4.7 SR 06-01-2020 - Laserfiche WebLink

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Sherburne County Multi -Hazard Mitigation Plan, 2020 patterns due to climate change may change the expected flow pattern. It is conceivable that bigger rainfalls at earlier times in the year could threaten a dam's designed margin of safety, causing dam operators to release greater volumes of water earlier in a storm cycle in order to maintain the required margins of safety. Such early releases of increased volumes can increase flood potential downstream. Climate change is adding a new level of uncertainty that needs to be considered with respect to assumptions made during dam construction. Vulnerability Although dam regulatory authorities vary between various federal and state agencies, all authorities attempt to classify dams according to the potential impacts from a dam failure or mis-operation. In response to the numerous classification systems, FEMA's Interagency Committee on Dam Safety created a hazard potential classification system that is adaptable to any agency's current system. Table 3o provides an overview of the main criteria agencies consider when determining a dam's hazard potential classification. This classification system does not imply that the dam is unsafe, but rather categorizes dams based on the probable loss of human life and the impacts on economic, environmental, and lifeline interests (2004). Table 30. Hazard Potential Classification Criteria Low None expected Low and generally limited to owner Significant _ None expected Yes Probable - one or Yes (but not High more expected necessary forthis classification) Source: (US Army Corps of Engineers, 2008) Minnesota's hazard classifications for dams are as follows: • High (Class 1) - loss of life or potential serious hazards; damage to health, main highways, high - value industrial or commercial properties, or major public utilities; or serious direct or indirect economic loss to the public; • Significant (Class 11) - possible health hazard or probable loss of high -value property; damage to secondary highways, railroads or other public utilities; or limited direct or indirect economic loss to the public otherthan that described in Class III (Low); and • Low (Class III) - property losses restricted mainly to rural buildings and local county and township roads that are an essential part of the rural transportation system serving the area involved. Class I dam owners are required to have an Emergency Action Plan (EAP) on file, notifying individuals whose lives, property, or health may be endangered by failure, mis-operation, or other circumstances affecting the dam (Minnesota Legislature - Office of the Revisor of Statutes, 2008). Page187