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For purposes of this chapter, the base flood elevation shall be determined as follows:
(a) The base flood elevation for riverine floodplains shall be as delineated on the base flood profiles in the F.I.S.
(b) The base flood elevation for each floodplain delineated as an "AH Zone" or "AO Zone" shall be the elevation (or depth) specified on the F.I.R.M.
(c) The base flood elevation for each of the remaining floodplains delineated as "A Zones" on the F.I.R.M. shall be as specified on the F.I.R.M. or, if no flood elevation is specified on the F.I.R.M., the applicant shall finance an engineering study and submit the resulting study to F.E.M.A. and I.D.N.R./O.W.R. for review and approval.
(d) The base flood elevation for any floodplain delineated as a "VE Zone" shall be the highest elevation specified on the F.I.R.M. among all zones affecting the development.
(e) Where the permit applicant disagrees with the base flood elevation established pursuant to subsections (a) through (d), the permit applicant may obtain, at the permit applicant's sole expense, an engineering study and submit the resulting study to F.E.M.A. and I.D.N.R./O.W.R. for review and approval.
(Added Coun. J. 7-21-21, p. 33505, § 2)
Within the floodway, and within all other S.F.H.A.s where a floodway has not been delineated, the following standards shall apply:
(a) Except as provided in subsection (b) of this section, no development shall be allowed which, acting in combination with existing and anticipated development, will cause any increase in flood heights or velocities. The following specific development activities shall be considered as meeting this requirement:
(i) Barge fleeting facilities meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 3;
(ii) Aerial utility crossings meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 4;
(iii) Minor boat docks meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 5;
(iv) Minor, non-obstructive activities meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 6;
(v) Outfall structures and drainage ditch outlets meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 7;
(vi) Underground pipeline and utility crossings meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 8;
(vii) Bank stabilization projects meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 9;
(viii) Accessory structures and additions to existing residential buildings meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 10;
(ix) Minor maintenance dredging activities meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 11;
\ (x) Bridge and culvert replacement structures and bridge widening meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 12;
(xi) Temporary construction activities meeting the conditions of I.D.N.R./O.W.R. Statewide Permit Number 13: and
(xii) Any development determined by I.D.N.R./O.W.R. to be located entirely in a flood fringe area.
(b) Other development activities not listed in subsection (a) of this section may be permitted only if:
(i) A permit has been issued for the work by I.D.N.R./O.W.R. (or written documentation is provided that an I.D.N.R./O.W.R. permit is not required); and
(ii) Sufficient data has been provided to F.E.M.A. under the map revision process and a CLOMR/LOMR has been obtained from F.E.M.A. when necessary.
(Added Coun. J. 6-28-91, p. 2766; Amend Coun. J. 6-29-05, p. 51811, § 1; Amend Coun. J. 7-21-21, p. 33505, § 3)
In Zone VE, all development must meet the following requirements:
(a) The use of fill for structural support of buildings is prohibited.
(b) Non-structural fill shall be permitted only if an engineering report demonstrates that the fill will not cause runup, ramping, or deflection of floodwaters that cause damage to buildings.
(c) Man-made alterations of sand dunes are prohibited unless an engineering report documents that the alterations will not increase potential flood damage by reducing the wave and flow dissipation characteristics of the sand dunes.
(d) Bulkheads, seawalls, revetments, and other erosion control structures shall not be connected to the foundation or superstructure of a building and shall be designed and constructed so as not to direct floodwaters or increase flood forces or erosion impacts on the foundation or superstructure of any building.
(Added Coun. J. 7-21-21, p. 33505, § 4)
(a) Construction or placement of a new building is valued at more than $1,000.00;
(b) Structural alterations made to an existing building increase the floor area by more than 20 percent, or the market value of the building by more than 50 percent;
(c) Reconstruction or repairs made to a damaged building are valued at or more than 50 percent of the market value (or depreciated replacement value, if no applicable market value) of the building before the damage occurred;
(d) A manufactured home is installed on a new site or a new manufactured home is installed on an existing site; this requirement does not apply to returning a manufactured home to the same site it lawfully occupied before it was removed to avoid flood damage; and
(e) The building is a recreational vehicle installed on a site for more than 180 days.
(Added Coun. J. 6-28-91, p. 2766; Amend Coun. J. 6-29-05, p. 51811, § 1; Amend Coun. J. 7-21-21, p. 33505, § 5)
Buildings located in Zones A, AO, AH or AE that are subject to Section 16-6-060 must meet the protection requirements described in this section.
(a) If a building is constructed on a permanent landfill:
(i) The fill shall be placed in layers no more than six inches deep before compaction and shall extend at least ten feet beyond the outside of the wall of the existing or proposed building;
(ii) The fill shall be protected against erosion and scour by vegetative cover, riprap or other structural measure;
(iii) The fill shall be homogeneous and isotropic;
(iv) The fill shall not adversely affect the flow of surface drainage from or onto the property;
(v) The foundation and supporting members shall be anchored and aligned in relation to flood flows and adjoining structures so as to minimize exposure to known hydrodynamic forces such as current, waves, ice and floating debris;
(vi) All areas below the F.P.E. shall be constructed of materials resistant to flood damage. The lowest floor (including basement) and all electrical, heating, ventilating, plumbing and air conditioning equipment and utility meters shall be located at or above the F.P.E. water and sewer pipes, electrical and telephone lines, submersible pumps and other waterproofed service facilities may be located below the F.P.E.
(b) If a building is elevated:
(i) The building improvements shall be elevated on posts, piers, piles, walls, or other foundation that is permanently open to flood waters.
(ii) The foundation and supporting members shall be anchored and aligned in relation to flood flows and adjoining structures so as to minimize exposure to known hydrodynamic forces such as current, waves, ice and floating debris;
(iii) All areas below the F.P.E. shall be constructed of materials resistant to flood damage. The lowest floor (including basement) and all electrical, heating, ventilating, plumbing and air conditioning equipment and utility meters shall be located at or above the F.P.E. water and sewer pipes, electrical and telephone lines, submersible pumps and other waterproofed service facilities may be located below the F.P.E.
(iv) If walls are used, all enclosed areas below the flood protection elevation shall address hydrostatic pressures by allowing the automatic entry and exit of floodwaters. Designs must either be certified by a registered professional engineer or by having a minimum of one permanent opening on at least two different walls no more than one foot above grade. The openings shall provide a total net area of not less than one square inch for every one square foot of enclosed area subject to flooding below the base flood elevation.
(v) Any area below the F.P.E. shall be used solely for parking, building access or storage and shall not later be converted to habitable space or other uses.
(c) A nonresidential building not built on permanent landfill and not elevated shall be floodproofed in accordance with the following:
(i) A registered professional engineer shall certify that the building has been designed so that below the F.P.E., the structure and attendant utility facilities are watertight and capable of resisting the effect of the base flood. The building design shall take into account flood velocities, duration, rate of rise, hydrostatic and hydrodynamic forces, the effects of buoyancy, and impacts from debris and ice;
(ii) Floodproofing measures shall be operable without human intervention and without an outside source of electricity.
(d) A recreational vehicle is to be installed on a site for more than 180 days, or a manufactured home, shall be elevated at or above the F.P.E. and anchored to resist flotation, collapse or lateral movement by being tied down in accordance with the rules and regulations issued pursuant to the Illinois Home Tie-Down Act, as amended.
(Added Coun. J. 6-28-91, p. 2766; Amend Coun. J. 6-29-05, p. 51811, § 1; Amend Coun. J. 7-21-21, p. 33505, § 6)
Buildings located in Zone VE that are subject to Section 16-6-060 must meet the protection requirements described in this section.
(a) All new construction and substantial improvements shall be elevated on pilings or columns so that the bottom of the lowest horizontal structural member of the lowest floor (excluding the pilings or columns) is elevated to or above the F.P.E., and the pile or column foundation and structure attached thereto is anchored to resist flotation, collapse, and lateral movement due to the effects of wind and water loads acting simultaneously on all building components.
(i) Water loading values used shall be those associated with the base flood.
(ii) Wind loading values shall determined in accordance with Title 14B.
(b) A licensed structural engineer or architect shall develop or review the structural design, specifications and plans for the construction, and shall certify that the design and methods of construction to be used are in accordance with accepted standards of practice for meeting the provisions of Section 16-6-071(a).
(c) All new construction and substantial improvements shall have the space below the lowest floor either free of obstruction or constructed with non-supporting breakaway walls, open wood lattice-work, or insect screening intended to collapse without causing collapse, displacement, or other structural damage to the elevated portion of the building or supporting foundation system.
(i) For the purpose of this section, a breakaway wall shall have a design safe loading resistance of not less than 10 and no more than 20 pounds per square foot.
(ii) Use of breakaway wails which exceed a design safe loading resistance of 20 pounds per square foot shall be allowed only if a licensed structural engineer or architect certifies that the designs proposed meet all of the following conditions:
(A) Breakaway wall collapse shall result from a water load less than that which would occur during the base flood; and
(B) The elevated portion of the building and supporting foundation system shall not be subject to collapse, displacement, or other structural damage due to the effects of wind and water loads acting simultaneously on all building components (structural and non-structural). Water loading values shall be those associated with the base flood. Wind loading shall be as specified in Title 14B.
(iii) All space enclosed by breakaway walls, open wood lattice-work, or insect screening below the lowest floor shall be used solely for parking of vehicles, building access, or storage.
(d) Placement or substantial improvement of manufactured homes must comply with Section 16-6-071(a) through (c).
(e) Recreational vehicles must either:
(i) Be on site for fewer than 180 consecutive days;
(ii) Be fully licensed and ready for highway use; or
(iii) Comply with Section 16-6-071(a) through (c).
(Added Coun. J. 7-21-21, p. 33505, § 7)
(b) No development within the S.F.H.A. shall include locating or storing of chemicals, explosives, buoyant materials, flammable liquids, pollutants, or other hazardous or toxic materials below the flood protection elevation unless such materials are stored in a floodproofed and anchored storage tank and certified by a professional engineer or are within a floodproofed non-residential building constructed in accordance with the requirements of Section 16-6-060.
(c) Public utilities and facilities such as sewer, gas and electric shall be located and constructed to minimize or eliminate flood damage.
(d) Public sanitary sewer systems and water supply systems shall be located and constructed to minimize or eliminate infiltration of flood waters into the system and discharges from the system into flood waters.
(e) New and replacement on-site sanitary sewer lines or waste disposal systems shall be located and constructed to avoid impairment to them or contamination from them during flooding conditions.
(f) Sanitary sewer manholes or other above- ground openings located below the F.P.E. shall be watertight.
(g) All other development within the S.F.H.A. shall be designed so as to not alter or block flood flows or increase the potential for flood damages.
(h) In Zone AO and AH, drainage paths shall be provided around buildings on sloped ground to guide water around and away from the buildings.
(Added Coun. J. 6-29-05, p. 51811, § 1; Amend Coun. J. 7-21-21, p. 33505, § 8)
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