Project Location: Project is located at the U.S. 52 Sabula causeway in the Mississippi River in Sabula in Section 8 & 17, Township 84 North, Range 7 East, Jackson County, Iowa. Latitude/Longitude 42.090209, -90.1738742.
Project Description:
A. The applicant has proposed to reconstruct, widen the shoulders, stabilize the roadway embankment and repave approximately 2 miles of the U.S. 52 from the west approach of the Mississippi River Bridge crossing to the north approach of the Mississippi River Overflow Bridge north of Sabula, Iowa. The entire area is within the Upper Mississippi River National Wildlife and Fish Refuge managed by the United States Fish and Wildlife Service (USFWS). The applicant’s stated purpose and need of the proposed maintenance and stabilization project is to provide a more safe, modern, and stable roadway within the project limits. The existing roadway embankment along U.S. 52 is settling due to repeated flooding occurrences, resulting in a saturated embankment, then resulting longitudinal cracking in the pavement happens. There is roadway instability from when flood waters recede, and the saturated soil filters out of the embankment.
B. The project will place fill along 2 miles of the U.S. 52 causeway for a total fill in submerged aquatic emergent wetlands and the Mississippi River of 1.62 acres. The roadway will not be raised in elevation. Guardrails, utilities, and new pavement will be installed for the length of the project. The proposed embankment stabilization includes the placement of revetment approximately five feet below the channel bottom to one foot above flat pool elevation or the actual water level and from the toe of the existing embankment to the toe of the proposed widening. One foot of erosion stone and one foot of macadam stone is proposed above the revetment platform. Approximately 72,010 tons of erosion stone and macadam stone is also
required for stabilization of the roadway. Utilities will be installed within the footprint of the new U.S. 52 roadway embankment and under the new pavement. Temporary construction in the Mississippi River backwaters may include an appropriate combination of land-based dredging, construction, and hauling equipment; trench boxes, and temporary work platforms; barges, work boats, barge mounted dredging and construction equipment; temporary slips or bulkheads; temporary supports, temporary anchors, and temporary cofferdams.
C. Dredging and removal of unsuitable material will be needed for construction of the proposed causeway embankment and may be needed to support construction activities in and around the work area. Dredging for embankment construction shall be restricted to an approximate 80-foot-wide area adjacent to U.S. 52 for the length of the project. Dredging for transportation of equipment and barges and materials to/from the construction area, if different than the construction area itself, shall be restricted to a 50-foot-wide area. Dredging for the embankment work will be within a few feet of the top of slope. This includes temporary channels through adjacent backwater areas utilized to provide access to/from more navigable areas in the river environment. Dredged material will be removed by the contractor to an approved off-site location and no dredged material will be placed back into the backwaters. Construction of the project will require temporary work surfaces, and all work will remain within the existing right of way. The project will be constructed in three stages.
D. Avoidance and Minimization. The applicant has stated that impacts to backwater wetlands are limited to the minimum necessary to construct this project. The applicant has provided an alternatives analysis to include a no action, the applicant’s preferred, and two on-site alternatives. No off-site alternatives were provided as creating a new roadway would likely result in great impacts to waters of the U.S. The Corps will review these alternatives to ensure compliance with Section 404 that the final issued permit is for the least damaging practicable alternative.
E. The applicant’s proposed mitigation is to purchase 1.62 emergent wetland credits from a Corps approved mitigation bank. Stream mitigation is not proposed for this project.
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