(a) Classification. Known geologically hazardous areas within the city of Selah consist of erosion hazard areas, including steep slopes. As more information is obtained that demonstrates the existence of other types and/or areas of geologically hazardous areas, these types and/or areas shall be classified and protected in accordance with the provisions of this section.
(1) The following general classification system will be used to determine the level of protection necessary for geologically hazardous areas, based upon the risk to development:
(A) Known or suspected risk;
(B) No risk;
(C) Risk unknown.
(2) The following criteria shall be used in determining the status of an area as a particular type of geologically hazardous area:
(A) Erosion hazard areas are those that contain all three of the following characteristics:
(i) A slope of fifteen percent or greater;
(ii) Soils identified by the Natural Resources Conservation Service (NRCS) as having a high potential for erosion hazard. The approximate location and extent of erosion hazard areas are shown on a Yakima County map titled "Erosion Hazard Areas of Yakima County" and, for areas in Selah, were identified by using the "Soil Survey of Yakima County Area, Washington"; and
(iii) Areas that are exposed to the erosion effects of wind or water.
(B) Landslide hazard areas are those that may contain any of the following circumstances:
(i) All areas that have historically been prone to landsliding;
(ii) All areas containing soil types identified by the Natural Resources Conservation Service (NRCS) as unstable and prone to landslide hazard;
(iii) All areas that show evidence of or are at risk from snow avalanches; or
(iv) All areas that are potentially unstable as a result of rapid stream incision or stream bank erosion.
(1) Geologically Hazardous Areas. Each type of geologically hazardous area is designated based on different factors. The designation process for each type is as follows:
(2) Erosion Hazard Areas. NRCS soil erosion-hazard ratings are interpretations of the potential for erosion, applied to broadly generalized map units. The NRCS maps will be used to identify areas of erosion potential. The soil information needs to be combined with site-specific information (rills, inter-rills, and wind erosion) to determine if an erosion hazard is present on the site.
(3) Landslide Hazard Areas. Lands that meet the classification criteria are hereby designated as landslide hazard areas and should be mapped as resources become available.
(4) Mine Hazard Areas. Lands that meet the classification criteria are hereby designated as mine hazard areas and will be mapped as resources become available.
(5) Seismic Hazard Areas. There are no known active faults in the city of Selah. The majority of the city is located within Seismic Zone C in accordance with the International Building Code (2009 Edition, or as amended).
(6) Volcanic Hazard Areas. There are no volcanic hazard areas in the city of Selah. There are, however, several active volcanoes that could have impacts on the city, particularly the fallout of ash. There is no way to prevent the impacts of fallen ash, but there are ways to respond to the ash that could lessen its impacts.
(c) Standards. In addition to the general provisions of these regulations and the requirements of the underlying zoning district, the following minimum standards shall apply to development activities within and adjacent to geologic hazard areas:
(1) All projects shall be evaluated through a geotechnical report to determine whether the project is proposed to be located in a geologically hazardous area, and if so, what is the project's potential impact on the geologically hazardous area and the potential impact of the geologic hazard on the proposed project; except that if the project site is only in an erosion hazard area and not a potential geologically hazardous area of another type, the protection measures will be accomplished by implementing the regulatory standards for erosion and drainage control required under this title (Building Codes). Any future storm water program erosion control measures that may be formally adopted by the city council shall supersede Title 11 erosion control requirements. Standards to meet Title 11 requirements can be met by the application of the best management practices (BMPs) in the Stormwater Management Manual for Eastern Washington (WDOE Publication No. 04-10-076) or equivalent manual adopted by the city of Selah, or any other approved manual deemed appropriate by the building official, including but not limited to applicable Natural Resources Conservation Service (NRCS) Field Office Technical Guide (FOTG) BMPs and the Washington Department of Transportation Highway Runoff Manual. Application of the Environmental Protection Agency (EPA) "Construction Rainfall Erosivity Waiver" is at the discretion of the building official on a case-by-case basis;
(2) All projects shall comply with the applicable federal, state and local regulations, including the most recently adopted International Building Code;
(3) Any appropriate buffers determined by the site-specific study shall be maintained between all permitted uses and activities and the designated geologically hazardous area(s);
(4) The existing native vegetation within the buffer area(s) shall be maintained, except that normal, nondestructive pruning and trimming of vegetation for maintenance purposes is allowed;
(5) As determined through the site-specific study, appropriate drainage, grading, excavation and erosion control measures shall be implemented in the geologically hazardous area(s);
(6) As determined through the site-specific study, mitigation measures shall be implemented that maintain the integrity of the geologically hazardous area(s);
(7) As determined through the site-specific study, appropriate management and monitoring plan(s) shall be developed and implemented to preserve and protect both the geologically hazardous area(s) and the project, with any necessary surety to ensure compliance with such plan(s) being provided in Section 11.50.080(c)(4)(J) (Critical Areas Report); and
A use or structure established prior to April 22, 2014, which does not conform to standards set forth herein is allowed to continue and be reasonably maintained; provided, that such activity or structure shall not be expanded or enlarged in any manner that increases the extent of its nonconformity, unless otherwise approved. (Ord. 2124 § 2 (Att.), 2021.)