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100 Pine Street. 1 Oen Floor San Francisco. CA 94111 (415) 434.9400 • FAX (415) 434-1365 GEOMATRIX 19 March 1997 Project 3 76 1.01 Ms. Katie Hower Chevron Pipe Line Company P.O. Box 5059 San Ramon, California 94583-0959 Subject: Technical Approach to Site Evaluation and Decision-Making Old Valley Pipeline Sites - Central Valley Region Dear Ms. Hower: This document has been developed by Geomatrix Consultants, Inc. (Geomatrix), on behalf of Chevron Pipe Line Company (CPL) to provide a consistent approach for site evaluation and decision-making regarding petroleum releases attributed to the historical Wait-Mendota- Richmond (Old Valley) Pipeline within the Central Valley-Regional Water Quality Control Board's(RWQCB)jurisdiction(Figure 1). The purpose of this approach is to protect groundwater and human health, allow for property development of affected parcels, and make site management and site closure decisions per draft RWQCB "Low Risk Criteria" (RWQCB, 1996)or applicable updates. The value of conforming to a consistent approach for evaluating these sites was agreed to in a meeting among representatives of RWQCB, CPL, and Geomatrix on 10 October 1996. This approach makes use of technical lessons learned on several past Old Valley Pipeline sites, most notably the Dividend Property in Tracy. BACKGROUND The Old Valley Pipeline carried San Joaquin Valley crude oil north from the Kern River Oil Fields to Standard Oil Company's Richmond Refinery starting in approximately 1902. Sections of the pipeline south of Tracy were removed from service in the 1930s. Portions of the pipeline north of Tracy were used to transport Bunker C locomotive fuel oil from the refinery to railroad distribution areas from the 1920s to the 1950s. Due to the high viscosity of both types of petroleum, the line was heated and incorporated a series of pump stations to facilitate flow. The pipeline north of Tracy was removed from service in the early 1950s and most sections of the pipeline were removed from the ground in the 1970s. The crude oil/Bunker C oil carried by the pipeline consisted of predominantly middle- to high- boiling petroleum hydrocarbons. These constituents have low solubility in groundwater and, therefore, demonstrate limited environmental mobility. Furthermore,because of the age of the releases (minimum of 40 years old), the petroleum associated with the Old Valley Pipeline is typically highly weathered and has lost the majority of the relatively low levels of volatile and water soluble constituents (e.g., benzene, toluene, ethylbenzene, and xylenes [BTEX] and low molecular weight polynuclear aromatics [PNAs]) present in the original oil. Weathering has likely occurred as a result of a combination of evaporation, biodegradation, and water solubilization. At many sites in the Bay Area and Central Valley with shallow groundwater tables, the vertical Geomatrix Consultants, Inc. Engineers.Geologists.and Environmental Scientists