Copper Creek Sewer Interceptor Relocation

The Copper Creek Sewer Interceptor Relocation addressed aging infrastructure that had become increasingly vulnerable to flooding and structural failure. The City of Omaha contracted Benesch to assess the feasibility, value and potential alternative solutions to rehabilitate, relocate, or replace a 90-inch, steel aerial sewer crossing Copper Creek or to replace it with a multi-barrel inverted siphon.

The existing aerial crossing over Copper Creek consists of a 90-inch steel pipe, with approximately 50 feet of pipe exposed four feet above the creek bottom. This aerial crossing is a part of a primary trunk sewer line, owned and operated by the City of Omaha, which carries flow to the Papillion Creek Water Resource Recovery facility and carries an average daily flow of 35 million gallons. The 90-inch RCP interceptor located beneath the surface, constructed in the early 1970s, carries an average daily flow of 35 million gallons and was reaching the end of its expected service life. Inspections revealed corrosion to the concrete and exposed reinforcement. This, in addition to previous damage to the aerial pipe from storm events, created an increased risk of a loss of service to customers and sewage flows entering the creeks and reaching Waters of the State, a violation of the Clean Water Act, impacting the environment and the community.

The design alternative selected consisted of installing a siphon system, approximately 200 feet upstream of the existing crossing, and a total of approximately 2,950 linear feet of new 96-inch lined HDPE pipe. Complex hydraulic calculations were involved with the design of the siphon pipes and structures and also the interceptor up and downstream of the siphon system. Benesch was contracted to perform the subsequent construction management, observation and materials testing as needed during the relocation of the interceptor.

Additionally, Benesch provided grant management services, as this project was the recipient of funding through the FEMA Hazard Mitigation Grant Program (HMGP) and a Department of Economic Development Community Disaster Block Grant – Disaster Recovery (CDBG-DR) Grant.