Siena is a vital water supply infrastructure located in Lafayette, Colorado, along the Coal Creek-TR river system. This Earth dam, completed in 2004, stands at a height of 40 feet and has a storage capacity of 640 acre-feet, with a normal storage level of 450 acre-feet. The dam has a spillway width of 17 feet and a maximum discharge capacity of 690 cubic feet per second, ensuring proper water management in the region.

Owned and regulated by the local government, Siena is subject to regular inspections and enforcement measures to maintain its satisfactory condition and high hazard potential. The dam's design, by BASEPOINT DESIGN CORPORATION, incorporates stone core types and foundations of rock and soil, contributing to its structural integrity. With a risk assessment rating of moderate (3), the dam is equipped to handle emergencies, though the Emergency Action Plan (EAP) status and risk management measures could benefit from further updates to ensure maximum safety and preparedness.

Situated within the Omaha District of the US Army Corps of Engineers, Siena serves as a critical infrastructure for water supply purposes in Broomfield County, Colorado. The dam's strategic location and design underscore its essential role in water resource management and climate resilience efforts in the region, highlighting the importance of proactive maintenance and risk mitigation strategies to safeguard this valuable asset for the community.