2. That the Ninth Street bridge should be rebuilt as soon as practicable with a center pier and two wide spans conforming to those of the Sixth Street and Seventh Street bridges. The design of the new Ninth Street bridge, however, should not be finally determined and erection begun until a definite plan for comprehensive improvements in the traction system between the two sides of the river has been decided upon. Unless new circumstances develop before the construction of this bridge is begun that materially affect the problem of clearance height, the elevation should be fixed in accordance with the closing paragraph below.
3. That all questions pertaining to changing the elevation of the Sixth Street, Seventh Street, Fort Wayne, Thirtieth Street and Junction Railroad bridges be deferred to await the report of the Pittsburgh Flood Commission and the resultant action; to await the report on a comprehensive plan for traction improvements; to await the completion of the work projected by the City in cutting down some streets and filling others; and to await the results of investigation of river-boat design and construction provided for in the River and Harbor bill just passed by Congress.
4. That, if it is deemed essential and necessary at present to decide upon the elevation to which all Allegheny River bridges must be made to conform, this elevation be fixed so that there shall be a clear head room of substantially 37 feet above pool level, varied so as to give at each bridge a clear head room of 28 feet when the river is at a 15-foot flood stage. This height to be maintained over the entire main span where there is a central span and for 180 feet on each side of the central pier where there is a central pier.
We have the honor to be, very respectfully,
Your obedient servants,
Thomas W. Symons,
Col. Corps Engineers U. S. A., retired,
Frederick Law Olmsted.
APPENDIX I
Amount and Importance of Bridge Traffic.—Highway Bridges.—The following table gives the records of counts made in the fall of 1909, and spring of 1910 on the various bridges over the Allegheny River:
| Location of bridges | Period of count | Street cars | Heavy wagons | Light wagons | Carriages | Automobiles | Pedestrians |
|---|---|---|---|---|---|---|---|
| Sixth Street | Aug. 24-Oct. 23 | 89,354 | 55,791 | 79,247 | 9,534 | 24,583 | 1,605,793 |
| Ninth Street | Aug. 26-Sept. 30 | 72,854 | 8,961 | 14,846 | 613 | 960 | 185,158 |
| Sixteenth Street | Oct. 4-Oct. 17 | [37]4,444 | [37]7,764 | 76,495 | |||
| Thirtieth Street | Aug. 24-Oct. 23 | 9,844 | 10,184 | 667 | 447 | 96,485 | |
| Forty-third Street | Aug, 23-Nov 1 | 8,159 | 8,165 | 987 | 2,179 | 130,744 |
| Location of bridges | Period of count | Passenger vehicles | Delivery vehicles | Single trucks | Double trucks | Pedestrians |
|---|---|---|---|---|---|---|
| Seventh Street | Feb. 28-Mar. 3, 4, 5, 7 | 401 | 4,800 | 273 | 1,035 | 29,146 |