Plans to build a new sewage treatment plant south of the Wakarusa River may cost more than Lawrence city leaders once envisioned.

The massive project attracted only two bidders and costs came in about $5 million above what engineers had estimated, Dave Wagner, the city’s director of utilities, said Tuesday. Base bids came in at about $50 million, compared to the approximately $45 million engineer’s estimate, he said.

City officials now will review the bids in more detail to see if there are items that can be cut or whether other adjustments can be made to keep the project on schedule.

“We’re going to go through a lot of adding tape in the next few days,” Wagner said.

City Manager David Corliss said the earliest a recommendation would be made to city commissioners is at the March 10 meeting. He said staff members will be looking for a way to build the project without raising sewer rates any more than what has already been planned for, which range between 5 percent to 7 percent per year through 2017.

“That will be our goal,” Corliss said. “It may require us to say no to some other projects, but this is a very important project for the community.”

The new plant — which would be on the south side of the Wakarusa River about where O’Connell Road dead ends — is designed to provide the community more sewage treatment capacity to accommodate future growth and also to meet stricter environmental standards being mandated by regulators.

The two bidders on the project were Garney Construction and Crossland Heavy Contractors, Wagner said.

City commissioners at their Tuesday evening meeting took action on several other items. They included:

• Repealed an ordinance that required some inmates of the Douglas County Jail to pay the city about $70 for each day spent in the jail. That is how much the city is charged by Douglas County for jail inmate costs. The ordinance gave the city’s municipal judge the authority to order inmates to reimburse the city for the jail fees. The ordinance was criticized as being unfair to low income residents who were released from jail and were trying to turn their lives around.

• Commissioners agreed to have a special meeting at 5:45 p.m. Monday to discuss the findings of an audit that studied the controversial $12 million worth of infrastructure costs at Rock Chalk Park. Commissioners said they did not want to have the item on their regular Tuesday evening agenda, because March 2 is the primary election for City Commission races. Commissioners traditionally try to have short meetings on election nights in order to give commissioners time to watch elections returns.