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} Closure Request Addendum ReportI. 1,2-DCA Investigation July 22,2002 Former American Forest Products Site,Stockton,California Page 2 of eight sampling locations were proposed in the Work Plan. However, field conditions encountered during the investigation limited sampling to five locations (HP-1, HP-2,HP-6,HP-7, and HP-8). The f- locations where samples were collected are identified in Figure 3. Drilling was conducted by TEG of Rancho Cordova, California,under the supervision of a URS geologist. Boreholes were advanced using a direct-push, van-mounted rig equipped with 1.5-inch diameter steel rods. -_ Upon reaching the target sample depth, the drill string was pulled back, and a stainless steel bailer was lowered into the open borehole. Only limited amounts of water were encountered. In order to increase the ! ] amount of water available for sampling, the drill rods were pulled back approximately six to ten feet, depending on location. Because of the limitation of available water quantity, the implementation of the Work Plan was modified to >=� sample at one depth per location instead of two depth-oriented samples at each location. This allowed for the collection of a more complete set of lateral-coverage samples within the time available to complete the field work. A total of six samples were collected. The samples were labeled according to the final depth of the open borehole. For example, sample HP-6150 was collected at location HP-6 at a final depth of 50 feet below ! ground surface(bgs). Approximately 120 milliliters(mL) of groundwater were recovered at each location,using the stainless steel bailer. The groundwater was transferred immediately to three 40-mL VOA vials, and labeled - -=- according to location,depth, and time. The samples were placed on ice immediately following collection, and kept in coolers until shipment to the laboratory for analysis. Water samples were analyzed for a total of fifty-nine individual VOCs using EPA Method 8260B. Analytical services were provided by STL of Sacramento, California. Equipment decontamination was conducted to minimize the potential for cross contamination between well ;E.. locations. Prior to and after use, sampling and testing equipment was washed in a non-phosphate (Alconox) solution,rinsed with potable water, and rinsed again with distilled water. The drill holes were abandoned immediately following the collection of the water samples. Abandonment consisted of grouting the borehole with a bentonite/cement slurry,using a PVC tremie pipe" No soil r, cuttings or purge water were generated during the direct-push sampling procedure. 3.0 RESULTS Two VOCs, 1,2-DCA, and tetrachloroethene(PCE), were reported in samples collected at the site. Prior to this investigation, the only VOC detected in groundwater samples from the site was 1,2-DCA. The distribution of current and historical VOC detections is illustrated in Figure 3. Analytical results are summarized in Table 1. A copy of the analytical laboratory report is attached in Appendix A. 1,2-DCA was detected at two of the five sampling locations. The concentrations ranged from 4 ltg/L -� (HP2/52) to 170 p.g/L(HP-1/50). The locations where 1,2-DCA was detected are situated within forty feet j GAAF IREPORTIDCA_Final_rpt.doc