Changing the face of Charleston : The unbuilding of the Grace and Pearman Bridges
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January 25, 2006:
Adventures with drilling and the jackup barge

Of all the amazing things that I have learned during the building of the Ravenel Bridge and the unbuilding of the Grace and Pearman Bridges, today was up there at the top. It was all Mickey Roger's fault. He suggested I learn a bit about drilling from the jackup barge - so I spent the afternoon with Captain Bill Freaney and his jackup barge team, Ken and Mike King and with Mickey's drilling team:Felix Butler, Ernest Asby (better known as Junior), Kerry Spencer and Silas Presot. And of course, life without Sharon's taxi service is simply not much of a life. So we started with Sharon passing what remains of the Grace and Pearman trusses - no longer over Town Creek.

The jackup barge was standing beside C3 - the third Cooper River pier within the Coooper River ship channel

A closer look. Now something about the jackup barge - from Capt. Bill and Mike. The legs are 150' in lenght and at the base are pads, 14' in diameter and 3' thick. The barge itself weights about 1,300,000 pounds. In the belly are two preload tanks that can each hold 350,000 pounds of water - and there are two steering propellers. So, with the legs in the up position, the jackup barge drives like a small ship. However when the jackup barge wants to plant its feet, then the three legs, controlled by a pair of racks and 4 pinions, driven by hydraulic motor, are lowered. When they touch the bottom, the trick is to slowly slowly lift the hull off the surface of the water while adjusting the extension of each leg in order to maintain a level orientation. So what happens when the river bottom is not level. Capt. Bill has a pair of carpenter levels in his pilot house that he watches and with inspiration, shear determination and skill, adjusts the legs so that they sink into the mud and establish a firm base. The trick is that the river bottom is not level and the legs can slip - which requires what I consider extraordinary skill in order to prevent the barge from tilting and perhaps falling over. Here is the jackup barge fully extended.

Once stabilized, preload tanks are filled with water, adding additional weight to stabilize the footing. To undock, the preload tanks are emptied whuch creating a positive buoyancy which can pull the legs free of the bottom. Additional positive buoyancy can be generated by emptying the preload tanks. (And please provide any corrections to this description).

Next Calvin Konya (from Precision Blasting Services in Montville Ohio), Mickey and I took the elevator from Sharon's taxi to the barge. On the left you can see our elevator cab, suspended by the crane, slowly descending - and on the right, climbing in.

On the way up, there was a great view of the foundation of the 1/4 mile long Mt. Pleasant pier

You can see the correspence with the Pearman foundations shown on this schematic

and on the barge, Mickey's team was busy finishing drilling holes for imploding the pier.

Kerry and Silas were drilling into the pier cap. With your curious eyes, you see some red areas have 1 hole, some have 2, 3 or maybe 7 holes. The problem is that of lacking X-ray vision. When they start drilling a hole, they may encounter embedded rebar - so they start a new hole until they find a clear path for completing the hole.

Felix and Ernest were drilling into the column. Click for a video of drilling (13 Mb quicktime).

A closer view of Felix and Ernest drilling

Captain Bill decided I needed a reminder that I actually visited his pride and joy and challenge

The yellow cylinders shown here are the tops of the barge legs - left leg

and right leg with the rack (vertical gear) visible

and a wider view

and back leg - you can see two teeth of the rack on the left side

Here is the hydraulic motor that drives the pinion

Kerry and Silas are drilling into the cap while Felix and Junior are drilling into the column

When finished, these almost-martians (because of the breathing filters) come down

while Kerry and Silas continue drilling

and when finished, return to earth

The control room - with the carpenter's level in front of Capt. Bill. A great example of low-tech tools for maintaining the attitude of the jackup barge.

The start of our descent - which takes about 20 minutes

The view coming down is simply spectacular - here you see the roots of D28 - D23 that were imploded over the past 2 weeks

and a closer view when we reached the river surface

Looking east - another view of the Mt. Pleasant pier foundation

and a closer view when we reached the river surface looking east. An excavator (in the background - requires curious eyes to see it) with its hammer is busy working on one of the pier bases.

Capt. Bill drives us to C2 where Mickey's team will drill tomorrow

and once we are in position, Bill slowly drops the 3 legs, while watching his levels. Note the bubble is perfectly centered.

This is high tech at its highest - his right angle array of carpenter levels.

The Gunny is coming to help position us

and as the sun drops, the Gunny also has a golden hue

and finally, when the legs are in place, the surface is lifted to maintain the 1.3 million pounds of weight on the 3 legs

Mike King prepares the ladder so that we can escape

while Ken operates the crane

and smiles

A view as we leave - note that the hull is completely elevated above the river surface

Compare this with the 2nd photo from the top - when the jackup barge was standing beside C-3

Now - it is positioned adjacent to C-2

and the late afternoon sun gives the Ravenel diamonds a golden hue

The Gunny takes us back to Town Creek - where our iron workers have been working. Sparky spent the afternoon with them - stay tuned

The East Grace truss

and the West Pearman and Grace trusses

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Attribution: C. Frank Starmer and Sparky Witte from