_Disposal of Spoil._--The materials excavated from the tunnels were
dumped at the 35th Street pier on barges furnished by the Railroad
Company under another contract, and were towed to points near the
Bayonne peninsula where the spoil was used principally in the
construction of the Greenville Freight Yards and the line across the
Hackensack Meadows to the tunnels. Details of this work will be given in
a subsequent paper. After December, 1907, when the excavation was about
85% completed, the contractor furnished the barges and effected the
complete disposal of the spoil.
_Difficulties of Excavation._--As stated in a previous paper, the
excavation of the Twin Tunnel in 33d Street was continued westward to
the west line of Fifth Avenue on the original grade. At that point the
contractor started three drifts in the three-track section. The relation
of the drifts to each other and to the cross-section are shown by Fig. 3.
The center heading was driven a little in advance of those on the
sides. At a distance of 65 ft. west of Fifth Avenue the rock surface was
broken through in the top of the heading, and a very fine sand was
encountered. For some distance east of this point the rock was badly
disintegrated, and the heading required timbering. Through the soft
material, tight lagging was placed on the sides and roof of the heading,
and the face was protected by breast boards.
Pages:
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31