NOAA Unit Checking Washington Monument's Level

Experts from the National Oceanic and Atmospheric Administration's National Geodetic Survey are completing a leveling survey to determine whether an August 2011 earthquake shifted the ground beneath it.

The tallest and possibly most recognizable monument on the broad National Mall in Washington, D.C., is the Washington Monument. It sustained damage during a 5.8-magnitude earthquake centered in Virginia on Aug. 23, 2011, with some stones being cracked and mortar loosened. A survey is now under way to determine whether additional damage occurred that cannot be seen with the naked eye.

A group of experts from the National Oceanic and Atmospheric Administration's National Geodetic Survey are performing a leveling survey to determine whether ground shifted beneath the monument. NOAA says this is the first phase of a planned effort to help the National Park Service by regularly surveying the grounds of the National Mall.

Preliminary analyses indicated the earthquake did not cause significant vertical motion in the monument, but even slight changes could affect plans for repairing it, a job currently expected to cost $15 million, according to NOAA.

NOAA surveyors will take GPS measurements from the top of the monument later this year to determine whether it tilted because of the earthquake. NGS expects to update its leveling data for the mall every three to five years; the mall "is built largely on landfill and is slowly settling over time, causing ongoing maintenance concerns with many of the heavy monuments in the area," according to NOAA. "This long-term effort will provide the Park Service with better information to help in the preservation of historical structures, while providing a low-cost field training opportunity for NGS personnel. NGS and its predecessor agency have conducted periodic surveys of National Park Service sites around Washington since 1884.

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