(1) In accordance with the requirements of this subsection, the department may designate a tank or container storage area at a facility as a temporary unit for the purpose of treating or storing remediation waste that originates at the same facility in order to implement remedies under this section or to implement other cleanup actions. The department may replace the design, operating and closure standards applicable to dangerous waste tank and container treatment and storage units under this chapter with alternative requirements that protect human health and the environment.

(2) Any temporary unit to which alternative requirements are applied in accordance with subsection (1) of this section will be:

(a) Located within the facility boundary; and

(b) Used only for treatment or storage of remediation wastes managed pursuant to implementation of the corrective action requirements of WAC 173-303-64620 at the facility.

(3) In establishing standards to be applied to a temporary unit, the department will consider the following factors:

(a) Length of time unit will be in operation;

(b) Type of unit;

(c) Volumes of wastes to be managed;

(d) Physical and chemical characteristics of the wastes to be managed in the unit;

(e) Potential for releases from the unit;

(f) Hydrogeological and other relevant environmental conditions at the facility which may influence the migration of any potential releases; and

(g) Potential for exposure of humans and environmental receptors if releases were to occur from the unit.

(4) The department will specify the length of time, not to exceed one year, a temporary unit will be allowed to operate. The director will also specify design, operating, and closure requirements for the temporary unit.

(5) The department may extend the operating period of a temporary unit for up to one additional year, provided the director determines that:

(a) Continued operation of the unit will not pose a threat to human health and the environment; and

(b) Continued operation of the unit is necessary to ensure timely and efficient implementation of remedial actions at the facility.

(6) Incorporation of the designation of and requirements for a temporary unit or a time extension for a temporary unit into an existing permit will be:

(a) Approved in accordance with the procedures for agency-initiated permit modifications under WAC 173-303-830(3); or

(b) Requested by the owner or operator as a Class II modification according to the procedures under WAC 173-303-830(4).

(7) The department will document the rationale for designating a temporary unit and for granting time extensions for temporary units and will make such documentation available to the public.