MDC TUNNEL PROJECT HITS MAJOR MILESTONE
Tunnel Boring Machine holes through after four-mile journey

(HARTFORD, CT) – The Metropolitan District (MDC) announced that the South Hartford Conveyance
and Storage Tunnel (SHCST) reached a major milestone on Tuesday, January 4 when the tunnel boring
machine (TBM) “Iris” reached its destination at the MDC’s retrieval facility located on Talcott Road in
West Hartford.  The TBM began its’ journey in the Spring of 2019 across the street from MDC’s Hartford
Water Pollution Control Facility (HWPCF) on Brainard Road in Hartford and traveled four miles, 200 feet
below the surface before holing through the retrieval shaft on Talcott Road on Tuesday.
The SHCST is a four-mile long deep rock tunnel designed to temporarily store excess combined
wastewater and storm water during rain events, and then convey the flows to the HWPCF for treatment.
The tunnel’s capacity of 41.5 million gallons will help prevent the HWPCF from being overwhelmed
during storms.  The 18-foot diameter tunnel is built in bedrock approximately 200 feet below ground.  The
tunnel is a major component of the MDC’s Clean Water Project, an over $2 billion wastewater system
improvement program required by the US EPA and State of CT DEEP.
 
The project is the first of its kind in Connecticut and the tunnel construction portion of the project, which
cost approximately $279M, is the largest contract ever awarded by the MDC, and the largest project ever
funded by the State Clean Water Fund. The Kenny Obayashi joint venture was awarded the contract to
build the tunnel and in addition, the MDC also partnered with AECOM on the engineering design and
Jacobs on the construction management of the project.
“The SHCST is a key element of the Clean Water Project with the goal of limiting combined sewer
overflows to a one-year storm level, eliminating overflows to the Wethersfield Cove, which will continue
to improve local water quality for our towns and ultimately benefitting the entire region including the
Connecticut River and Long Island Sound. We are thrilled to have reached this milestone and are grateful
to our Board of Commissioners as well as the federal, state and municipal officials from the MDC’s towns
for their part in securing critical grant and loan funding to minimize the cost of the project and impact on
ratepayers.  We are also thankful to our partners at DEEP for their help executing this project and making
funding available,” stated MDC CEO Scott Jellison.

https://themdc.org/app/uploads/2022/01/TBM-Iris-Milestone-1.6.22.pdf