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OUAIiIMY a!WUNMAIE"Paowama nrF OFtr 1399 Eaat YoGefnite Mamie.ManlecO.CA10=10 3.0 DISt;t1S51011 Presented below Is a summary of results of Aegis'groundwater elevation monitoring and groundwater analytical testing. 3.1 Groundwater Biovati€-ns Groundwater elevations were observed to range from V.28 to 14.30 feet above mean sea �— level during the April 23, 1991, sampling event. The groundwater surface was approximately 25 to 27 feet below existing grade. Based on groundwater elevation contouring of the water level measurements, the hydraulic flow direction has continued in a west to northwesterly direction. The calculated average hydraulic gradient for the April 1991 data was approximately 0.0005 feet per foot (ft/ft). Groundwater elevation contour maps have been drafted from the groundwater elevations measured on February 1, and April 23, 1991, and are presented as Figures 3 and 4. These contour maps indicate the flow direction and calculated hydraulic gradient. Monitoring well hydrographs have been prepared showing the fluctuation of groundwater levels with time since the installation of the wells. The hydrographs are included as Figure 5. 3.2 Groundwater Analytleal Results ,Monitoring wells were purged and groundwater sample were collected from each well according to Aegis' SOP, Appendix A. The highest concentrations of petroleum hydrocarbons in water continued to be observed in MW-1A. MW-2 and MW-3 did not show reportable concentrations of petroleum hydrocarbons. The detected concentrations of 1,2 dichloroethane reported for the February 1991 sampling of MW-1A and MW-3 were not found in the wells in April 1991. Laboratory analyses of groundwater samples are summarized in Table 2. These results will be compared to ensuing groundwater sampling/results to determine if these conditions are an anomaly or a changing trend in groundwater chemistry. 4.Q SALE The next quarterly monitoring Is scheduled for the end of July 1991. -- ---- --- 4--