1150 
- The degree of turbulence is specified in terms of the 
bridled-cup turbulence integrator [19], as developed by 
Gill. This instrument may be described as a gust accel- 
erometer. Hach change of wind speed of 2 mph causes a 
deflection in the trace made by a moving pen. The 
degree of turbulence is specified as the number of 
deflections per half hour; if this number is multiplied 
by four, the horizontal gust acceleration in miles per 
hour per hour is obtained. The turbulence integrator 
thus measures a basic parameter of the turbulence 
field. It has been found that winds at Trail from the 
north, east, south, southwest, and intermediate direc- 
tions, and with a speed of 5 mph or more, generally do 
not carry the smoke downvalley and into the state of 
Washington, and so are considered favorable. Winds 
from directions other than these and a wind in any 
direction with a speed of less than 5 mph are unfavor- 
TasiLe J. Maximum PERMISSIBLE SULFUR EMISSION 
(tons of contained sulfur per hour) 
Turbulence* 
Time Season 
0-74 | 75-149 | 150-349 | >350 
Midnight to3 a.m.) Growing 2 EG OQ wai} wil 
Nongrowing | 2 8|6 11)9 i1| 11 
3 a.M. to 3 hr | Growing Q@ Bie AIA 6 6 
after sunrise Nongrowing |0 4|4 6/4 6 6 
3 hr after sunrise | Growing 2 ElG OOo wie) wl 
to 3 hr before | Nongrowing | 2 8|6 11/9 11] 11 
sunset 
3 hr before sunset | Growing A GS Cie O 9 
to sunset Nongrowing |}2 7|/5 9/7 9 9 
Sunset to mid- | Growing B NO My OQ wie | Ail 
night Nongrowing |3 9|6 11/9 i7]| il 
* Deflections of turbulence integrator per half hour. Sulfur 
emission for unfavorable winds (left columns) and for favor- 
able winds (right columns). 
able. Because the degree of susceptibility of vegetation 
to damage by sulfur dioxide varies with the time of 
day and the season of the year, the permissible maxima 
have corresponding variations—high maxima for low 
susceptibility and vice versa. Overriding safeguards 
are provided in other clauses of the control regime. 
Because of the great difficulty of forecasting winds and 
turbulence in a valley such as that in which the smelter 
is located, the control is based on contemporary, not 
forecast, conditions. Over more regular terrain it should 
be possible to forecast the pertinent parameters to a 
satisfactory degree of accuracy. 
Methods of forecasting smog for the Los Angeles 
area, to permit control of the amount of contaminating 
substances discharged into the air when smog is im- 
minent, are being developed [54, 98]. A study of the 
relationship between past occurrences of smog and 
past weather conditions has led to the development of 
a smog index S which is expressed in terms of mete- 
orological variables. 
il 1/2 
(1) 
10(T> + 10) 
Ds RW 
(12) 
ATMOSPHERIC POLLUTION 
where: 7p = deviation in degrees Fahrenheit of the 
24-hour mean temperature from the mean 
temperature for that particular day of 
the year; 
R = relative humidity at noon; 
W = total 24-hour wind movement in miles; 
V = noon visibility in miles; and 
I = inversion intensity from the equation 
(Aa)* 
D 34 zh’ (18) 
where: A? = change in potential temperature in de- 
grees Kelvin through the inversion layer; 
z = height of the inversion base, im hectom- 
eters; and 
Az = thickness of the inversion: layer, in hec- 
tometers. 
Agreement is marked between days for which the smog 
index is large (indicating smog conditions) and days on 
which more than the minimum of four complaints of 
smog were received by the Los Angeles County Air 
Pollution Control District. The success of this index 
led to a method of forecasting smog in terms of the 
relationship between the presence or absence of smog 
and upper-air pressures and air movements. Smog oc- 
curs only when the three-day sum of the deviations 
from the normal height of the 700-mb surface lies within 
the limits 0 and +1000 ft (700-mb surface higher than 
normal) and the three-day sum of the daily average 
wind speeds at 10,000 ft is less than 80 mph (light winds 
at 10,000 ft). When the two parameters lie outside these 
limits there is a high probability that smog will not 
occur on the day for which the computation was made 
nor on the two following days. 
Investigations made by Smith [76] and associates at 
Brookhaven National Laboratory have laid the founda- 
tion for a program of meteorological control of effluents 
from the nuclear reactor there. Predominant gustiness 
is classified according to types denoted by the symbols 
A, B, C, and D, corresponding to marked thermal 
turbulence, a combination of thermal and mechanical 
turbulence, marked mechanical turbulence, and tur- 
bulence with small vertical components of motion, 
respectively. These four types are illustrated in Fig. 5. 
The occurrence of each type in terms of gradient wind 
speed, vertical temperature distribution, time of day, 
and season of the year is specified; such specifications 
simplify the forecasting of the gustiness. The effluent 
to be controlled is argon-41, with a half-life of 110 
minutes; the stack concentrations are so low that no 
health hazard is encountered from instantaneous maxi- 
mum concentrations. Rather, it is mean radiation dos- 
age over a number of days which has been selected as 
the operating criterion. A series of templates, each 
giving contours of mean hourly radiation dosage at 
ground level for a particular combination of wind speed 
and gustiness, were prepared on the basis of experi- 
mental data on oil-fog concentrations. The forecast 
radiation dosage, obtained from the templates, is added 
to the accumulated dosage over a period of days ob- 
tained by use of the templates in conjunction with the 
