Corps recommends opening spillway to divert Mississippi
By KEVIN MCGILL
Mar. 05, 2018
NEW ORLEANS (AP) — A flood control structure upriver from New Orleans will likely be opened Thursday to keep pressure off the levee system that protects the city, a U.S. Army Corps of Engineers official said.
Col. Mike Clancy, commander of the Corps' New Orleans district, told reporters Monday that the plan is for the Bonnet Carre Spillway to be partially opened beginning at 10 a.m. Thursday to divert some of the rising river's flow into nearby Lake Pontchartrain.
Clancy said he recommended opening the structure and expected to get a final decision from the commander of the Corps' Mississippi Valley District by Tuesday. Clancy said the river had reached 14 feet (4.3 meters) at a key New Orleans gauge Monday. It was expected to reach 15 feet (4.6 meters) by Wednesday. A rising river means a faster and more powerful current, and that means more pressure on the levees.
"We don't want the water to be higher than 17 feet (5.2 meters) in New Orleans," Clancy said during an outdoor news conference at the Corps' New Orleans headquarters on the river.
The Corps said in a news release that heavy rains on the Mississippi and Ohio rivers and their tributaries have caused high water throughout the Mississippi River Valley.
Gov. John Bel Edwards and other local officials were to be briefed on the opening before the final decision is announced, Clancy said.
The spillway, built in the 1930s, is a system of concrete bays bordering the river northwest of the city. Opening it involves cranes lifting up heavy timbers — called needles — that are arranged vertically in each bay. As the needles are removed, river water rushes over a 5.7-mile (9.2-kilometer) floodway that empties into Lake Pontchartrain and, eventually, into the Gulf of Mexico.
Clancy said needles would be removed from 10 of the structure's 350 bays Thursday. The flow will be monitored and adjusted daily.
Opening the spillway raises environmental concerns. It sends river water into the brackish lake, which changes its salinity and can affect shrimp and crab harvests. "We don't want to put any more water into Lake Pontchartrain than we have to," Clancy said.