The Tappan Zee Bridge/I-287 corridor project hit major milestones last year, with the project team splitting the environmental review and later selecting a combination of bus rapid transit and commuter rail to run across the bridge. Hudson Valley newspapers singled out the project as the biggest transportation newsmaker of the year. However, the Journal News hit on perhaps the largest remaining question: “Riddle for 2009: How on earth do we pay for it?”

That question was not answered by a preliminary financing study by the Tappan Zee project team, released after years of work in November 2008. But the study does make it clear that conventional funding mechanisms will come nowhere close to meeting project needs.

The report predicts that federal earmarks and bonds supported by federal transit aid and Tappan Zee Bridge tolls could raise only $4 billion, and that in a best-case scenario. The replacement bridge and bus rapid transit/commuter rail combination selected for the corridor by NYSDOT is projected to cost $16 billion — and the financial report authors expect that the true cost will be $23 billion after inflation and debt-related fees.

One answer is a public-private partnership, which the report devotes most of its pages to. It examines 12 case studies ranging from the Miami Port Tunnel in Florida to the Tsing Ma toll road and rail bridge in Hong Kong. A state commission studying PPPs has also taken quite a bit of testimony on the Tappan Zee.

It also appears that the planned bus rapid transit line, with capital costs estimated in the range of $0.9-2.5 billion, would be easier to finance using conventional means than the commuter rail or bridge portions of the project. As a point of reference, a $1-2 billion BRT line would represent less than 10% of a typical MTA five-year capital plan. This is still a considerable sum, but it would certainly be easier to finance than the rail ($8 billion) and bridge ($5.2 billion) components. (Just to be clear, there is no indication that the MTA would build or operate a Tappan Zee BRT system).

The financial study will continue “not in phases — but on a continuum,” its authors write, which makes it hard to predict when the next piece of the financing study will be released.  The eventual financing package for the TZ project could include additional Thruway toll revenues (not just from TZ bridge tolls as originally envisioned), using a design-build construction approach to save money, funds from a state infrastructure bank, and other strategies.