Isidro Carranza, a water-quality technician with D.C. Water, prepares to take samples of water from a fire hydrant near the corner of the intersection of Quackenbos and 7th streets NW. (Matt McClain/The Washington Post)

Thirty-one staffers from the District’s water utility and other city agencies had a problem: Residents had begun reporting that their water smelled of petroleum, signaling possible contamination in part of the city’s drinking water supply.

The scenario was purely theoretical, but the large conference room at D.C. Water’s Bryant Street Pumping Station in Northwest Washington began buzzing with questions.

“Where were the calls from?” one D.C. Water staffer asked. “What’s the current message out to the public?” asked another.

Jason Hughes, playing the role of incident commander, directed the group to come up with a detailed “incident action plan”: Determine how and where to collect water samples, get the samples tested, draft a message to the media and notify “critical” customers, such as hospitals and schools.

“The laboratories will need to be contacted,” interjected Jessica ­Edwards-Brandt, D.C. Water’s manager of water quality.

Jonathan Reeves, at left, in planning vest, talks with teammates during a contamination exercise. Reeves is D.C. Water's emergency management director. (Katherine Shaver/The Washington Post)

It was exactly what Jonathan Reeves, D.C. Water’s emergency management director, had in mind for the start of a three-day “functional exercise” — the most far-reaching emergency drill he said the utility has conducted to practice responding to a drinking water crisis in the nation’s capital.

“We protect the water for the center of the free world,” Reeves said as staffers clustered together at tables marked “Command,” “Operations” and “Planning.” “We are held to higher standards.”

Like many government agencies, D.C. Water has held smaller emergency planning events and “tabletop” discussions of “what if?” ­scenarios. This week’s “functional” exercise went a step further, for the first time enacting an emergency response plan by working with a half-dozen other agencies, collecting water samples at fire hydrants and businesses, and seeing how six area labs would provide results.

“This is the next step,” Reeves said. “You actually do something to see if it works.”

The U.S. Environmental Protection Agency, which regulates drinking water, sponsored the event, as it has other emergency water utility exercises around the country. Water distribution systems are considered critical because safe drinking water is necessary for households, hospitals, schools and businesses. Plus, fire hydrants must have water.

Even so, utility industry experts say, many water and sewer agencies have taken a while — it’s been 14 years since the Sept. 11 terrorist attacks — to expand their core missions from supplying safe water and sewage disposal to anticipating a large-scale, extended water outage, be it from a terrorist attack, a hurricane or a fuel spill.

With Reeves’s hiring in 2009, D.C. Water became one of the first U.S. water utilities to dedicate someone full-time to emergency preparedness. Reeves’s office has since grown to six people — one of the largest for a U.S. water utility.

Lab supervisor Robert Hoffa poses for a portrait at Washington Aqueduct on Thursday in Washington. (Matt McClain/The Washington Post)

Several recent incidents, particularly a West Virginia chemical spill in 2014 that led to a five-day ban on drinking water for nearly 300,000 people in the Charleston area, have given utilities a new sense of urgency, officials said.

George S. Hawkins, D.C. Water’s general manager, said water utilities generally respond well to daily emergencies, such as breaks in mains, but they’re less equipped for major events. He mentioned the 2011 earthquake that hit the Washington area, the 2012 derecho thunderstorms and Hurricane Sandy’s widespread impact on the Northeast.

“We realized it’s not the problems we know of, because we’re prepared for those,” Hawkins said. “It’s the one that’s rare and unlikely to occur, but if it does, it’s on a catastrophic scale that requires different players.”

Reeves said he couldn’t recall the District having a citywide drinking water emergency, largely because the distribution system has enough redundancy that the utility usually can route water around problems. But he recalled some “near-misses” when major pumps failed or particularly large water mains burst.

The drill was reminiscent of a three-day “Do Not Drink” advisory that D.C. Water put out to the Shaw neighborhood in December 2014 after some residents smelled petroleum in their water. The odor dissipated after the system was flushed, and D.C. Water never determined a cause.

Sorin Schwartz, D.C. Water’s safety operations manager, said this week’s exercise helped him get to know people he didn’t normally work with but would need to coordinate with closely in an emergency. As the mock incident’s safety officer, Schwartz plotted how to keep workers safe in the field.

“If someone gets hurt” responding to an emergency, he said, “it can slow everything down.”

Next year, Reeves said, the utility plans to take it up a notch, to a full-scale drill in which agencies across the Washington region — from fire departments’ hazardous materials teams to the police and health departments — will respond as if in a real emergency.

“I hope it’s all for naught,” Hawkins said. “But we’ve seen it happen often enough that the likelihood is something will happen at some point, and we’ll respond much better.”