It’s a relief to read that the Washington Monument is structurally sound after a “Damage assessment at the top” [front page, Sept 28; “Team examines quake damage,” Metro, Sept. 28].
But what about at the bottom? What do we know about the monument’s foundation, and the soil and water table conditions beneath that foundation?
The monument is not built on bedrock, a fact that historically prompted structural engineers to reject any major excavations or vibrations near this iconic obelisk. It’s the reason the 1902 McMillan Plan’s elaborate Monument Garden was never built. Too dangerous.
Measurements taken in the 1960s and ’70s by the National Geodetic Survey showed an increased rate of foundation settlement, which engineers attributed to the lowering of the water table as a result of construction taking place nearby.
What effect would an earthquake have? Engineers compare the sand and clay soil under the monument foundation to jello. The earthquake shook that jello hard and with it the 555-foot solid masonry obelisk.
Are experts on site to measure any signs of trouble underground? Are subsurface conditions being evaluated? In the case of the monument, what we cannot see is at least as important as what we can.
Judy Scott Feldman, Rockville
The writer is president of the National Coalition to Save Our Mall.