Case study: Standby power installations

Between mid-August and late September 2004, Hurricanes Charley, Francis, Ivan and Jeanne hit Florida, with three of the four impacting the east central portion of the state. These storms provided an opportunity to compare performance of facilities constructed before Hurricane Andrew to facilities constructed after Hurricane Andrew. In August 1992, Hurricane Andrew hit the southern portion of Florida. It remains the most destructive hurricane to hit the state in terms of structures damaged and destroyed.  

As with many catastrophic events, building requirements typically addressed by more stringent codes are put in place to limit future impacts. After Hurricane Andrew, increased building requirements included designing buildings to withstand high winds, including both positive and negative pressures, and to mitigate damage from windborne debris. 

This case study looks at a water treatment plant designed/constructed in the early 1990s and a wastewater treatment plant designed/constructed in the late 1990s. They are located within five miles of each other on the east coast of Florida. The case study will examine the design of the standby power system at each facility, the performance of each system during the 2004 hurricane season and improvements following the 2004 season.

Water treatment plant

The water treatment plant’s standby power system was in a pump station constructed of a concrete column and beam structure with concrete masonry unit infill. The standby generator was in a room at one end of the building. The generator room consisted of one interior wall and three exterior walls. The longest exterior wall had two large wall openings covered by steel wall hoods for air intakes. A large exhaust louver with direct attachment to the radiator shroud was located on one of the short exterior walls.  

During the 2004 storm season, the building did not sustain much damage. However, the air intake hoods for the generator room allowed significant water penetration into the facility, described by plant personnel as “like it was raining inside the room.” The radiator exhaust shroud was damaged by back–pressure from the wind blowing against the radiator fan. The damage resulted in extended facility downtime. 

Wastewater treatment plant

The wastewater treatment plant standby power system was in the electrical generator building, which was constructed of reinforced concrete masonry units. The standby power system consisted of a generator located in a room at one end of the building. The generator room consisted of one interior building wall and three exterior building walls. Intake and exhaust louvers for this standby power system were located at each end of the room and were both protected by plenums.  

During the 2004 storm season, the building sustained no damage. The facility did not see any downtime. 

Power system improvements

The standby power systems and severe weather protection measures at the wastewater treatment plant performed as designed and no improvements were made to this system. 

Due to the performance of the standby power system and severe weather protection measures at the wastewater treatment plant, the owner decided to include a new standby power system at the water treatment plant. The new standby power system was designed and constructed as part of the water treatment plant expansion project. The new standby power system consisted of two generators in a single space with intake and exhaust plenums. 

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