How Design-Build Delivery Facilitated a Revolutionary Sewer Tunnel Rehabilitation

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CONTENT EXPIRES: December 31, 2023

The Colsman Tunnel is a 7600-foot long hard-rock sewage conveyance tunnel operated by the Southgate Sanitation District. The tunnel was constructed in 1977 using hand-tunneling and road header methods and conveys 100 percent of the District’s flows with no backup or bypass. Previous assessments and suggested rehabilitation approaches had done little to reduce the District’s concerns for this single-point-of-failure facility. Southgate turned to a Design-Build delivery approach in hopes of creating a collaborative environment capable of producing a cost-effective solution to mitigate the greatest risk in their system.


1. Implementing Design-Build when the project scope is uncertain 

2. Creating a collaborative environment that encourages innovation while maintaining project momentum 

3. Engaging specialty trades appropriately during project development 

4. Evaluating alternative approaches during critical construction difficulties

Mike Hale

Project Manager

Garney Construction

Mike started in the construction industry in 2002 gaining experience in renovating wastewater treatment plants. He has held several positions in the industry, including Mechanical Laborer, Estimator, Superintendent, and now Project Manager. Mike graduated from Colorado State University with a degree in Construction Management. In his four years at Garney, he has built several collaborative delivery projects, including progressive design-build and CMAR projects along the Front Range.

Randy Parks, PE

Project Manager


Randy has 40+ years of experience with technical expertise in civil and structural design for water and wastewater projects. He is a specialist in welded steel, prestressed and pretensioned concrete cylinder, and reinforced concrete pipelines. Randy graduated from Colorado State University with a Bachelor's degree in Civil Engineering and holds a Master's degree in Civil/Structural Engineering from Cal Poly. He has complete numerous water and wastewater projects along the Front Range and in Arizona.


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1.00 CEU credit  |  Certificate available
1.00 CEU credit  |  Certificate available