32 BULLETIN I486, U. S. DEPARTMENT OF AGRICULTURE 
difficult. If the bottom is soft, the channel is very apt to erode at 
the bridge, but to shoal below it, thus obstructing navigation. 
In general the points above enumerated pertain to the safety and 
adequacy of the bridge opening as regards the passage of water 
traffic. It is true that the bridge engineer in general is serving a 
client or clients who are interested primarily in the safeguarding and 
service of traffic over the bridge rather than through it. However, 
the bridge engineer, especially if he be serving as a public official, 
should be interested not only in the welfare of the particular branch 
of the State which he serves, but also in that of the public at large and 
no bridge structure which obstructs and hinders water traffic can be 
said to truly serve in the development of the country as a whole, 
regardless of its excellency as a carrier of land traffic. 
It seems highly essential and desirable that the bridge engineer 
view his problem in a broader light than formerly and take into 
consideration the. points enumerated above and any other features 
which affect the safety of and service to water traffic. 
Plans for bridge structures over navigable streams must be sub- 
mitted to the War Department for approval. The engineers in this 
department are generally among the highest authorities in the 
country as regards river and harbor control and improvement. They 
are jealously guarding the navigable waterways of the country, 
which Congress has entrusted to their care and will permit of no con- 
struction which, in the slightest degree, will hamper or hinder the 
free and natural use of such waterways (which is, of course, exactly as 
it should be). 
If the bridge engineer in his location does not take cognizance of 
the interests of navigation, the War Department engineers will do 
it for him. It will be much better to try to anticipate the viewpoint 
of the navigation interests and the river and harbor engineers, so that 
final approval by the War Department can be made with minimum 
of change. ■ 
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