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The Death of the Williamson Bridge Myth

By Ken Koscik

As the boats on our lakes continue to get larger and larger, more and more boats cannot get under the Mendota gate at the Tenney Park Locks. Several questions regarding this and the Williamson Street Bridge surface every summer. The old timers claim that if your boat could get under the Williamson Street Bridge, you could easily get under the gates at Tenney.

Perhaps this was true before the lake elevation on Mendota was changed or before new lake levels were established by the Wisconsin DNR.

One large variable is lake elevation. If Lake Mendota is at elevation 849.60, you might get your boat under and thru the gates. If Lake Mendota is six inches higher or one foot higher, you might not get your boat thru.

The death of the myth occurred when we decided to go and physically measure the openings at the Locks and at the Williamson Street Bridge. The drawing below graphically shows the openings.

image of bridge calculations

The clearance under each structure will vary with lake elevations. Just because you got thru them one weekend, does not mean that you will get thru the next weekend.

The Mendota gate at Tenney Park Locks usually will determine if you can make it under all the bridges. Unless you're in a canoe or small boat, use caution when going from lake to lake.

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