Spring Hill’s current wastewater treatment plant located on Mahlon Moore Road. // Photo by Matt Blois
By MATT BLOIS
The growing population in Spring Hill has strained the sewer and water treatment plants, and now the city has asked for a study looking into how to expand those services.
The Board of Mayor and Alderman approved funding for two studies at its board meeting last night.
The studies will result in plans to expand the facilities, which are required to receive low interest rate loans for those projects from the Environmental Protection Agency and state government. The study for the wastewater plant will also include a water quality study needed to get a permit to discharge more wastewater into a local creek.
Spring Hill’s wastewater treatment plant currently processes about 3.7 million gallons of wastewater per day with some spikes. It can consistently handle up to 5 million gallons a day with occasional spikes up to 14 million gallons a day. The treatment plant is equipped to handle sewage on an average day, but days with lots of sewage occasionally exceed the plant’s maximum capacity. The city predicts that it will outgrow the plant by 2024.
However, the Spring Hill can’t expand the sewage treatment plant right away. The plant dumps treated water into Rutherford Creek, and the Tennessee Department of the Environment and Conservation won’t allow the city to discharge more than the current plant’s capacity. That permit expires in October, so the city is hoping to get permission to put more water into the creek.
Infrastructure Director Phillip Stuckert said putting more treated wastewater into Rutherford Creek will add more nutrients like ammonia, nitrogen and phosphorous to the water. The creek was only recently removed from a list of threatened and impaired waters, so he isn’t sure that the state will allow Spring Hill to do that.
“They don’t want it to degrade … and neither do we. We’re stewards of the community,” he said. “So we have to do a water quality study on Rutherford Creek … What threshold can we discharge?”
If the city doesn’t get permission to put more nutrients into the creek it will have to remove more nutrients before discharging the treated water. But removing the nutrients creates another problem: solid waste. Removing extra nutrients creates solid waste that the city has to dispose of.
Stuckert said one option would be incinerating the waste at a facility in Lebanon, but that tends to be expensive. Other options include spraying the waste onto empty fields or dripping it into the ground.
Spring Hill’s water treatment plant is in a similar situation. The city has a permit to draw up to 6 million gallons of water every day from the Duck River, and the water treatment plant can produce 4 million gallons of drinking water a day. Stuckert said right now, the plant only needs to process about 2.5 million gallons on an average day.
By 2037, Spring Hill’s water treatment plant will need to have the ability to produce 10 million gallons a day when there is especially high demand for water. That’s much higher than the current plant can produce, and even more than the city is allowed to take out of the river.
Spring Hill had already anticipated the need for more water. It has a contract with Columbia Power & Water Systems to provide extra an extra 2.9 million gallons of water per day if needed. Right now the city doesn’t use much of that water. Stuckert called the contract a backup plan that gives the city more time to figure out how to expand its own water treatment plant.
But late last year the Columbia water provider announced that its water treatment plant wasn’t able to produce as much water as it previously thought. As a result, it probably won’t be a able to provide extra water if Spring Hill needs it in the future. That contract expires in spring 2019, and it’s not clear whether Spring Hill will be able to get water from Columbia after that. Without a back up plan, the city now needs to move quickly to make sure it can provide enough drinking water in the long run.
The state has only given Spring Hill permission to use 6 million gallons of water per day from the Duck River. The plan is to first build a plant that can produce that much water. In a memo for board members, Stuckert wrote that the upgraded plant could be online by 2021, which would solve the short term problem.
To solve the long-term problem, the city hopes to get permission from the state to draw 10 million gallons of water per day from the Duck River. Stuckert didn’t recommend planning for a plant that could process 10 million gallons a day because there’s a chance the state wouldn’t give the city permission to use that much water.
Columbia Power & Water Systems also expects to increase its treatment capacity during the next decade and could potentially sell Spring Hill water in the future. The city hasn’t determined if it makes more sense to build its own water treatment plant, or buy water from Columbia Power & Water Systems.