The Gerald Desmond Bridge in Long Beach, California spans the Wilmington Oil Field – one of the largest oil fields in the continental United States, with more than 6,000 oil wells.
In order to construct the new bridge, all active and inactive wells that interfere with the deep foundation system for the new bridge had to be abandoned and partially removed. This required that all wells be capped and the well casing (surface casing, conductor pipe and well pipe) be removed to an average depth of 195 feet below grade. The idea was simple but the execution was more challenging because the well casing had to be removed without disturbing the existing ground around it. This was complicated by the fact that there was no reference for such operation and the diameter, wall thickness and verticality of the well casing varied from location to location.
After determining that the well casing was not as plumb as originally thought, it was decided to twist an oversized temporary steel casing over the well casing to encapsulate it and then remove the well casing from within the temporary casing from the top down. The installation of the temporary casing was accomplished by oscillating and rotating segmental steel into the ground.
This stabilized the native material outside of the temporary casing and encapsulation the well casing for removal. Some of the native material inside the segmental casing was removed to free up the well casing. This allowed for the cutting of the well casing in segments from the inside out–or the outside in–to finally allow for its removal.
Once the well casing and all of the native material inside the temporary casing was removed to the desired depth, a low strength self-compacting concrete was placed using the tremie method to backfill the excavated shaft. The temporary casing was successfully extracted without disturbance of the surrounding soil and nearby structures.