Quake did not sink Washington obelisk

WASHINGTON — The Washington Monument did not sink any farther into the ground as a result of last year’s 5.8-magnitude earthquake, government surveyors said in a report released Tuesday.

The upper part of the monument sustained several large cracks during the quake on Aug. 23, 2011, and the iconic obelisk will likely be closed for repairs until 2014.

The repairs, estimated to cost at least $15 million, will require large scaffolding to be built around the 555-foot monument.

The monument, built on land that used to be underwater, has sunk about 2.2 inches since 1901. Surveyors expected at least some modest settling as a result of the earthquake, but in a report released Tuesday, the National Geodetic Survey said the quake had made no discernible difference.

Dave Doyle, the project manager for the survey, said the lack of settling was a credit to the engineers who shored up the monument’s foundation in the 1880s.

“We’re talking about a rather huge object - 90,000 tons,” Doyle said. “It sits on a base that is constructed mainly of sand and gravel and clay. With a 5.8-magnitude earthquake, you sort of thought that there might be a little bit of motion.”