ILLINOIS POLLUTION CONTROL BOARD
September 7, 1978
COMMONWEALTH EDISON CO.,
)
Petitioner,
)
v.
)
PCB 78-71
)
ENVIRONMENTAL PROTECTION AGENCY,
)
Respondent.
OPINION AND ORDER OF THE BOARD (by Mr. Dumelle):
This matter comes before the Board on the March 14, 1978
Petition of Commonwealth Edison Company for a determination
pursuant to Rule 203(i) (5) of Chapter 3 of the Regulations, that
thermal discharges from its Dixon Generating Station have not
caused and cannot reasoi~ablybe expected to cause ecological
damage to the receiving waters. The Agency’s Response, filed
May 5, 1978, waived all right to file a Recommendation in the
matter and requested a decision on the pleadings. A mandatory
hearing was held on July 14, 1978. No members of the public were
present. Petitioner’s representative testified that the Dixon
Station was to be retired from operation one week from the date
of the hearing. No evidence was offered in addition to the report
prepared by Petitioner in support of its petition and attached
thereto. No challenge was made by the Agency at the hearing to
any of the facts and conclusions stated in this report. Therefore,
all data referred to in this opinion are found in Petitioner’s
report and it is the sole basis for the Board’s determination
under Sec. 203(i) (5).
The Dixon Generating Station is located on the Rock River at
Dixon, Illinois. It contains two coal—fired units having a total
net generating capacity of 119,000 kw. These units have been
in commercial operation since 1945 and 1953, respectively. Plant
capacity factor over the five year period 1972—1976 ranged from
62.5 (1973) to 27.2 (1976) with a projected future capacity
factor of 30-35 until retirement in October, 1978 (p. 3). Each
unit uses a once—through condenser cooling system, drawing water
from the Rock River upstream from the station and discharging it
downstream. Four circulating water pumps are used with maximum
pumping rates of 50,000 gpm and 53,000 gpm respectively.
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—2—
The Rock River is characterized as a moderately fast—moving
river, with an average velocity of 2.4 fps (p. 13). However,
since it is also relatively shallow (7—15 feet), current velocities
are less near the edges than in the deeper centers. The Rock
River experiences seasonal changes in flow, with annual high flows
in spring and early summer and annual low flows in fall and winter
(p. 11). The plant intake of cooling water parallels the seasonal
flow; intake studies conducted at the station during 1975—6 showed
plant average flow in fall and winter as roughly half that of
spring and summer (Table 3, pp. 7-10). Comparison of average
river flow with plant cooling water flow during repeated 24-hour
periods throughout the year (see Table 3) showed that less than
six percent of the Rock River was utilized in the cooling system
over the test year, with a quarterly mean of less than 2 in all
quarters except summer, 1975.
Plume Studies. A demonstration pursuant to Rule 203(i) (5)
shall include the information delineated in Rule 602(a)-(d) of
the Procedural Rules. The objective of requiring such material is
to permit definition of the temperature effects on water quality
and aquatic biota caused by the thermal discharge not only under
conditions existing at the time of testing, but also under
statistically determined typical seasonal and “worst case” conditions
of river flow, ambient water temperature, and plant operation.
These factors affect the area of the plume; i.e., the area in
which heated discharges raise the temperature of the water greater
than 5°F.
In this respect, the data submitted in Petitioner’s report
are incomplete. Inclusion of relevant data on flow, temperature,
plant loading and meteorological conditions in the actual plume
studies is haphazard and no data on plant loading are included.
The information provided in Table 8 (p. 30) may comply with NPDES
requirements but does not fulfill the requirements of Sec. 602(c)
for theoretical plume studies under typical and worst case condi-
tions. The actual plume studies conducted quarterly during the
year April, 1975
—
March, 1976 (Fig. 5—8, 26—29) demonstrate a
relatively small thermal plume, ranging from 0.6 to 1.5 acres.
However, Table 8 provides little basis for analysis of what
changes in conditions either in the plant operation or river or
climate produced estimated maximum increases in plume area to
5-10 acres during 1976—1977. Failure to include models for
“average” and “extreme” conditions leaves the 1975—76/76—77
statistics without a frame of reference; i.e., to what extent
they represent or deviate from normal seasonal conditions.
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—3—
Effects on water qua1it~’ and aquatic biota. Petitioner’s report
summarizes results of biological and water quality studies con-
ducted by Espey, Huston and Associates from March, 1975 to
February, 1976. Sampling for phytoplankton, zooplankton, pen-
phyton, benthos and fish was done quarterly from three locations:
at the intake area, discharge area and at a point 800 meters down-
stream of the station (see fig. 9). They conclude that the plant’s
thermal discharges have no significant effect on the growth, density
or species diversity of the above populations.
Phvtoplankton was observed to produce large blooms in the
fall, and were largely dominated by diatoms in all three locations.
Very low densities of zooplankton were found during summer, fall
and winter. Summer samples included only two species of crustaceans,
found only at the downstream sampling location. Abundant popula-
tions were found in the spring, however, with the same organisms
dominant and in nearly identical proportions at each sampling
location and no significant variation in density attributable to
thermal discharge (fig. 12). Macroinvertebrate population was
studied by sampling the river bottom at sampling locations (fine
sediment) and providing artificial substrate samples. Although
the “natural substrate” benthos showed a depressed population at
the discharge location (see fig. 15, p. 46) as against the down-
stream and intake (control) points, no corresponding depression
was found on the artificial substrate collections which had been
placed near the discharge and directly exposed to the thermal
effluent. The same species dominated at all three locations and
no consistent pattern of species diversity between locations
receiving thermal effluent and the control located upstream of the
intake point was found.
Fish sampling in the spring, summer and fall showed a predom-
inance of rough and forage species over game species. Although
sampling showed lower numbers of species and individuals in the
discharge area than in the upstream control location in the summer
months, indicating an avoidance of the discharge area, the downstream
location also produced significantly fewer individuals in summer
and fall, suggesting that differences may have been due to factors
other than temperature (Table 12, p. 51). The study concludes that
since such a small area of the Rock River is involved with the
thermal plume, little impact to the fish of the area is expected
(p. 55,57).
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—4—
It should be noted that these studies were conducted during the
period of time actual plume studies indicated very small plume
area greater than the 50 isotherm being produced by the Dixon
Stations’s discharge in all seasons. Petitioner’s report does not
discuss possible thermal effects on river biota caused by the 5-10
acre plume area predicted to occur after 1975, or under theoretical
extreme conditions. For example, the one day samplings taken in
July, 1976 and July, 1977 (Table 8) show significantly lower river
flow than during July, 1975 (Table 3, p. 8 which must be converted
to cfs for comparison purposes). That of July 6, 1977 is less than
the 7 day, 10 year flow of 1,444 cfs (p.11). According to Table
8, cooling water utilized by the station on that date would equal
approximately 20 of the Rock River flow. (Average use in July,
1975 was 3.65.) The report gives no indication of whether such
a combination of low river flow and high temperatures approach
theoretical “worst case conditions” as shown by historical records
or is closer to typical for the month of July; nor the frequency
with which such conditions can be expected to occur over the years.
No information was given as to what percentage of the total
river flow would be occupied by the estimated 10—acre plume in
sumr~ner months. Such information is significant when temperatures
within the plume may reach the high 90’s and cause morbidity among
nonmobile organisms.
In sum, Petitioner’s submitted report demonstrates that as of
the date of the studies, no significant impact was observed on
river quality and aquatic biota as a result of the Dixon Station’s
thermal discharges into the Rock River. The demonstration, however,
does not meet the requirements of Rule 602(d) (1), (2) and (3).
Absence of a consideration of potential effects under “typical” and
“worst case” conditions, and of a discussion of factors causing
estimated plume areas significantly larger in recent years than
those actually observed in earlier years, renders it difficult to
make a determination that Petitioner’s Dixon Station discharges
cannot reasonably be expected to cause significant ecological
damage to the receiving waters under 203(1) (5).
Nevertheless, if the Dixon Generating Station is in fact
retired from operation on October 1, 1978, as scheduled, or on
July 21, 1978 (R.8) as testified, the need for any further studies
is rendered academic. Thus it is not necessary for the Board to
make a finding on the merits because the plant is presumed to be
no longer in operation.
ORDER
It is the Order of the Pollution Control Board that the instant
proceeding be dismissed as moot.
I, Christan L. Moffett, Clerk of the Illinois Pollution Control
Board, hereby certify the abpve Opinion and Order were adopted on
the __________day of ‘~,
~
, 1978 by a vote of~/()
Christan L. Moff~’t4~Cle~k
Illiflois Pollution Control Board
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