Many people likely never notice the state Department of Transportation's salt storage shed on Jefferson Street by Exit 46 of the Merritt Parkway.

But that's unlikely to be the case in the near future.

The DOT plans to demolish the shed and replace it with a much bigger structure. The plan will be the topic of a public meeting on its proposal Monday night in Fairfield Warde High School's library. An open forum for residents to speak with DOT officials is scheduled at 6:30 p.m., followed by a formal presentation at 7.

Robert Messina, the DOT's project manager, said the replacement shed would be 45 feet wide, 96 feet long and 35 feet tall. Messina didn't have dimensions of the existing shed, but estimated it is about 20 feet wide, 30 feet long and 20 feet tall. He said the replacement shed would be similar in appearance to one built two years ago by the Merritt's southbound Exit 37 in New Canaan. "It's pretty much the exact same building there now," he said. But, he added, the New Canaan building was "much more visible from the parkway than this one's going to be."

Messina said the existing shed in Fairfield was built in the early 1960s and has been "basically decaying to the point where we can't even use it anymore." He said the DOT also can use the existing shed only to store salt, while the replacement shed would be large enough to mix sand and salt, and allow trucks to enter and dump salt. Now, trucks have to dump salt outside the structure and the salt has to be pushed into the shed with a payloader, Messina said.

"It leaves a lot of salt on the ground unless you're really careful about cleaning it up," he said.

The replacement shed would be built farther away from Jefferson Street than the existing shed, so trucks can turn around in a circle and not have to back up, Messina said. He said it would be safer if trucks didn't have to back up and also would eliminate beeping noises in the neighborhood. "The project we're proposing is going to improve the operation quite a bit," he said.

The existing shed is only a few yards away from Jefferson Street, not far from the entrance to the commuter lot, and siting the replacement shed farther away from Jefferson Street gives the DOT more of an opportunity to screen it, he added.

DOT operations on the property wouldn't change after the replacement shed is built, Messina said. He said the DOT wouldn't use the shed to perform maintenance or store its trucks.

The Fairfield shed is where DOT drivers pick up salt to lay down on the Merritt Parkway during snowstorms, Messina said. He said the Jefferson Street site is the end of runs for trucks based at DOT facilities in Trumbull and New Canaan. "This is the end of the run for each one and they load up with new materials," he said.

The DOT's plan to build the replacement shed, which has an anticipated construction timeframe of April to October 2014, is part of a broader program taking place around the state since the late 1980s, Messina said. He said 85 new sheds have been built so far and that the DOT plans to build 10 more.

The cost to build the replacement shed is about $2.5 million, with $500,000 for the building and the balance for site work, drainage and landscaping, Messina said. He said the project will be funded entirely by the state.

A file in the town's Engineering Department identifies site work as including a paved loading/operations area, a personnel shelter, a calcium chloride tank, landscaping and site illumination.

Messina said the Fairfield site likely has polluted soils from years ago, when trucks would retrieve sand from roadways and deposit it on the Jefferson Street property. The sands back then would pick up residual amounts of leaded gasoline and hydrocarbons from vehicles' exhaust, he said.

Consultants on the project will test soils, and Messina said he expects they'll find pollutants at low levels. He said trace amounts have been found during other shed replacement projects and that's what likely will be found in Fairfield. "It's nothing that leeches. It's not classified as a contaminated site," he said.

Today, the DOT uses far less sand because it has a liquid de-icing material for the parkway, Messina said.

The file in the town's Engineering Department says the town is concerned about the project's impact on the Mill River watershed and that the state Department of Energy and Environmental Protection would review the project and put in stormwater quality measures.

Assistant Town Planner James Wendt said the replacement shed won't be reviewed by the Town Plan and Zoning Commission because it's on state property.

Several neighbors contacted Wednesday said they had received a notice of Monday's meeting, but hadn't seen the plans and declined to comment. A list of neighbors in a file in the town's Engineering Department identifies the closest as living on Stevenson Road, Jefferson Street, Weeping Willow Lane and Hillary Circle.

Andrew Brophy is a freelance writer.