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October 17, 2000 <br /> Page 2 <br /> Additional excavation and sampling was completed on April 15, 1999 to remove the unidentified <br /> piping discovered on April 8, 1999 Over-excavation in the southern portion of the site was <br /> terminated to protect the structural integrity of the station canopy supports <br /> Following removal of the former station canopy, canopy footings and kiosk, additional over- <br /> excavation excavation was completed on June 1 and 2, 1999 An additional 960 tons of soil were <br /> removed to a maximum depth of 31 feet bgs Over-excavation was terminated when, the <br /> structural integrity of the sidewalk was endangered and groundwater was encountered <br /> Groundwater was encountered during additional over-excavation activities at a depth of <br /> approximately 31 feet bgs One water grab sample was collected from the excavation The grab <br /> water sample contained elevated TPH-g and BTEX concentrations <br /> Four groundwater monitoring wells (MW-1 through MW-4) were installed on December 9 and <br /> 10, 1999 at the locations shown on Figure 2 The wells were screened from 5 feet above to 15 <br /> feet below the current water level Initial depth to water in MW-1 was 36 feet, therefore the well <br /> was set at 50 feet bgs Groundwater rose to approximately 30 feet bgs after well completion <br /> Groundwater sampling events identified low intermittent concentrations of benzene and MtBE <br /> Four Geoprobe borings (GP-1 through GP-4) were completed on July 20 and 21, 2000 at the <br /> locations shown on Figure 2 The borings encountered petroleum hydrocarbon impacted soil and <br /> groundwater at depths of approximately 50 to 60 feet bgs Following this investigation IT <br /> recommended onsite soil sampling below 60 feet bgs for vertical delineation and installation of <br /> deeper level monitoring wells for assessment of groundwater impacts <br /> PROPOSED SCOPE OF WORK <br /> As stated previously, this investigation is being performed to further evaluate the lateral and <br /> vertical extent of impacted soil and groundwater at the subject site The scope of work proposed <br /> for this investigation will include the installation of four monitoring wells Proposed monitoring <br /> well locations are based upon data collected in previous investigations, an east to southeast <br /> groundwater gradient and a historical groundwater low of 70 feet bgs <br /> As required by the Occupational Health and Safety Administration (OSHA) Standard <br /> "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910 120), and by <br /> California Occupational Health and Safety Administration (Cal-OSHA) "Hazardous Waste <br /> Operations and Emergency Response" guidelines (CCR Title 8, Section 5192), IT has prepared a <br /> Site-Specific Health and Safety Plan (SSP) Prior to the commencement of fieldwork the SSP <br /> will be updated with appropriate field personal and subcontractor information The field staff <br /> and contractors will review the SSP before beginning field operations at the site A draft SSP has <br /> been included in Attachment A <br /> The specific scope of work is discussed below <br /> �i <br /> N\ranefpllProjects\Projects1911101111A101021911011 wp doc <br />