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1 <br /> <br /> <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />1 <br /> <br />Aggregate Industries - F Street Site Characterization Repor[ <br />Project Number 1001018 PnxncoN <br />October 9, 2001 <br />Page 10 <br />northem on-site dewatering trench is located approximately 650 feet downgradient of the <br />spill area. The analytical results for a water sample collected from the northern on-site <br />dewatering trench on May 15, 2001 are summarized in Table 3 in Appendix B (Sample <br />Name =Discharge Point 2). Potential impacts to surface water bodies do not appear to be <br />likely at this time since significant BTEX contamination in groundwater has not been <br />observed to date at the site. <br />7. CONCLUSIONS AND RECOMMENDATIONS <br />The following conclusions are made based on information obtained during the soil and <br />groundwater abatement and assessment activities. <br />1. Approximately 2,000 cubic yards of contaminated soil was excavated at the site and <br />incorporated into asphalt pavement mix. <br />2. Approximately 83,000 gallons of groundwater/product mixture was pumped from the <br />abatement excavation for off-site treatment and disposal. Approximately 450 gallons <br />of the 83,000-gallon mixture was free-phase product which was reportedly <br />transported to Mesa Oil for recycling. An additional 20,000 gallons of groundwater <br />was pumped from the excavation and that water was used for dust suppression in the <br />asphalt plant. <br />3. The TEPH concentrations observed in the West Wall North End, Bottom #1, South <br />Wall Middle, Class 7 Run and Stockpile soil samples exceeded the TPH Threshold <br />standard. The lateral and vertical extent of TEPH contamination in soil appears to be <br />bracketed by abatement excavation confirmation samples, test pit samples or soil <br />boring samples. <br />4. The BTEX and PAH concentrations observed in the soil samples analyzed from the <br />site did not exceed the Tierl RBSLs. <br />5. Groundwater was observed at depths ranging from approximately 5.6 to 24.7 feet <br />below the TOC in MW-t through MW-4 and EW-1 during the four (4) groundwater <br />elevation measurement events. Free-phase petroleum has not been observed in the <br />monitoring wells during the four (4) groundwater elevation measurement events. <br />6. The regional groundwater flow generally appears to be in a northeasterly direction <br />with a more northerly component on the east side of the site while the local <br />groundwater flow direction appears to be to the east-northeast in the vicinity of the <br />spill area. The hydraulic gradient was estimated to range from approximately 0.006 <br />to 0.03 for the overall site while the hydraulic gradient was estimated to range from <br />approximately 0.002 to 0.006 for the spill area. <br />t <br />