|
Site History and Previous Investigations
<br />Former Chevron Service Station No. 94054
<br />In February 1996, Terra Vac supervised the installation of three groundwater monitoring wells
<br />(MW-10, MW-11 and MW-12). Monitoring well MW-10 was installed in the westbound lane of
<br />Elmwood Avenue, north of the site, MW-11 was installed in the southbound lane of Franklin
<br />Avenue, north of the site, and MW-12 was installed in the westbound lane of Elmwood Avenue,
<br />northeast of the site (Terra Vac Corporation, 1996). Petroleum hydrocarbon constituents were
<br />detected in one soil sample collected during the associated monitoring well installations.
<br />TPH-GRO was detected at a concentration of 3.5 mg/kg in the soil sample collected from MW-
<br />12 at 4.3 feet bgs. Petroleum hydrocarbon constituents were not detected at concentrations
<br />above their respective laboratory method detection limits (MDL) in any other soil samples
<br />collected during the associated monitoring well installations.
<br />In September 1997, Terra Vac supervised the advancement of ten Geoprobe borings (GP-1, GP-
<br />2, GP-3, GP-4, GP-4B, GP-5, GP-6, GP-7, GP-8 and GP-9). GP-1 was advanced in the southwest
<br />corner of the site and GP-2 was advanced in the northwest corner of the site. GP-3 was
<br />advanced in the center of Franklin Avenue, east of the site. GP-4, GP-4B and GP-5 were
<br />advanced in the former gasoline UST pit. GP-6 and GP-7 were advanced along the eastern
<br />edge of the site, near SB-7. GP-8 was advanced slightly north of the former gasoline UST pit and
<br />GP-9 was advanced slightly west of the former gasoline UST pit (Terra Vac
<br />Corporation, 1998). Soil, water and soil gas samples were collected from the Geoprobe borings,
<br />however, not each sample medium was collected from each boring. The greatest
<br />concentrations of petroleum hydrocarbon constituents detected in the soil samples collected
<br />during the associated Geoprobe advancements were in the soil samples collected from GP-3 at
<br />23 feet bgs, GP-5 at 17.2 feet bgs and GP-9 at 23 feet bgs. TPH-GRO, benzene, toluene and total
<br />xylenes were detected at concentrations of 2,200, 18, 31 and 210 mg/kg, respectively, in the soil
<br />sample collected from GP-9 at 23 feet bgs. Ethylbenzene was detected at a concentration of 18
<br />mg/kg in the soil sample collected from GP-5 at 17.2 feet bgs. Methyl tertiary butyl ether (MTBE)
<br />was detected at a concentration of 18 mg/kg in the soil sample collected from GP-3 at 23 feet
<br />bgs (Terra Vac Corporation, 1998). The greatest concentrations of petroleum hydrocarbon
<br />constituents detected in the groundwater samples collected during the associated Geoprobe
<br />advancements were in the groundwater sample collected from GP-3. TPH-GRO and BTEX were
<br />detected at concentrations of 56,000, 6,200, 4,600, 2,000 and 5,700 pg/L, respectively, in the
<br />groundwater sample collected from GP-3. The only petroleum hydrocarbon constituent
<br />detected in the soil gas samples collected during the Geoprobe advancement was toluene.
<br />Toluene was detected at a concentration of 0.44 pg/L in the soil gas sample collected from GP-
<br />8 at 5 feet bgs and at a concentration of 0.42 pg/L in the soil gas sample collected from GP-8 at
<br />15 feet bgs.
<br />In September and October 2000, Terra Vac supervised the installation of a DVE system. The
<br />system included 16 extraction wells (DVE-1, DVE-2, DVE-3, DVE-4, DVE-5, DVE-6, DVE-7, DVE-8,
<br />DVE-9, DYE-b, DVE-11, DVE-12, DVE-13, DVE-14, DVE-15 and DVE-16) and six sparge wells (SP-1,
<br />SP-2, SP-3, SP-4, SP-5 and SP-6). The six sparge wells were installed in February 2000. DVE-1, DVE-2,
<br />DVE-3, DVE-4 and DVE-5 were installed from west to east in a line parallel to the property line
<br />starting with DVE-1 in the northwest corner of the site. DVE-6, DVE-7, DVE-8 and DVE-9 were
<br />installed from west to east in a line parallel to the property line starting with DVE-6 in the west,
<br />located slightly northeast of MW-4. Extraction wells DVE-10, DYE-11, DVE-12 and DVE-13 were
<br />installed in a line parallel to the property line starting with DVE-10 in the west, located
<br />approximately 25 feet southeast of DVE-6. DVE-14, DVE-15 and DVE-16 were installed from west
<br />to east in a line parallel to the property line starting with
<br />DVE-14 in the west, located approximately 10 feet northwest of MW-8. Sparge wells SP-1,
<br />Stantec
<br />4
|