A stretch of Montebello Boulevard is about to close for the next 42 months. Here’s why.

About a half mile stretch of Montebello Boulevard will close Monday, July 8, kicking off more than three years of road improvements.

The estimated $190.8 million Montebello Corridor Grade Separation Project underpass will close Montebello Boulevard between Whittier Boulevard and Mines Avenue. Traffic on Montebello will be detoured to Paramount Boulevard on the east and Garfield Avenue on the west.

Olympic Boulevard will be limited to one lane in each direction. Local residents and businesses will continue to have access on Montebello, Los Angeles Avenue, Olympic, Greenwood Avenue, Montebello Way and Mines.

According to the San Gabriel Valley Council of Governments, an average of 49 trains per day go through Montebello. Montebello Boulevard carries an average of 21,000 vehicles a day.

The project will construct a bridge at the Union Pacific Railroad crossing at Montebello and Olympic, creating a roadway underpass.

The closure is expected to be place for three and a half years. Most work will be done weekdays from 7 a.m. to 4 p.m. with some weekend and night work when necessary.

For more information, visit theaceproject.org.