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Ms. Connie Davis/Aggregate Indusfries - F S[reet Soil and Groundwater Abatement Re ort <br />Project Number 1001018 ~'!\R!\GON <br />July 6, 2001 <br />Page 3 <br />3. GROUNDWATER ABATEMENT A ~IVITIES <br />Approximately 83,000 gallons of groundwater/free-phase product mixture was pumped from <br />the abatement excavation for temporary storage on site. The liquid was transported by Key <br />Energy 'Services to Arvada Treatment Center (ATC) for treatment and disposal. ATC <br />reported that approximately 450 gallons of free-phase'-'p~o~duct was recovered from the liquid <br />shipments and transported to Mesa Oil for recycling. An additional 20,000 gallons of <br />groundwater was pumped from the excavation and is currently being stored on site. Thai <br />water will be used for dust suppression in the asphalt plant. <br />Two (2) groundwater samples were collected during the abatement process. One (1) <br />groundwater sample was collected from the abatement excavation to document the <br />concentrations of petroleum hydrocarbons which were present in the groundwater in the <br />abatement excavation while one (1) groundwater sample was collected from a downgradient <br />mining dewatering trench to confirm that the dewatering trench had not been significantly <br />impacted by petroleum hydrocarbons. The dewatering trench is located several hundred feet <br />northeast of the abatement excavation. The groundwater samples were transported under <br />standard Paragon chain-of-custody procedures to TLI for BTEX and TEPH analyses. The <br />groundwater sample results are discussed in Section 4.2 of this report. <br />4. CONTAMINANT CFIAR~CTERISTICS <br />Soil attd groundwater sample results are discussed in the following sections of the report. <br />Copies of TLI laboratory reports for the samples collected from the site are enclosed in <br />Appendix C. <br />4.l Soil Sample Results <br />Laboratory results for soil samples collected from the site during the abatement process are <br />summarized in Table 1 in Appendix B of this report. The analytical results for the <br />assessment samples aze also shown on Figure 3 in Appendix A. As seen in Table 1 and on <br />Figure 3, BTEX concentrations ranged from not observed above the laboratory detection <br />limits of 2 micrograms per kilogram (µg/Kg) to approximately 11,789 µg/Kg while TEPH <br />concentrations ranged from not observed above the laboratory detection limit of 10 <br />milligrams per kilogram (mg/Kg) to 4,399 mg/Kg in the 11 assessment soil samples. <br />Relatively high concentrations of TEPH were observed in the West Wall North End, Bottom <br />#1, and South Wail Middle assessment samples. It should be noted that the Bottom #1 soil <br />sample was collected from beneath the groundwater table at a depth of approximately 13 to <br />15 feet below grade and the sample was lifted through the apparently impacted groundwater. <br />The West Wall North End, Bottom ~1, and South Wall Middle soil samples were also <br />analyzed for PAHs since the TEPH concentrations exceeded the TPH Threshold but the <br />BTEX concentrations did not exceed the Tier 1 Risk-Based Screening Levels {RBSLs). Test <br />pits i and 2 were later completed beyond the extent of the excavation near the West Wall <br /> <br />