2025 2 10 Work Session PACKET 1

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ORDINANCE NO. 1138 
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(31) A rainfall event is defined as any occurrence of rain preceded by 10 hours without 
precipitation that results in an accumulation of 0.01 inches or more. Instances of rainfall 
occurring within 10 hours of each other will be considered a single rainfall event. 
(32) Registered Engineer and Registered Landscape Architect An engineer or 
landscape architect certified and registered by the State Board of Architectural and 
Engineer Examiners pursuant to Section 62-202, Tennessee Code Annotated, to practice 
in Tennessee. 
(33) Runoff coefficient means the fraction of total rainfall that will appear at the 
conveyance as runoff. Runoff coefficient is also defined as the ratio of the amount of 
precipitation that is not absorbed by the surface to the total amount of precipitation that 
falls during a rainstorm. 
(34) Sediment means solid material, both inorganic (mineral) and organic, that is in 
suspension, is being transported; or has been moved from the site of origin by wind, 
water, gravity or ice as a product of erosion. 
(35) Sediment basin A temporary basin consisting of an embankment constructed 
across a wet weather conveyance, an excavation that creates a basin, or by a combination 
of both. A sediment basin typically consists of a forebay, dry & wet storage, permanent 
pool, primary spillway, secondary or emergency spillway and surface dewatering device. 
The size and shape of the basin depends on the location, size of drainage area, incoming 
runoff volume and peak flow, soil type and particle size, land cover, and receiving stream 
classification (i.e., waters with unavailable parameters, Exceptional TN Waters, or waters 
with available parameters). 
(36) Sedimentation means the action or process of forming or depositing sediment. 
(37) Significant Contributor is defined as a source of pollutants where the volume, 
concentration, or mass of a pollutant in a stormwater discharge can cause or threaten to 
cause pollution, contamination, or nuisance that adversely impact human health or the 
environment and cause or contribute to a violation of any applicable water quality 
standards for receiving water. 
(38) Soil or Topsoil means the unconsolidated mineral and organic material on the 
immediate surface of the earth that serves as a natural medium for the growth of plants. 
(39) Steep Slope or Steep Grade means a natural or created slope of 35% grade or 
greater.  
(40) Stormwater means rainfall runoff, snow melt runoff, and surface runoff and 
drainage. 
(41) Stormwater control measure or SCM means permanent practices and measures 
designed to attenuate peak stormwater runoff flow in addition to reducing the discharge 
of pollutants from new development projects or redevelopment projects. 
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