(A) All required stormwater retention/detention facilities must be constructed and in operation prior to paving and building construction, unless otherwise approved by the Department of Public Works.
(B) The capacity of the downstream drainage course is required to be evaluated for a minimum distance of one-fourth mile from the point of discharge of the development.
(1) The downstream conveyance system must be adequately sized to handle off-site peak flows conveyed through the development plus the on-site developed peak flow discharged to the drainage course from the controlling ten-year storm.
(2) This system should be shown on the drainage layout.
(3) The size of the controlled outlet shall be calculated for the total drainage basin when the total run-offs from both off-site and on-site areas are combined.
(C) The limits of the FEMA mapped 100-year floodplain shall be required to be delineated on the final plat, as well as the engineering drawings for plat construction.
(D) Arrows indicating drainage direction in all public and private property shall be shown on the construction drawings for all hydraulic conveyance systems.
(E) (1) A topographical map sufficient in area to show all areas draining onto the proposed land development must be submitted and show enough of abutting downstream properties to indicate natural or human-made drainage course into which the proposed land development is to drain.
(2) The direction of flow, acreage of areas contributing drainage to the development, the outline of the development and location of intermittent streams or drainage courses which are within the site boundaries shall be indicated on this map.
(F) Surface water entering the subject property shall be received at the naturally occurring location, and surface water exiting the subject property shall be discharged at the natural location, with adequate energy dissipaters within the subject property to eliminate the potential for detriment to the existing downstream infrastructure.
(Prior Code, § 11.05.040.040) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)