For the purpose of this subchapter, the following definitions shall apply unless the context clearly indicates or requires a different meaning.
BY-PASS CHANNEL. A channel formed in the topography of the earth’s surface to carry stormwater runoff through a specific area.
CONTROL STRUCTURE. A structure designed to control the volume of stormwater runoff that passes through it during a specific period of time.
DRY BOTTOM STORMWATER STORAGE AREA. A facility that is designed to be normally dry and that contains water only when excess stormwater runoff occurs.
EXCESS STORMWATER. That portion of stormwater runoff which exceeds the transportation capacity of storm sewers or natural drainage channels serving a specific watershed.
GROUNDWATER RECHARGE. The replenishment of existing natural underground water supplies.
GROUNDWATER RECHARGE CAPACITY. The amount of water absorbed into the ground as determined by a percolation test.
LOW FLOW. Any amount of runoff less than design conditions.
NATURAL DRAINAGE. Channels formed in the existing surface topography of the earth by natural causes prior to changes made by unnatural causes.
POSITIVE GRAVITY OUTLET. The drainage of an area by means of natural gravity so that it lowers the free water surface to a point below the existing grade or invert of storm drains within the area.
RECOGNIZED AGENCY. An agency or governmental unit that has statistically and consistently examined local, climatic and geologic conditions and has maintained records as they apply to stormwater runoff, e.g. the Metropolitan Sanitary District of Greater Chicago, the United States Weather Bureau, the University of Illinois Engineering Experiment Station, the Illinois State Water Survey and the like.
RUNOFF RATE COEFFICIENT. A numerical factor used to determine the percentage of stormwater that will not be absorbed by the ground.
SAFE STORM DRAINAGE CAPACITY. The quantity of stormwater runoff that can be transported by a channel or conduit without having the water surface rise above the level of the earth’s surface over the conduit or adjacent to the waterway.
STILLING BASIN. An artificially enclosed area to collect stormwater which will permit soil and debris to settle out.
STORMWATER RELEASE RATE. The volume of water in gallons per minute at which stormwater runoff is released from a control structure.
STORMWATER RUNOFF. Water that results from precipitation which is not absorbed by the soil or plant material.
STORMWATER STORAGE AREA. An area designated to store excess stormwater.
TRIBUTARY WATERSHED. All of the area that contributes stormwater runoff to a given point.
WET BOTTOM STORMWATER STORAGE AREA. A facility that is designed to be maintained as a free water surface or a pond.
(2000 Code, § 15.84.010)