Work to replace light-rail tracks in the Sunset Tunnel along the N-Judah route will begin in March.

The San Francisco Municipal Transportation Agency board of directors approved Tuesday a construction contract with Proven Management Inc., for $16.1 million.

The work will replace existing tracks, overhead wires, seismically upgrade the portal walls in the Sunset tunnel and adding more signal loops to give light-rail vehicles signal priority at nine intersections on Judah and Irving streets.

The tracks, installed in 1975, need replacement due to wear and tear, according to transit documents. The overhead wiring system is also in need of repair due to “severe rust and extensive water damage.”

Vince Harris, director of capital programs and construction, said the tunnel work is a major project for the N-Judah line, which has a daily ridership of 40,000 riders:

“This work provides infrastructure improvements that will enhance system reliability and efficiency, reduce infrastructure maintenance and upgrade the structural performance of the portal retaining walls.”

Work will also include upgrading the sprinkler system and painting and removing graffiti from the portal walls.

The work though will inconvenience N-Judah riders. The N-Judah will shutdown over a period of 15 weekends between March 2014 and February 2015.

The transit agency will issue advances notices before each weekend shutdown. Buses will substitute rail service during the weekend shutdowns.

The transit agency will have ambassadors on hand to advise riders about the bus substitution along with posted signs directing riders to transfer points from between rail and bus service.

The total cost of project is $29.6 million. Funding for this project is from federal funds, SFMTA operating funds and revenue bonds.

Muni riders interested to learn more about the Sunset Tunnel Improvement Project can attend two public meetings: