This photo shows how they have to split the standard tow in half in order to get through the 600' lock. I noticed that this is a 16-barge tow instead of the typical 15-barge tow. I don't understand why they don't normally put barges next to the towboat to get a 17-barge tow. It is very rare to have even the 16th barge.
"The maximum lift is eight feet with an average lift of four feet. It takes approximately seven minutes to fill or empty the lock chamber. The movable dam has eight submersible Tainter gates (20 feet high by 64 feet long) and three submersible roller gates (20 feet high by 100 feet long). The dam system also includes one non-overflow earth and sand-filled dike; two transitional dikes; and a submersible earth and sand-filled dike."
[This is a more typical 15-barge tow doubling through the lock.]
Significance: The U.S. Army Corps of Engineers Nine-Foot Channel Project (1927-1940) represents the culmination of a 100-year effort to improve the navigability of the Upper Mississippi River between the mouth of the Missouri River and Minneapolis, Minnesota. This specific project arose as a response to the farm crisis of the 1920s. Proponents of the New Deal adopted the project and gave speed to its construction as a means of providing public enjoyment during the more general depression of the 1930s. By the 1940s, the completed project had converted over 650 miles of free-flowing river into a series of interconnected reservoirs which ensured enough water for fully loaded modern boats and barges to navigate the system. This constituted a significant alteration of the natural environment of the Upper Mississippi River. However, the project also brought economic benefits to the communities along and around the river corridor and lead to new recreational opportunities for the entire region. [HAER-data]
|HAER ILL,66-NEBO,1-, cropped|
11. VIEW OF ROLLER GATE #6 BEING ERECTED, VIEW FROM SOUTH. June 1938
This Apr 2019 flood image is currently on Google Map. (I used Google Earth to find the date.) I realized I was looking at high water when I could not see the fixed embankment part of the dam.
A closeup shows the gates are wide open and the lock walls are almost under water. Barge traffic is obviously shutdown and the lock is being used as a safe haven to park some equipment. There is a crane on the big barge.
The lock walls did become submerged. I wonder where the electric motors that operate the gates and valves are located.
Bloomberg Floodwaters surround Lock and Dam 17 on the Mississippi River as seen in an aerial photograph taken near New Boston, Ill., on Friday.
"Hundreds of barges are stalled on the Mississippi River." [paywall]
I fired up Google Earth to get a more normal image of the river. I learned that in many of the images the fixed embankment was under water. But here is one with it exposed.
|Google Earth, Sep 2017|
But the water seems to be almost as high on the downstream side of the roller gates as it is on the upsteramside.
|Google Earth, Sep 2017|
|Dewatered, photo 1|
During a winter 2017 dewatering at Lock 17, crews accessed areas of the lock not normally exposed and repaired damaged portions of the concrete wall.
|Dewatered, photo 2|
A hydro-demolition machine being used at Lock 17 on the Mississippi River to remove old concrete from the lock walls.
There is so much detail in this document that I had a hard time understanding it. I was hoping to get a feel for how much water these river dams pass to compare with discharge rates for spillways in reservoir dams. I did learn that the gates are submerged in the winter when there is no navigation on the river. That would allow the ice to flow over the gates. I think the 65.5 kcfs in this table is the flow during normal operations when the upper pool is at 9.3'. Flood flows would be way above this figure because the gates would be wide open and water would be flowing over the fixed embankment.
|USGS, p48 via pubs|
Because the calibration of this gauge is too lax, the data is retained for only 120 days. The data is not considered suitable for archiving. So I can't find the levels for last Spring, let alone the 2019 floods.
This was the photo that motivated me to look at D&L #17 because this photo struck me as a high dam for the Mississippi River. I soon realized that this was a different D&L #17.
|Craig Dodson posted|
Lock 17 the uppermost dam on the black warrior