Erosion and Sediment Pollution Control Program Manual.pdf

Organic Soil -----Soil composed predominantly of organic rather than mineral material. Equivalent to
Histosol.
Organics -----Particles of vegetation or other biologic material that can degrade water quality by
decreasing dissolved oxygen and by releasing organic solutes during leaching.
Orifice -----An opening with a closed perimeter through which water may flow. It is usually sharpedged,
and of regular form in a plate, wall, or partition.
Orifice Flow -----In a barrel/riser type spillway, it refers to either:
1) Water entering the riser through perforations in the riser.
2) Water entering the top of the riser when the water level has reached a certain elevation
above the riser.
OSHA -----Occupational Safety and Health Administration (U.S. Dept. of Labor).
Outcrop -----Surface exposure of bedrock.
Outfall -----The point where water flows from a pipe, conduit, channel, etc.
Outfall Structure -----An endwall, splash pad, riprap apron, ditch, conduit, diffuser, or diversion used
as an outfall. An authorization is required.
Outlet -----The point of water disposal from a stream, river, lake, tidewater, or artificial drain.
Outlet Basin -----Outlet protection for a barrel/riser type sediment trap or a temporary slope pipe
conveying clean water. See Standard Construction Detail 8-6.
Outlet Channel -----A suitably sized and protected channel for the purpose of conveying the discharge
from a culvert, pipe, or impoundment to the receiving waters.
Outlet Control -----In culverts, it is the condition where the culvert barrel is not capable of conveying as
much flow as the inlet will accept.
Outlet Protection -----An apron, dissipater, basin, or other device placed below a pipe or channel
outfall to prevent scour.
Outslope -----The exposed area sloping away from the top of a fill or bench.
Overbank Drainage -----Water flow over top of the bank and down the slope.
Overbank Flow -----Water flow over the top of the bankfull channel onto the floodplain.
Overburden -----The earth, rock, and other materials that lie above a coal or mineral deposit.
Overland Flow -----Also called sheet flow. In determining travel time (TC), it is the flow regime before
shallow concentrated flow.
Overseeding -----Seeding into a dormant turf with cool season grasses in order to provide a playable
surface, as on a golf course, during winter months, or for aesthetics.
Overstory -----The uppermost part of a plant community.
Overtopping -----The passing of water over the top of a natural or artificial structure as a result of wave
action or surging.
Owner ----- A person who holds legal title to the land subject to construction activity. This term also
includes the person(s) who held legal title to the land subject to construction activity at the time
such activity was commenced on a site.
Oxbow -----An abandoned meander in a river or stream system.
Oxidation -----The chemical process in which electrons are removed from an atom, ion, or compound.
Oxidation always occurs as part of an oxidation-reduction reaction.
P
P -----Symbol for wetted perimeter - In a channel, it is the length of the boundary between the water and
the channel sides and bottom.
PA DCNR Bureau of Forestry -----The state agency responsible for the protection of over 2 million
acres of forest land in the Commonwealth from forest fire, insects and disease.
PA DCNR Bureau of Topographic and Geologic Survey -----Plans, administers, and conducts
comprehensive and detailed surveys of the geology, mineral resources, topography and ground
water resources of PA.
PA DEP Bureau of Safe Drinking Water -----The state agency responsible for setting drinking water
standards..
363-2134-008 / March 31, 2012 / Page 535