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3330 Data Drive Delta Suite 100 Rancho Cordova.CA 95670 ironmental 9161"env916/6038-2485 Consultants,Inc. FAX: 9161638-8385 October 5, 1994 Mr. Kenneth Earnest Ultramar Inc. 525 West Third Street Hanford, California 93230 Subject: Work Plan for Monitoring Well Destruction Beacon Station No. 696 2448 West Kettleman Lane Lodi, California Delta Project No. D093-916 Dear Mr. Earnest: Delta Environmental Consultants, Inc. (Delta), has been authorized by Ultramar Inc. (Ultramar) to destroy two ground water monitoring wells at Beacon Station No. 696, located at 2448 West Kettleman Lane, Lodi, San Joaquin County, California. The monitoring wells are located in an area . where a new station building is to be constructed_ The location of the site is shown in Figure 1 and a site map is included as Figure 2. Project Background Prior to acquisition of the site by Ultramar in July 1990, the site was owned and operated by Conoco, Inc. The presence of petroleum hydrocarbons in soil and ground water beneath the site was detected prior to 1985. Since that time, numerous investigations have been conducted at the site. There have been 36 ground water monitoring or soil vapor extraction wells installed at the site and on adjacent properties. A total of 19 of these wells and a domestic water supply well have been previously destroyed. Three single-walled underground fuel storage tanks were removed from the site in March 1989, and were replaced by three double-walled tanks. Remedial activities have included the installation of a soil vapor extraction system, which began operation in December 1989 and was turned off in April 1994. Scope of Work The proposed work includes destruction of monitoring wells MW-20 and MW-25. Previous reports indicate that monitoring well MW-20 is a 4-inch diameter well with a total depth of 69 feet and a screened interval between 59 and 69 feet. Monitoring well MW-25 is a 6-inch diameter well with - -, a total depth 53 feet, the screened interval is not known. Ground water at the site is typically present at depths of 50 to 58 feet below grade. The wells are to be destroyed by pressure grouting with a neat cement/bentonite slurry. The grout will be emplaced from the bottom up by pumping through a tremie pipe. After grouting each well, an airtight slip cap will be placed on the wellhead and the casing will be pressurized to approximately 10 to 15 pounds per square inch by injecting air through a valve in the cap. Grout will subsequently be added to till each well to within approximately 3 feet of the ground surface. Providing a Competitive Edge