August 8th, 2017
By Josh Bennett
The use of expert witnesses is very important in the defense of a blasting damage claim. The blasting contractor will likely need to retain more than one individual to act as an expert witness in the case. As we discussed in the last post of this series, one of those individuals will likely be an explosives engineer/seismologist.
In addition to an explosives engineer/seismologist, the blasting contractor will usually need to retain a structural engineer with a construction background to determine whether the owner’s alleged damages were caused by something other than the blasting by looking at construction deficiencies and pre-existing damages.
Claims for blasting damages are usually for cracks in a structure. Very few buildings have been subjected to forces generated by blasting, yet it is extremely rare to find a structure completely free of cracking (Whittle, 2012). Temperature variations cause repeated expansion and contraction of materials, leading often to the development of cracks in cement block foundations, stucco walls, and other brittle substances (Whittle, 2012). Additionally, settling, slippage, and other earth movements place stresses on foundations and the structures they support resulting in damage (Whittle, 2012). Thus, there often forces at work other than blasting that caused the owner’s alleged damages. In fact, the United States Bureau of Mines has published a list of 40 causes of cracks in walls and ceilings (Thoenen & Windes, 1942). After a full inspection of the property, the structural engineer/contractor should be able to determine the cause of the cracking and highlight any construction deficiencies.
The structural engineer/contractor may also be in the best position to determine whether the damages pre-existed the blasting. The preferred way to determine the existence of pre-existing damages is the review of a pre-blast survey performed at the property. If such a pre-blast survey exists, a comparison of pre-blast and post-blast conditions becomes a simple and effective method of proving a lack of causation.
In my next post of this series, we will turn to a discussion on pre-blast steps that can be taken in an effort to maximize the effectiveness of the blasting contractor’s usual defenses.