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1117 Lone Palm Avenue <br /> Suite B <br /> y Modesto CA 95351 <br /> 209 579 2221 <br /> = Fax 209 579 2225 <br /> A S s o c I A 7 E S I N C <br /> June 1, 1999 <br /> 17292 0001 <br /> Mr Jeff Wong <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br />' 304 E Weber Street, Third Floor <br /> Stockton, California 95202 <br /> 1 Subject Additional Subsurface Investigation at Franklin High School, 300 North Gertrude <br /> Avenue, Stockton, California <br />' Dear Mr Wong <br /> ATC Associates Inc has completed the Subsurface Investigation of the above referenced site <br /> The attached report summarizes our activities and findings Based on the analytical results and <br /> field observations, soil and groundwater beneath the location of the former UST is currently <br /> impacted by petroleum hydrocarbon constituents The impacted soil appears to be generally <br />' limited to the upper 25 feet of the soil column with methyl tert-butyl ether (MTBE) detected at a <br /> low concentration at 35 feet bgs Laterally, impacted soil appears limited to an area within <br /> approximately eight feet from the former UST excavation (as exhibited by B-2 and B-3 data) <br />' Groundwater impaction is currently not defined although the initial groundwater analytical data <br /> suggest petroleum hydrocarbons do exceed current California water quality goals for drinking <br />' water <br /> In the judgment of ATC, additional groundwater monitoring appears appropriate to confirm <br />' current dissolved hydrocarbon concentrations in groundwater Based on the chemical results of <br /> the additional monitoring, investigative work further defining groundwater impaction may be <br /> warranted This additional work may include the installation of additional monitoring wells to <br />' evaluate groundwater chemical characteristics and hydrology <br /> Two existing on-site monitoring wells (MW-308 and MW-220) are located approximately 100 <br />' feet south of the site's former UST location These two wells appear to be a component of a <br /> separate subsurface investigation associated with an adjacent site located immediately east of the <br /> school grounds Also, according to Mr Butch Schmidt of SUSD, additional monitoring wells <br />' are present at the site These wells are a potential conduit for dissolved petroleum hydrocarbons <br /> detected in groundwater and therefore should be addressed appropriately <br />