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r S i groundwater monitoring wells (MW-1 through MW-3) Soil samples collected from four of-the six borings"contained detectable"concentrations of petroleum-hydrdearbons 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 [[g/L]) and benzene (2,200 µg/L)'were detected iri the sample from monitoring well MW-i 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 y 1998 --- -- Based on these-initial-investigation,results;the SJC/EHD requested additional m.oanito Trig- wells be installed to better define- the horizontal extent* of-soil and rgroundwater- contamination After discussion with Ms Lon 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 1999 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