A stretch of the Duck River in Maury County. (Photo: John Partipilo)
A pipeline supplying water from the Cumberland River to the fast-growing Maury and Williamson counties is feasible, but it could cost up to $1.9 billion in 2025 dollars, according to a feasibility study released this week by the Mallory Valley Utility District.
The study examined the projected costs, needs and construction timeline for approximately 30 miles of pipeline that would connect the Harpeth Valley Utilities District, which draws its water from the Cumberland, to the water utility in Columbia by 2033.
The pipeline is one of several pathways under consideration to provide reliable, long-term water supply for southern Middle Tennessee. More than 250,000 residents in the area are currently served by water withdrawn from the Duck River, the most biologically diverse freshwater river in North America. Recent bouts of drought paired with growing water needs for an expanding population and industrial developments are ramping up pressure on the Duck and the dozens of species it supports.
Gov. Bill Lee issued an executive order in November creating the Duck River Watershed Planning Partnership — a panel of state and local officials, utility representatives, and conservation group leaders — to explore ways to balance the river’s preservation and drought management with the region’s increasing water needs.
The partnership met Thursday and is expected to meet again on Nov. 4 before releasing its first interim report on Nov. 20. The partnership’s final report and recommendations are expected in December 2026.
The feasibility study began in March and was funded by the Mallory Valley Utility District, Maury County Water System, City of Mt. Pleasant Water Department, Columbia Power and Water Systems, and the City of Spring Hill.
Projected costs and hurdles
The study presents estimates for two alternatives: one 54-inch steel pipeline or two 42-inch steel pipelines (which, though more expensive, builds in redundancy in the case of interruptions). The pipeline would require two pump stations capable of moving up to 60 million gallons of water per day.
The pipeline would be built either within or near existing Tennessee Valley Authority property easements. While it would impact around 200 properties, no residents or businesses would be displaced, the study states.
The total estimated cost for the new infrastructure is between $1.7 billion and $1.9 billion, according to the study.
The study did not provide specific estimates for the cost of the pipeline to ratepayers. The Harpeth Valley Utilities District, which would treat and deliver water to the pipeline, reported that it was not able to estimate its service charges until the U.S. Army Corps of Engineers completes its study of the Cumberland River Basin in 2026.
Operation and maintenance of the pipeline would cost an estimated $6.2 million for the first year of operation if the pipeline initially provided 35 million gallons of water per day. The pipeline would be designed to serve up to 60 million gallons of water per day.
Depreciation costs, or the amount charged per year to amass funds for eventual replacement, would run between $11.2 million and $17.2 million per year, depending on the pipeline option selected and assumed lifespans of 80 versus 100 years.
The estimated costs, which would be covered by each of the utilities in proportion to their demand, could be decreased if the project’s stakeholders seek state or federal grants.
The study estimates a total cost per thousand gallons at $12.08 “for illustrative purposes only,” assuming that the project costs $2 billion (with a 30-year bond at 3% financing and no state or federal support), serves 35 million gallons each day, and the Harpeth Valley Utilities District’s charges were consistent with their current rates.
For the project to be viable, it would need to obtain authorization from the U.S. Army Corps of Engineers (USACE) to withdraw water from the Cumberland River. It would also need to secure permitting approval from the Tennessee Valley Authority, Tennessee Department of Environment and Conservation, USACE, and the Tennessee Department of Transportation.
Funding may be bottom line for Spring Hill
The pipeline proposal is one of several regionalization options under scrutiny. Others include raising the Normandy Dam, increasing intake from the Duck River, or creating a system of reservoirs.
At a Spring Hill Board of Mayor and Aldermen meeting on Monday, Spring Hill Water General Manager and Assistant City Administrator Dan Allen cautioned city leaders that many conversations will happen in the next few months, and the city’s posture should be one of collaboration to find “environmentally responsible as well as fiscally sustainable solutions.”
“It certainly appears to be a feasible project in terms of technical feasibility … the challenge that we see is primarily a funding discussion,” Allen said.
Spring Hill, which contributed funding for the feasibility study, would take about 40% to 45% of the water available in the pipeline, and could thus be responsible for the same proportion of costs, he added.
“Even at $1.7 billion, a 40-45% amount of that … I don’t believe is feasible for our ratepayers. This is where you have to start having a conversation about state assistance as well as federal assistance,” Allen said.
Jason Gilliam, one of the leaders of Columbia Dam Now, a group supporting the reconstruction of the dam on the Duck River, called the pipeline project “ridiculous” at the group’s most recent meeting on Tuesday. The cost, he said, would be too high.
The group reported in July that it is working with U.S. Rep. Andy Ogles to secure congressional funding to fast-track a feasibility study for rebuilding the dam. The initial effort to build the dam that started in the 1960s ran into multiple snags ranging from environmental concerns to ballooning costs to permitting issues and a flawed cost-benefit analysis, according to a Congressional report published in 1980. The dam was eventually dismantled.
It’s not clear what the construction of a similar dam would cost in today’s dollars.
In a statement to Tennessee Lookout on Thursday, Gilliam wrote that while the process is slow, there is a “concerted effort” to secure congressional funding for a Columbia Dam feasibility study by the end of the year.