Final Report

Pueblo Airport Generation Site Risk Analysis

Black Hills Electric Corporation Colorado PUC E-Filings System

November 25, 2014

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Final Report

Pueblo Airport Generation Site Risk Analysis

Black Hills Electric Corporation

November 25, 2014

This report has been prepared for the use of the client for the specific purposes identified in the report. The conclusions, observations and recommendations contained herein attributed to Leidos constitute the opinions of Leidos. To the extent that statements, information and opinions provided by the client or others have been used in the preparation of this report, Leidos has relied upon the same to be accurate, and for which no assurances are intended and no representations or warranties are made. Leidos makes no certification and gives no assurances except as explicitly set forth in this report. © 2014 Leidos, Inc. All rights reserved.

Pueblo Airport Generation Site Risk Analysis Black Hills Corporation

Table of Contents Letter of Transmittal Table of Contents List of Tables List of Figures

Section 1 INTRODUCTION AND PURPOSE ...... 1-1

Section 2 PAGS POWER PLANT FACILITIES ...... 2-1 2.1 Existing PAGS Power Plant...... 2-1 2.2 Approved PUC Expansion – Future Generation ...... 2-1 2.3 Future Generation ...... 2-1

Section 3 LOCATION RISK ...... 3-1 3.1 Extreme Seismic and Weather Events ...... 3-1 3.1.1 Earthquake (Seismic) ...... 3-1 3.1.2 Tornado ...... 3-1 3.1.3 Ice Storm ...... 3-1 3.1.4 Flooding ...... 3-2 3.2 Substation Interconnection ...... 3-2 3.3 Generation Planning Constructability Review ...... 3-3 3.4 Environmental and Regulatory Risks ...... 3-3 3.5 Gas Supply ...... 3-5 3.5.1 Gas Supply Characteristics ...... 3-6 3.5.2 Future Expansion ...... 3-6 3.6 Water Supply ...... 3-7

Section 4 TRANSMISSION SYSTEM INTEGRATION & STABILITY ...... 4-1 4.1.1 Transmission System Reliability ...... 4-1 4.1.2 100 MW Generation Deployment Scenarios ...... 4-1 4.1.3 Interconnection Studies ...... 4-1 4.1.4 Regional Transmission System Issues ...... 4-2 4.1.5 Existing Site Substation and Expansion ...... 4-3

Section 5 CONCLUSIONS ...... 5-1 5.1 Weather ...... 5-1 5.2 Natural Gas Supply ...... 5-1 5.3 Transmission and Interconnection ...... 5-1 5.4 Environmental ...... 5-2 5.5 Water Supply ...... 5-3

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Table of Contents

List of Appendices A Earthquakes and Extreme Weather

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Table of Contents

List of Tables

Table A-1 Other Extreme Weather Events ...... A-23 Table A-2 Historical Tornado Events ...... A-24

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Table of Contents

List of Figures

Figure 2-1: Pueblo Airport Generating Station Vicinity Map ...... 2-2 Figure 2-2: Pueblo Airport Generating Station Property Boundary ...... 2-3 Figure 2-3: PAGS Site Plan ...... 2-4 Figure 2-4: Pueblo Airport Generating Station Google Image ...... 2-5 Figure 3-1: Pipeline Future Expansion ...... 3-7 Figure A.2: Colorado Seismic History Map ...... A-1 Figure A.3: U.S. Seismic Hazard Chart ...... A-1 Figure A.4: Isoeismal Map ...... A-3 Figure A.5: States with the Most Quakes ...... A-4 Figure A.6: Magnitude Scale and Designation ...... A-16 Figure A.7: Average Annual Number of Tornadoes 1991-2010 ...... A-20 Figure A.8: Annual Tornado Map 1955 ...... A-21 Figure A.9: Annual Tornado Map 1993 ...... A-21 Figure A.10: Annual Tornado Map 2003 ...... A-22 Figure A.11: Maximum Ice Severity Levels for the Western Part of the United States ...... A-25 Figure A.12: Ice Event Map for the Western Part of the United States ...... A-26 Figure A.13: Arkansas River at Avondale ...... A-29 Figure A.14: Arkansas River Floodplain ...... A-29

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Section 1 INTRODUCTION AND PURPOSE

Black Hills/Colorado Electric Utility Company L.P. ( “Black Hills”) contracted with Leidos Engineering LLC (“Consultant”) to prepare a “Risk Assessment” associated with Black Hills proposed expansion of the Pueblo Airport Generating Station (“PAGS”). The PAGS facility is operated by Black Hills Corporation and serves the load serving entity of Black Hills Energy in the Pueblo, Colorado community. PAGS is currently a nominal 380 MW power plant located one mile and a quarter west of the runway at the Pueblo, Colorado Airport. The purpose of this report is to address the Colorado Public Utilities Commission’s (“PUC”) direction in Docket 0445E, 0446E and 0447E, Stipulation and Settlement Agreement, November 7, 2013, that Black Hills shall “study and address the issue of location risk and mitigation of any such risk” in conjunction with a proposal to expand the generation at PAGS beyond the previously approved plan to install a new LM6000 at the PAGS site.

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Section 2 PAGS POWER PLANT FACILITIES

2.1 Existing PAGS Power Plant The existing PAGS facility is situated on a 240 acre site located near Pueblo, Colorado as shown in Figure 2-1. PAGS consists of two simple cycle and two combined cycle generating units with a total nominal capacity of approximately 380 MW that began commercial operation on January 1, 2012. Units 1 and 2 are General Electric (GE) model LMS100 units each rated at 90 MW at ambient temperature of 95°F. Units 3 and 4 are GE model LM6000 combined cycle units in a 2x1 configuration, each with a capacity of 100 MW, at ambient temperature of 95°F. Figures 2-2 and 2-3 illustrate the layout of the PAGS generating facility in relation to the existing 240 acre site. Figure 2-4 is Google Map photo of the site and facilities. Gas supply to the PAGS site is delivered via two 12-inch gas lines which connect to CIG. Water supply to the PAGS site is delivered via two 16-inch water lines that feed the site from two different City of Pueblo (“City”) pressure zones to provide additional water system reliability. PAGS is electrically interconnected to the region grid via the existing on-site Baculite Mesa 115 kV Substation which is shown in Figure 2-3. This substation is a breaker and one-half configuration with two normally energized buses. The configuration includes one open bay that can accommodate additional new generation. The substation has five 115 kV transmission lines terminating at that site.

2.2 Approved PUC Expansion – Future Generation Black Hills has filed and received approval from the PUC to add an additional LM6000 combustion turbine to the PAGS site. This new unit is currently planned to be installed on the south side of the two existing combined cycle units, as shown on Figure 2-3.

2.3 Future Generation In response to its All Source Resource Acquisition in Phase II of its 2013 Electric Resource Planning proceeding, Black Hills is considering the potential addition of approximately 60 MW of renewable generation, in order to satisfy renewable portfolio standards (“RPS”) prescribed by the PUC and to satisfy future Black Hills generation resource needs. This new renewable generation may utilize adjacent property to the PAGS site.

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Section 2

Figure 2-1: Pueblo Airport Generating Station Vicinity Map

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PAGS POWER PLANT FACILITIES

Figure 2-2: Pueblo Airport Generating Station Property Boundary

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Section 2

Figure 2-3: PAGS Site Plan

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PAGS POWER PLANT FACILITIES

Figure 2-4: Pueblo Airport Generating Station Google Image

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Section 3 LOCATION RISK

3.1 Extreme Seismic and Weather Events

3.1.1 Earthquake (Seismic) The 2014 United States Geological Survey (“USGS”) web site and associated database was used to evaluate and compare the degree of risk associated with the PAGS site. Several maps and charts are located in the appendix and will be references in this section. Based on our analysis, the location risk associated with Seismic Events for the proposed expansion of the PAGS site is low. Overall, Colorado ranks 14 in the U.S. for earthquakes but the frequency is very low. The PAGS site clearly is not associated with a defined and probable risk for the earthquakes. It should also be noted that two of the most significant seismic events were closely associated with human events; although geologists could not conclude that the seismic events at the Rocky Flats and Trinidad were “caused” by manmade events they did not rule this out.

3.1.2 Tornado Several sources were used to determine the historical tornado events near the PAGS site and understand the risk. The National Oceanic and Atmospheric Administration (“NOAA”) U.S. Tornado Climatology records and history was analyzed. This data provides a very good summary and mapping of tornado frequency and is included in the Appendix A. The PAGS site falls at least 30 miles west of most of the historical tornadoes near Pueblo Colorado that were large enough to present a risk to property. The data clearly indicates that the PAGS site historically has not been a location with tornado risk. The NOAA tornado database includes maps from 1952-2011 showing the location of tornadoes in the U.S. These maps were reviewed and demonstrate that very few, if any, tornadoes have occurred near the PAGS site. Most of the tornadoes have been located east of the PAGS site a safe distance. Although the existence of tornadoes of lower magnitude have been sighted, they are not defined as a significant threat. An example of some of the maps are included in the Appendix A. Therefore, based on extreme storm events in the category of tornados, the PAGS site would rank low in terms of risk.

3.1.3 Ice Storm Ice storm risk was evaluated through several sources of analysis. The NOAA database was used along with the Electric Power Research Institute (“EPRI”) reports on ice

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storm classification. The PAGS site and the surrounding Pueblo area is classified as a very low threat for ice storm damage or zero threat based on the historical incidents, as documented in the EPRI Report TR-106762-Ice Storm Database and Ice Severity Maps” published in September of 1996. According to this extensive analysis, the PAGS site would be classified as a zero for the U.S. Ice Severity Map and a level 2 for the “Maximum” Ice Severity Map. Based on this analysis, the PAGS site would represent a very low or almost non- existent risk to ice storm damage.

3.1.4 Flooding For all the extreme storm classifications evaluated near the PAGS site, flooding represented the most significant based on historical data and extreme weather analysis. There have been extreme floods in 1904, 1921 and 1965 that resulted in substantial property loss and deaths near Pueblo. Appendix A (subsection A.8) provides a listing of Colorado floods. This listing does not include the flooding that occurred in Colorado during 2013. PAGS lies directly north of the Arkansas River approximately 3.5 miles. The altitude of the Arkansas River directly south of the PAGS plant is 4604 FASL. The altitude of the PAGS Plant is 4687 FASL. The city of Pueblo, Colorado lies at the foothills of the Rocky Mountains. Flooding in and around Pueblo occurs from the western Rocky Mountains to the eastern Plains in a west to east drainage direction along the Arkansas River. The Arkansas River winds its way in almost a direct west to east path. The flood stage gage height is 10 feet at the Arkansas River and the highest recordable gage height was not more than 17 feet. This is 4.88 times the highest recorded flood gage height. U.S. Highway 50 that is an east to west highway approximately one half mile north of the Arkansas River also separates the PAGS site from the Arkansas River floodplain. According to the FEMA flood map, the PAGS site lies outside of the 100-year flood zone in an area classified as “areas of minimal flood hazard”. It should be noted that the Pueblo Reservoir is designed to mitigate flooding and was constructed to address the historical floods noted. Evaluation of flood history pictures and NOAA data suggests that the PAGS site and the Baculite Mesa substation are located at an elevation that would be well above the flood level in the area. The data and evaluation also suggests that this location may be ideal for flood avoidance and represents a low risk for flooding. It should be noted that the FEMA map includes a flood zone arroyo extending north to south across the PAGS main road entrance; however, the PAGS site has two additional entrance points so access to the site would still be possible.

3.2 Substation Interconnection Interconnection of new generation at the PAGS site to the existing Baculite Mesa 115 kV Substation provides opportunity to effectively and efficiently control and monitor generation at a single location, while minimizing operation and maintenance

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LOCATION RISK manpower that may be necessary for a separate site location. To assure that interconnections at the Baculite Mesa substation satisfy electric system reliability and system stability requirements new interconnections are evaluated under Black Hill’s Large Generator Interconnection Procedures (“LGIP”), which is discussed in Section 4 of this report. This interconnection review process rigorously reviews the impacts, defines upgrade requirements and analyzes system stability issues to assure that interconnection risks are mitigated as part of the approval process.

3.3 Generation Planning Constructability Review The existing PAGS site offers a number of features that would benefit the development of a new generation at the site. These features include:  The existing generation complex and layout on the site provide adequate space to add one or more gas turbines on the site (see Figures 2-2, 2-3 and 2-4).  Adjacent property to the PAGS site provides opportunity to develop additional generation whether it is gas generation or renewables.  The existing PAGS site has a sufficient amount of property owned by Black Hills as well as adjacent property that could be used for temporary storage laydown of equipment.  Pueblo has population of 108,000 people and over 25 hotels that could support smaller construction projects associated with PAGS generation expansion.  Local construction labor coupled with available labor from the Colorado Front Range would adequately support the required construction labor.  The current PAGS site has at least three access points. Site access is not expected to be a problem with planned expansion and may include a fourth access point depending on the future layout of any PAGS expansion. Based on these features, the PAGS does not present any significant constructability risks associated with new generation additions being planned.

3.4 Environmental and Regulatory Risks In general, the overall location risk for the PAGS site from an environmental standpoint is low due to the existing industrial activity and disturbed nature of the site. The phase I Environmental Site Assessment dated November 20, 2009, prepared by URS, did not identify any recognized environmental conditions for the PAGS site. Adjacent parcels, which could be used for wind or solar PV generation, would have a somewhat higher environmental risk associated with location due to the undisturbed nature of the sites. These risks can be mitigated by the pre-construction wildlife and cultural resource surveys and wetlands/waters of the U.S. investigations that would be a part of the siting process. A measure of the air quality of a region is whether the National Ambient Air Quality Standards (“NAAQS”), which are federal clean air standards set by the U.S. Environmental Protection Agency as required by the Clean Air Act for pollutants considered harmful to public health and the environment, are

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being met. Pueblo County is currently designated as attainment/unclassifiable for all criteria pollutants as per 40 CFR Part 81. The permitting and regulatory requirements risks associated with new generation development at the PAGS site would be different for natural gas-fired generation versus renewables. One of the main permits required for natural gas-fired generation would be the air quality construction permit. This permit is required before construction can be commenced on a new unit addition to the existing power plant, and would likely be permitted as a major modification under the New Source Review permitting program. Specifically the Prevention of Significant Deterioration (“PSD”) program is applicable because the Pueblo County is currently designated as unclassifiable or attainment for the NAAQS. The requirements of the PSD program include applying the Best Available Control Technology and demonstrating compliance with ambient air quality standards through a dispersion modeling analysis, such as was conducted for the existing PAGS units. The results of such analyses for the proposed expansion are unknown. The timeframe for obtaining a PSD permit is typically around one year, this duration is workable with the current Black Hills Energy resource plan. As renewable energy projects such as PV solar and wind do not generate air emissions, such permitting and analyses are not required; however, a dust control plan/approval will be required prior to land disturbing activities. This type of approval is generally ministerial in nature. For solar and wind energy generating facilities with a generating capacity greater than two megawatts, a 1041 Permit from Pueblo County is required. The permit application requirements for this permit include detailed information addressing environmental impacts, such as potential impacts to wildlife and historical or archeological sites. Typically in order to guide the siting process, solar and wind energy projects include pre-construction surveys and consultation with state and federal agencies regarding sensitive species and their habitats, such as threatened and endangered species, as well as wetlands and jurisdictional waters. Appropriate surveys would need to be conducted that could reveal risks currently unknown. Maps available on the Pueblo County web site indicate the PAGS site and adjacent properties are not located in a potential conservation area or wetland or riparian zone, although several arroyos draining to the Arkansas River are present. The existing PAGS site required coverage under a U.S. Army Corps of Engineers Nationwide Permit (“NWP”). Additional development on the existing PAGS site would not be expected to require such coverage, while a wind or solar project on adjacent properties may require a permit as there are several arroyos that drain to the Arkansas River. Coverage under a NWP can usually be obtained quickly, while an Individual Permit is a more involved, longer process. Thus, if impacts are over the thresholds to qualify for a NWP this could present a risk for a solar project. Mitigation would include avoiding some or all impacts; however, this would affect the overall project footprint. Specifically for a wind energy project, it would be prudent for the developer to follow the U.S. Fish and Wildlife Service (“USFWS”) “Land-based Wind Energy Guidelines” (WEG) published in March 2012. The WEG are intended to guide

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LOCATION RISK developers and wildlife agencies using a five-tiered approach that provides a detailed framework for evaluating impacts on species and habitat, beginning with site evaluation and continuing through post-construction studies. Following the WEG is voluntary and does not relieve a project proponent from responsibility to comply with the regulations or preclude enforcement, but as stated in the Guidelines “…if a violation occurs the Service will consider a developer’s documented efforts to communicate with the Service and adhere to the Guidelines.” In April 2013, the USFWS issued the “Eagle Conservation Plan Guidance,” which is a supplement to the WEG that specifically addresses bald and golden eagles. USFWS recommends preparation of site-specific plans that outline a project’s actions applying the documents, referred to as Bird and Bat Conservation Strategies and Eagle Conservation Plans, which can be stand-alone documents or combined. Discharges of storm water from the site during construction should qualify for coverage under the general permit, which requires preparation of a Storm Water Pollution Prevention Plan including best management practices for controlling runoff. If the project construction site exceeds one acre in size, coverage is required under the storm water general permit. Colorado does not require an Industrial Storm Water permit for natural gas combined cycle combustion turbine projects (natural gas steam generating units). Water is supplied to the site under a Water Supply Agreement with the City of Pueblo as described in Section 3.6 below. Currently the PAGS site does not discharge wastewater off-site, but utilizes a wastewater treatment system and an evaporation pond. Wastewater discharge associated with new natural gas-fired generation would also go to the evaporation pond and would be very small in quantity as compared to the existing PAGS units.

3.5 Gas Supply Black Hills currently uses a combination of delivered natural gas supply from Cross Timbers and firm interstate pipeline transportation contracts on CIG to serve the existing PAGS units. There are currently three pipeline contracts that are being used to supply the PAGS facilities:  New interstate pipeline transportation capacity acquired directly from CIG.  Interstate pipeline transportation capacity included with the natural gas fuel supplied by Cross Timbers  Interstate pipeline transportation capacity redesignated from existing transportation agreements between Black Hills Utility Holdings (“BHUH”) and CIG currently used to serve Colorado Gas. The first delivery contract is the CIG transportation agreement which reserves 13,000 Dth/Day of capacity on CIG’s Raton line for deliveries from CIG’s North Raton Lateral. The specific receipt point (Purgatoire) is in the Raton production basin in southern Colorado. The delivery point for this pipeline capacity is at the CIG

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lateral connecting PAGS to the Raton line. CIG designates this delivery point as the Black Wolf Delivery Point. Black Wolf is a new delivery point on CIG’s system. The second contract for interstate pipeline capacity is included with the natural gas supply to be delivered by Cross Timbers directly at CIG’s Black Wolf Delivery Point. Accordingly, by purchasing the natural gas supply at that delivery point, there will be no need to purchase additional interstate capacity to transport supply to PAGS. The third contract for interstate pipeline transportation capacity comes from an amendment to the existing interstate natural gas transportation agreement between Black Hills and CIG. The amendment permits Black Hills to extend delivery of up to 47,000 Dth/Day of the existing interstate transportation pipeline capacity originally obtained for delivery of natural gas to Colorado Gas customers at various points in Colorado. Gas Supply Services, a BHUH subsidiary, sought an amendment from CIG of the existing BHUH and CIG pipeline agreements to provide for new service for PAGS at CIG’s newly created Black Wolf delivery point. Sharing this restructured interstate pipeline transportation capacity will benefit customers of both Black Hills and Colorado Gas.

3.5.1 Gas Supply Characteristics As shown in Figure 3-1 the PAGS project is located at or near the “Null” point on CIG’s North Raton Lateral (Line Segment 255). Natural gas typically flows north to south (i.e., from CIG’s Cheyenne Hub down to Pueblo, Colorado) on CIG’s system. “Near Pueblo” is the current delivery point where gas may flow south to north on CIG. Gas Supply Services worked closely with CIG to establish improvements needed on the CIG pipeline system to ensure the minimum natural gas pressure requirements needed at the PAGS facilities. As with any gas power plant, compressors could be added at the PAGS site, if needed in the future.

3.5.2 Future Expansion The addition of more generation at PAGS could require Black Hills to purchase additional interstate pipeline capacity from CIG. The pipeline has hourly requirements which dictate the most cost effective approach for gas supply to the site. Depending on the size of new gas generation additions at PAGS, CIG may need to expand its pipeline. These options were previously evaluated in 2006 by Black Hills and could be reexamined if needed.

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LOCATION RISK

Figure 3-1: Pipeline Future Expansion

3.6 Water Supply To support the development and operation of PAGS, Black Hills initially entered into a contract with the Board of Water Works of Pueblo, Colorado that represents the water interests of the City of Pueblo (“City”). This water agreement (“Agreement”) for the PAGS plant was executed on March 16, 2010 in support of the PAGS planned Commercial Operation Date of June 1, 2011. The Agreement includes provisions for water supply up to 2530 acre-feet per year and a maximum of 2000 gallons per minute (gpm). The term of the Agreement is 10 years with options to extend the Agreement for at least ten (10) years commencing January 1, 2032 if Black Hills provides notification per the Agreement by January 1, 2031. Additional 10 year options are also included as requested by Black Hills extending to December 31, 2051. The Agreement also includes provisions for Black Hills to construct additional future generation in or near the City for expansion purposes. The Agreement includes provisions to modify the Agreement after some period of operation. In accordance with this provision, Black Hills reduced the annual minimum water consumption amount to 1440 acre-feet per year for calendar years starting in 2015. This reduction was based in part on plant historical water consumption over the initial three years of operation and aligns with the “as-built” water requirements for the PAGS facilities.

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Based on water use data provided by Black Hills for the overall PAGS facilities, the current maximum water consumption at 95°F ambient temperature and full load operation of all existing units is estimated at 1,467 gpm. Average water consumption, assuming annual average meteorological conditions is estimated at 915 gpm or 1,475 acre-feet per year. Addition of new gas fired generation, in the form of one or two LM6000 units operating in simple cycle operating mode, would have little or no effect on the overall water consumption, assuming the use of dry low NOx combustion systems, no inlet chilling, no performance enhancements (GE’s SPRINT™ system) and no inlet evaporative cooling. If Black Hills deploys inlet chilling systems, SPRINT™ systems or evaporative systems, on one or two LM6000 units, this will increase the maximum water requirements during summer operations but it is not expected to have a noticeable impact on overall operations. This possible water consumption increase is expected to be within the current water supply operating margins of the PAGS facility. Renewable energy projects would have little impact on water requirements. Both solar and wind power generation facilities do require small amounts of water for cleaning but this is not needed continuously or at peak load times, and such water consumption is not expected to impact the PAGS water requirements under the Agreement. As part of the Agreement, the City and Black Hills agreed to construct an “emergency, standby pump station” to address unforeseen water supply conditions and to improve water system reliability. This emergency standby pump station was completed and is now in service. Based on the water consumption for the existing PAGS facilities and assuming that new gas fired generation would be constructed similar to the existing facilities, the provisions of the existing water supply Agreement with the City are adequate and reasonable. Based on these findings, the water supply risks for the addition of new gas-fired generation and/or renewable generation at PAGS are considered low.

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Section 4 TRANSMISSION SYSTEM INTEGRATION & STABILITY

4.1.1 Transmission System Reliability Black Hills, as a transmission provider, currently has three executed Interconnection Agreements (“IAs”) with Black Hills, as a utility generator owner, and Black Hills Colorado IPP, LLC for 400 MW of installed and operating generation including two natural gas-fired combined cycle units and two LMS-100 units at PAGS. Black Hills, as a transmission provider, has an executed IA with itself, as the generator owner, an additional 100 MW of not yet installed generation for a total installed capacity of 500 MW at the site. There are no specific build-out plans- the additional capacity could be natural gas-fired generators, renewables, or a combination of the two. Black Hills received approval from the Public Utilities Commission (“PUC”) to construct a 40 MW LM6000 unit to replace the 42 MW (total) Clark Station coal units, leaving 60 MW of unplanned interconnection capacity under the IA. This report section addresses the interconnection and transmission risks associated with the build out of the additional 100 MW at the PAGS site not yet installed under the existing IA.]

4.1.2 100 MW Generation Deployment Scenarios There are multiple scenarios for the additional 100 MW build-out and these include:  40 MW LM6000 (already planned and approved by the PUC).  Remaining 60 MW of the 100 MW.  60 MW renewables only.  60 MW all natural gas.

4.1.3 Interconnection Studies Per the provisions of the Black Hills Colorado Transmission (“BHCT”) tariff, each proposed project must go through the interconnection study process as outlined in the Large Generator Interconnection Procedures (“LGIP”) to analyze the impacts to the transmission system. The Black Hills Transmission Planning Group (“BHTPG”) performs these studies and coordinates with interconnection customers through Black Hills’ FERC Tariff Administration group. Black Hills filed an interconnection request (queue position G6) on November 11, 2010 for the interconnection of a 100 MW LMS-100 to the Baculite Mesa 115 kV Substation. Black Hills requested to bypass the Feasibility Study (“FeS”) and proceed directly with a System Impact Study (“SIS”) and subsequent Facility Study (“FS”). The SIS was completed on May 17, 2011 analyzing the steady state, transient stability and short circuit analysis, along with definition of required network upgrades to mitigate any adverse impacts on

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Section 4 the BHCT system with the interconnection of the project. The SIS concluded there was approximately 65 MW available for interconnection that required no additional network upgrades to be performed. To enable the full 100 MW, Black Hills would be required to provide the following network upgrades:  Changing the Boone to DAT Tap 115 kV line multi-ratio current transformer (“MRCT”) ratio.  Replace the 336 ACSR conductor spans on the Overton to Northridge 115 kV transmission line.  Replace limiting facilities at the Northridge 115 kV substation terminal equipment and substation bus. Rebuild the 4-mile Baculite Mesa to Overton 115 kV line. Per the SIS, Black Hills could choose to implement a remedial action scheme (“RAS”) to reduce the generation from 100 MW to something less during critical contingency events rather than perform the upgrades identified above. These upgrades will be required to interconnect the 100 MW of generation requested by Black Hills as well as meet load serving and reliability needs. Because the SIS and the FS was conducted for a 100 MW LMS-100 unit, which is greater than the PUC-approved 40 MW LM6000 unit, Black Hills has indicated the SIS and FS would not be required to be updated to analyze the transient stability for the LM6000 unit based on system performance and results from other transmission planning studies. With respect to the remaining 60 MW of the 100 MW capacity previously studied further system impact studies will likely not be needed based on the technology deployed (natural gas, solar, wind etc.). At a minimum, the network upgrades identified in the list above will be required. In addition, should Black Hills propose renewables as the generation addition, only a transient stability analysis may be required to confirm performance, of any low voltage ride-through (LVRT) and reactive power controls. If Black Hills decides to install more than 60 MW, in addition to the LM6000 unit, a new LGIA request would be required for the incremental capacity above the exiting 100 MW request.

4.1.4 Regional Transmission System Issues Pursuant to the SIS, FS and discussions with BHTPG, the following are observations regarding the regional area transmission system:  There are no significant transient stability issues near PAGS or on the Black Hills transmission system.  Annual stability analysis conducted by BHTPG shows that a Category D failure of the Baculite Mesa Substation (outage of main substation) still permits full deliverability of the power to Pueblo.  For the addition of solar or wind, there are likely no transient/stability issues but LVRT controls may be required.

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TRANSMISSION SYSTEM INTEGRATION & STABILITY

In addition to the interconnection evaluations and procedures summarized above, BHTPG annually conducts system contingency analyses of the overall regional network of transmission lines and substation. Such analyses evaluate the potential loss of major substations, such as Baculite Mesa, and the impacts of such loss in serving the local loads.

4.1.5 Existing Site Substation and Expansion The Baculite Mesa 115 kV substation is a breaker-and-a-half configuration including two buses; however, both buses are energized during normal operation. For every two circuits there are three circuit breakers with each circuit sharing a common center breaker. Any breaker can be removed for maintenance without affecting the service on the corresponding exiting feeder, and a fault on either bus can be isolated without interrupting service to the outgoing lines. With this configuration, the PAGS generating units interconnect into their own terminal at the Baculite Mesa substation, meaning that there is not a single transmission component failure that would result in the outage of more than one PAGS generating unit. There is one current open bay in the substation. The Baculite Mesa 115 kV substation has five 115 kV transmission lines terminating at that site. Generator interconnection studies have demonstrated that ~500 MW of generation injection can be accommodated with three of the five transmission lines. This assumes two Baculite Mesa transmission lines are out of service, consistent with Black Hills planning practices. There is currently one open bay (labeled GSU #3) in the Baculite Mesa 115 kV Substation that is available for the additional 100 MW studied in the SIS and FS. Black Hills intends to interconnect the LM-6000 40 MW to this open bay. This leaves an additional 60 MW under the current executed IA. Should more than 60 MW be proposed by Black Hills a new LGI request would be required for the incremental generation above the approved 100 MW. BHTPG will need to work with Black Hills for agreement to use remaining 60 MW capacity and may be required to generate contractual arrangements such as a shared facilities agreement.

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Section 5 CONCLUSIONS

Based on the evaluations and information reviewed and discussed herein, we offer the following conclusions.

5.1 Weather The PAGS site and the Baculite substation have low overall location risk associated with weather, specifically:  Historical records indicate that there have been no extreme weather events that suggest Pueblo, Colorado is an unacceptable site for a primary power generation and, relative to other locations in the State of Colorado and the region, the existing PAGS site is considered a lower risk for extreme weather events.  The most significant extreme weather event with some long-term probability of occurrence in the Pueblo area is flooding. The PAGS facility and the Baculite substation are located on “higher ground” than much of the Pueblo region and therefore impacts due to flooding are mitigated. This was confirmed with evaluation of elevation, gage height, FEMA maps and historic data evaluation of Pueblo flood events.  Tornado events do occur in southern Colorado near Pueblo and eastward. However, historical records suggest that the PAGS site and Baculite substation are located about 30-50 miles west of locations that are more prone to tornado occurrence.

5.2 Natural Gas Supply The gas supply is considered acceptable for future expansion of the PAGS site, considering Black Hill’s current strategy of using multiple gas supply and transportation contracts for supply to PAGS Currently, the CIG Company has expansion available through compression in a “worse case” scenario.

5.3 Transmission and Interconnection Electric interconnections at on-site Baculite substation have been and are being evaluated to assure that electric system reliability and system stability requirements are consistent with Black Hill’s LGIP. This interconnection review process rigorously reviews the impacts, defines upgrade requirements and analyses system stability issues to assure that interconnection risks are mitigated as part of the approval process. Specifically,  Black Hills has four IAs for the interconnection of up to 500 MW at Baculite Mesa, of which 380 MW is currently installed.

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 Black Hills received approval from the Public Utilities Commission (“PUC”) to construct a 40 MW LM6000 unit to replace the 42 MW (total) Clark Station coal units, leaving 60 MW of the remaining 100 MW of capacity not used under the remaining IAs.  Black Hills has completed the required interconnection studies and has an executed interconnection agreement for the addition of 100 MW of generation (proposed as an LMS-100) at Baculite Mesa 115 kV substation. The design change from the 100 MW LMS-100 to 40 MW LM-6000 will require interconnection study updates and may require an IA amendment. This leaves an additional 60 MW of capacity available to be interconnected at Baculite Mesa 115 kV Substation.  A transient stability analysis will likely not be required for the integration of 60 MW of renewable energy and a new interconnection request will be required should Black Hills chose to interconnect more than 60 MW at the Baculite Mesa 115 kV Substation.  BHTPG has identified network upgrades required to accommodate the addition of 100 MW (at GSU #3) and Black Hills has configured the Baculite Mesa 115 kV substation to minimize common mode transmission contingency impacts. These upgrades will accommodate the LM-6000 40 MW unit and 60 MW of additional generation. Should more than 60 MW be proposed by Black Hills, a new LGI request will be required for the incremental generation above 100 MW.  Black Hills will be required to work with the LGIA holder for the shared use and contractual arrangements necessary to utilize the additional 60 MW of the 100 MW studied.  The Baculite Mesa 115 kV substation has five 115 kV transmission lines terminating at that site, three of the five can accommodated up to 500 MW following implementation of the identified network upgrades. This assumes two Baculite Mesa transmission lines are out of service, consistent with Black Hills planning practices. No additional transmission expansion is anticipated. In addition to the interconnection evaluations and procedures summarized above, BHTPG has also conducted system contingency analyses which address the loss of major substations, such as Baculite Mesa; and such analyses confirm that the loss of all the PAGS generation resources due to an outage of the entire Baculite Mesa substation would not compromise Black Hill’s ability to serve the Pueblo electric loads.

5.4 Environmental  In general the overall location risk for the PAGS site from an environmental standpoint is fairly low due to the existing industrial activity and disturbed nature of the site. Adjacent parcels, which could be used for wind or solar PV generation, would have a somewhat higher risk associated with location due to the undisturbed nature, although this can be mitigated by pre-construction surveys conducted as part of the siting process.

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 New natural gas-fired generation would likely require a modification to the existing PSD permit, which includes applying Best Available Control Technology and demonstrating compliance with ambient air quality standards through a dispersion modeling analysis.  For solar and wind energy generating facilities with a generating capacity greater than two megawatts, a 1041 Permit from Pueblo County is required, which includes detailed information addressing environmental impacts, such as potential impacts to wildlife and historical or archeological sites. Appropriate surveys would need to be conducted that could reveal risks currently unknown.

5.5 Water Supply Based on the water consumption for the existing PAGS facilities and assuming that new gas fired generation would be constructed similar to the existing facilities, the provisions of the existing water supply Agreement with the City are adequate and reasonable. Addition of renewable energy projects, such as solar or wind, near the PAGS site would have little impact on water requirements, since solar and wind power generation facilities require only small amounts of water for .periodic cleaning. Based on these findings, the water supply risks for the addition of new gas-fired generation and/or renewable generation at PAGS are considered low.

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Appendix A EARTHQUAKES AND EXTREME WEATHER

This appendix includes the earthquake and extreme weather maps and charts referenced in Section 3 of this report.

A.1 Seismic Analysis for PAGS and Pueblo Colorado Area

A.1.1 USGS 2014 Peak Acceleration Map Insert from PDF file.

A.1.2 Colorado Seismic History Map

Figure A.2: Colorado Seismic History Map

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A.1.3 U.S. Seismic Hazard Chart

Figure A.3: U.S. Seismic Hazard Chart

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A.1.4 Historic Earthquakes

Largest Earthquake in Colorado

Near Denver, Colorado 1882 11 08 01:30 UTC Magnitude 6.6 Intensity VII

Source: Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993. Figure A.4: Isoeismal Map

A.1.5 Top Earthquake States The webpage shown below is updated in January of each year to incorporate any relevant data from the previous year.

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Legend 1. Alaska 1 2. California 3. Hawaii 2 4. Nevada 5. Washington 6. Idaho 7. Wyoming 8. Montana 9. Utah 10 Oregon ______1. Alaska: The number of earthquakes is under reported, even though Alaska already accounts for more than 50 percent of all US earthquakes. Events in the magnitude range of 3.5 to 4.0 in the Aleutian Islands are not recorded on enough seismograph stations to be located. 2. Hawaii: The earthquake count was obtained from the USGS Hawaiian Volcano Observatory (HVO). Hawaii and Nevada are essentially tied in the rates of earthquakes of magnitude 5.0 and greater.

Figure A.5: States with the Most Quakes

Notes for Figure A.5  Earthquakes centered in one State may produce damage in another.

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 This list does not reflect the extent to which earthquake activity might be concentrated in a few small areas of the State or spread throughout the State.

 This list does not show how earthquakes are distributed with respect to the population of the State.

 This list does not account for how earthquake waves are attenuated as they travel away from the earthquake epicenter. This attenuation affects the area over which an earthquake will cause damage or be felt. Attenuation is different in different parts of the United States.

 Some important earthquake source regions are distributed among several States. For example, the New Madrid Seismic Zone source region is "shared" between southeastern Missouri, southern Illinois, western Kentucky, western Tennessee, and northeastern Arkansas. If the New Madrid Seismic Zone activity were concentrated in one State, that State would be ranked number 11 on the list with 40 earthquakes.

 The distribution of earthquakes varies with time. Selecting earthquakes from a different 30-year interval would likely produce some changes in the ranking of the States.

A.1.6 U.S. Earthquake History Selected earthquakes of general historic interest. All earthquake dates are Universal Time (UTC), not local time.  2011 12 31 - Youngstown-Warren Urban Area, Ohio - M 4.0  2011 11 06 - Lincoln County, Oklahoma - M 5.6  2011 08 23 - Louisa County, Virginia - M 5.8  2011 08 23 - Southwest of Trinidad, Colorado - M 5.3  2011 02 28 - Arkansas - M 4.7  2010 01 10 - Offshore Northern California - M 6.5  2009 08 18 - Colorado - M 3.7  2009 06 08 - San Francisco Bay Area, California - M 3.5  2009 05 18 - Greater Los Angeles Area, California - M 4.7  2009 04 30 - Northern California - M 3.5  2009 04 14 - Island of Hawaii, Hawaii - M 5.2  2009 03 30 - Northern California - M 4.3  2009 03 08 - San Francisco Bay area, California - M 3.5  2009 02 03 - New Jersey - M 3.0  2009 01 30 - Seattle-Tacoma Urban Area - M 4.5  2009 01 24 - Southern Alaska - M 5.8  2009 01 09 - Greater Los Angeles Area, California - M 4.5  2008 07 29 - Greater Los Angeles area, California - M 5.5  2008 05 09 - Guam region - M 6.8  2008 05 02 - Andreanof Islands, Aleutian Islands, Alaska - M 6.6

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 2008 04 30 - Northern California - M 5.4  2008 04 26 - Nevada - M 5.0  2002 04 26 - Mariana Islands - M 7.1  2008 04 18 - Illinois - M 5.4  2008 04 16 - Andreanof Islands, Aleutian Islands, Alaska - M 6.6  2008 02 21 - Nevada - M 6.0  2007 12 26 - Fox Islands, Aleutian Islands, Alaska - M 6.4  2007 12 19 - Andreanof Islands, Aleutian Islands, Alaska - M 7.2  2007 10 31 - San Francisco Bay Area, California - M 5.6  2007 08 15 - Andreanof Islands, Aleutian Islands, Alaska - M 6.5  2007 08 14 - Island of Hawaii, Hawaii - M 5.4  2007 08 09 - Greater Los Angeles area, California - M 4.4  2007 08 02 - Andreanof Islands, Aleutian Islands, Alaska - M 6.7  2007 07 20 - San Francisco Bay area, California - M 4.2  2007 07 02 - Central California - M 4.3  2007 05 09 - Offshore Northern California - M 5.2  2007 05 08 - Western Montana - M 4.5  2006 10 20 - Northern California - M 4.5  2006 10 15 - Hawaii region, Hawaii - M 6.7  2006 10 02 - Maine - M 3.8  2006 07 27 - Southern Alaska - M 4.8  2006 03 22 - Western Montana - M 4.2  2006 02 10 - Colorado - M 3.8  2006 01 02 - Illinois - M 3.6  2005 12 19 - New Mexico - M 4.1  2005 10 31 - Western Montana - M 4.5  2005 09 22 - Central California - M 4.7  2005 08 10 - New Mexico - M 5.0  2005 07 26 - Western Montana - M 5.6  2005 07 17 - Hawaii region, Hawaii - M 5.1  2005 07 15 - Hawaii region, Hawaii - M 5.3  2005 06 17 - Off the Coast of Northern California - M 6.6  2005 06 16 - Greater Los Angeles Area, California - M 4.9  2005 06 15 - Off the Coast of Northern California - M 7.2  2005 06 14 - Rat Islands, Aleutian Islands, Alaska - M 6.8  2005 06 12 - Southern California - M 5.2  2005 05 06 - Central California - M 4.1  2005 05 01 - Arkansas - M 4.2  2005 02 10 - Arkansas - M 4.1  2004 09 28 - Central California - M 6.0  2004 09 17 - Eastern Kentucky - M 3.7  2004 08 29 - Wyoming - M 3.8  2004 08 19 - Alabama - M 3.6

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 2004 07 12 - Offshore Oregon - M 4.9  2004 06 28 - Southeastern Alaska - M 6.8  2004 06 28 - Illinois - M 4.2  2004 05 30 - Pine Mountain Club, California - M 3.0  2004 04 07 - Wyoming - M 4.0  2004 01 07 - Wyoming - M 5.0  2003 12 22 - San Simeon, California - M 6.6 Fatalities 2  2003 12 09 - Virginia - M 4.5  2003 11 17 - Rat Islands, Aleutian Islands, Alaska - M 7.8  2003 10 19 - near Orinda, California - M 3.5  2003 10 07 - near Imperial Beach, California - M 3.6  2003 09 22 - Rathdrum, Idaho - M 3.3  2003 09 13 - near Simi Valley, California - M 3.4  2003 09 05 - near Piedmont, California - M 4.0  2003 08 27 - Volcano, Hawaii - M 4.7  2003 08 27 - Val Verde, California - M 3.9  2003 08 26 - New Jersey - M 3.8  2003 08 21 - Wyoming - M 4.5  2003 08 15 - Humboldt Hill, California - M 5.3  2003 07 22 - Near the coast of Massachusetts - M 3.6  2003 06 23 - Rat Islands, Aleutian Islands - M 6.9  2003 06 20 - Carnation, Washington - M 3.6  2003 06 06 - Western Kentucky - M 4.0  2003 05 30 - Port Orchard, Washington - M 3.7  2003 05 26 - Muir Beach, California - M 3.4  2003 05 26 - Seven Trees, California - M 3.8  2003 05 25 - South Dakota - M 4.0  2003 05 25 - Santa Rosa, California - M 4.2  2003 05 24 - Brawley, California - M 4.0  2003 05 05 - Virginia - M 3.9  2003 04 30 - Blytheville, Arkansas - M 4.0  2003 04 29 - Alabama - M 4.6  2003 03 17 - Rat Islands, Aleutian Islands, Alaska - M 7.1  2003 03 11 - Twentynine Palms Base, California - M 4.6  2003 02 22 - Big Bear City, California - M 5.2  2003 02 19 - Unimak Island Region, Alaska - M 6.6  2003 02 02 - Dublin, CA, Swarm - M 4.1  2003 01 25 - Keene, California - M 4.7  2003 01 16 - Blanco Fracture Zone - Offshore Oregon, - M 6.3  2002 12 25 - Redford, New York - M 3.3  2002 12 24 - Pacifica, California - M 3.6  2002 11 24 - Swarm near San Ramon, California - M 3.9  2002 11 11 - Seabrook Island, South Carolina - M 4.4

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 2002 11 03 - Denali Fault, Alaska - M 7.9  2002 10 23 - Denali, Alaska - M 6.7  2002 10 22 - Alpine Northeast, Wyoming - M 4.2  2002 09 21 - Friday Harbor, Washington - M 4.1  2002 09 03 - Yorba Linda, California - M 4.8  2002 06 29 - near Mt. Hood Volcano, Oregon - M 4.5  2002 06 18 - Darmstadt, Indiana - M 4.6  2002 06 17 - Bayview, California - M 5.3  2002 06 16 - Kitsap Peninsula, Washington - M 3.7  2002 05 24 - Plattsburgh Aftershock - M 3.6  2002 05 14 - Gilroy, California - M 4.9  2002 04 20 - Au Sable Forks, New York - M 5.1  2002 03 16 - near Channel Islands Beach, California - M 4.6  2002 02 06 - near Knik, Alaska - M 5.3  2001 02 28 - Nisqually, Washington - M 6.8  2000 09 03 - Napa, California - M 5.0  1999 10 16 - Hector Mine, California - M 7.1  1998 09 25 - Pennsylvania - M 5.2  1996 06 10 - Andreanof Islands, Alaska - M 7.9  1995 02 03 - Wyoming - M 5.3 Fatalities 1  1994 09 01 - Cape Mendocino, California - M 7.0  1994 01 17 - Northridge, California - M 6.7 Fatalities 60  1994 01 16 - Pennsylvania - M 4.6  1993 09 21 - Klamath Falls, Oregon - M 6.0 Fatalities 2  1993 08 08 - South of the Mariana Islands - M 7.8  1992 09 02 - Utah - M 5.6  1992 06 29 - Little Skull Mountain, Nevada - M 5.7  1992 06 28 - Big Bear, California - M 6.5  1992 06 28 - Landers, California - M 7.3 Fatalities 3  1992 04 25 - Cape Mendocino, California - M 7.2  1992 04 23 - Joshua Tree - M 6.2  1991 08 17 - Honeydew, California - M 7.0  1991 06 28 - Sierra Madre, California - M 5.6 Fatalities 2  1990 01 13 - Maryland - M 2.5  1989 10 18 - Loma Prieta, California - M 6.9 Fatalities 63  1989 08 08 - Santa Cruz County, California - M 5.4 Fatalities 1  1988 03 06 - Gulf of Alaska - M 7.7  1987 11 30 - Gulf of Alaska - M 7.8  1987 11 24 - Superstition Hills, California - M 6.7  1987 11 24 - Superstition Hills, California - M 6.5 Fatalities 2  1987 10 04 - Whittier Narrows, California - M 5.6 Fatalities 1  1987 10 01 - Whittier Narrows, California - M 5.9 Fatalities 8  1987 06 10 - Near Olney, Illinois - M 5.1

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 1986 07 21 - Chalfant Valley, California - M 6.2  1986 07 08 - North Palm Springs, California - M 6.1  1986 05 07 - Andreanof Islands, Alaska - M 7.9  1986 01 31 - Northeast Ohio - M 5.0  1984 11 23 - Round Valley, California - M 5.8  1984 04 24 - Morgan Hill, California - M 6.2  1984 04 23 - Lancaster County, Pennsylvania - M 4.4  1983 11 16 - Kaoiki, Hawaii - M 6.7  1983 10 28 - Borah Peak, Idaho - M 6.9 Fatalities 2  1983 10 07 - Blue Mountain Lake, New York - M 5.3  1983 05 02 - Coalinga, California - M 6.4  1980 11 08 - Humboldt County, California - M 7.2  1980 07 27 - Maysville, Kentucky - M 5.2  1980 05 27 - Mammoth Lakes, California - M 6.0  1980 05 25 - Mammoth Lakes, California - M 6.2  1980 05 18 - Mount St. Helens, Washington - M 5.0  1980 01 27 - Livermore, California - M 5.8  1980 01 24 - Livermore Valley, California - M 5.8  1979 10 15 - Imperial Valley, Mexico - California Border - M 6.4  1979 08 06 - Coyote Lake, California - M 5.7  1979 02 28 - Mt. St. Elias, Alaska - M 7.5  1976 03 11 - Newport, Rhode Island - M 3.5  1975 11 29 - Kalapana, Hawaii - M 7.2 Fatalities 2  1975 08 01 - Oroville, California - M 5.8  1975 07 09 - Western Minnesota - M 4.6  1975 06 30 - Yellowstone National Park, Wyoming - M 6.1  1975 03 28 - Eastern Idaho - M 6.2  1975 02 02 - Near Islands, Alaska - M 7.6  1973 04 26 - Island of Hawaii, Hawaii - M 6.2  1972 07 30 - Sitka, Alaska - M 7.6  1971 02 09 - San Fernando, California - M 6.6 Fatalities 65  1969 11 20 - Southern West Virginia - M 4.5  1969 10 02 - Santa Rosa, California - M 5.7 Fatalities 1  1968 11 09 - Southern Illinois - M 5.4  1967 08 09 - Denver, Colorado - M 5.3  1966 09 12 - Truckee, California - M 5.9  1966 08 07 - Rat Islands, Alaska - M 7.0  1966 06 28 - Parkfield, California - M 6.1  1966 01 23 - Dulce, New Mexico - M 5.1  1965 04 29 - Puget Sound, Washington - M 6.5 Fatalities 7  1965 03 30 - Rat Islands, Alaska - M 7.3  1965 02 04 - Rat Islands, Alaska - M 8.7  1964 03 28 - Merriman, Nebraska - M 5.1

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 1964 03 28 - Prince William Sound, Alaska - M 9.2 Fatalities 128  1962 04 10 - Vermont - M 4.2  1959 08 18 - Wyoming - M 6.5  1959 08 18 - Hebgen Lake, Montana - M 7.3 Fatalities 28  1959 07 21 - Arizona - Utah Border - M 5.6  1958 07 10 - Lituya Bay, Alaska - M 7.7 Fatalities 5  1958 04 07 - Huslia, Alaska - M 7.3  1957 03 22 - Daly City, California - M 5.3 Fatalities 1  1957 03 16 - Andreanof Islands, Alaska - M 7.0  1957 03 14 - Andreanof Islands, Alaska - M 7.1  1957 03 12 - Andreanof Islands, Alaska - M 7.0  1957 03 09 - Fox Islands, Alaska - M 7.1  1957 03 09 - Andreanof Islands, Alaska - M 8.6  1955 10 24 - Concord, California - M 5.4 Fatalities 1  1954 12 21 - Eureka, California - M 6.5 Fatalities 1  1954 12 16 - Dixie Valley, Nevada - M 6.8  1954 12 16 - Fairview Peak, Nevada - M 7.1  1954 08 24 - Stillwater, Nevada - M 6.8  1954 07 06 - Fallon-Stillwater area, Nevada - M 6.6  1953 01 05 - Near Islands, Alaska - M 7.1  1952 08 22 - Kern County, California - M 5.8 Fatalities 2  1952 07 21 - Kern County, California - M 7.3 Fatalities 12  1952 04 09 - El Reno, Oklahoma - M 5.5  1951 08 21 - Kona, Hawaii - M 6.9  1949 04 13 - Puget Sound, Washington - M 7.1 Fatalities 8  1947 11 23 - Southwest Montana - M 6.3  1947 10 16 - Wood River, Alaska - M 7.2  1947 08 10 - Southern Michigan - M 4.6  1947 05 06 - Wisconsin  1946 04 01 - Unimak Island, Alaska - M 8.1 Fatalities 165  1944 09 05 - Between Massena, New York and Cornwall, Ontario, Canada - M 5.8  1944 07 12 - Sheep Mountain, Idaho - M 6.1  1943 11 03 - Skwenta, Alaska - M 7.4  1940 12 24 - Ossipee Lake, New Hampshire - M 5.5  1940 12 20 - Ossipee Lake, New Hampshire - M 5.5  1940 05 19 - Imperial Valley, California - M 7.1 Fatalities 9  1938 11 10 - Shumagin Islands, Alaska - M 8.2  1938 01 23 - Maui, Hawaii - M 6.8  1937 07 22 - Central Alaska - M 7.3  1937 03 09 - Western Ohio - M 5.4  1935 10 31 - Helena, Montana - M 6.0 Fatalities 2  1935 10 19 - Helena, Montana - M 6.3 Fatalities 2  1935 10 12 - Helena, Montana - M 5.9

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 1934 06 08 - Parkfield, California - M 6.1  1934 05 04 - Chugach Mountains, Alaska - M 7.1  1934 03 12 - Kosmo, Utah - M 6.6 Fatalities 2  1934 01 30 - Excelsior Mountains, Nevada - M 6.5  1933 03 11 - Long Beach, California - M 6.4 Fatalities 115  1932 12 21 - Cedar Mountain, Nevada - M 7.2  1932 06 06 - Eureka, California - M 6.4 Fatalities 1  1931 12 17 - Charleston, Mississippi - M 4.6  1931 08 16 - Valentine, Texas - M 5.8  1930 10 19 - Napoleonville, Louisiana - M 4.2  1929 10 06 - Holualoa, Hawaii - M 6.5  1929 03 07 - Fox Islands, Aleutian Islands, Alaska - M 7.8  1928 11 03 - Eastern Tennessee - M 4.5  1927 11 04 - Lompoc, California - M 7.1  1927 10 24 - Southeast Alaska - M 7.1  1926 10 22 - Monterey Bay, California - M 6.1  1926 06 29 - Santa Barbara, California - M 5.5 Fatalities 1  1925 06 29 - Santa Barbara, California - M 6.8 Fatalities 13  1925 06 28 - Clarkston Valley, Montana - M 6.6  1923 01 22 - Humbolt County, California - M 7.2  1922 03 10 - Parkfield, California - M 6.1  1922 01 31 - Eureka, California - M 7.3  1918 10 11 - Mona Passage - M 7.5 Fatalities 116  1918 04 21 - San Jacinto, California - M 6.8 Fatalities 1  1916 10 18 - Irondale, Alabama - M 5.1  1916 02 21 - Waynesville, North Carolina - M 5.2  1915 10 03 - Pleasant Valley, Nevada - M 7.1  1915 06 23 - Imperial Valley, California - M 6.3 Fatalities 6  1914 03 05 - Georgia - M 4.5  1912 07 07 - Paxson, Alaska - M 7.2  1911 07 01 - Calaveras fault, California - M 6.5  1911 06 02 - South Dakota - M 4.5  1910 09 09 - Rat Islands, Aleutian Islands, Alaska - M 7.0  1910 08 05 - Oregon - M 6.8  1909 09 27 - Wabash River Valley, Indiana - M 5.1  1909 05 26 - Aurora, Illinois - M 5.1  1909 05 16 - North Dakota - M 5.5  1908 05 15 - Gulf of Alaska - M 7.0  1906 11 15 - Socorro area, New Mexico - Intensity VII  1906 07 12 - Socorro area, New Mexico - Intensity VII  1906 04 18 - San Francisco, California - M 7.8 Fatalities 3000  1905 04 13 - Iowa  1904 08 27 - Fairbanks, Alaska - M 7.3

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 1904 03 21 - Southeast Maine - M 5.1  1901 12 31 - Cook Inlet, Alaska - M 7.1  1901 05 17 - Near Portsmouth, Ohio - M 4.2  1901 03 03 - Parkfield, California - M 6.4  1900 10 09 - Kodiak Island, Alaska - M 7.7  1899 12 25 - San Jacinto, California - M 6.7 Fatalities 6  1899 09 23 - Copper River delta, Alaska - M 7.0  1899 09 10 - Yakutat Bay, Alaska - M 8.0  1899 09 04 - Cape Yakataga, Alaska - M 7.9  1899 04 16 - Eureka, California - M 7.0  1898 04 15 - Mendocino County, California - M 6.8  1898 03 31 - Mare Island, California - M 6.3  1897 06 20 - Calaveras fault, California - M 6.3  1897 05 31 - Giles County, Virginia - M 5.9  1895 10 31 - Charleston, Missouri - M 6.6  1892 04 21 - Winters, California - M 6.4  1892 04 19 - Vacaville, California - M 6.4 Fatalities 1  1892 02 24 - Imperial Valley, California - M 7.8  1890 02 24 - Corralitos, California - M 6.3  1886 09 01 - Charleston, South Carolina - M 7.3 Fatalities 60  1884 09 19 - Near Lima, Ohio - M 4.8  1884 08 10 - New York City, New York - M 5.5  1882 11 08 - Denver, Colorado - M 6.6  1879 01 13 - St. Augustine, Florida  1877 11 15 - Eastern Nebraska - M 5.1  1873 11 23 - California - Oregon Coast - M 7.3  1872 12 15 - Lake Chelan, Washington - M 6.8  1872 03 26 - Owens Valley, California - M 7.4 Fatalities 27  1871 10 09 - New Jersey - Delaware border  1871 10 09 - New Jersey - Delaware border  1871 02 20 - Lanai, Hawaii - M 6.8  1868 10 21 - Hayward, California - M 6.8 Fatalities 30  1868 04 03 - Ka'u District, Island of Hawaii - M 7.9 Fatalities 77  1868 03 29 - Ka'u District, Island of Hawaii - M 7.0  1867 11 18 - Puerto Rico Region  1867 04 24 - Manhattan, Kansas - M 5.1  1865 10 08 - Santa Cruz Mountains, California - M 6.5  1865 08 17 - Memphis, Tennessee - M 5.0  1857 01 09 - Fort Tejon, California - M 7.9 Fatalities 1  1843 01 05 - Northeast Arkansas - M 6.3  1838 06 - San Francisco area, California - M 6.8  1836 06 10 - South San Francisco Bay region, California - M 6.5  1823 06 02 - South flank of Kilauea, Hawaii - M 7.0

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 1812 12 21 - West of Ventura, California - M 7.1 Fatalities 1  1812 12 08 - Southwest of San Bernardino County, California - M 6.9Fatalities 40  1812 02 07 - New Madrid Region - M 7.7  1812 01 23 - New Madrid Region - M 7.5  1811 12 16 - New Madrid Region - M 7.0  1811 12 16 - New Madrid Region - M 7.7 Fatalities Several  1791 05 16 - Moodus, Connecticut  1787 05 02 - Puerto Rico - M 8.0  1783 11 30 - New Jersey - M 5.3  1780 02 06 - Northwest Florida  1755 11 18 - Cape Ann, Massachusetts  1744 06 14 - Southern Cape Ann, Massachusetts region  1727 11 10 - Northern Cape Ann region, Massachusetts  1700 01 26 - Cascadia Subduction Zone - M 9.0  1568 - Moodus-East Haddam, Connecticut - Intensity VI

A.1.7 USGS Colorado Earthquake History Colorado is considered a region of minor earthquake activity, although there are many uncertainties because of the very short time period for which historical data is available. The northwestern and southwestern corners, and the Sangre de Cristo Mountains in the south-central section of the State, have had no activity in historic times. Eastern Colorado is nearly aseismic, with just a few epicenters in the Arkansas and Platte River Valleys. Most shocks in the history of this State have centered west of the Rocky Mountain Front Range. F.A. Hadsell, writing in the Colorado School of Mines Quarterly (vol. 63, No. 1, Jan. 1968), reports the first known reference to an earthquake in Colorado occurred on December 7, 1870. The Colorado Transcript states, ``A careful observer at Fort Reynolds, 20 miles east of Pueblo, noted that bottles standing 1 inch apart were knocked together violently.'' Hadsell also notes that, although the first seismograph in Colorado was installed by Father Armand W. Forstall at Regis College in 1909, seismographs of sufficient quality and quantity were not available to monitor Colorado earthquakes until about 1962. Thus, between 1870 and 1962, newspaper accounts are the prime source of published data on Colorado shocks. The earthquake of November 7, 1882, the first ever to cause damage at Denver, probably centered in the Front Range near Rocky Mountain National Park, and is the largest historical earthquake in the state. The magnitude is estimated to be about 6.6 on the Richter scale. In Boulder County the walls of the depot cracked, and plaster fell from walls at the university at Boulder. The quake was felt as far away as Salina, Kansas and Salt Lake City, Utah. The Longmont Ledger of November 10, 1882, states: “It is claimed by the oldest settlers in Denver that this is the first known instance of an earthquake having visited Colorado... that this is the first and only instance in the political history of Colorado when a fall election has ever been carried by the ... party.

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Appendix A

It was probably nature's protest ... uttered at the time of closing the polls Tuesday evening ... when the polls were closed, and it became evident that the ... party was finally to take control of our state government, she could no longer control her feelings, but uttered a groan of anguish which caused the very mountains to tremble. Curious but true.” An earthquake on November 15, 1901, cracked windows and rolled boulders onto the highway in Buena Vista; the water of Cottonwood Lake was reportedly agitated. Another shock of similar intensity (VI) did not occur until September 8, 1944. During this tremor, bricks fell from chimneys and walls and chimneys cracked at Basalt, about 100 miles west of Denver. Eleven years later, in August 1955, a strong earthquake left cracks in chimneys and ground at Lake City, about 170 miles southwest of Denver. On October 11, 1960, a shock cracked a foundation and loosened cupboards from walls at Montrose. Windows, plaster, and chimneys were damaged in several towns in southwestern Colorado. In 1961, a 12,000-foot well was drilled at the Rocky Mountain Arsenal, northeast of Denver, for disposing of waste fluids from Arsenal operations. Injection was commenced March 1962, and an unusual series of earthquakes erupted in the area shortly after. It was 32 minutes after 4 a.m. on April 24 when the first shock of the Denver series was recorded at the Cecil H. Green Geophysical Observatory at Bergen Park, Colorado. Rated magnitude 1.5, it was not strong enough to be felt by area residents. By the end of December 1962, 190 earthquakes had occurred. Several were felt, but none caused damage until the window breaker that surprised Dupont and Irondale on the night of December 4. The shock shuffled furniture around in homes, and left electrical wall outlets hanging by their wires at Irondale. Over 1,300 earthquakes were recorded at Bergen Park between January 1963 and August 9, 1967. Three shocks in 1965 – February 16, September 29, and November 20 -- caused intensity VI damage in Commerce City and environs. The Denver series was forgotten, however temporarily, in October 1966, when a southeast Colorado tremor rocked a 15,000 square-mile area of that State and bordering New Mexico. Minor damage, in the form of broken windows and dishes and cracked walls and plaster, occurred at Aguilar, Segundo, Trinchera, and Trinidad. Another strong shock rumbled through the Denver area on November 14, 1966, causing some damage at Commerce City and Eastlake. Slighter rumblings (below magnitude 3.0) occurred throughout the remainder of 1966, and through the first week of April 1967. Then, on April 10, the largest since the series began in 1962 occurred; 118 windowpanes were broken in buildings at the Rocky Mountain Arsenal, a crack in an asphalt parking lot was noted in the Derby area, and schools were dismissed in Boulder, where walls sustained cracks. Legislators quickly moved from beneath chandeliers in the Denver Capitol Building, fearing they might fall. The Colorado School of Mines rated this shock magnitude 5.0.

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Boulder sustained minor damage to walls and acoustical tile ceilings on April 27, 1967, as result of a magnitude 4.4 earthquake. Then a year and half after the Rocky Mountain Arsenal waste dumping practice stopped, the strongest and most widely felt shock in Denver's history struck that area on August 9, 1967, at 6:25 in the morning. The magnitude 5.3 tremor caused the most serious damage at Northglenn, where concrete pillar supports to a church roof were weakened, and 20 windows were broken. An acoustical ceiling and light fixtures fell at one school. Many homeowners reported wall, ceiling, floor, patio, sidewalk, and foundation cracks. Several reported basement floors separated from walls. Extremely loud, explosive-like earth noises were heard. Damage on a lesser scale occurred throughout the area. During November 1967, the Denver region was shaken by five moderate earthquakes. Two early morning shocks occurred November 14. They awakened many residents, but were not widely felt. A similar shock, magnitude 4.1, centered in the Denver area November 15. Residents were generally shaken, but no damage was sustained. A local shock awakened a few persons in Commerce City November 25. Houses creaked and objects rattled during this magnitude 2.1 earthquake. The second largest earthquake in the Denver series occurred on November 26, 1967. The magnitude 5.2 event caused widespread minor damage in the suburban areas of northeast Denver. Many residents reported it was the strongest earthquake they had ever experienced. It was felt at Laramie, Wyoming, to the northwest, east to Goodland, Kansas, and south to Pueblo, Colorado. At Commerce City merchandise fell in several supermarkets and walls cracked in larger buildings. Several persons scurried into the streets when buildings started shaking back and forth. During 1968, ten slight shocks were felt in Colorado. Only one, on July 15, caused minor damage at Commerce City. In September of that year, the Army began removing fluid from the Arsenal well at a very slow rate, in hope that earthquake activity would lessen. The program consisted of four tests between September 3 and October 26. Many slight shocks occurred near the well during this period.

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Appendix A

Figure A.6: Magnitude Scale and Designation

On January 7, 1971, a minor 3.8 earthquake shook the Glenwood Springs area. Most residents were frightened by the tremor, but damage was light, chiefly cracked windows and broken knick-knacks. The sheriff's office received numerous call about the unexpected event. A minor 3.0 earthquake rumbled through the East Denver - Commerce City area on March 11. The early morning tremor caused no damage, but aroused several in the region from their beds. Two earthquakes were felt throughout the Denver area in August 1971. The first at 11:22 p.m. local time on August 7, the second at 1:30 a.m. local time on August 8. The initial shock was assigned a magnitude 4.4; the second, smaller shock was rated at magnitude 3. No damage was reported for either tremor. A sharp earthquake struck western Colorado January 30, 1975. The magnitude 3.7 earthquake occurred at 7:49 a.m. MST. Police and fire departments received many telephone calls from residents wanting to know what was going on. The quake was felt strongest at Colorado National Monument and in the Fruita area. It was also felt throughout Grand Junction and other adjoining area. Maximum intensity V. The residents in the northeast Denver area were shaken by a mild earthquake on June 10, 1978 at 2:58 p.m. MDT. The magnitude 2.9 earthquake was centered approximately 10 km northeast of Denver and was felt sharply in the east Denver, Commerce City, Thornton, and Northglenn areas. There were no reports of damage (MM IV). In 1979, a small but rare earthquake occurred in the central part of the State on January 5 at 6:59 p.m. MST. The magnitude 2.9 tremor was centered about 50 km northwest of Colorado Springs near Florissant and Lake George. Some minor damage

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(MM VI) was reported at Cripple Creek and Royal Gorge. In March 1979, the northwestern part of the State experienced two earthquakes, one, magnitude 3.4, on March 19 at 8:00 a.m. MST and the other, magnitude 2.6, on March 29 at 3:07 p.m. MST. Both earthquakes were located about 10 km northwest of Rangely and were felt (MM V) in the Rangely area. On April 2, 1981 at 9:10 a.m. MST, a sharp earthquake, magnitude 4.1, occurred that was centered approximately 20 km north of downtown Denver in the Thornton area. Some slight damage (MM VI) was observed at Commerce City and Thornton. The quake was felt in other parts of Adams County and in parts of Arapahoe, Boulder, Clear Creek, Denver, Douglas, Jefferson, Gilpin, and Weld Counties. This earthquake was preceded by a small tremor located in the same area on March 24 at 6:04 a.m. MST with magnitude 2.8. It was felt in the Commerce City and Northglenn-Thornton area. The north-central part of Colorado experienced a small earthquake on September 16, 1981 at 1:59 p.m. MDT. The magnitude 2.1 tremor was located in the Commerce City-Thornton area and was felt by a few people in that area. A minor but alarming earthquake occurred in the north-central part of Colorado on November 1, 1981, at 8:03 p.m. MST. The magnitude 3.1 tremor was centered in the Evergreen area about 22 miles southwest of Denver. The effects registered MM V, and were experienced in the Conifer, Evergreen, and Pine Junction areas. It was also felt in other parts of Jefferson County and in parts of Clear Creek and Park Counties. Several earthquakes occurred in 1982. On March 11 at 4:55 p.m. MST a very minor 2.8 earthquake occurred. It was located about 12 miles north of downtown Denver in the Thornton area. It was felt in the Commerce City, Northglenn, and Thornton areas. MM III effects were experienced in the Thornton area. On September 18 at 10:12 a.m. MDT, a small part of the north-central part of Colorado was shaken by a very minor earthquake. The magnitude 2.8 tremor was located about 12 miles north of downtown Denver in the Thornton area. MM III effects were noted at Thornton; it was also felt at Commerce City and Northglenn. A very minor earthquake occurred in the northwestern part of Colorado on November 22 at 3:09 a.m. MST. The magnitude 2.9 quake was located about 18 miles northeast of Rifle and was felt at a fish hatchery in the area. A minor earthquake occurred in western Colorado on August 14, 1983, at 1:09 p.m. MDT. This shock was located about 28 miles southeast of Montrose in a sparsely populated area. It was felt lightly at Cimarron. The northwestern corner of Colorado was shaken by a light earthquake on September 24 at 10:58 a.m. MDT. It was a magnitude of 4.0 and was located about 25 miles north of Dinosaur National Monument. MM III effects were experienced at Maybell and Rangely; it was also felt at Point Rocks, Wyoming. In 1984, a very minor earthquake occurred in the Denver metropolitan area on February 25 at 2:18 a.m. MDT. This magnitude 2.5 tremor was located about 13 miles north of downtown Denver in the Thornton area where it was felt lightly. The western part of the State experience a series of earthquakes beginning with a magnitude 2.4 on April 12 at 1:17 p.m. MST. These quakes were located about 5 miles south of Carbondale. The largest quake located in the area occurred on April 22 at 10:31 MST and had a magnitude of 3.1 which was felt in the Carbondale and Glenwood Springs

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Appendix A area. Of the hundreds of earthquakes that occurred in the Carbondale area, 12 were reported as felt. This series of earthquakes continued during the month of May. The largest to occur in May were a magnitude 3.1 on May 3 at 12:29 p.m. MDT and a 3.2 on May 14 at 4:14 a.m. MDT. Both earthquakes were felt in the Carbondale area. A minor earthquake occurred in the south-central part of the State on March 16, 1985, at 2:55 p.m. MST. The magnitude 3.3 earthquake was located about 15 km northeast of Salida and was felt in the Salida-Nathrop area. Several earthquakes occurred in 1986. A very minor earthquake occurred in the central part of the State on April 10 at 11:17 p.m. MST. The magnitude 2.9 earthquake was located about 15 km southwest of Aspen. This quake produced MM III intensities at Basalt and Snowmass Village and was also felt in the Aspen area. Another minor earthquake occurred on May 9 at 3:55 p.m. MDT. The magnitude 2.7 tremor was located about 25 miles southwest of Aspen and was felt in the Aspen area. This series of small earthquakes continued during August and September. These earthquakes were located about 1 km northwest of Crested Butte and about 25 km southwest of Aspen. During August, 14 earthquakes were located in the area. The series began on August 12 with a magnitude 2.6 earthquake at 8:43 p.m. MDT. The largest was a magnitude 3.0 on August 17 at 7:15 p.m. MDT and a magnitude 3.1 on August 25 at 8:06 p.m. MDT. Many of these earthquakes have been felt in the Aspen- Snowmass Village-Crested Butte-Redstone area. The quake on August 17 was also felt at Carbondale. A magnitude 3.5 occurred on September 3 at 20 minutes after midnight about 13 km northwest of Crested Butte. Intensity MM V effects were noted at Aspen and Crested Butte; it was also felt at Gunnison. Other quakes in the series included a magnitude 3.2 on September 17 at 10:53 p.m. MDT and a magnitude 3.4 on September 18 at 3:27 a.m. MDT. Both of these earthquakes were felt in the Aspen- Crested Butte-Snowmass Village area. Additional smaller earthquakes were not reported felt. A very minor earthquake, magnitude 2.5, occurred on September 21 at 3:21 a.m. MDT, about 35 km west of downtown Denver in the Conifer area; it was felt at Conifer and Tiny Town. A small earthquake occurred in the western part of Colorado on September 14, 1987, at 2:32 p.m. MDT. The magnitude 2.5 earthquake was located 20 km southeast of Aspen and was felt in the Aspen area. A minor earthquake occurred in the southern part of the State on January 15, 1988, at 33 minutes after midnight. The magnitude 3.1 earthquake was located about 60 km west of Alamosa near Summitville where it was felt. On February 14 at 11:33 a.m. MST a minor earthquake took place in the northwest corner of the State. The quake had a magnitude of 3.3 and was located about 80 km west of Craig. It produced MM IV effects at Maybell. In 1989, a very minor earthquake occurred in the northwestern part of Colorado on June 30 at 6:53 a.m. MDT. The magnitude 2.2 earthquake was located about 120 km northeast of Grand Junction near Meeker. It was felt at Meeker. A minor earthquake occurred in the north-central part of the State on November 7 at 11:14 p.m. MST. The magnitude 2.5 earthquake was located about 10 km north of downtown Denver.

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Intensity MM III effects were noted at Eastlake, Montbello, Northglenn, Thornton, and in parts of Denver. The earthquake was also felt at Commerce City. The western part of Colorado experienced four earthquakes during September and October of 1990. The first, on September 12 at 3:39 p.m. MDT, had a magnitude of 3.0 and was located about 40 km southwest of Fraser near Frisco and Vail. Intensity MM V effects were produced at Vail and intensity MM IV effects at Frisco and Minturn. The quake was also felt at Avon, Dillon, Copper Mountain and Silverthorne. On October 18, two earthquakes occurred, the first at 6:32 p.m. MDT and the second at 6:43 p.m. MDT. Both earthquakes were located about 35 km west of Glenwood Springs in the vicinity of New Castle. The earthquakes had magnitude of 2.3 and 2.1 respectively, and both were felt at New Castle. On December 12 at 24 minutes after midnight, another very minor earthquake occurred in the western part of Colorado. This magnitude 2.7 tremor was located about 35 km west of Glenwood Springs near New Castle. It was felt in the New Castle area. On April 21, 1991 at 6:46 a.m. MDT, a very minor earthquake occurred in the western part of Colorado. The magnitude 2.0 earthquake was located about 10 km south of Aspen. The tremor was felt in the Aspen area. On May 10, residents of the southwestern part of Colorado felt four small earthquakes. The first, at 6:16 a.m. MDT, had a magnitude of 3.4 and was located about 40 km northeast of Pagosa Springs in the Summerville area. This earthquake was felt strongly at Summerville. Intensity MM III effects were experienced at Chromo and Pagosa Springs. The first quake was followed by three aftershocks: a magnitude 2.4 at 6:22 a.m., a magnitude 2.0 at 7:24 a.m., and a magnitude 2.4 at 8:21 a.m. MDT. These aftershocks were also felt at Summerville.

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Appendix A

A.2 Tornado Maps & Charts

Figure A.7: Average Annual Number of Tornadoes 1991-2010

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Figure A.8: Annual Tornado Map 1955

Figure A.9: Annual Tornado Map 1993

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Appendix A

Figure A.10: Annual Tornado Map 2003

A.3 Extreme Event Indices

The following is a summary comparison of extreme events for Pueblo, Colorado as compared to the State of Colorado and the United States. This data was taken from the references in Section 3.

Earthquake Index, #486 Pueblo, CO 0.02 Colorado 1.32 U.S. 1.81 The earthquake index value is calculated based on historical earthquake events data using USA.com algorithms. It is an indicator of the earthquake level in a region. A higher earthquake index value means a higher chance of an earthquake.

Volcano Index, #187 Pueblo, CO 0.0000 Colorado 0.0009 U.S. 0.0023 The volcano index value is calculated based on the currently known volcanoes using USA.com algorithms. It is an indicator of the possibility of a region being affected by a possible volcano eruption. A higher volcano index value means a higher chance of being affected.

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Tornado Index, #315 Pueblo, CO 41.79 Colorado 117.98 U.S. 136.45 The tornado index value is calculated based on historical tornado events data using USA.com algorithms. It is an indicator of the tornado level in a region. A higher tornado index value means a higher chance of tornado events.

A.4 Other Extreme Weather Events A total of 1,777 other weather extremes events within 50 miles of Pueblo, CO were recorded from 1950 to 2010. The following is a break-down of these events:

Table A-1 Other Extreme Weather Events

Type Count Type Count Type Count Type Count Type Count Avalanche: 0 Blizzard: 0 Cold: 0 Dense Fog: 1 Drought: 4 Dust Storm: 0 Flood: 115 Hail: 1,315 Heat: 0 Heavy Snow: 0 High Surf: 0 Hurricane: 0 Ice Storm: 0 Landslide: 0 Strong Wind: 1 Thunderstorm Tropical 209 0 Wildfire: 9 Winter Storm: 0 Winter Weather: 0 Winds: Storm: Other: 123

A.5 Volcanos Nearby No volcano is found in or near Pueblo, CO.

A.6 Historical Earthquake Events No historical earthquake events that had recorded magnitudes of 3.5 or above found in or near Pueblo, CO. No historical earthquake events found in or near Pueblo, CO.

A.7 Historical Tornado Events A total of 10 historical tornado events that had recorded magnitude of 2 or above found in or near Pueblo, CO.

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Appendix A

Table A-2 Historical Tornado Events

Distance Start End Property Crop Affected Date Magnitude Length Width Fatalities Injuries (miles) Lat/Log Lat/Log Damage Damage County

1984- 38°15'N / 1.00 50 1.7 2 0 0 3K 0 Pueblo 08-21 104°36'W Mile Yards 1977- 38°40'N / 1.00 100 29.3 2 0 0 250K 0 El Paso 04-11 104°49'W Mile Yards 2001- 38°49'N / 38°50'N / 0.50 200 40.1 2 0 4 8.0M 0 El Paso 05-28 104°23'W 104°23'W Mile Yards 2001- 38°50'N / 38°50'N / 0.30 30 40.3 2 0 5 100K 0 El Paso 05-28 104°24'W 104°24'W Mile Yards Brief Description: A slow moving supercell thunderstorm stayed over the Ellicott area of eastern El Paso county for over an hour on Memorial Day evening. For over an hour, heavy rain and large hail pelted the area. Then another thunderstorm cell merged with the supercell, causing a brief time of extreme winds and three small tornadoes. A large mesocyclone developed, and the extreme winds rotated around its northeastern quarter. All of the debris from the damaged structures was moved to the west-northwest or west. Straight-line and twisting microburst winds, in some areas causing F2 damage, damaged or destroyed nearly 100 mobile homes, many occupied. Embedded within these winds, three tornadoes occurred. One, rated F2, struck the junior-senior high school building, totally destroying nearly one half of the structure. That tornado lifted briefly and set down again about 3/4 of a mile northwest of the school building and destroyed several mobile homes. Another tornado, rated F1, occurred about one mile west of the school building, flipping a mobile home. 1979- 38°51'N / 38°50'N / 4.30 50 41.7 3 0 1 250K 0 El Paso 06-24 104°55'W 104°50'W Miles Yards 1953- 38°30'N / 2.00 200 48.4 2 0 0 3K 0 Otero 10-20 103°46'W Miles Yards 1990- 38°50'N / 2.00 100 48.6 2 0 2 250K 0 El Paso 06-06 104°04'W Miles Yards 1977- 38°56'N / 38°55'N / 4.90 100 48.9 3 0 0 0K 0 El Paso 06-13 105°01'W 104°55'W Miles Yards 1960- 38°02'N / 49.2 2 0 0 3K 0 Custer 07-04 105°28'W 1978- 37°37'N / 0.30 50 49.4 2 0 2 25K 0 Huerfano 07-10 104°15'W Mile Yards ______The information on this page is based on the global volcano database, the U.S. earthquake database of 1638-1985, and the U.S. Tornado and Weather Extremes database of 1950-2010.

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Figure A.11: Maximum Ice Severity Levels for the Western Part of the United States

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Appendix A

Figure A.12: Ice Event Map for the Western Part of the United States

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A.8 Noteworthy Colorado Floods Information on many flood events in Colorado is sketchy, particularly for floods before 1900, and this is not intended to be a complete list. The following floods are noteworthy either for loss of life, extent of property damage , or other unusual circumstances. This data excludes the flooding experienced in Colorado in 2013.

May 19-20, 1864 - Heavy rain over the upper basin of Cherry Creek caused 19 deaths along Cherry Creek and the South Platte River in Denver.

July 24, 1896 - Cloudburst centered on Cub Creek near Morrison killed 27 people.

August 7, 1904 - Heavy rain resulted in a train wreck near Pueblo. One hundred people died.

October 5, 1911 - Heavy rains caused flooding from Del Norte to Monte Vista in the San Luis Valley, closing the railroad temporarily.

October 5, 1911 - Heavy rains near Durango caused the Animas River to rise to 8 feet above flood stage.

June 3-5, 1921 - Cloudbursts between Canon City and Pueblo caused flooding which killed at least 78 people. Over 20 million dollars in damage was reported.

June 29, 1927 - Snowmelt and heavy rains flooded the Rio Grande River from Rio Grande Reservoir to past Alamosa. Five bridges were destroyed and train serviced halted. Three persons died.

July 7-8, 1933 - A cloudburst centered near Idledale and Saw Mill Gulch killed 5 people.

August 2-3, 1933 - Three to nine inches of rain in 9 hours caused Castlewood Dam on Cherry Creek to fail. Seven people died in Denver. Damage was estimated at 1 million dollars.

August 9, 1934 - Cloudbursts centered on Mount Vernon Canyon killed 6 people.

May 30, 1935 - Cloudbursts along Monument Creek in Colorado Springs killed 4 people.

May 30 - 31, 1935 - Up to 10 inches of rain fell in the Republican River Basin in Eastern Colorado, causing 6 deaths and more than a million dollars in damage.

July 11-12, 1935 - Cloudbursts over Wolf Creek at Granada caused flooding which killed 8 people.

September 2-3, 1938 - Nearly 8 inches of rain in 6 hours at Morrison trapped and drowned 6 people in a car between Morrison and Kittredge.

August 24, 1946 - Heavy rain near Idledale drowned 1 person stranded in a car.

August 2-3, 1951 - Over 4 inches of rain at Waterdale caused a dam failure on Buckhorn Creek. Four persons died and many were made homeless.

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May 9, 1957 - Four inches of rain in 5 hours in the Toll Gate Creek Basin caused flooding which killed 3 people in a car in Aurora.

June 14-18, 1965 - A general storm with numerous cloudbursts affected most of Eastern Colorado. Approximately 20 people died. Approximately 600 million dollars damage was incurred. Two people died when a dam failed in Prowers County, causing 18 million dollars in damage at Holly, Granada and Lamar.

May, 1973 - Prolonged rains of up to 6 inches on May 5th and 6th in the South Platte Basin, along with melting of a large snowpack, produced major flooding during the next two weeks along the South Platte River. One person died and damages were estimated at around 120 million dollars.

July 31, 1976 - Cloudbursts produced around 12 inches of rain near Glen Haven, mostly between 6 and 11 pm, causing a record flood on the Big Thompson river. Approximately 150 people died.

July 2-3, 1981 - Intense rains of up to 10 inches near Trinidad caused the failure of a railway bridge and derailment of a train.

July 15, 1982 - Lawn Lake Dam in Rocky Mountain National Park failed, causing 2 deaths in Rocky Mountain National Park and around 30 million dollars in damage near Estes Park.

July 28, 1997 - Up to 10 inches of rain in around 5 hours fell in the vicinity of Fort Collins on ground already saturated from previous rains. There was over 100 million dollars in damage at Colorado State University alone. Five persons died when a trailer park along Spring Creek was inundated.

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Figure A.13: Arkansas River at Avondale

Figure A.14: Arkansas River Floodplain

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