How I was tyrannized by the obvious during an engineering investigation

It can happen to any of us, and it finally did to me.  I was tyrannized by the obvious when investigating the cause of flooding in a large, three story building.

A building renovator called me after water was seen on the furnace room floor by staff of a veterinary practice.  They had gone to the room where materials were stored and saw a few millimetres of water on the floor.  Not a lot but still.

The renovator said the building which was erected in the 1960s was on a concrete, ground-floor slab, on low land and near a lake.  The furnace room was enclosed by concrete block walls.  The flood water had pooled on the slab.  He estimated that the concrete floor slab was about five feet above the nearby lake surface.

When i went to examine the site I saw that the five feet was about right and that the furnace room was an estimated 50 feet from the lake shore.  I was also told that the lake level was higher than normal due to a lot of rain this spring.

The grounds around the building sloped down slightly to the lake shore.  The front and right side of the building were paved.  There was a lawn at the back and an old paved boat ramp on the left.  The surface of the boat ramp was bumpy after many years.

The corners of the furnace room were still wet where the concrete block walls rested on the concrete floor.

I had a good look around then walked across the floors of the different rooms in the practice.  They were a little uneven which wasn’t so unusual for an old building.  But my look around wasn’t as good as it might have been and I neglected to look in the small room adjacent the furnace room.

My examination complete I met with the owner and the renovator.  I noted how the water rises in a lake during frequent rain storms.  It also rises in dug wells.  The water in a well is the water table. The surface of the water table in the ground near a lake shore is usually higher than the lake.  There is also water in the soil above the water table due to capillary action – this is when water rises in the small voids in the soil above the water table (Check high school physics)

This higher water table plus some surface water runoff across the asphalt at the side of the building could explain the presence of the water in the furnace room.  It was obvious.  I mean, the building was so close to the lake with high water levels not seen in recent years and the furnace room floor was near the lake surface and the water table.

The irregular boat ramp was typical of frost heave due to water in the ground – a high water table and capillary action during wet springs over the years – and would back up this obvious conclusion further.

I talked about different ways of preventing water getting into the furnace room.  These included the obvious – terrible word – better perimeter footing drains and/or a sump pump.in the furnace room.  A sump pump is a pump in a depression or hole in the ground – a sump.

The sump pump was decided on as the least expensive and one that could be constructed several feet below the water table to draw it down below the furnace floor.  That decision was left with the building renovator.

I left the site after about an hour – an efficient examination and consultation, or a  hurried one?

A few hours later the renovator called to explain that a staff member had gone in the wash room – the one room I hadn’t gone in – adjacent the furnace room and found a burst water pipe, the real cause of the flood in the furnace room.

I was tyrannized by the obvious and guilty of expectation bias.  The moral of the story?  If it’s obvious, keep on truckin’ and do more investigation.

 

 

 

 

So, who knew the St. John River would flood like that?

I thought of the news reports on a Friday or Saturday that predicted the Saint John River flood would peak the following Tuesday.  And that happened as predicted.  But I was surprised that the record-breaking nature of the flooding was not also predicted – a week, 10 days or two weeks beforehand.  I can’t help but think that somebody knew or should have.

I’m certain there are well-developed and accurate models of flow in the St. John River and of contributing factors in the river’s watershed including snow cover and weather.  These would be hydrologic and meteorologic models developed from empirical data collected in the watershed over many generations if not centuries.  We have models in forensic engineering investigation that serve us well too.

Sounds technical but hydrology is simply the study of the flow of water in a watershed and meteorology is the study of weather.  Put them together and you’ve got a powerful tool for predicting if a river is going to flood, when this will happen and how high.

A model is simply a set of ideas and numbers that describe the past, present or future of something such as an economy, business or, flow in a river.  Models are built using measurements and observations – empirical data – of the things that characterize what you’re interested in.

A street map is a model.  It shows the location of streets and other features of interest in an area.  Things like businesses, buildings, the local coffee shop, etc.  It doesn’t show things you’re not interested in like the height of the buildings and the level of the streets.

Good and accurate models:

  • Fit the empirical data from which they’re built
  • Explain past observations – like why the river flooded in the past
  • Predict future observations – like when the river will flood again
  • Are simple and inexpensive to use

Exhaustive data collection and study of flow in the River would have been done for design and construction of the Mactaquac Dam in 1968 – a few kilometres up river of Fredericton – and during the 50 years, half a century, after the Dam was operating.  So why not an accurate prediction of the historic flooding – not an inch or so above all previous highs but something like a foot?

We rely on models in the forensic engineering investigation of the cause of foundation failure.  Foundation design and construction is closely tied to the semi-empirical science of soil mechanics – a science partly based on measurements and observations and partly on theory.  This science developed in the early 1900s and holds us in good stead in a forensic investigation.

Annual flooding in the St. John River was being recorded each year long before the early 1900s, and the weather – temperature and rainfall – and conditions in the watershed – snow pack – were being noted.

So, I would put my money on the existence of accurate models that would predict with a respectable degree of accuracy, a week or two in advance, that New Brunswick was going to be flooded-out.  These models would include data on how the Mactaquac Dam is operated in storing and releasing water.

I was in contact with a professional forester who lives in Douglas a short distance up river of Fredericton.  He wonders too about the flooding and also noted the Dam and it’s operation as a feature in the watershed.

I can’t help but wonder if a similar situation exists in British Columbia with the flooding there.

References

  1. Giere, Ronald N, Bickle,John, and Mauldin, Robert F., Understanding Scientific Reasoning, 5th ed., 2006, Thompson Nelson, Toronto
  2. Wikipedia, May 14 and 15, 2018

How you can help break the expert evidence logjam

It sounds like a commercial but you can help break the logjam by reading Dr. Ruth M. Corbin’s paper on how we experts are helping. (Ref. 1)  Then you suggest what might be included in follow-up studies to her pilot study of 152 experts.

You might remember from my blog earlier this week that the logjam is the different perspective of expert evidence held by the courts as distinct from the experts. (Ref. 2)

Ruth calls for follow-up research on the following questions:

  1. Empirical research to strengthen the evidence-based foundation of future policy
  2. Economical modeling to complement the Supreme Court’s call for a “cost-benefit” analysis of expert testimony, and,
  3. Practical steps toward creating a forum for direct communication between experts and courts

We’ve got to get Atlantic Canada input to these follow-up studies – there’s no information on the role we had in the earlier studies.

In my earlier blog, I suggested including the following in follow-up studies: :

  1. Future studies and perspectives must be evidence-based.  I was prompted to suggest this on learning that the court’s view of expert evidence as revealed in the pilot studies was not so evidence-based.  It was this view as I understood it that influenced the policy on rules governing experts
  2. Economic modelling to complement the Supreme Court’s call for a “cost-benefit” analysis of expert testimony must include an identification of the principles governing the cost control of civil litigation involving experts.  You can’t do a reliable cost-benefit analysis without accurate expert costs arising from conformance to these principles.
  3. The role of the middle man, the advocate, in direct communications between experts and courts must be carefully spelled out.

Summary

Read Dr. Corbin’s paper – you’re in for a treat -, and possibly my blog and take on the situation, then send your comments to her.  Don’t be too refined, just get something out there like in brain storming.  Send your comments and suggestions to info@corbinpartners.com  I found Dr. Corbin’s assistant very good, responding quite quickly to my queries and promptly forwarding comment onto Ruth.

References

  1. Corbin, Ruth M., Chair, Corbin Partners Inc. and Adjunct Professor, Osgoode Hall School, Toronto, Breaking the Expert Evidence Logjam: Experts Weigh In, presented at Expert Witness Forum East, Toronto, February, 2018 (Google the paper and Ruth’s name)
  2. How experts are helping break the expert evidence logjam.  Posted April 30, 2018