Designing a High Hydraulic Asphalt Core Rockfill Dam for Colorado

Although the use of hydraulic asphalt concrete (HAC) for the primary water retaining feature of embankment dams has been used successfully for over fifty years globally, the technology has not been used to construct dams in the United States. The final design for the Chimney Hollow Reservoir Project near Loveland, Colorado is nearly completed and the construction is planned to start in 2019 or 2020. After an alternatives evaluation weighing the benefits of various dam configurations, the asphalt concrete rockfill dam (ACRD) configuration was selected for the main dam with a jurisdictional height of approximately 332 feet.
This paper presents an overview of the design process and the resulting dam configuration. The main dam section will include a central HAC core that will vary in thickness from approximately 3.3 feet at the bottom to about 2 feet at the top of the core. The design leverages international practice used to construct over 170 asphalt concrete embankment dams (ACED) around the world, as well as input from global experts for its review. The various analyses performed in support of the design will be summarized. The information presented will include highlights of activities required to translate international asphalt bitumen grading, as well as HAC specifications and placement requirements, to Colorado.