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S5# 6348, Tracy QM Report, 411192 . pit was overexcavated, however, overexcavation was restricted by the proximity of the pit to the product storage tanks In July, 1991 four monitoring wells were installed, and additional soil borings were drilled Hydrocarbons as gasoline (TPHg) were identified to soil near the fill spout of the south underground product storage tank. Additional borings were drilled to identify the lateral extent of this contamination Following well development, groundwater was sampled from the four wells on July 15, 1991 and again on August 15, 1991 Due to the fact that contamination was reported at MW-4 from the July sampling and was not detected from the August sampling, that well alone was again sampled on September 11 , 1991 No TPHg or BTEX was detected at that time, or from subsequent sampling events Laboratory results are summarized in Table 2 FIRST QUARTER, 1992 ACTIVITIES Following discussion with San Joaquin County Department of Public Health personnel, MW-1 has been dropped from the sampling program because, based on previous sampling, that well is situated to an upgradtent position and no contamination appears to have affected the location from on or . off site On March 13, 1992, all four wells were monitored by taking water level measurements and examining the water for any abnormalities Materials and instruments used for monitoring and for collecting samples were washed between each well with biodegradable soap and tap water and rinsed to distilled water The measurement of groundwater depth was made from the top of the PVC casing using an electronic water sounder. A bailer was lowered into the well to obtain a water sample which was observed for the presence of free product, sheen, or odor MW-2, MW-3, and MW-4 were bailed until at least two of the three parameters of temperature, pH, and conductivity had stabilized to within 10% of the previous reading Following this purging, water was collected to fill three 40 ml VOA vials so that no air remained in the vial following closure with a teflon- lined cap The vials were labelled, placed on ice, and sent to a state-certified laboratory under chain-of-custody control for analysts of TPHg and BTEX Fl DINGS Water-level measurements indicate that on March 13, 1992 the depth from the surface to the groundwater averaged approximately 7 feet The flow direction was to the N54W with a gradient of 0 0028 foot per foot These Mand earlier measurements are listed in Table 1 -2-