Emerald Lake 1 Ler
Emerald Lake 1 Ler is an earth dam located in San Mateo County, California, built in 1885. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Emerald Lake 1 Ler
The primary purpose of Emerald Lake 1 Ler is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by Emerald Lake Country Club (private). It impounds the Tr San Fran Bay near Redwood City.
The dam stands 57 feet tall and stretches 280 feet across, creates a reservoir covering 4 acres, has a maximum storage capacity of 45 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1885, the structure is over a century old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 06/25/2025.
At 57 feet, this dam is taller than 95% of all dams in the United States.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The California dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | California |
| County | San Mateo |
| Nearest City | Redwood City |
| River/Stream | Tr San Fran Bay |
| Coordinates | 37.46730, -122.26250 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 57 ft |
| Dam Height | 57 ft |
| Dam Length | 280 ft |
| Year Completed | 1885 (141 years old) |
Storage & Hydraulics
| NID Storage | 45 acre-ft |
| Max Storage | 45 acre-ft |
| Surface Area | 4 acres |
| Drainage Area | 0 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Emerald Lake Country Club |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 06/25/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00668 |
| Federal ID | CA00668 |
| More Info | State Dam Safety Program |