SITE INFORMATION AND CORRESPONDENCE

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Mr.M. Scott Mansholt—CEMC Second Quarter 2007 Groundwater Monitoring and Sampling Report July 24,2007 Vernalis Pump Station Page 2 of 5 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'. From 1902 to 1935, Standard Oil(predecessor of Chevron)operated the Vernalis Pump Station, which was the part of the former OVP system that transported heated heavy petroleum(crude oil) from San Joaquin Valley oil fields in Bakersfield to a refinery in Richmond, California. The OVP was located along the northeastern side of the site and parallel to the existing UPRR tracks and Highway 33. Site features included a boiler house, a pump house, a sump, an incinerator, a rubbish pit, cottages, and three bulk-storage tanks with secondary containment structures. These surface structures were located on the Arcos property. The property located immediately southeast of the Arcos property was a former Tidewater Associated Oil Company(TAOC; predecessor to Texaco and now Chevron)pump station(TAOC Ohm Pump Station). According to the 1995 Environmental Site Assessment,the former pump station was owned by Vernalis Enviropur-West, and was used for bulk storage of petroleum and oil products'. GROUNDWATER MONITORING AND SAMPLING MONITORING Groundwater monitoring and sampling began in 1998 and wells were monitored on an irregular basis until July 2005,when quarterly groundwater monitoring and sampling began. Second quarter 2007 monitoring activities were conducted on April 30 and May 1,2007,when depth to groundwater was measured in wells MW-1,MW-2,MW-3,MW-4,MW-6 and MW-7 using a hydrocarbon/water interface probe. The depth to groundwater was not measured at well MW-5 until May 8,2007, due to site access issues. Cumulative depth-to-groundwater measurements, groundwater elevations, and separate phase oil(SPO)thickness measurements are presented in Table 1. A map showing the May 2007 site potentiometric surface is presented on Figure 3. Field data sheets are included as Attachment A. A summary of the second quarter 2007 site monitoring results are presented as follows: • Site Wells in Program: MW-1,MW-2,MW-3,MW-4,MW-5,MW-6 and MW-7. Well MW-5 is flush mounted with the ground. The other six wells are above-ground, stovepipe-type wells. • Depth to Groundwater at Site: Ranged from 33.99 feet below top of casing(btoc) (MW-6)to 38.27 feet btoc (MW-1). Based on all depth-to-groundwater measurements collected to date from these wells,the average depth to groundwater at the site is 36.52 feet btoc. • Calculated Groundwater Elevation: Ranged from 68.11 feet(MW-1)to 71.29 feet (MW-3 and MW-5)above mean sea level(MSL). Based on all groundwater elevation measurements collected to date from these wells,the average groundwater elevation at the site is 71.01 feet above MSL. • Approximate Groundwater Flow Direction/Gradient: East at 0.001 feet per foot (ft/ft). Data from both the site and the adjacent US Can—Welty Road site were used in calculating the groundwater flow gradient. Wells that were found to contain SPO were not used in the groundwater flow-gradient calculations. 1. Geological Technics,Inc., 1995. Preliminary Environmental Site Assessment: Vernalis Property,35500 Welty Road, Vernalis, California. February.