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Thornton - North Washington Wastewater Pump Station Expansion
Tetra Tech RTW designed an expansion of this pump station from 20 mgd to 40 mgd. A firm station capacity required that 27,000 gpm be pumped with the single largest unit out of service. Two of the four existing pumps were replaced with 9,000-gpm variable-speed pumps; one was replaced with a 250-hp constant-speed pump. The fourth pump, a constant-speed pump, was retained for the interim term until daily flows increased. Many possible combinations of the constant-speed pumps would allow flexibility in operation and the potential for improved energy efficiency. Use of the less-efficient variable-speed pumps would be limited to that of pacing flows above the various combinations of the constant-speed pumps.
The existing control system was revised around a PLC-based system that would communicate with the District's Central Wastewater Treatment Plant via leased-line telemetry. All major systems were interfaced to the PLC, permitting two-way communication between them and the plant's computer.
Other work included improvements in screening and grinding, replacement of the electrical feed system, HVAC system revamping, enhanced lighting and potable water distribution, and structural improvements to the roof, concrete, and grating.