ARCHIVED REPORTS XR0000729 - Laserfiche WebLink

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S E C0 R In June 2002, SECOR performed a Geoprobe assessment in order to delineate Petroleum hydrocarbons in soil and groundwater downgradient and cross-gradient of the site, and to determine future locations for additional off-site groundwater monitoring . wells. Nine Geoprobe borings were completed at approximately 15 feet bgs. Petroleum hydrocarbons and fuel oxygenates were not detected in any soil samples above laboratory reporting limits. TPHg and constituents of benzene, toluene, ethylbenzene, J' and total xylenes (BTEX) were detected in borings GP-1 through GP-3, GP-8, and GP-9, =` with maximum concentrations of TPHg and benzene reported at 17,000 ppb (GP-1) and 170 ppb (GP-2), respectively. MTBE was detected in groundwater from borings GP-8 and GP-9 at a maximum concentration of 230 ppb (GP-8). Petroleum hydrocarbons and fuel oxygenates were not detected above laboratory reporting limits in groundwater samples from borings GP-4 through GP-7. s In November 2002, six groundwater monitoring wells (MW-10 through MW-15) were installed. The groundwater plume was delineated in all directions with the exception of northeast of MW-12. In October 2003 SECOR conducted a pumping well influence study at the site to determine if surrounding wells influence groundwater flow direct or gradient at the site. It =:;y was determined that surrounding wells (particularly site Lathrop Grammar School ' irrigation well) do not influence groundwater flow direction or gradient beneath the site. In November 2003, well MW-16 was installed northeast of MW-12. MTBE was reported s •y in MW-16. y On June 12, 2004, SECOR supervised the advancement of five geoprobe borings (GP- 10 through GP-14). The purpose of the work was to delineate the lateral extent of petroleum hydrocarbon impact in soil and groundwater downgradient of the site and to determine the placement of wells that will complete delineation of the plume. Soil samples at 10 and 15 feet bgs from geoprobe borings GP-10 through GP-14 were collected and submitted for laboratory analysis. Soil samples were analyzed for TPHg, BTEX, and fuel oxygenates by EPA Method 8260B. TPHg, xylenes, and ethanol were reported in soil sample GP-13@10 at concentrations of 1.2 mg/kg, 0.0095 mg/kg, and 0.65 mg/kg, respectively. No detectable concentrations of petroleum hydrocarbons were reported in the soil samples from GP-10, GP-11, GP-12, and GP-14. Groundwater "grab" samples collected from each of the geoprobe boring locations were analyzed for TPHg, BTEX, and fuel oxygenates by EPA Method 8260B. MTBE was reported at a concentration of 0.88 ug/L in boring location GP-12 and ethanol was reported at a concentration of 610 ug/L in boring location GP-13. In February 2005, two deep direct push borings (DGP-1 and DGP-2) and three wells (MW-17, MW-18, and MW-19) were completed. Installation of wells MW-17, MW-18, and MW-19 completed lateral delineation of the dissolved plume to low or non-detect levels. Petroleum hydrocarbons were detected in groundwater samples collected in the deep direct push borings at maximum concentrations of 1,400 ug/I TPHg (DGP-1 @52) and 29 ug/I MTBE (DGP-1 @52). A groundwater sample from DPG-1 at 72 feet bgs contained TPHg and MTBE at concentrations of 260 ug/I and 6.1 ug/l, respectively. A A.1 groundwater sample from DPG-2 at 70 feet bgs contained TPHg, benzene, MTBE at w ' .' concentrations of 1,300 ugll, 0.64ug/i, and 6.1 ug/l, respectively. n