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Interim Emergency Remedial Action/Monitoring Well Installation Work Plan Page 2 <br /> Former Union Facility,-Cutter Lumber <br /> Projeu No 102 2 <br /> May 20, 1997 <br /> groundwater sample collected from this water well Based upon the discovery of this <br /> contamination, the client's former consultant, Geological Technics Inc , conducted a <br /> review of public records A former "Oil Supply" building and at least one associated <br /> gasoline UST, several diesel ASTs and a dispenser island were identified during this <br /> record review These installations were formerly situated 40 to 50 feet south of the <br /> apparently contaminated domestic water well <br /> Geological Technics Inc subsequently installed five 10-foot deep, hand augered soil <br /> borings and soil samples were collected which contained significant (i e TPH-G >1 x 103 <br />' mg/Kg) levels of gasoline range petroleum hydrocarbons One of the borings installed in <br /> the area of the former dispenser island also contained detectable diesel range petroleum <br /> hydrocarbons which would suggest the piping associated with the diesel dispenser may <br /> also have leaked <br /> Between March 12 and March 16, 1997, the former domestic water well was properly <br /> abandoned as were three of the monitoring wells in the vicinity of the release which was <br /> discovered in 1989 A total of 9 soil borings were drilled in the vicinity of former Oil <br /> Supply" building to begin to characterize the lateral and vertical extent of gasoline and <br /> diesel contamination in the soil and groundwater <br /> 1.2 Proposed Scope of Work <br /> 12.1 Reasoning <br /> A more complete discussion of the scope of the environmental issues associated with the <br /> subject site was elucidated in the April 8, 1997 report, Preliminary Soil and Groundvi ater <br /> Investigation, which was submitted by Geo-Phase Environmental Inc It is known, based <br /> upon soil and groundwater data, that the groundwater at the subject site has been <br /> adversely impacted by gasoline released from the former 1,000 gallon UST High <br /> concentrations (in excess of 5,000 ppm) in capillary fringe soil samples as well as grab <br /> water samples from select borings collected during the March-April investigation, suggest <br /> that underneath the tank pit, free floating product may exist on the groundwater surface <br /> Laterally, the contaminant plume in the groundwater extends at least 180 feet north from <br /> the point of release There appears to be a substantial volume of highly contaminated soil <br /> in the vadose zone at the point of release which takes the approximate form of an inverted <br /> cone with the broad end in direct contact with the groundwater It is our interpretation <br /> that highly contaminated soil is acting as a secondary source for ongoing groundwater <br /> contamination, and that the groundwater plume is unlikely to experience natural <br /> degradation until this source of continuing contaminant recharge is substantially removed <br /> Furthermore, if the presence of free product is used as the main criteria for qualifying a <br /> site as "high risk", the suspected presence of free product on the groundwater surface <br /> would appear to make this a"high risk" site <br /> 2937 Veneman Ave, #13240 Geo-Phase Environmental Inc Phone(209) 569-0293 <br /> Modesto, CA 95356 Fax(209) 569-0295 <br /> I <br />