With more than 8.3 million residents and 52 million visitors a year, New York City has a lot going on. Accordingly, the network of utilities, subway lines, and other underground infrastructure that supports the metropolis is immensely complex. And perhaps one of the most complicated stretches of underground networking is that found below West Street/Route 9A, along Manhattan’s west side.
The once-elevated highway has been redesigned into a multilane, landscaped urban boulevard that is now a major attraction for the neighborhoods along Manhattan’s west side. However, its transformation was decades in the making.
From Westway to today
Almost as complicated as its subsurface utility networks is Route 9A’s past. The reconstruction effort began in 1973 when a truck fell through the then-elevated highway. With the reality that the existing road was no longer safe, planning began to reconstruct the highway. The original proposal, known as Westway, called for filling in 1,000 feet of the Hudson River, placing the roadway in a tunnel, and using the newly created land for development and recreation. That plan was unpopular with neighbors and environmental groups, so after years of deliberation, the city and state moved to develop an alternative that wouldn’t encroach upon the river.
The revised plan called for an at-grade, neighborhood-oriented urban boulevard, varying from six to eight lanes and complete with a bike path and pedestrian walkway. The project broke ground in 1995 and, by 2001, was nearly complete. Then tragedy struck: The 9/11 attacks collapsed the World Trade Center towers, filling the corridor with mountains of debris and damaging the utilities underneath. With access to and from Lower Manhattan at a virtual standstill, engineers now had to focus on rebuilding the corridor and all the utilities severed in the attacks. As time moved on and plans took shape for a memorial at the World Trade Center site, rebuilding the roadway also meant providing for pedestrian access to the 9/11 Memorial site.
The utility puzzle
Lower Manhattan’s extreme density complicated rebuilding of the roadway. Because it is one of the few wide streets in Manhattan, Route 9A had become the busiest utility corridor in the city, accommodating a maze of fiber-optic, gas, electric, telephone, and steam lines, plus huge storm sewer interceptors and the “bath tub” — the slurry wall built to prevent the Hudson River from inundating World Trade Center basements. Rebuilding the roadway and utility service meant not only solving the puzzle of how they all fit together, but also ensuring service continued throughout the construction process.
Water and sewer — Working with only one small piece of land at a time — both to preserve utility service and to coordinate with other construction work all over the area — the design team got to work. Because access to the 9/11 Memorial site was designed to be a flat plane, the roadway was raised 5 feet, which meant also raising the water mains. That additional fill meant a lot more weight would be placed on the existing utilities below, such as the 78-inch interceptor sewer.
The design team considered lining them with typical 4- to 6-inch grout, but the cure time would take too long and it would be impossible to get into the pipe if it needed repairs. They also considered an undercut topped with a lightweight fill, but the city was concerned the depth would prevent access for future repairs. Relocating the lines was essentially out of the question given the already crowded corridor. As the major north/south roadway on the west side of Manhattan, the New York State Department of Transportation needed to maintain six lanes of traffic during any construction, thus making relocation of the 20-foot-deep, 78-inch interceptor sewer impossible. Ultimately, the design team elected to line the sewer with a thin, quick-set lining. The quick application and curing period would help get the sewer lines up and running, and the lining gave the structure enough strength to carry the added load.
Telecommunications — Relocating and coordinating around all the telecommunications lines on the site were also major challenges. At the heart of Manhattan’s Financial District, the site was home to the World Financial Centers (now called Brookfield Place) and the presence of huge global companies such as American Express, Goldman Sachs, and Merrill Lynch. The project site by itself contained more telephone lines than all but the top 50 cities in America. With so many businesses relying on these critical systems, moving them was a delicate affair, involving temporary lines, splicing, and carefully weaving lines through very narrow, competing spaces.
River water cooling lines — The site also included large river water lines that essentially pump in water from the Hudson River to the chiller plant for the former World Trade Center. The new buildings and memorial on the site utilize the same system, so the design plan needed to accommodate those four, 42-inch pipes as well.
“The Governor’s Office and the state challenged us to come up with a new design that could get the river water lines constructed sooner and out of way,” said Karl Rubenacker, P.E., with Stantec.
With space at such a premium, the team stepped up and devised a plan to use abandoned parking garage ramps from the former World Trade Center complex to house the pipes. The relocated river water lines were designed and constructed in just over a year — two years ahead of schedule — thanks to some creative efficiencies identified by the project team. First, using the existing ramps obviously removed the need to design and dig new trenches. Also, the team was able to coordinate staging and access with the other projects along Route 9A and the World Trade Center site, ultimately getting the work done way ahead of schedule and at significantly reduced costs.
An urban boulevard
Throughout the redesign of Route 9A and the World Trade Center site, the state, the city, and the community remained committed to the urban boulevard concept. That concept meant adding trees — and lots of them. The design plan called for more than 500 trees within the highway right of way, as well as on and around the World Trade Center site, which further complicated the utility design plan since tree roots and utility lines don’t mix.
The plan needed to ensure the trees would thrive but would avoid conflicts with utility lines — water mains in particular — as they grow and establish themselves. The design provides a very thin concrete “rat-slab” layer below each tree that discourages the roots from growing straight down but is fragile enough to break through if utility crews need to repair the lines. That way, if a problem with a water main occurs, the city could repair the water main without disturbing the trees that define the neighborhood. The water mains also have vinyl sheeting installed to provide ease of future repairs.
Relocating and rebuilding water mains all for the sake of trees is nearly unheard of in hyper-urban settings such as Lower Manhattan. But given the decades of work among city officials, environmental organizations, neighborhood committees, and other groups to come to consensus on the urban boulevard design, the mindset was different going in. In this case, beauty trumped function and the design needed to find a way to accommodate both.
NYSDOT Commissioner Joan McDonald said, “Route 9A in this area is one of the widest urban roadways in Manhattan, and the perception of a quality, tree-lined pedestrian-scale environment greatly enhances the experience of the millions of people who will visit lower Manhattan in the years to come.”
September 11, 2011
As the 10th anniversary of the 9/11 attacks drew closer, the pressure was on for the city to complete reconstruction around the site to meet Mayor Bloomberg’s target of officially opening the memorial on Sept. 11, 2011. Since the attacks, dozens of projects were happening simultaneously, the pedestrian Concourse under 9A in particular, working through everything from roadway realignment and bridge modifications to utility connections and aesthetics. Construction staging and scheming offered no room for error and involved coordinating — sometimes by the minute — with many agencies, consultants, and contractors. As a whole, the Route 9A projects involved more than 30 government agencies and private land owners, plus dozens of engineering and construction consultants working on each project.
As these teams worked feverishly to complete their projects, Route 9A became the primary route for getting crews and equipment to and from the site. So the Route 9A team not only was working on the various utility and tree coordination efforts, but also had to manage the constantly changing phases and circumstances of the surrounding projects. What began as a six-stage effort multiplied into 66 stages, forcing the team to focus its efforts and energies on each small parcel of land as it became available.
Today, Route 9A serves as the front door of the World Trade Center site and the 9/11 Memorial and has become a fitting entrée to such a nationally significant destination. The urban boulevard, as originally imagined, is a beautiful, tree-lined corridor that invites everyone — whether by foot, bike, or car — to visit the solemn site, all the while surrounded by a park-like setting on one side and some of the world’s most influential businesses on the other.
Joseph T. Brown, P.E., is regional director with the New York State Department of Transportation. Toby Hansson, P.E., a senior principal, and Olga Gorbunova, P.E., a senior engineer, are both with Stantec in New York City. Contact the authors at email@example.com, firstname.lastname@example.org, and email@example.com, respectively.