(A) A Downstream Impact Analysis shall be submitted at the time of development plan submission for all proposed development that requires development plan approval. Development plans that are not subject to the stormwater management regulations of LDO Section 7.3 are exempt from this section 14.7.9.
(B) The Downstream Impact Analysis shall calculate the pre- and post-development discharges for each discharge point from the area subject to the development plan.
(1) If the calculated post-development discharge is less than the calculated pre-development discharge for the two (2), five (5), ten (10) and one hundred (100)-year peak discharges at each discharge point, then no further analysis is needed.
(2) If the calculated post-development discharge is greater than the calculated pre-development discharge for the two (2), five (5), ten (10) or one hundred (100)-year peak discharges at any discharge point, then one of the options below shall be required.
(a) Provide onsite detention to fully mitigate each storm event to calculated pre-development discharge; or
(b) Provide an engineering model demonstrating no adverse impacts from the development on downstream properties and infrastructure.