United States and Mexico, United States Section; Notice of Availability of a Final Environmental Assessment and Finding of No Significant Impact for Sediment Removal Downstream of Retamal Diversion Dam, in the Lower Rio Grande Flood Control Project, Located in Hidalgo County, Texas

AGENCY:

United States Section, International Boundary and Water Commission (USIBWC), United States and Mexico.

ACTION:

Notice of availability of final Environmental Assessment (EA) and Finding of No Significant Impact (FONSI).

SUMMARY:

Pursuant to section 102(2)(c) of the National Environmental Policy Act of 1969, the Council on Environmental Quality Final Regulations (40 CFR parts 1500 through 1508), and the U.S. Section's Operational Procedures for Implementing Section 102 of NEPA, published in the Federal Register September 2, 1981 (46 FR 44083), the U.S. Section hereby gives notice that the Final Environmental Assessment and Finding of No Significant Impact for Sediment Removal Downstream of Retamal Diversion Dam, in the Lower Rio Grande Flood Control Project, located in Hidalgo County, Texas are available. A notice of finding of no significant impact dated October 7, 2003, provided a thirty (30) day comment period before making the finding final. The notice was published in the Federal Register on October 17, 2003 (68 FR 59818).

FOR FURTHER INFORMATION CONTACT:

Daniel Borunda, 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) 832-4701, email: danielborunda@ibwc.state.gov.

SUPPLEMENTARY INFORMATION:

Proposed Action

The project includes dredging the sediment and beneficially use or dispose of all the material on vacant Mexican Federal government land adjacent to the river at the dredging location. The size of the project area is approximately 4.94 acres, which includes 2.1 acres of wetland. The EA analyzes potential impacts from dredging approximately 54,000 cubic yards of sediment material, either hydraulically (Option 1) or mechanically (Option 2), during the non-irrigation season between September and February when water levels in the Rio Grande are maintained at lower levels. Construction activities include transporting dredged materials to dewatering cells on the Mexican riverbank. A hydraulic piping system may be set up to transport the slurry mix directly to the final disposal area or the materials may be transported by trucks provided by Mexico, depending on the disposal method. A coffer dam may also be constructed to de-water alternate sides of the river during dredging activities. The EA provides details of the action, explains the purpose and need for the action, and assesses the potential impacts of the proposed action and alternatives.

Alternatives Considered

The USIBWC proposes to remove the vegetated island and sandbar by dredging the sediment, either hydraulically (Option 1) or mechanically (Option 2), and beneficially use or dispose of all the material on vacant Mexican Federal government land adjacent to the river at the dredging location.

The sandbar and island downstream of the Retamal Diversion Dam will not be removed in the no action alternative. The accumulation of sediment will likely continue in the channel on the U.S. side of the Rio Grande and along the concrete apron beneath the flood gates, thus potentially impairing the ability of the gates to operate effectively to properly control flood events. The main channel in the river could continue shifting toward the Mexican side, thus potentially changing the boundary location between the two countries.

Availability

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 www.ibwc.state.gov.