Laserfiche WebLink
Metadata
Document management portal powered by Laserfiche WebLink 9 © 1998-2015 Laserfiche. All rights reserved.
33 <br /> CLEARWATER <br />' G R O U P <br /> Environmental Servrces <br /> 1 <br /> mg/kg TPHd, and 48 mg/kg benzene TPHk, and TPHmo were not detected in any of the four <br />' samples <br />' On September 25, 1997, Clearwater Group (Clearwater) supervised the drilling of six soil <br /> borings to depths from 32 to 38 feet bgs Three of the borings were converted to groundwater <br />' monitoring wells (MW-1 through MW-3) Soil samples collected from four of the six borings <br /> contained detectable concentrations of petroleum hydrocarbons The highest concentrations of <br /> TPHg (570 mg/kg) and benzene (4 0 mg/kg) were detected in the sample from SB-2 at a depth of <br />' 25 feet bgs Groundwater samples collected September 29, 1997 from all three monitoring wells <br /> contained detectable concentrations of dissolved petroleum hydrocarbons The highest <br />' concentrations of TPHg (32,000 micrograms per liter [µg/L]) and benzene (2,200 �Lg/L) were <br /> detected in the sample from monitoring well MW-1 Low concentrations of TPHd were detected <br />' in soil samples from SB-5 (11 mg/kg) and SB-6 (2 mg/kg), and in the groundwater sample from <br /> MW-1 (300 µg/L), however, subsequent groundwater sample results have been non-detect for all <br />' three wells, and with approval from the SJCEHD, analysis for TPHd has been discontinued <br /> Results of these efforts were presented in Clearwater's Subsurface Investigation Report, dated <br /> November 20, 1997 <br /> 1 <br /> Based on these initial investigation results, the SJCEHD requested monitoring wells be installed <br />' to better define the aerial extent of soil and groundwater contamination After discussion with <br /> Lon Duncan of the SJCEHD, Clearwater submitted the Workplan for Site Investigation dated <br />' November 18, 1998 An addendum to the workplan, dated December 10, 1998 was submitted in <br /> response to SJCEHD comments The workplan and addendum were approved by the SJCEHD <br />' on December 15, 1998 <br /> In January 1999, Clearwater supervised the installation of three additional groundwater <br />' monitoring wells (MW-4 through MW-6) to delineate the extent of dissolved-phase <br /> contammation The results of the investigation indicated that the extent of sorbed-phase <br />' contamination was delineated and existed from approximately 10 to 25 feet bgs near the former <br /> USTs Results of the groundwater samples indicated that the extent of dissolved-phase <br />' contamination remained undelineated downgradient from the former UST system However, <br /> . high contaminant concentrations in wells located in cross-gradient positions from the former <br /> USTs suggested that off-site sources may be contributing to contamination detected beneath the <br /> 1 <br />' zB 178C CAP 2 November 20,2002 <br />