Crews with I-CON Underground were installing a sewer line material that goes over existing lines without having to excavate the ground for access. The blue polyester material will become a Cured-In-Place-Pipe.

A sewer-maintenance company has been leaving bright green signs on the doors of Lawrence residents. And those who haven’t received theirs yet will in the next 10 years.

The sign — from I-CON Underground — notifies the resident of a scheduled sewer-line reconstruction. It usually states the project will last all day and cut off the residence’s access to the main sewer line for that time.

By 2019, Lawrence Department of Utilities expects to have about 175 miles of the city’s main sewer lines redone.

Rather than tearing up Lawrence streets, lawns and trees, the city decided to reline as many pipes as it can with a technique called Cured-In-Place-Pipe.

“For a much lower cost, we can extend the life of a city main sewer line another 40 to 50 years,” said Bob Brower, field operations manager for the utilities department. “We’re saving time and money, and we’re improving the system life and health by using this liner.”

Jeanette Klamm, utilities programs manager, said the cost of the CIPP construction probably won’t affect utility rates this year because the city includes the cost of the work in the budget.

Last year, the utilities department spent almost $1.2 million for CIPP construction. Although city commissioners voted to increase water rates by 12 percent starting Jan. 1, sewer rates remained the same.

“The water rates increased last year, but it wasn’t because of Cured-In-Place,” Klamm said. “If anything, it saves us money.”

The department contracted I-CON to reline 31,000 feet in 2009. The cost for this year’s CIPP work will be about $921,927.

The utilities department began CIPP replacements in 1998. Since then, more than 30 miles of piping has been relined.

CIPP takes a fraction of the time and costs about five times less than replacement methods, Brower said. A line that would have taken two or three weeks to install, he said, takes eight hours with the CIPP process.

CIPP covers the older pipe — some more than 150 years old — with a thin liner. The liner covers the cracks in the older pipe and allows sewage to move more easily through the pipes.

The process also prevents tree roots from breaking through the pipe — a leading cause of sewage backup — and helps keep groundwater out of the sewer system, said Mark Slack, president and founder of I-CON.

Since beginning the process, Brower said, the reports of main-line sewer backups has decreased from 156 calls a year to 33 calls.