Modesto Effluent Storage
Modesto Effluent Storage is an earth dam located in Stanislaus County, California, built in 1987. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
About Modesto Effluent Storage
The primary purpose of Modesto Effluent Storage 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 City Of Modesto (local government). It impounds the Offstream.
The dam stands 20 feet tall and stretches 25,000 feet across, creates a reservoir covering 596 acres, and has a maximum storage capacity of 7,830 acre-feet. Completed in 1987, the structure is 39 years 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. 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 03/25/2025.
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Location
| State | California |
| County | Stanislaus |
| River/Stream | Offstream |
| Coordinates | 37.53750, -121.08240 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 20 ft |
| Dam Height | 20 ft |
| Dam Length | 25,000 ft |
| Year Completed | 1987 (39 years old) |
Storage & Hydraulics
| NID Storage | 7,830 acre-ft |
| Max Storage | 7,830 acre-ft |
| Surface Area | 596 acres |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Modesto |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 03/25/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA01286 |
| Federal ID | CA01286 |
| More Info | State Dam Safety Program |