SITE HISTORY - Laserfiche WebLink

Home Browse Search

grab groundwater samples for total petroleum hydrocarbons as gasoline(TPH-g),TPH-d, BTEX constituents, and five oxygenates were all below reported laboratory limits(HETI 2001). August 28-29, 2000: HETI constructed three groundwater monitoring wells(MW-1, MW-2, and MW-3) to 50 fbg with 15 feet of screen (Figure 2). Soil samples were not collected for analysis from wells MW-1, MW-2, and MW-3 due to the close proximity of previously installed borings B-1, B-4, and B-5, respectively. TPH-d was detected in groundwater samples collected from each of the three wells. Quarterly monitoring was initiated in September 2000 (HETI 2001), and continued through February 2002. The wells were dry during both the November tool and February 2002 monitoring events (HETI 2004). Groundwater data collected from these wells are included in Tables 1 and 3. These wells were subsequently destroyed in 2005 in preparation for Site excavation activities. August 20, 2001: HETI installed an additional groundwater monitoring well (MW-4) in the former diesel UST excavation (HETI 2004). June 2oo4: HETI advanced five additional soil borings (B-7 through B-11) to total depth of 50 fbg. All analytical results for TPH-g and BTEX constituents were below laboratory reporting limits. TPH-d was detected in soil samples at a maximum concentration of 4,300 mg/kg in the sample collected at 25 fbg from B-11. TPH-d was detected in two grab groundwater samples at a maximum concentration of 2,900 micrograms per liter(µg/L) in the sample collected from B-8 (HETI 2004). June 12-18, 2oo8: TRC completed six(6) onsite soil borings to groundwater and converted three (3) of the soil borings to groundwater monitoring wells (MW-5 through MW-7). Soil borings were completed to total depths ranging from 68 feet below grade (fbg) to 85 fbg depending upon soil and groundwater conditions. The maximum concentration of TPH-d reported in groundwater was 1,300 micrograms per liter(µg/L) in the grab groundwater sample collected from boring B-12/MW-5 (TRC, 2008). Monitoring wells were completed to a depth of 67 fbg based on lithologies observed during drilling. Twenty(20) feet of 0.020 inch slotted well screen was installed in each monitoring well. Groundwater MonitorinZ: Groundwater elevations and water quality have been monitored quarterly from September 2000 until May 20o9,and semi-annually through the third quarter 2010. Monitoring wells MW-1 through MW-3 were sampled during the initial and first quarterly monitoring event. Subsequent attempts to gauge and sample these wells failed due to a lack of groundwater in the wells.These wells remained dry until their destruction in June 2005. Monitoring well MW-4 was never gauged nor sampled since,the well remained dry until its destruction in June 2005. 2.3.1 Summary of Remedial Actions Bohm Environmental Solutions(BES) prepared a Remedial Action Work Plan for the Site on April 16, 2005. The Work Plan determined remediation by excavation provided the most effective process for removing soil(hot spots) containing elevated levels of petroleum hydrocarbons. CLS Environmental Services submitted a Remedial Feasibility Evaluation as part of the Remedial Action Report (RAR) submitted on December 12, 2oo6. The Feasibility Evaluation also indicated that excavation was the most efficient clean-up method. Soil vapor extraction was not deemed feasible at the Site due to the compacted soil conditions present and the inability of diesel to readily volatilize. Microbial injection was considered a viable option. 3