WATER: Jump Start

A Michigan city uses a steam-cured lining system to speed up its water main rehabilitation program while reducing disruption to traffic and daily lives

With a water system that dates back more than a century, the city of Monroe, Mich., has always had to pay attention to repair and upkeep of its cast iron mains.

But two things have come together to put the city on a much more intensive rehabilitation program. One is trenchless technology. The other is a low-interest loan program through the state and federal governments.

Together, the financing and the technology — a new steam-cured lining system — have led the city to put in place a three-year plan to replace or repair 77,000 feet of water main. That’s just under 15 miles of the 282 miles of pipe the city’s water system owns.

“We’ve always had a strong capital improvement program,” says Barry LaRoy, P.E., director of Water & Wastewater Utilities for the city. “In the past, though, the focus was on replacement. We would do less than a mile annually of replacement. In the three-year program, we’re doing about 5 miles a year of rehab and replacement.”

Thus, in half the time, the city will have covered nearly three times as much line as under the old program.

Aging mains

Monroe, just off of Interstate 75 halfway between Detroit and Toledo, covers about 10.5 square miles, but the water system, which draws from Lake Erie, serves a much larger area. Much of the expansion took place in the last 15 years as the city extended service to surrounding communities. Today it serves 119 square miles, covering several townships. It also sells wholesale water to the Village of Dundee and the City of Peters-burg, about 15 and 20 miles west, respectively.

The system is oldest in Monroe itself. LaRoy says the city is a member of the “cast iron club,” a designation awarded by the American Cast Iron Association in the 1990s for systems with cast iron lines older than 100 years. Those lines show their age. “We have on average 50 or more main breaks every year, a lot of them on cast iron lines,” LaRoy says. “Eighty to 90 percent of them are in the city limits.” The city has typically spent about $700,000 per year to replace aging lines.

Pilot project

Monroe launched its latest program with a pilot project at the request of a major industrial customer. The factory had an old fire protection system that the owners wanted to remove. But until the city could give assurances that it could provide adequate water to the area under the proper pressure, fire protection authorities wouldn’t let the factory shut down the system. Complaints of rusty, unpalatable water were common, too.

“We did a leak detection survey for that area,” LaRoy recalls. “We found a few main breaks underground that weren’t providing any evidence at the surface. So we made those repairs. We found some closed valves and opened those. That helped a little bit.”

But it wasn’t enough: “The fire marshal would not allow them to get rid of their fire protection system because we couldn’t provide them adequate fire flow.” The next step was to take that part of the system out of service and clean the main thoroughly. That improved flow significantly, but water-quality issues persisted.

That’s when LaRoy learned about Thermopipe liner from Insituform Technologies Inc. The city was a past customer, having the company’s sewer pipe-lining products, and LaRoy was intrigued by the Thermopipe liner methodology.

Unlike other pipe liners, Thermopipe liner doesn’t adhere to the inside of the pipe — instead it simply rests free inside. LaRoy liked the fact that the heat-cured liner didn’t have to rely on the integrity of the host pipe over the long term. “I was looking for a solution that would be a structural liner,” he says. “So if the host pipe ever does give way, it could be a full replacement and provide another 50 to 75 years of service life.”

First in the state

Monroe was the first municipality in Michigan to win approval from the state Department of Environmental Quality to use Thermo-pipe liner. In the spring of 2007, the city conducted a pilot project on a 1,900-foot stretch of main serving the industrial customer. “The results were very positive,” LaRoy says. “The water-quality and low-pressure issues went away.”

The positive experience led the city to launch its much more ambitious project, which began in 2008. It consists of 14,000 feet of lining and another 13,000 feet of main to be replaced. The lining/replacement program is normally budgeted at $800,000 to $900,000 annually, but because the three-year project covers so much more line, it will cost about five times that amount each year.

The first year was city-funded, but for the second year, Monroe applied for and will receive a low-interest loan of about $5 million from the Drinking Water Revolving Loan Fund. The EPA provided seed money, and the state DEQ matched it.

The second-year program will consist of 7,000 feet of lining and 17,700 feet of replacement. Year three will cover 11,600 feet of lining and 13,700 feet of replacement. Monroe will seek a loan for that project, as well.

City staff drew up a comprehensive plan for all three years, segmented from year to year. Projects are coordinated with road resurfacing and reconstruction to reduce disruption to traffic and business. If needed, sanitary sewer lines can be replaced or repaired at the same time.

Going small

Replacement projects are aimed at smaller mains. “We have a lot of 4-inch cast iron mains,” LaRoy says. “With the tuberculation buildup in these mains, you’re talking about a 2-inch or less water main. When they were designed back in the late 1800s and early 1900s, they met the requirements for the time. But now, when we have fire demands in the 2,500-gpm range for industrial parks and a minimum of 1,000 gpm for residential areas, it just doesn’t meet the fire code. You’ve got to upsize them.”

The city’s replacement specifications call for ductile iron class 52 pipe for mains in the roadway, fastened with stainless steel bolts and poly-wrapped to prevent corrosion. Water mains outside the roadway area call for PVC C900 or C909.

For the lining projects, the city focuses on 8-inch cast iron sections with a history of rusty water complaints, low pressure and low fire flow. Along with lining, the city is replacing hydrants and valves and replacing lead service lines with copper.

“Insituform’s thinking is that the lining will last 50 to 75 years on its own without the host pipe, but if the host pipe gives you another 20 to 30 years on top, there’s a lot to gain from that,” LaRoy says. “A lot of these host pipes, surprisingly, are still in pretty good shape structurally.”

The lining process

In the lining process, a pipe segment is taken out of service and a temporary bypass system with a minimum of 2-inch HDPE pipe is then put in place, attached to customers’ outside faucets and fed from a fire hydrant with a backflow prevention system. After disinfection, the bypass system is turned on and the regular system’s curb stops are turned off. Customers get their water free during the renovation and only pay quarterly service charges.

Access pits 8 to 9 feet long and 5 to 6 feet deep are dug at every valve point, fire hydrant and intersection cross-street water main. The valve and fire hydrant sections are removed, and crews clean and video inspect the water lines. They also log the locations of all services.

Crews grind down the water service corporations inside the main so they are flush with the inside of the pipe wall. “You don’t want those corporations sticking out,” LaRoy explains. “Then it could rub on the liner and break it.”

The liner itself is polyester-reinforced polyethylene matrix. Available in diameters from 2.75 to 12 inches, it has an internal pressure rating of 170 psi (230 psi for 4- through 8-inch diameters). Wall thickness ranges from 0.08 inch to 0.20 inch.

The liner comes from the factory flattened and folded lengthwise like an inverted letter C and wound on a reel. At installation, it is winched into the cleaned host pipe from the reel and pulled through. Then it is inflated with air into a full cylinder and heated with steam, which supplies heat and pressure to remove all creases from the folding and fits it tightly to the host pipe. End couplers and service connection ferrules are attached after a short cool-down period. “The lining process takes maybe 20 minutes,” LaRoy says.

City specifications require a pressure test. Afterward, services are internally tapped in using an iTap robotic reinstatement cutter. The system uses stainless steel, self-tapping T-nuts and gaskets to seal the liner against the host pipe, locking it down to keep water from seeping around the nut. Disinfec-tion follows, and then service is reinstated to customers. External taps are necessary on larger services.

Good for the city

How long it takes to do a segment depends on how many services it includes and the location of the installation. About 150 feet of lining per day is average. Crews finished one 2,000-foot length with only a few services in about two weeks.

But other complications can occur. A segment of 12-inch line under Interstate 75 that was only 700 feet long took 10 days because of the location, while another 3,500-foot section elsewhere took 12 days — almost 300 feet per day.

“I really like the lining technology,” LaRoy says. “If you can line a water main that’s in the roadway and only have to dig every couple hundred feet versus tearing up the whole roadway, it’s a lot faster and it’s less disruptive to the customer. That’s a big plus for an urban environment.”



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