The director may, at his or her discretion for any categorical pretreatment standard,
calculate the equivalent mass per day limit, or concentration limit respectively,
when the other is stated. Compliance with these equivalent measures shall be required
the same as compliance with categorical standards. In establishing discharge restrictions,
discharge standards, discharge limits, or categorical pretreatment standards pursuant
to this chapter, if the director establishes concentration limits to be met by an
industrial user, the director may, in lieu of, or in addition to concentration limits,
establish mass limits of comparable stringency for an individual user.
