Lake Valley Auxiliary is a private hydroelectric dam located in Placer, California, near the North Fork American River. Built in 1889, this Earth-type dam stands at a height of 28 feet and has a maximum storage capacity of 7,964 acre-feet. With a surface area of 298 acres and a drainage area of 4.5 square miles, the dam plays a crucial role in regulating water flow and generating hydroelectric power for the region.

Managed by the Federal Energy Regulatory Commission, Lake Valley Auxiliary has a significant hazard potential and is subject to regular state inspections and enforcement. While the dam's condition assessment is not currently available, its emergency action plan was last revised in December 2020, indicating ongoing efforts to ensure safety and preparedness in case of emergencies. The dam's spillway, with a width of 100 feet, helps control water levels during periods of high discharge, contributing to effective water resource management in the area.

Overall, Lake Valley Auxiliary serves as a key infrastructure for water resource and climate enthusiasts, providing insights into the intersection of hydroelectric power generation, dam safety regulations, and emergency response planning. Located in a picturesque setting near Washington, California, this historic dam continues to play a vital role in water management and renewable energy production in the region, highlighting the importance of sustainable practices for a resilient future.