Air-blast and your house

Posted by Stop Ajax Mine on April 14th, 2016 11:53am

What effects will air-blast from the Ajax mine have on you and your house?

In 2013, Golder Associates was hired by the City of Kamloops to review  data from two test blasts done by KGHM in 2011, to determine whether air-blast should be part of the application information requirements.

What is air-blast?

Golder:  Air-blast is that loud noise or “sonic boom” that is created by large blasts (with a frequency greater than 20 Hz). At large receptor distances from a large blast, it is normally the air-blast, instead of ground vibration, that can be felt and can potentially cause distress and damage. The air-blast can cause a house to vibrate and could potentially break windows. Air-blast generated from a blast can be disturbing to persons and wildlife.

What are the concerns with air-blast?

Golder: *It is anticipated that air-blast will be one of the first widely noticed and controversial impacts of the proposed development of the city of Kamloops and environs, the residents and wildlife.
*The effects of blasting on property values is of concern to residents.
* Air-blast will affect a very large area and large number of people. 
*Under normal conditions air-blast will be very loud (at frequencies greater than 20 Hz) and disturbing to residential receptor locations.
* Under some environmental conditions air-blast levels have the potential to be more elevated.

What factors affect the intensity of air-blast?

Golder: *The size and location of the blast
*the blast design which includes charge weight per delay and stemming depth;
*the blast shot direction;
*the terrain;
*wind direction and speed;
*cloud cover; and
*temperature inversions.

Air-blast will affect a very large area and a large number of people.

Golder calculates that air-blast from the proposed mine will extend at least 10 km from the mine site with little diminishing intensity over that distance .  A 10 km radius from the pit reaches as far as Kamloops Airport, Tranquille Road, Sun Rivers subdivision, and west Juniper Ridge.

The Application measurements, however, are skewed because the air-blast is calculated from the extreme west end of the pit, beside Jacko Lake.  This is fine for assessing the effects on fish, but for effects on humans, KGHM should use blasting zone data from the east end of the pit which is closest to residences in Aberdeen and Knutsford.  Moving the blast location to the east end of the pit will elevate the decibel levels at residences in  Kamloops and Knutsford.

How will weather conditions affect air-blast intensity?

The 2013 Golder Associates report notes that weather conditions – wind, cloud cover and temperature inversions – will intensify the air-blast effects, up to 20 dBL.

However the Application does not take these weather conditions – wind over 15 km/hr, cloud cover, and temperature inversions – into account in its air-blast modelling.

If a 20 dBL increase in air-blast effect is factored into the data, most receptors will be over the acceptable limit: (keeping in mind that the air-blast effect will be even more elevated if the measurements are taken from the east end of the pit).

It is imperative that KGHM calculate the effects of air-blast on people and structures, emanating from a blast at the east end of the pit, closest to Aberdeen and Knutsford residences, and extending from there in a 10 km radius. Weather conditions should be factored into the data. This would then give a more accurate picture of effects on people, windows, and structures.

What about potential damage to your house?

Malartic resident, Diane Gagnon, urged Kamloops residents to ensure that KGHM is required to pay for engineering inspection of all residences within a certain radius of the pit before construction of the mine begins.  Such a permitting condition exists at the Mt. Arthur BHP coal mine in Australia, where everyone within a 3 km radius of the blast zone is entitled to an inspection by an engineer before any blasting occurs, with such inspection being paid for by the mine.  Furthermore, should the mine go into operation,  KGHM should compensate residents for any damage to their houses and any loss of property value. 


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