SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

with sealing materials. If the hole is deeper than 30 feet, sealing materials must be placed under pressure and tremied to prevent separation of the grout components. In addition, the San Joaquin County Environmental Health Department(SJCEHD)requires that sealing materials for all holes deeper than 10 feet shall be triemied. Sealing materials must be placed continuously from bottom to top unless conditions in the well dictate that seal operations be conducted in a staged manner. It must be verified that the volume of sealant equals or exceeds the volume of the casing to be filled and sealed. Suitable sealing materials include neat cement, sand-cement, and bentonite (DWR, 1991). 3.5.6 In order to minimize the possibility of vertical fluid migration and annular channeling between aquifers after abandonment,the casing will be perforated and pressure sealed. A mill knife or hydraulic device will be lowered into the hole to perforate (rip) the casing at selected intervals. An average of four perforations per linear foot of casing will be cut at 90 degree intervals around the casing circumference and will be at least 1/4-inch wide and 2 inches long. The wells will then be abandoned by continually backfilling the casing with grout. 3.5.7 The consistency of the grout should be sufficient to flow through the screen and into the filter pack. The grout will be tremied from the bottom of each well by continuously withdrawing the tremie pipe as the grout is emplaced. The bottom of the tremie pipe will remain below the calculated grout level to prevent bridging of the grout. 3.5.8 Displaced groundwater generated by abandonment activities shall be contained in D.O.T. approved drums and disposed of by the contractor, in accordance with paragraph 2.8 CONTAINERIZATION OF DEVELOPMENT WATER, AND DRILL CUTTINGS. 3.5.9 After the casing has been backfilled with grout,the protective casing will be removed and the well casing cut off at least 2 feet below grade and removed. Additional grout will continue to be added to the casing if any settlement occurs. Approximately 24 hours after the backfilling is completed,the grout will be topped off and any surface depressions filled with soil material and slightly mounded to allow for settlement. 3.5.10 Following the abandonment, a Well Completion Report(Form DWR 188) specifying the well destruction must be submitted to the State of California DWR. The Well Completion Report must be signed by a representative of the well driller contracted to perform the abandonment. 3.6 WET T. ACCEPTANCE It is the responsibility of the Contractor to properly construct,install, and develop all monitoring wells according to the requirements of this scope of work so that they are suitable for the intended purpose. If the Contractor installs wells that are not functional or not in accordance with these specifications, the COE representative or the base IEC will disapprove the well and direct the Contractor to repair or replace it, and to abandon the disapproved well in accordance with this specification. 02671-0011