Chapter 19.400
GEOLOGICALLY HAZARDOUS AREAS
Sections:
19.400.410 Geologically hazardous area categories.
19.400.415 Development standards.
19.400.405 Purpose.
This section applies to all regulated uses included in this title within the largest buffer or setback in areas designated as geologically hazardous areas, as categorized in Section 19.400.410 below. The intent of this section is to:
A. Provide standards to protect human life and property from potential risks;
B. Regulate uses of land in order to avoid damage to structures and property being developed and damage to neighboring land and structures;
C. Control erosion, siltation, and water quality to protect anadromous and resident fish and marine shellfish;
D. Provide controls to minimize shoreline erosion caused by human activity;
E. Use innovative site planning by placing geologically hazardous areas and buffers in open space and transferring development density to more suitable areas on the site.
(Ord. 351 (2005) § 30, 2005: Ord. 217 (1998) § 3, (part), 1998)
19.400.410 Geologically hazardous area categories.
A. Classification. The following categories shall be used in classifying geologically hazardous areas.
1. Areas of High Geologic Hazard.
a. Areas with slopes greater than or equal to 30 percent and mapped by the Coastal Zone Atlas or Quaternary Geology and Stratigraphy of Kitsap County as “Unstable” (U), “Unstable Old Land Slides” (UOS) or “Unstable Recent Slides” (URS).
b. Areas with slopes greater than 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.
2. Areas of Moderate Geologic Hazard.
a. Areas designated U, UOS, or URS in the Coastal Zone Atlas or Quaternary Geology and Stratigraphy of Kitsap County, with slopes less than 30 percent; or areas found by a qualified geologist to meet the criteria for U, URS, and UOS with slopes less than 30 percent; or
b. Slopes identified as “Intermediate” (I) in the Coastal Zone Atlas or Quaternary Geology and Stratigraphy of Kitsap County, or areas found by qualified geologist to meet the criteria of I; or
c. Slopes 15 percent or greater, not classified as I, U, UOS, or URS, with soils classified by the U.S. Department of Agriculture Natural Resources Conservation Service as “highly erodible” or “potentially highly erodible”; or
d. Slopes of 15 percent or greater with springs or groundwater seepage not identified in subsections (a), (b) or (c) above; or
e. Seismic Areas subject to liquefaction from earthquakes (Seismic Hazard Areas) such as hydric soils as identified by the Natural Resources Conservation Service, and areas that have been filled to make a site more suitable. Seismic areas may include former wetlands which have been covered with fill.
B. Site Specific Determinations. A geologic or geotechnical report is a site investigation process to evaluate the on-site geology affecting a subject property and proposed development. Should an applicant question the information the county must rely on to determine whether a location contains a geologically hazardous area or area of geologic concern, the county may ask the applicant to submit the appropriate geotechnical or geologic report to confirm or modify the existing information known about the area. The requirements for reports are contained in Special Reports, Chapter 19.700.
The intent of this provision is to allow obviously non-geologically hazardous sites to be determined as such. Where there is any ambiguity about the potential for geologic hazards whatsoever, the department will require a geotechnical or geological report, rather than make a non-geologically hazardous determination.
(Ord. 351 (2005) § 31, 2005: Ord. 217 (1998) § 3, (part), 1998)
19.400.415 Development standards.
This section applies to all regulated uses within designated geologically hazardous areas and their setbacks.
A. Review. Where applicable the department will approve, approve with conditions or deny the development proposal based on the department’s evaluation of site-specific conditions. The department will also consider any proposed mitigation measures included in a geotechnical report, if one is required.
B. Minimum Buffer Requirement. The buffer for all geologically hazardous areas shall include native vegetation from the toe of the slope to twenty-five feet beyond the top of the slope unless otherwise allowed through a geological report or a site-specific determination (Refer to Section 19.400.410(B)).
C. Building/Impervious Surface Setback Requirements.
1. Areas of High Geologic Hazard. Minimum building and impervious surface setback from the top of slope 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.
2. Areas of Moderate Geologic Hazard. Minimum building and impervious surface setback shall be forty feet from the top of slope. As required in Section 19.400.410(B), above, the twenty-five feet adjacent to the top of the slope shall be retained as a native vegetation buffer, with an additional minimum fifteen-foot building and impervious surface setback. The department may decrease the setback when such a setback would result in a greater than 1:1 slope setback or as may be allowed under Section 19.400.410(B) (Site Specific Determinations).
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 Title 14.04 of this code, the Kitsap County Building and Fire Code will apply.
D. Buffer and Building Setback Modifications.
1. Report Recommendations. The minimum native vegetation buffer 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 hazard and/or landslide hazard area (See Chapter 19.700). Should the geotechnical report indicate that a greater buffer and/or building setback are required than specified in subsections (B) and/or (C) above, the greater buffer and/or building setback shall be required. The department may determine through a site visit, a special report or mapping that an increased buffer and/or building setback is required from the critical area.
2. Vegetation Removal. Minor pruning of vegetation or tree removal for view enhancement, or elimination of danger trees to maintain slope integrity may be allowed, provided that such activity is approved by the department. The thinning of limbs on individual trees is preferred to the removal or topping of trees for view corridors. At a minimum, no more than thirty percent of the live tree crowns shall be removed. Total buffer thinning shall not exceed twenty-five percent.
E. Seasonal Restrictions. Clearing and grading shall be limited to the period between May 1 to October 1, 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.
F. 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.
G. Cut and Fill Slopes. The faces of all cut and fill slopes shall be protected to prevent erosion as required by the engineered erosion and sedimentation control plan.
H. Storm Water Standards. Storm water discharges shall be in compliance with Title 12 of this code (Storm Water Management).
I. Development Risk Standard. In cases where a special report indicates a significant risk to public health, safety and welfare, the department shall deny or require revision of the site development proposal.
J. Additional Clearing Standards.
1. Only the clearing necessary to install temporary erosion control measures will be allowed prior to the clearing for roads and utilities construction.
2. Clearing for roads and utilities shall be the minimum necessary and shall remain within marked construction limits.
3. Clearing for overhead power lines shall be the minimum necessary for construction and will provide the required minimum clearances of the serving utility corridor.
K. Existing Logging Roads. Where existing logging roads occur in geologically hazardous areas, a geological or geotechnical report (See Section 19.700.725) may be required prior to use as a temporary haul road or permanent access road under a conversion or COHP forest practices application.
L. Clustering Requirements. The department may require clustering to increase protection to geologically hazardous areas.
M. Vegetation Enhancement. The department may require enhancement of buffer vegetation to increase protection to geologically hazardous areas.
N. Seismic Hazard Area Development Standards.
1. Proposed new development within a seismic hazard area shall be in accordance with Chapter 14.04 of this code, the Kitsap County Building and Fire Code.
2. Applicants for public and commercial building proposals within seismic hazard areas shall submit a geotechnical report (See Section 19.700.725) addressing any fill or grading that has occurred on the subject parcel. Any fill placed for such development shall have documented construction monitoring as required by Title 14.04 of this code, the Kitsap County Building and Fire Code.
3. The development proposal may be approved, approved with conditions or denied based on the department’s evaluation of the proposed mitigation measures in the geotechnical report to reduce seismic risk.
O. Prohibitions.
1. Critical facilities, as defined in Chapter 19.150, are prohibited in areas of high geologic hazard.
2. In areas of high geologic hazard with slopes greater than eighty percent, no development will be allowed either on or within the defined buffer area, unless approved by the department after review of a geotechnical report. The defined buffer zone for geologically hazardous areas is defined in subsection (C) above.
3. On-site sewage disposal should be avoided in areas of high geologic hazard and their buffers. In cases where such areas cannot be avoided, review by a geologist or a geotechnical engineer licensed in the state of Washington will be required in coordination with the Kitsap County Health District.
(Ord. 351 (2005) § 32, 2005)