Mccaslin is a privately owned dam located in Boulder, Colorado, specifically in the city of Longmont, along the St Vrain Creek-TR. Completed in 1908, this earth dam stands at a height of 16 feet and spans 435 feet in length, with a storage capacity of 167 acre-feet. Its primary purpose is for irrigation, serving the local agricultural community in the area. Mccaslin is regulated by the Colorado Department of Water Resources (DWR) and undergoes regular inspections to ensure its structural integrity and compliance with state regulations.

Despite being classified as having a low hazard potential and fair condition assessment, Mccaslin poses a moderate risk due to its location and the potential impacts of a breach or failure. Its spillway, of uncontrolled type with a width of 44 feet, can handle a maximum discharge of 600 cfs. The dam has not been significantly modified over the years, and emergency action plans and risk management measures are not explicitly outlined in the available data. Joe Neguse, a Democratic Representative, oversees the congressional district where Mccaslin is situated, emphasizing the importance of maintaining the safety and functionality of this vital water resource infrastructure amid changing climate conditions and increasing water demands in the region.