Lake Helen
Lake Helen is an earth dam located in Sonoma County, California, built in 1966. It carries a High hazard potential classification and has a poor condition assessment.
About Lake Helen
The primary purpose of Lake Helen 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 Robert Maddocks (private). It impounds the Tr Russian Rv near N/a.
The dam stands 39 feet tall and stretches 355 feet across, creates a reservoir covering 14 acres, has a maximum storage capacity of 192 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1966, the structure is well into its service life at over 50 years 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 poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 04/30/2025.
At 39 feet, this dam is taller than 86% 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 | N/a |
| River/Stream | Tr Russian Rv |
| Coordinates | 38.44810, -122.91320 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 39 ft |
| Dam Height | 39 ft |
| Dam Length | 355 ft |
| Year Completed | 1966 (60 years old) |
Storage & Hydraulics
| NID Storage | 192 acre-ft |
| Max Storage | 192 acre-ft |
| Surface Area | 14 acres |
| Drainage Area | 0 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Robert Maddocks |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 04/30/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA01060 |
| Federal ID | CA01060 |
| More Info | State Dam Safety Program |