Harllee Branch Generating Plant Windscreen & Free-Standing Internal Steel Flues
Because the weight of the two (2) internal steel flues, measuring 23’ and 29’ in diameter respectively, were carried at grade, the 1,000’ tall reinforced concrete column was technically a windscreen. The free-standing internal flues rose 7’ above the top of that column to make the overall height of the Harllee Branch Plant chimney 1,007’.
The concrete column weighed 54,637,080 lb and the internal steel flues weighed 3,594,171 lb bringing the total weight of the structure to a total of 29,115 short tons. CDI’s engineered design of preparation of the concrete column and internal flues needed to allow for at least a 100% Factor of Safety for each of those structures under maximum historic wind loads for the months while the structure would stand in its prepared state. CDI’s design also needed to carry the dynamic loads imposed on the structural components during the careful rotation of the structure along a center line of fall designed to keep the falling debris within a 6,000 gallon/minute hydraulic mist envelope placed around the fall zone for the structure. Like most public generating companies, Georgia Power is concerned about mitigating visible emissions from the felling of its structures.
Simultaneously, CDI used its historic data and engineered design to demonstrate that the active switch yard, 420’ northeast of the base of the windscreen, would not be compromised by fly of debris or vibration associated with the felling of the structure.
Although CDI was ready to fell the chimney after a month of detailed preparation, the shot was delayed when Hurricane Matthew was forecast to sweep a glancing blow along the east coast of Georgia. Georgia Power did not want its planned temporary outage of the Harllee Branch Plant switch yard to compromise its ability to re-route transmission in the event of power outages in southeastern Georgia.
A week later, on October 15, 2016, CDI detonated 463 lb of explosives placed in 260 holes CDI had drilled in the windscreen and a total of 18 lb of linear shaped charge explosives placed on temporary wide flange columns called for under CDI’s preparation of the differential diameter asymmetrically placed steel flues. The structure was felled precisely on time in a coordinated effort between Georgia Power, Envirocon and CDI. The structure landed within 1.75° of the previously designed center line of fall to the west/northwest, well within the relatively narrow hydraulic envelope installed by Envirocon around the fall area.
Independent vibration monitoring efforts demonstrated that CDI could use its historic data and site-specific information to accurately predict vibration from the fall of such structures at various locations of interest around the fall zone. There was no interruption of Georgia Power transmission capabilities as a result of CDI’s operations.
The felling of this 1,007’ tall (307-meter-tall) structure represents a new world record for the explosives felling of chimney structures.
Click HERE to watch the Harllee Branch implosion.