Cass County, MO Surface Water Management

Section 400.510 Background Of Storm Water Management Regulations.

[Res. No. 07-06, Zoning Order Art. 8 § A, 7-12-2007]

Under the Federal Clean Water Act of 1972 and additions, storm water management regulations must be implemented for Cass County, in particular to demonstrate compliance with the National Pollutant Discharge Elimination System (NPDES) Phase II section of that law. The County is required to implement a storm water management program for the management of the impact and potential for pollution of the waters of the County and the State resulting from rainfall. The Big Creek, Mount Pleasant, and Raymore townships are specifically designated as requiring permitting for any new use which leads to disturbance of the existing soil surfaces or which may contribute polluting materials to existing drainage systems.

The Missouri Clean Water Law and the Missouri Code of State Regulations also require specific permitting in order to regulate activities that cause land disturbance. A land disturbance permit requires the development and implementation of a Storm Water Pollution Prevention Plan (SWPPP) that includes controls to protect against soil erosion and to limit waste and pollutants on sites, through inspection, monitoring, reporting and record keeping.

In response to these regulatory requirements, the County has established regulations limiting impacts to the waters of the County from any land use which damages, alters or removes natural vegetation such that soil erosion may occur, or which introduces pollutants as defined by State and Federal standards to a site without limiting the potential for such pollutants to extend into the public way and waters. Such uses, include, but are not limited to:

Land clearance operations or construction activities,

Land uses, such as animal density, which diminish the natural ground cover to the extent that there is a potential for soil erosion, without creating new protective covering by utilizing best management practices, (BMPs),

Uses which introduce polluting substances of a type, or by methods, or to the extent that they have the potential to leave the property during storm events and reach public lands or waterways, and for which BMPs are not utilized to limit this potential.

Such land uses shall be considered as violations of this Zoning Order, a misdemeanor. The administration and enforcement response by the County shall be as described in the Administration Article of the Zoning Order.

Section 400.520 Management Methods.

[Res. No. 07-06, Zoning Order Art. 8 § B, 7-12-2007]

Effective techniques to aid in storm water management are referred to as best management practices (BMPs). BMPs seek to maintain or reduce the amount of storm water runoff generated within a watershed by maintaining watershed hydrology and natural ground cover. Treatment is then applied to the runoff where possible to remove the pollutant load. The County maintains, under separate order, descriptions of BMPs that are recommended by the Federal Environmental Protection Agency and the Missouri Department of Natural Resources. BMPs may include structural facilities, non-structural solutions or biological controls to achieve the following management practices:

Preserve and promote natural hydrology of a site by maintaining or reducing the amount of additional storm runoff created by uses on the site, and by promoting natural hydrological characteristics of the site and its surfaces. New uses or alterations to surfaces for existing uses, or failure to maintain surfaces and ground cover for optimal run off characteristics for existing uses, shall not have the affect of increasing the volume of storm water leaving the site from those levels that existed before the change; nor shall the rate at which run off leaves the site or the direction and location be altered; nor shall there be any suspended polluting materials in this storm water.

Install erosion and sediment controls which, when implemented, prevent or minimize erosion of the surface soils and control the amount of sediment or pollutants leaving a site. Such controls may be accomplished by the following:

Stabilizing exposed soils through temporary or permanent plantings, seeding, grass sod placement, and mulching, using native plants wherever practical.

Installing perimeter controls to intercept and detain small amounts of sediment, such as silt fences, straw bale barriers, check dams, diversions, grass lined channels and using sediment trapping devices to intercept sediment in run-off water.

Installing structures for protection at inlets to storm water conveyance piping and providing outlet stabilization structures and sediment basins at outflow locations.

Provide and protect buffering zones along sensitive water bodies from new uses, or alterations to surfaces for existing uses which restrict the approach to shorelines of wetlands, streams and lakes within the County, in order to protect these areas from disturbance or encroachment, and to sustain the integrity of their ecosystems and habitats. Protective measures shall be in the form of:

Water pollution hazard setbacks which separate a potential pollution hazard from a waterway.

Vegetated buffers and natural areas that divide active land uses from encroaching on the buffering zones.

Engineered buffers specifically designed to treat storm water such as depressions, grass filter areas, and forested strips.

Provide and protect water quality through treatment of runoff from rainfall by incorporating designed elements which infiltrate and reduce the amount of runoff and pollutants carried by it, or filter and detain runoff to reduce discharge velocities and remove pollutants. Such practices include:

Installing detention systems which store excess runoff before entry into a principal drainage system. Detention areas must be designed to be easily maintained, and may take the form of wet ponds, wetlands, and dry basins.

Installing filtration systems at or near the source of runoff routes which direct the most contaminated first flush of rainfall through an engineered natural filter such as grass lined channels, dry swales, sand filters, or bioretention areas.

Installing infiltration basins or trenches which capture a volume of storm water runoff, retain it, and infiltrate that volume of water into the ground.

Utilize low impact or cluster design BMP's to maximize controls as close to sources of potential run off and pollution transfer as topography and design conditions permit.

Implement good housekeeping practices such that materials used in production, retail uses and construction, and site wastes resulting from a use are properly managed and disposed of to reduce the risk of pollution from such materials. Surplus or refuse materials or solid waste must be contained within structures or suitable containers such that they do not have a potential to enter storm water runoff or bodies of water.

New commercial and industrial uses shall demonstrate BMPs plans for trash disposal and recycling, proper material handling and spill prevention and cleanup in order to demonstrate that there will not be polluting impact from the new use.

Existing commercial and industrial uses which fail to demonstrate management of trash disposal and recycling, material handling and spill prevention and cleanup such that there is a continuing polluting impact from the existing use shall, upon notification by the Zoning Department of the condition, put into place management plans acceptable to the County for the control of the polluting impact of their use within thirty (30) days of notification. Failure to prevent pollutants from impacting the waters of the County shall be a violation of the Zoning Order and a misdemeanor.

Section 400.530 Stream Buffer Requirements.

[Res. No. 07-06, Zoning Order Art. 8 § C, 7-12-2007]

The County has adopted an overall urban watershed protection strategy which includes stream buffer protections based on three (3) zones of protection along streams, active and seasonal. The effective stream buffer width zones are the Streamside, Middle Core and Outer Zones. Each zone performs a different function and has a different width, vegetative target and management scheme.

Two (2) major goals of a stream buffer network are to maintain an unbroken corridor of riparian forest and to protect the upstream and downstream passage of natural wildlife in the stream channel.

A stream shall be considered as follows: an active channel subject to a water flow with a duration of at least three (3) continuous twenty-four (24) hour periods during any seasonal period.

Setbacks are based upon contributing area of the watershed involved as follows:

Contributing Drainage Area	Streamside Zone (in feet)	Middle Core Zone (in feet)	Outer (in feet)
Watershed less than 40 acres	25	25	25
40 acres to 160 acres	25	40	25
160 acres to 5,000 acres	25	50	25
Greater than 5,000 acres	25	75	25

The Streamside Zone protects the physical and ecological integrity of the stream ecosystem. The minimum width is to be measured from each stream bank, and the stream bank is considered to extend to the limits of ordinary high water, as determined by the County. Land use is highly restricted, limited to storm water channels, footpaths, and minimal utility or roadway crossings.

The vegetative target is mature riparian forest that can provide shade, leaf litter, woody debris, and erosion protection to the stream.

The Middle Core Zone extends from the outward boundary of the Streamside Zone and varies in width depending on stream characteristics, the extent of the one percent (1%) (one-hundred-year) floodplain as administered by the County under the requirements of the National Flood Insurance Program, any adjacent topography, and adjacent protected wetland areas within the watershed. The minimum width of the Middle Core may be expanded based on stream size, slope, or the presence of critical habitats and final determination will be subject to approval by the County.

The function of the Middle Zone is to protect key stream components and provide distance between adjacent land uses and the stream. The vegetative target for this zone is also mature forest, but some clearing may be allowed for storm water management, access and recreational uses when permitted by the County, provided such vegetation does not require the use of additional fertilizer pollutants. A wider range of activities and uses are allowed within this zone, such as bike paths and storm water best management practices (BMPs).

Agrarian uses, such as cultivated cropland or pasturage, on land in an Agricultural District, are permitted to intrude upon the Middle Core Zone, so long as they do not contribute to a state of non-compliance with Federal, State and County regulations.

The Outer Zone is an additional setback from the outward edge of the Middle Core Zone to the nearest permanent above or below ground structure. Uses which do not require structures are generally permitted within this zone. Gardening, compost piles and other common residential activities are promoted within the zone.

The vegetative target for the Outer Zone, as it may well include adjacent residential yard space, is usually natural vegetation, although the property owner is encouraged to plant shrubs and trees. The use of fertilizers which contribute to pollution is prohibited in this zone.

Buffer Crossings, such as roads, bridges, underground utilities, enclosed storm drains or outfall channels shall define a minimum crossing width for maintenance access and use a crossing angle of ninety degrees (90°) where possible to minimize buffer clearing crossing angles, provided such plan is consistent with the stream character and topography.

All such proposed uses which have an impact within the floodplain shall follow the regulations of the Flood Plain Order of this Zoning Order.

Crossing frequency will not exceed one (1) road crossing within each subdivision, and permit no more than one (1) fairway crossing for every one thousand (1,000) feet of buffer in the case of golf courses.

Crossing elevations shall have all direct outfall channels, where effluent is discharged into receiving waters, discharge as required by the Flood Plain Order, at the invert elevation, or the lowest point of the stream channel. In case of a conflict, the Flood Plain Order requirements shall govern.

Storm water management practices utilizing BMPs may be incorporated into the Outer and Middle Core Zones of the stream buffer where they include a grass/forest filter strip, under limited circumstances.

The buffer by itself may only effectively treat incoming flow from adjacent impervious areas to a perpendicular distance of approximately seventy five (75) feet of the contributing adjacent watershed. The design of additional methods to supplement the buffer plantings, such as with constructed filters and detention biofilters, must include a calculated maximum runoff velocity, for both a six-month and a two-year storm, from each overland flow path, based on the slope, soil and vegetative cover. If the calculations indicate that velocities will be erosive under either condition, greater than three (3) feet per second (fps) for a six-month storm, five (5) fps for a two-year storm), the allowable area of contributing flow should be reduced.

When the buffer receives flow directly from an impervious area of an adjacent use, the BMP must include a calculated maximum runoff velocity, for both a six-month and a two-year storm, from each overland flow path, based on the slope, and impervious surfacing and such controls as required to spread run off evenly over the filter strip, and control and pollution elimination measures.

In order for the stream buffer to be used as a storm water filtering system, basic maintenance must be assured, such as routine mowing of the grass filter and annual removal of accumulated sediments at the edge of the impervious areas and the grass filter. An enforceable and long term maintenance agreement that requires the adjacent use to provide this maintenance is required, as defined in the Subdivision Regulations. An annual inspection shall be performed by the Zoning Department to assure the maintenance standards are maintained, and shall include a fee as established by the County Commission.

Location of storm water ponds and wetlands may be permitted by the County within the stream buffer zones under limited conditions. Constructed ponds and wetlands which may provide for the dry weather flow of a stream to maintain water levels and prevent nuisance conditions, and ponds and wetlands which are designed to create a greater diversity of habitat types and structure may be included as part of a combined storm water management plan and a stream buffer protection plan for new uses and the disturbance of surfaces of existing uses. In addition, storm water ponds and retention wetlands specifically designed to remove pollutants utilizing BMPs acceptable to the County, as part of a proposed new use, may be permitted.

Buffer regulation which provides for flexibility, in particular for existing uses that may be proposing alterations which will affect the land surfaces that are immediately adjacent to the buffer zones, may be utilized by the County to mitigate negative impacts to the existing uses associated with the creation of stream buffer strips. Design methods may include the following, at the discretion of the County:

Buffer averaging where the buffer is permitted to become narrower at some points along the stream, as long as the average width meets the minimum requirement.

Zoning District regulation variances to create compensation methods, such as additional density of use on the site in some areas in order to compensate for land lost to the buffer protections when a Mixed Use Overlay process is being used. Usable land is considered to be the buffer area remaining after the one-hundred-year floodplain, wetland and steep slope areas have been subtracted. When more than five percent (5%) of usable land is consumed, designs which allow greater flexibility in setbacks, frontage distances, or minimum lot sizes may also be considered by the County.

Cluster design in a Mixed Use Overlay process may allow for the recovery of usable land that is taken out of production due to buffers or storm water management plans. Designs to place uses in more compact groupings as a means to open up more of the site for buffer and other uses may be considered by the County.

Low impact design BMPs utilizing pervious paving, disbursed filters and retention areas.

Conservation easements may be permitted, allowing the landowner the option of protecting lands within the buffer with a perpetual conservation easement.

Variances may be permitted by means of the process described in the Zoning Order in situations where an existing property owner can demonstrate severe economic hardship or unique circumstances which make it impossible to meet some or all buffer requirements when making alterations in the existing use which may impact the buffer zones.