Design of Hydraulic Structures for a 350 MGD Water Supply System

The design of hydraulic structures for large water supply systems is crucial to the operations of large diameter pipeline projects. The hydraulic structures are used to control flow rate and surge pressures and in some instances to create pressure drops. The hydraulic design should consider operating conditions, valve flow control capability, potential noise vibrations and cavitation, cost, and reliability. The Eagle Mountain Connection Project for the Tarrant Regional Water District is a 350 MGD water supply system that features several unique hydraulic applications which are essential to the delivery of raw water to TRWD's larger customers. The hydraulic applications to be discussed in this paper are listed as follows, 1) 120 MGD River Outlet Structure with Flow Control Valve, 2) 118 Million Gallon Balancing Reservoir and Bypass Standpipe, and 3) 280 MGD Lake Outlet with Flow Control Valves and Subaqueous Discharge Pipe. The goal is to provide TRWD and their customers with the most flexible, reliable, and cost effective design which will produce the desired objectives. As a result, each structure in this project serves more than one of the following purposes: water storage, outlet structure, surge protection, flow control, and maintenance bypass. This paper covers each application and hydraulic requirements, options evaluated, advantages and disadvantages of each option, and final selection. Lessons learned while investigating and designing each particular application are also discussed. The Eagle Mountain Connection Project is scheduled to be in operation by the end of January 2008. It is anticipated that approximately 18 months years will be needed to mobilize, construct, start up and test the project. The design of the hydraulic structures for the $130-million project is crucial to serving future infrastructure needs of a rapidly growing community.