Transcript State of Maryland Perspectives on Cooling Water Intake

Overview of CWA Section 316(a)
Evaluations of Power Plants with
Thermal Discharges in Maryland
Presented at
EPRI Workshop on 316(a) Issues:
Technical and Regulatory Considerations
October 16 – 17, 2003 AEP Headquarters
Columbus, Ohio
Steve Schreiner
William Richkus
Versar, Inc.
Rich McLean
MDNR Power Plant Research Program
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What is the Power Plant Research
Program (PPRP)?
• Created by state legislation in 1971
• Funded by an environmental
surcharge on electricity use
• Small technical/administrative staff
supported by integrator contractors
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What does PPRP do?
• Provides technical support to Maryland Public
Service Commission with regard to licensing of
new projects, including NPDES permitting and
316 compliance
• Provides technical support to Department of
the Environment, Maryland’s permitting
agency, for renewal of power plant NPDES
permits and demonstrations and 316
compliance
• Conducts research relating to major impact
issues of proposed and existing power plants
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How does PPRP perform its functions?
• As a result of review of applications, may recommend
316 studies by applicant
• Conducts technical reviews of applicants= study plans
and study results
• Develops cooperative 316 studies with applicants
• May conduct independent 316 studies
• Since inception of the program, have carried out such
activities at all power plants in Maryland with regard to
thermal and cooling water intake impacts
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Maryland Thermal Regulations
• Describe factors, criteria, and standards for
thermal effluent limitations, including mixing
zones
• Dischargers unable to meet mixing zone
criteria can request alternative effluent
limitations which “assure the protection and
propagation of a balanced, indigenous
community of shellfish, fish and wildlife in
and on the body of water into which the
discharge is made.”
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Maryland Thermal Regulations, cont.
• Alternate Effluent Limitations need to
consider:
– Cumulative impacts from other sources
– Potential increase in nuisance species
– Change in biological productivity
– Impairment of economic or recreational resources
– Reduction in Representative Important Species
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Code of Maryland
Regulations 26.08.03
Discharge Limitations
Water Quality Impact Assessment for Thermal Discharges
(26.08.03.03)
50 ft
mixing
zone
Temp. outside
mixing zone
adheres to
Designated Uses
(32ºC max)
If any
fail
Alternate
Effluent
Limitations
Case-by-case
mixing zone
Thermal mixing
zone criteria
Tidal
Nontidal
Thermal mixing
zone criteria
(2ºC isotherm)
Tidal
< ½ tidal
excursion
(indicates
degree of
dispersion
by currents)
Nontidal
< 50% crosssection
(indicates
potential
thermal barrier)
If any
< 5% of
bottom
beneath tidal
excursion
(limits exposure
to benthos)
fail
Alternate Effluent Limitations
< distance
traveled by
stream flow in
6 hrs
(indicates degree
of dispersion by
currents)
< 50% crosssection
(indicates
potential
thermal barrier)
< 5% of
bottom
passed by 6
hrs of stream
flow
(limits exposure
to benthos)
If any
fail
Alternate Effluent Limitations
Locations of power plants in Maryland
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Thermal Discharge Status of
Maryland Plants
• 7 facilities passed thermal mixing zone
criteria
• 4 facilities failed criteria under at least
some conditions
• 1 facility (Wagner) requested case-bycase mixing zone due to unusual flow
regime in receiving water
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Maryland Case Studies
• Calvert Cliffs: passes mixing zone
criteria; large estuary facility
• Chalk Point: fails mixing zone criteria;
small estuary facility
• Dickerson: fails some mixing zone
criteria; riverine facility
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Calvert Cliffs Nuclear Power Plant
• Owned by Constellation Nuclear, a member of
Constellation Power Source, Inc., (formerly
BGE)
• Located on Chesapeake Bay main stem in
Calvert County
• 1,675 MW
• Once-through cooling, 3600 mgd
• Discharge orifice 4 m high, 3 m deep, 268 m
offshore, high velocity
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Chesapeake Bay near Calvert Cliffs
Width, m
0
2000
4000
6000
8000 10000
Depth, m
0
10
20
Cross-Section
Allowable
Est. Max.
30
40
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Calvert Cliffs Nuclear Power Plant Mixing Zone Dimensions and
Compliance with Maryland Regulations
Mixing Zone Specification
Allowed
Dimensions
Estimate of
Actual
Dimensions
Ratio of
Actual to
Allowed
Dimension
5.3
1.8
34 %
2EC-above ambient
isotherm thermal barrier, 24hr average (% of crosssection) (km)
9.1 - 14.3
3.5
25 - 38 %
Area of bottom touched by
waters heated 2EC or more
above ambient (km2)
3.1
0.34
11 %
Maximum radial extent of
2EC-above ambient
isotherm, 24-hour average
(km)
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Conclusions – Calvert Cliffs
• Thermal mixing zone limits passed
• No further 316a studies required
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Chalk Point Power Plant
• Owned by Mirant Energy (formerly PEPCO)
• Located on the estuarine portion of the Patuxent
River in Prince George's County
• 2,415 MW (total generation)
• Units 1 & 2, once-thru system, 360 mgd per unit;
units 3 & 4, closed cycle cooling tower, 374 mgd per
unit
• 2 km long discharge canal, 2.3 m deep, 28 m wide
at mouth, shoreline discharge to Patuxent River
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Patuxent River near Chalk Point
Width, m
0
400
800
1200
1600
0
Depth, m
1
Cross-section
2
3
Allowable
Est. Min
Est. Max
4
5
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Chalk Point Steam Electric Station Mixing Zone Dimensions and
Compliance with Maryland Regulations
Mixing Zone Specification
Allowed
Dimensions
Maximum radial extent of
2EC-above ambient
isotherm, 24-hour average
(m)
2,500 - 2,650 2,500 - 4,600
2EC-above ambient isotherm
thermal barrier, 24-hr
average (% of cross-section)
(m)
Area of bottom touched by
waters heated 2EC or more
above ambient (ha)
Estimate of
Actual
Dimensions
Ratio of
Actual to
Allowed
Dimension
94 - 184%
50
55 - 100
110 - 200%
33 - 49
62 - 96
127 - 291%
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Chalk Point Tempering Pumps
• Included in original plant design to manage
delta T in discharge canal
• High mortality of entrained fish and crabs
(including early life stages, juveniles
and adults) from mechanical injury
• Permit was modified to eliminate the
requirement for augmenting discharge flow
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Conclusions
• Thermal mixing zone criteria not
passed
• Further studies required on thermal
impacts
• Studies showed no significant
ecosystem changes attributable to the
thermal discharge
• Alternate Effluent Limitations granted
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Dickerson Generating Station
• Mirant Energy (formerly PEPCO)
• Located on the Potomac River in
Montgomery County
• 556 MW
• Once-through cooling, 400 mgd
• 532 m discharge canal, 18 m wide at
mouth
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Potomac River near Dickerson
Width, m
0
50
100
150
200
250
Depth, m
0
0.2
0.4
Cross-section
0.6
Estimated
Allowable
0.8
1
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Dickerson Steam Electric Station Mixing Zone Dimensions and
Compliance with Maryland Regulations (low to high summer flows)
Mixing Zone Specification
Allowed
Dimensions
Estimate of
Actual
Dimensions
Ratio of
Actual to
Allowed
Dimension
Maximum downstream extent
of 2EC-above ambient
isotherm, 6-hour travel time
(km)
7.3 - 19.6
2.5 - 14
34 - 192 %
2EC-above ambient isotherm
thermal barrier, average lowflow (% of cross-section) (m)
140 - 155
192
(maximum
extent)
123 - 137 %
Area of bottom touched by
waters heated 2EC or more
above ambient, 6-hour travel
time (103 m2)
110 - 295
45 - 1400
41 - 1,273 %
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Conclusions – Dickerson
• Thermal mixing zone criteria
failed under some conditions
• Further studies required
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Dickerson Conclusions, Cont.
• Heated discharges have only a minor
seasonal effect on fish distributions,
and no adverse long-term impacts
have occurred
• Smallmouth bass near the discharge
were found to have significantly larger
mean length across age groups than
bass collected upstream
• Alternate Effluent Limitations granted
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Conclusions based on 30 years of PPRP
Experience
• All studies confirmed that thermal
mixing zone criteria are protective
• Thermal criteria also valuable in
identifying facilities with a potential for
impacts
• Detailed assessments served as a
basis for technically-based regulatory
decisions
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