Laserfiche WebLink
I <br />' November 10, 1992 <br /> Job No R92024 <br /> Page 3 <br /> I <br /> hydrocarbon concentrations were detected at depth intervals of 15 feet and 60 feet <br />' in MW-4. <br /> o The boring logs indicate soil lithologies in the unsaturated zone are predominantly <br />' silts and clays interspersed with silty sand lenses at 50 feet (in B-1), and 15 feet and <br /> 50 feet (in MW-4). Occurrence of lateral contaminant migration via the sand lenses <br /> is indicated by the chemical data. <br /> o Soil contamination extends beyond the area studied during this investigation <br /> o Groundwater at the site has been minimally impacted by one hydrocarbon <br /> constituent, xylene. The concentration of xylene, detected at 0 6 gg/L, was well <br /> below the MCL of 1750 gg/L. <br />' o Based on MW-4 data theg roundwater table at the site is currently 80 feet below <br /> grade surfaces. During the past ten years, groundwater in the vicinity of the site has <br /> been 50 feet or higher. The existing monitor wells, MW-1, MW-2, and MW-3, which <br /> were installed to a depth of 65 feet, are reportedly dry The presence of <br /> contamination, detected at depths from 50 feet to 60 feet in MW-4, indicates <br /> hydrocarbons have been adsorbed onto soil as the water table has declined <br /> 1 <br /> RECOMMENDATIONS <br />' RS recommends that additional soil assessment be performed by installing four additional soil <br /> borings to delineanate the extent of contamination and provide further information for soil <br />' remediation design RS recommends that the four additional borings be drilled in locations as <br /> shown on Figure 1 No additional groundwater morutor wells are recommended at this time. The <br /> need for additional wells should be evaluated after four quarters of monitoring data from MW-4 <br /> are collected, or sooner if groundwater conditions change. <br /> RS's preliminary recommendations for soil remediation design is to excavate impacted soil to a <br />' depth of 20 feet to 30 feet in areas that are readily accessible, and to install a bloventing system <br /> for remediation of the deeper and/or inaccessible areas The additional assessment recommended <br /> above would provide information needed for the bioventing system design <br /> R E M E U I AT I O N <br /> SERVICES INC <br />