WORK PLANS - Laserfiche WebLink

Home Browse Search

this investigation,dissolved hydrocarbons were detected in all five new monitoring wells(WESTON, 1992). Subsequent quarterly groundwater monitoring results indicated that the highest concentrations of dissolved hydrocarbons were present in monitoring well MW-8,which is located on Market Street near USTs owned by the City of Stockton. ` Following the Phase II investigation,monitoring wells MW-2 and MW-3 went dry due to a drop in the regional groundwater table. Additional deeper wells(MW-2A and MW-3A)were installed in 1995, during the Phase III investigation. Monitoring well MW-3 was abandoned during this investigation. Soil samples were collected from the boreholes of the new monitoring wells. During the installation of monitoring well MW-2A, free product was observed in soil samples, and a sheen was observed in groundwater samples. Petroleum hydrocarbons were not detected in soil or groundwater samples collected from monitoring well MW-3A. A Phase IV investigation was conducted in August 1996 to collect additional soil contaminant concentration data in the vicinity of MW-2A and to collect upgradient groundwater contaminant data. As part ofthe planning of the Phase IV investigation,Capital Projects and the EHD agreed that one year of quarterly groundwater monitoring would be performed. It was also agreed that a CAP would be prepared following the completion ofone year ofquarterly groundwater monitoring(WESTON, 1996). The fourth quarter ofPhase IV groundwater sampling was completed in May 1997. The Phase IV investigation and year of groundwater sampling confirmed that residual contamination is present in monitoring well MW-2A and that groundwater contamination is not present south of the former USTs. 1.2 January 1998 Corrective Action Plan Summary The CAP was submitted to EHD in January 1998. The purpose ofthe CAP was to provide an assessment of the impacts and,through an evaluation ofpotential alternatives,select a proposed action that would adequatelyprotect human health,safety,and the environment and that would restore or protect current or potential beneficial uses ofwater. Capital Projects selected the Intrinsic Remediation with Monitoring alternative as the most cost effective and least disruptive alternative available for the site. Receptors were not identified and therefore,site specific risk-based cleanup levels were not developed(WESTON,1998). 1.3 Report Organization V Section 1.0 ofthis CAP review provides the introduction. Section 2.0 presents the physical characteristics ofthe site. Section 3.0 presents the nature and extent ofcontamination at the site. Section 4.0 identifies various technologies,screens them based on site-specific criteria,and identifies data gaps to fill prior to submitting the site for low risk closure consideration. Section 5.0 further develops and analyzes the alternatives presented in Section 4.0. Section 6.0 briefly compares the alternatives and presents the recommended remedial action. Section 7.0 presents the references. Appendix A presents the detailed cost estimates for each remedial alternative. 2