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tl CLEAIRR`�N' TER G R O U P I N C Enve ronmrn to! Services [gg/L]) and benzene (2,200 gg/L) were detected in the sample from monitoring well MW-1 Low concentrations of TPHd were detected in soil samples from SB-5 (11 mg/kg) and SB-6 (2 mg/kg), and in the groundwater sample from MW-1 (300 jig/L), however, subsequent groundwater sample results have been non-detect for all three wells, and with approval from the EHD, analysis for TPHd has been discontinued Results of these efforts were presented in Clearwater's Subsurface Investigation Repos t, dated November 20, 1997 Based on these initial investigation results, the EHD requested morutormg wells be installed to better define the aerial extent of soil and groundwater contamination After discussion with Lori Duncan of the EHD, Clearwater submitted the Workplan for Site Investigation dated November 18, 1998 An addendum to the workplan,dated December 10, 1998 was submitted in response to EHD comments The workplan and addendum were approved by the EHD on December 15,1998 In January 1999, Clearwater supervised the installation of three additional groundwater monitoring wells (MW-4 through MW-6) to delineate the extent of dissolved-phase contamination and performed a sensitive receptor survey The results of the investigation indicated that the extent of sorbed-phase contamination was delineated and existed from approximately 10 to 25 feet bgs near the former USTs Results of the groundwater samples indicated that the extent of dissolved-phase contamination remained undelineated downgradient from the former UST system 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 suggested and was latter confirmed that there is existing fuel transport line in the area if the site, and that it is currently filled with nitrogen gas Based on this information, Clearwater recommended additional investigation along South Fresno Avenue to better understand the distribution of contamination and possible contribution from potential off-site sources The results of this phase of investigation were presented in Clearwater's Well Installation and Groundwater Monitoring Report - First Quarter 1999 In March 2000, Clearwater supervised the completion of one hydropunch, six soil borings, the destruction of MW-5, and three of the borings were converted into monitoring wells (MW-SB, MW-7, and MW-8) All three wells were placed ten the downgradient portion of the plume to help determine the downgradient extent of contaminants The hydropunch was performed in the former UST location to assess the vertical extent of groundwater contamination at 36 feet bgs Three soil borings were • performed to define the lateral extent of soil and groundwater contamination an the northeastern CGI-ZB178C-2QT00 2 June 20,2000