A joint venture of Kenny and Obayashi is the apparent low-bidder for the tunnel and shaft construction components of the South Hartford Conveyance and Storage Tunnel (South Tunnel) project, in Hartford, Connecticut, with a bid price of $279.4 million. Other bidders included S.A. Healy/Salini Impregilo, with a bid of $285.56 million, Traylor/Kiewit, with a bid of $298.27 million, and Shea/Skanska with a bid of $313.65 million.
The South Tunnel project is a significant component of the Metropolitan District’s (MDC) Clean Water Project, which will reduce combined sewer overflows; eliminate sanitary sewer overflows; and reduce nitrogen released into the Connecticut River.
During wet weather, when combined stormwater and sanitary sewage flows overwhelm the capacity of the existing MDC system, the new South Tunnel will receive overflows that are currently discharged directly into the watershed.
MDC is carrying out the project under a number of contracts, including the tunnel and shaft contract that comprises a 21,800ft (6.64km) long deep rock tunnel, lined with pre-cast concrete segments to an internal diameter of 18ft (5.5m); a 35ft (10.5m) i.d. launch shaft near the Hartford Water Pollution Control Facility (HWPCF); a 28ft (8.5m) i.d. retrieval shaft in West Hartford; a 70ft (21m) i.d. tunnel pump station shaft; fifteen small diameter drilled shafts; eight small diameter adit tunnels; seven deaeration chambers; a 48in (1,220mm) suction header tunnel; and main air treatment facility.
Aecom carried out the final design of the tunnel and shafts. The TBM-bored tunnel will be excavated in siltstone and basalt through several fault zones. For the soil sections of the large diameter shafts, secant piles or slurry diaphragm walls will be used to control water infiltration. Rock sections of the shafts will be constructed using drill and blast with rock dowels and shotcrete for support. Final shaft liners will be cast-in-place concrete.
MDC is currently evaluating the submission of the apparent low bidder, in keeping with the terms of the solicitation, with an official award expected in May 2016. Notice to Proceed will follow shortly after that, with site mobilization likely to commence in June 2016. TBM tunneling will commence in Fall 2017 with project completion currently slated for December 2022.