Plan Now for Water Infrastructure Future
By Lake Oswego (OR) Mayor Jack Hoffman
July 19, 2010
When I talk with other mayors, a reoccurring concern is our infrastructure. Safe and reliable infrastructure is one of many components of a great community. Our city, like all the cities in our region and like tens of thousands of cities across our nation, has aging infrastructure. If we don’t responsibly invest and maintain it, we risk potential loss of property or life that could financially burden our citizens. Clean water, safe sewerage systems and good roads are just part of our paramount responsibilities. This year, Lake Oswego celebrates its centennial. For me, this has not only been a time to contemplate how far we’ve come with our infrastructure, but just how much attention we need to continue to give to it in order to ensure that our investments last.
Lake Oswego is located in northwest Oregon just eight miles south of Portland with some 35,000 residents and a very attractive 405 acre lake. One of the biggest modern day challenges we have tackled in Lake Oswego is the replacement of our sewer interceptor system. It’s old, failing and undersized. More than 90 percent of the interceptor pipe lies within Oswego Lake, its bays, and canals. Originally designed to serve 4,500 acres, the Lake Oswego Interceptor Sewer system (LOIS) today serves an area of 5,500 acres. When too much rainwater enters the sewer during periods of sustained, heavy rains, the interceptor system becomes surcharged and backs up, spilling untreated wastewater through manholes at various locations adjacent to and within Oswego Lake. Additionally, the system’s steel and timber pile supports are corroding and are at risk of collapse in a moderate seismic event. If this were to occur, millions of gallons of untreated wastewater would enter the lake and millions of gallons of lake water would drain downstream to the treatment plant, overwhelming its capacity.
A series of public hearings and community briefings were held in 2007 on replacement alternatives. As a result, the city council accepted the city engineer’s recommendation to replace the system with a combination of pile'supported pipe and a submerged, buoyant, gravity-flow pipeline.
When construction of this project began in October 2009 the city promised residents that it would complete the project on time and within budget. I am proud to say that this complex and innovative $100 million project is on schedule for completion in late 2011 and is under budget.
The new sewer interceptor line is the first of its kind to use a submerged pipeline in a gravity flow design. High-density polyethylene (HDPE) pipe was selected for the project to enable creation of a pipeline with a life cycle expected to exceed 100 years, according to the Plastics Pipe Institute (PPI), because it won’t rust, and can withstand seismic activity and still perform under drought and flood conditions that would lower and raise the level of water in the lake. The new interceptor system will be held under the lake’s surface by ground anchors. Custom fabricated stainless steel wire rope tethers connect the ground anchors to tether brackets that hold the main pipe and additional buoyancy ‘baskets’ in place at specified grades to allow wastewater to flow by gravity to the wastewater treatment plant.
Another favorable attribute of this design is that using HDPE pipe to construct a shorter, less disruptive gravity-flow pipeline is a “low-impact development” approach. It will consume fewer natural resources during construction, limit digging up our land and it will take less energy to operate, all of which produces a smaller carbon footprint.
The cost of the in-lake portions of the new system is estimated at $65 million. The city is financing this project through revenue bonds and residents will see user rates increase by 30 percent for three years to pay for the new system. Nonetheless, the price tag for the in-lake system was about $20 million less in life-cycle costs than an around-the-lake, pumped system.
Lake Oswego is fortunate for the good decisions of the past 100 years that have created, protected and enhanced our property values and the quality of life we continue to enjoy today. Our generation of mayors will be judged on how well we protect and enhance that quality of life and provide sustainable and secure infrastructure solutions for the next generation.