FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

r Phase l Update and Pre-Gas Station Phase 11 Report Proposed Safeway Store#1769 Gas Station Stockton, California December 12, 2000 3.0 PRE-GAS STATION PHASE II SAMPLING On November 27, 2000, HSI GeoTrans drilled and sampled four soil borings (SB-1 through SB-4) on the Property. The purpose of the sampling was to obtain a baseline assessment of soil and groundwater conditions on the Property. The soil borings were completed to depths of 11 and 16 feet below ground surface (bgs) and soil and groundwater samples were collected from each boring for possible laboratory analysis of petroleum hydrocarbon compounds and volatile organic compounds. The four groundwater samples and the 10-foot soil samples from borings SB-2 and SB-3 were submitted for laboratory analysis. Boring SB-2 was completed in the proposed fueling island area and boring SB-3 was completed in the proposed UST(s) location. Depth to first groundwater was encountered between 10 and 14 feet bgs. Static depth to groundwater ranged from 8.5 to 12 feet below grade. No chemicals were detected in the two soil samples. With the exception of the groundwater sample from boring SBA, chemicals were not detected in the four groundwater samples. MTBE and xylenes were detected in groundwater at SBA at concentrations of 8.7 and 2.4 pg/L (ppb), respectively. These concentrations are below the respective MCL values for MTBE and xylenes of 13 ppb and 1,750 ppb, respectively. Boring SBA was completed at the northeast corner of the Property within approximately 100 feet of the nearby 7-11 gas station release site. High concentrations of gasoline, MTBE and BTEX compounds have been detected in groundwater at the 7- 11 site. As such, it is reasonable to suspect the MTBE and xylenes detected in groundwater at SBA are likely a result of the groundwater contamination at the 7-11 site. The Phase II investigation is discussed in the attached report (Appendix C). P:IPROJECTSeafeway4284\Stakron-10311789_EA Updele.doc 7