Laserfiche WebLink
GRANITE CONSTRUCTION— FRENCH CAMP Page 5 <br /> WKA No 2088 09 <br /> October 10, 2005 <br /> ' From September 1993 through January 1995 five additional monitoring wells (MW4 through <br /> MW8) were installed to depths of 40 feet bgs at the site to further evaluate the extent of <br /> groundwater contamination beneath the site The two-inch diameter monitoring wells were <br /> constructed using 0 02-inch screen from 20 to 40 feet bgs A licensed California surveyor <br /> surveyed the location and casing elevation of the wells <br /> On September 28, 1993 approximately 700 cubic yards of diesel-contaminated soil was <br /> excavated from beneath the former dispenser island and stockpiled and aerated onsite Results of <br /> laboratory analysis of soil samples obtained from the excavation revealed low but detectable <br /> 1 concentrations of TPH as diesel San Joaquin County Environmental Health Department did not <br /> require additional excavation of soil The UST excavations were lined with plastic and <br /> backfilled with clean fill upon authorization from SJCEHD The stockpiled soil remains on site <br />' and is currently located in the southwest corner of the property <br /> Quarterly groundwater monitonng and sampling was performed at the site from 1993 until 2004 <br /> 10 Predominate groundwater flow direction beneath the site has been to the northwest The <br /> estimated hydraulic gradient beneath the site has ranged from 0 001 feet/foot to 0 0073 feet/foot, <br /> with an average hydraulic gradient of 0 003 feet/foot Depth to groundwater beneath the site has <br /> ranged from 15 to 30 feet bgs <br /> Groundwater has been impacted primarily with gasoline and benzene There has been a <br /> significant decreasing trend in concentrations of gasoline and benzene Concentrations of TPH <br /> as gasoline have decreased by an order of magnitude (from 3,200 p.g/l to 220 µg11) and benzene <br /> has decreased by two orders of magnitude (from 510 µg/1 to 12 µg/1) During the latest sampling <br /> event (October 2004) TPH as gasoline was only reported in well MW 1 at a concentration of 220 <br /> µg/l MTBE has been analyzed in the wells from 1998 through 2004 MTBE has never been <br /> detected in any of the monitoring wells, with the exception of a trace concentration reported in <br /> MW8 (0 56 µg11) during the October 2004 sampling event Results of the latest laboratory <br /> 1 analysis shows concentrations of TPH as diesel reported in wells MW1, MW2, MW3, MW6 and <br /> MW7 at concentrations ranging from 87 to 180 µg/1 <br /> 1 0 <br /> `�W <br />' WALLACE KUHL <br /> Recycled paper &ASSOCIATES INC <br />