Process of Elimination

Western Townships Utilities Authority in southeast Michigan budgeted $600,000 to replace 3000 feet of sanitary sewer that runs along the bottom of a ravine at depths of more than 20 feet. When closed circuit televising revealed open joints, cracks, and groundwater infiltration, the authority decided to restore the 64-year-old interceptor using in-situ lining. Because leakage at the joints and cracked pipe would inhibit curing, they were pressure-grouted before the lining was installed. Total cost: less than $200,000.

Landmark tree-lined streets: A spider web of buried utility lines. The Detroit suburb of Grosse Pointe Farms saved $100,000 while preserving tree roots by replacing 9000 feet of 4- and 6-foot deteriorated cast-iron water main with 8-inch HDPE pipe. Here, workers guide a bursting head into a launch pit. As the old pipe is 'bursted' out of the way, the new pipe is pulled in behind.

At first, it looked like pipe bursting was the ideal way to replace a force main in Ann Arbor, Mich. But a geotechnical analysis showed that soils at the pipe's elevation were loose, and that it was dangerously close to an old, 16-inch water main. That, and because the main had to cross a cemetery entrance as well as an interstate bridge, prompted the city to leave the old pipe alone and lay 3700 feet of 8-inch HDPE at a deeper elevation using horizontal directional drilling. Savings over open-cut construction: $400,000.

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