Left Hand Valley
Left Hand Valley is an earth dam located in Boulder County, Colorado, built in 1952. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Left Hand Valley
The primary purpose of Left Hand Valley is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Left Hand Ditch Company (terry Plummer) (private). It impounds the Dry Creek near Boulder.
The dam stands 68 feet tall and stretches 1,035 feet across, creates a reservoir covering 113 acres, has a maximum storage capacity of 2,814 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1952, 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 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 06/23/2022.
At 68 feet, this dam is taller than 96% of all dams in the United States.
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 Colorado 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 | Colorado |
| County | Boulder |
| Nearest City | Boulder |
| River/Stream | Dry Creek |
| Coordinates | 40.09967, -105.26135 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 68 ft |
| Dam Height | 54 ft |
| Dam Length | 1,035 ft |
| Year Completed | 1952 (74 years old) |
Storage & Hydraulics
| NID Storage | 2,814 acre-ft |
| Max Storage | 2,814 acre-ft |
| Normal Storage | 1,624 acre-ft |
| Surface Area | 113 acres |
| Drainage Area | 3 sq mi |
| Max Discharge | 12,367 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | LEFT HAND DITCH COMPANY (TERRY PLUMMER) |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 06/23/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CO00177 |
| Federal ID | CO00177 |
| More Info | State Dam Safety Program |