Caltrans bases its estimates for the Devil's Slide tunnel on faulty comparisons to other tunnels with much higher wear-and-tear as indicated by the Average Daily Traffic (ADT) figures (with maintenance cost per mile figures included for reference):

  Devil's Slide Caldecott* Eisenhower
in Colorado
ADT 10,000 to
54,000 to
Maintenance ? $1,250,000 $1,270,000
* The Caldecott figures were not supplied in the FEIS document and were obtained directly from Caltrans. The Posey tube has an ADT of 60,000 and the Webster tube an ADT of 54,000.

Since the Caldecott and Eisenhower tunnels have two to six times the traffic, why has Caltrans not adjusted the maintenance figures accordingly? Is this a mistake or an attempt to bias the figures against the tunnel? In either case, we can adjust the maintenance costs to reflect actual traffic, giving us lower figures:

To this we would add $160,000 for maintenance of the remainder of Highway 1 between the ChartHouse and Linda Mar, giving a range of $374,000 to $695,000 for tunnel maintenance. This is to be compared to Caltrans' estimate of $340,000 for bypass maintenance.

Thus the tunnel might cost from $34,000 to $355,000 per year more than the bypass to maintain if we accept all of Caltrans figures and make only reasonable assumptions about maintenance being roughly proportional to traffic. Of course, other considerations doubtless come into play and we would need better figures before settling on a final amount. It seems, though, that a detailed look at maintenance will favor a figure at the lower end of this range.

For example, included in the cost of the Eisenhower tunnel is a dedicated fifty man crew with its own fire equipment (required since the Eisenhower is 20 minutes away from the nearest town). The Devil's Slide tunnel would be located minutes from help coming from either Pacifica or Montara and would presumably not need its own dedicated fire department.

The Eisenhower staffing requirements are also not comparable to what might be needed at Devil's Slide. Bypass project manager Dennis Bosler estimated that a full-time crew of three would be required -- for a total staff of perhaps 12 to 15, less than a third of the Eisenhower headcount.

In order to continue the analysis, though, let's take an average of the two figures above -- or $187,000 per year -- as an estimate of the additional yearly cost to maintain the tunnel route rather than the bypass. Then, using Caltrans' method of finding the net present value of this extra expense, we find an additional lifetime cost for maintenance of $4,675,000 -- not $21,750,000 as Caltrans would have us believe.

On p 33 of their document, Caltrans estimates the capitalized cost of an $870,000 expense stream (with interest at 6.5% T-bill rates and inflation at 2.5% a year) to be $21,750,000. That is, the net present value of each extra dollar of maintenance expense is:

21,750,000/870,000 = $25

From this, we can estimate the net present value of $187,000 per year as:

25 * 187,000 = $4,675,000

The point is not that these estimate is surely correct, but rather that Caltrans' estimate is surely wrong. It is transparently wrong because Caltrans has used inappropriate examples to arrive at inflated costs. Caltrans' maintenance cost estimates cannot be allowed to stand, and with them must fall their overall cost arguments against full consideration of the tunnel.