(1) Decommissioning standards for all UIC wells:

(a) Wells must be decommissioned in a manner that prevents movement of fluid containing any contaminant into the groundwater (40 C.F.R. 144.82); and

(b) When decommissioning wells, the owner or operator must dispose or otherwise manage any soil, gravel, sludge, liquids or other materials removed from or adjacent to the wells in accordance with all applicable federal, state, and local requirements (40 C.F.R. 144.82b).

(2) Decommissioning standards for UIC wells that are determined to be an imminent public health hazard or prohibited:

(a) Class I wells are prohibited and must be decommissioned in accordance with 40 C.F.R. 146;

(b) Class III wells are prohibited and must be decommissioned in accordance with 40 C.F.R. 146;

(c) Class IV wells that are prohibited must be decommissioned in accordance with 40 C.F.R. 144, 146; or

(d) Class V wells that are determined to be an imminent public health hazard or are prohibited in this rule must be decommissioned at the earliest extent possible as approved by the department and meet the decommissioning standards, except for:

(i) Existing cesspools that serve twenty or more people per day or an equivalent design capacity of 3,500 gallons or larger per day must be decommissioned immediately (40 C.F.R. 144.88); and

(ii) Motor vehicle waste disposal wells must be decommissioned immediately.

(3) Decommissioning standards for allowed UIC wells:

(a) Class II wells must meet the closure requirements found in chapter 344-12 WAC General rules;

(b) Class V wells must be decommissioned by filling or plugging the well so that it will not result in an environmental, public health or safety hazard, and will not serve as a channel for movement of water or pollution to an aquifer:

(i) UIC wells that are in contact with an aquifer, even if they are in contact with only the seasonal high aquifer, must be decommissioned in accordance with the most applicable method found in chapter 173-160 WAC Minimum standards for construction and maintenance of wells; or

(ii) UIC wells that are not in contact with an aquifer must be decommissioned by:

(A) Removing any structure within three feet of the land surface;

(B) Backfilling up to three feet below the land surface with material that is uncontaminated, chemically and biologically inert, and that drains equal to or more slowly than the native material surrounding the UIC well; and

(C) Filling the remaining three feet directly below the land surface with native soil or other structurally sound material common with current engineering practices.

(c) Septic systems that receive only sanitary waste and serve twenty or more people per day or an equivalent design capacity of 3,500 gallons or larger per day must be decommissioned in accordance with chapter 246-272B WAC Large on-site sewage system regulations or chapter 246-272A WAC On-site sewage systems;

(d) The department may require additional measures to those above prior to the decommissioning of a UIC well if such measures are deemed necessary to protect the public health and safety.

(4) Decommissioning recordkeeping requirements for UIC wells:

(a) The owner or operator of a Class I, II, III, or IV well must notify the department thirty days prior to decommissioning the UIC well;

(b) An owner or operator of a Class V well that is determined to be an imminent public health hazard or that is prohibited must notify the department thirty days prior to decommissioning the well (40 C.F.R. 144.88); or

(c) After adoption of this rule, an owner or operator of a Class V well that is determined not to be an imminent public health hazard and is not prohibited must notify the department within one year of the closure except for existing UIC wells used for stormwater management and septic systems that are permitted and meet the requirements of chapter 246-272B WAC Large on-site sewage system regulations. The owner or operator must submit to the department, on an annual basis, an update on the wells that have been decommissioned, once the initial well registration(s) has been sent to the department.