Kim Endsley, Joseph Poniatowski
Papers # 2016 Berlin
In order to free itself from the rising costs of water supplied by the Detroit Water and Sewerage Department, the Karegnondi Water Authority proposed a new water intake and delivery system from Lake Huron to Flint, Michigan. Because of the recent introduction of the zebra mussel into North America’s Great Lakes, a chemical dosing system was needed to keep the intake line free of zebra mussels, which restrict flow and clog pipe. A coextruded Advanced polyethylene double contained pipe was chosen for the sodium hypochlorite system because of its excellent chemical, corrosion, and impact resistance.
The Karegnondi Water Authority (KWA), formed in 2010, is building a new water pipeline to supply Flint, Michigan and surrounding communities with their own fresh water supply from Lake Huron. The project was conceived because of increasing water rates from Flint’s previous water provider, the City of Detroit.
A major challenge in the project was the zebra mussel infestation in the Great Lakes region, which would quickly clog the new 78-inch diameter pipeline. Zebra mussels adhere to water intake lines clogging pipes and the machinery for the water delivery system resulting in millions of dollars in repairs. Infestations can be so severe that they result in the shut-down of water treatment facilities and the loss of water to surrounding communities. The US Fish and Wildlife Service estimates that the economic impact of zebra mussel infestaions will be between three and five billion US dollars over the next 10 years.
Though there are many available methods for combatting the zebra mussel problem such as temperature treatments, barrier filtration, electric currents, and sonic vibration, these techniques have yielded only limited success. A regular dosing of sodium hypochlorite in the water intake structure has proven to be an effective means of preventing the zebra mussels from clogging the intake pipelines.
The dosing system in Flint required double contained pipe to prevent a sodium hypochlorite leak into the surrounding waters, and part of the sytem required horizontal directional drilling. An Advanced PE double wall pipe system with four-inch SDR11 carrier and six-inch SDR17 containment was chosen because it met both of these criteria, as well as being resistent to the oxidizing properties of sodium hypochlorite.
The unitary construction of the pipe, the inherent physical properties of Advanced PE, and the joining and installation methods used throughout the KWA’s pipeline project saved the water authority, its member communities, and Michigan taxpayers money and peace of mind.