Dam Failure *

Description:

Dam:

According to Maine law, Title 37-B MRSA c. 24 CHAPTER 24 “DAM SAFETY”:

"Dam" means any artificial barrier, including appurtenant works, the site on which it is located and appurtenant rights of flowage and access that impounds or diverts water, and that:

A. Is 25 feet or more in height from the natural bed of the watercourse measured at the downstream toe of the barrier or from the lowest elevation of the outside limit of the barrier to the maximum water storage elevation and impounds at least 15 acre-feet of water; or

B. Is 6 feet or more in height from the natural bed of the watercourse measured at the downstream toe of the barrier or from the lowest elevation of the outside limit of the barrier to the maximum water storage elevation and has an impounding capacity at maximum water storage elevation of 50 acre-feet or more.

Dam Failure:

Dam failure is the spontaneous release of water resulting from improper operation or structural collapse of the structure. Dam failure can cause rapid downstream flooding, loss of life, damage to property, and the forced evacuation of people. The inundation zone is usually estimated by assuming a mode and time of failure under two distinct regimes; the “sunny day” breach and the “spillway test flood” condition. The area downstream at risk must be mapped showing each condition flood line and used for emergency action planning.

Secondary Effects:

The secondary effects of dam failure can be the disruption of the local and state economies by damage to buildings and roads, the severance of communications, the disruption of supply and delivery mechanisms, additional welfare, and emergency aid to the recovering economy.

Vulnerability:

Maine has nine major rivers, twenty-one smaller coastal rivers supporting over 1,000 dams grouped by “regulating authority” and “hazard”.

Dam “height” is the height of the dam from toe to dry crest. In Maine, one high hazard dam exceeds 100’ in height and thirty-one high hazard dams are below 25’ in height. Eleven of the MEMA regulated dams are “flood control dams”, which means they are operated empty or partially full and thus have a lower risk of failure. Five high hazard dams are common to the same hydropower project.

There are 174 dams in Maine, and a further eleven in New Hampshire, which are regulated by the Federal Energy Regulatory Commission (FERC). These are mostly hydro-power dams inspected regularly by independent engineers. Of these thirty-three plus one in New Hampshire are high hazard dams, and thirteen plus seven in New Hampshire are significant hazard dams.

An additional fifty dams regulated by the New Hampshire Department of Environmental Protection can impact Maine through common watersheds.

It is not known how many dams in Canada would impact Maine if they failed.

There are 841 dams in Maine under State regulation. Of these twenty-six are high and eighty-seven are significant hazard dams requiring two- and four-year inspection cycles respectively. There are also an unknown number of temporary dams built for logging and agriculture.

Maine has a high rainfall and a large spring runoff sometimes exacerbated by hurricanes. Dams in Maine are regularly tested by flooding and icing.

Maine is an earthquake zone and most dams have not been designed for earthquake loading.

Most Maine dams over fifty years old and nearing the end of their life cycle. These dams all show signs of weathering and movement to various degrees. While FERC dams, which are mostly revenue producing, can sustain repairs and maintenance on a regular basis most of the State regulated dams cannot and their continual deterioration should be a cause for concern.

Most State regulated dams have no construction records and cannot be structurally assessed without considerable investigation and cost.

Most of FERC regulated high and significant hazard dams have emergency action plans (EAPs) and close to 100% of State regulated dams.

Many high and significant hazard dams in Maine are close to international borders. Most are unguarded. All are vulnerable to terrorist attack.

The Maine State Dam Safety Program (MEDSP) is currently understaffed.

Mitigation:

The FERC maintains a constant inspection program of Maine dams using five engineers.

Since 1998 the State Dam Safety Program has been run using Federal assistance provided by grants totaling $192,198 from FEMA. This grant has enabled the Maine Dam Safety Program (MEDSP) to hire transport, purchase equipment and employ personnel to assist with the program. Currently the State Dam Inspector (SDI) has dealt with 328 dams in four years including thirty-six high hazard (H) dams, fifty-seven significant (S) hazard dams, 170 low hazard (L) dams, fifty-six (N) minor dams and nine NH dams.

The MEDSP is supervised by the Deputy Director, MEMA, and has one full-time SDI employed since October 1998 who carries out general administration, conducts dam safety inspections, and facilitates the development, review, and testing of EAPs. The SDI also attends FERC dam inspections when time permits. Currently the SDI is assisted by the Supervisor and one part-time administrative assistant.

The MEDSP does have one technical assistant post and one administrative assistant post allocated to it by the State, but these posts have never been filled.

The MEDSP maintains files on 1077 dams of which 841 are the responsibility of the State of Maine. Of the remainder, 174 are the responsibility of FERC, fifty of the NHDES, and an undetermined number on rivers flowing into ME from Canada.

In addition to dam condition inspections, the MEDSP is responsible for facilitating and maintaining EAPs for 113 high and significant hazard state dams and keeping and updating EAPs for forty-six FERC dams.

* An occurrence of this hazard could possibly be initiated by a deliberate act.

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MAINE PREPARES

Dam Failure *

Description:

Secondary Effects:

Vulnerability:

Mitigation:

MAINE HAZARDS