By way of derogation from Article 21(3), the competent authority may set:
(a)
emission limit values that ensure that, within 6 years of publication of a decision on BAT conclusions in accordance with Article 13(5) relating to the main activity of an installation, emissions do not, under normal operating conditions, exceed emission levels associated with emerging techniques as laid down in the decisions on BAT conclusions;
(b)
indicative environmental performance values consistent with the decisions on BAT conclusions.