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Project report, leveling of the Washington Monument and the Washington Mall
  • Published Date:
    2012
Filetype[PDF - 620.02 KB]


Details:
  • Corporate Authors:
    National Geodetic Survey (U.S.)
  • Description:
    "On Tuesday, August 23, 2011 the mid-Atlantic area was shaken by a magnitude 5.8 earthquake centered near Mineral, Virginia. Events of this magnitude are highly unusual for the region around the nation's capital. Fortunately the effects of quake were generally mild and caused only modest amounts of structural damage to buildings and other structures. One structure that did incur some significant damage was the Washington Monument. In part due to its height of slightly more than 555 feet, the upper portion of the Monument suffered several significant cracks that have forced the closure of the structure until such time as repairs can be made by the National Park Service (NPS). Since that time NPS has been actively engaged in a number of efforts to determine the extent of damage caused by the quake to not only the Washington Monument but also the numerous other monuments and memorials in the area of the Washington Mall. One area of concern was what, if any, settlement or subsidence occurred in the area of the Washington Monument and others structures to the west including the Jefferson and Lincoln Memorials. Few visitors to the sites today appreciate that all of the structures from the Washington Monument west to the Potomac River are constructed on fill of sand, gravel and blue clay. A 1950 report by the U.S. Geological Survey shows the 25 foot deep foundation of the Monument is approximately 65 feet above bedrock. This type of fill can be especially vulnerable to the effects of soil liquefaction as have been noted in numerous other earthquakes. As it just so happened, at the time of the event, the National Geodetic Survey (NGS) had been engaged in developing an agreement with NPS to perform periodic geodetic leveling observations in the vicinity of the Mall area. NGS and its predecessor agency the U.S. Coast & Geodetic Survey (USC&GS) had conducted 17 different leveling campaigns in and around the area since 1884. Many of the surveys were performed as small projects including only certain parts of the area commonly referenced as 'The Mall.' This area is most often recognized by the public as that portion of the city which 2 extends from just east of the Capitol building to the Potomac River and sandwiched between Constitution Avenue on the north and Independence Avenue on the south. Many of city's biggest attractions are located in this area including buildings of the Smithsonian Institution and the National Gallery of Art on the east side and numerous memorials on the west such as those honoring Washington, Jefferson and Lincoln as well as World Wars I and II, Korean War and Viet Nam conflict. This hugely popular area is administered by NPS National Mall and Memorial Parks (NMMP). Since the various leveling campaigns did not cover large enough areas to give a consistent picture of any height changes that might be occurring in the area, the agreement being development between NGS and NPS would call for periodic reobservations of the Mall area, typically every 3-5 years that would provide sufficient measurements to bench marks outside of the Mall and in the same epoch so as to provide an accurate assessment of vertical motions that may be occurring"--Pages 1-2.

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