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Working to Restore Nature ' September 1993 Quarterly Groundwater Sampling & Analysis December 1, 1993 Quik Stop Market No 132, Stockton, California F7132 93 ' three underground fuel storage tanks (USTs) were removed in October and November 1990 Following tank removal, excavation and soil sampling were continued until laboratory analyses of soil samples indicated that gasoline hydrocarbon affected soil above the water table in the vicinity of the storage tank excavation had been removed All of the excavated gasoline hydrocarbon affected soil was removed from the station and properly disposed (Exceltech, November 1990) New double-walled fiberglass UST's were installed at the site and the remaining excavation was backfilled with clean fill The canopy, pumps, and concrete surface were replaced and the station put back in operation in March 1991 ' Well MW-1 was destroyed on October 3, 1990, due to concerns that it may have connected two water bearing units On April 2, 1991, RESNA replaced the destroyed groundwater monitoring well with two monitoring wells designated as MW-1R and MW-5 MW-1R was designed to monitor the lower aquifer and MW-5 to monitor the upper aquifer discovered during the installation of MW-1 Analyses of all subsurface and analytical data indicated the presence of two aquifers beneath the eastern portion of site It was found that the lower aquifer had no detectable TPHg or BTEX, and the upper aquifer contained TPHg and some BTEX components (Exceltech/RESNA, July 1991) At the time of the initial groundwater sampling for MW-1R and MW-5, the San Joaquin County Publtc Health Services (SJCPHS) required that groundwater samples be collected ' from all monitoring wells and analyzed for fecal coliform On April 8, 1991, groundwater sampling for fecal coliform was performed Analytical results found that fecal coliform was only detected in the sample collected from MW-2 SJCPHS requested that the groundwater samples from this well should continue to be analyzed for fecal coliform Analytical results of subsequent samplings detected no fecal coliform in this well It is known that a main sewer line is located beneath West Hammer Lane, approximately 30 to 40 away from MW-2 ' Since this is the only well in which fecal coliform has been detected and it is the well closest to this sewer line, it appears that this sewer line may be the source of the fecal coliform The purpose of these monitoring wells is evaluate the presence and/or extent of gasoline hydrocarbons in the groundwater RESNA recommended that Quik Stop Markets be permitted to discontinue fecal coliform testing of the groundwater collected from monitoring well MW-2 in a letter to Quik Stop Markets dated December 5, 1991, the SJCPHS ' reduced the required fecal coliform sampling frequency in monitoring well MW-2 to semi- annual (every other quarter) (SJCPHS, December 5, 1991) Since the initial occurrence of fecal coliform in April 1991 fecal coliform has not been detected in this well A-2