Description

As a subconsultant to Elcon Associates, Inc., T/WI designed the modifications to the HVAC system at the wastewater pump stations and one wastewater diversion structure. The modifications are to bring the facilities' HVAC system into compliance with the current codes and to modernize the stations.

The North Beach Pump Station involved the remodel of a 30-year old, 4.3 MGD pump station to upgrade the HVAC system to meet NFPA 820 code and replacement of the engine-generator set. The design included replacement of existing supply and exhaust fans serving both the dry well and wet well, replacement of the dry well heater and replacement of the existing 125 KW engine generator set with a 250 KW set. The new generator set will have a remote radiator in place of the existing heat exchanger and will utilize once through cooling with City of Seattle water. Automatic dampers were included in the dry well system to recirculate 75% of the air to save energy when the station is unoccupied.

The Duwamish Pump Station involved the remodel of a 29 year old 100 MGD pump station to replace obsolete and/or failed equipment and upgrade the ventilation and gas monitoring systems to conform with the latest edition of NFPA 820. Design included calculating the ventilation rates required, adding a wet well supply fan and a dry well exhaust fan and revising the existing ductwork to provide additional points of ventilation. System controls were changed from pneumatic to electrical electronic type. Wet well gas monitoring and smoke detectors were added per code.

The Dexter Avenue Regulator Station involved the remodel of the HVAC system to meet NFPA 820 code and replacement of obsolete equipment. The regulator station is an underground diversion structure with large hydraulically operated slide gates to regulate flow in different interceptors. The design replaces two ceiling mounted fans with one wall-mounted fan and modifies the duct work as necessary to accommodate the new fan.

The Carkeek Pump Station involved the remodel of a 5-year old, 8.4 MGD pump station to upgrade the ventilation system to meet the latest edition of NFPA 820. Design included calculating the ventilation rates required, adding a new wet well supply fan, modifying the dry well exhaust fan to the ductwork, eliminating two existing fans, and adding smoke detectors and gas monitoring. Also included were fan failure sensors, a wet well hazardous gas sensor and automatic dampers to recirculate 75% of the dry well air to conserve energy when the pump station is unoccupied.