep bedrock Site wells. Uranium is prevalent in residential wells to the east of the Site and in the eastern portion of Strawberry Lane. Arsenic is prevalent in the wells to the west of the Site and to a lesser degree, in the western portion of Strawberry Lane. The lowest concentrations of arsenic and uranium exist to the north. The majority of the wells to the east of the Site contain elevated levels of uranium above the drinking water standard of 30 ppb. The majority of the wells to the west of the Site contain elevated levels of arsenic above the drinking water standard of 10 ppb. Residential wells in the Southern Group have a mix of low arsenic and elevated arsenic levels. Groundwater samples collected from the Site wells contain both arsenic and uranium in the groundwater. Uranium concentration (87 ppb) in well MOT_MW-101D was above the drinking water standard of 30 ppb. The arsenic concentration (25.2 ppb) in well MOT_MW-102D was above the drinking water standard of 10 ppb. In well MOT_MW-100D neither uranium nor arsenic was above drinking water standards. Figure 16 (TCE Concentrations Summary for all 2009 Sam pling Eve nts) is a color-coded drawing showing the detection of TCE in residential wells in the majority of the Western Group. TCE was detected in the on-site deep bedrock well MOT_MW-102D (source area) at a concentration of 41 ppb. TCE was not detected in MOT_MW-100D and MOT_MW-101D (except below the laboratory reporting limit) which indicates that the pathway for TCE to migrate to the residential wells in the Western Group is most likely within fractures that are not intersected by MOT_MW_100D or 101D. TCE was not detected in the residential wells in the Northern Group, Eastern Group or the Southern Group (except below the laboratory reporting limit). Figure 17 (Arsenic Concentrations Summary for all 2009 Sampling Events) shows a color-coded drawing showing the detection of arsenic in residential wells. Most of the wells in the Western Group have arsenic above the drinking water standard. Arsenic was detected in the on-site deep bedrock well MOT_MW-102D (former drum disposal area) at a concentration of 25.2 ppb. Arsenic was generally not detected in groundwater samples collected from the Eastern Group. The Northern Group has only a few wells above the arsenic standard. The Southern Group has a mixture of wells above and below the arsenic drinking water standard of 10 ppb. Figure 18 (Groundwater Level E levation C ontours) shows the estimated bulk groundwater elevation contours for the deep bedrock and is provided as a conceptual indication of the bulk

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groundwater flow pattern in the site area. Based upon the contours, the bulk groundwater in the deep bedrock flows in a western / northwestern direction consistent with the overall trends in surface topography. Groundwater flow in bedrock is controlled by bedrock fractures under the influence of hydraulic head gradients. The direction of groundwater flow beneath the site is based on the orientation of specific fractures and may contradict the direction of groundwater flow in the deep bedrock indicated on Figure 18. The deep bedrock groundwater within specific fractures is also very likely influenced by near-by residential well pumping. The current data set does not provide clear indication of specific influences from residential pumping but certain water quality trends indicate a potential influence of pumping from the south (Strawberry Lane) and from the west (Windemere Drive). As indicated above, the bulk deep bedrock groundwater flow from the Site is generally toward the west / northwest. Due to historic detections of TCE in certain Strawberry Lane residential wells, site groundwater flow to the south in the past (USEPA Remedial Investigation Report, 1990) was probably due to residential well pumping along Strawberry Lane. Recent detections of TCE in water samples collected from certain residential wells in the Windmere Drive area (Western Grouping of wells) indicates that residential well pumping is likely pulling site groundwater in the west / northwestern direction within specific fractures. Flow of site groundwater within certain fractures could likely re-occur to the south if the residential wells in the Windmere Drive area were no longer used. If no residential well pumping was to occur west and south of the Site, the flow direction of groundwater from the Site would be likely to be in a northern direction. Due to the strong hydraulic gradient toward the west, flow of Site groundwater would not be expected to flow toward the east (Blake Road area). The lack of data does not currently allow an assessment of the potential of residential wells along Blake Road (east of the Site) to draw contaminated water to the east if residential wells on the western and southern side of the Site were not used. Figure 20 (Residential W ater Redo x Process) located in Appendix B shows the estimated prevalent ORP process water chemistry that was determined for each sampled well using the USGS model (USGS Fact Sheet 2009/3041, June 2009) developed for estimating the type of groundwater ORP process. The figure shows a wide variation in the ORP processes determined. Table 4 (Well Redox Process Type Data) lists the ORP process for each well based on the water chemistry parameters. The Western Group residential wells seem to contain a significant number of wells which have an anaerobic ORP process chemistry compared to the other areas. The anaerobic ORP chemistry promotes the release of naturally occurring arsenic from the bedrock into the groundwater. Figure 21 (Residential Water Type By Piper Diagrams) shows the water chemistry type for each deep bedrock well sampled. The Piper Diagrams are located in Appendix M. Although the findings were inconclusive, it appears that the chemistry type of the groundwater in the on-site well MOT_MW_102D (deep bedrock well nearest the former disposal area, MOT_MW-102D) is similar to chemistry type that is fairly prevalent in the Western Group residential wells (calcium bicarbonate chemistry).

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Table 6 (Interval Sam pling At 31-33 Blue berry Hill Road ) lists the analytical results from January 2010 sampling the groundwater using a low flow bladder pump at the depth intervals at 100 feet (from top of casing), 269 feet, and 284 feet from residential well MOT_DW-13 (31-33 Blueberry Hill Road). Geophysical logging indicated that the majority of groundwater entering the well was flowing from the fractures located at approximately 285 feet. The data indicates that TCE is entering the well at 285 feet at a concentration of 8.2 ppb. The fractures at 285 feet appear to be providing the majority of the water so the TCE concentration remains close to 8 ppb throughout the well. The observed orientations of the fractures at 285 feet have a dip azimuth of 79 to 90 degrees magnetic north and a dip angle of 27 to 29 degrees. The strike of this fracture set is at a general north-south orientation. Table 8 (Quadrant Comparison Boxes) is a statistical method to examine differences in arsenic concentrations above detection levels for residential wells in designated groupings. The observed difference is a function of a geochemical redox plume generated from the Site. For example, in the quadrant comparison box shown below, 83.3 percent of the wells in the Western Group that exceed the arsenic drinking water standard have a pH greater than or equal to 7.4. This condition is not true in the Southern Group as the percentage is zero.

5 0

6 3

1.94 x na x

3 4

7 8

pH ≥ 7.4 83.3% na x

Western Group Southern Group

pH < 7.4 42.9% x 50.0%

0.0%

0.9

In the quadrant comparison box shown below, 77.8 percent of the wells in the Western Group that exceed the arsenic drinking water standard have a DO level less than or equal to 1.2. This condition in the Southern Group is only 25 percent.

6 1

8 4

3.11 x 0.58 x

2 3

5 742.9%0.6 x25.0%DO > 1.2

Western Group Southern Group

x 25.0%DO ≤ 1.2 77.8% 3.1

Additional quadrant comparison boxes are presented in Table 8 . Comparisons between the different groupings of wells, as illustrated in Figure 15 , do not indicate a condition of high

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percentage of wells exceeding the arsenic drinking water standard except for the Western Group. This type of analysis indicates that it is likely that the chemistry of the groundwater in the Western Group wells is being influenced by the chemistry of the Site groundwater. In this case, the analysis indicates that the reduced groundwater condition is likely creating elevated arsenic concentrations. USGS research discussed earlier in the report has shown that in the Berwick bedrock formation and the ―main‖ Berwick, unnamed member bedrock formation the normal occurrence of high arsenic levels in the groundwater would be approximately 7 to 31 percent, respectively. The percentage of wells in the Western Group exceeding arsenic drinking water standard is shown to be much higher in the quadrant comparison boxes. The quadrant comparison boxes show that the arsenic concentration in the Western Group of residential wells are higher than normally expected based on the USGS studies referenced earlier in this report. The presence of the site contaminant TCE in the Western Group area and similarities in the reductive nature of the groundwater are strong lines of evidence that Site groundwater conditions are causing an increase in arsenic release in the Western Group area resulting in elevated arsenic concentrations in the residential wells. Figure 9 (Depth to Bedrock Map) located in Appendix B shows the interpreted bedrock surface of the Site area. The map was created using available water well data, bedrock outcrops from UNH mapping, borehole data from NHDES files, and Department of Transportation borings (i.e., not all data points are shown, just water wells ). The darker shading indicates deeper overburden deposits residing over the bedrock, while the lighter color indicates shallower deposits of overburden on top of the bedrock. The map is shown with a 2-foot contour interval and all depths to bedrock are reported to the nearest foot. The figure shows that the potential flow of contamination along the bedrock surface from the former drum disposal area (prior to encountering fractures in the bedrock) would have potentially been toward the south toward Strawberry Lane and also north then west toward the 31-33 Blueberry Hill Road / Windmere Drive area. Figure 19 (Bedrock Surface Elevation C ontours) shows similar bedrock surface characteristics and is focused on the site area.

X. CONCEPTUAL SITE MODEL AND GEOLOGICAL SETTING

The conceptual model presented herein is a modification of previously developed conceptual models for the Site and is intended to advance the understanding of contaminant migration in the deep bedrock beneath the Site and the distribution of site related contamination and naturally occurring arsenic and uranium. This section serves as a general presentation of findings of the supplemental data collection activities performed and use of existing information. Figure 22 in Appendix B was developed as a conceptual picture guide to understanding the Site geological features and contaminant transport issues discussed below. The discussion of the conceptual model also reflects input from the USGS following our collective review and interpretation of site data. X.1 ENVIRONMENTAL SETTING

The Site is located on Blueberry Hill Road in Raymond, New Hampshire (Figure 1 ). The Mottolo property includes approximately 50 acres of primarily undeveloped wooded land, roughly divided in half by a small brook and associated wetlands. About 2 acres in the southwest part of the property remain cleared near the former piggery and the hazardous-waste-removal operations. Site structures in and near the cleared area include two concrete pads for the former

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piggery building, a shed housing a boiler, and a dug well of unknown depth and construction. The Site is surrounded by private residences each with its own water supply well. The Site is within the Exeter River drainage basin. The Exeter River is approximately 1,500 feet west of the Site boundary at its closest point. Brook A is a perennial stream that flows north across the Mottolo property, draining approximately 285 acres at its confluence with the Exeter River (north of the map area on Figure 1). An ephemeral stream drains approximately four acres of the undeveloped woodland between the cleared portion of the Site, Blueberry Hill Road, and Strawberry Lane. Runoff in the ephemeral stream flows south to north into Brook A. A drainage swale crosses the site from west to east, just north of the former disposal area, and also discharges to Brook A. Figure 3 (Topographic Features) located in Appendix B shows the Site in relation to the topographic features of the ground surface. The surface topography in the former disposal area slopes downward to the north and the northeast toward Brook A which is consistent with the overburden and shallow bedrock groundwater flow. Figure 4 (Well Cross Se ction Li nes) and Figure 5 (Well C ross Sections) located in Appendix B shows the relative bedrock surfaces observed based on well logs. In Figure 5, cross-section A – A’ indicates the potential for past contamination migration from the former disposal area (location of well MOT_MW-102D) along the surface of the bedrock (prior to seepage into bedrock fractures) is into the page following the depression shown. Cross-section B – B’ indicates a low potential for past contamination migration from the former disposal area (location of well MOT_MW-102D) along the surface of the bedrock to the east due to the presence of the depression represented by Brook A and the rise of the bedrock surface elevation east of Brook A. The 1999 RI/FS report states the geology of the Site is generally characterized by glacial till and outwash deposits (overburden) overlying bedrock. The till consists of unsorted to poorly sorted mixtures of clay, silt, sand, cobbles, and boulders, and may contain some gravel (Gephart, 1987). Exceptions to this are stratified glaciolacustrine deposits consisting of boulders, cobbles, sand and silt, and more recent swamp deposits consisting of muck, peat, silt, sand and minor clay which are mapped along the Exeter River and along Brook A to a point approximately 1,000 feet south of the Exeter River. The bedrock consists of Berwick Formation schists intruded by Devonian-age granites and a few pegmatite dikes (Peters and others, 2006, Freedman, 1950, 2002, Utsunomiya and others, 2003). These lithologies are bounded three miles to the northwest by the Flint Hill Fault, and nine miles to the southeast by Devonian-age plutons (Hussey, 1985). Both structural margins trend northeast, with secondary structural trends present throughout the region. Bedrock core samples previously collected at the site have been observed to be consistent with the Berwick Formation with granitic intrusions. Bedrock core samples have been described as gray, fine to medium grained composed of biotite, feldspar, and quartz with lenses of calc-silicate rich rock. Pink to gray granite was also observed in rock cores. The area bedrock has been deformed and faulted resulting in a predominant northeast-southwest fault and joint orientation and a secondary southeast-northwest joint orientation. Precipitation that infiltrates the soil, and is not lost to evapo-transpiration or replenishment of soil moisture, percolates downward to recharge groundwater. Depending upon topography, the permeability of the soil and underlying bedrock, and the amount of precipitation, the groundwater table may exist within the soil and/or bedrock. Groundwater within the overburden would, in part, flow laterally within overburden sediments from higher elevations to lower elevations, discharging as surface water in the valleys. Groundwater within the overburden also tends to percolate downward into fractures and joints, where present, at the soil/bedrock interface.

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The flow of water through the bedrock is controlled by the frequency and nature of fractures within the bedrock. Water entering bedrock through fractures of higher elevations flows laterally and vertically downward through the bedrock and may discharge from fractures at lower elevations to the overburden and contribute to surface water flow in the valleys. Because groundwater flows from higher elevations (e.g., ridges) to lower elevations (e.g., valleys), the groundwater flow regime generally coincides with surface water drainage basins. Groundwater flow in bedrock is fractured controlled influenced by potentiometric heads influenced by variations in topography. With respect to the conceptual hydrogeologic model, three principal flow systems can be described within the Mottolo study area. Due to the moderate topographic relief, shallow depth to bedrock, the fractured nature of the bedrock, and the limited saturated thickness of overburden material, local groundwater flow systems will develop in overburden and upper bedrock with discharge ultimately to Brook A. Beneath the local flow systems, an intermediate groundwater flow system likely exists within the weathered upper bedrock and moderately fractured bedrock such that on a larger scale, consistent with the study area, groundwater in joints and fractures flows toward and into the Brook A valley, and ultimately flows toward the Exeter River located to the north of the site. This intermediate groundwater flow system is expected to exist in bedrock beneath the local groundwater flow systems located within the study area, including the Mottolo site. Beneath the intermediate flow system, groundwater migration in deeper bedrock is controlled by the secondary porosity of bedrock fractures and joints. Based upon previously performed geologic studies, the dominant trends of fractures and joints in the study area include a primary north-east/south-west orientation and a secondary trend of north-west/south-east. It is anticipated that the majority of bulk groundwater flow in the deeper unit would be controlled by these two dominant orientations. X.2 NATURE AND EXTENT OF SOURCE AREA CONTAMINATION

Based upon a review of data collected during the remedial investigation (RI) conducted prior to 1999, two source areas of contamination previously existed. An area of contaminated soils approximately 150 feet by 75 feet in the former disposal area was the most significant source area contributing to groundwater contamination identified during the RI as a result of previous waste disposal activities. The piggery operation area was identified as a second potential source area west of the piggery building in the vicinity of a large concrete pad where overburden and bedrock groundwater contamination was identified. The specific source of contamination in the piggery operation area was never identified and no detectable concentrations were detected in samples collected from this area from recent Geoprobe explorations. Historical site data indicate that volatile organic compounds were previously identified as the contaminants present at the most significant concentrations in soils, sediments, groundwater and surface water. The greatest concentrations of VOCs detected in soils were found at or above the water table in the former disposal area and included aromatic hydrocarbons (toluene, xylenes, and ethylbenzene), chlorinated VOCs (trichloroethene, methylene chloride, and tetrachloroethene), and the ketone acetone. Of the VOCs, toluene, ethylbenzene, xylenes, and methylene chloride were generally reported at the greatest concentrations (greater than 1 ppm). Based on the available data, there appears to be a subtle bedrock surface high, or "ridge" that transects the northeast section of the Mottolo Site. The ridge trends northwest, and is highlighted by the black line with arrows along its axis shown on Figure 9. The slope of the bedrock surface underlying

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the former drum site dips toward the northeast into a subtle basin that includes Brook A. It is presumed that TCE contaminant mass migrated downward through overburden materials to the bedrock surface as a dense non aqueous phase liquid (DNAPL). Since TCE is heavier than water, the TCE mass would migrate downward in response to gravity through overburden soils and groundwater, traveling along the top of the bedrock surface in an easterly direction in response to the slope of the bedrock and infiltrating into the fractured bedrock. TCE mass would migrate further into the deep bedrock following preferential pathways of the fracture system. Dissolved TCE in groundwater would migrate through the preferential fracture system in response to the hydraulic gradients within specific fractures. The slope of the bedrock surface and location of shallow bedrock fractures in the weathered zone provides a dominant influence on DNAPL migration proximate to the source area. In deeper bedrock the interconnected fractures associated with the structural bedrock fabric of the area controls the movement of contaminants from the source area. The borehole geophysical logs presented in this report indicate a general competent bedrock with limited and isolated fractures. The geophysical data indicates a dominant northeast-southwest striking, and westerly dipping fracture pattern for the area. Steel casings installed in domestic wells and the monitoring wells installed during this study specifically are intended to seal the well into competent rock to bypass the effects of near-surface weathered rock. The geophysical logs do not provide information on the potential fractures in the upper weathered bedrock due to the presence of the steel casing. X.3 VOLATILE ORGANIC CHEMICAL DISTRIBUTION

VOCs have historically been the most common contaminant associated with previous waste disposal practices at the Site. VOCs initially detected at the Site during the remedial investigation have included the aromatic compounds toluene, ethylbenzene, and xylenes and chlorinated hydrocarbons VC, 1,2-DCE, TCE, and 1,1,1-TCA, and THF. Historical overburden and shallow bedrock groundwater quality data indicate that the contaminants migrate in the predominantly east from the former disposal area discharging to Brook A in the general vicinity of surface water monitoring location SW-2. Contaminant concentrations in the surface water of the brook were not detected after September 1998. The distribution of VOCs in deep bedrock has been the focus of this present study due to the detection of TCE in certain residential drinking water wells in the Site vicinity. The conceptual model of VOC migration in the deep bedrock is based on the anticipated fractured controlled flow in the bedrock formation. In general, bulk groundwater flow in the deep bedrock is driven by the hydraulic gradients of the site area (flow from high to low hydraulic head), and flowing within bedrock fractures. Groundwater flow within fractured bedrock is very complex with flow following specific fractures with varying orientations, dip angles, and aperture size, driven by the local hydraulic gradient. The direction of groundwater flow can be extremely variable within the bedrock in localized areas and inconsistent with the average hydraulic gradients. Based on previously performed bedrock characterization work at the Site, the deep bedrock groundwater flow is anticipated to predominantly flow along the preferential fractures in the area consistent with the primary northeast-southwest and secondary northwest-southeast fracture sets of the area (see conceptual diagram below). Therefore, VOC-contaminated groundwater in the deep bedrock would likely tend to migrate from the former source area in a general northerly direction (from high to low hydraulic head), following preferential bedrock fractures of various orientations that may be different than the average bulk groundwater flow. Residential drinking water wells that have detectable concentrations of site related VOCs, obtain water from fractures that are connected to the fracture system associated with the contaminant plume emanating from the Mottolo source area.

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Conceptual Diagram of Bedrock Fracture Transport

Based upon the studies conducted in 2009, the primary source for contaminants detected in groundwater at the Mottolo site is likely residual contaminant mass remaining in subsurface soils and or bedrock. Groundwater quality data collected during the monitoring program indicate a general decreasing trend in dissolved VOC concentrations downgradient of the source area. It is likely that residual contaminant mass exists in the subsurface soils or bedrock proximate to the source area that contributes to the low concentrations that persist in groundwater beneath the Site. In general, the extent of groundwater contamination appears to be governed by advective groundwater transport through the overburden and fractures in bedrock. As such, the southern and eastern boundaries of the shallow contaminated groundwater plume originating from the former disposal area appeared to be well defined. Dispersion also influences the spreading of the VOC plume to the north in both the overburden and shallow bedrock on the west side of Brook A. Diffusion processes also are anticipated to contribute to contamination distribution and the influence of diffusion processes are most likely dampened by the fracture controlled groundwater flow. Diffusion processes would be anticipated to have the greatest influence the closer to the source area where the concentration gradients are the highest. Data indicate that VOCs in overburden and shallow bedrock groundwater ultimately discharge to the Brook A area where they volatilize and dilute to non-detectable levels over a distance of a few hundred feet. Since the drums were removed in 1980 and no other source has been identified, it is likely that desorptive processes are currently occurring across the site in residually contaminated soils and in the deep bedrock. A comparison of historic groundwater quality analytical data collected indicated that contaminant concentrations have decreased in surface water and groundwater throughout this period. VOC concentration reduction factors between 2 and 20 indicate that impacts of the Mottolo Site on groundwater quality have declined with time and are likely to continue to do so in the future. Anaerobic TCE biodegradation occurs by reductive dechlorination (see below diagram), a reaction in which hydrogen atoms sequentially replace chlorine substituents. In the commonly observed TCE transformation pathway, TCE is sequentially reduced to DCE, VC, and ethene. Because VC is a potent human carcinogen, its formation and persistence in groundwater are of

Primary Northeast-Southwest Preferential Fractures

Secondary Northwest-Southeast Fractures

Source

Groundwater Flow

31-33 Blueberry Hill Rd Well

Strawberry Lane

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concern at many TCE-contaminated sites. Vinyl chloride has been detected in on-site wells MOT_MO-3SR, MOT_MO-3DR, and MOT_OW-2DR for the majority of monitoring rounds since 2004. It was also detected in MOT_MO-2DR once during the Spring 2004 monitoring round. There were no detections of VC in any of the on-site wells installed in December 2009 / January 2010. There were no detections in residential wells in any of the sampling rounds (detection limit of 0.5 ppb). During the operation of the pig farm and for some unknown length of time following, elevated concentrations of TCE / DCE, pig waste and petroleum contamination very likely created a total organic loading of the Site groundwater sufficient to result in changes to the Site’s groundwater geochemistry. It is expected that the total organic loading created a reductive chemistry environment in the groundwater by creating a low dissolved oxygen level which would have enhanced the dechlorination degradation of the TCE in groundwater. In the anaerobic dechlorination process, TCE degrades to cis-DCE. Cis-DCE can bio-degrade further under anaerobic or aerobic processes. If cis-DCE is migrating in aerobic groundwater, the biodegradation process would be anticipated to decreasing the dissolved oxygen levels in the groundwater further. Anaerobic geochemical conditions are generally favorable to the mobilization of arsenic, an element commonly found in New Hampshire bedrock formations. Groundwater with a reductive chemistry moving through the fractured rock can mobilize naturally occurring arsenic, resulting in increasing the arsenic concentrations in the groundwater and creating elevated concentrations in water supply wells. In general there is a concern that the geochemical redox changes that occur in Site bedrock groundwater can be expected to persist for decades causing an ongoing environment for elevated release of naturally occurring arsenic into the groundwater even after contamination has disappeared.

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X.4 VARIATIONS OF GROUNDWATER CONTAMINATION MIGRATION

Prior to June 2009, TCE contamination was detected in two Strawberry Lane residential wells to the south of the Site. In June 2009, the TCE was detected in residential wells to the west of the Site. In the March 2005, residential well sampling at 31-33 Blueberry Hill Road showed no contamination to the west of the Site (well was installed in 1976). To evaluate the temporal and spatial changes in contamination migration, a timeline was drawn to consider water supply well installation timing in the Strawberry Lane and Blueberry Hill Road areas. Figure 8 in Appendix B shows the timeframe of when water supply wells were installed in the Strawberry Lane area, in the Windmere / Blueberry Hill Road area, and for the quarry located northwest of the Site. The figure also shows the TCE concentrations detected in the sampled residential wells on Strawberry Lane and Windmere Drive / Blueberry Hill Road areas. The arrows on the figure with numbers indicate when the quarry installed bedrock wells. The graph does not indicate that the quarry wells had a significant influence on area groundwater flow patterns, as TCE presence (or no presence) in residential water supply wells was not altered upon completion of the quarry wells. The figure suggests that the Strawberry Lane residential wells were most likely pulling the Site groundwater toward Strawberry Lane due to the TCE detection in those wells or that contamination was flowing through a natural pathway to the south. The Windmere Drive and 41 Blueberry Hill Road residential wells were installed between September 2005 and January 2006. Prior to January 2006, 41 Blueberry Hill Road used a dug well for a water supply. By September 2006 TCE concentrations in Strawberry Lane wells were generally decreasing. It appears that the groundwater use by the Windmere Drive / Blueberry Hill Road residential wells may have altered the direction of the groundwater flow toward the Windmere Drive / Blueberry Hill Road area and away from the Strawberry Lane area. The historical information would seem to indicate that the groundwater flow direction from the Site source area can be influenced by nearby residential pumping. Based on the NHDES laboratory’s review of the 2009 residential well analysis, the laboratory examined the analytical records and identified the presence of TCE below the RDL of 0.5 ppb in the residential water samples collected from 40 Blueberry Hill Road, 6 Strawberry Lane, and 10 Strawberry Lane. The actual concentrations are difficult to quantify below the RDL. Importantly, the NHDES laboratory records review indicate the presence of TCE below the RDL in the water samples collected from these wells. These data indicate limited TCE migration to the south of the Site in addition to the west / northwest of the Site. The conceptual hydrogeologic model for the site indicates that the residential wells to the west / northwest and the residential wells to the south have a hydrological connection through bedrock fractures. The hydrological connection to the residential wells on Strawberry Lane was observed in 2003 when transducer measurements of groundwater elevation level changes were recorded in monitor well MOT_MW-21D during January and February 2003. The transducer data shows groundwater levels influenced in MOT_MW-21D from pumping and installation activities of wells along Strawberry Lane. The transducer data indicate drawdown occurring in the monitoring well in the early morning and in the evening during the weekdays which are consistent with typical residential water use characteristics. Also, the weekend data of water level fluctuations indicate a general water level drawdown throughout the day with recharge during the night time. This is also consistent with residential activities typical of a weekend. X.5 ELEVATED ARSENIC AND URANIUM IN SITE GROUNDWATER

Elevated arsenic and uranium were detected in numerous water quality samples collected from residential wells in the NHDES study area sampling program. These data were evaluated along

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with the entire water quality data set for the Site to develop an opinion regarding whether these two constituents are associated with an anthropogenic (materials that are derived from human activities) source, or associated with the natural bedrock. In general, the information reviewed and data collected during the project support the concept that the uranium and arsenic detected in groundwater samples collected from the site vicinity are likely associated with the naturally occurring deposits (bedrock). The elevated uranium may be associated with the presence of granitic intrusions common in the area or associated with the Berwick formation. The highest uranium concentrations were observed in samples collected from wells installed along the topographic high of Blake Road. Although no specific lithologic data was collected in the Blake Road area, this topographic high may be consistent with other high elevation features (Rattlesnake Hill) in the area associated with granitic intrusive bodies. There is a strong correlation with the presence of granite and elevated uranium concentrations in groundwater in New Hampshire. Uranium has been detected in a number of residential wells during the NHDES sampling event in December 2009. The uranium is not considered a site contaminant based on the current observations and therefore the uranium concentrations in groundwater would not be a Superfund issue. The presence of uranium is considered a potential health related issue and therefore is documented in this report. The release of uranium into the groundwater environment from naturally occurring bedrock deposits requires an oxidative groundwater chemistry. It is generally only the oxidized hexavalent form, U(VI), that occurs significantly in solution. Under reducing conditions, dissolved concentrations are generally low because of the very low solubility of uraninite (Langmuir, 1978; Gascoyne, 1992). Reduction of uranium occurs concurrently with iron reduction (reduction of Fe(III) to Fe(II)) and before sulphate reduction (Finneran et al., 2002) (Berner, 1981), The reduction of U(VI) is facilitated significantly by microbial activity (Lovley et al., 1991); and laboratory experiments suggest that abiotic reduction reactions (e.g., by Fe(II) or sulphide) are ineffective (Finneran et al., 2002). Previous work conducted by USGS (USGS Fact Sheet 051-03, July 2003) has identified the Berwick Formation to be associated with elevated arsenic concentrations in groundwater. The Berwick Formation is a complex rock type with various members with varying mineral compositions associated with variations of parent material, deformation, and intrusive bodies. Such mineralogical variations in the Berwick make it difficult to develop broad statements of expected water quality associated with the formation. In general, elevated arsenic concentrations were observed in water samples collected in residential wells to the west of Blake Road with the highest concentrations in the Windmere Drive area. The spatial distribution of elevated arsenic is consistent with the Berwick Formation except in the Windmere Drive area, where the occurrence of arsenic in excess of the drinking water standard approached 80 percent of the residential bedrock wells. The specific arsenic concentrations in bedrock groundwater from the Berwick Formation would be anticipated to be variable and dependent upon local mineralogy, and ORP conditions. Area ORP chemistry is considered a key component of the overall geochemical conceptual model. Existing data indicates general oxidizing conditions to the east of the site (such as along Blake Road) and general reducing conditions to the west of the site (Blueberry Hill Road and Windmere Drive). In general, the solubility of uranium in groundwater is dependent in part on the complexation with other aqueous ions. Elevated uranium is likely associated with a granitic source and can be made more soluble by forming complexes with Ca and HCO3. Based on the initial review of the data, both anaerobic and aerobic conditions exist in the fractured bedrock aquifer in the site area. The ORP condition is expected to be fracture specific and it is expected that some of the bedrock fractures will contain groundwater under aerobic conditions and others

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may be under anaerobic conditions. The historic disposal practices at the Site likely create a perturbed groundwater condition with a biological oxygen demand resulting in the establishment of an anaerobic condition immediately down gradient of the source and extending for some distance. This reduced condition would facilitate reductive dechlorination of chlorinated VOCs which are used as electron acceptors in the absence of oxygen. Reducing conditions along with elevated pH would lead to the transformation of solid-phase arsenic contained within the bedrock fractures to soluble forms that can move with the groundwater. It is likely that the cluster of elevated arsenic concentrations in the Windmere Drive area may be related to the reducing condition of site groundwater that is influenced by the perturbed groundwater quality associated with the former contaminant source. The Site imposed reduced groundwater chemistry flowing along certain fractures would increase the dissolution of naturally occurring arsenic in the bedrock beneath the site area. As such, the elevated arsenic concentrations detected in water samples collected from the Windmere Drive area wells are likely associated with aggressive dissolution of arsenic from the Berwick Formation that is further elevated by the reduced groundwater chemistry associated from the Mottolo Site. Further details are contained in Appendix R regarding the presence and dissolution processes of arsenic and uranium in groundwater in southeastern New Hampshire. Further study is required to build more confidence in the conceptual model of hydrogeology and geochemistry of the site area. This would be accomplished through the collection of additional water quality samples, installation of additional monitoring wells, performance of borehole geophysical explorations, and bedrock aquifer characterization. The advancement of understanding of the water quality issues at the site has been and will continue to be an iterative process resulting in a stepwise building of understanding.

XI. FINDINGS

This section includes a summary list of primary findings of our study. GZA’s work presented in this report was focused on completing specific field investigation tasks and was not intended to be a comprehensive evaluation. The data collected has increased the understanding of the conceptual model of site contamination conditions. Below is a list of key findings considered important to decisions regarding future actions at the Site: 1. Tricholorethene (TCE) / dichloroethene (DCE) contamination has migrated into the deep

bedrock groundwater in the area of the former drum disposal area on site;

2. Overburden and shallow bedrock TCE groundwater concentrations near the former disposal area and former piggery operation area are currently below detection limits (less than 2 ppb). In addition, TCE concentrations detected in all other on-site overburden and shallow bedrock groundwater monitoring wells in August 2009 have decreased since the remedial investigation was performed indicating that past TCE source mass removal activities were successful in significantly decreasing contaminant mass beneath the site