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Risk and problem-solving

Making a site decision with incomplete information

By Review.LivePublished 3 min readHow we write

At 10:40 the excavator operator waves the superintendent over to footing C-6 of a new aircraft hangar. The bottom is soft, grey and wet, where the geotechnical report describes firm clay. Concrete for the 14 footings on lines A and B is booked for 13:00, and the geotechnical engineer cannot come before 08:00 tomorrow.

A cleared creek bank and survey markers show ground prepared for construction.
Photo: National Park Service (NPS Photo) on Wikimedia Commons · Hoover Creek Before Construction · Public domain — U.S. National Park Service · Cropped, resized, colour adjusted and sharpened. No claim to original U.S. Government works.

Decide on what you know, not on what you hope: write the decision in one line, separate the facts from the assumptions, and choose the option you could still undo if the missing fact goes against you. Waiting for every fact costs money, and so does guessing, and the pressure of the moment pushes people towards one or the other. Most site decisions are not all or nothing: part of the work can usually go ahead while the part in doubt waits.

  1. Write the decision in one line, with its deadline: "Do we pour lines A and B at 13:00 while C-6 is unresolved?"
  2. Make three columns: what you have seen or measured, what you are assuming, and what you do not know, with who can answer each unknown and when.
  3. Name the worst credible outcome of each option and whether you could recover: a footing poured on soft ground may have to be broken out; a footing held costs a day.
  4. Prefer what can be undone: concrete, backfill and cuts are permanent; a hold is not.
  5. Leave the condition as you found it until whoever owns the answer has seen it. Notice to the owner is covered in differing site conditions.
  6. Set a time to decide again, and record the basis the same day in a decision record.

Common mistakes

  • Waiting for certainty when part of the work could go on.
  • Digging deeper or adding fill before the person responsible has seen the condition.
  • Reading a report as fact for every square metre, when it rests on a few boreholes.
  • Not writing down what you knew at the time.

What to say

Reporting a decision made without every fact

  1. You:"Here is what I've seen, with photos."
  2. You:"This is what I'm assuming, and this is what I don't know."
  3. You:"I'm holding only this part; the rest goes ahead."
  4. You:"Nobody touches it until you've seen it."
  5. You:"We decide again at eight, when the answer is in."

Check your understanding

The drywall crew is about to board a corridor wall when it finds a pipe the drawings do not show, and the mechanical foreman is not answering. What is the reversible choice?

Show the answer
Leave that wall open, board the rest and photograph the pipe with a tape measure in the frame. Boarding would hide an unknown line behind a finished wall; one open wall costs little and can be closed tomorrow, once someone knows what the pipe is.

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