Lake Ponderosa Dam
Lake Ponderosa Dam is an earth dam located in Poweshiek County, Iowa, built in 1969. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Lake Ponderosa Dam
Lake Ponderosa Dam is a dam in Poweshiek, Iowa. The dam is owned by Poweshiek County Board Of Supervisors (local government). It impounds the Tr-moon Creek near Spring Valley.
The dam stands 50 feet tall and stretches 1,090 feet across, creates a reservoir covering 290 acres, has a maximum storage capacity of 5,850 acre-feet, and collects water from a drainage area of 6 square miles. Completed in 1969, 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 05/30/2024.
At 50 feet, this dam is taller than 93% of dams nationwide.
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 Iowa 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 | Iowa |
| County | Poweshiek |
| Nearest City | Spring Valley |
| River/Stream | Tr-moon Creek |
| Coordinates | 41.57900, -92.58220 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 50 ft |
| Dam Height | 50 ft |
| Dam Length | 1,090 ft |
| Year Completed | 1969 (57 years old) |
Storage & Hydraulics
| NID Storage | 5,850 acre-ft |
| Max Storage | 5,850 acre-ft |
| Normal Storage | 2,500 acre-ft |
| Surface Area | 290 acres |
| Drainage Area | 6 sq mi |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Other |
| Owner | Poweshiek County Board of Supervisors |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 05/30/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IA00972 |
| Federal ID | IA00972 |
| More Info | State Dam Safety Program |