A Hanging Cofferdam for the Repair of the Gray’s Ferry Bridge Over the Schuylkill River
Overview
Gray’s Ferry Bridge Over Schuylkill River – Buckley Construction contacted Hydro-Marine Construction and W.J. Castle & Associates about designing this system that is one of a kind. Castle designed the system, and Hydro is doing the construction work. The design for the system had to be approved by PennDOT before we could move forward. The work is being done on piers #6 and #7 of Gray’s Ferry Bridge over the Schuylkill River.
Castle developed a “hanging cofferdam” to be attached to the side of the pier so that repairs do not have to be accomplished underwater. These cofferdams are designed to attach to the four pier faces at the two ends and the two middle sections, and they can be removed to use again and again as needed.
The cofferdams are fabricated from ¼ inch steel plate and, when attached to the pier face, were 95 percent effective in keeping water out of the cofferdam. A hydraulic pump was used to withdraw any water that did enter.
The Problem
The issue to solve was how to work in the water but keep dry while doing the crack and spalling repairs without divers. After the design and fabrication of the cofferdams, Hydro installed them using divers.
The Solution
The cofferdams are attached to the face of the pier using anchor bolts and neoprene rubber to seal all the irregular surfaces on the concrete piers. Castle needed to take field dimensions since the bridge is at least 40 years old and confirm the size to fabricate. The cofferdams were brought to the site on a barge and installed. The cofferdams fit precisely to the face of the pier without needing any modifications.
The primary advantage of working inside the cofferdams is that no work is done in the “wet,” eliminating permit restrictions when working in the water during fish migration in the river.
Working Outside the Box on the Gray’s Ferry Bridge Over Schuylkill River
This design was a collaboration between Hydro and Castle, “working outside of the box,” to solve a problem by creating something new.
Due to the cold weather and other obstructions in the river, work on the project is on hold. We anticipate starting up again in mid-April.
Let us put our experience and innovation to work for you. Contact W.J. Castle & Assoc., P.C. to discuss your next project at 800.644.4713 or contact us here.