Allis is a privately owned dam located in Castle Rock, Colorado, constructed in 1906 for irrigation purposes along Carpenter Creek. Standing at 45 feet high and stretching 690 feet in length, the dam has a storage capacity of 225 acre-feet, with a normal storage of 140 acre-feet and a surface area of 12 acres. With a low hazard potential and a moderate risk assessment, the dam is classified as unsatisfactory in condition as of the last inspection in 2013.

Despite its age, Allis continues to serve its primary purpose of irrigation along with providing fire protection, stock, and small fish pond services. The dam's uncontrolled spillway width of 12 feet allows for a maximum discharge of 4100 cubic feet per second. The dam is under state jurisdiction and regulated by the Colorado Department of Water Resources, with permitting, inspections, and enforcement regularly conducted to ensure its safety and compliance.

Located in Douglas County, Allis plays a crucial role in water resource management in the region. While classified as having a moderate risk assessment, the dam's low hazard potential indicates a manageable level of risk. With its rich history dating back over a century, Allis stands as a testament to the importance of maintaining and regulating water infrastructure for both agricultural and environmental purposes in the face of changing climate patterns.