SACRAMENTO, Calif. -- Workers are swarming over a downtown Sacramento stretch of Interstate 5 as part of one of the biggest road projects the capital has seen in decades.

The California Department of Transportation and contractor C.C. Myers on Friday night shut down the northbound lanes of the freeway from the Highway 50 interchange to Richards Boulevard. Drivers were forced to take alternate routes. The southbound lanes remain open for now.

Work will take place over the next six weeks, with northbound and southbound lanes closed at different times.

"We really have never done this kind of project in Northern California, especially with a freeway with volumes like this," Caltrans spokesman Mark Dinger said. "So, it's really a new way to do business and we're just trying to get our work done faster."

Crews jumped on the project shortly after 8 p.m. Friday, and on Saturday the work was well underway. Tractors, big rigs and workers in hard hats could be seen around the job site.

Weekend drivers appeared to be adapting to the closure of the northbound lanes, but the real test is expected to come Monday during the first weekday commute since the project formally started.

People gathered Saturday along nearby overpasses to survey the work, which is centering a segment of road known as the boat section.

Dinger said repairs are needed because water from the nearby Sacramento River has seeped to the surface of the road. A draining system originally installed in the freeway has become clogged and the road has deteriorated over time.

More than 150 workers are tackling the project.