Construction monitoring requirements for projects taking place in or near NYCTA structures or tunnels are somewhat different than other construction projects. Pre-construction surveys and monitoring are required in most scenarios when these activities are taking place in or around NYCTA structures and other transit tunnels. Surface construction activities, including foundation work, NYCTA structures can adversely affect underground structures or the subway system. In addition, underground tunnel and subway construction projects can produce vibration levels that can potentially damage nearby streets, foundations, buildings and other structures.
In New York City, the Metropolitan Transportation Authority (MTA) requires vibration monitoring anytime drilling or excavating is done within 75 feet of a structure. Unlike other construction projects, the MTA requires that all monitoring in these projects be manned by a field technician. Remote monitoring is not permitted in these instances. All field technicians monitoring NYCTA structures and tunnel sites must be MTA Track Certified and OSHA 10 compliant.
MTA projects most often involve a combination of pre-construction inspections, optical surveying, vibration monitoring, and crack gauge monitoring. In the case of vibration monitoring, the MTA requires that a monitor be placed every 25 feet on structures adjacent to the construction activity. Construction site monitoring reports are provided on a weekly basis to the MTA while activity is ongoing, during various project phases. In the event of a trigger event, monitoring technicians will immediately notify both construction personnel and the MTA.
The Port Authority of New York and New Jersey has similar requirements for construction projects involving the Port Authority Trans-Hudson (PATH) transit system in Northern New Jersey.