The desire to obtain a dry tunnel, and the methods adopted to secure it, were responsible in a great measure for the decision to build the arch in short lengths, as well as the reasons given under the head of arches. Had the tunnels been dry throughout, the method shown at _A_, Fig. 18, could have been used exclusively, and, except for the fact that monolithic concrete might not have been obtained, there would have been no objection to building longer lengths. The quantity of water reaching the tunnel drains and flowing out of their lower ends after the completion of the lining was about 100,000 gal. per day, or 75 gal. per min.; of this it is estimated that considerably less than 1% comes through the lining in the form of leaks. The very general distribution of this water over the roof is indicated by the fact that, during the excavation of the first 1,000 ft. of both tunnels from the Weehawken end, oilskins had to be provided for the laborers to induce them to work at all. The success, therefore, of the rock packing as a means of diverting this water to the side drains, is shown, especially in view of the fact that, excluding the cut-and-cover section, only 10% of the length of the arch, 1,189 ft., was water-proofed. Considerable care was taken to make all joints in the concrete which were in such a position that water might follow through them to the inside of the tunnel lining, in such a manner that they would slope outward toward the rock. The top of the sand-wall is shown by Figs. 14 and 18. The slope of the back of the foundation may be noted in Fig. 18, and the method of making the joint in the arch, in the few instances where a section was not completed at one operation, is shown at _A_, Fig. 18. These joints in the arch were not allowed to be made above a point 60° above the springing line. HACKENSACK PORTAL AND APPROACH. The approach cut at the western end is 300 ft. long, the alignment being a 2° curve, as shown in Fig. 19. The bench-walls and conduit lines built throughout the length of the tunnels are extended through the approach cut, the top of the former gradually sloping from the portal to the mouth of the cut, where they are just level with the top of the rail, the conduits also being depressed to the same relative position with the tops of the benches. [Illustration: Fig. 19. [Full Page] BERGEN HILLS TUNNELS. Hackensack Portal and Approach. SECTIONS AND ELEVATIONS. PLAN OF APPROACH. PROFILE THROUGH APPROACH. SECTION SHOWING METHOD OF MAKING JOINT BETWEEN COPING AND WALL. PLAN SHOWING METHOD OF MAKING JOINT BETWEEN ADJOINING SECTIONS. SECTION OF BENCH AND RETAINING WALLS AND HALF ELEVATION OF PORTAL.]