Final Environmental Assessment Improvements to the North and Main Floodways Levee Systems
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Final Environmental Assessment Improvements to the North and Main Floodways Levee Systems Lead Agency: United States Section, International Boundary and Water Commission El Paso, Texas Cooperating Agency: Texas Parks and Wildlife Department Austin, Texas Technical Support: Parsons November 2007 Austin, Texas COVER SHEET FINAL ENVIRONMENTAL ASSESSMENT AND FINDING OF NO SIGNIFICANT IMPACT IMPROVEMENTS TO THE MAIN AND NORTH FLOODWAY LEVEE SYSTEMS Lead Agency: United States Section, International Boundary and Water Commission Cooperating Agency: Texas Parks and Wildlife Department Proposed Action: Raising approximately 76 miles of the Main and North Floodway Levee Systems to meet current requirements for flood control. Report Designation: Final Environmental Assessment Abstract: The United States Section, International Boundary and Water Commission (USIBWC) is considering raising portions of the 29-mile Main Floodway Levee System and portions of the 46-mile North Floodway Levee System to meet current flood control requirements. The Proposed Action would increase the flood containment capacity of the Main and North Floodways Levee System by raising elevation of a number of levee segments for improved flood protection. Fill material would be added to the existing levee to bring height to its original design specifications, or to meet a 2-foot freeboard design criterion. Typical height increases in improvement areas would be less than 1 foot and would not require expansion of the existing levee footprint. In some locations, up to 2 feet of fill material would be placed on top of the levee, extending levee footprint up to a maximum of 12 feet form the current toe of the levee. This expansion would take place along the approximately 20 feet service corridor currently utilized for levee maintenance, inside the maintained floodway, and entirely within the flood control project right-of-way. In some instances, adjustment in levee slope would be made to eliminate the need for levee footprint expansion, when required due to engineering considerations or for protection of biological or cultural resources. The need for excavation outside the levee structure is not anticipated. The Environmental Assessment assesses potential environmental impacts of the Proposed Action and the No Action Alternative. Potential impacts on natural, cultural, and other resources were evaluated, and mitigation measures were incorporated, as applicable, into the Proposed Action. A Finding of No Significant Impact was issued for the Proposed Action based on a review of the facts and analyses contained in the Environmental Assessment. FINAL ENVIRONMENTAL ASSESSMENT IMPROVEMENTS TO THE MAIN AND NORTH FLOODWAY LEVEE SYSTEMS Lead Agency: UNITED STATES SECTION, INTERNATIONAL BOUNDARY AND WATER COMMISSION UNITED STATES AND MEXICO Cooperating Agency: TEXAS PARKS AND WILDLIFE DEPARTMENT Technical Support: Parsons 8000 Centre Park Dr., Suite 200 Austin, Texas 78754 USIBWC Contract IBM04D0002, Task Order IBM06T0020 NOVEMBER 2007 Main and North Floodway Levee Systems Environmental Assessment Contents TABLE OF CONTENTS SECTION 1 PURPOSE OF AND NEED FOR THE PROPOSED ACTION......................................... 1-1 1.1 Purpose of and Need for Action........................................................................................ 1-1 1.2 USIBWC Authority ............................................................................................................1-1 1.3 Scope of the Environmental Review................................................................................. 1-2 1.4 Environmental Coordination and Compliance Analysis.................................................... 1-3 1.5 Organization of the Environmental Assessment............................................................... 1-5 SECTION 2 DESCRIPTION OF PROPOSED ACTION ...................................................................... 2-1 2.1 Levee System Description ................................................................................................ 2-1 2.2 Proposed Action................................................................................................................ 2-2 2.3 Alternatives Considered and Eliminated from Detailed study........................................... 2-8 2.4 Other Actions With Potential Cumulative Impacts ............................................................ 2-8 2.5 Summary Comparison of Environmental Consequences of the Alternatives................... 2-9 2.5.1 No Action Alternative............................................................................................... 2-9 2.5.2 Proposed Action...................................................................................................... 2-9 SECTION 3 AFFECTED ENVIRONMENT ...................................................................................3-1 3.1 Biological Resources ........................................................................................................3-1 3.1.1 Vegetation ............................................................................................................... 3-1 3.1.2 Wildlife..................................................................................................................... 3-4 3.1.3 Threatened and Endangered Species .................................................................... 3-6 3.1.4 Wetlands and Aquatic Habitat................................................................................. 3-6 3.2 Cultural Resources ........................................................................................................... 3-8 3.2.1 Previous Cultural Resources Studies ..................................................................... 3-9 3.2.2 Historic and Prehistoric Archaeological Resources .............................................. 3-11 3.2.3 Historic-age Resources......................................................................................... 3-13 3.2.4 Cemeteries............................................................................................................ 3-13 3.3 Water Resources ............................................................................................................ 3-16 3.3.1 Regional Flood Control ......................................................................................... 3-16 3.3.2 Water Flow ............................................................................................................ 3-17 3.4 Land Use......................................................................................................................... 3-19 3.4.1 Natural Resources Management Areas................................................................ 3-19 3.4.2 Agricultural Land ................................................................................................... 3-19 3.4.3 Urban Areas .......................................................................................................... 3-19 3.5 Community Resources.................................................................................................... 3-20 3.5.1 Socioeconomics .................................................................................................... 3-20 3.5.2 Environmental Justice ........................................................................................... 3-23 3.5.3 Transportation ....................................................................................................... 3-23 3.6 Environmental Health...................................................................................................... 3-24 3.6.1 Air Quality.............................................................................................................. 3-24 i USIBWC Main and North Floodway Levee Systems Environmental Assessment Contents 3.6.2 Noise ..................................................................................................................... 3-25 3.6.3 Hazardous and Toxic Waste................................................................................. 3-26 SECTION 4 ENVIRONMENTAL CONSEQUENCES ....................................................................4-1 4.1 Biological Resources ........................................................................................................4-1 4.1.1 Vegetation ............................................................................................................... 4-1 4.1.2 Wildlife..................................................................................................................... 4-1 4.1.3 Threatened and Endangered Species .................................................................... 4-4 4.1.4 Jurisdictional Wetlands and Aquatic Habitat........................................................... 4-5 4.1.5 Cumulative Effects .................................................................................................. 4-5 4.2 Cultural Resources ........................................................................................................... 4-6 4.2.1 Historic and Prehistoric Archaeological Resources ................................................ 4-6 4.2.2 Historic-age Resources........................................................................................... 4-6 4.3 Water Resources .............................................................................................................. 4-8 4.3.1 Flood Control..........................................................................................................