The First Underground Freight Tunnel

Today marks the one-hundredth anniversary of the operation of the first freight tunnel under a city. On August 15, 1906, the Illinois Tunnel Company announced the opening of a railroad tunnel underneath Chicago's central business district, a square mile known as The Loop. Eventually, Chicago's hidden railroad would span 62 miles and include a network of tunnels that paralleled most of the city's major streets. Buried 40 feet underground, the tunnels are approximately 6-ft. wide and 7.5-ft. tall. By 1928, the tunnel system included 96 elevators, 540 pumps, and almost 4000 lights. Tunnels that were designed to carry coal, remove ash, and transport freight provided 40 coal and cinder connections, 3 coal-receiving stations, 16 cinder-only connections, and 26 private platforms. By the 1940s, the rolling stock used in the tunnels consisted of 150 electric locomotives and 3,500 freight trucks. In a single year, haulers moved 600,000 tons of package freight and 120,000 truck loads of cinder. About 2,000 tunnel trucks of freight were delivered to railway terminals every day, while 800 trucks were loaded for delivery to local consignees.

Originally, Chicago's freight tunnels were designed to carry cables. The Illinois Telephone and Telegraph Company built the first 20 miles of tunnel, but financial problems forced the sale of the carrier's underground assets to the Illinois Tunnel Company. During the electric-railroad boom of the early twentieth century, the tunnel system's new owner began to lay tracks in areas that did not need them in the hope that customers would connect to them. After spending $25,000,000 (USD) and building over 60 miles of tunnels, expenses still outpaced receipts. When ownership passed to the Chicago Tunnel Company, the focus shifted from the movement of coal and cinder to the collection of package freight from warehouses. Freight cars ran on rails through warehouse basements, or were moved by elevator to loading docks on higher floors. Because of size and weight limitations, however, the Chicago Tunnel Company's elevators could only raise or lower one car at a time. Tunnel construction began in 1899 in the basement of a tavern at the heart of the Loop. First, workers dug a shaft to a point 40 feet below the intersection of LaSalle and Madison streets. They then carved tunnels by hand, using knives and pick axes to cut through layers of blue clay. To avoid the pedestrians, streetcars and horse-drawn wagons that clogged the city's streets by day, workers removed the excavated materials at night, dumping debris into Lake Michigan. In the tunnels, crews set wooden supports in place and packed a foot of concrete between the walls and forms. Gradually, the face of the supporting structure was lined with a layer of concrete, giving each tunnel a finished appearance. Eventually, the subterranean structure included waterproof doors, fireproof doors, and signs which identified the city streets above. When the Illinois Tunnel Company took control, the first two-foot gage railroad track was laid.

To prepare the first tunnel for service, trains with two locomotives and a series of freight cars were run along the tracks. The first four-wheeled engines received power from a cog in a slot between the two running rails. Later locomotives used an overhead trolley wire. To power the trains, the Chicago Tunnel Company built four electrical substations to provide 250-VDC power from Commonwealth Edison, a local utility. The overhead wires were positive. The rails were negative and ground. Because the energized wire was only about 6.5-ft. above the rails, personnel who sat in a metal locomotive or stood in a puddle of water risked electrocution. In the city's commercial district, warehouse owners erected wooden guards around the overhead wire in their basements to protect workers who loaded and unloaded cars.

Most freight cars in Chicago's underground tunnel system were 4-ft. wide, 12-ft. long, and capable of carrying loads up to six tons. The largest engines, members of the 525-534 series from the Baldwin Locomotive Works, could pull up to 15 cars at a time. Although the tunnel system never reported a serious accident, trains running on one-way tracks in dimly-lit places required strict controls. As a rule, freight trucks without brakes were parked along sidings with the wheels chocked. If a car rolled out of a siding, the wheels passed over an electrical switch and illuminated a sign that warned approaching trains. From a central station, a dispatcher with over 300 telephone connections monitored all movements and checked schedules continuously.

Chicago's underground tunnel system declined during the middle of the twentieth century because of existing inefficiencies and competition from new technologies and trends. Although tunnel trains avoided congestion on the city's streets, the process of loading and unloading freight cars was time-consuming and labor-intensive. First, each car had to be loaded with coal or freight and then lowered by elevator to a tunnel. Next, the train was assembled, moved to another elevator, and then disassembled. Each car was raised to the surface, unloaded, lowered again by elevator, and then reconnected. By contrast, a truck loaded with coal could drive to a loading dock on the side of a building and unload the coal directly into a bunker. In 1956, Congress passed landmark legislation that funded a 40,000-mile system of interstate roads that would reach every American city with a population of more than 100,000. When road construction began, the Eisenhower Interstate Highway System moved industrial development away from urban centers toward outlying areas, and towards new locations in the American South and West.

The Chicago freight tunnel system was closed in 1959. Scrappers removed all of the overhead copper wire and most of the pumps, freight cars and steel doors. During the early 1960s, the city reclaimed part of an abandoned tunnel near City Hall for use as a fallout shelter. Former workers from the Chicago Tunnel Company were hired to walk the tunnel and look for cracks and leaks. During the 1968 Democratic national convention, the Cook County Sheriff briefly considered using the tunnels to detain thousands of demonstrators. In the 1970s, Commonwealth Edison laid high voltage lines. In the 1980s, telecommunications firms laid fiber optic lines. As a conduit for cables instead of freight cards, Chicago's abandoned tunnel system was returned to its original purpose.

Resources:

http://www.todayinsci.com/cgi-bin/indexpage.pl?http://www.todayinsci.com/8/8_15.htm
http://www.hq.usace.army.mil/cepa/pubs/may02/story10.htm
http://mikes.railhistory.railfan.net/r047.html
http://users.ameritech.net/chicagotunnel/tunnel1.html