The Alaska Department of Transportation and Public Facilities (ADOT&PF), in cooperation with the Federal Highway Administration (FHWA) is proposing to replace the existing culverts and temporary bridge on the Marshall Airport Access Road with a new permanent bridge. The city of Marshall is located on the east bank of the Poltes Slough, a tributary of the Yukon River in the Yukon-Kuskokwim delta, about 400 miles west of Anchorage. The proposed bridge location occurs in Sections 25 and 36, (USGS Quadrangle Marshall D - 1) Township 21 North, Range 70 West, Seward Meridian (refer to Figure 1). The city of Marshall is located at 61.877780° North latitude and 162.08111° West longitude. DOWL Engineers has been contracted by ADOT&PF to provide environmental services for the project.
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The Marshall Airport was relocated in 2000. During the 1999 to 2001 construction period, high water levels in Wilson Creek damaged two 16-foot diameter culverts that had been installed as part of the construction project. Following this event, a two-lane rail car bridge was installed to provide access across Wilson Creek (see Figure 2). One of the two damaged culverts continues to function marginally. This access road is the only route to the airport for the community of Marshall.
The existing culverts at the Wilson Creek crossing are damaged and do not allow high flows to pass efficiently without causing erosion of the road embankment.
The temporary bridge is susceptible to seasonal flooding and is in need of replacement with a permanent bridge.
| Proposed Action | |
| The proposed action consists of the following (refer to Figure 2): |
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Relocate the existing rail car bridge as a detour during construction of the new bridge. |
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Remove the two existing 16-foot culverts, headwalls, and temporary rail car bridge. |
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Construct a new bridge over Wilson Creek, approximately 120-feet long, 23-feet wide, with two, 10-foot wide driving lanes (refer to Figure 3). |
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Realign approximately 250 feet of Wilson Creek to its previous configuration to prevent erosion from scour (refer to Figure 3) |
| Remove approximately 1,000 cubic yards of riprap that was installed in 2000 as part of the culvert placement. This riprap will be re-used with additional new material to provide scour protection at the new bridge location. | |
| Placement of approximately 20,000 cubic yards of embankment material from the gravel bar sources in Wilson Creek Slough and the Yukon River (Material Site A), and the old airport site (Material Site B). Additional embankment material will be reclaimed from the existing Wilson Creek crossing (refer to Figure 4). | |
To ensure that all factors are considered in the environmental document, your comments are requested no later than December 19, 2005. Below is a list of federal, state, and local entities that we are requesting input from. Please click on the organization that you represent. This will take you to a list of questions specific to your purview.
If you have any questions regarding this project, please call our Environmental Consultant, Kristen Hansen, at DOWL Engineers, at 562-2000, or by e-mail to khansen@dowl.com. Should you have any questions on the design of the proposed project, contact Lisa Reddaway, P.E., Design Engineer, at (907) 443-3413 or send e-mail to lisa_reddaway@dot.state.ak.us.
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Appendix A |
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Figure 1 - Location/Vicinity Map |
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Figure 2 - Existing Bridge Site Map |
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Figure 3 - Proposed Bridge Site Map |
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Figure 4 - Material Sources Site Map |
