2 BULLETIN 1486, IT. S. DEPAETMENT OF AGRICULTURE 
This may be illustrated by a crossing in southern Oregon. The logical 
site for the bridge and the one which was first chosen combined a 
very narrowly restricted neck in the river with exposed solid rock 
foundations. A steep, high cliff on one side of the stream furnished 
admirable support for an abutment at this point, thereby effecting 
a very marked saving in first cost. Unfortunately, however, it so 
happened that the adoption of a comparatively low level grade line 
necessitated intersecting the rock bluff at about half of its height, 
thus introducing several hundred feet of expensive rock cut. If, on 
the other hand, the grade line were raised to intersect the edge of the 
rim rock at its upper level, the far side of the approach would have 
been thrown off its support, thereby entailing a heavy expenditure 
for approach fills, involving rock borrow and overhaul. The only 
other feasible crossing involved a much greater river width and 
foundations on heavy gravel overlying bed rock, thereby entailing 
costly cofferdam construction. Comparative estimates embracing 
the bridge structure alone were such as to dictate the adoption of 
the first crossing by a large margin of saving. Comparative esti- 
mates covering the entire project, however, disclosed the fact that a 
distinct saving in the first cost could be made by adopting the more 
expensive bridge crossing in connection with the much less expensive 
approach construction. 
The above is but one of many instances wherein a study embracing 
the entire crossing project (bridge and approaches) leads to con- 
clusions quite different from those which would be the natural result 
of a study embracing the location of the structure alone. In view 
of this fact, therefore, it is felt that the matter of bridge location may 
be best treated by simply enumerating and discussing the various 
points of merit in location as affecting the first cost, maintenance, 
and operation of the structure itself, leaving it to each individual 
instance to balance such points of merit against similar points per- 
taining to the location of the adjacent portions of the project. 
LOCATION OF MINOR STRUCTURES 
For small structures, the location of the bridge or culvert itself is 
generally of importance secondary to that of the general alignment; 
in other words, it hardly ever pays to shift alignment to any marked 
extent as the accruing advantage is generally not worth the expense. 
In certain cases, however, waterway conditions even for minor struc- 
tures may be greatly improved through a slight modification in loca- 
tion. As an illustration, consider Figure 1. The submitted or 
original alignment involves (1), a skew culvert crossing which is in 
itself undesirable from a standpoint of first cost on account of the 
increased length of barrel and should be eliminated if a straight 
crossing can be obtained, and (2) the construction of a long wing 
at A to eliminate the tendency to erode the fill during flood periods. 
This is another element of added first cost. The stream encroaches 
so near the shoulder of the road at B that it is quite possible that even 
the length of wing shown may not always prove adequate during a 
succession of future flood periods. This tendency to cut behind and 
under wing walls is the source of a great deal of serious trouble in 
the maintenance of small bridge structures whose location has not 
been made with attention to this detail. The examples shown on 
