Laserfiche WebLink
It..s <br /> 1 ,12 <br /> �.W <br /> 2.4 Conclusi4ns <br /> From the results and findings of previous investigations, <br /> Alton Geoscience concludes the following: <br /> o The majority of adsorbed-phase hydrocarbon <br /> constituents in the soil onsite have been excavated <br /> and removed from the site. The excavated areas have <br /> been restored to grade level using clean backfill <br /> material. <br /> o No further investigation or remediation of <br /> adsorbed-phase hydrocarbon constituents in the soil <br /> appears warranted at this time. <br /> o Based on the hydrogeologic conditions at the site and <br /> results of the field activities and laboratory <br /> analyses, the extent of dissolved-phase hydrocarbon <br /> constituents in the ground water can be defined onsite <br /> and downgradient of the site. The dissolved-phase <br /> constituents are united to the northwest corner of <br /> the property, and extend offsite downgradient of the <br /> former underground and above ground tank areas to <br /> approximately the north side of Grant Line Road. <br /> O TPH-G, ethylbenzene, and total xylenes were detected <br /> only in the ground water samples from Monitoring <br /> Well AW-3 at concentrations ranging from 0.3 to <br /> 210 ppb. <br /> Q No further characterization of the dissolved-phase <br /> hydrocarbon constituents in ground water onsite, or <br /> offsite is necessary at this time. <br /> - 3.0 DESCRIPTION OF PREFERRED MITIGATION COURSE OF ACTION <br /> Based on the known geologic and hydrogeologic characteristics <br /> of the site and the extent of petroleum hydrocarbons .in the <br /> - ground water, the recommended course of.action to address the <br /> dissolved-phase constituents in the ground water is presented <br /> below: <br /> Task It Initiate Periodic Pumping Program <br /> An active periodic pumping program, utilizing either <br /> manual pumpouts or a portable, single-well, <br /> on-demand system will be initiated to remove <br /> apparently impacted ground water from AW-3. Weekly <br /> - pumping is proposed initially. The purpose of the <br /> program would be to induce formational ground water <br /> flow into the well beyond the limits. of quarterly <br /> purge: pumping, thus providing a means of capturing <br /> p he,site <br /> water more representative of- the _ - <br /> 4 <br />