302 FORESTS, RESERVOIRS, AND STREAM FLOW 
extensive purchase of lands outside. Such drawbacks are, of course, 
encountered in all similar work, but they are excessive in these sites. 
They are mentioned solely from their relation to the question of 
cost. No one can examine the maps of these sites and not be con- 
vinced that the cost of right of way and damages alone will con- 
siderably exceed Mr. Leighton’s estimate of the entire cost of the 
system. 
An element affecting cost is that of safety. Owing to the situation 
of many of these proposed reservoirs, the results of failure of the dams 
would be so appalling that no chances can be taken. The structures 
can be made safe, of course (except against earthquakes), but it will 
cost money. Nothing short of the highest type of construction 
—masonry for all the larger dams—can be considered. Mr. Leighton 
has cited certain dams upon the integrity of which great interests 
depend as evidence of the confidence of engineers in these structures, 
but if he will apply their costs, particularly those of important struc- 
tures in Europe, to his proposed system, the money value of safety 
will mount up to a prodigious figure.* 
A feature of this question of safety often overlooked is the depre- 
ciation of the market value of property, due to its location below a 
dam where failure of the dam would mean a disaster of great mag- 
nitude. However safe the structure may be, many people would not 
purchase property below it, and its market would be correspondingly 
diminished. While such loss can hardly be made a subject for dam- 
ages, it is a real loss to the owners. 
These reservoirs being built for flood protection, the sluices must 
be very large, so that at times they can be discharged practically as 
fast as the water runs in. This will be necessary during periods of 
prolonged precipitation in order to keep the reservoirs from filling 
too full before the danger is past. This detail of construction will 
add largely to the cost. 
*The recent failure of the Hauser Lake Dam on the Missouri River, near Helena, 
Mont., is a good illustration of how the unexpected may happen. Here was a dam 
built of steel and concrete, two materials whose properties are thoroughly under- 
stood. The case was one which “ordinary engineering’? might be expected to.handle 
successfully. The public had reason to feel confidence in the structure. Yet “it 
fell and great was the fall thereof,” not only in the total wreckage of the dam, but 
in the losses caused along the valley below. 
The accident affords also another illustration of the omnivorous claims put for- 
ward in these days in the supposed interests of forestry. The disaster was 
promptly cited as an example of the havoc wrought by floods in a country without 
forests. The normal flood discharge of the Missouri at this point is 20000 cu. ft. 
per sec.; for 1907, it was 26000 cu. ft.; the maximum on record is about 50000 
cu. ft. At the time of the accident the discharge was about 7000 cu. ft. per sec. 
