ARCHIVED REPORTS_XR0012710 - Laserfiche WebLink

Home Browse Search

Quik Stop Markets,Inc. October 23, 1991 Project No. 3-491,22-32 Page 4 data. A groundwater elevation contour map generated from these elevations is presented as Figure 3. Laboratory Analyses The groundwater samples were analyzed at Applied Analytical. The groundwater samples from all wells were analyzed for TPHG and BTEX and the sample from MW-2 was analyzed for fecal coliform, as required by the San Joaquin County Public Health Service (SJCPHS). A summary of the analytical results from current and past well samplings is a presented in Table 1. Laboratory analyses revealed no detectable TPHG or BTEX in samples from monitoring wells MW-111, MW-2, MW-3, or MW-4 while TPHG and BTEX constituents were detected in the sample from MW-5. In addition for the second consecutive time,no fecal coliform was detected in the groundwater sample from MW-2. The laboratory analytical reports are attached in Appendix B. The TPHG/BTEX results of the September 1991 sample analyses are as follows: Ethyl Total Sample Sample TPHG Benzene Toluene Benzene Xylenes Number Date (ppb) ( b) { b) {ppb} MW-1R 9/11/91 <50 <0.5 <0.5 <0.5 <0.5 MW-2 9/11/91 <50 <0.5 <0.5 <0.5 <0.5 MW-3 9/11/91 <50 <0.5 <0.5 <0.5 <0.5 MW4 9/11/91 <50 <0.5 <0.5 <0.5 <0.5 MW-5 9/11/91 1100 2.6 1.9 18 2.3 TPHG Total petroleum hydrocarbons as gasoline ppb Parts per billion(119/1) <0.5 Not detected at or above listed practical quantitation limit for the method Discussion Groundwater in the monitoring wells at the site was measured at depths ranging from 15.32 to 15.67 feet below the existing ground surface. These depths correspond to groundwater elevations of 11.78 feet to 12.09 feet below mean sea level based on available survey data. The groundwater surface has dropped approximately 0.2 foot since tll►e previous sampling. Groundwater contours for July show a predominant flow direction to the east at a gradient of 0.003. The July 1991 analytical results revealed that no TPHG or B-1EX constituents were detected in the water samples collected from the monitoring wells designed to monitor the lower aquifer (MW-IR, MW-2, MW-3, and MW-4). However, TPHG and BTEX . ... .. . . .. constituents were still detected in the water sample collected from the monitoring well designed to monitor the upper or perched aquifer(MW-5). These analytical results wouI _.. .. . . . .... support our opinion that two separate aquifers are present beneath this site. �i