FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

08 February 2000 AGE-NC Project No. 98-0398 Page 2 of 4 depths of 25 feet bsg(Preliminary Investigation and Evaluation Report, dated 12 June 1998). A total of four soil samples were submitted for laboratory analysis for total petroleum hydrocarbons quantified as gasoline (TPH-g); benzene, toluene, ethylbenzene and xylene (BTEX compounds); methyl tertiary butyl ether(MTBE),ethyl tertiary butyl ether(ETBE),di-isopropyl ether(DIPE),tert- amyl methyl ether (TAME) and tert-butanol (TBA). TPH-g was detected at a concentration of 24 milligrams per kilogram(mg/kg)in a soil sample collected from P-1 at a depth of 12 feet bsg. BTEX compounds were detected at concentrations ranging as high as 0.0067 mg/kg in a soil sample collected from P-1 at a depth of 15 feet bsg. The results of the analysis did not detect MTBE, DIPE, TAME, ETBE or TBA at or above laboratory reporting limits. The vertical extent of impacted soil at the site was delineated in boring P-I to depths less than 20 feet bsg; the lateral extent of the TPH-g impacted soil has not been fully determined, but AGE field notes indicate a lack of field indicators of hydrocarbon-impact to soil from historic cross-gradient probe boring collected from capillary fringe in P-2. The results of the soil sample analysis are presented and discussed in more detail in Preliminary Investigation and Evaluation Report, dated 12 June 1998 and prepared by AGE. A summary of the analytical reports for soil samples collected are presented in Table 1. Ground water was encountered on the site at approximately 12 feet bsg; the flow direction is generally toward the north-northeast in this portion of Stockton. One grab ground water sample was collected from P-1 and submitted for laboratory analysis. TPH-g was detected at a concentration of _ 1,700 micrograms per liter (4g/1); ethylbenzene and xylene were detected at concentrations of 48 µg/1 and 50µg/1,respectively. The lateral extent of impacted ground water was not fully determined, but the detected hydrocarbon concentrations encountered were minimal. Benzene, toluene, MTBE, DIPE, TAME, ETBE and TBA were not detected at or above the laboratory reporting limits. Additionally probe borings P-2 and P-3 were advanced at historic downward to cross-gradient locations from the former UST location. The attempt to collect ground water samples from probe boring P-2 and P-3 was unsuccessful between depths of 11 to 16 feet bsg and 16 to 21 feet bsg. A summary of analytical reports for ground water samples collected are presented in Table 2. 3.0. ASSESSMENT OF HYDROCARBON-IMPACTED SOIL AND GROUND WATER The State of California drinking water standards, adopted as a result of the Safe Drinking Water Act, have established maximum contaminant levels (MCLS) for benzene, toluene, ethylbenzene and xylenes at 1 µg/1, 150 4g11, 700 µg/1 and 1,750 µg/l, respectively. Concentrations of detected dissolved BTEX compounds detected in the grab ground water samples collected from P-1 were all below MCLs. Advanced GeoEnvironmental,Inc.