References » Shafts

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Drilled Shaft Foundation
Winyah Generating Station - SCR Retrofit Project Georgetown, South Carolina

Client:
   Santee Cooper (South Carolina Public Service Company)
Owner:
   Santee Cooper (South Carolina Public Service Company)
Design Engineer and
Technical Oversight: 
   Sargent & Lundy, Chicago, IL
Construction Period:
   April, 2003 through July, 2003

 

Scope of Work:

Coastal Caisson recently completed the drilled shaft foundations at the Winyah Generating Station in Georgetown, South Carolina. The project was for the addition of a Selective Catalytic Reduction (SCR) system to the existing power plant. The SCR is located directly above the power plant, thus necessitating the need to install the foundation system inside the existing structure, nestled in among the original foundations and framework.

All work was required to be completed during normal plant operations without any interruptions or outages to the service.

  
This project included the installation of 165 drilled piers, 36” ø with depths ranging from 40 feet to 60 feet.

Of these, 110 shafts were installed in very limited space with overhead clearance as low as 12 feet and as high as 20 feet. Every shaft was drilled and socketed into the Santee Formation (Limestone).

The entire project was scheduled to last 7 months for production and was accomplished in approximately 4 months. All quality control was the responsibility of Coastal Caisson an the work proved 100% in compliance after all testing was completed.

Coastal Caisson used a Bauer BG-22 to install the 55 drilled shafts which were in the open areas and used a variety of special tooling and equipment in the low overhead areas. The primary drilling machines were adapted by taking the rotary drive head from a Bauer BG-7 and mounting this to the front end of a loader. This provided the torque required to twist in and seat the permanent casings 37 feet long. A bay shore Systems Lo-Drill was then used to auger the overburden materials and some of the weathered rock. The loader with the BG-7 attachment was again used as needed to core the rock.

With the low overhead clearance, the reinforcing cages and concrete tremie pipes were installed in sections of 10 feet each and coupled together with mechanical couplers. The concrete was placed by pump through a 3 inch steel pipe which was left in the shaft once the concrete was completed.

Due to the seismic design criteria for this site, the design necessitated that the piles provide high lateral as well as axial load resistance. The first phase of construction included a load test program using a Statnamic Load Test System to test and economize the shaft design.

 

 

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