He emerged four hours later with bad news: two half-century-old drainage pipes near 29th Street had been crushed like soda straws and erosion was chewing the underpinnings of Baltimore's busiest road. Test borings, ground-penetrating radar and a camera-toting robot concurred.
The warning set in motion $2 million in emergency repairs that changed the way thousands of commuters begin and end their days.
Now about two weeks into the project, a 10-foot section of one pipe has been removed and excavators are closing in on the second pipe. Crews working 12-hour shifts are shoring up the soil and the surrounding drainage pipes to prevent a reoccurrence.
The target is to return the JFX to motorists the first full week in June.
In engineering and construction circles the project is small compared with road and bridge building jobs that run into the tens or hundreds of millions of dollars. But for city dwellers and Baltimore County residents it registers high on the lifestyle disruption meter, a fact that didn't escape transportation officials.
"There was no question that we were going to shut down lanes," said Scott Weaver, chief of the Baltimore Department of Transportation bridge engineering unit. "Public safety required it. But believe me, we didn't want to do it."
The reluctance is understandable. The JFX handles 120,000 vehicles each weekday, according to the most recent traffic counts. Taking away the left-hand lane in each direction cut capacity by more that 30 percent, forcing some motorists to find alternate routes.
But highway sinkholes are the kind of things that keep engineers up at night. During torrential rain last fall, two vehicles were swallowed when roads collapsed in Anne Arundel County and sinkholes closed lanes on Route 301 in Charles County.
"You can't afford to guess wrong on something like this. You can't afford to gamble," said Frank Murphy, deputy director of the city transportation department.
The JFX was built on a 35- to 40-feet thick bed of fill material — basically dirt and rock brought in from elsewhere. The damaged section of highway is the oldest, opened in December 1961. A gravity-fed drainage system there collects water from the road and funnels it into the Jones Falls.
At some point — engineers don't know when — age and the elements took their toll on a 15-inch diameter pipe about 61/2 feet below the surface and an 18-inch diameter pipe about 21 feet down.
With nowhere to go, water saturated the surrounding soil, turning a firm roadway foundation into a shaky base the consistency of wet beach sand. Water scoured away a space under the left-hand lane in each direction causing the pavement to sag.
While the city's construction engineers wrestled with the repair details, its traffic staff began plotting alternate routes and determining where traffic light cycles would have to be altered to prevent backups. Intersections without camera coverage were assigned to roving monitors in cars, said James Harkness, acting chief of the traffic division.
"Breakdowns and double-parked vehicles that are normally blips on our radar became major choke points that need to be handled quickly," he said.
On April 9, transportation officials briefed Mayor Stephanie Rawlings-Blake and her staff a final time and looked at the weather forecast.
"The issue was immediate closure versus waiting for the end of the week," Murphy said. "If the forecast had been rain, if there was any danger, we wouldn't have waited."
At the end of the evening rush hour on Friday the 13th, city workers pinched off the two lanes.