15.68.410 Floodway standards.
A. In addition to the other requirements of this chapter, a project to develop in the floodway as delineated pursuant to ACC 15.68.130(C), 15.68.130(D) or 15.68.150(E) shall meet the following criteria:
1. The applicant shall provide a certification by a registered professional engineer licensed in the state of Washington demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practices that the proposed development would not result in any increase in flood levels during the occurrence of the base flood discharge.
2. Construction or reconstruction of residential structures is prohibited within designated floodways, except for the following. The following exceptions must still meet all other requirements in this chapter, including subsection (A)(1) of this section.
a. Repairs, reconstruction, or improvements to a residential structure that do not increase the ground floor area, providing the cost of which does not exceed 50 percent of the market value of the structure, either: (i) before the repair or reconstruction is started, or (ii) if the structure has been damaged, and is being restored, before the damage occurred. Any project for improvement of a structure to correct existing violations of state or local health, sanitary, or safety code specifications that have been identified by a local code enforcement official, and which are the minimum necessary to assure safe living conditions, or to an historic structure, may be excluded from the 50 percent calculation;
b. 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:
i. The new farmhouse is a replacement for an existing farmhouse on the same farm site;
ii. There is no potential building site for a replacement farmhouse on the same farm outside the designated floodway;
iii. Repairs, reconstruction, or improvements to a farmhouse shall not increase the total square footage of encroachment of the existing farmhouse;
iv. A replacement farmhouse shall not exceed the total square footage of encroachment of the farmhouse it is replacing;
v. A farmhouse being replaced shall be removed, in its entirety, including foundation, from the floodway within 90 days after occupancy of a new farmhouse;
vi. 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;
vii. New and replacement water supply systems are designed to eliminate or minimize infiltration of floodwaters into the system;
viii. New and replacement sanitary sewerage systems are designed and located to eliminate or minimize infiltration of floodwater into the system and discharge from the system into the floodwaters; and
ix. All other utilities and connections to public utilities are designed, constructed, and located to eliminate or minimize flood damage.
c. 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).
d. Before the repair, replacement, or reconstruction is started, all requirements of the NFIP, the state requirements adopted pursuant to Chapter 86.16 RCW, and all applicable local regulations must be satisfied. In addition, the following conditions must be met:
i. There is no potential safe building location for the replacement residential structure on the same property outside the regulatory floodway.
ii. A replacement residential structure is a residential structure built as a substitute for a legally existing residential structure of equivalent use and size.
iii. Repairs, reconstruction, or replacement of a residential structure shall not increase the total square footage of floodway encroachment.
iv. The elevation of the lowest floor of the substantially damaged or replacement residential structure is a minimum of one foot higher than the BFE.
v. New and replacement water supply systems are designed to eliminate or minimize infiltration of floodwater into the system.
vi. New and replacement sanitary sewerage systems are designed and located to eliminate or minimize infiltration of floodwater into the system and discharge from the system into the floodwaters.
vii. All other utilities and connections to public utilities are designed, constructed, and located to eliminate or minimize flood damage.
e. Repairs, reconstruction, or improvements to residential structures identified as historic structures that do not increase the building’s dimensions.
B. In riverine Special Flood Hazard Areas where a floodway has not been delineated pursuant to ACC 15.68.130(C), 15.68.130(D) or 15.68.150(E), the applicant for a project to develop in the SFHA shall provide a certification by a registered professional engineer in the state of Washington demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practices that the proposed development and all other past or future similar developments would not cumulatively result in an increase of flood levels during the occurrence of the base flood discharge by more than one-half foot. (Ord. 6761 § 1 (Exh. A), 2020.)