Diesel fuel spilled from a storage tank to a backup power generator located on the roof of a downtown high-rise building in North Carolina. The spilled fuel passed through a roof drain, thereby entering the city storm drain system, and contaminating a local stream.
Diesel Generator
The bulk of the onsite diesel fuel was kept in an 8000-gallon storage tank located at the basement level. A smaller day-tank was located on the rooftop, adjacent to the power generator. When the fuel in the day-tank reached a low level, additional fuel was pumped from the basement storage tank up to the roof to refill the day-tank.
Basement Diesel Pumps
An EIS engineer was assigned to investigate the cause of the spill. During inspection and review of the building control system plans, it was discovered that the pumps that deliver the diesel fuel from the basement storage tank to the rooftop day-tank are activated by a pair of float switches located in the day-tank. When the fuel level in the day-tank reached a substantially low level, the float switches would activate the pumps. Similarly, when the day-tank was full, the float switches would deactivate the pumps. Two float switches were used in the day-tank to provide a safety measure; both float switches had to be in the same position for the pump to be activated.
Float Switches
Inspection of the float switches revealed that both switches were stuck in a manner representative of an empty day-tank. The generator underwent a test run the morning of the incident. When the day-tank fuel level got low, the basement fuel pumps were activated to fill the day-tank. But, with the float switches stuck, the pumps were never deactivated when the day-tank reached full capacity. The day-tank overflowed and continued to spill diesel fuel onto the roof until a building maintenance worker discovered the spill and manually arrested the pumps.
Diesel fuel spilled from a storage tank to a backup power generator located on the roof of a downtown high-rise building in North Carolina. The spilled fuel passed through a roof drain, thereby entering the city storm drain system, and contaminating a local stream.
Diesel Generator
The bulk of the onsite diesel fuel was kept in an 8000-gallon storage tank located at the basement level. A smaller day-tank was located on the rooftop, adjacent to the power generator. When the fuel in the day-tank reached a low level, additional fuel was pumped from the basement storage tank up to the roof to refill the day-tank.
Basement Diesel Pumps
An EIS engineer was assigned to investigate the cause of the spill. During inspection and review of the building control
system plans, it was discovered that the pumps that deliver the diesel fuel from the basement storage tank to the rooftop day-tank are activated by a pair of float switches located in the day-tank. When the fuel level in the day-tank reached a substantially low level, the float switches would activate the pumps. Similarly, when the day-tank was full, the float switches would deactivate the pumps. Two float switches were used in the day-tank to provide a safety measure; both float switches had to be in the same position for the pump to be activated.
Float Switches
Inspection of the float switches revealed that both switches were stuck in a manner representative of an empty day-tank. The generator underwent a test run the morning of the incident. When the day-tank fuel level got low, the basement fuel pumps were activated to fill the day-tank. But, with the float switches stuck, the pumps were never deactivated when the day-tank reached full capacity. The day-tank overflowed and continued to spill diesel fuel onto the roof until a building maintenance worker discovered the spill and manually arrested the pumps.
Diesel fuel spilled from a storage tank to a backup power generator located on the roof of a downtown high-rise building in North Carolina. The spilled fuel passed through a roof drain, thereby entering the city storm drain system, and contaminating a local stream.
Diesel Generator
The bulk of the onsite diesel fuel was kept in an 8000-gallon storage tank located at the basement level. A smaller day-tank was located on the rooftop, adjacent to the power generator. When the fuel in the day-tank reached a low level, additional fuel was pumped from the basement storage tank up to the roof to refill the day-tank.
Basement Diesel Pumps
An EIS engineer was assigned to investigate the cause of the spill. During inspection and review of the building control system plans, it was discovered that the pumps that deliver the diesel fuel from the basement storage tank to the rooftop day-tank are activated by a pair of float switches located in the day-tank. When the fuel level in the day-tank reached a substantially low level, the float switches would activate the pumps. Similarly, when the day-tank was full, the float switches would deactivate the pumps. Two float switches were used in the day-tank to provide a safety measure; both float switches had to be in the same position for the pump to be activated.
Float Switches
Inspection of the float switches revealed that both switches were stuck in a manner representative of an empty day-tank. The generator underwent a test run the morning of the incident. When the day-tank fuel level got low, the basement fuel pumps were activated to fill the day-tank. But, with the float switches stuck, the pumps were never deactivated when the day-tank reached full capacity. The day-tank overflowed and continued to spill diesel fuel onto the roof until a building maintenance worker discovered the spill and manually arrested the pumps.
