The city's water main also had a major failure once before -- in 1859. Allston-Brighton historian William Marchione wrote in Allston-Brighton in Transition: From Cattle Town to Streetcar Suburb:
In 1859 a major break occurred in the aqueduct at the point where it passed across the Charles River at the westerly end of Needham. Since the capacity of the four small storage reservoirs ringing the city was quite limited, it became necessary to thut off water service to Boston for all but domestic uses while repairs were being made. Had a major fire broken out at this point, the fast-growing metropolis might have found itself without water, with devastating consequences. This emergency prompted the Cochituate Water Board to recommend the construction of a much larger storage reservoir just outside of Boston.That new reservoir would be the Chestnut Hill Reservoir, the site of which was selected in 1864 and construction began in 1865. Its location was straddling the border between Brighton -- then an independent town not part of Boston -- and Newton. The purpose of the new reservoir was to provide a much larger backup water supply in case of catastrophe.
The reservoir consisted of two basins; the larger one still exists, while the smaller one was granted to Boston College, which, over time, filled it in to make way for an expansion of its campus (the "Chestnut Hill Lower Campus"). The main water pipe, however, continues to pass underground at the same location on the BC campus.
The reservoir is no longer used as part of the water supply system for Boston, but is reserved as a backup in case of emergency. Such as today.