Environmental Protection

Contractors Turn Strategy Into Reality

A Garland, Texas, interceptor project took five years to get to the street. Now the contractors are making capacity improvements a reality by installing 48-inch outside diameter (OD) pipe over about 18 months.

“Not a lot of people can do a big line,” said Larry Lisowski, an engineer who works for Gajeske Inc. of Houston. Business has been good because Gajeske can install large diameter pipe. Bob Gajeske Jr., vice president of the company, estimates 2007 revenues at $27 million.

The city of Garland awarded a $41.6 million contract to the Oscar Renda Contracting Co. of Roanoke, Texas. Renda awarded a $3.2 million subcontract to Gajeske, which employs about 50 people.

This bid project involves installation of a raw wastewater force main and sludge transfer force main linking the 24-million-gallons-per-day (mgd) Rowlett Wastewater Treatment Plant to the recently expanded 30- mgd Duck Creek Wastewater Treatment Plant. Gajeske’s part of the project was to provide nearly four miles of 48-inch OD high-density polyethylene pipe (HDPE), fuse those sections together, and also weld another 11 miles of 8-inch OD HDPE sludge force main sections that will transport solids from Duck Creek back to Rowlett.

“We are very excited about this project, which has some challenging sections and provides us with the opportunity to utilize our experience and expertise in large-diameter HDPE pipe,” said Gajeske.

Lisowski said that more cities have been specifying bigger diameter pipe so that the water and sewer lines could accommodate greater flows as cities continue to increase in population.

On the job
In a Garland park along Lake Ray Hubbard, miles of 48-inch HDPE pipe stretched out as far as the eye could see. The pipe was trucked in from Performance Pipe manufacturing facilities in Brownwood, Texas, and Wellford, S.C. The pipe company is a division of Chevron Phillips Chemicals Co. Many pipe sections already had been fused together on Oct. 4, ready to be put into a trench and transport excess flow from the Rowlett plant to the Duck Creek facility.

Rob Jaynes worked with other Gajeske crew members at the site, fusing large sections of pipe together using a 1648 MegaMc fusion machine from McElroy Manufacturing Co. The machine holds two pipe sections in large clamps, sheers the butt ends clean and level, and then applies 500 degrees Fahrenheit of heat for about two minutes. Jaynes flips a second switch, and the machine also applies 1,000 pounds of joining pressure to the sections. According to Gajeske, the joined pipe must cool completely, about 30 minutes, before the process is complete. Each section takes Jaynes one hour. Then a crew member starts up the Volvo crawler to pull the newly fused sections down the grassy length of city park and the cycle begins again.

The right pipe for the job?
This is where the HDPE meets the load. The Plastic Pipe Institute has said that HDPE has been used in sewers for more than 25 years without showing significant changes in physical or chemical properties. But not everyone is on board with that idea.

“It is true that HDPE pipe historically is not used extensively in wastewater applications,” said David Timmerman, P.E., Black & Veatch’s project manager who is working with the city. “The reason it was closely evaluated,” Timmerman explained, “is because we have a pumped transfer line from the Rowlett plant into the junction manhole, so we needed a pipe that was capable of pressure flow. The city also wanted a line that was relatively free of joints— fusion welded is an attractive feature. Another nuance is that the pipeline does not flow continuously uphill; the last quarter of the segment flows downhill, so the pipe will be partially full, which gives an opportunity for corrosion. HDPE won’t corrode.”

Timmerman said that the Texas Commission on Environmental Quality, Wastewater Permitting Section, does not typically approve HDPE for this kind of application. The agency requires force mains to have a minimum pipe working pressure of 150 pounds per square inch. The Black & Veatch team submitted documentation showing that, given this project’s hydraulic design conditions, HDPE pipe could safely convey the flow with a lower pipe design working pressure. The section approved a variance, allowing the HDPE pipe to be used.

The large-diameter HDPE pipe that Gajeske worked on will serve as the pump transfer line from Rowlett and ties to a manhole that ties to a new, 60-inch interceptor sewer, made from fiberglass, which will replace a smaller diameter pipe and expand city capacity. The 60-inch line was provided by HOBAS Pipe of Houston. The 8-inch, HDPE sludge force main sections were supplied by JM Eagle of Livingston, N.J. The smaller diameter pipe runs parallel to existing pipe and will allow the city to easily perform maintenance.

Work flow
As the primary contractor, Renda’s General Superintendent Chris Williams will oversee the work of Gajeske and construct and install the additional lines to provide more conveyance capacity through a portion of the drainage area and to the plants.

Jaynes said he has worked with a lot of contractors. He said he received instruction from Williams and then was left to do the job. “I like that the prime contractor didn’t feel the need to micromanage the process,” Jaynes said, adding that the teamwork of the groups on the project has made the job “more fluid.”

Garland’s interceptor project has taken so long to “get to the street” because almost all of the land used in the project is within a floodplain. “There was significant environmental work that had to be done,” Timmerman said.

And apparently there still is more construction work to be had. Timmerman said the city is about to put another contract out on the street for the Rowlett Transfer Pump Station. “We calculated flows to the plant and they exceeded capacity, so we are transferring flow from Rowlett to the collection system to the plant,” he explained. That contract will be about $6.5 million, he added.

This article originally appeared in the 12/01/2007 issue of Environmental Protection.

About the Author

L.K. Williams is editor of Water and Wastewater News.

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