Chapter 28 - Special Flood Hazard Area Development Regulations
Division 7 - Protecting Buildings

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SEC. 28.7. – PROTECTING BUILDINGS.

1. In addition to the damage prevention requirements of SEC. 28.6, all buildings to be located in the floodplain shall be protected from flood damage below the flood protection elevation. This building protection requirement applies to the following situations:
    
   1. construction or placement of a new building valued at more than $1,000;
       
   2. substantial improvements made to an existing building;
       
   3. structural alterations made to an existing building that increase the floor area by more than 20%;
       
   4. installing a manufactured home on a new site or a new manufactured home on an existing site (the building protection requirements do not apply to returning a manufactured home to the same site it lawfully occupied before it was removed to avoid flood damage); and
       
   5. installing a travel trailer on a site for more than 180 days.
       
2. Residential or non-residential buildings can meet the building protection requirements by one of the following methods:
    
   1. The building may be constructed on permanent landfill in accordance with the following:
       
      1. the lowest floor (including basement) shall be at or above the flood protection elevation;
          
      2. the fill shall be placed in layers no greater than one foot before compaction and should extend at least ten feet beyond the foundation before sloping below the flood protection elevation;
          
      3. the fill shall be protected against erosion and scour during flooding by vegetative cover, riprap, or other structural measure. If vegetative cover is used, the slopes shall be no steeper than 3 horizontal to 1 vertical;
          
      4. the fill shall be composed of rock or soil and not incorporate debris or refuse materials; and
          
      5. the fill shall not adversely affect the flow of surface drainage from or onto neighboring properties and when necessary, stormwater management techniques such as swales or basins shall be incorporated; or
          
   2. The building may be elevated in accordance with the following:
       
      1. The building or improvements shall be elevated on stilts, piles, walls, or other foundation that is permanently open to flood waters;
          
      2. The lowest floor and all electrical, heating, ventilating, plumbing, and air conditioning equipment and utility meters shall be located at or above the flood protection elevation;
          
      3. If walls are used, all enclosed areas below the flood protection elevation shall address hydrostatic pressures by allowing the automatic entry and exit of flood waters. Designs must either be certified by a registered professional engineer or by having a minimum of one permanent openings on each wall 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;
          
      4. the foundation and supporting members shall be anchored and aligned in relation to flood flows and adjoining structures so as to minimize exposure to hydrodynamic forces such as current, waves, ice and floating debris;
          
      5. the finished interior grade shall not be less than the finished exterior grade;
          
      6. all structural components below the flood protection elevation shall be constructed of materials resistant to flood damage;
          
      7. water and sewer pipes, electrical and telephone lines, submersible pumps, and other service facilities may be located below the flood protection elevation provided they are waterproofed; and
          
      8. the area below the flood protection elevation shall be used solely for parking or building access and not occupied as habitable space.
          
3. Manufactured homes, or travel trailers to be installed on site for more than 180 days, shall be:
    
   1. elevated to or above the flood protection elevation; and
       
   2. shall be anchored to resist flotation, collapse, or lateral movement by being tied down in accordance with the Rules and Regulations for the Illinois Mobile Home Tie-Down Act issued pursuant to 77 IL Adm. Code 870.
       
4. Non-residential buildings may be structurally dry floodproofed (in lieu of elevation) provided a registered professional engineer or architect certifies that:
    
   1. below the flood protection elevation the structure and attendant utility facilities are watertight and capable of resisting the effects of the base flood;
       
   2. the building design accounts for flood velocities, duration, rate of rise, hydrostatic and hydrodynamic forces, the effects of buoyancy, and the impact from debris and ice; and
       
   3. floodproofing measures will be incorporated into the building design and operable without human intervention and without an outside source of electricity.
       
   Levees, berms, floodwalls and similar works are not considered floodproofing for the purpose of this subsection.