News Feature | July 18, 2014

Could Microtunneling Technologies Mean The End Of Combined Sewer Systems?

Sara Jerome

By Sara Jerome,


U.S. cities are spending billions of dollars to update antiquated combined sewage systems that no longer serve their urban needs by drawing on underground tunnel-boring equipment that has improved in recent years. 

"More than 700 cities in the United States were built using a combined sewer system, in which wastewater — that's toilet water, shower water, whatever goes down the drain — and runoff from storms flow into a single pipe. Most of the time, that pipe can transport all of it, but when it rains, raw sewage often overflows into streets, basements, rivers and streams," USA Today reported

Washington D.C. is one city investing in major upgrades to its combined sewer operations. Sewage problems have plagued Washington D.C. since the Civil War. 

"When it rains, storm water mixes with everything you flush down the drain, routinely flooding some neighborhoods -- and spewing billions of gallons of raw sewage and runoff into the Potomac, Rock Creek, and the Anacostia," WUSA 9 reported

The project, which will run beneath huge swaths of the city, is "the most amazing and expensive construction project that no one ever will see," according to the Washington Post.

The effort is made possible by impressive engineering. The underground tunnel-boring machine, known as Ladybird, "is a marvel of technology, an underground factory 443 feet long and almost six times the weight of the Statue of Liberty. It does about a dozen things at once, and it moves," the report said.

For cities like Washington, advancements in microtunneling have facilitated the upgrade process from combined sewer systems.

"For many water and sewer lines, open-cut or rib-and-lag tunneling in conjunction with dewatering were common. Despite advances in microtunneling and its use in other parts of the world, many agencies stuck to tried-and-true methods. Until recently, that is," Trenchless Technology recently reported

"In 2011, Ward and Burke Construction, a heavy civil contracting company based in Ireland, re-introduced microtunneling to Toronto with the completion of the Gore Rd. project. That project involved the construction of a new 1,200-mm ID sanitary sewer pipe running directly under an existing 1,800-mm concrete pressure pipe water transmission line and an existing creek at Gore Road, in Brampton, Ont," the report said.

"Because of the presence of groundwater, cohesionless ground and the 1.5-m clearance between the two lines, settlement to the transmission line was a significant threat and traditional open-face tunneling methods were not suitable," it continued. 

"Due to the uniqueness of the project and limited options, Ward and Burke was able to bring microtunneling technology back to the area. The successful completion of the project then opened the door for additional projects in the area. The completion of each subsequent project then began opening the door a little wider," the report said. 

New Jersey struggles with defunct combined sewer systems, as well. 

"Every year, more than 7 billion gallons of raw sewage is dumped into New Jersey’s waterways -- a fault of an antiquated system in which combined sewer and stormwater lines can't cope with runoff from heavy storms," NJ Spotlight reported this month. 

"One of the major factors in failing to deal with the problem is its projected cost. It could run as much $40 billion to fix obsolete water and wastewater treatment systems, according to various reports. The cost will only rise the more officials delay addressing the problem," the report said, citing a study commissioned by New Jersey Future.

Check out Water Online's Wastewater Treatment Solution Center

Image credit: "Garrison Creek Sewer," © 2010, used under an Attribution-NoDerivs 2.0 Generic license:

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