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Notice of Availability of a Draft Environmental Assessment and Draft Finding of No Significant Impact for Flood Control Improvements to the Arroyo Colorado Floodway

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United States Section, International Boundary and Water Commission, United States and Mexico.


Notice of Availability of Draft Environmental Assessment (EA) and Draft Finding of No Significant Impact (FONSI).

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Pursuant to Section 102(2)(c) of the National Environmental Policy Act (NEPA) of 1969 (42 U.S.C. 4321 et seq.), the Council on Environmental Quality Final Regulations (40 CFR Parts 1500 through 1508), and the United States Section, International Boundary and Water Commission's (USIBWC) Operational Procedures for Implementing Section 102 of NEPA, published in the Federal Register September 2, 1981 (46 FR 44083); the USIBWC hereby gives notice of availability of the Draft Environmental Assessment and Draft FONSI for Flood Control Improvements to the Arroyo Colorado Floodway, which is part of the interior floodways in the Lower Rio Grande Flood Control Project.

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Rita Crites, Environmental Protection Specialist, Environmental Management Division, United States Section, International Boundary and Water Commission; 4171 N. Mesa, C-100; El Paso, Texas 79902. Telephone: (915) 832-4781; e-mail:

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The Draft EA and Draft FONSI will be available April 27, 2009.

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The Arroyo Colorado is an ancient distributary of the Rio Grande, and it serves as drainage for crop irrigation, municipal wastewater returns, and as a floodway during periods of heavy precipitation in the Lower Rio Grande Valley. The project area includes 2.1 miles of the Divisor Dike, and approximately 8.4 miles of the Arroyo Colorado north levee.

The USIBWC prepared this EA for the proposed action to increase flood containment capacity of the Arroyo Colorado Levee System by raising the elevation of this segment for improved flood protection. This action will also address the 100-year flood protection criteria established by the Federal Emergency Management Agency (FEMA).

The beginning of this project is at the Divisor Dike near the juncture point of the Arroyo Colorado and the North Floodway in Hidalgo County and the ending is at White Ranch Road in Cameron County, Texas.

The proposed levee rehabilitation improvements consist of: (1) Raising the top-of-levee elevation, (2) conducting geotechnical investigations and testing to determine the type and extent of any required remediation improvements due to slope stability, seepage, levee settlement, and any other geotechnical issues that may cause levee failure during a 100-year flood event and (3) modifying, if necessary, hardware or structures located along the levee reaches. Any modifications will be in compliance with the Texas Historical Commission recommendations. The top elevation of the levee-raising improvements will be to provide containment of flood flows with a minimum freeboard of 3 feet for water surface elevations as calculated in the USIBWC 2003 Hydraulic Model for the LRGFCP. Raising on the riverside of the levee will be the most probable alternative given the nature of the right-of-way in the area.


The USIBWC completed an EA of the potential environmental consequences of raising the Arroyo Colorado Floodway to meet current requirements for flood control. The EA, which supports the Finding of No Significant Impact, evaluated the Proposed Action and No Action Alternative.


Single hard copies of the Final Environmental Assessment and Final Finding of No Significant Impact may be obtained by request at the above address. Electronic copies may also be obtained from the USIBWC Home Page at​home.html.

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Dated: April 17, 2009.

Robert McCarthy,

General Counsel.

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[FR Doc. E9-9322 Filed 4-23-09; 8:45 am]