PATCO Viaduct Preservation Project

Project Description

The Port Authority Transit Corporation (PATCO) viaduct throughout Collingswood and Westmont, NJ, requires repairs, including concrete spall repairs, crack repairs, cleaning and painting of bridge bearings, as well as joint replacement and railing installation in areas. PCA was requested to document background noise and vibration levels within the project study area, develop recommended project-specific noise and vibration level limits and evaluate the potential for construction-related noise complaints and vibration-induced structural damage. PCA was also requested to assist with development of the noise section of contract specifications.

CA performed long-term noise and vibration measurements in four locations for approximately three weeks to adequately determine background levels within the project study area. All measurement data was filtered based on PCA’s three-step process to remove data resulting from 1) abnormal site conditions, 2) adverse meteorological conditions, and 3) extraneous noise and vibration sources. Once filtered, average weekday and weekend background noise levels and maximum weekday and weekend vibration levels were identified. PCA utilized average background noise levels to develop construction noise level limits based on a discrete allowable increase over background, which typically allows the contractor to perform construction activities with reasonable mitigation measures, while maintaining a level of protection for the adjacent community. Vibration limits were developed based on AASHTO Designation: R 8-81 (1990), which establishes vibration limits for preventing damage to engineered structures. Both 'action' and 'stop work' levels were recommended to protect the viaduct.

PCA performed construction-related noise and vibration assessments to determine the feasibility of meeting recommended noise and vibration criteria. SoundPLAN, a 3D acoustical modeling software, was used to perform the construction noise assessment, as the model allows for the prediction and visualization of noise effects from a variety of different project types. Area sources were created to represent each noise source working anywhere within deck spans or at pier and abutment locations, which allowed for the model to determine the worst-case location of construction activities within the limits of work. Noise contour maps were generated for each construction scenario based on the recommended construction noise level limits to demonstrate the extent of potential construction noise level increases over average background noise levels. Mitigation measures were subsequently recommended for inclusion within contract specifications.

The potential for vibration-induced damage to the PATCO viaduct was conservatively assessed using Federal Transit Administration (FTA) reference vibration levels for jackhammers during concrete spall repairs. No potential for structural damage to the viaduct was predicted.

PCA reviewed and assisted in the development of the contract specifications to ensure mitigation measures were incorporated.