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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 2 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

3 3 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

4 4 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

5 5 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.”

6 6 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

7 Code of Maryland Regulations Discharge Limitations Water Quality Impact Assessment for Thermal Discharges ( ) 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 anyfail TidalNontidal

8 < 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 If any fail If any fail

9 9 Locations of power plants in Maryland

10 10 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

11 11 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

12 12 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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16 16 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 Maximum radial extent of 2 E C-above ambient isotherm, 24-hour average (km) % 2 E C-above ambient isotherm thermal barrier, 24- hr average (% of cross- section) (km) % Area of bottom touched by waters heated 2 E C or more above ambient (km 2 ) %

17 17 Conclusions – Calvert Cliffs Thermal mixing zone limits passed No further 316a studies required

18 18 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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22 22 Chalk Point Steam Electric Station Mixing Zone Dimensions and Compliance with Maryland Regulations Mixing Zone SpecificationAllowed Dimensions Estimate of Actual Dimensions Ratio of Actual to Allowed Dimension Maximum radial extent of 2 E C-above ambient isotherm, 24-hour average (m) 2, ,6502, , % 2 E C-above ambient isotherm thermal barrier, 24-hr average (% of cross-section) (m) % Area of bottom touched by waters heated 2 E C or more above ambient (ha) %

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24 24 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

25 25 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

26 26 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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31 31 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 2 E C-above ambient isotherm, 6-hour travel time (km) % 2 E C-above ambient isotherm thermal barrier, average low- flow (% of cross-section) (m) (maximum extent) % Area of bottom touched by waters heated 2 E C or more above ambient, 6-hour travel time (10 3 m 2 ) ,273 %

32 32 Conclusions – Dickerson Thermal mixing zone criteria failed under some conditions Further studies required

33 33 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

34 34 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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