US Army Corps of Engineers
Albuquerque District Website

SPA-2004-00406-ABQ - Pueblo of Isleta Rio Grande Island Removal and Bank Stabilization Project

Published July 11, 2013
Expiration date: 8/12/2013

SUBJECT: Public Notice for the Proposed Pueblo of Isleta Rio Grande Island Removal and Bank Stabilization Project

SUMMARY: The U.S. Army Corps of Engineers, Albuquerque District, (Corps) is evaluating a permit modification from the Pueblo of Isleta (POI) to remove vegetated sand bars and islands and alter channel geometry, and reclaim and stabilize 160 linear feet (ft.) of eroded bankline within the Rio Grande river channel. The proposed modifications to the 2005 permit reduce the quantity of excavation from 144,500 cubic yards (cy.) to 83,000 cy; incorporate 160 feet of bank line reclamation, access, and stabilization; and reduce the construction window from 10 years to six months. The project would result in permanent and temporary impacts to approximately 26.2 acres of waters of the United States and/or navigable waters of the United States in or adjacent to Rio Grande. The purpose of this public notice is to inform interested parties of the project and to solicit comments.

AUTHORITY: This application is being evaluated under Section 404 of the Clean Water Act for the discharge of dredged or fill material in waters of the United States (U.S.).

APPLICANT: The Honorable E. Paul Torres, Governor, Pueblo of Isleta, Post Office Box 1270, Isleta, New Mexico 87022

LOCATION: The project site is located in the Rio Grande river below the Isleta Diversion Dam (IDD), Section 24, Township 8 N, Range 2 E, Latitude 34.9029°, Longitude -106.6863°, Pueblo of Isleta, Valencia and Bernalillo Counties, New Mexico.

PROJECT DESCRIPTION: In October 2005, POI was issued a Section 404 individual permit to conduct vegetated island removal activities. The Pueblo was authorized to excavate an estimated 130,000 cy of vegetated sand bars and islands from within the river channel. The permit was issued with a December 31, 2015 expiration date. However, the permitted project has not been executed and project modifications are being proposed.

The proposed project modifications would alter channel geometry within the project boundary by creating two earthen terraces along the upper east bank and lower west bank; incorporate 160 ft. of bank line reclamation, stabilization, and river access; fill 1,100 linear ft. of a low flow channel; and have a six-month construction window. Also included is a permanent 450 ft. riprap spur dike along the eastern bank terraces’ upstream edge, and the placement of three temporary earthen diversion structures. The Corps has determined that the proposed modifications warrant public notice issuance to provide for public comments. The modifications are described in more detail below.

Vegetated Island Removal and Channel Geometry. POI has stated that removing vegetated islands and bars provide views and better access across the river. These are regarded as essential activities to the Pueblo. The previous permit authorized POI to excavate 11.4 acres of vegetated islands and bars. Depth of excavation was authorized to match the channel bed elevation. The 2005 goal was to remove islands and bars leaving a wide, shallow river reach. The permittee has stated that data indicates a wide shallow channel would likely not be capable of transporting sediment downstream of the project boundary. Deposition in the subject reach would occur and periodic excavation would be required.

The proposed refinement would alter existing channel geometry, accommodate anticipated flow events, and also provide for sediment transport. The proposal consists of a low flow channel with terraced banks on the upper east bank and lower west bank. An estimated 83,000 cy of channel sediment would be excavated and deposited at an approved upland site to the east. POI estimates that 11.6 acres of vegetated bars and islands would be eliminated. The attached Sheet 2 of 9 is a plan view map of the proposal. A single low flow channel would convey flows up to 1,200 cubic feet per second (cfs).

The terraces will be constructed of sediment compacted atop existing bank-attached bars. Prior to deposition and compaction, the bars will be mowed and tree roots removed. The east and west terraced banks would be constructed to accommodate similar flow events. The lower set of terraces would accommodate flows up to 3,000 cfs and the second terraces for flows up to up to and greater than 7,000 cfs. The Pueblo proposes to allow low growth vegetation (grasses to low shrubs) to proliferate in order to provide additional stabilization as well as organic contributions.

The activity includes the construction of a 450-ft long spur dike to prevent mid-level and high-level flows from eroding the east bank terraces. The dike would also direct flows along the west bank and along a cultural site. The permanent spur dike profile will be set so its crest elevation matches the bench elevations on the east bank attached bar. The dike will be 6 ft from toe or base to crest, will have a 10-ft top width with 2:1 side slopes and be toed below channel invert to the scour line. The spur dike will have a compacted-earth core, and will be plated on top and both sides by a 3-ft thick layer of large diameter rip rap, D50=2.0 ft. The spur dike armoring will be large diameter rip rap, D50=2.0 ft such as basalt. A geotextile filter fabric will be used to prevent migration of fine materials from the bank into the river. The volume of rip rap for the spur dike is 1,400 cy. The volume of the compacted- earth core is 800 cy. The geotextile filter fabric will total 2000 sq. yards. The fabric does not need to be maintained and should have a 5 year life.

Two additional temporary diversion structures would be constructed, one in the upstream end to divert flow into the temporary channel along the east bank and the second in the downstream reach of the project to prevent backwater into the project during construction. The upstream diversion dike would extend north from the East Side Attached Bar to funnel flows into the temporary east side diversion channel. This temporary diversion dike would be 300 ft. long x 30 ft. wide; its average height would be 4 ft., with a ten-ft. top width and 2:1 side slopes. This diversion dike would be constructed of non-erodible materials. The diversion dike would contain 746 cy. of temporary fill. At the downstream end of the east bank attached bar, a temporary cofferdam would be built across the bed of the river to prevent backwater from flowing into the project site. This temporary backwater cofferdam, constructed of non-erodible materials, would be 250 ft. long x 30 ft. wide, 4 ft. high, with a ten-ft. top width and 2:1 side slopes. The backwater cofferdam would contain 622 cy. of temporary fill.

Bank Reclamation, Stabilization, and Access. This activity was not a component of the previously authorized work. POI has stated that the west bank below the IDD is an area of significance but is not open to the general public and that consistent flows along the west bank are an important feature. POI has also stated that the west bank has retreated further to the west and continued erosion would encroach on the existing levee, a tribal road, and possibly an irrigation headgate. POI believes IDD releases have accelerated the lateral erosion. The permittee has decided that constructing the west bank protection and access would be best achieved concurrent with island and bar/channel reforming efforts.

The permittee has proposed eliminating the nick point and reclaiming an average of 25 lateral f.t of bankline for 130 linear ft. Construction of a bank protection feature along the west bank designed so that the pedestrian access at the cultural site is not impacted during mid-level and high-level flow events. West bank protection also serves to stabilize the west bank to facilitate sediment transport under high velocity mid- and high-level flows away from the desired west bank low flow channel location. The bank protection will be constructed with large-diameter rip rap, D50=2.0 ft. A geotextile filter fabric will be used to prevent migration of fine materials from the bank into the river. The volume of rip rap for the west bank protection is 600 cy. The geotextile filter fabric will total 650 sq. yards. Pedestrian friendly river access would be created immediately downstream of the stabilized area and consist of 30 f.t wide concrete stepped structure constructed to the low flow channel’s scour line. The concrete would be earth-tone tinted and total 35 cy. A total of 160 ft. of bankline would be affected.

A temporary cofferdam 270-ft long, 6-ft high, with a ten-f.t top width and 2:1 side slopes will be constructed around the west bank stabilization site to divert river flows away from the bank during construction. The west bank cofferdam will be constructed of non-erodible material. The volume of the temporary cofferdam is 1320 cy. The cofferdam will be built from upstream down so that no flows are captured behind the cofferdam. Seepage under and through the cofferdam will be pumped out, settled, and discharged into the Belen Highline Canal.

Side Channel Fill. POI has proposed placing 4,000 cy of excavated sediment into 1,100 ft of an existing low flow channel located along the river’s west bank. The permittee has stated that filling the upper and middle reach of the channel will better promote sediment transport. The lower 100 ft. of the channel will be preserved and developed into a backwater area to increase RGSM habitat.

Construction Window: The 2005 permit authorized a 10-year construction window. The applicant has reduced the construction window to six months. POI anticipates that the shortened construction window will minimize effects to the aquatic system.

PURPOSE AND NEED: The project supports the Pueblo’s primary contact ceremonial use of the Rio Grande by providing safe pedestrian access and by protecting the west bank from eroding any further to the west. The purpose of the project is to meet the following cultural desires of the Pueblo of Isleta: 1) Restore the view of the Rio Grande from the cultural site. 2) Provide for year-round flows along the west bank. 3) Provide additional habitat for the Rio Grande silvery minnow (RGSM). POI has determined that the project will meet the need of improving ceremonial use opportunities.

PROPOSED MITIGATION: In spring of 2012, POI revegetated approximately 20 acres along the rivers’ east bank located above the project location. The riparian revegetation was conducted pursuant to special conditions in the 2005 permit and consisted of native riparian species common to the area. As described above, POI is proposing to reduce the construction window from 10 years to 6 months. Additionally, POI proposes to reduce quantity of excavation from 144,500 cy. to 83,000 cy.

Allowing native grasses and low growth shrubs to populate the terraces will provide the opportunity for RGSM egg and larval entrainment while also minimizing maintenance requirements and promoting terrace structural stability. POI has also proposed creating two backwater embayment areas at the downstream end of the east (0.27 acre) and west (0.16 acre) constructed terraces.


Tribal Water Quality Certification. The applicant is required to obtain water quality certification, under Section 401 of the Clean Water Act, from the Pueblo of Isleta Environment Division of the Public Services Department. Section 401 requires that any applicant for an individual Section 404 permit provide proof of water quality certification to the Corps of Engineers prior to permit issuance. For any proposed activity on Tribal land that is subject to Section 404 jurisdiction, where the tribe does not have water quality certifying authority, the applicant will be required to obtain water quality certification from the U.S. Environmental Protection Agency.


Environmental Setting. The project is located on the Rio Grande within the POI in Valencia County, New Mexico. The project site is located in the Mexican Highland section of the Basin and Range Physiographic Provence. The area has an arid climate with precipitation ranging from 7 to 10 inches. The POI is located about 13 miles south of Albuquerque. The pueblo, which is roughly rectangular in shape, is approximately 9 miles wide from north to south and 40 miles long from east to west. The pueblo’s language is Tiwa and the present village site dates to around 1500.

The project site is characterized by a braided channel with shallow, highly erodible banks. Flow through the site is controlled by releases through the IDD. An earthen levee along the west side confines flow to the existing channel. The east bank is subject to overbanking in high flow events. The project site begins approximately 200 feet below the IDD. There are approximately 1,960 linear feet of perennial streams that are waters of the U.S. within the proposed project area.

Alternatives. The applicant has provided information concerning project alternatives. Additional information concerning project alternatives may be available from the applicant or their agent. All reasonable project alternatives, in particular those which may be less damaging to the aquatic environment, will be considered.

EVALUATION FACTORS: The decision whether to issue a permit will be based on an evaluation of the probable impacts, including cumulative impacts, of the described activity on the public interest. That decision will reflect the national concern for both protection and utilization of important resources. The benefit, which reasonably may be expected to accrue from the described activity, must be balanced against its reasonably foreseeable detriments. All factors which may be relevant to the described activity will be considered, including the cumulative effects thereof; among those are conservation, economics, aesthetics, general environmental concerns, wetlands, historic properties, fish and wildlife values, flood hazards, floodplain values, land use, navigation, shoreline erosion and accretion, recreation, water supply and conservation, water quality, energy needs, safety, food and fiber production, mineral needs, consideration of property ownership and, in general, the needs and welfare of the people. The activity's impact on the public interest will include application of the Section 404(b)(1) guidelines promulgated by the Administrator, Environmental Protection Agency (40 CFR Part 230).

The Corps is soliciting comments from the public, Federal, State, and local agencies and officials, Indian tribes, and other interested parties in order to consider and evaluate the impacts of this proposed activity. Any comments received will be considered by the Corps to determine whether to issue, modify, condition, or deny a permit for this proposal. To make this decision, comments are used to assess impacts on endangered species, historic properties, water quality, general environmental effects, and other public interest factors listed above. Comments are used in the preparation of an Environmental Assessment and/or an Environmental Impact Statement pursuant to the National Environmental Policy Act. Comments are also used to determine the need for a public hearing and to determine the overall public interest of the proposed activity.

HISTORIC PROPERTIES: The Corps consulted district files and records, the latest version of the National Register of Historic Places (NRHP), and state records of NRHP-eligible and potentially eligible historic properties to determine if there are any historic properties that might be affected by the proposed undertaking. On May 31, 2013, the POI Cultural and Historic Preservation Office stated that the proposed project would have no effect on archaeological or cultural features. Based on this initial information, the Corps has made a preliminary determination that the proposed project will not likely affect any historic properties that meet the criteria for inclusion in the NRHP.

ENDANGERED SPECIES: The Corps has reviewed the U.S. Fish and Wildlife Service's latest published version of Federally-listed endangered and threatened species located in Valencia and Bernalillo Counties, New Mexico to determine if any listed species or their critical habitat may occur in the proposed project area. The Corps has made a preliminary determination that the proposed activity may affect Federally-listed endangered or threatened species or their critical habitat. The Corps will re-initiate consultation with the U.S. Fish and Wildlife Service pursuant to Section 7 of the Endangered Species Act, as appropriate.

FLOODPLAIN MANAGEMENT: The project is located on pueblo land and is not a part of designated floodplains.

CLOSE OF COMMENT PERIOD: All comments pertaining to this Public Notice must reach this office on or before August 12, 2013, which is the close of the comment period. Extensions of the comment period may be granted for valid reasons provided a written request is received by the limiting date. If no comments are received by that date, it will be considered that there are no objections. Anyone may request, in writing, that a public hearing be held to consider this application. Requests shall specifically state, with particularity, the reason(s) for holding a public hearing. If the Corps determines that the information received in response to this notice is inadequate for thorough evaluation, a public hearing may be warranted. If a public hearing is warranted, interested parties will be notified of the time, date, and location. Comments and requests for additional information should be submitted to:

    Ed Paulsgrove, Project Manager
    US Army Corps of Engineers, Albuquerque District
    4101 Jefferson Plaza NE
    Albuquerque, New Mexico 87109
    (505) 342-3279
    FAX: (505) 344-1514

Please note that names and addresses of those who submit comments in response to this public notice may be made publicly available through the Freedom of Information Act.