Compensatory storage is an artificially excavated, storage volume within the 100-year floodplain that is required to offset the loss of natural storage capacity caused by the placement of fill, structures, or other materials above the existing natural grade. Compensatory storage must meet the following requirements (For the full description of the requirements, please see the Section 15.68 of the Village’s Flood Hazard Protection Ordinance and the MWRD WMO, Article 6):
- Equal to at least 1.1 the volume of flood storage lost below the BFE;
- Be operational prior to the placement of any fill;
- Must be able to drain without the use of a pump or other mechanical means;
- Must be freely flowing into and out of the storage facility (no underground compensatory storage unless at least one end of the pipe/system is exposed to the invert of the pipe/system).