Planning Commission grants freeboard waiver for Demco bridal site after engineering review

The Livingston Parish Planning Commission voted June 4 to grant a waiver reducing the freeboard requirement for the Demco 4H Club bridal site plan, after the applicant’s engineer and parish engineering staff described site constraints and modeling.

John Gibson, identifying himself as the engineer for the Demco development, told the commission the site has a very shallow pond and a relatively high outlet and is a fill-mitigated site, which limits the ability to provide the full freeboard standard: "We're asking for a waiver on the freeboard requirement ... We have a very shallow pond and, a very high outlet ... This is also a fill mitigated site," he said. Gibson added that the design can hold the 100-year rainfall event based on the submitted calculations but that providing additional freeboard would require further raising or lowering site grades that are not feasible at this location.

A parish engineering staff member explained the freeboard requirement and recent rule changes: commercial freeboard was previously 1.0 foot but had been changed to 0.5 foot for commercial sites under the current drainage criteria. The staff member said freeboard serves as an extra safety margin above the 100-year water-surface elevation and noted that the applicant’s calculations indicate the retention pond’s high-water elevation would remain below the top bank even in a 100-year event.

Commissioners discussed the trade-offs between strict freeboard enforcement and the site’s physical constraints. Following a motion to approve the waiver, the commission voted in favor and the waiver was granted.

The commission’s action will allow the applicant to proceed with final site plan processing with the approved freeboard exception; parish engineering will continue to require drainage-impact documentation and will monitor final grading and permit conditions.