ARCHIVED REPORTS_REMOVAL ACTION COMPLETION REPORT

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Draft Removal Action Completion Report Neighborhood C, Mountain House,CA Page 6 3.4.2 Equipment Decontamination To prevent unnecessary exposure and related transfer of contaminants, excavation equipment was decontaminated. Equipment was decontaminated in a designated decontamination area, the entombment trench. Excavation equipment was decontaminated by removing residual soil from excavation equipment in the Great Valley Parkway encapsulation area by the contractor when the equipment was removed from dieldrin operations or upon final equipment use. To the extent practicable, the contractor used best available practices to minimize fugitive soil once the excavation phase of the project was complete. Best available practices included using hand tools, shovels and brooms, to remove heavy soil, in conjunction with washing with pressurized water hoses. Confirmation samples were collected by directly inserting sampling jars into soil and no decontamination or equipment blanks were necessary. Discrete depth samples were collected to assist with definition of additional excavation depths. Stainless steel hand augers used for discrete depth sampling were decontaminated to control contaminants, assure the quality of samples collected, and/or to avoid cross contamination. Hand augers were decontaminated using the following procedures: • Non-phosphate detergent and water wash,using a brush to remove material if necessary • Water rinse • Initial deionized water rinse • Final deionized water rinse Decontamination rinse water was disposed of in the encapsulation trench. 3.5 WASTE SOIL ENCAPSULATION The encapsulation area dimensions were approximately 4,060 feet long, 27 to 35 feet wide, and 16 to 18 feet deep, yielding an approximate capacity range of 70,000 cubic yards (Figures 7 through 9, Appendix A). All waste soil generated from the excavation activities was encapsulated beneath Great Valley Parkway. The area of Great Valley Parkway that was used for encapsulation is beneath the paved southbound lanes and the landscaped median from 25 feet north of the pipeline easements near Grant Line Road to 1,200 feet north of Grant Line Road measuring 16 feet deep and 35 feet wide. The northern portion of the encapsulation area measured 16 to 18 feet deep and 27 feet wide and includes the southbound lanes (from top of curb to top of curb) and does not include the landscape median (Figure 7, Appendix A). Utility crossings were excavated after primary placement so that the utilities would not be surrounded by impacted waste soil. All impacted waste soil excavated for the utility crossings was placed in the southern portions of the entombment trench. In variance to the RAW and as an additional engineering control, an orange geotextile marker fabric was placed on top of the dieldrin encasement and at the utility crossings, marking the interface between dieldrin waste soil and clean soil. A minimum of one foot of non-contaminated soil was placed on top of the marker fabric and within the utility crossing trenches(Figure 8,Appendix A). 3.6 AIR AND METEOROLOGICAL MONITORING This section provides the air and meteorological monitoring strategy and methods that were used during the removal action activities. Since contaminants are attached to soil, dust generated during removal action activities was the primary concern of the air and meteorological monitoring plan, which was designed to ensure public and Site worker safety.Air monitoring was conducted during dieldrin-impacted