reply to post by emptyOmind
Could it be an abondoned section of an early attempt at a subway system for the area?
Been searching for clues to a failed project, but no luck so far.
Those walls are very thick at 8 feet, the 17 foot width might have been planned to carry two sets of track to carry trains at 8 feet wide.
It's near the surface, so if it was intended for a failed underground transit system, this may have been where the terminus would have been.
Found this information on other old tunnels built during the 19th and early 20th century.
Tunnel
It was originally begun as a coal mine in 1825 by Jacob Beltzhoover.
The mine was extended to the south side of Mount Washington by 1861, and used as part of a system to transport coal from mines along the Saw Mill Run
valley to Pittsburgh, connecting with the 850 feet (260 m) Mt. Washington Coal Incline.
The lease to the tunnel was purchased by the Pittsburgh and Castle Shannon Railroad from Mrs Mary Anne Bailey in November 1871, with the height of
the tunnel being increased from 5.5 feet (1.7 m) to 12.5 feet (3.8 m) in 1874.
The tunnel provided passenger service beginning in 1874, but this was terminated in 1880, and its passenger duties assumed by the Castle Shannon
Incline. The tunnel was declared unsafe for passenger transport in 1893. However, the tunnel and the Horseshoe Curve continued to be used to transport
coal until May 1, 1912
While not the same area, it's interesting that the height of the tunnel in the quote above was raised to a 12 feet high, the same height as these
large concrete box sections are...might be connected?
I doubt a drainage system...no point having massive, over engineered concrete boxes that don't go anywhere..they wouldn't drain anywhere. Pipes have
been spotted entering or exiting from one of the boxes, could be for water, but could also be ducting pipes to carry cables.
Another possibility is they were put in to shore up loose ground, when they were building over the area. Maybe they didcovered the ground was
especially weak and put these in to add support? Although, it would have been simpler to have just filled them in completely i suppose.
edit on 10-3-2013 by MysterX because: added text and link
). buried 7 feet deep under the parking lot. no dimensions given for how thick the roof was. also not mentioned is
that it looks to be reinforced concrete. i'd love to hear what exactly that "black sludge" is. 
