Fern Lake
Fern Lake is an earth dam located in Sonoma County, California, built in 1921. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Fern Lake
The primary purpose of Fern Lake 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 Department Of General Services (state). It impounds the Tr Mill Creek near Eldrdge.
The dam stands 40 feet tall and stretches 300 feet across, creates a reservoir covering 14 acres, has a maximum storage capacity of 241 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1921, 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 12/04/2024.
At 40 feet, this dam is taller than 87% of dams nationwide.
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 | Sonoma |
| Nearest City | Eldrdge |
| River/Stream | Tr Mill Creek |
| Coordinates | 38.34310, -122.53110 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 40 ft |
| Dam Height | 40 ft |
| Dam Length | 300 ft |
| Year Completed | 1921 (105 years old) |
Storage & Hydraulics
| NID Storage | 241 acre-ft |
| Max Storage | 241 acre-ft |
| Surface Area | 14 acres |
| Drainage Area | 0 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Department of General Services |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 12/04/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00007 |
| Federal ID | CA00007 |
| More Info | State Dam Safety Program |