(b) Subdivisions and other new development.
(1) All subdivision proposals and all other proposed new development shall be consistent with the need to minimize flood damage and are subject to all applicable standards in these regulations;
(2) All subdivision proposals and all other proposed new development shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage;
(3) All subdivision proposals and all other proposed new development shall have adequate drainage provided to reduce exposure to flood damage;
(4) In all areas of special flood hazard (floodway or 100-year floodplain) where base flood elevation data are not available, the applicant shall provide a hydrologic and hydraulic engineering analysis that generates base flood elevations for all subdivision proposals and other proposed developments containing at least 50 lots or five acres, whichever is less. If a development is less than 50 lots or five acres, this hydrologic and hydraulic analysis may be required at the discretion of the City Engineer;
The hydraulic analysis shall consist of the following:
A. SWMM model (or other as agreed upon by the City Engineer) using tail water and back flow calculations;
B. Analysis of both the effects of the proposed development on the entire watershed and the adjacent parcels;
(5) In the absence of any more restrictive standard provided under the Ohio Revised Code or applicable state rules all new and replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the systems;
(6) In the absence of any more restrictive standard provided under the Ohio Revised Code or applicable state rules new and replacement sanitary sewerage systems shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharge from the systems into flood waters;
(7) In the absence of any more restrictive standard provided under the Ohio Revised Code or applicable state rules on-site waste disposal systems shall be located to avoid impairment to or contamination from them during flooding; and
(9) All wet ponds or other SCMs (as deemed necessary by the City Engineer) within a 1% (100-year) floodplain or floodway shall have their top of banks at a minimum height of one foot above the 1% (100-year) floodplain elevation.
(c) Residential Structures.
(1) New construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Where a structure, including its foundation members, is elevated on fill to or above the base flood elevation, the requirements for anchoring and construction materials resistant to flood damage are satisfied, as long as all requirements of the LOMR-F are satisfied.
(2) New construction and substantial improvements shall be constructed with methods and materials resistant to flood damage.
(3) 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 elevated so as to prevent water from entering or accumulating within the components during conditions of flooding.
(4) New construction and substantial improvement of any residential structure, including manufactured homes, shall have the lowest floor, including basement, elevated to the flood protection elevation (one and one-half feet above BFE).
(5) If there is no flood protection elevation data available based on the County Flood Insurance Maps, then the structure shall have the lowest floor, including basement, elevated at least two feet above the highest adjacent natural grade unless approved by both the City Engineer and the Floodplain Administrator.
(6) New construction and substantial improvements, including manufactured homes, that do not have basements and that are elevated to the flood protection elevation using pilings, columns, posts, or solid foundation perimeter walls with openings openings to allow the automatic equalization of hydrostatic pressure may have an enclosure below the lowest floor, provided the enclosure meets the following standards:
A. Be used only for the parking of vehicles, building access, or storage; and
B. Be designed and certified by a registered professional engineer or architect to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of flood waters; or
C. Have a minimum of two openings on different walls having a total net area not less than one square inch for every square foot of enclosed area, and the bottom of all such openings being no higher than one foot above grade. The openings may be equipped with screens, louvers, or other coverings or devices, provided that they permit the automatic entry and exit of flood waters.
(7) Manufactured homes shall be affixed to a permanent foundation and anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors.
(8) Repair or rehabilitation of historic structures upon a determination that the proposed repair or rehabilitation will not preclude the structure's continued designation as a historic structure and is the minimum necessary to preserve the historic character and design of the structure, shall be exempt from the development standards of this section.
(9) In AO and/or AH Zones, new construction and substantial improvement shall have adequate drainage paths around structures on slopes to guide flood waters around and away from the structure.
(10) If a new residential structure is being built into an existing residential subdivision after this chapter is enacted, then the final floor elevation of the new residential structure must be within one foot of the final floor elevation indicated on the final plat for the residential subdivision.
(11) Applicant shall adhere to the permitting requirement set forth in Section 1464.13(b)(2).
(d) Nonresidential Structures.
(2) New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall either have the lowest floor, including basement, elevated to or above the level of the flood protection elevation; or, together with attendant utility and sanitary facilities, shall meet all of the following standards:
A. Be dry floodproofed so that the structure is watertight with walls substantially impermeable to the passage of water to the level of the flood protection elevation;
B. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
C. Be certified by a registered professional engineer or architect, through the use of a Federal Emergency Management Agency Floodproofing Certificate, that the design and methods of construction are in accordance with Section 1464.23(d)(2)A. and (d)(2)B.
(e) Accessory Structures.
(1) Relief to the elevation or dry floodproofing standards within zones A, A1- 30, AE, AO, and AH may be granted for accessory structures containing no more than 600 square feet. Such structures must meet the following standards:
A. They shall not be used for human habitation;
B. They shall be constructed of flood-resistant materials;
C. They shall be constructed and placed on the lot to offer the minimum resistance to the flow of flood waters;
D. They shall be firmly anchored to prevent flotation;
E. Service facilities such as electrical and heating equipment shall be elevated or floodproofed to or above the level of the flood protection elevation (BFE);
F. They shall meet the opening requirements of Section 1464.23(c)(6)C.; and
G. They shall not be located within the floodway.
(f) Recreational Vehicles within zones A,A1-30, AE, AO, and AH.
(1) Recreational vehicles must meet at least one of the following standards:
A. They shall not be located on sites in special flood hazard areas for more than 180 days; or
B. They must be fully licensed and ready for highway use; or
C. They must meet all standards of Section 1464.23(c).
(g) Above-ground Gas or Liquid Storage Tanks.
(1) Within zones A, A1-30, AE, AO, and AH all above-ground gas or liquid storage tanks shall be anchored to prevent flotation or lateral movement resulting from hydrodynamic and hydrostatic loads if they are located on a lot that is within 1,000 feet of a floodway, 100-year floodplain, or a 500-year floodplain.
(h) Assurance of Flood-carrying Capacity.
(1) Pursuant to the purpose and methods of reducing flood damage stated in these chapters, the following additional standards are adopted to assure that the reduction of the flood-carrying capacity of watercourses is minimized:
(2) Development in floodways.
A. In floodway areas, development shall cause no increase in flood levels during the occurrence of the base flood discharge (i.e. there is no increase in the flood levels during a 100-year storm). Prior to issuance of a floodplain development permit, the applicant must submit a hydrologic and hydraulic analysis, conducted by a registered professional engineer, demonstrating that the proposed development activity within the floodplain would not result in any increase in the base flood elevation; or
B. Development in floodway areas causing increases in the base flood elevation may be permitted provided all of the following are completed by the applicant:
1. Meet the requirements to submit technical data in Section 1464.20(a):
2. An evaluation of alternatives, which would not result in increased base flood elevations and an explanation why these alternatives are not feasible;
3. Certification that no structures are located in areas that would be impacted by the increased base flood elevation;
4. Documentation of individual legal notices to all impacted property owners within and outside the community, explaining the impact of the proposed action on their property;
5. A CLOMR approval by FEMA prior to the acceptance of the Floodplain Development Permit;
6. A LOMR (or LOMR-F) approval by FEMA prior to issuance of any building permits for structures;
7. Certificate of compliance issued by the City prior to final occupancy permit issuance;
8. Concurrence of the Mayor of Avon and the Chief Executive Officer of any other communities impacted by the proposed actions; and
9. Concurrence of the City Engineer.
(3) Development in riverine areas with base flood elevations but no floodways.
A. In riverine special flood hazard areas identified by FEMA where base flood elevation data are provided but no floodways have been designated, the cumulative effect of any proposed development, when combined with all other existing and anticipated development, shall not raise the base flood elevation at any point. Prior to issuance of a floodplain development permit, the applicant must submit a hydrologic and hydraulic analysis, conducted by a registered professional engineer, demonstrating that this standard has been met; or
B. Development in riverine special flood hazard areas identified by FEMA where base flood elevation data are provided but no floodways have been designated causing any increase in the base flood elevation is not permitted.
(4) Alterations of a watercourse.
A. For the purpose of these chapters, a watercourse is altered when any change occurs within its banks. The extent of the banks shall be established by a field determination of the bankfull stage. The field determination of bankfull stage shall be based on methods presented in Chapter 7 of the USDA Forest Service General Technical Report RM-245, Stream Channel Reference Sites: An Illustrated Guide to Field Technique or other applicable publication available from a Federal, State, or other authoritative source. For all proposed developments that alter a watercourse, the following standards apply:
B. The bankfull flood-carrying capacity of the altered or relocated portion of the watercourse shall not be diminished. Prior to the issuance of a floodplain development permit, the applicant must submit a description of the extent to which any watercourse will be altered or relocated as a result of the proposed development, and certification by a registered professional engineer that the bankfull flood-carrying capacity of the watercourse will not be diminished.
C. Adjacent communities, the U.S. Army Corps of Engineers, and the Ohio Department of Natural Resources, Division of Water, must be notified prior to any alteration or relocation of a watercourse. Evidence of such notification must be submitted to the Federal Emergency Management Agency,
D. The applicant shall be responsible for providing the necessary maintenance for the altered or relocated portion of said watercourse so that the flood-carrying capacity will not be diminished. The Floodplain Administrator may require the permit holder to enter into an agreement with the City, specifying the maintenance responsibilities. If an agreement is required, it shall be made a condition of the floodplain development permit.
E. The applicant shall meet the requirements to submit technical data in Section 1464.20(a)(1)C. when an alteration of a watercourse results in the relocation or elimination of the special flood hazard area, including the placement of culverts.
(5) LOMAs/LOMRs/LOMR-Fs.
A. In areas that used to be in floodways or floodplains, but have been modified, with either a Letter of Map Amendment (LOMA) or a Letter of Map Revision (LOMR), or a Letter of Map Revision - Based On Fill (LOMR-F) the following must be followed for residential and nonresidential structures.
1. The lowest level of the structure, including basements, must not be below the BFE unless the following is followed:
a. The ground surface around the building and within 20 feet from the edge of the SFHA (special flood hazard area) must be one foot above the BFE.
b. The setback is the distance from the edge of the SFHA to the nearest wall of the basement.
c. The ground around the building must be suitable compacted fill; the fill material (or soil of similar classification and degree of permeability) must extend to at least five feet below the bottom of the basement floor slab if the soil below is not considered suitable.
d. The fill material must be compacted to at least 95% of Standard Laboratory Maximum Dry Density, according to ASTM Standard D-698. Fill soils must be fine- grained soils of low permeability, such as those classified as CH (clay of high plasticity), CL (clay of low plasticity, SC (sand with clayey fines), or ML (silt) according to ASTM Standard D-2487, Classification of Soils for Engineering Purposes.
e. The fill material must be homogeneous and isotropic; that is, the soil must be all of one material, and the engineering properties must be the same in all directions.
f. The elevation of the basement floor should be no more than five feet below the BFE.
g. A granular drainage layer beneath the floor slab, and a one-half HP sump pump (in accordance with Section 1050.14(a) with a backup power supply must be provided to remove the seepage flow. The pump must discharge above the BFE and away from the building. Sump pump discharge shall be routed above the BFE before down turning for discharge to gravity drainage.
h. The drainage system must be equipped with a positive means of preventing backflow.
i. Downspout collection systems must discharge via gravity to a storm sewer or other method as approved by the City Engineer. Foundation drains must discharge via a sump pump up to the gravity storm sewer system or other method as approved by the City Engineer.
j. The basement must be designed to withstand any hydrostatic pressures.
k. All work will be supervised by a licensed professional engineer. At the end of the project, a certified letter is required from said engineer stating that all work was done in compliance with this section.
l. A notarized letter, signed by the property owner, that acknowledges that there could be potential flooding of the basement and relieves the City from any and all responsibility, should flooding occur.
2. All other items indicated within Section 1464.23(c) must be adhered to.
(Ord. 96-08. Passed 7-14-08; Ord. 129-12. Passed 11-26-12; Ord. 78-15. Passed 7-13-15; Ord. 10-21. Passed 2-22-21.)