PATTERSON — Two proposals for a permanent structure to prevent flooding in St. Mary and surrounding areas from backwater during hurricanes and riverine events each are estimated to cost nearly $60 million.
Nicole Cutforth of Shaw Environmental & Infrastructure told the St. Mary Parish Levee District Thursday that the project, which consists of a levee and floodgate, is expected to cost about $59.81 million if the sill depth is at 22 feet and $59.62 million if the sill depth is at 12 feet deep for the floodgate, which is proposed to be placed across the Gulf Intracoastal Waterway just east of Bayou Boeuf. Both prices include contingency costs.
The protection also would require that a 5.2-mile stretch of levee construction would have to be undertaken from the Avoca Island levee to a railroad embankment south of U.S. 90 to raise it to nine feet.
The structure would include a 250-foot opening at a nine-foot elevation, a 270-foot steel swing barge with a nine-foot elevation. Two deck options were presented to match sill elevations.
Six 48-inch hydraulic pumps on the steel gates also would be installed for use when the gate is closed.
The levee construction costs are pegged at about $13.8 million, while the floodwall and additional materials needed for a 22-foot deep sill in the waterway are $31 million, while those for a 12-foot deep sill are about $33 million.
A floodgate with a 22-foot depth is $8.5 million, while one with a 12-foot depth is $6.3 million
The six 48-inch pumps necessary would cost about $1 million.
In other flood protection matters, Cutforth reported that in mid to late October, construction could begin on the Franklin Canal. She said funds should be released to the Office of Coastal Protection and Restoration on May 30, and land acquisition would begin after.