HAZARDS COMPONENT


The County will:

9.1	Definition of Hazard Areas

	Define hazardous areas as fault zones and land subject to dangers from liquefaction and other severe seismic impacts, unstable slopes, landslides, coastal cliff instability, flooding, tsunamis, fire, and steep slopes (over 30%).

9.2	Designation of Hazard Areas

	Designate hazardous areas in the Coastal Zone as those delineated on the Geotechnical Hazards Synthesis Map, the Floodway Boundary and Floodway Maps and Flood Insurance Rate Maps adopted under Chapter 35.5 of the San Mateo County Zoning Regulations, and the Natural Hazards Map in the Natural Hazards Chapter of the General Plan.

9.3	Regulation of Geologic Hazard Areas

	Apply the following regulations of the Resource Management (RM) Zoning Ordinance to designated geologic hazard areas:

	a.	Section 6324.6 - Hazards to Public Safety Criteria.

	b.	Section 6326.2 - Tsunami Inundation Area Criteria.

	c.	Section 6326.3 - Seismic Fault/Fracture Area Criteria.  Require geologic reports prepared by a certified engineering geologist consistent with "Guidelines for Geologic/Seismic Reports" (CDMG Notes #37) for all proposed development.

	d.	Section 6326.4 - Slope Instability Area Criteria.

9.4	Definition of High Risk Fire Areas

	Define fire hazard areas as those having a high potential for catastrophic fire.

9.5	Designation of High Risk Fire Areas

	Designate high risk fire areas in the Coastal Zone as those delineated by the State Division of Forestry and shown on the Hazards Map for the Coastal Zone.

9.6	Regulation of Development in High Risk Fire Areas

	Require residential development in high risk areas to be reviewed and conditioned by the County Fire Warden to insure that building materials, access, brush clearings and water storage capacity are adequate for fire flow and fire protection purposes.

9.7	Definition of Coastal Bluff or Cliff

	Define Coastal Bluff or Cliff as a scarp or steep face of rock, decomposed rock, sediment or soil resulting from erosion, faulting, folding or excavation of the land mass and exceeding 10 feet in height.

9.8	Regulation of Development on Coastal Bluff Tops

	a.	Permit bluff and cliff top development only if design and setback provisions are adequate to assure stability and structural integrity for the expected economic life span of the development (at least 50 years) and if the development (including storm runoff, foot traffic, grading, irrigation, and septic tanks) will neither create nor contribute significantly to erosion problems or geologic instability of the site or surrounding area.

	b.	Require the submittal of a site stability evaluation report for an area of stability demonstration prepared by a soils engineer or a certified engineering geologist, as appropriate, acting within their areas of expertise, based on an on-site evaluation.  The report shall consider:

		 (1)	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 transport.

		 (2)	Cliff geometry and site topography, extending the surveying work beyond the site as needed to depict unusual geomorphic conditions that might affect the site and the proposed development.

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

		 (4)	Evidence of past or potential landslide conditions, the implications of such conditions for the proposed development, and the potential effects of the development on landslide activity.

		 (5)	Wave and tidal action, including effects of marine erosion on seacliffs.

		 (6)	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 in surface drainage.

		 (7)	Potential effects of seismic forces resulting from a maximum credible earthquake.

		 (8)	Effects of the proposed development including siting and design of structures, septic system, landscaping, drainage, and grading, and impacts of construction activity on the stability of the site and adjacent area.

		 (9)	Any other factors that may affect slope stability.

		(10)	Potential erodibility of site and mitigating measures to be used to ensure minimized erosion problems during and after construction (i.e., landscaping and drainage design).

	c.	The area of demonstration of stability includes the base, face, and top of all bluffs and cliffs.  The extent of the bluff top considered should include the area between the face of the bluff and a line described on the bluff top by the intersection of a plane inclined a 20o angle from the horizontal passing through the toe of the bluff or cliff, or 50 feet inland from the edge of the cliff or bluff, which ever is greater.

	d.	Prohibit land divisions or new structures that would require the need for bluff protection work.

9.9	Regulation of Development in Floodplains

	a.	Channelization, dams, or other stream alterations shall incorporate the best mitigation measures feasible and be limited to:  (1) necessary water supply projects, (2) flood control projects where no other methods for protecting existing development or providing public safety exists, or (3) developments to enhance fish and wildlife habitat.

	b.	Development located within flood hazard areas shall employ the standards, limitations and controls contained in Chapter 35.5 of the San Mateo County Ordinance Code, Sections 8131, 8132 and 8133 of Chapter 2 and Section 8309 of Chapter 4, Division VII (Building Regulations), and applicable Subdivision Regulations.

9.10	Geological Investigation of Building Sites

	Require the County Geologist or an independent consulting certified engineering geologist to review all building and grading permits in designated hazardous areas for evaluation of potential geotechnical problems and to review and approve all required investigations for adequacy.  As appropriate and where not already specifically required, require site specific geotechnical investigations to determine mitigation measures for the remedy of such hazards as may exist for structures of human occupancy and/or employment other than those considered accessory to agriculture as defined in Policy 5.6.

	"Hazards areas" and "hazards" are defined as those geotechnical hazards shown on the current Geotechnical Hazards Synthesis Maps of the General Plan and the LCP Hazards Maps.  A copy of the report of all geologic investigations required by the California Division of Mines and Geology shall be forwarded to that agency.

9.11	Shoreline Development

	Locate new development (with the exception of coastal dependent uses or public recreation facilities) in areas where beach erosion hazards are minimal and where no additional shoreline protection is needed.

9.12	Limiting Protective Shoreline Structures

	a.	Permit construction of shoreline structures such as retaining walls, groins, revetments, and breakwaters only in accordance with the following conditions when:  (1) necessary to serve coastal-dependent uses, to protect existing development, or to protect public beaches in danger of erosion, (2) designed to eliminate or mitigate adverse impacts on local shoreline sand supply, and (3) non-structural methods (e.g., artificial nourishment) have been proved to be infeasible or impracticable.

	b.	Protect existing roadway facilities which provide public access to beaches and recreational facilities when alternative routes are not feasible and when protective devices are designed in accordance with the requirements of this Component and other LCP policies.

9.13	Limiting Shoreline Structures on Sandy Beaches

	To avoid the need for future protective devices that could impact sand movement and supply, prohibit permanent structures on the dry sandy beach except facilities necessary for public health and safety, such as lifeguard towers.

9.14	Shoreline Structure Design

	a.	Required that all protective structures are designed to:  (1) minimize visual impact by using appropriate colors and materials, (2) utilize materials which require minimum maintenance, and (3) provide public overlooks where feasible and safe.

	b.	Require that shoreline protective structures not impede lateral access along beach areas and provide vertical access where feasible.

	c.	Require that any shoreline alteration or structure project shall mitigate project impacts by adequate fish and wildlife preservation measures.

9.15	Emergency Provisions

	Waive the requirement for obtaining a Coastal Development Permit to:  (1) allow immediate action by a person or public agency performing a public service to protect life and public property from imminent danger or (2) restore, repair, or maintain public works, utilities, or services which have been destroyed, damaged, or interrupted by natural disaster, serious accident, or other emergencies if such action does not involve the permanent erection of structures valued at $25,000 or more.
9.16	Geologic Reports for Shoreline Structures

	Require that all applications involving shoreline structures shall be accompanied by a report prepared by a certified engineering geologist or a soils engineer, as appropriate, which analyzes the effect the project will have on physical shoreline processes.

9.17	Maintenance of Structures

	Require that project plans for shoreline structures specify agencies or persons responsible for the maintenance of proposed structure(s).

9.18	Regulation of Development on 30% or Steeper Slopes

	a.	Prohibit, unless no alternatives exist, development (including land divisions which would create parcels exclusively) on slopes of 30% or greater.  If no alternatives exist, require engineering geologic reports to enable minimizing of hazards.

	b.	Employ the siting and grading criteria of the Design Review Zoning Ordinance and the Community Design Manual for Development on Slopes 30% or Greater.




RG:cdn - RXGC1997.ACM
(8/17/92)