Union Auxiliary No. 7, located in Alpine County, California, is a private hydroelectric dam constructed in 1910 along the North Fork Stanislaus River. With a rockfill design and a dam height of 7 feet, the dam serves multiple purposes including hydroelectric power generation, recreation, and water supply. Its primary owner is the Federal Energy Regulatory Commission (FERC), with state regulation by the Department of Water Resources (DWR) ensuring its safety and compliance with permits and inspections.

Covering a drainage area of 15.2 square miles, Union Auxiliary No. 7 has a storage capacity of 3,283 acre-feet and a surface area of 215 acres. The dam's spillway, with a width of 52 feet, is uncontrolled. While the dam has a low hazard potential, a moderate risk assessment (3 out of 5) indicates the need for ongoing risk management measures. Despite its age, the dam's condition assessment is not available, highlighting the importance of regular inspections and emergency preparedness.

Overall, Union Auxiliary No. 7 is a significant water resource infrastructure in California, providing essential services for the region while requiring careful monitoring and maintenance to ensure its continued safety and functionality. Water resource and climate enthusiasts will find interest in its historical significance, engineering design, and ongoing regulatory oversight to protect the surrounding environment and communities.