Insituform® Process Makes Underground Pipe Rehabilitation Possible Without Damage to Environment

Few projects mean as many headaches for maintenance engineers as underground pipeline repair. Left alone, weakened underground pipes can rupture, causing floods, loss of water services, or sewage backups.

But the remedy is often as disruptive as the problem. Excavation is unsightly and problematic, especially when pipes run under roads, ski trails, or buildings. Plus there are environmental concerns associated with bringing in heavy equipment and digging, especially when the area in question is a national park or has other special designation.

Ski areas are joining the long list of environmentally conscious municipalities that have avoided the problems of excavation by using a non-disruptive process to rehabilitate aging and deteriorating pipes. Aspen, Breckenridge, Winter Park, Steamboat Springs, Summit County and many other municipal areas have undertaken the rehabilitation of their underground infrastructure with an innovative process that rehabilitates pipes from the inside - without disruptive excavation. Ecosystems weren't disturbed. Roads weren't closed. And best off all, entire pipe rehab projects can be completed in a matter of days, which is critical as off-season tourism becomes a more and more important industry for ski towns. The Purgatory Ski Area near Durango, Colorado, has seen the value of the technology, and recently completed an Insituform® pipe rehabilitation at its snowmaking reservoir.

The Insituform® process has been used all over the world for more than 25 years. Insituform®, which performed the world's first cured-in-place pipe rehabilitation in London in 1971, has an ongoing commitment to research and development that has resulted in a number of additional processes for use in municipal rehabilitations. These processes include methods for rehabilitating lateral connections and for completing isolated "spot repairs" inside a length of pipe. Insituform® can also rehabilitate pressurized and gravity lines, and its processes have been certified for use in drinking water systems.

Non-Disruptive Pipe Rehabilitation
The Insituform® pipe rehab process uses a polyester fiber felt tube that is serial vacuum impregnated with a liquid thermosetting resin. This tube, which is manufactured to precise specifications according to the project, is inserted into the damaged line, usually through an existing manhole, with an inversion process in which the tube is turned inside out by water pressure. This water pressure pushes the tube through the pipe, unfolding it and pressing it tightly against the pipe wall. As the tube progresses, it can negotiate bends as sharp as 90 degrees and "jump" offset joints. When the tube reaches the termination point, the water inside is heated with a mobile heat exchanger, causing the thermosetting resin to cure. The result is a jointless pipe-within-a-pipe that restores the structural integrity of the line. In addition to being cost-effective and non-disruptive, Insituform®'s pipe rehabilitation process was determined to have a minimum service life of 50 years in extensive testing funded by the U. S. Government. The Insituform® process has been used to rehabilitate more than 30 million feet of pipe across the world.

Insituform® has a wide variety of products, and has rehabilitated lines as small as four inches (10 cm) and as large as nine feet (2.75 meters) in diameter. The company has rehabilitated round lines as well as those with catenary or other less-conventional shapes. Insituform® has even completed installations under large bodies of water. Each year, the company reduces the number of access points necessary for installation, and has successfully completed single inversions as long as 2,400 feet.

Insituform® at Work at Purgatory
This non-disruptive technology was employed recently at the Purgatory Ski Area near Durango, Colorado. Purgatory's reservoir for snowmaking operations had developed leaks in an outfall line at Duncan Dam. The outlet works at the dam consist of a slide gate at the upstream end, 25 feet of 12-inch diameter corrugated metal pipe (with a 60-degree vertical bend) and a 100-foot length of 15-inch diameter corrugated metal pipe. The primary problem was internal corrosion of the pipes.

Replacement of the line would mean breaching the dam and excavating the pipe. After learning about the Insituform® process, Purgatory officials hired Insituform® to complete the pipe rehabilitation. Working out of Insituform®'s Littleton, Colorado, office, installers brought the polyester tubing to the site already impregnated with a vinyl ester resin. Insituform® had custom tailored the tubing to meet the corrosion resistance and capacity needs of this specific job: for the 25 feet of 12-inch pipe, a tube with .37 inches of wall thickness was specified, and for the 100 feet of 15-inch pipe, a wall thickness of .42 inches was used.

The reservoir was drained and the Insituform® pipe was installed. The Purgatory project cost $26,750, roughly a third of the estimated cost of the excavation alternative, and downtime was kept to a minimum.

"Best of all, it didn't disturb the environment," says Don Miller, Purgatory's director of trails. "It's our priority to maintain a top-notch, environmentally responsible ski area, and when we can save money on infrastructure repairs at the same time, everybody wins."

The methodology used in the selection process and the pipe rehabilitation choice made by the Department of Public Utilities proved to be correct in terms of cost-effectiveness, timeliness of completion, and minimization of inconvenience to the public. The result was a virtually trouble-free experience and a satisfactory project.