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'S CLEARWATER G R O U P Env-unmenla! Services On September 25, 1997, Clearwater supervised the drilling of six soil borings to depths from 32 to 38 feet bgs Three of the bonngs were converted to groundwater monitoring wells (MW-1 through MW-3) Soil samples collected from four of the six borings contained detectable concentrations of petroleum hydrocarbons The highest concentrations of TPHg (570 mg/kg) and benzene (4 0 mg/kg) were detected in the sample from SB-2 at a depth of 25 feet bgs Groundwater samples collected September 29, 1997 from all three monitoring wells contained detectable concentrations of dissolved petroleum hydrocarbons The highest concentrations of TPHg (32,000 micrograms per liter [pg/L]) and benzene (2,200 pg/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 µg/L) Subsequent groundwater sample results have been non-detect for all three wells and with approval from the SJC/EHD, analysis for TPHd has been discontinued Results of these efforts were presented in Clearwater's Subsurface Investigation Report, dated November 20, 1997 Based on these initial investigation results, the SJC/EHD requested additional monitoring wells be installed to better define the aerial extent of soil and groundwater contamination After discussion with Ms Lori Duncan of the SJC/SJC/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 SJC/EHD comments The workplan and addendum were approved by the SJC/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 Concurrently, Clearwater also 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 Analysis 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 positioned wells suggested that off site sources could be contributing to contamination detected beneath the site Inquiries suggested and later confirmed the existence of a fuel transport line in the area of the site The line was found to be 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 the installation of three monitoring wells (M W-5B, MW-7, and MW- 8) in three of the soil borings All three wells were placed on 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 taken to define the lateral extent of soil and groundwater ZB178C/3Q03 Monitoring Rpt 2 October 14,2003