ARCHIVED REPORTS_XR0003517 - Laserfiche WebLink

Home Browse Search

• 2 0 GROUNDWATER MONITORING, SAMPLING AND ANALYSIS On May 6, 2002, to comply with quarterly groundwater monitoring requirements, Ramage Environmental monitored and sampled the three on-site monitoring wells 21 Groundwater Monitoring Upon arrival at the site, each of the wellheads was inspected, unlocked and opened Depth-to- groundwater was measured in each of the wells using a water level indicator capable of measuring groundwater to within 0 01 foot No sheen or free product was observed in MW-1 ' The depth to static groundwater across the site ranged from 44 69 feet bgs in MW-3 to 45 47 feet bgs in MW-2 The corresponding groundwater surface elevation ranged from a high of 25 89 feet below mean sea level (ms]) at MW-1 to a low of 26 05 feet below msl at MW-3 The resulting groundwater surface appears as a regular plane dipping to the east-northeast at a gradient of approximately 0 0012 foot/foot A groundwater surface contour map is included as Figure 3 The well construction details and groundwater monitoring data are summarized in Table 1 22 Groundwater Sampling and Analysis Following the groundwater level measurements, all three wells were purged and sampled The wells were purged using a pump and dedicated disposable tubing, until at least three well casing volumes were extracted, and/or after groundwater temperature, pH and electrical conductivity ' values had stabilized Following well purging and recharge, groundwater was sampled from the wells using dedicated disposable bailers and laboratory-supplied containers Each sample container was transported in an iced cooler with chain-of-custody documentation to Excelchem Environmental Labs (Excelchem), a state of California certified hazardous waste testing laboratory (Certification #2119) Excelchem analyzed each of the groundwater samples for TPH-as- gasoline, and BTEX by EPA Method 8020/8015M, and for MTBE, di-isopropyl ether (DIPE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), tertiary butanol (TBA), and 1,2- dichloroethane (1,2-DCA) by EPA Method 8260B The groundwater samples collected from MW-1 and MW-2 contained elevated concentrations of TPH-as-gasoline, BTEX and MTBE Only benzene was detected in the groundwater sample collected from MW-3, at a concentration of only 0 5 micrograms per liter (µgll) The groundwater sample results are summarized in Table 2 and the laboratory reports are included as Appendix A 5