Tuesday, January 31, 2017

Mississippi Dams and Locks #26, Alton, IL

(John Weeks III New; see below for the Satellite; Birds-Eye View, note that they have the main lock bulk headed because they are having to already do repairs to the lift gate. Since the repairs are being done during the shipping season, they are probably emergency repairs. That is, something broke already. It is a good thing they built the second lock!)

1941 Aerail Photo from ILHAP
The old dam has been replaced by a new dam about two miles downstream. So I have to use an old aerial photo to show the original dam. It was opened in 1938, but the longest lock was 600 feet, and it was creating a traffic jam of tows waiting to lock through. So construction began on the replacement Melvin Price Locks and Dam began in 1979 and the main 1200x110 lock was opened in 1989 and the old dam was demolished the next year. The auxiliary 600x110 lock was completed in 1994. The new dam has an enhanced visitor center called the National Great Rivers Museum.

HAER IL-31 has a pictures of the old dam and the two old truss bridges just downstream from it. HAER also has documented the construction of the new dam as IL-32. The railroad bridge has been abandoned and removed while the US-67 bridge has been replaced with a cable stay bridge.

[WikipediaOld, WikipediaNewJohn Weeks III]

You can still see where the west end of the dam terminated. John Weeks III explains that the old dam suffered from holes being scoured in the bedrock. "The structure was also prone of large movements during high water." If water could move the dam, I'm surprised they waited over a half-century before replacing it!
Mike O'Neal posted
Park downtown Alton the train bridge is gone and a new Alton bridge is in place today the train bridge would open and close on the lock and Dan 26 to let the boats go through. The dam 26 is move down the river about a haft mile.
[This is just one of the construction photos from HAER IL-31]

Dave's comment:
To all the folks in Jersey and Madison counties,,check out this photo of Chautauqua from the bluffs facing east,,notice the river level before the lock and dam in Alton,Illinois

Birds-Eye View
The bluffs don't look as big, and then I realized that was his point. They must have piled a lot of dirt on top of those old railroad tracks to make an embankment for IL-100. I wonder how frequently that road gets flooded.

I include a satellite image of the main structures of the new dam because it caught a 15-barge tow entering the main lock.
J Clear caught the 110x42 feet Tainter gates in a raised position so that the river can run freely. It looks like the bottom of the gates have been badly damaged even though this is a relatively new dam. These gates look like a new covered truss design, and it appears the new design has failed. (The "link" in the caption gives you access to higher-resolution copies of this picture.)
By J Clear (talk) - I created this work entirely by myself., CC BY-SA 3.0, Link
HAER reports:
Lock and Dam No. 26R represent the present state of the art in river navigation control works. The basic components of the installation are comparable to those utilized in the 1930s. The most striking difference between the older installations and Lock and Dam No. 26R is the immense size of the new structures. The significance of the new installation is not limited to its size. Throughout the design and construction process, the Corps of Engineers and the various contractors have engaged in an extensive program of computer-assisted design, testing, and evaluation. These sophisticated studies represent perhaps the most significant difference between the older structures and Lock and Dam No. 26(R). 
The condition of those gates indicates designing with "engineer's gut feeling" is better than design by computer.

Clark's photo shows seven of the nine gates. The other two are between the two locks. I've never seen that before. This design strikes me as bad. There is the issue of increased construction costs because more guide walls need to be built because the locks don't share a wall. But there is also the operational issue that when those two gates are open, it creates an outdraft for the main lock. You can tell they are worried about an outdraft causing problems because of the two big, round buffers they built upstream of the gates. The HAER report implies that the lock was built on H-piles driven down to bedrock. Maybe the bedrock was significantly higher further from the shore to warrant the cost of extra guide walls. Also, they probably open these two gates only if the river flow is so high that the other 7 gates can't pass it. Maybe by that time the flow level on the river is so high that most shipping is shut down anyhow.

The upstream gate of the 1200' lock is a lift-gate instead of a miter gate. So this joins the list of the the Keokuk (#19) Lock and Lockport Lock as the three dams I know of that use a lift gate instead of a miter gate for the upstream side. I still have not found out why a lift gate would be used.

Update: During the 2017 flood, water covered the fixed part of the dam and was on part of the road on the levee on the MO side. On the Illinois side, the Great River Road and railroad by the bluffs were under water. And water was up to the mill.
Screenshot from 5/4/2017 video posted by KMOV

No comments:

Post a Comment