Pipeline rehab protects river
The Homosassa River in Homosassa, Fla., is home to thousands of fish, manatees and other marine and bird life. So when it was in peril of severe contamination by a leaking underground pipe, action had to be taken immediately. The ecology of the river was intact until the day this past April when a six-inch force main that lay 26 feet beneath the river began to leak. Potentially thousands of gallons per day of raw sewage could have begun seeping into this pristine river with drastic consequences.
The pipeline was shut down, and a trucking company was hired at a cost of $5,000 per day to transport the untreated waste-water 12 miles around the head-waters waters of the spring to a lift station on the opposite side of the river. Then RHV Utilities, which manages the lift stations on both sides of the river, called on its consulting engineers, Berryman St Henigar, Crystal River, Fla., to solve the contamination problem.
In past years, when the 12-year-old ductile pipe leaked, divers remedied the problem by placing steel repair clamps over the leak.
These two-foot repair sections worked well enough, but there were now a total of 36 clamps in place. The leaks had become more frequent, and adding more clamps was no longer an option because they cannot be overlapped.
The pipeline was in danger of total collapse. Consequently, it was obvious the leaks had to be stopped permanently. A polyvinyl chloride (PVC) liner was specified because of its low coefficient of linear thermal expansion, durability and long life expectancy. Griner’s Pipeline Services, Mount Dora, Fla., installed an Am-Liner, an EPA-approved, seamless, PVC pipe that is not susceptible to tracking or shrinkage, and, as a fold and form material, can be put into operation quickly and cost effectively.
The plan was designed to rehabilitate the pipe without disturbance to the river and with minimal downtime. The first day, pit excavations were made on both sides of the river, and the old pipe cut away to allow entry of cleaning equipment. The pipe was cleaned of debris with high-pressure jet equipment to expose any problems. Next, the company sent a robotic camera through a pipe for a visual inspection of the fractured pipeline. The second day, the folded pipe was installed by sending a tow line through the pipe and pulling the PVC material in place. Two-way radios were used to coordinate work on opposite sides of the river.
To ensure the new pipe structure’s strength, EPA required that it endure a 25-psi pressure test for two hours with zero loss of pressure. The system passed, and the job was completed by sunset on day two. The portable treatment plant was removed and the force main put back into operation.