Laserfiche WebLink
ARCO -4 - J April 2012 <br /> UPDATED, April 2009, the San Joaquin County LOP has directed the Responsible Party to <br /> conduct ozone injection. The Fund concurs and will review this site next year to track progress. <br /> UPDATED, April 2010, the Fund recommends that the San Joaquin County LOP transfer <br /> regulatory responsibility of this site to the Regional Board for enforcement. The approved <br /> remediation should begin without delay. The Fund will review this site next year to track <br /> progress. <br /> UPDATED, April 2011, current groundwater trends suggest Water Quality Objectives will be <br /> achieved without active remediation. Monitoring well MW-1 screened in the source area has <br /> consistently had elevated concentrations of residual fuel oxygenates in groundwater. However, <br /> after 10 years of monitoring, the groundwater plume is largely limited to the source area and <br /> groundwater concentrations are abating rapidly. The Fund recommends that the San Joaquin <br /> County LOP review this site for closure. <br /> UPDATED, April 2012, source area monitoring well MW-1 has historically had elevated <br /> concentrations of residual hydrocarbons in groundwater. However, after 12 years of monitoring, <br /> the groundwater plume is shrinking in size and concentration. Analytical data indicate that <br /> WQOs have been achieved in down gradient wells MW-4 and MW-7. Groundwater within the <br /> source area will likely remain above WQOs for years. The affected shallow groundwater is not <br /> used as a source of water supply nor is it likely to be used as a source of water supply in the <br /> foreseeable future. Water users in the vicinity of the site rely on the City of Stockton. Based on <br /> facts in the record and hydrologic and geologic conditions at the site, the limited residual <br /> petroleum hydrocarbons that remain in soil and groundwater pose little risk to human health, <br /> safety and the environment. The Fund recommends that the San Joaquin County LOP review <br /> this site for closure. <br /> KA Larson, P.G. Date Robert Trommer, C.H.G. Date <br /> Engineering Geologist Senior Engineering Geologist <br /> Technical Review Unit Chief, Technical Review Unit <br /> (916) 341-5663 (916) 341-5684 <br />