[R.O. 2012 §420.010]
A.
This
Chapter provides minimum standards, controls and criteria for storm
water management. The principal design consideration in this Chapter
is to minimize the harmful physical and economic effects of erosion,
sedimentation and flooding from storm water runoff. This is to be
accomplished through the requirement of special measures to mitigate
erosion both during and after construction, the detention and controlled
discharge of the differential runoff from the development, and a well
designed storm water conveyance system.
B.
The
developer shall provide storm water calculations that indicate that
the storm water generated from the developed conditions does not exceed
the storm water generated from the undeveloped condition. The storm
water design calculations shall be based on a 25-year frequency storm.
[R.O. 2012 §420.020]
A.
The
provisions of this Chapter further supplement other City ordinances
regulating:
1.
The subdivision, layout, and improvement of lands located within
the corporate limits of the City of Union, Missouri.
2.
The excavating, filling, and grading of lots, and other parcels or
areas.
3.
The construction of buildings, and the drainage of the sites on which
those structures are located, to include parking and other paved areas.
4.
The design, construction, and maintenance of storm water drainage
facilities and systems.
[R.O. 2012 §420.030]
A.
Before
starting any activities regulated by this Chapter, an applicant shall
comply with the requirements set forth in other applicable ordinances
with respect to submission of preliminary subdivision plats, improvement
plans, building and zoning permits, inspections, appeals, and similar
matters, along with those set forth in this Chapter and as may be
required by State Statutes (Missouri Clean Water Laws).
B.
NPDES Storm Water Permit. Construction sites where the area
to be disturbed is five (5) acres or more, must apply for a storm
water discharge permit from the Missouri Department of Natural Resources.
Permit requirements are set forth in 10 CSR20-6.200 of the Missouri
Clean Water Laws.
[R.O. 2012 §420.040]
For the purposes of this Chapter, the following definitions
are adopted:
A precipitation event having a one percent (1%) chance of
occurring in any one (1) calendar year.
Any deleterious impact on water resources or wetlands affecting
their beneficial uses including recreation, aesthetics, aquatic habitat,
quality, and quantity.
The elevation of all locations delineating the level of flooding
resulting from the 100-year frequency flood event.
Storm water runoff from an upstream property's tributary
to a property's drainage system, but not under the control of the
drainage system.
The maximum flow at atmospheric pressure that can be conveyed
by the facility without causing damage to the public or encroachment
upon private property. The capacity of a storm water drainage facility
is determined utilizing "Mannings Equations" or similar formulas.
Any river, stream, creek, brook, branch, natural or artificial
depression, ponded area, flowage, slough, ditch, conduit, culvert,
gully, ravine, wash, or natural manmade drainageway, or shoreline,
in or into which surface or ground water flows, either perennially
or intermittently.
Alteration of a channel by changing the physical dimensions
or materials of its bed or banks. Channel modification includes damming,
rip rapping, widening, deepening, straightening, relocating, lining,
and significant removal of bottom or woody rooted vegetation. Channel
modification does not include the clearing of debris or removal of
trash.
An artificially excavated, hydraulically equivalent volume
of storage within the floodplain used to balance the loss of natural
flood storage capacity when fill or structures are placed within the
floodplain.
An artificial storage provided to balance the loss of natural
flood storage capacity when fill or structures are placed within natural
upland depressional storage areas.
Any channel, pipe, sewer or culvert used for the conveyance
or movement of water, whether open or closed.
The facility constructed to regulate the volume of storm
water that is released during a specific length of time.
A closed conduit for the passage of surface drainage water
under a roadway, railroad, canal, or other impediment.
A storm of a specific duration expected to occur with a frequency
of once every twenty-five (25) years.
A facility constructed or modified to provide for the temporary
storage of storm water runoff and the controlled release of this runoff
at a prescribed rate during and after a flood or storm.
The temporary detaining or storage of storm water in storage
basins, on rooftops, in streets, parking lots, school yards, parks,
open space, or other areas under predetermined and controlled conditions,
with the rate of drainage therefrom regulated by appropriately installed
devices.
The mean residence time of storm water in a detention basin.
Any manmade change to real estate including: construction,
reconstruction or placement of a building, or any addition to a building;
installation of a manufactured home on a site, preparing a site for
a travel trailer; construction of roads, bridges, or similar projects;
redevelopment of a site; filling, dredging, grading, clearing, excavating,
paving, or other non-agriculture alterations of the ground surface;
storage of materials or deposit of solid or liquid waste; any other
activity that might increase the magnitude, frequency, deviation,
direction, or velocity of storm water flows from a property.
The time which it takes to drain the temporary flood storage
in a detention facility.
The difference in peak flow rate of water anticipated to
shed from a parcel of land between the existing and improved surface
condition, for each rainfall event.
The area from which water is carried off by a drainage system;
a watershed or catchment area above a given point.
Authorization by a property owner allowing use of a designated
portion of his/her property by others for drainage purposes.
A plan, including engineering drawing and supporting calculations,
which describes the existing storm water drainage system and environmental
features, as well as the drainage system and environmental features
which will be in place after development of a property.
A facility constructed or modified to provide for the temporary
storage of storm water runoff and the controlled release of this runoff
at a prescribed rate during and after a flood or storm.
The time period over which precipitation is measured.
A channel on the surface of the soil to carry excess storm
water runoff through a specific area from dominant to subservient
estates.
That land adjacent to a body of water with ground surface
elevations at or below the base flood or the 100-year frequency flood
elevation.
The channel and that part of the floodplain adjacent to a
stream or watercourse which is needed to store and convey the anticipated
existing and future 100-year frequency flood discharge with no more
than a one-tenth (0.1) foot increase in stage caused by any loss of
flood conveyance or storage and no more than a ten percent (10%) increase
in velocities.
That part of the floodplain outside of the regulatory floodway.
The difference in elevation between the top of the detention
basin dam and the design surface water elevation.
An expression or measure of how often a hydrologic event
of given size or magnitude should, on an average, be equaled or exceeded.
The inclination or slope of a channel, canal, conduit, etc.,
or natural ground surface, usually expressed in terms of the percentage
the vertical rise (or fall) bears to the corresponding horizontal
distance.
A graph showing, for a given location on a stream or conduit,
the flow rate with respect to time.
A term applied to material through which water cannot pass,
or through which water passes with great difficulty or at a very slow
rate.
The passage or movement of water into soil surfaces.
An opening into a storm water system for the entrance of
surface storm runoff, more completely described as a storm sewer inlet.
Flooding.
That part of a drainage system needed to store and convey
flows beyond the capacity of the minor drainage system.
That part of a drainage system designed for the convenience
of the public. It consists of street gutters, storm sewers, small
open channels, and swales, and is usually designed to handle the 25-year
runoff event or less.
Water flow by gravity along the true surface topography of
the earth or in channels prior to development.
The quantity of storm water runoff that can be transported
by means of a channel, passage, conduit, tube, duct, or combination
thereof, in such a manner that the elevation of the water does not
rise significantly above the level of the adjacent soil surface, and
cause damage or encroachment upon public or private property.
The maximum rate of flow of water at a given point in a channel
or conduit resulting from a predetermined storm or flood.
A term used to describe the drainage of an area in a manner
that will ensure complete removal of all surface water by means of
gravity.
The channel, including onstream lakes, and that part of the
floodplain adjacent to a stream or watercourse, as designated by the
DNR, which is needed to store and convey the existing and anticipated
future 100-year frequency flood discharge, with no more than a one-tenth
(.1) foot increase in stage caused by the loss of flood conveyance
or storage, and no more than a ten percent (10%) increase in velocities.
A natural or manmade watercourse with definite bed and banks
which periodically or continuously contain moving water or form a
connecting link between two (2) bodies of water.
All natural or manmade means used for conducting storm water
to, through, or from a drainage area to the point of final outlet
from a property. The storm water drainage system includes, but is
not limited to, any of the following: conduits and appurtenance features,
canals, channels, ditches, streams, culverts, streets, storm sewers,
detention basins, swales, and pumping stations.
Water that results from precipitation which is not absorbed
by soil or plant material; which does not evaporate and flow over
the surface of the ground; or is collected in channels, conduits,
or ponds.
To fill to excess or beyond normal capacity.
The elapsed time for storm water to flow from the most hydraulically
remote point in a drainage basin to a particular point of interest
in that watershed.
Any stream, creek, brook, branch, natural or artificial depression,
slough, gulch, reservoir, lake, pond, or natural or manmade drainageway
in or into which storm water runoff and floodwaters flow either regularly
or intermittently.
A basin designed to maintain a permanent pool of water after
the temporary storage of storm water runoff.
