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No Further Action Required Request Report ' Mountain House Development Site#6 September 15,2011 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. ' I. Demonstration that the plume is stable with either an overall annual decrease in size or an annual decrease in contaminant concentration trend. There are two areas of affected soil and groundwater, measuring approximately 250 by 175 feet and 770 by 320 feet, respectively. 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 former OVP and TAOC pipelines were decommissioned at least 40 years ' ago. Therefore, the residual hydrocarbons at the Site have been present at least 40 years, and the extent of hydrocarbons in the subsurface is certainly decreasing. No monitoring-well network was installed at the Site 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 the Site investigations due to natural attenuation of the residual hydrocarbons. Affected groundwater is anticipated to remain localized as it slowly and naturally attenuates to 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. 1 SAIC did not perform calculations or modeling to predict when WQOs would be achieved. Meaningful modeling that predicts when the WQOs would be achieved cannot be performed because initial concentrations are unknown and there are no monitoring wells to monitor concentration trends. 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 lite ' timeframe projected to meet WQOs. Institutional controls may be needed to prevent such use if this period is not sufficiently short. ' SAIC performed a search of California Department of Water Resources (DWR) files in 2008, to identify existing water-supply wells within a 2,000-foot radius of the Site. The search covered Township 2 South, Range 4 East, Sections 2, 3, 10, and 11. SAIC identified seven domestic water-supply wells within the search area. Five of the wells are located northwest and cross gradient from the Site. The remaining two wells are located southeast and cross gradient from the Site. ' Installation of additional water-supply wells is unlikely within or in the immediate vicinity of the affected shallow groundwater given its poor quality and likely low yield. The TDS SAIC