sent via email - anrweb.vt.gov

2113 Stony Brook Road

Northfield, VT 05663 (802) 485-9466

Sent via Email August 31, 2021 Mr. Dan Luneau 701 Highgate Road St. Albans, Vermont 05478 Re: Remedial Progress Report Former St. Albans Exxon 190 South Main Street St. Albans, Vermont (SMS #2002-2953) Dear Mr. Luneau: This report summarizes remedial activities and monitoring performed by Vermont HydroGeo, LLC (VHG) at the former St. Albans Exxon (Site or Property), located at 190 South Main Street in St. Albans, Vermont between May 26th and August 31st 2021 (Figures 1 and 2). Work was conducted in accordance with VHG’s Corrective Action Plan (CAP) dated August 30, 2019, which was subsequently approved by Mr. Gerold Noyes, P.E. of the Vermont Department of Environmental Conservation (VT DEC). The petroleum cleanup fund (PCF) budget tracking number for this phase of work is 27653. The overall remedial objective is to significantly reduce petroleum-contaminant mass at the Site in order to expedite Site closure and mitigate impact/risk to on-Site and off-Site sensitive receptors, including soil, groundwater, and indoor air. This report is organized in the following manner:

Section 1.0 describes the Site and project history; Section 2.0 provides soil vapor extraction (SVE) / air sparge (AS) system performance

results; Section 3.0 presents water quality monitoring data; Section 4.0 discusses the updated conceptual site model (CSM); and Section 5.0 provides conclusions and recommendations.

Mr. Dan Luneau - 2 - August 31, 2021 1.0 Site Description and History The former St. Albans Exxon Property is located at 190 South Main Street in St. Albans, Vermont, within a mixed commercial and residential setting, at a latitude of 44.80134º N and longitude of 73.08947º W (Figure 1). The Site is bordered on the north and south by residences, to the east by South Main Street (US Route 7), and to the west by railroad tracks; residences are located on the east side of the road, and west side of the tracks. A vicinity map is provided as Appendix A. A single-story brick building, with a concrete slab-on-grade foundation, is located on the eastern portion of the Property, which is currently vacant but formerly operated as a convenience store and motor fuel retailer until 2013. Mr. Luneau intends to renovate the building for office space. No other structures are present on the Site. The topography across the eastern portion of the Property is relatively flat, and the ground surface outside of the building footprint is generally covered with gravel; the concrete pad for the former pump island on the eastern side of the building was removed in summer 2018, and is currently surfaced with gravel as well. Prior to spring 2019, the western portion of the Site was wooded, and the topography behind the back of the building gradually sloped down to the west and leveled off into a relatively flat, low lying area. This area has now been largely cleared, and a considerable volume of fill has been trucked in to extend the area of higher elevation further westward. The Site and surrounding properties are serviced by municipal water and sewer systems. According to the Agency of Natural Resources website, there are several private bedrock supply wells located within a mile radius of the Site. No public water sources were identified with a mile radius of the Site. The closest private well is approximately 600 feet to the east of the Site. The Property was used as a service station since at least 1960, when four gasoline underground storage tanks (USTs) were reported on the Site. Diesel and kerosene tanks were also in use at the Site at various times, and four tanks were replaced in 1986. In 2001, petroleum contamination was discovered during piping replacement. In August 2002, ten soil borings were advanced under the supervision of Heindel & Noyes, Inc.; six of them were completed as groundwater monitoring wells. Groundwater monitoring was initiated at the Site in August 2002, and has been ongoing since that time. Monitoring wells MW-4 and MW-5 were replaced in July 2012. In July/August of 2015, four USTs, including, two 8,000-gallon gasoline, one 6,000-gallon gasoline, and one 2,000-gallon diesel, were removed from the Site and the soils were backfilled into the excavation. The highest level of contamination was noted in soils beneath the gasoline dispensers, although

Mr. Dan Luneau - 3 - August 31, 2021 contamination was also noted in the soils below the three gasoline USTs. There are currently no USTs reported on the Site. In October 2015, a supplemental site investigation was conducted by KAS, Inc. of Williston, Vermont in order to further delineate the degree and extent of the contaminant plume. Groundwater monitoring wells (MW15-01 through MW15-06) were installed in the vicinity of the former USTs and associated piping. Groundwater quality results from these wells indicated high levels of dissolved phase petroleum contamination. A Corrective Action Feasibility Investigation (CAFI) was completed by KAS in August 2016 to address the remediation of subsurface petroleum contamination. The investigation included: the installation of three additional groundwater monitoring wells; installation of one air sparge point (AS-1); installation of three soil vapor extraction (SVE) wells (SVE-1, SVE-2, and SVE-3); an updated Site survey; completion of a SVE/AS pilot test; slug testing; collection of subsurface parameters for evaluation of various remedial alternatives; and the completion of a full round of groundwater monitoring. Several remedial technologies and approaches were examined and compared. Ultimately, KAS recommended multi-phase extraction (MPE), and a MPE pilot test was at performed at the Site in February 2017. The Property sold to Mr. Dan Luneau in the summer of 2017, and Mr. Luneau hired Sprague GeoScience, LLC (SGS) of Huntington, Vermont to be his environmental consultant for this project. After review of KAS’s MPE pilot test results, SGS recommended that additional investigation be conducted including an evaluation of the upgradient extent of the contamination, the installation of deeper sparge wells, and additional AS pilot testing. VHG is now teaming with SGS on this project, acting as the prime consultant. In August and September 2018, VHG conducted an additional SSI at the Site, which included the installation of five monitoring wells (VHG-01 through VHG-05) and two sparge wells (AS-2 and AS-3) in the former pump island area, a Site-wide groundwater monitoring event, and an air sparging pilot study. The SSI better characterized contaminant distribution and pilot testing results suggested that SVE/AS can effectively be implemented at the Site to achieve remedial objectives in an expedited manner. VHG believes this technology is more technically viable and considerably less expensive to implement than dual-pump MPE, which was recommended by KAS. VHG recommended conducting a short-term SVE test to determine vapor abatement requirements, prior to developing a CAP. The pilot study and an additional Site-wide groundwater monitoring event were conducted in May 2019, with results reported to VT DEC in July 2019. Under an approved CAP, VHG constructed the remediation system in phases between early November 2019 and late May 2020, and started the system June 2, 2020. System operation

Mr. Dan Luneau - 4 - August 31, 2021 and maintenance (O&M) and groundwater monitoring is ongoing. The remediation system layout is provided on Figure 3. Mr. Luneau owns the Site, as well as properties directly north and south of the Site. Contact information for Mr. Luneau is provided in Table 1-1, below.

Table 1-1. List of Interested Parties Name Address Phone Number Email Address Dan Luneau 701 Highgate Road

St. Albans, Vermont 05478 (802) 309-9243 [email protected]

2.0 SVE/AS System Performance Results On June 2, 2020, VHG started the SVE/AS system. Since startup, the SVE/AS system has essentially operated continuously. Through August 11, 2021, the SVE system has recovered an estimated 56.11 pounds of gasoline in the vapor phase, which is equivalent to about 9.35 gallons (Graph 2-1). Within the first two days of startup, with SVE wells VE-1 and VE-2 online, a peak vapor-phase mass removal rate of 0.11 pounds per hour (lbs/hr) was observed, with an influent PID reading of 111 parts per million volume/volume (ppm v/v) and influent airflow rate of about 77 CFM. Vapor-phase removal rates with VE-1 and VE-2 online have decreased significantly since system startup. On July 26, 2021, VE-2 was taken offline, and VE-4 and sparge wells SP-16, SP-17, SP-18, and SP-20 were brought online. This action resulted in a sharp increase in mass recovery rates; however, rates are now beginning to decrease.

Mr. Dan Luneau - 5 - August 31, 2021

Graph 2-1. SVE System Mass Removal Rates

Applied vacuums at the SVE wells have generally been at about -5 inches of water column (“WC). Overall decreasing trends in PID readings are apparent at each extraction well (Graph 2-2).

Graph 2-2. PID Readings at SVE Wells

During this reporting period, sparging was cycled between sparge wells SP-2 through SP-10, and SP-15, SP-16, SP-17, SP-18, and SP-20, with continuous individual sparge rates typically ranging from about 2.6 to 2.8 CFM. In general, during O&M visits, each of the operating

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Gasolin

e Recove

ry Rate (Pounds/Hour)

Cumulative

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ass Recove

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(Pounds)

Date

Cumulative Gasoline Mass Recovered Gasoline Recovery Rate

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Date

VE‐1

VE‐2

VE‐4

Mr. Dan Luneau - 6 - August 31, 2021 sparge wells are temporarily shut down and then pulsed at higher sparge rates than those set for continuous operation. At system startup, under SVE-only operating conditions, headspace PID readings at source-area monitoring wells VHG-01, VHG-02, VHG-04, VHG-05, MW-15-5, and MW-15-6 were all <1 ppm v/v. Once sparging was initiated, PID readings peaked to over 1,000 ppm v/v at VHG-01, VHG-02, and MW-15-6 after about one day of operation; PID readings at these locations have decreased significantly since (Graph 2-3).

Graph 2-3. Headspace PID Readings at Source-Area Monitoring Wells

During this reporting period, the vapor-phase GAC units were rotated one time (Table 2-1). The SVE vapor abatement system consists of two vapor-phase GAC drums connected in series (C-1 followed by C-2). During each monitoring event, a PID reading is recorded at the “C-2 Effluent” port prior to discharge to the atmosphere. When the C-2 Effluent PID reading exceeds 5 ppm v/v, the GAC units are rotated. The initial GAC drum in the C-1 position was given a serial number (SN) 001, and the original drum in the C-2 position was assigned SN 002. During the first GAC rotation, SN 001 was taken offline, SN 002 was rotated to the C-1 position, and a new GAC unit (designated SN 003) was installed in the C-2 position. This process is repeated during each GAC rotation, with the new GAC unit being designated a progressively higher SN. New GAC units are provided by Vermont Carbon Filters, LLC (VCF); VCF also removes the spent GAC units for subsequent disposal.

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MW‐15‐6

VHG‐01

VHG‐02


Table 2-1. Vapor-Phase GAC Rotation Schedule

3.0 Groundwater Monitoring

3.1 Work Completed On August 9, 2021, VHG and SGS collected groundwater samples from the following monitoring wells: MW-3, MW-4R, MW-6, AS-3, MW-15-02, MW-15-03, MW-15-04, MW-15-05, MW-15-06, VHG-01, VHG-02, VH-04, and VHG-06. VHG-03 and VHG-05 were not sampled because they were dry; MW-16-09 was not sampled because there was a decaying skunk in close proximity to the well. Prior to collecting monitoring well samples, the depth-to-water in each of the monitoring wells was measured and recorded using an electronic interface probe and/or water-level meter. Monitoring wells were purged and sampled using a peristaltic pump and dedicated Teflon-lined polyethylene and silicone tubing. VHG proposed to sample the monitoring wells in accordance with United States Environmental Protection Agency (USEPA) Region I low-flow purging and sampling protocol. However, most wells do not yield sufficiently; as such, these wells were purged dry, and samples were collected once water levels recovered adequately. For the other monitoring wells, samples were collected after at least three well volumes were purged. VHG acquired quality assurance / quality control (QA/QC) samples appropriate to meet the data quality objectives for the Site. QA/QC samples consisted of the following:

DateC-2 Effluent PID Reading

(ppm v/v)Response

6/4/2021 0.5

6/27/2021 0.7

7/13/2021 0.6

7/22/2021 0.2

7/27/2021 2.5

7/28/2021 3.8

7/29/2021 5.8

7/30/2021 5.9

8/9/2021 10.6

8/11/2021 0.0 004 offline, 005 to C-1, and new 006 at C-2.


1 – Trip Blank; and 1 – Duplicate sample (from MW-15-04).

Following collection, samples were placed in an ice-filled cooler and transported under a chain-of-custody to Endyne Inc., located in Williston, Vermont, for analysis of target petroleum VOCs by EPA Method 8021B. Target VOCs included methyl tert-butyl ether (MTBE), benzene, toluene, ethylbenzene, total xylenes, 1,2,4-trimethylbenzene (TMB), 1,3,5 TMB, 1,2,3 TMB, and naphthalene.

3.2 Results

3.2.1 Hydrogeologic Observations

Hydrogeologic monitoring data for the August 2021 monitoring event are provided in Table 3-1.

Table 3-1. Groundwater Elevation Data: August 9, 2021

Notes: BTOC = Below Top of Casing Elevation values relative to an arbitrary Site datum of 100.00 feet.

A groundwater potentiometric surface map was generated using the August 2021 hydraulic head data (Figure 4). Overall, a semi-radial groundwater flow pattern was evident in the

Well I.D.Top-of-Casing

Elevation (feet)

Depth-to-Water (feet BTOC)

Depth-to-Bottom (feet BGS)

Saturated Thickness

(feet)

Groundwater Elevation

(feet)

MW-3 98.98 13.29 16.0 2.71 85.69MW-4R 96.80 12.40 17.3 4.90 84.40MW-6 99.02 11.93 14.3 2.37 87.09

MW-15-02 99.28 12.16 17.0 4.84 87.12MW-15-03 97.29 12.55 16.0 3.45 84.74MW-15-04 99.50 12.40 17.4 5.00 87.10MW-15-05 98.99 10.62 14.2 3.58 88.37MW-15-06 98.39 11.26 12.6 1.34 87.13

VHG-01 98.79 10.88 11.5 0.62 87.91VHG-02 98.65 10.65 11.9 1.25 88.00VHG-03 98.14 Dry 8.5 0.00 --VHG-04 98.52 10.15 12.6 2.45 88.37VHG-05 97.92 Dry 9.2 0.00 --VHG-06 99.41 16.22 18.0 1.78 83.19

AS-3 98.61 11.30 13.0 1.70 87.31

Mr. Dan Luneau - 9 - August 31, 2021 shallow overburden aquifer, with flow to the northwest, west, and southwest, generally consistent with previous monitoring events.

3.2.2 Quality Assurance / Quality Control

No VOCs were detected in the trip blank. The relative percent difference (RPD) value for sample MW-15-04 and its Field Duplicate sample ranged from 1.0 to 21.4 percent for individual VOCs. The maximum acceptable RPD for water samples is 30 percent.

3.2.3 Contaminant Distribution

Dissolved-phase VOC analytical results for the August 2021 monitoring event are included in Table 3-2 and Figure 5. Laboratory report forms are included in Appendix B. Time-series graphs for select monitoring wells are included in Appendix C.

Table 3-2. Water Quality Results: August 9, 2021

Notes:

Results reported in µg/L. Shaded values exceed the VGES. VGES = Vermont Groundwater Enforcement Standard. Underlined values indicate the laboratory detection limit that the respective compound was not detected above. Bold underlined values indicate detection limit was above VGES.

Sample Location

Total Target VOCs

MTBE Benzene Toluene Ethylbenzene Total

Xylenes 1,3,5 TMB

1,2,4 TMB

1,2,3 TMB

Total TMBs

Naphthalene

GroundwaterMW-3 189 10.0 2.5 5.0 92.6 19.4 5.9 64.6 5.0 70.5 6.0

MW-4R 2,572 20.0 17.0 23.1 541 1,080 78.1 639 123 840 71.2MW-6 2.0 2.0 0.5 1.0 1.0 2.0 1.0 1.0 1.0 1.0 0.5

MW-15-02 3,809 40.0 10.0 21.6 501 942 391 1,370 294 2,055 261MW-15-03 43,794 200 544 5,740 4,830 25,100 1,130 4,400 1,130 6,660 920MW-15-04 34,167 200 411 4,300 3,670 19,300 1,000 3,720 1,010 5,730 756MW-15-05 71 2.0 0.5 1.0 54.9 2.0 1.1 7.3 1.0 8.4 5.3MW-15-06 3,787 20.0 5.0 10.0 318 1,110 398 1,300 330 2,028 331

VHG-01 6,333 100 40.5 50.0 1,370 2,060 407 1,550 558 2,515 347VHG-02 506 10.0 2.5 5.6 63.6 171 33.2 137 55.3 225.5 39.9VHG-04 2.0 2.0 0.5 1.0 1.0 2.0 1.0 1.0 1.0 1.0 0.5VHG-06 2.0 2.0 0.5 1.0 1.0 2.0 1.0 1.0 1.0 1.0 0.5

AS-3 513 10.0 2.5 5.0 14.6 32.9 109 260 74.2 443 22.0

QA / QCMW-15-04 34,167 200 411 4,300 3,670 19,300 1,000 3,720 1,010 5,730 756

Dup 30,276 40.0 372 3,940 2,960 17,000 1,010 3,120 979 5,109 895RPD 12.1 -- 10.0 8.7 21.4 12.7 1.0 17.5 3.1 11.5 16.8

Trip Blank ND 2.0 0.5 1.0 1.0 2.0 1.0 1.0 1.0 1.0 0.5

VGES -- 11 5 1000 700 10000 23 0.5--

Mr. Dan Luneau - 10 - August 31, 2021 4.0 Updated Conceptual Site Model VHG has developed the following updated conceptual site model (CSM) based on the available contaminant distribution and hydrogeologic data available for the Site. The CSM includes discussion of Site geology/hydrogeology, how contaminants of concern were released at the Site, their transport pathways and fate mechanisms, as well as exposure routes for both ecological and human receptors based on current Site use. The CSM also discusses remedial progress since the SVE/AS system was implemented. GEOLOGY/HYDROGEOLOGY In general, within the eastern portion of the Site, fine sand to silty-fine sandy fill materials are present from ground surface to about seven to eight feet bgs, underlain by glacial till, with refusal encountered at depths ranging from 8.5 feet bgs to 13 feet bgs, presumably at or near the bedrock surface. The glacial till is reworked (weathered) in several areas, and contains interbedded layers of fine to coarse sand, with some silt and gravel. Similar stratigraphy is observed across the western portion of the Property, but the overburden thickens and bedrock is estimated to be present at depths between 18 to 20 feet bgs. Bedrock beneath the eastern portion of the Site, where the contaminant plume is present, is mapped as quartzite. Several quartzite bedrock outcrops are present east of the Site. Seasonal water table fluctuations vary between about 1.1 to 3.6 feet across the Site. The saturated thickness of the overburden aquifer in the contaminant source area in the eastern portion of the Site under low water table conditions ranges from none to 1.3 feet; under high water table conditions, the saturated thickness in this area ranges from about 2.2 feet to 4.6 feet. In the western portion of the Site near MW15-04, the saturated thickness fluctuates between about 5 to 7 feet. VHG generated a groundwater potentiometric surface map (Figure 4) using hydraulic head data from the August 2021 monitoring event. Overall, a semi-radial groundwater flow pattern was evident in the shallow overburden aquifer, with flow to the northwest, west, and southwest, generally consistent with previous monitoring events. Generally, most of the overburden aquifer, and contaminant plume, occurs within the glacial till unit. Vertical flow components of the overburden aquifer have not been quantified. KAS conducted slug testing at select wells, and determined the average (geometric mean) hydraulic conductivity (K) was 2.9 x 10-01 feet per day (ft/day). Groundwater seepage velocity can be calculated using the following equation:


V = (K * i) /ne

where: V is the groundwater seepage velocity (ft/day) K is hydraulic conductivity (ft/day) i is the hydraulic gradient (ft/ft) ne is the aquifer effective porosity (%)

Using KAS’ calculated geometric mean K-value, an assumed effective porosity of 30%, and a Site-specific hydraulic gradient of 0.046 ft/ft, the average groundwater seepage velocity for the overburden aquifer (where the bulk of contaminant flux occurs) is estimated to be about 0.044 ft/day, or 16 feet per year (ft/yr); however, higher flow velocities may occur through the more reworked zones in the glacial till. The rate of transport for dissolved VOCs through the aquifer would be slower due to retardation. The hydraulic relationship between the bedrock and overburden aquifer is unknown. The nearest surface water body is Rugg Brook, located about 200 feet south of the Site. CONTAMINANT DISTRIBUTION / FATE AND TRANSPORT There appears to be two source areas for petroleum contamination identified at the Site: 1) the former UST area, and 2) the former pump island. The former pump island appears to be the primary source area. Gasoline is the contaminant of concern, and is the focus of this CSM, although diesel fuel kerosene may have been released as well. The precise age of the release(s) is unknown. Gasoline has a density less than water and, as such, is considered a light non-aqueous phase liquid (LNAPL). Gasoline is comprised of hundreds of individual compounds. These compounds are typically readily sorbed to soil and organic matter, have a relatively low aqueous solubility, and are biodegradable (under both aerobic and anaerobic conditions). In general, once released to the subsurface, gasoline can partition into four phases: 1) vapor (i.e. soil gas), 2) aqueous (dissolved in pore water or ground water), 3) sorbed (to soil minerals and organic matter), and 4) remain as NAPL, either residual or mobile. The phase partitioning and migration of petroleum hydrocarbons, once released to the subsurface, depends on several factors, including: the volume of the release, the physical and chemical properties of the individual hydrocarbon compounds, and the physical and chemical properties of the media that the hydrocarbons were released into. At the former St. Albans Exxon Site, the gasoline release has impacted soil and groundwater, and hydrocarbons are known to be present in the vapor, sorbed, and dissolved phases. No measureable LNAPL was detected in any of the Site monitoring wells during the Site

Mr. Dan Luneau - 12 - August 31, 2021 investigations to date; however, LNAPL was observed on soil at borings ASTSB-6 (located south of the convenience store) and VHG-04 (located within the former pump island), and it is possible that some residual LNAPL remains elsewhere across the Site. It appears the gasoline release occurred beneath the pump islands and migrated vertically through the vadose zone under the influence of gravity until it encountered the capillary fringe (or possibly the top of bedrock beneath the former northern pump island where bedrock is shallow); en route, the gasoline partitioned into soil vapor, pore water, organic matter in the soil, and some NAPL likely snapped off as globules and ganglia within the pore spaces. Once in the capillary zone, the NAPL was further transmitted vertically by fluctuations in the water table, creating a “smear zone” where some residual NAPL likely remains. The NAPL within the former pump island area, as well as the NAPL released beneath the water table from the former USTs, dissolved into the shallow groundwater and generated a contaminant plume of VOCs that has migrated to the west in the direction of groundwater flow. These dissolved compounds travel at a slower rate than groundwater because naturally occurring organic carbon in the soil has a partitioning effect, which is termed “retardation”. The magnitude and extent of gasoline-related impact to soil and groundwater appears to be reasonably defined at this time. The dissolved phase plume has migrated at least 115 feet from the source areas, and at this time, the vast majority of the contamination across the Site appears to be primarily concentrated within the upper saturated zone. In the eastern portion of the Site near the former pump islands, contamination appears to be present directly on top of bedrock; it is currently unknown whether bedrock has been impacted. Current contaminant distribution at the Site is further discussed in the following section. REMEDIAL PROGRESS Time-series graphs for select monitoring wells are included in Appendix C. The November 2019 soil excavation within the former pump island area removed an estimated 354 pounds of gasoline contamination (equivalent to 59 gallons). Since startup in June 2020, the SVE/AS system has recovered an additional estimated 56.11 pounds of gasoline in the vapor phase, which is equivalent to about 9.35 gallons; the amount of mass reduction attributed to biodegradation has not been quantified. Significant improvements in groundwater quality have been observed in the former pump island area since active remediation was initiated. Prior to active remediation, much of the contaminant plume core was located near the front of the on-Site building and former pump island, and was characterized with monitoring data from key wells MW-15-06, AS-3, VHG-01, VHG-02, VHG-4, and VHG-05. To assist in evaluating remedial progress in this area, VHG calculated “baseline” contaminant concentrations for the wells using data from the monitoring events conducted prior to

Mr. Dan Luneau - 13 - August 31, 2021 startup of the SVE/AS system in June 2019; the “baseline” values for each well were obtained by taking the average contaminant concentration from the two pre-remedial monitoring events, except for AS-3, where data from the September 2018 monitoring event were used as “baseline” because this was the only the well was sampled prior to implementing active remediation. In order to graph the data, VHG then assigned these “baseline” values a monitoring date of June 1, 2019, which was the day before initiating active remediation. During the latest monitoring event in August 2021, total dissolved VOC concentrations in these individual key source-area monitoring wells were reduced by 10 to 100 percent relative to baseline values, while the average contaminant reduction from all the key wells was 90 percent. (Table 4-1 and Graph 4-1).

Table 4-1. Total Dissolved VOC Concentrations Compared to Pre-Remedial Baseline

Notes:

Results reported in micrograms per Liter. VHG-05 was dry on 7/16/20, 12/2/20, and 8/9/21.

6/1/20

(Baseline)

MW-15-06 23,361 18,558 12,330 727 3,787 83.8

AS-3 6,158 3,371 600 1,682 513 91.7

VHG-01 7,037 8,449 5,900 1,709 6,333 10.0

VHG-02 26,503 24,360 3,734 199 506 98.1

VHG-04 33,667 39,087 690 2.0 2.0 100.0

VHG-05 32,848 -- -- 131 -- --

Well Average 21,596 18,765 4,651 742 2,228

% Reduction 0 13 78 97 90

Well IDInvidividual Well % Reduction on

8/9/214/27/21 8/9/217/16/20 12/2/20


Graph 4-1. Total VOC Concentrations in Key Wells Since Air Sparging was Initiated

Prior to implementing active remediation, the core of the plume appeared to be in the former pump island area, extending beneath the building and to the area west of the building where monitoring wells MW-15-03 and MW-15-04 are located (Figure 6). The remedial activities conducted to date, which have been focused primarily on the eastern side of the building, have significantly improved water quality in this area (Figure 5). However, no significant improvement in water quality is evident to date at downgradient monitoring wells MW-15-03 and MW-15-04, as SVE/AS has only recently been expanded to this portion of the Site. In general, overall stable or decreasing trends in contaminant concentrations are evident at the Site monitoring wells (see time-series graphs/tables, Appendix C). Of note, prior to implementing active remediation, overall increasing trends in total TMBs and naphthalene concentrations were evident at downgradient monitoring well MW-4R; based on recent monitoring data, concentrations now appear to be stabilizing. During the most recent monitoring event in August 2021, detected total target VOC concentrations in groundwater samples ranged from 71 micrograms per Liter (µg/L) in monitoring well MW-15-05 to 43,794 µg/L in monitoring well MW-15-03. No target VOCs were detected in monitoring wells MW-6, VHG-04, or VHG-06. Benzene, toluene, ethylbenzene, total xylenes, total TMBs, and naphthalene were detected in one or more groundwater sample at concentrations above the respective VGESs. Of note, the laboratory detection limits for MTBE were above the VGES for several samples.

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Well Average

Mr. Dan Luneau - 15 - August 31, 2021 SENSITIVE RECEPTOR EVALUATION Based on VHG’s understanding of current contaminant distribution and area land use, only deep soil (e.g. >3 feet bgs) and shallow groundwater are known to be impacted by the petroleum contamination. Shallow bedrock may be also be impacted in the former pump island area, but private drinking water supplies in the area are not likely at significant risk based on their distance to the Site. Although soil and shallow groundwater are impacted, contaminant exposure pathways to human or ecological receptors do not appear to be complete at this time. However, any future Site redevelopment or intrusive activities could possibly result in exposure. The on-Site building, which is currently vacant, has not been assessed to determine if the vapor intrusion (VI) pathway is complete. However, with the SVE/AS operational, the risk of VI is likely low. 5.0 Conclusions and Recommendations VHG has drawn the following conclusions regarding remedial activities at the Site:

Soil excavation within the former pump island area removed an estimated 354 pounds of gasoline contamination (equivalent to 59 gallons).

Since startup in June 2020, the SVE/AS system has recovered an additional estimated 56.11 pounds of gasoline in the vapor phase, which is equivalent to about 9.35 gallons. During this reporting period, the SVE/AS recovered an estimated 5.33 pounds of gasoline in the vapor phase.

Vapor-phase removal rates with VE-1 and VE-2 online have decreased significantly since system startup. On July 26, 2021, VE-2 was taken offline, and VE-4 and sparge wells SP-16, SP-17, SP-18, and SP-20 were brought online. This action resulted in a sharp increase in mass recovery rates; however, rates are now beginning to decrease.

Overall, significant improvements in groundwater quality have been observed in the

former pump island source area since active remediation was initiated. During the latest monitoring event in August 2021, total dissolved VOC concentrations in individual key source-area monitoring wells were reduced by 10 to 100 percent relative to baseline values, while the average contaminant reduction from all the key wells was 90 percent.


During the August 2021 monitoring event, benzene, toluene, ethylbenzene, total xylenes, total TMBs, and naphthalene were detected in one or more groundwater sample at concentrations above the respective VGESs.

Given the above conclusions, VHG recommends continued O&M of the SVE/AS system and Site monitoring in accordance with the corrective action plan for the Site. The next groundwater monitoring event should occur in late fall 2021. ********************************************************************************************* I certify under penalty of perjury that I am an environmental professional and that all content contained within this deliverable is to the best of my knowledge true and correct. Please do not hesitate to contact me at (802) 485-9466 or [email protected] if you have any questions. Yours truly, Vermont HydroGeo, LLC Eric J. Swiech, P.G. Principal Hydrogeologist Figures Appendices cc: Mr. Gerold Noyes, PE (VT DEC) Ms. Cindy Sprague (SGS)

FIGURES

Site

(C) Copyright 2016, Trimble Navigation Limited

SCALE 1:18056

0 1000 2000 3000 4000 5000

Feet

Declination

MN 14.43° WGN 1.34° E

MN GN

Figure 1. Site Location Map

APPENDIX A

8,598

436.8

SAE Area MapVermont Agency of Natural Resources

6,513

© Vermont Agency of Natural Resources

331.0

1:

WGS_1984_Web_Mercator_Auxiliary_Sphere

Meters331.00

NOTES

Map created using ANR's Natural Resources Atlas

LEGEND

166.00

vermont.gov

DISCLAIMER: This map is for general reference only. Data layers that appearon this map may or may not be accurate, current, or otherwise reliable. ANR and

the State of Vermont make no representations of any kind, including but notlimited to, the warranties of merchantability, or fitness for a particular use, nor

are any such warranties to be implied with respect to the data on this map.

July 3, 2018

THIS MAP IS NOT TO BE USED FOR NAVIGATION

1" = 543 1cm = 65Ft. Meters

Land Use Restrictions

Class IV GW Reclass

Class VI GW Reclass

Deed Restriction

Easement

Land Record Notice

Other

Hazardous Site

Hazardous Waste Generators

Brownfields

Underground Storage Tank (working)

Dry Cleaner

Hiking Trail

Private Wells

GPS Location

screen digitized

E911 Address

Welldriller/Clarion

Unknown

Public Water Sources

Active

Proposed

Inactive

SurfaceWaterSPA

Active

Inactive

Ground Water SPA

Active

Proposed

Inactive

Waterbody

Stream

Parcels (Non-Standardized)

Town Boundary

APPENDIX B

Laboratory Report

SAEPROJECT:

DATE RECEIVED:

WORK ORDER:

DATE REPORTED:

100905Vermont HydroGeo

2113 Stony Brook Rd

Northfield, VT 05663

Atten: Eric Swiech SAMPLER:

August 18, 2021

2108-23227

Cindy Sprague

August 09, 2021

Reviewed by:

Enclosed please find the results of the analyses performed for the samples referenced on the attached chain of custody. All required method quality control elements including instrument calibration were performed in accordance with method requirements and determined to be acceptable unless otherwise noted.

The column labeled Lab/Tech in the accompanying report denotes the laboratory facility where the testing was performed and the technician who conducted the assay. A "W" designates the Williston, VT lab under NELAC certification ELAP 11263; "R" designates the Lebanon, NH facility under certification NH 2037 and “N” the Plattsburgh, NY lab under certification ELAP 11892. “Sub” indicates the testing was performed by a subcontracted laboratory. The accreditation status of the subcontracted lab is referenced in the corresponding NELAC and Qual fields.

The NELAC column also denotes the accreditation status of each laboratory for each reported parameter. “A” indicates the referenced laboratory is NELAC accredited for the parameter reported. “N” indicates the laboratory is not accredited. “U” indicates that NELAC does not offer accreditation for that parameter in that specific matrix. Test results denoted with an “A” meet all National Environmental Laboratory Accreditation Program requirements except where denoted by pertinent data qualifiers. Test results are representative of the samples as they were received at the laboratory

Endyne, Inc. warrants, to the best of its knowledge and belief, the accuracy of the analytical

test results contained in this report, but makes no other warranty, expressed or implied, especially no warranties of merchantability or fitness for a particular purpose.

___________________

Harry B. Locker, Ph.D.

Laboratory Director

160 James Brown Dr., Williston, VT 05495

Ph 802-879-4333 Fax 802-879-7103 ELAP 11263

www.endynelabs.com

NH203756 Etna Road, Lebanon, NH 03766

Ph 603-678-4891 Fax 603-678-4893

Laboratory Report

Vermont HydroGeo

Page 2 of 5

CLIENT:PROJECT: SAE

WORK ORDER:DATE RECEIVED:

2108-2322708/09/2021

8/18/2021REPORT DATE:

001 Date Sampled: 8/9/21Site: VHG-01 8/12/21 EEPWAnalysis Date:14:00

QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter

TEST METHOD: EPA 8260C

< 100 AMethyl-t-butyl ether (MTBE) ug/L 40.5 ABenzene ug/L

< 50.0 AToluene ug/L 1,370 AEthylbenzene ug/L

2,060 AXylenes, Total ug/L 407 A1,3,5-Trimethylbenzene ug/L

1,550 A1,2,4-Trimethylbenzene ug/L 558 U1,2,3-Trimethylbenzene ug/L

347 ANaphthalene ug/L 100 ASurr. 1 (Dibromofluoromethane) %

98 ASurr. 2 (Toluene d8) % 99 ASurr. 3 (4-Bromofluorobenzene) %

>10 UUnidentified Peaks


QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter

TEST METHOD: EPA 8021B

< 10.0 NMethyl-t-butyl ether (MTBE) ug/L < 2.5 NBenzene ug/L

5.6 NToluene ug/L 63.6 NEthylbenzene ug/L

171 NXylenes, Total ug/L 33.2 N1,3,5-Trimethylbenzene ug/L

137 N1,2,4-Trimethylbenzene ug/L 55.3 U1,2,3-Trimethylbenzene ug/L

39.9 NNaphthalene ug/L 97 NSurr. 1 (Bromobenzene) %

>10 NUnidentified Peaks


QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter



< 1.0 NToluene ug/L < 1.0 NEthylbenzene ug/L

< 2.0 NXylenes, Total ug/L < 1.0 N1,3,5-Trimethylbenzene ug/L

< 1.0 N1,2,4-Trimethylbenzene ug/L < 1.0 U1,2,3-Trimethylbenzene ug/L

< 0.5 NNaphthalene ug/L 104 NSurr. 1 (Bromobenzene) %

0 NUnidentified Peaks

004 Date Sampled: 8/9/21Site: AS-3 8/16/21 EEPWAnalysis Date:14:15

QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter



< 5.0 NToluene ug/L 14.6 NEthylbenzene ug/L

32.9 NXylenes, Total ug/L 109 N1,3,5-Trimethylbenzene ug/L

260 N1,2,4-Trimethylbenzene ug/L 74.2 U1,2,3-Trimethylbenzene ug/L

22.0 NNaphthalene ug/L 98 NSurr. 1 (Bromobenzene) %


Laboratory Report

Vermont HydroGeo

Page 3 of 5

CLIENT:PROJECT: SAE


2108-2322708/09/2021


005 Date Sampled: 8/9/21Site: MW-15-06 8/16/21 EEPWAnalysis Date:14:17

QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter



< 10.0 NToluene ug/L 318 NEthylbenzene ug/L

1,110 NXylenes, Total ug/L 398 N1,3,5-Trimethylbenzene ug/L

1,300 N1,2,4-Trimethylbenzene ug/L 330 U1,2,3-Trimethylbenzene ug/L

331 NNaphthalene ug/L 97 NSurr. 1 (Bromobenzene) %



QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter


< 2.0 AMethyl-t-butyl ether (MTBE) ug/L < 0.5 ABenzene ug/L

< 1.0 AToluene ug/L 54.9 AEthylbenzene ug/L

< 2.0 AXylenes, Total ug/L 1.1 A1,3,5-Trimethylbenzene ug/L

7.3 A1,2,4-Trimethylbenzene ug/L < 1.0 U1,2,3-Trimethylbenzene ug/L

5.3 ANaphthalene ug/L 98 ASurr. 1 (Dibromofluoromethane) %



007 Date Sampled: 8/9/21Site: Trip Blank 8/12/21 EEPWAnalysis Date:10:15

QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter



< 1.0 AToluene ug/L < 1.0 AEthylbenzene ug/L

< 2.0 AXylenes, Total ug/L < 1.0 A1,3,5-Trimethylbenzene ug/L

< 1.0 A1,2,4-Trimethylbenzene ug/L < 1.0 U1,2,3-Trimethylbenzene ug/L

< 0.5 ANaphthalene ug/L 98 ASurr. 1 (Dibromofluoromethane) %


0 UUnidentified Peaks


QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter


< 200 AMethyl-t-butyl ether (MTBE) ug/L 411 ABenzene ug/L

4,300 AToluene ug/L 3,670 AEthylbenzene ug/L

19,300 AXylenes, Total ug/L 1,000 A1,3,5-Trimethylbenzene ug/L

3,720 A1,2,4-Trimethylbenzene ug/L 1,010 U1,2,3-Trimethylbenzene ug/L




Laboratory Report

Vermont HydroGeo

Page 4 of 5

CLIENT:PROJECT: SAE


2108-2322708/09/2021



QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter


< 200 AMethyl-t-butyl ether (MTBE) ug/L 544 ABenzene ug/L

5,740 AToluene ug/L 4,830 AEthylbenzene ug/L

25,100 AXylenes, Total ug/L 1,130 A1,3,5-Trimethylbenzene ug/L

4,400 A1,2,4-Trimethylbenzene ug/L 1,130 U1,2,3-Trimethylbenzene ug/L





QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter



< 1.0 AToluene ug/L < 1.0 AEthylbenzene ug/L

< 2.0 AXylenes, Total ug/L < 1.0 A1,3,5-Trimethylbenzene ug/L

< 1.0 A1,2,4-Trimethylbenzene ug/L < 1.0 U1,2,3-Trimethylbenzene ug/L

< 0.5 ANaphthalene ug/L 98 ASurr. 1 (Dibromofluoromethane) %


0 UUnidentified Peaks

011 Date Sampled: 8/9/21Site: MW-4R 8/12/21 EEPWAnalysis Date:16:00

QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter


< 20.0 AMethyl-t-butyl ether (MTBE) ug/L 17.0 ABenzene ug/L

23.1 AToluene ug/L 541 AEthylbenzene ug/L

1,080 AXylenes, Total ug/L 78.1 A1,3,5-Trimethylbenzene ug/L

639 A1,2,4-Trimethylbenzene ug/L 123 U1,2,3-Trimethylbenzene ug/L




012 Date Sampled: 8/9/21Site: MW-3 8/12/21 EEPWAnalysis Date:14:45

QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter



< 5.0 AToluene ug/L 92.6 AEthylbenzene ug/L

19.4 AXylenes, Total ug/L 5.9 A1,3,5-Trimethylbenzene ug/L

64.6 A1,2,4-Trimethylbenzene ug/L < 5.0 U1,2,3-Trimethylbenzene ug/L




Laboratory Report

Vermont HydroGeo

Page 5 of 5

CLIENT:PROJECT: SAE


2108-2322708/09/2021



QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter



21.6 NToluene ug/L 501 NEthylbenzene ug/L

942 NXylenes, Total ug/L 391 N1,3,5-Trimethylbenzene ug/L




014 Date Sampled: 8/9/21Site: MW-6 8/16/21 EEPWAnalysis Date:17:20

QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter



< 1.0 NToluene ug/L < 1.0 NEthylbenzene ug/L

< 2.0 NXylenes, Total ug/L < 1.0 N1,3,5-Trimethylbenzene ug/L

< 1.0 N1,2,4-Trimethylbenzene ug/L < 1.0 U1,2,3-Trimethylbenzene ug/L

< 0.5 NNaphthalene ug/L 102 NSurr. 1 (Bromobenzene) %

0 NUnidentified Peaks

015 Date Sampled: 8/9/21Site: Duplicate 8/16/21 TRPWAnalysis Date:

QualNelac

Result

UnitResult

Result

ParameterQualNelac

Result

UnitResult

Result

Parameter


< 40.0 NMethyl-t-butyl ether (MTBE) ug/L 372 NBenzene ug/L

3,940 NToluene ug/L 2,960 NEthylbenzene ug/L

17,000 NXylenes, Total ug/L 1,010 N1,3,5-Trimethylbenzene ug/L




APPENDIX C

Graph 1. MW-15-02VOC Concentrations in Groundwater Over Time

St. Albans MobilSt. Albans, Vermont

Date Total VOCs MTBE Benzene TolueneEthyl

benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

10/23/15 6,403 40.0 22.3 57.4 1,060 2,190 2,702 3714/21/16 5,168 100.0 25.0 50.0 888 1,530 2,437 3139/12/18 3,440 8.5 4.9 14.6 500 511 871 1,530 13.175/17/19 540 10.0 2.8 5.0 111 98.9 293 29.6 9.98

11/19/19 5,095 19.7 8.3 18.5 901 1,280 2,585 282 10.887/16/20 5,597 24.8 12.7 23.0 898 1,290 3,060 301 11.98

12/02/20 5,203 200 50.0 100 905 1,260 2,780 258 11.7104/27/21 143 2.0 0.9 1.1 15.3 25.9 90.5 7.6 10.9708/09/21 3,831 40.0 10.0 21.6 501 942 2,055 261 12.16

VGES --- 11 5 1,000 700 10,000 23 0.5 ----

Notes: Results reported in micrograms per liter (µg/L)Bold values highlight detected concentrations.Underlined values are the detection limits; these values are used for graphing.VGES - Vermont Groundwater Enforcement StandardsMTBE - Methyl tert-butyl etherTotal TMBs = 1,2,4 TMB and 1,3,5 TMB, plus 1,2,3 TMB beginning on 11/19/19.Shaded areas denote VGES exceedance.

9

10

11

12

13

14

15

161

10

100

1,000

10,000

1/22/10 6/6/11 10/18/12 3/2/14 7/15/15 11/26/16 4/10/18 8/23/19 1/4/21 5/19/22

Dep

th-t

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ater

(fe

et B

TO

C)

Co

nce

ntr

atio

n (

µg

/L)

Date

Total TMBs Total VOCs Naph-thalene Depth-to-Water

Vermont HydroGeo, LLC




benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

10/23/15 39,579 200 728 6,670 5,140 20,500 5,830 7114/21/16 15,590 200 305 340 3,450 4,410 6,300 7859/12/18 31,299 200 602 5,400 3,570 17,600 3,300 827 13.495/17/19 9,825 200 406 413 2,410 4,440 1,900 256 11.10

11/19/19 44,211 200 565 7,980 4,280 24,600 5,860 926 13.707/16/20 44,672 200 585 7,760 4,560 24,300 6,550 917 12.51

12/02/20 38,060 200 426 5,540 4,330 21,300 5,630 834 12.3204/27/21 42,111 200 516 7,340 4,570 22,600 6,170 915 12.1508/09/21 43,794 200 544 5,740 4,830 25,100 6,660 920 12.55

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


9

10

11

12

13

14

15

161

10

100

1,000

10,000

100,000

1/22/10 6/6/11 10/18/12 3/2/14 7/15/15 11/26/16 4/10/18 8/23/19 1/4/21 5/19/22

Dep

th-t

o-W

ater

(fe

et B

TO

C)

Co

nce

ntr

atio

n (

µg

/L)

Date






benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

10/23/15 45,914 44.8 1,280 12,200 4,010 22,800 4,840 7394/21/16 57,018 400 1,330 14,600 5,370 29,300 5,480 9382/28/17 40,632 400 646 7,690 4,220 22,500 4,632 9449/12/18 30,491 200 719 5,000 3,240 17,000 3,699 833 13.065/17/19 35,813 200 529 5,190 3,970 20,300 4,860 964 11.22

11/19/19 43,642 200 502 6,250 4,140 24,900 6,730 1,120 11.797/16/20 40,936 200 704 6,250 4,250 22,800 6,000 932 12.24

12/02/20 39,145 200 553 7,190 4,090 21,000 5,530 782 12.1404/27/21 41,041 200 468 7,560 4,250 21,900 5,930 933 11.8508/09/21 34,167 200 411 4,300 3,670 19,300 5,730 756 12.40

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


9

10

11

12

13

14

15

161

10

100

1,000

10,000

100,000

1/22/10 6/6/11 10/18/12 3/2/14 7/15/15 11/26/16 4/10/18 8/23/19 1/4/21 5/19/22

Dep

th-t

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ater

(fe

et B

TO

C)

Co

nce

ntr

atio

n (

µg

/L)

Date






benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

10/23/15 54,130 400 200 6,630 5,520 28,000 12,770 1,2104/21/16 14,186 400 100 1,380 2,020 8,450 2,336 4009/12/18 3,569 20.0 10.0 10.0 2,090 220 1,112 147 12.115/17/19 470 10.0 5.0 5.0 134 66.3 239 31.3 8.04

11/19/19 123 2.0 0.5 1.0 72.1 4.9 31.6 14.7 9.297/16/20 268 2.7 0.5 1.0 99.4 26.8 123.7 17.9 10.43

12/02/20 265 4.7 0.8 4.6 129 44.7 62.0 19.3 10.2504/27/21 87 2.0 0.5 1.0 45.7 11.2 23.2 6.4 9.1208/09/21 69 2.0 0.5 1.0 54.9 2.0 8.4 5.3 10.62

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


8

9

10

11

12

13

14

151

10

100

1,000

10,000

100,000

1/22/10 6/6/11 10/18/12 3/2/14 7/15/15 11/26/16 4/10/18 8/23/19 1/4/21 5/19/22

Dep

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(fe

et B

TO

C)

Co

nce

ntr

atio

n (

µg

/L)

Date






benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

10/23/15 25,261 100 50.0 491 3,180 14,200 6,240 1,1504/21/16 29,107 200 50.0 167 4,250 18,200 6,490 1,2302/28/17 16,750 100 28.0 1,450 1,810 8,890 3,711 8619/12/18 16,959 200 100 111 2,090 9,740 4,018 1,000 11.895/17/19 22,052 200 50.0 132 2,960 12,200 5,660 1,100 9.32

11/19/19 24,639 20.0 5.6 163 2,940 12,600 7,550 1,380 9.737/16/20 18,558 200 50.0 100 898 7,870 8,270 1,520 10.90

12/02/20 12,680 200 50.0 100 620 4,510 6,190 1,010 10.7004/27/21 727 10.0 2.5 5.0 27.5 199 476 23.9 9.5108/09/21 3,787 20.0 5.0 10.0 318 1,110 2,028 331 11.26

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


9

10

11

12

13

14

15

161

10

100

1,000

10,000

100,000

1/22/10 6/6/11 10/18/12 3/2/14 7/15/15 11/26/16 4/10/18 8/23/19 1/4/21 5/19/22

Dep

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Co

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atio

n (

µg

/L)

Date



Graph 6. VHG-01VOC Concentrations in Groundwater Over Time



benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

5/16/19 7,615 200 50.0 682 552 4,600 1,530 251 8.7111/19/19 6,459 20.0 20.2 50.6 781 3,390 1,844 373 9.577/16/20 8,449 20.0 40.3 96.1 1,070 4,420 2,383 440 10.74

12/02/20 5,900 40.0 10.0 20.0 877 1,390 3,218 415 10.1804/27/21 1,709 40.0 10.0 20.0 241 488 852 128 9.1508/09/21 6,333 100 40.5 50.0 1,370 2,060 2,515 347 10.88

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


8

9

10

11

12

13

14

151

10

100

1,000

10,000

12/30/18 7/1/19 12/31/19 6/30/20 12/30/20 6/30/21 12/30/21

Dep

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(fe

et B

TO

C)

Co

nce

ntr

atio

n (

µg

/L)

Date






benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

9/12/18 33,452 200 110 8,590 2,150 17,600 4,340 662 11.515/16/19 1,533 10.0 5.0 28.3 127 928 404 45.6 8.31

11/19/19 51,473 20.0 223 11,100 4,440 27,800 6,770 1,140 11.907/16/20 24,360 200 50.0 2,100 1,050 12,800 6,360 2,050 10.42

12/02/20 3,734 200 50.0 108 352 1,780 1,302 192 9.9504/27/21 201 2.0 0.5 1.6 17.9 78.6 91.1 11.3 8.8808/09/21 506 10.0 2.5 5.6 63.6 171 225.5 39.9 10.65

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


8

9

10

11

12

13

14

151

10

100

1,000

10,000

100,000

7/1/18 12/30/18 7/1/19 12/31/19 6/30/20 12/30/20 6/30/21 12/30/21

Dep

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(fe

et B

TO

C)

Co

nce

ntr

atio

n (

µg

/L)

Date






benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

9/12/18 76,906 200 541 40,200 4,330 27,700 3,612 523 11.325/16/19 45,204 400 112 12,000 3,990 24,600 4,014 488 7.75

11/19/19 22,129 10.0 29.9 5,410 1,810 12,300 2,369 210 10.807/16/20 39,087 200 705 5,960 4,040 21,300 6,140 942 9.91

12/02/20 686 10.0 4.8 5.0 425 25.9 187 42.8 9.6804/27/21 2.0 2.0 0.5 1.0 1.0 2.0 1.0 0.5 8.6208/09/21 2.0 2.0 0.5 1.0 1.0 2.0 1.0 0.5 10.15

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


7

8

9

10

11

12

13

140

1

10

100

1,000

10,000

100,000

7/1/18 12/30/18 7/1/19 12/31/19 6/30/20 12/30/20 6/30/21 12/30/21

Dep

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(fe

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C)

Co

nce

ntr

atio

n (

µg

/L)

Date






benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

5/16/19 56,127 200 50.0 5,610 4,610 36,300 8,750 857 7.0011/19/19 9,570 2.0 0.6 65.2 1,150 5,770 2,325 259 8.314/27/2021 131 2.0 0.5 1.0 20.8 75.2 30.6 4.0 8.15

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


7

8

9

10

11

12

13

141

10

100

1,000

10,000

100,000

12/30/18 7/1/19 12/31/19 6/30/20 12/30/20 6/30/21

Dep

th-t

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ater

(fe

et B

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C)

Co

nce

ntr

atio

n (

µg

/L)

Date



Graph 10. MW-4RVOC Concentrations in Groundwater Over Time



benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

8/8/02 66.6 66.6 1.0 1.0 1.0 2.0 1.0 2.011/13/02 112.0 112 1.0 1.0 1.0 2.0 1.0 2.06/30/03 142.0 142 1.0 1.0 1.0 2.0 1.0 2.012/2/03 86.4 86.4 1.0 1.0 1.0 2.0 1.0 2.012/6/06 22.4 22.4 3.4 1.0 1.0 2.0 1.0 2.01/10/08 4.6 4.6 1.0 1.0 1.0 2.0 1.0 2.0

11/17/09 19.9 19.9 1.0 1.0 1.0 2.0 1.0 2.01/4/12 666 14.1 64.2 7.0 141 243 171 25.14/8/13 1,123 16.6 62.3 20.1 277 470 237 40.5

10/23/15 2,263 10.1 35.2 14.8 441 1,080 597 84.54/21/16 1,407 20.0 68.3 12.1 271 743 276 37.09/12/18 6,037 40.0 9.3 38.6 1,090 3,090 1,577 232 13.745/16/19 6,212 40.0 129 69.3 1,120 2,950 1,723 221 11.49

11/19/19 5,925 10.0 27.8 32.1 1,000 2,680 1,971 214 12.037/16/20 1,755 10.0 19.4 10.0 352 696 629 58.2 12.35

12/02/20 3,415 20.0 14.2 22.7 655 1,430 1,185 108 12.2604/27/21 4,550 20.0 23.2 53.2 703 1,810 1,810 151 11.9408/09/21 2,572 20.0 17.0 23.1 541 1,080 840 71.2 12.40

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


9

10

11

12

13

14

15

161

10

100

1,000

10,000

4/19/01 1/14/04 10/10/06 7/6/09 4/1/12 12/27/14 9/22/17 6/18/20 3/15/23

Dep

th-t

o-W

ater

(fe

et B

TO

C)

Co

nce

ntr

atio

n (

µg

/L)

Date



Graph 11. AS-3VOC Concentrations in Groundwater Over Time



benzeneXylenes

Total TMBs

Naph-thalene

Depth-to-Water

9/12/18 6,158 200 100 100 507 1,990 3,256 405 12.007/16/20 3,471 200 50.0 100 100 340 2,797 234 11.31

12/02/20 600 10.0 2.5 5.0 7.7 42.4 513 36.7 10.8704/27/21 1,682 10.0 2.5 5.0 23.2 127 1,434 97.6 9.8208/09/21 513 10.0 2.5 5.0 14.6 32.9 443 22.0 11.30

VGES --- 11 5 1,000 700 10,000 23 0.5 ----


9

10

11

12

13

14

15

161

10

100

1,000

10,000

7/1/18 12/30/18 7/1/19 12/31/19 6/30/20 12/30/20 6/30/21 12/30/21

Dep

th-t

o-W

ater

(fe

et B

TO

C)

Co

nce

ntr

atio

n (

µg

/L)

Date



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