NPDES Permits in New England
Mirant Canal Station Final NPDES Permit
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Background: EPA and the Massachusetts Department of Environmental Protection (MassDEP) have developed a Final National Pollutant Discharge Elimination System (NPDES) permit for the Mirant Canal Station (MCS, the Station) power plant in Sandwich, Massachusetts to meet the requirements of the Clean Water Act. MCS is a 1120 megawatt (MW) fossil fuel electrical generation facility that discharges pollutants, including heat, to, and withdraws cooling water from, the Cape Cod Canal (Canal). Steam turbine condenser waste heat is rejected to the Canal by means of a once-through cooling water system. Water for this cooling system is withdrawn from the Canal by the Station through two cooling water intake structures. Each operating day, the Station withdraws approximately 518 million gallons of water from the Cape Cod Canal and circulates it through the facility to condense the steam used to produce electricity. Water taken from the Cape Cod Canal by MCS contains millions of organisms including fish eggs and larvae. These organisms are pulled through (or "entrained") in the facility and killed by severe physical and chemical impacts and extreme water temperatures. Cooling water withdrawals also create a water velocity at the intake pipes which traps (or "impinges") many juvenile and mature fish against the intake screens causing injury or death.
EPA and the MassDEP last reissued the MCS federal and state permit number MA0004928 on June 23, 1989. This permit was scheduled to expire on June 23, 1994, but it has been administratively continued in effect pending reissuance of a new permit.
Major Permit Conditions: The major permit conditions to protect the water quality, aquatic life and designated uses of the Cape Cod Canal are as follows:
Construction of cooling towers or comparable technology: In order to reduce mortality to fish eggs and larvae that are entrained, MSC will be required to install cooling towers or alternative technologies and/or operational methods that may result in comparable reductions in entrainment mortality.
Improved Fish Return System: To reduce impingement mortality, the final permit requires that the cooling water intake structures are modified to include operational controls to reduce chlorine exposure, the use of fish holding buckets and low pressure spray washes, and the reconfiguration of the return system such that returned fish are transported away from the intake structures in order to reduce the probability of fish being re-impinged.
Discharge Temperature Limits: To ensure that the biological integrity of the receiving water is maintained, a thermal discharge limit was derived with two compliance points. There is a monitoring point in the discharge canal and also in the Cape Cod Canal. Compliance with the limits need to be achieved at both locations.
Internal Waste Streams: To ensure that dilution is not used as a means of compliance and in accordance with the federal regulations for the Steam Electric Power Generating point source category, metal cleaning waste water has been segregated from other internal waste streams for sampling.
Monitoring: To gather more information about the entrainment and impingement impacts from MCS and to gauge the effectiveness of protective measures, an extensive bio-monitoring program is required.
Public Comment: EPA accepted written public comments on the Draft Permit from December 22, 2005 to February 4, 2006. Federal regulations require EPA to respond to formal comments in writing. Summaries of these comments and EPA's responses to comments have been complied into a document listed below: "Responses to Comments for Mirant Canal Station."
Sharon DeMeo (firstname.lastname@example.org)
5 Post Office Square, Suite 100 (OEP06-1)
Boston, MA 02109-3912
Fax: (617) 918-1505
Mirant Canal Station (MCS) Final Permit Documents:
- Final Permit (PDF) (21 pp, 59K)
- Attachment A - Marine Chronic Toxicity Test Procedure and Protocol (PDF) (11 pp, 25K)
- Part II Standard Conditions (PDF) (25 pp, 142K)
- Response to Public Comments
- Introduction (PDF) (7 pp, 89K)
- Section I (PDF) (2 pp, 19K)
- Section II (PDF) (6 pp, 45K)
- Section III (PDF) (25 pp, 178K)
- Section IV (PDF) (6 pp, 80K)
- Section V (PDF) (1 p., 13K)
- Section VI (PDF) (22 pp, 112K)
- Section VII (PDF) (3 pp, 24K)
- Section VIII (PDF) (2 pp, 62K)
- Section IX (PDF) (94 pp, 416K)
- Section X (PDF) (3 pp, 24K)
- Section XI (PDF) (2 pp, 21K)
- Section XII (PDF) (2 pp, 15K)
- Section XIII (PDF) (4 pp, 31K)
- Section XIV (PDF) (3 pp, 19K)
- Thermal Figure 1
- Thermal Figure 2
- Thermal Figure 3
- Fact Sheet (PDF) (62 pp, 753K)