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Title 17E
Chapter 17E.030
Section 17E.030.160
 

Title 17E Environmental Standards

Chapter 17E.030 Floodplain Management

Section 17E.030.160 Floodways

Located within areas of special flood hazard established in SMC 17E.030.050 are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters that carry debris, potential projectiles, and increase erosion potential, the following provisions apply:

  1. No Rise Standard

Prohibit encroachments, including fill, new construction, substantial improvements and other development unless certification by a registered professional engineer is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels during the occurrence of the base flood discharge.

  1. Residential Construction in Floodways.

Construction or reconstruction of residential structures is prohibited within designated floodways, except for:

  1. repairs, reconstruction or improvements to a structure which do not increase the ground floor area; and
  1. repairs, reconstruction or improvements to a structure, the cost of which does not exceed fifty percent of the market value of the structure either:
      1. before the repair or reconstruction is started; or
      1. if the structure has been damaged, and is being restored, before the damage occurred.
  1. Any improvement to structures identified as historic places or to correct existing violations of state or local health, sanitary or safety code specification that have been identified by the local code enforcement official and are the minimum necessary to assure safe living conditions shall not be included in the fifty percent.
  1. Replacement of Farmhouses in Floodway.

Repairs, reconstruction, replacement, or improvements to existing farmhouse structures located in designated floodways and that are located on lands designated as agricultural lands of long-term commercial significance under RCW 36.70A.170 may be permitted subject to the following:

  1. The new farmhouse is a replacement for an existing farmhouse on the same farm site;
  1. There is no potential building site for a replacement farmhouse on the same farm outside the designated floodway;
  1. Repairs, reconstruction, or improvements to a farmhouse shall not increase the total square footage of encroachment of the existing farmhouse;
  1. A replacement farmhouse shall not exceed the total square footage of encroachment of the farmhouse it is replacing;
  1. A farmhouse being replaced shall be removed, in its entirety, including foundation, from the floodway within ninety days after occupancy of a new farmhouse;
  1. For substantial improvements and replacement farmhouses, the elevation of the lowest floor of the improvement and farmhouse respectively, including basement, is a minimum of one foot higher than the BFE;
  1. New and replacement water supply systems are designed to eliminate or minimize infiltration of flood waters into the system;
  1. New and replacement sanitary sewerage systems are designed and located to eliminate or minimize infiltration of flood water into the system and discharge from the system into the flood waters; and
  1. All other utilities and connections to public utilities are designed, constructed, and located to eliminate or minimize flood damage.
  1. Substantially Damaged Residences in Floodway.
  1. For all substantially damaged residential structures, other than farmhouses, located in a designated floodway, the Floodplain Administrator may make a written request that the Department of Ecology assess the risk of harm to life and property posed by the specific conditions of the floodway. Based on analysis of depth, velocity, flood-related erosion, channel migration, debris load potential, and flood warning capability, the Department of Ecology may exercise best professional judgment in recommending to the local permitting authority repair, replacement, or relocation of a substantially damaged structure consistent with WAC 173-158-076. The property owner shall be responsible for submitting to the local government and the Department of Ecology any information necessary to complete the assessment. Without a favorable recommendation from the department for the repair or replacement of a substantially damaged residential structure located in the regulatory floodway, no repair or replacement is allowed per WAC 173-158-070(1).
  1. Before the repair, replacement, or reconstruction is started, all requirements of the NFIP, the state requirements adopted pursuant to 86.16 RCW, and all applicable local regulations must be satisfied. In addition, the following conditions must be met:
  1. There is no potential safe building location for the replacement residential structure on the same property outside the regulatory floodway.
  1. A replacement residential structure is a residential structure built as a substitute for a legally existing residential structure of equivalent use and size.
  1. Repairs, reconstruction, or replacement of a residential structure shall not increase the total square footage of floodway encroachment.
  1. The elevation of the lowest floor of the substantially damaged or replacement residential structure is a minimum of one foot higher than the BFE.
  1. New and replacement water supply systems are designed to eliminate or minimize infiltration of flood water into the system.
  1. New and replacement sanitary sewerage systems are designed and located to eliminate or minimize infiltration of flood water into the system and discharge from the system into the flood waters.
  1. All other utilities and connections to public utilities are designed, constructed, and located to eliminate or minimize flood damage.
  1. If subsection (A) of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of SMC 17E.030.130, 17E.030.140, and 17E.030.130(F).

Date Passed: Monday, October 25, 2021

Effective Date: Thursday, December 2, 2021

ORD C36118 Section 12