Laserfiche WebLink
S E C O R <br /> 2003 Feasibility Study Report and Site Assessment Work Plan <br /> July 18, 2003 <br /> Page 22 <br /> monthly operation and maintenance visits and semi-annual groundwater sampling costs over ten <br /> year period using a discount rate of 2%. <br /> Chevron believes that the local community and State officials will accept this proposed remedial <br /> alternative. <br /> 8.0 POTENTIAL IMPACTS OF REMEDIAL ACTIONS <br /> Potential impacts of each remedial alternative identified to meet the WQOs are summarized below. <br /> 8.1 Groundwater Barrier <br /> Potential impacts of the proposed groundwater barrier consist of hydrocarbon impacts to deeper <br /> groundwater and off-site migration. Hydrocarbon-impacted groundwater, left in place or contained, <br /> could eventually percolate down and impact deeper water bearing zones. In addition, hydrocarbon- <br /> impacted groundwater may migrate around and under the barrier, which could impact off-site <br /> properties and receptors. <br /> 8.2 Hydraulic Control Line <br /> Potential impacts of the proposed hydraulic control line consist of hydrocarbon impacts to deeper <br /> groundwater and discharge of untreated groundwater to the storm drain or sanitary sewer. <br /> • Hydrocarbon impacted groundwater, left in place or contained, could eventually percolate down and <br /> impact deeper water bearing zones. Untreated groundwater could be discharged to the storm drain <br /> and enter nearby creeks and rivers or enter the sanitary sewer. This situation could occur if granular <br /> activated carbon was spent, which allowed hydrocarbon-impacted groundwater to pass through the <br /> treatment system and discharge. Depending on the discharge permit sampling requirements, <br /> untreated groundwater could be discharged over a period of 7 to 30 calendar days. <br /> 8.3 Combination of Groundwater Barrier and Hydraulic Control Line <br /> Potential impacts of the proposed combination groundwater barrier and hydraulic control line consist <br /> of hydrocarbon impacts to deeper groundwater and discharge of untreated groundwater to the storm <br /> drain or sanitary sewer. Hydrocarbon-impacted groundwater, left in place or contained, could <br /> eventually percolate down and impact deeper water bearing zones. In addition, hydrocarbon- <br /> impacted groundwater may migrate around and under the barrier, which could impact off-site <br /> properties and receptors. Untreated groundwater could be discharged to the storm drain and enter <br /> nearby creeks and rivers or enter the sanitary sewer. This situation could occur if the granular <br /> activated carbon was spent, which allowed hydrocarbon-impacted groundwater to pass through the <br /> treatment system and discharge. Depending on the discharge permit sampling requirements, <br /> untreated groundwater could be discharged over a period of 7 to 30 calendar days. <br /> 8.4 Groundwater oxygenation System <br /> Potential impact of the proposed groundwater oxygenation system consist of hydrocarbon impacts to <br /> deeper groundwater and off gassing of hydrocarbons in the vicinity of the site. Hydrocarbon- <br /> impacted groundwater, left in place, could eventually percolate down and impact deeper water <br /> bearing zones. As ambient air in injected into the saturated zone via the groundwater oxygenation <br /> points, hydrocarbon enriched gas could accumulate in the vadose zone and eventually pass to grade <br /> surface. Depending on the vapor concentrations, the off-gas could pose a hazard to terminal <br /> operations and off-site properties. <br /> I:\Chevron\1001621\REPO RTS\2003\2003FS\FS 2003 revD.doc <br />