The Concord gasholder is so named because it held volatile gas, which was a major fuel for streetlights and heating before natural gas and electricity came to the fore. It was built in 1888 and used through 1952.
Its round shape comes from its method of storing gas in a floating tank, a system often described as an upside-down cup.
Hereโs how it worked.
The round brick gasholder building sits over a 24-foot-deep basement that was filled with water and held a floating metal tank that lacked a bottom โ hence the upside-down cup comparison. The brick building served only as protection from the elements.
Gas was manufactured in a host of other buildings scattered around the 2.4-acre site, all of which were torn down in the 1990s. The gas was sent to the gasholder building through an underground pipe into the basement, where it bubbled up through the water into the floating tank.
As gas was pumped in, the floating tank would slowly rise from its initial position flush with the floor, guided by vertical rails still visible on the walls. When full, the metal tank was almost 24 feet above the ground, and covered all the windows.
As gas was pumped out, the tank would sink. As gas was pumped in, the tank would rise.
The amount of gas in the tank could be seen on a large, primitive-looking scale on the outside of the buildingโs east side, marked by a movable arrow attached to the top of the tank.
This same system was used in virtually all gasholders, including a metal tank that stood alongside the Concord gasholder from 1921 until it was torn down, apparently in the 1980s, along with other buildings on the site.
That metal tank was sealed and didnโt need a covering building, so passers-by could see the entire metal structure rise and fall as gas levels changed.
David Brooks
(Originally published Oct. 8, 2015.)
