Friday, September 9, 2005
New Orleans, Louisiana — After Category 4 storm Hurricane Katrina slammed into New Orleans, on the night before August 29, 2005, several flood control constructions failed. Much of the city flooded through the openings. One of these was the flood wall forming one side of the 17th Street Canal, near Lake Pontchartrain. The U.S. Army Corps of Engineers (USACE) is the primary agency for engineering support during such emergencies. A USACE team was assessing the situation in New Orleans on the 29th, water flow was stopped September 2nd, and the breach was closed on September 5th.
The breaches that occurred on the levees surrounding New Orleans were located on the 17th Street Canal Levee and London Avenue Canal Levee. The floodwall atop the canal levee was one foot wide at the top and widened to two feet at the base. The visible portion is a concrete cap on steel sheet pile that anchors to the wall. Sheet piles are interlocked steel columns, in this case at least 30 feet long, with 6 to 10 feet visible above ground.
Another breach was on a levee by Industrial Canal, which flooded the east side of the city during the storm.
The 17th Street Canal Levees and London Avenue Canal Levees were completed segments of the Lake Ponchartrain and Vicinity Hurricane Protection Project. Although other portions of the Lake Ponchartrain project are pending, these two segments were complete, and no modifications or improvements to these segments were pending, proposed, or remained unfunded.
The Corps was authorized by Congress to do a reconnaissance study back in 1999 to provide Category 4 or 5 protection. Money was received in 2000 and the reconnaissance study was completed in 2002, which indicated there was a federal interest in proceeding with the feasibility study. Preparation for that study is still underway, and involves issues such as environmental impacts, economics, and the engineering design of the project itself. The feasibility study was scheduled to begin in fiscal year 2006. It may take six years to complete, and there was nothing that could have been done to get this level of protection in place before this storm hit.
Within the city there are 13 subbasins, some of which became flooded. There are existing pumping stations to remove water from the basins. Usually there is much less water to remove, and the level became too high for some pumping stations to continue operation.
One of the services of the USACE is planning, designing, building and operating dams and other civil engineering projects. It has been deeply involved in creating the navigation waterways and flood control constructions around New Orleans, although construction and operation involves various levels of state and local involvement. The Corps is well suited toward emergency activities due to its combination of engineering expertise and being a component of the nation’s military forces. Assigned by the Department of Defense as the primary agency for Public Works and Engineering support, USACE supports FEMA during disasters.
On Saturday, August 27, while Katrina was a Category 3 storm gathering strength in the Gulf of Mexico, USACE’s Mississippi Valley Division was preparing and posturing elements from as far as Hawaii. Anticipating the possibility of a Category 5 storm placing water in New Orleans, preparations began for un-watering operations.
USACE District Engineer, Col. Richard Wagenaar, and a team worked out of an emergency operations shelter in New Orleans. Other teams waited in the storm’s path across the Gulf coast. Corps employees assessed the situation at the 17th Street Canal floodwall that was breached overnight. Corps engineers believed that water over-topped the floodwall, scoured behind the wall, and caused it to collapse. A second breach was known to have occurred on the Industrial Canal during the storm.
The Corps worked with the U.S. Coast Guard, Army National Guard and other state and federal authorities to bring in all assets available to expedite the process. “We’re attempting to contract for materials, such as rock, super sand bags, cranes, etc., and also for modes of transportation like barges and helicopters, to close the gap and stop the flow of water from Lake Pontchartrain into the city,” said Walter Baumy, Engineering Division chief and project manager for closing the breach.
Planning for repairs involved the Louisiana Department of Transportation and Development, the East Jefferson Levee District and Orleans Levee District, to locate materials and access to the breach area.
The New Orleans District’s 350 miles of hurricane levee had been built to withstand a fast-moving Category 3 storm. The fact that Katrina, a category 4-plus hurricane, didn’t cause more damage is considered a testament to the structural integrity of the hurricane levee protection system.
At 2 or 3 AM, Corps officials got a telephone report of a suspected 17th Street Canal breach.
Flooding had begun slowly, but the second disaster appeared as water poured in even as the winds abated. Storm surge and rainfall had raised the level of Lake Pontchartrain, providing an enormous amount of water which poured into the city. By the end of the day much of the city was under as much as 20 feet of water.
Plans were made to begin levee work, including use of 3,000-pound sand bags on the 17 Street Canal. Army National Guard helicopters are expected to begin assisting in the operation August 31.
The breach at the 17th Street Canal Levee, a levee-floodwall combination, is about 300 feet long. It’s believed that the force of the water overtopped the floodwall and scoured the structure from behind and then moved the levee wall horizontally about 20 feet, opening both ends to flow.
State Transportation workers began building a road toward the breach with available equipment.
The Corps released two contracts to close the breach in the 17th Street Canal. The 3,000 pound sandbag operation at the 17th Street Canal was postponed early in the day when U.S. Army Chinook helicopters were diverted for rescue missions. The Corps continued to coordinate with Army officials to have helicopters assist in placement of sandbags at the breaches. The 3,000 pound sandbags are each about 3 feet square.
Corps officials worked with Orleans Parish and Louisiana Department of Transportation officials and Boh Brothers Construction Company, headquartered in New Orleans, to place piling at the lakefront to stop flow in the 17th Street Canal. This would stabilize the water flow and allow work on the levee, while also helping to stabilize the rest of the levee system.
Along with local and state officials, the Corps contracted to build access roads to the breach sites and to fill in the breaches. Rock/stone/crushed concrete would be hauled by truck for road construction and to repair the breaches. One plan called for building an access road from Hammond Highway to the 17th Street breach, and then southward to the end of the breach. The road would have to be built to safely permit backing and dumping of heavy materials.
Lake Pontchartrain was almost back to normal levels, so little water flowed out of the city. This allows a change of plans, and marine equipment was used to drive sheet piling at the mouth of the 17th Street Canal to seal off the entire canal from the lake.
Shortly after 1 PM the first piece sheet piling is driven, to form a steel wall across the lake’s entrance to the 17th Street canal. The opening was expected to be closed by the end of the day. A contractor began bringing in rock to build a road toward the breach. The breach was south and east of the Hammond Highway bridge over the canal, with dry land on the west side of the bridge.
Rock was being transported from offsite to complete the access road and closure at the 17th Street breach. Once the rock required to build the roads arrived in New Orleans and the access road to the breach has been completed, the Corps estimated closure of the breach could be completed in three to four days. Several private firms have volunteered services and provided assistance in design of the closure.
The 17th Street Canal Levee, a levee-floodwall combination, was now estimated to have a breach 450 feet long. It was still believed water overtopped the floodwall, scoured the structure, and then moved the structure 20 feet horizontally.
On east side of the 17th Street Canal, closure by sheet piling of the 200-foot-wide canal was done after the Corps was confident that the lake had fallen to a normal level and water was not trapped inside the city that would otherwise drain out by gravity.
Water could no longer flow from the lake into the city.
With the mouth of the canal sealed, the sheet piling prevented lake water from getting to the levee breach. Since no additional water can get through the breach it was no longer necessary to seal the breach itself. The next step is to get existing pumps working, and to bring in additional pumps to drain the surrounding city and the canal. Later, the canal can be drained so permanent repairs will be made to the levee.
Helicopters were dropping large sandbags made of strong, synthetic materials in the breach. Heavy equipment on the ground has been placing rock. Ground access was created by building a rock road from Hammond Highway, which is about 700 feet lake-ward of the breach. The 17th Street Canal is a drainage canal whose dimensions and an important bridge, integral to the flood control system, would not permit entry of barges and towboats to haul rocks and placement cranes.
Work continued on the breach. The sheet piling still blocks water from flowing in.
17th Street Canal breach was closed. After the emergency is over, the canal will be drained and the wall repaired.
Blackhawk and Chinook helicopters had dropped over 200 sand bags. Approximately 125 sandbags had broken the surface of the water.
There were three 42″ mobile pumps staged and two 42″ and two 30″ pumps were placed at the sheet pile closure. Sewer & water board, electric utility and 249th Prime Power Engineer Battalion were completing pump house inspection.
When pumps began operation, a 40-foot-wide opening was made in the sheet piling to allow water to flow out the canal.
The pump stations began to get online on 17th Street Canal. Pump Station 10 was actually pumping at this point. Pump Station 6 was interrupted to clean up some debris out of the area.