The part of the drainage facility situated within the parcel, in addition to complying with the requirements stated under § 152.37:
(A) Shall drain each and every part of the parcel;
(B) Shall be sufficient to accept:
(1) The water runoff from the parcel after development;
(2) The present water runoff from developed areas upstream;
(3) The present water runoff from undeveloped areas upstream; and
(4) That part of the water runoff attributable to future development in undeveloped areas upstream, which is not reasonably likely to be accommodated in such upstream areas. The nature of the future development shall be that projected by applicant, subject to the Board’s agreement. The amount of water runoff not accommodated in connection with such future development shall be determined by good engineering practice, and may assume use of retention-detention systems except for:
(a) Land alteration for which a permit is not required by this section;
(b) Parcels too small to effectively use a retention-detention system;
(c) Parcels relative to which it is technically infeasible to use a retention-detention system; and
(d) Parcels relative to which the cost of providing a retention-detention system is substantially more than providing for increased runoff capacity through the parcel and through other downstream areas to a place adequate to receive the runoff.
(C) May include improvements such as retention-detention systems in the instance where the condition of the land makes use of such improvements feasible and appropriate.
(1991 Code, § 134.30)