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EEC#S1462-1 UmFirst Stockto November 12 2003 Geologic and Hydrogeologic Setting This site is located in the northern part of the San Joaquin Valley at an elevation of approcimately 15 feet above mean sea level The valley fill consist of late Mesozoic through Ecocene ' sedimentary deposits, predominately of marine origin These deposits are overlain by Tertiary sedimentary deposits which are composed primarily of sand, silt, gravel, and clay (CDMG, 1976) In the vicinity of the site, the late Cenozoic deposits are approximately 3,000 feet thick and generally consist of alluvial gravel, sand, silt, and clay Groundwater in these alluvial deposits is usually confined to semi-confined During a previous Phase I Environmental Site Assessment (EEC, 1998), near surface groundwater condition in the site vicinity were reviewed for several sites within a '/2 mile radius of the site The information was obtained from the California Regional Water Quality Control Board— Central Valley Region, leaking underground storage tank database The nearest of these ' sites is located approximately 0 11 miles southeast of the site Groundwater fluctuates between 29 and 45 feet below grade at this location and flows to the northwest and northeast Although this uppermost groundwater aquifer is considered to be a beneficial use aquifer, EEC did not find ' any indications that drinking water supplies are produced from the uppermost aquifer in the site vicinity ' Groundwater for municipal service is supplied by the California Water Service Company (CWSC) The CWSC operates 58 groundwater production wells in the Stockton area These wells are installed at depths between 250 and 603 feet bgs The nearest active well to the site ' vicinity are CWSC well number 53-01, and 26-01 Water quality data obtained from the State of California Department of Health Services (CDHS) shows no evidence that either of these wells has been impacted by petroleum hydrocarbons or the chlorinated compound tetrachloroethene (PCE), trichloroethene (TCE), or dichloroethene (DCE) Four wells, located within one to two miles of the site and in the assumed upgradient direction of groundwater flow, contain detectable concentrations of PCE Several hydrocarbon constituents typically associated with solvents or petroleum product have also been detected in wells within one to two miles of the site ' Current Field Activities ' The subject site is currently undergoing grading as part of a redevelopment project On Wednesday November 11, 2003 during grading operations at the site, soil with a strong odor was discovered in the northwest corner of the construction area UniFirst halted construction activity ' in this area and contacted EEC to evaluate the nature of the odor associated with this soil Since discovery of the affected soil all redevelopment and construction activities in this area have been discontinued, resulting in a substantial cost to the proposed project due to the equipment and ' personnel that are on standby at the site On Thursday, November 12, 2003, EEC initiated a site investigation to evaluate potential environmental concerns Seven soil samples were collected at the soil surface All samples were tcollected in brass sleeves and labeled with the date, time sampled, project name, and unique sample identification number Samples were placed on iced storage for transport to a State of California laboratory certified to perform the requested analysis utilizing proper Chain of Custody ' protocol The results of these samples are presented in Table 1 Based on the findings EEC determined that further investigation was necessary to determine the extent of the contamination in the soil at the site 1