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varies from 11.25 feet to 21.88 feet. By highest navigable water is meant the stage of water when by reason of floods or currents, navigation ceases. This Paris water-borne freight traffic on the Seine amounts to fully 7 times that of the Allegheny River and passes under 5 times as many bridges, with minimum available head room at high navigable stages just about one half that under the present bridges over the Allegheny at a Is-foot stage. The conditions of navigation on the Seine at Paris are practically the same as those on the Allegheny at Pittsburgh. In Paris the boats are made to fit the bridges and not the bridges to fit the boats.

From these and many other illustrations that could be given it is evident that it is not universally or even commonly considered necessary or advisable to sacrifice business interests crossing the bridges to navigation interests using the waterways, to any such extent as that demanded by the navigation interests of the Allegheny River.

Conclusions as to Clearance Heights. -- Disregarding for the moment the question of the time when changes in the present bridges should be required, it is believed, after very careful consideration, that the conditions brought out by our study of the problem would best be met by fixing the elevation for a substantial portion of each bridge in the center at a clear height above the pool level of substantially 37 feet, or 28 feet above the river at a 15-foot stage at each bridge. It is believed that this elevation will give fair, justifiable and all really needed accommodations to the. navigation interests. This height can be attained without extravagant and unjustifiable expense and inconvenience to the business interests involved in crossing the river, and while it cannot be hoped that it would be satisfactory to the extreme advocates of river and harbor interests, it ought to satisfy those who are able and willing to give proper and fair consideration to other interests than their own. There are no reasonable navigation demands, with bridges at this elevation, that cannot be met if the water-borne commerce be conducted with vessels of the best modern accepted type and not of extreme or unnecessary height.

Piers and Channels. -- For the benefit of the navigation interests there are certain changes in some of the bridges over the Allegheny that should be made without question. These relate to the location of piers and location and width of the navigable channels.

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Last modified on 22-Dec 1999
Design format: copyright 1997-1999 Bruce S. Cridlebaugh
Original document: Frederick Law Olmsted, 1910