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SOIL AND GROUNDWATER INVESTIGATION REPORT VERNALIS PUMP STATION VERNALIS, CALIFORNIA 1. INTRODUCTION At the request of Chevron Environmental Management Company(CEMC), Science Applications International Corporation(SAIC)performed this investigation of subsurface conditions beneath the former Vernalis Pump Station(the site). Since past pipeline leaks may impact future site uses, CEMC wants to assess the nature and extent of the leaks. SAIC performed this investigation in accordance with the Work Plan for Additional Soil Borings and Installation of Monitoring Wells(work plan) (SAIC, 2004),which was approved on July 9,2004 by the California Regional Water Quality Control Board (RWQCB). Further,this investigation generally conformed to the RWQCB-approved Technical Approach to Site Evaluation and Decision-Making, Historical Pipeline Portfolio, Central Valley Region, dated February 2005 (referred to as the CTA). The CTA is the principal document that serves to guide decision making during soil and groundwater investigations. Although this investigation was voluntarily initiated by CEMC,it is to some extent regulated by the RWQCB,which reviews and provides comments on work plans,reports, and schedules concerning CEMC's Historical Pipeline Portfolio projects. This investigation follows several past site characterizations that documented soil and groundwater affected by the following constituents of concern: total petroleum hydrocarbons(TPH);benzene,toluene, ethylbenzene, and total xylenes(BTEX); and polynuclear aromatic hydrocarbons (PAHs). The purpose of this investigation is to evaluate the extent of soil and groundwater impacted by the constituents of concern and,based on the investigation results,recommend future activities leading to a letter of No Further Action from the RWQCB. 2. BACKGROUND 2.1 LOCATION AND SITE DESCRIPTION The site is located at 35500 Welty Road,Vernalis, San Joaquin and Stanislaus counties, California (Figure 1). The site consists of two properties: the Bellini property(formerly known as the Roberts property)and the Arcos property. The Bellini property is located on the northern part of the site, and the Arcos property is located on the southern part of the site (Figure 2). The Bellini property is a triangular-shaped, 5.73-acre vacant lot. The Arcos property is irregularly shaped, is currently used as a storage facility for equipment and materials, and is occupied by a residence and an on-site office. The site is located in a rural and light-industrial area and is bordered by Welty Road to the west,Highway 33 and Union Pacific Rail Road(UPRR)tracks to the northwest, light- industrial facilities to the southeast, and agricultural areas to the south. Currently,Kinder Morgan Energy Partners,L. P. (KM)maintains a high-pressure,petroleum-product pipeline that reportedly transports gasoline,jet fuel,and diesel. The KM pipeline is located off site along the northeastern site boundary within the UPRR right of way(ROW). According to a previous environmental site assessment,the KM pipeline was installed approximately 4 to 5 feet below ground surface(bgs)during 1985,was constructed of 0.25 inch-thick wrapped steel, and was under the control of a subsidiary of Southern Pacific Pipeline Company(Geological Technics, 1995). From 1902 to 1935, Standard Oil(predecessor to Chevron) operated the Vernalis Pump Station,which was part of the former Old Valley Pipeline (OVP)system that transported heated crude oil from San 1 From Science to Solutions-