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1 1 1 t 1 1 1 1 1 Ms. Connie Davis/Aggregate Industries - F Street Soil and Groundwater Abatement Re ort Project Number 1001018 ~l~Rl~GQN July 6, ?001 Page 3 3. GROUNDWATER ABATEMENT ACTIVITIES Approximately 83,000 gallons of groundwater/free-phase product mixture was pumped from the abatement excavation for temporary storage on site. The liquid was transported by Key Energy Services to Arvada Treatment Center (ATC) for treatment and disposal. ATC reported [hat approximately 4~0 gallons of free-phase product was recovered from the liquid shipments and transported to Mesa Oil for recvclinQ. An additional 20,000 gallons of groundwater was pumped from the excavation and is~currently being stored on site. That water will be used for dust suppression in the asphalt plant. Two (2) groundwater samples were collected during the abatement process. One (1) groundwater sample was collected from the abatement excavation to document the concentrations of petroleum hydrocarbons which were present in the groundwater in the abatement excavation while one (1) groundwater sample was collected from a downgradient mining dewatering trench to confirm that the dewatering trench had not been significantly impacted by petroleum hydrocarbons. The dewatering trench is located several hundred feet northeast of the abatement excavation. The groundwater samples were transported under standard Paragon chain-of-custody procedures to TLI for BTEX and TEPH analyses. The groundwater sample results are discussed in Section 4.2 of this report. 4. CONTAMINANT CHARACTERISTICS Soil and groundwater sample results are discussed in the following sections of the report. Copies of TLl laboratory reports for the samples collected from the site are enclosed in Appendix C. ' d.l Soil Sample Results Laboratory results for soil samples collected from the site during the abatement process are summarized in Table 1 in Appendix B of this report. The analytical results for the ' assessment samples are also shown on Figure 3 in Appendix A. As seen in Table 1 and on Figure 3, BTEX concentrations ranged from not observed above the laboratory detection limits of 3 micrograms per kilogram (µg/Kg) to approximately 11,789 µg/Kg while TEPH ' concentrations ranged from not observed above the laboratory detection limit of 10 milligrams per kilogram (mg/Kg) to 4.399 mg/Kg in the I1 assessment soil samples. ' Relatively high concentrations of TEPH were observed in the West Wall North End, Bottom #1, and South Wall Middle assessment samples. It should be noted that the Bottom r#1 soil satnple was collected from beneath the groundwater table at a depth of approximately 13 to ' 15 feet below grade and the sample was lifted through the apparently impacted groundwater. The West Wall Nonh End. Bottom R1. and South Wall Middle soil samples were also analyzed for PAHs since the TEPH concentrations exceeded the TPH Threshold but the ' BTEX concentrations did not exceed the Tier 1 Risk-Based Screening Levels (RBSLs). Test pits 1 and 2 were later completed beyond the extent of the excavation near the West Wall