Consider ‘middle way’ on Maclay Bridge

Guest Column, Bob Sweitzer. Missoulian. October 23, 2017.

The Maclay Bridge, in one form or another, has been a part of Missoula's history for over 100 years. It was originally constructed by William Plunket in 1893. It has been washed out and replaced several times over the years, but has been in place as it presently exists since 1964.

Maclay Bridge is now a series of pieced-together spans to create the structure that appears today. Nevertheless, the condition of the bridge is quite good and it could be left as-is. Montana Department of Transportation bridge engineers said that the need for replacement of Maclay Bridge is low to moderate on their list of priorities for statewide bridge repair. In other words, doing nothing represents one extreme possibility.

Maclay Bridge was listed on the National Register of Historic Places in 2016. But the old bridge represents more than just historic perseverance to the majority of nearby urban interface residents. Over the passing years, it has taken on the welcome roll of "traffic calmer" for a bustling society hurrying to get someplace else. It offers scenic views of the Bitterroot River with all its changing moods, from rushing muddy spring torrents to clear fall colors and invitingly cool waters. Nearby neighborhoods developed and matured based on the Maclay Bridge traffic patterns. Homes along South Avenue tend to be closer to the street to minimize winter snow shoveling. Homes on North Avenue, leading to the bridge, tend to be set back farther, and a pedestrian walkway was developed from Clements nearly to the bridge.

A few years ago Missoula County commissioners decided Maclay Bridge should be replaced. They quietly nominated the bridge for replacement under state and federal programs for rehabilitation and replacement of “off-system” bridges. They very quickly decided that the bridge should not be rehabilitated, and never really considered rehabilitation options in spite of a preponderance of resident objections. County and Montana Department of Transportation engineers encouraged us to believe that an extension of South Avenue from its western dead-end, connecting to River Pines with a new two-lane bridge, was the only feasible plan.

Maclay Bridge must be removed if a new bridge is constructed. That is a condition required for mitigation of impacts to the river caused by installing two new piers. This South Avenue Bridge represents the other extreme possibility for “the" bridge. But it's not a done deal. Better alternatives can be found on our website at: 

A middle way was suggested by Dr. Jai Kim, a professor emeritus from Bucknell University, when he visited Missoula in the fall of 2016. Kim provided us with concept plans for strengthening the old Parker Truss portion of Maclay Bridge with superimposed arches to increase structural redundancy and capacity. In addition, the Warren Pony Truss and the two pre-stressed concrete spans on the east end of the bridge could be removed and replaced by a single-span, arch re-enforced, Parker Truss.

Interestingly, two existing piers under Maclay Bridge would be removed to improve river health. The single-lane feature could be retained for its cost and traffic calming qualities, while pedestrian and bicycle safety could be accommodated with an attached, cantilevered crossing. The cost for this plan was estimated at less than $2.5 million, as opposed to more than $13 million for the South Avenue replacement. That does not include an additional $1.9 million necessary to upgrade South Avenue from rural road to collector standards.

The “middle way” is less expensive, it's less intrusive on mature neighborhoods, and it does not require expensive road upgrades, likely to be borne by county taxpayers. Furthermore, it continues the historical legacy.

Bob Schweitzer is a member of the Maclay Bridge Alliance


©Maclay Bridge Alliance 2017
MBA • c/o Bob Schweitzer • 11905 Green Acres Road • Missoula, MT • 59804 • (406) 728-5302
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