Since late 2019, Brentwood residents have been expressing concerns during public meetings and to city commissioners about plans for the city’s sewer system, which has been undergoing improvements for the last 14 years. On Jan. 30, the city of Brentwood hosted a forum for city staff, engineers and state officials to respond to resident concerns.
The city is still working to complete a multiyear Corrective Action Plan to rehabilitate the sewer system with $30 million worth of projects, including relining pipelines throughout the city to reduce issues related to cracks and to prevent overflows from wet weather. However, the city is slated to begin a large-scale project this year to add more storage on the west side of the city, which could be done as early as 2022.
“We’re at the tail end of the CAP,” Brentwood Water Services Director Chris Milton said in the presentation. “We’re still doing work in the field. The biggest project, obviously, is construction of the storage. That’s the big one out there that has to be completed.”
In the summer of 2006, the Tennessee Department of Environment and Conservation issued an Agreed Order, a requirement for the city of Brentwood—as well as for Metro Nashville, which treats the city of Brentwood’s water—to reduce the number of sewer overflow events in the city, according to city documents.
According to the order, the city of Brentwood had 30 reported sewer overflows from February 2003 to May 2004 as well as a significant overflow event that May, which resulted in raw sewage overflowing from a manhole into the Little Harpeth River. Later that summer, the state division of water pollution control issued a violation notice to the city.
As part of the 2006 order, the state issued a moratorium on adding any new connections or line extensions or increasing the flow to the city’s pump station. Following the order, the city of Brentwood worked with an independent engineering firm, Barge Design Systems, to develop the CAP. The moratorium will remain in effect until the plan is complete, according to the order from the state.
“Your whole system, basically, is under a moratorium right now because at the very bottom of the system, you were having chronic overflow,” said George Garden, chief engineer for the TDEC division of water resources, during the Jan. 30 meeting. “The purpose of the moratorium is to get you to the point that that does not happen.”
To date, as part of the CAP, the city has relined more than 31 miles of pipeline throughout the city to reduce the number of pipe failures. City staff have also replaced about 1/3 of Brentwood’s manhole covers.
While the order was issued due to system failures in the city, Garden said sewer issues and overflows are an issue across the state, and that the city will not be immune from future issues once the plan is complete. Garden said the state is spending approximately $200 million annually to treat sewer-related issues.
“The takeaway point is, [Brentwood is] not alone. There are lots of people. Everybody is fighting this battle. It is not a sprint; it is a marathon,” Garden said. “It is not finished when you’ve done all the rehab you’ve done so far.”
Increased capacity, rainfall
During the meeting, officials said one of the biggest challenges to keeping the system from overflowing is managing inflow and infiltration, such as when groundwater leaks into the system or when residential water sources are not draining properly. When inflow and infiltration rates are too high, an overflow can become more likely when more water is introduced into the system.
“In simple terms, the sewer •system is not water-tight ... •water makes its way into the sewer system,” said Ryan Dean, a representative with Hazen and Sawyer, the engineering firm that helped develop the city’s master sewer plan. “This is not unique to Brentwood. This happens everywhere. It’s just how things happen. Roots intrude into pipes, joints are not sealed properly, cracks can occur from compressive loads on top of the ground—various things.”
Recent improvements, which Garden said have removed 46% of water flow from the system, allow the city to pump less water to Metro Nashville for treatment and to avoid overflows in the event of heavy rain, which has been one of the biggest reasons for overflows in the past, according to the city.
Since 2008, Brentwood has had a 56% decrease in overflow events despite a 65% increase in rainfall, according to Barge Design Solutions.
“This tells me that even though the rainfall has jumped way up here, ... the general trend is not much worse—even better considering the rainfall, in my opinion,” Garden said.
According to water department staff, the city has lowered its flow rates to about 40% of its pipe capacity with normal daily use. About 50% usage is expected at build-out; however, capacity varies across the city. Improvements are also being made to give Brentwood the capacity to handle what is called a two-year storm, which is up to 3.15 inches of rain in a 24-hour period.
Brentwood City Manager Kirk Bednar said projects included in the CAP to be completed in the next few years will help increase capacity to meet the storm standard.
“Today, we’re not meeting that two-year plan, so the rehab and the tank [were] designed to let us meet that,” he said.
In December, the city submitted a letter to the TDEC asking to extend the deadline to have sewer projects completed from 2018 to 2022, allowing them more time to complete a new storage facility. Garden said while the state is still reviewing the city’s request, it seems likely the extension will be approved, although the decision will be pending the design of the storage basin.
“We just need to make sure that we understand of those [projects] you recommended ... that that’s going to be adequate to get you to the point to remove you from the moratorium,” Garden said. “We want to make sure the results show you’ve got a control over the overflow.”
In addition to the CAP projects, the city is also working to complete projects identified in its 2016 Sewer Master Plan, which looks towards future efforts to help account for predicted growth. The plan includes three planning milestones: 2020, 2030 and Brentwood’s ultimate build-out, according to the city.
“It’s purposed for comprehensive long-range planning to meet the future capacity of the city through build-out,” Milton said. “It makes predictions; it’s not any different than a park master plan, a thoroughfare master plan, traffic plan, etc. ... This is the same principle. [It will] tell us what pipes need to be bigger to handle everything out through build-out of the entire city [and] through the service areas.”
This year, city officials said they hope to close on the purchase of a 40-acre tract of land that will give them space to build a new storage tank near the Brentwood pump station to accommodate sewer water.
According to Bednar, the city is working to negotiate a price with landowners on an area of land near Hillsboro Road and Petham Drive on the west side of the city. The land is appraised for $1.1 million, according to the city.
“The goal would be to have the design complete sometime in late spring to the middle of 2021, bid it, [and set] construction to be online by the end of 2022. That’s the goal we’ve laid out,” Bednar said.
While Bednar said negotiations are ongoing, if the city is not able to reach a deal in the coming months, the city may move to condemn the land, allowing it to purchase the property without an agreement. City staff were given the authority from the Brentwood City Commission to purchase or condemn the land Feb. 10.
“As always, [condemning] is our last resort. The end goal would be the agreed-upon purchase, whether that’s the entire property or just the portion we need,” Bednar said. “But by condemning the property, we are able to get control over it and proceed with design and engineering, if that’s what it costs.”