Aging Infrastructure in Sensitive Areas

Much of the utility infrastructure in the Pacific Northwest was constructed over 60 years ago and is approaching the end of its expected lifespan. Many utility systems were constructed in ravines containing streams which magnify the problem of the aging infrastructure. As development has increased, the flow in these streams has increased dramatically. This increased flow due to development or land use practices often leads to channel erosion and slope instability. These utility systems which were constructed under or adjacent to the stream channel with sufficient cover are now being threatened with the impacts of a potential failure, often causing significant environmental damage. As a utility provider, how do you recognize the risks you face in maintaining the integrity of your utility systems and how do you prevent these failures? This case study demonstrates the process Southwest Suburban Sewer District, located in King County, Washington, uses to protect their system.