Work began today on a two-week construction project in the West Portal neighborhood that will affect traffic flow for motorists.

Westbound traffic will be shut down on West Portal Avenue from 15th Avenue to Sloat Boulevard every weekday from 8 a.m. to 4:30 p.m., for a drainage project being overseen by the San Francisco Municipal Transportation Agency, which manages traffic in The City.

Motorists will be detoured south on 15th Avenue to Portola Drive and then back to Sloat Boulevard, the SFMTA said. The project is expected to be completed in two weeks. It will not affect transit service in the neighborhood.

The drainage work being carried out is the final segment of the agency’s $26 million overhaul of nearby St. Francis Circle, a complicated and heavily used intersection in the western portion of San Francisco.

wreisman@sfexaminer.com