SITE INFORMATION AND CORRESPONDENCE_FILE 2

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I i ff=Z Working To Restore Nature no consideration for site specific geology such as soil type/characteristics or surface features. An accurate prediction of the fate and transport of subsurface contaminants cannot be made using such models. RESNA and the City of Stockton are currently evaluating contaminant fate and transport modeling options. REGIONAL GROUNWATER QUALITY All groundwater in San Joaquin County is identified in the Water Quality Control Plan (Basin Plan) for the Sacramento-San Joaquin Delta Basin (Basin 5C) as having present and potential benficial uses. However, such designation does not mean that all groundwater within the basin is currently suitable for drinking or irrigation. It is widely documented in the literature that the shallow groundwater beneath much of Stockton is of increasingly poor quality to due the steady eastward migration of poor quality waters underlying the delta. In fact, the subject site lies at the approximate eastern edge of this groundwater saline front. Statements made by RESNA in the June 1994 Closure Request regarding the quality of shallow groundwater beneath the site were indeed subtantiated by the literature (see References, page 11, Closure Request). STOCKPILED SOIL At the direction and under the supervision of Ms. Meays, a RESNA technician collected four 2 to 1 field composite soil samples on July 31, 1992 to characterize the excavated material stockpiled at the City Corporation Yard (Figure 2). Only sample SP3-SS2E-F contained low levels of gasoline hydrocarbons (23 ppm, Table 1). The stockpiled soil was subsequently uncovered to promote aeration. On August 9, 1993, at the request of the City of Stockton, a RESNA technician attempted to sample the portion of the soil pile that had previously contained low levels of gasoline hydrocarbons. However, that portion of the soil pile had been inadvertently moved by City of Stockton personnel. In correspondence dated October 18, 1993, Mr. Jim Escobar of the City of Stockton summarized the City's efforts to locate the soil in question. It was determined that the soil had likely been used at various City Public Works projects such as for backfill material or on service roads. The remaining stockpiled soil has previously been shown through laboratory analyses to be free of contaminants (Table 1). The City Public Works Department proposes to use the remaining stockpiled soil as backfill material for a trenching project at the City Corporation Yard, scheduled for September 5, 1994. PHS/EHD concurrence for this use is requested prior to September 5, 1994. OW0148\Letters\L-082694.FNL