HDPE Pipe Helps Utah’s Dixie Region

Utah’s Washington County, in the state’s Dixie region, is a popular haven for retirees and recreational sports fanatics. Who could blame them? The beautiful red sandstone landscape, easy drive to Las Vegas, and moderate winter temperatures all work together to make the region one of the United States’ fastest growing communities.

However, a booming population equates to more demand on water in an area that receives little to no snowfall and approximately 11 inches of rainfall per year. With such a premium on water, the Washington County Water Conservancy District has turned to high-density polyethylene (HDPE) pipe, for its leak-free characteristics, durability, strength, flexibility and ease of installation.

“We have been nothing but successful with HDPE pipe,” said Chuck Carney, Operations Manager for the Washington County Water Conservation District. “We’ve been using it since 1986 and we’ve got it in all sizes from 1-inch to 63-inch.”

63-Inch Installation

In the fall of 2009, a new 1,400-foot, 63-inch IPS SDR 17 pipeline was installed, getting more water to a treatment plant that provides Saint George and the suburban areas of Washington, Ivins, Hurricane and Santa Clara with water services.

Two reservoirs provide the water to sustain life in Washington County – Quail Creek and Sand Hollow. The two bodies of water are separated by the Virgin River, requiring any pipelining created between the two reservoirs to be located under the river bottom. Previously, a steel pipeline ran from Sand Hollow to a hydroelectric plant. From that plant, another water line ran into Quail Creek with a bypass line tied in just before the pipes entrance to Quail Creek. The bypass line supplies water to the water treatment plant that makes it suitable for the public.

“We chose HDPE because we had to go under the river. We have a 54-inch steel line that forces us to sleep with one eye open,” said Carney. “We wanted to put HDPE in and not worry about a leak or corrosion.”

The goal of the new HDPE line is to get the water from Sand Hollow directly to the water treatment plant without taking a longer route to the hydroelectric plant and then onward to Quail Creek. This circumvention of the line allows the water district to simultaneously perform both actions; running water from the hydroelectric plant to Quail Creek, and running water from Sand Hollow to the water treatment plant. The ability to get increased water resources to the water treatment plant is critical as the 40 million gallons-a-day plant looks to double output for the booming population over coming years.

The installation of the pipe required contractor Interstate Rock to divert the Virgin River between the two reservoirs in order to lay the pipe underneath the riverbed. After laying the pipe, the river was allowed to flow along its natural boundaries once more. The entire length of pipe was installed with open trench methods.

The large sticks of 63-inch-diameter HDPE pipe were manufactured by PolyPipe and provided by High Country Fusion, while the MegaMc® 1600 four-jaw fusion machine used in joining the pipe was provided by ISCO Industries. Local contractor, Interstate Rock, performed the pipeline fusion and installation.

Pipe fusion is a widely accepted process that joins two pieces of thermoplastic pipe together with heat and pressure. Commonly associated with HDPE, the butt fusion process starts by “facing” or shaving the pipe ends simultaneously so that they can be joined together with heat to create a continuous, sealed pipeline. The welding of the pipes is accomplished by using a hot plate in contact with the pipe ends, which heats the plastic to a molten state. Then, after its removal, the pipe ends are pressed together under a controlled force to form a weld that is as strong as or stronger than the pipe itself. Third-party industry research indicates that HDPE pipe and joints can have a lifespan of more than 100 years.

The McElroy MegaMc 1600 uses 30,000 pounds of clamping force per jaw and 88,000 pounds of available fusion force, extremely useful when dealing with such large, heavy pipe. The drag forces and characteristics of this pipe required McElroy’s largest fusion machine to perform the operations. Washington County has successfully turned to HDPE in previous years.

Three Past HDPE Experiences

While the Washington County Water Conservation District has had HDPE in use for more than 20 years with numerous projects, three pipelines really standout in showing what the pipe can do for a district.

The water district is responsible for irrigation lines to farmers in the region. The irrigation was originally an open canal and ditch system that resulted in water losses due to leakage and evaporation. The unreliable water supply would cause outages that were expensive repairs and took away critical water resources from farmers when they needed them. The HDPE solution was to create a 12-mile-long pipeline consisting of 54- and 63- inch pipe with 16-inch connections for each farmer. By using the pipeline over the open canal, the district was able to eliminate the troublesome problem of the canal “sliding” off the hillside. HDPE also showed its mettle for Washington County during a 100-year-flood event in 2006. The Santa Clara River flooded after heavy snow and rains, washing out a 28-inch HDPE irrigation line. Carney reports that the HDPE line was never breached and all the fusion joints were intact, even after repeated contact with trees, boats, rocks and other flood debris.

The worst damage done to the 28-inch line was caused by the contractor, pulling it from the river. The retrieved HDPE pipe was sorted out, fused back together and put back into service. “The durability of the pipe continues to impress us,” said Carney. “No other type of pipe could have withstood the battering this pipe received and remained intact.”

For another water conservation measure, Washington County took to the mountains to create a 12-mile line of 36-inch HDPE pipe. The line was built to ensure that Kolob Reservoir would be full each year for downstream irrigators’ use. The reservoir’s main water source was mountain snow melt, and the pipeline stretched from a 9,500’ elevation down to the 8,000’ elevation height of the reservoir. This design allowed the pipe to capture the water at the source. By making this water capture so effective, it guaranteed that the reservoir would fill every year, even in years with minimal snowfall.

The environment for the pipeline was demanding, requiring the HDPE to traverse rocky terrain with steep slopes and corrosive soils. Prone to landslides, engineers chose HDPE for flexibility and strength when soil movement occurs. Because of the life span of the pipe, workers won’t have to repair or replace the pipe in areas with no road access.

Advice

Carney advises municipalities that there is some trade off when you use HDPE. He believes the confusion between inner and outer diameters of HDPE compared to other pipe materials frustrates municipalities that don’t fully understand all the benefits.

“A lot of communities don’t want to spend more to upsize to get the same size inner diameter they would with PVC or ductile iron. I tell them, ‘when you’re up at midnight digging that up and fixing it, I’m at home sleeping easy.’”

Written by Tyler Henning, McElroy Manufacturing, Inc., 833 N. Fulton Ave., Tulsa, OK 74115, 918-831-9286, E-mail: thenning@mcelroy.com, Web: www.mcelroy.com.