The following conversation did not happen in a mall retail store that was being demolished for a rebuild.
"Hello, Mr. Fleming. This is Joe out here at the job site. Since you are the architect on this job, I thought I should let you know that we finished taking out all the existing ceilings and found a big surprise you won't like."
"We found a large concrete box sticking down from the 2nd level deck above. It comes down to about 10 feet above our floor. Me and the boys couldn't figure out what it was, so we went up to the store above us and looked around. It is their elevator pit!"
"Mr. Fleming... the bad news is that the front half of that pit will stick out into the new sales floor which will mess up your plans for a new high ceiling. At least, that's the way we figure it looking at your drawings. You did want a 12 foot high ceiling in sales, right? Mr. Fleming? Mr. Fleming! Are you still there?"
A few months earlier when I did the survey, I caught a glimpse of that concrete "stick down." It was really hard to find a good vantage point to see it, and it was even harder to locate it accurately. There were lots of HVAC ducts routed around it which obscured it. At first, I thought I was looking at the side of a concrete beam.
This discovery was a surprise for me because I had the tenant drawings of the store, including the HVAC page. They showed no indication that it was there. In fact, they showed their main duct runs going right through the area where the elevator pit was located. Maybe the elevator pit was installed after my store was built. Maybe it was there all along, and the previous design architects did not know it. If so, the construction crews found it and had to improvise and do an "end run" with their ducts.
Whatever the case, the important thing was the obstruction was found, documented thoroughly, and red-flagged in my report. With this information, the client could come up with a plan for how to proceed before it was a last minute emergency!