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Phase I Environmental Site Assessment Update Report Neighborhood J,Mountain House,CA July 22,2022 Page 2 4. Condor considered the two active petroleum pipelines (a six-inch diameter Chevron/Texaco petroleum pipeline and a 12-inch diameter Kinder Morgan petroleum pipeline) paralleling Byron Road and the railroad tracks south of the Site a REC. 5. Condor considered the former burn locations of two homes a historic REC (HREC) and recommended the affected soil to be removed along with the debris. Changes to Environmental Databases The environmental database search provider (EDR) was the same provider used for the 2004 Phase I ESA, and the following changes to environmental databases follow. The Mountain House Water Treatment Plant (Mountain House CSD Water Treatment) are listed in the RCRA NonGen / NLR, CERS Haz Waste, CERS Tanks, CERS, and AST databases for hazardous chemical management and hazardous waste generator. This location does not appear to pose a risk to the Site based on lack of evidence of releases. The Chevron Mtn. House Sites#3,#2, and#1,relate to the Old Valley Pipeline. These locations are listed in the CPS-SLIC and CERS databases as having crude oil which affected the soil and groundwater. Remediation was completed and No Further Action was granted by the Regional Board on September 25, 2008 for sites#1 and#2, and on May 6, 2011 for site#3. The Old Valley Pipeline does not appear to pose a risk to the Site due to regulatory status. School site locations were listed in the DTSC Envirostor® database for the Proposed Questa Elementary School and the other school sites in Neighborhoods G and E. Condor performed all of the school site investigations at Mountain House and No Further Action was required by DTSC. None of the new listed locations appear to pose a risk to the Site. The EDR report is included in Attachment B. Changes to the Site and Adjoining Property Condor recently interviewed Mr. David Sargent who indicated that the entire Site and Neighborhoods I and K were graded in 2007 and 2008 by Independent Construction. During the grading activities, they removed the PG&E pipeline and there was no evidence of staining or odor associated with it. The Site and adjoining properties have remained vacant since then. The former burn locations were removed prior to grading activities. At the time of the Site reconnaissance, some earth moving activities were underway on the northwestern adjoining property,but no changes have occurred to the Site since 2008. Summary of Changes to RECs 1. Based on the results of the pesticide screening evaluation conducted by Condor, the former agricultural use of the Site no longer constitutes a REC. 2. Based on the remediation and case closures granted by the Regional Board, Condor no longer considers the Old Valley Pipeline a REC. 3. Based on removal of the PG&E pipeline and no evidence of staining or odor in 2008, Condor no longer considers this a REC. 4. The two active petroleum pipelines (a six-inch diameter Chevron/Texaco petroleum pipeline and a 12-inch diameter Kinder Morgan petroleum pipeline) paralleling Byron Road and the railroad tracks south of the Site still constitute a REC. Although no evidence of a current or past release associated with these pipelines has been found, there is a risk of future release that could pose a risk to the Site if the pipelines remain active and rupture. 5. Based on removal of the former burn locations of the structures, these no longer constitute a HREC. Zai CONDOR