Loading...
HomeMy WebLinkAbout4 Article V Geohazard Track ChangesArticle V. Geologically Hazardous Areas 18.22.500 Purpose. The purpose of this article is to reduce risks to human life and safety and reduce the risk of damage to structures and property from geologic hazards, to allow for natural geologic processes supportive of forming and maintaining fish and wildlife habitat, and to regulate and inform land use and planning decisions. It is recognized thatSince the elimination of all risk from geologic hazards is not feasible to achieve but, the purpose of this article is to reduce the risk to acceptable levels. [Ord. 5-20 § 2 (Appx. A)] 18.22.510 Classification/designation. Geologically hazardous areas have the same meaning as in JCC 18.10.070 G definitions. Unless specifically noted below, principal sources of geologically hazardous areas mapped information are the Washington State Department of Natural Resources Geologic Hazard Maps (https://dnr.wa.gov/washington-geological-survey/geologic-hazards-and-environment/geologic- hazard-maps). Geologically hazardous: are the following classification and designation criteria are considered when classifying geologically hazardous areas: (1) Erosion hazard areas (as defined in JCC 18.10.050) (2) Landslide hazard areas (as defined in JCC 18.10.120). Landslide hazard areas include any areas susceptible to landslide because of any combination of bedrock, soil, slope (gradient), slope aspect, structure, hydrology, or other factors, as follows: (a) Areas of historic failures, such as: (i) Areas delineated by United States Department of Agriculture, Natural Resources Conservation Service as having a significant limitation for building site development; (ii) Coastal areas mapped by the Washington Department of Ecology Coastal Atlas as unstable, unstable old slides, and unstable recent slides; or (iii) Areas designated and mapped as quaternary slumps, earthflows, mudflows, lahars, or landslide hazards by the Washington Department of Natural Resources or the United States Geological Survey. (iv) Composite layer produced from the SCS Soils source coverage for soils types in Eastern Jefferson County, the Department of Ecology Coastal Zone Atlas of Jefferson County, and a review of topographic contours indicating steep slopes. This composite layer does not give detail attributes, but it does give an attribute with a rating factor which is a weighted probable problem rating based on severity of slope. (b) Areas where all three of the following conditions occur: (i) Slopes are steeper than 15 percent; (ii) Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment or bedrock; and (iii) Spring or groundwater seepage. (c) Areas that have shown movement during the Holocene epoch (from 10,000 years ago to present) or have been underlain or covered by mass wastage debris of this epoch. (d) Areas with slopes that are parallel or subparallel to planes of weakness (such as bedding planes, joint systems, and fault planes) in subsurface materials. (e) Areas with slopes having gradients steeper than 80 percent subject to rockfall during seismic shaking. (f) Areas that are potentially unstable as a result of rapid stream incision, stream bank erosion, and undercutting by wave action, including stream channel migration zones. (g) Areas that show evidence of, or are at risk from, snow avalanches. (h) Areas located in a canyon or on an active alluvial fan, presently or potentially subject to inundation by debris flows or catastrophic flooding. (i) Areas with a slope of 40 percent or steeper and with a vertical relief of 10 or more feet, except areas composed of bedrock. (3) Seismic hazard areas (as defined in JCC 18.10.190). Seismic areas are areas subject to damage as a result of earthquake induced ground shaking, slope failure, settlement, soil liquefaction, debris flows, lahars, and tsunamis. 18.22.520 Applicability. (1) Any development, land disturbing activity or use within a geologically hazardous area or its associated buffer shall be subject to the provisions of this article, unless specially exempted in JCC 18.22.230. 18.22.530 Protection standards. Geologically hazardous areas are areas that because of their susceptibility to erosion, sliding, earthquake, or other geological events, are not suited to siting commercial, residential, or industrial development consistent with public health or safety concerns. Unless specifically noted below, principal sources of geologically hazardous areas mapped information are the Washington Department of Natural Resources Geologic Hazard Maps (https://www.dnr.wa.gov/programs-and- services/geology/geologic-hazards/geologic-hazard-maps). (1) The following are geologically hazardous areas and subject to the standards of this article when mapped as high or moderate geologically hazardous areas: (a) General Standards for Erosion hazard areas (as defined in JCC 18.10.050). (b) Hazard and All Landslide hazard areas (as defined in JCC 18.10.120). Landslide hazard areas include any areas susceptible to landslide because of any combination of bedrock, soil, slope (gradient), slope aspect, structure, hydrology, or other factors, as follows: (i) Areas of historic failures, such as: (A) Areas delineated by United States Department of Agriculture, Natural Resources Conservation Service as having a significant limitation for building site development; (B) Coastal areas mapped by the Washington Department of Ecology Coastal Atlas as unstable, unstable old slides, Hazard (slight, moderate and unstable recent slides; or (C) Areas designated and mapped as quaternary slumps, earthflows, mudflows, lahars, or landslide hazards by the Washington Department of Natural Resources or the United States Geological Survey. (ii) Areas where all three of the following conditions occur: (A) Slopes are steeper than 15 percent; (B) Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment or bedrock; and (C) Spring or groundwater seepage. (iii) Areas that have shown movement during the Holocene epoch (from 10,000 years ago to present) or have been underlain or covered by mass wastage debris of this epoch. (iv) Areas with slopes that are parallel or subparallel to planes of weakness (such as bedding planes, joint systems, and fault planes) in subsurface materials. (v) Areas with slopes having gradients steeper than 80 percent subject to rockfall during seismic shaking. (vi) Areas that are potentially unstable as a result of rapid stream incision, stream bank erosion, and undercutting by wave action, including stream channel migration zones. (vii) Areas that show evidence of, or are at risk from, snow avalanches. (viii) Areas located in a canyon or on an active alluvial fan, presently or potentially subject to inundation by debris flows or catastrophic flooding. (ix) Areas with a slope of 40 percent or steeper and with a vertical relief of 10 or more feet, except areas composed of bedrock. (c) Seismic hazard areas (as defined in JCC 18.10.190). (d) Channel migration zones (CMZs) (as defined in JCC 18.10.030). (e) Seiche and landslide generated wave hazard areas (as defined in JCC 18.10.190). (f) Tsunami hazard areas (as defined in JCC 18.10.200). (g) Other geologic events, such as coal mine hazards and volcanic hazards, are not a known risk in Jefferson County, and are therefore not subject to review as part of the permitting process. [Ord. 5-20 § 2 (Appx. A)] 18.22.520 Regulated activities. (1) Any development activity or action requiring a project permit or any clearing within an erosion or landslide area shall: (a) Comply with the requirements in an approved geotechnical report when one is required, including application of the largest buffer or building setback; (b) Utilize best management practices (BMPs) and all known and available technology appropriate for compliance with this chapter and typical of industry standards; (c) Prevent collection, concentration or discharge of stormwater or groundwater within an erosion or landslide hazard area and be in compliance with JCC 18.30.070, Stormwater management standards; and (d) Minimize impervious surfaces and retain vegetation to minimize risk of erosion or landslide hazards. (2) Any development activity or action requiring a project permit or any clearing within an erosion or landslide area shall not: (a) Result in increased risk of property damage, death or injury; (b) Cause or increase erosion or landslide hazard risk; (c) Increase surface water discharge, sedimentation, slope instability, erosion or landslide potential to adjacent downstream and down-drift properties beyond predevelopment conditions; (d) Adversely impact wetlands, fish and wildlife habitat conservation areas or their buffers; or (e) 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. [Ord. 5-20 § 2 (Appx. A)] 18.22.530 Protection standards. (1) high) (a) Clearing, Grading and Vegetation Removal. (a) Minor(i) Within landslide hazard areas only 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 25 percent and no more than 30 percent of the live tree crowns shall be removed. (b) ii) Vegetation shall not be removed from a landslide hazard area, except for hazardous trees based on review by a qualifiedcertified arborist or as otherwise provided for in a vegetation management and restoration plan as determined by DCD. (c) (iii) Development, land use activities or uses shall not be allowed in landslide hazard areas or their associated buffers unless a geotechnical report or engineered stormwater plan (special 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. (iv) 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. (d) v) Only the clearing necessary to install temporary erosion control measures will be allowed prior to clearing for roads and utilities construction. (e) vi) The faces of cut and fill slopes shall be protected to prevent erosion as required by the engineered erosion and sedimentation control plan. (f) vii) Clearing for roads and utilities shall be the minimum necessary and shall remain within marked construction limits. (g) viii) Clearing for overhead power lines shall be the minimum necessary for construction and will provide the required minimum clearances for the serving utility corridor. (2) b) 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.conversion option harvest plan pursuant to JCC 18.20.160. (3) (c) The department may also require: (a) i) Clustering of development to increase protection to geologically hazardous areas; or (b) ii) Enhancement of buffer vegetation to increase protection to geologically hazardous areas. (4) d) The provisions in this section are in addition to those required in JCC 18.30.060, 18.30.060, Grading and excavation standards, and JCC 18.30.070, 18.30.070, Stormwater management standards. (5) e) If there is a conflict between applicable published standards, the more restrictive protection requirement applies. (6) (f) Drainage and Erosion Control. (a) i) An applicant submitting a project applicationfor development shall also submit, and have approved, a stormwater site plan that meets all the requirements of JCC 18.30.070( 18.30.070(4)(e), when the project application involves either of the following: (i) A) The alteration of a high or moderately high geologically hazardous area or its critical areaassociated buffer; or (ii) B) The creation of a new parcel within a high or moderately high geologically hazardous area; and (b) ii) Shall discuss, evaluate, and recommend methods to minimize sedimentation of adjacent properties during and after construction. (c) iii) Surface drainage shall not be directed across the face of a marine bluff that is mapped as high or moderate erodible or susceptible to landslide or debris flow. The applicant mustshall demonstrate that the stormwater discharge cannot be accommodated on site or upland by evidence presented in a geological assessment as required by JCC 18.22.945, 18.22.945, unless waived by the administrator. If drainage mustshall be discharged from a bluff to adjacent waters, it shall be collected above the face of the bluff and directed to the water by tight line drain and provided with an energy dissipating device at the shoreline, above ordinary high water mark (OHWM). (d) iv) The applicant mustshall clearly demonstrate in the geological assessment that stormwater quantity, quality, and flow path post-construction will be comparable to pre-construction conditions. (7) v) Stormwater conveyance through a properly designed stormwater pipe when no other stormwater conveyance alternative is available. The pipe shall be located above ground and be properly anchored or designed so that it will continue to function in the event of a slope failure or movement of the underlying materials and will not increase the risk or consequences of static or seismic slope instability or result in increased risk of mass wasting activity. (g) Vegetation Retention. TheAll of the following provisions regarding vegetation retention shall apply: (a) i) During clearing for roadways and utilities, all trees and understory vegetation lying outside of approved construction limits shall be retained to the maximum extent practicable; (b) ii) Clearing limits, as shown on the approved site plan, shall be marked by orange construction barrier fencing to be installed prior to beginning any clearing, grading, or other land -disturbing activities, including but not limited to clearing and grading; (c) iii) Vegetation within identified clearing limits may be removed upon permit issuance. All vegetation within the high or moderate geologically hazardous area or its critical areaassociated buffer, but outside the marked clearing limits, shall be retained. Cleared vegetation shall not be placed within a high or moderate geologically hazardous area unless it is used as part of a mitigation plan consistent with other critical area mitigation provisions, is reviewed by the geotechnical professional, and is approved by the administrator; and, (d) iv) Within a high risk CMZ, vegetation removal shall not be allowed. Vegetation removal outside of a high risk CMZ shall not be reviewed under this article. Should this provision conflict with other vegetation retention requirements specified elsewhere within this title, the more restrictive protection requirement applies. (8) Erosion and 2) Landslide Hazard Development Standards. (a) 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 measuresstandards for moderate and high hazard. (b) a) 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 25 feet beyond the top of slope, with an additional minimum 15-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 shall be as follows: (i) 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 25 feet. (ii) For moderate landslide hazard areas, the setback shall be 40 feet from the top of slope. (9) Geotechnical Report for Toe of Slopeb) Building Setback May Be Required. A geotechnical report may be required based on setback from toe of slope. The setback shall be equal to half the height and stability indicators.of the slope (1:1 horizontal to vertical) plus 15 feet (per IBC 1808.7). (10) c) Larger Native Vegetation Width May Be Requirednative vegetation width may be required. 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) i) The adjacent land is susceptible to severe erosion and erosion control measures will not effectively prevent adverse impacts; (b) ii) The area has a severe risk of slope failure or downslope stormwater drainage impacts; or (c) iii) The minimum native vegetation width 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. (11) Seismic Hazard Development Standards. (a) Development activities or actions requiring a project permit occurring within 200 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. (b) Development activities or actions requiring a project permit within a seismic hazard area shall be in accordance with JCC Title 15. (12) d) Reducing Buffer Widths.buffer widths. The administrator may reduce geologically hazardous area buffers as follows: (a) i) Buffers may be reduced by up to 25 percent with a geotechnical report prepared by a geotechnical professional with a state stamp; provided, the geotechnical report identifies recommendations for preventing or minimizing risks post-development. The geotechnical report should at a minimum include the setback of structures from the landslide hazard area, the limits to removal of natural vegetation, the location of septic system and other utilities, limits to the timing of land disturbing activity and construction, and the location and method of stormwater management unless waived by the administrator. (b) All buffer reductions 25 percent or greater and all development within a high or moderate geologically hazardous area shall require a geotechnical report prepared by a geotechnical professional.ii) The administrator may require a third-party review based on JCC 18.22.930 18.22.930 or the applicant enters into an indemnity and hold harmless agreement with the countyCounty that is approved by the county’sCounty’s risk manager and the prosecuting attorney. If the administrator requires a third-party review of the geotechnical report, the administrator shall be responsible for identifying and transmitting the geotechnical report to the third-party reviewer. (13) e) Increasing Buffer Widthsbuffer widths. Buffer widths may be increased on a case-by- case basis, as determined by the administrator, to protect the functions and values of a geologically hazardous area and to reduce risks to public safety and welfare. Information that may be used to support this determination, includes but is not limited to: (a) (i) The landslide area is unstable and active.; (b) ii) The adjacent land is susceptible to severe landslide or erosion, and erosion control measures will not effectively protect the proposed project from the risks posed by the landslide hazard area.; and (c) (iii) The adjacent land has minimal vegetative cover. (14) Landslide Hazard Areas – Additional Standards. The following activities may be allowed in active landslide hazard areas when all reasonable measures have been taken to minimize risks and other adverse effects associated with landslide hazards, and when the amount and degree of the alteration are limited to the minimum needed to accomplish the project purpose: (a) The standards of subsection (1) of this section shall apply. (b) Developments that will not increase the threat to the health or safety of people and will not increase potential for landslides on or off the site and meet the reasonable economic use exception in JCC 18.22.260. (c) (f) with the exception of engineered tight-lines for stormwater, new utility lines are allowed within a landslide hazard or its associated buffer through a critical area variance under JCC 18.22.250. Utility lines and pipes that are above ground, properly anchored or designed so that they will continue to function in the event of a slope failure or movement of the underlying materials and will not increase the risk or consequences of static or seismic slope instability or result in a risk of mass wasting. Such utility lines may be permitted only when the applicant demonstrates that no other feasible alternative is available to serve the affected population. This would include finding and recommendations in the geotechnical report that the proposed development will not impact the slope stability of the slope of the surrounding area. (d) (g) New access roads are allowed within a landslide hazard or its associated buffer through a variance. Access roads and trails that are engineered and built to standards that minimize the need for major repair or reconstruction beyond that which would be required in nonhazardnonhazardous areas. Access roads and trails may be permitted only if the applicant demonstrates that no other feasible alternative exists, including through the provisions of Chapter 8.24 RCW.chapter 8.24 RCW. If such access through critical areas is granted, exceptions or deviations from technical standards for width or other dimensions and specific construction standards to minimize impacts, including drainage and drainage maintenance plans, may be required. (e) Stormwater conveyance through a properly designed stormwater pipe when no other stormwater conveyance alternative is available. The pipe shall be located above ground and be properly anchored or designed so that it will continue to function in the event of a slope failure or movement of the underlying materials and will not increase the risk or consequences of static or seismic slope instability or result in increased risk of mass wasting activity. (15) Seismic Hazard Areas – Standards. Development may be allowed in seismic hazard areas when all of the following apply: (a) The standards of subsection (1) of this section shall apply. (b) Structures in seismic hazard areas shall conform to applicable analysis and design criteria of Chapter 18.15 JCC. (3) Seismic hazard areas protection standards. (a) The placement of buildings or structures meet the requirements of title 15 JCC. (b) Critical facility necessary to protect public health, safety and welfare shall be allowed only when there are no feasible alternative locations, and geotechnical analysis and design are provided that minimize potential damage to these facilities from earthquakes. This includes, but not limited to, schools, hospitals, police stations, fire departments and other emergency response facilities, nursing homes, and hazardous material storage or production. (c) Public roads, bridges, utilities, and trailspublic facilities shall be allowed when there are no feasible alternative locations, and geotechnical analysis and design are provided that minimize potential damage to roadway, bridge, and utility structures, and facilities will not be susceptible to damage from seismically induced ground deformation. Mitigation measures shall be designed in accordance with the most recent version of the American Association of State Highway and Transportation Officials (AASHTO) Manual or another appropriate document. (16) Tsunami Hazard Areas – Standards. (a) Thehazard areas protection standards of subsection (1) of this section shall apply. (a) (b) Public roads, bridges, utilities, and public facilities shall be allowed when there are no feasible alternative locations, and geotechnical analysis and design are provided that minimize potential damage to roadway, bridge, and utility structures, and public facilities will not be susceptible to damage from inundation. (a)(b) For development within tsunami hazard areas the proposed development shall be designed to provide protection from the tsunami hazard that meets the projected hazard on the Washington Department of Natural Resources Tsunami Inundation Maps. (b)(c) (c) For other low-lying coastal areas not included on the inundation maps, development shall be designed to provide protection for debris impact and an inundation as determined by current Washington Department of Natural Resource modeling, unless other measures can be shown to provide equal or greater protection. [Ord. 5-20 § 2 (Appx. A)] 18.22.540 Required assessments and reports. (1) Map Review. The Jefferson 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. (2) When a Geological Assessment Is Required. A geological assessment shall be required when the proposed activity is located within a potential hazard area. (3) Work Must Be Performed by a Geotechnical Professional. A geotechnical professional, as defined in JCC 18.10.070, 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 (4) of this section. (4) Geological Assessment Types. The geological assessment shall be submitted in the most applicable form as follows: (a) A geological letter. When the geotechnical professional finds that no moderate or high hazard area exists within 200 feet of the site, a stamped letter may be submitted demonstrating those findings; (b) A geological report. When the geotechnical professional finds that a moderate or high geologically hazardous area exists within 200 feet of the site, but will not impact the site or need engineering design recommendations; (c) A geotechnical report. When the geotechnical professional finds that a moderate or high geologically hazardous area exists within 200 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. (5) The department shall review the geological assessment and either: (a) Accept the geological assessment and approve the application; or (b) Reject the geological assessment and require revisions or additional information. [Ord. 5- 20 § 2 (Appx. A)] 18.22.550 Recording and disclosure. (1) 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 Jefferson County or any officer or employee thereof for any damages that result from reliance on this chapter or any administrative decision lawfully made under this chapter. (2) Expiration of Geotechnical Reports. Unless there are documented significant changes, modifications, or other geologic events to render an existing geotechnical report invalid, an existing report shall be considered valid. Validity shall be examined upon submittal of proposed developments or every five years, whichever is later. (3) Geologically Hazardous Areas – Marking Limits. The limits (or outer extent) of a geologically hazardous area shall be marked on site as follows: (a) High or moderately high geologically hazardous areas shall be identified and staked by a geotechnical professional. For landslide hazards, the top or toe of slope closest to the proposed activity shall be marked. For erosion hazards, seismic hazards, and high-risk channel migration zones, the extent of the geologically hazardous area closest to the proposed activity shall be staked on site. (b) Stakes shall be installed and marked as necessary to clearly identify the geologically hazardous areas present; provided, the distance between each of the stakes shall not exceed 50 feet. (c) Staked limits of the geologically hazardous area shall remain on site based on the type of application, as follows: (i) Stakes for building or septic applications shall remain in place until a final building certificate of occupancy for a building permit or a final for a septic permit is issued. (ii) Staking for a subdivision, a planned rural residential development, a binding site plan, or a rezone shall remain in place until a final county approval is issued. If, at the time of subsequent building, septic, or other land use application, the stakes are no longer in place, the administrator may require restaking of the geologically hazardous area by the project geotechnical professional. (iii) Staking for any other application requiring land use review shall remain in place until the department of community development has made a site visit to review the staking relative to property boundaries and proposed activities, as shown on a submitted site plan. (d) The staked location of the on-site geologically hazardous areas shall be shown on a site plan submitted with an application. (e) If more than one geologically hazardous area is present, only the most restrictive geologically hazardous area (area closest to the proposed activity) shall be staked by the geotechnical professional. (4) Buffer Marking. The location of the outer extent of geologically hazardous area buffers shall be marked in the field as follows: (a) Geologically hazardous areas and buffers shall be shown on a site plan submitted with an application. (b) Geologically hazardous area buffers shall be staked on site prior to beginning any clearing, grading, or other land-disturbing activities. The administrator may waive this requirement if all development activities are outside of the geologically hazardous area buffer. (c) The administrator may require signs be posted at the buffer edge if the proposed activity is commercial or industrial, or if the proposed activity is proposed on public lands. [Ord. 5-20 § 2 (Appx. A)]