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t • 2 0 *J V 91 This work plan proposes 1) backfilling of the excavations and 2) disposition of the pipelines associated with the former USTs. 3.1 Backfilling of the Excavations Based on the results including non -detect for TPHg and TPHd levels significantly below 1,000 mg/kg, we propose no further soil removal in the tank excavation and no deeper excavation in the pipe trenches. Debris greater than three inches in diameter will be removed from the soil stockpiles and disposed of as debris (non -hazardous). The excavated soil will then be used to backfill the excavation in 12" lifts and clean fill will be imported to bring the excavation to match ground level. The intent for this portion of the facility is to asphalt the area in the future for use as employee parking, which will provide a much more impervious cover to prevent stormwater infiltration in the future. Concrete and/or brick debris that were removed from the excavation were staged onsite separate from the excavated soil. This debris will be removed as non -hazardous waste or recycled offsite. RION-2 MM MTM_ Two sets of pipelines associated with the former USTs have been identified at the site (see Figure 3). The first set in the northern of the two trenches consists of two three- inch diameter pipelines, one 11/2 -inch pipeline, and a 3/4" -inch pipeline. Through utility survey, placing a camera in the larger diameter pipes, and physical pot -holing along the pipelines, the location of these pipelines associated with the USTs has been identified up to where they enter the foundation of the building. These three larger pipelines run together straight from the former UST location approximately 45 feet, then turn south and head approximately 25 feet into the building. Pot -holes were excavated at approximately 22 feet west of the end of the excavation at the curb line and a break in the pipelines approximately 20 feet further west, at the 90 degree turn where the pipelines head south, and at the face of the building where these pipelines and several other pipelines not associated with the USTs enter the building. The 11/2 -inch line was extracted from the ground in two locations: at the end of the trench excavation near the curb line and at the 90 degree turn where the pipelines turn south toward the building. This piping will be cut and disposed of as hazardous waste. The 3/4 -inch line was observed to be deteriorated with advanced corrosion. Pieces were extracted from the curb line and farther west. The two 3 -inch lines were discovered to be broken or cut previously approximately 20 feet from the curb line, forming a "break" in the lines. These two lines will be cut at the building foundation. These two lines will be excavated and removed entirely from the building foundation to the open trench. CE Project No. 11 R-120 Work Plan — Cal Water Stockton