Gross
Gross is a concrete dam located in Boulder County, Colorado, built in 1955. It carries a High hazard potential classification and has a fair condition assessment.
About Gross
The primary purpose of Gross is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by Denver Water (local government). It impounds the South Boulder Creek near Eldorado Springs.
The dam stands 350 feet tall and stretches 1,050 feet across, creates a reservoir covering 413 acres, has a maximum storage capacity of 46,200 acre-feet, and collects water from a drainage area of 92 square miles. Completed in 1955, 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 fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 09/27/2022.
At 350 feet, this dam is taller than 99% 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 | Eldorado Springs |
| River/Stream | South Boulder Creek |
| Coordinates | 39.94800, -105.35790 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 350 ft |
| Dam Height | 340 ft |
| Dam Length | 1,050 ft |
| Year Completed | 1955 (71 years old) |
Storage & Hydraulics
| NID Storage | 46,200 acre-ft |
| Max Storage | 46,200 acre-ft |
| Normal Storage | 41,000 acre-ft |
| Surface Area | 413 acres |
| Drainage Area | 92 sq mi |
| Max Discharge | 10,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Denver Water |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 09/27/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CO00247 |
| Federal ID | CO00247 |
| More Info | State Dam Safety Program |