Hydraulic Modeling and Engineering Design for a Somerset Pump Station and its Water Distribution System

Hydraulic modeling is now commonly used to help engineers to design pump stations and water transmission/distribution systems. In this paper, a case study of a Somerset water system elaborates how to modeling programs and tools to size pumps and distribution networks. The Somerset water system is proposed to provide drinking water from the to-be-upgraded Somerset pump station to its serving areas including three different pressure zones: 830, 730, and 790. This project is a part of the San Antonio Water System's (SAWS) district special projects and upgrades to the facility are necessary to support integration of the pump station into the SAWS network. This system includes, but is not limited to, the Somerset pump station and water distribution network including ground and elevated storage tanks. The system has a design capacity of 5.441 million gallons per day (MGD) representing the maximum hourly demand of the system. Five steady state scenarios are evaluated to develop system head curves and hydraulic modeling data needed for sizing the new Somerset pump station: (1) 2017 maximum hour demand (MH); (2) 2017 maximum hour demand + fire flow (MH+FF); (3) 2017 maximum daily demand (MD); (4) 2017 MD with the lowest water level at the Somerset Pump Station Ground Storage Tanks (GST) and the highest water level at the highest elevated storage tanks (high end of the system head curve); and (5) 2017 MH+FF with the highest water level at the Somerset Pump Station ground storage tanks (GST) and the lowest water level at the highest elevated storage tanks (low end of the system head curve). In addition to meet year 2017 flow requirements, other constraints were listed below per the SAWS Water System Modeling Standards and Practices: (a) for 2017 MH scenario, the minimum pressure should be 35 psi, and (b) for 2017 MH+FF scenario, the minimum pressure should be 25 psi. Based on the hydraulic modeling results and generated system head curves, the recommended design duty point for the four new Somerset Pump Station pumps is 1.813 mgd = 1259 gpm, 270 ft. The 2017 MH scenario minimum pressure will be 37.376 psi (>35 psi as required by SAWS standards) and the MH+FF scenario minimum pressure is 26.255 psi (> 25 psi as required by SAWS standards).