Channel changes/realignments are generally discouraged, and shall only be approved where the applicant can demonstrate benefits or lack of adverse impact to fish life. Channel change/realignment 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 channel change and channel realignment projects:
When approved, a channel change may occur provided:
(1) Permanent new channels shall, at a minimum, be similar in length, width, depth, flood plain configuration, and gradient, as the old channel. The new channel shall incorporate fish habitat components, bed materials, meander configuration, and native or other approved vegetation equivalent to or greater than that which previously existed in the old channel.
(2) During construction, the new channel shall be isolated from the flowing stream by plugs at the upstream and downstream ends of the new channel.
(3) Before water is diverted into a permanent new channel, the applicant shall complete the following actions:
(a) Approved fish habitat components, bed materials and bank protection to prevent erosion shall be in place.
(b) Approved fish habitat components shall be installed according to an approved design to withstand the 100-year peak flows.
(4) 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) Diversion of flow into a new channel shall be accomplished by: (a) First removing the downstream plug; (b) removing the upstream plug; and (c) closing the upstream end of the old channel.
(6) Filling of the old channel shall begin from the upstream closure and the fill material shall be compacted. Water discharging from the fill shall not adversely impact fish life.
(7) The angle of the structure used to divert the water into the new channel shall allow a smooth transition of water flow.
(8) If fish may be adversely impacted as a result of this project, the permittee will be required to capture and safely move food fish, game fish or other fish life (at the discretion of the department) to the nearest free-flowing water. The permittee may request the department to assist in capturing and safely moving fish life from the job site to free-flowing water, and assistance may be granted if personnel are available.
[Statutory Authority: RCW 75.08.080
. WSR 94-23-058 (Order 94-160), § 220-110-080, filed 11/14/94, effective 12/15/94; WSR 87-15-086 (Order 87-48), § 220-110-080, filed 7/20/87. Statutory Authority: RCW 75.20.100
and 75.08.080. WSR 83-09-019 (Order 83-25), § 220-110-080, filed 4/13/83.]