Laserfiche WebLink
• In order to evaluate the extent of the "unknown hydrocarbon", additional drilling and sampling <br /> was performed below the impacted soil (to a depth of approximately 31 feet), and laterally a short <br /> distance in boring SB-4 (see Figure 1) to a depth of approximately 26 feet No detections were <br /> found of any analytes in the SB-3 boring below 26 feet bgs Similarly, no detections were found of <br />' any analytes in the SB-4 sample collected at 26 feet Based on our evaluation of the Septic Leach <br /> Area results, we believe the lateral and vertical extent of the detected hydrocarbon analytes has been <br />' adequately characterized <br /> 2.4 Site Hydrogeologic Conditions <br /> The site is underlain by a laterally competent deposit of clayey silt from the surface to <br /> approximately 62 feet bgs This silt deposit appears to be consistent in lithology with a typical <br />' composition of approximately 80% silt, 15% clay and 5% fine sand Between 62 and 80 feet bgs, <br /> a sandy zone is present At the Site, the sandy zone is an average of 15 feet thick and varies in <br /> texture from well sorted to poorly sorted, typically containing approximately 80% sand and 20% <br /> clay and/or silt Underlying this sandy zone are layers of silt and clay to the depths explored in <br /> this investigation The exception noted is of a sand deposit logged in the boring for well MW-4 <br /> ata depth of 102 feet bgs A copy of the SEA COR field boring logs is found in Appendix B A <br /> hydrogeologic cross section depicting the site subsurface conditions and based on the information <br /> developed in this investigation is presented as Figure 2 <br /> First encountered groundwater exists under unconfined conditions at an average depth of <br /> approximately 70 feet The zone of saturation for this groundwater is the sandy zone located <br /> between approximately 62 and 80 feet bgs Based on this and previous investigations, this zone <br /> appears to be the highest permeability pathway for groundwater and potential contaminant <br /> transport at the Site The groundwater level at the Site has fluctuated significantly due to seasonal <br /> recharge and local pumping influences The groundwater level appears to also exist below the <br /> base of the sandy zone within the silt and clay deposits (See Hydrogeologic cross section, Figure <br /> 2) <br /> N0026 001 01 ROF 5 August 1 1994 <br />