Lawrence city commissioners still want to build a sewage treatment plant that could cost as much as $88 million, but they want to make sure they’ll be spending the money – generated from monthly utility bills – at the right time.

During a study session Thursday, commissioners indicated that they would hire a consultant to help compile a new wastewater master plan. The study would outline projects needed during the next five years to meet the city’s sewer needs and how to finance them.

The key component of the study would be plans for a treatment plant south of town, along the Wakarusa River. Construction – as recommended in the city’s previous five-year master plan, completed in 2003 – had been expected to begin this year but was delayed because of a slowdown in the city’s population growth.

Now that commissioners are concerned about the economy and grappling with the slowest pace of residential construction in decades, they acknowledge that the project may need a fresh look. That means getting new population projections, cost estimates, and inflation data for the construction industry – the raw materials for deciding when to build the plant.

“Nobody can (definitively) anticipate what’s going to happen,” Commissioner Rob Chestnut said. “But once we throw the flag down, we want it to move forward as expeditiously as possible.”

The study is expected take six months to complete and cost more than $500,000.

Similar studies have been conducted every five years, giving commissioners and city staffers a lineup of projects intended to maintain the city’s existing sewer system and make additions to serve development.

The studies also outline how much the city would need to charge its sewer customers to pay for the projects, such as the $11 million in work completed since the 2003 plan was approved.

That’s the same plan that recommended building a treatment plant south of town and served as justification for several steps that already have been completed: buying land, making preliminary plans and devising cost estimates.

Now, before signing off on a contract for detailed designs and construction, commissioners would expect the next study to outline a variety of options – including a worst-case scenario for Lawrence, one of zero growth during the next five years – to help them understand what the project might mean financially.

“That’s so that when you buy it, you don’t have buyer’s remorse,” said David Corliss, city manager.

The 2003 plan had been based on Lawrence continuing to grow by at least 2 percent a year, the community’s historical average. That plan had maintained that the new plant would need to be operating by 2011, or else the city would face running short on its ability to handle sewage and, therefore, additional development.

Now that population growth has slowed – the city looks to reach 100,000 residents in 2017, not 2010 as previously expected – commissioners intend to look at just which projects might be needed and when.

Commissioners plan to consider the issue as part of a regular business meeting on March 11.