The Port Authority of NY&NJ and the consulting engineer, Langan Engineering, were concerned about damage to the tunnels during construction. They wanted a monitoring system to provide early warning of potential damage so that construction procedures could be modified, if necessary.
The monitoring system was to include piezometers, crackmeters, and vibration monitors in the tunnels and vent buildings. Implementation of the system would be difficult. The tunnels were active and did not lend themselves to traditional manned monitoring stations, due to safety, cost, and logistic issues.
To address these issues, GEO-Instruments suggested that the monitoring stations be linked to the internet wirelessly, and offered a real-time interface using IP wireless modems. This approach provided unlimited access to data during construction, without the delay, or costs of field visits to collect data manually.
The installed system used four automated vibration monitors to record vibration due to pile driving, twelve VW crackmeters to monitor structural displacements, twelve piezometers to monitor in pore pressures, and three data loggers with IP modems. An offsite computer retrieved data using the IP addresses of the modems and then processed and posted the data to project web site. The web site provided real time display, reporting, alarm notifications, and data archiving.
The monitoring system successfully implemented the early warning system specified and saved the owner countless man-hours in monitoring costs.