Lake Williams Reservoir Report

Last Updated: December 5, 2025

Lake Williams, located in York Township, Pennsylvania, is a private water supply reservoir built in 1912 with a primary purpose of water supply.


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Summary

The dam, standing at 58 feet in height and 700 feet in length, holds a maximum storage capacity of 5,800 acre-feet and a normal storage capacity of 3,370 acre-feet. The reservoir covers a surface area of 165 acres and drains an area of 45 square miles, with the East Branch of Codorus Creek serving as the primary water source.

Despite its important role in providing water to the region, Lake Williams faces significant challenges as indicated by its high hazard potential and poor condition assessment. In 2010, structural modifications were made to address safety concerns. The dam is regulated by the Pennsylvania Department of Environmental Protection, with state permitting, inspection, and enforcement in place to ensure compliance with safety standards. The reservoir also offers recreational opportunities in addition to its vital water supply function, serving as a hub for water resource and climate enthusiasts in the area.

As a key water resource in the region, Lake Williams serves as a critical infrastructure for water supply and recreational activities. With its historical significance dating back over a century, the reservoir continues to play a crucial role in the community. However, ongoing maintenance and monitoring are essential to address safety concerns and ensure the sustainable management of this valuable resource in the face of changing climate patterns and increasing water demands.

Years Modified

2010 - Structural

Year Completed

1912

Dam Length

700

Dam Height

58

River Or Stream

EAST BRANCH CODORUS CREEK

Primary Dam Type

Earth

Surface Area

165

Drainage Area

45

Nid Storage

5800

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

58
       
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.