Standards for piers and floats and overwater structures
Seattle Mun. Code § 23.60A.187
in effectA. In shoreline environments where piers, floats and associated overwater structures are allowed or allowed as a special use or a shoreline conditional use, they shall comply with the standards in Section 23.60A.172 and in this Section 23.60A.187 . B. Owners of piers and floats shall require moorage users at residential or non-residential moorage to use best management practices set out in Section 23.60A.155 to minimize impacts on the aquatic environment. The Director may establish appropriate best management practices to implement the requirements of this subsection 23.60A.187.B by Director's Rule. C. Piers and floats for residential development 1. Piers and floats are allowed as accessory uses for single-family and multi-family development on waterfront lots as set out in this subsection 23.60A.187.C and are otherwise prohibited. For the purpose of this subsection 23.60A.187.C, an accessory dwelling unit does not constitute an additional single-family or multi-family residence or dwelling unit. 2. Unshared piers are allowed as follows: a. Existing single-family residences and new single-family residential development of one residence if: 1) Located in freshwater; and 2) The length of the pier and float is 100 feet or less. b. Existing single-family and existing multi-family residences and new single-family residential development of one residence may have an unshared pier greater than 100 feet in length in freshwater if: 1) First, a mooring buoy is not practicable; and 2) Second, a shared pier is not practicable or cannot meet the standards in subsection 23.60A.187.C.6. c. Existing single-family and existing multi-family residences and new single-family residential development of one residence may have a pier or float in saltwater if: 1) First, a mooring buoy is not practicable; and 2) Second, a shared pier is not practicable or cannot meet the standards in subsection 23.60A.187.C.6. 3. New single-family development of two or more dwelling units and new multi-family development are required to share piers or provide a community dock facility, unless it is infeasible or cannot meet the standards in subsection 23.60A.187.C.6. Single-family residential development of greater than four residences and multi-family development shall also comply with subsections C, E and F of Section 23.60A.187 . 4. Piers are limited to overwater projections, walkways and open-bottom boat or jet-ski lifts. Covered moorage and overwater work sheds are prohibited. 5. Piers and floats shall be designed and used for access to watercraft. 6. Shared piers shall meet the following standards: a. The owners of the pier shall be owners of waterfront lots located no more than 800 feet apart. More than two property owners may share a pier. b. Shared piers may be located adjacent to or on both sides of a common lot line of two of the sharing property owners. c. An application to build a shared pier shall be submitted jointly by the eligible property owners and shall include easements or covenants identifying the location of the shared pier and assuring joint use of the entire facility. d. The minimum combined lot width for lots sharing a pier is 60 feet. 7. Unshared piers for single-family or multifamily development shall be on a waterfront lot with a minimum lot width of 45 feet. 8. No multifamily lot containing four or fewer dwelling units and no single-family lot shall have more than one pier or float, whether shared or unshared. A multifamily lot containing more than four units may have more than one pier as provided in subsection 23.60A.187.C.9, if overwater coverage is the minimum necessary. 9. Size and number of overwater structures a. Piers 1) Unshared single-family piers are allowed one linear walkway with one overwater projection and up to two open-bottom boat or jet ski lifts. 2) Shared single-family piers are allowed one linear walkway with one overwater projection per dwelling unit and two open-bottom boat or jet ski lifts per dwelling unit. 3) Multifamily piers are allowed one walkway per 15 dwelling units and one over water projection and open-bottom boat or jet ski lift per two dwelling units, which shall be designed to minimize total over water coverage. b. Walkways 1) Walkways are required to be located generally parallel to side lot lines and perpendicular to the shoreline. 2) If the shoreline or the lot lines are irregular or the side lot lines are not perpendicular to the shoreline, the Director shall determine the orientation of the walkway to minimize conflicts. 3) No walkway shall exceed 4 feet in width for piers that are not shared, or 6 feet in width for shared piers or piers serving multifamily lots. 4) In Lake Washington, Lake Union, and the Ship Canal, walkways are required to be fixed within 30 feet of the OHW mark. In Puget Sound, the Duwamish River, and Green Lake, walkways may be fixed or floating. c. Projections. Projections may be located overwater on the sides or waterward end of walkways. Each overwater projection is limited to 100 square feet and shall comply with the length and setback standards of this Section 23.60A.187 . d. Overwater projections, boat lifts, and areas used for boat moorage shall be located no closer than 30 feet from the OHW mark unless located in an area where the water depth is at least 8 feet deep at the ordinary low water level in freshwater or mean lower low water (MLLW) in marine water. e. Length of piers. Piers shall meet the following standards: 1) No pier shall extend waterward from the OHW mark more than to a point where the depth of the water at the end of the pier reaches 8 feet below the elevation of the ordinary low water level in freshwater or below MLLW in marine waters and no greater than 100 feet from the OHW mark in either fresh or salt water. 2) No pier shall extend beyond the Outer Harbor or Pierhead Line, except in Lake Union where piers are not allowed to extend beyond the Construction Limit Line as shown upon the Official Land Use Map, Chapter 23.32 , or except where authorized by this Chapter 23.60A and by DNR and the U.S. Army Corps of Engineers. 10. Improvement of Existing Piers. Existing single-family and multi-family residential piers that do not meet the standards of subsection 23.60A.187.C.9 shall comply with the provisions of Section 23.60A.124 ; however, if such piers are replaced or undergo substantial improvement, they shall meet either the standards of subsection 23.60A.187.C.9 for the entire pier or reduce the total area of the pier by 20 percent and increase conformity under subsection 23.60A.187.C.9 for any non-conforming portion of the pier. 11. The bottom of all structures over water, except floats or floating piers, shall be at least 1.5 feet above ordinary high water. No pier shall exceed 5 feet in height above the elevation of OHW, except that arched walkways may reach a height of 7 feet above the elevation of OHW within 30 feet waterward of the OHW mark. 12. Swimming floats are allowed in lieu of moorage piers if anchored off-shore a minimum of 30 feet from the OHW mark and limited to 100 square feet for single-family and two-family dwelling units and an additional 50 square feet per dwelling unit for three or more family dwelling units; such swimming floats are not required to meet the standards of subsections 23.60A.187.C.3 and 23.60A.187.C.9. 13. No pier shall be located within 15 feet of a side lot line unless the pier is shared with the owner of that adjacent waterfront lot. An existing pier not meeting this provision may be extended to the maximum length permitted in subsection 23.60A.187.C.9.e. 14. Piers and floats shall be fully grated with the maximum light permeability feasible. 15. Non-toxic material shall be used to the maximum extent reasonable. Wood treated with pentachlorophenol, creosote, chromate copper arsenate (CCA), or comparably toxic compounds is prohibited for decking or piling. 16. Fees or other compensation may not be charged for use of piers accessory to residences in the CR and UR Environments, except for piers and floats subject to subsection 23.60A.187.D. 17. Residential developments providing moorage in excess of 3,500 linear feet shall provide: a. Self-service sewage pump-out facilities or the best available method of disposing of sewage wastes from boats, as determined by the Director; and b. Either a vacuum apparatus or oil-absorbent materials and waste receptacles for disposal of bilge wastes. D. Single-family residential development of greater than four residences and multi-family residential development constructing piers and floats shall establish and operate the use as a recreational marina and shall comply with the standards of subsections 23.60A.187.C, 23.60A.187.F and 23.60A.187.G and subsections 23.60A.200.B, 23.60A.200.C and 23.60A.200.D. E. Non-residential development. Piers and floats accessory to non-residential development shall meet the following standards: 1. Piers and floats are allowed as follows and otherwise are prohibited: a. If the applicant demonstrates they are necessary to accommodate boat moorage, boat repair, or loading and offloading of passengers, goods or materials to and from vessel uses; b. If part of a parks and open space shoreline use; or c. Piers and floats solely for the purpose of public access if the applicant demonstrates a pier is necessary to accommodate a view that would otherwise be substantially blocked by adjacent overwater buildings. 2. The size of piers and floats allowed in subsections 23.60A.187.E.1.a through 23.60A.187.E.1.c is the minimum necessary for the intended use. 3. Covered moorage is prohibited. 4. Over water work sheds are allowed if they are: a. Located in the UC, UI and UM Environments and limited to 20 percent overwater coverage of the submerged portion of the development site; b. Accessory to a vessel repair use; and c. Maintain the maximum light permeability feasible. 5. Non-toxic material shall be used to the maximum extent reasonable. Wood treated with pentachlorophenol, creosote, chromate copper arsenate (CCA) or comparably toxic compounds is prohibited for decking or piling. 6. Light transmitting features are required to be installed for all new and replaced piers and floats to the maximum extent feasible taking into account the structural and use requirements of the pier and the potential for discharges that might pollute the water. If the site is used for the following, it is considered infeasible to include light transmitting features: a. The pier is used for average loads greater than 30 pounds per square foot. b. The pier functions as spill prevention or secondary containment for the following: 1) Toxic substances or material such as oil or fuel that is transported across the deck. This does not apply to the substances used to operate the equipment used on the deck; 2) Fueling of vessels; or 3) Storm water that is collected and recycled or treated prior to discharge. 7. Piers shall not extend beyond the Outer Harbor or Pierhead Line except in Lake Union where piers shall not extend beyond the Construction Limit Line as shown upon the Official Land Use Map, Chapter 23.32 , or except where authorized by this Chapter 23.60A and by DNR and the U.S. Army Corps of Engineers. F. Non-commercial slip-side vessel maintenance on piers and floats is limited to: 1. Interior vessel repair and cleaning, replacement of running gear and other cleaning and repair activities, excluding hull scraping, which is prohibited; 2. Twenty five percent of the exterior of the boat at one time. The Director may establish appropriate best management practices based on Department of Ecology's Resource Manual for Pollution Prevention in Marinas May 1998, Revised 2009 Publication #9811, in a Director's Rule. G. In applying mitigation sequencing pursuant to Section 23.60A.158 , adverse impacts to ecological functions to be addressed include, but are not limited to: shading of habitat and vegetation; adverse impacts to migration corridors; creation of habitat for non-native or abundant predator species; changes to the strength and pattern of wave and water movement; alteration of growing conditions and aquatic productivity; pollution resulting from boat and other uses (including maintenance of facilities and ancillary recreation uses); and remaining shading of habitat after installation of grating. (Ord. 124750 , § 15, 2015; Ord. 124105 , § 3, 2013.)
Source: Seattle Municipal Code (Municode library)URL: https://library.municode.com/wa/seattle/codes/municipal_codeFetched: 7/25/2026