GSA ENGINEERING GEOLOGY DIVISION RICHARD H. JAHNS DISTINGUISHED LECTURER: KABOOM! OR WHOOSH? (MITIGATING BLASTING IMPACTS WITHOUT DIMISHING EFFECTIVENESS)

Blasting can achieve its desired purpose and, when cautiously conducted, will have assurance of avoiding significant impacts or damage.

Blasting is an art, which is considered very dangerous by the public. Low-tensile materials (rock & concrete) that cannot be easily excavated mechanically may be effectively dislodged by blasting. Blasting is effective, because the chemical release of energy from the blasting agent results in detonation and in great gas-volume production in a very short time. The blaster uses empirical approaches and developed experience to perform the activity required and to create the blaster’s largest profit.

The three primary impacts due to blasting are: flyrock, noise, and vibrations (or pressure waves in an aquatic environment). Secondary effects from these impacts cause other hazards away from the blasting zone. These primary impacts can be controlled by the blasting parameters used, and for some projects, by additional mitigating measures. Achieving the required goal of blasting most effectively may be counter to adequately reducing the secondary effects that are possible. Mitigation research should be published for unusual blasting cases. Some of the cases noted include: quarry blasting’s possible disturbance of hibernating Indiana Bats; impacts upon a planned pipeline near an active quarry; dam removal; rock excavation near geologic hazards; and, adverse impacts from blasting of, or near, water-borne structures. Geophysical assessment of the site is required to understand wave passage and how vibratory, or pressure-wave, impacts may have damaging amplitudes beyond the blasting zone.

Each of these cases is briefly developed to note the proper approach to mitigating human, environmental, geologic and structural impacts without diminishing the capacity to effectively perform the blasting. The important issues are to research past similar projects, calculate anticipated impacts, resolve a means to measure impacts, anticipate important blasting parameters, and develop the blasting contract and information to complete the purpose of the blasting. Many projects require some education of the owner (client), engineer-in-charge, blasting firm, those that could be harmed by blasting, and/or the general public.