Crescent City, CA CALIFORNIA COASTAL ZONE RESOURCE PROTECTION PROCEDURES NATURAL AND MAN-MADE HAZARDS AVOIDANCE

Geologic Hazards. All proposed new development located in or near an area subject to geologic hazards shall be required to submit a geologic/soils/geotechnical study report prepared by a Certified Engineering Geologist, Geotechnical Engineer, or registered engineer qualified in hydrology and soil mechanics, as appropriate for the intended structural improvements, that identifies any geologic hazards affecting the proposed development site and any necessary mitigation measures. The geologic/soils/geotechnical report shall include a statement by the consulting professionals that the project site is suitable for the proposed development, that the development will be safe from geologic hazard, and that the development will in no way contribute to instability on or off the subject site. Such reports shall be subject to the review and approval of the department staff, and may include peer-review by a similarly-licensed professional.

Geology report. Applications for blufftop and shoreline development located in or near an area subject to geologic hazards, including but not limited to, areas of geologic hazard shown on the "National Seismic Hazards Maps" and/or the "Geology and Geomorphic Features Related to Landsliding" and "the North Coast Watersheds Mapping" series prepared for Del Norte County by the U.S. Geological Survey and California Geological Survey, respectively, shall be required to submit a geologic/soils/geotechnical study that identifies all potential geologic hazards affecting the proposed project site, all necessary mitigation measures, and contains a statement that the project site is suitable for the proposed development and that the development will be safe from geologic hazard.

Preparation and contents of geology report. A required geology report shall be prepared one or more qualified Certified Engineering Geologists (CEG), Registered Civil Engineers (RCE), Geotechnical Engineers (GE) or group of aforementioned disciplines approved by the city, with expertise appropriate to the site and anticipated hazard conditions, and shall be submitted with the planning permit application for the proposed development. The report shall consider, describe, and analyze the following:

Cliff geometry and site topography, extending the surveying work beyond the site as needed to depict unusual geomorphic conditions that might affect the site;

Historic, current, and foreseeable cliff erosion, including investigation of recorded land surveys and tax assessment records in addition to the use of historic maps and photographs where available, and possible changes in shore configuration and sand transport;

Geologic conditions, including soil, sediment, and rock types and characteristics, in addition to structural features such as bedding, joints, and faults;

Evidence of past or potential landslide conditions, the implications of such condition for the proposed development, and the potential effects of the development on landslide activity;

Impact of construction activity on the stability of the site and adjacent area;

Ground and surface water conditions and variations, including hydrologic changes caused by the development (e.g., introduction of sewage, effluent, and irrigation water to the groundwater system, alterations to surface drainage, and the like);

Potential erodibility of the site and mitigation measures to be used to ensure minimized erosion problems before and after construction (i.e., landscape and drainage design);

Effects of marine erosion on the coastal bluffs;

Potential effects of seismic forces resulting from a maximum credible earthquake;

Any other factors that might affect slope or bluff stability;

Whether the proposed project will be subject to or contribute to significant geologic instability throughout the one-hundred-year life span of the project;

Effects of future sea level rise on the development;

Slope stability and bluff erosion rate determination performed as outlined in Sections B.2 and B.3 below; and

An alternatives analysis of, and mitigation measures for, all potential impacts.

In addition to all applicable information required by sub-Section 3a-3n above, all applications for new shoreline structures shall include an analysis of beach erosion, wave run-up, and tsunami and flood hazards prepared by a licensed civil engineer with expertise in coastal engineering. These reports shall address and analyze the effects of said development in relation to the following:

The profile of the beach;

Surveyed locations of mean high tide lines acceptable to the State Lands Commission;

The availability of public access to the beach;

The area of the project site subject to design wave run-up, based on design conditions;

Foundation design requirements;

The long-term effects of proposed development on sand supply;

The Federal Emergency Management Agency Flood Insurance Rate Map (FEMA-FIRM) Base Flood Elevation and other mapped areas (A, B, or V zones);

Future projections in sea level rise; and

Project alternatives designed to avoid or minimize impacts to public access.

Blufftop and shoreline development hazards. A coastal development permit application for development with three hundred feet of a bluff line or edge as defined shall include the following supplemental information and analyses:

Public access information. Applications for blufftop or shoreline development, including but not limited to shoreline protective structures, shall include a site map that shows all existing easements, deed restrictions, or offers of dedication and/or other dedications for public access or open space and provides documentation that the development shall be located outside of and consistent with the provisions of such easement or offers.

Slope stability analysis. For the purpose of this section, quantitative slope stability analyses shall be undertaken as follows:

The analyses shall demonstrate a factor of safety greater than or equal to 1.5 for the static condition and greater than or equal to 1.1 for the seismic condition. Seismic analyses may be performed by the pseudostatic method, but in any case shall demonstrate a permanent displacement of less than fifty mm.

Slope stability analyses shall be undertaken through cross-sections modeling worst case geologic and slope gradient conditions. Analyses shall include postulated failure surfaces such that both the overall stability of the slope and the stability of the surficial units are examined.

The effects of earthquakes on slope stability (seismic stability) shall be addressed through pseudostatic slope analyses assuming a horizontal seismic coefficient of at least 0.15 grams, and shall be evaluated in conformance with the guidelines published by the American Society of Civil Engineers, Los Angeles Section (ASCE/SCEC), "Recommended Practices for Implementation of DMG Special Publication 117, Guidelines for Analyzing and Mitigating Landslide Hazards in California."

All slope analyses shall be performed using shear strength parameters (friction angle and cohesion), and unit weights determined from relatively undisturbed samples collected at the site. The choice of shear strength parameters shall be supported by direct shear tests, triaxial shear test, or literature references.

All slope stability analyses shall be undertaken with water table or potentiometric surfaces for the highest potential ground water conditions.

If anisotropic conditions are assumed for any geologic unit, strike and dip of weakness planes shall be provided, and shear strength parameters for each orientation shall be supported by reference to pertinent direct sheer tests, triaxial shear test, or literature.

When planes of weakness are oriented normal to the slope or dip into the slope, or when the strength of materials is considered homogenous, circular failure surfaces shall be sought through a search routine to analyze the factor of safety along postulated critical failure surfaces. In general, methods that satisfy both force and moment equilibrium (e.g., Spencer, Morgenstern-Price, and General Limit Equilibrium) are preferred. Methods based on moment equilibrium alone (e.g., Bishop's Method) also are acceptable. In general, methods that solve only for force equilibrium (e.g., Janbu's method) are discouraged due to their sensitivity to the ratio of normal to shear forces between slices.

If anisotropic conditions are assumed for units containing critical failure surfaces determined above, and when planes of weakness are inclined at angles ranging from nearly parallel to the slope to dipping out of slope, factors of safety for translational failure surfaces shall also be calculated. The use of a block failure model shall be supported by geologic evidence for anisotropy in rock or soil strength. Shear strength parameters for such weak surfaces shall be supported through direct shear tests, triaxial shear test, or literature references.

The selection of shear strength values is a critical component to the evaluation of slope stability. Reference should be made to American Society of Civil Engineers, Los Angeles Section (ASCE/SCEC), "Recommended Practices for Implementation of DMS Special Publication 117, Guidelines for Analyzing and Mitigating Landslide Hazards in California" when selecting shear strength parameters.

Bluff retreat rate. For the purpose of this chapter, the long-term average bluff retreat rate shall be determined by the examination of historic records, surveys, aerial photographs, published or unpublished studies, or other evidence that unequivocally show the location of the bluff edge through time. The long-term bluff retreat rate is an historic average that accounts both for periods of exceptionally high bluff retreat, such as during extreme storm events, and for long periods of relatively little or no bluff retreat. Accordingly, the time span used to calculate a site-specific long-term bluff retreat rate shall be as long as possible, but in no case less than fifty years. Further, the time interval examined shall include the strong El Niño winters of 1982-1983, and 1997-1998. The expected bluff retreat rate over the expected life of the development shall be based in part on the historic bluff retreat rate, but shall also include consideration of the effects of continued historic rates of sea level rise, potential accelerated sea level rise, increase in significant wave heights, and increase in storm intensity and frequency, as is expected under most scenarios of the Intergovernmental Panel on Climate Change or as anticipated in studies prepared for California coastal areas pursuant to Executive Order S-13-08.

Erosion control plan. All coastal development permit applications for development on blufftop and shoreline parcels shall include a site specific erosion control plan. The plan shall be prepared by a registered engineer qualified in hydrology and soil mechanics, and shall ensure that the development will not create nor contribute to the erosion or failure of any bluff face, and will eliminate or mitigate any adverse impacts on local shoreline sand supply to the maximum extent feasible. The plan shall identify drainage and erosion control features to ensure that surficial erosion or ground saturation will not that incorporate structural and non-structural stormwater runoff and water quality best management practices (BMPs) to control the volume, velocity, flow direction, and pollutant load of stormwater runoff from new development, including construction, grading, and landscaping, and bioswale treatment and/or other facilities designed to accommodate the eighty-fifth percentile one-hour rainfall event for volumetric-based systems and the eighty-fifth percentile twenty-four-hour precipitation event for flow-based facilities.

New Beachfront Development and Shoreline Structures. In addition to all applicable information required by sub-sections A and B above, all applications for new beachfront development or shoreline structures shall include an analysis of beach erosion, wave run-up, and tsunami and flood hazards prepared by a registered civil engineer with expertise in coastal processes. These reports shall address and analyze the effects of said development in relation to the following:

The profile of the beach;

Surveyed locations of mean high tide lines acceptable to the State Lands Commission;

The FEMA Base Flood Elevation and other mapped areas (A, B, or V zones);

Future projections in sea level rise;

The area of the project site subject to design wave run-up (normally the one-hundred-year wave event), based on design beach and water level conditions (normally taken to be an eroded, winter profile beach, high tide and the future erosion and sea level rise conditions appropriate for the project life);

Foundation design requirements;

The long-term effects of proposed development on sand supply; and

Project alternatives designed to avoid or minimize impacts to beach and public access.

Sea Level Rise Analysis. Applications for development adjacent to the shore or that may be subject to the influence of sea level over the life of the project shall include an analysis of possible impacts from sea level rise. The analysis shall take into account the best available scientific information with respect to the effects of long-range sea level rise for all requisite geologic, geotechnical, hydrologic, and engineering investigations. Residential and commercial development at nearshore sites shall analyze potential coastal hazard sensitivities for a range of potential global sea level rise scenarios, from three to six feet per century. The analysis shall also take into consideration regional sea level variability, localized uplift or subsidence, local topography, bathymetry and geologic conditions. A similar sensitivity analysis shall be performed for critical facilities, energy production and distribution infrastructure, and other development projects of major community significance using a minimum rise rate of four and one-half feet per century. These hazard analyses shall be used to identify current and future site hazards, to help guide site design and hazard mitigation and to identify sea level thresholds after which limitations to the development's design and siting would cause the improvements to become significantly less stable.

Public access information. Applications for blufftop or shoreline development, including but not limited to shoreline protective structures, shall include a site map that shows all existing easements, deed restrictions, or offers-of-dedication and/or other dedications for public access or open space and provides documentation that the development shall be located outside of and consistent with the provisions of such easement or offers. The application shall also identify all available beach access within one-half miles upcoast or downcoast of the proposed development site.

Floodplain development. A coastal development permit application for development within an identified floodplain in the coastal zone, including but not limited to those areas shown on FEMA-FIRM community panel series 0615C 0214E, 0615C 0218E, 06015C 0327E, and 0615C 0331E, shall include the following supplemental information and analyses:

Site plans and elevations depicting the height of the base flood elevation relative to the floor height of the structures; and

Copies of any flood elevation certificates, flood-proofing certificates, or other as-built verifications of floodplain management conformance prepared for the structures.

Tsunami runup and inundation. A coastal development permit application for development within an identified tsunami runup and/or inundation area, including but not limited to those areas depicted on the latest government-prepared tsunami hazard maps, shall include the following supplemental information and analyses:

An analysis of the vulnerability of any proposed structural improvements to instability or damage associated with tsunami inundation up to and including wave heights resulting from a near-source maximum credible Cascadia subduction zone seismic event. The analysis shall take into consideration local uplift or subsidence, and a three- to six-foot rise in sea level over one hundred years, a minimum of four and one-half feet of sea level rise over one hundred years for critical facilities, and greater sea level rise rates if development is expected to have a long economic life, the proposed development has few options for adaptation to sea level higher than the design minimum, or if the best available scientific information at the time of review supports a higher design level. The analysis shall address potential damage and instability from in-coming and out-flow waters, including wave strike and foundation scour. The analysis shall identify design and siting mitigation measures to feasibly reduce potential exposure of persons and property to flooding and instability risks;

A tsunami safety plan containing information as to the existence of the threat of tsunamis from both distant- and local-source seismic events, the need for prompt evacuation upon the receipt of a tsunami warning or upon experiencing seismic shaking for a local earthquake, and the evacuation route to take from the development site to areas beyond potential inundation.

Wildfire hazards. A coastal development permit application for development within an identified wildfire hazard areas, including but not limited to those areas depicted on the latest adopted fire hazard severity maps, shall include the following supplemental information and analyses:

A fire safe compliance plan, illustrating how the development would conform to the state and local agency emergency vehicle access, street signage, fuel modification, defensible space, fire-fighting water supply, and building code standards applicable to the class of development.

Hazardous materials. A coastal development permit application for commercial and/or industrial development proposing the use, storage, or transportation of hazardous materials subject to state and federal regulation, shall include the following supplemental information and analyses:

An accidental spill/release response and cleanup plan, detailing training and logistics for prompt response to, containment of, and clean up of, any accidentally released or spilled hazardous materials. The plan will include an inventory of spill/release containment and clean-up materials and equipment to be stockpiled at the project site, responsible parties for initiating a response activity and provisions for notification of responsible agencies, as appropriate, including but not limited to the county department of public health, county sheriff's office, police and fire departments, and state and federal oil spill responders.

(Ord. of 2-22-2011(1))

Development in areas subject to natural or man-made hazards shall only be authorized subject to the following conditions:

Geologic hazard areas.

All recommendations of the consulting Certified Engineering Geologist, Geotechnical Engineer, and registered engineer(s) and/or the department staff shall be incorporated into all final design and construction including foundations, grading, sewage disposal, and drainage. Final plans must be reviewed and approved for compliance with geologic recommendations by the consulting registered engineer(s) and the department staff; and

Final plans approved by the consulting professionals and the department staff shall be in substantial conformance with the plans approved by the final city decision making body relative to construction, grading, sewage disposal and drainage. Any substantial changes in the proposed development approved by the city which may be required by the project consultants or department staff shall require an amendment to the permit or a new coastal development permit.

Blufftop and shoreline sites.

The development is sited such that it will remain safe from coastal erosion and slope instability for the full span of its economic life (usually one hundred years);

The erosion control plan is implemented as part of the approved development;

Provisions are included in the authorization should slope instability and/or bluff retreat occur at locations or rates other than anticipated, the permittee is required to seek a permit amendment for relocation of the structure or to authorize other stabilizing actions once the blufftop edge or area of instability encroach within ten feet of the structure; and

Rights to future construction of a sea wall, cliff retaining wall, or other protective devices that would substantially alter natural landforms along bluffs and cliffs are waived by recorded deed restriction.

Floodplains and other flood-prone sites.

The development has been conditioned to meet all requirements of the flood damage prevention Chapter 21.45; and

Maintenance projects involving the removal of materials from erosion control and flood control facilities constructed on watercourses are required, where feasible, to be placed at appropriate points on the shoreline such that the movement of sediment and nutrients which would otherwise be carried by storm runoff into coastal waters are not impeded, and the continued delivery of these sediments to the littoral zone is facilitated. Such placement shall be done in accordance with feasible mitigation measures to minimize adverse environmental effects, taking into consideration physical and chemical properties of the removed materials, the method of placement, time of year of placement, and sensitivity of the placement area and receiving waters.

New permanent residential development created through land divisions located within mapped or modeled tsunami hazard areas.

Have floor elevations one-foot above the height of tsunami runup originating from the maximum credible near-source seismic event on the Cascadia Subduction Zone, as depicted on the latest government-prepared tsunami hazard maps or local modeling, taking into consideration local uplift and subsidence, and a three-foot rise in sea level over a one-hundred year period; and

The building has been designed to withstand the hydrodynamic, hydrostatic, and buoyancy forces associated with wave strike and back-flow, including the effects on foundation scour, without experiencing catastrophic

Wildfire hazards.

The development or use has been conditioned to be constructed or operated consistent with applicable fire safe standards for the local-or state-responsibility area in which it is located, provided that that all feasible protective measures are included such that impacts to coastal resources are minimized. Examples of these measures include, but are not limited to, siting and designing the development or use so that fuel modification clearing and access improvements in and in proximity to environmentally sensitive habitat areas and geologically unstable areas are minimized.

Hazardous materials.

The development or use has been conditioned to be constructed and/or operated consistent with an approved spill prevention, response, and clean-up plan.

(Ord. of 2-22-2011(1))