St. Helena Lower is a crucial water supply dam located in Napa, California, along the Tr Napa River. Built in 1878, this earth dam stands at a height of 44 feet and has a storage capacity of 210 acre-feet. The dam serves as a primary source of water for the local government, highlighting its importance in maintaining water security for the community.

Despite its age, St. Helena Lower has been regularly inspected, with the most recent assessment in November 2020 rating its condition as fair. With a high hazard potential, it is essential for the dam to undergo frequent inspections to ensure its structural integrity and safety. The dam's emergency action plan is also regularly updated, emphasizing the commitment to preparedness in case of any unforeseen events.

Managed by the local government and regulated by the California Department of Water Resources (DWR), St. Helena Lower plays a key role in water resource management in the region. Its location in the picturesque city of St. Helena adds to its significance, making it a vital infrastructure for water enthusiasts and climate advocates alike.