Lock and Dam 9 Maintenance

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The lock chamber at Lock and Dam 9 has been dewatered and maintenance work is being done to the gates at both ends as well as the chamber floor and walls. (Photos by Patrick Moes, U.S. Army Corps of Engineers)

Seven bulkheads (left) were placed and sealed in order to hold back water so that the lock chamber could be drained and pumped out. Seven bulkheads were also placed at the downstream end of the lock chamber. The upstream gate (above) and the downstream gate will be sandblasted, painted and have maintenance work performed on them.

Repairs are being done at various locations on both of the lock chamber walls. At the base of the wall are drain holes.

This is the view of the lock chamber from the downstream end.


Lock 9 near Lynxville has been dewatered 

and is undergoing $3.5 million maintenance project

By Ted Pennekamp


Motorists driving by on Highway 35 may have noticed that the lock at Lock and Dam 9 near Lynxville has been dewatered and maintenance work has been ongoing since Dec. 9. The tentative end date for the estimated $3.5 million project is March 17. A St. Paul District U.S. Army Corps of Engineers crew of 38 based in Fountain City, Wis. has been working day and night in all conditions to complete the project.

The lock and dam was last dewatered in 1993. The St. Paul District locks are dewatered approximately every 20 years for maintenance purposes. 

The lock chamber is 110-feet wide by 600 feet long. To stop the water from flowing into the chamber, seven bulkheads are placed with the coordinated effort of divers and crane operators at both ends. This process took two days. It then took 36 hours to pump down the chamber. 

The divers wear wetsuits that have hot water circulating through them and they are actually quite comfortable in the frigid water, said Kristin Moe, Maintenance and Repair Section Chief of the Corps of Engineers. Moe noted that the chamber is pumped down through the use of pumps and several drain holes at the base of the walls on either side at a rate of six inches per hour as pressure from the outside creates minute movements in the walls which are closely monitored.

About six to eight inches of water remains on the concrete chamber floor, which Moe said has several “weep holes” at various locations to alleviate ground water pressure so that the chamber floor doesn’t buckle. The chamber floor is on top of heavy timber beams and rock fill, she said. An elevation survey is done to make sure that the chamber floor is relatively level. 

Moe said that the highly skilled crew began staging for the project in November. Once the water is pumped and drained from the chamber, the structural steel miter gates, bubbler system and concrete walls and floor are inspected. Maintenance is then performed on the miter gates, bubbler system and damaged areas on the walls and floor. The gates are sandblasted and painted, and equipment is replaced as needed. Moe said that strut arms, pins and bushings on the gates are also inspected and replaced as needed. The numerous diagonals, which make sure the gates don’t flex, are taken off, inspected and repaired or replaced as necessary. In addition, each gate is lifted up about seven inches with the use of huge cranes, and the pintle ball upon which each gate pivots is inspected and replaced if necessary. The old bubbler system galvanized piping is removed and replaced with stainless steel. Zebra mussels are also removed from the bubbler system.

Lock and Dam 9 Lockmaster Darrel Oldenburg said that the lock and dam was constructed by the U.S. Army Corps of Engineers who completed it in 1937 as part of the overall nine-foot channel project. Lock and Dam 9 began operation that same year. The project was authorized as part of the Rivers and Harbors Act approved on July 3, 1930.

On average, more than 12.6 million tons of cargo and 4,300 recreational vessels pass through the lock each year. In 2015, there were 1,764 commercial lockages at Lock 9. The lockages supported 12,541,850 tons of commodities by the navigation industry, the highest amount since 2007. Between the lower and upper pools is a nine-foot drop. The dam consists of five roller gates and eight Tainter gates. The dam is a concrete structure 811 feet long and an earth embankment 9,800 feet long. The grouted overflow spillway is 1,350 feet long.

Numerous anglers each year fish below the lock and dam and also below the spillway. Anglers also fish in both pools 9 and 10 while standing or sitting in lawn chairs on the spillway which is accessible from the Iowa side.

The St. Paul District is responsible for supporting inland navigation by operating 13 locks and dams and by maintaining the nine-foot channel for 243.6 river miles.

In 2014, nearly 90 million tons of commodities were shipped on the Mississippi River within the St. Paul District’s area of operation. The industries making these shipments saved nearly $270 million by using the Mississippi River instead of overland shipping methods. 

According to the National Waterways Foundation, barges can move one ton of cargo 616 miles per gallon of fuel. A rail car would move the same ton 478 miles, and a truck only 150 miles. It takes one barge, 16 rail cars or 70 trucks to move 1,750 short tons of dry cargo. It takes one barge, 46 rail cars or 144 trucks to move 27,500 barrels of liquid cargo.

Nearly 650 U.S. Army Corps of Engineers, St. Paul District, employees working it more than 40 sites in five Upper Midwest states serve the American public in the areas of environmental enhancement, navigation, flood damage reduction, water and wetlands regulation, recreation sites and disaster response. Through the Corps’ Fiscal Year 2014 $100 million budget, nearly 1,600 non-Corps jobs were added to the regional economy as well as $155 million to the national economy.

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