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Ms. Connie Davis/Aggregate Industries - F Street July 2002 QMR/Closure Request <br />Project Number 1001018 Pl~RflGON <br />September 20, 2002 <br />Page 2 <br />was confirmed on May 7, 2001. The release was reported to the CDPHE on May 8, 2001. <br />Based on information provided by Aggregate Industries, the volume of the diesel-fuel spill <br />was estimated to be approximately 10,840 gallons and reportedly occurred over a relatively <br />short period of time from mid-March to the end of April 2001. <br />Contaminated soil was excavated from the spill area between May 8, 2001 and May 31, <br />2001 and stockpiled at the site for use in asphalt paving mix. The approximate extent of the <br />abatement excavation which was completed at the site is shown on Figures 3a and 4. <br />Approximately 103,000 gallons of groundwater/free-phase product mixture was also pumped <br />from the excavation during the abatement activities. Soil and groundwater sample results <br />from the abatement excavation were discussed in the July 6, 2001 Soil and Groundwater <br />Abatement Report. <br />Installation of groundwater monitoring wells was performed at the site in July 2001 and <br />October 2001 to obtain information regarding groundwater quality at the site. Information <br />regarding the assessment activities was summarized in the October 9, 2001 Site <br />Characterization Report (SCR) and October 2001 Quarterly Monitoring Report dated <br />November 16, 2001. The groundwater monitoring program proposed in the SCR included <br />the sampling of six (6) wells (MW-1 through MW-4, EW-1 and a proposed well) for <br />benzene-toluene-ethylbenzene-xylenes (BTEX) and total extractable petroleum hydrocarbon <br />(TEPH) analyses. <br />2. GEOHYDROLOGY <br />Groundwater elevations in wells MW-1 through MW-5 and EW-1 were measured by <br />Paragon prior to sampling on July 29, 2002. Groundwater elevation data for the site is <br />summarized in Table 1 which is attached to this report. As seen from Table 1, groundwater <br />was observed at depths ranging from approximately 6.2 to 24.5 feet below grade during the <br />July 2002 sampling event. Free-phase product was not observed during the July 2002 <br />sampling episode. <br />Piezometric surface diagrams for groundwater elevations observed on July 29, 2002 are <br />attached to this report as Figures 3 and 3a. The piezometric surface for the overall site, <br />including wells OW-1 through OW-4, is shown on Figure 3 while the piezometric surface in <br />the vicinity of the spill area is shown on Figure 3a. The piezometric surfaces were estimated <br />using the computer program Surfer® which is distributed by Golden Software. As seen from <br />Figure 3, the regional groundwater flow generally on July 29, 2002 appeared to be in a <br />northeasterly direction with a more northerly component on the east side of the site. As seen <br />