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Frequently Asked Questions

  1. What is the MTA monitoring?

    The MTA is monitoring PM10 concentrations along Second Avenue. PM10 is particulate matter (solid particles and liquid droplets) that are 10 microns and smaller. This is the air pollutant most closely associated with construction since it is generated by demolition, excavation, blasting, diesel exhaust, and other construction activities. The U.S. Environmental Protection Agency (US EPA) sets a health based national air quality standard for PM10 at 150 µg/m3 measured as a daily concentration. The PM10 concentrations recorded along Second Avenue thus far have been very low – generally about a third of the standard – and reflect traffic and local sources in addition to Second Avenue Subway construction.

  2. Why is the MTA only monitoring for PM10?

    The Parsons Brinckerhoff Air Monitoring Study confirmed that the pollutant of concern for SAS construction is PM10. Construction dust and blast emissions are composed of dust particles of varying size. Most of what can be seen are coarse particles that settle close to the construction activity and are not dangerous. (Blast emissions are also visible because water vapor is formed.) PM10 are smaller particles of dust that can travel relatively far and have been shown to cause respiratory problems when inhaled at certain levels for extended periods of time. Construction activities contribute to PM10 concentrations in the corridor, however, all levels monitored to date have been well below the level established by US EPA to protect public health.

    The ongoing PM10 monitoring program will ensure that dust levels are mitigated to the greatest practical extent and that the air remains safe. Other pollutants identified in the study are either not a result of construction activities (conclusive tests confirmed that there is no source of sulfur dioxide (SO2) on the Project), or do not contribute significantly to pollutant concentrations in the environment (PM2.5 and silica, for example).

  3. The study criticized the contractor's air monitoring program. Have improvements to the program been made?

    Yes, the current program incorporates the recommendations from the PB study and is now subject to enhanced oversight and quality control. Monitors are being inspected and calibrated on a daily basis.

  4. OSHA issued a violation for high levels of silica. Why isn't silica monitored in this program?

    The OSHA violation was issued because a couple of workers did not have their respirators on correctly and one worker could not document that he was adequately trained in its use. Silica is generated in the tunnels when shot-crete (a liquid form of concrete) is sprayed to line the tunnels. The amount of silica generated via this operation requires workers to wear respiratory protection when working in the immediate vicinity of the shot-crete. Silica testing is performed routinely throughout the tunnel to determine the zone where workers need respiratory protection, which is typically around 50 feet.

    The levels of silica recorded at the surface in the Parsons Brinckerhoff Air Monitoring Study were very low and confirmed that silica is not being released from the construction shaft or any other construction activity in any significant amount.

  5. Why should we believe an MTA study?

    The Parsons Brinckerhoff Air Services Group has the requisite expertise and national reputation for completing air monitoring studies of this type. The methodology used to conduct the air monitoring and the results presented in the report were reviewed and accepted by the US EPA and NYSDEC. In addition, Environ Corporation, a global environmental services firm, was retained to peer review the study.