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The Metropolitan District South Hartford Conveyance Tunnel

The Metropolitan District South Hartford Conveyance Tunnel. Clean Water Project. Project Description.

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The Metropolitan District South Hartford Conveyance Tunnel

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  1. The Metropolitan District South Hartford Conveyance Tunnel Clean Water Project

  2. Project Description • Completion of the south conveyance tunnel (SCT) is important to meet the requirements of a CT DEP Combined Sewer Overflow (CSO) consent order and Storm Sewer Overflow (SSO) consent decree. It will be designed and constructed over an estimated three years. • CSOs from the southwestern part of Hartford will be captured and directed to the SCT, and later SSOs from West Hartford and Newington will be captured and routed to the SCT. This work will relieve the South Branch of the Park River drainage area and reduce the storage otherwise required of the new deep rock tunnel.

  3. Pre-Design and Geological Testing • Risk (1) – Discovery of Large Caverns limits site possibilities • Consequence of occurrence - 4 • Re-site tunnel • Increased Overall Cost • Increased Time • Likelihood of occurrence – 1 • Unlikely to find Limestone under Hartford: Caverns require Limestone • Cost/Time Reserve • 20% cost Reserve • 40% time Reserve

  4. Pre-Design and Geological Testing • Risk (2) – Access to Land for Testing • Consequence of occurrence • Delays in Siting Decisions - 3 • Increased Overall Cost • Increased Time • Likelihood of occurrence – 4 • Large number of property owners • Weather Uncertainty • Cost/Time Reserve • 5% cost Reserve • 10% time Reserve

  5. Contractor Selection • Risk (3) – Delays due to Addendums • Consequence of occurrence - 2 • Delays Award Date and therefore construction • Likelihood of occurrence - 5 • Common Occurrence • Cost / Time Reserve • 30% cost Reserve • 10% time Reserve

  6. Contractor Selection • Risk (4) – Lawsuits Challenging Contractor Selection • Consequence of occurrence - 5 • Delays Award Date and therefore construction • Likelihood of occurrence – 1 • Cost / Time Reserve • 20% cost Reserve • 20% time Reserve

  7. Building the Tunnel • Risk (5) – Unknown Conditions (“Unknown Unknowns”) • Consequence of occurrence - 2 • Plan Redesign / Change Orders • Higher Cost • Longer Duration • Likelihood of occurrence – 5 • Cost / Time Reserve • 25% cost Reserve • 25% time Reserve

  8. Building the Tunnel • Risk (6) – Large Tunneling Equipment Failure • Consequence of occurrence - 4 • Delays • Higher Cost • Likelihood of occurrence - 1 • Cost / Time Reserve • 10% cost Reserve • 50% time Reserve

  9. On time to market issues • Subject to penalties by DEEP • Higher Risks associated with Overflows • Increased Pollution of public waterways • Backed up Houses

  10. Project cost issues • Budget Overruns resulting from delays • Increased cost associated with Unknowns • Penalties for late completion

  11. Risk Profile

  12. Risk Mitigation • Lots of Test Pits • Public Information Campaign • Attorney Review • Objective Bid Scorecards • Cost and Time Reserves • Bonding of Contractors

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