DEEP: Introduction to Dams

Dams In Connecticut: Their History, Use & Regulation

History

The construction of dams in Connecticut began with the arrival of the first colonial settlers in the 1630s. Soon, mill dams facilitated economic development and production of grain, cotton and wood in Connecticut's early history. As the state's economy evolved, dams were used for manufacturing, water supply, mechanical power and for fire protection. Today they continue to play a vital role in the productivity of the state. One of the oldest continuously running sawmills in the United States is located on the Silvermine River near Norwalk and has been in operation since 1688.

Since dams have been an important part of our state's infrastructure, Connecticut has exercised the regulatory oversight of dams and reservoirs beginning in 1878. In addition to the historic economic benefits provided by Connecticut's dams, they are also used for flood control, water supply, recreation and for mitigating the impact of increased runoff typically caused by land use changes associated with property development.

What is a dam?

Dams are man-made or artificial barriers usually constructed across a stream channel to impound water. Dams are typically provided with spillway systems to safely pass a broad range of flows over, around or through the dam.

Various materials are used for dam construction such as timber, rock, concrete, earth, steel or a combination of these materials. However, in Connecticut, most dams are constructed of earth or combinations of earth and other materials. Spillways are commonly constructed of non-erosive materials such as concrete or rock.

Dams are typically constructed with a drain or similar mechanism to control water levels in an impoundment for normal maintenance or emergency purposes.

The Department of Environmental Protection (DEEP), Bureau of Water Protection and Land Reuse's Inland Water Resources Division, maintains a computerized inventory of over 4,000 dams in Connecticut. Of these, approximately 1,500 fall under the Department's regulation since their failure may cause loss of life or property damage. The remaining dams are typically small and do not pose a significant hazard to the public. The ownership of Connecticut's dams is diverse. Approximately 84% (percent) are held privately and the remainder are held by public or non-profit entities. Over 40 flood control dams in the state are owned and operated at the federal and state level. The DEEP holds title to more than 200 dams, most of which are located in state parks and forest areas.

The Importance of Dam Safety

By definition, a disaster is any event that causes great harm or damage, serious or sudden misfortune. Dam failures clearly fit this definition. Because of the sudden and unexpected manner in which dam failures can occur, they are potentially as destructive as earthquakes, hurricanes and tornadoes.

There have been about 200 notable dam and reservoir failures worldwide in the twentieth century. More than 8,000 people have died in these disasters. The following table highlights some of the recent failures which occurred outside of Connecticut.

Table 1. Recent Dam Failures in the U.S.

Year Name Location Damage
1972 Buffalo Creek Dam West Virginia 125 deaths $400M
1972 Canyon Lake Dam South Dakota 139 deaths $60M
1976 Teton Dam Idaho 11 deaths $4M
1977 Tacoa Falls Dam Georgia 39 deaths $30M
1982 Lawn Lake Dam Colorado 3 deaths $21M

While there have been numerous dam failures in Connecticut's recent history, the following are two of the most catastrophic events:

Table 2. Recent Dam Failures in CT

Year Name Location Damage
1963 Spaulding Pond Dam Norwich 6 deaths $6M
1982 Bushy Hill Pond Dam Deep River 0 deaths $50M

On the weekend of June 5-6, 1982, Connecticut suffered its worst flooding since 1955. Throughout the State, 17 dams failed and another 31 were damaged resulting in losses totaling approximately $70 million. The failure of these dams serves as a solemn reminder that dams do fail and underscores the need for aggressive dam safety programs at both the state and national levels. Furthermore, the potential for dam related disasters continues to grow with increasing residential and commercial development downstream of dams, within the areas likely to be inundated by dam failures.

Connecticut's Dam Safety Program

The Dam Safety Section of the Inland Water Resources Division is charged with the responsibility for administration and enforcement of Connecticut's dam safety laws. The existing statutes require that permits be obtained to construct, repair or alter dams, dikes or similar structures and that existing dams, dikes and similar structures be registered and periodically inspected to assure that their continued operation and use does not constitute a hazard to life, health or property. The dam safety statutes are codified in Section 22a-401 through 22a-411 inclusive of the Connecticut General Statutes. Sections 22a-409-1 and 22a-409-2 of the Regulations of Connecticut State Agencies, have been enacted which govern the registration, classification, and inspection of dams.

Permitting

Prior to obtaining a permit for construction, repair or alteration of a dam, dike or similar structure, detailed plans and specifications prepared and certified by a professional engineer registered in Connecticut must be submitted to the Dam Safety Section of the Inland Water Resources Division for review and approval. As part of Public Act 93-428, permit applicants are required to publish notice of their application and submit proof of same by providing the Department with a certified copy of the notice as published in the newspaper. Before issuing a dam construction permit, the Department must issue a "Notice of Tentative Determination", which provides the public with a detailed description of the proposed activity and an opportunity to comment on the application or request a hearing. Once a permit is issued, a registered engineer, familiar with dam construction, must inspect the construction, certify completion of the construction and prepare "as-built" plans of the structure. These requirements ensure that dams and similar structures are properly and safely constructed according to state approved plans and specifications.

Registration/Inspection

Connecticut Public Act 83-38 required that the owner of a dam or similar structure provide information to the Commissioner of DEEP by registering their dam by July 1, 1984. To date, of the 4,400 known dams, 3,088 have been registered with the DEEP.

Dam Inspection Regulations require that over 600 dams in Connecticut must be inspected annually. The Department currently prioritizes inspections of those dams which pose the greatest potential threat to downstream persons and properties. The Department has also targeted a limited number of lower hazard dams for inspection, which have not been inspected in the past twenty years. Other structures are inspected as time and funding permit, and upon notification of potentially significant deficiencies or emergency conditions.

Enforcement

Dams found to be unsafe under the inspection program must be repaired by the owner. Depending on the severity of the identified deficiency, an owner is allowed reasonable time to make the required repairs or to remove the dam. If a dam owner fails to make necessary repairs to the subject structure, the Department may issue an administrative order requiring the owner to restore the structure to a safe condition and may refer noncompliance with such an order to the Attorney General's Office for enforcement. As a means of last resort, the Commissioner is empowered by statute to remove or correct, at the expense of the owner, any unsafe structures which present a clear and present danger to public safety.

The Owner's Responsibility

Dam owners should be aware of their legal responsibilities for the continued safe operation of their dams and the structure's maintenance and inspection requirements. Negligence by owners in fulfilling these responsibilities can lead to the creation of extremely hazardous conditions which may lead to a potential dam failure and thereby threaten downstream residents and properties.

Failure of a dam can result in loss of life, considerable loss of property and loss of income. In addition, the loss or significant lowering of a reservoir can cause hardship for those dependent on it for their livelihood or water supply, in addition to significantly altering the existing wetlands and associated biotic communities.

Reservoirs may also artificially elevate groundwater levels which in turn support shallow domestic wells. Loss of a reservoir ponded behind a dam may lead to the failure of such wells. In the event of dam failure, the owner can be subject to costly liability claims, which arise from damages occurring downstream. Consequently, dam owners should consider obtaining insurance to provide coverage in the event of damages and claims resulting from a dam failure.

Dam Maintenance and Operation

When a dam is properly designed and constructed, can the owner assume it is safe? The answer to this question may seem obvious, but several small dams in Connecticut have failed due to lack of timely maintenance. In most cases, the failure could have been prevented if the structure had been properly maintained after its construction.

Dams and dikes cannot be thought of as a part of the natural landscape, but rather as artificial structures which require ongoing inspection, and maintenance (and in the case of high and significant hazard dams carefully developed emergency operation plans). Maintenance is an ongoing process that not only involves such routine items as mowing grass and clearing spillways, conduits, channels, trashracks, etc., but also requires regular inspections of the structure and its various components.

Key dam operation, maintenance and inspection measures should include:

  1. Keeping spillways clear of debris.
  2. Watching for undermining of the spillway outlet or uncontrolled flow beneath or around spillway structures.
  3. Eliminating burrowing animals and taking measures to prevent their habitation in and on earth embankments.
  4. Maintaining a healthy stand of grass on earth dam embankments and vegetated spillways to prevent erosion.
  5. Watching for uncontrolled seepage on the dam face and around all metal, masonry and concrete structures passing through the dam embankment.
  6. Making sure that gates, valves and all water control mechanisms are operable.
  7. Watching for any sign of settlement, cracking, unstable slopes or other soil movement.
  8. Inspecting all dam components and their appurtenances closely for signs of deterioration.
Summary

Dams and their associated reservoirs have been and continue to be an important resource and economic factor in Connecticut's economy. These structures have provided mechanical and hydroelectric power, municipal water supply sources, flood control protection and recreational amenities. In the future, our dams will continue to provide these benefits and services to Connecticut's citizens. However, since dams are man-made structures, they must be appropriately maintained and repaired to assure their safety and integrity. The Department's efforts are directed to ensuring the safety of dams through a program of periodic inspections and the administration and enforcement of Connecticut's dam safety statutes and regulations.

Should you have any questions regarding the safety of a particular dam, promptly notify the Dam Safety Section of the Inland Water Resources Division at 860-424-3706. After normal business hours, please call 860-424-3333.

Dams

Content last updated on March 15, 2012