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Overview of CWA Section 316(a) Evaluations of Power

Plants with Thermal Discharges in MarylandPresented at

EPRI Workshop on 316(a) Issues: Technical and Regulatory Considerations

October 16 – 17, 2003 AEP Headquarters

Columbus, Ohio

Steve SchreinerWilliam Richkus

Versar, Inc.

Rich McLeanMDNR 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

Code of Maryland Regulations 26.08.03 Discharge Limitations

Water Quality Impact Assessment for Thermal Discharges (26.08.03.03)

Temp. outside mixing zone adheres to

Designated Uses (32ºC max)

50 ft mixing zone

Alternate Effluent

Limitations

Case-by-case mixing zone

Thermal mixing zone criteria

If any failTidal Nontidal

< 5% of bottom beneath tidal

excursion (limits exposure to

benthos)

< 50% cross-section (indicates

potential thermal barrier)

< ½ tidal excursion (indicates degree of

dispersion by currents)

< distance traveled by

stream flow in 6 hrs

(indicates degree of dispersion by

currents)

< 5% of bottom passed

by 6 hrs of stream flow

(limits exposure to benthos)

< 50% cross-section (indicates

potential thermal barrier)

Thermal mixing zone criteria (2ºC

isotherm)

Tidal Nontidal

Alternate Effluent Limitations Alternate Effluent Limitations

If any fail If any fail

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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-by-case 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

0

10

20

30

40

0 2000 4000 6000 8000 10000

Width, m

Dep

th, m

Cross-Section

Allowable

Est. Max.

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Calvert Cliffs Nuclear Power Plant Mixing Zone Dimensions and Compliance with Maryland Regulations

Mixing Zone Specification

Allowed Dimension

s

Estimate of Actual

Dimensions

Ratio of Actual to Allowed

Dimension

Maximum radial extent of 2C-above ambient isotherm, 24-hour average (km)

5.3 1.8 34 %

2C-above ambient isotherm thermal barrier, 24-hr average (% of cross-section) (km)

9.1 - 14.3 3.5 25 - 38 %

Area of bottom touched by waters heated 2C or more above ambient (km2)

3.1 0.34 11 %

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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

0

1

2

3

4

5

0 400 800 1200 1600

Width, m

Dep

th, m

Cross-section

Allowable

Est. Min

Est. Max

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Chalk Point Steam Electric Station Mixing Zone Dimensions and Compliance with Maryland Regulations

Mixing Zone Specification

Allowed Dimension

s

Estimate of Actual

Dimensions

Ratio of Actual to Allowed

Dimension

Maximum radial extent of 2C-above ambient isotherm, 24-hour average (m)

2,500 - 2,650

2,500 - 4,600

94 - 184%

2C-above ambient isotherm thermal barrier, 24-hr average (% of cross-section) (m)

50 55 - 100 110 - 200%

Area of bottom touched by waters heated 2C or more above ambient (ha)

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

0

0.2

0.4

0.6

0.8

1

0 50 100 150 200 250

Width, m

Dept

h, m

Cross-section

Allowable

Estimated

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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 Dimension

s

Estimate of Actual

Dimensions

Ratio of Actual to Allowed

Dimension

Maximum downstream extent of 2C-above ambient isotherm, 6-hour travel time (km)

7.3 - 19.6 2.5 - 14 34 - 192 %

2C-above ambient isotherm thermal barrier, average low-flow (% of cross-section) (m)

140 - 155 192 (maximum

extent)

123 - 137 %

Area of bottom touched by waters heated 2C 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