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MOUNTAIN HOUSE PROPOSED ALTAMONT HEIGHTS TENTATIVE MAP 4. ,ENVIRONMENTAL C[ECKL[ST 4.7 HAZARDS SETTING The proposed Altamont Heights project.is part of Specific Plan III for the Mountain House Community. A historical review of.potential hazards in the Specific Plan III area is presented Jn.the SPII.IEIR(EDAW, 2005b): Environmental Data Resources, Inc.,performed a .computer-gcnerated database search of recorded hazardous materials use and storage and contaminated sites within a one-mile radius ofthe'Specific Plan III area. These databases contain records kept by federal, state, and local agencies responsible for permitting the use, transfer, storage, and disposal of hazardous materials and for recording incidents of contamination. The record search found two hazardous materials sites on Grant Line Road that are within a one-mile radius of the center of the proposed Altamont Heights project. These sites include an inactive underground storage tank and a small quantity generator(of hazardous materials). No action is required for either site (EDAW, 2005b, Figure 4.9-2 and Table 4.9-1). A Phase I Environmental Site Assessment has been conducted for the project site (Kleinfelder, 2005). The assessment found the following: • On properties with a history of agricultural use, such as the project site, underground "transite" (i.e., asbestos)pipe drains may exist. However, no "transite"pipes were observed during the assessment, and since the site was used for dry farming of oats and was never irrigated, underground drains probably do not exist at the site._ • On properties with a history of agricultural use, such as the project site, persistent pesticides may be present. Five soil samples were taken during the assessment, and no detectable organochlorine pesticides were detected. There were significant amounts of contaminants found at 20058 Grant Line Road, the residence on the west side of the project site, including 55-gallon drums, paint and oil containers, batteries,miscellaneous building materials and mechanical parts, debris and burn piles. However, no leaking, staining or stressed vegetation was observed. There is a septic tank and leach-field at the residence. This portion of the project site would be cleaned prior to construction of the proposed streets and residences. On December 4, 2003, the 18-inch Chevron crude oil pipeline that crosses the Specific Plan III area from northwest to southeast approximately 600 feet northeast of the center of the Altamont Heights project site was accidentally ruptured by farm equipment. Approximately 21,000 gallons of crude oil were released. The incident caused localized soil contamination, which is currently being assessed and remediated under Central Valley Regional Water Quality Control Board (RWQCB) Oversight. No contamination from this accident extended to the area of Specific Plan III (EDAW, 2005b). 4-35