50 VALUATION, DEPRECIATION AND THE RATE-BASE
puted theoretical or geometrical quantities in all cases where the
actual quantities are likely to be greater, the adoption of liberal
rather than minimum prices for the various items of work, and
a further allowance for contingencies. If the plans are incomplete,
 so that many minor features are omitted, he properly
adds more for omissions and contingencies than where the plans
are in greater detail.
“In the valuation of a public service property, the same ideas
should be kept in view and the percentage or sum to be allowed
for contingencies should be governed, to a considerable extent,
by the completeness of the inventory and the amount already
allowed for omissions, by the extent to which additions have
been made to the computed theoretical quantities and by the
degree of liberality of the prices affixed to the various items of
the inventory, but in no case should the contingencies be omitted
or reduced to a small figure. Large contingent expenses are
necessarily incurred in practically all important public works.
They may occur from very many causes, among which may be
enumerated the failure of contractors and the cost and legal
expenses incident thereto; to the delay of certain parts of the
work caused by such failure; to injunctions or to the inability
to obtain possession of the land in due season, thereby necessitating
 the execution of such portions of the work under winter
conditions or other adverse circumstances; to stringencies in the
money market, causing a temporary shortage of funds, and a
consequent disorganization of the forces employed on the work;
to protracted strikes; to the necessity of rebuilding parts of the
work which have failed because of improper design or unforeseen
 causes; to making alterations found to be necessary or desirable
 after the work is built; to the slipping of earth or rock;
and to making changes in plans which increase the cost of the
work.
“ Such contingent expenses as those above enumerated, with
the exception of the last two, should be included as contingent
expenses in any valuation of an existing property because the
existence of the property does not give any clew to the amount
of most of the contingent expenses involved in its creation.”
Am. Soc. C. E. Committee, Insurance and Risk. — “There is another
 subject closely related to contingencies which may be classed
as insurance or risk. For instance, if an owner of property is
constructing a building he runs the risk that it may be burned.
If a fire occurs when a building is nearly finished and the owner
has to rebuild it, the cost of the completed structure, if he has