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northwest and northeast. Groundwater gradients ranged from 0 002 to 0 005 foot per foot (ft/ft) 23 HIGH AND LOW GROUNDWATER LEVELS Based on quarterly monitoring data collected by Mittel hauser between July 12, 1991, and March 17, 1994, the highest known groundwater level was measured at 7.60 feet below top of casing (toc) and the lowest groundwater was measured at 10 03 toc Cumulative onsite groundwater level data are presented in Mittelhauser's Fourth ' Quarter 1993 Monitoring and Sampling Report, dated January 1994 Subsequent groundwater level data were collected by MPDS and this information is presented in their quarterly monitoring and sampling reports. ' 24 TABULATED ANALYTICAL RESULTS Cumulative and recent onsite groundwater analytical data are presented in the MPDS Quarterly Data Report, dated October 7, 1994 Table 3 (included here as Appendix ' B) of that report displays analytical data indicating that constituents of concern were not detected in the last four quarters of sampling As shown in the attached ' Additional Site Characterization report, dated February 1995, analysis of two confirmation groundwater grab samples also did not detect any of the constituents of ' concern ' As shown in Figure 3, petroleum hydrocarbons were found primarily in the former UST area, with minimal detections in the pump island area The most recent round of post- remediation confirmation sampling, done at the request of the Technical Advisory Committee, specifically focused on the areas of the known releases. All (ACS-1 ' through ACS-4) of the soil and groundwater confirmation samples reported non-detect ' for hydrocarbon constituents One sample did show a positive result for bis-2-ethyl- hexel phthalate, a common laboratory artifact known to leach out of plastic 2168R71 wpWarch 1996 3 4ittelhauser� C 0 R P 0 R A T 1 0 M