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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />Outdoor life safety hazards <br />If associated with a severe winter <br />weather system, heavy snow, strong <br />winds, falling temperatures and <br />dangerous wind chills may follow the <br />�w <br />ice storm. Persons caught outside <br />unprepared can face disorientation, 26 <br />frostbite, hypothermia, and death. <br />25% of winter storm casualties occur ,r <br />among those caught outside in the <br />storm. <br />Power/utilities <br />Ice storms can cause power outagespo,aadipuraw�lNrmu'ro'Car0 <br />mm <br />from direct loading on electrical wires, 40 ale <br />and more commonly from indirect sodxt <br />sources, for example when tree limbs 28 10 1) 4 11" <br />Temperature profiles associated with freezing rain. Source: Midwest <br />become overloaded with ice and fall Regional Climate Center. <br />onto wires. Ice accumulations greater <br />than a quarter inch can cause <br />widespread power outages, and strong winds exacerbate this impact. The duration of service outages <br />is typically related to the complexity of the outage pattern, along with the ability of crews to get to <br />repair sites. Thus, prolonged ice storms with strong winds are associated with higher outage numbers <br />and longer service delays. <br />Structural damage <br />Ice storms can damage roofs at residences, and at larger commercial facilities as well. Large roof spans <br />lacking consistent support are especially vulnerable. Secondary damage from falling ice -coated tree <br />limbs is especially common. These falling limbs are often significantly heavier because of the ice and <br />can break windows and damage downspouts and gutters. In if the rain is especially heavy, ice can <br />penetrate vulnerable locations in roofs, deforming them and often leading to significant water damage <br />to plaster and drywall materials inside the structure. <br />Transportation <br />Ice storms are especially dangerous to the transportation. Major ice storms can paralyze the entire <br />transportation system, including public transportation and airports. Spinouts and accidents frequently <br />number in the hundreds. However, most large ice storms are anticipated, and road treatments are <br />possible ahead of time. Smaller events from freezing drizzle only cause minor ice accumulations, but <br />when unforeseen, can be devastating. A thin glaze from freezing drizzle on November 20-21, 2010, <br />resulted in several hundred reported accidents, and at least two fatalities. <br />4.3.13.4. Potential for cascading effects <br />Extended power outages <br />An ice storm that knocks out power becomes much more dangerous as the time to restore service <br />increases. This is especially true of storms that are followed by a rapid drop in temperatures. Residences <br />and facilities dependent on electrical power for heat distribution can become dangerously cold within <br />hours of power loss. <br />206 <br />