The taste may be gone, but the memory still lingers.

Leaders at Lawrence City Hall haven’t forgotten about last summer’s problems with geosmin, a nontoxic but also very nontasty algae byproduct, which created an earthy, musty taste and odor in the city’s drinking water supply.

“I think it still needs to be a priority,” Mayor Bob Schumm said of figuring out how to control the taste and odor issues, which recently have been more prevalent in the summer.

Now, commissioners will have to figure out how much they’re willing to spend to fix the problem.

Commissioners at their meeting Tuesday are scheduled to begin the process of figuring out just how much a taste and odor fix may cost. City staff members are asking for approval to negotiate a contract with Burns & McDonnell to prepare a study on various options the city could pursue.

But staff members also are telling commissioners that water rates likely will need to increase if the city wants to seriously tackle the issue.

One rough estimate produced by city staff members pegs the cost to install advanced ozone equipment at both the Kaw Water Treatment Plant and the Clinton Water Treatment Plant at $18.5 million.

Dave Wagner, director of utilities for the city, said there likely will be cheaper options that are discovered, but he said the community will have to decide how much it wants to spend in an effort to ward off the taste and odor issues.

“It really will end up being a community value decision,” Wagner said. “All of these events are very episodic. We don’t know when they are coming or how severe they are going to be. I can tell you that last summer’s event was a very unusual event. But I can’t tell you that it won’t happen again next week.”

The city’s water plant operators, however, are learning more about geosmin. The city has purchased equipment that allows plant operators to measure the geosmin amounts in the water supply, where previously the city had to send water samples off-site to be tested.

Wagner said he’s confident the city’s current treatment system, which relies a lot on carbon powder to filter the water, can remove about 90 percent of all the geosmin. Normally, that’s enough to ensure the average resident won’t notice any taste or odor issues.

But during last summer’s event, geosmin levels spiked to about four times their normal levels, which caused the city’s treatment processes to fall behind.

The city is part of a study with the U.S. Geological Survey and the U.S. Army Corps of Engineers to better understand geosmin, which basically is a compound produced when algae die. Whether intense geosmin outbreaks like the one last summer will become more common is a matter of debate in scientific circles.

“But as the reservoirs age, I don’t think there are many people saying that they’re going to become less likely,” Wagner said.

The Burns & McDonnell report will examine ways to improve the city’s treatment processes, several new treatment options, and even will look at the feasibility of the city shifting its primary water source away from the Kansas River and Clinton Lake and over to ground wells that would be recharged by the Kansas River.

Wagner said he’s not sure how likely that switch would be, but he said the report will provide a good starting point for discussions.

Those discussions ultimately will turn to future water rates. City staff members already have recommended the city undertake a five-year rate plan that would increase the average monthly bill of a residential water and sewer user by a total of $13.66 over the five-year period.

The bulk of that increase would go to pay for deferred maintenance on the city’s water and sewer system and to build a new sewage treatment plant south of the Wakarusa River.

City officials now are estimating that the average monthly bill would need to increase by another $2 over the five-year period, if the city wants to aggressively tackle the taste and odor problems.

Schumm said he believes the new report, however, may come up with cheaper options. Schumm also said he wants to schedule a City Commission study session to get more details about the proposed rate increases.

The city is still negotiating a price for the proposed Burns & McDonnell study. Once approved, the report is expected to take six months to complete.