The total amount of freight of all kinds passing Dam No. 1 on the Monongahela in 1909, was 5,417,873, or a little more than ten times the amount on the Allegheny, while the tonnage passing over the Allegheny bridges is thirty times greater than the tonnage on the Allegheny River.[44] Yet, if conceivably the traffic on the Allegheny should equal that now on the Monongahela, it would still be only one-third that over the Allegheny bridges.
Since the figures for the present traffic over the Allegheny River bridges are used for comparison with the present river traffic, and since the former must continue to grow steadily with the growth of the Pittsburgh industrial district, it seems quite clear that no conceivable growth in the latter can seriously affect the overwhelming predominance of the bridge traffic in amount and value.[44]
FOOTNOTES:
[32] Appendix II.
[33] The maximum gradients here given assume the improvement of the short pitches now existing on some of the bridge approaches.
[34] Gradients for this clearance height are greater than those shown on United States Engineers' plans because of greater width of channel. If United States Engineers' plans were adopted the maximum gradients would be as follows: Sixth Street, 4.35%; Seventh Street, 4.93%, and Ninth Street, 4.98%.
[35] 3.64 per cent (United States Engineer's Office) or 4.0 per cent, (City Bureau of Construction.)
[36] Given as 6.35 per cent on United States Engineers' Sections.
[37] Automobiles and carriages included in counts for light and heavy wagons.