[Federal Register Volume 74, Number 116 (Thursday, June 18, 2009)]
[Notices]
[Pages 28952-28954]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E9-14314]


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INTERNATIONAL BOUNDARY AND WATER COMMISSION


United States Section; Notice of Availability of a Final 
Environmental Assessment and Final Finding of No Significant Impact for 
Flood Control Improvements to the Arroyo Colorado Floodway, Hidalgo and 
Cameron Counties, TX

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

ACTION: Notice of Availability of Final Environmental Assessment (EA) 
and Final Finding of No Significant Impact (FONSI).

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SUMMARY: 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 Final 
Environmental Assessment and FONSI for Flood Control Improvements to 
the Arroyo Colorado Floodway, a component of the

[[Page 28953]]

interior floodways system of the Lower Rio Grande Flood Control 
Project.

FOR FURTHER INFORMATION CONTACT: 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: 
[email protected].

DATES: The Final EA and FONSI will be available June 11, 2009.

SUPPLEMENTARY INFORMATION:

Background

    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 two segments of the 
flood control levee system with a combined length of 11 miles.
    The USIBWC prepared this EA for the proposed action to increase 
flood control of the Arroyo Colorado Levee System by raising the 
elevation of these two levee segments for improved flood protection.
    The beginning of this project is a 2.1 mile Divisor Dike near the 
juncture point of the Arroyo Colorado and the North Floodway in Hidalgo 
County, extending a total of 6.9 miles to the Willacy Canal. The 
remaining segment is 4.0 miles from the Willacy Canal ending at White 
Ranch Road in Cameron County, Texas.

Proposed Action

    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; 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. A centered levee expansion is assumed for most areas of the 
Arroyo Colorado Levee system, except south of La Feria reservoir, where 
levee expansion will be offset to the riverside of the existing levee.
    The proposed action will increase the height of the levee up to 2 
feet for approximately 8.6 percent of the 11-mile segment. 
Approximately 4 percent of the levee segment will be increased from 2 
to 4 feet, and approximately 2.4 percent will be increased from 4 to 6 
feet. The existing levee is a raised trapezoidal compacted-earth 
structure with a crown width of 16 feet, a typical height ranging from 
10 to 15 feet, and approximately 3:1 side slope ratio (horizontal run: 
vertical rise). For a typical levee cross-section at the ACF that 
requires additional fill material to the crown the levee footprint 
would be expanded at a 1:6 ratio (crown height: footprint length). The 
footprint expansion would be equally divided between the riverside and 
landside (centered expansion) or entirely on one side (offset 
expansion). Moderately higher increases will be needed in a small 
segment that accounts for less than 1.2 percent of the total length. In 
areas where existing topography is too steep to allow levee expansion, 
construction solutions, including armored banks (riprap) or retaining 
walls, will be used. Excavation outside the existing right-of-way is 
not anticipated.
    The EA 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 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 EA.

Summary of Findings

    Pursuant to the National Environmental Policy Act (NEPA) guidance 
(40 CFR 1500-1508), The President's Council on Environmental Quality 
issued regulations for implementing NEPA, which included provisions for 
both the content and procedural aspects of the required EA. The USIBWC 
completed an EA of the potential environmental consequences of raising 
the Arroyo Colorado Floodway (ACF) levee system to meet current 
requirements for flood control. The EA, which supports this Finding of 
No Significant Impact, evaluated the proposed action and no action 
alternative.

Levee System Evaluation

No Action Alternative

    The no action alternative was evaluated as the single alternative 
action to the proposed action. The no action alternative will retain 
the current configuration of the ACF levee system, with no impacts to 
biological and cultural resources, water resources, land use, soil, 
community resources, or environmental health issues. In terms of flood 
protection, however, current containment capacity under the no action 
alternative may be insufficient to fully control Rio Grande flooding 
under severe storm events, including associated risks to personal 
safety and property. The levee system will not meet FEMA requirements 
for levee system certification.

Proposed Action

Biological Resources
    Biological resources in the vicinity of the levee systems are 
dominated by agricultural fields, rangelands, and non-native 
grasslands. There are some woody species along the margins of the 
Arroyo Colorado, drainage ditches from irrigation fields, and adjacent 
to borrow pits. The 160-foot wide biological survey corridor, centered 
on the existing levee, includes approximately 221 acres, primarily 
composed of non-native grasslands dominated by buffelgrass and king 
ranch bluestem.
    The proposed action will raise the levee using a centered 
expansion, except in areas south of La Feria reservoir, where an offset 
expansion will be utilized. The proposed levee expansion will remove 
non-native grasslands on the levee slopes and adjacent areas. Native 
grasses will be planted immediately after the completion of the 
project, and the levee expansion will not occur in wooded areas. Less 
than one-half acre of non-jurisdictional wetlands will be affected, but 
no jurisdictional wetlands will be affected by the levee expansion. No 
habitats used by federally or state-listed threatened or endangered 
species will be impacted by the levee expansion.
    In areas adjacent to sensitive areas such as water bodies, levee 
expansion may be altered to an offset expansion toward the riverside of 
the levee to avoid impacting sensitive resources. In areas where the 
existing topography is too steep to allow levee expansion, construction 
solutions, including armored banks, will prevent erosion of the levee 
slopes. The construction solutions will not affect sensitive habitats, 
including wooded areas, habitats for threatened and endangered species, 
or jurisdictional wetlands.
Cultural Resources
    Improvements to the ACF levee system may adversely affect 
prehistoric and historic archaeological resources.

[[Page 28954]]

Some areas adjacent to the toe of the levee contain intact 
archaeological resources. Adverse effects to archaeological resources 
may occur from the use of heavy equipment during levee construction 
that could disturb surface or shallowly buried deposits. Adverse 
effects may also occur to archaeological deposits that will be buried 
by the addition of the fill material on the surface above them. 
Alternatively, levee footprint expansion may protect archaeological 
resources by capping with fill material, preserving those resources in 
place.
    Architectural resources may be adversely affected by levee height 
increases or by expansion of the levee footprint. Potential effects 
include vibration and ground disturbance from the use of heavy 
equipment during construction. Design for levee improvements is 
primarily considering avoidance of the structures as much as possible. 
However, if structures have to be removed or modified, USIBWC will 
consult with the Texas Historical Commission (THC) to determine the 
appropriate level of documentation prior to any modification. In 
addition to documentation, mitigation of impacts to cultural resources 
may include their replacement with ``in-kind'' structures that will 
look and operate the same.
    Native American resources may be affected by the levee 
improvements; consultation with the Native American tribes is ongoing 
to identify resources or concerns regarding the project.
    Under NEPA, there will be no significant impacts (i.e., 
``unresolvable'' adverse effects under National Historic Preservation 
Act [NHPA]) to cultural resources because all cultural resources will 
be identified and evaluated for National Register of Historic Places 
(NRHP) eligibility. Any impacts to National Register of Historic 
Places-eligible resources will be mitigated prior to implementation of 
levee height increases or footprint expansion, in consultation with the 
Texas Historical Commission and Native American Tribes.
Water Resources
    Flood control improvements to the ACF will increase flood 
containment capacity to control the design flood event with a 
negligible increase in water surface elevation. Levee footprint 
expansion will not affect water bodies.
Land Use
    Footprint levee expansion, where required, will take place 
completely within the existing ROW. No urban or agricultural lands will 
be affected.
Soil
    Improvement activity contributing to soil disturbance will include 
geotechnical investigations and adding soil to the top and sides of the 
levee. Levee fill material will come from local commercial sources and 
not from borrow areas in the floodplain. The disturbance of soil will 
occur within areas where soil has been disturbed and modified by prior 
levee construction and maintenance activities. Therefore, alteration of 
soil previously unassociated with the existing levee will not occur.
Community Resources
    In terms of socioeconomic resources, the influx of federal funds 
into Hidalgo and Cameron Counties from the flood control improvement 
area will have a positive but minor local economic impact. The impact 
will be limited to the construction period, and represent less than 1 
percent of the annual county employment, income, and sales values. No 
adverse impacts to disproportionately high minority and low-income 
populations were identified for construction activities. Moderate 
utilization of public roads will be required during construction; a 
temporary increase in access road use will be required for equipment 
mobilization to staging areas.
Environmental Health Issues
    Estimated air emissions of five criteria pollutants during 
construction will be discontinuous and represent less than 0.13 percent 
of the annual emissions inventory within the air quality control region 
of Hidalgo, Cameron, and Willacy Counties. There will be a moderate 
increase in ambient noise levels due to construction activities. No 
long-term and regular exposure is expected above noise threshold 
values. A database search indicated that no waste storage and disposal 
sites were within the proposed ACF levee improvement area, and none 
will affect, or be affected by, the levee improvement project.
Best Management Practices
    When warranted due to engineering considerations, or for protection 
of biological or cultural resources, the need for levee footprint 
expansion will be eliminated by levee slope adjustment or use of 
retaining walls or armored banks. Best management practices during 
construction will include development of a storm water pollution 
prevention plan to avoid impacts to receiving waters, and use of 
sediment barriers and soil wetting to minimize erosion.
    To protect vegetation cover, the embankment improvement areas will 
be re-vegetated with native herbaceous species. To protect wildlife, 
construction activities will be scheduled to occur, to the extent 
possible, outside the March to August bird migratory season.

Availability

    Single hard copies of the Final Environmental Assessment and 
Finding of No Significant Impact may be obtained by request at the 
above contact information. Electronic copies may also be obtained from 
the USIBWC Home Page at http://www.ibwc.gov/Organization/Environmental/reports_studies.html.

    Dated: June 12, 2009.
Robert McCarthy,
General Counsel.
[FR Doc. E9-14314 Filed 6-17-09; 8:45 am]
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