- (1) Secondary containment walls constructed of earth shall be allowed at permanent storage facilities when a liner is used: Provided, That only permanent storage facilities having storage containers of one hundred thousand gallons or greater capacity can use clay liners.
- (2) Earthen walls shall have a horizontal to vertical slope of at least three to one, unless a steeper slope is consistent with good engineering practice, and shall be packed and protected from erosion.
- (3) The top of earthen walls shall be no less than two feet six inches wide.
[Statutory Authority: RCW 15.54.800. WSR 00-23-075, § 16-201-029, filed 11/17/00, effective 12/18/00.]