(1) No person shall dispose of designated extremely hazardous wastes at any disposal site in the state other than the disposal site established and approved for such purpose under provisions of this chapter, except:

(a) When such wastes are going to a processing facility which will result in the waste being reclaimed, treated, detoxified, neutralized, or otherwise processed to remove its harmful properties or characteristics; or

(b) When such wastes are managed on-site as part of a remedial action conducted by the department or by potentially liable persons under a consent decree issued by the department pursuant to chapter 70A.305 RCW.

(2) Extremely hazardous wastes that contain radioactive components may be disposed at a radioactive waste disposal site that is (a) owned by the United States department of energy or a licensee of the nuclear regulatory commission and (b) permitted by the department and operated in compliance with the provisions of this chapter. However, prior to disposal, or as a part of disposal, all reasonable methods of treatment, detoxification, neutralization, or other waste management methodologies designed to mitigate hazards associated with these wastes shall be employed, as required by applicable federal and state laws and regulations.