The Maryland Transportation Authority reopened all lanes of the Bay Bridge around noon today, after unusual vertical movements had triggered an unscheduled review by about 30 inspectors.

Maryland Transportation Authority Executive Secretary Harold Bartlett said the inspectors determined there had been no damage from the vertical movements, and he expected both spans to be open for the evening commute.

The authority chief said that as far as officials could determine, the cause of the up-and-down movement appeared to be some heavy-duty tarpaulins that were installed about two weeks ago to catch paint chips and other debris from the current power-washing project on the bridge from falling into the bay below. He said the vertical movement was likely caused when an unusual wind system moved through the area, catching the tarp like a sail.

"The wind probably caught it at just the right angle and created some lift," he said. "It's been dismantled at this point. We've completely taken it down."

Bartlett said the authority would seek a better method of keeping debris from polluting the water.

"It just means that as we go forward here we're going to have to determine a different way to do the containment system."

Westbound traffic on U.S. 50 was backed up for more than six miles at the Chesapeake Bay Bridge Tuesday morning, due to the unplanned closure of the western span.

The backup of westbound traffic at times extended to the Kent Narrows Bridge on the Eastern Shore, according to state officials.

Bartlett said the MdTA decided to keep the three-lane westbound bridge closed and to wait for daylight for a visual inspection. He said the authority set about 30 inspectors onto the bridge and used a device called a "snooper" to examine the underside of the span.

"Every incident that happens on the bridge we take seriously. We're always going to err on the side of being safe and cautious," he said.

In the early hours, traffic was limited to one lane in each direction on the eastbound span. Bartlett said that when the westbound backups became especially severe, the authority cleared the bridge and allowed two lanes of traffic to drive west on the eastbound span. When the eastbound traffic then backed up, he said, two-way traffic was restored.

Bartlett said the closing of an entire span during peak travel hours was "very unusual."

"Under most circumstances the only time we have a closing is for work we're doing on the bridge," he said. In most cases scheduled maintenance work that involves lane closings takes place at night.

Though she finally got to work at about 11:52 a.m., Jill Kubatko, a Grasonville resident who commutes to the Natural Resources Police office near Sandy Point State Park, had been sitting in westbound traffic for three hours at about 10:40 a.m. and still hadn't reached the bridge itself.

Kubatko, a former Sun employee who said her commute normally takes 15 minutes, said she passed the time by redoing her makeup, having breakfast and signing on to Facebook. Considering the extreme delays, she said, her fellow drivers seemed to hold up well.

"Everyone seems fairly calm," she said. "One guy stepped out and went to the bathroom."

August is one of the busiest travel months for the Bay Bridge, said Kelly L. Melhem, deputy director of communications for the Maryland Transportation Authority. According to MdTA statistics, she said, an average of 82,000 vehicles a day cross the bridge in August, 41,000 in each direction. From July 1, 2010 to June 30, 2011, more than 27 million vehicles used the bridge, she said.

Edward Gunts contributed to this report.

michael.dresser@baltsun.com