City of Excelsior Springs, MO
Clay County
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Table of Contents
Table of Contents
[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:
1. 
Appropriate setbacks that preserve the wetlands or wetland functions;
2. 
Wetland mitigation, including wetland replacement;
3. 
Wetland restoration or enhancement.
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.