Old Longs Mill Dam Reservoir Report

Last Updated: December 5, 2025

Old Longs Mill Dam, also known as Tratebas Mill Dam, is a private-owned structure located in Porter, Indiana, along Coffee Creek.


°F

°F

mph

Wind

%

Humidity

Summary

Built in 1930, this earth dam stands at a height of 20 feet and stretches 200 feet in length, providing a surface area of 10.25 acres and a storage capacity of 81 acre-feet. While its primary purpose is for recreation, the dam is regulated by the Indiana Department of Natural Resources (IDNR) and undergoes regular inspections to ensure its safety and compliance with state regulations.

Despite its historical significance and recreational value, Old Longs Mill Dam poses a significant hazard potential due to its poor condition assessment. With a high risk rating of 2, there are concerns about the dam's ability to withstand potential emergencies and protect downstream areas from flooding. Although currently lacking an Emergency Action Plan (EAP) and updated risk assessment measures, efforts are being made to address these deficiencies and mitigate any potential risks associated with the dam.

As a popular spot for outdoor enthusiasts and nature lovers, the Old Longs Mill Dam serves as a reminder of the importance of maintaining and monitoring water resource infrastructure to ensure the safety of both the environment and nearby communities. With ongoing assessments and potential risk management measures in place, stakeholders are working towards safeguarding this historic structure and its surrounding ecosystem for future generations to enjoy.

Year Completed

1930

Dam Length

200

Dam Height

20

River Or Stream

COFFEE CREEK

Primary Dam Type

Earth

Surface Area

10.25

Drainage Area

7.59

Nid Storage

81

Outlet Gates

None

Hazard Potential

Significant

Nid Height

20
       
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.