- SPECIAL REPORTS
- THE MAGAZINE
“This project had all the challenges one could imagine--and some you wouldn’t think of,” says James F. Steere, III, PLS, principal in charge at Hackettstown, N.J.-based Medina Consultants. “These types of projects are not your typical surveys; they require a planned strategy and a highly skilled and motivated staff. All the pieces must work together.”
They did, and thanks to technology, safety and organizational smarts, Medina’s surveying and mapping services for the massive project were met ahead of schedule.
The Project That Has It AllThe Metropolitan Transportation Authority and Long Island Railroad (MTA/LIRR) initiated the East Side Access Project in 1999 to provide a direct connection to Grand Central Terminal and to increase capacity for Long Island commuters into Manhattan. The project, which could last for 10 years or more, outlines the construction of new tunnels beneath Sunnyside Yard in Queens, connecting LIRR’s main line and Port Washington Branch to new tracks in the lower level of the 63rd Street Tunnel in Manhattan. New tunnels will also be constructed from the bell mouth of the 63rd Street Tunnel, curving southwest under Park Avenue to a new terminal beneath Grand Central Terminal and ending near East 38th Street. The site is massive--and busy.
As a subconsultant to the General Engineering Consultant (GEC) Tri-Venture Team, the Medina Consultants survey teams were responsible for the surveying and mapping of this significant transportation project covering the Sunnyside Yard Complex plus 8,700 feet of the 63rd Street Tunnel. The Medina teams selected surveying and mapping technologies to enhance the design solutions offered for the project. Linking GPS, low altitude mapping, 3D laser scanning, and conventional surveying and robotics, they simultaneously located and mapped the project for accurate design.
The project that “has it all,” according to Steere, was not only interesting and challenging, but later became award-winning.
The Technology SpectrumWorking within the active train site required several mandatory precautions, one of which was to work collaboratively with Tri-Venture’s design team, LIRR and/or Amtrak forces. The comprehensive monitoring program established by Tri-Venture minimized many of the complexities of working with numerous consultants on the constrained site. Medina’s understanding of these constraints, combined with the intelligent selection of advanced surveying technology, helped them to mitigate the challenges posed on the site.
“From a survey standpoint, any work that minimized or eliminated disruptions to the yard or use of rail safety personnel (watchmen) was viewed as favorable,” says Joseph Messina, PLS, Medina’s project manager and director of survey.
The logistics of entering the tunnel are very detailed and require prior arrangements of safety personnel as well as the need for Personal Protective Equipment (PPE). Adherence to the established safety plans is a must, including the use of breathing equipment (Scot packs as used by firefighters), lighting, etc.
To overcome the logistical and safety factors associated with the active rail facility, Medina integrated several surveying technologies and methodologies. The Medina survey teams established intervisible primary control stations along the East River in Queens, on Roosevelt Island and in Manhattan, and utilized GPS static observation for secondary control. Additional control stations were established along the project perimeter. With Leica Geosystems (Norcross. Ga.) 500 Series GPS units, Medina achieved positional accuracy better than 1:100,000 for the control points, significantly exceeding GPS Order B constraints.
Medina also specified low altitude mapping photography (LAMP) to expedite completion of the aerial mapping tasks, reduce survey team track involvement and increase accuracy over traditional aerial mapping. LAMP uses a camera mounted on a helicopter flown at a low level of 600 feet above the surface, rather than on a fixed-wing aircraft, providing photography with a high resolution of surface features and higher accuracy. This option avoided radial distortion or “building lean” effects, obviating the need to field locate all surface features and reducing the need for extensive field edits.
The subsurface mapping of the existing 63rd Street Tunnel was tied into the primary control through two vent facilities (structures that allow for the exchange or input of fresh air into a tunnel) located in Queens and on Roosevelt Island. A Leica Geosystems nadir plummet was utilized to bring subsurface control to the tunnel floor at either end. “We had to drop a horizontal position from the top of the vent building to the tunnel surface approximately 80 feet down,” says Project Surveyor Ken Moscetti. “The nadir plummet laser has a low radial distortion as it is projected long distances.”
The field team used a Leica Geosystems TCRA 1101 robotic total station to establish a survey baseline, which linked the surface control to the tunnel baseline subsurface control.
The team’s 3D laser scanning system, a Leica Geosystems High Definition Surveying (HDS) 2500 Series, aided the mapping of the tunnel and associated rooms. This technology scanned entire tunnel rooms and stairwells in minutes and was later modeled and linked into the project datum, providing the design team with superior mapping of the entire tunnel for track geometry and design development.
“The reasoning behind using the scanner was to capture high inventory data,” Messina says. “We can obtain the whole tunnel’s features with the ability to extract data as needed. Conventional survey data will capture specific items as requested. If additional data is needed it would normally require additional site visits. Having the 3D model allowed us to extract multiple requests for data by various members of the design team as needed without additional site visits.”
Medina also utilized 3D HDS scanning technology within the Sunnyside Yards area. Detailed survey locations were required for many features, including the underside of all overhead bridges, active overhead roadways that transverse the property and existing tunnel portal entrances. For tunnel portal survey location work, the Medina crew was able to perform 3D scanning from a safe distance, which reduced the impact to rail traffic.
The effort to map existing utilities demanded extensive measuring of surface features that were reconciled with existing utility plates. Conventional surveying and GPS technology using the Leica Geosystems 500 Series with RTK capabililties collected the utility locations. This data was then integrated into the base mapping.
With the use of a “field to finish” data collection system, the survey team performed conventional location activities efficiently. The survey field teams adhered to pre-established field coding designations, which were seamlessly processed into a CADD environment with appropriate level structures, symbology and line styles. Tri-Venture established a comprehensive “CADD library” manual that included pre-established file naming, level structures, cells/symbols and linetype/linestyles.
At the onset of the project, Medina established a project-specific field coding list, which was used for the tag descriptors of all located features. All field locations were imported into Bentley (Exton, Pa.) Inroads Site Survey Module, and attribute features were automatically assigned to proper levels with the accompanying cells/symbols and linetype/styles. InRoads also allowed for the defining of point elevations and breakline features, which were used in the development of a digital terrian model (DTM) for automated contour line development.
A Satisfying EndMedina’s selection of integrated surveying and mapping technologies helped to advance the East Side Access Project, leaving the Medina crews satisfied with a job well done. “East Side Access is a significant transportation project that will have a positive impact on the New York metro area for generations to come,” Messina says. “I am pleased that our survey team helped make that happen. These types of major projects leave a physical structure that one can talk about with one’s granchildren. To have the ability to say ‘I was involved on that project’ is very rewarding.”
Reward will also eventually come in the form of easier transit for New York commuters, contributing to the solutions engaged to quash the New York metro area’s “mobility crisis.”