Highway improvements near the Maine Mall totaling $7 million will get under way this summer, including a long-awaited sound wall to keep traffic from disturbing a nearby South Portland neighborhood.

The Maine Department of Transportation was scheduled to open sealed bids this week from contractors vying to make improvements to a stretch of Interstate 295 in South Portland that is the most heavily traveled road segment in Maine.

The highway work is expected to start in mid-July and finish in November.

Ernie Martin, the MDOT project manager, said the state has 30 days to review the proposals and choose the contractor with the lowest bid that most closely matches the project’s specifications.

Federal highway funds will cover 90 percent of the cost, with the state paying the rest.

Martin said he hopes the bids will fall below the state’s projections, noting that there is more competition for fewer major construction projects in the recession.

The highway project focuses on improving traffic flow between exits 3 and 4 on I-295, and reducing noise in residential neighborhoods bordering the highway.

Lanes will be added on both the northbound and southbound roads. At Exit 3, a second lane will be built to better accommodate northbound vehicles accessing I-295. At Exit 4, the off-ramp will be extended to allow southbound vehicles to more easily access Exit 3 to Westbrook Street.

Improved highway signs and lighting will be installed as well.

Prior to the construction, crews will erect a temporary cable guard rail in the median between exits 3 and 4 to protect workers from vehicles that might accidentally swerve across the highway.

While work is done on Exit 4, traffic will be redirected to a temporary ramp at Exit 5 in Portland to let vehicles access I-295 south from Congress Street.

Installing the sound wall will take place as the ramp upgrades are made.

The state plans to erect the tall sound barrier between Exits 3 and 4, where the back yards of several homes abut the highway and noise levels exceed federal safety standards.

Home owners have lobbied for years for a sound barrier to reduce the constant din of traffic from I-295.

The sound wall will be made from concrete or a concrete composite material. It will stretch 3,550 feet and vary in height from 10 to 20 feet.

The wall’s cost is estimated to be $50 per square foot for a total of $2.5 million, Martin said.

Although noise barriers are common in more populated states, from Massachusetts to Florida, the wall will be only the second one in Maine. The other noise barrier is in Bangor, near a retail hub.

Late last year, state transportation officials met with about 50 home owners to detail the plan and get their endorsement before moving ahead with the project.