Getting it Right the Third Time. Reconstruction of Interstate 476 over Unstable Karst in Plymouth Meeting, PA

Geophysics enhanced with confirmation test borings is fast becoming a reliable method to determine problems in karst areas over a large area. Government Transportation Agencies should provide additional funds to cover the additional investigation needed in these regions. Geotechnical engineers should be involved with project scoping to make sure this funding is placed into the project early. Armed with real data, sinkhole remediation recommendations for construction can be provided with a level of comfort, readiness and knowledge that the roadway will last its intended design life. This paper will discuss the reconstruction Interstate 476, the primary north-south corridor in eastern Pennsylvania carrying traffic from the Philadelphia region to Scranton. This project is located on the Mid-County Expressway portion of Interstate 476 which is located in Philadelphia’s western suburbs and links Interstate 95 to Interstate 276 (the east-west PA Turnpike). It is locally called the Blue Route and as one of the most controversial Interstate Highways in Pennsylvania, construction of I-476 began in 1967, but was not completed until 1991. In addition to reconstructing the roadway, the Pennsylvania Department of transportation (PENNDOT) will widen the left and right shoulders, upgrade acceleration-deceleration lanes, and replace drainage. The project also includes reconstruction of the I-476 bridge over the Schuylkill River, presently in construction. Construction of the project – for which costs have been estimated at $100M - is scheduled to begin in September 2009 and is anticipated to take approximately two years. Including original construction this will be the third attempt to construct the roadway properly, but this time undertaking an extensive and serious attempt to reinforce the subgrade, control surface water, repair existing karst related problems, minimize future sinkhole development and significantly reduce future maintenance.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; Maps;
  • Pagination: pp 169-178
  • Monograph Title: Proceedings of the 60th Highway Geology Symposium

Subject/Index Terms

Filing Info

  • Accession Number: 01142303
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Oct 21 2009 8:29AM