United Electric Cooperative Hazard Mitigation Plan Section 1: Introduction

Section 4: Identified Hazards and Risk Assessment Methodology
Natural hazards in northwest Missouri vary widely in regard to intensity, frequency and the scope of impact. Because of the large area United Electric serves and the extent of its assets in varying types of terrain and conditions, the cooperative is exposed to many hazards. Some, such as earthquakes and tornadoes, arrive with little to no warning, while others, such as floods and severe winter weather, provide a period of warning which allows for preparation. For all types of natural threats, hazard mitigation planning can lessen the negative impact regardless of onset time.

The following natural hazards have been identified as potential threats for the service region of United Electric:

• 
  Tornadoes
  
• 
  Thunderstorms, Hail and High Winds
  
• 
  Floods and Levee Failure
  
• 
  Severe Winter Weather
  
• 
  Earthquakes
  
• 
  Dam Failures
  
• 
  Wildfires
  

A number of hazards may be eliminated from consideration in the local plan due to Missouri’s geographic location and because of United Electric’s location within the state. The following hazards have been eliminated for United Electric’s plan:

• 
  Drought
  
• 
  Heat Wave
  
• 
  Land Subsidence
  
• 
  Landslide
  

Drought can impact northwest Missouri, but water availability does not have a direct impact on delivering electricity or other services for UEC. Heat wave has also been eliminated from consideration because although heat can increase electric usage and potentially tax the system, it does not directly damage the cooperative’s assets. The effect of heat wave on equipment should be considered a cascading event rather than damage caused by the hazard itself. Land subsidence and landslide have also been eliminated based on local soil structure categorization by USGS. Limestone, carbonate rock, salt beds and other naturally dissolving rock which are most susceptible to forming sinkholes and landslides do not form the basis of soil through United’s service region.

For the purpose of this risk assessment, the identified hazards for United Electric’s service area have been divided into two categories: historical and non-historical hazards.

Historical hazards are those hazards that previously had a measurable impact upon the service area. General damage costs and a chronology of occurrences are available. The associated vulnerability assessments utilize the number of events and cost of each event to establish an average cost per incident. For United Electric, hazards with historical data are tornado, thunderstorm/high wind/hail, flood and levee failure, severe winter weather, and wildfire.

Non-historical hazards are hazards with no previous record of impact upon the local service area. The associated vulnerability assessments for each of these hazards will have an occurrence probability of less than 1 % in any given year, but the extent of damage will vary considerably. For United Electric, hazards without historical data are earthquakes and dam failure.
Probability of Occurrence

A simple formula was used to determine the potential frequency of occurrences. For historical hazards, the number of recorded events for the service area was divided by the number of years of record. This number was then multiplied by 100 to provide a percentage. This formula was used to determine future probability for each hazard. For non-historical hazards, a probability of less than 1 % was automatically assigned because the hazard cannot be excluded from the possibility of occurrence. Likewise, when discussing the probable risk of each hazard based upon historical occurrences, the following scale was utilized:

• 
  Less than 1% chance of an event occurring in any given year.
  
• 
  1-10% chance of an event occurring in any given year.
  
• 
  10-99% chance of an event occurring in any given year.
  
• 
  Near 100% chance of an event occurring in any given year.
  

The number of occurrences was further refined to focus on damage-causing events. Those occasions which were known to cause damage were divided by the total number of recorded events to obtain a percentage of total storms which result in infrastructure damage. (Formula: Number of damage-causing events / total number of events = Percentage of occurrences which cause damage.) When exact figures were not available, estimates were developed based on United’s internal records.

The primary source of information on historic hazards was the National Climatic Data Center. This data is sorted on a county basis, with specific locations identified when applicable. United Electric serves a portion of eight different counties, but there are portions of each county, such as incorporated cities, that the cooperative does not serve. Some natural hazards, such as severe winter weather, extend over a broad geographic area while others are limited to specific locations.
Potential Extent of Damage

Vulnerability assessment matrices for each hazard are included on the following pages. These worksheets detail loss estimates for each hazard affecting the cooperative’s service area. Loss estimates were calculated using the asset summary created by internal United Electric records. Each hazard has a unique impact upon the service area, requiring each hazard to utilize a different valuation amount depending upon the level of impact. Non-historical hazards assume damage to all general assets. For historical hazards, assets were divided into two groups based upon historical impact which were utilized in the hazard damage analysis:

• 
  Overhead infrastructure assets and buildings
  
  • 
    Used for tornado damage assessments
    
  • 
    Valued at $430,000,000
    
• 
  Overhead infrastructure assets only
  
  • 
    Used for:
    
    • 
      Severe Thunderstorm/High Wind/Hail
      
    • 
      Flood
      
    • 
      Severe Winter Weather
      

• 
  Valued at $352,000,000
  

Historical hazards with recorded damages were used to identify an average cost per event. (Formula: Total cost of damages / total number of events = Average damage cost per event.) When discussing the extent of potential damages for all hazards, the following scale was utilized:

• 
  Less than 10% potential damages to total cooperative infrastructure
  
• 
  10-25% potential damages to total cooperative infrastructure
  
• 
  25-50% potential damages to total cooperative infrastructure
  
• 
  More than 50% potential damages to total cooperative infrastructure
  

For the purposes of this assessment, the data set for the last 10 years has been used. United Electric has electronic records of power outages beginning in 2000. Records from 2000 to 2005 are partially complete and records from 2006 to 2010 are complete. This makes it possible to gather information about outages related to natural disasters during this time period. Information about outages and damage prior to 2000 is on record, however, those files are not easily assessable and are incomplete. Concentrating on the last 10 years of natural hazards and related outages and damages over the eight-county region makes it possible to create a more accurate assessment of risk.

Regardless of hazard categorization, the following matrix (Table 1.6) will be utilized to identify the potential damage extent and likelihood of occurrence for each natural hazard type.

Table 1.6 Sample United Electric Cooperative Infrastructure Vulnerability Assessment Matrix Hazard: SAMPLE		Probability of Hazard Occurrence
		Less than 1% in any given year	1-10% chance in any given year	10- 99% chance in any given year	Near 100% probability in any given year
Potential Extent of Damage	Less than 10% of damage to system
	10-25% damage of system
	26-50% damage of system
	More than 50% damage of system

Natural hazard events occur without causing significant damage to the cooperative’s infrastructure in many instances. The more significant impact of natural hazard episodes comes in the form of reported customer outages. The infrastructure may not be significantly harmed by an ice storm, but may result in prolonged and widespread outages in the cooperative’s service area. In considering the potential impact of a hazard, loss of function provides a more concise picture for comparison of events and geographic regions of the state. This chart incorporates the probability of damage causing occurrence (Formula: Number of damage-causing events / total number of events = Percentage of occurrences which cause damage.) In addition to system damage, each hazard will be evaluated on the average number of reported or estimated outages per event occurrence. (Formula: Average number of outages reported or estimated / Total number of customers = Average percentage of outages reported per event)

Table 1.7 Sample United Electric Cooperative Service Interruption Vulnerability Assessment Matrix Hazard: SAMPLE		Probability of Hazard Occurrence
		Less than 1% in any given year	1-10% chance in any given year	10- 99% chance in any given year	> Near 100% probability in any given year
Potential Extent of Impact	Less than 10% of customers report outages
	10-25% of customers report outages
	26-50% of customers report outages
	More than 50% of customers report outages

Section 5: Risk Assessment

Outage information

United Electric has information for total outages related to major storm events; however, the cooperative does not have data available for individual outages related to each individual storm event. Table 1.8 shows the outage information for major storm events from 2006-2010.

Table 1.8	Outages for United Electric 2006-2010
Year		2006	2007	2008	2009	2010	Five-Year Average
Number of Outages		178	2,288	334	295	480	715
Number of Customers Affected		5,794	16,358	5,399	3,597	4,990	7,227
Consumer Hours		11,464	1,135,683	11,554	7,216	14,246	236,032
Consumer Minutes		687,880	68,141,007	693,288	432,966	854,758	1,416,979
Average Number of Consumers Affected		9,818	9,923	9,837	9,782	9,846	9,841
Source: UEC Internal Records

For these five years, an average of 7,227 customers lost power due to major storms. This figure accounts for approximately 70 % of United’s 10,000 customers. At this time, data is not available to find detailed information about how many outages a particular storm caused, so estimates will be used.

1. 
   Historical Hazards
   

Tornadoes

Throughout United Electric’s service territory, in the last 60 years there have been 143 tornadoes. Since 2000, there have been 14 distinct tornadoes in the eight-county area. Figure 3 provides a pictorial representation of recorded tornado touchdown sites and recorded paths from 1951 to 2010.

Figure 3 – Tornado map

The National Climatic Data Center provides information on a county basis, with specific locations identified when possible. As discussed previously, for the purposes of this assessment, the data set for the last 10 years has been used. From 2000 to 2010, the UEC service area in Missouri experienced 14 tornadic events. Using the methodology described in Section 4, the probability of a tornadic event in United Electric’s service area is 100 %. (14 events/10 years >100 %)

Table 1.9 provides a summary of event dates, location and EF-scale ratings of tornadoes from 2000 through 2010.

Table 1.9	UEC Tornadic Event Summary
Date		Location	EF Scale Rating
5/26/2000		Maryville	EF1
4/11/2001		Denver	EF 2
5/24/2004		Craig	EF1
5/24/2004		Stanberry	EF2
5/29/2004		Osborn	EF2
5/29/2004		Weatherby	EF4
5/29/2004		Plattsburg	EF1
5/29/2004		DeKalb	EF3
6/4/2005		Worth	EF1
6/4/2005		Gentry	EF1
6/4/2005		St. Joseph	EF0
3/20/2006		Fillmore	EF2
4/15/2006		Stewartsville	EF2
5/12/2010		Plattsburg	EF0
Source: NCDC

Based on the last 10 years of historical event records, the average tornado in the UEC service area was an EF1 rating. Detailed information on the extent of damages caused by individual storms is not available. No cooperative records indicate that a tornado caused considerable damage, reflecting that less than 10 % of UEC’s total overhead assets and building valuation. Table 1.10 demonstrates the probability in conjunction with the potential extent of damage.

Table 1.10 United Electric Cooperative Infrastructure Vulnerability Assessment Matrix Hazard: TORNADO		Probability of Hazard Occurrence
		Less than 1% in any given year	1-10% chance in any given year	10- 99% chance in any given year	Near 100% probability in any given year
Potential Extent of Damage	Less than 10% of damage to system
	10-25% damage of system
	26-50% damage of system
	More than 50% damage of system

When compared with the total number of customers served by the cooperative, it can be projected that less than 10 % of customers may report outages during any given tornadic event. Table 1.11 demonstrates the probability of occurrence, with the potential impact on customers.

Table 1.11 United Electric Cooperative Service Interruption Vulnerability Assessment Matrix Hazard: TORNADO		Probability of Damage-Causing Hazard Occurrence
		Less than 1% in any given year	1-10% chance in any given year	10- 99% chance in any given year	> Near 100% probability in any given year
Potential Extent of Impact	Less than 10% of customers report outages
	10-25% of customers report outages
	26-50% of customers report outages
	More than 50% of customers report outages