ML20037B490
| ML20037B490 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/19/1977 |
| From: | Desiree Davis Office of Nuclear Reactor Regulation |
| To: | Bolger R COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8010100501 | |
| Download: ML20037B490 (3) | |
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50-249 lE= 9 Ng Comonwealth Edison Company ATT i: Mr. R. L. Bolger Assistant Vice President P. O. Box 767
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Chicago, Illinois 60690 Gentlenen:
W By letter dated August 30, 1976, you described the recent changes made in the NPDES Pemit for Dresden Station, Unit Nos.1, 2 and 3.
The (0
amended NPDES Pemit allows continuous discharges from the Unit Nos.
M,E 2 and 3 discharge cooling lake to be as large as 500,000 gpm. The E=
staff's assessment in the Fin.1 Enviromental Statement (FES) of the H=
inpact on the Illinois River by Unit Hos. 2 and 3 used the value of p~..
50,000 gpa for blowdown.
Environmental Technical Specifications have not yet been issued for the Dresden Station. Therefore, to assure
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that the FES findings are still valid, by letter dated January 11, i~
1977, we requested data to evaluate the acceptability of this increased E
blovJown and intake on the physical and biological characteristics of the affected water bodies.
Your responses dated February 18, 1977, and March 10, 1977, addressed our questions on the size of the themal plume, and questions concerning impact at the intake caused by impinge-
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- ent and entrainment.
c have evaluated your submittal with regard to discharge effects.
I Seven thernal plune studies were nade during periods when the blowdown p
rate was approxinately 500,000 gpm.
During these periods the size of h=7 the themal plune was rtapped and found to average 16.9 acres, with a naxirun of 24.6 acres. The impact assessment in the FES is based on a 50,000 gpm blowdown and a maximun size of the 5*F themal plume
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isothem of 26 acres.
Your study shows that, even with the higher b1cxdown rate, the piutte size is within 26 acres. As it is the size of the plune rather than the blowdown rate which causes adverse envi-romental effects due to blowdor, we conclude that this mode of operation does not change the basis of the FES as to acceptable plume size, so no unacceptable impacts from the discharge will occur because of this change in operating modes.
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Comenwealth Edison Company f/,Ay 1S 1977 E
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Two other areas which are likely to be affected by increased flow are the entrainnent rate of young fishes and ichthyoplankton and the inpingenent rate.
From our review of your entrainment study, we conclude that the yearly entrainment rate would be about five tillion fish eggs and about four million larval fish, assuming that L
the blowdown rate was continuously 500,000 gpn. These are conserva-tive estimates since the blowdown rate is usually lower than 500,000 gpm.
From given fecundity values for the major species in the vicinity of the site, the average fecundity for all the species listed was 7
193,400 eggs / mature female.
Thus, t'rmgh entrainment of eggs, the plant is effectively cropping the egg prc tuction by about 28 fish.
This loss is insignificant in conparison to the average fecundity rate, so the number of fishes affected is small, and the irpact is acceptable.
The entrainment study found that most of the species of larval fish entrained were ninnows, suckers and herring.
The average fecundity of these species is 412,182 eggs / nature female. Thus, the Dresden Station's cropping effect is to remove the egg production of about
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ten fish through entraiment of larvae. This latter estinate may E
not be conservative because the cropping is at an older age group than the eggs.
Even though the effective cropping due to larval entrainment nay be socewhat larger than estimated, we conclude that it is insignificant because of the small number involved, and because the types of species involved are neither game species nor of importance to the ecosysten.
Our review of your fish inpingement studies indicates that an estimated one half nillion fish weighing apprcximately 21,000 pounds are impinged yearly at Dresden Station. Most of the fish impinced during the study period were young-of-the-ycar individuals which have high natural nortality rates.
Of the estimated 1,400 fish impinged daily, less than 5" may be considered game type species, so that an estinated average of 64 fish of game species having a total weight of less than 4.5 pounds are impinged daily. The game fish icpinged have an average weight of about one ounce, indicating that the large majority of them are snall young-of-the-year fishes.
Larger, nature individuals, which represent the reproductive potential of a species, constituted only a small pro-portion of the impingenent loss.
In view of the small size of the fish impinged, the larce fraction of rough fish, and the small actual numbers of qame species fish lost conpared to fecundity, we judge these impinge-ment losses to be acceptable.
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Comonwealth Edison Company MAY iu 1977 E..
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In sumary, we find that your submittals of February 18,1977 and E.....
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March 10,1977 verify the acceptability of the increased blowdown L?
rate allowed by the amended NPDES Permit. These new limits will be 7
incorporated in the proposed environnental technical specifications 1 :;;;;;
for the station.
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Sincerely, Or @ l
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Don K. Davis, Acting Chief Operating Reactors Branch #2 Division of Operating Reactors
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