ARCHIVED REPORTS XR0001845 - Laserfiche WebLink

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(7) A preliminary site conceptual model based on the available data suggests the following (1) source . contaminant mass is primarily on site and is approximately 9,400 cubic yards This source area is located beneath and adjacent to the former UST pit and dispenser locations (2)The contaminant soil mass extends over approximately 5,700 square feet on the site which forms the primary source area This contaminant mass has the following estimated petroleum hydrocarbon constituent concentrations benzene(1 to 10 mg/kg),toluene (2 to 50 mg/kg), ethylbenzene (2 to 15 mg/kg), xylene(5 to 220 mg/kg), TPH-gas (10 to 2, 100 mglkg) (3)The mechanism for spread of the petroleum hydrocarbons in groundwater is vertical movement of petroleum hydrocarbon compounds vertically downward through the soil column to the groundwater and then through the groundwater surface by diffusion (4)Petroleum hydrocarbon contaminated groundwater plume extends over an area of approximately 62,500 square feet at a depth of about 48 feet bgs A minor amount of free-product may still exist at the site between MW-1 and MW-3 under the former UST pits Vertical rise and fall of the groundwater surface has spread the movement of petroleum hydrocarbon compounds vertically through the soil/groundwater contact where highest concentrations appear to be located The groundwater plume appears to have the following maximum petroleum hydrocarbon concentrations present in it benzene(290 µg/l), toluene(1300 µg/1 ethylbenzene (400 µg/1), xylene(1800 }ig/l), TPH-gas(11,000 µg/1) Oxygenate compounds present in the groundwater include MTBE(8 3 µg/l) Lead scavengers present in the groundwater plume include 1,2-DCA(10 µg/1) and 1,2-EDB (1 2 pg/l) Recommendations for further work include (1)installation of at least an additional three groundwater monitoring wells along the southern portion of Murray Street and a single monitoring well on the east side of Cherokee Lane, (2) continue quarterly groundwater monitoring of the monitoring well network, (3) complete the sensitive Receptor Survey described in the workplan, (4)complete and update the Site Conceptual Model and associated Preliminary Problem Assessment Report after an additional two quarters of groundwater monitoring have been completed, (5) lnitate a remediation feasibility study Mmn\D 1En,ronnicnL-d\ParmarTexaco\R \snx12o3� Page 26