Announcements

Chris Tonzi: Tunneling To Success

"For a geotechnical engineer, The Tunnel is the project of a lifetime.  In a way, I feel that a lot of my career has been leading up to this," says Chris Tonzi, PE, a Senior Geotechnical Engineer at Freeman Companies.

1. Downtown Hartford is seen in the background with the Construction Contract 2 site on the left, and the edge of the water treatment plant on the right.

"The Tunnel" is the Metropolitan District Commission's South Hartford Conveyance and Storage Tunnel (SHCST), a deep rock tunnel which will start at the Hartford Water Pollution Control facility on Brainard Road, run hundreds of feet below the city streets, and end at Talcott Road in West Hartford.  The project is a key component of the MDC's Clean Water Project, a CTDEEP and EPA-mandated, over 20-year plan designed to control and reduce the overflow of untreated sewage into natural waterways resulting from Combined Sewer Overflows (CSOs).  Occurring during heavy rainfall, CSOs have caused existing infrastructure to push unwanted wastewater into the Connecticut River and Long Island Sound with major storm events.  Once fully constructed, the 18-foot diameter, four-mile long tunnel structure will handle sewage from Hartford, West Hartford, and Newington and will be able to store  41.5 million gallons until the stored wastewater can be treated at the MDC's Hartford Water Pollution Control Facility.  Ultimately, this large capacity of storage will dramatically reduce CSOs from much of the South Hartford area.

2. A map of the SHCST once it is completed.

Freeman Companies, the Hartford-based engineering design, land development and environmental service firm, has been involved in the SHCST project since 2012 throughout its many phases of design and construction, including geotechnical engineering technical support and CSO conduit 3D basemapping for the Prime Engineer AECOM as well as geotechnical instrumentation for the recently completed preparatory utility relocation work, called "Contract 1", which enabled the tunnel and shaft construction titled "Contract 2", to proceed.  For Contract 2, Chris Tonzi, PE, leads a comprehensive team of engineers and land surveyors providing geotechnical instrumentation and vibration monitoring, as well as implementation inspections, routine inspections and stormwater monitoring for compliance to the Stormwater General Permit for the Prime Contractor, Kenny / Obayashi IV, A Joint Venture.  At $279.4 million in construction cost, Contract 2 is the largest contract ever awarded by the MDC and represents one of the region's largest infrastructure investments.

3. A geologic location profile of the proposed deep rock tunnel.

Geotechnical instrumentation is typically performed in two different instances; either when measuring rock and soil for such properties as permeability, strength, and chemical makeup during the design phase of a project, or for performance monitoring and how the soil or bedrock reacts to machinery during construction.  Essentially it is measuring what the ground does, and what it might do once equipment disrupts it.  While not well known to the general public, geotechnical instrumentation and monitoring are essential functions to most large infrastructure projects, and the Tunnel is no exception.

Protecting this important infrastructure investment as well as the neighborhoods above which it runs is Chris Tonzi's primary responsibility.  To put it simply, Chris "coordinates what's coming next," he says.  "I think about what instrumentation needs to be installed before the next segment needs to be constructed, coordinate the schedule for proposed instrumentation, and make sure that the instrumentation we have in the ground delivers data in coordination with the project specifications."  This is all being provided by the Land Surveyors, Civil, and Geotechnical Engineers at Freeman Companies until the project's completion.

4. Freeman Companies' Chris Tonzi, PE is seen next to one of the project's drop shafts on site.

The SHCST is being constructed by tunneling 200 to 250 feet below ground surface and involves multiple components, such as a launch shaft, retrieval shaft, pump station excavation shaft, six drop shafts, de-aeration chambers, odor control buildings and more.  With much to build and a schedule to keep, blasting is the most efficient method to extract enormous volumes of bedrock and Hartford's infamous, non-permeable clay soil out of the ground.  "Vibration monitoring, in particular, is a component of the process that is far more essential to the project's efficacy than one might think," says Tonzi.

5. Vibration monitoring equipment installed at the earth's surface, powered by a solar panel and battery installed by Freeman Companies on the site.  Multiple instruments surround the project boundaries.

Before real blasts occur, smaller tests blasts of bedrock are conducted. These vibration monitoring instruments monitor how the blasts affect the surrounding ground.  Results are documented for a fully remote condition diagnosis service that allow engineers to estimate (and ultimately eliminate) any potential damage to the surrounding embankments, wetlands, homes, and buildings when the larger blasts occur.  The more accurate the calculations of the blast, the less risk.  "The point of conducting vibration monitoring is for risk prevention," says Tonzi, "and to me, a sign of a good project is preventing issues, not fixing them once they show up."

6. The edge of Wethersfield Cove across the embankment, a priority for protection by the engineers on site.

Blasting is one of the most dangerous elements of the project. Above the project site, there is a large embankment where I-91 and the Hartford levee system call home next to the tail end of Wethersfield Cove.  "Should anything go wrong," says Tonzi, "that could undo a lot of the construction we've been able to accomplish so far."  By design, Chris and his team are confident that nothing in the area will be damaged,  and   the  blasts will do nothing more than sound  like distant thunder.

7. Left: The largest launch shaft thus far on site excavated at 75 feet with 125 more feet to go; 8. Right: View from the bottom of the launch shaft earlier in the excavation stage.

After the blasts occur, the sandstone, siltstone and basalt that lie underneath the ground's surface is excavated and the remaining space is lined with cast-in-place concrete to create a concrete shaft large enough to bring necessary equipment down the 200 foot below grade level.

While a project of this type is new to the Hartford region, storage tunnels similar to the SHCST are being built across the nation, all federally-mandated infrastructure projects constructed to prevent CSOs.  They include the Deep Tunnel Project in Milwaukee; the Three Rivers Protection & Overflow Reduction Tunnel (3RPORT) in Fort Wayne, Indiana; The Kaneohe-Kailua Waste Water Conveyance Tunnel in Honolulu, Hawaii; and the Blue Plains Tunnel in the District of Columbia to name just a few.

The majority of these projects were awarded to joint ventures like the Kenny / Obayashi IV, A Joint Venture here in Hartford, committed to hiring small businesses and women and/or minority owned contractors.  Complex design and construction phases necessitate a professional construction team composed of many firms offering a wide range of capabilities which increases employment opportunities for Small and Minority Business Enterprises.  As a Small and Minority business, Freeman Companies' involvement in the SHCST project represents the MDC's and Kenny / Obayashi's commitment to diversity and local sourcing in the hiring process.

9. Highly recognized in the industry for safety training, this is the Kenny / Obayashi's fourth Joint Venture.

"With a project of this magnitude, a lengthy timeline with many firms involved is vital if we want every element completed and completed well," says Tonzi, "and each firm brings their strengths.  We have a strong geotechnical instrumentation division at Freeman Companies so it's exciting to be part of such a knowledgeable team."   After the blasting phase of the project, however, Tonzi says it won't be time to exhale just yet.

10. As I-91 bustles in the background, sheets of railway waiting to be installed are guarded by excavated rock and shaft covers made to prevent sediment fly-aways when the blasts take place. 

Once the bedrock excavation is complete and the shafts are fixed with cast-in-place concrete, a rail system will be installed beneath the project site in the spring of 2018 to facilitate a tunnel boring machine which will allow the bulk of the tunnel to be created.  The railway will also deliver pre-cast tunnel pieces, carry out excavated waste rock and soil, and bring workers and materials forward to build the tunnel as it's being excavated.

Explains Tonzi, "The interesting thing about projects like these is people think we carry out one entire step of the project-like carving out the tunnel underground-and then build within it.  What they don't know is we're actually carving it out and constructing it as we go."  This process aids in speeding up the project timeline and in bringing down the overall project cost.  Initial construction of the tunnel began in August of 2016 and is expected to be finished no later than 2023.

11. Excavators reaching groundwater as they remove soil from the developing pump station shaft.

"We still obviously have a long way to go with the tunnel," says Tonzi. "But the blasts will be the true beginning of everything that's to come.  The whole process is truly spectacular."

For more information on the SHCST's progress, visit TheCleanWaterProject.com