The Garden State Parkway in New Jersey connects land in the state separated by Great Egg Harbor, with two recently replaced bridge structures separated by Drag Island. South of the island is the structure over Great Egg Harbor Bay, made up of 21 spans of precast, pre-stressed concrete bulb tee girders varying in length from 148 ft to 250 ft, with an overall bridge length of more than 3,800 ft. To the north of the island is the structure over the Drag Channel, consisting of 10 spans of precast, pre-stressed concrete I-beams, 77 ft in length.
The two spans are replacements of original structures built over 60 years ago. The new structures were built in close proximity to the existing bridges, only about 12 ft away. Since the new structure was being built so close to the old, and the new structure required deep foundations and piles, vibration monitoring was required to make sure the existing structure was not settling or suffering any damage. “Installation of piles requires driving and construction impacts such as vibrations that could, if you’re not careful, impact the existing structure that was open to traffic the entire time that the new structure was being constructed,” Bob Supino, project engineer for Hardesty & Hanover, told Roads & Bridges.
Among the project goals for these structures included designing both southbound replacements with improvements to lane and shoulder widths, profile, drainage and grading. In addition, the western side of the new structures would be given a 10-ft-wide walkway/bikeway. “Part of the permitting process was to provide for pedestrian and bicycle traffic in the area,” Glen Schetelich, P.E., project manager for Hardesty & Hanover, told Roads & Bridges.
The site of the bridges is home to wetlands as well as endangered marine and shore life, requiring an environmentally sensitive solution for the 21-span structure. Supino explained the bridge was laid out to minimize impacts to the water. “Pre-stressed concrete was used because of the corrosive marine environment—concrete is usually better than steel in marine environments,” he said. The spans were made as long as possible, approximately 180 ft in length, to reduce the number of piers in the water. “The pre-stressed concrete spans are the longest that we’ve designed and I believe the longest in the Northeast.” A section over the channel is comprised of spliced post-tensioned spans—150-ft-long pieces of the spans were brought out, temporarily supported and spliced into place to create longer spans.
The significance of the bridge for the region is that it can act as an emergency route due to severe weather events. “The bridge is made in such a way that we could put more lanes of traffic on it so that in times of evacuations, the bridge could be opened up to more lanes going northbound,” Schetelich said. The southern Jersey Shore area was heavily impacted by Hurricane Sandy in 2012, making the widened bridge necessary for future emergencies.
Project: Garden State Parkway over Great Egg Harbor
Location: Upper Township and Somers Point, N.J.
Owner: New Jersey Turnpike Authority
Designer: Hardesty & Hanover
Contractor: Route 52 Constructors, Joint Venture of Wagman Heavy Civil Inc. & RE Pierson Construction Co. Inc.
Cost: $142 million
Length: 3,834 ft
Completion Date: Oct. 1, 2016