(a) For each Class I waste management unit, the regional board shall specify in the waste discharge requirements the point of compliance at which the water quality protection standard of section 2550.2 of this article applies. The point of compliance is a vertical surface located at the hydraulically downgradient limit of the waste management unit that extends through the uppermost aquifer underlying the unit. For each Class I waste management unit, the regional board shall specify monitoring points at the point of compliance and additional monitoring points at locations determined pursuant to section 2550.7 of this article at which the water quality protection standard under section 2550.2 of this article applies and at which monitoring shall be conducted.

(b) If the facility contains contiguous waste management units and monitoring along a shared boundary would impair the integrity of a containment or structural feature of any of the units, the point of compliance may be located at the hydraulically downgradient limit of an area described by an imaginary line along the outer boundary of the contiguous waste management units. This provision only applies to contiguous waste management units that have operated or have received all permits necessary for construction and operation before 7-1-91.