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U) RaMWorkPl Plan to Destroy Existing Monitoring and Remedial Wells 76 Station No.5886 April 18,2011 f I fieldwork. The HASP will be reviewed by the field staff and contractors before beginning field operations at the site. • Permitting. Well destruction permits will be obtained from the SJCEHD prior to the commencement of drilling activities. Additionally, an encroachment permit will be.. obtained from the City of Stockton to facilitate the destruction of off-site monitoring wells ' MW-8S/I/D through MW-10S/I/D. • UndergroundUtility Location and Clearance. In advance of field activities, Stantec; will mark the location of the wells in accordance with the Underground Service Alert (USA) guidelines, and notify USA of upcoming subsurface activities so that existing,; underground utilities in the area of proposed work can be located and avoided. Stantec will contact a private utility locator to confirm the locations of underground utilities in the vicinity of the well location. • Well Destruction—Overdrilling. Select monitoring and remedial wells at the site (see Table 1 and Figure 2) will be over-drilled using hollow-stem auger drilling equipment. Upon completion of drilling, the boreholes will be backfilled with cement grout emplaced via tremmie pipe, the well vaults will be removed, and the surface pavement repaired to match the surrounding pavement. Field procedures are included in Attachment 2. i • Well Destruction — Pressure Grouting. Select monitoring and remedial wells at the site (see Table 1 and Figure 2) will be destroyed through the emplacement of pressurized cement grout. Cement grout will be emplaced in the bottom of each well , casing via tremmie pipe. Once cement extends to the top of the well casing, an air pressure of 40 PSI will be applied to the well casing. Additional cement will be poured into the top of the well casing as necessary. Each well will be deemed successfully destroyed when a pressure of 40 PSI can be maintained for 5 minutes with the grout dropping less than one foot. Upon completion of pressure grouting, the well vaults will be removed and the surface pavement repaired to match the surrounding pavement. Additionally, the top five feet of well casing will be removed from all wells being pressure grouted. Field procedures are included in Attachment 2. Well Destruction — UST Cavity Well. Because the UST cavity well was installed in the backfill of the current UST tank pit, Stantec has determined that destroying the well by over,drilling presents an unacceptable risk to the integrity of the USTs and associated product piping. Additionally, while the precise construction details of the UST cavity well could not be located, it is likely that at least some of the well screen is set within the UST tank pit backfill (assumed to be pea gravel). Accordingly, destroying the well utilizing pressurized cement grout would be problematic. Stantec proposes destroying the UST cavity well by emplacing a bentonite grout within the well casing. Once the well casing is fully backfilled, the well vault will be removed and the surface will be repaired to match the surrounding pavement. • Waste Profiling. Composite soil samples will be collected and sent under chain-of- custody procedures to a California State-certified laboratory. The soil samples will be analyzed for TPHg, BTEX, and MTBE by EPA Method 8260 and for total lead by EPA Method 6010. The analytical data will be utilized for waste profiling purposes only. • Soil and Water Disposal. Soil cuttings generated during drilling operations will be stored in a steel roll-off bin or in Department of Transportation (DOT)-approved." 4 ,