Khurram Saeed, ksaeed@lohud.com
Sheet piles will be installed just off River Road to create a temporary support wall for the Rockland landing of the new bridge.
Work is starting later this week to install 60-foot-long flat sheet piles along the northbound Thruway near River Road. The work will last about three weeks and take place only during the day, said Carla Julian, spokeswoman for bridge builder Tappan Zee Constructors. The sheet piles, which are different from the round pipe piles being used in the Hudson, will create a temporary continuous wall that will support the Thruway during the excavation and construction for the Rockland landing of the new bridge, Julian said in an email.
About 45 to 50 sheets are needed to cover approximately 100 feet, and crews typically average three piles per day, Julian saidThe site formerly housed a state Thruway Authority maintenance building; it was demolished a few weeks ago. A 165-foot tall crane positioned just off River Road will install the piles into the ground using a vibratory hammer, an alternative to louder pile driving.
The interlocking sheets are installed in sequence. Julian said crews first install a 25-foot-high template, lift and swing a sheet into the template, position it and drive enough of the pile to stand in the template, drive additional sheets, move the template and drive the piles the remaining depth.”The actual pile driving is the fastest part of the process and is not done in one shot,” she said.Tappan Zee Constructors crews are expected to be on the site Wednesday to mobilize and plan to begin work on Thursday or Friday.The pile work will require the closure of the right lane on the northbound Thruway for some of the operation, Julian said.
The lane will be closed this week from 10 a.m. to 3 p.m. Wednesday and Thursday, and from 10 a.m. to 1 p.m. on Friday. The project team has a video on YouTube providing an animated look at the construction of the new bridge’s main span foundation and towers.