Large Pipe-Cleaning System Tackles Nashville Challenge

By Jeff Griffin, Senior Editor | November 2012, Vol. 67, No. 11

Project owner was the city of Nashville. For the large-pipe segment cleaning, Doetsch was a subcontractor for prime contractor Compliance Enviro Systems (CES), Baton Rouge, LA. CES cleaned the smaller pipes and brought in Doetsch for the larger lines. Throughout the project, the debris was not consistent, ranging from grit to heavy debris. Large adhered deposits also had to be removed with high-pressure water. Emergency cleaning was necessary after flooding caused much of the sewer system to be filled with sediment and debris.

Doetsch’s segments of pipe were 72-inch reinforced concrete pipe that was in good condition.

“When we were contacted by CES, there were only three access points, one at each end and one near the middle,” Schotthoefer said. “We prepared to clean from two setups, one at 3,800 feet and one at 5,200 feet. Nashville was very challenging due to the immense length in between access points as well as the depths to 70 feet.”

The middle access point was in the heart of all the downtown activity and is a heavily-traveled destination for tourists and residents.

“After our initial upstream set up, we were able to locate a vertical drop shaft upstream from this access point,” he continued. “The difficulty with this set up was that the 24-inch vertical drop shaft was offset 15 feet from the main tunnel and connected by a smaller tunnel. This made for a challenging and difficult operation for feeding hose and extracting debris.”

After this 2,900-foot run was complete, the process was repeated from the downstream side to the middle access point at historic Fort Nashborough, a shorter run at 1,600. The final run, from the fort to an apartment complex, was the longest at 4,600 feet.

“This access point was in an apartment complex, very close to the dwellings,” Schotthoefer said. “We were able to set up the equipment behind the apartments and operate from the access point remotely. This eliminated heavy truck traffic and noise inside the complex. Our ability to adapt to other staging areas allowed us to move away from the areas that would be disrupted the most. The equipment also was noise attenuated.”

Environmentally friendly

Throughout the cleaning process, there was a continuing communication with the city and the residents.

“An important benefit of the Doetsch large-pipe cleaning method is that it is environmentally responsible,” said Schotthoefer. “The entire operation utilizes recycled sewer water for cleaning operations, reclaiming and continuously recycling sewer water and vacuuming to prevent migration.”