William O Nannen Pond Dam Reservoir Report

Last Updated: December 6, 2025

William O Nannen Pond Dam, also known as Murphy Lake, is a private dam located in Ellicottville, New York.


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Summary

Completed in 1964, this earth dam stands at a height of 15 feet and has a length of 1230 feet. The dam serves primarily for recreation purposes, with a storage capacity of 36 acre-feet and a surface area of 4 acres. It is situated on TR-GREAT VALLEY CREEK and is regulated by the NYS DEC.

With a significant hazard potential and a moderate risk assessment rating, William O Nannen Pond Dam has not been rated for its condition assessment. The last inspection was conducted in October 2017, with a frequency of every 4 years. The dam features an uncontrolled spillway type and has a maximum discharge capacity of 48 cubic feet per second. Despite being a private structure, the dam is subject to state regulation, permitting, inspection, and enforcement by the New York regulatory agencies.

Water resource and climate enthusiasts will be intrigued by the unique features and regulatory aspects of William O Nannen Pond Dam. Its location in Cattaraugus County, New York, and its association with recreational activities make it a noteworthy structure in the region. The dam's significance lies in its function for water storage, flood control, and environmental impact, showcasing the intersection of human infrastructure with natural resources in the area.

Year Completed

1964

Dam Length

1230

Dam Height

15

River Or Stream

TR-GREAT VALLEY CREEK

Primary Dam Type

Earth

Surface Area

4

Drainage Area

5.6

Nid Storage

36

Hazard Potential

Significant

Nid Height

15
       
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.