As part of the New NY Bridge project’s Environmental Performance Commitments, Tappan Zee Constructors, LLC (TZC) installed environmental monitoring stations at various locations near the construction site. The monitors continuously measured noise, air quality, and vibration levels and published real-time results within one minute on NewNYBridge.com. As of June 2020, the monitors are no longer active. Below is an archive of the project data.
Noise monitoring is performed with a Larson Davis 831 sound level meter. The noise meter is configured to express sound pressure levels as A-weighted decibels (dBA).
Effects of sound on the environment and on human hearing are typically measured as an exposure to sound over a period of time, expressed as the time-average sound level (Leq). The noise meter obtains the 15-second Leq (Leq(15-sec)). The 1-hour Leq (Leq(1-hr)) are calculated and presented on the noise monitor graphs.
TZC reduces noise levels through the use of specialized equipment and techniques, including:
- Vibratory pile driving where possible to minimize the amount of impact pile driving
- Sound mitigating shrouds during impact pile driving.
- Temporary and movable noise barriers
- Minimizing the use of backup alarms and implementing the use of alternate backup devices when possible
Construction activities will be restricted late night (10 p.m. to 6 a.m.), Saturday morning until midday and Sunday all day. During that time, no equipment will be used that emits noise above 70 dBA max measured at an offset distance of 50 feet if the work is on land and at the nearest point of the shoreline if the work is in the water. Pile driving is restricted to 7 a.m. to 7 p.m. In addition, pile driving near the Rockland County shoreline is restricted to 8 a.m. to 6 p.m. on weekdays and to 12 p.m. to 6 p.m. on Saturdays.
Vibration monitors continuously measured ground movement at the project site. Common construction activities which create ground-borne vibration include pile driving, drilling, jackhammering, pavement breaking and earthmoving.
Vibration monitoring stations continuously collected peak particle velocity (PPV), 24-hours a day/7 days a week. Vibration levels, PPV, that exceed 0.005 inches per second were recorded and sent to the project website. Results of the vibration monitoring were updated on the project website every minute.
Vibration monitoring is performed with an Instantel Minimate Pro4 vibration meter. The vibration meter uses 4-channel International Society of Explosives Engineers (ISEE) compliant seismographs in conjunction with ISEE standard triaxial geophones.
PPV is generally measured in inches per second (in/sec.) and represents the movement of the ground from construction or other activity. PPV is used to measure potential effects to structures or human reaction as the result of ground borne vibration.
Air Quality Monitoring
The project monitored air quality to ensure that construction dust was controlled and construction equipment had the proper emission controls.
The station monitors collected data continuously, 24-hours a day/7 days a week, during project construction.
TSI Model DRX Particle Monitors are being used to measure air quality. These are light-scattering laser photometer-type instruments (also referred to as nephelometers) that detect particulate matter/aerosols by measuring the total amount of light they scatter and provide real-time aerosol/particulate mass readings in micrograms/cubic meter (µg/m3).
Photometer-type meters are commonly used to measure particulate concentrations as part of Community Air Monitoring Programs (CAMPs) to document particulate concentrations during construction-type activities because they provide real-time data that can be assessed quickly and subsequently corrective measures can be implemented quickly as well.
PM is measured in two size categories: PM2.5 (particles smaller than 2.5 micrometers, e.g. diesel exhaust) and PM10 (particles smaller than 10 micrometers, e.g. dust). The particulate matter data averaged over 1-hour and 24-hour intervals are calculated and presented. The graphs are updated every minute. Data from each instrument is compared with the data collected from the stations on the same shoreline to determine if anomalies are observed requiring a review of the instruments and the construction equipment engineering controls.
TZC reduces particulate matter through the use of specialized equipment and techniques, including:
- Ultra low sulfur diesel fuel for diesel engines
- Diesel particulate filters (DPFs) on nonroad, non-marine diesel engines with a power rating of 50 horsepower (HP)
- Wet suppression
- Restricting non-productive idling to 5 minutes or less
- Engines with a U.S. EPA Tier level of 3 or greater on nonroad, non-marine diesel engines with a power rating of 50 HP or greater
- Engines with a U.S. EPA Tier level of 2 or greater on nonroad, non-marine diesel engines with a power rating of less than 50 HP