Stormwater Management Standards Manual - Toledo Metropolitan ...

1. Dry Detention Basin
A basin that remains dry except for short periods following large rainstorms or snow melt events. This
type of basin is less effective at removing pollutants.
2. Extended Dry Detention Basin
A dry detention basin that has been modified to increase the length of time that Stormwater will be
detained, typically between 24-40 hours. Extended detention allows pollutants to settle out before
Stormwater is discharged from the basin.
3. Wet Detention Basin
A wet detention facility is designed to maintain a permanent pool of water after the temporary storage of
stormwater runoff. Pollutant removal rates are dependent on the volume to the pool. Permanent pool
volume equal to 0.5-1.0 in. of runoff per acre impervious area will reliably achieve moderate to high
removal rates.
Detention Time
The amount of time that a volume of water will remain in a detention basin.
Development
Development shall be defined as finalization of a plat, re-plat, lot-split, or man-made change to real
estate by private or public agencies including:
• Construction, reconstruction, significant repair, or placement of a building or any addition to a
building;
• Installation of a manufactured home on a site, preparation of a site for a manufactured home, or
placement of a recreational vehicle on a site for more that 180 days;
• Drilling, mining, installation of utilities, construction of roads, bridges, or similar projects;
• Clearing of land in excess of one (1) acre as an adjunct of construction;
• Construction or erection of levees, walls, fences, dams, or culverts; channel modification; filling,
dredging, grading, excavating, paving, or other alterations of the ground surface; storage of
materials; deposit of solid or liquid waste;
• Any other activity that might change the direction, height, volume or flow of drainage runoff and
collection.
Discharge
The rate of flow typically expressed as a volume of water passing a point in a given time. Usually
expressed as cubic feet per second.
Disturbed Area
An area of land subject to erosion due to the removal of vegetative cover and/or soil moving activities,
including filling.
Ditch
An excavated channel for the purpose of drainage or irrigation. May or may not be maintained by a
county agency.
Drainage
The removal of excess surface water or groundwater from land by surface or subsurface drains.
Drainage Improvement
An improvement as defined in O.R.C. 6131.01(C), and/or conservation works of improvement as defined
in O.R.C. 1511 and 1515.
Third Edition Stormwater Standards Manual September 2008 Page 140