Spillway Passes Flood Test
When a Freese and Nichols Southeast Division team replaced the Jones Creek Spillway, west of Houston, they designed and built it to withstand an extreme scenario. But they probably didn't expect such an event to happen so soon.
On May 11, four days after completion, the Spillway was tested by a storm just under the 100-year storm event: a flood that resulted in headwaters only one foot below the design elevation. The project passed the test, and the team was pleased to see it operate as intended.
The design included installation of flood gauges on the upstream side of the structure. After the May 11 storm, the team also provided the Gulf Coast Water Authority (GCWA) a system rating curve for the Spillway. These tools will allow the GCWA to truly quantify the flow over the Spillway for the first time. Freese and Nichols is providing this capability to the GCWA on all of its projects so that the GCWA can better understand its system.
The project replaced a failed spillway with a reinforced concrete spillway. It impounds water for the creation of Oyster Creek, which helps GCWA supply water to Sugar Land, Missouri City and Water Control Improvement District No. 2. The structure consists of 1.5-foot-thick wingwalls, a 2.5-foot-thick foundation slab, and a 2-foot-thick weir wall.
Freese and Nichols practiced innovation on this project by dropping the original stilling basin slab elevation for hydraulic efficiency, splitting the monolithic foundation design into three segments for easier constructability through rainy conditions, letting the contractor use the existing sheet pile as formwork, and using part of the structure to bypass flows during construction.