(1) Applicability. The closure requirements of subsections (2), (3), and (4) of this section apply to all disposal facilities. The post-closure requirements of subsections (5), (6), and (7) apply to monofills subject to WAC 173-306-440.

(2) Closure performance requirements. Each owner and operator shall close the facility in a manner that:

(a) Minimizes the need for further maintenance;

(b) Controls, minimizes, or eliminates threats to human health and the environment from post-closure escape of ash constituents, leachate, monofill gases, contaminated rainfall or ash decomposition products to the ground or soil, groundwater, surface water, and the atmosphere; and

(c) Prepares the facility for the post-closure period.

(3) Closure plan and amendment. Closure as defined in WAC 173-306-100 includes, but is not limited to, grading, seeding, landscaping, contouring and screening.

(a) Each owner or operator shall develop and use a plan of closure approved by the department as part of the permitting process of WAC 173-306-310.

(b) The closure plan shall project time intervals at which closure activities must be implemented, and shall identify estimated closure costs and project fund withdrawal intervals from the approved financial assurance instrument, where applicable.

(c) No owner or operator may begin disposal operations in any part of a facility until a closure plan for the entire facility has been approved by the department, and until a financial assurance instrument has been provided, as required by WAC 173-306-470.

(d) The department may determine at its discretion and for cause that a facility closure plan is invalid and may require an owner or operator to:

(i) Amend the facility closure plan and obtain the department's written approval; and/or

(ii) Cease facility operation or closure activities in whole or in part until an approved closure plan is obtained.

(e) Each owner or operator shall close the facility in accordance with the approved closure plan and all approved amendments.

(4) Closure procedures.

(a) Each owner or operator shall notify the department and, where applicable, the financial assurance instrument trustee, of the intent to implement the closure plan in whole or in part, no later than one hundred eighty days before the projected final receipt of waste at part of or at the entire facility.

(b) The owner or operator shall begin implementing the closure plan in part or whole within thirty days after receipt of a final volume of ash and/or attaining the final monofill elevation at part of or at the entire facility as identified in the approved facility closure plan.

(c) Ash may not be accepted for use in closure except as identified in the closure plan approved by the department, as required in subsection (3)(a) of this section.

(d) When facility closure is completed in part or whole, each owner or operator shall submit to the department:

(i) Facility closure plan sheets signed by a professional engineer registered in the state of Washington. The plan shall reflect all as-built changes to final closure construction as approved in the closure plan; and

(ii) An affidavit signed by the owner or operator and a professional engineer registered in the state of Washington that the site has been closed in accordance with the approved closure plan.

(e) Maps and a statement of fact concerning the location of the final ash disposal must be recorded as part of the deed with the county auditor not later than three months after closure. Records and plans specifying ash amounts, locations and periods of operation must be submitted to the local zoning authority or the authority with jurisdiction over land use and must be made available for inspection.

(f) When the department finds the facility has been closed in accordance with the specifications of the approved closure plan and the closure requirements of this section, the department shall:

(i) Issue a certificate of closure for the site to the owner or operator and the department; and

(ii) Notify the owner or operator and the department that the facility post-closure period has begun in whole or in part on a specified date.

(5) Post-closure performance standard. Monofill owners or operators shall perform post-closure activities as needed to protect human health and the environment.

(6) Post-closure plan and amendment. Post-closure includes monitoring of groundwater, surface water, and air quality; maintenance of the facility, facility structures, and monitoring systems; and other activities deemed appropriate by the department.

(a) The owner or operator shall develop and use a post-closure plan approved as a part of the permitting process in WAC 173-306-310. The post-closure plan shall address facility maintenance and monitoring activities for a thirty-year period.

(b) The post-closure plan shall project time intervals at which post-closure activities are to be implemented, and identify post-closure cost estimates and projected fund withdrawal intervals from the selected financial assurance instrument, where applicable, for the associated post-closure costs.

(c) No owner or operator may begin disposal operations in any part of a facility until a post-closure plan for the entire facility has been approved by the department, and until a financial assurance instrument has been provided, where applicable, as required by WAC 173-306-470. Facility post-closure activities must be completed in accordance with the approved post-closure plan or the plan must be so amended with the approval of the department.

(d) The department may determine, at its discretion and for cause, that a facility post-closure plan is invalid and may require an owner or operator to:

(i) Amend the facility post-closure plan and obtain the department's written approval; and/or

(ii) Cease facility operation or closure activities in part or wholly until an approved post-closure plan is obtained.

(7) Post-closure procedures.

(a) Each owner or operator shall begin post-closure activities after completing closure activities outlined in subsection (4)(d)(i) and (ii) of this section. The department may direct that post-closure activities cease until the owner or operator has received the department's certification of closure and a notice to proceed with post-closure activities.

(b) When post-closure activities are complete, the owner or operator shall submit an affidavit to the department, signed by the owner or operator and a professional engineer registered in the state of Washington, stating why post-closure activities are no longer necessary.

(c) If the department finds that post-closure activities have stabilized the facility, the department may, at its discretion, authorize the owner or operator to gradually reduce or discontinue post-closure maintenance and monitoring activities. The department shall certify the end of the post-closure care period by issuing a certificate of post-closure completion to the facility owner or operator.