Upper 4s Ranch is an arch dam located in San Diego County, California, built in 1927. It carries a Low hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 28 ft28 ft tall and 246 ft long, taller than 62% 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 arch section and the water level is illustrative.
About Upper 4s Ranch
The primary purpose of Upper 4s Ranch 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 4s Ranch Master Association (private). It impounds the Lusardi Creek.
The dam stands 28 feet tall and stretches 246 feet across, creates a reservoir covering 10 acres, has a maximum storage capacity of 48 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1927, the structure is well-established, with more than 75 years of service.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. The most recent inspection on record was 04/23/2025.
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Location
| State | California |
| County | San Diego |
| River/Stream | Lusardi Creek |
| Coordinates | 33.00050, -117.10350 |
Physical Characteristics
| Dam Type | Arch |
| NID Height | 28 ft |
| Dam Height | 28 ft |
| Dam Length | 246 ft |
| Year Completed | 1927 (99 years old) |
Storage & Hydraulics
| NID Storage | 48 acre-ft |
| Max Storage | 48 acre-ft |
| Surface Area | 10 acres |
| Drainage Area | 1 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | 4s Ranch Master Association |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Satisfactory |
| Last Inspection | 04/23/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | CA00779 |
| Federal ID | CA00779 |
| More Info | State Dam Safety Program |