- ENGINEERING INFO
- CASE STUDIES
The Outer Banks of North Carolina are a national treasure and a destination for hundreds of thousands of travelers every year, from beachcombers and sunbathers to fishermen. Those visitors, and the fulltime residents, are provided water by a variety of agencies that need to balance summer peaks against typical off-season usage, making treatment and distribution a challenge. The National Park Service chose to manage its system by eliminating wells and building a 28,000 foot pipeline from Nags Head to Bodie Island Lighthouse, and further to the Oregon Inlet Fishing Center, replacing part of an AC water line. The town of Nags Head will provide potable water and maintain the pipeline in the park.
The project began in late 2010 as a design-build with Team Henry Enterprises winning the work. Their designer, Parsons Brinkerhoff, considered the traditional dig and bury installation, but ultimately discarded that approach due primarily to environmental concerns, but also due to narrow rights-of-way, running sands, and a high water table. With horizontal directional drilling (HDD) as the preferred approach, pipe material selection was limited to fused plastics due to corrosion concerns and the need for tensile strength across the joint. After careful review, the team selected 6" and 8" Fusible C-900® pipe over upsized 8" and 10" HDPE due to cost, maintenance, and connection considerations. "The ability to connect directly from PVC to DIP fittings at hydrants and valves was important, as we knew dewatering would be a challenge and trying to fuse adapters to PE in a wet trench was not desirable," says Lewis White, P.E., of Parsons Brinkerhoff.
Webb, Incorporated was hired to do the pipe installation and subcontracted the HDD to Down Below, LLC of Rice, Virginia. With its Vermeer 80/100 drill, Down Below was able to stay off the shoulder of Highway 12 and shoot rods a distance of up to 1,000 feet before attaching reamer, swivel, and pull head and pulling the pipe back through the borehole. On more than one occasion, Down Below managed 4,000 feet in a single week. Bill Frank, owner of Down Below, states, "I must admit to being unsure of the benefits of Fusible PVC® pipe, but after this project I can see many applications down the road. My company is now a license holder for fusion of Underground Solutions' Fusible PVC® products, and I am sure we will be using that ability repeatedly in the future."
The connection points between drill shots were completed in a trench box with dewatering by sump pump to allow the crew to affix mechanical fittings and restraints. The entire line tested to 150 psi without any joint leaks, including the approximately 700 joints fused by Down Below
|Pipeline Details and Project Summary|
|Project:||Bodie Island Water Main|
|Location:||Cape Hatteras National Seashore|
|Length:||25,000' - 8"; 3,000' - 6" Fusible C-900®|
|Pressure Test:||150 psi|
|Owner:||National Park Service|
|Contractor:||Team Henry Enterprises|