Mirant Kendall Station Final NPDES Permit

Permit Modification for the Mirant Kendall Station Power Plant in Cambridge, MA Revises Cooling Water Intake Structure Provisions

On December 18, 2008, EPA modified the NPDES Permit for the Mirant Kendall Station (MKS) power plant in Cambridge, Massachusetts. This modification will improve upon the Final Permit's provisions to protect the resident and migratory fish species of the lower Charles River and Boston Harbor by requiring the permittee to install technologies that will minimize the entrainment and impingement of all life stages of fish and will further advance the ecological restoration of the Charles River as sustainable fish habitat and a valuable recreational resource.

The Final Permit was issued jointly by the EPA's New England Regional Office and the Massachusetts Department of Environmental Protection (MassDEP) on September 26, 2006. However, the Final Permit was appealed by the permittee (Mirant Kendall) and also by the Conservation Law Foundation (CLF), with Charles River Watershed Association (CRWA) as a co-petitioner. This action brought the Final Permit before EPA's Environmental Appeals Board in Washington, DC for review. This Final Permit has not yet gone into effect pending the resolution of these appeals. On July 9, 2007, EPA formally suspended a regulation (the “Phase II Rule”) upon which the Final Permit was partly based. EPA withdrew the provisions of the Final Permit informed by the Phase II Rule, and issued this permit modification addressing the withdrawn portions.

This permit modification establishes requirements which require the installation and operation of exclusion technologies that meet specified design and operational standards to minimize entrainment and impingement at Mirant Kendall. In particular, required design standards include a specific maximum opening size, a maximum through-media velocity, and an induced sweeping velocity in front of the exclusion technology to carry eggs and larvae away. Now that the permit modification is final, EPA will address the appeals of the Final Permit and seek a resolution to all of the outstanding issues in order to have the Final Permit go into effect.

Final Permit Modification (PDF) (42 pp., 466 KB, about PDF)
Response to Comments (PDF) (269 pp., 2.77 MB, about PDF)

Background: EPA and the Massachusetts Department of Environmental Protection have issued a final National Pollutant Discharge Elimination System (NPDES) permit for the Mirant Kendall Station (MKS) power plant in Cambridge, Massachusetts to meet the requirements of the Clean Water Act. This final permit seeks to address potential adverse impacts to sustainable fish populations, aesthetics, and recreation due to heat, excessive algae growth, reduced water clarity and the intake of cooling water. This permit is an important component of continuing broader public and private efforts to restore the health of the Charles River Basin and Boston Harbor. press release »

Major Permit Conditions: This permit includes the following new protective requirements and conditions:

Zone of Passage and Habitat: A seasonal safe "zone of passage and habitat", which covers roughly fifty percent of the Lower Basin, has been created along the Boston side of the Charles River in order to protect fish populations and aquatic habitat. Two species of river herring, alewife and blueback herring, use the Lower Charles River Basin for their annual adult migration and spawning run. The Charles River supports one of the largest river herring runs in Massachusetts Bay.
In-stream Temperatures: Maximum seasonal allowable in-stream river temperatures have been established within the zone of passage and habitat. Critical river temperature permit limits range from 61 degrees Fahrenheit during early spring for yellow perch up to 81 and 83 degrees Fahrenheit during the summer for river herring. In addition, river temperatures in this safety zone cannot increase by more than 5 degrees Fahrenheit above upstream ambient river temperatures during a 24-hour average period. If real-time monitoring indicates that any of these temperature limits are exceeded, the power plant will need to modify its operations to reduce thermal discharges to the river.
Discharge Temperature and Location: An annual average of 70 MGD of non-contact cooling water can be discharged at temperatures up to 105° F from the present discharge pipes as long as these in-stream temperatures are not exceeded.
Barrier Net: A fine-mesh barrier net system or other similar protective device must be installed in front of the facility's cooling water intake structure to limit the number of fish that are trapped or pulled into the power plant when river cooling water is pumped into the facility.
Real-time Monitoring: Continuous water quality monitoring will be required in the Lower River Basin. This monitoring will provide real-time temperature measurements at eight strategic upstream and downstream river locations. The real-time discharge monitoring information will be made available to EPA and MassDEP to ensure continued permit compliance and immediate protection of the Charles River.

Public Comment: EPA accepted public comment on the draft permit between June 14, 2004 and October 14, 2004. A public hearing was held on September 13, 2004. EPA received numerous written and oral comments on the draft permit. EPA greatly appreciates the time, effort, information and expertise that commentors have contributed to the development of this permit. Summaries of these comments and EPA's responses to comments have been complied into a document listed below. "Responses to Comments: Public Review of Mirant Kendall Station".

Contact
George Papadopoulos (papadopoulos.george@epa.gov)
US EPA, Suite 1100 (CIP)
1 Congress Street
Boston, MA 02114
Phone: (617) 918-1579
Fax: (617) 918-1505

For more detailed information: The documents contained on this page are PDF'd (portable document format) copies of the originals. These documents include the final permit and supporting documents, the Responses to Public Comments, and documents related to the draft permit. Documents may be downloaded and printed using Adobe Acrobat Reader. See EPA's PDF page to learn more about PDF, and for a link to the free Acrobat Reader.

Mirant Kendall Station (MKS) Documents Related to Final Permit