Unless specifically defined below, words or phrases used in this chapter shall be interpreted so as to give them the same meaning as they have in common usage and to give this chapter its most reasonable application. For the purpose of this chapter, the words MUST and SHALL are mandatory and not permissive. All distances, unless otherwise specified, shall be measured horizontally. As used in this chapter, the following words and terms shall have the meanings ascribed to them in this section.
100-YEAR FLOOD ELEVATION. The elevation of water resulting from the Critical Duration Flood Event. See definition of Critical Duration Flood event.
BEST MANAGEMENT PRACTICES (BMP’s). Measures taken to minimize negative effects on water resources and systems as documented in the Minnesota Construction Site Erosion and Sediment Control Planning Handbook (MBWSR, 1988), Protecting Water Quality in Urban Areas (MPCA, 2000) and the Minnesota Stormwater Manual (MPCA, 2014) as amended.
BETTER SITE DESIGN (BSD). An approach to managing runoff that seeks to attain post development hydrology which mimics the undeveloped condition in terms of volume, rate and timing of runoff. The goals of BETTER SITE DESIGN include reducing the amount of impervious cover, increasing the amount of natural lands set aside for conservation, using pervious areas for more effective stormwater treatment, innovative grading and drainage techniques and through the review of every aspect of the project site planning process. BETTER SITE DESIGN involves techniques applied early in the design process to reduce impervious cover, conserve natural areas and use pervious areas to more effectively treat stormwater runoff and promote a treatment train approach to runoff management.
BIOFILTRATION. A bioretention practice in which an underdrain is used. Typically, most of the water entering the biofiltration practice enters the underdrain and is returned to the stormwater system, but some water infiltrates (unless the BMP has an impermeable liner) or evapotranspires. The underdrain may be at or elevated above the bottom of the practice (i.e. at the media-soil interface).
BIORETENTION. A soil and plant-based stormwater management best management practice (BMP) used to filter runoff.
BRIDGE. A road, path, railroad or utility crossing over a waterbody, wetland, ditch, ravine, road, railroad or other obstacle.
BRIDGE SPAN. The clear span between the inside surfaces of a bridge's terminal supports.
CHANNEL. A perceptible natural or artificial depression, with a defined bed and banks that confine and conduct water flowing either continuously or periodically.
CONSTRUCTION ACTIVITY. Activities including clearing, grading, and excavating, that result in land disturbance of equal to or greater than one acre, including the disturbance of less than one acre of total land area that is part of a larger common plan of development or sale if the larger common plan will ultimately disturb equal to or greater than one acre. This includes a disturbance to the land that results in a change in the topography, existing soil cover (both vegetative and nonvegetative), or the existing soil topography that may result in accelerated stormwater runoff that may lead to soil erosion and movement of sediment. Construction activity does not include a disturbance to the land of less than five acres for the purpose of routine maintenance performed to maintain the original line and grade, hydraulic capacity, and original purpose of the facility. Routine maintenance does not include activities such as repairs, replacement and other types of non-routine maintenance. Pavement rehabilitation that does not disturb the underlying soils (e.g., mill and overlay projects) is not construction activity.
CONVEYANCE SYSTEM. Open channel, pipe or tile that is not a public drainage system. A portion of a conveyance system is defined as “regional” if it carries flows from a drainage area of greater than 200 acres.
CRITICAL DURATION FLOOD EVENT. The 100-year precipitation or snow melt event with a duration resulting in the maximum 100-year return period water surface elevation. The CRITICAL DURATION FLOOD EVENT is generally either the 100-year, 24 hour rainfall event as found in NOAA Atlas 14 or the ten-day snow melt event assumed to be 7.2 inches of runoff occurring on frozen ground (CN=100); however, other durations (e.g., 6-hour) may result in the maximum 100-year return period water surface elevation.
DETENTION BASIN. Any natural or man-made depression that stores stormwater runoff temporarily.
DEVELOPMENT. Any land-disturbing activity resulting in creation or reconstruction of impervious surface including, but not limited to, municipal road construction. Normal farming practices part of an ongoing farming operation shall not be considered a DEVELOPMENT.
DRAINAGE SYSTEM. A system of open channel, pipe or tile, to drain property, including laterals, improvements, and improvements of outlets, which may or may not be a public system under the jurisdiction of a watershed district under M.S. Chs. 103B, 103D, or 103E.
EMERGENCY OVERFLOW (EOF). A primary overflow to pass flows above the design capacity around the principal outlet safely downstream without causing flooding.
EXCAVATION. The displacement or removal of soil, sediment or other material.
FILTRATION. A stormwater quality BMP that uses either natural media such as soil or vegetation or manufactured media to trap pollutants such as nutrients and particles in surface water.
FLOOD FRINGE. That portion of the floodplain outside of the floodway. Flood fringe is synonymous with the term FLOODWAY FRINGE used in the Flood Insurance study for Anoka County.
FLOODPLAIN. The beds proper and areas adjoining a wetland, lake or watercourse which have been or hereafter may be covered by the regional flood.
FLOODWAY. The bed of a wetland or lake and the channel of a watercourse and those portions of the adjoining floodplain which are reasonably required to carry or store the regional flood discharge.
FREEBOARD. Vertical distance between the 100-year flood elevation or emergency overflow elevation of a water basin or watercourse and the elevation of the regulatory elevation of a structure.
IMPERVIOUS SURFACE. A compacted surface or a surface covered with material (i.e., gravel, asphalt, concrete, Class 5, etc.) that increases the depth of runoff compared to natural soils and land cover. Including but not limited to roads, driveways, parking areas, sidewalks and trails, patios, tennis courts, basketball courts, swimming pools, building roofs, covered decks, and other structures.
INFILTRATION. Water entering the ground through the soil.
LAND-DISTURBING ACTIVITY. Any disturbance to the ground surface that, through the action of wind or water, may result in soil erosion or the movement of sediment into waters, wetlands or storm sewers or onto adjacent property. LAND-DISTURBING ACTIVITY includes but is not limited to the demolition of a structure or surface, soil stripping, clearing, grubbing, grading, excavating, filling and the storage of soil or earth materials. The term does not include normal farming practices as part of an ongoing farming operation.
LANDLOCKED BASIN. A water basin lacking an outlet at an elevation at or below the water level produced by the critical duration flood event, generally the ten-day snowmelt event.
LOW ENTRY ELEVATION. The elevation of the lowest opening in a structure.
LOW FLOOR ELEVATION. The elevation of the lowest floor of a habitable or uninhabitable structure, which is often the elevation of the basement floor or walk-out level.
MILL, RECLAMATION AND OVERLAY. Removal of the top layer(s) of an impervious surface (e.g. roadway, parking lot, sport court) by mechanical means, followed by the placement of a new layer of impervious surface, without exposure of the underlying native soil.
NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES) STORMWATER DISCHARGE PERMIT. A permit issued by the Minnesota Pollution Control Agency that authorizes the discharge of pollutants to the waters of the state.
NATIONWIDE URBAN RUNOFF PROGRAM (NURP). Urban Runoff Program developed by the Environmental Protection Agency to study stormwater runoff from urban development.
ORDINARY HIGH WATER LEVEL (OHW). The highest water level elevation that has been maintained for a sufficiently long period of time to leave evidence upon the landscape. The OHW is commonly that point where the natural vegetation changes from predominantly aquatic to predominantly terrestrial. If an OHW has been established for a waterbody by the Minnesota Department of Natural Resources, it will constitute the OHW under this definition.
OWNER. The person or party possessing the title of the land on which the construction activities will occur; or if the construction activity is for a lease, easement, or mineral rights license holder, the party or individual identified as the lease, easement, or mineral rights license holder; or the contracting government agency responsible for the construction activity.
POLLUTANT. A substance that pollutes something, especially water or the atmosphere.
PUBLIC LINEAR PROJECT. A project involving a roadway, sidewalk, trail or utility not part of an industrial, commercial, institutional or residential development.
RECONSTRUCTION. Removal of an impervious surface such that the underlying structural aggregate base is effectively removed and the underlying native soil exposed.
REGIONAL FLOOD. A flood which is representative of large floods known to have occurred generally in Minnesota and reasonably characteristic of what can be expected to occur on an average frequency in the magnitude of the 1% chance or 100-year recurrence interval. REGIONAL FLOOD is synonymous with the term BASE FLOOD used in the Flood Insurance Study.
SEASONAL HIGH WATER TABLE. The highest known seasonal elevation of groundwater as indicated by redoximorphic features such as mottling within the soil.
SEDIMENT CONTROL. Methods employed to prevent sediment from leaving the site. SEDIMENT CONTROL practices include silt fences, sediment traps, earth dikes, drainage swales, check dams, subsurface drains, pipe slope drains, storm drain inlet protection, and temporary or permanent sedimentation basins.
SHORELAND. Land located within the following distances from the ordinary high water elevation of public waters:
(a) Land within 1,000 feet from the normal high watermark of a lake, pond or flowage; and
(b) Land within 300 feet of a river or stream or the landward size of a floodplain delineated by ordinance on the river or stream, whichever is greater.
STABILIZED. The exposed ground surface has been covered by appropriate materials such as mulch, staked sod, riprap, erosion control blanket, mats or other material that prevents erosion from occurring. Applying mulch, hydromulch, tackifier, polyacrylamide, or similar erosion prevention practices is not acceptable stabilization in temporary or permanent drainage ditches or areas where concentrated overland flow occurs. Grass seeding is not stabilization.
STORM SEWER. A pipe system for stormwater conveyance.
STORMWATER. Defined under Minn. Rules 7077.0105, Subd. 41(b), meaning precipitation runoff, stormwater runoff, snowmelt runoff, and any other surface runoff and drainage.
STORMWATER FACILITY, PRIVATE. Any BMP that is maintained by a private property owner, or other private entity and not maintained by a public agency.
STORMWATER MANAGEMENT PLAN. A plan for the permanent management and control of runoff prepared and implemented in accordance with the standards set forth in this chapter.
STORMWATER POND. Constructed basins placed in the landscape to capture stormwater runoff.
SUBDIVISION. The legal separation of an area, parcel, or tract of land under single ownership into two or more parcels, tracts, lots.
SURFACE WATERS. All streams, lakes, ponds, marshes, wetlands, reservoirs, springs, rivers, drainage systems, waterways, watercourses, and irrigation systems whether natural or artificial, public or private.
UNDERGROUND WATERS. Water contained below the surface of the earth in the saturated zone including, without limitation, all waters whether under confined, unconfined, or perched conditions, in near surface unconsolidated sediment or regolith, or in rock formations deeper underground. The term GROUND WATER shall be synonymous with underground water.
WATER QUANTITY BEST MANAGEMENT PRACTICE. The use of on-site runoff management practices such as biofiltration, infiltration, buffers/conservation areas, impervious disconnection, and greenway connections to satisfy stormwater management requirements.
WATERS OF THE STATE. As defined in M.S. § 103G.005, Subd. 17 means surface or underground waters, except surface waters that are not confined but are spread and diffused over the land. Waters of the state includes boundary and inland waters.
WETLAND. Land transitional between terrestrial and aquatic systems, as defined in M.S. § 103G.005, Subd. 19.
(Ord. 09-15, passed 10-26-2015; Am. Ord. 10-22, passed 1-9-2023)