water overtopped the floodwall and scoured the structure from behind and then moved the levee wall horizontally about . This hypothesis was later refuted by eyewitnesses. 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 the placement of sandbags at the breaches. The 3,000 pound sandbags were each about square (1 m). Corps officials worked with Orleans Parish and Louisiana Department of Transportation officials and Boh Bros. Construction Co., L.L.C., headquartered in New Orleans, to place piling at the lakefront to stop the 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 was hauled in by truck for road construction and repairing 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. To assist in draining the city, the Corps delivered two 5,000 cubic feet per second (140 m³/s) pumps to the Louisiana Superdome. Construction With Lake Pontchartrain almost back to normal levels, little water was flowing out of the city. This allowed 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 1:00 p.m., the first piece of sheet piling was driven, to form a steel wall across the lake's entrance to the 17th Street canal. A contractor began bringing in rock to build a road toward the breach, which 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 was completed, the Corps estimated closure of the breach could be completed