Chapter 19.400
GEOLOGICALLY HAZARDOUS AREAS
Sections:
19.400.405 Purpose and applicability.
19.400.410 General requirements.
19.400.415 Designation of geologically hazardous areas.
19.400.420 Erosion hazard areas.
19.400.425 Landslide hazard areas.
19.400.430 Seismic hazard areas.
19.400.435 Development standards.
19.400.445 Recording and disclosure.
19.400.405 Purpose and applicability.
A. This chapter regulates uses and activities in those areas susceptible to erosion, sliding, earthquake, or other geologic events. Some geological hazards can be reduced or mitigated by engineering, design, or modified construction or mining practices so that risks to public health and safety are minimized.
The intent of this chapter is to:
1. Provide standards to protect human life and property from potential risks;
2. Regulate uses of land in order to avoid damage to structures and property being developed and damage to neighboring land and structures;
3. Control erosion, siltation, and water quality to protect anadromous and resident fish and shellfish;
4. Provide controls to minimize erosion caused by human activity; and
5. Use innovative site planning by placing geologically hazardous areas and buffers in open space and transferring development density to suitable areas on the site.
B. This chapter applies to development activities, actions requiring project permits, and clearing, except those identified as exempt in Section 19.100.125 and except those activities related to soils testing or topographic surveying of slopes for purposes of scientific investigation, site feasibility analysis, and data acquisition for geotechnical report preparation, provided it can be accomplished without road construction.
(Ord. 545 (2017) § 5 (Appx. (part)), 2017: Ord. 351 (2005) § 30, 2005: Ord. 217 (1998) § 3, (part), 1998)
19.400.410 General requirements.
A. Any development activity or action requiring a project permit or any clearing within an erosion or landslide area shall:
1. Comply with the requirements in an approved geotechnical report when one is required, including application of the largest buffer and/or building setback;
2. Utilize best management practices (BMPs) and all known and available technology appropriate for compliance with this chapter and typical of industry standards;
3. Prevent collection, concentration or discharge of storm water or groundwater within an erosion or landslide hazard area and be in compliance with Title 12 (Storm Water Drainage);
4. Minimize impervious surfaces and retain vegetation to minimize risk of erosion or landslide hazards.
B. Any development activity or action requiring a project permit or any clearing within an erosion or landslide area shall not:
1. Result in increased risk of property damage, death or injury;
2. Cause or increase erosion or landslide hazard risk;
3. Increase surface water discharge, sedimentation, slope instability, erosion or landslide potential to adjacent downstream and down-drift properties beyond predevelopment conditions;
4. Adversely impact wetlands, fish and wildlife habitat conservation areas or their buffers; or
5. Be identified as a critical facility necessary to protect public health, safety and welfare. This includes, but is not limited to, schools, hospitals, police stations, fire departments and other emergency response facilities, nursing homes, and hazardous material storage or production.
C. Field Marking Requirements. The proposed clearing for the project and all critical area buffers shall be marked in the field for inspection and approval by the department prior to beginning work. Field marking requirements for construction of a single-family dwelling will be determined on a case-by-case basis by the department. The field marking of all buffers shall remain in place until construction is completed, and final approval is granted by the department. Permanent marking may be required as determined necessary to protect critical areas or its buffer.
D. Clearing, Grading and Vegetation Removal.
1. Minor pruning of vegetation for view enhancement may be allowed through consultation with the department. The thinning of limbs on individual trees is preferred to topping of trees for view corridors. Total buffer thinning shall not exceed twenty-five percent and no more than thirty percent of the live tree crowns shall be removed.
2. Vegetation shall not be removed from a landslide hazard area, except for hazardous trees based on review by a qualified arborist or as otherwise provided for in a vegetation management and restoration plan.
3. Seasonal Restrictions. Clearing and grading shall be limited to the period between May 1st and October 1st, unless the applicant provides an erosion and sedimentation control plan prepared by a professional engineer licensed in the state of Washington that specifically and realistically identifies methods of erosion control for wet weather conditions.
4. Only the clearing necessary to install temporary erosion control measures will be allowed prior to clearing for roads and utilities construction.
5. The faces of cut and fill slopes shall be protected to prevent erosion as required by the engineered erosion and sedimentation control plan.
6. Clearing for roads and utilities shall be the minimum necessary and shall remain within marked construction limits.
7. Clearing for overhead power lines shall be the minimum necessary for construction and will provide the required minimum clearances for the serving utility corridor.
E. Existing Logging Roads. Where existing logging roads occur in geologically hazardous areas, a geological assessment may be required prior to use as a temporary haul road or permanent access road under a conversion or COHP forest practices application.
F. The department may also require:
1. Clustering to increase protection to geologically hazardous areas; or
2. Enhancement of buffer vegetation to increase protection to geologically hazardous areas.
(Ord. 545 (2017) § 5 (Appx. (part)), 2017)
19.400.415 Designation of geologically hazardous areas.
The county has designated geologically hazardous areas pursuant to RCW 36.70A.170 by defining them and providing criteria for their identification. Project proponents are responsible for determining whether a geologically hazardous area exists and is regulated pursuant to this chapter. The department will verify on a case-by-case basis the presence of geologically hazardous areas identified by project proponents. Specific criteria for the designation of geologically hazardous areas are contained in this chapter. While the county maintains some maps of potentially geologically hazardous areas, they are for informational purposes only and may not accurately represent all such areas.
(Ord. 545 (2017) § 5 (Appx. (part)), 2017)
19.400.420 Erosion hazard areas.
A. General. Erosion hazard areas include areas likely to become unstable, such as bluffs, steep slopes, and areas with unconsolidated soils. These include coastal erosion-prone areas and channel migration zones, and may be inclusive of landslide areas.
B. Potential Erosion Hazard Areas. Potential erosion hazard areas are depicted on the Kitsap County erosion hazards map. These potential erosion hazard areas are identified using the following criteria:
1. Areas of High Erosion Hazard.
a. Channel migration zones, as mapped by the Washington Department of Ecology;
b. Coastal erosion with a sediment source rating value of 0.6 to 1.0, per the Prioritization Analysis of Sediment Sources in Kitsap County;
2. Areas of Moderate Erosion Hazard.
a. Slopes fifteen percent or greater, not classified as I, U, UOS, or URS, with soils classified by the U.S. Department of Agriculture NRCS as “highly erodible” or “potentially highly erodible”;
b. Coastal erosion with a sediment source rating value of 0.3 to 0.6 per the Prioritization Analysis of Sediment Sources in Kitsap County.
C. Erosion Hazard Indicators. The project proponents are responsible for determining actual presence and location of an erosion hazard area. These areas may be indicated by, but not limited to, the following:
1. Any of the above criteria currently identified in subsection (B) of this section or amended hereafter.
2. Coastal Erosion Hazards.
a. Areas with active bluff retreat that exhibit continuing sloughing or calving of bluff sediments, resulting in a vertical or steep bluff face with little or no vegetation;
b. Lands located directly adjacent to freshwater or marine waters that are identified as regressing, retreating, or potentially unstable as a result of undercutting by wave action or bluff erosion. The limits of the active shoreline erosion hazard area shall extend landward to include that land area that is calculated, based on the rate of regression, to be subject to erosion processes within the next ten-year time period.
3. Channel Migration Zones. The lateral extent that a river or stream is expected to migrate over time due to hydrologically and geomorphologically related processes, as indicated by historic record, geologic character, and evidence of past migration over the past one hundred years.
(Ord. 545 (2017) § 5 (Appx. (part)), 2017)
19.400.425 Landslide hazard areas.
A. General. Landslide hazard areas include those areas at risk of mass movement due to a combination of geologic, topographic, and hydrologic factors, such as bedrock, soil, slope (gradient), slope aspect, structure, hydrology, and other factors. Landslide hazards are further classified as either shallow or deep-seated.
B. Potential Landslide Hazard Areas. Potential landslide hazard areas are depicted on the Kitsap County landslide hazards map. These potential landslide hazard areas are identified using the following criteria:
1. Areas of High Landslide Hazard.
a. Shallow landslide areas with factor of safety (FS) of 0.5 to 1.5. FS is a method (Harp, 2006) for determining slope stability based on the angle of the slope from LiDAR elevation data and strength parameters.
b. Areas with slopes greater to or equal to 30 percent in grade and deemed by a qualified geologist or geotechnical engineer to meet the criteria of U, UOS, or URS.
c. All deep-seated landslide areas.
2. Areas of Moderate Landslide Hazard.
a. Shallow landslide areas with FS of 1.5 to 2.5.
b. Slopes of fifteen percent or greater and not classified as I, U, UOS, or URS, with soils classified by the U.S. Department of Agriculture NRCS as “highly erodible” or “potentially highly erodible”; or slopes of fifteen percent or greater with springs or groundwater seepage.
c. Slopes in all areas equal to or greater than forty percent.
C. Landslide Hazard Indicators. Project proponents are responsible for determining the actual presence and location of a landslide hazard area. These areas may be indicated by, but not limited to, the following:
1. Any of the above criteria currently identified in subsection (B) of this section or amended hereafter;
2. Areas of historic failures, including areas of unstable, old and recent landslides or landslide debris within a head scarp;
3. Areas within active bluff retreat that exhibit continuing sloughing or calving of bluff sediments, resulting in a vertical or steep bluff face with little or no vegetation;
4. Hillsides that intersect geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment or bedrock;
5. Slopes that are parallel or sub-parallel to planes of weakness, such as bedding planes, joint systems, and fault planes in subsurface materials;
6. Areas exhibiting geomorphological features indicative of past slope failure, such as hummocky ground, back-rotated benches on slopes, etc.;
7. Areas with tension cracks or ground fractures along and/or near the edge of the top of a bluff or ravine;
8. Areas with structures that exhibit structural damage such as settling and cracking of building foundations or separation of steps or porch from a main structure that is located near the edge of a bluff or ravine;
9. The occurrence of toppling, leaning, bowed, or jackstrawed trees that are caused by disruptions of ground surface by active movement;
10. Areas with slopes containing soft or liquefiable soils;
11. Areas where gullying and surface erosion have caused dissection of the bluff edge or slope face as a result of drainage or discharge from pipes, culverts, ditches, and natural drainage courses;
12. Areas where seeps, springs or vegetative indicators of a shallow groundwater table are observed on or adjacent to the face of the slope;
13. Areas that include alluvial or colluvial fans located at the base of steep slopes and drainages;
14. Areas within two hundred feet of areas classified as U, UOS, or URS.
(Ord. 545 (2017) § 5 (Appx. (part)), 2017)
19.400.430 Seismic hazard areas.
A. General. Seismic hazard areas are areas subject to severe risk of damage as a result of earthquake-induced land sliding, seismic ground shaking, dynamic settlement, fault rupture, soil liquefaction, or flooding caused by tsunamis and seiches.
B. Potential Seismic Hazard Areas. Potential seismic hazard areas are depicted on the Kitsap County seismic hazards map. These potential seismic hazard areas are identified using the following criteria:
1. Areas of high seismic hazard are those areas with faults that have evidence of rupture at the ground surface.
2. Areas of moderate seismic hazard.
a. Areas susceptible to seismically induced soil liquefaction, such as hydric soils as identified by the NRCS, and areas that have been filled to make a site more suitable for development. This may include former wetlands that have been covered with fill.
b. Areas identified as Seismic Site Class D, E, and F.
c. Faults without recognized evidence of rupture at the ground surface.
C. Seismic Hazard Indicators. Project proponents are responsible for determining actual presence and location of a seismic hazard area. These areas may be indicated by, but not limited to, the following:
1. Any of the above criteria currently identified in subsection (B) of this section or amended hereafter;
2. Areas identified as potential landslide areas, including slopes that can become unstable as a result of strong ground shaking, even though these areas may be stable under nonseismic conditions;
3. Areas identified as high and moderate liquefaction and dynamic settlement hazard areas by the Washington Department of Natural Resources, including areas underlain by unconsolidated sandy or silt soils and a shallow groundwater table (static groundwater depth less than thirty feet) capable of liquefying in response to earthquake shaking. Dynamic settlement hazard areas are those underlain by more than ten feet of loose or soft soil not susceptible to liquefaction, but that could result in vertical settlement of the ground surface in response to earthquake shaking;
4. Tsunami and seiche hazard areas. Generally, these are areas that are adjacent to Puget Sound marine waters and lakes that are designated as “A” or “V” zones as identified by FEMA and depicted on the FEMA maps or other maps adopted by Kitsap County;
5. Fault rupture hazard areas, including areas where displacement (movement up, down, or laterally) of the ground surface has occurred during past earthquake(s) in the Holocene Epoch, and areas adjacent that may be potentially subject to ground surface displacement in a future earthquake.
(Ord. 545 (2017) § 5 (Appx. (part)), 2017)
19.400.435 Development standards.
A. Erosion and Landslide Hazard Development Standards.
1. Development activities or actions requiring project permits or clearing shall not be allowed in landslide hazard areas unless a geotechnical report demonstrates that building within a landslide hazard area will provide protection commensurate to being located outside the landslide hazard area and meets the requirements of this section. This may include proposed mitigation measures.
2. Top of Slope Building Setback. All development activities or actions that require project permits or clearing in erosion and landslide hazard areas shall provide native vegetation from the toe of the slope to twenty-five feet beyond the top of slope, with an additional minimum fifteen-foot building and impervious surface setback, unless otherwise allowed through a geologic assessment. The minimum building and setback shall be increased from the top of the slope as follows:
a. For high landslide hazard areas, the setback shall be equal to the height of the slope (1:1 horizontal to vertical) plus the greater of one-third of the vertical slope height or twenty-five feet.
b. For moderate landslide hazard areas, the setback shall be forty feet from the top of slope.
3. Toe of Slope Building Setback. A geotechnical report may be required based on slope height and stability indicators. Where slope hazard indicators are not identified, the requirements of Chapter 14.04, the Kitsap County Building and Fire Code, will apply.
4. The department may require a larger native vegetation width than the standard buffer distance as determined above, if any of the following are identified through the geological assessment process:
a. The adjacent land is susceptible to severe erosion and erosion control measures will not effectively prevent adverse impacts; or
b. The area has a severe risk of slope failure or downslope storm water drainage impacts.
5. The minimum native vegetation width and/or building setback requirement may be decreased if a geotechnical report demonstrates that a lesser distance, through design and engineering solutions, will adequately protect both the proposed development and the erosion or landslide hazard area. The department may decrease the setback when such a setback would result in a greater than 1:1 slope setback.
B. Seismic Hazard Development Standards.
1. Development activities or actions requiring a project permit occurring within two hundred feet of a “high hazard” seismic hazard area may be allowed with an approved geotechnical report that confirms the site is suitable for the proposed development and addresses any fill or grading that has occurred on the subject parcel.
2. Development activities or actions requiring a project permit within a seismic hazard area shall be in accordance with Chapter 14.04, the Kitsap County Building and Fire Code.
(Ord. 545 (2017) § 5 (Appx. (part)), 2017: Ord. 351 (2005) § 32, 2005. Formerly 19.400.415)
19.400.440 Review procedures.
A. Map Review. The Kitsap County geologically hazardous areas maps (erosion, landslide, and seismic) provide an indication of where potential geologically hazardous areas are located within the county. The department will complete a review of the map to determine if the proposed activity is located within a hazard area.
B. A geological assessment shall be required when the proposed activity is located within a potential hazard area.
C. A qualified professional, as described in Section 19.700.715, shall complete a field investigation and geological assessment to determine whether or not the site for the proposed activity is affected by the geologic hazard, as provided in subsection (D) of this section.
D. The geological assessment shall be submitted in the most applicable form as follows:
1. A geological letter. When the geologist or geotechnical professional finds that no hazard area exists within two hundred feet of the site, a stamped letter may be submitted demonstrating those findings;
2. A geological report. When the geologist finds that a geologically hazardous area exists within two hundred feet of the site, but will not impact the site or need engineering design recommendations;
3. A geotechnical report. When the geotechnical engineer finds that a geologically hazardous area exists within two hundred feet of the site, and will require engineering design recommendations or other mitigation measures necessary in order to construct or develop within the geologically hazardous area.
E. The department shall review the geological assessment and either:
1. Accept the geological assessment and approve the application; or
2. Reject the geological assessment and require revisions or additional information.
(Ord. 545 (2017) § 5 (Appx. (part)), 2017)
19.400.445 Recording and disclosure.
The following information shall be included in a notice to title that must be signed, notarized, and recorded with the county auditor prior to permit issuance for development in a geologically hazardous area requiring a geotechnical report:
A. An abstract and description of the specific types of risks identified in the geotechnical report;
B. A statement that the owner(s) of the property understands and accepts the responsibility for the risks associated with developments on the property given the described condition, and agrees to inform future purchasers and other successors and assignees of the risks; and
C. A statement that the owner(s) of the property acknowledge(s) that this chapter does not create liability on the part of Kitsap County or any officer or employee thereof for any damages that result from reliance on this chapter or any administrative decision lawfully made thereunder.
(Ord. 545 (2017) § 5 (Appx. (part)), 2017)