Emerald Lake 1 Lower, also known as Lower Emerald Lake, is a privately owned dam located in Redwood City, California. Completed in 1885, this earth dam stands at a height of 57 feet and has a storage capacity of 45 acre-feet. With a primary purpose of water supply, this structure also serves for recreational activities in its 4-acre surface area. Situated on the Tr San Fran Bay river/stream and falling under the jurisdiction of the California Department of Water Resources, Emerald Lake 1 Lower is regulated, permitted, inspected, and enforced by state authorities to ensure its safety and functionality.

Despite its age, the dam's condition assessment in September 2017 deemed it satisfactory, with a high hazard potential due to its location and storage capacity. Regular inspections are conducted, with the last one taking place in March 2021 and emergency action plans in place. The dam's emergency contact information is updated, and it meets guidelines for risk management measures. While there are no inundation maps prepared or specific risk assessments outlined, the structure continues to provide essential water supply and recreational opportunities in the area, under the watchful eye of state regulators.