Saint John, also known as St Johns, is a privately owned irrigation dam located in Oneida, Idaho. Completed in 1918, this earth dam stands at a height of 43.4 feet and has a hydraulic height of 39 feet, serving the primary purpose of irrigation for the surrounding area. With a storage capacity of 630 acre-feet and a drainage area of 10.6 square miles, Saint John utilizes a controlled spillway type with slide gates for water release.

Despite its age, Saint John poses a high hazard potential due to its unsatisfactory condition assessment and very high risk rating. The dam has a history of modifications and inspections are conducted every four years to ensure its safety. In the event of an emergency, the dam lacks an Emergency Action Plan (EAP) and its inundation maps are not prepared, raising concerns for the surrounding community's safety in case of a breach.

Located on Birch Creek and the Malad River, Saint John is regulated by the Idaho Department of Water Resources (IDWR) and is subject to state permitting, inspection, and enforcement. With its critical role in providing irrigation water, the dam's maintenance and risk management measures are essential to safeguard both the structure and the downstream population from potential hazards.