A news service of the NGWA Scientists and Engineers Division.
Recent Earthquake Could Impact Water Wells
What happens above the Earth’s surface was dramatically apparent from the August 23 Virginia earthquake in places from Mineral, Virginia, to Washington, D.C., but what’s not so obvious are impacts beneath the surface to groundwater.
While it’s too early to assess in Virginia and surrounding environs, earthquakes commonly cause fluctuations in groundwater levels and damage to water wells systems, said NGWA Public Awareness Director Cliff Treyens.
“Since aquifers are water-bearing subsurface formations, it makes sense that water levels and wells would be affected,” Treyens said. “One well driller after a California quake cited a well that produced 60 gallons per minute prior to a moderate earthquake slowing down to ‘practically nothing’ after.”
Sometimes the reason for such impacts is obvious. In bedrock formations, for instance, the well will be drilled until it hits a fracture or crevice that holds water. A moderate earthquake could easily alter that configuration, Treyens said.
Aquifers consisting of unconsolidated materials can compact, or become unstructured as a result of the seismic energy moving though them during the earthquake, in a process called “liquefaction.” This results in a loss of storage for groundwater and subsidence on the ground’s surface.
While surface structures are often designed to be earthquake resistant, the same cannot be said of water well construction. The result is that often wells are destroyed. Earthquakes also can affect groundwater quality, sometimes causing turbid well water.
There is one other earthquake/groundwater connection less well known. Water wells can actually function as seismometers of sorts.
In a sense, water wells can reflect the Earth tide, which is a separate, but related, phenomenon to the ocean tides. The Earth is “pulled” by the Moon much in the same way the ocean is. This “surface tide” can cause the water in a well to go up and down in the hole, referred to as oscillation. This oscillation can occur in the aftermath of an earthquake.
A water well in Christianburg, Virginia, has become renown, picking up 200 large earthquakes around the world since real-time monitoring began in 2004.
In related news, with Hurricane Irene on the way and water well flooding a real possibility in some areas of the East Coast, NGWA has information to provide water well customers on flooded wells.
An obvious concern is that floodwater loaded with bacteria, chemicals, or other pollutants may have gotten into the well, Treyens said. A less obvious concern is electrical shock if a nonsubmersible pump or any part of the well electrical system is flooded.
After a flood one should:
- Stay away from the well pump while it's flooded to avoid electrical shock
- Not drink the water from the well or use it for washing to avoid becoming sick
- Get help from a qualified water well contractor or pump installer to:
o Clean and turn on the pump
o Flush the well
o Disinfect the well
o Perform any other necessary maintenance.
As water wells are specialized systems that require knowledge and expertise to repair and disinfect, use bottled water or boil your water until a qualified water well system contractor can check out your well system, Treyens said.
Check with local health or environmental health authorities about other substances to test in well water following a flood, as there may be pollutants of local concern. Use a qualified drinking water testing lab to advise you on how the sample should be taken to analyze the results, Treyens added.
Learn more about information on water testing and water well maintenance that you can provide customers by visiting www.wellowner.org.
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