South Hartford Conveyance Tunnel (SHCT), Hartford, CT

Project Value: $279.4 million. Reference: Jim Sullivan, AECOM (860) 383-5316

The South Hartford Conveyance Tunnel project was completed in 2 stages. The project was completed for the Hartford Metropolitan District Commission (MDC) to store and convey combined sewer overflow as part of a long-term control plan to eliminate discharge into local bodies of water during high intensity events. The following represents the scope of work:

  • 56 borings were completed for the project ranging from 50 feet to 300 feet in depth.

  • 26 geotechnical borings were part of the scope that ranged from 230 feet to 300 feet in depth with overburden ranging from 30 feet to 160 feet

  • Environmental and continuous sampling was performed in 4 of the borings
  • 18 groundwater monitoring wells were set ranging from 20 feet to 300 feet in depth
  • Overburden drilling included dealing predominantly with heaving sands while performing standard penetration testing, split spoon sampling, and Shelby tube sampling
  • 12 piezometers were installed in the geotechnical borings
  • Each piezometer was set with a flush mounted cover and a concrete pad stamped for identification
  • Approximately 400 Packer tests were performed
  • 3 of the borings were performed at a 20 degree incline
  • A total of approximately 3,600 feet of HQ-size rock was cored during the project
  • Quality of rock cores obtained required minimal to no preparation by the laboratories to perform designated testing
  • A total of approximately 3,200 feet of overburden was drilled and/or sampled

    The drilling schedule for this project required the use of up to 2 rigs at one time and lasted approximately 8 months. The drilling program was completed on schedule and under budget.