WORK PLANS - Laserfiche WebLink

Home Browse Search

Ir �. sparging well SP -1 in September 1994. Locations of the wells and borings are presented on Figure 3. Soil samples were collected from most of the borings during drilling and submitted for laboratory analysis. The analytical data for soil are presented in Table 2. Between 1987 and ' 1994, relatively low concentrations of petroleum hydrocarbons in soil were only detected in 10 samples collected from borings MW -1, MW -2, MW -3, MW -6, MW -13, 90-1, and 90-2. The w maximum detected concentrations were TPH-g at 130 mg/kg benzene at 0.010 mg/kg, toluene at 0.038 mg/kg, ethylbenzene at 0.005 mg/kg, and xylenes at 0.12 mg/kg. L" Soil Vapor Extraction Pilot Test (1994) ` .. PSC performed a soil vapor extraction (SVE) and air sparging (AS) pilot test in October and November 1994 to evaluate the effectiveness of these remediation technologies at the Site. SVE tests were performed using well MW -1, and air sparging tests were performed using well SP -1. PSC reported the results of the tests in the February 1, 1995 Final Remediation Plan, which indicated that SVE and air sparging would be effective for the remediation of hydrocarbons in the subsurface. In June 1995, PSC installed air sparging wells SP -2 through v SP -6. However, implementation of the air sparging and SVE system was postponed due to naturally -occurring reductions in petroleum hydrocarbon concentrations that were observed at the time. Subsurface Investigation (1999) 4 r' In May 1999, PSC performed a subsurface investigation using CPT technology. Soil and �- groundwater samples were submitted for laboratory analysis from three CPT borings (CPT -1, CPT -2, and CPT -3). The CPT investigation indicated that the lateral extent of impacted groundwater was largely contained within the Earthgrains property boundaries. PSC reported the results of this investigation in the May 1999 Subsurface Investigation and Groundwater Monitoring Report. V — Air Spar2in2/Soil Vapor Extraction (2000 through 2002) v Vapor extraction well VW -1 was installed and an additional AS/SVE pilot test was performed in June 2000. The pilot test results indicated that the combined use of these technologies would r. be an effective method of remediating petroleum hydrocarbons at the Site. Operation of a full- scale AS/SVE remediation system was initiated on April 25, 2001. PSC installed a new air sparging well (SP -A) on March 14, 2002, upon determining that air injection at well SP -1 was not adequately remediating the petroleum hydrocarbon impact in groundwater. In December 2002, the remediation system was disengaged, since its effectiveness to remove contaminants had become limited. Post -remediation monitoring was performed to evaluate the concentrations of petroleum hydrocarbons in groundwater and the stability of the plume. The SL_AIR SCM and RI. WP 7 L.