[Ord. No. 3025, 8-7-2018]
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 floodplain 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 or access to orifices and drops; and preventing
aesthetic nuisances due to excessive slopes, cuts and fills, and other
conditions.
C.
Adherence To City Stormwater Design Manual. All stormwater facilities
and BMPs shall be designed to the standards of the City stormwater
design manual, unless a variance is granted or the applicant is exempt
from such requirements. The design manual provides guidance for minimum
requirements. A variance is not needed to exceed the 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 preliminary stormwater management
plans, as deemed reasonable and necessary to control the volume, timing,
rate or quality of runoff. The Director may restrict the use of certain
stormwater BMPs, require additional pretreatment, or require a post-construction
stormwater pollution prevention plan in certain circumstances. These
include, but are not limited to, stormwater generated from stormwater
hot spots, 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 wooded
areas 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 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. 3025, 8-7-2018]
A.
Replicating Pre-development Hydrology. Stormwater management designs
shall preserve the natural hydrologic functions, drainage ditch characteristics,
and groundwater recharge of the predeveloped site as outlined in the
City stormwater design manual and to the maximum extent practical.
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.
B.
Overland Flood Routes. Overland flood routing paths shall be used
to convey stormwater runoff from the one-hundred-year storm event
to an adequate receiving water resource or stormwater BMP such that
the runoff is contained within the drainage casement for the flood
routing path and does not cause flooding of buildings or related structures.
The peak one-hundred-year water surface elevation along flood routing
paths shall be at least one (1) 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.
C.
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.
D.
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.
E.
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, or be
captured in a BMP.
[Ord. No. 3025, 8-7-2018]
A.
Riparian Buffers. Riparian buffers will be required as part of all
new development and redevelopment in the City in order to promote
the health, safety, comfort, or general welfare; conserve the values
of property throughout the City; and lessen or avoid undue impact
of stormwater runoff on adjoining properties and the environment.
Buffers adjacent to stream systems provide numerous environmental
protection and resource management benefits which can include restoring
and maintaining the chemical, physical and biological integrity of
the water resources, removing pollutants delivered in urban stormwater,
reducing erosion and controlling sedimentation, stabilizing drainage
ditch banks, providing infiltration of stormwater runoff, maintaining
the base flow of the drainage ditches, contributing the organic matter
that is a source of food and energy for the aquatic ecosystem, providing
tree canopy to shade streams and promote desirable aquatic organisms,
providing riparian wildlife habitat, furnishing scenic value and recreational
opportunity, protecting the public from flooding, property damage
and loss, and providing sustainable, natural vegetation. This Section
establishes minimum acceptable standards for the design of riparian
buffers to protect the streams, wetlands, floodplains and riparian
and aquatic ecosystems of the City.
1.
Riparian Buffer Plan Requirements.
a.
General Plan Requirements. All administrative surveys, plats,
development plans, subdivision improvement plans and building permit
site plans, shall set forth an informative, conceptual and schematic
representation of the proposed riparian buffers by means of maps,
graphs, charts, or other written or drawn documents so as to enable
the Director an opportunity to make a reasonably informed decision
regarding the proposed activity.
b.
Specific Plan. Riparian buffer plans shall contain the following
information and shall be shown on one (1) or more sheets as required
by the Director:
(1)
A site plan map at a minimum scale of one (1) inch
equals two hundred (200) feet.
(2)
Map delineated and surveyed streams, springs, seeps,
bodies of water and wetlands [include a minimum of two hundred (200)
feet into adjacent properties].
(3)
Riparian buffer plans for an individual single-family
or two-family dwelling or an administrative survey are not required
to survey the features listed above.
(4)
Delineated riparian buffers.
(5)
Limits of the one-hundred-year floodplain as shown
on the adopted floodplain maps.
2.
Plan Submittal. The buffer plan shall be submitted in conjunction
with the required development permit application or land disturbance
plan for any development, whichever is submitted first. The buffer
must be clearly delineated on the site grading plan. Provide a note
on the site grading and drainage plans or development site plan stating,
"There shall be no clearing, grading, construction or disturbance
of vegetation except as specifically approved by the Director."
3.
Temporary Boundary Markers. Markers will be installed by the
applicant prior to commencing clearing and grading operations and
maintained throughout the applicant's development activities. The
markers will be placed on the outside edge of the buffer zone prior
to the start of any activity within fifty (50) feet of the buffer
or as shown on a land disturbance plan approved by the City. Markers
shall be clearly visible and shall be spaced at a maximum of one hundred
(100) feet. The markers shall be joined by marking tape or fencing.
Orange construction fencing should be used to delineate the limits
of the riparian buffer.
4.
Plan Preparation. Riparian buffer plans, except for single-family
dwellings, or two-family dwellings, shall be prepared by a professional
surveyor, engineer or architect licensed to practice in the state.
5.
Design Standards For Riparian Buffers.
a.
General. An adequate buffer for a drainage system shall consist
of a predominantly undisturbed strip of land extending along both
sides of the drainage ditches and their adjacent wetlands. The buffer
width may be adjusted to include contiguous sensitive areas, such
as steep slopes or erodible soils, where disturbance may adversely
affect water quality, drainage ditches, wetlands, or other water bodies.
All specified riparian buffer widths are minimums and may be increased
as specified in these regulations or on a voluntary basis by the property
owner.
b.
Buffer Measurement. The buffer shall begin and be measured from
the ordinary high-water mark of the channel during base flows.
c.
Minimum Buffer Width. The required base width for all buffers
shall be thirty (30) feet or the width of the one-hundred-year floodplain
as shown on the City flood insurance rate map, whichever is greater.
d.
No Buffer Required. A riparian buffer shall not be required
for portions of a drainage ditch that are less than one hundred fifty
(150) feet in length due to the drainage ditch having been previously
enclosed within a pipe or box structure immediately upstream and downstream
of the subject location. In such cases, the ditch portion may be similarly
enclosed in a pipe or box structure. Also, this Article shall not
be construed so as to prevent modifications to drainage ditches or
wetlands if such modifications have been approved and permitted by
a federal agency such as the U.S. Army Corps of Engineers.
e.
Riparian Buffer Averaging. The riparian buffer width may be
relaxed and the buffer permitted to become narrower at some points
to allow for structures existing on the date of adoption of these
regulations, provided:
f.
Waivers And Variances. The Director may grant a waiver for those
projects or activities serving a public need, where no feasible alternative
is available, or for projects where the repair and maintenance of
public improvements is necessary, where avoidance and minimization
of adverse impacts to wetlands and associated aquatic ecosystems have
been addressed.
(1)
Application. The applicant shall submit a written
request for a waiver to the Director. The application shall include
information specified by the Director and specific reasons justifying
the variance and any other information necessary to evaluate the proposed
variance request. The Director may require an alternatives analysis
that clearly demonstrates that no other feasible alternatives exist
and that minimal impact will occur as a result of the project or development.
(2)
Review By Director. Upon receipt of all application
materials, the Director shall have twenty (20) working days from the
date of the complete application in which to issue a decision. If
during review of the application the Director requests additional
information, then the time between when the request was made and when
the information is submitted shall not count against the review period.
B.
Ditchside Zone. The zone immediately adjacent to the drainage ditch,
twenty (20) feet in width.
1.
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 streamside zone is undisturbed indigenous
vegetation.
2.
Allowable uses in the streamside zone: flood-control structures,
stream-gauging and water-quality-monitoring equipment, stormwater
treatment facilities in accordance with an approved plan:
a.
Utility crossings.
b.
Permeable-surfaced foot and bicycle paths.
c.
Road crossings.
d.
Utilities where no practical alternatives exist as determined
by the Director.
e.
Ditch restoration, ditch bank restoration or restoration of
indigenous vegetation in accordance with an approved plan.
f.
Roads, that exist on or before the date of adoption of these
regulations, and associated maintenance activities.
3.
Restricted Uses In The Ditchside Zone. The following uses are
prohibited except where incidental to an allowable use:
a.
Clearing of existing vegetation.
b.
Grading, stripping or other soil-disturbing practices.
c.
Filling or dumping.
d.
Draining the buffer area by ditching, underdrains or other systems.
e.
Use, storage or application of pesticides, except for the spot
spraying of noxious weeds or other species consistent with recommendations
of the state department of conservation, United States Department
of Agriculture or University of Missouri Extension Service.
f.
Storage or operation of motorized vehicles except for maintenance,
inspection or emergency use.
g.
Walls, solid fences, chain-link fences, woven or welded wire
fences.
h.
Structures or any type of impervious surface except as provided
above.
[Ord. No. 3025, 8-7-2018]
A.
Runoff Reduction. In order to replicate pre-development hydrologic
conditions, and to promote base flow to streams and wetlands, ten
percent (10%) of the water quality volume shall be permanently reduced.
This may be accomplished by disconnecting impervious areas, maintaining
sheet flow to areas of natural vegetation such as riparian corridors,
infiltration practices where soil conditions allow for collection
and reuse of runoff.
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-channel habitats and reduce
in-channel erosion.
[Ord. No. 3025, 8-7-2018]
A.
Water Quality Protection. In order to protect the receiving waters
from non-point source pollution, the remainder of the water quality
volume that was not removed through runoff reduction shall be treated
through filtration BMPs such as sand filters, vegetated swales, or
proprietary products.
B.
Treatment Of The Water Quality Volume. Post-development runoff from
the water quality rainfall event that is not permanently removed through
the application of the runoff reduction criterion shall be captured
and treated in a water quality BMP to prevent or minimize water quality
impacts from land development. Up to ten percent (10%), of a site's
total impervious surface may discharge in a sheet flow condition through
existing established vegetation such as may exist in a riparian buffer
without otherwise being treated.
C.
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
BMPs. Up to ten percent (10%) of a site's total impervious surface
may discharge in a sheet flow condition in a non-erosive manner through
existing established vegetation such as may exist in a riparian buffer
without otherwise being treated.
D.
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.
E.
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.
[Ord. No. 3025, 8-7-2018]
A.
Land development that qualifies as redevelopment shall meet (1) one
of the following criteria:
1.
Reduce Impervious Cover. Reduce existing site impervious cover
by at least twenty percent (20%).
2.
Provide Treatment. Provide runoff reduction and water quality
treatment for at least twenty percent (20%) of the site's pre-development
impervious cover and one hundred percent (100%) of any new impervious
cover through stormwater BMPs designed in accordance with the criteria
in this Article and the City stormwater design manual.
3.
Apply Innovative Approaches. Utilize innovative approaches to
reduce stormwater impacts across the site.
4.
Provide Off-Site Treatment. Provide equivalent stormwater treatment
at an off-site facility within the same watershed and as immediately
downstream of the site as feasible.
5.
Address Downstream Issues. Address downstream channel and flooding
issues through channel restoration, increase in existing system capacity
or other off-site remedies.
