Lake County, IL Environmental Rules: Coastal Development (2026)

149(I) sets the building protection requirements for the Coastal High Hazard Area (CHHA), the zone shown on the Flood Insurance Rate Map subject to high-velocity wave action off Lake Michigan. Every new structure and every substantial improvement in or partly in the CHHA must be elevated on pilings or columns so the bottom of the lowest horizontal structural member sits at or above the base flood elevation (BFE) plus one foot, with the pile or column foundation anchored against flotation, collapse, and lateral movement from combined wind and water loads.

A licensed professional structural engineer or architect must develop or review the structural design and certify that it meets these standards. The space below the lowest floor must stay free of obstruction or use only breakaway walls, open lattice-work, or insect screening designed to fail without damaging the elevated structure; a standard breakaway wall carries a design safe loading resistance of 10 to 20 pounds per square foot, and anything stronger needs an engineer's certification that it will still collapse before the elevated structure is compromised.

Manufactured home placement and substantial improvement must meet the same pile/column and breakaway-wall standards, and recreational vehicles must either stay fewer than 180 consecutive days, remain fully licensed and highway-ready, or comply with the same building protection requirements. The subsection flatly bars using fill for structural support of any building in the CHHA; non-structural fill is allowed only when an engineering report shows it will not cause wave runup, ramping, or floodwater deflection that damages buildings. Man-made alteration of sand dunes in the CHHA is likewise prohibited unless an engineering report documents that the alteration will not reduce the dunes' wave and flow dissipation and increase flood damage potential.

Bulkheads, seawalls, revetments, and other shoreline erosion-control structures cannot be tied into a building's foundation or superstructure and must be designed so they do not redirect floodwaters or add flood or erosion forces onto neighboring structures. The section was adopted as Ord. 5 on 10-13-2009 and last amended by Ord. 23-1056, passed 8-8-2023.