Chesapeake Bay Bridge – Tunnel Construction

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The Chesapeake Bay Bridge and Tunnel Commission has awarded the Dragados Team a contract to construct a new parallel tunnel at the Thimble Shoal Channel.

The Dragados Team, a joint venture composed of Dragados USA, Inc. and Schiavone Construction Company LLC, submitted the lowest price proposal at $755,987,318.

The Dragados Team’s proposal included a bored tunnel and construction will begin on Island 1 in the fall of 2017. Total construction of the parallel tunnel at the Thimble Shoal Channel is expected to take approximately five years.

In May, the Commission invited each of the three teams that had submitted fully-compliant proposals to submit revised proposals for a re-scoped Project. The District determined that the best interests of the Project would be served by re-engaging with all of these shortlisted teams to re-scope the Project after all of the original price proposals exceeded the cost estimate for the Project.

The conceptual design for the Project RFP initially included the widening of the man-made islands 250 feet to the west of the existing islands to provide physical space for either an immersed tunnel or bored tunnel to transition to the existing trestle alignment of the CBBT. Jeff Holland, Executive Director of the CBBT, states that:

“The Project was originally envisioned with a substantial expansion of the portal islands. As such, the expanded southern island would have created space for the future public amenities at little additional cost. When all of the teams competing for the Project focused on reducing cost, it became apparent that island expansion could be very limited or non-existent. As a result, the inclusion of the space sizing for the public amenities of a restaurant, retail shop and 200 additional parking spots that would otherwise require substantial island expansion became cost prohibitive and not necessary to meet the basic mission of the CBBT: providing the traveling public with a safe, cost effective, and unique driving experience across the scenic Chesapeake Bay. This scope change, combined with others, allowed the Commission to substantially reduce the cost of the Project by nearly $260 million from the low price received during the first phase of design-build proposal prices.”

The Sea Gull Fishing Pier at Island 1 will be closed and renovated during the construction project. The pier is expected to re-open to the public in 2022, upon completion of the Project.

One of the Chesapeake Bay’s most familiar fishing piers, the Sea Gull Pier has been popular for decades with fishermen, birdwatchers, travelers, and others.

Tunnel Construction

The new Parallel Thimble Shoal Tunnel will consist of a bored tunnel design. Construction will begin on Island 1 with the construction of a large pit.

The Tunnel Boring Machine (TBM) will be delivered to the site in several large pieces and will be assembled in the bottom of the excavated pit. After assembly of the TBM, construction of the tunnel will begin.

The TBM will excavate and build the tunnel as the machine progresses from Island 1 to Island 2. As the machine excavates, the soil will be conveyed back to Island 1 for removal. At the same time, new precast concrete tunnel segments will be delivered to the TBM.

The TBM will be equipped with automatic controls that will precisely place the precast concrete tunnel segments as the TBM progresses. After the TBM reaches Island 2, the machine will be disassembled and removed from the site. After the tunnel liner is installed, construction crews will install the final roadway, lighting, and mechanical systems.

source: Chesapeake Bay Bridge and Tunnel Commission

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