INITIAL SITE INVESTIGATION REPORT 3 Greenfield Terrace ... · 3 Greenfield Terrace, Montpelier, VT Applied GeoSolutions, LLC Initial Site Investigation Page 2 The nearest surface

2113 Stony Brook Road Northfield, Vermont 05663

(802) 485-9466

INITIAL SITE INVESTIGATION REPORT

3 Greenfield Terrace Montpelier, Vermont

(SMS #2007-3705)

Latitude: 044° 16’ 17.10 N Longitude: 072° 35’ 15.63” W

November 12, 2007

Prepared for:

John and Sarah Vowles 3 Greenfield Terrace

Montpelier, Vermont 05602

Prepared by:

Applied GeoSolutions, LLC

Contact: Eric J. Swiech, P.G.

Principal Hydrogeologist

TABLE OF CONTENTS Page EXECUTIVE SUMMARY i 1.0 INTRODUCTION ....................................................................................................... 1 2.0 BACKGROUND ......................................................................................................... 1 2.1 Site Description and Physical Setting ................................................ 1 2.2 UST Removal ........................................................................................ 2 3.0 WORK COMPLETED ................................................................................................. 2 3.1 Soil Borings / Sampling ....................................................................... 2 3.2 Monitoring Well Installations ............................................................. 3 3.3 Monitoring Well Survey ....................................................................... 3 3.4 Hydraulic Monitoring .......................................................................... 3 3.5 Ground Water Sampling ...................................................................... 4 3.6 Sub-Slab Vapor Screening .................................................................... 4 4.0 INVESTIGATION RESULTS….. ............................................................................... 5 4.1 Geology/Hydrogeology ...................................................................... 5 4.2 Contaminant Distribution .................................................................... 5 4.2.1 Field PID Screening .................................................................... 5 4.2.2 Ground Water .............................................................................. 7 4.2.2.1 VOCs .................................................................................... 7 4.2.2.2 TPH ...................................................................................... 7 5.0 CONCEPTUAL SITE MODEL ............................................................................... 8 6.0 SENSITIVE RECEPTOR SURVEY ........................................................................ 9 7.0 CONCLUSIONS AND RECOMMENDATIONS ............................................. 10 FIGURES Figure 1 Site Location Map Figure 2 Site Plan Figure 3 Water Table Contour Map – 10/13/07 Figure 4 Contaminant Distribution – PID Readings (10/05/07) Figure 5 Contaminant Distribution – Ground Water (10/13/07) Figure 6 Hydrogeologic Cross Sections TABLES Table 1 Liquid Level Monitoring Data Table 2 Water Quality Analytical Results

APPENDIX A: Photographs APPENDIX B: Field Notes APPENDIX C: Soil Boring Logs APPENDIX D: Laboratory Reports

EXECUTIVE SUMMARY

Applied GeoSolutions, LLC (AGS) was retained by John and Sarah Vowles to complete an Initial Site Investigation (ISI) at their residence at 3 Greenfield Terrace, in Montpelier, Vermont (Site or Property). The purpose of the ISI was to characterize the impact of petroleum contamination identified during the removal of a 500-gallon, heating oil underground storage tank (UST) system at the Site, and to evaluate the risk that the release posed to sensitive receptors. On August 29, 2007, Precision Industrial Maintenance (PIM) removed an abandoned, 500-gallon heating oil UST from the Site. The UST had been discovered along the front of the residence during excavation activities associated with the installation of a foundation drain. The UST was in poor condition, with several holes present on the underside. Soil samples from beneath the UST had a peak photoionization detector (PID) reading of 130 parts per million volume (ppmv). Ground water was not encountered during the excavation; the maximum exploratory depth was about three feet beneath the bottom of the UST. The extent of petroleum impact was not determined, and all excavated soils were backfilled. In order to further investigate the impact of the heating oil release, AGS implemented a soil boring/ monitoring well installation program, conducted field screening of Site soils using a PID, and collected ground water samples for laboratory analysis. Soils encountered during the soil boring program generally consisted of loose, reworked, poorly sorted glacial till overlying an interbedded fine to coarse sand and silt unit, approximately two to three feet thick. These stratified deposits lie on top of dense, basal glacial till; both of these units appear to dip to west or southwest. Sand and gravel fill was present within the former UST grave. Bedrock was not encountered during the boring program.

On October 13, 2007, depth-to-water measurements in the overburden monitoring wells ranged from 3.81 feet below top-of-casing (BTOC) in monitoring well MW-2 to 9.23 feet BTOC in monitoring well MW-3. The average water-table gradient across the investigated area of the Site was about 0.13 feet/foot, with apparent shallow ground water flow in the overburden aquifer generally to the south. During the ISI, a maximum PID reading of 615 ppmv was recorded within the former UST grave. The heating oil release impacted soil, soil gas, and ground water. No free-phase product was observed.

The contaminant distribution has been reasonably defined, except in the downgradient direction. The majority of the contaminant mass appears to be localized in the general vicinity of the former UST, encompassing an area of about 100 square feet. Vertically

EXECUTIVE SUMMARY

within this area, the upper two to four feet of soil is significantly impacted (at relative elevations between about 95 and 99 feet); the hydrocarbons do not appear to have significantly penetrated the underlying dense, basal glacial till. On October 13, 2007, no volatile organic compounds (VOCs) were detected above respective Vermont Groundwater Enforcement Standards (VGESs) in samples collected from the on-Site monitoring wells. However, during the monitoring event, the water table was below the zone of significantly elevated PID readings observed in soil borings SB-2 (MW-1) and SB-6 (MW-3). As such, dissolved VOC concentrations could increase in MW-1 and MW-3 if the water table rises and remobilizes sorbed or residual contaminants within the smear zone. TPH (for diesel range organics) was detected at a concentration of 1.2 mg/L in the ground water sample collected from monitoring well MW-1. TPH was not detected in ground water samples collected from monitoring wells MW-2 or MW-3. There is currently not a VGES established for TPH. Sensitive receptors either impacted or at risk from the petroleum release at the Site include soils, ground water, indoor air, and underground utility corridors.

In order to mitigate the risk to sensitive receptors, the grossly contaminated soils within the general vicinity of the former UST should be excavated and disposed off-Site at an appropriate facility. These soils should include the 10’ x 10’ area south of the water and sewer lines, and may include the area on top and north of these utilities if significant contamination is encountered and impacted soils can be removed without compromising the integrity of the utilities. The depth of excavation should extend down to the top of the basal till unit, targeting the 95 to 99 foot relative elevation interval. Soils excavation should only occur where overlying “clean” soils have already been stripped in preparation for the foundation drain installation. The total volume of excavated soils is expected to range from about 15 to 20 cubic yards. This work should be implemented immediately to avoid frost complications.

Once soils excavation is complete, an appropriate remedial strategy should be developed for addressing downgradient contaminant impacts.

3 Greenfield Terrace, Montpelier, VT Applied GeoSolutions, LLC Initial Site Investigation Page 1

1.0 INTRODUCTION Applied GeoSolutions, LLC (AGS) was retained by John and Sarah Vowles to complete an Initial Site Investigation (ISI) at their residence at 3 Greenfield Terrace in Montpelier, Vermont (Site or Property) (Figure 1). The purpose of the ISI was to characterize the impact of petroleum contamination identified during the removal of an abandoned 500-gallon, heating oil underground storage tank (UST) system at the Site, and to evaluate the risk that the release posed to sensitive receptors. The ISI was completed via the Vermont Department of Environmental Conservation (VT DEC) Sites Management Section (SMS) “Expressway Method”. The expressway notification form was enclosed in a letter from AGS to Mr. Chuck Schwer of the VT DEC, dated October 8, 2007. This ISI complies with the requirements set forth in the VT DEC’s Site Investigation Procedure document, effective June 2005. 2.0 BACKGROUND

2.1 Site Description and Physical Setting The Site is located in a residential setting at 3 Greenfield Terrace, in Montpelier, Vermont, at an approximate latitude of 044° 16’ 17.10” N and longitude of 072° 35’ 15.63” (Figure 1). The Site is bound by Greenfield Terrace to the west, and residential properties to the north, south, and east. Residences in the area are served by municipal water and sewer. The Property is about 0.36 acres, and trapezoidal in shape. The on-Site residence is about 40 feet x 28 feet, and has a poured concrete basement. The abandoned UST was located beneath a former set of concrete steps on the front side of the residence (Figure 2).

The topography of the Property generally slopes down to the southwest; at the front of the Property, the slope is relatively steep (about 0.3 feet/foot). Ground cover at the Property is generally grassed, with the exception of an asphalt driveway (Figure 2). A newly installed foundation drain is located a few feet north of the former UST. The southwestern portion of the building foundation is currently exposed by a 3 foot-wide trench with six to seven foot high sidewalls (Photo #1, Appendix A).


The nearest surface water body is an unnamed, intermittent tributary of the Winooski River, which is located about 500 feet west of the former UST at its closest point. 2.2 UST Removal

On August 29, 2007, Precision Industrial Maintenance (PIM) removed an abandoned, 500-gallon heating oil UST from the Site. The UST had been discovered along the front of the residence during excavation activities associated with the installation of a foundation drain. The age of the UST is unknown. The UST was in poor condition, with several holes present on the underside. Soil samples from beneath the UST had a peak photoionization detector (PID) reading of 130 parts per million volume (ppmv). Ground water was not encountered during the excavation; the maximum exploratory depth was about three feet beneath the bottom of the UST. The extent of petroleum impact was not determined, and all excavated soils were backfilled.

Based on the findings of the UST Site Assessment, additional investigation was required to define the degree and extent of the contamination, and assess the risk to sensitive receptors.

3.0 WORK COMPLETED Copies of field notes for the project are provided in Appendix B.

3.1 Soil Borings / Sampling On October 5, 2007, AGS conducted a soil boring / soil sampling program at the Site to help determine the degree and extent of potential petroleum impact to the subsurface. A total of nine soil borings were completed (SB-1 through SB-6, and HA-1, HA-2, and HA-3). Soil boring locations are provided on Figure 2. Soil boring logs for SB-1 through SB-6 are provided in Appendix C. Soil borings SB-1 through SB-6 were advanced by Stone Environmental, Inc. (SEI) using a track-mounted Geoprobe® unit (model 6610 DT), under the supervision of AGS. Soil samples were generally collected in five-foot intervals, using macrocore sampling liners or dual tube sampling technology. Soil borings HA-1, HA-2, and HA-3 were advanced by hand with a 3 ¼-inch diameter stainless-steel bucket auger. Soil samples were logged by AGS for texture and screened for the possible presence of VOCs using a portable photoionization detector (PID) (Ion


Science Model 1000+), with a 10.6 eV lamp. The PID was calibrated using ambient air and 100 ppmv isobutylene.

Soil boring SB-1 was advanced to 6.5 feet bgs; SB-2, SB-3, and SB-5 were advanced to 10 feet bgs; SB-4 was advanced to 5 feet bgs; and SB-6 was advanced to 12 feet bgs. Hand-augered borings HA-1, HA-2, and HA-3 were advanced to about 1, 1.5, and 2 feet bgs, respectively. 3.2 Monitoring Well Installations

In order to further assess contaminant and hydrogeologic conditions at the Site, monitoring wells were constructed within three of the soil borings: monitoring well MW-1 was installed in soil boring SB-2; MW-2 was installed in SB-5; and MW-3 was installed in SB-6. The locations of the monitoring wells, relative to Site features, are presented on Figure 2.

Monitoring wells MW-1, MW-2, and MW-3 were installed to depths of about 5, 10, and 12 feet bgs, with factory-slotted 0.010”screen lengths of 3, 7.5, and 10 feet, respectively. Wells were constructed using schedule 40 poly-vinyl chloride (PVC) with flush-threaded joints. PVC riser was added to extend the top of the casings to approximately 1 to 2 feet above grade. Monitoring wells MW-1 and MW-2 are one-inch in diameter; monitoring well MW-3 is two-inch in diameter. For monitoring wells MW-1 and MW-2, the annulus around the screened sections were backfilled with #1 sand to at least 1 foot above the top of screen. For monitoring well MW-3, a pre-packed well screen was utilized. A bentonite-chip seal was set within each annulus immediately above the sand pack.

3.3 Monitoring Well Survey

On October 5, 2007, AGS surveyed the newly installed monitoring wells relative to existing Site features using an automatic level with an elevation accuracy of ± 0.01 feet and azimuth accuracy of ± 1 foot. The top-of-casing elevations were surveyed relative to an arbitrary Site datum of 100.00 feet (MW-1).

3.4 Hydraulic Monitoring On October 13, 2007, AGS collected a synoptic round of liquid levels in newly installed Site monitoring wells (MW-1, MW-2, and MW-3) using an electronic interface probe. No free-phase petroleum product was observed in the monitoring wells. Ground water elevations were subsequently calculated for each monitoring well by subtracting the measured depth-to-water readings from


the respective surveyed top-of-casing elevations, which are relative to an arbitrary Site datum of 100.00 feet. 3.5 Ground Water Sampling

On October 13, 2007, AGS collected ground water samples from monitoring wells MW-1, MW-2, and MW-3 for subsequent laboratory analysis.

Prior to purging, AGS measured and recorded the depth-to-water in the monitoring wells using an electronic interface probe; the depth to the bottom of each well was also recorded. Monitoring wells were purged dry using either a peristaltic pump with dedicated, polyethylene and silicone tubing, or a disposable polyethylene bailer. Samples were subsequently collected via dedicated polyethylene micro-bailers and drop line.

A trip blank was collected to evaluate sample quality assurance / quality control (QA/QC); a duplicate sample could not be collected due to insufficient sample volume. Following collection, all samples were properly preserved and placed in an ice-filled cooler for transport under a chain-of-custody to Endyne, Inc. of Williston, Vermont. All samples were analyzed for VOCs by EPA Method 8021B; all samples, except the trip blank, were analyzed for total petroleum hydrocarbons (TPH) by EPA Method 8015-DRO.

3.6 Sub-Slab Vapor Screening On October 13, 2007, AGS utilized a PID to screen sub-slab vapor samples at three locations within the basement, directly adjacent to the former UST (VP-1, VP-2, and VP-3. An apparent void was observed at VP-1 between about 4 to 10 inches below the top-of-slab; therefore, VP-2 and VP-3 were advanced in relative close proximity to VP-1 to further evaluate the occurrence of the void. Locations were within about 12-inches of each other; as such, for clarity, only VP-3 is displayed on the Site plan (Figure 2).

A hammer drill with a 3/8-inch diameter drill bit was used to bore through the concrete slab to a depth of 12 inches below the top-of-slab. The concrete slab was about 4 inches thick. Once the borehole was completed, the tip of the PID (Ion Science, model 1000+) was inserted in the respective borehole beneath the concrete slab, and the borehole annulus was sealed with a nitrile glove. Once readings stabilized, the final PID reading was recorded. The area over the


boreholes was then covered with a sheet of plastic and sealed to allow access for possible future monitoring.

4.0 INVESTIGATION RESULTS

4.1 Geology/Hydrogeology

Soils encountered during the soil boring program generally consisted of loose, reworked, poorly sorted glacial till overlying an interbedded fine to coarse sand and silt unit, approximately two to three feet thick. These stratified deposits lie on top of dense, basal glacial till; both of these units appear to dip to west or southwest (Figure 6). Sand and gravel fill was present within the former UST grave. Bedrock was not encountered during the boring program. On October 13, 2007, depth-to-water measurements in the overburden monitoring wells ranged from 3.81 feet below top-of-casing (BTOC) in monitoring well MW-2 to 9.23 feet BTOC in monitoring well MW-3. Calculated relative ground water elevations ranged from 95.28 feet at monitoring well MW-2 to 92.83 feet at monitoring well MW-3 (Table 1).

A water-table contour map was generated using the available hydraulic head data. The average water-table gradient across the investigated area of the Site was about 0.13 feet/foot. Assuming ground water flow is perpendicular to equipotential hydraulic-head contours (Figure 3), apparent shallow ground water flow in the overburden aquifer was generally to the south. On October 13th, the water table appeared to be below the invert elevations of the foundation drain and water/sewer lines (immediately north of the former UST). As such, these underground utility corridors were not influencing shallow ground water flow on this date; however, as the water table rises, these features could possibly act as preferential pathways for ground water flow.

No Site-specific hydraulic conductivity (K) values from the overburden aquifer have been obtained to date. Also, vertical ground water flow components within the overburden aquifer were not quantified during the ISI. 4.2 Contaminant Distribution 4.2.1 Field PID Screening

Field PID screening results are provided on the soil boring logs (Appendix C). Peak PID readings are displayed on Figure 4.


At soil boring SB-1, located immediately south of the former heating oil UST grave, a peak PID reading of 406 ppmv was detected on soils collected from ground surface to 1 foot bgs (within the fill materials). PID readings within the dense glacial till decreased to 28 ppmv at about 2 to 3 feet bgs, and 1.2 ppmv at about 4 to 5 feet bgs. At soil boring SB-2, located within of the former heating oil UST grave, a peak PID reading of 615 ppmv was detected on soils collected from about 2 to 3 feet bgs (within the fill materials). PID readings decreased to 40 ppmv and 22 ppmv at about 4 and 5 feet bgs, respectively (within the dense glacial till). At soil boring SB-3, located about 6 feet downgradient of the former heating oil UST grave, a peak PID reading of 189 ppmv was detected on soils collected from about 2.5 feet bgs (within the stratified deposits). PID readings decreased to 11 ppmv and 0.3 ppmv at about 5 and 10 feet bgs, respectively (within the dense glacial till). At soil boring SB-4, located about 8 feet north of the former heating oil UST grave, a peak PID reading of 191 ppmv was detected on soils collected from ground surface to 1 foot bgs (within the crushed stone sub base for the driveway). PID readings decreased to 1.3 ppmv and 0.7 ppmv between about 2 to 5 feet bgs (within the dense glacial till). At soil boring SB-5, located about 12 feet northwest of the former UST grave, no instrument response (NIR) was observed on soils to about 9.5 feet bgs. A peak PID reading of 0.3 ppmv above background was detected on soils collected about 10 feet bgs. At soil boring SB-6, located about 14 feet downgradient of the former heating oil UST grave, PID readings ranged from 3 to 31 ppmv within the upper five feet. A peak PID reading of 205 ppmv was detected on soils collected from about 5 to 6 feet bgs (within the stratified). PID readings decreased to less than 10 ppmv between about 6 to 12 feet bgs (within the stratified deposits and dense glacial till). At soil boring HA-1, located about 5 feet south of the former heating oil UST grave, a peak PID reading of 183 ppmv was detected on soils collected from ground surface to 1 foot bgs (at auger refusal).


At soil boring HA-2, located about 7 feet south of the former heating oil UST grave, a peak PID reading of 1.2 ppmv was detected on soils collected from ground surface to 1.5 foot bgs. At soil boring HA-3, located about 25 feet downgradient of the former heating oil UST grave, PID readings ranged from 1.4 ppmv to 22 ppmv on soils collected from ground surface to about 2 feet bgs. PID readings of about 10, 15, and 20 ppmv were recorded at sub-slab vapor locations VP-1, VP-2, and VP-3, respectively.

4.2.2 Ground Water

Dissolved-phase analytical results are included in Table 2, and on Figure 5 Laboratory report forms are included in Appendix D. 4.2.2.1 VOCs

Total target VOC concentrations in ground water samples ranged from none detected in upgradient monitoring well MW-2 and downgradient monitoring well MW-3, to 36.3 micrograms per Liter (µg/L) in source-area monitoring well MW-1. Target VOCs include methyl tert-butyl ether (MTBE), benzene, toluene, ethylbenzene, total xylenes, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, and naphthalene. No target VOCs were detected above the respective Vermont Ground Water Enforcement Standard (VGES).

No analytes were detected in the Trip Blank. 4.2.2.2 TPH

TPH (for diesel range organics) was detected at a concentration of 1.2 milligrams per Liter (mg/L) in the ground water sample collected from monitoring well MW-1. There is currently not a VGES established for TPH. TPH (for diesel range organics) was not detected above the detection limit in ground water samples collected from monitoring wells MW-2 or MW-3. The laboratory detection limit was 0.40 mg/L.


5.0 CONCEPTUAL SITE MODEL Petroleum-related contamination was discovered at the Site on August 29, 2007 during the removal of a 500-gallon, abandoned heating oil UST system. The UST had been discovered along the front of the residence during excavation activities associated with the installation of a foundation drain. The UST was in poor condition, with several holes present on the underside; it appears that the heating oil leaked into the subsurface through these holes. In general, once released to the subsurface, petroleum hydrocarbons may partition into four phases: 1) vapor (i.e. soil gas), 2) aqueous (dissolved in pore water), 3) residual (sorbed to soil minerals and organic matter), and 4) remained as non-aqueous phase liquid (NAPL). 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. During the ISI, a maximum PID reading of 615 ppmv was recorded within the former UST grave. The release appears to have impacted soil, soil gas, and ground water. No free-phase product has been observed. The contaminant distribution has been reasonably defined, except in the downgradient direction (see Figure 6). The majority of the contaminant mass appears to be localized in the general vicinity of the former UST, encompassing an area of about 100 square feet. Vertically within this area, the upper two to four feet of soil is significantly impacted (at relative elevations between about 95 and 99 feet); the hydrocarbons do not appear to have significantly penetrated the underlying dense, basal glacial till.

Based on a soil gas PID reading of 205 ppmv obtained at about 5.5 feet bgs (or 95.5 feet relative elevation) from soil boring SB-6, located about 14 feet downgradient of the former UST, the downgradient extent of the hydrocarbon impact has not been fully defined. On October 13, 2007, no VOCs were detected above respective VGESs in samples collected from the on-Site monitoring wells. However, during the monitoring event, the water table was below the zone of significantly elevated PID readings observed in soil borings SB-2 (MW-1) and SB-6 (MW-3). As such, dissolved VOC concentrations could increase in MW-1 and MW-3 if the water table rises and remobilizes sorbed or residual contaminants within the smear zone.


Heating oil is comprised of hundreds of individual compounds. These compounds are typically readily sorbed to soil, are not highly volatile, have a relatively low aqueous solubility, and are biodegradable. As such, these constituents generally are not highly mobile in the subsurface. 6.0 SENSITIVE RECEPTOR SURVEY Several potential sensitive receptors were identified during the ISI. These receptors, and a quantitative and/or qualitative evaluation of their risk of impact by contamination associated with the petroleum releases, are discussed below.

• Unconfined Shallow Aquifer – No VOCs were detected above respective VGESs

in samples collected from the on-Site monitoring wells. However, during the monitoring event on October 13, 2007, the water table was below the zone of significantly elevated PID readings observed in soil borings SB-2 (MW-1) and SB-6 (MW-3). As such, dissolved VOC concentrations could increase in MW-1 and MW-3 if the water table rises and remobilizes sorbed or residual contaminants within the smear zone. An elevated TPH concentration (1.2 mg/L) was detected in source-area monitoring well MW-1; there is currently no VGES established for TPH.

• Drinking Water Supplies – Drinking water for the Site, and surrounding properties, is provided by the municipal water supply. According to the Agency of Natural Resources GIS Internet Mapping web site, one supply well is located within about 1,000 feet of the Site. However, this well is located about 750 feet upgradient of the Site. As such, no drinking water supplies appear to be at risk of impact from the petroleum constituents at the Site.

• Surface Water – The nearest surface water body is an unnamed tributary of the Winooski River, which is located about 500 feet west of the former UST at its closest point. Since no target VOCs were detected in shallow ground water samples at the Site, the potential risk of impact to the river appears to be relatively low.

• Indoor Air – A maximum PID reading of 20 ppmv was observed in sub-slab

vapor sample VP-3, located beneath the concrete slab in the basement immediately adjacent to former UST. PID readings within the ambient air in this portion of the basement were not detected above background concentrations. No compound-specific testing was performed.


The indoor air quality of the on-Site building does not appear to be at significant risk based on the absence of elevated PID readings in the basement and the presence of a fairly competent concrete slab (which appears to be a sufficient vapor barrier). However, if fractures are present (or occur) within the slab, and a negative pressure is created within the basement (e.g. due to heating during the winter months), vapor intrusion could possibly impact indoor air quality.

• Soil – Exposure pathways for humans through impacted soils include dermal

absorption (via direct contact), ingestion, and inhalation. Elevated PID readings were observed in shallow soils (within the upper 3 feet bgs) at several soil borings during the soil boring program. The “grossly” contaminated soils in the immediate vicinity of the former UST would need to be excavated in order to install the proposed foundation drain along the building foundation, which could possibly result in exposure.

• Underground Utilities – Several underground utilities are located in close proximity to the former UST, including the water line, sanitary sewer line, and foundation drain. Given the relatively high PID readings detected at soil borings SB-2, SB-3, and SB-4, and the relatively close proximity of the borings to these utilities, the utilities may be impacted or at risk of impact.

7.0 CONCLUSIONS AND RECOMMENDATIONS Based on the results of the UST closure and ISI, AGS has drawn the following conclusions:

• An abandoned, 500-gallon heating oil UST was discovered at the Site in August 2007 during the installation of a foundation drain. The UST was removed by Precision Industrial Maintenance (PIM) on August 29, 2007; PIM observed numerous holes in the UST and determined that petroleum constituents had been released to the subsurface based on field PID readings. Installation of the drain, and other construction activities, is currently on hold.

• In October 2007, AGS was retained by John and Sarah Vowles to complete an ISI to better characterize the magnitude and extent of contamination. During the ISI, a maximum PID reading of 615 ppmv was recorded within the former UST grave. The release has impacted soil, soil gas, and ground water. No free-phase product has been observed.

• The contaminant distribution has been reasonably defined, except in the downgradient direction. The majority of the contaminant mass appears to be


localized in the general vicinity of the former UST, encompassing an area of about 100 square feet. Vertically within this area, the upper two to four feet of soil is significantly impacted (at relative elevations between about 95 and 99 feet); the hydrocarbons do not appear to have significantly penetrated the underlying dense, basal glacial till.

• Based on a soil gas PID reading of 205 ppmv obtained at about 5.5 feet bgs (or 95.5 feet relative elevation) from soil boring SB-6, located about 14 feet downgradient of the former UST, the downgradient extent of the hydrocarbon impact has not been fully defined.

• On October 13, 2007, no VOCs were detected above respective VGESs in samples

collected from the on-Site monitoring wells. However, during the monitoring event, the water table was below the zone of significantly elevated PID readings observed in soil borings SB-2 (MW-1) and SB-6 (MW-3). As such, dissolved VOC concentrations could increase in MW-1 and MW-3 if the water table rises and remobilizes sorbed or residual contaminants within the smear zone.

• TPH (for diesel range organics) was detected at a concentration of 1.2 mg/L in

the ground water sample collected from monitoring well MW-3. TPH was not detected in ground water samples collected from monitoring wells MW-2 or MW-3. There is currently not a VGES established for TPH.

• Sensitive receptors either impacted or at risk from the petroleum release at the

Site include soils, ground water, indoor air, and underground utility corridors.

Given the above conclusions, AGS recommends the following:

• In order to mitigate the risk to sensitive receptors, the grossly contaminated soils within the general vicinity of the former UST should be excavated and disposed off-Site at an appropriate facility. These soils should include the 10’ x 10’ area south of the water and sewer lines, and may include the area on top and north of these utilities if significant contamination is encountered and impacted soils can be removed without compromising the integrity of the utilities. The depth of excavation should extend down to the top of the basal till unit, targeting the 95 to 99 foot relative elevation interval. Soils excavation should only occur where overlying “clean” soils have already been stripped in preparation for the foundation drain installation. The total volume of excavated soils is expected to range from about 15 to 20 cubic yards. This work should be implemented immediately to avoid frost complications.


• Once soils excavation is complete, an appropriate remedial strategy should be

developed for addressing downgradient contaminant impacts.

Copyright (C) 1997, Maptech, Inc.

Name: MONTPELIERDate: 9/27/2007Scale: 1 inch equals 2000 feet

Location: 044° 16' 18.40" N 072° 35' 14.82" W NAD 27Caption: Figure 1. Site Location Map

SITESITESITESITE

Magnetic Declination

16° W

SCALE 1:24000 0 1 MILES

0 1000 YARDS

0 1 KILOMETER

TABLE 1Liquid-Level Monitoring Data

3 Greenfield TerraceMontpelier, Vermont

Monitoring Date: 10/13/07

Well I.D.Top-of-Casing

Elevation (feet)

Depth-to-Water (feet BTOC)

Ground Water Elevation

(feet)

MW-1 100.00 5.53 94.47MW-2 99.09 3.81 95.28MW-3 102.06 9.23 92.83

TOC elevations surveyed by AGS on 10/5/07.BTOC = Below Top-of-Casing

TABLE 2.Water-Quality Analytical Results

Sampling Date: 10/13/07

3 Greenfield TerraceMontpelier, Vermont

Sample Location MTBE Benzene Toluene Ethylbenzene Total Xylenes Total TMBs Naphthalene Total Target

VOCsTPH

(DRO)

Ground WaterMW-1 ND<2.0 ND<1.0 ND<1.0 5.5 15.1 15.7 ND<2.0 36.3 1.2MW-2 ND<2.0 ND<1.0 ND<1.0 ND<1.0 ND<2.0 ND ND<2.0 ND ND<0.40MW-3 ND<2.0 ND<1.0 ND<1.0 ND<1.0 ND<2.0 ND ND<2.0 ND ND<0.40

QA / QCTrip Blank ND<2.0 ND<1.0 ND<1.0 ND<1.0 ND<2.0 ND ND<2.0 ND --

VGES 40.0 5.0 1,000.0 700.0 10,000.0 350.0 20.0 -- --

Notes: All concentrations reported in micrograms per Liter (µg/L), except TPH, which is reported in milligrams per Liter (mg/L).VOCs = Volatile Organic Compounds (analyzed by EPA Method 8021B)TPH = Total Petroleum Hydrocarbons (analyzed by EPA Method 8015 DRO)ND = None Detected above quantitation limitVGES = Vermont Ground water Enforcement StandardMTBE = Methyl tert-butyl etherTotal TMBs = Trimethylbenzenes (1,2,4 trimethylbenzene and 1,3,5 trimethylbenzene)

Applied GeoSolutions, LLC

Photo #1. Exposed foundation (west side of house). Geoprobe sitting on former UST location.

Photo #2. Installation of soil boring SB‐6. Note stressed tree in center of photo.

Site Name: 3 GT Client: John and Sarah Vowles Permit No.: NALocation: 3 Greenfield Terrace Drilling Dates: 10/5/2007Project: Field Log By: Eric SwiechDriller: Marcus Pante Company: SEI Drilling Method: Geoprobe (6610 DT)

5-foot macrocoresLatitude: Longitude: Borehole Diam. (in.): 2.25"State Plane Coordinate Feet (North): Outer Casing: NAState Plane Coordinate Feet (East): Inner Casing: NAOuter Casing (OC) Elevation (feet): NA Casing Length (feet): NAInner Casing (IC) Elevation (feet): NA Screen Length (feet): NAGround Elevation (feet): NA Screen Slot Size: NADatum: MSL Sand Pack: NANotes:

Depth (feet) PID Response (ppm) Recovery Sample IDs0-5' Run

1 0-12": Grey f-c SAND, some f-c Grave. Loose. Strong odor. Moist. 406

242"

3 28

41.2

55-6.5' Run

6 0-9": Pulverized schist. 0.0 18"

Drilling Log

Boring SB-01

Description

12-24": grey/brn Silt, little f Sand and f-c Gravel (few f Sand lense). Moist - dry.

24-42": Poorly sorted grey/brn f-c Sand, and f-c Gravel and Silt. Dense. Dry. (Glacial Till).

0.07

8

9

10

E.O.B. @ 6.5'.Note: PID readings obtained w/ Ion Science Model 1000+.

9-18": Glacial Till (as above). Dry.

Vowles_Boring Logs - SB-1


5-foot macrocoresLatitude: Longitude: Borehole Diam. (in.): 3.25State Plane Coordinate Feet (North): Well Diam. (in.): 1State Plane Coordinate Feet (East): Casing Length (feet): 2Outer Casing (OC) Elevation (feet): NA Screen Length (feet): 3Inner Casing (IC) Elevation (feet): NA Screen Slot Size: 0.010"Ground Elevation (feet): NA Sand Pack: #1Datum: MSLNotes:


1 0-16" Brn f(+)-c(-) Sand, and Silt, little Gravel.54

2 12327 39"

3 31030-39": Brn Silty Glacial Till. 384

4 48

55-10' Run

6

Drilling Log

Boring SB-02/MW-1

Description

16-30":Grey f SAND, little Silt w/ c Sand and Gravel pockets. Moist-wet. Black staining @ 28".

7 57"0.0

8

9

10

E.O.B. @ 10'.Set well at 5' bgs with 3 feet of screen.Note: PID readings obtained w/ Ion Science Model 1000+.

Dense, poorly sorted f-c Sand, and f-c angular Gravel in Silt matrix (Glacial Till). Dry.



5-foot macrocoresLatitude: Longitude: Borehole Diam. (in.): 3.25State Plane Coordinate Feet (North): Well Diam. (in.): NAState Plane Coordinate Feet (East): Casing Length (feet): NAOuter Casing (OC) Elevation (feet): NA Screen Length (feet): NAInner Casing (IC) Elevation (feet): NA Screen Slot Size: NAGround Elevation (feet): NA Sand Pack: NADatum: MSLNotes:


1 0-19": Brn f(+)-c(-) Sand, and Silt, little f-c Gravel. Moist. 457.9

2189 45"

331-45": Silty glacial till (moist). 151

411

55-10' Run

6 0-23": As above. 2

749"

8 0.4

90.3

10

E.O.B. @ 10'.

Note: PID readings obtained w/ Ion Science Model 1000+.

Drilling Log

Boring SB-03

Description

19-31": Grey inerbedded f-c Sand layers/lenses and Silt lenses. Black staining at 24-31". Wet.

23-49": Dense,sand/gravel Glacial Till. No odor.



5-foot macrocoresLatitude: Longitude: Borehole Diam. (in.): 3.25State Plane Coordinate Feet (North): Well Diam. (in.): NAState Plane Coordinate Feet (East): Casing Length (feet): NAOuter Casing (OC) Elevation (feet): NA Screen Length (feet): NAInner Casing (IC) Elevation (feet): NA Screen Slot Size: NAGround Elevation (feet): NA Sand Pack: NADatum: MSLNotes:


1 191

212-24": Pulverized schist. 39"

3 1.3

40.7

5

6

7

8

9

10

E.O.B. @ 5'.

Note: PID readings obtained w/ Ion Science Model 1000+.

Drilling Log

Boring SB-04

Description

0-12": Crushed angular Gravel/Cobbles w/ Silty Sand matrix. Wet. Odors.

24-39": Brn poorly sorted f. Sand, and Silt, some Gravel. Dry. Glacial Till.



5-foot macrocoresLatitude: Longitude: Borehole Diam. (in.): 3.25State Plane Coordinate Feet (North): Well Diam. (in.): 1State Plane Coordinate Feet (East): Casing Length (feet): 2Outer Casing (OC) Elevation (feet): NA Screen Length (feet): 7.5Inner Casing (IC) Elevation (feet): NA Screen Slot Size: 0.010"Ground Elevation (feet): NA Sand Pack: #1Datum: MSLNotes:


1 0-8": Asphalt/Gravel.

20.0 45"

324-45": Dense Glacial Till.

4

55-10' Run

6

Drilling Log

Boring SB-05/MW-2

Description

8-24": Interbedded f. Sand, and Silt. Wet.

7 0.052"

8

90.3

10

E.O.B. @ 10'.Set well at 10' bgs with 7.5 feet of screen.Note: PID readings obtained w/ Ion Science Model 1000+.

As above.



5-foot macrocoresLatitude: Longitude: Borehole Diam. (in.): 3.25State Plane Coordinate Feet (North): Well Diam. (in.): 2State Plane Coordinate Feet (East): Casing Length (feet): 2Outer Casing (OC) Elevation (feet): NA Screen Length (feet): 10Inner Casing (IC) Elevation (feet): NA Screen Slot Size: 0.010"Ground Elevation (feet): NA Sand Pack: Pre-packDatum: MSLNotes:


1 14

231 48"

3

4 2.9

55-10' Run

6 0-19": Brn f-c SAND, some Gravel. Loose. Dry. Strong odors. 205

Drilling Log

Boring SB-06/MW-3

Description

Brn/tan friable (loose) Silty, reworked galcial till. Dry. Roots throughout core.

7 6.856"

88.5

952-56": Dense Glacial Till. 0.2

1010-12.5' Run

11 As above 0.0 33"

12E.O.B. @ 12'.Set well at 12' bgs with 10 feet of screen.Note: PID readings obtained w/ Ion Science Model 1000+.

19-27": Dense, brn f-c Sand, some Gravel/Cobbles and Silt. Moist.

27-52": Brn/grey interbedded f Sand, f Silty Sand, and Silt layers/lenses. Wet.


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