18.05.260 Critical area – Geologically hazardous areas.
A. Purposes. It is the intent of the city to reduce the threat posed to the health and safety of its citizens from commercial, residential or industrial development that may be sited in areas of significant geologic hazard. In some cases, it is recognized that risks from geologic hazards can be reduced or mitigated to acceptable levels through engineering design or modified construction practices. In other cases where technological efforts are not sufficient to reduce associated risks, building is best avoided. The following reflect the goals and policies of the community:
1. Goal. Provide appropriate measures to either avoid or mitigate significant risks that are posed by geologic hazard areas to public and private property and to public health and safety.
2. Policies. When probable significant adverse impacts from geologically hazardous areas are identified during the review of a development application, documentation that fully addresses these potential impacts and identifies alternative mitigation measures to eliminate or minimize the impacts will be required.
B. Identification. Geological hazards pose a threat to public health and safety. Adequate identification and development standards reduce these risks. Hazards of concern that exist in the city include any land containing soils, geology or slopes that meet any of the following criteria:
1. Erosion Hazard Areas. Erosion hazard areas are those areas that contain all three of the following characteristics:
a. A slope of 40 percent or greater;
b. Areas identified by the Natural Resources Conservation Service (NRCS) as having a “moderate to severe,” “severe,” or “very severe” rill and inter-rill erosion hazard; and
c. Areas that are exposed to the erosion effects of wind or water.
2. Landslide Hazard Areas. Landslide hazard areas include 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, aspect, structure, or hydrology. Examples include, but are not limited to:
a. Areas that have historically been prone to land sliding.
b. Areas containing soil types identified by the Natural Resources Conservation Service (NRCS) as unstable and prone to landslide hazard.
c. Areas with slopes greater than 15 percent, hillsides with intersecting geologic contacts with relatively permeable sediment overlying a relatively impermeable sediment or bedrock, and springs or groundwater seepage.
d. Areas that are potentially unstable as a result of rapid stream incision or stream bank erosion.
e. Areas with slopes of 40 percent or steeper and with a vertical relief of 10 or more feet except areas composed of consolidated rock.
3. Mine Hazard Areas. Mine hazard areas include areas that are directly underlain by, adjacent to, or affected by mine workings such as adits, tunnels, drifts, or air shafts with the potential for creating large underground voids susceptible to collapse, tailings piles, and waste rock. In addition, steep and unstable slopes created by open mines, tailings and waste rock piles have the potential for being mine hazard areas. Mine hazard areas are based upon the identification of active or historic mining activity and site-specific information regarding topography and geology. There are no known mine sites in Kettle Falls.
4. Seismic Hazard Areas. Seismic hazard areas are subject to severe risk of damage as a result of earthquake induced ground shaking, slope failure, settlement or soil liquefaction. There are no known active faults in Kettle Falls.
5. Volcanic Hazard Areas. Volcanic hazard areas are subject to pyroclastic flows, lava flows, and inundation by debris flows, mudflows, or related flooding resulting from volcanic activity. There are no such areas in the City of Kettle Falls.
C. Mapping. NRCS maps shall be used to identify areas of erosion potential. Soils information should be combined with site-specific information (rills, inter-rills, and wind erosion) to determine if erosion hazard is present on the site.
D. Standards. In addition to the general provisions of this chapter and the requirements of the underlying zone, the following minimum standards shall apply to development activities within and adjacent to geologic hazard areas:
1. Any critical areas report for a geologically hazardous area shall include a geotechnical analysis completed by a qualified professional with expertise in the particular hazard(s) present in a given critical area.
2. Alterations of geologically hazardous areas or associated buffers may only occur for activities that:
a. Will not increase the threat of the geological hazard to adjacent properties beyond predevelopment conditions;
b. Will not adversely impact other critical areas;
c. Are designed so that the hazard to the project is eliminated or mitigated to a level equal to or less than predevelopment conditions; and
d. Are certified as safe as designed and under anticipated conditions by a qualified engineer or geologist, licensed in the state of Washington.
3. 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).
4. 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 required, to assist in stabilization of the areas and to discourage establishment of invasive plants.
5. Structures and improvements shall be clustered to avoid geologically hazardous areas and other critical areas.
6. Every erosion hazard area mitigation plan shall include a runoff management plan or an erosion control plan to reduce sedimentation problems.
7. Development and activities located within landslide or erosion hazard areas shall provide for long-term slope stability, and design shall incorporate the following standards:
a. 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;
b. Structures and improvements shall be located to preserve the most critical portion of the site and its natural landforms and vegetation;
c. The proposed development shall not result in greater risk or a need for increased buffers on neighboring properties;
d. The use of retaining walls that allow the maintenance of existing natural slope area is preferred over graded artificial slopes; and
e. Development shall be designed to minimize impervious lot coverage.
8. 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.
9. Subdivision of lands in erosion, landslide, and mine hazard areas is subject to the following:
a. 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.
b. 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.
10. Should a mine hazard area be identified in Kettle Falls, the site shall be noted on site plans for any development activity, and a geotechnical analysis shall be required to determine safety distances.
11. Prior to development of a site that is contaminated from previous mining activities, and where a significant hazard to health or the environment may be identified, the landowner or other project proponent shall be required to prepare and implement a reclamation plan.
All development activities in seismic hazard areas shall be required to conform to the applicable provisions of the Uniform Building Code that contains structural safeguards to reduce the risks from seismic activity.
E. The city shall require a geotechnical report for all development proposed in a geologically hazardous area.
1. All geotechnical reports shall be prepared by a civil engineer licensed to practice in the state of Washington.
2. A geotechnical report shall include a description of geology of the site, conclusions and recommendations regarding the effect of geologic conditions on the proposed development, and the options and recommendations on the suitability of the site to be developed. The report shall evaluate the actual presence of the geologic conditions giving rise to the geologic hazard and an evaluation of the safety of the proposed project and identification of construction practices, monitoring programs and other mitigation measures necessary. A bibliography of scientific citations shall be included as necessary.
3. The geotechnical report shall include a certification from the engineer preparing the report, including the engineer’s professional stamp and signature, stating all of the following:
a. The risk of damage from the project, both on and off site, is minimal;
b. The project will not materially increase the risk of occurrence of the hazard;
c. The specific measures incorporated into the design and operation plan of the project to eliminate or reduce the risk of damage due to the hazard; and
d. Mitigation of adverse site conditions including slope stabilization measures and seismically unstable soils, if applicable.
4. All mitigation measures, construction techniques, recommendations and technical specifications provided in the geotechnical report shall be applied during the implementation of the proposal. The engineer of record shall submit sealed verification at the conclusion of construction that development occurred in conformance with the approved plans. (Ord. 1803, §1, 2022).