There’s more to slip, trip and fall accidents than the skid resistance of flooring and the tread of the footwear.  The cause of an accident also varies with the location of the accident and these can be categorized. (Refs 1, 2)  When an expert is asked about cause at the case- or insurance-claim assessment stage, he wants to know about accident location.  The category tells him a lot.

He thinks differently according to the category.  This is the same as him thinking differently according to the type of structure, component or material that fails in the built environment, as posted in earlier blogs. (Ref. 3)

You mention location in your briefing on the accident and the expert goes through the same process in forming an initial hypothesis on cause – an initial oral report – as for a structure that fails.  He considers::

• Your briefing – The location, category, technical issues and facts in your description of the accident
• His experience – What he’s learned investigating slip, trip and fall accidents
• Published material – The helpful information out there – a lot – on the different categories of accident location

There are many categories. (Refs 1, 2):

1. Level walkway surface
2. Level walkway surface and water
3. Floor mats – For example, mats can move as I found in one case
4. Changes in level
5. Lawns – Example, wet grassy slopes
6. Ice and snow – Including black ice on a sloping asphalt driveway that I slipped and fell hard on last winter.  Also skating ice that I fell on a couple years ago but I was wearing my ski helmet and only hurt my pride
7. Ladders – Reaching too far when on the upper rungs of a ladder and falling which happened to me a few years ago
8. Porches and balconies
9. Roads and sidewalks
10. Parking areas
11. Trucks – Getting in and out of trucks and also hurting yourself when securing load
12. Work place and construction sites
13. Residences (single and multi-family)
14. Play grounds and recreational facilities
15. Swimming pool decks and locker and shower rooms – Note how many have “Caution: slippery-when-wet signs”, and skid-resisting mats on dry sauna floors
16. Saunas – Floors can get wet from water bottles and dripping bathing suits
17. Ramps – I was very conscious recently of a very slight ramping-up to the entrance of a car show room.  It was subtle but there – and it was wet. 
18. Bathrooms – Examples: walk in showers and tubs
19. Kitchens
20. Stairs
21. Handrails and guardrails – Examples: rail graspability also rails that are too far apart on wide stairs
22. Elevators – For example, when they don’t stop exactly at floor level
23. Escalators

You might be interested in knowing that falls in the work place are the number one preventable loss type.  And in public places, falls are far and away the leading cause of injury. (Ref. 1)  There are lots of work places and lots of public places as can be seen in the above list.

I haven’t seen them but I’m certain percentages have been worked out for the occurrence of accidents at each of the above locations.  Also, on looking closer at each location, I’m certain percentages have been worked out for the following different elements in a slip, trip or fall accident at each location: (Ref. 4):

1. Surface covering
2. Lubricant
3. Shoe (slider)
4. Ambient parameters
5. Activity

And looking closer still at each location, I’m certain percentages exist of accidents that can be traced back to each of the following: (Ref. 1):

1. Design of the physical location
2. Managing the location
3. Maintaining it
4. Monitoring the location

Categorizing the location of slip, trip and fall accidents like this can help determine the cause of an accident.  This is similar to categorizing the structures in the built environment as a means of determining the cause of failure of one of the structures or one of the components.  This categorizing is why an expert can give you some understanding of cause at the case- or claim-assessment stage.

We categorize people to help a society function – and this works when done thoughtfully.  Why not categorize accident locations to help determine cause?

References

1. Di Pilla, Steven, Slip, Trip and Fall Prevention; A Practical Handbook, 2nd ed., CRC Press, Boca Raton 2010
2. Sotter, George, Stop Slip and Fall Accidents!: A Practical Guide, 2nd ed., Sotter Engineering Corporation, Mission Viejo, CA 2014
3. Jorden, Eric E., Update: Where does an expert’s initial hypothesis come from?  Posted March 18, 2019
4. Sebald, Jenn, System oriented concept for testing and assessment of the slip resistance of safety, protective and occupational footwear, Berlin 2009

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada. April 30, 2019 ejorden@eastlink.ca)   

Blog Update

I was remiss last week in not commenting on how the situation in sinkhole country relates to the interests of many of you in civil litigation and insurance.  I remember a vague feeling at the time that something was missing from my blog – I neglected to refer to the standard of care. (Ref. 1)

Last week’s blog commented on what an experienced engineer would do in an area susceptible to the formation of sinkholes – see below.

You’re certain to want to know for a failure in the built environment or an insurance claim that the standard of care was observed at a construction site.  We check this during a forensic investigation.

The standard of care for an undeveloped building site in an area with known foundation problems – like the risk of sinkholes – requires, at the very least, carrying out a geotechnical investigation.  Something similar applies to a developed site.

The investigation can be fairly routine for a compact site like a single building, bridge, wind turbine, etc. and the results can be quite accurate.  The investigation can also be inexpensive considering the cost of these structures.

Reference

1. How the standard of care is determined when a failure or accident occurs in the built environment. Posted June 28, 2014 and updated October, 2017

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Sinkhole news highlights a problem that can be fixed

(Originally posted last week, March 31, 2019)

That was quite a picture in the newspaper a few days ago of a sinkhole that appeared last August in Oxford, Nova Scotia. (Ref. 1)  And the pictures of the sinkholes in British Columbia a few weeks ago (Ref. 2) and before that – back to Nova Scotia – some time ago in Falmouth..

Striking pictures but sad too when homes are lost, and scary at the thought of potential injuries and death.

But it’s time to stop.  There’s no need for the formation of sinkholes to surprise anyone nor pose a risk..  Nor be a “…a money pit”. (Ref. 1)  There would be no news and no pictures if experienced engineers were involved before these areas were developed.  And every chance some of these areas would have been undeveloped.  Engineers would carry out a standard geotechnical investigation of the ground at a site proposed for construction.  Simple as that.

The news story mentioned a geophysical survey.  That’s an engineering technique that’s been around a long time.  The fact that this is sinkhole country – Karst terrain – has been known a long time too.

Karst is an irregular limestone area with sinkholes, underground streams and caverns. (Ref. 3)

Remote sensing geophysical surveys – sort of like MRIs in medicine – detect features in the ground of interest to land owners.  Features like voids or conditions conducive to the formation of voids.  Sinkholes start as voids in the ground.

Limestone bedrock, gypsum and salt dissolve in the water in the ground to form voids, caverns and underground streams.  The voids get larger with time and eventually the top, or roof of the void, appears at the ground surface – a sinkhole. The voids are said to migrate to the ground surface.

The most recent picture shows red soil around the perimeter of the sinkhole.  This is glacial till – soil deposited by glaciers 1,000s of years ago.  The soil is heavy and would cause the top of a void to break and appear at the ground surface sooner rather than later.

Investigating undeveloped Karst country for sinkholes

What would an engineer do if asked to investigate the foundation conditions at a proposed construction site?  For example, the site of a building, or any of the structures in an urban area, or a residential subdivision or a strip mall.  This would be an engineer experienced in geotechnical or geological work.

They’re not always asked – and it appears not always in Karst country – but what would he do if he were?

He would first check.the published geology maps and aerial photographs of the area available to all of us.  It’s called terrain analysis in engineering.  He would see in the maps that a large area of Nova Scotia – many square kilometres – is underlain by Karst terrain.  He would also see in the photographs evidence of large sinkholes like the one in the picture.  He would tell you that the area is susceptible to the formation of sinkholes.  He would also tell you that he can’t predict where the sinkholes will appear in a large area.

But tell him approximately where you want to construct a subdivision or strip mall and he’ll give you a pretty good idea of the risk of sinkhole development in a small area like that.  Not the location of all future sinkholes but the location of some, and the risk of others.  He would do this after carrying out a geophysical survey.  The survey could be expensive for an area proposed for a subdivision or strip mall.

I did a geophysical survey of an airport runway on South Andros Island in the Bahamas one time.  I was looking for voids that might form sinkholes.  A runway is not unlike a residential street or a strip mall.  You can be sure I ran a lot of closely spaced survey lines down the runway looking for voids.

Tell the engineer precisely where you want to build a house, a multistory building, a bridge, a road, etc., a tiny area, and he will tell you if and where sinkholes will form and undermine your structure.  He would do a geophysical survey.  This wouldn’t be that expensive for a single structure and a good investment considering construction costs.  You might consider relocating the structure after the survey..

If the risk of sinkholes forming is low and you still want to build there then he would drill boreholes at the location of your structure and any features of interest found during the geophysical survey.  Boreholes retrieve samples of bedrock like limestone or indicate when the borehole passed through a void.  It’s called ground proofing in engineering work that relies on non invasive, non destructive geophysical surveying and terrain analysis.

Summarizing, this is what the experienced engineer might do depending on what you need:

1. Terrain analysis of a large area of Karst country – square kilometres in size – using published maps and photographs
2. Geophysical survey of a small area possibly with a few boreholes
3. Geophysical survey of a tiny area – a proposed construction site – plus some boreholes  .

It wouldn’t take a “money pit” of money to investigate for sinkhole-forming voids if you know the precise location of your proposed structure.

Investigating developed Karst country for sinkholes

If you are concerned about the stability of a developed area, particularly foundation stability, then, depending on the size of the area and the preciseness of the information wanted, the engineer would go through the above steps.  The emphasis would be on Step #2 if you are concerned about a small area.  Or Step #3 if you are concerned about a single structure and wanted precise information.

***

The approach for developed or undeveloped land would be much the same – that of a fairly routine engineering investigation by an experienced person.  It wouldn’t be so expensive for a single structure, a tiny area – a few 1,000s of dollars rather than many 10,000s.  But more, of course, for a larger area, particularly if a lot of precise information was wanted.

It wouldn’t be so newsworthy either particularly if undeveloped land was being investigated.  The reporter’s eyes would glaze over at the thought of covering an engineering story like that.

That’s where we need to get to in Karst country – investigate before at reasonable cost not after when newsworthy sinkholes and problems develop.

References

1. The Chronicle Herald, Thursday, March 14, 2019 page A3
2. What’s wrong with this (sinkhole) picture near Vancouver. Posted February 20, 2019
3. Merriam-Webster dictionary, March, 2019