The Douglas County Wastewater Treatment plant is halfway through its construction and is set to open in January of 2018. The total cost for the project is about 4 million and it will serve western and southern Lawrence.

A new sewage treatment plant south of the Wakarusa River is taking shape, and city engineers say the multimillion-dollar project is now more than half complete.

At more than $74 million for the plant and related infrastructure, the project is one of the largest the city has recently undertaken.

“What this plant can treat is almost half of town, area wise,” said Melinda Harger, utilities engineer for the city.

The Wakarusa Wastewater Treatment Plant will give the city greater capacity to handle growth and meet new treatment regulations by the Environmental Protection Agency. Harger said the new plant, at 2300 E 41st St., will increase the capacity of the city by 2.5 million gallons per day, or by about 20 percent.

The plant will treat sewage from West and South Lawrence that is currently following a long track through city infrastructure to be treated at the city’s lone plant on the northeastern edge of town. Harger said the new plant will bring more efficiency to the process.

“Everything right now goes to our existing plant,” she said. “So what happens is that water is being pumped, or flowing by gravity, around the south side of town and then it goes over to some pump stations by Burroughs Creek and then is pumped north to the existing wastewater plant.”

The plant’s main site is about 25 acres and will include four basins and six buildings, according to Harger. Each facility contributes to a step in cleaning the water — trash and grit screens, chemical cleansers, ultraviolet disinfection — as well as an administration building that will house a control room and labs.

The plant will be equipped to follow tightened state and federal environmental regulations to clear pollutants from the water. One of the basins will be used for biological nutrient removal, so that nutrients such as phosphorus and nitrogen that can be disruptive to the ecosystem are removed before the water is released into the Wakarusa River, Harger said.

“If you want a healthy stream ecosystem, you want to limit some of those nutrients,” Harger said. “Basically what we’re putting back into the river, it’s a lot cleaner than the river that’s already there.”

Harger said the existing wastewater treatment plant, at 1400 E. Eighth St., will have to be updated to perform nutrient removal in the next five to 10 years. The Wakarusa plant is also designed so that it can be expanded in the future for additional nutrient removal capacity.

The new plant is being paid for through previously approved rate increases for water and wastewater. In 2013, city commissioners approved a new five-year rate plan that increases water and sewer rates by 5 to 7 percent each year. The most recent rate increase under that plan went into effect this month. Commissioners are in the process of drafting a new three-tiered rate plan that will increase rates based on level of use, and will help pay for additional infrastructure needs of the city’s utilities department.

The “peak flow” storage basin makes up another large part of the site. The vast concrete basin has a 5 million gallon capacity and will help with stormwater runoff during heavy rain, specifically on the 31st street corridor, Harger said.

“During wet weather events a big surge of water is going to our existing plant and our system can get close to being overloaded,” she said. “And the more development that takes place, the more water is going down those sewers, so this will help mitigate that.”

The Wakarusa Wastewater Treatment Plant is scheduled to begin operating in January 2018 and will require a staff of two to five people.