Contractors who have spent the better part of the past two summers updating water pipes by digging under pavement and concrete in downtown Lawrence are coming back again.

Beginning Monday, crews from Nowak Construction will be working along the west side of Massachusetts Street from 11th Street to South Park. Lanes will be narrowed but remain open for two-way traffic.

The Goddard company is embarking on the city’s third summer of waterline replacement work in the central business district. The task: Replace 120-year-old cast-iron pipes with new ones made from a more modern version of the durable metal and configured so that they can carry more water at higher pressures and with an ability for service to be shut off in small sections when future maintenance is required.

“There’s no convenient time to do this,” said Philip Ciesielski, who has been working with the contractor as utilities engineer for the city. “I’m just hoping we’ve done a good job during the past two years and we can knock it out again this year.”

As part of its $1.93 million construction contract, Nowak is required to be finished with the first round of work by May 18 so the area can be cleaned up for Kansas University’s commencement weekend.

The contractor will be cleared to begin work on the second phase of the project – along the east side of Massachusetts, from Ninth to 11th streets – May 21 through July 12. Crews then will switch to the west side July 13 through Sept. 7.

All three phases will require the temporary elimination of parking spaces in affected areas. To help ease inconveniences for merchants and customers, the city will provide free parking on the top level of the municipal garage in the 900 block of New Hampshire Street.

“We don’t want to inconvenience anybody any more than we have to,” said Roger Steinbrock, a city spokesman. “We want to make their downtown experiences as positive as possible. That’s why we’re offering this additional free parking.”