[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:
(1) 
The average width of the riparian buffer must meet the minimum requirement specified.
(2) 
There is no reduction in the width of the streamside zone.
(3) 
No new structures are built in the one-hundred-year floodplain. This does not restrict allowable uses in the streamside zone as defined below.
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.
(3) 
Other Variances. Where undue hardships or practical difficulties may result from strict compliance with this Section, the developer may file a variance in accordance with Section 420.490.
6. 
Uses.
a. 
All uses allowed in Ditchside Zone, and surfaced biking/hiking paths, detention/retention structures, utility corridors, stormwater BMPs, residential yards, landscaped areas.
7. 
Function.
a. 
Protect the physical and ecological integrity of the stream ecosystem.
b. 
Protect key components of the stream, filter and slow velocity of water runoff.
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.
6. 
Combination Of Measures. Any combination of Subsection A(1) through (5) of this Section that is acceptable to the City.