When Diane and Peter Jamieson moved into their brand-new home on Hobart Street in 1972, there were woods behind their house. Today there’s a four-lane highway.

Retail growth in South Portland has come at a price for homeowners near Interstate 295 where it exits at the Maine Mall. Traffic volumes are among the highest in Maine, with constant noise from vehicles exceeding federal safety limits for residents whose back yards abut the highway between Exits 3 and 4.

After years of lobbying from neighbors and local leaders, the Maine Department of Transportation has agreed to install a so-called “sound barrier” to muffle highway noises. The concrete or wood wall will be 3,400 feet long and up to 20 feet high in some areas. It will be installed within the city’s existing right-of-way, near a fence that currently separates residential yards from the interstate.

The wall will cost about $1.5 million and likely be installed in 2008, if neighbors approve the plan. The money will come from state and federal highway funds.

The 51 homeowners most impacted by traffic noises will need to vote on the plan at a public hearing that will be scheduled soon by the Transportation Department. The impacted neighbors must support the plan by a three-quarters majority for the road project to move forward.

Transportation officials say homeowners on the following streets should hear less noise after the noise wall is installed: Glen Way, Broadway, Evergreen, Hobart, Linton, Fellows, Brigham and Dawson. Highway officials predict that the wall will mitigate traffic noise in surrounding neighborhoods by more than 50 percent.

Diane Jamieson, who lives at the end of Hobart Street, said it is impossible to hear anything other than constant traffic noises in her back yard. She is unable to recall the last time it was quiet at her house, without the din of hundreds of car engines running.

Jamieson said she cannot imagine any of the identified property owners voting against the plan. “This is something that we have asked for over several years,” said Jamieson, who keeps most of her home windows shut year around to muffle the highway sounds. But they never go away.

Likewise, Ed McDonough of Fellows Street said, “Since the turn of this century, we have seen the noise grow to an intolerable level, which prompted us to look for help.”

Sound walls or barriers are common sights along highways in congested metropolitan areas across the nation, including in Massachusetts. But they are rare sights in Maine, where the only other sound barrier is located off I-95 in Bangor.

“You really cannot carry on a conversation (outdoors), and simply being in the yard for any period of time becomes stressful,” said McDonough, a 28-year resident of Fellows Street.

Jamieson says the traffic noise is loudest during morning and evening rush hour. The sounds of vehicle engines running never cease, and horns and sirens are common, even in the middle of the night.

The couple also hears accidents. Jamieson recalls several years ago awakening to the sound of a man screaming for help. Her husband rushed out to the highway, and discovered that a vehicle had just struck a woman walking along the interstate after her car broke down. Police were just arriving at the scene as well.

Although a chain-link fence separates the Jamiesons’ yard from the Interstate, the couple has planted a lot of trees and shrubs over the years to shroud the highway and silence the noise. Tall pines grow in their backyard, and there is a small garden and bird feeders. Still, the noise is loud and constant.

“Motorcycles are the worst,” Jamieson said.

Nathan Howard, Transportation Planner with the Maine DOT, said the sound barrier – which will range in height from 10 to 20 feet – is a simple and effective means for mitigating noise next to highways. The sound barrier will be built, as part of a widening project on the busy stretch of I-295. The widening will be done on the west side of the highway – where traffic travels south – and be built after the sound barrier is erected, he said.

“As part of the widening, we are required to do an environmental review and look at things such as noise impacts and mitigation, just like we would do in a wetland analysis,” Howard said. He said state highway workers took noise readings at several residential locations and determined they exceeded levels considered safe for people.

City Planning Director Tex Haeuser said noise barriers are common along Route 1 in Massachusetts. In South Portland, Haeuser said that “everyone has accepted there is a significant noise problem out there. This is a relatively small price to pay to fix that and improve the quality of life for neighbors.”

He said accidents and drivers weaving in and out of traffic have been a particular problem between Exits 3 and 4 on I-295. He said the widening should lessen the problem.

City Councilor Jim Hughes, who lives off Broadway, said easing traffic congestion and improving quality of life for homeowners who live near busy roads are major concerns for him. Hughes said he originally ran for office out of frustration over oil rigs rumbling along Broadway.

“We started talking about this issue when I first got on the Council,” said Hughes, who is finishing his second term. “It was something that we had to keep in front of the DOT.”

In 2004, the City Council passed a resolution asking the Maine Department of Transportation and the Federal Highway Administration to address “the increasing noise pollution from the growth of traffic and speed of vehicles… from Interstate 295.”

In 2007, Rep. Brian Kaenrath, D-South Portland, introduced a bill to draw attention to the need for noise abatement measures along Interstate 295, particularly near Exits 3 and 4, and to get abatements for impacted property owners. The bill failed.

McDonough said neighbors, with the support from state and local leaders, pressed hard for change. They regularly spoke with City Councilors, attended Council meetings and legislative hearings, and contacted their congressional delegation.

“At every point along the way, we have tried to stay informed as to what was or was not happening with this issue, to follow up on any next steps, and to keep our neighbors informed as well,” said McDonough, who learned about the DOT decision to build the sound barrier at the end of July.

“There is no doubt it will help.” McDonough said. “Anything will help. The noise is just crazy out there. Everyone I talk to is pretty excited about the sound barrier.”

Homeowner Diane Jamieson said she and her husband, Peter, have added landscape to their backyard to block the view of Interstate 295. The constant sound of traffic is so loud it is not possible to have a conversation on their back deck.Interstate 295 highway abuts several residential streets on the city’s west side. The state plans to erect a “sound wall” or “sound barrier” to muffle the noise.