SEWER: From Mains to Manholes

A comprehensive cleaning, inspection and rehabilitation program helps a small Michigan community control severe I&I problems

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Positioned between Lansing and Saginaw in central Michigan, Corunna was a small town with big problems. For more than 30 years, its sewer system was burdened by stormwater, infiltration and illicit connections. By 2003, something had to give.

Flows exceeding 110 percent of contract capacity at the Owosso Mid-Shiawassee County Wastewater Treatment Plant had contributed to peak flows of 15 times the daily average. During wet-weather events, more than half this flow came from inflow and infiltration. Sanitary sewer overflows and residential backups occurred.

As one of four municipalities contributing just over 9 percent of the plant’s flows, Corunna was placed under a building moratorium. “For years, we weren’t allowed to extend sewer infrastructure,” recalls city manager Joe Sawyer. “We have industrial and retail acreage, but we’re only about half-way built out.”

City council members understood that the collection system problems were a serious impediment to growth. Finally, a state administrative consent order demanded that Corunna address the I&I issue. Director of public works Tim Crawford knew that inaccurate flow reporting accounted for some of the extreme flows figures, but he was sure the aging sewers needed serious repair.

In the end, the city attacked its problem with a thorough system inspection and evaluation, followed by a rehabilitation program that covered sewer mains and manholes and will soon extend to sewer laterals. Rehabilitation included cured-in-place lining for mains and various sealing, grouting and rebuilding methods for manholes.

To date, the program has reduced I&I by an estimated 20 to 30 percent and has enabled the city to lift its building moratorium.

Phasing in

At the outset, Crawford and Sawyer worked with Gary Arnold of C2AE, a Grand Rapids engineering firm. “We were careful about thinking ahead,” Sawyer says. “We didn’t have accurate maps, and we knew that was the priority from day one. All other decisions stemmed from what we found during the inspection and evaluation.”

Funding was the main challenge. “We assumed the only way we’d ever fix our system would be through conventional construction,” Sawyer says. “We put a $30 million price tag on that, which meant we couldn’t even consider it. So the technology aspect of it, such as the lining program, is invaluable.”

The team divided the work into four phases. Phase 1, investigation and evaluation, ran from October 2003 to December 2004 and included a complete inventory, as well as cleaning and televising mains and laterals and all connections, lift stations and manholes. For this, the city won a $157,500 Economic Development Fund (EDF) grant from the Michigan Economic Development Corporation (MEDC).

Phase 2, final cleaning and lining of the mains along with lateral service inspection and manhole rehabilitation, ran from November 2005 through October 2006 and cost $1.1 million, all paid by the city.

Phase 3, from August to Nov-ember 2007, included complete rebuilding of the Ferry Street Pump Station ($750,000) and construction of a new interceptor sewer ($613,500). Funding included a $575,000 MEDC grant.

Phase 4 will consist of rehabilitating failing lateral connections and is still in the planning and engineering stage.

Facing challenges

Crawford and Sawyer knew that a key to the project’s success was to get the decision makers onboard. In late 2002, Crawford’s crew did smoke testing on the sewer system and recruited city council members to walk along with them.

“They came out with clipboards and cameras, walking the streets and yards to find leaks,” says Sawyer. “Involving them was invaluable for when we had to go ask for money. It was lots more effective than numbers on a spreadsheet.”

The testing let everyone know there were significant deficiencies in many lines, and the project moved into planning for the televising stage. The city had inspected some mains 20 years earlier, but it wasn’t a comprehensive survey, and the quality of the video was uneven.

“We wanted to have a vision of the future based on being pro-active, so we knew our first priority was to find out what we had underground,” Crawford says. “Our first project was to televise the sewer mains.” The estimate cost $125,000, but only $90,000 had been budgeted. The Economic Development Fund grant ultimately covered the cost.

The winning bidder for Phase 1 work was DownUnder Municipal Services LLC of Kalamazoo, Mich. The resulting digital video was priceless in assessing the system and setting repair priorities.

“We found sagging, broken and clogged mains,” Sawyer says. “We found a one-block section where groundwater was leaking into a main through abandoned laterals that hadn’t been properly bulkheaded off. Eighty percent of our sewer mains were clay tile with a joint every 2 feet. There were lots of bad joints and crumbling grout. We found mains we didn’t know we had, and discovered that some we thought we had didn’t exist.”

In planning for Phase 2, Sawyer and Crawford investigated rehabilitation technologies: conventional replacement, pipe bursting and cured-in-place pipe (CIPP) lining. In 2003, Crawford went to a trenchless technology show and saw a lining demonstration. Sawyer and Crawford also asked other communities what they were using.

Making the fixes

Insituform Technologies USA Inc. had done a small CIPP project for Corunna and came in as part of a competitive block grant bid on Phase 2. Crawford and Sawyer had expected to line about 4 miles of sewer main, but the bids allowed them to line 6 miles, a full one-third of the system.

“We have a few more segments that need to be done,” says Sawyer. “We’re talking with a few neighboring communities to see if we could get some economies of scale. Another third of our system is either in good condition or needs traditional work.”

In the end, Insituform cleaned and inspected 30,967 feet of 6- to 18-inch mains and installed CIPP liners. The company also cleaned and inspected 440 service laterals, in the process finding many sewer mains with dead ends that had no manholes. “These are very difficult to clean, and you need a manhole to install Insitu-form lining,” says Crawford. “So we installed about eight new manholes in those areas.”

Meanwhile, Corunna removed and replaced four manholes, grouted 45, and lined two. Another 24 were rehabilitated through adjustments such as raising to grade, replacement, or sealing the chimney. Compeau Brothers Excavating of Rockford, Mich., exposed the structures using a small backhoe. Kim Construction of Steger, Ill., made traditional mortar repairs.

New lid assemblies cast by East Jordan Iron Works were installed. Replaced and new manholes received custom lids bearing the city’s name. Since the city bought in bulk, the custom die came at no extra charge. Rebuilt manholes did not receive custom lids. The difference helps the city track which manholes have been rehabilitated. “The new lids are hard to steal, too,” adds Crawford.

Lateral televising

Insituform crews televised laterals in areas where they had lined the mains, using a Lateral Evaluation Television System (LETS) camera from Aries Industries Inc., which can travel 1,500 feet down a main line and send a tractor-mounted launch unit 150 feet up the lateral.

To televise laterals in other areas, Terra Contracting, a division of DownUnder Municipal Services, used explosion-proof CCTV units from Pearpoint Inc. with tractor-mounted pan-and-tilt camera heads.

“The purpose of this secondary video was to identify laterals we didn’t need,” says Sawyer. “We took that opportunity to bulkhead off those unnecessary laterals by not reinstating them once the liner cured.” We anticipated that we might inadvertently eliminate service to someone who needed it, but that didn’t happen.

“We did have two where we weren’t sure if we should leave them closed,” Sawyer recalls. “Even through dye testing and other inspections, we just couldn’t be sure if they might be drains or something important, so we erred on the side of caution and left them open.” A state grant covered the cost of this video.

“We now have a complete video inventory of our entire system,” says Sawyer. “This allows us to do the whole project at once, instead of piecemeal with many different contractors. That benefits I&I across the system.

“We have to be able to demonstrate a positive return on investment — that each lateral contributes enough I&I so that cost of treatment exceeds cost of repair or replacement,” Sawyer says. “These inspections determine that, and homeowners will be given a timeline to make repairs.”

Secondary additions

A second grant funded Phase 3, rebuilding of the main pump station, which moves 90 percent of Corunna’s flow. High wet-weather flows had been taxing the station.

The computerized Ferry Street Pump Station uses the RSView 32 monitoring package from Rockwell Automation. A laptop computer equipped with PC Anywhere software from Symantec turns pumps on and off remotely.

The new interceptor replaced a badly degraded and undersized line that crossed a floodplain and contributed substantial I&I. The new pipe upsized the line from 15 to 21 inches, and 24-inch PVC was installed to take the flow under the river to the pump station.

The city is now putting together a Phase 4 plan to address private laterals and the remaining lift stations. Sawyer expects that as many as 300 laterals will need replacement at a cost of about $1 million.

“We’re still not sure what to do with the lateral connections,” he says. “We’re looking at a top hat or boot seal system. We’re still undergoing engineering on this. We don’t want to have to tear up yards and take down century-old trees. We’re even considering purchasing a lateral lining system so we can do it in-house.”

Crawford knows one thing for sure: Actions speak louder than words The city’s action on the I&I issues give him confidence to ask system users to step up to the plate and do their part. “A lot of our problem was our own main lines, and no one likes a hypocrite,” he says. “Having fixed the mains, we can now go to the homeowners and say we’ve done what we can on our end.”



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