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Widespread flooding in the Seaford area during a severe storm of June 2006 caused overtopping of the Hearns Pond Dam which was subsequently repaired. Inspections of all regulated dams in the state are conducted under the new Dam Safety Regulations to identify any rehabilitation needs.
Photo by David Twing, DNREC Division of Watershed Stewardship
The Delaware Dam Safety Law was adopted in 2004 and provides the framework for proper design, construction, operation, maintenance, and inspection of dams in the interest of public health, safety, and welfare. The law requires licensing, inspections and preparation of emergency action plans (EAPs) for publicly owned dams with a high or significant hazard potential. A dam’s hazard potential classification depends upon the threat to downstream communities and infrastructure in the event of a dam failure and is not related to the condition of a dam.
The Delaware Dam Safety Program was developed to reduce the risk of failure of dams and to prevent injuries to persons, damage to downstream property and loss of reservoir storage. The Dam Safety Regulations, adopted on December 11, 2009, establish requirements for licensing existing dams; permitting construction of new dams and repairs to existing dams; conducting inspections; performing maintenance; and preparing EAPs. In 2007, DNREC was awarded state funding to develop Emergency Action Plans for Delaware’s highest priority, state-owned, high-hazard dams. The emergency action plans for these dams will be completed in 2010.
Downstream Hazard Potential Classification
Delaware uses a Hazard Potential Classification system for dams that is based on federal dam safety guidelines published by FEMA. The hazard potential classification of a dam is determined by the impact that a failure would have on the population, infrastructure and development located downstream, not on the condition or size of the dam. These hazard potential classifications are:
- High Hazard Potential Dam - any dam whose failure or misoperation will cause probable loss of human life.
- Significant Hazard Potential Dam - any dam whose failure or misoperation will cause possible loss of life, economic loss, environmental damage, disruption of lifeline facilities, or can impact other concerns.
- Low-hazard potential dam - any dam whose failure or misoperation is unlikely to cause loss of human life but may cause minor economic and/or environmental losses.
Owners of regulated dams in Delaware are required to conduct informal inspections of their dams at least quarterly, and regular inspections at least once each year for high hazard dams and once every two years for significant hazard dams. Regular inspections must be performed by a Delaware-licensed professional engineer, and a comprehensive written report must be prepared and submitted to the DNREC Dam Safety Program for each inspection.
Regular inspections for all state-owned, regulated dams are performed jointly by professional engineers from the DNREC Dam Safety Program and DelDOT.
Emergency Action Plans
An Emergency Action Plan (EAP) is a written plan that identifies emergency conditions at a dam and specifies preplanned actions to minimize loss of life and property damage in the event of a potential dam failure. Every regulated dam in Delaware is required to have an EAP prepared by the dam owner and approved by the DNREC Dam Safety Program. EAPs have been prepared for all state owned, regulated dams.
Water Level Monitoring at State-Owned Dams
In 2015, instrumentation to provide near real-time monitoring of pond/lake water levels was installed at nine state-owned dams. The US Geologic Survey (USGS) installed monitoring gauges at these three dams as part of DelDOT’s statewide weather monitoring network:
- Hearns Pond Dam near Seaford
- Haven Lake Dam in Milford
- Garrisons Lake Dam in Smyrna
Click here to access information recorded by the gages at the above dams.
Gauges at these six dams were installed by the Delaware Environment Observing System (DEOS) at the University of Delaware:
Chipmans Pond Dam near Laurel
Concord Pond Dam near Laurel
Fleetwood Pond Dam near Laurel
Records Pond Dam in Laurel
Craigs Pond Dam near Seaford
Williams Pond Dam in Seaford
Click here to access information recorded by the gauges at the above dams.
Delaware Dam Inventory
A comprehensive inventory of dams in Delaware was performed between 2006 and 2008. Using information from previous inventories performed in 1974 and 1981, and an update in 2003, over 300 potential dam sites were reviewed and 86 structures were considered to be dams of interest. 63 of those dams were then classified as being potentially regulated. Since 2008 however, further, more in-depth review of each dam has reduced the number of regulated dams to the current 48.