Lexington will spend up to $550,000 to develop new odor control systems for two of its sewage treatment plants.

The Lexington-Fayette Urban County Council gave initial approval Tuesday for a contract for the design of new odor control systems. The move comes after hearing repeated complaints from neighborhoods surrounding the West Hickman Wastewater Treatment Plant near southern Fayette County and the Town Branch Wastewater Treatment Plant off of South Forbes Drive and Leestown Road. Residents have complained for months about the “rotten egg” smell.

The city has already spent $75,000 for Webster Environmental Associates, an environmental consulting firm, to examine the city’s odor control policies and equipment this fall and to make recommendations for improvements.

Webster recommended the city change its odor control equipment. The up to $550,000 contract initially discussed Tuesday will pay Webster to come up with the design, specifications and project management for those new odor control systems. A final vote on the contract will come later this month.

The city has set aside more than $1 million to deal with odor problems from unspent money in other accounts.

Odor has been sporadically problematic near the city’s sewage treatment plants particularly during dry weather. With no stormwater running through the system, untreated sewage can sit, causing foul odors.

But neighborhoods near the two treatment plants have complained of noxious odors even during wet seasons. Those complaints ramped up this fall, city officials have said.

Charlie Martin, the director of the city’s water quality division, said the city has not had an employee dedicated to air quality since at least 2008. The city has been working since 2011 and before on water quality problems. The city has been under a U.S. Environmental Protection Agency consent decree to fix its overflowing sewer and wastewater treatment system for more than a decade.

That’s why the city needs Webster to help it find air quality solutions and make sure the city’s money is being spent wisely, Martin said during Tuesday’s council meetings. The scrubbers, a key piece of equipment at the two wastewater treatment plants which help remove odors, need to be replaced, Webster found.

“They will replace the old scrubber with a new scrubber that treats the odor more reliability than the old equipment does,” Martin said.

Martin said after Webster develops the specifications, the project will be bid. That can take time, Martin cautioned.

The city will also do smoke testing on parts of its sewer lines to determine where there are possible problems and leaks in the system, he said. The city is also looking at tweaking its chemical processes to keep odors at bay, he said.