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<br />- Mr. Carl Mount/DMG - F Street Additional Soil Abatement & Sampling PnRnGON <br />Project Number 1001018 <br />October 26, 2007 <br />Page 2 <br />Paragon Consulting Group, Inc. (Paragon) returned to the subject site on December 11, 2006 <br />to collect soil samples from the three (3) area which exhibited total extractable petroleum <br />hydrocarbon (TEPH) concentrations above. the TPH Threshold of 500 milligrams per <br />kilogram (mg/Kg) during the May 2001 soil abatement activities. The benzene-toluene- <br />ethylbenzene-xylenes (BTEX) and polynuclear aromatic hydrocarbon (PAH) concentrations <br />observed in the soil samples analyzed from the site in May 2001 did not exceed the Tierl <br />Risk-Based Screening Levels (RBSLs). The TPH Threshold and Tier 1 RBSLs were <br />established by the Colorado Department of Labor and Employment Division of Oil and <br />Public Safety (OPS) for assessment of soil contamination associated with regulated <br />petroleum storage tanks in the state of Colorado. <br />The analytical results for soil samples collected from the site during this project are <br />summarized in Table 1 which is attached to this report while the soil sample locations are <br />shown on Figures 3 and 4. Samples which were collected from areas with apparent residual <br />contamination consisted of the West Wall North End, Bottom #1 and South Wall Middle. <br />As seen from Table 1, the BTEX and TEPH concentrations observed in the West Wall North <br />End, Bottom and South Wall Middle soil samples were generally much lower in the samples <br />collected in December 2006 compared to May 2001. With the exception of the TEPH <br />concentration observed in the sample collected from the West Wall North End, the BTEX <br />and TEPH concentrations observed in the three (3) follow-up soil samples collected from the <br />site in December 2006 did not exceed the Tier 1 RBSLs or TPH Threshold. <br />Since the TEPH concentration observed in the sample collected from the West Wall North <br />End in December 2006 exceeded the TPH Threshold, additional soil abatement activities <br />were performed in that area of the site on October 8, 2007. Approximately 25 cubic yards of <br />contaminated soil was excavated and stockpile at the site for on-site aeration. Five (5) soil <br />samples were collected from the walls and bottom of the abatement on October 8, 2007 for <br />BTEX and TEPH analyses. As seen from Table 1 and Figure 4, BTEX and TEPH were not <br />observed above the laboratory detection limits in the five (5) soil samples collected from the <br />walls and bottom of the abatement on October 8, 2007. <br />A groundwater sample was also collected from the abatement excavation on October 8, 2007 <br />for BTEX and TEPH analyses. As seen from Table 2, BTEX were not observed above the <br />laboratory detection limits or were observed at relatively low concentrations in the <br />groundwater sample collected from the abatement excavation in October 2007. As also seen <br />from Table 2, TEPH was observed at a concentration of 93 milligrams per liter in the <br />