Hoe ram work eliminates need for lengthy bridge closures
The demolition of the old Jamestown Bridge moved into a new phase last week, using a mechanical demolition device called a hoe ram that will break apart the remaining concrete piers without the use of above-water explosives.
The device uses a long arm with a jackhammer-like head that breaks apart the piers. The progress of this technique will vary depending on how porous the concrete is, according to a press release from the state Department of Transportation.
The smaller piers will be demolished using this method, and Cashman Equipment Corp., will also use the hoe ram on the two center piers as an alternative to more explosives.
The top 50 feet of the center piers was demolished on May 18, along with 2,200 feet of deck truss and girderspan decking. The through truss span that the center piers supported was demolished on April 18. Both events required a closure of the adjacent bridge. The use of mechanical demolition on the center piers should negate the need for another four-hour maximum closure.
Mechanical demolition does generate some noise, but how much noise residents will hear, if any, will be determined by several factors, such as wind direction and distance. The decibel level will be lower than that caused by pile driving, a heavy construction method. The days that mechanical demolition will be underway will vary over the summer, and the contractor is restricted to using the tool between 7 a.m. and 5 p.m., Monday through Friday. In areas close to the shore where dust may become an issue, Cashman will incorporate a shoreline mist spray into the operation.
Taking place simultaneously is concrete deck removal, girder span removal, and pier drilling. Once the piers are demolished to the waterline, underwater explosive charges will be used to remove pier sections to a depth safe for navigation. When that occurs, motorists can expect to hear about plans for 30-minute closures of the Jamestown-Verrazzano Bridge.