ARCHIVED REPORTS_XR0004600 - Laserfiche WebLink

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Corrective Action Plan • Quarterly Ground Water Monitoring, October 1995, by Park • Quarterly Ground Water Monitoring, December 1995, by Park ' Quarterly Ground Water Monitoring, February 1996, by Park • Quarterly Ground Water Monitoring, April 1996, by Park ' a Well Construction Report and Groundwater Monitoring Report, August 1996, by Park • Quarterly Ground Water Monitoring, October 1996, by Park Although there are numerous and important inconsistencies in some of the documents cited above, including switching of well identification designations and incorrect reporting of well data, particularly in the data reported by Blymer, a careful review of all of the available documentation has given OST a comprehensive and, what we consider accurate, understanding of the site history and subsurface conditions with respect to gasoline-impacted soil and groundwater. The following paragraphs summarize DST's comprehension as to the relevant history of the site and its present condition with respect to the presence of gasoline contaminants. ' One 500-gallon gasoline underground storage tank (UST) was removed from the property in 1985. Reportedly,at the time of the UST removal, an unknown amount of hydrocarbon-impacted ' soil was excavated and disposed. However,the amount or disposition of this soil was apparently undocumented. The location of the former UST has been reported at different locations throughout the history of successive investigations. Based upon the earliest, and what OST believes to be the most ' accurate diagram of the tank location by Blymer, we believe with reasonable certainty that the location of the former UST was immediately adjacent to and southeast of the soil boring designated as B-9. In addition, OST agrees with Park's interpretation that the present ' monitoring well, BEI-MW3, might have been drilled within the boundary of the former UST backfill area as illustrated on the Site Map, Figure 2. A copy of the Blymer sketch diagram upon which the tank location is based is included in Appendix B. ' Subsequent phases of site investigation involving groundwater monitoring well installations were conducted on three occasions: ' In December 1989, Blymer installed three monitoring wells,presently designated as BEI-MW I, BEI-MW2,and BEI-MW3. Analyses of soil samples collected during the drilling of MW-2 (now ' designated BEI-MW2) and MW-3 (now designated BEI-MW 1) detected no significant concentrations of either Total Petroleum Hydrocarbons as gasoline (TPHg) or BTEX in the samples collected at 5 and 10 feet bgs; however, both wells contained moderate concentrations ' of TPHg (270 millgrams per kilogram [mg/kg] and 96 mg/kg, respectively) at 15 feet bgs. BEI- MW2 also contained detected TPHg concentrations of 130 mg/kg at 20 feet bgs. Analytical results of all soil sampling events are summarized in Table 1. OST 705-1-2.cap Page 4