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Huntsville Undertakes Nation’s Largest Root Control Project
"We've been fighting roots for years," says Mark Huber, collection system manager of the Huntsville Water Pollution Control Department. "In the past we've used conventional methods to cut roots out of pipes."
However, the process is time consuming, labor intensive and the cutting process actually encourages faster, thicker regrowth. Mechanical cutting tools cannot reach roots that are penetrating through joints, and the cutting process itself can cause damage to pipes.
Searching for a better, longer lasting solution to dealing with roots, Huber said chemical control methods were considered for the first time. Before committing to a full scale program, a test was performed in 2002 on 7,000 feet of pipe with a history of root problems and which had required field crews to clean or cut roots two times or more per year.
A Duke's crew applied chemicals to the test section, and it was monitored over a four year period. There was not a single root problem during that time, says Huber.
In the drought years of 2005 and 2006, Huntsville's root problems intensified.
"Our sewer lines became the only source of water for the roots, so inside the pipes is where they went," says Huber.
With the documented success of the chemical test program, it became clear that large scale chemical treatment for roots could free field crews to focus on more preventative methods and that such a program also would prolong the life of the pipes in the collection system.
"To target segments of lines to be treated," says Huber, "we reviewed the previous 20 years of line cleaning and repair data and put those with a history of root problems into the chemical treatment program. The lines needing attention were located throughout the city."
Inspections revealed that the majority of the lines to be treated were structurally sound and with chemical maintenance should not soon need to be rehabilitated or replaced.
The contract for the 1.6 million feet of pipe was awarded to Duke's and work began in April 2007.
"A two man crew treated sections of main lines between manholes," says Stuart Tillery, Duke's southeast sales manager. "We use specially equipped trucks with mixing supply tanks, hoses and a closed mixing system. The totally liquid formulation permits a completely closed mixing and application system."