NEGLECTED ADVERSE IMPACTS INDUCED BY BLASTING

Vibrations and water-borne pressure waves [defined together as wave production] are common issues of concern for structures, when dynamic-energy programs are conducted. A number of secondary adverse impacts, which differ from potential damage to structures and may be due to atypical ambient environs, can be induced by varied dynamic-energy sources. This presentation will be restricted to blasting programs, but the same principles apply for pile-driving and other dynamic-energy sources.

Many adverse impacts are infrequently considered as potential risks, when blasting may be conducted. Adverse impacts may not only affect nearby structures. Blasting may: involve harm to the blasting crew or workers developing the project; have a detrimental public response; and, cause or trigger impacts to historic or vibration-sensitive features, to geologic hazards (slope instability, sinkhole collapse, …), and to natural resources (flora and fauna). Documented cases have noted these adverse impacts triggered by blasting.

Blasting, when properly limited by a performance specification and conducted well, will have a lower risk of inducing adverse impacts. A potential adverse impact needs to be recognized to assess proper specification’s restrictions to reduce the likelihood of inducing the impact. Such assessments need to be conducted to further lessen plausible risks. Merely monitoring parameter amplitudes and frequencies only documents those parameters, when an impact has been induced.

The potential adverse impacts can be controlled by restrictions placed in the performance spec on certain blasting factors, on maximum monitored parameter amplitudes (at specified frequencies), and, for some projects, by additional mitigating measures. Geophysical assessment may be required to estimate: the wave parameters, which could trigger a noted adverse impact; potential wave parameters from the blasting program versus distance; and, if a mitigation measure will be undertaken, how the mitigation measure may constructed and operated to be most effective and its performance predicted.