September 20th, 2017
By Josh Bennett
As explained in previous posts in this series, through the use of expert witnesses, an entity involved in a blasting claim may assert the defense that the damage was caused by some non-blasting reason or pre-existed the blasting and the peak particle velocity of the blast was not at the level necessary to cause damage to the structure. However, there are steps that can and should be taken in an effort to maximize the effectiveness of these defenses and these steps should occur before the first blast is ever detonated.
A pre-blast survey is a valuable tool that a blasting contractor can use to show that an owner’s damages pre-existed the blasting. A pre-blast survey is the inspection and documentation of the existing condition of a structure prior to any blasting (Ludwiczak, n.d.). According to the claims manager of an insurance carrier, the pre-blast survey will eliminate 96 percent of nuisance blasting claims and is an easy way to combat the claim that the owner’s home never had any cracking prior to the blasting (Whittle, 2012).
However, even though the effectiveness of a pre-blast survey in fending off blasting claims is well known, most pre-blast surveys fall short of their maximum potential. Often times, the pre-blast survey of a property will consist of a few pages and photographs while the post-blast survey will be hundreds of pages long. This is often indicative of a lack of detail in the inspection, leading to a weak defensive position on pre-existing damages. Consequently, the following are suggestions for the pre-blast inspection that may strengthen the ability of a defense attorney to successfully use the pre-blast survey in the defense of a blasting claim:
By procuring a complete and detailed pre-blast survey, blasting entities can secure the evidence necessary to prove that the owner’s damages existed prior to the blasting occurring. While some may see an exhaustive pre-blast survey as costly and time consuming, the survey will be worth its weight in gold if a claim is eventually filed (Ludwiczak, n.d.).
In addition to proving pre-existing damages, as explained above, a successful defense to a blasting claim usually involves showing the vibration of the blast was not at the level necessary to cause damage to the structure based on established limits. The most appropriate instrument for measuring ground and building vibrations produced by blasting is one that directly records the particle velocity associated with the vibration (Whittle, 2012). Thus, the blasting contactor’s use of a seismograph that records peak particle velocity at every blast greatly enhances the ability of the defense attorney to point to the peak particle velocity level as an indication that the owner’s damages were not cause by blasting. Of course, the seismograph reports and applicable blast logs should be well organized and safely secured for future use.