An ancient city water main – which broke under the Jones Falls Expressway late last night – continues to gush water and cause traffic delays around Guilford Avenue, Madison Street and the Fallsway downtown.

The 30-inch main, which dates back to the 19th century according to a city official, has undergone multiple breaks – most recently in November 2012, when the pipe burst about 200 feet west of today’s location at Madison and Guilford, spilling water into a small shopping center on Guilford.

Last night’s break caused pressurized water to spurt out of manholes and cracked pavement and quickly filled Madison Street with up to three feet of water, according to an eyewitness interviewed by The Brew.

Water service to businesses and residences in the Mt. Vernon area has been affected by the break, but the number of customers impacted has not been reported by the city.

While the water level was substantially lower this morning, the main still hasn’t been turned off to let crews assess the damage to the roadway, sidewalks, underground utility conduits and, possibly, the pillars of the elevated JFX.

Jeffrey Raymond, a spokesman for the Department of Public Works, said personnel from the Office of Emergency Management and Department of Transportation, as well as DPW, were “all on scene coordinating last night so that word got out prior to today’s morning rush.”

The agency tweeted out news of the break about midnight and warned of localized disruptions of water service and detoured traffic today.

Westbound traffic on Madison was detoured this morning at Fallsway, which was closed between Madison and Centre streets. The Guilford Avenue exit ramp on the JFX was also closed, with the street blocked between Chase and Madison.

No word yet from DPW on when Madison Street might be reopened, but personnel at the scene said the break was one of the most serious they’ve seen in months.