Crossing the Hudson
A landmark New York bridge is being protected by GCP Applied Technologies’ ELIMINATOR® Waterproofing System
Designing bridges to stand the test of time is no mean feat. When it came to replacing the old Tappan Zee Bridge with a new three-mile twin span bridge across the Hudson River, the New York State Thruway Authority (NYSTA) and design-builder Tappan Zee Constructors (TZC) needed to ensure the highest level of protection was achieved. With the added challenge of variable and extreme weather conditions, restricted working hours and short possession times, the choice of waterproofing solution was crucial. Here we explore how these challenges were tackled, and review the results following the project’s completion.
A massive fast-tracked waterproofing project
The Governor Mario M. Cuomo Bridge is the largest single design-built contract for a transportation project in the US and the longest bridge in the State of New York. Constructed of precast concrete deck panels that sit atop steel girders, the bridge is designed to achieve a 100-year service life.
Both the scale and the construction schedule of the $3.98 billion project are noteworthy. This extends to the waterproofing of the bridge, which required surface preparation as well as the application of two layers of liquid waterproofing over 1.2 million square feet in just three months.
Early design support
When it came to selecting the waterproofing solution, the specifiers were looking for a product with a proven track record on long span bridge decks. This led them to discover GCP Applied Technologies’ ELIMINATOR® system from Stirling Lloyd (now GCP Applied Technologies). This liquid waterproofing membrane system has been used to protect the deck of many of the world’s biggest steel and concrete deck bridges for more than 25 years.
After conducting an in-depth site visit, including inspection of the bridge deck, GCP Applied Technologies’ Design Support Team worked closely with the project team to develop the waterproofing specifications. This called for a solution that would provide speed and ease of installation, minimising traffic disruption and facilitating contract progression. The ELIMINATOR® waterproofing system satisfied these requirements, as it is spray applied and cures quickly (typically within the hour) to form a highly durable, seamless membrane.
GCP also conducted compatibility testing of the bridge deck with the ELIMINATOR® membrane, and realised exceptional adhesion results. The specifications also called for the use of a thin asphalt wearing course.
Veteran waterproofing applicators working together
Due to the massive scale of the waterproofing operation, a site visit by pre-selected certified ELIMINATOR® applicators was scheduled by TZC. It was recognised that only a select few, highly experienced, well-trained and well-equipped applicators would be able to perform all the work required within the parameters of the project construction schedule. A shortlist of experienced ELIMINATOR® applicators visited the site to get a hands-on view of the scale, scope and timeline for waterproofing. TZC selected a joint venture led by Venture Construction, the largest ELIMINATOR® applicator in North America, and Thomarios, the applicator with the longest track record in North America, to install the ELIMINATOR® system.
Supported by Venture’s large fleet of surface preparation machines and multiple crews from Venture and Thomarios, the applicators were able to cover 250,0002 feet a week, including surface preparation and application of the tack coat.
Preventing common application delays
In addition to the demands of waterproofing such a large surface area in just three months, there were additional logistical challenges to the project. Work was being executed at other locations on the bridge deck at the time that waterproofing commenced. This could have created a problem with other waterproofing systems.
However, the ELIMINATOR® waterproofing system gave the applicators the flexibility to have multiple crews working at the same time. They could stop the waterproofing application at a certain place and come back at time later to tie-in the day joints.
In addition, the waterproofing membrane was being applied at the height of the summer. Many liquid waterproofing membranes react with naturally occurring moisture and suffer severe limitations in hot conditions, which severely hampers productivity on-site. The versatility of the ELIMINATOR® system meant the crews could maintain productivity in hot temperatures (up to 120° F) and high periods of humidity without shutting down.
On-the-spot QA tools
Quality assurance (QA) was also an integral part of each step of the waterproofing project. First, adhesion testing was done to validate early on that there was a full chemical bond between both the waterproofing layer and the substrate below. Wet film-thickness testing was then performed to verify that the liquid waterproofing was being applied at the specified thickness. Film thickness was checked at the time of application rather than post-application, enabling real-time QA checks to be taken.
Since this QA step could be done immediately, applicators were able to swiftly identify and touch up any areas in need of additional waterproof coating. The ELIMINATOR® system was applied in two colour-coded layers, making it easy to see at a glance that all surface areas were covered. This gave the applicators greater confidence that the membrane would perform optimally.
A successful, fast-tracked project
The combination of a high-performance waterproofing membrane and seasoned waterproofing experts working together enabled the project team to open the first span of the bridge to traffic in the summer of 2017 followed by its second span a year later. More than 50 million vehicles cross the Governor Mario M. Cuomo Bridge annually.
For more information, please see: www.gcpat.com