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Thirty-Ninth Periodic/Fourth Long Term Monitoring of Surface Water and Groundwater (Fall 2008)

Union Chemical Company Site 214 Main Street Hope, Maine

Submitted to: United States Environmental Protection Agency – Region 1 and Maine Department of Environmental Protection

March 27, 2009

Thirty-Ninth Periodic/Fourth Long Term Monitoring of Surface Water and Groundwater (Fall 2008) Union Chemical Company Site 214 Main Street Hope Maine

Submitted to: United States Environmental Protection Agency - Region 1 and Maine Department of Environmental Protection

March 27, 2009

[•11;lTETRA TECH RIZZO

March 27, 2009

Mr. Terry Connelly U.S. Environmental Protection Agency

Region 1

1 Congress Street, Suite 1100 (HBT)

Ms. Rebecca Hewett

Maine Department of Environmental Protection

State House Station 17

August, ME 04333

Re: Thirty-Ninth Periodic/Fourth Long Term Monitoring of Surface Water and Groundwater (Fall 2008) 214 Main Street Hope, Maine

Dear Mr. Connelly and Ms. Hewett:

Attached is the Tetra Tech Rizzo (Rizzo) Thirty-Ninth Periodic/ Fourth Long Term Monitoring of Surface Water and Groundwater (Fall 2008) report detailing the activities performed by Rizzo at the above mentioned Site in November 2008 .

If you have any questions concerning this report please contact Bob Ankstitus at 508903-2415.

Very truly yours,

Dimitri Gounis, P.G., CHMM Robert J. Ankstitus, P.E. Project Geologist Senior Project Manager

P:1Pre-FY200812000124201Q39 • Fall 2008 ,039 L TM-4 Report .doc

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Table of Contents 1.0 Introduction...................................................................................................................................... 1

1.1 Background......................................................................................................................... 1

1.2 Groundwater Target Cleanup Levels .................................................................................. 5

1.3 Surface Water and Groundwater Monitoring Work Plan Objectives and

Modifications ...................................................................................................................... 5

1.4 Groundwater Wells Installed Since 2000 ........................................................................... 6

2.0 Sampling and Analysis Program...................................................................................................... 6

2.1 Measurement of Groundwater Elevations .......................................................................... 7

2.2 Installation of Dedicated Sampling Tubing ........................................................................ 7

2.3 Water Sampling and Analysis............................................................................................. 7

2.4 Sampling of the ITW-1 Well .............................................................................................. 8

2.5 Sampling of Wells with Unreacted Permanganate ............................................................. 8

2.6 Residuals Management ....................................................................................................... 9

3.0 Data Quality Assurance/Quality Control ......................................................................................... 9

3.1 Quality of Samples Collected ............................................................................................. 9

3.2 Laboratory Data Validation and Review .......................................................................... 10

3.2.1 Laboratory Data Review...................................................................................... 10

3.2.2 Data Validation Summary of Findings ................................................................ 10

Conclusion ..................................................................................................................................... 11

4.0 Water Level Elevation Survey Results .......................................................................................... 11

4.1 Survey of Groundwater Monitoring Wells ....................................................................... 12

4.2 Groundwater Elevations ................................................................................................... 12

5.0 Analytical Results .......................................................................................................................... 13

5.1 Water Quality Indicator Parameters.................................................................................. 13

5.2 Groundwater Analytical Results ....................................................................................... 14

5.2.1 Dissolved 1,1-DCA.............................................................................................. 17

5.2.2 Dissolved TCE..................................................................................................... 17

5.2.3 Dissolved 1,2-DCE .............................................................................................. 18

5.2.4 Dissolved DMF.................................................................................................... 18

5.3 Surface Water Analytical Results ..................................................................................... 19

5.4 ITW-1 Water Sample Analytical Results ......................................................................... 19

6.0 Summary........................................................................................................................................ 19

6.1 Data Usability ................................................................................................................... 19

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6.2 Groundwater Elevations ................................................................................................... 20

6.3 Contaminant Distribution ................................................................................................. 20

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List of Tables Table 1 Groundwater Elevation Data (Measured 11/15/07)

Table 2 Comparative Groundwater Table Elevations (11/8/99-11/15/07)

Table 3 Water Quality Indicator Parameters

Table 4 Summary of Constituents Detected

Table 5 Constituent Maximum Concentration Found and Performance Standards – Overburden Wells

Table 6 Constituent Maximum Concentration Found and Performance Standards – Bedrock Wells

Table 7 Comparative Quarterly Groundwater Sampling Results

Table 8 Comparative Quarterly Surface Water Sampling Results

List of Figures Figure 1 Site Locus Plan

Figure 2 Site Plan

Figure 3 Groundwater Potentiometric Surface Map - Intermediate Overburden (Q39)

Figure 4 Groundwater Potentiometric Surface Map – Shallow Bedrock (Q39)

Figure 5 Intermediate Overburden Contaminant Plume Extents (Q39)

Figure 6 Bedrock Contaminant Plume Extents (Q39)

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List of Appendices Appendix A Groundwater and Surface Water Analytical Results

Appendix B Water Quality Indicator Parameter Trend Graphs

Appendix C Contaminant Trend Graphs by Well

Appendix D Contaminant Trend Graphs by Compound

Appendix E Low Flow Sampling Methodology (correspondence dated March 24, 2000, Rev. 1)

Appendix F Laboratory Certificates of Analysis: Spectrum Analytical Inc

Appendix G Limitations

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Thirty Ninth Periodic/Fourth Long Term Monitoring of Surface Water and Groundwater (Fall 2008)

214 Main Street, Hope, Maine

1.0 Introduction This Thirty-Ninth Periodic/Fourth Long Term (Q39/LTM-4) Monitoring Report has been prepared to document a surface and groundwater monitoring event conducted at the Union Chemical Company (UCC) Site (The Site) in Hope, Maine in November 2008. This report provides a summary of Site background; previous monitoring events; recent remedial activities at the Site; groundwater target cleanup levels; work plan objectives and modifications; and recent groundwater conditions at the Site. Detailed discussions on each of these topics has previously been submitted to the U.S. Environmental Protection Agency (EPA) and the State of Maine Department of Environmental Protection (MEDEP). The EPA and MEDEP are collectively referred to in this document as the agencies.

1.1 Background

Periodic surface water and groundwater monitoring began for the Site in Summer 1992. Periodic sampling was performed quarterly until Fall 1997 (Quarters 1 through 22) when the monitoring frequency was switched to semi-annual (Q23 through Q35). Following Q35 (Q36/LTM-1 to Q39/LTM-4) monitoring was performed annually or bi-annually. Beginning in Spring 2002 (Q31), responsibility for sampling, monitoring and related activities was transferred to and conducted by Rizzo Associates, Inc. of Framingham, Massachusetts, now doing business as Tetra Tech Rizzo (Rizzo).

The Surface Water and Groundwater Monitoring Program was established pursuant to the UCC Superfund Site Record of Decision (ROD), dated December 27, 1990; the ROD Statement of Work, dated July 26, 1991; and the Explanation of Significant Difference (ESD), dated June 30, 1994. Approval of the Source Control (SC)/Management of Migration (MOM) design documents, including the Surface Water and Groundwater Monitoring Work Plan (Work Plan), was received from the EPA in correspondence dated April 5, 1995. Changes to the monitoring work plan are made periodically to account for changes in data needs over time. Changes are not implemented until approved by the EPA, after opportunity for review and comment by the MEDEP.

The SC remediation (i.e., the soil treatment component) was completed in 1998. Following the submittal of the Closure Action Plan for Soils, Findings and Summary (CAP-SFS) report, EPA, following review by ME DEP, approved the CAP-SFS in correspondence dated December 17, 1999. This marked the conclusion of the source control component for the Site.

From 1997 through 2000, in an attempt to accelerate the overall objectives of the MOM, the remedial program incorporated the field application of potassium permanganate solution to groundwater to oxidize chemical constituents in the adsorbed or dissolved phase. A synopsis of the completed permanganate activities is as follows:

A pilot test of a dilute permanganate solution was first conducted in the Fall of 1997;

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Wider application of permanganate was conducted from June through August 1998 within the source area;

Re-treatment and expanded permanganate additions were then conducted during the Summer and early Fall of 1999; and,

Additional permanganate treatment was conducted in contaminant areas identified by the Q26 and Q27 sampling/monitoring events during the Summer and Fall of 2000.

Permanganate additions have not been conducted since the Fall of 2000.

Following completion of permanganate additions in Fall 2000, a bioremediation pilot test consisting of field addition of carbon source solutions to the Site groundwater were performed. The carbon source additions served as a reduced substrate to assist in the depletion of residual permanganate and provide an electron donor/carbon source to enhance anaerobic, reductive dechlorination of 1,1- dichloroethane (DCA) along with remaining chlorinated ethenes and ethanes. Initially, carbon sources used for solution additions included molasses and sodium lactate. Site groundwater data from Fall 2000 (Q28) and Spring 2001 (Q29) were used to establish pre-carbon source addition conditions. A synopsis of the completed carbon source activities is as follows:

Approximately 200 gallons of dilute molasses were added to four wells located within the eastern portion of the Site during two separate events in August and November 2001;

Approximately 23 gallons of 6% sodium lactate solution were added to three wells located within the south central portion of the Site between August and November 2001;

The potential impact of the carbon additions was evaluated during Spring 2002 (Q31) through sampling and analysis of target wells for VOCs and monitored natural attenuation (MNA) parameters. A comparison of previous contaminant concentrations reported during Fall 2000 (Q28) through Fall 2001 (Q30) was used to determine which carbon source more effectively enhanced the microbial activity in the subsurface.

Sodium lactate was selected as the preferable carbon source at the Site based on the evaluation of microbial activity following the Q31 monitoring event.

Rizzo personnel performed sodium lactate additions to the designated pumping wells and monitoring wells throughout the Site in August 2002. Stoichiometric requirements previously calculated by IT in their 2001 work plan were used to estimate the quantity of carbon source material necessary to deplete (dissolved) oxygen, react with residual permanganate, and provide at least a 25- to 100-fold excess of carbon source concentrations in the groundwater versus detected volatile organic compound (VOC) concentrations in the wells.

In an effort to further define the overburden and bedrock aquifer properties and close data gaps identified in the second revision of the Conceptual Site Model, pump tests were performed on wells B-6A-D and OPW in July of 2005. The goals of the pump test included an evaluation of

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potential hydraulic connections between pumped wells B-6A-D and OPW and other bedrock wells B-8A-D, ODW-U and/or ODW-L; evaluating potential connectivity of the overburden aquifer to the bedrock aquifer; and the calculation of hydraulic properties for each aquifer including vertical and horizontal hydraulic conductivity, transmissivity and storativity. The pump test data was further used to estimate the range of groundwater velocities encountered during seasonal groundwater recharge events at the Site in overburden and bedrock aquifers, and was presented in the third revision of the Site Conceptual Site Model. The well B-6A-D pump test was performed as a 27-hour pump test. The well OPW pump test was performed as a 120.5 hour pump test.

The well B-6A-D pump test demonstrated a limited hydraulic connectivity between well B-6A-D and the bedrock wells that were selected for drawdown monitoring under pumping conditions with an apparent low connectivity to the bedrock wells across the Site. The shallow bedrock wells closest to well B-6A-D, including wells OW-1-1D, B-5C-D, B-12A-D, and B-8AD showed the greatest measured drawdown. Bedrock wells MW-15-D, NPW and MW-13A-D showed the least measured drawdown amongst the bedrock wells, and a moderate hydraulic connection was observed at well OPW. The overburden wells did not exhibit a significant drawdown nor a significant hydraulic connection to the shallow bedrock during the B-6A-D pump test.

The OPW pump test demonstrated a stronger relative hydraulic connectivity between the bedrock monitoring wells than those observed during the B-6AD pump test. Each of the selected bedrock gauging wells had drawdown of greater than one foot at the conclusion of the OPW pump test except for well B-8A-D (0.78 feet). The most significant measured drawdown values (during the OPW pump test) were measured at wells NPW and ITW, which are bedrock wells with similar construction (open boreholes) and closest to the pumping well OPW. The shallow bedrock wells B-6A-D and OW-1-1D each had significant measured drawdown. Wells MW-15-D, NPW and MW-13A-D showed much greater measured drawdown during OPW pump test than the B-6A-D pump test; however, the higher pumping rate is believed to be the reason for the observed larger drawdown differences between the well B-6A-D pump test (pumping rate of approximately 0.88 gallons per minute (gpm))and the well OPW pump test (approximately 5 gpm).

To put the different observed drawdowns into context, the results of the 2005 bedrock well pump tests and review of the historical rock core logs were used to define the hydraulic and structural properties of the bedrock aquifer. Shallow bedrock was defined in the CSM as the bedrock lithologic unit that lies at depths between approximately 85 and 225 feet below ground surface (bgs) and consists of an upper weathered bedrock surface that becomes more competent with depth. Between approximately 85 feet bgs and 110 feet bgs in the vicinity of the on-Site cap, the bedrock lithology is defined as a folded quartz-mica-schist and granite that transitions to gneiss and intruded granite pegmatite at depths greater than 110 feet bgs. Outside of the on-Site cap area, the bedrock lithology is not folded and is defined as gneiss and intruded granite pegmatite from approximately 85 feet bgs to 225 feet bgs. The strike of the fold axis is northeast-southwest and the dip of the fold is east-southeast toward Quiggle Brook. Core logs from several of the shallow bedrock wells on-Site indicate that the upper thickness of rock is moderately to highly fractured due to the deformational folding of the rock. Jointing of the bedrock was noted in the

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upper portions of the cores and is likely related to glacial erosion and regional uplift, and a general decrease in fracture frequency and aperture was noted with depth. A small number of steeply dipping fractures observed in bedrock core samples taken from borings advanced on the limbs of the bedrock fold were observed as deep as 100 feet bgs, and groundwater migrating under downward gradients on the western and central portions of the Site could move through the weathered bedrock layer to these fractures and could flow down-dip (southeast), deeper into the bedrock formation and to a lesser degree along the strike (southwest) of the fractures. As with the overburden soils and the weathered bedrock, upward hydraulic gradients in the shallow bedrock occur along the eastern portion of the Site where groundwater follows the fractures along the foliated layers of the fold in the rock and is released from the fractures via connection to weathered bedrock fractures and ultimately to Quiggle Brook. This bedrock feature which is located adjacent to Quiggle Brook, results in the ability of the VOCs/SVOCs to migrate to the southeast in the shallow bedrock to Quiggle Brook.

The review of the core logs and definition of the hydraulic properties concluded that there is a small range of hydraulic conductivities that dominates within the fractured bedrock and shallow bedrock and those hydraulic conductivities are primarily dependent upon lithology (quartz-mica schist) and the dip orientation of the structural fold (southeast). The apparent changes in drawdown under pumping conditions were adequately explained by the rate of pumping during each pump test; however the different pumping conditions were beneficial in showing existing preferential pathways more clearly and highlighted the role that fracture pathways have on groundwater flow at different depths in the bedrock. The conclusion of the CSM was that groundwater in bedrock flows southeasterly along the dominant fracture directions and along the orientation of the structural fold toward Quiggle Brook, which overlies a low spot in the fold. The results of these two pump tests also indicated that while some minor connections may exist between the bedrock and overburden aquifers at the Site, in general, the two aquifers behave as separate hydrologic units. Therefore, for the purpose of presenting the groundwater quality data in this report, separate plume figures are appropriate to represent site conditions and groundwater impacts. The likely direction for migration of the contaminant plumes and the inferred limits of the plume(s) were based on the geology of the Site to the extent practicable.

Following the completion of the pump tests, pumping was continued to allow for the injection of hydrogen peroxide. The goal of the hydrogen peroxide oxidant addition was to potentially oxidize VOC’s within the hydraulic connections between selected bedrock monitoring well points. The hydrogen peroxide injection events occurred between July 25, 2005 and August 4, 2005 and between September 26, 2005 and September 29, 2005. Simultaneous pumping of wells B-6A-D and OPW was performed during both hydrogen peroxide injections in order to maintain a depressed water table within the bedrock aquifer and provide hydraulic control to draw injected hydrogen peroxide from the selected injection wells towards the pumping wells. This combined pumping likely increased the oxidant coverage within the hydraulic connections between fractures in bedrock aquifer. Hydrogen peroxide injection points included monitoring wells B-8A-D, B-9A-I, EW-1, ODW-L, ODW-U, OW-1-1D, NBW-L, NBW-U, P-20 and B-6A-D (injections were performed in well B-6A-D while only well OPW was being pumped). A total of 1100 gallons of 35% hydrogen peroxide solution was added to these wells during the two oxidant injection events.

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1.2 Groundwater Target Cleanup Levels

EPA has established groundwater target cleanup levels for the Site, based on Maximum Contaminant Levels (MCLs) established under State and Federal laws and the State of Maine’s Maximum Exposure Guidelines (MEGs), for several of the contaminants identified in the groundwater at the Site. EPA has determined that MCLs are the Applicable or Relevant and Appropriate Requirements (ARARs) for this Site, and that the State MEGs are to be considered to establish the groundwater cleanup levels for those constituents for which no MCL exists. Data results and comparisons are presented within the context of these groundwater cleanup levels.

1.3 Surface Water and Groundwater Monitoring Work Plan Objectives and Modifications

The objectives of the Surface Water and Groundwater Monitoring Plan are to obtain surface water and groundwater data to:

monitor the extent of contaminants of concern at the Site;

assess the progress of remedial activities; and,

monitor for potential impacts to surface water and groundwater as a result of remedial activities.

The Surface Water and Groundwater Monitoring Program was modified during several meetings and teleconferences between EPA, MEDEP, American Environmental Consultants (AEC – Trust representative), IT and Rizzo in 1998, 2000, early 2002, and 2004. The frequency of sample collection was changed from quarterly to twice-annually (completed in April and October of each year) beginning in April 1998. Subsequently, the frequency of sample collection was changed from twice annually to annual or bi-annual to be completed in October or November of each year beginning in November 2004. Due to elevated residual peroxide concentrations in several of the designated monitoring wells for these monitoring events no formal monitoring event took place in the Fall of 2005. Beginning with the Q27 (April 2000) sampling round, groundwater samples have been collected using low flow sampling procedures.

Currently, annual or bi-annual sampling is being performed under the Draft Long Term Monitoring Plan prepared by Rizzo and dated September 10, 2004. The wells to be sampled and target analytes for Q39/LTM-4 were approved by the EPA and MEDEP based upon the revised 2008 Work Plan for the Site dated September 10, 2008. Surface water and groundwater samples were analyzed for volatile organic compounds (VOCs), and select groundwater samples were analyzed for N, N-Dimethylformamide (DMF). The sampled monitoring wells included: wells located within the identified source area; areas of elevated groundwater contaminant concentrations; and downgradient boundaries of previous detectable contaminant concentrations. This Q39/LTM-4 report includes both current and historical laboratory analytical data presented in tabular format with graphical trend analysis.

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1.4 Groundwater Wells Installed Since 2000

During 2001, a new groundwater pumping well (ITW-1) was installed at the Site to provide a water source (non-potable) for decontamination purposes and the various remedial activities at the Site. The well is pumped periodically and sampled for volatile organic compounds during each pumping event. The ITW-1 well was pumped by Rizzo personnel briefly for the purposes of sampling on October 19, 2006 and was sampled by EPA in October 2007. Groundwater analytical results from EPA in 2007 had reported concentrations of TCE (1.5 ug/L) and MTBE (1.2 ug/L); however, these concentrations were below the applicable Performance Standards.

In October 2003, three new two-inch diameter monitoring wells were installed to replace the previously installed B-5 series wells that consisted of one-inch diameter monitoring wells. Replacement wells were advanced approximately 10 feet north of the existing B-5 series well triplet using a track-mounted ATV drilling rig, and included the installation of two overburden monitoring wells and one bedrock monitoring well. The intent was to screen the new wells over the same depth intervals as the B-5 series wells being replaced. The shallow replacement well, B-5E-S, was screened over the same interval as the previously installed shallow well, B-5B-S. However, the previously installed intermediate well (B-5B-I) and previously installed bedrock well (B-5A-D) were completed using only two-foot sections of well screen. In an attempt to provide additional available well screen area for contact with the groundwater for sampling events, the intermediate and bedrock replacement wells (B-5D-I and B-5C-D) were completed using 5-foot sections of well screen. In general, the screened intervals in the replacement wells included the intervals over which the original B-5 wells were screened. A more detailed discussion of the replacement of the B-5 series well triplet was presented in the Bedrock Well Installation and Geophysical Evaluation report prepared by Rizzo dated April 30, 2004 which was submitted to the agencies.

In November 2003, a new bedrock well couplet (NBW) was installed at the Site to provide additional coverage of the bedrock aquifer in the area southwest of the source area and cross-gradient to the B-8 series wells. Air-rotary drilling techniques were used to advance a boring approximately 300 feet below the ground surface. Hager GeoScience, Inc (Hager) performed a geophysical evaluation of the newly installed bedrock boring to identify potential water bearing fractures/zones. Based on the results of Hager’s geophysical evaluation, a deep bedrock well (NBW-L) was set and screened from 115 to 120 feet below the top of the installed metal casing, and a shallow bedrock well (NBW-U) was set and screened from 56 feet to 66 feet below the top of the casing. A more detailed discussion of the installation of this bedrock well couplet and the geophysical evaluation performed by Hager was presented in the Bedrock Well Installation and Geophysical Evaluation report prepared by Rizzo dated April 30, 2004 which was submitted to the agencies.

2.0 Sampling and Analysis Program Rizzo conducted Q39/LTM-4 monitoring activities and sample collection on November 12-13, 2008. The observed conditions and reported analytical results from this sampling event are included in the figures, tables and discussions within this report.

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2.1 Measurement of Groundwater Elevations

Water levels in the wells selected for sampling during Q39/LTM-4 were measured on November 12, 2008 using an electronic water level indicator. As part of the Q39/LTM-4 monitoring event, depth to water measurements were collected from 10 monitoring wells at the Site (4 intermediate wells, 6 bedrock wells). The water level measurements were obtained on the same day and within an 8-hour period. The well locations and calculated groundwater potentiometric surface maps for Q39/LTM-4 are shown on Figures 3 and 4.

2.2 Installation of Dedicated Sampling Tubing

Dedicated sampling tubing was installed in each of the Q39/LTM-4 wells during previous Site activities. 0.25-inch diameter tubing has been installed in each well as close to the mid-point of the well screen as possible. Groundwater sample collection tubing included 0.5-inch diameter tubing and/or 1-inch diameter outer tubing. The outer tubing was used as a protective sleeve in some wells to provide additional rigidity to overcome the contact frictional forces between the well casing and the small diameter tubing.

2.3 Water Sampling and Analysis

Groundwater samples were collected during the Q39/LTM-4 sampling event from a total of 10 monitoring wells and one downstream surface water point. The downstream surface water sample was collected from the QB-4 sampling station (Quiggle Brook).

The weather conditions at the Site during the November 2008 groundwater sampling event were seasonally cold. Tubing and low flow equipment were wrapped in insulation to avoid cold ambient air temperature effects when necessary.

The Q39/LTM-4 wells listed in the table below were purged in accordance with the low flow sampling procedures attached in Appendix E, using a peristaltic pump and the dedicated tubing for each sample location. The Q39/LTM-4 sampling was the thirteenth consecutive sampling event using low flow sampling procedures. Previous sample flow rates and sample times were used as references during the purging for each well location. However, since the measured groundwater parameters have fluctuated over the thirteen sampling events, groundwater purging continued, and groundwater parameters were recorded, until stabilization was observed. For wells with dissolved oxygen (DO) concentrations less than 1.0 mg/L, three consecutive readings within a compared difference of 0.10 mg/L were considered the benchmark for stabilization regardless of whether the readings were within the 10% stabilization threshold for DO. However, during the Q-39/LTM-4 groundwater sampling event, stabilization of measured groundwater parameters was achieved within the required threshold for each of the sampled wells. While the median dissolved oxygen (DO) readings were reported at concentrations less than 1.0 mg/L, elevated levels were recorded in four monitoring wells (ODW-U; ODW-L; NBW-U and NBW-L). The elevated DO levels likely represent the continued presence of residual oxygen from the now expended hydrogen peroxide oxidant additions conducted in Summer/Fall 2005.

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Groundwater in the wells was purged until field parameters (dissolved oxygen, oxidation-reduction potential, pH, specific conductivity, temperature and turbidity) reached stabilization. Collected groundwater samples were analyzed for VOCs by EPA Method 8260 and for DMF as shown in the Q39/LTM-4 Sampling Summary table below.

Union Chemical Company Site

Q39/LTM-4 Sampling Summary

Sample Source Disposition Location(s) Sampled for VOCs

Location(s) Sampled for DMF

Additional Action Taken

Monitoring Wells (5)

Samples collected 11/12/08

B-5D-I, B-12B-I, NBW-L, NBW-U,

and ODW-U

B-5D-I, B-12B-I, NBW-L, NBW-U,

and ODW-U

Monitoring Wells (5)

Samples collected 11/13/08

B-8A-D, B-6A-D, B-9A-I, ODW-L

and P-20

B-8A-D, B-6A-D, B-9A-I, ODW-L and

P-20

Duplicate sample collected from B-8A-D

Surface Water Monitoring Station (Quiggle Brook)

Sample collected 11/13/08

QB-4 QB-4 None

2.4 Sampling of the ITW-1 Well

While concentrations of VOCs were reported for a water sample collected from the ITW-1 well in 2005, subsequent sampling conducted by EPA in October 2007 indicated that concentrations of TCE (1.5 ug/L) and MTBE (1.3 ug/L) were below the applicable Performance Standards. Though reported analytical results from well ITW were below the applicable Performance Standards, well ITW was not used as source for decontamination water during the Q39/LTM-4 sampling event.

2.5 Sampling of Wells with Unreacted Permanganate

During a previous groundwater monitoring event in April 2001 (Q29), IT Corporation, in concert with EPA’s mobile laboratory, conducted a field test and analysis of preservation methods for groundwater samples containing measurable concentrations of unreacted permanganate (as evidenced by color, either prior to or during purging). The purpose of the field test was to determine which type of sample preservation best represented the VOC concentrations in groundwater.

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IT Corporation and the regulatory agencies subsequently determined that collected groundwater samples which exhibited visual evidence of permanganate would be preserved using sodium thiosulfate in lieu of hydrochloric acid prior to analysis for VOCs. Additional details regarding the preservative study, data collected and analysis may be found in separate correspondence dated May 31, 2001, which highlighted the study.

No wells sampled for laboratory analysis during the Q39/LTM-4 monitoring event exhibited visual evidence of residual permanganate.

2.6 Residuals Management

Liquids from the decontamination of sampling equipment and personal protective equipment (PPE) were handled in accordance with the SC/MOM 100% Design for Persistent Organic Pollutants (POP). Purge water was left in a 55-gallon drum in the locked metal storage trailer on-site.

3.0 Data Quality Assurance/Quality Control The primary purpose of the quality assurance/quality control (QA/QC) program is to meet the data quality objectives (DQOs) for the Surface Water and Groundwater Monitoring Program as outlined in the SC/MOM 100% Design Field Sampling Plan (FSP) and Quality Assurance Project Plans (QAPP). Data collected during Q39/LTM-4 consists of Level I, III, and IV data. The QA/QC review examines both the quality of the samples being collected and the validity of the chemical analyses performed on the samples at the laboratory.

3.1 Quality of Samples Collected

Groundwater samples were collected using the EPA approved low flow sampling protocol (Appendix E). The sampling protocol utilizes stringent acceptance criteria with respect to stabilization of water quality parameters in the field. The physical groundwater parameters met the acceptance criteria of the low flow sampling protocol, indicating that the collected groundwater samples were likely representative of the surrounding aquifer. Inconsistencies of physical parameters noted during the purging process were recorded in the sampler’s field book. Occasionally, specific parameters are found to be inconsistent or the monitoring probe indicates error messages. In these instances, a backup monitoring device is used to either confirm the observed measurements or to replace the instrument probe that reported the erroneous reading. If several parameter readings appear erroneous, the monitoring is stopped; the meter/probe is recalibrated; and the purging is re-started. The instruments utilized during the Q39/LTM-4 sampling/monitoring event did not behave abnormally during the sampling event.

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3.2 Laboratory Data Validation and Review

Level III or IV data that fails to be properly validated is flagged in the laboratory reports and summarized in the sections which follow. A review of the data is conducted with an appropriate response depending upon the following:

the magnitude of the rejection,

the data quality objectives (DQOs) for the data, and

the "value" of the data to the DQO.

Any deviations or rejected data are documented in the sections that follow, including the development of appropriate response activity, if necessary.

3.2.1 Laboratory Data Review

The14 samples collected during Q39/LTM-4, including groundwater (10), surface water (1), and field QA/QC (3) samples, were included in the data validation review.

The samples were submitted under chain of custody to Spectrum Analytical Inc. of Agawam, Massachusetts and analyzed by the following methods:

VOCs by EPA Method 8260B and;

Organic analyte N,N - dimethylformamide (DMF) by EPA Method 8270C.

3.2.2 Data Validation Summary of Findings

Spectrum Analytical conducted an internal data validation of the Q39/LTM-4 results. Review of the laboratory data validation report by Tetra Tech Rizzo has indicated that the Q39/LTM-4 results are of acceptable quality for the DQOs as described in the SC/MOM 100% Design Sampling and Analysis Plan. The laboratory did not identify any samples that did not meet the laboratory protocol for the analyte and analytical holding times. The following summarizes the case narrative provided by Spectrum Analytical with the analytical data and Tetra Tech Rizzo review of the data. A copy of Spectrum Analytical case narratives are provided in Appendix G.

Samples were received in acceptable condition, at 5.1 degrees C, on ice, and in accordance

with sample handling, preservation and integrity guidelines.

Method Blank - No exceptions noted.

Laboratory Control Sample Results – For Method 8260B analyses: Laboratory Control

Samples (LCS) 8111368-BS1, 8111368-BSD1, 8111369-BS1 and 8111369-BSD1 had

recoveries that were out of acceptable range (high bias) but there were no reported

concentrations in the sample for 1,4 dioxane, ethanol and tert butanol/butyl alcohol; LCS

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8111 368-BS1 had recoveries out of acceptable range (high bias) for chloroethane, ethyl ether, and vinyl chloride; LCS 8111369-BS1 had recoveries was out of acceptable range (high bias) for chloroethane and vinyl chloride; and LCS 8111820-BSD1 had a recovery out of acceptable range (low bias) for 2 Hexanone (MBK). The high bias in the recoveries indicates that the lab instrument would likely report higher concentrations for these compounds than what may actually be present in the sample. For 8270C: LCS 8111353-BS1 had one recovery out of acceptable range (low bias) but there were no reported concentrations in the sample for Hexachlorocyclopentadiene. The low bias in the recovery for this compound indicates that the lab instrument would likely report lower concentrations than what may actually be present in the sample.

Surrogate Recoveries – 8260B: Samples B-8AD-Dup and VP-20 had surrogate recoveries outside control limits (high bias) for dibromofluoromethane but the data was accepted based on valid recovery of the remaining surrogates. 8270C: Sample ODW-L had surrogate recoveries outside control limits (high bias) for 2,4,6-tribromophenol but the data was accepted based on valid recovery of remaining surrogates. The high bias in the recoveries indicates that the lab instrument would likely report higher concentrations for these compounds than what may actually be present in the sample.

Matrix Spike (MS)/Matrix Spike Duplicate(MSD) Results – 8260B: For 8111369-MS1 and 8111369-MSD1 the spike recovery was outside the acceptance limits for the MS and/or MSD for 1,1 dichloroethene (high bias). The high bias in the recoveries indicates that the lab instrument would likely report higher concentrations for these compounds than what may actually be present in the sample. The batch was accepted based on acceptable Lab Control Sample (LCS) recovery and acceptable recoveries of the other spike compounds.

Other – 8270C: The reporting limits for sample B-9A-I were raised to account for matrix

interference.

Conclusion

The analytical data generated during the Q39/LTM-4 monitoring event is of acceptable quality for the DQOs as described in the Sampling and Analysis Plan. No QC issues related to the sampling and analysis were identified that would indicate the data could not be used for an evaluation of Site conditions. The data produced by the sampling activities and the analysis at the lab is of acceptable quality.

4.0 Water Level Elevation Survey Results Groundwater surface elevations measured on November 12, 2008 are presented in Table 1. This data is also compared to historical groundwater levels collected over the previous twelve quarters (Q26 through Q38) in Table 2.

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4.1 Survey of Groundwater Monitoring Wells

On April 25, 2002, the groundwater monitoring wells at the Site were surveyed relative to an established benchmark elevation in the Site area (367.86’: boulder located 4 feet northwest of telephone pole P165). The wells were surveyed due to concerns that modifications to well casings and/or standpipes during remedial activities may have altered the reference elevation of the wells. In addition, the well survey was conducted to establish (and mark) new reference points on each groundwater monitoring well (top of PVC or top of exterior casing) that may be used for future groundwater gauging events. Elevations of wells that were cut or otherwise altered as a part of Site activities during the Summer of 2002 were re-surveyed on November 24, 2002, and tied into the April 25, 2002 survey with back sight references to un-altered well elevations. Monitoring wells that were replaced or installed in November 2003, were surveyed on November 21, 2003 and tied into the April 25, 2002 survey with back sight references from un-altered well elevations.

4.2 Groundwater Elevations

Potentiometric surface maps for groundwater in the overburden intermediate and bedrock units were interpreted from the November 12, 2008 water level gauging data for the Q39/LTM-4 wells, and are presented on Figures 3 and 4, respectively. The groundwater potentiometric surface contours were generated using a krigging algorithm. Krigging is a method of interpolation which predicts unknown values using know values recorded in the field data logs. The resolution contours for these figures are limited by the number of wells that were gauged during the Q39/LTM-4 gauging event. To express the spatial variation from the field data points, a variogram model was used within the krigging method.

The overburden water table during the Q39/LTM-4 gauging event exhibited elevations and conditions similar to previously reported seasonal data for the Site during non-pumping conditions. The inferred intermediate overburden potentiometric surface for Q39/LTM-4 (Figure 3) indicated that groundwater flow in the overburden is in an easterly direction. There were no indications of groundwater mounding or depressions observed in the intermediate overburden during this monitoring event.

The bedrock potentiometric surface map for the Q39/LTM-4 gauging event indicates that the inferred general groundwater flow trends toward the south-southeast (Figure 4). Historical evaluations of groundwater movement through the Site’s bedrock that included additional shallow bedrock wells not included in this evaluation indicate that regional groundwater flow occurs along limited fractures which may not be represented on this limited potentiometric drawing. However, based on a review of recent and historical groundwater elevation data which is provided in Table 2, groundwater elevations measured in Q39/LTM-4 for both the Site overburden and bedrock wells were comparable to previous quarterly/semi-annual monitoring events.

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5.0 Analytical Results Groundwater samples for Q39/LTM-4 were collected from Site groundwater monitoring wells on November 12-13, 2008 and submitted to Spectrum Analytical on November 14, 2008 for laboratory analysis.

5.1 Water Quality Indicator Parameters

Water Quality Indicator Parameters were measured and recorded for the 11 sampled locations during Q39/LTM-4, including 10 monitoring wells and 1 surface water station. The final results of the water quality parameter measurements collected during the Q39/LTM-4 sampling event are presented in Table 3. Measurements for the water quality parameters including pH, specific conductance, dissolved oxygen (DO), turbidity, oxidation/reduction potential (ORP), and temperature were recorded during the low-flow purging of the wells. All measurements were completed using a YSI 600XL water quality meter and flow-through cell unless otherwise noted. Turbidity measurements were completed using a turbidimeter and turbidity samples were collected from an in-line sampling port prior to the groundwater entering the flow-through cell. Along with the water quality parameters, the groundwater purging rate and total drawdown measurements for each Q39/LTM-4 well were also recorded and these data are presented in Table 3.

Our review of the water quality parameter data for Q39/LTM-4 indicates that the measurements are consistent with previous and historical measurements. Wells with extremely low hydraulic conductivities continue to show elevated concentrations of dissolved oxygen related to the expenditure of hydrogen peroxide which suggests a lack of groundwater dilution. Wells observed with elevated dissolved oxygen concentrations during this monitoring event included NBW-U, NBW-L, ODW-L, and ODW-U. The Q39/LTM-4 water quality indicator parameter data is graphically compared to historically monitored data in the figures and included in Appendix B. The water quality parameter data for this sampling event are summarized as follows:

The final groundwater pH measurements obtained during Q39/LTM-4 ranged from 3.6 (NBW-L) to 9.5 (B-12B-I). Measured pH in Site wells were within approximately 1 pH unit from the recorded pH range observed during the last groundwater sampling round.

The final specific conductance measurements during Q39/LTM-4 were within a range from 31 micro Siemens per centimeter (μS/cm) (QB-4) to 4,894 μS/cm (B-9A-I). The prior observed specific conductivity in well B-9A-I in Q38/LTM-3 was 3,772 μS/cm. While elevated relative to other intermediate overburden wells, specific conductivity in this well continues to be below that observed during Q36/LTM-1, which was reported as 10,624 μS/cm. This reading was taken following the 2002 lactate additions, and was likely due to residual lactate in the well. The lower relative conductivity readings in well B-9A-I since October 2006 are believed to be indicative of the gradual return of well groundwater to background conductance levels observed prior to carbon source additions via dilution. In bedrock wells, specific conductance readings ranged from 357 to 803 us/cm for Q39/LTM 4. Prior observed readings during the Q37/LTM-2 monitoring which were noted as above

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historical observations were likely the result of hydrogen peroxide additions. Those readings were reported during Q37/LTM-2 as 1,642 μS/cm in well ODW-L; 269 μS/cm in well ODW-U; and 642 μS/cm in well NBW-U. Based on the conductance readings taken prior to the addition of remedial additives (including additions of lactate, molasses, bromide, potassium permanganate and hydrogen peroxide) there is a correlation between the addition of an additive and the increase in conductance readings recorded in Site groundwater monitoring wells following remedial additions at the Site. Consequently, the decrease in recorded conductance readings since the additions is a qualitative measure of the rate of groundwater flow and the associated dilution rates in the vicinity of these wells.

Final ORP readings during Q39/LTM-4 ranged from negative 209 millivolts (mV) (P-20) to a positive 390 mV (ODW-L). Observed ORP readings for each well monitored during this monitoring event displayed a decreasing trend over those observed since the Q-37/LTM-2 monitoring event. This general decrease (move toward negative readings) in ORP readings is likely related to the dilution of high dissolved oxygen waters created in the subsurface via the 2005 hydrogen peroxide additions with fresh aquifer water, returning the subsurface aquifer to reducing conditions. The majority of overburden and bedrock wells had negative ORP readings and have shown decreases in ORP of 100mv or more since the Q37/LTM-2 monitoring event. Bedrock couplet wells ODW and NBW each had positive ORP readings, indicating that residual dissolved oxygen derived from the expenditure of hydrogen peroxide remains within the subsurface at these wells, suggesting a slow rate of dilution. These conditions in the deeper bedrock wells are indicative of the extremely low hydraulic conductivities at depth at the Site.

Final Dissolved Oxygen (DO) readings ranged from 0.1 milligrams per liter (mg/L) (P-20) to 72.2 in well NBW-L and 74.6 mg/L in well ODW-L. DO readings in Site overburden and shallow bedrock wells have displayed a downward trend since the addition of hydrogen peroxide in 2005 and are indicative of a return to reducing conditions (DO below 1.0 mg/L) via dilution. DO readings for the relatively deeper bedrock well couplets ODW and NBW remained elevated (>30 mg/L), indicating that residual oxygen from the 2005 hydrogen peroxide additions remains in these wells. The DO readings in ODW-U well showed a sharper relative drop than in other wells with elevated DO levels, suggesting oxidant expenditure in this well is proceeding at a slightly faster rate than that observed in other bedrock wells with residual elevated dissolved oxygen levels.

Final turbidity readings in the wells ranged from 0.0 NTU (B-8A-D) to 18.4 NTU (P-20). The observed turbidity readings were generally lower than historical readings, with the exception of wells B-5-DI, ODW-U and P-20, which were slightly higher. The observed turbidity readings are consistent with turbidity readings measured during previous sampling rounds (since Q31).

5.2 Groundwater Analytical Results

Data generated by the Q39/LTM-4 sampling indicates that 17 VOC analytes (shown below) and semi-volatile organic compounds (DMF) were detected in groundwater at concentrations greater

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than or equal to the method detection limit, or had laboratory detection limits above their corresponding Performance Standards. Of the 17 VOC analytes, 10 were detected at concentrations exceeding their corresponding Performance Standards. DMF was also detected above its respective Performance Standard. Detected VOCs that exceeded Performance Standards in Q39/LTM-4 samples are shown in the bold text below. For three wells, reported method detection limits for some compounds were greater than the corresponding Performance Standard, but the number of wells with this condition are fewer than historically observed when Resource Labs analyzed the groundwater samples (up to Q38/LTM-3). When this occurs it is not possible to know if the Performance Standard was exceeded or not; therefore, for the purposes of this report, a method detection limit greater than the appropriate Performance Standard is considered a Performance Standard exceedance.

1,1-Dichloroethane Ethylbenzene Trichloroethene

1,1-Dichloroethene Methyl t-butyl ether Vinyl Chloride

2-Butanone (MEK) (MTBE) Xylenes

4-Methyl-2-Pentanone Tetrachloroethene cis-1,2-Acetone

Chloroethane

Tetrahydrofuran (THF)

Toluene

Dichloroethene

trans-1-2-Dichlroethene

Dimethylformamide

(DMF) Tert-butyl alcohol 3 & 4 methylphenol

A summary of the compounds detected in the groundwater samples during Q39/LTM-4 is presented in Table 4. Complete tabulated lists of the analytical results for groundwater and surface water are provided in Appendix A. The laboratory analytical report is provided in Appendix G. Graphs depicting the historical contaminant concentrations for selected monitoring wells are presented in Appendices C and D. Maximum contaminant concentrations, frequency of detections and comparisons to the Performance Standards for groundwater samples in overburden and bedrock are provided in Tables 5 and 6. Historical sampling results are provided in Tables 7 and 8.

From the Q39/LTM-4 groundwater sample data, inferred plume extent maps (Figures 5 and 6) were prepared to illustrate the distribution of the most prevalent analytes (1,1-DCA, TCE, cis 1,2-DCE and DMF) in the intermediate overburden groundwater and bedrock groundwater aquifers. The isoconcentration contours were inferred using the analyte data from wells sampled during Q39/LTM-4.

Our general observations regarding the inferred plume maps include:

The configuration(s) of the contaminant isoconcentration contours in the intermediate overburden and shallow bedrock aquifers indicate that the highest concentrations of the most

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prevalent contaminant analytes are located predominantly along the central, eastern, and southeastern portions of the Site.

The intermediate overburden contaminant plume(s) that was inferred from the Q39/LTM-4 data is presented as Figure 5. Detected concentrations of the target analytes suggest that 1,1-DCA continues to represent the largest contaminant plume area of the four selected analytes in the overburden aquifer. The Q39/LTM-4 data suggests that the 1,1-DCA plume (in the overburden) extends through the central, south and east portions of the Site cap area and to the south/southeast of the cap. The inferred TCE and cis 1,2-DCE plumes cover similar areas extending from the north central portion of the cap area to the area southeast of the cap near Quiggle Brook. A comparatively small DMF plume area in the overburden exists to the southeast of the on-Site capped area proximate to well B-12B-I. Based on our comparison with the Q27 through Q38 inferred plume areas and the contaminant plume areas inferred from the Q39/LTM-4 data, we conclude that the general plume extent areas have remained stable and have exhibited evidence of shrinking due to apparent reductions in the contaminant concentrations that have been observed over time. This observation indicates that the contaminant plume(s) have remained nearly identical in location over a monitoring period of approximately nine years. It should also be noted that previous Spring season sampling rounds have historically shown site-wide reductions in contaminant concentrations, while previous Fall season sampling rounds have often shown more elevated concentrations. However, during this Fall season sampling round (Q39/LTM-4), contaminant concentrations in the sampled overburden wells were generally reduced, in some cases by over 50% when compared to the previous Fall season sampling round (Q38/LTM-3).

The bedrock plume that was inferred from the Q39/LTM-4 data is presented as Figure 6. Detected concentrations of the selected analytes suggest that the 1,1-DCA plume extends from well B-6A-D to just prior to well ODW-U to the south and just prior to well NBW-U to the west. The detected concentrations of TCE, cis 1,2-DCE and DMF suggest that their respective inferred plume extent covers a comparatively smaller area that is generally contained within the larger 1,1-DCA plume.

Both increases and decreases in the average detected VOC concentrations were observed between Q36/LTM-1 and Q39/LTM-4 in the groundwater samples collected from across the Site (overburden and bedrock). During this sampling period, statistically significant increases in the detected VOC concentrations were observed in bedrock wells B-6-AD and B-8AD only. In the other bedrock wells and the overburden wells tested, decreases were observed in detected VOC concentrations between Q38/LTM-3 (Fall 2007) and Q-39/LTM-4 (Fall 2008). The site-wide trend dating back to Q30 and Q31 continues to indicate that VOC concentrations are gradually decreasing and that the dissolved phase contaminant plumes in both the overburden and bedrock aquifers are stable. Sections 5.2.1 through 5.2.4 provide additional detail for these observations. The detected VOC and DMF concentrations for Q39/LTM-4 in most wells are below the detected VOC and DMF concentrations for Q31.

VOCs were not detected in the surface water sample collected from QB-4 above the laboratory method detection limits for Q31 through Q39/LTM-4.

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5.2.1 Dissolved 1,1-DCA

The inferred 1,1-DCA isoconcentration contours from the Q39/LTM-4 data in the overburden suggest a plume configuration that is likely shrinking when compared to the inferred Q36/LTM-1 plume configuration. The highest concentrations have historically been observed on the eastern portion of the Site along Quiggle Brook and in the central portion of the Site. The maximum reported concentration of 1,1-DCA in the overburden during this sampling round was detected in well B-12B-I (2,210 ug/L). Concentrations of 1,1-DCA reported in well B-12B-I have ranged between 2,300 ug/L in Q34 (Fall 2003) and 2,800 ug/L in Q37/LTM-2 (Fall 2006). Concentrations have been reported as high as 3,800 ug/L in well B-9A-I Q36/LTM-1 (Fall 2004) in the central portion of the Site. However, reported concentrations in well B-9A-I have decreased during each of the previous two sampling rounds, with reported concentrations of 360 ug/L in Q38/LTM-3 ( Fall 2006) and 168 ug/L in Q39/LTM-4 (Fall 2008).

The 1,1-DCA plume within the bedrock was inferred to be an elongated oval trending in a north-south direction and widening with lower concentrations as it moves south. The bedrock wells B-6A-D, B-8A-D, NBW-U, ODW-U and ODW-L were used to delineate the bedrock plume. The maximum detected concentration of 1,1-DCA in the bedrock during this sampling round was detected in well B-6A-D (3,630 ug/L). B-6A-D also had the maximum 1,1-DCA concentration observed in Q38/LTM-3 (1,200 ug/L), Q37/LTM-2 (3,000 ug/L), Q36/LTM-1 (4,200 ug/L) and Q34 (3,300 ug/L). The concentrations of 1,1-DCA reported in well NBW-U (12.7 ug/L) and well ODW-U (8.6 ug/L) were above the Performance Standard of 5 ug/L; however, concentrations reported in both wells during this sampling round were lower than Q38/LTM-3.

Increases and decreases in the detected concentration of 1,1-DCA were observed when comparing the Q38/LTM-3 results to the Q39/LTM-4 results. The greatest increase in detected 1,1-DCA concentration from Q38/LTM-3 to Q39/LTM-4 was observed in well B-6A-D (1,200 ug/L to 3,630 ug/L). The greatest decrease in detected 1,1-DCA concentration (Q38/LTM-3 versus Q39/LTM-4 ) was observed in well B-5D-I (300 ug/L to 22.6 ug/L).

5.2.2 Dissolved TCE

The inferred TCE isoconcentration contours in the overburden indicate an oval plume with the highest concentrations observed in the central portion of the capped area. The highest concentration of TCE in the overburden was detected in the groundwater sample collected from well P-20 (439 ug/L).

A TCE plume within the bedrock was observed to be limited in horizontal extent. Reported concentrations above the method detection limit were reported solely in well B-8A-D during this sampling round at the same concentration reported during Q37/LTM-2 (11 ug/L). The concentrations reported in well B-6A-D were below the method detection limit (25U ug/L). It should be noted that well B-6A-D has historically had the highest bedrock TCE concentration as reported in the Q34, Q35, Q36/LTM-1, and Q37/LTM-2 sampling events.

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In general, decreases were observed in the detected concentration of TCE when comparing the Q38/LTM-3 results to the Q39/LTM-4 results. The lone increase in detected TCE concentrations from Q38/LTM-3 to Q39/LTM-4 was in well B-12B-I (25 ug/L to 28.8 ug/L). The greatest decrease in TCE concentration from Q38/LTM-3 to Q39/LTM-4 was observed in well P-20 (1,000 ug/L to 439 ug/L).

5.2.3 Dissolved 1,2-DCE

The inferred 1,2-DCE isoconcentration contours in the overburden indicate an oval plume with the highest concentrations observed in the central portion of the capped area. The plume appears to be shrinking and reported concentrations indicate the plume is stable. The highest concentration of 1,2-DCE in the overburden was detected in well P-20 (2,600J ug/L).

The 1,2-DCE plume within the bedrock was observed primarily in the southern and southeastern portions of the Site. Concentrations of 1,2-DCE were reported in wells B-6A-D and B-8A-D. Well B-6A-D and well B-8A-D were the two bedrock wells sampled during Q39/LTM-4 with reported concentrations of 1,2-DCE (1,380 and 87 ug/L, respectively) above the 1,2 DCE Performance Standard of 70 ug/L. B-6A-D also had the highest bedrock 1,2-DCE concentration in the Q37/LTM-2, Q36/LTM-1, Q35 and Q34 sampling events with concentrations of 2,100 ug/L, 2,400 ug/L, 2,200 ug/L and 2,500 ug/L respectively.

In general, decreases in the detected concentrations of 1,2-DCE were observed when comparing the Q38/LTM-3 results to the Q39/LTM-4 results, with increases observed in bedrock wells and decreases observed in intermediate overburden wells. The greatest decrease in 1,2-DCE concentrations from Q38/LTM-3 to Q39/LTM-4 was observed in well B-12B-I (470 ug/L to 376 ug/L). The greatest increase in 1,2-DCE concentrations (Q38/LTM-3 to Q39/LTM-4 ) was observed in well B-6A-D (620 ug/L to 1,380 ug/L). While the reported concentrations during Q39/LTM-4 in well B-6A-D were higher than the reported concentrations duringQ38/LTM-3, the 1,2 DCE concentrations in well B-6A-D show a decreasing trend over time (Q37/LTM-2, 2,100 ug/L; Q38/LTM-3, 620 ug/L; Q39/LTM-4, 1,380 ug/L).

5.2.4 Dissolved DMF

The inferred DMF isoconcentration contours in the overburden indicate a generally round or oval-shaped plume observed on the eastern portion of the Site. The highest concentration of DMF in the overburden was detected in well B-12B-I (556 ug/L). B-12B-I has had the highest historical overburden DMF concentrations, with concentrations during the Q37/LTM-2, Q36/LTM-1, Q35 and Q34 sampling events of 1,500 ug/L, 1,000 ug/L, 1,400 ug/L and 1,400 ug/L respectively.

The inferred DMF isoconcentration contours in the bedrock indicate a generally oval-shaped plume observed on the southern portion of the Site. The highest concentration of DMF in the bedrock was detected in well B-8A-D (556 ug/L). Well B-8A-D also had the highest bedrock

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DMF concentration in the Q37/LTM-2, Q36/LTM-1, Q35 and Q34 sampling events with concentrations of 1,200 ug/L, 800 ug/L, 770 ug/L and 1,800 ug/L respectively.

Increases and decreases in the detected concentration of DMF were observed when comparing the Q38/LTM-3 results to the Q39/LTM-4 results. The greatest decreases in DMF concentrations from Q38/LTM-3 to Q39/LTM-4 were observed in well B-8A-D (1,100 ug/L to 556 ug/L) and B-12B-I (1,400 ug/L to 556 ug/L). The greatest increase in DMF concentration from Q38/LTM-3 to Q39/LTM-4 was observed in well B-6A-D (120 ug/L to 252 ug/L).

5.3 Surface Water Analytical Results

The surface water sample QB-4 was also analyzed for VOCs and DMF. VOCs and DMF were not detected in the QB-4 sample above the laboratory method detection limits.

A Summary of Analytical Constituents Detected in surface and groundwater samples is provided in Table 4. Complete analytical results for surface water are tabulated in Appendix A. The laboratory analytical report is provided in Appendix G.

5.4 ITW-1 Water Sample Analytical Results

The water sample from well ITW-1 was not sampled during this groundwater monitoring event. Well ITW-1 was last sampled by EPA as described in Sections 1.4 and 2.4.

6.0 Summary Rizzo completed the thirty-ninth sampling and monitoring event and fourth long term monitoring event (Q39/LTM-4 ) on November 12-13, 2008. As part of the Q39/LTM-4 activities water levels were recorded in 10 monitoring wells, and a total of 11 samples, plus 3 QA/QC samples (two trip blanks and one duplicate well sample), were collected for laboratory analysis. Representative water samples were collected from the 10 groundwater monitoring wells and one surface water sample location. Laboratory analysis of the Q39/LTM-4 periodic monitoring well and surface water samples was completed by Spectrum Analytical of Agawam, Massachusetts for volatile organic compounds (VOCs) by USEPA Method 8260 and analysis for a semi-volatile organic analyte N,N-dimethyl-formamide (DMF) by USEPA Method 8270C.

6.1 Data Usability

The Q39/LTM-4 groundwater samples were sampled using the low flow sampling protocol as described in Appendix E. During purging, stabilization of the measured parameters was accomplished for each of the sampled wells.

The analytical data generated during the Q39/LTM-4 monitoring event is of acceptable quality for the DQOs as described in the Sampling and Analysis Plan. VOCs and surrogate recoveries

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were within of the acceptable laboratory QC limits for the 14 water samples that were analyzed by the lab which include two trip blanks, 10 groundwater wells with one duplicate sample and one surface water sample that were generated during the Q-39/LTM-4 monitoring event as described in Section 3.2.2.

6.2 Groundwater Elevations

Groundwater flow in the overburden and bedrock is described in the in the Site Conceptual Site Model (CSM). The CSM defined the occurrence of groundwater in the overburden and bedrock separately and generally defined two aquifers (with small subdivisions) separated by a confining layer. The dominant factor that controls overburden groundwater flow is regional topography. Overburden groundwater west of Quiggle Brook consistently flows east toward Quiggle Brook and overburden groundwater east of Quiggle Brook flows west toward Quiggle Brook. The dominant feature that controls groundwater flow in the bedrock is the local structural fold, associated fractures and bedrock lithology type. Bedrock groundwater flows generally southeast toward Quiggle Brook down-dip and along foliation fractures related to the Site structural fold. Limited groundwater flows occur down-strike to the southwest. In addition, artesian conditions have been observed in some intermediate and bedrock wells located adjacent to Quiggle Brook.

Potentiometric surface maps for the overburden, intermediate and bedrock stratigraphic units were interpreted from the November 12, 2008 water level elevations measured in the Q39/LTM-4 wells using a krigging method. Based on the wells measured, the overburden groundwater potentiometric surface during the Q39/LTM-4 gauging event was similar to those observed during previous sampling rounds for the Fall season and non-pumping conditions. The depth to groundwater ranged from approximately 1.46 to 14.23 feet below the ground surface in the intermediate overburden; and 4.30 to 17.73 feet below ground surface in the bedrock aquifers. The inferred overburden groundwater contours for Q39/LTM-4 indicated a general easterly direction of groundwater flow across the Site. The groundwater elevation data in bedrock for the Q39/LTM-4 gauging event resulted in an inferred groundwater flow toward the southeast. The Q39/LTM-4 gauging data and potentiometric surface maps generated from the Q39/LTM-4 gauging data support the Conceptual Site Model of groundwater flow in the overburden and bedrock aquifers.

There were no observations of groundwater mounding or depressions observed in the overburden or bedrock wells measured in the Q39/LTM-4, as reported during groundwater pumping activities (2005). Based on a review of recent and historical groundwater elevation data, which are provided in Table 2, groundwater elevations measured in Q39/LTM-4 for both overburden and bedrock aquifers show seasonal fluctuations that are comparable to previous Fall season monitoring events.

6.3 Contaminant Distribution

Contaminant distribution in the overburden and bedrock is described in the Site Conceptual Site Model (CSM). Inferred contaminant plume maps for the detected analytes 1,1-DCA, TCE, total

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1,2-DCE and DMF were prepared for the intermediate overburden and bedrock groundwater units.

The inferred overburden plumes that were inferred from the Q39/LTM-4 data are presented on Figure 5. Detected concentrations of the target analytes suggest that concentrations of 1,1-DCA continue to represent the largest plume area out of the four selected analytes in the overburden aquifer. The Q39/LTM-4 data suggests that the 1,1-DCA plume in the overburden extends through the central, south and east portions of the Site cap area and to the south/southeast of the cap. The TCE and 1,2-DCE plumes cover similar areas with the highest concentrations of TCE and 1,2-DCE located in the northern portion of the capped area. A smaller DMF plume in the overburden was observed to the east of the cap proximate to well B-12B-I.

VOC contaminant concentrations in the overburden are declining as a trend and have been substantially reduced by the SC/MOM. The overburden aquifer VOC/SVOC contaminant plumes are expected to gradually migrate in the down-gradient (east/southeast) direction, however the VOC/SVOC plume migration appears to be occurring at a very slow rate such that little change or shift in the VOC/SVOC plume location and areas has been observed over the post- SC/MOM shutdown period of nearly 8 years. Due to the apparent low velocity of the Site groundwater flow through the till, sorption of VOC/SVOC contaminants to the till matrix is believed to be retarding the migration of the VOC/SVOC plumes. In the areas of the Site with the lowest groundwater flow velocities (till with clays and silts), sorption may be strong enough to negate advective transport entirely and slow the diffusion and partitioning of the VOCs into the groundwater from the soil matrix. Though this Site condition mitigates the migration of the VOC/SVOC contaminant plumes, these sorptive properties of the overburden soils may extend the amount of time required to flush the VOC/SVOC contaminants from the overburden aquifer and thereby reduce their concentrations to meet the Performance Standards for the Site. This condition graphically displays as a stable contaminant isoconcentration contour map in both overburden and bedrock aquifers. Dilution and localized areas where microbial degradation of the VOC/SVOC contaminants are expected to further reduce the contaminant concentrations; however, the reductions due to these material processes will also occur at a slow rate in the overburden soils.

The bedrock plume that was inferred from the Q39/LTM-4 data is presented on Figure 6. Detected concentrations of the selected analytes suggest that the 1,1-DCA plume extends from well B-6A-D to beyond well ODW-U to the south and approximately to well NBW-U to the west. The detected concentrations of TCE, total 1,2-DCE and DMF suggest that their respective plumes encompass a smaller area that is generally contained within the larger 1,1-DCA plume area.

Detected concentrations of the VOCs/SVOCs within the shallow bedrock contaminant plume suggest that the VOC/SVOC plume extends beyond the area of the contaminated overburden soils to the south and southeast of the Site cap. The shallow bedrock VOC/SVOC contaminant plumes inferred from the Q39 sampling data are nearly identical in size and location to shallow bedrock plumes inferred from the Q30 through Q38 sample events covering the previous six years. With the exception of well B-6A-D, the Site wide trend dating back to Q30 and Q31 indicates that VOC/SVOC concentrations are gradually decreasing in the shallow bedrock and

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have been substantially reduced by the remediation activities at the Site. Migration of the VOC/SVOC contaminant plume(s) within the shallow bedrock is expected to primarily occur within the weathered strata at the bedrock surface, and to a lesser degree, through the available fractures in the more competent shallow bedrock. Potential contaminant migration and groundwater flow in the shallow/weathered bedrock is anticipated to be towards Quiggle Brook (east/southeast) along the weathered bedrock thickness, the shallow competent bedrock and along the strike and dip surfaces of the shallow bedrock fractures.

VOCs were not detected in the surface water sample collected from QB-4 above the laboratory method detection limits for Q31 through Q39/LTM-4. Impacts to Quiggle Brook and/or down-gradient receptors have not been identified by biannual sampling rounds conducted to date.

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Table 1 GROUNDWATER ELEVATION DATA

Surface Water and Groundwater Monitoring November 12, 2008

Union Chemical Company Hope, Maine

Monitored Reference Measured Depth Groundwater Well Stratigraphic Elevation (Ft. Reference to Groundwater Elevation

Location Zone MSL) Point (Ft.) (Ft. MSL) B-5D-I Intermediate 352.66 Steel 3.14 349.52 B-6A-D Bedrock 355.51 PVC 4.30 351.21 B-8A-D Bedrock 359.98 PVC 6.00 353.98 B-9A-I Intermediate 371.94 PVC 14.23 357.71

B-12B-I Intermediate 349.51 Steel 1.46 348.05 NBW-L Bedrock 358.58 Steel 10.54 348.04 NBW-U Bedrock 358.58 Steel 5.05 353.53 ODW-L Bedrock 356.92 Steel 16.46 340.46 ODW-U Bedrock 356.92 Steel 17.73 339.19

P-20 Intermediate 370.32 Steel 12.19 358.13

FR - Frozen NA- Well not gauged + - indicates that actual water table elevation exceeds the indicated elevation due to artesian conditions or groundwater seeping from the base of the well standpipe

Table 2

Comparative Water Table Elevations Surface Water and Groundwater Monitoring - Q39/LTM-4


Well Location Date Groundwater

Elevation (Ft. MSL) Change in Water Table

Elevation (Ft.) B-5B-I 11/8/1999 346.59 NA B-5B-I 4/8/2000 NA NA B-5B-I 10/23/2000 340.65 -5.94 B-5B-I 4/29/2001 343.43 2.78 B-5B-I 10/29/2001 344.31 0.88 B-5B-I 4/22/2002 343.77 -0.54 B-5B-I 11/7/2002 342.75 -1.02 B-5B-I 3/31/2003 348.64 5.89 B-5D-I* 11/10/2003 345.03 -3.61 B-5D-I* 4/13/2004 349.44 4.41 B-5D-I* 11/8/2004 349.33 -0.11 B-5D-I* 10/19/2006 349.24 -0.09 B-5D-I* 11/15/2007 348.6 -0.64 B-5D-I* 11/12/2008 349.52 0.92 * B-5 series wells replaced prior to November 2003 (Q34) gauging/sampling B-6A-D 11/8/1999 350.36 NA B-6A-D 4/8/2000 351.81 1.45 B-6A-D 10/23/2000 346.91 -4.9 B-6A-D 4/29/2001 351.84 4.93 B-6A-D 10/29/2001 345.48 -6.36 B-6A-D 4/22/2002 352.17 6.69 B-6A-D 3/31/2003 352.44 0.27 B-6A-D 11/10/2003 351.14 -1.3 B-6A-D 4/13/2004 351.31 0.17 B-6A-D 11/8/2004 350.38 -0.93 B-6A-D 10/19/2006 350.65 0.27 B-6A-D 11/15/2007 352.19 1.81 B-6A-D 11/12/2008 351.21 -0.98 B-8A-D 11/8/1999 350.2 NA B-8A-D 4/8/2000 350.68 0.48 B-8A-D 10/23/2000 344.83 -5.85 B-8A-D 4/29/2001 350.95 6.12 B-8A-D 10/29/2001 343.18 -7.77 B-8A-D 4/22/2002 350.8 7.62 B-8A-D 11/7/2002 348.71 -2.09 B-8A-D 3/31/2003 351.71 3 B-8A-D 11/10/2003 350.39 -1.32 B-8A-D 4/13/2004 350.95 0.56 B-8A-D 11/8/2004 349.64 -1.31 B-8A-D 10/19/2006 352.28 2.64 B-8A-D 11/15/2007 354.45 4.81 B-8A-D 11/12/2008 353.98 -0.47

+ indicates that actual water level exceedes refrence elevation due to artesian conditions

Table 2

Comparative Water Table Elevations Surface Water and Groundwater Monitoring - Q39/LTM-4


Well Location Date Groundwater

Elevation (Ft. MSL) Change in Water Table

Elevation (Ft.) B-9A-I 11/8/1999 358.06 NA B-9A-I 4/8/2000 358.53 0.47 B-9A-I 10/23/2000 355.4 -3.13 B-9A-I 4/29/2001 358.13 2.73 B-9A-I 10/29/2001 351.23 -6.9 B-9A-I 4/22/2002 358.48 7.25 B-9A-I 11/7/2002 356.53 -1.95 B-9A-I 3/31/2003 359.4 2.87 B-9A-I 11/10/2003 357.94 -1.46 B-9A-I 4/13/2004 357.67 -0.27 B-9A-I 11/8/2004 357.15 -0.52 B-9A-I 10/19/2006 357.51 0.36 B-9A-I 11/15/2007 358.32 1.17 B-9A-I 11/12/2008 357.71 -0.61 B-12-B-I 11/8/1999 341.78 NA B-12-B-I 4/8/2000 348.35 6.57 B-12-B-I 10/23/2000 343.62 -4.73 B-12-B-I 4/29/2001 348.1 4.48 B-12-B-I 10/29/2001 346.7 -1.4 B-12-B-I 4/22/2002 348.02 1.32 B-12-B-I 11/7/2002 348.11 0.09 B-12-B-I 3/31/2003 348.47 0.36 B-12-B-I 11/10/2003 348.73 0.26 B-12-B-I 4/13/2004 347.98 -0.75 B-12-B-I 11/8/2004 347.47 -0.51 B-12-B-I 10/19/2006 347.82 -0.16 B-12-B-I 11/15/2007 348.31 0.33 B-12-B-I 11/12/2008 348.05 -0.26 NBW-L 4/13/2004 348.7 NA NBW-L 11/8/2004 347.69 -1.01 NBW-L 10/19/2006 347.2 -1.5 NBW-L 11/15/2007 348.92 0.22 NBW-L 11/12/2008 348.04 -0.88

NBW-U 4/13/2004 352.12 NA NBW-U 11/8/2004 351.53 -0.59 NBW-U 10/19/2006 353.29 1.76 NBW-U 11/15/2007 353.94 2.41 NBW-U 11/12/2008 353.53 -0.41 ODW-L 4/13/2004 340.92 NA ODW-L 11/8/2004 339.11 -1.81 ODW-L 10/19/2006 338.51 -0.6 ODW-L 11/15/2007 340.75 1.64 ODW-L 11/12/2008 340.46 -0.29 ODW-U 4/13/2004 340.06 NA ODW-U 11/8/2004 338.49 -1.57 ODW-U 10/19/2006 337.86 -0.63 ODW-U 11/15/2007 339.86 1.37 ODW-U 11/12/2008 339.19 -0.67

P-20 4/13/2004 358.36 NA P-20 11/8/2004 357.46 -0.9 P-20 10/19/2006 357.77 0.31 P-20 11/15/2007 359.11 1.65 P-20 11/12/2008 358.13 -0.98

+ indicates that actual water level exceedes refrence elevation due to artesian conditions

Table 3

WATER QUALITY INDICATOR PARAMETERS Surface and Groundwater Monitoring - Q39/LTM-4

Union Chemical Company Superfund Site Hope, Maine

Well Location

LTM-1 Well

Perox Add. Well

Date Purge Rate ml/min

Total Drawdown

(ft)

Temperature (OC)

Conductivity (uS/cm) pH

Oxidation/Reduction Potential (mV)

Dissolved Oxygen (mg/l)

Turbidity (ntu)

B-5D-I x 11/12/2008 80 2.49 6.7 181 7.9 -95.3 0.79 4.1 B-6A-D x x 11/12/2008 60 1.87 7.85 449 7.6 -182 0.36 0.6 B-8A-D x x 11/12/2008 25 3.35 7.5 357 7.7 -130.6 0.4 0.0 B-9A-I x x 11/12/2008 80 5.08 8.25 4894 7.8 -183 0.22 2.96 B-12B-I x 11/12/2008 70 0.24 7.97 519 9.6 -170.1 0.36 1.1 NBW-L x x 11/12/2008 45 3.69 7.61 769 4.1 302.2 72.2 0 NBW-U x x 11/12/2008 45 2.81 8.00 406 6.6 237.1 58.7 0.0 ODW-L x x 11/12/2008 45 4.24 4.03 803 3.9 390 74.6 0.8 ODW-U x x 11/12/2008 15 0.21 7.00 384 5.5 280.0 30.18 4.9 P-20 x x 11/12/2008 60 0.90 5.25 575 9.2 -209 0.1 18.4 QB-4 x 11/12/2008 NA NA 4.90 31 8.0 18.5 16.5 NA

NA-parameter not measured S - sample too silty for turbidity reading * Reading from backup DO meter **Interference expected to be impacting parameter Page 1

TABLE 4 Page: 5 of 7 SUMMARY OF CONSTITUENTS DETECTED

Surface and Groundwater Monitoring - Q38/LTM-3

Union Chemical Superfund Site

Hope, Maine

Sample Location B5DI B6AD B8AD B8AD-Dup B9AI B12 BI NBW-U ODW-L ODW-U VP 20 QB 4 NBW-L Trip Blank Trip Blank-2 Laboratory ID SA87563-01 SA87563-10 SA87563-07 SA87563-08 SA87563-09 SA87563-02 SA87563-03 SA87563-12 SA87563-05 SA87563-11 SA87563-06 SA87563-04 SA87563-13 SA87563-14

CONSTITUENT Sample Date 12-Nov-08 15:00 13-Nov-08 08:35 13-Nov-08 10:15 13-Nov-08 10:17 13-Nov-08 11:20 12-Nov-08 15:00 12-Nov-08 14:30 13-Nov-08 08:45 12-Nov-08 16:20 13-Nov-08 10:15 13-Nov-08 10:45 12-Nov-08 14:45 13-Nov-08 10:50 13-Nov-08 11:25 SW846 8260B (µg/l) Acetone 10U 250U 100U 100U 1740J 250U 10U 91.7 10U 50U 10U 414 10U 10U 2-Butanone (MEK) 10U 250U 100U 100U 1280J 250U 10U 10U 10U 50U 10U 50U 10U 10U Chloroethane 2U 50U 20U 20U 300 58.0 2U 3.2 2U 10U 2U 10U 2U 2U 1,1-Dichloroethane 22.6 3630 833 898 168 2210 12.7 6.3 8.6 5U 1U 5U 1U 1U 1,1-Dichloroethene 1U 228 182 200 5U 114 1U 1U 1U 5.0 1U 5U 1U 1U cis-1,2-Dichloroethene 1U 1380 87.0 93.5 6.4 376 1U 1.9 1U 2600J 1U 5U 1U 1U trans-1,2-Dichloroethene 1U 25.8 10U 10U 5U 25U 1U 1U 1U 920 1U 5U 1U 1U Ethylbenzene 1U 3120 10U 10U 22.7 178 1U 1U 1U 5U 1U 5U 1U 1U 4-Methyl-2-pentanone (MIBK) 10U 250U 100U 100U 95.6 250U 10U 10U 10U 50U 10U 50U 10U 10U Toluene 1U 25.8 10U 10U 41.6 25U 1.0 2.4 2.9 5U 1U 5U 1U 1U Trichloroethene 1U 25U 11.0 11.8 5.6 28.8 1U 1U 1U 439 1U 5U 1U 1U Vinyl chloride 1U 729 16.1 18.1 5U 32.0 1U 1U 1U 103 1U 5U 1U 1U m,p-Xylene 2U 2060 20U 20U 27.0 60.0 2U 2U 2U 10U 2U 10U 2U 2U o-Xylene 1U 25U 10U 10U 9.8 25U 1U 1U 1U 5U 1U 5U 1U 1U Tert-Butanol / butyl alcohol 10U 250U 100U 100U 50U 250U 10U 297 36.0 50U 10U 275 10U 10U SW846 8270C (µg/l) Dimethyl formamide 62.5U 252 556 557 125U 556 62.5U 62.5U 62.5U 62.5U 62.5U 62.5U 3 & 4-Methylphenol 125U 125U 125U 125U 254 125U 125U 125U 125U 125U 125U 125U

NA = Not analyzed D = The analyte was identified in an analysis at a secondary dilution factor U = Below quantitation limit J = The reported result is an estimate.

TABLE 5 - CONSTITUENT MAXIMUM CONCENTRATION FOUND AND PERFORMANCE STANDARDS - OVERBURDEN WELLS Surface Water and Groundwater Monitoring -Q38/LTM-3


Constituent Detection1 Average Concentration2

(ug/L)

Performance Standard

(ug/L)


Exceedences3

Maximum Reported

Concentration (ug/L)

Location of

Maximum

Q38 Location of Maximum

(conc, ug/L)


(conc, ug/L)


(conc, ug/L)

vinyl chloride 2 / 4 35.3 2 2 / 4 103 P-20 P-20 (70) P-20 (110) P-20 (210) chloroethane 2 / 4 92.5 NA NA 300 B-9A-I B-9A-I (480) B-9A-I (670) B-12B-I (170) acetone 1 / 4 430 NA NA 1740J B-9A-I B-9A-I (2600) B-9A-I (1000) B-9A-1 (2600J) 1,1-dichloroethene 2 / 4 31.25 7 1 / 4 114 B-12B-I B-12B-I (140) B-12B-I (250) B-12B-I (240) trans-1,2-dichloroethene 1 / 4 237.75 100 1 / 4 920 P-20 P-20 (1400) P-20 (570) P-20 (1500) 1,1-dichloroethane 3 / 4 601.4 5 3 / 4 2210 B-12B-I B-12B-I (2400) B-12B-I (2800) B-9A-I (3800J) 2-butanone (MEK) 1 / 4 372.5 170J 1 / 4 1180J B-9A-I B-9A-I (2600) B-9A-I (1000J) B-9A-I (4600J) cis-1,2-dichloroethene 3 / 4 645.8 70 2 / 4 2600J P-20 P-20 (3200) P-20 (1500) P-20 (3600) tetrahydrofuran (THF) 0 / 4 90 70 1 / 4 250U B-12B-I B-12B-I (26) 9A-I/B-12B-I/P-20 (5 B-9A-I/B-12B-I/P-20 (100V) trichloroethene 3 / 4 118.6 5 3 / 4 439 P-20 P-20 (1000) P-20 (570) P-20 (2400) 4-methyl-2-pentanone (MIBK) 1 / 4 90 NA NA 95.6 B-9A-I B-12B-I (150) B-12B-I (230) B-9A-I/B-12B-I (300) toluene 1 / 4 18.1 2000 0 / 4 41.6 B-9A-I B-9A-I (71) B-9A-I (72) B-9A-I (90J) tetrachloroethene 0 / 4 9 5 1 / 4 25U B-12B-I B-12B-I (10U) 9A-I/B-12B-I/P-20 (1 B-9A-I/B-12B-I/P-20 (20V) ethylbenzene 2 / 4 51.6 700 0 / 4 178 B-12B-I B-12B-I (320) B-12B-I (460) B-12B-I (230) total xylenes 3 / 4 17.4 10000 0 / 4 60 B-12B-I B-12B-I (250) B-12B-I (380) B-12B-I (300) Dimethylformamide 1 / 4 201.5 390 1 / 4 556 B-12B-I B-12B-I (1400) B-12B-I (1500) B-12B-I (1000)

NOTES: 1Frequency of detection indicates the number of wells in which a constituent was detected over the number of wells sampled for each analyte. 2Average Concentration calculated using the typical detection limit if the compound tested was not detected. 3Performance Standard Exceedences indicate the number of wells in which the constituents reported concentration or Method Detection Limit exceeded the constituents Performance Standard over the number of wells sampled for each analyte. 1

NA = Maine Maximum Exposure Guideline or EPA Maximum Contaminant Level standards are not available for this compound

J = The reported result is an estimate.

TABLE 6 - CONSTITUENT MAXIMUM CONCENTRATION FOUND AND PERFORMANCE STANDARDS - BEDROCK Surface Water and Groundwater Monitoring - Q38/LTM-3


Constituent Detection1 Average Concentration2

(ug/L)


(ug/L)


Exceedences3

Maximum Reported

Concentration (ug/L)

Location of

Maximum

Q38 Location of Maximum (conc, ug/L)




vinyl chloride 2 / 6 125.52 2 2/ 6 729 B-6A-D B-6A-D (130) B-6A-D (220) B-6A-D (160) B-6A-D (70) chloroethane 1 / 6 14.5 NA NA 3.2 ODW-L B-6A-D (20U) B-6A-D (20U) B-6A-D (20V) B-12A-D (10) acetone 2 / 6 145.9 NA NA 414 NBW-L NBW-L (280) NBW-L (120) B-6A-D (100V) MW-15D (30) 1,1-dichloroethene 2 / 6 69.6 7 2 / 6 228 B-6A-D B-8A-D DUP (190) B-6A-D (310) B-6A-D (420) B-6A-D (370) methyl t-butyl ether (MTBE) 0/6 7.1 NA NA 25U B-6A-D B-6A-D(20U) ODW-U (3) B-6A-D(20U) B-6A-D(20U) trans-1,2-dichloroethene 1 / 6 21.25 100 0 / 6 25.8 B-6A-D B-6A-D (67) B-6A-D (45) B-6A-D(20U) B-6A-D(20U) 1,1-dichloroethane 5 / 6 749.27 5 5 / 6 3630 B-6A-D B-6A-D (1200) B-6A-D (3000) B-6A-D (4200) B-6A-D (3300) 2-butanone (MEK) 0 / 6 71.67 170J 1 / 6 250U B-6A-D B-6A-D (100U) B-6A-D (100UJ) B-6A-D (100V) B-12A-D (1000) cis-1,2-dichloroethene 3 / 6 246 70 2 / 6 1380 B-6A-D B-6A-D (620) B-6A-D (2100) B-6A-D (2400) B-6A-D (2200) tetrahydrofuran (THF) 0 / 6 71.6 70 1 / 6 250U B-6A-D B-8A-D DUP (88) B-8A-D (100U) B-8A-D (100) B-12A-D/B-8A-D (50) trichloroethene 1 / 6 7.3 5 2 / 6 11 B-8A-D B-6A-D (37) B-6A-D (66) B-6A-D (60) B-6A-D (60) 4-methyl-2-pentanone (MIBK) 0 / 6 40 NA NA 100U B-6A-D/B-8A-D B-6A-D (100U) B-8A-D (340) B-8A-D (890) B-8A-D (810) toluene 0 / 6 7.8 2000 0 / 6 25.8 B-6A-D B-6A-D (20U) B-6A-D (

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