Project Location:
− East of Valley Drive, over the Grand River, east of Afton, Iowa.
− Section 19, Township 72 North, Range 28 West.
− Union County, Iowa.
− UTM NAD-83 Zone 15.
− Lat 41.0219 Long -94.1144.
Project Description and Purpose:
A. The applicant proposes to replace an existing 446-foot-long double track railroad bridge consisting of a 5-span Pratt deck truss style fixed metal bridge supported on concrete piers and timber piles over the Grand River. The bridge was originally constructed in 1901, with significant maintenance occurring in the late 1940’s and early 1950’s. The new project proposal is a double track bridge approximately 468 feet long and will be comprised of 6-spans (3-spans of prestressed concrete beam, 2-spans of deck plate girders, and 1-span of rolled steam beams) with the piers and abutment on drilled shafts or steel H-piles. The applicant’s stated purpose and need is for the BNSF Bridge No. 0001-0379.51 over Grand River on the Ottumwa Subdivision will be reconstructed as part of the BNSF general maintenance program to maintain a safe and efficient bridge for the transportation of interstate freight and passenger rail (Amtrak). The applicant has stated that the existing bridge must be replaced due to condition and reaching the end of its service life.
B. Work within waters of the U.S. consists of bridge replacement, temporary trestle bridge construction and removal, temporary staging areas, site access routes, and permanent riprap. Piers and abutments are located outside of the ordinary high-water mark (OHWM). All fill materials will be sourced from an existing commercial supplier or directly onsite within the project limits. Portions of the staging areas and site access routes will be topped with gravel to provide a stable foundation for equipment. The gravel will be removed upon project completion. Impacts are proposed to 2.64 acres of wetland (2.54 acres of forested wetland and 0.10 acres of emergent wetland), 0.004 acres (174 square feet) below the OHWM for temporary trestle bridge piers and abutments, and 0.021 acres of wetland are permanently impacted for riprap embankment protection, with no riprap below the OHWM. The applicant is currently reviewing the plans to determine which impacts will be permanent, temporary, or a combination of both. Any temporary impacts to wetlands will require a monitoring plan to ensure restoration success. Temporary impacts will be monitored and will have performance standards that must be met. Permanent impacts will be purchased at a 1:1 ratio for in-kind at a wetland mitigation bank. If there are insufficient wetland credit types available for purchase at a mitigation bank, then a permittee responsible mitigation plan will be required and must be approved by the Corps prior to final permit issuance.
C. The applicants stated avoidance and minimization efforts include:
• No Action Alternative: In order to provide a safe and efficient bridge for the transportation of interstate freight and passenger rail (Amtrak), the existing bridge must be replaced due to
condition and reaching the end of its service life. The bridge has been continuously maintained over its life; however, it requires upgrading to modern materials and design standards for current rail traffic. A no action alternative is not possible to meet the purpose and need for the project.
• Alternative 1 (Inline) (Preferred): The existing bridge will be removed, and the proposed bridge will be located on the same alignment and profile to minimize overall permanent impacts associated with the project. The inline alternative requires no permanent track embankment widening, minimizes permanent adverse impacts to environmental resources, and maintains all permanent construction within existing BNSF right-of-way. The temporary impacts to environmental resources associated with the inline alternative are minimized to the maximum extent to allow for construction. BNSF engaged an industry leading heavy bridge contractor, in addition to their staff, to help determine the minimum staging area and access requirements to feasibly construct the project.
• Alternative 2 (Offline South) (Rejected): The existing bridge will be removed, and the proposed bridge and track alignment would be shifted to the south of the existing bridge. The offline south alternative requires extensive permanent track embankment widening, results in significant permanent adverse impacts to environmental resources, lengthens the construction duration, requires construction outside of BNSF’s existing right-of-way, and increases overall project costs. The temporary impacts to environmental resources associated with the offline south alternative are greater than the inline alternative. This alternative was rejected due to additional permanent adverse impacts to environmental resources and permanent construction outside of BNSF’s existing right-of-way, which is not possible.
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