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Soil &Groundwater Excavation Work Plan Advanced Environmental Concepts, Inc. L 4.0 WORK PLAN The following sections describe the methods and procedures to be used for implementing the scope of services. V 4.1 Soil Profile r,.. The near surface sediments encountered in the assessment borings conducted at the site are very similar across the geographical area. The dominant grain sizes are in the silty clay and silty sand range, with one or the other predominant depending on the specific energy level present during sedimentation at that time and place in the depositional cycle. Generally, clays are deposited in quiet, low energy areas,with progressively faster and higher energy stream flows depositing silts, sands, and then gravels. ,.., Most of the sediments at the sites are clayey sift and silty sand,comprising an estimated eighty percent of the soil type encountered through the average boring depth of 15-feet. Of the remaining fraction, about ten percent is made up of sand particles, usually in discrete beds. V 4.2 Estimated Excavation Limits Excavation of the former gasoline emplacement will have surface dimensions of 70'x 45'x 14' and centered over the former UST locations. Excavation of the former diesel emplacement will have surface dimensions of 10'x 10'x 12'. It is estimated that from grade level to 4 feet BGl_the soil will be "clean"and will be stockpiled separately from the contaminated soil. Contaminated soil is estimated between 5 feet and 13 feet BGL(Appendix A,Figure 2). The excavation will also include removal of the water bearing zone and will continue to the perching silt/clay layer that has continually tested clean. V 4.3 Excavation Methods ,.., A track-mounted excavator will be used to remove the hydrocarbon impacted soil to the appropriate depth at the site. The soil will be transported by truck, or loader, to the central treatment pad for treatment by landfarming and microbial degradation. All excavated soil will be field screened during the excavation work. Field screening will be accomplished with a Photoionization detector(PID) equipped with a 10.6 eV lamp to separate clean from gasoline impacted soil. The clean soil,indicating less than 10 ppm at a distance of 3-inches from the PID,will be stockpiled separately and adjacent to the excavation for later use as backfill. 4.4 Sampling Methods Upon complete excavation of the gasoline impacted soil at the former UST emplacements, soil sampling will be conducted to confirm satisfactory remediation. The excavator will retrieve representative samples of native soil from approximately every 100 square feet of exposed sidewall and from the floor of the excavation. V V Project: AEC 97V--1805 7 .ENVIRONMENTAL CONCEPTS WITH DESIGN IN MIND. .+ 4400 ASHE ROAD.0206 BAKERSFIELD.CA 93313 8051831-1646 . FAX 8051831-1771