Williamson No. 1 is an earth dam located in El Dorado County, California, built in 1926. It carries a Significant hazard potential classification and has a poor condition assessment.
Dam profile
NID height · 42 ft42 ft tall and 240 ft long, taller than 88% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Williamson No. 1
The primary purpose of Williamson No. 1 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 Macy Mak Chan, Michael Chan, and Melinda Lau (private). It impounds the Tr Weber Creek.
The dam stands 42 feet tall and stretches 240 feet across, creates a reservoir covering 11 acres, has a maximum storage capacity of 117 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1926, the structure is well-established, with more than 75 years of service.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. The most recent inspection on record was 04/15/2025.
At 42 feet, this dam is taller than 88% of dams nationwide.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | California |
| County | El Dorado |
| River/Stream | Tr Weber Creek |
| Coordinates | 38.75550, -120.93720 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 42 ft |
| Dam Height | 42 ft |
| Dam Length | 240 ft |
| Year Completed | 1926 (100 years old) |
Storage & Hydraulics
| NID Storage | 117 acre-ft |
| Max Storage | 117 acre-ft |
| Surface Area | 11 acres |
| Drainage Area | 1 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Macy Mak Chan, Michael Chan, and Melinda Lau |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Poor |
| Last Inspection | 04/15/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | CA00608 |
| Federal ID | CA00608 |
| More Info | State Dam Safety Program |