Gulf Coast residents who have lived around fishing for a lifetime took a skeptical view Thursday of the federal government’s plan to hollow out a salt dome for oil storage in southeast Mississippi.

About 50 million gallons of fresh water per day for five years from the Pascagoula River would be used to hollow out a salt dome the size of the Astrodome. The resulting brine will be pumped into the Mississippi Sound. Opponents of the project expressed concerns about how an increase in salty water in the Sound might affect marine life.

“The Mississippi Sound flows in our backyard,” said oysterman Avery Bates of Bayou La Batre, a spokesman for south Alabama’s fishing industry. That “backyard” is Alabama oyster beds, he said.

Bates contends elevating the salt level and drawing fresh water from the river would be a “double-whammy” for marine life.

U.S. Department of Energy officials concluded four days of public hearings in Mississippi on the $4.2 billion proposal. While construction won’t begin until 2012, federal officials collected public comment, pointing to the environmental success of similiar projects in Texas and Louisiana.

A video presentation at Thursday’s hearing showed how pipelines that dispose of the brine are built to spread the substance at intervals so that it’s properly diluted when released.

Bill Bozzo, an environmental spokesman for DOE contractor DynMcDermott, said the U.S. Environmental Protection Agency monitors the releases.

Alice Maier was unconvinced, however.

“I’ve lived here all my life. My opinion is I wished they wouldn’t do it,” said Maier, who lives in a beachfront home in Pascagoula.

John Ford of Jackson County said he had concerns about the pipeline and peppered a DOE worker with engineering questions.

“I’m learning, trying to fill in the gaps,” Ford said.

DOE’s David F. Johnson, director of planning and engineering, said the agency is still considering its options for the Richton project. He touted the environmental safety and economic benefits of the project.

Once the public comments are compiled, the agency will move ahead with a draft environmental impact statement next year.

Johnson said judging from comments he heard at this week’s hearings the use of the Pascagoula River appeared to bother most of those who attended.

“There’s concern because it’s a free-flowing river,” Johnson said.

Local, state and federal officials also have panned the idea of taking water from the Leaf and Pascagoula rivers, fearing the drain will cause low flow in the important waterways. But Johnson said a suggestion to run a pipeline to the Mississippi River appeared unworkable because it’s 180 miles away.

Another suggestion was to use Gulf of Mexico waters. He said Mobile Bay and the Tombigbee River in Alabama are nearby, but that raises the issue of crossing into another state.

According to DOE, salt formations offer cheap methods of storing crude oil for long periods. The caverns are 2,000-4,000 feet below the surface.