Expanding wastewater infrastructure

August 2008 » Feature Articles
More than 20 million people visit Utah’s resorts during ski season to enjoy what the state displays on some of its license plates—"Greatest Snow On Earth." But not only tourism is on the rise, so also is the local population. And, the state’s recent significant growth is expected to continue well into the future. Consequently, local municipalities are taking a closer look at their current infrastructures.
Kimberly Paggioli, P.E.

Project
Jordan River Outfall Sewer, Salt Lake County, Utah

Civil engineer
Bowen, Collins & Associates, Draper, Utah

Product application
South Valley Sewer District adds collection capacity with installation of 4,000 feet of 48-inch pipe.


Sewer district in Utah invests in collection and treatment capacity to keep pace with expected growth.

More than 20 million people visit Utah’s resorts during ski season to enjoy what the state displays on some of its license plates—"Greatest Snow On Earth." But not only tourism is on the rise, so also is the local population. And, the state’s recent significant growth is expected to continue well into the future. Consequently, local municipalities are taking a closer look at their current infrastructures.

The South Valley Sewer District (SVSD), which encompasses approximately the southern third of Salt Lake County, serves the cities of Bluffdale, Copperton, Draper, Herriman, Riverton, South Jordan, and South Sandy. District municipalities reportedly include more than 4,400 building lots that are not yet connected to the existing system. These lots will require more than 1.5 million gallons per day (mgd) of additional capacity. However, rapid growth during the last several years has stressed the district’s existing facilities.


The South Valley Sewer District’s Jordan River project in Salt Lake County, Utah, ensures sufficient capacity to transport sewage to an existing treatment facility until a new treatment plant is complete. The outfall sewer line includes approximately 4,000 feet of 48-inch pipe and 16 seven-foot manholes.

To combat the problem, SVSD is investing roughly $3 million in its infrastructure; relief lines and new facilities, including a wastewater treatment plant, are being designed and constructed. Since March 2002, SVSD officials have been seeking approval for an ultra-filtration treatment plant to be located in Riverton that will enable them to keep pace with the growth in southern Salt Lake County. The new facility will provide enough capacity for the next 10 to 15 years.

Upon completion, the Riverton facility will add 15 mgd to the district’s treatment capacity, with potential for more upon future expansion. The sewer district will retain 13.2 mgd capacity at the existing South Valley Water Reclamation Facility (SVWRF), which is currently under expansion. When the SVWRF plant expansion is complete in two years, the SVSD will acquire an additional 3 mgd.

Outfall pipeline
To be sure that sewage can be transported to the existing treatment facility until the new plant is complete, additional piping networks are necessary. One of the most recent projects was the Jordan River Outfall Sewer. The primary purpose for this new line was to mitigate capacity problems with an existing 48-inch line that has been in operation since the early 1980s. According to Michael H. Foerster, P.E., district engineer with SVSD, the Jordan River project, put out to bid in January 2007, included approximately 4,000 feet of 48-inch HOBAS pipe and 16 seven-foot manholes. It is one of the district’s main outfall lines to the treatment facility.

Bowen, Collins & Associates of Draper, Utah, which specializes in providing water, wastewater, stormwater, groundwater, civil engineering, and environmental services to clients in the Intermountain West, was hired to design the outfall. Allied Construction and Development, Inc., of Logan, Utah, was awarded the bid to install the pipe.

Installation included both direct bury and boring. SVSD specified use of HOBAS centrifugally cast, fiberglass-reinforced, polymer mortar (CCFRPM) pipe. "The Jordan River Project was mostly direct bury with several installations of [pipe] through steel casings," said Bart LaMont, project manager, Allied Construction and Development. "The pipe installed well and had no problems with visible deflection and joint leakage."

The direct bury portion of the project ranged from 15 to 30 feet in depth and was installed primarily through good, clean, sandy material. The embedment specified and used was 1-inch-minus stone with filter fabric to prevent migration of native soil into the embedment zone.

"We worked with the HOBAS engineering staff to help us specify the appropriate pipe stiffness rating based on depth and soil conditions," said Brent Packer, P.E., design engineer, Bowen, Collins & Associates. "They also provided us the appropriate pipe zone backfill specification requirements for HOBAS pipe."

"The goal of our staff is to provide sound engineering support," said Rene Garcia, senior engineering associate with HOBAS Pipe USA in Houston. "We are always willing to provide assistance to designers and installers to make their projects as successful as possible. But this customer support begins well before HOBAS pipe is chosen for the project. During plant tours of the HOBAS facility, engineers provide detailed explanations on flexible conduit theory, manufacturing capabilities, and quality control, as well as [answer] any concerns or questions related to specific installation."

The Jordan River project required additional planning because of the extensive groundwater that was present. "The project is in an area of high groundwater and has experienced some hydrogen sulfide (H2S) degradation of the existing concrete pipe. [We] chose HOBAS for its H2S resistance and water tightness," said Foerster.

The pipe used in this project has a nominal stiffness (SN) of 46 pounds per square inch, which is standard for direct bury and tunneling applications. This high stiffness allows for routine burying methods with predictable performance that can handle deep covers. "The HOBAS pipe was easier to install than reinforced concrete pipe and held rigidity better than the profile PVC piping that we have used in the past," said LaMont.

HOBAS push-together FWC couplings were used for the Jordan River project installation, factory assembled to one end of each pipe for easier use in the field. The sealing design includes both lip and compression elements so the joint is suitable for both non-pressure and pressure service. The joining method allowed for the bells and gaskets to remain clean because they were the first thing installed with each new stick of pipe.

Kimberly H. Paggioli, P.E., is the marketing manager for Hobas Pipe USA. She can be contacted at kpaggioli@hobaspipe.com.


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