WAC 173-160-460   What is the decommissioning process for resource protection wells?  (1) Resource protection wells and geotech soil borings that were not constructed in accordance with these regulations, or for which a drilling report required under this section is missing, shall be decommissioned 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 cement grout, neat cement, or bentonite slurry; or

     (b) Withdraw the casing and fill the bore hole with cement grout, neat cement, or bentonite as the casing is being withdrawn.

     (2) 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, cement grout, or neat cement.

     (3) Wells with an inside casing diameter less than one inch shall be decommissioned by pressure grouting the entire casing length.

     (4) Vibrating wire piezometers installed per WAC 173-160-450 are exempt from these decommissioning procedures.

     (5) Direct push wells shall be decommissioned in accordance with this section.

     (6) Geotechnical soil borings, or boring, shall be decommissioned by sealing from bottom to land surface with bentonite, bentonite slurry, 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 cement, neat cement grout, or neat cement is used to seal below the static 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 grout, the discharge end of the tremie tube shall be submerged in the 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.



[Statutory Authority: Chapter 18.104 RCW. 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.]