[Ord. No. 14-04-09 §1, 4-21-2014]
For land development that results in land disturbance less than
one (1) acre, no stormwater detention/retention or permanent stormwater
quality treatment best management practices are required. For all
other land development, the following criteria must be met.
[Ord. No. 14-04-09 §1, 4-21-2014]
A.
Compliance With Federal And State Regulations. All stormwater
facilities and conveyance systems shall be designed in compliance
with all applicable state and federal laws and regulations, including
the Federal Clean Water Act and all applicable erosion and sediment
control, wetland and flood plain regulations.
B.
Protect Public Health, Safety And General Welfare. The design
of stormwater BMPs shall consider public health, safety, and general
welfare. These considerations include, but are not limited to: preventing
the flooding of structures; safe passage of vehicles on roadways;
preventing standing water in facilities, manholes, inlets, and other
structures in a manner that promotes breeding of mosquitoes; preventing
attractive nuisance conditions and dangerous conditions due to velocity
or depth of water and/or access to orifices and drops; and preventing
aesthetic nuisances due to excessive slopes, cuts and fills, and other
conditions.
C.
Adherence To KC-APWA 5100, KC-APWA 5600 And MARC BMP Manual. All stormwater facilities and BMPs shall be designed to the standards
of the KC-APWA 5100, KC-APWA 5600 and MARC BMP Manual, unless a variance
is granted or the applicant is exempt from such requirements.
D.
Stormwater Authority Discretion. If hydrologic, geologic,
topographic, or land use conditions warrant greater control than that
provided by the minimum control requirements, the Director may impose
additional requirements prior to the approval of the stormwater management
plans, as deemed reasonable and necessary to control the volume, timing,
rate and/or quality of runoff. The Director may restrict the use of
certain stormwater BMPs, require additional pretreatment, and/or require
a post-construction stormwater pollution prevention plan in certain
circumstances. These include, but are not limited to: stormwater generated
from stormwater hotspots, stormwater discharges that are conveyed
with non-stormwater discharges, or areas where geologic conditions
are conducive to groundwater contamination.
E.
Hydrologic Computation Assumptions. Hydrologic parameters
shall reflect the ultimate land development and shall be used in all
engineering calculations. All pre-development calculations shall consider
woods and fields to be in good condition, regardless of actual conditions
at the time of application.
F.
Location Of Stormwater Facilities On Lots. Stormwater facilities
within residential subdivisions that serve multiple lots and/or a
combination of lots and roadways shall be on a lot owned and maintained
by an entity of common ownership, unless an alternative arrangement
is approved by the Director. Stormwater practices located on individual
lots shall be placed within an easement and either maintained by the
lot owner or maintained by an entity of common ownership.
[Ord. No. 14-04-09 §1, 4-21-2014]
A.
Replicating Pre-Development Hydrology. Stormwater management
designs shall preserve the natural hydrologic functions, stream channel
characteristics, and groundwater recharge of the pre-developed condition
to the maximum extent practicable. This shall be accomplished by treating
runoff at the source, disconnecting impervious surfaces, preserving
or enhancing natural flow paths and vegetative cover, preserving or
enhancing natural open spaces and riparian areas, and other measures
that replicate pre-development hydrologic conditions. The Director
shall exercise discretion in the application of this standard, especially
in cases of infill development, redevelopment, or other unique circumstances.
Capture and treatment of the Water Quality Volume per the MARC BMP
Manual shall be considered the acceptable standard of meeting this
requirement.
B.
Velocity Dissipation. Velocity dissipation devices shall
be placed at discharge locations of the stormwater conveyance system
and along the length of any outfall to provide non-erosive flow velocity
from the structure to an adequate receiving stream or channel so that
the natural physical and biological characteristics and functions
of the receiving stream are maintained and protected.
C.
Discharges To Adjacent Property. Concentrated discharges
from the stormwater conveyance system or stormwater best management
practices shall not be discharged onto adjacent property without adequate
conveyance in a natural stream or storm sewer system. Drainage easements
are required where stormwater discharges must cross an adjacent or
off-site property before reaching an adequate conveyance.
D.
Flow Toward Streets. In order to have sufficient traffic
safety, any concentration of surface flow in excess of two (2) cubic
feet per second (cfs) for the ten-year frequency rain shall be intercepted
before reaching the street right-of-way and shall be carried by a
storm drain to connect with a drainage structure at the low point
in the street right-of-way or to discharge to a watercourse.
E.
Drainage Onto Sidewalks. Tributary areas where sidewalks
exist or are proposed, and which drain across a public sidewalk, must
not exceed three thousand (3,000) square feet of impervious area,
including roofs discharging upon paved areas, or nine thousand (9,000)
square feet of sodded areas, or in proportional amounts for a combination
of such areas. Paved, roofed or other impervious areas exceeding three
thousand (3,000) square feet shall be provided with drains for discharge
into storm conduits, channels or street gutters.
F.
Downspouts. Downspouts shall not be discharged directly
onto sidewalks or entrance ways. When downspouts are connected to
the gutterline of the street or the public drainage system, they shall
be connected by a method approved by the City. Downspouts shall not
discharge within the building setback unless there is a drainage swale
established to carry the water to the front or rear of the property
or closest natural drainage course. Downspouts may also discharge
within the building setback if discharging into a rain garden, rain
barrel or other stormwater best management practice.
G.
Existing Storm Drains. No cuts shall be made nor fill deposited
over existing storm drains nor shall existing storm drains be altered
without the approval of the Department of Public Works.
[Ord. No. 14-04-09 §1, 4-21-2014]
A.
Stream Preservation And Buffer Zones/Building Setbacks. All
streams having a tributary area in excess of 40 acres shall be preserved
according to the standards set forth in KC-APWA 5600. This shall be
accomplished by establishing stream buffer zones to reduce the encroachment
of development on these natural systems and provide filtration and
infiltration of runoff prior to discharge. Buildings shall be set
back from the outer edge of the stream buffer at least an additional
ten (10) feet. Adjustments in widths of the buffer zone or adjacent
building setback may be made when approved by the Public Works Director
when local conditions justify deviation from the standard widths.
B.
Plans. Stream buffers shall be delineated on all surveys,
plats and development plans. Any plans that require construction within
the stream buffer as allowed by this Chapter, shall provide stream
assessment and other calculations as needed to show compliance with
the standards set forth in KC-APWA 5600.
C.
Stream Buffer Function. The function of the streamside zone
is to protect the physical, biological and ecological integrity of
the stream ecosystem. The vegetative target for the stream buffer
is undisturbed indigenous vegetation. Wherever the designated buffer
zone must be disturbed, mitigation measures shall be taken to re-establish
vegetative filtration and stream stabilization to the maximum extent
practicable.
D.
Adjoining Wetlands. The buffer width will begin and be measured
from the ordinary high water mark. Wetlands that adjoin the buffer
shall be added to the buffer. There shall be a fifteen (15) foot buffer
around any edge of the wetland that is not within the stream buffer.
E.
Allowable Uses In The Stream Buffer.
1.
Flood control structures, stream gauging and water quality monitoring
equipment, stormwater treatment facilities in accordance with an approved
plan.
2.
Utility crossings.
3.
Permeable surfaced foot and bicycle paths.
4.
Road crossings.
5.
Utilities where no practical alternatives exist as determined by
the Director.
6.
Stream restoration, stream bank restoration or restoration of indigenous
vegetation in accordance with an approved plan.
7.
Roads, that exist on or before the date of adoption of these regulations,
and associated maintenance activities.
F.
Restricted Uses In The Stream Buffer. The following uses
are prohibited except where incidental to an allowable use:
1.
Clearing of existing vegetation.
2.
Grading, stripping or other soil-disturbing practices.
3.
Filling or dumping.
4.
Draining the buffer area by ditching, underdrains or other systems.
5.
Use, storage or application of pesticides, except for the spot spraying
of noxious weeds or other species consistent with recommendations
of the Missouri Department of Conservation, Clay County Soil and Water
Conservation District, United States Department of Agriculture or
University of Missouri Extension Service.
6.
Storage or operation of motorized vehicles except for maintenance
or emergency use.
7.
Walls, solid fences, chain link fences, woven or welded wire fences.
8.
Structures or any type of impervious surface except as provided above.
G.
Stream Buffer Management And Maintenance.
1.
Management, responsible party. The stream buffer,
including wetlands and floodplains, shall be managed by the landowner
to enhance and maximize the unique value of these resources. Management
includes specific limitations on alteration of the natural conditions
of the land and vegetation.
2.
Allowed maintenance practices and activities in the buffer. All allowed uses may be maintained subject to the review of the
City. Any entity conducting an allowed activity within the streamside
zone shall restore any disturbed area to its previous condition or
in accordance with a plan approved by the Director. In addition to
maintenance of allowed uses, the following maintenance activities
may be conducted:
a.
Roads, bridges, paths, and utilities existing as of the date of adoption
of these regulations.
b.
Rights-of-way for roads and utilities should be the minimum width
to allow for installation, access and maintenance.
c.
Removal of diseased or dead trees, brush and trash.
d.
Maintenance of all City-approved improvements, including utilities.
e.
Removal of debris which could cause flooding.
f.
Selective (spot) spraying of noxious or other vegetation.
3.
Restricted maintenance practices and activities within the stream
buffer:
a.
Clearing of existing vegetation.
b.
Soil disturbance by grading, stripping, or other practices.
c.
Filling or dumping.
d.
Drainage by ditching, under drains or other systems.
e.
Use, storage, or application of pesticides.
f.
Storage or operation of motorized vehicles, except for maintenance
and emergency use approved by the City or when operated on a legally
established roadway.
H.
Stream And Wetland Crossings. All stream and wetland crossings
subject to Section 404 of the Clean Water Act and/or state stream
and/or wetland regulations shall minimize impacts on streams and wetlands,
to the extent practical and achievable, by crossing streams and wetlands
at a right-angle, reducing the footprint of grading and fill, matching
the existing stream profile grade, and utilizing bridges, open bottom
arches, spans, or other structures that do not restrict or alter stream
or wetland hydrology. If culverts are placed within streams and/or
wetlands, at least one culvert shall be countersunk at least one (1)
foot below the natural channel flowline (or 10% of the pipe diameter)
to allow movement of aquatic organisms. As much as possible, the natural
multi-stage channel shape shall be mimicked.
[Ord. No. 14-04-09 §1, 4-21-2014]
A.
Water Quality Protection. In order to protect the receiving
waters from nonpoint source pollution, the water quality volume shall
be captured and treated to the level of service prescribed by the
MARC BMP Manual.
B.
Channel Protection Criteria. The stormwater system shall
be designed so that post-development discharges will not erode natural
channels or steep slopes. This will protect in-stream habitats and
reduce in-channel erosion. Channel protection shall be provided by
controlling the post-development peak discharge rate of the 2-year,
twenty-four-hour storm event to the pre-development rate.
C.
Flood Control Criteria. Downstream overbank flood and property
protection shall be provided by controlling the post-development peak
discharge rate to the pre-development rate. This criterion shall be
met for the 10-year, twenty-four-hour storm event on residentially
zoned properties and the 25-year, twenty-four-hour storm event on
non-residentially zoned properties. Stormwater BMPs that impound water
shall demonstrate that the 100-year storm can safely pass through
the structure without overtopping or creating damaging conditions
downstream.
D.
Overland Flood Routes. Overland flood routing paths shall
be used to convey stormwater runoff from the 100-year storm event
to an adequate receiving water resource or stormwater BMP such that
the runoff is contained within the drainage easement for the flood
routing path and does not cause flooding of buildings or related structures.
The peak 100-year water surface elevation along flood routing paths
shall be at least one (one) foot below the finished grade elevation
at the structure. When designing the flood routing paths, the conveyance
capacity of the site's storm sewers shall be taken into consideration.
[Ord. No. 14-04-09 §1, 4-21-2014]
A.
Treat Entire Land Development. The stormwater design shall
provide for treatment of runoff from the water quality rainfall event
to the maximum extent practicable through the use of structural and
non-structural BMP to the Level of Service required by the MARC BMP
Manual.
B.
Landscape Plan. The design of vegetative stormwater BMPs
shall include a landscape plan detailing both the vegetation to be
in the practice and how and who will manage and maintain the vegetation.
C.
Pretreatment. Each stormwater BMP shall have an acceptable
form of water quality pretreatment if required to provide adequate
long term operation and maintenance of the BMP.
D.
Treatment Of Off-Site Stormwater. Off-site stormwater conveyed
through a land development shall be placed within an easement and
conveyed in a manner that does not increase upstream or downstream
flooding. Off-site stormwater shall be conveyed around on-site stormwater
BMPs, unless the facilities are designed to manage the off-site stormwater.
The Director may allow the treatment of off-site stormwater in lieu
of up to ten percent (10%) of the site's water quality volume.
E.
Wetland Protection. Wetlands meeting the Army Corps of Engineers
definition of a jurisdictional wetland must be protected in all watersheds.
Protection methods for wetlands include:
F.
The
Director may approve the removal and replacement of a wetland as approved
by the U.S. Army Corps of Engineers or the elimination of setbacks
from a constructed wetland that is primary use is for water quality
control.
