The city of Austin may increase sewer rates this year to stay on top of future maintenance and repair issues at the city’s wastewater treatment plant.

After discussing and approving a $365,000 design project for upgrades to the treatment plant’s anaerobic waste digestors, the Austin City Council and city officials discussed a potential sewer rate increase during a work session Monday in order to replenish capital funding gained through sewer usage fees for future treatment plant projects.

“I think it will be something that will be brought up at future work sessions,” said Council Member Judy Enright.

City officials annually set aside about $650,000 from water usage bills to fund future treatment plant projects, according to Finance Director Tom Dankert. Yet the $10 million or so in that fund will disappear over the next two years, as the city has about $10.7 million in treatment plant projects scheduled in 2013 and 2014 under its capital improvement plan.

The average Austin household pays about $20 to $22 a month for sewer services, according to Public Works Director Steven Lang. Residents hooked up to the city’s sewer system pay a $7.25 fixed fee each month, which goes toward the underground sewer infrastructure. In addition, residents pay $1.85 per unit of water used each month, which goes to treatment plant operation and maintenance. A unit comes to about 750 gallons of water and a typical family of four uses about seven units of water each month, Lang said.

The city council last raised sewer rates in 2010, raising the rates from a $6.10 fixed fee and $1.66 per unit a month, which council members set in 2001.

A feasibility study done by consultants at Short Elliott Hendrickson, Inc. last year identified several upgrades and maintenance projects needed at the treatment plant. While council members brought up potentially increasing sewer rates in 2012, the council and city officials didn’t think treatment plant project funding would run out as soon as projected.

After the study was done, council members are “going to have to address sewer rates,” Enright said, starting with the $3 million project to upgrade digestors this year.

The city has more than $3 million in treatment plant projects scheduled between 2015 and 2017, which will include reducing phosphorus, building a holding/transfer facility to handle sanitary sewer waste, and various building improvements. City officials say improvements and upgrades will be needed as the treatment plant is an older facility, built between 1938 and 1958.

“As time goes on, restrictions usually increase, so there are improvements that need to be made to meet those requirements,” Lang said.

Lang said city officials are currently evaluating a potential rate increase.