New sewer lining shortens traffic-tying digs

Molly Ball

Friday, June 25, 2004 | 9:07 a.m.

A fancy, high-tech method is being used to bring the city's sewers up to date. It's a complicated process involving space-age materials and chemical reactions.

"Basically, it's a sock," said John O'Connell, project manager for the Charleston Boulevard sewer improvement. "It looks like just a big sock."

This newfangled sock, officials say, is saving the city time, money and frustration by reducing what would have been a traffic-clogging yearlong dig to just four weeks of single-lane closures. It works by coating the inside of the old pipe, giving it a new, sturdy plastic lining.

Work began June 4 on the $5 million project, which will line more than two miles of major pipeline that runs under Charleston from Honolulu Street, just west of U.S. 95, eastward to Nellis Boulevard. The whole thing should be finished by July 8.

"The alternative to doing this is to dig up the roads for the length of the pipe," said Tom Scott, a technician for Insituform Technologies Inc., the company that makes the sock. "If we dug up all the roads, it would take at least six months to a year."

John Day, a city project engineer, agreed with Scott's assessment and estimated that a conventional dig would have cost $8 million to $10 million. "But that was out of the question anyway because of the traffic concerns," he said.

Other "trenchless" processes that don't involve digging exist, but this one was cheapest, Day said.

Between the lower cost, the shorter time-frame and the lessened traffic disruption, using the sock instead of digging "is a win-win situation for the city," O'Connell, the project manager, said.

A couple of weeks ago, Scott, wearing an orange construction vest and sunglasses, stood in front of the exposed end of the sock, which is made of several layers of flexible white felt. It descended vertically from a scaffold into the manhole at Charleston and Prince Lane.

The 1,500-foot section that Scott and other workers were putting in place on at that time would line a stretch of extremely large pipe -- 51 inches, or more than four feet, in diameter -- from Prince Lane to Lamb Boulevard. That pipe is a main collector that takes waste from surrounding neighborhoods and carries it directly to the city's wastewater treatment plant.

That portion of the installation required closing only one lane of traffic on Charleston, one of the valley's busiest streets with up to 50,000 vehicles a day.

The city has gained confidence in the technology because of the success of smaller projects done this way, but "this is the first project of this size," Packer said.

Day, the city engineer, said a mile-long section of smaller pipe under Ogden Street downtown was lined using the same process in 2002. That project took just two weeks and cost about $500,000.

That job, Day said, "was done quickly and smoothly. There were a lot of questions about how quickly they could do it and make sure none of the downtown casinos were affected." The city was impressed.

Next month, another pipe-lining will begin on Sahara Avenue. That project will rehabilitate a pipeline from Las Vegas Boulevard to Arden Street, a length of nearly four miles, and has an estimated cost of $2.6 million.

The Charleston sewer that's being lined was originally installed in 1956. It is made of unlined concrete, a material that is no longer used because it tends to deteriorate when exposed to hydrogen sulfide, the acidic gas that sewage produces.

The lifespan of a concrete sewer pipe is about 50 years.

"The Charleston line is in fair condition," Day said. "It's not going to collapse, but it shows some deterioration. It probably wouldn't last five more years."

City officials want to make sure aging sewers are replaced or rehabilitated before they break.

"Clark County experienced a collapse on their line; that's what we want to avoid," Day said.

He was referring to an unlined concrete pipeline near the Strip that collapsed in February, spilling 2 million gallons of sewage, some of it in the Caesars Palace parking lot. That breakage, the largest the area has ever seen, is still not fixed. County officials say the job will end up costing more than $1 million.

Three to 4 percent of the city's 1,500 miles of sewer pipe are unlined concrete. The rest are old pipes made of sturdy clay or new ones made of plastic. The concrete pipes, though a small portion of the total, make up most of the largest-diameter lines, Day said.

When unlined concrete pipes were new, in the 1950s and '60s, no one anticipated that they would eventually decay the way they do. But Day said engineers are not worried that the newer plastic pipes will have similar shortfalls down the line. They are tested rigorously, he said.

Insituform, the St. Louis-based company that makes the Charleston sock liner, is the largest of several American firms that manufacture and install the lining process. Michele Lucas, a spokeswoman for Insituform, said the technology was invented in England and patented in 1971 by Insituform's parent company.

Lucas said that in addition to testing the materials for durability, Insituform has revisited its early installations in England.

"We've taken out samples of pipe that's been in the ground for 30 years or more, and it basically has the same properties as when we put it in," she said.

Insituform is a subcontractor of Las Vegas Paving on the Charleston job but will be the chief contractor on the upcoming Sahara project.

Lining the pipe reduces its diameter slightly -- in the case of the Charleston sewer, by more than an inch -- but actually improves the line's flow because the plastic's surface is smoother than concrete, Scott, the technician, said.

As the crew waited for the sock to turn into a pipe, Terry Packer, the city's construction manager for the project, mused on the underappreciated service his work provides.

"I ask people, 'Do you know where the water goes when you flush the toilet?' " he said. "They say, 'No, not really. It's just gone.' "