ARCHIVED REPORTS XR0004320 - Laserfiche WebLink

Home Browse Search

1 Additional Site Assessment and Second Quarter 1999 Monitoring and Sampling Report 2 7-Eleven Inc,Store#19976, 1399 N Main St,Manteca,California July 15, 1999 to wet, but no visual accumulation of groundwater was observed in the tank pit excavation or at the sample locations I On September 20, 1996, a total of seven soli samples were collected from the floor of the additional tank pit excavation six samples at 13 feet BGS and one sample at 15 feet BGS Soil samples were collected using the same protocol and analyzed for the same parameters as the samples collected beneath the ' USTs I In February 1998, SJCPHS required a work plan for further subsurface investigation of the vertical and ' lateral extent of contamination at this sde I I On April 29, 1998,to fulfill the requirements of the SJCPHS, Fluor Daniel GTI supervised the ' advancement of three geoprobe points(GP-1 through GP-3) near the underground storage tank (UST) i pad and pump island (Figure 2) Using a truck-mounted hydraulic drill and direct push techniques, discrete soil samples were collected from each of the soil bonngs Sod samples were collected at 5- foot intervals beginning at 5 feet below grade A total of 19 soil samples were submitted for laboratory analysis for BTEX, MTBE, and TPH-G using EPA methods 8020/modified 8015 One sample from each sod boring was also analyzed for the oxygenates, ' MTBE,tert-butanol (TBA), diisopropyl ether (DIPE), ethyl-tert-butyl ether(ETBE), and tert-amylmothyl ether (TAME) using EPA method 8260 Table 1 summarizes the laboratory analytical results for the soil samples collected from the three soil borings drilled April 29, 1998 The highest concentrations of benzene, MTBE and TPH-G were reported ' in sample GP-3-35 at 15 milligrams per kilogram (mg/kg), 27 mg/kg and 2,600 mg/kg, respectively MTBE, TBA, DIPE, ETRE, and TAME,were not detected in the three samples using EPA method 8260 Soil samples taken from the UST pit and soil borings indicate the dissolved hydrocarbon source area is between the pump island and former UST pd ' Fallowing completion of the bonngs,grab groundwater samples were collected from sod borings GP-1, GP-2, and GP-3 using disposable bailers, then decanted into 40-milliliter glass vials treated with ' hydrochloric acid to preserve the samples The samples were sealed using Teflon®-septum caps, labeled, placed on ice in an insulated container, and transported under chain-of-custody manifest to Core Laboratones The groundwater samples were analyzed for BTI X, MTBE, and TPH-G, using EPA 1 1