SITE INFORMATION AND CORRESPONDENCE

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No Further Action Required Request Report Mountain House Development Site#6 September 15,2011 The analytical results indicated that no COPCs were detected above laboratory reporting limits in I either well. 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 I concentrations in groundwater at the Site range from 2,190 to 2,560 mg/L, which exceed numerous State of California and federal TDS standards for drinking water as well as agricultural-use criteria. Any new water supply well would have a sanitary seal at least 50feet in depth, as required by California Well Standards, Bulletin 74-90(DWR, 1991). Therefore, it is unlikely that a new water-supply well would be installed at the Site to a depth likely to be impacted by the shallow affected groundwater. Use of the shallow affected groundwater is not anticipated at the Site. There is no surface water within the area of affected soil or groundwater. No other potential ecological, human, or environmental sensitive receptors are known. 4. Provide a map showing the location of all water supply wells used for municipal, domestic, agricultural, industrial and other uses within 2,000 feet of the site. Provide well details and distances in a table. A site vicinity map with the location of the water-supply wells identified in the DWR file search is shown on Figure 1. Well details are provided in Table 2. ' S. Provide scaled site maps of the area impacted showing locations of former and existing tank systems, excavation and sample locations, boring and monitoring well locations, groundwater elevation contours, subsurface utilities, buildings, streets, and any nearby 1 surface waters. The locations of current structures, former pipelines, and sampling locations are indicated on Figure 2. Two areas of affected soil and groundwater, measuring approximately 250 by 175 feet ' and 770 by 320 feet, respectively, have been delineated. The extent of affected soil and groundwater is indicated on Figure 3. Monitoring wells were not installed at the Site; therefore, no groundwater elevation contours were generated. 6. Provide boring logs and cross-sections to show site lithology. ' Boring logs from the SAIC site investigations are provided as components of Appendices A.1, A.5, and A.7. Cross sections were not generated as part of any of the investigations. 7. Report the volume of excavated soil disposed off-site, or remaining on site. Soil excavation has not been conducted with the exception of minor amounts of soil removed during boring activities. No excavated soil remains at the Site. 8. Describe the fate of any remaining monitoring and remediation wells (destroyed, ownership transferred, or to remain in use). No monitoring wells or remediation wells were installed at the Site. 9. Provide tabulated results of all groundwater elevations and depths to water. During the 2008 and 2010 site investigations, SAIC measured the depth to static groundwater between approximately 4.5 and 10.2 feet bgs. Surveying the surface elevations of borings was ' 8 SAIE 1