Sinkhole or drywell collapse in New York (C) Daniel Friedman Sinkholes & Sudden Ground Subsidence: Action Guide

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Immediate safety actions to take if you discover a sinkhole.

This document suggests some safety-steps if you observe a sudden yard collapse - a potential or actual ground subsidence, and discusses safety concerns as well as 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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What to do if a Sinkhole or Soil Subsidence is Observed or Suspected at a property

Photograph of a sink hole swallowing a house in FloridaThe 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.

Quoting from our sink holes article

If a sinkhole is already visible near an inspected property or if signs of a sinkhole are observed the observer and/or property owner should contact local authorities (building department, police, fire department, depending on the size, location, and apparent seriousness, and the area should be roped off for safety.

If a sinkhole is noticed during a building inspection this information should be cited by the inspector as a potential safety concern and significant expense requiring immediate professional action. Synonyms and similar terms for sink holes include: shake hole, swallow hole, swallet, doline, cenote, moulin, and glacier mill.

Safety Warning: Sinkholes or even small soil subsidences can be an immediate potential life-safety concern. For home owners, inspectors, professional and trade association standards, building inspection & home inspection standards, and in some states, inspector licensing regulations (should) require you make to appropriate notifications.

  • Notify all parties: occupants, owners, real estate agents, buyers
  • Notify the local Water Management District
  • Fence or rope the hole off or arrange for this action to be taken immediately
  • Keep children away!
  • Protect the area from garbage and waste
  • The property owner should be advised to contact their homeowners insurance company
  • You may inform the parties that there are engineering firms specializing in detection and evaluation of potential or evident sinkholes
  • Record in your report the notifications and actions you took

Article Contents

  • Inspecting a property for signs of sink holes
  • Report of sudden back yard collapse
  • Causes of sinkholes and sudden soil subsidence
  • Sink hole damage and risks to buildings
  • When to hire a geotechnical engineer for sinkhole or soil testing
  • Directory of geotechnical engineers with whom to consult for help in assessing sinkholes & subsidences & their effect on buildings (see SINKHOLE DAMAGE REPAIRS )

How to Research an Apparent Sinkhole in Your Neighborhood

  • Dig: Hire a professional contractor experienced with sinkholes to excavate a bit in the hole before it is filled-in, to see what debris is in the opening. You may find components of an old septic tank, cesspool, drywell, dug well, building foundation, or other material that can help explain the cause of this sinkhole.
  • Check with local building officials for reports of other subsidence events in the neighborhood and identify their cause
  • Check with area contractors, excavators, who offer services that cause them to encounter soil subsidences and apparent sinkholes to ask what has been observed in your area.
    All American Water Line & Sink Hole Repair Service‎New Brunswick, NJ 08901(732) 249-2151‎ may have people who can assist.
  • Pay for an initial consult with local geotechnical engineers to ask the same question.
  • Determine the type of sinkhole and its cause. Keep in mind that people use the term "sink holes" more broadly than the classic sinkholes that I discuss at our website.

Classic sinkholes have their origin in earth formations, possibly aggravated by very large scale human-directed operations such as coal mining, oil, gas, or water removal from the earth, etc. Those sinkholes have large-scale underlying conditions.

Local, individualized "sinkholes" may be caused for example by soil wash-out from a burst water main below a city street. Or a sudden collapse of a buried cesspool, or soil subsidence over locally-buried brush and trees.

Local individualized sinkholes may still be dangerous, but once their cause is understood, affected property owners can more reliably and more easily estimate the chances of that sinkhole's spreading, increasing, or suddenly reappearing under a nearby building.

What to do About a Sudden Subsidence or Yard Collapse

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.

We are elated that no one fell in to the hole, and that no one walked-over and fell into what may have been an imminent collapse well before it was so visible - such catastrophes can be fatal.

Better Off if it is Not a Sinkhole

If the back yard cave-in is nowhere near any buildings, and if you can establish that it is not a true sink-hole but rather something local like an old cesspool collapse, it probably is not a risk to the building foundation. At events such as this one it is proper to ask if the cause was an old septic tank, drywell, or cesspool, long abandoned and not filled in.

Local Flooding and Sinkholes

However the area where this back yard sinkhole was observed has been reported to produce (smaller) soil subsidences and "sinkholes" due to the combination of clay soils, poor drainage, and a history of local flooding in times of heavy rain.

For example see Sinkholes in Whitestone New York Associated with Flooding Conditions.

Signs of Old Septic or Drywell Components

Look at and in the hole itself and at any debris to see if you see pieces of piping (upper right near the drywell in the photo) - identifying these can save you some future worry and maybe geotechnical engineering costs - that is, if we can be sure it was an old tank and not a sinkhole the risk of other sudden collapses and sinkholes is of course less. In this case the piping visible in the photo was identified by the owner as electrical, from an electrical lighting pole that fell into the opening, not septic components.

The light colored material in the hole in our photo above was considered to be due to clay soils, not sewage waste.

Finally, if it was an old septic tank, or cesspool, warn neighbors whose homes are of similar age that they might have the same condition and the same hazards lurking.

What if it Is a Real Sink Hole?

IF there remains a concern that this is a true sinkhole the risk of other property subsidence that could also threaten buildings could be important.

Your local county and highway or building departments can tell you if sink-holes have been found in your area - you may need the services a local geotechnical engineer to inspect the site, possibly taking soil borings, and then advise you further. Other clues about imminent sink-holes and sink-hole collapses are discussed at SINKHOLES, WARNING SIGNS.

Sinkhole Repair Services

Companies identify themselves as sinkhole damage repair experts are listed at SINKHOLE DAMAGE REPAIRS or select a topic from the More Reading links shown below.


Continue reading at SINKHOLES COURSE - X-Ray Vision? or select a topic from the More Reading links shown below.

Suggested citation for this web page

SINKHOLES - IMMEDIATE SAFETY ACTIONS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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