chapter - 1 introduction - Meghalaya State Pollution Control Board

Hills Cement Co. Limited.
simultaneously and their resultant incremental concentration of the pollutant
can be predicted.
Extrapolation of Wind Speed
Power law as given below calculates wind speed at stack level.
U stack = U10 (Stack height/10) p
Where U10 is the wind speed at 10-meter level and p is the power law
coefficient (0.07, 0.07, 0.10, 0.15, 0.35 and 0.55 for stability classes A, B, C,
D, E and F respectively) as per Irwin for rural areas (USEPA, 1987).
Stability Classification
Hourly stability is determined by wind direction fluctuation method as
suggested by Slade (1965) and recommended by CPCB (PROBES/70/1997-
1998).
1a = Wdr/6
1a is standard deviation of wind direction fluctuation; W dr is the overall wind
direction fluctuation or width of the wind direction in degrees. The table for
stability classes is given as under.
Stability
Class
1a (degree)
A > 22.5
B 22.4 – 17.5
C 17.4 – 12.5
D 12.4 – 7.5
E 7.4 – 3.5
F < 3.5
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