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J J Ms. (;onnie Davis/Aggregate Industries - F Street Soil and Groundwater Abatemeo[ Re ort Project Number 1001018 ~'!~Rl1GON Juty 6, 2001 Page A North End and South Wall Middle assessment samples in an effort to bracket the TEPH contamination. As also seen in Table 1, BTEX concentrations ranged from not observed above the laboratory detection limits of 2 µg/Kg to approximately 3,194 µg/Kg while TEPH concentrations ranged from approximately 4,283 to 4,611 mg/Kg in the two (2) waste soil samples. The Class 7 Run soil sample was the fine soil material after processing the impacted soil with the crusher while the Stockpile sample was unprocessed material. It should be noted that the Stockpile sample was collected approximately two (2) days after the impacted soil had been excavated from the spill area. The Tier 1 RBSLs for the leachate to groundwater ingestion exposure pathway and TPH Threshold soil standards, as published in Section 5.3 of the Storage Tank Regulations (7C(:R 1101-14), are also summarized in Table 1. As seen from Table 1, the TEPH concentrations observed in the West Wall North End, Bottom #1, South Wall Middle, Class 7 Rttn and Stockpile soil samples exceeded the TPH Threshold standard. The BTEX and PAH concentrations observed in the soil samples analyzed from the site did not exceed the Tierl RBSLs. 1 4.2 Groundwater Sample Results One (1) groundwater sample was collected from the abatement excavation on May 17, 2001 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 on May 15, 2001 to confirm that the dewatering trench had not been significantly impacted by petroleum hydrocazbons. The laboratory results for the groundwater samples collected from the site are summarized in Table 2 in Appendix B of this report. As seen from Table 2, BTEX were not observed above the laboratory detection limits of 0.5 micrograms per liter (µg/L) in the Dischazge Point 2 and Abatement Pit samples with the exception of xylenes which were observed at a concentration of 47 µg/L in the Abatement Pit sample collected on May 17, 2001. TEPH was not observed above the laboratory detection limit of 0.~ milligrams per liter (mg/L) i^ the Discharge Point 2 groundwater sample while TEPH was observed at a concentration of 126 mg/L in the groundwater sample collected from the abatement excavation on May 17, 2001. The Maximum Contaminant Levels (MCLs) for BTEX are also summarized in Table 2. As seen from Table 2, the MCLs for BTEX are 5.0; 1.000; 680 and 10,000 µg/L, respectively. Those standards aze the statewide interim organic pollutant standards published in "The Basic Standards for Ground Water" Regulation 41, (5 CCR 1002-41). It should be noted that TEPH is not regulated by a numeric standard in Colorado at this time. The BTEX concentrations observed in the groundwater samples collected from the dewatering trench and abatement excavation in May '_001 did not exceed the MCLs. The groundwater sample J