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N February 10, 2014 Page 3 of 4 Reference: Well Destruction Work. Plan ARCO No. 2130 ,y MW-6 was installed in 1992 and is now located immediately adjacent to an underground SY`1 ) � •� electrical line/box in the right-of-way. This utility service location had to be installed post-welly � ' installation and cannot be locked out or tagged out. There are also utility and overhead signage �. limitations. � ' k03 � Well construction details and the proposed well destruction method for each well are included in Table i. Review of as-builtsand a private ut1 was conducted in preparation of this Work Plan. The findings of these efforts are included o Figure t. 1 y 2 i Prior to pressure-grouting activities, the well casing will be inspected for obstructions; if obstructions are found, they will be removed prior to grouting. +� gl'" 11h C �- The 19 wells recommended for pressure-grouting above will be pressure grouted with neat cement using a 4'u f U a 1. tremie pipe system forming a mushroom grout cap/surface seal. ` If groundwater is expelled during the grouting process, it will be properly contained, characterized, and disposed of After completing the grouting activities, the well borehole around each well will be air-knifed to approximately three feet bgs - and each well casing will be cut at approximately three ft below ground surface (bgs). Given the risks associated with the subsurface structures at MW-6, AS-a, AS-3, VW-3, VW-6, and VW-u, Stantec k recommends air knifing to approximately one ft bgs, and each well casing will be cut at approximately one > eA ft bgs. The borehole locations will be backfilled and resurfaced with appropriate materials to match the uI it existing grade. a- r +fei [�Vtr0 , i , . ret` IJV a7rovl ? A total of 18 wells will be destroyed by over-drilling. Each well borehole will be air-knifed to approximately six ft 6 inches bgs to investigate that no underground facilities exist within the area of SSc Y, u drilling. Each well will be over-drilled using a drill rig equipped with a hollow stem auger (auger to be 1 f► u F eight or ten inch diameter depending on the borehole diameter) to remove material within the original borehole including the well casing, filter pack, and annular seal. The borehole will then be grouted with neat cement using a tremie pipe system forming a grout cap/surface seal from the bottom of the borehole oto one ft bgs. If groundwater is expelled during the grouting process, it will be properly contained, characterized, and disposed. The borehole locations will be backfilled and resurfaced with appropriate materials to match the existing grade. I Waste Management All investigation derived waste, including soil and groundwater (if present) from the well and soil vapor probe destruction activities will be stored on-site in Department of Transportation-approved 55-gallon drums pending proper disposal. All waste will be transported and disposed of at an appropriate State- certified disposal facility. — NezW #*49 n 1 -1( f ( J Limitations 4 This report was prepared in accordance with the scope of work outlined in Stantec's contract and with generally accepted professional engineering and environmental consulting practices existing at the time i this report was prepared and applicable to the location of the Site. It was prepared for the exclusive use of ARC for the express purpose stated above. Any re-use of this report for a different purpose or by others i not identified above shall be at the user's sole risk without IiabIlity to Stantec. To the extent that this Jy Design with community in mind W