The pipes are lined with meters which measure temperature and pressure, and valves to alter the pressure or shut down the pipes.
The tunnels are lit by hanging lights spaced out by ten feet. These lights cast a bright beam directly under them, but only a dim picture beyond until the next light.
Tsymbal, the daring explorer, describes the tunnels as "hot and steamy with lots of puddles on the floor. It has poor lighting in some areas like the tunnels in the movie 'Aliens.'"
This summer, workers jackhammered through a large section of the roof of the tunnel under Memorial Drive and fixed up the walls with steel reinforcing. They also poured new concrete for the roof, Hawkes says.
Many sections of the tunnel have chips in the concrete which are either left there, paved over or reinforced with steel.
Four maintenance employees now work full time reading meters, checking the tunnels and fixing the pipes when called for. They primarily look for leaks and check expansion joints.
The pipes are prone to leaks in the valves so workers check the valves and often repack them to prevent leaks.
Their other main function is to check the expansion joints. Because the temperature in the pipes can vary between 70 and 400 degrees when the steam is turned on and off, the steel is constantly expanding and contracting.
These expansion joints allow for the horizontal expansion when the steam is turned on around Sept. I and contraction when the steam is turned off after commencement, Hawkes says.
These joints are likely sites for leaks to develop, and must be inspected and maintained continuously. Hawkes says that leaks are most likely to occur where there is packing. The packing is located at sites where there is moving, "for example, at the expansion joint or the valve stems where the valve opens and closes at the valve joint," Hawkes says.
The steam tunnels are not the University's only tunnel system. Food tunnels link five river houses to the University's central kitchen, says Michael P. Berry, the director of Harvard Dining Services.
Berry says these tunnels run parallel to Memorial Drive, and are used to transport food from the central kitchen to each of the dining halls.
The food tunnel system has its own quirky historical tales as well.
Berry said that U.S. Secretary of Defense Robert S. McNamara came to Harvard during the Vietnam anti-war period. Students demonstrating against the war opposed McNamara's presence, forcing him to be "exited away from protesters through the food tunnels," Berry says.
But the funny stories are not the only connection between the two tunnel systems.
"There are some places where the food and steam tunnels run side by side," Hawkes says. "Obviously you can't carry the food through the steam tunnels."