The existing Lake Townsend Dam (and integral raw water pump station) in Greensboro, NC (City) was failing due to alkali silica reaction (ASR) issues with the concrete, Brown and Caldwell was selected to perform the fast-track design of the new 30MGD raw water intake and pump station. Deep excavation along the shoreline of a lake can be very expensive. The challenge of this project was to design a raw water pump station that would have a long life, be easy to maintain, and meet the client’s budget. To add to the project’s complexity, the design had to be fast-tracked to meet a schedule driven by other commitments already under way. A team of experts was assembled to evaluate design alternatives and work with the City to determine the best approach to meet the tight design and construction schedule. The initial conceptual design followed Hydraulic Institute guidelines, but preliminary construction cost estimates proved to be too high. The design professionals presented the City with a unique concept. The pump station footprint was decreased by 10 feet by incorporating the design of patent pending pump cans, which saved over one million dollars in construction costs and reduced construction time in comparison with a traditionally sized station. To protect the client, prove the viability of the pump station configuration, and promote the highest hydraulic efficiency, a quarter scale physical model of the pump station was built and hydraulically tested at all design parameters. Potential fatal flaws were evaluated and the final design “tweaked” to optimize efficiency. In addition, the sizes of the pumps were significantly decreased to allow better flexibility and additional equipment and space savings. Only 500 HP was required, and replaced over 1,300 HP in the existing pump station.
How a Physical Pump Model Helped Saved Construction Costs and Reduce O&M Headaches
Authors: Robert A. Teem and Sami Sarrouh