Section 173-160-460 - What is the decommissioning process for resource protection wells?(1) For resource protection wells and geotechnical soil borings that were not constructed in accordance with these regulations, or for which a drilling report required under this section is missing, remove all debris, accumulated sediment, equipment and obstructions from the well casing, except well screens and packers, and decommission in one of the following ways: (a) Perforate the casing from the bottom to land surface and pressure grout the casing. (i) Perforations shall be at least four equidistant cuts per row, and one row per foot. Each cut shall be at least one and one-half inches long.(ii) Apply enough pressure to force the sealing material through the perforations, filling any voids on the outside of the casing.(iii) The remainder of the casing shall be filled with neat cement grout, neat cement, or bentonite slurry; or(b) Withdraw the casing and fill the bore hole with neat cement grout, neat cement, bentonite or bentonite slurry as the casing is being withdrawn.(2) For resource protection wells and geotechnical soil borings that were constructed in accordance with these regulations, remove all debris, accumulated sediment, equipment and obstructions from the well casing, except well screens and packers and then decommission in one of the following ways:(a) Wells with an inside casing diameter equal to or greater than one inch and constructed in accordance with these regulations as verified through a field examination and review of the drilling report shall be decommissioned by filling the casing from bottom to land surface with bentonite, bentonite slurry, neat cement grout, or neat cement.(b) Wells with an inside casing diameter less than one inch shall be decommissioned by pressure grouting the entire casing length with bentonite slurry, neat cement grout, or neat cement.(c) Vibrating wire piezometers installed to meet or exceed the sealing requirements of WAC 173-160-450, 173-160-457, and 173-160-458 are exempt from the decommissioning procedures and decommissioning reporting requirements provided here.(d) Direct push wells shall be decommissioned in accordance with this section.(e) Geotechnical soil borings, or boring, shall be decommissioned by sealing from bottom to land surface with bentonite, bentonite slurry, neat cement grout, or neat cement. Sealing material placed below the static water level shall be piped directly to the point of application or placed by means of a dump bailer or pumped through a tremie tube. If bentonite slurry, neat cement grout or neat cement is used to seal below the water level in the well, the material shall be placed from the bottom up by methods that avoid segregation or dilution of the material. When used to place bentonite slurry, neat cement or neat cement grout, the discharge end of the tremie tube shall be submerged in the bentonite slurry, neat cement or neat cement grout to avoid breaking the seal while filling the annular space. Provided the material does not dilute or segregate and the resulting seal is free of voids, sealing material may be hand poured above the static water level.Wash. Admin. Code § 173-160-460
Statutory Authority: Chapter 18.104 RCW. 09-01-125 (Order 08-10), § 173-160-460, filed 12/19/08, effective 1/19/09; 06-23-121 (Order 06-08), § 173-160-460, filed 11/21/06, effective 12/22/06; 98-18-104 (Order 98-17), § 173-160-460, filed 9/2/98, effective 10/3/98. Statutory Authority: Chapter 18.104 RCW and RCW 43.21A.080. 98-08-032 (Order 97-08), § 173-160-460, filed 3/23/98, effective 4/23/98.