ARCHIVED REPORTS XR0008710 - Laserfiche WebLink

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` � �axparatl'on May 16, 2000 A Member of The IT Croup ` Mr Ed Ralston Page 2 Additional excavation and sampling was completed on April 15, 1999 to remove the unidentified piping discovered on April 8, 1999 Over-excavation in the southern portion of the site was terminated to protect the structural integrity of the station canopy supports Following removal of the former station canopy, canopy footings and kiosk, additional over- excavation excavation was completed on June 1 and 2, 1999 An additional 960 tons of soil were removed to a maximum depth of 31 feet bgs Over-excavation was terminated when, the structural integrity of the sidewalk was endangered and groundwater was encountered Groundwater was encountered during additional over-excavation activities at a depth of approximately 31 feet bgs One water grab sample was collected from the excavation The grab water sample contained elevated TPH-g and BTEX concentrations Four groundwater monitoring wells (MW-1 through MW-4) were installed on December 9 and 10, 1999 at the locations shown on Figure 2 The wells were screened from 5 feet above to 15 feet below the current water level Initial depth to water in MW-1 was 36 feet, therefore the well was set at 50 feet bgs Groundwater rose to approximately 30 feet bgs after well completion PROPOSED SCOPE OF WORK The scope of work proposed for this investigation will include the installation of three geoprobe borings to delineate the vertical extent of hydrocarbons in the soil and groundwater Proposed geoprobe borings locations are based upon results of previous assessment activities, results of overexcavation and assessment activities and are shown in Figure 1 As required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910 120), and by California Occupational Health and Safety Administration (Cal-OSHA) "Hazardous Waste Operations and Emergency Response" guidelines (CCR Title 8, Section 5192), IT has prepared a Site-Specific Health and Safety Plan (SSP) Prior to the commencement of fieldwork the SSP will be updated with appropriate field personal and subcontractor information The field staff and contractors will review the Site-Specific Health and Safety Plan before beginning field operations at the site A draft SSP has been included in Attachment A The specific scope of work is discussed below • Geoprobe Baring. Three geoprobe borings (GP-1 through GP-3) will be driven using a CPT rig in the general locations shown on Figure 1 The borings will be advanced until two consecutive soil samples show absence of impact GP-2 will be advanced to five feet beyond the historic groundwater low Based on information from the SJCPHS/EHD the local historic groundwater low is approximately 70 feet bgs Once total depth has been reached a discrete water sample will be collected Soil samples will not be collected from Geoprobe borings located within the area of overexcavation until a depth greater than 30 feet bgs All work will be done in accordance with stipulations of permits obtained from the SJCEHD 11SACRFPIICOMMONIrancfpITrojectsTrojects191I\0I I\1 A101021Workplan2 doc