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C_L_E__A__,* RW-ATER In January 1999, Clearwater supervised the installation of three additional grow nd«ater monitoring wells (MW-4 through MW-6) to delineate the extent of dissol-,ed-phase contamination The results of the investigation indicated that the extent of sorbed-phase contamination v,,as delineated and existed from approximately 10 to 25 feet bgs near the former USTs Results of the grog-mdwater samples indicated that the extent of dissolved-phase contamination remained undelineated don%ngradient from the former UST systern However, high contaminant concentrations in cross-gradient position of wells suggested that off-site sources may be contributing to contamination detected beneath the site Initial inquiries suggest that there may be a former or etisting fuel transport lane in the area if the site Based on these results, Clearwater recommended additional investigation along South Fresno A-�enue to better understand the distribution of contamination and possible contribution trom potential off-sate sources The results of this phase of investigation were presented in Clear.iters Well hit 4allation and Grozordwater Mo)ritoring Report - Fo st Quartet 1999 GROUNDWATER MONITORING AND SAMPLING ACTIVITIES Date of ground-,-,ater sampling December 14, 1999 Wells gauged MW-1 through MW-4, and MW-b Wells purged and sampled MW-1 through MW-4, and MW-6 _ Analytes tested TPHg/BTEX/MTBE (EPA Method S015NI/8020) Laboratory Entech Analvtical Labs, (Sunn<<ale, CA) • Remarks None GROUNDWATER MONITORING AND SAMPLING RESULTS Depth to groundwater 9 97 to 10 53 feet below top of casing Flow direction Southeast at 0 0012 ft/ft TPHg concentration range 63 gg/L (MW-2) to 9,900µg/L (1IW-1) Benzene concentration range <0 50 µg/l_ (MW-2,MW-4) to 560 ug/L (MW-1) MTBE concentration range <5 0 µg/L (MW-2, MW-4, MW-6) to 83 µg/l_ (MW-1) Remarks During recent paving and construction activities on-site, both MW-2 and MW-5 were damaged The well box and top of casing of MW-2 were damaged, so the depth to water in this well was not used in calculating a groundwater elevation MW-5 was damaged beyond repair and will require proper abandonment and re-installation Once MW-5 as re-installed, all the wells will be re- surveyed prior to the next monitoring event MTBE was detected by EPA 8020 in groundwater samples collected this quarter Previously MTBE has been confirmed as "non-detectable"by EPA 8260 PROJECT STATUS&RECOMMENDATIONS The EHD responded to Clearwater's Well Installation and Groundwater Monitoring Report - First Quarter 1999 in a letter dated Jame 25, 1999 The EHD concurred n%ath the recommendations for additional assessment of groundwater contamination downgradient or the former UST system A • workplan to complete the lateral and vertical delineation of the contaminant plume has been approved CGI C-178 4Q99 2 Decerrber 28,1999