Project Location:
− North of Route 34, over the Skunk River west of Mt Pleasant, Iowa.
− Section 3, Township 71 North, Range 7 West.
− Henry County, Iowa.
− UTM NAD-83 Zone 15.
− Lat 40.9840 Long -91.6602.
Project Description and Purpose:
A. The applicant proposes to replace an existing 1,020-foot-long double track railroad bridge consisting of a multi-span Pratt deck truss style fixed metal bridge supported on concrete piers and
abutments over the Skunk River. The bridge was originally constructed in 1899, with most of it being rebuilt in 1931. The new project proposal is a multi-span double track bridge approximately 1,068 feet long and will be comprised of 10-sans (8-spans of steel deck plate girders and 2-spans of precast concrete beams) with the bents bearing on drilled shafts or steel H-piles. The applicant’s stated purpose and need is for the BNSF Bridge No. 0001-0239.24 over Skunk 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. (WUS) consists of bridge replacement, temporary trestle bridge construction and removal, placement of piers and abutments, temporary staging areas, site access routes, and permanent riprap. All fill materials will be sourced from an existing commercial supplier or directly onsite within the project limits. Proposed impacts are 2.29 acres of emergent wetland, 3.41 acres of forested wetland, and 0.071 acres of freshwater pond. The applicant is currently reviewing the plans to determine if they 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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