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Location of sinkhole type soils in Virginia - VA DMME Sinkholes & Subsidences in Virginia

Sinkholes in Virginia.

This article describes the location & type of sinkholes occurring in Virginia.

This article series explains what sinkholes are and why they occur, describes their effects on buildings, and gives building and site inspection advice useful in identifying areas where there is an increased risk of sink holes at properties.

The photograph (above-left) of a sinkhole opening in a residential yard in Pennsylvania is from Kochanov, W.E. and illustrates the child hazard or even adult sinkhole hazard that can be formed by storm water drainage.

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Sinkholes in Virginia

Virginia sinkhole photo - VA DMME

The Virginia Department of Mines, Minerals, and Energy reports that sinkholes have been reported in that state since colonial times.

“In the spring of the year 1780, the earth at the bottom of this sink suddenly gave way and fell into the cavity below, forming a circular aperture about the ordinary circumference of a common artificial well . . .

There being no artificial or natural means to prevent the earth immediately about the well from falling in, the aperture is greatly enlarged, forming a sloping bank, by which a man on foot can easily descend within eight or ten feet of the water

.... The whole depth of the cavity is thirty or thirty-five feet” (Kercheval, 1850, p. 273).

As in several of the other locations of sinkholes around the U.S., Canada, and other countries, in Virginia sinkholes are associated with karst formations. The sinkhole photograph above (from Virginia's DMME) shows a sinkhole that formed in Russell County, Virginia. According to the DMME, [quoting]

In Virginia the formation and modification of sinkholes (also known as sinks, dolines and dolinas) is a natural process in areas underlain by limestone and other soluble rock. The location and rate at which sinkholes form can be affected by man’s activities.

Sinkholes are basin-like, funnel shaped, or vertical-sided depressions in the land surface. In general, sinkholes form by the subsidence of unconsolidated materials or soils into voids created by the dissolution of the underlying soluble bedrock.

The rock exposed in a collapsed sinkhole is usually weathered and rounded, but some sinkholes contain freshly broken rock along their steep sides. Freshly broken rock may indicate that the sinkhole has formed by the collapse of a cave (naturally occurring) or a mine (man-made).

Where sinkholes and caves have formed by the dissolution of soluble rock, such as limestone, dolomite, and gypsum, surface water is uncommon and streams may sink into the ground.

This type of topography, formed by dissolution, is referred to as karst terrain. In karst terrain, sinkholes are input points where surface water enters the groundwater system.

Also see WHAT IS KARST ?

Signs of sinkhole formation in Virginia

Although a sinkhole can form suddenly and without warning, this list, courtesy of the state's department of geology, lists several specific signs that can signal potential development:

Location of Sinkholes in Virginia

Location of sinkhole type soils in Virginia - VA DMME

The VA DMME [and the Virginia Division of Geology and Mineral Resources within the DMME]provides the map showing the location of sinkholes by underlying cause and probability. Quoting:

Sinkholes are most prevalent in karst terrains, but they occur throughout Virginia. Areas which may contain sinkholes:

  1. Subsidence/sinkholes are related to mining activity or soil piping;
  2. Karst, sinkholes are related to the dissolution of limestone and dolomite (refer to Hubbard, 1983 and 1988, for more detail) or soil piping;
  3. Sinkholes are very rare and are related to soil piping;
  4. Sinkholes are rare and are related to soil piping or dissolution of sparse carbonate rock;
  5. Sinkholes are related to the dissolution of shell concentrations in sand and soil piping.

Readers should see SINKHOLES - IMMEDIATE SAFETY ACTIONS, and also

see FOUNDATION CRACKS & DAMAGE GUIDE

and CESSPOOL SAFETY WARNINGS.

The bare minimum that a property owner needs to know about sinkholes or any other sudden subsidence of soils at a property is that these conditions might be very dangerous.

Someone falling into a sink hole or into a collapsing septic tank could be seriously injured or even die.

If a suspicious hole, subsidence, or depression appears at a property the owner should rope off and prevent access to the area to prevent anyone from falling into the opening, and then should seek prompt assistance from a qualified expert, geotechnical engineer, septic contractor, excavator, or the like.

Virginia Sinkhole & Subsidence Resources

Daniel Friedman - Florida Suncoast ASHI Educational Seminar - 1 May 2004, updated 2007, 2008, 2014, 2019, 2022.

Portions of this text are extracted, quoted, or paraphrased from references provided; a key resource author was Sarah Cervone at Reference-1.The text document is InspectAPedia.com/vision/Sinkholes_Subsidences.php - © 2020 - 2021 Daniel Friedman All Rights Reserved

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: are there sinkholes in Rockingham County VA?

Red area marks sinkholes and karst terrain, Virginia Division of Geology and Mineral Resources: Geologic Hazards cited & discussed at InspectApedia.comArianne Young said:

I heard where Misty and Meadows meet in Rockingham County, Va are over a sink hole. How can I find out if the builders built these duplexes over a sink hole?

Some of us have notices doors don't close tight, windows as well can be difficult to close...this is zip code 22801

Thank you for any direction or guidance you can give us. Thank you.

Image source, VA, DMME, retrieved 2019/11/18 original source: www.dmme.virginia.gov/DGMR/sinkholes.shtml

[Click to enlarge any image]

Reply:

Arianne,

Rockingham county is just north of where I went to school, in Rockbridge County Virgina; by this map provided by the VA Division of Geology and Mineral Resources, both Rockbridge and Rockingham are along the northwestern state border - that RED area in the DMME's map, showing where there are significant karst formations - i.e. in areas of sinkhole risk.

We already know that. There's not "one" or "a" sink hole along that area; rather it's an underlying type of rock formation (karst or limestone) that means there's risk of sinkholes and subsidences.

Beyond that, if there is settlement or signs of settlement where your duplex homes are located, it'd make sense to bring in a local geotechnical engineer who can inspect the properties for patterns of subsidence or movement and if justified, and if a specific sinkhole issue is not already known, she can conduct soil borings to investigate further.

Let me know what you're told as that'll certainly help other Virginia readers in Rockingham and nearby areas.


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