Vibrations and Air Concussion Exceeding Legal Limits



(1)(a) No person responsible for the operation of a quarry shall permit any blasting on site to exceed the following limits:

Concussion (Air Blast) 128 dBA

Ground Vibration 0.5 in./sec.
(12.5 mm/s) Peak Particle Velocity

(2) Every person responsible for the operation of a quarry shall have a technical blast design prepared by a qualified person which ensures the ground vibration and air concussion outlined in VIII (1) can be achieved.

The above is a direct quote from the Nova Scotia Pit and Quarry Guidelines.
report written by a renowned blasting expert with 50 years experience, a PhD in physics, and the creator of a blasting simulator, stated that the first plan provided by Scotian Materials for blasting, which was written by Golder Associates, would result in vibrations of 58.2 mm/s at the natural gas pipeline, which is approximately 200m away. Dr. Favreau noted that it also exceeds the limit imposed by Hydro-Ontario for hydroelectric structures. Six other simulations with variations gave values from 32.9 mm/s to 86.4 mm/s, all far exceeding the limit as noted above of 12.5 mm/s. Dr. Favreau stated that the vibration level of 86.4 mm/s could cut the pipeline. Dr. Favreau tested further situations which are not uncommon such as multiple holes detonating at once. The vibration levels could reach 238.5 mm/s, which again could shear the pipeline in one blast.
The second blasting plan was written by Dyno Nobel for Scotian Materials. Dr. Favreau’s modelling showed that it would result in vibrations of 59.7 mm/s at the natural gas pipeline, which also exceeds the level of 12.5 mm/s.  It too could expect for some holes to reach 84.9 mm/s. Dr. Favreau noted, “should more than one hole detonate on the same delay then the vibration level can reach values above 200 mm/s, i. e. so high as to very likely break the pipeline. The writer has regularly been aware of situations where inadvertently more than one hole detonated simultaneously.”
Dr. Favreau also explained that several blasting contractors use the “One Third Practice,” the practice of predicting that vibration to be expected is so unreliable that contractors use blasts designed to produce 1/3 the value of the allowed vibration limit. This would be a plan to produce 4.2 mm/s and not 59.7 mm/s as is expected regularly from one hole detonating based on Dyno Nobel’s plan.
Dr. Favreau also modelled the concussion air blast based on Golder’s blast plan, and it produced values from 95.4 to 146.8dBA, with eight of ten predicted values exceeding the allowable limit of 128dBA. Examining Dyno Nobel’s plan, Dr. Favreau predicted that the air concussion blast would exceed 128dBA at 1.3km away. This is unfortunately the distance where people reside.
Dr. Favreau took issue with the fact that it was difficult to obtain the information required for his analysis, that Dyno Nobel used a simulator that has been proven in a real-life scenario to underestimate the maximum distance for flyrock, and that the analysis and plan does not include variations from the norm due to regularly-occurring variables such as using a combination of explosives, the bench not breaking fully off, or weakening the blast method. He pointed out that neither explosives plan was signed, which he felt was due to a lack of confidence or taking ownership of the plan. He also noted that if the plan were to abide by the Canada Oil and Gas regulations, not a single bore hole could be blasted because it contains too much weight in explosives for the proximity to the pipeline.

In addition, the results of Dr. Favreau’s blasting simulations show that for the variations of the values of the blast parameters that Dr. Favreau has encountered in quarries, the type of blasts intended for the proposed Scotian Materials quarry will without any doubt send dangerous fly rock regularly, and this is an unacceptable situation for the nearby inhabitants and the traveling public on Highway 102.

The table below shows the maximum predicted levels of vibrations for locations near the proposed site:

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It is unfortunate that the Scotian Material people do not use the reliable methods available (see references 4 and 3) for predicting accurately the vibration levels due to the intended blast methods for the proposed quarry… The planners of the proposed quarry give the impression that they have not enough concern for the security of the inhabitants and the traveling public on Highway 102 near the proposed quarry to even get the required accurate properties of the rock from an exploratory drill hole..As a final conclusion, the writer is of the opinion that the authorities must not under any circumstances give approval to the proposed quarry, because blasting in the location of the proposed quarry is unacceptably dangerous. New quarries should be located far from inhabited regions and pipelines. Quarry operators should accept this, even if it raises their costs of transportation of the excavated stones.”

~ Dr. R. F. Favreau, PhD, Professor Emeritus, Royal Military College

 We can also apply Dr. Favreau’s simulation results to applicable guidelines for the protection of fish. The Guidelines for the Use of Explosives In or Near Canadian Fisheries Waters state:

No explosive is to be detonated that produces, or is likely to produce, a peak particle velocity greater than 13 mm/s in a spawning bed during the period of egg incubation.

There are watercourses and wetlands surrounding the proposed quarry footprint where people regularly fish. The closest are within 30m, as described above in the setbacks section. These are far closer than the pipeline, so it may be inferred from the results above that if at 200m the ground vibrations far exceed the limit of 12.5 mm/s, that it is also totally impossible under the proposed blasting plans to abide by these guidelines and prevent the destruction of fish eggs.
Furthermore, these guidelines set a limit of 100kPa be produced in the swim bladders of fish. The table given in the guidelines does not exceed 100kg of explosives, so it is not possible to determine the appropriate setback. At 35kg of explosives, which is a single charge, the nearest value is 50kg. At this weight of explosives, the explosives must be 35.6m or more from the fish habitat. Yet again, this is a colossal failure on the part of Scotian Materials to protect wildlife in this plan, as the proposed blasts involve 8,888 to 24,893kg, and not 35kg, and the setbacks are less than 35.6m.
Member of the Nova Scotia Road Builder’s Association Robert MacPherson. Scotian Materials Limited. Rob MacPherson. Contact. Address: 100 Venture Run, Suite 103. Dartmouth. #scotianmaterials Halifax quarry quarries aggregate gravel #noFRquarry  Scotian Materials Ltd.