"In the early planning stages, the decision was made to use a drilled caisson
system, which is more costly, rather than a driven pile system for noise abatement," said Simona.
However, based on the CM's experience, the design team was swayed toward a drilled caisson
bridge that would significantly reduce disruption to the stream and avoid costly temporary shoring.
Iron Woman used a crane to set HP14 x 117 pounds, 45-foot long I-beams into the drilled caissons
, and a skid-steer backfilled to the engineer-prescribed depth while crew members kept the beams aligned and square.
Douglaston had to drive 2,000 piles into rock from 50 to 90 feet below grade, many of them highly technical drilled caissons
, using a process that consists of drilling holes and placing reinforcing steel and concrete into the holes while sheeting, shoring and dewatering the earth below grade.