Outfall structure projects shall incorporate mitigation measures as necessary to achieve no-net-loss of productive capacity of fish and shellfish habitat. The following technical provisions shall apply to outfall structure projects:
(1) The outfall structure shall be constructed according to an approved design to prevent the entry of fish, except where fish passage could enhance fish life or habitat.
(2) The watercourse bank and bed at the point of discharge shall be armored to prevent scouring.
(3) Excavation for placement of the structure or armoring materials shall be isolated from the wetted perimeter.
(4) Alteration or disturbance of banks and bank vegetation shall be limited to that necessary to construct the project. All disturbed areas shall be protected from erosion within seven days of completion of the project using vegetation or other means. The banks shall be revegetated within one year with native or other approved woody species. Vegetative cuttings shall be planted at a maximum interval of three feet (on center), and maintained as necessary for three years to ensure eighty percent survival. Where proposed, planting densities and maintenance requirements for rooted stock will be determined on a site-specific basis. The requirement to plant woody vegetation may be waived for areas where the potential for natural revegetation is adequate, or where other engineering or safety factors preclude them.
(5) Structures containing concrete shall be sufficiently cured prior to contact with water, to avoid leaching.
(6) All piling, lumber, or other materials treated with preservatives shall be sufficiently cured to minimize leaching into the water or bed. The use of wood treated with creosote or pentachlorophenol is not allowed in lakes.
[Statutory Authority: RCW 77.12.047
. WSR 05-14-001 (Order 05-131), § 220-110-170, filed 6/22/05, effective 7/23/05. Statutory Authority: RCW 75.08.080
. WSR 94-23-058 (Order 94-160), § 220-110-170, filed 11/14/94, effective 12/15/94. Statutory Authority: RCW 75.20.100
and 75.08.080. WSR 83-09-019 (Order 83-25), § 220-110-170, filed 4/13/83.]