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John A. Weeks III
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Highways, Byways, And Bridge Photography
MN-210 Bridge (Side Channel)
MN-210 Saint Louis River Highway Crossing
Thomson, MN

MN-210 Bridge (Side Channel)

• Structure ID: NBI: 91032
• Location: River Mile 29.2
• River Elevation: 1,001 Feet
• Highways: MN-210
• Daily Traffic Count: 1,350 (2004)
• Bridge Type: Steel Culvert
• Bridge Length: 18 Feet
• Bridge Width: 28 Feet (Estimated), 2 Lanes
• Navigation Channel Width: Non-Navigable
• Height Above Water: 2 Feet (Estimated)
• Date Built: 1961
The main Saint Louis River Crossing for MN-210 is a 1961 steel through truss bridge. The National Bridge Inventory lists a second bridge as part of this river crossing, an 18 foot long steel culvert. I normally would not consider a culvert to be a bridge, but since the NBI listed it, it goes on my list, too.

The Saint Louis River is mostly diverted into the Forbay Canal on the east end of the Thomson Reservoir, but a portion of the river water is allowed to flow down the historic river channel bypassing the hydroelectric power plant. The river channel at highway MN-210 is relatively narrow where it passes between two rock outcroppings. As a result, during periods of high water, this gap in the rocks would become a choke point.

To help prevent the bridge site from becoming a dam, and causing the water to eventually overtop and possibly wash out MN-210, an relief valve was installed. That relief is this 18-foot diameter steel culvert, the MN-210 Side Channel Bridge. The side channel bridge is set about a dozen feet above the normal river level. As a result, the river normally flows under the main highway truss bridge. If, however, the water level rises, a significant fraction of that water is diverted through the side channel culvert, bypassing the narrow spot under the truss bridge.

The photo above is looking southwest across the river channel towards the north face of the highway MN-210 Side Channel Bridge. The vantage point is the parking lot of the University of Minnesota Duluth Outpost. The outpost is part of the Recreational Sports Outdoor Program at UMD, and offers canoe, kayak, and whitewater classes.


MN-210 Bridge (Side Channel)
The photo above is the north end of the bridge culvert, with the Saint Louis River channel visible in the background. The photo below is the south end of the bridge culvert. The trees and brush around the culvert hide the cliff located just beyond the edge of the roadway.

MN-210 Bridge (Side Channel)
MN-210 Bridge (Side Channel)
The photo above is another view of the north end of the bridge culvert. The 18-foot diameter corrugated pipe is trimmed at an angle at its north end. A steel I-beam has been attached to the to the exposed edge of the culvert, presumably to reinforce the culvert from damage from debris during periods of high water. The photo below is a view looking northwest across the MN-210 Side Channel Bridge. The bridge is not marked or readily visible to traffic crossing the structure.

MN-210 Bridge (Side Channel)

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