General Plan

Sections:

21.010          Intent.

21.020          Statutory Authorization.

21.030          Findings of Fact.

21.040          Statement of Purpose.

21.050          Methods of Reducing Flood Losses.

21.060          Definitions.

21.070          Lands to Which This Chapter Applies.

21.080          Basis for Establishing the Areas of Special Flood Hazard.

21.090          Compliance.

21.100          Abrogation and Greater Restrictions.

21.110          Interpretation.

21.120          Warning and Disclaimer of Liability.

21.130          Establishment of Development Permit.

21.140          Designation of Floodplain Administrator.

21.150          Duties and Responsibilities of the Floodplain Administrator.

21.160          Standards of Construction.

21.170          Standards for Utilities.

21.180          Standards for Subdivisions.

21.190          Standards for Manufactured Homes.

21.200          Floodways.

21.210          Variance Procedures.

21.010     Intent.

The FP, flood plain combining district, is intended to establish special requirements and regulations to be applied to those areas of the county subject to inundation in order to prevent loss of life and property damage.

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21.020     Statutory authorization.

The Legislature of the State of California has in Government Code Sections 65302, 65560 and 65800 conferred upon local government units authority to adopt regulations designed to promote the public health, safety, and general welfare of its citizenry.

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21.030     Findings of fact.

1. The flood hazard areas of Mono County are subject to periodic inundation that may result in loss of life and property, health and safety hazards, disruption of commerce and governmental services, extraordinary public expenditures for flood protection and relief, and impairment of the tax base, all of which adversely affect the public health, safety and general welfare.
2. These flood losses may be caused by the cumulative effect of obstructions in areas of special flood hazards that increase flood heights and velocities, and when inadequately anchored, damage uses in other areas. Uses that are inadequately flood proofed, elevated or otherwise protected from flood damage also contribute to the flood loss.

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21.040     Statement of purpose.

1. It is the purpose of this chapter to promote the public health safety and general welfare, and to minimize public and private losses due to flood conditions in specific areas by provisions designed:    
2. To protect human life and health;
3. To minimize expenditure of public money for costly flood control projects;
4. To minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public;
5. To minimize prolonged business interruptions;
6. To minimize damage to public facilities and utilities such as water and gas mains, electric, telephone and sewer lines, streets and bridges located in areas of special flood hazard;
7. To help maintain a stable tax base by providing for the sound use and development of areas of special flood hazard so as to minimize future flood blight areas;
8. To ensure that potential buyers are notified that property is in an area of special flood hazard; and
9. To ensure that those who occupy the areas of special flood hazard assume responsibility for their actions.

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21.050     Methods of reducing flood losses.

1. In order to accomplish its purposes, this chapter includes regulations for:
2. Restricting or prohibiting uses that are dangerous to health, safety, and property due to water or erosion hazards, or that result in damaging increases in erosion or in flood heights or velocities;
3. Requiring that uses vulnerable to floods, including facilities that serve such uses, be protected against flood damage at the time of initial construction;
4. Controlling the alteration of natural floodplains, stream channels, and natural protective barriers, which help accommodate or channel flood waters;
5. Controlling, filling, grading, dredging, and other development that may increase flood damage; and
6. Preventing or regulating the construction of flood barriers that will unnaturally divert flood waters or that may increase flood hazards in other areas.

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21.060     Definitions.

Unless specifically defined below, words or phrases used in this chapter shall be interpreted so as to give them the meaning they have in common usage and to give this chapter its most reasonable application.

"Appeal" means a request for a review of the Floodplain Administrator's interpretation of any provision of this ordinance or a request for a variance.

"Area of Special Flood Hazard" means the land in the floodplain within a community subject to a 1% or greater chance of flooding in any given year. (See "Special Flood Hazard Area.”)

"Base Flood" means the flood having a 1% chance of being equaled or exceeded in any given year (also called the "100 year flood").

"Basement" means any area of the building having its floor subgrade (below ground level) on all sides.

"Breakaway Walls" are any type of walls, whether solid or lattice, and whether constructed of concrete, masonry, wood, metal, plastic or any other suitable building material that is not part of the structural support of the building and that is designed to break away under abnormally high tides or wave action without causing damage to the structural integrity of the building on which they are used or any building to which they might be carried by flood waters. A breakaway wall shall have a design safe-loading resistance of not less than 10 and not more than 20 pounds per square foot. Use of breakaway walls must be certified by a registered engineer or architect and shall meet the following conditions:

1. Breakaway wall collapse shall result from a water load less than that which would occur during the base flood; and
2. The elevated portion of the building shall not incur any structural damage due to the effects of winds and water loads acting simultaneously during the base (a 100-year event) flood.

"Development" means any man-made change to improve or unimproved real estate, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations located within the area of special flood hazard.

"Flood" or "Flooding" means a general and temporary condition of partial or complete inundation of normally dry land areas from:

1. The overflow of inland or tidal waters and/or;
2. The unusual and rapid accumulation or runoff of surface waters from any source; and
3. The collapse or subsidence of land along undermining caused by waves or currents of water exceeding anticipated cyclical levels or suddenly caused by an unusually high water level in a natural body of water, accompanied by a severe storm, or by an unanticipated force of nature, such as flash flood or an abnormal tidal surge, or by some similarly unusual and unforeseeable event that results in flooding as defined in definition.

"Flood Boundary/Floodway Map" means the official map on which the Federal Emergency Management Agency or Federal Insurance Administration has delineated both the areas of flood hazard and the floodway.

"Flood Insurance Rate Map (FIRM)" means the official map on which the Federal Emergency Management Agency or Federal Insurance Administration has delineated both the area of special flood hazards and the risk premium zones applicable to the community.

"Flood Insurance Study" means the official report provided by the Federal Insurance Administration that includes flood profiles, the Flood Insurance Rate Map (FIRM), the Flood Boundary and Floodway Map, and the water surface elevation of the base flood.

"Floodplain or Flood-Prone Area" means any land area susceptible to being inundated by water from any source (see definition of "Flooding").

"Floodplain Management" means the operation of an overall program of corrective and preventive measures for reducing flood damage and enhancing where possible natural resources in the floodplain, including but not limited to emergency preparedness plans, flood control works, floodplain management regulations, and open-space plans.

"Floodplain Management Regulations" means land development regulations, subdivision regulations, building codes, health regulations, special purpose ordinances (such as floodplain ordinance, grading ordinance and erosion-control ordinances) and other applications of police power that control development in flood-prone areas. The term describes such state or local regulations in any combination thereof, which provide standards for the purpose of flood damage prevention and reduction.

"Floodproofing" means any combination of structural and non-structural additions, changes or adjustments to structures that reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, structures and their contents.

"Floodway" means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than one foot. Also referred to as "regulatory floodway.”

"Functionally Dependent Use" means a use that cannot perform its intended purpose unless it is located or carried out in close proximity to water. The term includes only docking facilities, port facilities that are necessary for the loading and unloading of cargo or passengers, and ship building and ship-repair facilities, but does not include long-term storage or related manufacturing facilities.

"Hazard Mitigation Plan" means a plan that incorporates a process, whereby the potential of future loss due to flooding can be minimized by planning and implementing alternatives to floodplain management community-wide.

"Highest Adjacent Grade" means the highest natural elevation of the ground surface prior to construction next to the proposed walls or a structure.

"Lowest Floor" means the lowest floor of the lowest enclosed area (including basement). An unfinished or flood-resistant enclosure, usable solely for parking of vehicles, building access or storage in an area other than a basement area is not considered a building's lowest floor, provided that such enclosure is not built so as to render the structure in violation of the applicable non-elevation design requirements of this chapter.

"Manufactured Home" means a structure, transportable in one or more sections, that is built on a permanent chassis and is designed for use with or without a permanent foundation when connected to the required utilities. For floodplain management purposes the term "manufactured home" also includes park trailers, travel trailers and other similar vehicles placed on a site for greater than 180 consecutive days.

"Manufactured-Home Park or Subdivision" means a parcel (or contiguous parcels) of land divided into two or more manufactured-home lots for sale or rent.

"Mean Sea Level" means, for purposes of the national Flood Insurance Program, the National Geodetic Vertical Datum (NGVD) of 1988 or other datum, to which base flood elevations shown on a community's Flood Insurance Rate Map are referenced.

"New Construction" means, for floodplain management purposes, structures for which the "start of construction" commenced on or after the effective date of floodplain management regulation adopted by Mono County.

"One Hundred Year Flood" or "100-Year Flood" means a flood that has a 1% annual probability of being equaled or exceeded. It is identical to the "base flood,” which will be the term used through this chapter.

"Person" means an individual or his agent, firm, partnership, association or corporation, or agent of the aforementioned groups, or this state or its agencies or political subdivisions.

"Remedy a Violation" means to bring the structure or other development into compliance with state or local floodplain management regulations, or, if this is not possible, to reduce the impacts of its noncompliance. Ways that impacts may be reduced include protecting the structure or other affected development from flood damages, implementing the enforcement provisions of this chapter or otherwise deterring future similar violations, or reducing federal financial exposure with regard to the structure or other development.

"Riverine" means relating to, formed by, or resembling a river (including tributaries), stream, brook, etc.

"Special Flood Hazard Area (SFHA)" means an area having special flood or flood-related erosion hazards, and shown on an FHBM or FIRM as Zone A, A1-30, AE or A99.

"Start of Construction" includes substantial improvement, and means the date the building permit was issued, provided the actual start of construction, repair, reconstruction, placement, or other improvement was within 180 days of the permit date. The actual start means either the first placement of permanent construction of a structure on a site, such as the pouring of slab or footings, the installation of piles, the construction of columns, or any work beyond the stage of excavation; or the placement of a manufactured home on a foundation. Permanent construction does not include land preparation, such as clearing, grading and filling; nor does it include the installation of streets and/or walkways; nor does it include excavation for a basement, footings, piers, or foundations or the erection of temporary forms; not does it include the installation on the property of accessory buildings, such as garages or sheds not occupied as dwelling units or not part of the main structure.

"Structure" means a walled and roofed building, including a gas or liquid storage tank that is principally above ground, as well as a manufactured home.

"Substantial Improvement" means any repair, reconstruction, or improvement of a structure, the cost of which equals or exceeds 50% of the market value of the structure either:

1. Before the improvement or repair is started; or
2. If the structure has been damaged and is being restored before the damage occurred.

For the purposes of this definition "substantial improvement" is considered to occur when the first alteration of any wall, ceiling, floor, or other structural part of the building commences, whether or not that alteration affects the external dimensions of the structure.

The term does not, however, include either:

1. Any project for improvement of a structure to comply with existing state or local health, sanitary or safety code specifications that are solely necessary to assure safe living conditions; or
2. Any alteration of a structure listed on the National Register of Historic Places or a state Inventory of Historic Places.

"Variance" means a grant of relief from the requirements of this chapter that permits construction in a manner that would otherwise be prohibited by this chapter.

"Violation" means the failure of a structure or other development to be fully compliant with the County's floodplain management regulations. A structure or other development without the elevation certificate, other certifications, or other evidence of compliance required in this chapter is presumed to be in violation until such time as that documentation is provided.

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GENERAL PROVISIONS

21.070     Lands to which this chapter applies.

This chapter shall apply to all areas of special flood hazards within the jurisdiction of Mono County.

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21.080      Basis for establishing the areas of special flood hazard.

The areas of special flood hazard identified by the Federal Emergency Management Agency or the Federal Insurance Administration in a scientific and engineering report entitled "Flood Insurance Study for the County of Mono," dated February 18, 2011, with an accompanying Digital Flood Insurance Rate Map is hereby adopted by reference and declared to be part of this chapter, and all subsequent amendments and/or revisions. The Flood Insurance Study is on file at the Public Works Department, Bridgeport, California. This Flood Insurance Study is the minimum area of applicability of the chapter and may be supplemented by studies for other areas that allow implementation of this chapter and that are recommended to the Board of Supervisors by the Floodplain Administrator.

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21.090     Compliance.

No structure or land shall hereafter be constructed, located, subdivided, extended, converted or altered without full compliance with the terms of this chapter and other applicable regulations. Violations of the provisions of the chapter by failure to comply with any of its requirements (including violations of conditions and safeguards established in connection with conditions) shall constitute a misdemeanor. Nothing herein contained shall prevent the Board of Supervisors from taking such lawful action as is necessary to prevent or remedy any violation.

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21.100     Abrogation and greater restrictions.

The chapter is not intended to repeal, abrogate, or impair any existing easements, covenants, or deed restrictions. However, where this ordinance and another ordinance, easement, covenant, or deed restriction conflict of overlap, whichever imposes the more stringent restrictions shall prevail.

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21.110     Interpretation.

In the interpretation and application of this chapter, all provisions shall be:

1. Considered as minimum requirements:
2. Liberally construed in favor of the governing body; and,
3. Deemed neither to limit nor repeal any other powers granted under State statutes.

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21.120     Warning and disclaimer of liability.

The degree of flood protection required by this chapter is considered reasonable for regulatory purposes and is based on scientific and engineering considerations. Larger floods can and will occur on rare occasions. Flood heights may be increased by man-made or natural causes. This chapter does not imply that land outside the areas of special flood hazards or uses permitted within such areas will be free from flooding or flood damages. This chapter shall not create liability on the part of Mono County, any officer or employee thereof, or the Federal Insurance Administration, for any flood damages that result from reliance on this chapter or any administrative decisions they lawfully make thereunder.

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21.125 Severability

This ordinance and the various parts thereof are hereby declared to be severable. Should any section of this ordinance be declared by the courts to be unconstitutional or invalid, such decision shall not affect the validity of the ordinance as a whole, or any portion thereof other than the section so declared to be unconstitutional or invalid.

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21.130     Establishment of development permit.

A development permit shall be obtained before construction or development begins within any area of special flood hazards established in Section 21.080. Application for a Development Permit shall be made on forms furnished by the Floodplain Administrator and may include but not be limited to: plans in duplicate certified by a registered civil engineer or architect, drawn to scale showing the nature, location, dimensions, and elevation of the area in question; existing or proposed structures, fill, storage of materials, drainage facilities; and the location of the foregoing. Specifically, the following information is required:

1. Proposed elevation in relation to mean sea level, of the lowest floor (including basement) of all structures and elevation of highest adjacent grade;
2. Proposed elevation in relation to mean sea level to which any structure will be flood proofed;
3. All appropriate certifications listed in Section 21.150-D of this chapter; and
4. Description of the extent to which any watercourse will be altered or relocated as a result of proposed development.

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ADMINISTRATION

21.140     Designation of floodplain administrator.

The Public Works director is hereby appointed as Floodplain Administrator and authorized to administer and implement this chapter by granting or denying development permit applications in accordance with its provisions.

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21.150     Duties and responsibilities of the floodplain administrator.

The duties and responsibilities of the Floodplain Administrator shall include, but not be limited to:

1. Review of all development permit applications to determine that:
   1. The permit requirements of this chapter have been satisfied including determination of substantial improvement and substantial damage of existing structures;
   2. All other required state and federal permits have been obtained;
   3. The site is reasonably safe from flooding; and
   4. The proposed development does not adversely affect the carrying capacity of areas were the base flood elevation has been determined, but a floodway has not been designated. For purposes of this chapter, "adversely affects" means the cumulative effect of the proposed development when combined with all other existing and anticipated development will not increase the water surface elevation of the base flood more than one foot at any point.
2. Use of Other Base Flood Data

When base flood elevation data has not been provided in accordance with Section 21.080, the Floodplain Administrator shall obtain, review, and reasonably utilize any base flood elevation and floodway data available from a federal, state or other source, in order to administer Section 21.160. Any such information shall be submitted to the Board of Supervisors for adoption.

3. Alteration of Watercourses 

Whenever a watercourse is to be altered or relocated:

1. Notify adjacent communities and the Department of Water Resources prior to such alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration; and
2. Maintain the flood-carrying capacity of the altered or relocated portion of said watercourse (required).

4. Information to be Obtained and Maintained

Obtain and maintain for public inspection and make available as needed:

1. The certification required in Section 21.160-C-1 (floor elevations);
2. The certification required in Section 21.160-C-2-c (elevation or floodproofing of nonresidential structures);
3. The certification required in Section 21.160-C-3-a or 21.160-C-3-b (wet floodproofing standard);
4. The certification required in Section 21.180-B (subdivision standards);    
5. The certification required in Section 21.200-A (floodway encroachments); and

5. Interpretation of Flood Insurance Rate Map (FIRM) Boundaries

Make interpretations where needed as to the exact location of the boundaries of the areas of special flood hazards (for example, where there appears to be conflict between a mapped boundary and actual field conditions). The person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation as provided in Section 21.210.

6. Remedy Violations

Take necessary action to remedy violations of this chapter as specified in Section 21.090 herein.

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21.160     Standards of construction.

In all areas of special flood hazard the following standards are required:

1. Anchoring
   1. All new construction and substantial improvements shall be anchored to prevent flotation, collapse or lateral movements of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
   2. All manufactured homes shall meet the anchoring standards of Section 21.190.
2. Construction Materials and Methods
   1. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
   2. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.
   3. All new construction and substantial improvements shall be constructed with electrical, heating, ventilation, plumbing and air conditioning equipment, and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding.
3. Elevations and Floodproofing
   1. New construction and substantial improvement of any structure shall have the lowest floor, including basement, elevated to or above the base flood elevation  (i.e., the depth number specified in feet on the FIRM), or at least two feet above the highest adjacent grade if no depth number is specified. Nonresidential structures may meet the standards in Section 21.160- C-2. Upon completion of the structure the elevation of the lowest floor, including basement, shall be certified by a registered professional engineer or surveyor, or verified by the county Building Inspector to be properly elevated. Such certification or verification shall be provided to the Floodplain Administrator.
   2. Nonresidential construction shall either be elevated in conformance to Section 21.160-C-1 together with attendant utility and sanitary facilities:
      1. Be flood-proofed so that, below the base flood level, the structure is watertight with walls substantially impermeable to the passage of water:
      2. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
      3. Be certified by a registered professional engineer or architect that the standards of this subsection are satisfied. Such certifications shall be provided to the Floodplain Administrator.
   3. Require, for all new construction and substantial improvements, that fully enclosed areas below the lowest floor that are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:
      1. Either a minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided. The bottom of all openings shall be no higher than one foot above grade. Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of flood waters; or
      2. Be certified to comply with a local floodproofing standard approved by the Federal Insurance Administration.
   4. Manufactured homes shall also meet the standards in Section 21.190.

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21.170     Standards for utilities.

1. All new and replacement water supply and sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the system and discharges from the system into flood waters.
2. On-site waste disposal systems shall be located to avoid impairment to them, or contamination from them during flooding.

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21.180     Standards for subdivisions.

1. All preliminary subdivision and land division proposals shall identify the flood hazard area and the elevation of the base flood. This shall apply to those divisions greater than 50 lots or five acres, whichever is the lesser.
2. All final subdivision plans will provide the elevations of proposed structure(s) and pads. If the site is filled above the base flood, the final pad elevation shall be certified by a registered professional engineer or surveyor and provided to the Floodplain Administrator.
3. All subdivision proposals shall be consistent with the need to minimize flood damage.
4. All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.
5. All subdivisions shall provide adequate drainage to reduce exposure to flood hazards.

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21.190     Standards for manufactured homes.

All new and replacement manufactured homes and additions to manufactured homes shall:

1. Be elevated so that the lowest floor is at or above the base flood elevation; and
2. Be securely anchored to a permanent foundation system to resist flotation, collapse or lateral movement.

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21.200     Floodways.

Located within areas of special flood hazard, established in Section 21.080, are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of flood waters that carry debris, potential projectiles, and erosion potential, the following provisions apply:

1. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.
2. If Section 21.200-A is satisfied all new construction and substantial improvements shall comply with all other applicable flood hazard reductions provisions of Sections 21.160 through 21.200.

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21.210     Variance procedures.

1. Appeal Board
   1. The Mono County Planning Commission shall hear and decide requests for variances from the requirements of this chapter.
   2. The Mono County Planning Commission shall hear and decide appeals when it is alleged there is an error in any requirement, decision or determination made by the Floodplain Administer in the enforcement or administration of this chapter.
   3. The Board of Supervisors shall hear appeals of actions of the Planning Commission in the manor set forth in Chapter 47, Appeals.
   4. In passing upon such requests or appeals, the Board of Supervisors or Planning Commission shall consider all technical evaluations, all relevant factors, standards specified in other sections of this chapter, and:
      
      1. The danger that materials may be swept onto other lands to the injury of others.
      2. The danger to life and property due to flooding or erosion damage.
      3. The susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the individual owner.
      4. The importance of the services provided by the proposed facility to the community.
      5. The necessity to the facility of a waterfront location, where applicable.
      6. The availability of alternative locations for the proposed uses that are not subject to flooding or erosion damage.
      7. The compatibility of the proposed use with existing and anticipated development.
      8. The relationship of the proposed use to this General Plan and floodplain management program for that area.
      9. The safety of access to the property in times of flood for ordinary and emergency vehicles.
      10. The expected heights, velocity, duration, rate of rise, and sediment transport of the flood waters expected at the site.
      11. The costs of providing governmental services during and after flood conditions, including maintenance and repair of public utilities and facilities such as sewer, gas, electrical, and water system, and streets and bridges.
   5. Generally, variances may be issued for new construction and substantial improvements to be erected on a lot of one-half acre or less in size contiguous to and surrounded by lots with existing structures constructed below the base flood level, providing items a through k in Section 21.210 A-4 have been fully considered. As the lot size increases beyond the one-half acre, the technical justification required for issuing the variance increases.
   6. Upon consideration of the factors of Section 21.210 A-4 and the purpose of the chapter, the Board of Supervisors or Planning Commission may attach such conditions to the granting of variances as it deems necessary to further the purpose of this chapter.
   7. The Floodplain Administrator shall maintain the records of all appeal actions and report any variances to the Federal Insurance Administration upon request.
2. Conditions for Variances
   1. Variances may be issued for the reconstruction, rehabilitation or restoration of structures listed in the National Register of Historic Places or the state Inventory of Historic Places, without regard to the procedures set forth in the remainder of this section.
   2. Variances shall not be issued within any designated floodway if any increase in flood levels during the base flood disharge would result.
   3. Variances shall be issued upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief.
   4. Variances shall only be issued upon:
      
      1. A showing of good and sufficient cause. Variances issued for economic considerations, aesthetics, or because variances have been used in the past, are not good and sufficient cause;         
      2. A determination that failure to grant the variance would result in exceptional hardship to the applicant; and
      3. A determination that the granting of a variance will not result in increased flood heights, additional threats to public safety, extraordinary public expense, create nuisances, cause fraud on or victimization of, the public, or conflict with existing local laws or ordinances.
   5. Variances may be issued for new construction and substantial improvements and for other development necessary for the conduct of a functionally dependent use provided that the provisions of Section 21.210 A-1 through 21.210 A-2 are satisfied and that the structure or other development is protected by methods that minimize flood damages during the base flood and create no additional threats to public safety.
   6. Any applicant to whom a variance is granted shall be given written notice that the structure will be permitted to be built with lowest flood elevation below the base flood elevation and that the cost of flood insurance will be commensurate with the increased risk resulting from the lowered floor elevation. A copy of the notice shall be recorded by the Floodplain Administrator in the office of the Mono County Recorder and shall be recorded in a manner so that it appears in the chain of title of the affected parcel of land.

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Significant potential hazards to public health and safety exist in Mono County. These hazards include: avalanches; floods; fires; geologic hazards such as landslides and mudflows; seismic hazards; and volcanic eruptions. The following section briefly discusses the constraints to development posed by each of these hazards.

Seismic Hazards

Earthquakes

Mono County covers an area that is relatively young by geologic standards. It is located at a stress point where the earth's crustal plates are exerting opposite pressures against each other. This combination creates both "tectonic" earthquakes (e.g., land mass movement) and volcanic activity that can trigger earth shaking (e.g., magma chamber movement and lava dyke formations).

Fault Movement

Earthquakes are usually caused by sudden movement along geologic faults. The California Department of Conservation, Division of Mines and Geology (DMG), has evaluated potentially and recently active faults throughout Mono County including most of the community areas. Based upon these DMG studies, fault hazard zones (Alquist-Priolo Special Studies Zones) have been designated for the county (see the MEA or General Plan Map).

Ground Shaking

The primary seismic hazard in the county is strong to severe ground shaking generated by movement along active faults. The entire county, except for a small portion of the Sierra crest, is in an area where intense ground shaking is possible. This area has been designated as a Seismic Zone D, the zone of greatest hazard defined in the California Building Code. Probabilistic Seismic Hazard Assessment (PSHA) maps prepared by the California Geological Survey (CGS) and the USGS show that the areas with the greatest earthquake shaking hazard in Mono County include the Long Valley Caldera, the western portion of the Mono Basin extending north along the Eastern Sierra escarpment, the western edge of the White Mountains, the southeast corner of the county around Oasis, and the northern tip of the county around Topaz.

The Long Valley-Mammoth Lakes region has experienced numerous earthquakes caused by the movement of magma below the earth's surface. The oval-shaped Long Valley Caldera spans an area approximately 10 by 20 miles, and is among the largest volcanoes in the continental United States. Scientists suspect that the earthquakes are caused by shifts of buried stone slabs that are made unstable as magma moves within the volcano.

Ground Failure

Ground failure induced by ground shaking includes liquefaction, lateral spreading, lurching, and differential settlement, all of which usually occur in soft, fine-grained, water-saturated sediments, typically found in valleys. Areas at high risk are mapped in the MEA. During the 1980 Mammoth Lakes earthquake sequence, ground failure was prevalent at Little Antelope Valley, along margins of the Owens River in upper Long Valley, along the northwest margins of Lake Crowley, and along Hot Creek Meadow.

All of Mono County is situated within Seismic Zone D, and consequently new construction in the county must comply with stringent engineering and construction requirements. Existing buildings that may be subject to seismic hazards must comply with the requirements of the unreinforced masonry building law (Government Code § 8875).

Other Geologic Hazards

Rockfall, Mudflow and Landslide Hazards

Rockfalls and landslides are particularly common along the very steep slopes of the eastern scarp of the Sierra Nevada, where talus slopes provide evidence of abundant past rockfalls. During the winter and spring months, rockfalls can be lubricated with snow and ice and can become extremely fast moving and destructive. Landslides in areas of hilly and mountainous terrain can be triggered by ground shaking, heavy rains or human activities such as road cuts, grading, construction removal of vegetation, and changes in drainage.

The state Department of Conservation, Division of Mines and Geology has yet to prepare maps of earthquake-induced landslide hazards for Mono County as required by the Seismic Hazards Mapping Act. Maps of rockfall hazard areas are based upon slope conditions and local and historical knowledge. Community areas in the county affected by rockfall hazards include Lundy Canyon and the June Lake Loop (primarily the Down Canyon area). The remaining rockfall risk areas are outside community areas.

Mud and debris flows involve very rapid downslope movement of saturated soil, sub-soil, and weathered bedrock. Large mud and debris flows, such as the one that occurred in 1989 in the Tri-Valley area, can be destructive, particularly at the mouths of canyons. Previous evidence of extensive mud and debris flows are evident in the large alluvial fans in the Tri-Valley area.

Subsidence

Subsidence in Mono County has been caused primarily by the tectonic movement of the earth and the movement of magma beneath the Long Valley Caldera. During the May 1980 sequence of earthquakes near Mammoth Lakes, the ground surface dropped about four inches at several locations near the Hilton Creek fault, and up to 12 inches of vertical offset occurred along the Mammoth Yosemite Airport fault zone. Magma movement in the Long Valley Caldera has caused bulging of the resurgent dome in the Casa Diablo area by about two and a half feet since 1980.

No subsidence has been observed in the county due to fluid withdrawals, or hydrocompaction of water impoundment. All major groundwater basins (see the MEA), however, have been identified by the Division of Mines and Geology as areas where subsidence could occur as a result of excessive groundwater pumping.

Volcanic Hazards

Evidence of volcanic activity in Mono County extends from Black Point north of Mono Lake to the deposits of Bishop Tuff in southern Mono County. The source of volcanic risk in Mono County is the Inyo-Mono crater chain and the Long Valley Caldera. Vents in the Inyo-Mono crater chain have erupted about every 500 years over the last 2,000 to 3,000 years, with the most recent eruption occurring approximately 500 years ago. Eruptions in the Long Valley Caldera have occurred approximately every 2,000 years over the last 7,000 years. The volcanic hazards mapped in the MEA estimate the extent of explosive blasts, hot flowing material, and ash flow.

Flooding

Flood Hazards

The Federal Emergency Management Agency (FEMA) has prepared Flood Insurance Rate Maps illustrating 100-year flood hazard areas for several streams. Floods in these areas have a 1% probability of occurring in any given year. Such flooding could result in the loss of life and property, health and safety hazards, disruption of commerce and governmental services, and extraordinary public expenditures for flood protection and relief. Flood losses may be increased by the cumulative effect of obstructions in flood hazard areas that increase flood heights and velocities, and when inadequately anchored, can damage downstream uses.

Flooding is a potential risk to private properties situated in the vicinity of several waterways within the county. The community areas most likely to be impacted by a 100-year flood include properties along the East and West Walker River, Reversed Creek, and Spring Canyon Creek including portions of the Antelope Valley, Bridgeport Valley, the June Lake Loop, and the Tri-Valley area.

Some FEMA maps lack information regarding the base flood elevation, and are therefore of limited use for local development review and site-specific planning purposes. Some maps lack information concerning local alluvial fan and mudflow hazards. There is a significant need to update the flood hazard maps where these deficiencies exist. The California Department of Water Resources publishes flood-awareness area maps that, while non-regulatory, can provide additional flooding potential information, particularly for areas that remain unmapped by FEMA.

Dam Failure

The Mono County Multi-Jurisdictional Local Hazard Mitigation Plan (LHMP) indicates that 18 dams are located in Mono County. The Lower and Upper Twin Lakes, Lundy Lake, Long Valley/Crowley Lake, Rush Creek meadows, and Saddlebag dams are identified as presenting some threat to downstream developed areas if dam failure were to occur.

The MEA illustrates the areas subject to flood hazards and dam failure inundation, as well as the area that would be inundated if the dam at Crowley Lake were raised an additional 20 feet to provide an increased storage area.

Seiches

Seiches are earthquake-generated waves within enclosed or restricted bodies of water such as lakes and reservoirs. Similar to the sloshing of water in a bowl or a bucket when it is shaken or jarred, seiches can overtop dams and pose a hazard to people and property within their reach. There is no available evidence that seiches have occurred in Mono County lakes and reservoirs.

Fire

Wildland Fires

The combination of highly flammable fuel, long dry summers and steep slopes creates a significant natural hazard of wildland fire potential in most of Mono County. Wildland fires can result in death, injury, economic loss, and significant public investment in firefighting efforts. Woodlands and other natural vegetation can be destroyed resulting in a loss of timber, wildlife habitat, scenic quality and recreational resources. Soil erosion, sedimentation of fisheries and reservoirs, and downstream flooding can also result.

Fire hazard severity has been mapped by Cal Fire for most of the privately owned land in Mono County. All areas except the Bridgeport Valley and Antelope Valley have been rated as having a very high fire hazard. The Bridgeport Valley has a moderate fire hazard rating, and the Antelope Valley has not been rated. With the exception of the Antelope Valley, all privately owned lands in Mono County are within the State Responsibility Area (SRA).

The Mono County Community Wildfire Protection Plan (CWPP) and the Cal Fire San Bernardino/Inyo/Mono Unit Fire Plan are incorporated by reference into this Safety Element. The CWPP provides community-level data concerning fire hazards in the county, including community fuel reduction treatment areas and fuel breaks and other wildfire mitigation recommendations, particularly in Wildland-Urban Interface areas.

Much of the privately owned land in the county is located outside of fire protection districts, and therefore lacks formal emergency fire protection service. It is difficult for existing fire districts to receive additional property tax revenues for annexation of these unserved areas, or for new fire districts to be formed. Consequently, future development in these areas without adequate fire protection will be limited.

The State of California recently updated wildland protection regulations for future development in the SRA; Mono County has adopted and periodically updates a local ordinance that has the same practical effect as the Cal Fire regulations (Mono County Land Use Element Ch. 22, Fire Safe Regulations).

These fire safe regulations address requirements for adequate clearance of flammable vegetation around individual structures and clusters of structures and construction methods to prevent the spread of fire from the wildland to structures, and from structures to wildlands. Minimum water capacities for fire protection purposes are established in the regulations to ensure the availability of water for fire suppression purposes. Adequate road widths and load capacities are required to ensure ready movement of fire engines, and other heavy firefighting equipment to developed areas of the county; the Mono County Department of Public Works also has established similar road improvement standards for new development.

Structural Fires

The 11 fire protection districts in the county provide fire-prevention services through such activities as education and development review. The districts also provide varying levels of fire suppression and emergency medical response services to community areas. The Community Services Section of the MEA provides a summary description of fire district service levels and capabilities, including the general capabilities and availability of local community water service in the county.

Avalanche

Avalanche Hazards

Although avalanches in Mono County occur primarily on national forests in the Sierra Nevada backcountry, some avalanche hazards present a significant risk to community areas. Both property damage and loss of life have resulted from avalanches in Mono County. Community areas influenced by avalanche hazards include Swauger Creek, Twin Lakes, Virginia Lake, Lundy Lake, June Lake, Long Valley/McGee Creek, and Wheeler Crest. In addition, roadway sections threatened by potential avalanches include portions of Lower Rock Creek Road; US 395 at Long Valley, Wilson Butte, and just north of Lee Vining; S.R. 158 entering the June Lake Loop; and several County roads entering eastern-slope community areas.

Avalanche Studies and Maps

In accordance with State law, avalanche hazard maps have been developed to illustrate areas of known avalanche occurrences. These maps were prepared by five Board-appointed avalanche advisory committees consisting of local residents and landowners. All pertinent information concerning the work of the five appointed committees and the avalanche policy formulation process – including committee recommendations and position papers – is on file in the county Planning Division. Other County avalanche hazard studies prepared by avalanche consultants and that project potential avalanche run-out areas, and an archive of photographs documenting evidence of avalanche damage and occurrences are also on file in the Planning Division.

Avalanche Monitoring and Evacuation

A backcountry avalanche monitoring program is operated by the Eastern Sierra Avalanche Center. This monitoring program issues avalanche hazard warnings during periods of high avalanche danger in the backcountry. The county Sheriff's Department keeps in contact with avalanche experts and should a hazardous situation develop, advises those within the hazard-prone area of the critical nature of the hazard.

Evacuation Routes

The Mono County Local Hazard Mitigation Plan indicates that major routes (State and County), immediate access routes to community areas, and internal community street systems could be subject to closure by avalanches, landslides, snow and fog whiteouts, and flooding. In addition, imminent hazards such as high avalanche hazard conditions could prohibit travel even along open access routes. The developed areas of Wheeler Crest, Lundy Lake, Virginia Lakes, and Twin Lakes all have only one access.

The Mono County Local Hazard Mitigation Plan, sets forth site-specific evacuation plans as well as general evacuation procedures for various emergency situations. Several community area plans also call for development of additional emergency access routes into the community areas.