Mary Street
Mary Street is an earth dam located in Riverside County, California, built in 1981. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Mary Street
The primary purpose of Mary Street is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Riverside County Flood Control And Water Conservation District (local government). It impounds the Alessandro Wash near Riverside.
The dam stands 40 feet tall and stretches 1,035 feet across, creates a reservoir covering 19 acres, has a maximum storage capacity of 320 acre-feet, and collects water from a drainage area of 6 square miles. Completed in 1981, the structure is 45 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 12/01/2025.
At 40 feet, this dam is taller than 87% 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 California 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 | California |
| County | Riverside |
| Nearest City | Riverside |
| River/Stream | Alessandro Wash |
| Coordinates | 33.93310, -117.37740 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 40 ft |
| Dam Height | 40 ft |
| Dam Length | 1,035 ft |
| Year Completed | 1981 (45 years old) |
Storage & Hydraulics
| NID Storage | 320 acre-ft |
| Max Storage | 320 acre-ft |
| Surface Area | 19 acres |
| Drainage Area | 6 sq mi |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Riverside County Flood Control and Water Conservation District |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 12/01/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA01211 |
| Federal ID | CA01211 |
| More Info | State Dam Safety Program |