KINGSPORT — The final 50 feet of a 1,100-foot tunnel is being dug from the Holston River to the city’s water plant. Once the work is done, the Model City will have a much more reliable raw water intake system, one that will serve the city for at least the next 100 years.
Last November, work started on a $13.7 million upgrade to the facility (located off Konnarock Road near John B. Dennis Highway), with the main thrust of the project being the tunnel dug through the cliff.
Currently, Kingsport gets its roughly 15 million gallons of water a day from the river — water flows into a giant pipe and is then pumped over the cliff to the nearby water treatment plant. However, the system is old and a catastrophic failure could leave 100,000 people without water.
The solution was to bore a subway-style tunnel 14 stories below John B. Dennis from the river to the plant. J. Cumby Construction of Cookeville started with a hole 25 feet wide and 30 feet deep near the old intake valve, using it as a staging ground for the tunnel.
During the past nine months, crews have been using a road header drilling machine to bore through the clay and limestone underneath John B. Dennis, initially using a dig-and-blast method to bust through the more dense earth, then lately just the drilling machine.
The result has been a 9-by-9-foot tunnel going slightly downhill from the river. The idea is that the water will be gravity fed to the plant. Once the water is at the plant, a new pumping station, which is also under construction, will pump the water uphill roughly 130 feet into the facility for treatment.
Members of the Board of Mayor and Aldermen recently took a tour of the nearly-complete tunnel, hearing an update on the project from the company performing the work. The Times-News accompanied the BMA on the tour.
Ryan Carroll, project engineer at the site, said crews have removed more than 4,000 cubic yards of earth during this process. Earth work is expected to wrap up in the coming weeks, and the project is scheduled to finish by October.
Ryan McReynolds, assistant city manager for operations, said the purpose of the project is all about reliability.
“To make sure we provide water to our customers at all times,” McReynolds said.
Kingsport's raw water intake system dates back to the 1920s. While improvements were made to the system in the 1940s and 1970s, the system is fastened to a cliff with the water going through a tunnel 40 to 50 feet off the river. In the late 1970s, Kingsport actually had an issue with the system, where people went about two to three days without water.
Kingsport's Water Department serves portions of five counties in two states.