To add to your debate have you guys seen this?
This is impact assessment that accompanied the revised statutory guidance. I don't know its status but its quite clear when they revised the statutory guidance that the government intended for a less conservative approach to remediation to be widely accepted. So effectively accepting that the SGVs are too onerous/conservative and more 'pragmatic' criteria are required = C4SLs.

The reason being to move forward brownfield redevelopment, and the only way that takes place is through planning therefore C4SLs are derived for use in planning.

End of argument.

Jenny Day
(Independent Consultant)