A. General Standards: In all areas of special flood hazard, the following standards are required:
1. Anchoring: All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure and capable of resisting the hydrostatic and hydrodynamic loads.
2. Construction Materials And Methods:
a. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
b. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.
c. 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. Utilities:
a. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system;
b. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters; and
c. On site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
B. Floodway:
1. Uses Allowed Without Permit: The following open space uses shall be allowed without a permit anywhere within the floodway, provided that such uses are not prohibited by any other resolution or statute, do not require structures other than portable structures, do not require alteration of the floodplain such as fill, excavation or permanent storage of materials or equipment, do not require large scale cleaning of the riparian vegetation within fifty feet (50') of the mean high water mark, will not cause flood losses on other land or to the public:
a. Agricultural uses such as tilling, farming, irrigation, harvesting, grazing, etc.;
b. Accessory uses such as loading and parking areas, or emergency landing strips associated with industrial or commercial facilities;
c. Private and public recreational uses such as picnic grounds, swimming areas, parks, trap, skeet, target, shooting, and archery ranges, wildlife management and natural areas, hunting and fishing areas, or hiking and horseback riding trails;
d. Forestry, including processing of forest products with portable equipment;
e. Residential uses such as lawns, gardens, parking areas, and play areas;
f. Irrigation and livestock supply wells, provided that they are located at least five hundred feet (500') from domestic water supply wells;
g. Fences, except permanent fences crossing channels;
h. Recreational vehicle use provided that they be on the site for fewer than one hundred eighty (180) consecutive days or be fully licensed and ready for highway use. A recreational vehicle is ready for highway use if it is on its wheels or jacking system with wheels intact, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions.
2. Uses Requiring Permits: The following nonconforming uses and artificial obstructions may be permitted within the designated floodway, provided that such uses conform to all regulations and are approved for permit issuance by the floodplain administrator:
a. Excavation of material from pits or pools provided that:
(1) A buffer strip of undisturbed land of sufficient width to prevent flood flows from channeling into the excavation is left between the edge of the channel and the edge of the excavation;
(2) The excavation meets all applicable laws and regulations of other local and state agencies; and
(3) Excavated material is stockpiled outside the designated floodway. (However, for short term gravel mining operations, the floodplain administrator may allow stockpiling in the floodway fringe if there is no other alternative and there is no significant [1/2 foot] rise in the BFE. A "no rise" certification signed by a licensed engineer shall be required.)
b. Railroad, highway, street and stream crossings, provided that:
(1) The crossings are designed to offer minimal obstructions to the flood flow;
(2) Where failure or interruption of transportation facilities would result in danger to the public health or safety, the bottom of bridge spans shall have freeboard to at least two feet (2') above the BFE;
(3) If possible, normal overflow channels are preserved to allow passage of sediments to prevent aggradations;
(4) Midstream supports for bridges, if necessary, must have footings buried below the maximum scour depth; and
(5) Stream crossings shall not increase the elevation of the 100-year flood nor cause a significant increase in flood velocities. The applicant shall provide a "no rise" certification signed by a registered professional engineer. However, if the applicant receives a CLOMR from FEMA and LOMR, a half foot rise may be permitted.
c. Limited filling for highway, street, and railroad embankments not associated with stream crossings and bridges provided that:
(1) Reasonable alternate transportation routes outside the designated floodway are not available;
(2) The encroachment is located as far from the stream channel as possible;
(3) Measures are provided to mitigate the impact to property owners and the natural stream function; and
(4) The encroachment shall not result in a cumulative increase in base flood elevation, after the allowable encroachment into the floodway. A "no rise" certification signed by a registered professional engineer shall be provided by the applicant. However, if the applicant receives a CLOMR from FEMA and LOMR, a half foot rise may be permitted.
d. Buried or suspended utility transmission lines, provided that:
(1) Suspended utility transmission lines are designed such that the lowest point of the suspended line is at least six feet (6') higher than the elevation of the flood of 100-year frequency;
(2) Towers and other appurtenant structures are designed and placed to withstand and offer minimal obstruction to flood flows;
(3) When technically feasible, the crossing will not disturb the bed and banks of the stream and alternatives such as alternative routes, directional drilling, and aerial crossings are considered; and
(4) Utility transmission lines carrying toxic or flammable materials are buried to a depth of at least twice the calculated maximum depth of scour for a flood of one hundred (100) year frequency. The maximum depth of scour may be determined from any of the accepted hydraulic engineering methods, but the final calculated figures shall be subject to approval by the floodplain administrator.
e. Storage of materials and equipment provided that:
(1) The material or equipment is not subject to major damage by flooding and is properly anchored to prevent flotation or downstream movement; and
(2) The material or equipment is readily removable within the limited time available after flood warning. Storage of flammable, toxic or explosive materials shall not be permitted.
f. Irrigation, livestock and domestic water supply wells, provided that:
(1) They are driven or drilled wells located on ground higher than surrounding ground to assure positive drainage from the well;
(2) They require no other structures (e.g., a well house);
(3) Well casings are watertight to a distance of at least twenty five feet (25') below the ground surface;
(4) Water supply and electrical lines have a watertight seal where the lines enter the casing;
(5) All pumps and electrical lines and equipment are either of the submersible type or are adequately floodproofed;
(6) Check valves are installed on main water lines at wells and at all building entry locations; and
(7) Irrigation and livestock supply wells are located at least five hundred feet (500') from domestic water supply wells.
g. Only those wastewater disposal systems that meet the requirements and separation distances under ARM 17.36.101-116 and ARM 17.36.301-345 are allowed.
h. Fences crossing channels.
i. Residential uses not requiring buildings such as lawns, gardens, parking areas and play areas.
j. Public or private recreational uses not requiring structures such as campgrounds, golf courses, driving ranges, archery ranges, wildlife management and natural areas, alternative livestock ranches (game farms), fish hatcheries and shooting preserves provided that:
(1) Access roads require only limited fill and do not obstruct or divert floodwaters;
(2) There are no dwellings or permanent mobile homes;
(3) There is no rise in the BFE;
(4) Off property impacts have been considered and found to be nonexistent, neutral or can be mitigated;
(5) There is no large scale clearing of riparian vegetation within fifty feet (50') of the mean annual high water mark; and
(6) Recreational vehicles and travel trailers are licensed and ready for highway use. They are ready for highway use if on wheels or jacking system with wheels intact, are attached to the site with only quick disconnect type utilities and securing devices, and have no permanently attached additions.
k. Structures accessory to the uses permitted in this section, such as boat docks, loading and parking areas, marinas, emergency airstrips, permanent fences crossing channels, picnic shelters and tables, provided that:
(1) The structures are not intended for human habitation or supportive of human habitation;
(2) The structures will have low flood damage potential as certified by a registered professional engineer on a "no rise" certificate;
(3) The structures will, insofar as possible, be located on ground higher than the surrounding ground and as far from the channel as possible;
(4) Only those wastewater disposal systems that meet the requirements and separation distances under ARM 17.36.101-116 and ARM 17.36.301-345 are allowed;
(5) Service facilities within these structures such as electrical, heating and plumbing are floodproofed in accordance with subsection E of this section;
(6) The structure will be constructed and placed so as to offer a minimal obstruction to flood flows and is firmly anchored to prevent flotation;
(7) The use does not require fill and/or substantial excavation; and
(8) The use does not require the large scale clearing of riparian vegetation within fifty feet (50') of the mean annual high water mark.
l. Replacement of manufactured homes in an existing manufactured home park, sites outside of a park or subdivision, or subdivision on a developed site of the same dimensions with servicing utilities. (Previous home could have been destroyed by fire, flood, etc.) The replacement home must be elevated on a permanent foundation so the lowest floor is two feet (2') above the base flood elevation. The foundation must be reinforced concrete, reinforced mortared block, reinforced piers, or other foundation elements of equal strength. The mobile home chassis must be securely anchored to the foundation system so that it will resist flotation, collapse or lateral movement. Methods of anchoring may include, but are not limited to:
(1) Over the top ties to ground anchors be provided at each of the four (4) corners of the mobile home, with two (2) additional ties per side at intermediate locations for mobile homes less than fifty feet (50') long;
(2) Frame ties to ground anchors be provided at each corner of the home with five (5) additional ties per side at intermediate points, for mobile homes more than fifty feet (50') long;
(3) All components of the anchoring system be capable of carrying a force of four thousand eight hundred (4,800) pounds;
(4) Any additions to the mobile home must be similarly anchored; and
(5) Adequate surface drainage and access for a hauler are provided.
m. Agricultural structures (except buildings, dwellings and fuel storage) that will have low flood damage potential, or be located on higher ground and as far from the channel as possible, and meet the floodproofing requirements of subsection E of this section.
n. New surface water diversions and changes in place of diversion for agricultural uses and other uses, designed by a registered engineer to meet the following requirements:
(1) A copy of the water right permit or change authorization permit from MTDNRC water rights bureau for new surface water diversions and changes in place of diversion;
(2) Documentation that the proposed diversion or modification will not increase the upstream elevation of the base flood to the detriment of a neighboring property. Any increase to the BFE will require a CLOMR and LOMR;
(3) The proposed diversion is designed and constructed to minimize potential erosion from a base flood;
(4) For a permanent diversion structure crossing the full width of the stream channel:
(A) All other options should be studied and considered first;
(B) The structure is designed and constructed to withstand up to a base flood; and
(C) The diversion is not an obstruction to the passage of watercraft or fish.
o. The following flood control measures designed by a registered professional engineer to comply with the conditions set forth (structural flood control works often significantly obstruct and affect floodway flow capacity):
(1) Levees and floodwalls (new, reconstruction and/or maintenance) if:
(A) The proposed levee or floodwall is designed and constructed to safely convey a 100-year flood; and
(B) The cumulative effect of the levee or floodwall combined with allowable floodway fringe encroachments does not increase the unobstructed base flood elevation more than one-half foot (1/2'). The floodplain administrator may establish either a lower or higher permissible increase in the base flood elevation for individual levee projects only with concurrence from the Montana department of natural resources and conservation and the federal emergency management agency based upon consideration of the following criteria:
(i) The estimated cumulative effect of any anticipated future permissible uses; and
(ii) The type and amount of existing development in the affected area.
(C) The proposed levee or floodwall, except those to protect agricultural land, is constructed at least three feet (3') higher than the base flood elevation.
(D) For levee structures to be recognized on a FEMA map as providing flood protection, the structure must meet the criteria outlined in 44 CFR 65.10. Without the criteria being met, the area behind the uncertified structure will be shown to be in the floodplain of the flood source (river).
(2) Bank stabilization projects, such as hand placed riprap, native revetments, weirs, barbs, etc., if:
(A) It is designed to withstand a 100-year flood;
(B) It does not increase the base flood elevation;
(C) It will not increase erosion upstream, downstream, or adjacent to the site;
(D) Consideration will be given to accommodate the safe passage of watercraft in low flows; and/or
(E) It is preventive maintenance for bridge abutments, roads, industrial uses and public infrastructure.
(3) Channelization projects if they do not significantly increase the magnitude, velocity, or base flood elevation in the proximity of the project.
(4) Dams, provided that:
(A) They are designed and constructed in accordance with the Montana dam safety act and applicable safety standards; and
(B) They will not increase flood hazards downstream either through operational procedures or improper hydrologic/hydraulic design.
p. All other artificial obstructions, substantial improvements, or nonconforming uses not specifically listed in or prohibited by these regulations.
3. Prohibited Uses: The following artificial obstructions and nonconforming uses are prohibited within the floodway:
a. A building, dwelling or structure for living purposes, place of assembly or permanent use by human beings;
b. New construction of any residential dwelling, commercial or industrial building;
c. Encroachments, including fill, new construction, buildings, substantial improvements, excavations and other development that would cause water to be diverted from the established floodway, erosion of embankment, obstruction of the natural flow of waters, reduce the carrying capacity of the floodway or increase flood levels within the community during the occurrence of the 100-year flood;
d. The construction or permanent storage of an object subject to flotation or movement during the 100-year flood;
e. Mobile homes and manufactured homes;
f. Storage and disposal of solid waste, hazardous waste, toxic, flammable, or explosive materials;
g. Only those wastewater disposal systems that meet the requirements and separation distances under ARM 17.36.101-116 and ARM 17.36.301-345 are allowed;
h. Cemeteries, mausoleums, or any other places of burial of human remains.
C. Floodway Fringe:
1. Uses Allowed Without Permits: All uses allowed in the floodway without permit according to the provisions of these regulations, shall also be allowed without a permit in the floodway fringe.
2. Uses Requiring Permits: All uses allowed in the floodway subject to the issuance of a permit according to the provisions of these regulations shall also be allowed by permit within the designated floodway fringe. In addition, new construction, substantial improvements, alterations to structures (including, but not limited to, residential, commercial, agricultural and industrial), and suitable fill shall be allowed subject to the following conditions:
a. Flood Fringe: Except an encroachment is not required for development in the designated flood fringe;
b. Floodplain: The allowable encroachment increase for developments in the designated floodplain without a floodway and with or without a base flood elevation is 0.5 foot unless a lesser amount is specified in the specific supporting hydraulic analysis supports the floodplain designation study adopted herein;
c. Otherwise Prohibited: Such structures or fill must not be prohibited by any other statute, regulation, ordinance, or resolution;
d. Comprehensive Plans: Such structures or fill must be compatible with local comprehensive plans, if any;
e. Residential: The new construction, alterations, and substantial improvements of residential dwellings including manufactured homes must be constructed on suitable fill with a permanent foundation such that the lowest floor elevation (including basement) is two feet (2') or more above the BFE (base flood elevation). The suitable fill shall be at an elevation no lower than the elevation of the 100-year flood and shall extend for at least fifteen feet (15'), at that elevation, beyond the dwelling(s) in all directions. Replacement manufactured and mobile homes in an existing mobile home park or subdivision may, instead of using suitable fill, be elevated on a concrete or mortared block foundation, or other suitable permanent foundation, and anchored to prevent flotation or downstream movement.
(1) Crawl space must be designed to allow internal flooding and must be limited to storage of equipment or materials not appreciably affected by floodwaters. The floors and walls shall be designed and constructed of materials resistant to flooding to an elevation no lower than two feet (2') above the BFE. Walls shall be designed to equalize hydrostatic forces by allowing for entry and exit of floodwaters. Openings may be equipped with screens, louvers, valves, and other coverings or devices which permit the automatic entry and exit of floodwaters.
(2) For all new construction and substantial improvements, 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 must meet or exceed the following minimum criteria:
(A) A minimum of two (2) openings;
(B) Openings shall have a total net area of not less than one square inch for every square foot of enclosed area subject to flooding;
(C) The bottom of all openings shall be no higher than one foot (1') above grade;
(D) Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
f. Nonresidential: The new construction, alteration, and substantial improvement of commercial and industrial buildings must be constructed on suitable fill with a permanent foundation such that the lowest floor elevation (including basement) is two (2) or more feet above the BFE (base flood elevation), or the building must be adequately floodproofed to an elevation no lower than two feet (2') above the elevation of the 100-year flood. The building is required to be designed by a registered professional engineer, architect, or other qualified person that floodproofing methods are adequate to withstand the flood depths, hydrodynamic and hydrostatic pressures, velocities, impact, buoyancy, and uplift forces associated with the 100-year flood.
(1) If the building is designed to allow internal flooding of the lowest floor, use of the lowest floor must be limited to parking, loading areas, and storage of equipment or materials not appreciably affected by floodwaters. The floors and walls shall be designed and constructed of materials resistant to flooding to an elevation no lower than two feet (2') above the BFE. Walls shall be designed to equalize hydrostatic forces by allowing for entry and exit of floodwaters. Openings may be equipped with screens, louvers, valves, and other coverings or devices which permit the automatic entry and exit of floodwaters.
(2) Buildings whose lowest floors are used for a purpose other than parking, loading, or storage of materials resistant to flooding shall be waterproofed to an elevation no lower than two feet (2') above the BFE. Floodproofing shall include impermeable membranes or materials for floors and walls and watertight enclosures for all windows, doors and other openings. These buildings shall be designed to withstand the hydrostatic pressures and hydrodynamic forces resulting from the base flood.
(3) Floodproofing of electrical, heating and plumbing systems shall be accomplished in accordance with subsection E of this section.
g. Manufactured Homes: All manufactured homes placed in the floodway fringe shall be installed using methods and practices which minimize flood damage and must have the chassis securely anchored to a foundation system that will resist flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, over the top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces. The following conditions also apply:
(1) When a manufactured home is: a) altered, b) replaced because of substantial damage as a result of a flood or c) replaced on an individual site, the lowest floor must be elevated two feet (2') above the base flood elevation. The home can be elevated on fill or raised on a permanent foundation of reinforced concrete, reinforced mortared block, reinforced piers, or other foundation elements of at least equivalent strength.
(2) Replacement or substantial improvement of manufactured homes in an existing manufactured home park, site outside a manufactured home park or subdivision, or subdivision must be raised on a permanent foundation. The lowest floor must be two feet (2') above the base flood elevation. The foundation must consist of reinforced concrete, reinforced mortared block, reinforced piers, or other foundation elements of at least equivalent strength.
(3) Manufactured homes proposed for use as commercial or industrial buildings must be elevated and anchored, rather than floodproofed.
h. Fill Material: Fill material placed in the floodway fringe must be stable, compacted, well graded, pervious, generally unaffected by water and frost, devoid of trash or similar foreign matter, devoid of tree stumps or other organic material, and appropriate for the purpose of supporting the intended use and/or permanent structure;
i. Roads, Streets, Highways And Rail Lines: Roads, streets, highways and rail lines shall be designed to minimize any increase in flood heights. Where failure or interruption of transportation facilities would result in danger to the public health or safety, the facility shall be located two feet (2') above the elevation of the 100-year flood;
j. Agricultural Buildings: Agricultural buildings that have a low damage potential, such as sheds, barns, shelters, and hay or grain storage structures must be adequately anchored to prevent flotation or collapse and all electrical facilities shall be placed two feet (2') above the base flood elevation;
k. Recreational Vehicles: Recreational vehicles must meet the following requirements:
(1) Be on the site for fewer than one hundred eighty (180) consecutive days, or
(2) Be fully licensed and ready for highway use, or
(3) Meet the permit requirements of subsection 12-1-7C of this chapter, and the elevation and anchoring requirements for "manufactured homes" in subsection C2g of this section. A recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions.
3. Prohibited Uses: The following artificial obstructions and nonconforming uses are prohibited within the floodway fringe:
a. Only those wastewater disposal systems that meet the requirements and separation distances under ARM 17.36.101-116 and ARM 17.36.301-345 are allowed;
b. Storage and disposal of solid waste, hazardous waste, toxic, flammable, or explosive materials; and
c. Cemeteries, mausoleums, or any other places of burial of human remains.
D. Standards For Subdivision Proposals:
1. Review subdivision proposals and other development, including manufactured home parks or subdivisions, to determine whether such proposals will be reasonably safe from flooding. If a subdivision or other development proposal is in a flood prone area, assure that such proposals minimize flood damage.
2. Base flood elevation data shall be generated for subdivision proposals and other proposed development including the placement of manufactured home parks and subdivisions which is greater than fifty (50) lots or five (5) acres, whichever is lesser.
3. All subdivision proposals including the placement of manufactured home parks and subdivisions shall have adequate drainage provided to reduce exposure to flood hazards.
4. All subdivision proposals including the placement of manufactured home parks and subdivisions shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize or eliminate flood damage.
E. Floodproofing Requirements:
1. Certification: If the following floodproofing requirements are to be utilized for a particular structure in accordance with these regulations, the methods used must be certified as adequate by a registered professional engineer, architect, or other qualified person.
2. Conformance: Permitted floodproofing systems shall conform to the conditions listed below and the floodproofing standards listed in subsection C2f of this section for commercial and industrial buildings:
a. Electrical Systems:
(1) All incoming power service equipment, including all metering equipment, control centers, transformers, distribution and lighting panels, and all other stationary equipment must be located at least two feet (2') above the elevation of the 100-year flood.
(2) Portable and movable electrical equipment may be placed below the elevation of the 100-year flood, provided that the equipment can be disconnected by a single plug and socket assembly of the submersible type.
(3) The main power service lines shall automatically operate electrical disconnect equipment of manually operated electrical disconnect equipment located at an accessible remote location outside the designated floodplain and above the elevation of the 100-year flood.
(4) All electrical wiring systems installed below the elevation of the 100-year flood shall be suitable for continuous submergence and may not contain fibrous components.
b. Heating Systems:
(1) Float operated automatic control valves must be installed in gas furnace supply lines so that fuel supply is automatically shut off when floodwaters reach the floor level where the furnace is located.
(2) Manually operated gate valves must be installed in gas supply lines. The gate valves must be operable from a location above the elevation of the 100-year flood.
(3) Electric heating systems must be installed in accordance with the provisions of subsection E2a(1) of this section.
c. Plumbing Systems:
(1) Sewer lines, except those to be buried and in sealed vaults, must have check valves installed to prevent sewage backup into permitted structures.
(2) All toilets, stools, sinks, urinals, and drains must be located so the lowest point of possible entry is at least two feet (2') above the 100-year flood elevation. (Ord. 325-11, 8-23-2011, eff. 9-1-2011)
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