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| Re: Possible Major Evidence of Tunnel To 76TH STREET! (1553201) | |||
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Re: Possible Major Evidence of Tunnel To 76TH STREET! |
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Posted by K. Trout on Thu Jul 16 03:21:58 2020, in response to Re: Possible Major Evidence of Tunnel To 76TH STREET!, posted by HANDBRAKE on Tue Jul 14 15:07:33 2020. So if I understand correctly, the A7/A8 leads were connected to K5/K6 once the Liberty Av connection became the only connection south of Euclid? If so, the original plan which had both the Pitkin mainline and Liberty Av branch likely didn't have a connection from Liberty Av to the yard (or it was less intricate).I've sketched out my best understanding of the area. My guesses at the yard leads are based on OpenStreetMap. From this post showing an A2-411 signal, and knowing that the south end of Euclid is at 427+55 (from that old list of IND chaining locations for each station), I estimate that the bumper blocks are around 1600 feet past end of the platform, which is between Grant Av and Eldert Ln. The vent and emergency exit you mentioned along the Pitkin Av mainline are easily visible. There are a couple of vent grates I can't quite place, though, which I marked with question marks. I think the eastern one is a grate for the Liberty yard connector, but I have no idea what the western one is, unless it's part of the extra-wide Pitkin mainline tunnel. The thing that bothers me is that if the track alignments shown on OpenStreetMap are correct, there's no way the A7/A8 leads could have possibly reached Pitkin. The angle would have been far too sharp. I think there are two possibilities: 1) The point where the A7/A8 changes to K5/K6 is the northern limit of the original 1940ish construction of the yard leads, and they were never connected to anything until the Liberty connector was built. 2) A7/A8 originally made a more gentle curve to the east. There may be remnants of these tunnels east of the point where K5/K6 connect. I can't speculate on how far they might go. The mainline tunnel retained the spacing between local and express tracks for them to eventually join in a mirror image of A5/A6, though possibly from above instead of below. I also think "were the yard leads ever extended to the mainline?" and "how far does the mainline tunnel go?" are two separate questions. The key would be finding the construction contracts indicating the route and section. From what I understand much of the IND construction was split up into small chunks for different structural features. I marked a possible location of such a boundary on the map - it would be as far east as a hypothetical point where the A7/A8 tunnel, with a more gentle curve, might meet the mainline tunnel, but not the actual mainline flyover. |
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