Robertson is an earth dam located in Johnson County, Wyoming, built in 1970. It carries a Low hazard potential classification and has a fair condition assessment.
Dam profile
NID height · 28 ft28 ft tall and 408 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 embankment section and the water level is illustrative.
About Robertson
The primary purpose of Robertson is fire protection, stock, or small fish pond. The dam maintains a small impoundment used for fire suppression, livestock watering, or as a fish pond. The dam is owned by 48 Ranch (private). It impounds the Terry Draw near Arvada.
The dam stands 28 feet tall and stretches 408 feet across, creates a reservoir covering 6 acres, and has a maximum storage capacity of 74 acre-feet. Completed in 1970, the structure is well into its service life at over 50 years old.
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 fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. The most recent inspection on record was 06/12/2025.
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Location
| State | Wyoming |
| County | Johnson |
| Nearest City | Arvada |
| River/Stream | Terry Draw |
| Coordinates | 43.61583, -106.52556 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 28 ft |
| Dam Height | 28 ft |
| Dam Length | 408 ft |
| Year Completed | 1970 (56 years old) |
Storage & Hydraulics
| NID Storage | 74 acre-ft |
| Max Storage | 74 acre-ft |
| Normal Storage | 41 acre-ft |
| Surface Area | 6 acres |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Fire Protection, Stock, Or Small Fish Pond |
| Owner | 48 Ranch |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Fair |
| Last Inspection | 06/12/2025 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | WY00510 |
| Federal ID | WY00510 |
| More Info | State Dam Safety Program |