Over 300,000 cubic yards of concrete will be required to build the New NY Bridge. Transporting that amount of concrete by land would add over 30,000 concrete trucks to local roadways over the next four years. However, Tappan Zee Constructors, LLC (TZC) is implementing a highly efficient and environmentally conscious system that will supply a majority of the project’s concrete without the use of local roads. By using two floating batch plants on the Hudson River, TZC will be able to produce and deliver concrete “on demand” directly to the 3.1-mile project site.
The floating batch plants, which are about 60 feet wide by 200 feet long, are like mobile operation centers sitting atop barges on the river. They can easily be maneuvered by tugboats to different points on the project site and produce concrete as needed. The towers of the batch plants hold the raw materials, which are then mixed in precise proportions by an onboard operator. The final concrete mixture is then pumped with a specialized hose to the various sections of the new bridge.
The project’s floating batch plants utilize computer controlled systems to mix additives with raw materials such as stone, water and cement, producing concrete to meet stringent specifications. This method of assembly allows TZC to control both the quality and quantity of the concrete to serve the project and build a bridge that will last a century without major repairs. In addition, TZC has incorporated concrete testing laboratories on the batch plants to perform assessments alongside their work. These testing laboratories are certified by the New York State Department of Transportation and will help ensure the quality of the concrete used on the project.
Each plant will produce an average of 125 cubic yards of concrete per hour, rivaling the capabilities of most land-based batch plants. The real advantage however, is that TZC’s mobile plants are used exclusively on the New NY Bridge project. Normally, different projects must compete for the limited amount of concrete produced at land-based plants on a daily basis, which can lead to shortages and delays during peak construction season. TZC’s mobile plants also eliminate the risk associated with a narrow delivery window (90 minutes from batching to placement). With no traffic or distance to contend with, the possibility of concrete setting en route is no longer a concern.
The raw materials for the floating batch plants’ mixes – including crushed stone from a nearby quarry – are delivered to the project site by barge, much like the project’s other materials such as steel pipe piles and girders. Thanks to water-based transportation along the Hudson River, the project team is more effectively able to control the quality of the concrete.
The floating batch plants include several environmentally friendly features. An advanced air-quality system reduces dust from escaping the plants during production and highly efficient “clean” engines reduce the equipment’s carbon footprint. All of the systems on the plant and its support barge are contained to prevent spillage into the river, with all by-products from the cleaning process stored for proper disposal off-site.
With fewer wasted resources, reduced environmental impact, and less project construction traffic on local roads, the state-of-the-art floating batch plants are crucial to the efficient construction of the New NY Bridge.
The first floating batch plant arrived on the project site this July, and is currently producing high-quality concrete for the new bridge’s pile caps. A second batch plant will follow in the coming months.