A bridge that has carried millions of cars back and forth from Westchester County New York to bustling New York City has lived a long life. The 60-year-old Tappan Zee's deteriorating structure carries an average of 138,000 vehicles per day, substantially more traffic than its designed capacity.

Unlike other major bridges in metropolitan New York, the Tappan Zee was built to last only 50 years due to wartime material shortages at the time of its construction. Due to political disagreements between New York and New Jersey, the bridge was erected at one of the widest points of the Hudson River. Work began on the unprecedented three-mile structure in March 1952 and opened to traffic on December 15, 1955.

A new Tappan Zee bridge now rises in parallel to its predecessor, intended to last at least 100 years. Before the foundations of the New NY Bridge project ever were installed, Tappan Zee Constructors, LLC (TZC) engaged experts at HDR Inc., an architectural and engineering firm based in Pearl River, New York, to build the new crossing in a virtual world.

BIM - A Critical Link in a Complex Project

As the largest bridge and highway project to date in North America, the scale and complexity of this endeavor led HDR to utilize building information modeling, or BIM. According to the TZC team, this is the first project nationally to be designed, built and maintained using a BIM program from start to finish.  This process of collaborative design using a single coherent system of computer models rather than separate sets of drawings, BIM enables designers to visualize a structure in three dimensions (3-D) and from endless view points. BIM identifies potential design conflicts long before a pile is driven or steel girder is erected, and allows designers to discover efficiencies that can help improve construction scheduling and reduce costs.

In this case, BIM helped on multiple fronts: to quantify and organize the materials needed for the project; integrate all environmental details associated with the structure; allow the design build team to organize an enormous amount of data; and, precisely manage design and construction. As a result, BIM maximizes efficiencies throughout the process, including scheduling and tracking of each element of the bridge's construction progress.

BIM technology serves as a visual logbook for designers and engineers to ensure that construction proceeds in strict accordance with design plans. To date, project engineers have matched and linked millions of documents and photos to different parts of the "virtual" bridge. This highly efficient record keeping process, gathered in a single source with no duplication, is proving to be an invaluable resource for both TZC and the state of New York.

Long after the bridge is complete, BIM will continue to serve the Thruway Authority. Future maintenance teams will need to quickly access and analyze the data that has been collected in the BIM database. Utilizing video game-based technology, HDR developed a user-friendly viewer program that displays the bridge model in a realistic and interactive manner.

"While the BIM model certainly enhances design and construction, the 3-D technology will also be invaluable to Thruway engineers in the planning and execution of its maintenance program for the New NY Bridge," said Larry Soeller, a Thruway Authority Senior Highway Maintenance Engineer. Each of the approximately 500,000 bridge elements can be viewed with links to pertinent design and maintenance information. Maintenance crews will be able to view the model from mobile devices, laptops or desktop computers, allowing them to see every piece of the bridge at every possible

Choosing a Team With Experience

TZC is a consortium of design-builders formed to successfully build and deliver the New NY Bridge on time and within budget, with a goal of achieving the highest environmental standards. With a continuous presence in New York since 1900, members of the TZC team have constructed a majority of the major crossings in the New York metropolitan area, including the existing Tappan Zee Bridge.

According to project officials, the TZC team partnership is based on aligning cultures within each firm that steer strategic planning throughout the project, with a focus on safety. TZC invests great resources and planning to ensure that each employee is trained and prepared to work in a safe environment.

Financing and Stimulus

Financing for the project came from federal funds. The New NY Bridge received the largest TFIA loan to date for an infrastructure project, with $1.6 billion in funds from the Trans Infrastructure Financing and Innovation Act (TIFA), through the U.S. Department of Transportation. According to Brian Conybeare, Special Advisor to Governor Andrew Cuomo, the project was given presidential priority by President Obama as one of 13 most important infrastructure (shovel ready) projects in the country.

The job stimulus for municipalities in the Hudson River Valley has been significant. Thus far, more than 3,000 people with some 1,459 subcontractors have worked on the New NY Bridge project. Conybeare was onsite recently and a contractor who came to an initial meeting for sub-contractors from the area came up to him and gave him a hug, saying, "Hey, don't you remember me? You told me to put in a bid, so I did and I got the contract - thanks!" 

People are excited to be part of a bridge building project, says Conybeare.  "It's been 50 years since the Verranzano Narrows was built. Everyone is so interested in this." 

Environmental Considerations

The State of New York put a number of environmental protection programs in place for area wildlife such as sturgeons and falcons, including the Endangered Peregrine Falcon. "Part of our commitment is to protect the bridge area environment," notes Conybeare. "We have spoken to over 50,000 students in our outreach. The project has a FalconCam onsite and schools are loving that."

A pair of falcons incubated their eggs this spring for approximately a month before three young falcons (two females and one male) hatched between April 24 and 27. Plans for a naming contest were soon set in place and following a week-long campaign in which more than 3,000 ballots were cast, the project announced the winners of its 2015 falcon naming poll in early June.  Hudson, Bridge-ette and Zee received the greatest number of votes among 10 candidate names provided by local elementary schools.

The three winning schools were recognized with award certificates and commemorative posters of the named falcons. The naming contest was conducted to introduce local children to the endangered birds, serving as an entry point for them to learn how major steps are being taken to avoid harming the falcons during construction. The three chicks and their parents currently occupy a man-made nest box in the existing Tappan Zee Bridge.

Only a day after results were announced, the newly named offspring took inaugural flights, returning to the nest box three hours later with their first self-caught prey.  Based on the date they hatched, the falcon chicks' first flights were not anticipated until later in June. They will remain around the nest for several months as they learn to hunt and survive on their own.

The New York State Department of Environmental Conservation (DEC) later tagged the chicks with identifying bands. These ankle bands allow the project team and DEC to identify the falcons and track their health and migration habits. The New NY Bridge also will include a specially designed peregrine falcon nest box, high atop its towers.

The Long Road Ahead

 According to New York Thruway Authority officials, this five-year, $4 billion project is set for completion in 2018. Conybeare says placing the pilings in the water and working in the marine environment have been a huge challenge and now that they're out of the water, logistics continue to be an ongoing challenge. Much of the work is pre-cast so that sections of the bridge are actually built offsite and shipped to the location. With the help of equipment such as a nearly 8,000-ton floating barge crane known as the I Lift NY, these massive pre-built sections are put in place. Originally known as the Left Coast Lifter, this barge crane was used in the replacement of the eastern span of the Oakland-San Francisco Bay Bridge between 2009-2011. "The fact that these sections can be built to an exact dimension, on time and in order, and then put in place, is simply amazing." comments Conybeare.