The proposed exemption for…

The proposed exemption for Aggregate Reuse Depots indicates that 'the aggregate must be known to be of a quality that it can be reused in an infrastructure project', but does not clarify the standards that would apply. It is presumed that it is intended that the volume-independent ESQS would apply. If so, this should be reconsidered as many of the assumptions applied in the development of these standards would not be applicable in the context of this specific reuse situation, and would be overly conservative. The listed requirements for this reuse already specify that the materials to be recycled must comprise aggregates 'used to meet a specific engineering need and not as general fill or mixed earth', and would be reused as 'an aggregate product in an infrastructure or building project (not general fill or soil amendment)'. Given these limitations in source and reuse, the potential for leaching concerns is significantly reduced considering both typical construction practices related to aggregate layer thickness, and since these materials would typically be placed underlying lower permeability structures (e.g., pavement or concrete). Under those circumstances, both the dilution factor (S-GW3) and well bore dilution (S-GW1) factors used in the derivation of the leaching based criteria would be increased, mitigating the volume concerns. The Ministry should consider removing the volume restriction for recycled aggregates (i.e., the small volume standards would apply irrespective of the actual volume used, provided the reuse is in line with the other requirements noted). Clarification could also potentially be included that the more conservative standards may need to apply for some specific applications (e.g., underlying permeable pavement structures). The concern this would address is that the volume independent ESQS may be exceeded with some frequency in these materials (e.g., low levels of PHCs slightly exceeding the volume independent ESQS can occur in these materials), and where this is the case, the reuse of these materials for the purposes intended would both not pose any actual concern, and avoid unnecessary disposal of these materials as waste.