Chatham County Hazard Mitigation Plan UpdateSteering Committee Meeting

August 13, 2009

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Agenda

• Introductions

• Mitigation Planning

• Plan Update

• Chapter 1

• Chapter 2

– Hazard exercise

• Chapter 3

• Next Steps

• Important Dates

Plan Update

• Reorganization and reformatting of plan in accordance with state guidance

• Significant portions of chapters 1-3 complete.– Addition of hazards

• Today’s meeting– Review progress to date

– Review hazard profiles

– Qualitative ranking of hazards

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Chapter 1

• More recent and additional census data has been added.

• Addition of a summary of critical facilities and buildings/structures.

• Description of planning process to date.

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Chapter 2

• Updated hazard information

• Additional hazards considered

• New risk assessments

• Need to update land use and development trends

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Coastal Hazards and StormsCoastal Hazards and Storms

• Five hurricanes since 1979

• Want to include accurate accounting of historical events

• Coastal storms include:– Tropical depressions

– Tropical storms

– Hurricanes

– Nor’easters

Updated Information

• NCDC data

• U.S. Landfalling Hurricane Probability Project

• Critical infrastructure inventory

• NOAA data

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High Wind Hurricane Risk 2009 Probabilities

Probability of 1 or more named storms making landfall 1.5 percent

Probability of 1 or more Hurricanes making landfall 0.6 percent

Probability of 1 or more Intense Hurricanes making landfall 0.2 percent

Probability of Tropical Storm Force Wind Gusts >= 40mph 8.7 percent

Probability of Hurricane Force Wind Gusts >= 75mph 2.4 percent

Probability of Intense Hurricane Force Wind Gusts >= 115 mph 0.9 percent

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High Wind Hurricane 50 Year Probabilities

Probability of 1 or more named storms making landfall 56.4 percent

Probability of 1 or more Hurricanes making landfall 30.5 percent

Probability of 1 or more Intense Hurricanes making landfall 9.4 percent

Probability of Tropical Storm Force Wind Gusts >= 40mph 99.5 percent

Probability of Hurricane Force Wind Gusts >= 75mph 74.6 percent

Probability of Intense Hurricane Force Wind Gusts >= 115 mph 39.5 percent

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Risk Assessment Results

• Most severe damage in coastal areas

• Non-coastal areas can be affected by flooding, tornadoes, and high wind

• Potential impact: 113,067 structures/buildings with total value of $45 billion

• Exercise:– Risk to people: low/med/high

– Risk to buildings: low/med/high

– Risk to infrastructure: low/med/hi

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Tornado

• Vortex of high wind with strong damage potential

• 23 tornadoes recorded since 1955

• All buildings at risk; however, not all buildings in county likely to be impacted in one tornado event

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Updated Information

• Hazard frequency tables

• Tornado scenario utilized to show potential damage

• Critical infrastructure data updated

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Previous Tornado Touchdowns

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Risk Assessment Results

• All of Chatham County at risk for up to an EF-5 tornado event

• Exercise:– Risk to people: low/med/high

– Risk to buildings: low/med/high

– Risk to infrastructure: low/med/hi

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Sample Tornado Track

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Impacted Properties from Tornado Scenario

Use Type Total Properties Total Value

Chatham County

Agricultural$109,179,020

Commercial52 $44,918,920

Historic

Industrial24 $80,125,010

Residential648 $64,623,300

Transitional

Utilities1 $47,713

V

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Rainwater Flooding

• Flooding can occur almost anywhere

• 43 percent of the county is in the100-year flood plain (1 percent chance of reaching flood elevation in any year)

• One quarter of critical infrastructure in the county is potentially affected by flooding

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Updated Information

• Repetitive Flood Loss Properties (RLs)

• Properties within flood plain identified

• Critical facilities within flood plain identified

• Current land and facility values updated

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Floodplain

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Risk Assessment

• 29,511 buildings/structures in the county within the 100-year floodplain, for a total value of almost $14 billion

• Exercise:– Risk to people: low/med/high

– Risk to buildings: low/med/high

– Risk to infrastructure: low/med/hi

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Critical Facilities in Relation to Floodplain

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Storm Surge

• Accompanies hurricanes & tropical storms

• Much of the county, particularly in coastal areas, is potentially exposed to storm surge

• SLOSH model is used to estimate storm surge

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Updated Information

• NHC SLOSH modeling maps, now including data for category 4 and 5 hurricanes

• Repetitive Loss Properties in storm surge zones

• Critical infrastructure and facilities identified

• Properties located within surge zones

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Potential Surge Zones

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Critical Facilities Located in Storm Surge Zones

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Risk Assessment

• $38 billion total value of buildings at risk

• Critical infrastructure affected

• Exercise:– Risk to people: low/med/high

– Risk to buildings: low/med/high

– Risk to infrastructure: low/med/hi

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Fire

• Fire was not addressed in 2005; is being added in update

• Need to incorporate data on fire occurrences & risk

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Risk Assessment Results

• Risk assessment: Fire

• Exercise:– Risk to people: low/med/high

– Risk to buildings: low/med/high

– Risk to infrastructure: low/med/hi

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Chapter 3

• New hazards being addressed in update: technological hazards– Hazardous materials incidents

– Terrorism

– Transportation incidents

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Hazardous Materials Incident

• Hazardous materials incidents are being incorporated into the mitigation plan update

• Hazardous materials can be explosives, flammable or combustible substances, toxic releases, & waste materials. They are most often released as a result of transportation accidents or in manufacturing or storage facilities.

• Can cause property damage & human health hazards, depending on substance

Scenario for discussion

A call was made to 911 around 2:30 on a Wednesday morning regarding a tractor trailer that was leaking a product and creating a cloud. The truck was at a truck stop on Hwy 21 in Port Wentworth at I-95. The truck was supposedly carrying a mild, non-toxic, non-caustic soap solution. One police officer was affected by the plume and was transported to the hospital for respiratory irritation. Hwy 21 (an artery into Savannah and a major trucking lane) was shut down for almost 3 hours while the incident was managed. Seventy-one people were evacuated, and one hotel was told to "protect in place".  

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Scenario continued

The product was actually a strong sodium hydroxide solution (caustic alkaline) that was reacting with the aluminum transportation tank holding the product. Sodium hydroxide causes burns, irritation, and can be toxic if inhaled on ingested.

This incident was no-fault to the driver. He was sleeping in the truck at the time. There was no act of negligence by anyone on-scene and no intent to harm (criminal act).

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Risk Assessment

• Risk assessment: hazardous material incident

• Exercise:– Risk to people: low/med/high

– Risk to buildings: low/med/high

– Risk to infrastructure: low/med/hi

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Terrorism

• Terrorism is being added to the mitigation plan update

• Hard to predict or gauge actual risk

• Fortunately, no historical data in Chatham County

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Risk Assessment

• Risk assessment: Terrorism

• Difficult to quantify risk because of range of possible incident types, locations & impacts

• Exercise:– Risk to people: low/med/high

– Risk to buildings: low/med/high

– Risk to infrastructure: low/med/hi

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Transportation Incident

• Transportation incident being incorporated into the mitigation plan update

• Chatham County has a range of transportation modes & hubs, including airports, rail, roadways, and the Savannah River

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Risk Assessment Results

• Risk assessment: Transportation incidents

• Exercise:– Risk to people:

low/med/high

– Risk to buildings: low/med/high

– Risk to infrastructure: low/med/hi

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Next Steps

• Incorporate additional local data

• Respond to Steering Committee, CEMA, county & municipal official, and public comments

• Capability Assessment Survey

• Chapters 4 and 5: Mitigation Strategies

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Important Dates

• Municipality Meetings – August 14

• Steering Committee Meeting #3 – September 15

• LEPC Meeting Presentation – September 16

• Review plan draft

• Steering Committee Meeting #4 – January 19– Project Closeout