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Posted on Sun. Nov. 25, 2012 - 12:46 am EDT

Sewer fix saves City Utilities millions

Lining existing pipes cheaper than installing new ones

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For thousands of years, the only way to fix a leaking or broken pipe was to dig it up.

But a different approach invented four decades ago is being used more and more, saving City Utilities millions of dollars in the last decade alone.

Now, crews frequently form a new pipe inside the damaged one, with no digging, few disruptions, and dramatically lower costs.

“You can put sewer pipe in a new subdivision for $40 or $50 a foot,” said Matt Wirtz, deputy director of engineering for Fort Wayne City Utilities.

“But that’s digging in a cornfield. It is brutal work to dig up sewers – the pipe in the ground is the small piece. It’s all the disruption.”

Now, there’s a better way, called “cured in place.” Invented in 1971 in England by Eric Wood, the method uses water pressure to unroll a felt liner into the pipe, the way you unroll a sock, only the felt liner is impregnated with resin. Crews then fill the pipe with steam or hot water, which cures the resin into a hard, PVC-like coating – a new pipe within the pipe. A robotic device is then used to drill out holes where other pipes join, and the process is complete.

The first time the method was used in Fort Wayne was in 1979 for a sewer line beneath Calhoun Street between Berry and Washington that was built in 1867. With historic buildings on each side and numerous underground utilities, digging up the sewer would have been incredibly hazardous and expensive, said Mike Hicks, who oversees sewer repair and replacement for the city.

“We just camera’d it three years ago and it’s in great shape,” Hicks said.

Cured-in-place pipes are essentially new pipes, which are designed to last 50 years.

How much cheaper is it?

Since 1998, the city has used cured-in-place on 691,083 feet of sewers at a cost of $34.7 million. Replacement using traditional excavation, using the lowest bid the city received in that time period, would have cost $220.7 million. Using its average excavation cost would have run to $511.6 million, according to city figures.

“The cost savings are just tremendous,” Hicks said.

The time savings are immense, as well.

Cured-in-place crews can complete up to 400 feet of pipe a day; old methods can replace 50 feet a day, at best.

Saving time and money is all well and good, but for Fort Wayne, the issue is critical.

The city has 1,346 miles of sewer pipe underground and needs to replace at least 1 percent of it a year. But all those pipes weren’t installed evenly over the years, so large swaths of the city have pipes hitting the end of their useful life all at once.

Most of the core of the city, geographically, has pipes between 75 and 99 years old, and by 2048, 51 percent of the system will be more than 75 years old.

“Cities and towns around the country are going crazy doing (cured in place), but you have to,” Hicks said.

The liner does reduce the inside diameter of the pipe about a half-inch, but that is more than made up for, officials said, because there are no joints between manholes and the liner is slick. Hicks said they’ve found that flow increases at least 10 percent in a lined pipe, and the effluent moves up to 14 percent faster.

No joints also means there is nowhere for tree roots to invade the pipe.

A technique that was revolutionary just a few decades ago is now the status quo: 97 percent of the city’s pipe rehab work is now cured in place.

“Before 2000, we didn’t do a lot (of rehabbing). There just wasn’t funding,” Wirtz said. “So we’re still behind, but now – thanks to this – we’re catching up.”

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