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California, Water Well Standards Bulletin 74 (Bulletin 74), as modified herein, as shown on the plans, described in these special provisions, and directed by the Engineer. The fill and sealing materials for destruction shall be as specified in Bulletin 74 except as modified herein. Native soils are not acceptable as fill materials. impervious material may be substituted for fill material. All well casings shall be perforated as required for gravel packed wells. The existing wells shall be filled and sealed to prevent the interchange of water between aquifers in accordance with Figure 9C for Urban Areas (Bulletin 74). Sand or other suitable inorganic material may be placed opposite non-producing formations where impervious material is not required. To prevent the vertical movement of water from the producing formations, impervious material shall be placed opposite confining formations above and below the producing formation for a distance of 10 feet or more. It is assumed the producing formations exist opposite the screened intervals in the existing wells. See the attached Visual Well frog for the Lewis Manor Well. The City does not have any information for the Ballpark and Corporation Yard Wells. The Contractor shall investigate the existing condition of the Ballpark and Corporation Yard wells to determine their construction and condition before destroying them in accordance with the requirements of Bulletin No. 74. Placing of Seals: Impervious seals shall be placed using the Pressure-Grouting Method described in Appendix B of Bulletin 74. The well casing between the well and the face of the bore hole shall be thoroughly perforated, ripped, or otherwise disintegrated as the necessary first step. The calculated amount of impervious material required to fill the well interval (not less than 10 feet) plus the volume of the empty hole shall be placed within the space to be sealed, running the material through a special cementing packer manufactured for this purpose and installed immediately above the perforated or ripped zone. +•� The seal material shall be injected at a pressure calculated to be at least 50 pounds per square inch greater than the normal hydrostatic pressure within the well at the point of injection. The pressure shall be maintained until the seal has set. The set time shall be �. as defined in Bulletin 74. Well discharge piping will be valved off by the City upon the request of the Contractor, �.. prior to the start of the Work. All piping with the exception of well discharge piping to the existing water distribution system shall be removed to 12 inches below grade, and the ends of the remaining piping shall be plugged with concrete at least 1-foot thick and abandoned in place. The abandoned pipe shall be isolated from the water main at the shut off valve. A minimum of 2 feet shall be provided between the abandoned pipe and shut off valve. Plug all abandoned piping with 1-foot-thick concrete plugs. The shut off �.. valve shall be sealed off with a blind flange provided with a thrust restraint and encapsulated with a protective coating to inhibit corrosion. Take care to avoid contaminating the portions of the well discharge line to remain in service. Disinfect them in accordance with AWWA C651, Section 9. Division III-34