Mendocino County Municipal Code Ch. 20.500 Hazard Areas

This Chapter shall apply to all development proposed in the Coastal Zone unless and until it is determined by the County Coastal Permit Administrator that the project is not subject to threats from geologic, fire, flood or other hazards.

(Ord. No. 3785 (part), adopted 1991.)

(A) The purpose of this section is to insure that development in Mendocino County's Coastal Zone shall:

(1) Minimize risk to life and property in areas of high geologic, flood and fire hazard;

(2) Assure structural integrity and stability; and

(3) Neither create nor contribute significantly to erosion, geologic instability or destruction of the site or surrounding areas, nor in any way require the construction of protective devices that would substantially alter natural landforms along bluffs and cliffs.

(Ord. No. 3785 (part), adopted 1991.)

(A) Determination of Hazard Areas.

(1) Preliminary Investigation. The Coastal Permit Administrator shall review all applications for Coastal Development Permits to determine threats from and impacts on geologic hazards.

(2) Geologic Investigation and Report. In areas of known or potential geologic hazards such as shoreline and blufftop lots and areas delineated on the hazard maps, a geologic investigation and report prior to development approval, shall be required. The report shall be prepared by a licensed engineering geologist or registered civil engineer pursuant to the site investigation requirements in Chapter 20.532.

(B) Mitigation Required. Where mitigation measures are determined to be necessary, the foundation, construction and earthwork shall be supervised and certified by a licensed engineering geologist or a registered, civil engineer with soil analysis expertise who shall certify that the required mitigation measures are incorporated into the development.

(Ord. No. 3785 (part), adopted 1991.)

(A) Faults.

(1) Residential, commercial and industrial structures shall be sited a minimum of fifty (50) feet from a potentially, currently or historically active fault. Greater setbacks shall be required if warranted by geologic conditions.

(2) Water, sewer, electrical and other transmission and distribution lines which cross fault lines shall be subject to additional standards for safety including emergency shutoff valves, liners, trenches and the like. Specific safety measures shall be prescribed by a licensed engineering geologist or a registered civil engineer.

(B) Bluffs.

(1) New structures shall be setback a sufficient distance from the edges of bluffs to ensure their safety from bluff erosion and cliff retreat during their economic life spans (seventy-five (75) years). New development shall be setback from the edge of bluffs a distance determined from information derived from the required geologic investigation and the setback formula as follows:

Setback (meters) = structure life (75 years) × retreat rate (meters/year)

Note: The retreat rate shall be determined from historical observation (aerial photos) and/or from a complete geotechnical investigation.

(2) Drought tolerant vegetation shall be required within the blufftop setback.

(3) Construction landward of the setback shall not contribute to erosion of the bluff face or to instability of the bluff.

(4) No new development shall be allowed on the bluff face except such developments that would substantially further the public welfare including staircase accessways to beaches and pipelines to serve coastal-dependent industry. These developments shall only be allowed as conditional uses, following a full environmental, geologic and engineering review and upon a finding that no feasible, less environmentally damaging alternative is available. Mitigation measures shall be required to minimize all adverse environmental effects.

(C) Tsunami. In tsunami inundation areas, as illustrated on resource maps or land use maps, only harbor development and related uses shall be allowed. These uses shall be allowed only if a tsunami warning plan has been developed.

(D) Landslides.

(1) New development shall avoid, where feasible, existing and prehistoric landslides. Development in areas where landslides cannot be avoided shall also provide for stabilization measures such as retaining walls, drainage improvements and the like. These measures shall only be allowed following a full environmental, geologic and engineering review pursuant to Chapter 20.532 and upon a finding that no feasible, less environmentally damaging alternative is available.

(2) Where landslides pose an immediate threat to existing development, emergency steps to stabilize the slide may be taken without benefit of the reviews specified above, but must conform with Section 20.536.055 of this Division for permits for approval of emergency work.

(E) Erosion.

(1) Seawalls, breakwaters, revetments, groins, harbor channels and other structures altering natural shoreline processes or retaining walls shall not be permitted unless judged necessary for the protection of existing development, public beaches or coastal dependent uses. Environmental geologic and engineering review shall include site-specific information pertaining to seasonal storms, tidal surges, tsunami runups, littoral drift, sand accretion and beach and bluff face erosion. In each case, a determination shall be made that no feasible less environmentally damaging alternative is available and that the structure has been designed to eliminate or mitigate adverse impacts upon local shoreline sand supply and to minimize other significant adverse environmental effects.

(2) The design and construction of allowed protective structures shall respect natural landforms, shall provide for lateral beach access and shall minimize visual impacts through all available means.

(3) All grading specifications and techniques will follow the recommendations cited in the Uniform Building Code or the engineer's report and Chapter 20.492 of this Division.

(4) Within the Gualala Town Planning area, a special condition shall be attached to all coastal permits for blufftop residential or commercial development, requiring recordation of a deed restriction that states the following:

(a) The landowner understands that the site may be subject to extraordinary geologic and erosion hazard and the landowner assumes the risk from such hazards;

(b) The landowner agrees that any adverse impacts to property caused by the permitted project shall be fully the responsibility of the applicant;

(c) The landowner shall not construct any bluff or shoreline protective devices to protect the subject permitted residence, guest cottage, garage, septic system or other improvements in the event that these structures are subject to damage, or other natural hazards in the future;

(d) The landowner shall remove the subject permitted house and its foundation when bluff retreat reaches the point where the structure is threatened. In the event that portions of the subject permitted house, garage, foundations, leach field, septic tank, or other improvements associated with the residence fall to the beach before they can be removed from the blufftop, the landowner shall remove all recoverable debris associated with these structures from the beach and ocean and lawfully dispose of the material in an approved disposal site. The landowner shall bear all costs associated with such removal.

(e) The requirements of Subsection (d) shall not apply to residences or associated improvements on the property that pre-date the subject coastal permit.

(Ord. No. 3785 (part), adopted 1991; Ord. 4083 (part), adopted 2002.)

(A) Fire hazard areas shall be identified using the California Department of Forestry's Fire Hazard Severity Classification System which classifies hazards into three categories: moderate, high or extreme hazard.

(B) Land Use Restrictions.

(1) All new development shall be sited taking into consideration the fire hazard severity of the site, the type of development and the risk added by the development to the fire hazard risk. Where feasible, areas of extreme high risk should be avoided for development except agricultural and open space uses.

(Ord. No. 3785 (part), adopted 1991)

(A) The flood hazard areas fall within the one hundred (100) year flood zone boundaries as mapped by the Federal Emergency Management Administration (FEMA).

(B) Land Use Restrictions.

(1) No new development, except flood control projects to protect existing structures, non-structural agricultural uses and seasonal uses shall be permitted in the one hundred (100) year floodway unless mitigation measures in accordance with FEMA regulations and Chapter 22.17 of the Mendocino County Code.

(Ord. No. 3785 (part), adopted 1991)

(Ord. No. 4418, § 6, 11-6-2018)