2007-11-20_REVISION - M1982015 (12)

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The current on-site groundwater is not being used for domestic or commercial consumer water supply. The water in quarry ponds and surrounding groundwater is being contained using a slurry wall which is being constructed around the quarry ponds. The ponds are planned for recreational usage (swimming, boating, and fishing). Drinking water supply for the development will be obtained from the Little Thompson Water District. On-site groundwater supply wells will not be installed for any domestic or commercial water supply (Carma, Tyler Packard, 2007). C. The applicant should provide information concerning the nature and extent of any contamination and release of hazardous wastes which have occurred at the site, including but not limited to: ' - Identification of the chemical nature and extent, both onsite and offsite, of contamination that has been released into the soil, groundwater or surface water at the property, and/or releases of substances from each of 1 the source areas identified, including estimated volumes and concentrations of substances discharged at each area, discharge point, or leakage point. The source, nature, extent, and estimated volumes of the ' release are important in the overall evaluation of risk. If deemed necessary, the results of indoor air investigations to evaluate impacts due to volatile organic compounds should also be presented. ' On September 29, 2006, approximately 5 barrels (225 gallons) of gasoline was released from an 8" diameter gasoline pipeline operated by Rocky Mountain Pipeline when excavating equipment nicked the pipe ' creating a small hole. At the time of the release, GeoCon had excavated a trench to ' approximately 27 feet below the ground surface (bgs) and extending approximately 350 feet west of the gasoline pipeline for completion of the earth and slurry wall. The slurry wall was designed to contain water in the quarry ponds from infiltration to the St. Vrain River. The pipeline is ' located 18 feet bgs. A concrete protective collar was placed around the pipeline extending approximately 5 feet in either direction from the pipeline / slurry wall intersection. Most of the trench was filled with ' bentonite slurry which is used to allow the excavation to remain open for completion of the earth and slurry wall. The pipeline was damaged while digging the slurry wall trench around the pipeline and protective collar. ' Gasoline leaked from the pipeline and mixed with the slurry in the excavation to the west of the pipe. In the effort to repair the pipe, the slurry was displaced using backfill from the trench and pumped into a ' "slurry holding trench" (SHT) which was constructed to contain the slurry for future management. ' At the time of the release, Rocky Mountain Pipeline performed emergency response activities which included free product removal and soil excavation and disposal. E-21 has requested information from Rocky ' Mountain for details of their work, however, no response has been received to date. E-21 will submit this information to CDPHE as an addendum to this report when it becomes available. 7