Grinding Rock Reservoir Report

Last Updated: December 5, 2025

Grinding Rock is a vital water resource infrastructure in California, specifically located in Snelling, Tuolumne County.


°F

°F

mph

Wind

%

Humidity

Summary

This earth-type dam was completed in 1979 and stands at a height of 55 feet, with a hydraulic height of 50 feet, serving the primary purpose of water supply. With a storage capacity of 330 acre-feet, the dam plays a crucial role in flood risk reduction, irrigation, and water supply for the surrounding area. Managed by a public utility, Grinding Rock is regulated and inspected by the Department of Water Resources, Safety of Dams division, ensuring its continued safe operation for the community.

The dam's low hazard potential and satisfactory condition assessment as of 2017 reflect its robust construction and ongoing maintenance. With an associated drainage area of 0.2 square miles and a surface area of 14 acres, Grinding Rock contributes significantly to the water management efforts in the region. Its location on the Tr Turnback Creek, under the jurisdiction of the state of California, highlights its importance in meeting the water needs of the local population and supporting agricultural activities in the area.

Grinding Rock's history of reliable water supply and its role in mitigating flood risks make it a critical asset for the community. As part of the water infrastructure network in California, this dam stands as a testament to effective water resource management and serves as a reminder of the interconnected relationship between water resources and climate resilience in the region.

Year Completed

1979

Dam Length

525

Dam Height

55

River Or Stream

Tr Turnback Cr

Primary Dam Type

Earth

Surface Area

14

Hydraulic Height

50

Drainage Area

0.2

Nid Storage

330

Hazard Potential

Low

Nid Height

55
       
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.