Grizzly Valley, located in Portola, California, is a state-regulated dam on the Big Grizzly Creek that serves primarily as a water supply source. Built in 1966, this earth dam stands at a height of 115 feet and has a storage capacity of 83,000 acre-feet, providing essential water resources for the region. With a surface area of 4032 acres and a drainage area of 44 square miles, Grizzly Valley plays a vital role in the local water supply infrastructure.

Despite its age, Grizzly Valley has been deemed to be in satisfactory condition and has a high hazard potential due to its location and the volume of water it can hold. The dam undergoes regular inspections, with the last assessment conducted in October 2020, ensuring its structural integrity and safety. In case of emergencies, the dam's Emergency Action Plan is in place, although details on its preparedness and compliance with guidelines are not provided in the data. Overall, Grizzly Valley remains a crucial asset for water management in the area, supporting both recreation and water supply needs.