ILLINOIS POLLUTION CONTROL BOARD

February 15, 1979

ILLINOIS POWER COMPANY,

)

Petitioner,

v.

)

PCB 79-7

ENVIRONMENTAL PROTECTION AGENCY,

Respondent.

CONCURRING OPINION

(by Mr. Dumelie):

This proceeding evolved from R75-5 decided on December 14,

1978 with my concurring vote.

I had advocated

a 6.8 lbs./MBTU

emission standard

in lieu of the former 6.0 lbs./MBTU limit

enacted in 1972.

The 6.8 figure was a part of the Board’s first

draft of R75-5 but was dropped upon final enactment.

The instant Order holds Illinois Power

(at their request)

to 6.0 lbs./MBTU which is less than the 6.8 figure

I had advocated.

Thus

I have no problem with this emission limit.

What the Board must do

in this proceeding, however,

is

in essence to make a finding that a breach of the air quality

standards will not ever occur under foreseeable meteorological

conditions.

To do this, actual monitoring

data must be studied.

In addition,

since monitors are not always located at the “hot

spots,” modelling must be done.

Models are not absolutely accurate.

The model used

in

the Baldwin Study

is “state of the art”.

There are two trouble-

some points.

First, background concentrations were not taken

into consideration in the model.

The second point

is that the

Briggs plume rise equation, which was used,

tends to overpredict

plume rise from tall stacks,

(which Baldwin has) and thus under-

predicts ground—level concentrations.

The fact that the modelled

concentrations were lower than the monitored concentrations

points out the need to take background concentrations and a more

site specific plume—rise equation into account when determining

if a power plant such as Baldwin will violate air quality stan-

dards or PSD increments.

Since the modelling was only done to a distance of 20 km.

from the plant, Baldwin’s impact on the St. Louis metropolitan

area may not have been adequately considered.

Even though the

accuracy of a model

is unknown at distances greater than 20 km.

(especially for short averaging times), a “ball-park” estimate

of Baldwin’s annual average impact would have been useful.

32—569

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—2—

Without this information it

is difficult to determine if Baldwin

could be contributing to air quality problems

in the Carondelet

or Wood River areas.

The Coalition

for the Environment discussed long range

transport and the conversion of sulfur dioxide to sulfates and

to “acid rain”.

No Federal health standard has yet been promul-

gated for sulfates and thus

it appears to me that the epidi-

meological and medical bases for one must be still under study.

A Midwest “acid rain” monitoring network was set up in 1978

and in a year or two should give valuable data on levels of

acidity and trends in Illinois.

Under the instant Order,

Illinois Power will have to apply

for a new operating permit not more than 21 months from today.

The ambient monitoring and dispersion modelling program results

will show then the accuracy of the model and of the assumptions

used.

Because of questions as to the accuracy of the meteorological

models,

I concur.

Jacob

D. Dumelle

I, Christan L. Moffett, Clerk of the Illinois Pollution

Control Board, hereb~certify the above Concurring Opinion was

filed on the

________________

day of

b~UaJLL~

,

1979.

C1W~\

at

mN~Q±*

I

Christan L. Moftett,

Clerk

Illinois Pollution Control Board

32—570