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Sinkhole & subsidence warning signs:
This article describes the visual signs that a sinkhole is likely or is already developing in an area: sinkhole warning signs.
We also discuss 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.
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- Daniel Friedman - Florida Suncoast ASHI Educational Seminar - 1 May 2004, updated 2007, 2008, 2014
Portions of this text are extracted, quoted, or paraphrased from references provided; a key resource author was Sarah Cervone at Reference-1.
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.
See "Developing your X-Ray Vision - A Promotion Theory for Forensic Observation of Residential Construction - Levels of Fear, and how to use them to find and report significant, hidden problems, http://InspectAPedia.com/structure/x-ray.htm
Also see The Nature of Vision - Inspecting Complex Systems - When and Why Inspectors "See" or "Don't See" Things Which are Present - InspectApedia.com/vision/vision.htm. Comments and content suggestions are invited.
How big are sinkholes?
Most sinkholes are 10 to 12 feet in diameter.
A discussion of foundation repair methods such as driven piers, helical piers, or other structural repair methods may seem in order, but if a sink hole is big enough to swallow a home, the first order of business for areas where those problem soils are found (California sinkholes, Florida sinkholes, Pennsylvania sinkholes over mines, Texas sinkholes, often over salt domes and possibly affected by wastewater disposal back into the ground during oil drilling, others) is to recognize the signs that sinkholes have plagued a neighborhood and/or that a sinkhole is possible, probable, or an imminent risk.
Synonyms and similar terms for sink holes include: shake hole, swallow hole, swallet, doline, cenote, moulin, and glacier mill.
Significant to property inspectors, the first signs that a sinkhole was developing in Dasietta Texas was the opening up of cracks in the ground and in the roadway on the morning of the collapse. Because a sinkhole can develop suddenly and expand rapidly, the sudden appearance of cracks in the earth should be taken as a serious safety hazard at any location, more so in an area where sinkholes are known to occur.
What about cases where a sinkhole collapse may be ongoing or imminent? Recognizing indicators of potential sinkholes can reduce but not eliminate this risk. This limitation should be stated clearly by any home inspector in an area where sinkholes are known to occur or wherever one is suspected.
If a sinkhole is already visible near an inspected property or if signs of a sinkhole are observed this information should be cited by the inspector as a potential safety concern and significant expense requiring immediate professional action.
Is it a sinkhole or some other kind of soil collapse? Does a soil collapse threaten nearby buildings? Is a soil collapse dangerous?
Examples of other possible buried components that can lead to sudden or gradual soil subsidence, apparent sink holes, and collapses are given below. These, too, can be very dangerous, as we describe in the case of collapsing cesspools or even buried trees and stumps. But their probable impact on nearby structures may be less than from a classic sinkhole provided the collapse is not already close - within 50 feet - of a building.
Be careful: excavation or soil subsidence near a building can lead to a dangerous foundation collapse. Here are some other collapsing ground hazards:
Note on cesspool collapse hazard - question about sudden back yard cave in
Watch Out: Immediately rope off the area of any soil subsidence or suspected old septic tank or cesspool area, and mark it plainly as unsafe so that a wandering neighbor, adult or child, does not go near nor fall into this hole. It could be quite dangerous.
See CESSPOOL SAFETY WARNINGS for examples of potentially fatal cesspool collapse hazards.
Although a sinkhole can form without warning, specific signs can signal potential development: 
Site and Neighborhood Observations - ordered from general-area to site-specific to property-specific
This constitutes an immediate potential safety concern. ASHI Standards require you make appropriate notifications.
A rapid sinkhole caused by well drilling or other sudden alterations to the terrain may not give any warning signs. Otherwise, the collapse process usually occurs gradually enough that a person may leave the affected area safely.
The final breakthrough leading to a sudden sink hole collapse can develop over a period of a few minutes to a few hours.  or select a topic from the More Reading links shown below.
Continue reading at SINKHOLES - IMMEDIATE SAFETY ACTIONS or select a topic from the More Reading links shown below.
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Frequently Asked Questions (FAQs)
Question: insurane company won't cover sinkhole damages
(Aug 20, 2011) Jackie Venable said:
Jackie, you may need to consult an independent insurance adjuster who will function as your advocate. S/he will in turn charge a fee, hire experts to evaluate the problem and basis for your claim, will negotiate with the insurance company in your behalf, and generally annoy them.
Question: sinkhole below brick sidewalk?
(Mar 13, 2013) Anonymous said
A brick just fell though and there ia sand about six inches below. It ia a sidewalk. What do u think
I think you should rope off the area and ask the city to take a look - could be a water main or other thing undermining the walk - you haven't said where you area or if it's a sinkhole prone area.
Question: cracks across a street need inspection
(Jan 28, 2014) Anonymous said:
Call your city building department
Question: my yard appears to be sinking, what do I do?
(Feb 18, 2014) Anonymous said:
I am starting to see areas in my back yard that appear to be sinking. I have been watching them for a few months and they appear to be getting larger. What should I do?
(Mar 7, 2014) lee said:
there is a crack coming in the back yard seems to be getting wide quite quickly also around the foundation of house in same area the ground is sinking near the foundation leaving a wide gap all happening quickly we don't live in a comon sink hole area
Anon you don't say where you live - in some areas sink holes are a common and serious hazard
But just from your description it sounds as if you ought to
1. from a good distance away rope off or prevent access to the sinking area immediately
2. call your city building department and ask for an onsite inspection and advice
If you want to send us photos using the CONTACT link found at page bottom or top I may be able to comment further; do keep us posted.
There are lots of causes of sudden subsidence besides a geological formation associated with sinkholes; examples are underground water piping or sewer line leaks, buried stumps and trees, or collapse due to mining activity; for safety it would make sense to ask for help from your building department as a start, and to rope off or keep people out of the area.
Question: husband stepped into a hole yesterday that was approx. 1 ft. deep - Kentucky Sinkhole warnings
(Mar 12, 2014) Anonymous said:
My husband stepped into a hole yesterday that was approx. 1 Ft. deep. We have had smaller ones outside under our large weeping Willow tree. Our neighbor has a underground well close to our home, which is close to our Weeping Willow tree. (75 ft.). The hole he stepped in was close to an entrance to his building outback.
He had to put something over it until he can fill it in. He has filled other holes up in the past. Our house has a door that won't close right, and a crack in our ceiling over the same door, (The crack has been there for years, but is getting worse, and in the garage ceiling. Last year it was my sons bedroom door that was hard to shut, but it is okay now. Just was wondering what could be going on. Thank you. Sandy
I live in Eastern Daviess County Ky. Thanks
Sandy, if it were just a small hole opening up in a yard I might suspect settlement around old buried debris.
But when you add that a door no longer closes and the ceiling is cracked, those suggest more serious foundation settlement - enough that it's worth having a more expert assessment. Foundation settlement can occur due to sinkholes but also due to soil compaction combined with water movement (roof spillage, surface drainage, underground water etc).
Certainly sinkholes do occur in Kentucky. Recently (3/5/2014) the Washington Post reported that a sinkhole opened beneath the Corvette Museum in Bowling Green south of Louisville.
And as has been studied by the University of Kentucky, there are karst formations in your state - a principal source of sinkhole formation.
I suggest contacting your building department to ask for some assistance. We can't say if the sinkhole risk to you is urgent or not based just on a text exchange.
I will add Kentucky karst references and information to the article above.
I add according to the U.K. experts at the Kentucky Geological Survey - U.K., www.uky.edu/KGS/gis/sinkpick.htm no sinkholes have been mapped in Daviess - your county in Kentucky.
So if investigation confirms that you and your neighbor are seeing actual sinkholes that could be important
Question: sinkhole risks to adjacent properties
(July 27, 2014) JoAnne Hahn said:
If there is a repaired sinkhole in an adjacent property is my house at greater risk?
We can't assess that sinkhole risk by text. You need an onsite spent. On one hand we now know your house is in an immediate sinkhole area. On the other we can't guess how unspecified work at a neighbor might reduce or increase your risk.
The risk to your house depends on the type of sinkhole and the general sinkhole risk in your area too.
Question: pulling slate out of the ground exposed a tiny hole
(Aug 22, 2014) kim said:
I pulled a few pieces of slate out of the ground in my driveway, I noticed a quarter sized hole. It was weird, so I took the hose to see if it would fill up, but it didn't.
The quarter sized hole was inside of the 10-12 inch hole where I pulled out the piece of slate.
Kim I can't know what you are seeing, but it MIGHT be an old cover over an old septic tank or drywall and so is indeed qyuite possibly very dangerous.
Or it might be a rodent hole - not dangerous unless you get bitten.
You want to rope off the area and keep people away until an excavator or other expert has figured out what's there. Nobody but a mouse is going to fall into a quarter-sized opening, but if there is a larger hidden problem you don't want someone falling into the opening.
Questions & answers or comments about sinkholes: what causes sinkholes, what are sinkhole warning signs, and what visual clues can indicate that sinkholes have occurred or are a risk at a property
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