2009/11/02 Comanche Peak COL - FW: Responses To RAIs

GeologyThe geology of North Central Texas is made up of sedimentary rock strata, including a variety oflimestones, sandstones, shales, and alluvial deposits. Bedrock is overlain by soil horizons of variablethicknesses. Rock strata ages at the surface ranges from Pennsylvanian-age (325-290 million yearsbefore present (mybp)) found in the northwestern corner of the region to large expanses of Cretaceousaged rocks (120-65 mybp) throughout the central portions of the region. Tertiary-aged strata (60-35mybp) make up easternmost portions of the region, while much younger unconsolidated alluvial depositsare found along major rivers and tributaries across the region, generally accredited as Pleistocene-aged(1.8 mybp – 11,000 tybp) or younger flood deposits.The region is structurally positioned on the margins of the Texas craton, a large, relatively stable tectonicfeature in west-central Texas. The western half of the region is separated from eastern portions by thelinear Ouachita fold/thrust front near Dallas. The Ouachita front developed through North Texas duringPaleozoic time (around 300 mybp) and exists now as an eroded and buried fold belt (about 8,000 feetbelow sea level), underlying parts of Ellis, Kaufman, Dallas, Navarro and Collin Counties. Severalsignificant tectonic structures may be found in the eastern and western portions of north central Texasand are typically linked to the Ouachita front.The eastern region includes the East Texas Embayment, a Mesozoic-aged graben (around 100 mybp)that is part of the greater Mesozoic/Tertiary-aged Gulf Basin, which extends southeast towards themodern Gulf of Mexico. The structure contains several petroleum-producing regions, including theCorsicana Oil Field, significant as the first major oil and natural gas field in Texas. Minor faults associatedwith the Luling-Mexia-Talco fault system parallel this graben feature but are generally inactive,subsidence-related normal faults with little appreciable throw.West-central portions of the region are underlain by the Fort Worth basin, a large synclinal feature.Portions of Tarrant, Denton, Wise and Parker counties are areas of active exploration and drilling as aresult of recent gas discoveries related to the Barnett Shale formation found throughout this region. TheNewark East field of Denton County contains the largest active natural gas producing region in the Stateof Texas.The northwestern quarter of the region is a surface exposure of the area’s oldest rocks, due to uplift onthe east margin of an arch feature related to the Fort Worth Basin and Ouachita Front formation. Uplifthere has removed younger Cretaceous rocks, allowing the older westward-dipping strata to be exposedin Palo Pinto and western Wise and Parker Counties.North Central Texas is generally characterized as having minor seismic activity. Several minor faultzones are present within the region but are not considered active. Microquakes have occurred alongseveral faults within the region, which may be initiated by drilling and well injection activities. Other faultsmay be found in association with other regional structural features. In the North Central Texas area, thelast indication of significant fault movement is about 11 million years ago, and no evidence of later faultinghas been found in younger rocks. Other major regional fault systems are more active, such as Oklahoma,Missouri and West Texas.See HazMAP map 1-4SoilsThe soils of the NCTCOG region are varied in texture, composition and character, and due to the size ofthe region, change widely among the various physiographic regions of North Central Texas.HazMAP Multi-Hazard Risk AssessmentNorth Central Texas4Forewarnings of Natural Hazards to the Year 2030Approved by the NCTCOG Executive Board January 22, 2004

The Eastern Cross Timbers portion of the easternmost area of the NCTCOG region is characterized bywell drained, rolling hills with sandy soils in the uplands, and narrow clay-rich river bottoms. Soils rangefrom alfisols on uplands, to mollisols and entisols in flood bottoms.The majority of the central and east-central portions of the NCTCOG region are comprised of uniformdark carbonate-rich alkaline soils, developed on a gently sloping to level area underlain by limestones,shales and marlstones. Clays may include montmorillionite and may be carbonatic. Soils in this regiontypically do contain high amounts of expansive clay minerals. Soil classes are primarily vertisols, alfisolson terraces and in uplands, and mollisols in flood bottoms.In the center of the NCTCOG region, a thin standout portion of Eastern Cross Timbers soils typescoexists with the surface exposures of the Eagle Ford Shale formation. West of this region, thetopography and soil composition are that of the Grand Prairie region. This region is primarily an area ofgently rolling to hilly, dissected limestone plateaus, which are relatively resistant to erosion. Carbonatic ormontmorillionic vertisols dominate, with lesser alfisols and mollisols and entisols.Westernmost portions of the NCTCOG region are typified by the widely ranging alfisols of the WesternCross Timbers region. These range from somewhat stoney, sandy or clayey argillaceous, acidic soils tomore limited alkaline soils. The rocks underlying this region are varied, from limestones, to sandstonesand shales of varying composition, and the topography is rugged to hilly.See HazMAP map 1-5 and HazMAP map 1-6HydrologyThe North Central Texas region represents the largest urban metropolitan area in the nation located onan inland waterway. The majority of the region, or approximately 64.95 percent, is situated within theupper Trinity River basin, while the remaining land is situated in the Sabine River basin (5.86 percent),the Brazos River basin (27.37 percent) and the Red River basin (1.81 percent). The Metroplex dependson a number of reservoirs in the upper Trinity River basin, which impound water on several forks of theTrinity primarily for flood prevention or water supply purposes. At present, there are 38 major waterreservoirs in the sixteen county region. These areas account for over 233,400 surface acres of water.An extensive system of water transmission facilities brings water to many urban and suburbancommunities from the network of reservoirs. The region faces the challenges of water quality impactsresulting from urban activities, storm water discharges, and the discharge of treated wastewater from alarge metropolitan center. The prairie waterways in North Central Texas, including the Trinity River,experience widely variable flow scenarios. These conditions range from critical low flow situations duringdrought periods, to periodic severe flooding events. NCTCOG is the area wide water quality managementplanning agency as designated in 1975 by the Governor and the Texas Commission on EnvironmentalQuality. For over 25 years NCTCOG has been reporting on the water quality issues affecting the UpperTrinity River basin.See HazMAP map 1-7Demographics, Housing & EmploymentSince January 1, 2002, North Central Texas has added 152,600 persons for a January 1, 2003 totalpopulation of 5,714,150. The region has now averaged over 150,000 new persons per year for the pastfour years and this marks the seventh consecutive year to add over 100,000 persons.According to the NCTCOG 2003 Current Population Estimates publication, single-family housingconstruction trailed last year’s record growth only slightly as historically low interest rates continued tostimulate construction. Multi-family construction in 2002 actually outpaced 2001 by over 3,000 units. Thisresulted in a net increase of 2,200 units over last year. However, population growth was mitigated in alarge part due to significant declines in multi-family occupancy rates. Multi-family markets have sufferedHazMAP Multi-Hazard Risk AssessmentNorth Central Texas5Forewarnings of Natural Hazards to the Year 2030Approved by the NCTCOG Executive Board January 22, 2004

losses from the aforementioned single-family shifts and tend to be most affected by employment lossesfrom the current slumping economy.The North Central Texas region as a whole grew 45.93% adding 935,107 new jobs to the area from 1990to 2000. During this period of exceptional growth, the City of Dallas continued to lead the region inemployment growth by adding 228,664 jobs bringing their total employment base to 1,038,314. The Cityof Fort Worth follows Dallas adding just under 120,000 jobs for a total of 449,793 in 2000. Irving andPlano were next adding 60,598 and 58,835 new jobs bringing their total employment to 165,435 and115,048 respectively. Arlington was close behind adding just over 50,800 new jobs for a 2000 total of140,947 jobs. Together, these five cities account for 55% of all job growth from 1990 to 2000. The labormarket performance in the late 1990s was the strongest in a decade both nationally and locally. From1990 to 2000, Flower Mound and Frisco experienced the fastest job growth in the region, with each citygrowing by 230%. Not far behind, the City of Coppell grew 190%. The City of Keller was next growing171% followed by Colleyville and Allen each growing over 150%. It is interesting to note that the growth ineach of these cities is due to numerous and varied sources rather than job increases by large individualemployers.According to the Texas Workforce Commission, the North Central Texas region is a major center ofemployment for telecommunications, transportation, construction, electronics, manufacturing, and dataprocessing. Some of the products that are produced from more 1,000 plants of the region include planes,electronic equipment, helicopters, mobile homes, chemicals, foods, and plastics. The four core countiesof the 16-county North Central Texas region, Dallas, Tarrant, Denton, and Collin counties, account for 94percent of the major employer establishments of this region. As stated in the North Central Texas Councilof Governments 2003 Major Employers publication, the three largest employers in North Central Texasinclude American Airlines, Lockheed Martin, and the University of North Texas. The Dallas/Fort WorthInternational Airport – the third busies airport in the world - continues to serve as the regional centralbusiness district (CBD) of North Central Texas. Approximately 2.1 million jobs, 83 percent of the MPAtotal, are within a 20-mile radius of the airport.Land UseSee HazMAP map 1-8 for the 2000 Regional Land Use MapSee HazMAP map 1-9 for the 2000 Commercial Land Use Density MapSee HazMAP map 1-10 for the 2000 Residential Land Use Density MapSee HazMAP map 1-11 for the 2000 Vacant Land Use Density MapHazMAP Multi-Hazard Risk AssessmentNorth Central Texas6Forewarnings of Natural Hazards to the Year 2030Approved by the NCTCOG Executive Board January 22, 2004

HazMAPChapter 2Critical FacilitiesIn order to understand what assets in the region can be affected by hazard events, an inventory of criticalfacilities was compiled. Using the Department of Homeland Security’s The National Strategy for thePhysical Protection of Critical Infrastructures and Key Assets as a guide, NCTCOG staff organized theregion’s assets int

Sent Date: 11/2/2009 5:02:38 PM Received Date: 11/2/2009 5:02:48 PM From: Monarque, Stephen Created By: Stephen.Monarque@nrc.gov . North Central Texas Approved by the NCTCOG Executive Board January 22, 2004 3. Geology The geology of North Central Texas is made