Dredges at Work as Forecasters Keep Eye on River LevelsView Source
Dredges At Work As Forecasters Keep Eye On River Levels
SEPTEMBER 22, 2023 BY SHELLEY BYRNE
Dredges continued to address problem spots as lack of rainfall worsened drought conditions along much of the Mississippi River basin.
The dredge Jadwin was at work at Lower Mississippi Mile 735, and it was expected to continue dredging through September 30.
The dredge Hurley completed work at mile 870 on September 21 and continued to the vicinity of Mile 792, where it was expected to remain three to four days.
The dredge Wallace McGeorge was working at Mile 485-486, Stack Island, and was expected to remain in place for at least a week.
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One problem area continued to be Mile 756, Dean Island, said Randy Chamness, co-chairman of the Lower Mississippi River Committee (LOMRC).
“The Corps is doing a good job for industry,” Chamness said. “Right now I feel like the channel is stable as long as we have the dredging ongoing. Having three dredges at work between Cairo and Baton Rouge is key for us.”
On the Upper Mississippi, the dredge Potter completed its work at Upper Mississippi Mile 28.5 Buffalo Grain) and relocated to 24.5 (Sliding Towhead) with about seven days of work expected there.
Chamness added that keeping buoys maintained on the middle and Lower Mississippi is another important part of the work, with LOMRC continuing to work with the Coast Guard to make sure the channel is well marked.
“This is key to mitigating risk of groundings,” Chamness said.
The Memphis Engineer District reported that between June 1 and September 19, 22 groundings had been reported. The only grounding reported September. 15-19 was at Lower Mississippi Mile 612, Dennis Landing.
Locations where other groundings have taken place include: Mile 790 (Merriwether); Mile 738 (above Interstate 40); Mile 690 (Commerce); Mile 681 (Battle Axe); Mile 605 (Clay Wilson); and Mile 725 (Memphis Harbor).
Nine of the groundings had resulted in closures, according to information provided by the Memphis district. Only one grounding was reported as lasting for more than 24 hours. It was located at Williams-Beckwith, Miles 925-928.
Companies were working closely with the U.S. Coast Guard and industry task forces, reducing loading drafts and tow sizes and trying to prevent groundings. Several segments of the Lower Mississippi were reported at a 9-foot depth.
The Corps of Engineers, Coast Guard and industry continued to watch river forecasts closely. While the gauge read –9.4 in Memphis, the two-week forecast called for the river to remain steady instead of falling farther. When the gauge drops below –10 at Memphis, it is a signal of increasing concern, Chamness said.
The river reached within 1 foot of last year’s record low gauge at Memphis over the past week.
“We’re a month ahead of where we were last year,” Chamness said. “Last year we didn’t set the record in Memphis until mid-October. That’s what has us concerned a little bit.”
The Corps’ Mississippi Valley Division also reported issues with saltwater intrusion caused by extremely low flows in September. While construction of a saltwater sill was constructed on July 27, the low flows are allowing the wedge to again advance up the river toward New Orleans.
“Long-range forecasts indicate the wedge could advance far enough to overtop the existing sill and advance upriver towards freshwater intakes at Belle Chasse, La., as early as October 3,” the Mississippi Valley Division said in its low-water update.
The Corps of Engineers was meeting bi-weekly with LOMRC as well as conducting as needed meetings with the River Industry Action Committee (RIAC) and River Industry Executive Task Force (RIETF). Districts within the Mississippi Valley Division also continued to meet weekly to prioritize dredging projects.
On the Ohio River, the dredge Bill Horman was working in the area around Ohio River Mile 975 on September 20 and was expected to continue doing so for 10 to 11 days.
Shawn Kenney, Operations Division Technical Support Branch chief for the Louisville Engineer District, noted that the land-side chamber at Olmsted Locks and Dam (Ohio River 964.6) has been closed for improvements and repairs since August 9 and is expected to reopen within the next couple of weeks. There will then be intermittent closures of the river-side chamber.
While the lock chamber closure was not the primary cause of traffic delays, Kenney said, it did contribute to them. The primary cause driving delays was a couple of intermittent river closures on September 5-6 for channel maintenance dredging just downstream of Olmsted, followed by a couple of groundings September 7 and September 11 that required the river to be closed while clearing the scene and dredging.
“The reduced capacity at the locks did slow progress in clearing the queue after these river closures, but as of September 18, marine traffic at Olmsted is moving well with minimal delay,” Kenney said.
Cumberland And Tennessee Rivers
Robert Dillingham, hydraulic engineer in the Nashville Engineer District’s Water Management Section, said the Tennessee and Cumberland basins are faring better.
“Because of the large tributary storage reservoirs in the headwaters of the Cumberland River Basin (Wolf Creek, Dale Hollow, Center Hill, and J Percy Priest), the Nashville district is not currently experiencing significant low water issues,” he said. “However, we are working closely with the Tennessee Valley Authority to coordinate our releases from Barkley Dam on the Cumberland River with their releases from Kentucky Dam on the Tennessee River, and other USACE districts downstream to coordinate releases and help as we are able.”Over the past several weeks, the combined flow from the Cumberland and Tennessee rivers (from Barkley and Kentucky dams) has made up approximately half of the total flow in the lower Ohio River and approximately one-third of the total flow in the Mississippi River at Memphis, Dillingham said.
“Without additional rainfall, we will continue to be able to maintain similar release rates from Barkley and Kentucky as we continue the drawdown of our upstream storage reservoirs into the fall season,” he said.
Chamness said that upstream storage was important, but he also noted that once those reservoirs are drawn down to their winter pool, downstream flows will be dependent on rainfall. Additionally, he added, the reduction of flows from the Missouri River starting in late November will also reduce the volume of the Mississippi downstream from their confluence near St. Louis.
Caption for photo: The Hurley is one of several large Corps dredges working to try to keep the rivers open. (File photo/Memphis Engineer District)