The city of Lawrence has officially embarked on one of the larger projects in its history — a new $64 million sewage treatment plant — and Lawrence residents soon will discover that the bill for it and a host of other projects is in the mail.

City commissioners at their Tuesday evening meeting unanimously agreed to approve new water and sewer rates that will increase the monthly bill of an average household by about 6 percent, but sets the city on a path to complete more than $160 million worth of utility improvements that staff members say are badly needed before 2017.

“This plan is very important for the community not only this year, but really for the decades to come,” City Manager David Corliss told commissioners.

The largest project staff members will begin working on is a new sewage treatment plant that will be constructed on city-owned ground south of the Wakarusa River, just south of where O’Connell Road meets the river.

The project will create a second sewage treatment plant for the city. The plant is designed partly to provide the community the ability to accommodate more growth in coming decades, but also is needed to take pressure off of the city’s current treatment plant during wet weather events. The city’s current plant is drawing scrutiny from the Environmental Protection Agency on how it functions during heavy rains.

City officials hope to hire the necessary engineers to begin designing the project this year. Design work is expected to last until late 2014, when construction will begin. The plant is expected to open by 2018.

The project, though, will take more than just a 6 percent increase of water and sewer bills this year. Technically, commissioners on Tuesday approved a multiyear plan that calls for similar rate increases each year through 2017. But future commissions will have to approve those increases before they take effect.

The higher rates for 2013 will start showing up on bills in coming weeks. The city estimates the average household that uses 4,000 gallons of water per month would see its monthly water/sewer bill rise to $50.51 per month in 2013, up from $47.64 per month currently.

No one from the public spoke either for or against the rate increases. But the room was full of private engineers who were on hand to watch the city open the door on more than $160 million worth of infrastructure projects in the city.

The 2013 rates are scheduled to fund about $37 million in water and sewer projects, including a new water intake for the aging Kaw Water Treatment plant, replacement of water tanks on Mount Oread, and a new water transmission line across the Kansas River to North Lawrence.

The remaining $125 million worth of projects — including $19 million to address taste and odor issues with the drinking water — are planned for years 2014 through 2017, and will require future City Commissions following through on rate increases to fund the projects.

Mayor Bob Schumm said he thought it would be unwise for the city to wait any longer to address the significant utility needs. He said several projects — completion of the South Lawrence Trafficway, the Farmland industrial park, the new recreation center and others — would spur growth in the next decade.

“For us to not take the challenge and move this forward where we can accommodate the growth, would be penny-wise and pound-foolish,” Schumm said.

Other commissioners agreed. City Commissioner Mike Amyx, the lone commissioner running for re-election, said he thought parts of the city’s utility system were at risk of failure if work wasn’t undertaken.

“These are basic, core services that we’re talking about here,” Amyx said.