Director of Engineering Northern Water Berthoud, Colorado
The Northern Water Municipal Subdistrict has been working to deliver the Chimney Hollow Reservoir for over 20 years. Chimney Hollow is a new 90,000 acre-ft reservoir that will provide a supplemental water supply for nearly 1 million people in Northern Colorado. The reservoir will have two embankment dams including a 350-ft tall high hazard asphalt core rockfill dam, one of the first large asphalt core dams built in the United States. Chimney Hollow is an off-channel reservoir that will be filled with Colorado River basin water that is delivered through the U.S. Bureau of Reclamation’s Colorado-Big Thompson (CBT) project. The reservoir project was conceived in 2002 with final permits obtained in 2017. In order to obtain permits, significant environmental mitigation and enhancements were committed in the Upper headwaters of the Colorado River. Design was completed on the project in 2019 and construction began in 2021. The project is currently under construction with first fill planned during summer 2025.
Over the last 20-years, Northern Water has direct experience addressing the numerous challenges that make it difficult to build a new reservoir in the United States. This paper will outline some of those challenges and provide first-hand account of lessons-learned addressing the concerns with new dams. This paper will discuss successfully permitting and mitigating a new large dam, working while the project is in litigation, partnering with regulatory agencies, educating the public and making a case for new water storage projects, and developing a new dam safety program at an organizational level.
Additionally, this program will discuss key decisions made at the organizational level to address major design and construction risks. These types of decisions include developing and selecting a project team, adopting a Project Review Board, adopting new technology (asphalt core embankments) in a highly regulated and risk-adverse field, selecting the type of project delivery, setting a budget and project financing, managing a quality control program, advocating for a safety culture, teambuilding, managing public responses during construction, and proactive risk management during construction.
Northern Water has established a road map for building a new reservoir project, and although the path can be difficult at time, the Chimney Hollow Reservoir Project provides an example that local governmental agencies can build dams in the 21st century.
