PRAIRIEVILLE — A draft environmental assessment for a proposed 3.7-mile widening of La. 42 in Ascension Parish recommends against adding sound walls or taking other measures to reduce traffic noise.

A December report on traffic noise issues included in the Louisiana Department of Transportation and Development assessment found that many noise-reducing options are not available or feasible due to the two-lane highway’s nature and its traffic mix.

The report’s analysis projects noise levels would increase on La. 42 by the year 2030 whether or not the highway is expanded.

The report also notes the corridor is commercializing, potentially displacing future residents who would hear such increased traffic noise.

DOTD officials plan to submit the draft assessment — including the noise analysis — to the Federal Highway Administration early next week, Dustin Annison, department spokesman, said Friday.

State highway officials held a public hearing last month on the assessment, which lays out DOTD’s preferred plans. If federal highway officials approve the draft, DOTD can continue the project.

The proposed expansion of two-lane La. 42 to a four-lane highway between Airline Highway and a point 1,500 feet past La. 44 near Woodhaven Drive is projected to cost $43.4 million, the environmental assessment says. The expansion is not fully funded.

With sound measurements taken in January 2009 during morning and evening rush hours, a traffic noise model found the widened highway would affect more sites and increase noise more at most of those sites, on average, by the year 2030 than if the highway were not widened.

The average increase approaches 5 decibels, the model’s data show. The loudest location tested, a gasoline station, would hit about 77 decibels.

That’s close to the noise from a vacuum cleaner at 80 decibels, a 1970s U.S. Environmental Protection Agency report says.

But the DOTD report noted noise along La. 42 would increase by slightly less than 3 decibels, on average, even if there were no expansion due to increased traffic expected through 2030.

Options such as lower speed limits and reduced truck traffic are not feasible, the report says. The speed limit on La. 42 is already low at 45 mph. Heavy truck traffic constitutes less then 1 percent the traffic mix, the report says.

Sound walls are not feasible, the report says, because of the number of driveways on La. 42 that would require openings, reducing effectiveness of such anti-noise walls.

A DOTD-required noise reduction of at least 8 decibels is not possible with the large number of driveway openings, the report says.