The 900 and 1000 blocks of Massachusetts Street will be closed to all traffic from 9 a.m. to 11 a.m. today as part of the city’s waterline replacement project.

The street closing will allow construction crews to reposition equipment for the third phase of this summer’s waterline work, which will begin on the western side of the street.

Once the street reopens this afternoon, traffic will be limited to one lane northbound on Massachusetts Street, and parking will be prohibited on the western side of the street.

The move is a sign that the project is significantly ahead of schedule, city leaders said. The work, which is replacing a century-old waterline, is scheduled to be completed by early September, but crews are almost 30 working days ahead of schedule.