1. page 1
    2. page 2
    3. page 3
    4. page 4
    5. page 5

Exelon Generation Company, L.L.C.
Quad Cities Nuclear Power Station
Dear Mr. Gideon
The Agency has completed its technical review of the attached provisional variance
extension request submitted by Exelon Generation Company, L .L.C. Quad Cities Nuclear
Power Station (Exelon's Quad Cities Station) on August 1, 2006
Based on the review, the Agency GRANTS the requested variance subject to specific
conditions set forth below for a period of 45 days
Exelon's Quad Cities Station is a nuclear fueled steam electric generating facility located
on the Mississippi River at River Mile 506.8 near Cordova, Illinois. It operates its
cooling water system in open cycle mode. Cooling water is taken from the Mississippi
River, passes through the plant system and is then discharged by diffusers into the
Mississippi River. Maximum design flow of this system is 2,253 cfs
Exelon's Quad Cities Station seeks a variance from Special Condition 6A and 6B of
NPDES Permit IL0005037 .
These conditions establish thermal discharge limits for
Exelon's Quad Cities Station. Additionally, 6B allows Exelon's Quad Cities Station
excursion hours from these limits . Excursion hours are periods of time in which the
temperature at the edge of the mixing zone may be 3°F warmer than the temperature limit
in the permit. Exelon's Quad Cities Station may only utilize 1% (87 .6) of the hours in a
12 month period ending with any month as excursion hours
August 2, 2006
Provisional Variance From Special Condition 6A and 6B
of NPDES Permit IL0005037
Pollution Control Board
IEPA - 07-01
(Provisional Variance-Water)
u 2006
IEPA 07-7

The permit also requires that water temperature in the Mississippi River at the edge of the
mixing zone shall at no time exceed by 3°F the maximum limits of 86°F in July and
August and 85°F in September. Normally, Exelon's Quad Cities Station can operate
within these limits because the ambient temperature in the Mississippi River at the intake
points (or above the plant) remain below the non-excursion hour temperature limit
Ordinarily, the Mississippi River has significant river flows
These significant river
flows act to enable Exelon's Quad Cities Station to meet its permit conditions even when
ambient temperatures approach non-excursion hour temperature limit . However, at this
time, the Mississippi River is at extremely low flow condition
The river flow is
currently at 12,800 cfs compared to a normal river flow of 68,000 cfs . This low flow
condition coupled with high ambient river temperatures and the need to maintain power
on the grid with stability problems during this extreme weather condition period is the
basis of the need for this provisional variance. Exelon's Quad Cities Station has already
derated its two units by 200 megawatts in order to comply with the 91 degree limit of the
provisional variance granted in IEPA 07-01
On July 31, 2006 the Army Corps of Engineers made two significant reductions in the
amount of flow in the Mississippi River . The first reduction reduced the flow from
23,000 cfs to 18,000 cfs. The second reduction reduced the flow from 18,000 cfs to
13,000 cfs. As of August 1, 2006 the flow is at 12,800 cfs . Upstream river temperatures
are currently at 87.1 degrees Fahrenheit and the downstream temperature is currently 90
degrees Fahrenheit .
In addition to the current conditions of the Mississippi River there is also a very high
demand of power due to the extreme weather conditions with a resulting high load
condition of the grid which is currently having stability problems . At the current time
PJM (organization responsible for power distribution) anticipates the implementation of
Emergency Procedures to meet the high load demands in the Northern Illinois area in an
attempt to prevent brownouts and rolling blackouts . Should PJM issue a warning then
the Quad Cities Plant will need to ramp up power to meet demands. This power demand
could result in the river temperatures increasing up to 7 degrees Fahrenheit which would
result in a maximum downstream temperature of 93 degrees Fahrenheit . This condition
would last until such time as emergency condition exits after which time the plant would
resume operations to maintain the 5 degrees delta T allowed in the TEPA Order 07-01
The Agency has reviewed the requested provisional variance and has concluded the
1 . The environmental impact from the requested relief will be closely monitored and
the Agency will be immediately notified of any significant impact along with
actions taken to remedy the problem ;
2. No other reasonable alternatives appear available

3 .
No public water supplies will be affected ;
4. No federal regulations will preclude the granting of this request; and
5. Exelon Quad Cities Station will face an arbitrary and unreasonable hardship if the
request is not granted
The Agency hereby GRANTS the Exelon Quad Cities Nuclear Power Station a
provisional variance from Special Condition 6A and 6B of NPDES Permit IL0005037 for
a period of 45 days subject to the following conditions
1 .
During the period of time that
either river flow is less than 27,500 cfs or
upstream ambient river temperature exceeds 83 degrees Fahrenheit, Exelon's
Quad Cities Station may exceed the maximum temperature limit stated in Special
Condition 6B in NPDES permit IL0005037 by no more than 5 degrees
(August 91
degrees Fahrenheit and September 90 degrees
During any period when either river flow is less than 27,500 cfs or upstream
ambient river temperature exceeds 83 degrees Fahrenheit, and PJM issues an
Emergency Warning Exelon's Quad Cities Station may exceed the maximum
temperature limit stated in Special Condition 6B in NPDES permit IL0005037 by
no more than 7 degrees Fahrenheit .
(August 93 degrees Fahrenheit and
September 92 degrees Fahrenheit)
This variance is subject to the following conditions
A. During the variance period Exelon Quad Cities Station must continuously
monitor intake, discharge and receiving water temperatures and to visually
inspect intake and discharge areas at least three times daily to assess any
mortalities to fish and other aquatic life
B. Exelon Quad Cities Station shall document environmental conditions
during the term of the provisional variance, including the activities
described in A above of this Section, and submit the documentation to the
Agency and the Department of Natural Resources within 30 days after the
provisional variance expires ;
C. Exelon's Quad Cities Station shall continue ongoing biological studies to
characterize how fish and mussels respond to thermal conditions present in
the affected portion of the Mississippi River. These studies include those
mentioned on page 5 of Exelon's July 17, 2006 Emergency Application
for Provisional Variance. These same studies were described in a July 11,
2006 e-mail message (attached) from Exelon to Mr . Rob Thompson of

USEPA Region 5 relating the efforts by Exelon to study aspects of river
biology suggested at recent meetings concerning long-term relief from
existing water quality standards at this site
In addition, Exelon must
conduct a mussel study specific to this provisional variance; to document
this activity; and to submit the documentation for the mussel study to the
Agency and the Department of Natural Resources within 60 days after
completing the survey described herein
Specifically, Exelon's Quad
Cities Station must prepare a study plan within three days of the beginning
date of this provisional variance to address the issue of increased
excursion hours (increase in thermal stress) on unionid mussels in the
Mississippi River in the vicinity of the discharge . The plan must include a
survey of the mussel beds identified in a recent report : Draft Report
Unionid Mussel Biothermal Assessment for the Quad Cities Nuclear
Station, Mississippi River Miles 503 .0 to 506 .9 (attached). The survey
must address the apparent health of the mussels within the mussel beds
given the higher than allowed river temperatures and longer duration of
temperature excursions. Survey dives to ascertain effects on the mussel
beds must begin as soon as possible after either the increase of excursion
hours or maximum temperature relief afforded by the provisional variance
are utilized. Conditions pertinent to the mussel populations to be recorded
during the surveys will be much the same as conducted for the baseline
study referenced above. These must include but are not limited to mussel
species occurrence and density, age, zebra mussel infestation and apparent
i .e ., any outward signs of heat stress such as morbidity, reflex
time, position in the substrate, etc. Plant discharge temperatures, upstream
river temperatures, incidence of excursion hours and other pertinent
information must be provided to build an understanding of the conditions
to which the mussels have recently been exposed. Surveys must continue
until excursion hours are no longer being utilized, or in other words, until
the weather conditions causing the need for more excursion hours have
moderated . The final report for this study must address the changes noted
in mussel populations from the previous study. Verbal reports are due to
the Agency at regular intervals during the surveys. These reports must
include any information on mussel die-off. If mussel die-off downstream
from the discharge is found and is attributable to the thermal affects of the
effluent, as compared to the condition of upstream populations, a
monetary settlement will be required as calculated by the formula the
Illinois Department of Natural Resources uses for mussel die-off
settlements ;
D. Exelon Quad Cities Station shall immediately notify the Agency and the
Department of Natural Resources of any unusual conditions, including
mortalities to fish or other aquatic life ; to immediately take action to
remedy the problem; to investigate and document the cause and
seriousness of the unusual conditions while providing updates to the
Agency and the Department of Natural Resources as changes occur until

P.O. Box 19276,
62794-9276-(217) 782-3397
R .
IL 60601 -(312) 814-6026
R .
AUG 0 4 2006
Dorothy M. Gunn, Clerk
Illinois Pollution Control Board
James R. Thompson Center
100 West Randolph Street, Suite. 11-500
7- -7
Chicago, Illinois 60601
Re :
Exelon Generation Company, L.L.C. (Quad Cities Nuclear Power Station)
(Provisional Variance)
Dear Ms. Gunn :
Attached please find a letter from the Illinois Environmental Protection Agency (Illinois EPA) granting a
provisional variance to Exelon Generation Company, L .L.C. for its Quad Cities Nuclear Power Station,
effective upon the presence of certain conditions . The Illinois EPA is hereby submitting the letter to the
Pollution Control Board for publication. Thank you for your assistance in this matter . If you have any
questions regarding this matter, please contact the assigned attorney, James Day, at (217) 782-5544
Sinc ely,
q 4
Robert A. Messina
Chief Legal Counsel
Division of Legal Counsel
ROCKFORD-4302 North Main Street, Rockford, It 61103 - (815) 987-7760
DES PLAINES-9511 W. Harrison 5t., Des Plaines, IL 60016-(847) 294-4000
ELGIN- 595 South State, Elgin, It 60123-(847) 608-3131
PEORIA-5415 N. University St., Peoria, IL 61614-(309) 693-5463
- PEORIA-7620 N . University St ., Peoria, IL 61614-(309) 693-5462
CHAMPAIGN- 2125 South First Street, Champaign, IL 61820-(217) 278-5800
SPRINGFIEI D-4500 S. Sixth Street Rd ., Springfield, IL 62706-(217) 786-6892
COLLINSVILLE-2009 Mall Street, Collinsville, IL 62234 -(618) 346-5120
MARION - 2309 W. Main St., Suite 116, Marion, IL 62959 - (618) 993-7200
(217) 782-5544

Back to top