Drainage Terms A-Z
P
peak discharge
The maximum flow rate at a point in time at a specific location resulting from a given storm condition.
peakedness
A measure of the sharpness of a rainfall profile; that is, the ratio of the maximum to the mean rainfall intensity.
peaking factor
The multiple of dry-weather flow used for design of pipe sizes and gradients.
percentage runoff
The percentage of the rainfall volume falling on a specified area that enters the storm water drainage system.
percentile
The percentage of occurrences within a stated range; also applied to rainfall profiles (see peakedness).
pervious surface
A type of ground surface that allows infiltration of water, although some surface runoff may still occur.
point rainfall
Rainfall rate at a location, in contrast to the average for the region or surrounding area.
pollutant
Dissolved or particulate material washed into and through sewers. When discharged into receiving waters, pollutants cause an adverse environmental impact.
pollution
The addition to a natural body of water of any material that diminishes the optimal use of the water body by the population which it serves, and that has an adverse effect on the surrounding environment.
PR equation
Usually refers to the Wallingford Procedure runoff equation (HR Wallingford and Institute of Hydrology 1981a).
primary treatment
The first major treatment in a wastewater treatment facility, usually sedimentation.
private sewer
A sewer for which responsibility is not vested in the sewerage undertaker. Generally it is collectively owned and maintained by the owner(s) of the building(s) it serves.
public sewer
A sewer for which responsibility is vested with the sewerage undertaker to maintain it.
pumping station
A structure containing pumps and appurtenant piping, valves and other mechanical and electrical equipment for pumping water, wastewater and other liquids. |
