Washington Administrative Code › Title 173 - Ecology, Department of (See also Titles 197, 317, 372, and 508) › Chapter 173-160 - Minimum standards for construction and maintenance of wells › Part TWO - GENERAL REQUIREMENTS FOR RESOURCE PROTECTION WELLCONSTRUCTION AND GEOTECHNICAL SOIL BORING › Section 173-160-450 - What are the well sealing requirements?

Current through Register Vol. 24-14, July 15, 2024
(1) All resource protection wells constructed
				shall have a continuous seal, which seals the annular space between the bore
				hole and the permanent casing. The seal shall be constructed to prevent
				interconnection of separate aquifers penetrated by the well, and shall provide
				casing stability. Except for environmental investigation wells, the seal shall
				have a minimum diameter of four inches larger than the nominal size of the
				permanent casing, and shall extend from land surface to the top of the filter
				pack. The filter pack shall be no less than one foot or greater than five feet
				above the screen interval. See Figure 7. Wells that are installed using direct
				push technology will follow the sealing guidelines of WAC
				173-160-451.
(2) After the permanent casing has been set
				in final position, the filter pack (optional) and sealing material shall be
				placed in the open bore hole annular space that must be a minimum of four
				inches greater in diameter than the nominal size of the permanent casing. After
				installing the filter pack (optional) a layer of bentonite shall be placed on
				top of the filter pack to maintain separation between the seal material and the
				screened interval. Insure that placement will not disturb the filter pack. The
				remaining annular space shall be filled to land surface in a continuous
				operation with bentonite, neat cement, or neat cement grout. If neat cement,
				neat cement grout or bentonite slurry is used as the sealant, it shall be
				installed with a tremie tube and pumped from the top of the bentonite plug
				(above the filter pack) to land surface. Use only potable water to hydrate the
				mixture.
(3) The completed annular
				seal shall fully surround the permanent casing, be evenly distributed, free of
				voids, and extend from the permanent casing to undisturbed or recompacted
				soil.
(4) All sealing materials
				used shall conform to one of the following minimum requirements:
(a)
Bentonite sealants:
(i) Bentonite used to prepare slurries for
				sealing or decommissioning shall be specifically designed for this purpose. All
				bentonite slurries shall be prepared and installed according to the
				manufacturer's instructions. Active solids content (bentonite) shall be twenty
				percent by weight or greater in all bentonite slurries. The active solids shall
				be checked by using the following formula:
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(ii)
				Unhydrated bentonite--pelletized, granulated, powder, or chip bentonite may be
				used in the construction of seals or in decommissioning of wells. The bentonite
				material shall be specifically designed for sealing or decommissioning and be
				within the industry tolerances for dry western sodium bentonite. Placement of
				bentonite shall conform to the manufacturer's specifications and result in a
				seal free of voids or bridges.
(iii) All bentonite used in any well shall be
				certified by NSF/ANSI approval standards for use in potable water supply wells,
				or equivalent standards as approved by the department. The product shall be
				clearly labeled as meeting these standards.