NEW ORLEANS — Crews have been busy in recent days tearing out an old flood-control structure on Bayou St. John that has outlived its usefulness and actually become an impediment to a healthy ecosystem, according to those involved with the project.

The dam structure, decorated with rocks and foliage, was built 50 years ago at the bayou and Robert E. Lee Boulevard. Many said it should have been removed years ago, especially after a new flood-control structure was built at the mouth of the bayou at Lake Pontchartrain nearly two decades ago.

The goal of its removal is to improve water flow and fisheries along the Lake Pontchartrain tributary that was once used as the city’s main shipping waterway. The work is being funded by a Gulf of Mexico Sea Grant through a partnership with the National Oceanic and Atmospheric Administration Restoration Center.

The structure is made up of a concrete bulkhead with a drain and several valves designed to allow water flow. Many of those valves, however, are nonfunctional, with some fully closed or and others mostly closed, said Rusty Gaude with the LSU AgCenter and Louisiana Sea Grant office.

“This water control system is actually a vestige of a system that should have been taken out when the last one was installed,” he said. “With the new one, the old one is completely redundant. Not only is it redundant, it didn’t work.”

The new flood-control structure operates properly and could increase water and fish access to the bayou, but that has been inhibited by the obsolete old structure, which acts like a door, Gaude said.

“The door had a small crack in it, and whatever could find its way through the small crack is what made its way up Bayou St. John,” he said.

Gerry Gillen, executive director of the Orleans Levee District, the agency that controls the floodgates at the mouth of the bayou, said there will be key times during the year when the sector gates will be opened a bit to allow a full water column into the bayou.

That, he said, could help improve its ecosystem even more than it would be with the main gates closed and only the sluice gates — basically a metal screen— that allow marine organisms and water to flow, but in a limited amount.

“Hopefully we can have some positive results,” he said.

Gaude said he’s certain there will be a positive change with the structure removed.

“The possibilities of getting a normal ecosystem in there were severely slowed by this old gate,” he said of the dam structure. “Even if you were to open the sector gates and just let the water flow back and forth it still would have piled up at the dam. It had very little flow.”

With a price tag of $156,400, Gaude said the main holdup in removing the dam structure was money. The only reason it’s finally being torn out, he said, is thanks to cooperation among several agencies and the public.

“This is a true community project,” he said.