NYCDDC 9th Street Vibration Monitoring and Reporting

Project Description

The New York City Department of Design and Construction (NYCDDC) 9th Street Infrastructure Improvements project includes replacement of the existing 12-inch storm sewer and installation of a new 18-inch diameter outfall at the Gowanus Canal bulkhead. Seven historic structures in the Gowanus Historic District are located within close proximity of several planned construction activities.

Due to the location of the historic structures, and the nature of construction activities necessary to replace storm stewers and install outfalls, Paul Carpenter Associates, Inc. (PCA) was tasked with implementing a Construction Protection Plan (CPP), following guidelines within the New York City Department of Buildings (DOB) Technical Policy and Procedure Notice and Section 523 of the City Environmental Quality Review (CEQR) Technical Manual. Due to the potential for vibration-induced structural damage during construction, the CPP included the following:

  • a vibration monitoring plan
  • continuous building condition monitoring using crack gauges
  • compliance vibration monitoring
  • communication protocols to inform authorized personnel of ‘action’ and ‘stop work’ vibration levels
  • a compliance enforcement program to ensure contract requirements are met and mitigation plans are properly implemented

Seven state-of-the-art vibration monitors were installed at predetermined locations, chosen based on proximity and sensitivity to construction operations. Monitoring protocols and locations were approved by NYCDDC prior to commencement of construction activities. The vibration monitors continuously recorded peak particle velocity (PPV) levels at 1-minute intervals and wirelessly transmitted recorded data to a web interface, which was specifically created for the project to allow authorized individuals with access to view real-time vibration data. Vibration monitors were programmed to automatically send alerts to the PCA staff in the event vibration levels exceeded Action or Stop Work levels. PCA staff prepared a detailed Weekly Vibration Monitoring Log and Crack Gauge Inspection Report at the end of each work week, which was submitted to NYCDDC personnel.