ARCHIVED REPORTS_XR0011920 - Laserfiche WebLink

Home Browse Search

Page3j(rnli, liuAMP 2l111n further assessment of the extent ol'contarmination was requested by the Public Health 4crvrc e, 1=nvironme;ntal Health Division (PI-lS/f'HD) of San ioaquin County Riehe%in R Associates of Danville, California was retained in November, 1990 to perforin further %UbsurtaLC iiiWstigatlon I wo borings were drilled, one was complelLd as ,.e groundwater monitoring well, and soil and water samples were colli.cted for anaNsis I lydrotarbons were; detected to the bottom of the ~oil boring (70 feet) and to a depth of 95 feet in the monitoring well, and both gasoline and diesel wire detected in the groundwater sample from the well Upgradient was retained in August, 1994 and supervised the installation of two additional monitoring wells in September Five soil samples from G 1-1 (Figure 2) were selected for laboratory analysis, and all five contained both diesel and gasoline-range hydrocarbons Total Petroleum Hydrocarbon (TPH) concentrations decreased downward from 7050 mg/kg at 35 feet to 104 mg/kg at 55 feet Three Samples were selected from GT-2 for analysis A TPH concentration of 288 mg/kg was reported at a depth of 55 feet, no contamination was detected at 50 feet or 60 feet Diesel was detected in the groundwater sample trom both wells, and gasol 1n was also detected in the sample from GT-2 No hydrocarbons were detected in the groundwater sample from MW-1 Groundwater elevations measured to September did not provide conclusive evidence regarding the direction of groundwater flow, but suggested flow to the northwest Data previously published by the San Joaquin County Public Works Department had indicated that the prevailing flow direction was to the south or southwest Therefore, Upgradient measured the depth to groundwater in both November and December to obtain additional information on flow direction As reported in the 4th Quarter Report, groundwater elevations in all wells were nearly equal, but suggested groundwater flow to the south 4.0 MONITORING PROCEDURES Groundwater monitoring took }dace on January 13, 1995, under the supervision ot'Mr Steve Sasson of ITIS/EFID Upon arrival at the site, Upgradient personnel noted that G'I'-I and G l'-2 were buried beneath a thin layer of mud and water, presumably as a result of recent heavy rainfall A petroleum sheen was visible on the water overlying G'f-l, and several motor vehicles were parked nearby The mud and water were removed before the wells were opened and allowed to equalise with atmospheric pressure A Solinst water level meter was then used to measure the depth to groundwater in each well prior