Mary Street Reservoir Report

Last Updated: December 5, 2025

Mary Street is a vital flood risk reduction structure located in Casa Blanca, California, along the Alessandro Wash.


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Summary

Owned by the local government, this earth dam stands at a height of 40 feet and was completed in 1981. With a storage capacity of 320 acre-feet and a drainage area of 6.7 square miles, Mary Street plays a crucial role in mitigating potential flooding events in the region.

Regulated by the California Department of Water Resources for dam safety, Mary Street has a high hazard potential but is currently assessed to be in satisfactory condition. Regular inspections ensure its structural integrity, with the last assessment conducted in September 2017. In the event of an emergency, the dam has emergency action plans in place, although the details of their preparation and adherence to guidelines are not specified in the data. Overall, Mary Street serves as a key infrastructure for water resource management and climate resilience in Riverside County.

Represented in Congress by Mark Takano, Mary Street is part of the flood risk reduction infrastructure under the jurisdiction of the Los Angeles District of the US Army Corps of Engineers. Its location at the confluence of multiple waterways highlights its strategic importance in protecting surrounding communities from potential inundation. As climate change continues to impact precipitation patterns and increase the frequency of extreme weather events, the maintenance and proper management of structures like Mary Street are essential for safeguarding lives and property in the region.

Year Completed

1981

Dam Length

1035

Dam Height

40

River Or Stream

Alessandro Wash

Primary Dam Type

Earth

Surface Area

19

Hydraulic Height

33

Drainage Area

6.7

Nid Storage

320

Hazard Potential

High

Nid Height

40
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.