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1 Surface and Subsurface Contamination Report Page 12 <br /> VELASQUEZ PROPERTY September 5,2008 <br /> WKA No. 8237.01 <br /> copper. The solution was changed to an acid copper chromate in 1982. Other features at <br /> ' the site included retention ponds, catch basins, drywells,building structures, and asphalt <br /> surfaces. The site is located in Stockton and is surrounded by a high school, residences <br /> and commercial establishments. <br /> ' Wood treating activities at the site contributed to the releases of hazardous substances in <br /> soils and groundwater. Chromium levels in the groundwater exceed federal and state <br /> ' drinking water standards at and downgradient in an easterly direction from the MCTC site. <br /> Response and closure activities have been implemented to address the contaminants in soil <br /> 1 and groundwater. Municipal wells and monitoring wells are sampled and monitored <br /> regularly to identify chromium contaminant movement. An insitu calcium polysulfide <br /> ' solution injection pilot study is underway to determine the efficiency of reducing the <br /> hexavalent chromium in groundwater to the unsoluble trivalent state(DTSC, undated). <br /> A 2007 DTSC fact sheet for the facility indicated that in 1990 arsenic contaminated surface soils <br /> from this facility were excavated to an off-site disposal facility. Contaminated sediments in the <br /> ' pipes and culverts were cleaned out and sent to an off-site disposal facility. Subsurface soils <br /> were addressed by replacing a synthetic liner used to capture fluid leaking in the retort pit <br /> (pressure vessel used for wood treatment)with an upgraded liner and installation of a leak <br /> detection system. Groundwater cleanup included expansion of an on-site water treatment plant, <br /> installation of groundwater extraction systems, and groundwater monitoring to ensure that the <br /> extraction systems were working properly(DTSC, 2007). <br /> ' WKA reviewed the Semi Annual Groundwater Monitoring Report for SPX Cooling Technologies <br /> Facility, Stockton, California (dated April/July 2007) prepared by DUDEK, which indicated that <br /> 1 the MWs observed by WKA just east of the site are MW430 and MW 464 related to the <br /> investigation of Marley Cooling Tower Company. The 2007 report indicated that Total <br /> Dissolved Chromium was detected in April 2007 below the laboratory reporting limit. The �y <br /> Iconcentrations were estimated to be approximately 6 micrograms per liter (µg/L) and 7 µg/l_ <br /> respectively. The two wells were not sampled in July and were both wells not sampled for <br /> 1 Hexavalent Chromium (DUDEK, 2007). <br />