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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />4.1.4.11.3. Weight: Fallen volcanic ash is heavy and poses <br />a risk to buildings close to the eruption, particularly those <br />with flat roofs. A dry layer of ash 4 inches thick weighs 120 <br />to 200 pounds per square yard, and wet ash weight is <br />usually double the dry totals. Ash weight should not be a threat <br />to Minnesota structures. <br />4.1.4.11.4. Prevailing winds. Both east -west zonal flow and <br />Alberta Clipper systems bring winds to Minnesota from <br />regions that host active volcanoes. <br />4.1.4.12. Prevention <br />Unknown, pending conclusion of the Hennepin County Emergency <br />Management assessment in 2024. <br />4.1.4.13. Mitigation <br />4.1.4.13.1. Avoidance. Avoidance of flight through ash clouds is vital to aviation safety. Ash cloud <br />alerts and warnings provide air route control centers the information they need to vector aircraft <br />away from ash clouds. <br />4.1.4.13.2. Personal protection. Personal protective equipment such as filtration masks and eye <br />protection from covered goggles are needed to avoid some of the health risks posed by volcanic <br />ash. <br />4.1.4.13.3. Barriers. Sealing off rooms that have sensitive electronics can be done with plastic <br />sheets and duct tape. Covering individual devices may also help protect them against ash. <br />4.1.4.14. Response <br />Unknown, pending conclusion of the Hennepin County Emergency Management assessment. <br />4.1.4.15. Recovery <br />Unknown, pending conclusion of the Hennepin County Emergency Management assessment. <br />32 <br />