Retired engineer says river’s drain could bring landslide|[05/11/08]

Published 12:00 am Sunday, May 11, 2008

With the Mississippi River falling at such a rapid rate after high stages saturated its steep banks in Vicksburg for more than a month, one retired engineer is convinced conditions are ripe for a massive landslide.

Don Neumann”We’ve got the potential for a real disaster down at the riverfront,” said Don Neumann, who has lived in Vicksburg for 50 years. “Nobody seems concerned about finding out what’s going on, or finding a solution to fix the problem.”

The theory is not new, nor is Neumann’s warning. He has photographed the area over time and performed studies as well as creating drawings.

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Many engineers and soil specialists agree a landslide is possible that would wreck the river bridges, hotels, casinos, road and railways along the city’s western edge. Most, however, doubt the probability of sudden event and see little benefit of sinking money into a major stabilization project.

“I’m not going to call Don Neumann a kook. It is something to worry about, and people need to know this is a possibility,” said Dr. Bill Marcuson, director emeritus of the Geotechnical Lab at the U.S. Army Corps of Engineers Waterways Experiment Station,and the 2007 president of the American Society of Civil Engineers.

“Some planning may be in order, but I don’t know if I would spend a huge amount of money on fixing what is essentially a problem with limited potential,” added Marcuson, who referred to Neumann as “a personal friend and colleague.”

Mississippi RiverTODAY’S STAGE: 42.8 feetFELL: 0.3 footFLOOD STAGE: 43 feetSTEELE BAYOU:Landside: 91.6Riverside: 91.3On Saturday evening the Mississippi River stage at Vicksburg was 42.8 feet, a fall of 0.6 foot in 24 hours. It marks the first time since March 29 the river has dipped below flood stage of 43 feet at the city. On April 19 the river crested at 50.9 feet — the highest recorded stage in Vicksburg since 1973. After a slow initial fall, the river has been receding at a much quicker pace. Since May 1, it has fallen 5.9 feet.

The soil makeup below Vicksburg is largely silt, said Marcuson, which has created some smaller scale slides in and around the city over the years. Silt erodes and is responsible for the local topography known as “hills and hollows.” There’s a difference between slow, steady erosion and soil movement and a catastrophic slough perhaps triggered by a seismic shift that Neumann foresees.

Currently, neither the City of Vicksburg nor the Corps regularly monitors the city for any slides, although both acknowledge the slow process is unremitting.

“Everything in the city is moving toward the river at a very minute pace. That’s just the nature of the geology here,” said Garnet Van Norman, engineer for the city of Vicksburg. “You can go around town and see where things have moved down the hill over time.”

Neumann said physical evidence of slope failure supports his prediction. He points to a visible, mile-long crack stretching from the I-20 and U.S. 80 bridges north though Riverfront Park, and to DiamondJacks Casino. A routinely patched crack running through the Ameristar Casino parking lot is a part of the fissure, he said.

High river stages help hold the bank up, but water penetrates. At lower stages, the support is lost. “When the river drops fast, a big crevasse opens up — usually about 6 inches wide,” Neumann said.

Marcuson said it might be worthwhile to place some devices around the Vicksburg riverfront hillside to measure the amount of slide over time and prepare an emergency plan should the rate of movement increase, but only if it could be implemented at a reasonable cost.

“Neumann’s views make complete sense from a scientific point of view, but from an engineering point of view, we’ve got bigger fish to fry,” he said.

Eddie Templeton speculated if a massive landslide were to take place in Vicksburg, even measurement devices would most likely prove ineffective.

“If there would be a catastrophic landslide in Vicksburg it would probably occur too quickly for any instruments to help,” said Templeton, an engineer with Burns, Cooley and Dennis. The Jackson-based geotechnical engineering firm designed the $18.5 million stabilization wall completed in Natchez in 2002.

For flood assistanceIndividuals and small business owners can begin applying for FEMA assistance by registering at, or by calling 1-800-621-3362To schedule a Red Cross flood damage assessment of your home call 601-636-9182. Assessments are required to receive financial assistance from the Red Cross.Though the two cities may seem topographically similar, Templeton said the stabilization effort in Natchez is actually quite different than the potential problem facing Vicksburg.

“The bluff instability (in Natchez) really didn’t have anything to do with the river. The wall was built on the upper part of the bluff, which was nearly vertical,” he said. “In Vicksburg, most of the land is much more sloping, and much more stable for the most part.”

Nonetheless, Templeton, too, acknowledged a massive landslide is a possible in Vicksburg, but did not want to speculate on the probability of such an event.

“Most failures occur during a rapid recession of a river, and there are certainly geologic conditions and soil conditions in the Vicksburg area that are problematic in terms of landslides,” he said. “However, the best measure of the probability of a failure is to look back through history. The river has been high many times, and has there been a rash of landslides? No.”

Neumann said the reasoning his engineering counterparts give for not supporting a large-scale stabilization project in Vicksburg amounts to apathy.

“Look at the I-35 bridge collapse in Minneapolis,” he said. “They knew they had a problem, and they ignored it because it would impede on their normal operations. We have the same situation and we’re ignoring it.”

However, Marcuson contends the bridge collapse that occurred in Minnesota last summer and the landslide Neumann speculates is possible in Vicksburg are two entirely different disasters.

“You have to look at the potential for catastrophic loss of life,” he said. “A landslide along the river in Vicksburg would not kill a lot of people. If we’re talking about a collapse of the I-20 bridge, then yes, that would probably be a catastrophic loss of life and maybe we should look into it.”

Neumann said a massive slide could, in fact, topple the bridges in Vicksburg — which have both shown slow movement.

Opened in 1930, the U.S. 80 bridge has been restricted to rail traffic since 1998. In an annual inspection report released in November 2003, the bridge was said to be in “fair to good” condition. However, it also noted Pier 2 — which is the second closest to the river bank on the Mississippi side — “has historically experienced large westerly movements.” While no movement has been observed since October 2006, the pier moved 9.25 inches since February 1997, when repair work was ordered.

A structural report released in 2006 on the I-20 bridge said it showed “significant movement” in the E2 Pier, which sits directly parallel to the U.S. 80 bridge Pier 2.

“We don’t know if that movement is part of a slide or not, nobody has really checked into the cause. It could be a different problem entirely, but either way we’ve got some serious situations down by the river,” said Neumann.

While areas north, south and west of Vicksburg are largely flat, the city itself is built on bluffs formed by deposits of prehistoric dust storms. The Loess soil type is rare and has specific characteristics — among them a low content of rock and clay and a tendency to retain vertical stability even though its fine particles erode quickly on slopes.

Until about 20 years ago, there was little development on lower tiers along the steep bank fronting the river. In the area of the sharpest inclines are the river bridge approaches, the two casinos and one hotel and Riverfront Park. Before either casino was built in the early 1990s, extensive soil engineering was conducted before both were built inside massive concrete cofferdams. Their properties also include sunken drainage features that capture water seeping through the soil and pump it out to limit the slow shifting that has taken place through the decades.