October 16, 2002

Emergency dredging clears channel for stranded Missouri River barge traffic

arlier this month, the MV JACK FLAHAUT, a 539 ton towboat operated by Memco Barge, labored for three long days retrieving grounded barges just upstream of the Osage River confluence near mile marker 130 in Miller County, Missouri. The river channel had shifted and silted in, causing excessive shoaling conditions, which made the channel too shallow to allow scheduled towboat and barge navigation. The threatening shoaling conditions were hastily reported to the Corps of Engineers, who are responsible for maintaining proper Missouri River channel conditions during the mandated annual Lower Missouri River navigation season.

After official evaluation and confirmation of the reported river channel shoaling conditions, on Friday October 4th, the Kansas City District of the Corps of Engineers requested Emergency Dredging for the Missouri River at miles 51 and 130. Approvals were quickly granted by the Corps of Engineers Northwestern Division, with coordination of Corps Headquarters and the various state of Missouri and Federal resource agencies. Emergency dredging support was provided by the St. Louis District of the Corps of Engineers. 

The Corps dispatched the Dredge POTTER which was moored at St. Louis. The POTTER is a dustpan-type dredge ideal for the type of material and shallow conditions encountered on the Missouri River. The Dustpan is very efficient for excavating sandy material from the river bottom. 

Dustpan Dredging Operations

When operating on station, the dredging head is submerged towards the river bottom at the bow of the boat. Water jets in the head agitate the sand and gravel into a slurry which is then pumped up through the head up into the dredge. Once vacuumed off the river bottom, the captured slurry is then pumped away through a long 800 foot pipe over a maneuverable "chain" of floating pontoons or small support barges. At the end of the pipe on last support barge is a small control building where the baffle plate operator can direct the high pressure in the pipe to move the entire pipeline forward or backward as needed in order to eject the sand and gravel discharge deposits outside of the navigable channel. While working, the dredge is pulled forward by large winches attached to 1" diameter steel cables which are anchored to the river bottom. The Dredge POTTER can move forward at a rate of about 3000 feet in 12 hours while cutting through up to 20 feet of sand and gravel. 

In heavily graveled bottoms, the sound of the rocks passing through the metal pipe can be heard for miles. The goal is to ensure that the river is deep enough for barge traffic. Fully loaded barges have a nine-foot draft. Therefore, the dredge must maintain a depth of at least a 12 ½ feet. Dredging is coordinated with other Government Agencies so that operations are conducted in an environmentally sensitive manner.

Dredge POTTER History

Originally assigned to the Memphis District and transferred to St. Louis in 1979, the 68 year-old repowered POTTER is the oldest dredge in the Corp's fleet (a year ahead of her sister dredge, the Vicksburg-based Dredge JADWIN, which was launched in 1933 and then repowered in 1985). Named in honor of Brig. Gen. Charles Lewis Potter, a Memphis District Engineer from 1900 to 1903 and then President of the Mississippi River Commission from 1920 to 1928, she was originally a steam-powered paddlewheeler, was built for the once-considerable sum of $520,000 and launched in 1932. She helped keep the Mississippi River open to navigation for almost 70 years.

In 2001 the POTTER underwent a $20 million repowering project by the district and the Corps’ Marine Design Center in Philadelphia together with subcontractor Halter Marine, Inc., of Gulfport, Mississippi. On October 31, 2001, she departed Halter Marine's New Orleans shipyard with the same overall profile (sans smokestacks) and capabilities, but with an all-new stern and a diesel-electric power plant. 

Accomplishing The Mission 

After fueling and provisioning the POTTER, Captain James Pierce (The POTTER's skipper since her launch after refitting in 2001) left port upbound into the Missouri River through the Columbia Bottoms to begin the first upbound leg.

The first destination was reached on Monday October 7th. This was a reported shoaling area near river mile 51, just past the confluence of Femme Osage Creek opposite Darst Bottoms just South of St. Albans Island. Once work in this area was completed, the POTTER made way upbound to river mile 130, the confluence of the Osage River.

By the time the POTTER arrived to the area at noon on Wednesday October 9th, advance corps survey personnel already had the shoaling site identified for Captain Pierce. After deploying, dredging operations began at the confluence of the Osage River where the river had built up significant amounts of silt. After working all night, early Friday morning on October 10, the dredge POTTER completed had completed 8 passes at 35 feet wide. The first five passes were about 1400 feet long and the last 3 passes were about 1000 feet long. Resultant river channel depths cut to 15 feet. After the river bottom settled out, the channel cut was 12 feet as confirmed by final survey personnel. Once completed, the crew of the POTTER set to task removing huge snag mass. Capt. Jim Pierce remarked that it was probably "An underwater beaver dam". This mass was acting like an underwater reef deflecting flows away from the main navigation channel. 

The Dredge POTTER team was skilled, efficient and extremely cooperative. It took just nine days from the call on October 4 to return moorage on October 13. The combined efforts of the Corps of Engineers St. Louis and North West districts resulted in the timely response and actions taken to reestablish river navigation, which is critical at this time of year with the approaching end of the navigation season.

Special acknowledgement goes to John LaRandeau of the Corps of Engineers, Northwest Division, for providing reference material for this article.