Fast Draw

A utility in Texas becomes the first to do in-house sewer lining projects using a new manhole-to-manhole cured-in-place process
Fast Draw
From left, Jeff Martinez, collection crew chief; Jaime Garcia, collection operator; Doug Clifton and Alex Alvarado, collection crew chiefs; and Doug McCollough, Perma-Liner trainer, prepare to shoot a 240-foot liner.

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Years of drought interrupted by occasional cloudbursts dropping up to 12 inches in one day caused problems in the older sections of New Braunfels, Texas.

During winter of 2009-10, the Telog sewer data acquisition system showed that four of 23 lift stations ran continuously for 36 hours after rains. Unprecedented rains increased flows at the treatment plant from 6 to 10 mgd – the design capacity.

An inspection by Pipeline Analysis, an engineering firm in Dallas, revealed structural issues in the clay and reinforced concrete sewers in older neighborhoods. Root intrusion also contributed to inflow and infiltration. The firm advised the utility what manpower and equipment it would need to attack the problem in-house.

“We bought a new 200 Series PD Camel combination machine from Super Products with Warthog nozzles from StoneAge Tools to assist our Vactor 2100 PD combination truck,” says Trino Pedraza, operations and maintenance division manager for New Braunfels Utilities. “We also bought two Pathfinder cameras, an inspection van, and a trailer (Aries Industries), and hired two more people.”

The goal was to clean and inspect 10 percent of the 331 miles of sewer lines every year. The city contracted for cured-in-place pipe lining to fix the worst problems. “When we saw the process, we wondered why we couldn’t do it,” Pedraza says.

Although engineering firms and installers warned him that utility workers could not take on that level of work, Pedraza’s division lined 3,240 feet of 6- and 8-inch mains running through a wooded canyon with no asphalt roads. The utility was the first in Texas to use the Top Gun manhole-to-manhole system from Perma-Liner for an in-house sewer lining project.

 

Breaking trail

Comparing contractor bids for the repair convinced Pedraza and chief engineer, Ian Taylor, that they could save $2,000 over the lowest bid by buying the lining equipment and doing the work themselves. “We were nervous,” says Pedraza. “No other municipalities were doing it because everybody said it couldn’t be done. To gain experience, we bought the Perma-Liner point repair system.” Workers did 17 point repairs from two to 18 feet in 6- to 21-inch pipes.

The utility then purchased Perma-Liner’s 20-foot-long climate-controlled trailer, lateral inversion system, and Top Gun system with Viper compact steam unit. It also paid for additional field support to ensure the project’s success. Company president Jerry D’Hulster arrived with colleagues Jim Gould, Doug McCullough and Andrew Dietsch.

The average run was 200 feet between manholes. “The terrain was so horrible that we had to build our own paths to get in,” says Pedraza. “Since we didn’t have heavy flows, we plugged where we wanted to line and kept the Camel unit upstream to vacuum sewage if it rose too high.” The crew also had a 6-inch Gorman-Rupp bypass pump with more than 500 feet of hose for backup.

Two crews totaling seven workers were on the job, enabling everyone to learn the process. For runs of 90 to 150 feet, they wetted out liners in the trailer, installed the inversion unit over the manhole, and hand-fed the liner into the top of the gun to begin the inversion process. After clamping the liner to the gun’s bottom lip, they blew in air at 12 to 16 psi, and the liner shot down the pipe at 12 inches every 1.7 seconds.

 

Working out bugs

The first week was a learning curve. “The heat in Texas forces us to work more slowly,” says Pedraza. “The lining process required a faster pace than initially expected.” After crews wetted longer runs outdoors on concrete registering 100 degrees F, two liners cooked off in the trailer before reaching the job site. Technical support, believing they should have caught the mistake, replaced the liners for free.

From then on, work began at 5 a.m. while it was cooler, and the workers wetted out liners in an equipment bay after hosing down the concrete floor to lower the temperature. The schedule enabled them to shoot one liner before and after lunch, then return and cut the next day’s liners.

“I learned that the cured-in-place process isn’t difficult,” says Pedraza. “The difficulty is in the planning and preparation.” The second week of the three-week project went much more smoothly.

On the day personnel arrived from San Antonio Water System to watch, utility workers shot 257 feet of 6-inch liner in two minutes and 30 seconds. “San Antonio is having identical infrastructure problems,” says Pedraza. “They liked what they saw.”

Curing required one worker controlling the steam unit and another with a walkie-talkie at the far manhole to relay temperatures. Once both ends of the liner reached 200 degrees, they shut off the steam and applied air at 5 psi until the liner cooled. It took an average of 30 to 40 minutes to heat liners and 15 to 20 minutes to cool them.

 

Bold and confident

Workers initially resisted the technology and the change in how they did things, but they became excited as they got the hang of it. Before long, they wanted to push themselves to see what they could do. “We decided to shoot 700 feet by going through the middle manhole in an 8-inch line,” says Pedraza.

During inversion, the worker at the middle manhole looked for a red mark drawn on the liner to indicate its approach, then radioed the air operator to reduce pressure. Using a rod, he guided the liner through the manhole and back into the pipe. When the air pressure was increased, it forced some liner material into the hole and pushed the remainder downstream. “Reinstating the manhole left just enough lip for us to smooth and fair the edges,” says Pedraza.

Half the city’s sewer is PVC and less than 20 years old. The utility’s target is to line 6,000 to 9,000 feet of clay, ductile iron, and reinforced concrete pipes per year. It is smoke-testing laterals and televising those that leak to combine them with bigger mainline CIPP projects.

“The equipment paid for itself on the first job, so everything else is a return on our investment,” says Pedraza. “But the best thing is how the success of the guys’ efforts empowered them. When 48 people are engaged at that level, productivity shoots through the roof without management doing a thing.”



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