Citys choice to build unique kind of sewer system is paying major benefits

Already the recipient of several high honors for construction projects, the Lake Oswego Interceptor Sewer project has been named a 2012 Public Works Project of the Year by the American Public Works Association. The honor was announced on July 19 at the APWA headquarters in Kansas City, Mo.

“We’re extremely pleased with this recognition,” said Joel Komarek, engineer for the city of Lake Oswego and director of the LOIS project. “We’re very pleased to be selected for this award. It’s a tribute to all the hard work, creativity and also the vision of the design.

“It is also a tribute to the vision of our city council in 2008. They had the choice of having a one-type in the world kind of project or having a more conventional sewer system with six pump stations and thousands of more feet of pipe. They chose the innovative system, and the dividends for that choice are starting to accrue.”

Komarek will be on hand in Anaheim, Calif., on Aug. 26-29 when the city of Lake Oswego is honored, along with Advanced American Construction, James W. Fowler Co., and consultant Brown and Caldwell.

In 2008 Lake Oswego was faced with an undersized, corroding and seismically vulnerable pile-supported interceptor sewer in Oswego Lake. The city, along with Brown and Caldwell, devised an innovative, submerged, buoyant, gravity sewer with a 100-year lifespan. The centerpiece of LOIS is a 2-mile reach of buoyant HDPE sewer held to proper grade safely beneath the lake surface.

More than 29,000 feet of new pipe, 18 inches to 42 inches in diameter, were installed. The sewer itself is configured in a serpentine alignment with thermal expansion loops that maintain grade despite wide-ranging water temperatures. The sewer is held to proper grade beneath the lake surface by 428 ground anchors and tethers that are fastened into solid bedrock beneath a thick, soft sediment layer at the lake bottom.

For maintenance and cleaning purposes, submerged buoyant stainless steel manholes were installed along the pipeline, with access via removable aluminum caissons.

The project was completed on time and with a final budget of $94 million, which was well under the original cost estimate. The city estimates that the LOIS gravity system will save an estimated $20 million in operations and maintenance costs during its service life.