Minor drainage system. The subdivider shall install
all minor drainage system components necessary to reduce inconvenience
and damages from frequent storms. Minor drainage components shall
include all inlets, piping, gutters, channels, ditching and other
facilities designed to accommodate the postdevelopment runoff resulting
from a five-year frequency rainfall (ten-year rainfall for commercial
zoning district) event. Temporary accumulations of storm runoff from
ponding or flowing water, in or near minor system components, shall
be permitted, provided such accumulations do not allow the water to
flow across the crown of the street from one side to the other. For
arterial streets and streets located in commercial districts, ponding
within normal traffic lanes (10 feet on each side of the center line
of the street) is prohibited. In streets, drainageways and drainageway
easements, accumulations of water shall not inundate beyond the limits
of the street right-of-way or drainageway easement for up to including
the one-hundred-year, twenty-four-hour rainfall storm, as determined
in the most current edition of the Natural Resources Conservation
Service Technical Release 55 (TR 55). Cross-street drainage channels
(valley gutters) shall not be permitted except on cul-de-sac or permanent
dead-end streets serving fewer than 10 dwelling units and where the
minimum grade in the valley gutter and street gutter between the valley
gutter and the next downstream drainage inlet is not less than 1%.