St. Marys Lake is an earth dam located in Clear Creek County, Colorado, built in 1889. It carries a Significant hazard potential classification.
Dam profile
NID height · 9 ft9 ft tall and 210 ft long. 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 St. Marys Lake
The primary purpose of St. Marys Lake 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 Coors Brewing Co. Land & Water Resources (santange (private). It impounds the Silver Creek-os near Idaho Springs.
The dam stands 9 feet tall and stretches 210 feet across, creates a reservoir covering 7 acres, and has a maximum storage capacity of 51 acre-feet. Completed in 1889, the structure is over a century old.
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. An emergency action plan is in place for this dam. The most recent inspection on record was 09/28/2022.
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Location
| State | Colorado |
| County | Clear Creek |
| Nearest City | Idaho Springs |
| River/Stream | Silver Creek-os |
| Coordinates | 39.83263, -105.64544 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 9 ft |
| Dam Height | 9 ft |
| Dam Length | 210 ft |
| Year Completed | 1889 (137 years old) |
Storage & Hydraulics
| NID Storage | 51 acre-ft |
| Max Storage | 51 acre-ft |
| Normal Storage | 38 acre-ft |
| Surface Area | 7 acres |
| Max Discharge | 220 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Coors Brewing Co. Land & Water Resources (santange |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Last Inspection | 09/28/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CO01188 |
| Federal ID | CO01188 |
| More Info | State Dam Safety Program |