16.20.550 Geologically hazardous areas | Electric City Municipal Code

16.20.550 Geologically hazardous areas.

(a) Geologically hazardous areas include those with the following characteristics:

(i) Erosion Hazard Areas. Erosion hazard areas are at least those areas identified by the U.S. Department of Agriculture’s Natural Resources Conservation Service as having a “moderate to severe,” “severe,” or “very severe” rill and inter-rill erosion hazard. Erosion hazard areas are also those areas impacted by shore land and/or stream bank erosion and those areas within a river’s channel migration zone. Erosion hazard areas are those that contain all three of the following characteristics:

(A) A slope of 30 percent or greater;

(B) Soils identified by the Soil Conservation Service as unstable and having a high potential for erosion; and

(ii) Landslide Hazard Areas. Landslide hazard areas are areas potentially subject to landslides based on a combination of geologic, topographic, and hydrologic factors. They include areas susceptible because of any combination of bedrock, soil, slope (gradient), slope aspect, structure, hydrology, or other factors. Landslide hazard areas are those that may contain any of the following circumstances:

(A) All areas that have historically been prone to landsliding;

(B) All areas containing soil types identified by the Natural Resource Conservation Service (NRCS) as unstable and prone to landslide hazard;

(D) All areas that are potentially unstable as a result of rapid stream incision or stream bank erosion.

(iii) Seismic Hazard Areas. Seismic hazard areas are areas subject to severe risk of damage as a result of earthquake induced ground shaking, slope failure, settlement, soil liquefaction, lateral spreading, or surface faulting. Settlement and soil liquefaction conditions occur in areas underlain by cohesionless, loose, or soft-saturated soils of low density, typically in association with a shallow ground water table. Seismic hazards shall be as identified in the Washington State Department of Natural Resources seismic hazard and liquefaction susceptibility maps for Eastern Washington and other geologic resources.

(iv) Mine Hazard Areas. Mine hazard areas are those areas underlain by or affected by mine workings such as adits, gangways, tunnels, drifts, or airshafts, and those areas of probable sink holes, gas releases, or subsidence due to mine workings. Factors that should be considered include: proximity to development, depth from ground surface to the mine working, and geologic material.

(v) Volcanic Hazard Areas. Volcanic hazard areas are areas subject to pyroclastic flows, lava flows, debris avalanche, and inundation by debris flows, lahars, mudflows, or related flooding resulting from volcanic activity.

(vi) Other Hazard Areas. Geologically hazardous areas shall also include areas determined by the mayor to be susceptible to other geological events including mass wasting, debris flows, rock falls, and differential settlement.

(vii) Known geologically hazardous areas within the city 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 chapter.

(a) All projects shall be evaluated through a geotechnical report, completed by a qualified professional with expertise in the particular hazard(s) present in a given critical area, 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;

(b) All projects shall comply with the applicable federal, state and local regulations, including the International Building Code;

(i) Will not increase the threat of the geological hazard to adjacent properties beyond pre-development conditions;

(ii) Will not adversely impact other critical areas;

(iii) Are designed so that the hazard to the project is eliminated or mitigated to a level equal to or less than predevelopment conditions; and

(iv) Are certified as safe as designed and under anticipated conditions by a qualified engineer or geologist, licensed in the state of Washington;

(d) Mitigation plans for geologically hazardous areas shall establish setbacks and buffer widths as needed to eliminate or minimize risks of property damage, death, or injury resulting from development of the hazard area. Where established, buffers shall be maintained between all permitted uses and activities and the designated geologically hazardous area(s);

(e) 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;

(f) Unless otherwise provided or as part of an approved alteration, removal of vegetation from an erosion or landslide hazard area or related buffer shall be prohibited. Where removal of vegetation is unavoidable, reseeding and replanting with native vegetation shall be preferred. In lieu of a native restoration planting an erosion control mix recommended by the Natural Resource Conservation Service, the Grant County conservation district, the WSU cooperative extension office, or other qualified agent to assist in stabilization of the areas and to discourage establishment of invasive plants may be substituted;

(g) As determined through the site-specific study, appropriate drainage, grading, excavation and erosion control measures shall be implemented in the geologically hazardous area(s);

(h) Every erosion hazard area mitigation plan shall include a runoff management plan or an erosion control plan to reduce sedimentation problems;

(i) Development and activities located within landslide or erosion hazard areas shall provide for long-term slope stability, and design shall incorporate the following standards:

(i) Structures and improvements shall minimize alterations to the natural contour of the slope and foundations shall be tiered where possible to conform to existing topography;

(ii) Structures and improvements shall be located to preserve the most critical portion of the site and its natural landforms and vegetation;

(iii) The proposed development shall not result in greater risk or a need for increased buffers on neighboring properties;

(iv) The use of retaining walls that allow the maintenance of existing natural slope area is preferred over graded artificial slopes; and

(v) Development shall be designed to minimize impervious lot coverage;

(j) Utility lines and pipes shall be permitted in erosion and landslide hazard areas only when the applicant demonstrates that no other practical alternative is available;

(k) Subdivision of lands in erosion, landslide, and mine hazard areas is subject to the following:

(i) Land that is located wholly within an erosion, landslide or mine hazard area or its buffer may not be subdivided. Land that is located partially within an erosion, landslide or mine hazard area or its buffer may be divided; provided, that each resulting lot has sufficient buildable area outside of, and will not affect, the geologic hazard area.

(ii) Access roads and utilities may be permitted within the erosion, landslide or mine hazard area and associated buffers only if no other feasible alternative exists;

(l) As determined through the site-specific study, mitigation measures shall be implemented that maintain the integrity of the geologically hazardous area(s);

(m) 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 as described hereinabove; and

(n) A use or structure established prior to the effective date of this chapter 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;

(i) Site-specific considerations may warrant additional performance standards, to be determined during the permit process, to ensure the protection of critical areas.

(ii) Development specific considerations may warrant additional performance standards based on level of impact to critical areas. (Ord. 484 § 2, 2014)