ARCHIVED REPORTS_XR0008886 - Laserfiche WebLink

Home Browse Search

t21 December 2001 AGE NC Project No 95-0143 ' Page 2 of 5 ' Details of the SVE/IAS system installation were reported in Quarterly Report-May 1999, dated 30 July 1999 and Quarterly Report - August 1999, dated 05 October 1999, both prepared by AGE Operation of the SVEAA.S system was initiated in November 1999 and continued until November ' 2000 The SVE system was shut down due to a significant decrease in hydrocarbon concentrations in soil gas drawn from the vadose zone The decrease in hydrocarbon concentrations coincided with an increase in ground water elevation that may have "drowned"the portion of vadose zone m which ' the extraction wells were screened Approximately 830 gallons of petroleum hydrocarbons were extracted during operation of the SVE system ' On 15 and 16 March 2001, five soil borings (MW-22, MW-23, MW-24, EW-3 and EW-4) were advanced at the site Borings MW-22, MW-23 and MW--24 were completed as 2-inch ground water ' monitoring wells, borings EW-3 and EW-4 were completed as 4-inch ground water extraction wells Extraction wells EW-3 and EW-4 were installed to address hydrocarbon-impacted ground water at the former UST No 7 location and to induce draw-down in local ground water Draw-down of local ' ground water would increase vadose zone and enhance SVE performance at the former UST pit location Procedures and results of the well installation were summarized in AGE's Quarterly Report . -- First Quarter 2001, dated 30 May 2001 3.0. PROCEDURES Field activities were performed in accordance with guidelines issued by the Regional Water Quality Control Board - Central Valley Region (RWQCB) and by the San Joaquin County Public Health I Services - Environmental Health Division(PHS-EHD) for the investigation of underground storage tank (UST) sites and sampling of ground water monitoring wells, respectively Field procedures for the performance of ground water monitoring and sampling are described below 3 1 WELL MONITORING AND EVACUATION On 14 November 2001, a Solinst water level meter was used to measure the depth to ground water P in twelve monitoring wells at the site and in fourteen monitoring wells at the neighboring Madison site relative to the tops of the well casings The ground water elevations (Table 1) and hydraulic gradient (Figure 3) were determined from these data fAfter measurement of depths to water, casing water in each monitoring well was evacuated(purged) using a two-stage submersible purge pump The pump was decontaminated prior to purging each well using an Alconox solution and clean tap water Temperature,pH and conductivity of the purged water were measured at regular intervals during purging using an Oakton and a Hydac water analyzers Approximately 5 to 14 gallons of water were removed from each well except for MW-9, from which 50 gallons ofwater were purged(approximately three casing-water volumes) All purged Advanced GeoEnvironmental,Inc I