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i No Further Action Required Request Report Tracy Byron Road-Tracy,California December 1,2011 3. TRI-REGIONAL RECOMMENDATIONS FOR A NO FURTHER ACTION REQUIRED REQUEST REPORT Section 3.1 provides information outlined in section 6.5 of the Tri-Regional Recommendations to support this request for closure at this low-risk site. Section 3.2 supports a decision by the Central Valley RWQCB to issue an NFAR letter with documentation outlined in section 6.6 of the Tri-Regional Recommendations. A completed Checklist of Required Data for No Further Action Requests is provided in Table 1. 3.1 NO FURTHER ACTION REQUEST FOR CASES EXCEEDING WATER QUALITY OBJECTIVES A narrative response follows to address each numbered item in section 6.5 of the Tri-Regional Recommendations. 1. Demonstrate that the plume is stable with either an overall annual decrease it: size or an annual decrease in contaminant concentration trend The affected areas at the Site encompass approximately 27 acres. Areas 1, 2, and 3 measure approximately 200 feet by 1,400 feet,375 feet by 2,000 feet, and 200 feet by 650 feet, I respectively. The residual weathered crude-oil hydrocarbons in the subsurface are not very mobile. Crude oil is composed of long hydrocarbon chain lengths, and is therefore slow to degrade. The sources of hydrocarbon-affected soil and groundwater at the Site,the former OVP and TAOC pipelines, were decommissioned over 30 years ago. Therefore, residual hydrocarbons have been present for at least that length of time and the extent of hydrocarbons in the subsurface is certainly decreasing. No monitoring-well network related to the former OVP and TAOC pipelines was installed to track plume stability or concentration trends. Significant changes in groundwater plume size or COPC concentrations would not be expected on a quarterly, semi-annual, or even an annual basis. Plume size and current concentrations of the COPCs at the Site are believed to be less than levels recorded during prior investigations due to natural attenuation of the residual hydrocarbons. Affected groundwater is anticipated to remain localized as it slowly and naturally attenuates to TPH concentrations less than applicable WQOs. 2. Calculations or modeling results,including monitoring verification of model conclusions, which show when WQOs are predicted to be achieved I SAIC did not perform calculations or modeling to predict when WQOs would be achieved. Meaningful modeling that predicts when the WQOs would be obtained cannot be performed because initial concentrations are unknown. Residual weathered crude oil at the Site is relatively immobile. Natural attenuation will continue to remove hydrocarbons from the subsurface; however,natural attenuation will occur at a relatively slow rate. As a result, concentrations of the COPCs in groundwater are expected to be stable or declining. Current or future uses of the affected groundwater are not anticipated,as described in the response to Item 3. 3. Verification that there are no current or anticipated uses of the impaired water within the timeframe projected to meet WQOs. Institutional controls may be needed to prevent such use if this period is not sufficiently short In cooperation with the RWQCB, SAIC sampled groundwater from 12 water-supply wells in October 2003. The wells were located at residences and businesses along the West Byron Road 4 , SAIC