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6.5.10 Geologic Hazards: Earthquakes and Sinkholes

6.5.10.1 Hazard Identifications

Descriptions of the Earthquake and Sinkhole Hazards

Earthquakes An earthquake is the motion or trembling of the ground produced by sudden displacement of rock in the Earth's crust. Earthquakes result from crustal strain, volcanism, landslides, or the collapse of caverns. Earthquakes can affect hundreds of thousands of square miles; cause damage to property measured in the tens of billions of dollars; result in loss of life and injury to hundreds of thousands of persons; and disrupt the social and economic functioning of the affected area.

Most earthquakes are caused by the release of stresses accumulated as a result of the rupture of rocks along opposing fault planes in the Earth’s outer crust. These fault planes are typically found along borders of the Earth's ten tectonic plates. These plate borders generally follow the outlines of the continents, with the North American plate following the continental border with the Pacific Ocean in the west, but following the mid-Atlantic trench in the east. As earthquakes occurring in the mid-Atlantic trench usually pose little danger to humans, the greatest earthquake threat in North America is along the Pacific Coast.

Sinkholes Sinkholes are a natural and common geologic feature in areas with underlying limestone and other rock types that are soluble in natural water. Most limestone is porous, allowing the acidic water of rain to percolate through their strata, dissolving some limestone and carrying it away in solution. Over time, this persistent erosional process can create extensive underground voids and drainage systems in much of the carbonate rocks. Collapse of overlying sediments into the underground cavities produces sinkholes. The three general types of sinkholes are: subsidence, solution, and collapse. Collapse sinkholes are most common in areas where the overburden (the sediments and water contained in the unsaturated zone, surficial aquifer system, and the confining layer above an aquifer) is thick, but the confining layer is breached or absent. Collapse sinkholes can form with little warning and leave behind a deep, steep sided hole. Subsidence sinkholes form gradually where the overburden is thin and only a veneer of sediments is overlying the limestone. Solution sinkholes form where no overburden is present and the limestone is exposed at land surface.

Severity of the Earthquake and Sinkhole Hazards

Earthquakes Earthquakes are measured in terms of their magnitude and intensity. Magnitude is measured using the Richter Scale, an open-ended logarithmic scale that describes the energy release of an earthquake through a measure of shock wave amplitude (see Table 6.5.10.1-1). Each unit increase in magnitude on the Richter Scale corresponds to a ten-fold increase in wave amplitude, or a 32-fold increase in energy. Intensity is most commonly measured using the Modified Mercalli Intensity (MMI) Scale based on direct and indirect measurements of seismic effects. The scale levels are typically described using roman numerals, with a I corresponding to imperceptible (instrumental) events, IV corresponding to moderate (felt by people awake), to XII for catastrophic (total destruction). A detailed description of

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the Modified Mercalli Intensity Scale of earthquake intensity and its correspondence to the Richter Scale is given in Table 6.5.10.1-2. Table 6.5.10.1-1 Richter Scale Richter Magnitude Earthquake Effects Less than 3.5 Generally not felt, but recorded. 3.5-5.4 Often felt, but rarely causes damage. At most slight damage to well-designed buildings. Can cause major Under 6.0 damage to poorly constructed buildings over small regions. Can be destructive in areas up to about 100 kilometers across where 6.1-6.9 people live. 7.0-7.9 Major earthquake. Can cause serious damage over larger areas. Great earthquake. Can cause serious damage in areas several hundred 8 or greater kilometers across.

Table 6.5.10.1-2 Modified Mercalli Intensity Scale for Earthquakes Corresponding Scale Intensity Description of Effects Richter Scale Magnitude I Instrumental Detected only on seismographs II Feeble Some people feel it <4.2 III Slight Felt by people resting; like a truck rumbling by IV Moderate Felt by people walking V Slightly Strong Sleepers awake; church bells ring <4.8 Trees sway; suspended objects swing, objects fall off VI Strong <5.4 shelves VII Very Strong Mild Alarm; walls crack; plaster falls <6.1 Moving cars uncontrollable; masonry fractures, poorly VIII Destructive constructed buildings damaged Some houses collapse; ground cracks; pipes break IX Ruinous <6.9 open Ground cracks profusely; many buildings destroyed; X Disastrous <7.3 liquefaction and landslides widespread Most buildings and bridges collapse; roads, railways, XI Very Disastrous pipes and cables destroyed; general triggering of <8.1 other hazards Total destruction; trees fall; ground rises and falls in XII Catastrophic >8.1 waves Source: North Carolina Division of Emergency Management.

As is discussed further in this section, the majority of occurrences of the earthquake hazard in the planning area were limited to a III or IV on the Mercalli Scale, indicating that they were slight or moderate, and were generally felt by

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people either at rest or engaged in walking. One incident was recorded as a V, which is strong enough to ring church bells and wake sleepers.

Based on the historical occurrences and the distance from identified fault lines, the planning area should expect to continue to experience the same range on the Mercalli Scale – III or IV, with the occasional V event.

Sinkholes Unlike other geologic hazards, no scale currently exists for measuring or determining the severity of sinkholes. However, it is possible to determine where sinkholes are possible to occur, based on the structure and condition of the earth in the area. Sinkholes are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by ground water circulating through them. As the rock dissolves, spaces and caverns develop underground. Sinkholes are dramatic because the land usually stays intact for a while until the underground spaces get too big. If there is not enough support for the land above the spaces, then a sudden collapse of the land surface can occur. These collapses can be small or they can be large, and they can occur under a house or road.

The figure below illustrates the formation of a typical sinkhole.

Figure 6.5.10.1-1 Typical Sinkhole Formation

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A significant number of sinkholes tend to occur in the years that follow a drought. When an area has a long-term lack of rain and water levels decrease, there’s usually a correlated link to an increase in incidences of sinkholes being reported. Historically, years where dry weather has been followed by wet weather have resulted in some of the greatest increases in sinkhole occurrences. Given that Texas is prone to periodic droughts – some of which can be exception - sinkholes are a geologic feature that can be expected to occur in the planning area. The planning area can expect to experience sinkholes from the very small to the very large, with the potential for significant property damage.

Impacts to People and Property from the Earthquake and Sinkhole Hazards

Earthquakes Most property damage and earthquake-related deaths are caused by the failure and collapse of structures due to ground shaking. The level of damage depends upon the amplitude and duration of the shaking, which are directly related to the earthquake size, distance from the fault, site and regional geology. Other damaging earthquake effects include landslides, the down-slope movement of soil and rock (mountain regions and along hillsides), and liquefaction, in which ground soil loses the ability to resist shear and flows much like quick sand. In the case of liquefaction, anything relying on the substrata for support can shift, tilt, rupture, or collapse.

Specific, local data is required to fully assess the potential impacts of earthquakes to the planning area. See Section 8 (Mitigation Action Plan) for action to address data deficiency.

Sinkholes Sinkholes occur in many shapes, from steep-walled holes to bowl or cone shaped depressions. Sinkholes are dramatic because the land generally stays intact for a while until the underground spaces get too big. If there is not enough support for the land above the spaces, then a sudden collapse of the land surface can occur. Under natural conditions, sinkholes form slowly and expand gradually. However, human activities such as dredging, constructing reservoirs, diverting surface water, and pumping groundwater can accelerate the rate of sinkhole expansions, resulting in the abrupt formation of collapse sinkholes. Although a sinkhole can form without warning, specific signs can signal potential development:  Slumping or falling fence posts, trees, or foundations;  Sudden formation of small ponds;  Wilting vegetation;  Discolored well water; and/or  Structural cracks in walls, floors. Sinkhole formation is aggravated and accelerated by urbanization. Development increases water usage, alters drainage pathways, overloads the ground surface, and redistributes soil. According to the Federal Emergency Management Agency (FEMA), the number of human-induced sinkholes has doubled since 1930, insurance claims for damages as a result of sinkholes has increased 1,200 percent from 1987 to 1991, costing nearly $100 million.

Specific, local data is required to fully assess the potential impacts of sinkholes to the planning area. See Section 8 (Mitigation Action Plan) for action to address data deficiency.

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Occurrences of the Earthquake and Sinkhole Hazards

Earthquakes Though earthquakes are not likely to affect Texas, their effects have been felt throughout history. Table 6.5.10.1-3 lists recorded earthquakes in the planning area. Because of the limited impact of sinkholes on the region, past occurrences and their probability have not been mapped.

Table 6.5.10.1-3 Recorded Earthquakes in the Planning Area Modified Date of Miles from Mercalli Intensity Location County Occurrence Epicenter (if known) 08/16/1931 III Fredericksburg Gillespie 512 08/16/1931 IV Hondo Medina 506 08/16/1931 III Jourdanton Atascosa 576 08/16/1931 V Karnes City Karnes 637 08/16/1931 IV New Braunfels Comal 593 08/16/1931 III Pearsall Frio 528 08/16/1931 IV San Antonio Bexar 564 06/20/1936 unknown San Antonio Bexar 718 07/23/1983 III Schertz Guadalupe 91 07/23/1983 III Campbellton Atascosa 16 03/03/1984 IV Christine Atascosa 7 03/03/1984 V Jourdanton Atascosa 11 03/03/1984 IV Pleasanton Atascosa 11 03/03/1984 IV Poteet Atascosa 24 03/03/1984 III Leming Atascosa 24 08/08/1984 IV Pleasanton Atascosa 23 Source: National Geophysical Data Center

No participants in the plan update reported experiencing any significant earthquake event in the previous 10 years.

Sinkholes The most well-known occurrence of a sinkhole in the State of Texas is in Rocksprings, located to the west of the planning area. This sinkhole is known as the Devil’s Sinkhole, or simply The Sinkhole, and is a National Natural Landmark. It was discovered by Anglo settlers in 1867. Currently, this sinkhole is a vertical cavern with an opening measuring approximately 40 feet by 60 feet, and a vertical drop to the main cavern of about 140 feet. The main cavern is circular and reaches a total depth of 350-400 feet.

The Bering Sinkhole (41KR241) in northwestern Kerr County is a natural sinkhole that was used as a cemetery by native peoples for over 5,500 years from the latter Early Archaic to the Late Archaic periods. Human remains and burial offerings from the sinkhole provide a glimpse of the health and beliefs of hunting and gathering peoples living in the central Edwards Plateau.

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The sinkhole was discovered by accident while brush was being cleared along the property line between two ranches in the central portion of the Edwards Plateau about 20 miles southeast from Junction. Sinkholes are fairly common on the Plateau—they form as solution cavities in porous limestone bedrock. In this case, the landowner found an oval- shaped opening measuring some 7by12 feet from which a dead tree protruded. Beneath this was a dark hole that proved to be a vertical shaft filled to within about 10 feet from the surface. To satisfy his curiosity, the landowner used a track hoe to probe into the fill from the opening above. Animal and human bones and several Indian artifacts were found in the soil removed from the sinkhole, prompting the landowner to contact area universities to find someone who could examine the finds. As a result, archeologists from the Texas Archeological Research Laboratory conducted hand excavations at Bering Sinkhole between 1987 and 1991.

In 2008, a massive sinkhole formed about 60 miles northeast of Houston, TX, in the Liberty County community of Daisetta. This community was built on top of a salt dome, which is a type of structural dome that is formed when a thick bed of evaporite minerals found at depth vertically intrudes into the surrounding strata. This zig-zagged shaped opening was estimated to be approximately 600 feet by 525 feet in diameter and 150 feet deep. It swallowed farm equipment, oil field equipment and utility equipment during its formation, and caused the termination of utilities in the area, including underground pipelines.

In 2010, a sinkhole threatened approximately 5 residential structures in the Rivermist subdivision in San Antonio. Though there was some damage, engineers were able to stabilize the area before any structures were destroyed.

Probability of Future Occurrences of the Earthquake and Sinkhole Hazards

Earthquakes Figure 6.5.10.1-2 shows the probability that ground motion will reach a certain level during an earthquake. The data show peak horizontal ground acceleration (the fastest measured change in speed, for a particle at ground level that is moving horizontally due to an earthquake) with a 10 percent probability of exceedance in 50 years. The map was compiled by the U.S. Geological Survey (USGS) Geologic Hazards Team, which conducts global investigations of earthquake, geomagnetic, and landslide hazards.

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Figure 6.5.10.1-2 Peak Acceleration with 10 Percent Probability of Exceedance in 50 Years

Source: U.S. Geological Survey.

Based on the USGS probability figure above, and using the established criteria described in the introduction to this section, the probability of a future earthquake event in the planning area is low.

Sinkholes The following image, produced by the US Geological Survey (USGS), illustrates the areas of the US that are prone to sinkhole development. Note that the planning area is defined as bring within an area prone to sinkhole development.

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Figure 6.5.10.1-3 Areas of the US Prone to Sinkhole Development

Source: US Geological Survey

Based on historic occurrences, the above image, and the ground conditions and periodic drought cycles that occur in the planning area, and using the established criteria described in the introduction to this section, the probability of a future occurrence of the sinkhole hazard is moderate.

Location and Extent of the Earthquake and Sinkhole Hazards

Sinkholes Sinkholes are of interest to Central and Western Texas because they are one of the predominant landform features of those areas of the state. Their development may be sudden and may result in property damage or loss of life. Sinkholes can vary greatly in both diameter and depth. Recorded occurrences have ranged from a few feet to more than 2,000 feet, both in depth and diameter. Portions of Gillespie, Kerr, Bandera, Medina, Frio, Comal, Bexar and Atascosa counties are located in karst regions, which are susceptible to cave and sinkhole development due to the geology and geomorphology of the area. However, limited property damage or loss of life due to sinkholes in these areas has been recorded. Given the geologic composition of the area, the planning area can expect to experience a variety of sinkholes, in varying depths and diameters.

At the time this plan update was developed there was no known source that could be used to map past occurrences, or to determine extent or probability of sinkholes. More information may be included in the five-year update of this plan. See the MAP in Section 9 for mitigation actions included to address this data deficiency.

Earthquakes The areas of greatest tectonic instability occur at the perimeters of the slowly moving plates, as these locations are subjected to the greatest strains from plates traveling in opposite directions and at different speeds. Deformation

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along plate boundaries causes strain in the rock and the consequent buildup of stored energy. When the built-up stress exceeds the rocks' strength, a rupture occurs. The rock on both sides of the fracture is snapped, releasing the stored energy and producing seismic waves, generating an earthquake.

Maps 6.5.10.1-1 through 6.5.10.1-10 illustrate the known fault lines in the planning area. No data was available for Kerr County; therefore, no map is included for this area. These are the most probable locations for an occurrence of the earthquake and sinkhole hazard. Maps 6.5.10-11 through 6.5.10.19 illustrate the potential for soil liquefaction.

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Map 6.5.10.1-1 Known Fault Lines in Atascosa County

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Map 6.5.10.1-2 Known Fault Lines in Bandera County

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Map 6.5.10.1-3 Known Fault Lines in Bexar County

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Map 6.5.10.1-4 Known Fault Lines in Comal County

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Map 6.5.10.1-5 Known Fault Lines in Frio County

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Map 6.5.10.1-6 Known Fault Lines in Gillespie County

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Map 6.5.10.1-7 Known Fault Lines in Guadalupe County

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Map 6.5.10.1-8 Known Fault Lines in Karnes County

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Map 6.5.10.1-9 Known Fault Lines in Medina County

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Map 6.5.10.1-10 Known Fault Lines in Wilson County

Maps 6.3.10-11 through 6.3.10-20 illustrate the soil makeup and potential for liquefaction in the planning area. No data was available for Bandera or Wilson counties; therefore, no maps are included.

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Map 6.5.10.1-11 Soil Liquefaction Potential in Atascosa County

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Map 6.5.10.1-12 Soil Liquefaction Potential in Bexar County

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Map 6.5.10.1-13 Soil Liquefaction Potential in Comal County

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Map 6.5.10.1-14 Soil Liquefaction Potential in Frio County

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Map 6.5.10.1-15 Soil Liquefaction Potential in Gillespie County

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Map 6.5.10.1-16 Soil Liquefaction Potential in Guadalupe County

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Map 6.5.10.1-17 Soil Liquefaction Potential in Karnes County

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Map 6.5.10.1-18 Soil Liquefaction Potential in Kerr County

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Map 6.5.10.1-19 Soil Liquefaction Potential in Medina County

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6.5.10.2 Risk Assessment

This subsection of the Plan Updates provides estimates of future losses from these geologic hazards, i.e. risk. Each of the loss calculations is based on best available data, but they must be considered estimates because highly detailed engineering was not performed as part of this planning process.

Methodology and Limitations

After discussion and review of the best available data regarding this hazard, and in consideration of the potential impacts of this hazard to the planning area, the EMC determined that the risk assessment should include both qualitative and quantitative analyses, to the extent possible, but that the quantitative analysis should be limited to earthquakes, which have a more definable hazard area.

Discussion indicated that while sinkholes are a concern and are a threat to the planning area, their area of impact relative to the planning are as a whole made them less of a concern, as did the lack of options to effectively mitigate the hazard. It was determined that, given the lack of ability to define specific areas of occurrence, no quantitative assessment would be performed.

Qualitative Each participating jurisdiction was asked to provide a qualitative risk assessment ranking regarding the earthquake and sinkhole hazards. (For definitions of these rankings, please see Table 6.4-1, earlier in this section.) The results of this assessment for earthquake are presented in the table below.

Table 6.5.10.2-1 Qualitative Risk Assessment Results – Geologic Hazards: Earthquakes Jurisdictions Ranking Jurisdictions Ranking Jurisdictions Ranking Hazards as Low Hazards as Moderate Hazards as High Bandera County Gillespie County City of San Antonio Atascosa County City of Bandera City of Fredericksburg City of Charlotte Bexar County Guadalupe County City of Christine City of Alamo Heights City of New Berlin City of Jourdanton City of Balcones Heights City of Schertz City of Lytle City of Converse City of Seguin City of Pleasanton City of Helotes Karnes County City of Poteet City of Kirby City of Karnes City of Pearsall City of Leon Valley City of Kenedy City of Live Oak City of Runge City of St. Hedwig City of Falls City City of Somerset Kerr County City of Terrell Hills City of Ingram City of Universal City City of Kerrville City of Von Ormy Medina County City of Windcrest City of Castroville Comal County City of Devine City of Garden Ridge City of Hondo City of Bulverde City of Natalia City of New Braunfels Wilson County

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Jurisdictions Ranking Jurisdictions Ranking Jurisdictions Ranking Hazards as Low Hazards as Moderate Hazards as High Frio County City of La Vernia City of Dilley City of Stockdale San Antonio River Authority

The results of this assessment for sinkholes are presented in the table below.

Table 6.5.10.2-2 Qualitative Risk Assessment Results – Geologic Hazards: Sinkholes Jurisdictions Ranking Jurisdictions Ranking Jurisdictions Ranking Hazards as Low Hazards as Moderate Hazards as High Bandera County Gillespie County City of San Antonio Atascosa County City of Bandera City of Fredericksburg City of Charlotte Bexar County Guadalupe County City of Christine City of Alamo Heights City of New Berlin City of Jourdanton City of Balcones Heights City of Schertz City of Lytle City of Converse City of Seguin City of Pleasanton City of Helotes Karnes County City of Poteet City of Kirby City of Karnes City of Pearsall City of Leon Valley City of Kenedy City of Live Oak City of Runge City of St. Hedwig City of Falls City City of Somerset Kerr County City of Terrell Hills City of Ingram City of Universal City City of Kerrville City of Von Ormy Medina County City of Windcrest City of Castroville Comal County City of Devine City of Garden Ridge City of Hondo City of Bulverde City of Natalia City of New Braunfels Wilson County Frio County City of La Vernia City of Dilley City of Stockdale San Antonio River Authority

Quantitative Each participating jurisdiction provided information regarding the location and type of critical facilities within their planning area. These facilities were mapped in relation to the Texas Earthquake Risk Zones provided by the Texas Hazard Mitigation Package (THMP) as shown in Figure 6.5.10.2-1. Relative risk areas defined by ground acceleration associated with earthquakes are categorized into 12 classes using the “natural breaks” method. This method defines classes based on natural groupings of data values; break points are identified by looking for patterns inherent in the data; then ranges are set where there are relatively big jumps in the data values. Given the lack of building specific data (only location and use type were available at this time) this analysis assumes that all facilities located within the Earthquake Risk Zones are potentially at risk from seismic activity. Table 6.5.10.2-3 lists the facilities at risk from earthquakes by jurisdiction.

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Figure 6.5.10.2-1 Texas Earthquake Risk Zones for the AACOG Planning Area

Source: Texas Hazard Mitigation Package Website

Table 6.5.10.2-3 Quantitative Risk Assessment Results – Earthquake Facilities in Zone Facilities in Zone Facilities in Zone Facilities in Zone Jurisdiction 2 4 6 8 1 – Fire Station 5 – Airport 1 – Airport 1 – Nursing Home 1 – Courthouse 2 – Fire Stations 3 – Schools 7 – Fire Stations 2 – Nursing 1 – Water Supply 1 – Hospital Homes Atascosa 6 – Nursing 1 – Police Station

Homes 1 – School 1 – Police Station 5 – Water Supply 1 – Power Plant 17 – Schools 8 – Water Supply 1 – City Hall 2 – Communications 5 – Communications 1 – Court 2 – Courthouses 2 – Day Care 4 – Courts 2 – Emergency 2 – Daycares Response 1 – Emergency 3 – Fire Bandera Response Departments 6 – Fire 1 – Hospital Departments 6 – Other 2 – Hospitals 2 - Schools 1 – Nursing Home 20 – Other 2 – Police Departments

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Facilities in Zone Facilities in Zone Facilities in Zone Facilities in Zone Jurisdiction 2 4 6 8 2 – Power Supply 6 – Schools 1 – Transportation 1 – Water Supply 12 – Airport 11 – Airports 8 – City Halls 3 – City Halls 27 – Communications 19 – Communications 4 – Corrections 3 – Corrections 3 – Courthouse 14 – Day Cares 27 – Day Cares 1 – Emergency 1 – Emergency Response Response 18 – Fire 46 – Fire Departments Department 6 – Fire Stations 19 – Fire Stations 13 – Hospitals 55 – Hospital 32 – Nursing 5 – Military Homes Bexar 136 – Nursing 9 – Other Homes 5 – Police 18 – Other Departments 16 – Police 3 – Police Stations Department 1 – Power Plant 24 – Police 4 – Power Supply Stations 6 – Public Works 16 – Power Supply 143 – Schools 11 – Public Works 3 – Stadiums 378 – Schools 19 – Water Supply 2 – Stadiums 5 –Town Halls 2 – Transportation 55 – Water Supply 5 – Airport 1 – Communications 1 – Courthouse 5 – Fire Stations 1 – Hospital Comal 11 – Nursing Homes 1 – Power Plant 38 – Schools 12 – Water Supply 5 – Airport 2 – Communications 1 – Courthouse Frio 3 – Fire Stations 3 – Hospitals 3 – Nursing Homes

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Facilities in Zone Facilities in Zone Facilities in Zone Facilities in Zone Jurisdiction 2 4 6 8 3 – Police Stations 1 – Power Plant 7 – Schools 4 – Water Supply 11 – Airports 1 – Courthouse 1 – Daycare 1 – Fire Department 5 – Fire Stations 1 – Hospital 8 – Nursing Gillespie Homes 10 – Other 1 – Police Department 1 – Power Supply 1 – Public Works 15 – Schools 2 – Water Supply 13 – Airport 1 – Airport 3 – Communications 1 – Water Supply 1 – Courthouse 13 – Fire Stations 1 – Hospital Guadalupe 11 – Nursing Homes 2 – Police Stations 4 – Power Plants 36 – Schools 11 – Water Supply 1 – Airport 5 – Airport 1 – City Hall 2 – City Halls 1 – Emergency 1 – Courthouse Response 5 – Daycares 2 – Fire Stations 1 – Emergency 1 – Nursing Home Response 1 – Other 1 – Fire 1 – Police Department Karnes Department 3 – Fire Stations 3 - Schools 3 – Hospitals 11 - Nursing Homes 10 – Other 2 – Police Departments 1 – Police Station 12 – Schools

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Facilities in Zone Facilities in Zone Facilities in Zone Facilities in Zone Jurisdiction 2 4 6 8 5 – Water Supply 6 – Unclassified 10 – Airport 1 – City Hall 6 – Communications 1 – Courthouse 9 – Daycares 5 – Fire Departments 8 – Fire Stations 2 – Fuel Supply 5 – Hospitals Kerr 11 – Nursing Homes 4 – Other 3 – Police Departments 1 – Police Station 3 – Power Supply 79 – Schools 4 – Transportation 3 – Water Supply 6 – Airport 1 – Communication 1 – Courthouse 6 – Fire Stations 1 – Hospital Medina 1 - Airport 6 – Nursing Homes 3 – Police Stations 22 – Schools 5 – Water Supply 2 – Airports 6 – Airports 2 - City Halls 2 – City Halls 8 – Communications 2 – Communications 10 – Day Care 1 – Courthouse 3 – Fire 10 – Day Cares Departments 3 – Fire Stations 5 – Fire Stations 5 – Fuel Wilson 2 – Nursing Distributors Homes 2 – Hospitals 3 – Other 3 – Nursing 1 – Police Homes Department 4 – Other 1 – Power 2 – Police Supply Departments 12 – Schools 1 – Power Supply

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Facilities in Zone Facilities in Zone Facilities in Zone Facilities in Zone Jurisdiction 2 4 6 8 15 – Water 20 – Schools Supply 11 – Water Supply

Given the lack of building specific data (only location and use type were available at this time) this analysis assumes that all facilities located within the planning area are potentially at risk from seismic activity. Table 6.5.10.2-4 lists the facilities at risk by jurisdiction.

Table 6.5.10.2-4 Quantitative Risk Assessment Results – Sinkhole Emergency Residential / Transportation / Jurisdiction Utilities Services Heavily Occupied Other 10 – Fire Station 9 – Nursing Home 1 – Courthouse 6 – Airport Atascosa 2 – Police Station 21 – Schools 1 – Power Plant

1 – Hospital 14 – Water Supply 3 – Emergency 3 – Hospitals 7 – Communications 1 – City Hall Response 1 – Nursing Home 2 – Power Supply 2 – Courthouses Bandera 9 – Fire 8 – Schools 1 – Water Supply 5 – Courts Departments 4 – Daycares 26 – Other 2 – Police 1 – Transportation Departments 2 – Emergency 68 – Hospital 46 – Communications 23 – Airport Response 168 – Nursing 20 – Power Supply 11 – City Halls 70 – Fire Homes 1 – Power Plant 7 – Corrections Department 521 – Schools 17 – Public Works 3 – Courthouse Bexar 19 – Fire Stations 5 – Stadiums 74 – Water Supply 5 – Military 21 – Police 41 – Day Cares 27 – Other Department 5 –Town Halls 27 – Police 2 – Transportation Stations 1 – Hospital 1 – Communications 5 – Airport 5 – Fire Stations 11 – Nursing 1 – Power Plant 1 – Courthouse Comal Homes 12 – Water Supply 38 – Schools 3 – Fire Stations 3 – Hospitals 2 – Communications 5 – Airport 3 – Police 3 – Nursing 1 – Power Plant 1 – Courthouse Frio Stations Homes 4 – Water Supply 7 – Schools 1 – Fire 1 – Daycare 1 – Power Supply 11 – Airports Department 1 – Hospital 1 – Public Works 1 – Courthouse Gillespie 5 – Fire Stations 8 – Nursing 2 – Water Supply 10 – Other 1 – Police Homes Department 15 – Schools

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Emergency Residential / Transportation / Jurisdiction Utilities Services Heavily Occupied Other 1 – Hospital 1 – Airport 13 – Airport 13 – Fire Stations 11 – Nursing 1 – Water Supply 1 – Courthouse 2 – Police Guadalupe Homes 3 – Communications Stations 36 – Schools 4 – Power Plants

11 – Water Supply 2 – Emergency 3 – Hospitals 5 – Water Supply 6 – Airport Response 12 - Nursing 3 – City Halls 1 – Fire Homes 5 – Daycares Department 15 – Schools 11 – Other Karnes 5 – Fire Stations 1 – Courthouse 6 – Unclassified 3 – Police Departments 1 – Police Station 5 – Fire 9 – Daycares 6 – Communications 10 – Airport Departments 5 – Hospitals 2 – Fuel Supply 1 – City Hall 8 – Fire Stations 11 – Nursing 3 – Power Supply 1 – Courthouse Kerr Homes Homes 3 – Water 4 – Other 3 – Police 79 – Schools Supply 4 – Transportation Departments 1 – Police Station 6 – Fire Stations 1 – Hospital 1 – Communication 7 – Airport 3 – Police 6 – Nursing 5 – Water 1 – Courthouse Medina Stations Homes Supply 22 – Schools 3 – Fire 20 – Day Cares 10 – Communications 8 – Airports Departments 2 – Hospitals 5 – Fuel 4 – City Halls 8 – Fire Stations 5 – Nursing Distributors 1 – Courthouse Wilson 3 – Police Homes 2 – Power Supply 7 – Other Departments 32 – Schools 26 – Water Supply

All critical facilities in the planning area are at risk from geologic hazards; however, it is not anticipated that many would actually be affected by geologic hazards, under the present conditions.

Data to collect in order to improve this methodology prior to the Plan Update includes:

Data regarding building construction (materials, protection systems, etc.)

Risk Assessment Conclusions

The geology of the planning area makes it vulnerable to sinkhole formation. However, when sinkholes do occur they tend to be relatively contained and small in size, in relation to the planning area, which limits the potential for damage from this hazard.

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A significant number of critical facilities within each jurisdiction fall within the various Earthquake Zones. Jurisdictions should consider an evaluation of these facilities to determine if mitigation actions are needed.

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