2113 Stony Brook Road Northfield, VT 05663 (802) 485-9466 January 13, 2015 Mr. James Donaldson Vermont Department of Environmental Conservation Waste Management Division 1 National Life Drive – Davis 1 Montpelier, Vermont 05620-3704 Re: Semi-Annual Groundwater Monitoring Report – October 2014 Washington Street Apartments 14 Washington Street Barre, Vermont 05641 (SMS Site #93-1437) (Site or Property) Dear James: On behalf of the Barre Housing Authority, Vermont HydroGeo, LLC (VHG) is pleased to present the results of a semi-annual groundwater monitoring event completed at the above- referenced Site in October 2014 (Figures 1 and 2). Work was completed in accordance with a work plan and cost estimate dated September 17, 2014, which you approved via email. The Petroleum Cleanup Fund (PCF) budget tracking number for this work is 13619. This report is organized in the following manner: • Section 1.0 describes the Site location and physical setting; • Section 2.0 provides background information on the Site; • Section 3.0 describes monitoring methods; • Section 4.0 presents monitoring results; • Section 5.0 discusses an updated conceptual site model; and • Section 6.0 provides conclusions and recommendations. 1.0 SITE DESCRIPTION AND PHYSICAL SETTING The Site is located in a mixed commercial/residential setting at 14 Washington Street in Barre, Vermont (Figures 1 and 2). The Property is bound to the north by Jefferson Street, to the east by the First Baptist Church, to the south by Washington Street, and to the west by the Aldrich Public Library.
Transcript
2113 Stony Brook Road Northfield, VT 05663
(802) 485-9466
January 13, 2015 Mr. James Donaldson Vermont Department of Environmental Conservation Waste Management Division 1 National Life Drive – Davis 1 Montpelier, Vermont 05620-3704 Re: Semi-Annual Groundwater Monitoring Report – October 2014 Washington Street Apartments
14 Washington Street Barre, Vermont 05641 (SMS Site #93-1437) (Site or Property)
Dear James: On behalf of the Barre Housing Authority, Vermont HydroGeo, LLC (VHG) is pleased to present the results of a semi-annual groundwater monitoring event completed at the above-referenced Site in October 2014 (Figures 1 and 2). Work was completed in accordance with a work plan and cost estimate dated September 17, 2014, which you approved via email. The Petroleum Cleanup Fund (PCF) budget tracking number for this work is 13619. This report is organized in the following manner:
• Section 1.0 describes the Site location and physical setting; • Section 2.0 provides background information on the Site; • Section 3.0 describes monitoring methods; • Section 4.0 presents monitoring results; • Section 5.0 discusses an updated conceptual site model; and • Section 6.0 provides conclusions and recommendations.
1.0 SITE DESCRIPTION AND PHYSICAL SETTING The Site is located in a mixed commercial/residential setting at 14 Washington Street in Barre, Vermont (Figures 1 and 2). The Property is bound to the north by Jefferson Street, to the east by the First Baptist Church, to the south by Washington Street, and to the west by the Aldrich Public Library.
Mr. James Donaldson - 2 - January 13, 2015 An apartment complex, with a footprint of about 8,400 ± ft2, is located on the Property. The balance of the Property is comprised primarily of asphalt and concrete surfaces. The building, and surrounding properties, is served by the municipal water and sewer. The Property is currently owned by the Barre Housing Authority. Prior to serving as an apartment complex, the on-Site building functioned as a hotel. The topography at the Site is generally flat. The nearest surface water body is the Stevens Branch of the Winooski River, which is located about 750 feet southeast of the Site at its closest point. 2.0 BACKGROUND Petroleum contamination was discovered at the Site in 1993 during the removal of a #2 heating oil underground storage tank (UST), which was located along the east side of the building. K-D Associates, Inc. completed subsequent investigations to determine the magnitude and extent of petroleum contamination at the Site. The initial investigation included the advancement of 18 soil borings in the vicinity of the former UST, with field screening of select soil samples using a photoionization detector (PID). These borings were followed by the installation of 11 monitoring wells (MW-1 through MW-11) across the Property, during multiple phases, to investigate the hydrogeology and groundwater quality at the Site. In addition, in October 1993, eight ambient air samples were collected within the on-Site building and the church using charcoal sorbent tubes; K-D Associates, Inc. reported that proper sampling procedures were followed and no volatile organic compounds (VOCs) were detected in any of the samples. Quarterly to semi-annual water quality monitoring was conducted on select monitoring wells between 1995 and 2000. Free-phase product, identified as #2 heating oil via petroleum fingerprinting, has historically been detected in monitoring well MW-3, which is located in the vicinity of the former heating oil UST. Through October 2000, free product was recovered from this well by manual bailing and absorbent pads. Between 1995 and 2000, benzene was consistently detected at concentrations above the Vermont Groundwater Enforcement Standard (VGES) of 5.0 micrograms per Liter (µg/L) in groundwater samples collected from monitoring wells MW-4 and MW-9. Site monitoring ceased after October 2000. In spring 2008, the Vermont Department of Environmental Conservation (VT DEC) contacted the Barre Housing Authority requesting that work resume on the project. The Barre Housing Authority subsequently retained Applied GeoSolutions, LLC (AGS) for assistance.
Mr. James Donaldson - 3 - January 13, 2015 Since 2008, a series of additional Site investigations were initiated to further characterize contaminant conditions and the risk to sensitive receptors. The results of these investigations have been documented in the following reports:
• Supplemental Site Investigation Report. Applied GeoSolutions, LLC. December 12, 2008.
o Geophysical surveys were conducted on-Site (14 Washington Street) and off-Site at 30 Washington Street to determine whether out-of-service gasoline USTs depicted on Sanborn fire insurance maps remained in the ground. In addition, AGS supervised the installation of one downgradient monitoring well (MW-12) and three upgradient monitoring wells located at 30 Washington Street (MW-13, MW-14, and MW-15), and completed a Site-wide groundwater monitoring event.
• Additional Site Investigation Report. Stone Environmental, Inc. January 26, 2011.
o Nine sub-slab vapor samples were collected within the basement of the apartment building at 14 Washington Street from temporary vapor points TVP-01 through TVP-08 and permanent vapor point V-1 and analyzed for target petroleum VOCs via EPA Method 8260. One indoor air sample was collected from within the laundry room of on-Site building (basement level). Eight additional monitoring wells were installed at the Site, including shallow water-table monitoring wells MW-16, MW-17, MW-18S, MW-19S, MW-20S and deeply-screened monitoring wells MW-18D, MW-19D, and MW-20D, which were paired with shallow wells. Groundwater samples were collected from all the newly installed wells and most of the existing ones and analyzed for target petroleum VOCs via EPA Method 8260.
• Supplemental Site Investigation Report. Vermont HydroGeo, LLC. January 29, 2013.
o An active soil gas survey was completed along the eastern exterior of the on-Site apartment building and the eastern exterior of First Baptist Church in order to: 1) further evaluate the potential source of elevated benzene concentrations previously detected in sub-slab soil gas beneath the on-Site apartment building; and 2) quantify target VOC concentrations in soil gas to better assess vapor intrusion pathways for the on-Site apartment building and the First Baptist Church. Five exterior soil gas sampling locations were monitored: two along the eastern side of the church (TPV-09 and TPV-10), and three along the eastern side of the on-Site apartment building (TPV-11, TPV-12, and TPV-13). Three indoor air samples were collected from within the basement of the apartment building (IA-01, IA-02, and IA-03) and one ambient outdoor air sample (OA-01) was obtained. In addition, groundwater samples were collected from select
Mr. James Donaldson - 4 - January 13, 2015
monitoring wells and analyzed for target petroleum VOCs via EPA Method 8260.
Following the 2013 SSI, a semi-annual monitoring program was implemented for select groundwater monitoring wells. 3.0 WORK COMPLETED Groundwater Monitoring VHG conducted groundwater monitoring at the Site on October 17, 2014. VHG collected groundwater samples for subsequent laboratory analysis from monitoring wells MW-3, MW-4, MW-9, MW-13, MW-16, MW-17, MW-18S, MW-18D, MW-19S, and MW-19D. Monitoring well MW-10 was not sampled due to insufficient sample volume. Prior to collecting groundwater samples, VHG obtained and recorded liquid-level measurements from select on-Site and off-Site monitoring wells. Liquid levels were manually measured to the nearest 0.01 foot using an electronic oil/water interface probe. Monitoring wells were purged and sampled in general accordance with United States Environmental Protection Agency (USEPA) Region I low-flow purging and sampling protocol using a peristaltic pump and dedicated Teflon-lined polyethylene and silicone tubing. A trip blank and duplicate sample (from MW-4) were acquired to evaluate quality assurance / quality control (QA/QC).
Following collection, all samples were placed in an ice-filled cooler and transported to Endyne, Inc. of Williston, Vermont for analysis of target petroleum VOCs by EPA Method 8021B. Target VOCs include Methyl tert-butyl ether (MTBE), benzene, toluene, ethylbenzene, total xylenes, 1,2,4- trimethylbenzene (TMB), 1,3,5- TMB, and naphthalene. 4.0 MONITORING RESULTS
4.1 Liquid-Level Measurements During the October 2014 monitoring event, depth-to-water measurements in the flush-mounted overburden monitoring wells ranged from 12.70 feet below top-of-casing (BTOC) in monitoring well MW-13 to 14.49 feet BTOC in monitoring well MW-14. LNAPL was detected within monitoring well MW-14 at a thickness of 1.09 feet. LNAPL was not detected in any other monitoring well. Calculated relative groundwater elevations ranged from 83.04 feet at monitoring well MW-19D to 86.40 feet at monitoring well MW-15 (Table 4-1). On average, the groundwater
Mr. James Donaldson - 5 - January 13, 2015 elevations were about one foot lower than during the previous monitoring event in May 2014.
Table 4-1. Liquid-Level Monitoring Data: October 17, 2014
4.2 Quality Assurance / Quality Control During the October 2014 monitoring event, relative percent difference (RPD) values for individual VOCs from sample MW- and its field duplicate sample (Dup) ranged from 2.1 to 15 percent. The maximum acceptable RPD for water samples is 30 percent. No VOCs were detected in the trip blank.
4.3 Analytical Results
The physical/chemical parameters recorded in the field during monitoring well purging for the October 2014 event are summarized in Table 4-2. Groundwater laboratory analytical results are included in Table 4-3 and on Figure 4. Laboratory report forms are included in Appendix A. Time-series graphs for select monitoring wells are provided in Appendix B.
Mr. James Donaldson - 7 - January 13, 2015 No target VOCs were detected in groundwater samples collected from monitoring wells MW-3 or MW-19S.
Detectable total target VOC concentrations ranged from 35.3 µg/L in monitoring wells MW-16 to 25,877 µg/L in MW-13.
MTBE (MW-13 and MW-18D), benzene (MW-4, MW-9 and MW-13), toluene (MW-13), ethylbenzene (MW-13), total TMBs (MW-4, MW-13, MW-18S, and MW-18D), and naphthalene (MW-4, MW-9, MW-13, MW-18S, and MW-18D) were detected at concentrations above respective VGESs.
4.4 LNAPL Monitoring
LNAPL monitoring data for monitoring wells MW-3 and MW-14 are provided in Tables 4-4, and Table 4-5, respectively.
LNAPL (#2 oil) has not been detected in monitoring well MW-3 since the oleophilic “sock” was removed in January 2013.
LNAPL (presumably gasoline) was first detected in MW-14 during the November 2012 monitoring event, at a thickness of 0.81 feet. LNAPL has been present in this well during each of the four subsequent monitoring events. On November 20, 2013, no LNAPL was detected with the interface probe; however, LNAPL was observed in the flow-through cell
Mr. James Donaldson - 8 - January 13, 2015 during purging. During the most recent monitoring event in October 2014, 1.09 feet of LNAPL was measured, which is the greatest thickness recorded to date.
Table 4-5: LNAPL Monitoring Data at MW-14.
5.0 UPDATED CONCEPTUAL SITE MODEL
Geology / Hydrogeology Soil stratigraphy varies significantly across the areas of concern. In general, varying percentages of sand, silt, and gravel (artificial fill and/or native fluvial deposits) are present within the upper two to 10 feet bgs. These materials appear to overlie native fluvial silt/clayey-silt deposits (with interbedded fine sands) within the northern and southern portions of the Site to depths of at least 20 to 25 feet bgs (the maximum depth of borings). The silt unit was not encountered at monitoring wells MW-4, MW-8, or MW-15; rather, fine to coarse stratified sands were present at these locations to depths of at least 20 to 28 feet bgs, respectively. These relatively coarse deposits may indicate the presence of a meandering former stream channel; hydraulic head and contaminant distribution data suggest the channel may traverse between MW-12 and MW-5 on the west side of the building. Bedrock has not been encountered across the Site to a maximum exploratory depth of about 28 feet bgs. The depth-to-water across the Site varies seasonally between about 11 to 14 feet bgs. Apparent shallow groundwater flow in the overburden aquifer is generally to the southwest within the northern portion of the Site, and to the northwest within the southern portion of the Site, with flow converging towards the apparent buried stream channel (Figure 3). The water-table gradient across the Site typically ranges from about 0.01 feet/foot to about 0.03 feet/foot. Hydraulic-head data from cluster wells MW-9/MW-10, MW-18S/MW-18D, and MW-19S/MW-19D indicate that vertical flow components within the overburden aquifer fluctuate both upward and downward. A buried stream channel (former Potash Brook) is located on the west side of the apartment building, flowing north to south. It is believed that the
Mr. James Donaldson - 9 - January 13, 2015 structure is a concrete box culvert. Leakage from the box culvert may recharge the shallow overburden aquifer and create the downward vertical groundwater flow component observed at cluster wells MW-19S/MW-19D. Several underground utilities are located within the investigation area, including sanitary sewer, water, and storm water lines. The invert elevations of these known utility corridors, as well as the foundation footings for the apartment building and church, are likely above the water table; as such, these features do not likely influence shallow groundwater flow. Contaminant Distribution/ Fate & Transport Based on available contaminant distribution and hydrogeologic data, and historic on-Site and off-Site operations, there may be at least three sources for the petroleum contamination identified at the Site: 1) the former #2 heating oil UST; 2) a former gasoline UST system located immediately in the vicinity of the former heating oil UST; and 3) a former gasoline UST system located off-Site, on the property bordering the First Baptist Church to the east of the Site (30 Washington Street). The volume of the petroleum releases associated with these former UST systems is unknown. Since the former on-Site gasoline and heating oil USTs appear to have been located in close proximity to each other, VHG has combined these apparent contaminant sources into one general area of concern (AOC #1) for discussion purposes. VHG has designated the former off-Site UST system at 30 Washington Street as AOC #2. Recent detections of MTBE in on-Site and off-Site monitoring wells suggest there may be an additional source(s) for petroleum contamination observed at the Site. In general, once released to the subsurface, petroleum hydrocarbons (e.g. gasoline and #2 heating oil) can partition into four phases: 1) vapor (i.e. soil gas), 2) aqueous (dissolved in pore 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 Washington Street Apartment Site, the petroleum releases have impacted soil and groundwater, and hydrocarbons are present in the vapor, sorbed, dissolved, and NAPL phases. Gasoline and #2 heating oil are 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, although the rate of anaerobic biodegradation is one to two orders of magnitude lower than the rate of aerobic biodegradation.
Mr. James Donaldson - 10 - January 13, 2015 AOC #1 In AOC #1, mobile LNAPL released from the former #2 heating oil UST system had historically been present in monitoring well MW-3, which is located within the footprint of the former heating oil UST. On December 19, 2012, 0.26 feet of LNAPL was present in MW-3; this product was removed on January 4, 2013 using an oleophilic “sock”, and LNAPL has not been detected in the well during eight subsequent monitoring events completed to date. The horizontal extent of LNAPL (#2 oil) appears to have been confined to the vicinity of monitoring well MW-3. Heavy sheening was observed on soils at borings MW-16 and MW-17, located downgradient of MW-3 in close proximity to the on-Site building, but no measurable LNAPL has been detected in these wells to date. Dissolution of the #2 oil released at the Site has generated a dissolved-phase target VOC plume within the overburden aquifer (Figure 4). Monitoring wells MW-16, MW-18S, and MW-18D, located within the vicinity of the former heating oil UST system on the eastern side of the apartment building, have historically contained total TMBs and naphthalene at concentrations above the respective VGESs (Graphs 5, 7, and 8, Appendix B). In addition, MTBE has been detected above the VGES in MW-18D during the last five monitoring events, and in MW-18S during the November 2013 monitoring event. No VOCs have been detected at concentrations above the VGESs in downgradient monitoring wells located on the western side of the apartment building, suggesting the plume is relatively limited in extent. Based on apparent groundwater flow direction, it is possible that the heating-oil related plume co-mingles with the gasoline-related plume from AOC #2 beneath the apartment building downgradient of monitoring wells MW-9 and MW-10. Based on the analytical data available to date, total TMB and naphthalene concentrations appear to be stable or declining at monitoring wells MW-16 and MW-18D. At MW-18S, contaminant concentrations appear to vary widely in response to the water table elevation, with relatively high contaminant concentrations occurring under low water-table conditions; however, a decreasing trend in contaminant concentrations is beginning to develop in the low water table data set. Exposure pathways to human receptors from soil and groundwater contamination associated with AOC #1 do not currently appear to be complete, as impacted soils are relatively deep and covered with asphalt, and impacted groundwater at the Site is not used as a potable source. However, any future intrusive activities in this area may present a risk of exposure. The heating oil release has also generated a vapor-phase plume of select target VOCs via partitioning from the LNAPL, sorbed and/or dissolved phases. Five of the six shallow (3 feet bgs) and near-slab (8 feet bgs) vapor samples collected on the eastern side of the apartment building in December 2012 yielded detectable naphthalene concentrations ranging from 33 to 162 micrograms per cubic meter (µg/m3), which are above the Vapor Intrusion Screening
Mr. James Donaldson - 11 - January 13, 2015 Value (VISV) of 3 µg/m3 (Figure 5). No other target VOCs (either petroleum or chlorinated) were detected in these samples at concentrations above respective VISVs. Benzene was detected at a concentration of 1.7 µg/m3 in TPV-13 at 8 feet bgs, which is three orders of magnitude below the VISV of 1,180 µg/m3; benzene was not detected above the laboratory reporting limit of 16 µg/m3 in the five other vapor samples collected. In September 2012, benzene was detected in three of the eight sub-slab vapor samples collected beneath the apartment building, with a peak concentration of 130 µg/m3 detected at TPV-03, located downgradient of the former heating oil UST; naphthalene was not detected in any of the sub-slab vapor samples collected, however, the laboratory reporting limit for those samples was elevated at 100 µg/m3. In December 2012, benzene was detected above its target indoor air concentration of 1.18 µg/m3 in each of the three indoor air samples collected within the basement of the apartment building, with concentrations ranging from 1.3 to 1.7 µg/m3. Benzene was also detected in the exterior ambient air sample at a concentration of 0.82 µg/m3. Given the ambient air results, the good integrity of the concrete slab, and the fact that benzene concentrations in sub-slab and near slab soil vapor samples were either non-detect, or one to three orders of magnitude below the soil gas screening value, it is unlikely that the benzene concentrations detected in indoor air are attributed to vapor intrusion from the subsurface. Benzene is a common indoor air pollutant that is present in cigarette smoke, vehicle emissions, and in some petroleum-based household products such as furniture wax, glues, paints, and lubricants. Although naphthalene was present in near slab soil vapor at concentrations one to two orders of magnitude above the soil gas screening value of 3 µg/m3, it was not detected in any of the indoor air samples at concentrations above the laboratory reporting limit of 2.6 µg/m3. However, the laboratory reporting limit was about 9 times greater than the target indoor air value of 0.3 µg/m3; as such, while these data demonstrate there is not a risk of acute exposure, they are not conclusive for determining whether the vapor intrusion pathway for naphthalene is complete and there is risk of chronic exposure, since it is possible that naphthalene was present in indoor air at concentrations above the target indoor air value, but below the laboratory reporting limit. To achieve a detection limit for naphthalene at or below the target indoor air value of 0.3 µg/m3, air samples would need to be analyzed via EPA Method TO-15 using selected ion monitoring (SIM). Like benzene, naphthalene is also a common indoor air pollutant. PCE was detected in indoor air sample IA-03 at a concentration 3.0 µg/m3, which is above its target indoor air concentration of 0.57 µg/m3. Since PCE is not a contaminant of concern at the Site, and it was not detected in any of the recent soil vapor sample collected at the Site, it is probable that the presence of PCE in this sample is attributed to an interior source rather than vapor intrusion. PCE can off-gas from clothing that has been dry cleaned, and is present
Mr. James Donaldson - 12 - January 13, 2015 in certain household products, including spot removers and paint removers. An exhaustive inventory of products possibly containing PCE was not conducted; however, VHG did not identify any products of concern in the general vicinity of each of the sampling locations. Finally, in the early 1990s, K-D Associates completed 18 soil borings with PID screening in the vicinity of the former on-Site heating oil and gasoline USTs. These screening data, specifically from borings B-7, and B-13 through B-16, indicate the apparent presence of VOCs in the vadose zone and saturated zone upgradient of the former heating oil UST system, and suggest there may be another source for the contaminants identified in AOC #1. Given its proximity, the former gasoline UST system is a possible source. Releases could have occurred via leaks from the former UST and appurtenances (including the former fuel dispenser, the location of which is unknown), and/or spills associated with fueling. However, if releases of gasoline did occur in this area, the impact to groundwater does not appear to be significant, and it may be co-mingled with the dissolved-phase heating oil contamination. AOC #2 Gasoline-related contamination detected at monitoring wells MW-13 and MW-14, located in the southwest portion of the property at 30 Washington Street, appears to be related to the former gasoline UST system that was identified on the 1925 (revised 1949) Sanborn Map. Although the former USTs appear to have been removed, significant gasoline contamination remains present within the subsurface at this property. LNAPL (as gasoline) has routinely been detected in monitoring well MW-14, and LNAPL was recorded at a thickness of 1.09 feet during the most recent monitoring event in October 2014. Gross contamination (e.g. PID readings >1,000 ppm v/v on soils) within the investigated portion of this area is present between about 8 to 20 feet bgs. The upgradient boundary of the source-area contamination has not been defined. Based on apparent shallow groundwater flow and available contaminant distribution data, it appears that the dissolved-phase VOC plume has migrated from this source area, beneath the First Baptist Church, and onto the Washington Street Apartments’ Site. The VOC impact at monitoring wells MW-4, MW-9, and MW-19D likely originates from 30 Washington Street. Data from cluster wells MW-9/MW-10 and MW-19S/MW-19D suggest the VOC plume is “diving” in this portion of the aquifer, and has migrated beneath the apartment building. There appears to be a relatively “clean” water lense above the plume in this portion of the Site. The downgradient extent of the VOC plume has been reasonably delineated, and the plume does not likely extend much beyond MW-19D. During the most recent monitoring event in May 2014, detectable total target VOC concentrations ranged from 97.6 µg/L in deeply-screened cluster monitoring well MW-19D, located on the west side of the apartment building, to 25,877 µg/L in MW-14, which is located in the southwest corner of the parcel at 30 Washington Street. MTBE, benzene, toluene, ethylbenzene, total TMBs, and naphthalene
Mr. James Donaldson - 13 - January 13, 2015 were detected in one or more monitoring well impacted by AOC #2 at concentrations above the respective VGESs. Although total dissolved VOC concentrations in MW-4 and MW-9 have fluctuated over time since monitoring commenced in 1995, an overall decreasing trend appears evident from each data set (Graphs 1 and 2, Appendix B). Within the source area, total VOC and benzene concentrations have fluctuated up and down in MW-13 over the seven monitoring events completed at this well to date (Graph 3, Appendix B); concentrations may vary in response to fluctuations of the water table within the smear zone. Partitioning from the gasoline LNAPL released in AOC #2 has generated a vapor-phase plume of select target VOCs. The near-slab (8.5 feet bgs) soil vapor sample collected at TPV-09 near the southeast corner of the church in December 2012 yielded benzene and total xylenes concentrations of 14,849 and 194,270 µg/m3, respectively, which are above the soil gas screening values for these compounds of 1,180 µg/m3 and 100,000 µg/m3 (Figure 5). Naphthalene was detected above its screening value in both the shallow (3 ft) and deep (8 ft) vapor samples collected from TVP-10, located about 17 feet north of TVP-09; the chromatograms for these soil vapor samples differed considerably from the chromatogram for TPV-09-8.5’, and appear more indicative of heating oil rather than gasoline-related contamination. Based on the December 2012 soil gas data, the basements of the First Baptist Church and the southwest portion of the office space at 30 Washington Street may be at risk of vapor intrusion from the petroleum release(s) in AOC #2. However, based on PID screening data from October 2008, there was not a risk of acute exposure within the church basement, as PID readings of 0.0 ppm v/v were measured throughout the basement (within the breathing zone and along the eastern foundation walls), with the exception of a reading of 0.1 ppm v/v that was recorded within the nursery, located in the southwest corner of the basement. The basement of the church provides multiple functions, including a kitchen, nursery, fellowship room, and youth Sunday school. A boiler and associated #2 oil aboveground storage tank (AST) for the church’s heating system are located within the northwest corner of the basement, within a separate room. The basement of the office building at 30 Washington Street has not previously been screened with a PID. PID screening of the ambient air within the office building at 30 Washington Street and compound-specific analysis of indoor air samples from both the church and the office building would help determine if the vapor intrusion exposure pathway is complete at these structures. Monitored natural attenuation (MNA) appears to be a plausible remedial alternative for addressing the downgradient dissolved plume associated with AOC #2. However, the presence of gasoline LNAPL in MW-14, and the elevated concentration of benzene detected in near-slab soil gas in this area, appears to warrant some form of active remediation to
Mr. James Donaldson - 14 - January 13, 2015 remove the LNAPL and mitigate the risk of vapor intrusion. VHG is in the process of conducting a soil vapor extraction (SVE) pilot test to evaluate whether this remedial technology is suitable for: 1) removing LNAPL via volatilization; and 2) mitigating the risk of vapor intrusion (by inducing a negative pressure in the subsurface immediately adjacent to the building foundations).
MTBE Source(s) During the November 2012 monitoring event, MTBE was detected in groundwater at the Site for the first time since monitoring commenced in 1995. MTBE concentrations in monitoring wells MW-9 and MW-18D exceeded the VGES for this compound of 40 µg/L, while MTBE was detected in downgradient monitoring well MW-19D at a concentration of 5.0 µg/L. Since that time, MTBE has been detected in several other monitoring wells, and has consistently exceeded its VGES in monitoring well MW-18D. During the May 2014 event, MTBE was detected for the first time in monitoring well MW-13, which is located upgradient of the Site; however, laboratory detection limits during previous monitoring events were elevated due to the presence of other high level contamination, so it is possible that MTBE was present at this location previously. MTBE is an octane-enhancing additive of gasoline that came into wide-spread use circa 1979. Since the removal of the former on-Site gasoline UST is believed to have been taken out of service prior to 1979, and MTBE was not previously detected in on-Site monitoring wells, the release of MTBE that has been detected in monitoring wells within and near AOC#1 appears to have occurred relatively recently. While the source of the MTBE is not known at this time, it is possible that it is attributed to parking lot runoff that may have leaked from the storm water catch basin that is located hydraulically upgradient of monitoring wells MW-9 and MW-18D. It is not clear when the gasoline USTs at 30 Washington Street were removed. If they were removed after 1979, these former USTs may be the source for the MTBE detected in MW-13. If the USTs were removed before 1979, the MTBE detected in MW-13 must be attributed to another unknown release.
Mr. James Donaldson - 15 - January 13, 2015 6.0 CONCLUSIONS AND RECOMMENDATIONS Based on the results of the October 2014 monitoring event and historic Site data, VHG has drawn the following conclusions:
• There appears to be multiple sources for the petroleum contamination identified at the Site, including: 1) the former #2 heating oil UST; 2) a former gasoline UST system believed to have been located immediately north of the former heating oil UST; and 3) a former gasoline UST system located off-Site, on the property bordering the First Baptist Church to the east (30 Washington Street). The former on-Site gasoline and heating oil USTs appear to have been located in close proximity to each other, and are combined into one general area of concern (AOC #1); if a release did occur from the former on-Site gasoline UST system, the impact is overshadowed by the release from the former heating oil UST. The former off-Site UST system at 30 Washington Street is designated as AOC #2. Recent detections of MTBE suggest there may be additional sources for petroleum contamination observed at the Site.
• LNAPL released from the former #2 heating oil UST system has historically been present in monitoring well MW-3, which is located within the footprint of the former heating oil UST. However, no LNAPL has been detected in this well since January 2013.
• Dissolution of the #2 oil released at the Site in AOC #1 has generated a dissolved-
phase target VOC plume within the overburden aquifer that appears to be relatively limited in extent. Monitoring wells MW-16, MW-18S, and MW-18D, located within the vicinity of the former heating oil UST system on the eastern side of the apartment building, have historically contained total TMBs and naphthalene at concentrations above the respective VGESs. MTBE has recently been detected above the VGES in MW-18S and MW-18D; the source of MTBE in these wells may be related to parking lot runoff. During the October 2014 monitoring event, total TMBs and naphthalene were detected in monitoring wells MW-18S and MW-18D at concentrations above the VGESs; MTBE also exceeded the VGES at MW-18D. Based on the limited analytical data available to date, total TMB and naphthalene concentrations appear to be stable or declining at monitoring wells MW-16 and MW-18D. At MW-18S, contaminant concentrations appear to vary widely in response to the water table elevation, with relatively high contaminant concentrations occurring under low water-table conditions; however, a decreasing trend in contaminant concentrations is beginning to develop in the low water table data set.At this time, continued MNA appears to be a viable remedial alternative for addressing the dissolved plumes associated with AOC #1.
Mr. James Donaldson - 16 - January 13, 2015
• Significant gasoline-related contamination is present within the subsurface at 30 Washington Street which appears to be related to a former gasoline UST system on this property (AOC #2). Gasoline (as LNAPL) was present in monitoring well MW-14 during the October 2014 at a thickness of 1.09 feet. The upgradient boundary of the source-area contamination has not been reasonable defined. The dissolved-phase VOC impact at monitoring wells MW-4, MW-9, and MW-19D likely originates from AOC #2, although there may be some co-mingling with contamination from AOC #1. The VOC plume is “diving” in this portion of the aquifer, and has migrated beneath the church and the apartment building at 14 Washington Street. The downgradient extent of the plume appears to have been reasonably delineated, and does not likely extend much beyond MW-19D. During the most recent monitoring event in October 2014, detectable total target VOC concentrations ranged from 97.6 µg/L in deeply-screened cluster monitoring well MW-19D, located on the west side of the apartment building, to 25,877 µg/L in MW-14, which is located in the southwest corner of the parcel at 30 Washington Street. MTBE, benzene, toluene, ethylbenzene, total TMBs, and naphthalene were detected in one or more monitoring well impacted by AOC #2 at concentrations above the respective VGESs. MNA appears appropriate for addressing the downgradient dissolved plume associated with AOC #2. However, active remediation may be prudent to recover gasoline LNAPL and mitigate the risk of vapor intrusion related to AOC #2.
• In December 2012, naphthalene was present in near slab soil vapor at concentrations one to two orders of magnitude above the soil gas screening level of 3 µg/m3, but it was not detected in any of the indoor air samples in the basement of the apartment building at concentrations above the laboratory reporting limit of 2.6 µg/m3. However, the laboratory reporting limit was about 9 times greater than the target indoor air value of 0.3 µg/m3; as such, while these data demonstrate there is not a risk of acute exposure, they are not conclusive for determining whether the vapor intrusion pathway for naphthalene is complete and there is risk of chronic exposure, since it is possible that naphthalene was present in indoor air at concentrations above the target indoor air value, but below the laboratory reporting limit. To achieve a detection limit for naphthalene at or below the target indoor air value of 0.3 µg/m3, air samples would need to be analyzed via EPA Method TO-15 using SIM mode.
• The December 2012 soil gas data from TPV-09 and TPV-10 suggest the basements of
the First Baptist Church and the southwest portion of the office space at 30 Washington Street may be at risk of vapor intrusion from benzene, total xylenes, and naphthalene present at elevated concentrations within the subsurface at AOC #2. The basement of the church provides multiple functions, including a kitchen, nursery, fellowship room, and youth Sunday school. The first floor at 30 Washington Street is occupied by tenants for use as office space.
Mr. James Donaldson - 17 - January 13, 2015 Given the above conclusions, VHG offers the following recommendations:
• Groundwater monitoring of select monitoring wells should continue on a semi-annual basis in accordance with the VT DEC-approved work plan to track temporal changes in water quality. The next monitoring event should occur in spring 2015, and include monitoring wells MW-3, MW-4, MW-9, MW-10, MW-13, MW-14, MW-16, MW-17, MW-18S, MW-18D, MW-19S, and MW-19D. Samples should be analyzed for target VOCs via US EPA Method 8021B.
• An additional round of indoor air monitoring should be conducted within the basement of the apartment building to determine whether the vapor intrusion pathway is complete for naphthalene. The interior (and ambient) monitoring should be coupled with one or two additional sub-slab samples near the former UST area, (collected immediately following the indoor/ambient air sampling). All samples should be analyzed for target petroleum and chlorinated VOCs via US EPA Method TO-15 using the SIM mode to achieve detection limits equal to or less than the indoor air target values for the compounds of concern. The monitoring round should be completed during the heating season, when “stack” effects are expected to be greatest. If results indicate the vapor intrusion exposure pathway is not complete, no additional monitoring should be required. If multiple lines of evidence suggest the exposure way is complete, mitigation may be necessary.
VHG is in the process of conducting an SVE pilot test in the vicinity of monitoring well MW-14 to evaluate whether this remedial technology is suitable for removing LNAPL and mitigating the risk of vapor intrusion at the church and 30 Washington Street. VHG conducted the step-testing phase of an SVE pilot study in November 2014, and is slated to finish the constant-rate test portion of the study in mid-January 2015. The results of the SVE pilot will be reported under separate cover. **************************************************************************************
Mr. James Donaldson - 18 - January 13, 2015 Please do not hesitate to contact me if you have any questions. Yours truly, Vermont HydroGeo, LLC Eric J. Swiech, P.G. Principal Hydrogeologist Phone / 802-485-9466 E-Mail / [email protected] cc: Ms. Jaime Chioldi, Barre Housing Authority Mr. Rick Davis, Property Owner (30 Washington Street) Figure 1 Site Location Map Figure 2 Site Plan Figure 3 Water-Table Contour Map: October 17, 2014 Figure 4 Groundwater Contaminant Distribution Map: October 17, 2014 Figure 5 Air Quality Analytical Results Appendix A Laboratory Reports Appendix B Time-Series Graphs
FIGURES
Copyright (C) 1997, Maptech, Inc.
Name: BARRE EASTDate: 7/7/2008Scale: 1 inch equals 2000 feet
Location: 044° 11' 52.25" N 072° 29' 53.69" W NAD 27Caption: Figure 1. Site Location Map
SITESITESITESITESITESITE
Magnetic Declination
16° W
SCALE 1:24000 0 1 MILES
0 1000 YARDS
0 1 KILOMETER
APPENDIX A
Laboratory Report
WSAPROJECT:
DATE RECEIVED:
WORK ORDER:
DATE REPORTED:
100905Vermont HydroGeo
2113 Stony Brook Rd
Northfield, VT 05663
Atten: Eric Swiech SAMPLER:
October 31, 2014
1410-22300
Eric Sweich
October 24, 2014
Reviewed by:
Harry B. Locker, Ph.D.
Laboratory Director
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.
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 4
CLIENT:PROJECT: WSA
WORK ORDER:DATE RECEIVED:
1410-2230010/24/2014
10/31/2014REPORT DATE:
001 Date Sampled: 10/17/14Site: MW-3 10/27/14 MHMWAnalysis Date:13:17
