Visit the corner of Bowery and East Houston Street in Manhattan, and you will find a bustle of activity. Pedestrians hurry about their business on the sidewalks, and cars, buses, and taxis crowd the busy streets. There’s just as much going on underground. Subway trains run just 8 feet below grade. The location is also an important telecommunications hub where several major duct banks — housing voice, data, and video cables — cross the area, some containing more than 120 conduits. Add sewer, water, gas, and electric utilities, and you have one of the highest densities of underground utilities in the world.
As part of the City of New York’s ongoing effort to update its water supply system, the city is rebuilding and replacing many of the water mains in Manhattan — including one running under East Houston Street. The East Houston Street Trunk Water Main Improvement Project will connect to City Tunnel No. 3, one of the largest public works projects in history. At a projected cost of $6 billion, City Tunnel No. 3 will allow New York to close and rehabilitate the two water tunnels that have served the city for decades.
With a new trunk water main added to the mix, utility density under East Houston Street and Bowery is about to increase even more. Empire City Subway Company, a wholly owned subsidiary of Verizon that is responsible for the telecommunication conduit infrastructure in the area, wanted to minimize the project’s interference on the operations of its customers, so it hired Stantec, an engineering and planning firm, to undertake a utility routing study for the new water main.
“The Bowery and East Houston Street area is a vital communications hub for the city,” said Glenn Castro, Stantec’s project manager for the East Houston Street project. “The water main alignment the city presented to our client included a number of interferences with existing communications infrastructure. The telecommunications infrastructure operator asked us to map a better course for the city’s construction teams to follow. Given the complexity underground, our client wanted a 3D model of the proposed alternative route.”
Stantec’s New York-based civil engineers have extensive experience on public works projects that involve navigating the city’s complex underground environment. That’s one of the reasons the communications operator chose to work with the firm. Another key reason was the firm’s experience creating 3D models of underground infrastructure using building information modeling (BIM) software from Autodesk.
Castro explained the advantage of BIM: “Traditionally, a project like Houston Street would have entailed developing 2D maps and profiles showing existing underground infrastructure and proposed new underground assets. But 2D maps and profiles can be hard to interpret for people not used to reading such information. By comparison, with BIM we create an easy-to-understand 3D model of what’s happing underground.”
The Stantec team got started by acquiring asset maps from all of the organizations with infrastructure in the area. Often existing only as paper drawings in old map books, the plans required substantial cross-referencing. Undertaking the painstaking process of interpreting the plans, the team began drawing master 2D sections that combined all available information in traditional 2D software. They then brought the 2D information into AutoCAD Civil 3D software, a BIM solution from Autodesk, to use as an overlay to guide the creation of the 3D model.
“Traditional 2D software provided a faster way to collect existing information about the project area,” said Tom Sergi, the CAD manager for Stantec. “We basically used it to create a master drawing of infrastructure maps showing the seven kinds of utilities under East Houston Street. It served as a bridge that helped us move from a compiled version of 2D information to a BIM solution.”
Finding the way
With 2D sections of the area as an overlay, the team began creating the 3D model. The project went quickly in part because the team did not have to create a new model of each utility type; the team simply pulled parametric parts of pipes and structures from an extensive parts library of intelligent objects created on prior projects.
“We have a huge library of intelligent objects representing things like pipe sections, valves, manholes, and chambers,” said Sergi, BIM coordinator for Stantec. “Once we have the basic object, we can easily manipulate it to match the current environment. We just drag, place, and manipulate the objects. The 3D model adjusts to changes dynamically. Steven Costa, an AEC BIM specialist at Microsol Resources, helped us get started with the library of intelligent objects on an earlier project, and we’ve been expanding it ever since.”
As the model of existing infrastructure came together, the team added the proposed route for the water main, and found a number of points of interference between the proposed alignment of the water main and existing infrastructure. Within the model, the team explored less disruptive routes for the water main, finally settling on a suggested new alignment that minimized interferences.
“In 3D, you see issues more quickly,” explained Sergi. “There was one spot where a proposed water main valve chamber intruded several feet into the existing subway tunnel. Now, we would obviously spot that doing profiles in a 2D interference exercise. But it not only jumps out in 3D, you don’t have to do all those profiles manually. Once the model is set up, we can create a profile in minutes. Drafting a similarly detailed profile in 2D could take more than 10 hours.”
In order to aid the client in visualizing the conflicts that existed in the original design, Stantec brought the model into Autodesk Navisworks Simulate software. Navisworks Simulate software has the ability to aggregate models of the existing environment and any proposed studies into a single, easy-to-explore model. In a presentation to the client, Stantec showed how any solution could be viewed by using a 3D fly-through of the model.
Stantec was able to present models in real time to clients. And they could direct the fly-through and look at whatever aspects of the model were of interest to them. It became obvious where a suggested route had plenty of clearance or where it might be a little challenging to construct. They could also see the complexities of the underground environment and visualize where changes could be implemented.
Fewer risks and lower costs
Pleased with the effectiveness of the visualization developed by Stantec, the client presented it to the New York City Department of Design and Construction using the 3D model. “We were able to demonstrate that alternate routes were less disruptive to existing underground infrastructure,” said Castro. “We then delivered our 2D and 3D files to the city to use as the basis for their continuing design. Thanks in part to BIM, our client will experience less risk of interference with its conduit infrastructure assets, which should also result in a quicker, more efficient installation.”
Robert Spinale is BIM coordinator for Stantec.