Freese and Nichols designed and constructed a reinforced concrete spillway to replace a previously failed spillway for Gulf Coast Water Authority (GCWA). The Jones Creek Spillway impounds water for the creation of Oyster Creek, which helps GCWA supply Sugarland, Missouri City and Water Control Improvement District No. 2 with water. The structure consists of 1.5-foot-thick wingwalls, a 2.5-foot-thick foundation slab, and a 2-foot-thick weir wall. The design also included installation of flood gauges on the upstream side of the river.
Within four days of completion, the spillway was tested by a 100-year storm event: a flood that resulted in headwater levels reaching just one foot below the design elevation. The structure withstood the high water levels and successfully passed the test. The storm prompted Freese and Nichols to provide the GCWA with a system rating curve for the spillway, as well as for all GCWA projects. These tools will allow the GCWA to truly quantify the flow over the spillway for the first time and better understand its system for all projects.
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 weather conditions, letting the contractor use the existing sheet pile as formwork, and by using part of the structure to bypass flows during construction.
Gulf Coast Water Authority
Water Districts/River Authorities
Construction Services, Dams and Levees, Structural