A new way to part the sea

Nov. 13, 2015

It’s a strange sensation to walk along a 300-ft roadway that rests at the bottom of a lakebed with the actual lake surrounding you on both sides. But that was the case in Asbury, NJ, this past summer, where the new Sunset Bridge project was underway.

As general contractor Kyle Conti Construction was managing the demolition of the 80-year-old Sunset Avenue Bridge, they were also considering their next steps for the construction of the new replacement bridge. They needed to drive foundation piles into the lakebed and were looking at all options on how to accomplish the task safely and efficiently. The contractor contacted Mabey Inc. to see if its DuraBase matting system could provide a stable roadway at the bottom of the lake for better site access. Kyle Conti needed a solution that was safe for their crew and equipment but also aligned with EPA and New Jersey Department of Transportation regulations.

Kyle Conti installed an elaborate dyke system to dam the work area and remove water down to the lakebed itself in preparation for the project ahead. Mabey’s engineers developed a comprehensive design plan that included a 300-ft temporary roadway and three work pads. Mabey installed 430 mats to create a stable, reliable roadway to accommodate the heavy bridging equipment. Since the matting configuration included work pads that branched off the roadway, it enabled the contractor to get their cranes closer to the piles than originally forecasted. Kyle Conti was able to downgrade the need for a 150-ton crane down to a 120-ton crane to do the same job, saving money and delivering less impact to the lakebed. 

Mabey’s DuraBase mats are made from prefabricated composite material, each molded as a seamless, one-piece, 8-ft x 14-ft mat. Although the contractor continuously pumped out any rainwater or lake water that seeped into the excavation, water was still present. However, since Mabey’s mats do not absorb water, the roadway was unaffected.

Mabey’s mats piece together like a puzzle with an interlocking pin design to create a continuous roadway. The mats are engineered to be flexible to conform to uneven terrain but strong enough to support equipment such the 120-ton crane utilized in Deal Lake. The stability and reliability of the roadway provided equipment operators the confidence to perform their work without worry that the roadway would shift or move.

Additionally, DuraBase mats have a built-in tread pattern and anti-skid surface to help prevent slips, which is important when working in an excavation carved out of a lake. Since the mats do not absorb water, they can be removed easily from sodden earth and then rinsed off to prevent cross-contamination from site to site. Traditional wood mats absorb water, are slick when wet and are hard to remove once exposed to wet conditions. Decontaminating a waterlogged wood mat is near impossible.

After the contractor set the trusses with the crane and was able to get the decking installed on the bridge, Mabey returned to Asbury Park to remove the roadway. The rest of the bridge work continued from above the lakebed and is estimated to conclude by May 2016.