SITE INFORMATION AND CORRESPONDENCE

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WORK PLAN FOR ADDITIONAL SOURCE AREA ASSESSMENT ' Former Georgia-Pacific Corporation Tracy Chemical Packaging Plant 75 West Valpico Road,Tracy,California AME Project No. 16014.01 -2- pumped at an average rate of 75 gallons per minute. Extracted ground water was treated in an air stripping tower and discharged alternately to the basin and to an irrigation canal operated by the ' Westside Irrigation District. When treated water was returned to the basin, chloroform concentrations were observed to increase in adjacent monitoring wells. The increased concentrations were attributed to the returned water flushing chloroform from the vadose zone ' soil. Extracted water chloroform concentrations up to 1,400 µg/L in July 1986 declined to less than 100 pg/L one year later. Chloroform was reported at 6.3 pg/L in the influent water on system shut down in September 1991. ' The soils in the site vicinity consist of a heterogeneous mix of sand and gravel layers separated by layers of clay and silt. Ground water is typically encountered at a depth of approximately ' 40 feet bgs and flows to the north to northwest. In the vicinity of the BC-12/BC-13/BC-17 monitoring well cluster (Figure 2), four water-bearing ' units were identified. Unit I was encountered at depths of 12 to 36 feet bgs and is dry in some places. Unit 2 is encountered at depths of 51 to 64 feet bgs. The majority of site monitoring wells are screened in either Units 1 or 2. Unit 3 is encountered at depths of 78 to 82 feet bgs and ' is monitored by offsite well BC-13. Unit 4 is encountered at 93 to 97 feet bgs. Unit 4 is monitored by offsite well BC-17. Chloroform concentrations are typically reported at less than the laboratory reporting limit in ground water samples from monitoring well BC-17. 3.0 PROPOSED WORK TASKS The following tasks are associated with the proposed scope of work. ' Task 1 - Permittine ' Soil boring permits will be obtained from the San Joaquin County Public Health Service Department(San Joaquin County). Site access will be acquired from San Joaquin County. Task 2 - Site Health and Safety Plan ' The Site Health and Safety Plan is included in Appendix A. Task 3 - Soil Borines Three soil borings (PB-CPTI, PB-CPT2, and PB-CPT3) will be advanced across the east-west axis of the storm water basin (Figure 2). Borings will be advanced to a depth of 70 feet bgs, which is anticipated to correspond to the water-bearing zone screened by downgradient monitoring well BC-13 (Unit 3). Depths referred to in this section are referenced against the basin floor, which is approximately 17 feet bgs. R2001-032.doc