SR0084138 - Laserfiche WebLink

Home Browse Search

Second Semi-Annual 2021 Groundwater Monitoring, Batch Extraction Results Report & Supplemental Site Investigation Waterloo Food and Fuel 3032 East Waterloo Road, Stockton, California Page 7 issues associated with the extraction wells EW-1 through EW-3 within the Underground Storage Tank System Leak Investigation Report of Findings, prepared by Apex Envirotech, Inc, and dated June 14, 2021. Mid Zone Three monitoring wells were available to for sample collection form this zone from wells identified as MW-5B, MW-7B and MW-11. TPHg was detected in ranging in concentration from 210 p.g/L in MW-5B to 32,000 lig/L in MW-7B. TPHd was detected above the laboratory detection limit of <50 [ig/L only in MW-7B with a reported concentration of 970 pig/L. Benzene was detected in ranging in concentration from <50 pg/L in MW-11 to 5,500 p.g/L in MW-7B. MTBE was detected in ranging in concentration from 26 µ,g/L in MW-11 to 130 pg/L in MW-7B. Groundwater elevations decreased an average of 9.46 feet compared to the last sampling event. Groundwater flow direction was reported to be to north 36° east with a gradient of 0.063 ft/ft (Figure 4b). Deep Zone Concentrations of MTBE reported in well MW-10 at 100 pz/L, respectively. Groundwater flow direction for Deep Wells MW-5F, MW-6F, MW-7F, and MW-9 was reported to be to north 54° east with a gradient of 0.009 ft/ft (Figure 4c and 4d). BATCH EXTRACTION On September 27, 2021, Apex completed the first of three planned Batch Extraction events in an effort to remediate TPHd impacts localized around EW-1, EW-2, and EW-3. The batch extraction date and the duration of the extraction at each well is included below. Using a vacuum truck equipped with "stingers," Apex observed the extraction of approximately a total of 1,500 gallons of TPHd-impacted groundwater from the extraction wells on September 27, 2021. The stingers utilized were comprised of corrugate hoses constructed with an angled cut on the bottom of the hose. Depth to groundwater in EW-2 was measured at 45.37 feet below ground surface (bgs) prior to the initiation of extraction. Extraction began at 8:20 and ceased at 10:30(2 hours 10 minutes). The depth to groundwater at the end of the extraction was 47.68 feet bgs. Depth to groundwater in EW-3 was measured at 44.87 feet bgs prior to initiation of extraction. Extraction began at 10:45 and ceased at 12:50 (2 hours 5 min). The depth to groundwater at the end of the extraction was 49.93 feet bgs. Depth to groundwater in EW-1 was measured at 45.20 feet bgs and depth to Free Product was 44.98 feet bgs (0.25 feet of Free Product) prior to initiation of extraction. Extraction began at 12:55 and ceased at 15:20 (2 hours 25 min). The depth to groundwater at the end of the extraction was 49.01 feet bgs. A log of the groundwater extraction is presented in Appendix D. The following table summarizes the extraction efforts at each of the well locations.