A major water main break in downtown Minneapolis flooded streets and cut off water to a substantial swath of the city just before rush hour Thursday afternoon, forcing workers in businesses left without plumbing to head home early, snarling traffic and disrupting nightlife.

Crews planned to work through the night to repair the damage caused by 14 million gallons of rushing water, but Hennepin Avenue from Washington Avenue N. to NE. Main Street, which includes the Hennepin Avenue Bridge, along with nearby stretches of N. 1st and 2nd Streets, will remain closed through the morning rush hour, officials said.

"We want to make sure the rushing water didn't undermine the pavement or utilities below the roadway," said Public Works Director Steve Kotke.

In addition, about a half-dozen buildings in a three-block area along N. 2nd Street  from 3rd Avenue N. to Hennepin Avenue are likely to be without water until Saturday evening while crews make repairs and disinfect the water main, he said.

The break occurred about 2:30 p.m. on N. 2nd Street at Hennepin, where a $70 million retail-apartment complex is under construction. The project, called 222 Hennepin, will be a 580,000-square-foot mixed-use development that will contain 286 luxury apartments and be anchored by a Whole Foods Market. Work began last February and is expected to finish this summer.

Scott Beron, public safety director for the developer, Ryan Companies, said a subcontractor, United Sewer and Water, was boring under the street to hook up city utilities to the project when the break occurred. The crawler hoe that might have punctured the main fell onto its side as water gushed out and undermined the soil beneath it.

Minneapolis City Attorney Susan Segal said the city will seek reimbursement for its cleanup costs and any other damages from the party responsible for the break.

The 36-inch pipe was "a main transmission line for the southern half of the city," Kotke said. Residents as far south as Lake of the Isles were affected when pressure dropped.

Everywhere, a mess

At the height of the deluge in downtown Minneapolis, a pickup truck drove across the rushing stream, water coming up over its bumper. Two hours later, as the water began to recede, an adventurous bicyclist on fat tires plowed through ankle-deep water only to wipe out on the ice-glazed sidewalk across the street.

Workers without running water or toilets headed home early, and cars and buses were rerouted as water gushed onto N. 2nd Street, flooding Hennepin, pooling near the Hennepin Avenue bridge and cascading to the parkway below. The water in some spots near the bridge rose 2 1/2 feet when storm sewer drains couldn't keep up.

By the time workers shut off the water an hour and 20 minutes after it began to flow, nearby sidewalks were glazed in ice. As the water slowly ebbed, backhoes scraped layers of mud left behind while others covered the street in salt to break up the fast-forming ice and keep sewers open.

The Mill City Museum closed at midafternoon, and the Guthrie Theater canceled Thursday night's performance of "A Servant of Two Masters."

"Water main breaks are pretty common in the winter," said Stephen Johnson, building engineer at the Crossings condominiums. "But this one is huge. Usually there are only a couple of buildings that are affected."

After getting permission from the city, his building tapped a nearby fire hydrant to provide water to the 304 condominiums.

At the U.S. Postal Service Building, which sustained the most damage of any building, four firefighters donned insulated, waterproof "Mustang" suits, gloves and boots to search the building's basement. The four carried axes and hammers, wading through chest-high water, but said they found no victims, took off their suits and returned to their south Minneapolis station.

As the firefighters changed, the intercom at the post office warned employees they wouldn't be able to get to their cars in the underground parking ramp. One official estimated that 20 employee cars were partly submerged, as well as roughly 30 postal vehicles.

At the Local restaurant at S. 10th Street and Nicollet Mall, the kitchen closed, leaving the staff serving beer and wine in disposable cups. General Manager Josh Petzel said he had numerous dinner reservation cancellations. He said his staff was able to save water in buckets to continue washing their hands.

At Hennepin County Medical Center in downtown Minneapolis, surgeries and other operations remained on schedule despite the water loss thanks to a backup system, a spokeswoman said.

'We'll work into the night'

Late Thursday afternoon, at the corner where the pipe burst, CenterPoint Energy spokeswoman Becca Virden said natural-gas crews would be out all night monitoring their pipelines, a major gas passageway. "Our main concern is the integrity of the pipeline," she said. Underneath the intersection is a 3-inch natural-gas line as well as the pipeline of at least 16 inches, she said.

Later Thursday, crews began inspecting the water main damage next to the toppled construction hoe, which will have to be removed by a crane.

Marie Asgian, the city's water distribution supervisor, said the cast-iron pipe will be repaired by cutting it and placing a sleeve over the break.

"We'll work into the night, whatever needs to be done," Asgian said. "Nobody is going home until this is complete."

Staff writers Kelly Smith and Rochelle Olson contributed to this report. Steve Brandt • 612-673-4438 Twitter: @brandtstrib