Six million gallons of water per day (MGD) sounds like a lot of water, and it is, but it wasn’t enough to meet Limestone County’s projected demands for drinking water. Around 1,000 customers were being added each year, and a number of inquiries had been made about increased industrial development.
The solution for the Alabama county, which borders Tennessee to the north and Madison County (Huntsville, Alabama) to the west, came to the Limestone County Water and Sewer Authority (LCWSA) after years of planning and coordinating with local, state and federal authorities: Install a large-diameter water transmission line that would allow Limestone County the capacity to purchase up to 15 MGD of water from Decatur Utilities, the water authority of its southerly neighbor, Decatur, Alabama.
The only catch – you have to cross the Tennessee River to get to Decatur. And while the width of some major rivers is only a few hundred feet at points, the prime spot across the Tennessee River (and a portion of Wheeler Lake) for this project is 1.67 miles wide. To intensify the challenge, this location is just a few thousand feet upstream of one of the busiest ports on the river.
Designing a safe, environmentally sound approach to this pipeline project was just one of the many challenges facing engineering firm Hethcoat & Davis, Inc. and the contractor Garney Construction. Leading Garney’s team was Jeff Seal, director of Nashville Pipe Operations.
“The overall project included ductile iron pipe as well as steel pipe. AMERICAN manufactures both products and was able to supply the entire job. We have a long-lasting relationship with AMERICAN. We know they will stand behind their product.” –
Jeff Seal, Director of Nashville Pipe Operations for Garney Construction
“The overall project included ductile iron pipe as well as steel pipe,” said Seal. “AMERICAN manufactures both products and was able to supply the entire job. We have a long-lasting relationship with AMERICAN. We know they will stand behind their product.”
The project featured “unusual complexities,” according to the contractor, including a 3,000-foot section using horizontal directional drilling (HDD) for a river crossing on the Tennessee River and approximately 5,800 feet of subaqueous, or underwater, pipe installation. Negotiations and coordination related to building across roughly three acres of designated wetlands, along with other legal and environmental issues, were required with the Tennessee Valley Authority, the Corps of Engineers, Norfolk Southern, Alabama Department of Transportation and others. The permitting process included nearly a dozen agencies and took almost three years to complete.
With the route finalized, pipeline materials were specified. For the HDD portion, 36-inch AMERICAN SpiralWeld Pipe with a wall thickness of 0.75 inches was selected. With minimum yield strength of 35,000 PSI, the pipe contained an interior lining of 20 mils polyurethane and an exterior coating of 25-mils of polyurethane with an additional 40 mils of abrasion resistance coating over the polyurethane.
For much of the 5,800 feet of subaqueous pipe, 36-inch AMERICAN SpiralWeld Pipe was also selected. Class 250 cement-lined AMERICAN Ductile Iron Pipe was used for the remainder of the pipeline. For additional pipeline protection in the fragile Decatur Day Park wetlands area, a polyethylene encasement was employed. AMERICAN also provided Flex-Ring restrained joint fittings for the project. In addition, AMERICAN Flow Control supplied four 36-inch resilient wedge gate valves with Flex-Ring ends.
In the end, the project was completed ahead of schedule. Limestone County Water and Sewer Authority CEO Daryl Williamson is pleased with the role AMERICAN products played in the successful job. “Because of this project, we are in a good position to serve the public and industry for the next 20 to 30 years,” he said.
Seal added, “We have high expectations, nothing short of perfection. And AMERICAN met our expectations.”