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• SITE CONCEPTUAL MODEL and <br /> FOURTH QUARTER 2002 REPORT <br /> KWIKEE FOODS <br /> 2081 Country Club Boulevard <br /> Stockton, California <br /> EXECUTIVE SUMMARY <br /> This report presents a generalized interpretation (conceptual model) of the hydrogeology of two <br /> parcels of property located at 2081 and 2103 Country Club Boulevard in Stockton, California. The <br /> report also includes a relatively detailed history of groundwater flow and migration of the plume of <br /> gasoline-impacted groundwater that underlies the sites. Both sites were formerly 'operated as <br /> gasoline fueling stations, and gasoline was stored in underground fuel tanks. Investigation at the <br /> Kwikee Foods site was started in 1990, while investigation at the neighboring site, a former <br /> Chevron station, was begun in 1986. <br /> Both sites are underlain primarily by fine-grained sediment (clay) at shallow depths, but a <br /> curvilinear, channelized sand bed that is mostly less than 10 feet thick is present at a depth of <br /> approximately 20 feet. This bed contains water (overlying and underlying clay beds do not) and <br /> has been impacted by gasoline that was released at one or more leak points at the Chevron site. <br /> These leak points could not be precisely located with the data available within the time frame for <br /> this report. At least one leak point has also been identified at the Kwikee site. A 1-centimeter <br /> hole was visible in one of the underground storage tanks when it was removed in 1998, and <br /> gasoline-contaminated soil and groundwater were sampled from the pit. However, in contrast to <br /> the Chevron site, samples collected before and after the tanks-were removed have failed to find <br /> evidence of any significant migration of this gasoline out of the tank pit. <br /> Subsequent development and evolution of the plume of gasoline-impacted groundwater has been <br /> traced using a series of 1) groundwater elevation maps and 2) Total Petroleum Hydrocarbon <br /> concentration maps. These were the primary data sources available for this report, and the maps <br /> were compared to the conceptual model for validation of its basic tenets. This time-variant analysis <br /> demonstrates that the history of groundwater flow and plume development has been more complex <br /> than predicted by the model, but analysis of the variations in groundwater flow and depth to <br /> groundwater is capable of resolving most of the details and aberrations of plume growth and <br /> contraction. <br /> Although the spread of hydrocarbons in groundwater led to contamination of all of the Kwikee <br /> Foods property in the 1990's, much of this contamination has attenuated naturally as a result of <br /> changes in groundwater flow patterns, perhaps supplemented by biological or other oxidation <br /> processes. More recently, efforts to actively remediate soil and groundwater at the Chevron site <br /> 1 <br />