Monday, July 12, 2021

1937 Mississippi Lock and Dam #7 at La Crescent, MN

(John A. Weeks III; Satellite, 353 photos)

USACE
"Site underwent major rehabilitation from 1989 through 2002. Dam consists of concrete structure 940 feet long, five roller gates and 11 tainter gates. Two segments of earth embankment 8,100 feet long from dam to French Island. One concrete spillway 1,000 feet long. And 2,400 feet long from French Island to Onalaska Wis. The a concrete spillway is 670 feet long."

John Weeks

Brochure

Note that the photo in the brochure caught the river at a high level. The roller gates are up all of the way to get them out of the water.
The above zoomed in to 175%

David Webster posted
#whereiswebbie
[Quite a few different locks were suggested. But given the clump of trees to the left of the dam, I'm going with the #7 answers. Note that the river is high enough to cover the trunks of the trees in the right background.]

1 of 3 photos posted by David Webster durng the Spring 2023 flood
Steve Pfeiffer: LaCrosse

Craig Every posted in Rivermen & Riverboats
Tough conditions at Lock 7!
Mrs P was there 1/2 mile out and pushing to the wall.
Jakob Thompson: That dam is known for having a horrible out draft. Sometimes takes 2 tugs to get barges through safely. I talked with an army corps hydrology engineer from St. Paul district. He says they’ve done numerous studies on the out draft and can’t completely figure out why. All data shows the only way to currently fix it would be to completely start over with a new dam…which is very unlikely to happen.
Dylan Schweer: I was always told it use to be a pretty easy one to get into in pool water especially. It ain’t no more. Super shallow above the lock. Massive out draft. A few boats mess up there every year for a reason.
Craig Every: There’s a strong tail wind and the current is up due to all the rain. I guess there’s a pretty strong out draft at this lock too.
Richard Greer: Craig Every yes sir. It’ll pull you on that dike fast.
[I gather from some of the comments that the tow is on rocks. Why would it be shallow on the upstream side of a dam? Does this dam have very little head?
Some comments indicate the dike was rather recently added and it made navigation bad.]
 
USACE Outdraft Study


A video of a towboat in the lock  Basically, it shows that it takes more than a minute before they start filling the lock because I never did see it start to go up.


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