Warner Gap Hollow Dam Reservoir Report

Last Updated: December 5, 2025

Warner Gap Hollow Dam, also known as Edgemont, is a vital water supply structure located in Washington County, Maryland.


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Summary

Built in 1902, this earth dam stands at a height of 65 feet and spans 700 feet in length, containing a storage capacity of 296 acre-feet. It serves the primary purpose of providing water supply to the surrounding area, with a drainage area of 2.3 square miles and a normal storage level of 246 acre-feet.

Despite its historical significance, Warner Gap Hollow Dam has been classified with a high hazard potential and an unsatisfactory condition assessment, prompting regular inspections and maintenance measures. The dam's spillway operates on an uncontrolled basis, with a spillway width of 25 feet. In 1993, the dam underwent hydraulic and structural modifications to enhance its safety and reliability, under the supervision of Whitman, Requardt & Assoc. The dam is subject to state regulatory oversight by the Maryland Dam Safety agency, ensuring compliance with safety standards and enforcement measures.

Warner Gap Hollow Dam's association with the Warner Gap Hollow Creek and its critical role in water supply maintenance make it a significant infrastructure element in the region. With a moderate risk assessment rating and notable historical background, the dam presents an intriguing case study for water resource and climate enthusiasts interested in the intersection of infrastructure, environmental regulations, and risk management practices.

Years Modified

1993 - Hydraulic, 1993 - Structural

Year Completed

1902

Dam Length

700

Dam Height

65

River Or Stream

Warner Gap Hollow Creek

Primary Dam Type

Earth

Surface Area

12

Drainage Area

2.3

Nid Storage

296

Outlet Gates

Slide (sluice gate) - 0

Hazard Potential

High

Foundations

Rock

Nid Height

65
       
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.