Bridge Calculator notes

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Below are some details on how the Bridge Calculator works and where the numbers come from. A key point to remember is all amounts are shown (as best I can) in the equivalent of current 2011 dollars. So, for example, the government's last bond payment in 2046 might be the equivalent of $4.5 million in 2011 dollars, but with the inflation protection built into the bonds, the actual amount paid in 2046 might be $9 million. Similarly, the tolls are inflation adjusted, and a $275 toll today might be $550 in 2046 (assuming 2% inflation). But almost everything else will also roughly increase with inflation - the GNWT's tax revenues, people's incomes, maintenance costs, etc. Expressing everything in 2011 dollars lets us add up amounts over 35 years and express it in a way that means something to us today.

Capital Costs

  • Bond repayments - the formula for the repayment schedule was provided me some time ago by Transportation. The amount borrowed was $165.4 million.
  • Cost overruns - the $36 million is the approximately $16 million the GNWT had to kick in after taking over the project, plus the additional $10 million they announced in December 2011 due to the Steel Delay, and the further $10 million announced in June 2012.
  • Tolling infrastructure capital costs - all the equipment needed for toll operations. $1 million amount provided to me by Transportation.

Operating Costs

The yearly costs associated with the bridge.

  • Operations and Maintenance (Bridge O&M) - the numbers from Transportation have bounced around a bit since they took over the project, but seems to around $350,000.
  • Toll Collection Costs (Toll O&M) - figure provided by Transportation, covers any satellite, software or other fees or costs to collect the tolls.
  • Grants - the money provided to Fort Providence groups under the Community Opportunities and Involvement Agreement.

Toll Revenue

There are two main sources of toll traffic for the bridge. [[1]] for both were done by PROLOG in 2006, for "Conservative" and "Probable' cases.

  • Community Resupply - supplies for communities north of the crossing. The "Conservative" case seems to be not to far off, and the calculator's starting point of 350,000 tonnes is not much lower that what PROLOG suggests. The calculator follows PROLOG in increasing this by 1% annual, as well as another small amount known as "uplift".
  • Mining Projects - supplies to the mines. The recession and cutbacks by the diamond mines have made even the "Conservative" forecast to be wildly overstated - the 350,000+ tonnes for 2012 will actually be more like 210,000. The calculator allows you to choose from a variety of values to use for mine freight volumes. It uses this number for each year - simplistic, but also what the PROLOG Conservative case does. The actual mine freight, and thus the tolls, are actually going to vary quite a bit depending on what mines open and close over the next 35 years.

Ferry Savings

The $2.7 million figure was provided by Transportation, and covers the costs of both the ferry and the ice bridge.

Hypothetical Historical Tolls

In 2008 the GNWT installed a new "weigh-in-motion" scale on Highway 3 just beyond its juncture with Highway 1. It is able to break down traffic into specific axle groups, and is supposedly capturing data well. Transportation was kind enough to provide me statistics from this scale for 2008-2011, and it is easy to convert the northbound numbers into the equivalent Bridge tolls. The main caveat is that traffic that activates the scale but doesn't subsequently cross the river would tend to produce overestimates. Since there aren't any destinations for trucks between the scale and the ferry, the only likely cause of overestimation would be the traffic for bridge construction itself.

Based on these estimates for past years, the conversion from tonnages to tolls on the calculator may run a few percent higher that the real world. There are a couple of assumptions about the mix of trucks and their cargo weights in PROLOG that introduce a bit of fuzziness.