Proposed Changes to O.REG…

Proposed Changes to O.REG. 244/97

We are in general agreement with the comments provided by Gravel Watch Ontario in its letter dated March 2020. However, we do wish to address the issue of flyrock risk in particular, as considered in Section 3.1.3 for new and existing operations.

It is important to understand that the risk associated with flyrock is the product of the probability of ejection of flyrock from the quarry site times the consequences of such ejection should it occur. The probability of “wild flyrock” leaving the site is low, but not zero, in spite of the best efforts of competent blasting contractors. However, the consequences of flyrock can be catastrophic, and therefore the associated risk cannot be ignored. The Ontario aggregate industry relies solely on the low probability of ejection to justify its practice of ignoring flyrock risk in blasting impact assessments. This has not prevented cases of damaging flyrock in Ontario.

In Ontario, Professional Engineers are required to sign off on blast impact assessments, and in practice have done so without considering flyrock risk, justified because the ARA does not specifically require this element of impact assessment. Professional Engineers are obliged by oath to protect the health and safety of citizens as an overarching responsibility in engineering works, and yet the profession has steadfastly refused to seek any professional standards regarding this issue.

Wild flyrock ejection is not predictable. The prevailing opinion of experts in the field is that it is not possible to reliably detect inconsistencies in subsurface structures such as fractures, voids and clay seams that provide pathways for the propagation of blasting energy and the ejection of flyrock as ballistic material. It is clear that the only protection against flyrock risk is the provision of sufficient setback between the blast site and receptors such as structures including residences, personnel and the public. Indeed, since the Ontario Ministry of Environment, Conservation and Parks regards the ejection of flyrock as prohibited, safe setback must be to the site perimeter.

Good practice in the aggregate extraction industry globally uses one of two models to determine safe setback, one established by the US Bureau of Mines (USBOM), and the other by Terrock Consulting Engineers (TCE) of Australia. Both models yield the same or similar setbacks for given situations.

Numerous jurisdictions internationally as well as within Canada (Nova Scotia for instance) set minimum requirements for blasting setback from buildings and personnel. Ontario does not.
Conclusion

In conclusion, we support the spirit of the requirement being considered in Section 3.1.3: Implement measures to prevent fly rock from leaving the site during blast events if a sensitive receptor is within 500 metres of the boundary of the site.

However, we believe that there must be a higher degree of specificity in the requirements:
1. In view of the MOECP requirement that flyrock ejection from the site is prohibited, the setback must be to the site boundary;
2. 500 metres must be regarded as a minimum requirement;
3. Industry good practice for setback calculation, employing either the USBOM or TCE models, must be incorporated into Blast Impact Assessments for new site applications, and applied retroactively to existing operations.