CHICAGO (CBS) — A 40-day nightmare; those are the words many commuters are using to describe a new construction project on Lake Shore Drive.

The two-mile resurfacing project downtown will cost about $2 million, and before it’s complete, it could cause about 2 million headaches for regular users of Lake Shore Drive.

The city plans to repave all lanes of Lake Shore Drive between Monroe Street and Grand Avenue before the Chicago Marathon on Oct. 7. Crews will also make repairs to the bridge over LaSalle Drive near North Avenue.

The work began Sunday night, and picked up again before Monday morning’s rush.

Well before dawn’s early light, construction crews had begun tearing up asphalt on Lake Shore Drive, and traffic immediately began backing up south of Monroe Street.

By the time daylight hit, the line of stalled northbound traffic stretched all the way to Roosevelt Road and beyond.

“It is going to be a major impact. There’s about 111,000 cars that go through this area every day. So it’s a substantial amount of traffic, but these repairs are critical. We haven’t had resurfacing on this segment of Lake Shore Drive for about 15 years,” Chicago Department of Transportation First Deputy Commissioner Tom Carney said.

Starting Monday morning, Lake Shore Drive will be reduced from four lanes in each direction to two between North Avenue and Monroe Street.

The project will require workers to close two lanes in each direction between Monroe and North Avenue, starting with the inner lanes so crews can resurface the road and the ramps at Randolph Street, Illinois Street, and Lower Wacker Drive. Once the first phase of the work is complete, crews will close the outer lanes so the road and left-side entrance and exit ramps can be repaired.

City officials said the project was timed to squeeze in the resurfacing work between the Chicago Triathlon this past weekend and the Chicago Marathon on Oct. 7.

Drivers are being urged to avoid Lake Shore Drive downtown by using public transportation, or using an alternative route.

Allen Nichols said he planned to take Interstate 94 to get downtown while Lake Shore Drive is under construction.

“I’ll do 94 for sure,” he said. “This is a nightmare.”

Carney said he hopes many commuters will opt to ride bikes to work, if possible, to avoid adding congestion to the Dan Ryan or Kennedy expressways.

“If you can use Divvy, if you can use a bicycle to get where you need to go, we strongly encourage it,” he said.

Despite the short-term pain, Carney said the project will be worth it, because the stretch of Lake Shore Drive being repaved has the most pothole and car damage complaints.