Salt corrosion likely led to manhole blasts

Snow melt, mixed with road salt, may have contributed to the underground fires that caused four manhole covers to blow their tops in downtown Monday afternoon, according to a utility company spokesman.

The runoff, mixed with the salt used all winter to fight road icing, can corrode the casings around underground cables, said Patrick Stella, a spokesman for National Grid.

The corrosion may have been a contributing cause to the fires in two secondary transmission lines — one near South Swan Street and Washington Avenue, the other near State Street and Broadway — that are believed to have caused the 200- to 300-pound covers to "dislodge."

While the exact cause in this instance is not yet known, Stella said the explosions can be caused when the fires ignite gases that build up in cement vaults that encase the cables.

No one was injured and no power was lost.

Stella said the underground systems are inspected every five years and that Albany's system was last looked at in 2005-06.

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