In When the Going Gets Tough – Analyzing Concurrent Delays, Thelen Reid's Andrew D. Ness writes that "Proving or disproving a construction delay claim is a substantial undertaking in the best of circumstances. But the analysis of construction delays takes a major leap in difficulty when there are multiple sources or causes of delay with interrelated effects." The construction expert witness can opine on what Ness describes as:
One Activity – Multiple Delays
The most straightforward situation involving multiple sources of delay occurs when there are two separate causes of delay to a single work activity. For example, an owner-directed change may have caused a particular activity to be less efficient while at the same time the contractor may have used a smaller crew or less efficient equipment than planned to perform the work. How then is the extended duration of the activity to be apportioned between owner and contractor? Almost every impact claim contains issues of this nature. It may seem apparent that the owner-directed change had an adverse effect on the time to perform a particular activity, but whether the impact was substantial or insignificant is debatable, and it is a challenge for either side to quantify the effect specifically.