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uik Stop p M arket No 120 February 10, 1992 Project No. 3-49120-31 Page 2 converting the borings to groundwater monitoring wells and collecting groundwater samples for laboratory analysis. During the course of this investigation it was found that product lines were leaking and petroleum hydrocarbons had affected the soil and groundwater beneath the site. The product lines were repaired, contaminated soil l excavated and removed, and the excavation backfilled with clean fill These activities and findings were detailed in our Soil And Groundwater Investigation report dated ' October 9, 1990. In December 1990, a quarterly groundwater monitoring program was initiated. ' In April 1991, due to regulatory concerns about hydrocarbons found in groundwater during the December sampling and analysis, an additional sampling and analysis was ' performed. This sampling and analysis confirmed the non-detectable results of the March 1991 sampling and analysis. Field Operations Prior to sampling, RESNA measured the depth to groundwater and checked for the ' presence of floating product at each well using an optical interface probe. No measurable floating product was detected in any of the wells. The groundwater in each well was checked for the presence of surface sheen with a clear acrylic bailer none was observed. Groundwater samples were then collected from each well following the procedures outlined in our groundwater sampling protocol (Appendix A). Approximately four well-casing volumes of groundwater were removed from each well before sampling. Groundwater removed from the wells and equipment rinse water were placed in Department of Transportation-approved drums and left on-site pending the laboratory analytical results Groundwater Elevations ' Depth to groundwater measurements were obtained prior to sampling and ranged from 44 68 to 45.62 feet below the surface and are included with the well elevations in Table 1 Groundwater elevations calculated from these measurements ranged from 33.40 to 33 60 feetell w mean sea level (MSL) based on available survey data. A groundwater elevation contour map generated from these elevations is included as Figure 3 The groundwater contour map shows a gently inclined groundwater surface with a predominantly easterly flow at a gradient of approximately 0.0020. ' Laboratory Analyses The groundwater samples were transported to RESNA Environmental Laboratories (a state-certified laboratory) located in Fremont, California and analyzed for TPHD, TPHG, and BTEX components. A summary of the analytical results from current and past well samplings is presented in Table 1. The laboratory analytical reports are attached in Appendix B