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II �i�7 �j Quik Stop Market No. 132 Working to Regtolr 93ature Project No. F7132.93 June , 4 Groundwater Sampling k Groundwater samples were collected on March 17, 1993 from five of the seven monitoring wells in accordance with RESNA's groundwater sampling protocol (Appendix B). In December 1992, the San Joaquin County Public Health Services approved semi-annual of ! sampling for monitoring wells MW-3 and MW-4 and in February 1993 they approved discontinuation of sampling for these wells. Groundwater purged from the wells and equipment decontamination water was placed in drums approved by the Department of I' Transportation for this purpose and left on-site pending removal b a licensed hauler. The P PrP P g Y volume of groundwater removed from each well and other measured sampling parameters are noted on the groundwater sampling field log included in Appendix C. 1iterly We11 Pumping�,_ As agreed upon the with San Joaquin County Public Health Services (see Background Section-Appendix A), monitoring well-MW-S 'is pumped out on a quarterly basis as an ,I interim remedial`measure: This quarter pumping was conducted on March 2, 1993. Prior to pumping a groundwater sample was obtained from the well and labeled MW-5. The well was then pumped for about three hours and approximately 200-gallons of water was removed from the well. After pumping was complete, another groundwater sample was collected and labeled MW-5B. Laboratory Analyses The groundwater samples were transported to RESNA Environmental Laboratories, a state- certified laboratory,located in Fremont, California. Samples were analyzed for the presence of TPHG following modified Environmental Protection Agency (EPA) Method 8015 and for BTEX following EPA Method 8020/602. The laboratory analytical report and chain-of- custody document are attached in Appendix D. Summary of Results A summary of the analytical results from current and past well samplings is presented Table 1. Plates 2 and 3 show the groundwater elevation contour maps for the upper and lower ' aquifers based on the water level data in Table 1. In the local upper aquifer, groundwater elevations rose an average of 3.48 feet since last quarter. In the local lower aquifer, groundwater elevations rose an average of 3.52 feet since last quarter. The apparent groundwater flow direction in the local upper aquifer is easterly at a gradient of I approximately 0.005 and in the local lower aquifer easterly at a gradient of approximately OA33. 2