South Prong Dam Reservoir Report

Last Updated: December 5, 2025

South Prong Dam, located in Ellis, Texas, is a vital structure designed by Forrest and Cotton in 1956 for water supply purposes.


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Summary

This earth dam stands at a height of 62 feet and spans 4100 feet in length along the South Prong Waxahachie Creek. With a maximum storage capacity of 22,764 acre-feet and a normal storage of 13,500 acre-feet, the dam plays a crucial role in managing water resources in the region.

Managed by local government authorities and regulated by the Texas Commission on Environmental Quality (TCEQ), South Prong Dam has been inspected regularly to ensure its structural integrity and operational efficiency. The dam features an uncontrolled spillway with a width of 1600 feet and two uncontrolled outlet gates. Its condition assessment in April 2021 deemed it to be satisfactory, reflecting its reliability in water storage and supply. While the hazard potential is not available, the risk assessment categorizes the dam as moderate (3), highlighting the importance of ongoing risk management measures to ensure its safety and functionality for the community.

Overall, South Prong Dam stands as a crucial infrastructure piece in the water resource management system of Ellis, Texas. With its historical significance, structural soundness, and regulated operation, the dam continues to serve its primary purpose of providing water supply to the region while maintaining a moderate risk level that necessitates ongoing monitoring and management efforts.

Years Modified

1995 - Structural

Year Completed

1956

Dam Length

4100

Dam Height

62

River Or Stream

SOUTH PRONG WAXAHACHIE CREEK

Primary Dam Type

Earth

Surface Area

690

Hydraulic Height

62

Drainage Area

29

Nid Storage

22764

Structural Height

62

Outlet Gates

Uncontrolled - 2

Hazard Potential

Not Available

Foundations

Soil

Nid Height

62
       
Seasonal Comparison

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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.