§ 24.15.150. Slope stabilization—New.

The approval authority may authorize stabilization of a steep slope or marine bluff only where they determine it to be necessary to protect lawfully established threatened existing structures as defined in this title and by the Shoreline Master Program for the Thurston Region (1990) as amended and applicable, and that cannot be relocated with less impact to geologic hazard areas or other critical areas. Stabilization of marine shorelines is subject to standards within the Shoreline Master Program for the Thurston Region, as amended, TCC 24.25, and consistent with this section. Any proposal for slope/bluff stabilization must be supported by a geological assessment from a qualified geotechnical professional and a biologist and shall adhere to the following preferential order:

A.

Nonstructural Shoreline Protective Techniques. When stabilization methods are deemed necessary by the director, nonstructural shoreline protective techniques are preferred to concrete bulkheads or other types of shoreline armoring. Nonstructural techniques may include but are not limited to: beach nourishment, coarse beach fill, gravel berms, vegetation plantings and bioengineering. Best available science shall be used to evaluate the best techniques for protection as determined by the director. Refer to the Washington Department of Ecology publications "Slope Stabilization and Erosion Control Using Vegetation" (1993, Publication 93-30), and "Marine Shoreline Armoring and Puget Sound" (2010, Publication 10-06-003).

B.

Bioengineering. If necessary, stabilization of slopes and marine bluffs shall be accomplished with bioengineering or similar "soft" stabilization techniques unless the applicant's qualified engineer and biologist demonstrate that such techniques are not sufficient to protect structures and facilities listed above from erosion and slope failure. The stabilization shall be designed and installed to minimize adverse impacts on the habitat's functions.

C.

Combination of Bioengineering and Hard Armoring. If the applicant's qualified engineer and/or biologist demonstrates to the approval authority that bioengineering alone will not be sufficient to protect structures and facilities listed above, the approval authority may authorize a combination of bioengineering and structural solutions that is least damaging to the habitat. The stabilization shall be designed and installed to minimize any adverse impacts on habitat functions. The structural stabilization solutions shall comply with subsection (D) below.

D.

Structural Techniques (e.g., Bulkhead, Gabion, Riprap, Revetments, or Wall). If the applicant's qualified engineer and biologist demonstrates to the approval authority's satisfaction that the techniques provided above are not possible or will not be sufficient to protect structures and facilities listed above from erosion and slope failure, they may, in consultation with a biologist and qualified engineer at the applicant's expense, approve a structural stabilization solution consistent with the following:

1.

Hard armoring, such as rip-rap and bulkheads may only be allowed when the applicant demonstrates to the approval authority that a public facility, public road, utility (not individual service lines that can be relocated), sole access road, or occupied structure cannot be safely and practically maintained without such measures. The armoring shall be the minimum length necessary to protect the structure.

2.

Structural techniques shall only be allowed along the toe of a marine bluff when:

a.

It is to protect a legally permitted threatened structure; and

b.

The residence and normal appurtenances are located within the 2:1 slope measured from the toe of the bluff or within the fifty-foot top of slope buffer, whichever is greater; and

c.

Only if a marine bluff geotechnical assessment completed per Chapter 24.35 TCC finds that the structure to be protected will be threatened based on the long-term erosion rate (thirty—fifty year average) within the next three years if toe protection is not provided.

3.

Hard armoring shall not be allowed along Type F and S waters in salmonid rearing areas unless it is necessary to protect critical public facilities, human life, or threatened dwellings.

E.

Retaining Wall (Not a Bulkhead). The approval authority may allow retaining walls to provide protection for a threatened existing legally established single-family residence or public road where other nonstructural or bioengineering techniques have not been successful or would not be appropriate. Design, placement and mitigation shall be established by a geotechnical assessment and revegetation plan as described in Chapter 24.35 TCC.

F.

Designed by Engineer. A professional engineer licensed in the State of Washington with demonstrated expertise regarding hydraulic actions along shorelines shall design stabilization projects along streams and marine shorelines in consultation with a qualified biologist.

G.

Avoid Intrusion into the Important Habitat Area of a Geologic Hazard Area. Any new or replaced shoreline protective structures shall be placed as close to the existing bank as possible and parallel to the natural shoreline. In areas where dry land has been previously created by fill behind the bulkhead, the replacement structure should be designed to remove the fill and place the new structure as close to the historical OHWM as possible.

H.

Nontoxic Materials. Approved stabilization shall only use materials that do not pose a risk to water quality, consistent with best available science.

I.

Slope Stabilization. Slope stabilization is only allowed in geologic hazards, if consistent with Chapter 24.25 TCC, Fish and Wildlife Habitat Conservation Areas and Chapter 24.20 TCC, Frequently Flooded Areas, and only where erosion or landsliding threatens a use listed in this section. Bioengineering shall be used where possible.

J.

A mitigation plan for impacts to geologic hazard areas including the shoreline ecological functions as a result of the armoring shall be prepared by a qualified biologist and implemented immediately following construction. Mitigation measures may include temporary or perpetual beach feeding with appropriate substrate, additional woody debris, revegetation of the adjacent upland area, or other measures designed to minimize the impacts to the nearshore environment from armoring.

K.

Prior to any approval of shoreline armoring, the applicant shall demonstrate that other measures have been taken to address the erosion or other threats to the structure. This includes improving or installing a functioning drainage system, minimizing impervious areas, restoration of trees and other native vegetation on the adjacent buffer slope or bluff, possible relocation of structures, or other measures that would improve stabilization and reduce the threat to the structure.

(Ord. No. 14773, § 3(Att. B), 7-24-2012)