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EPA and DEP issue draft water discharge permit for Kendall power plant in Cambridge

Release Date: 06/10/04
Contact Information: Contact: Peyton Fleming, EPA Press Office (617-918-1008)

For Immediate Release: June 10, 2004 Release # 04-06-10

BOSTON - The US Environmental Protection Agency's New England Office and the Massachusetts Department of Environmental Protection today announced a proposed draft water discharge permit for the Mirant Kendall Station power plant that will limit the Cambridge facility's environmental impacts on the Lower Charles River. The 283-megawatt facility is the largest industrial discharger on the Charles River.

The jointly issued draft permit, subject to a 45-day public comment period, focuses primarily on the potential environmental impacts from the power plant's once-through cooling system, which requires water withdrawals from the Charles River and heated discharges back into the river.

The draft permit requires seasonal barrier nets or other devices to limit the number of fish that are trapped or pulled into the power plant when cooling water is pumped into the facility. It also requires new continuous water quality monitoring, including temperature readings, that will evaluate the ecological health of the Lower Charles River Basin, including potential impacts the facility may be having on the lower basin. It also includes new limits on heated-water discharges when water temperatures in the river's lower basin become excessively warm, thereby jeopardizing the ecological health of the river, including native and migratory fish populations.

"This draft permit is an important component of continuing public and private efforts to restore the health of the Lower Charles River and Boston Harbor," said Robert W. Varney, regional administrator of EPA's New England Office. "With sound science as its foundation, this draft permit provides an appropriate balance between the power plant's operational needs and protecting the Charles River ecosystem, one of New England's most valuable natural resources."

In 1995, EPA's New England Office launched an ambitious effort to restore the river so that it is safe for fishing and swimming by 2005. The partnership, known as Clean Charles 2005, includes federal, state and local agencies, nonprofit organizations, businesses and various other groups.

"The Lower Charles is an active ecosystem that currently struggles to support dozens of species of aquatic life," said DEP Commissioner Robert W. Golledge Jr. "This draft permit requires the use of an innovative, real-time water quality monitoring system that, once installed, will provide immediate protection within this critical waterbody."

Last year, the Kendall power plant completed a major facility upgrade, including the installation of a new natural gas fired generator and an increase in its electrical generating capacity from 113 megawatts to 283 megawatts. The upgrades make it possible for the power plant to shift from providing electricity only during peak electrical demand to a base-load power plant which operates nearly year-round.

While the conversion from oil to gas for powering the plant provides a benefit to air quality, the facility can have major impacts on the river's water quality. The Kendall station uses a once-through cooling system that withdraws an average of 70 million gallons a day from the Charles River and discharges it back into the river at temperatures up to 20 degrees Fahrenheit warmer, or as hot as 105 degrees Fahrenheit. The plant's current water usage is up to five times greater than the flow of the Charles River during low flow periods.

In developing the draft permit, EPA and DEP paid especially close attention to the facility's potential impacts on fish populations in the river -- in particular, resident fish such as yellow perch and migrating fish such as river herring. Two species of river herring, alewife and blueback herring, use the Lower Charles River Basin for their annual adult migration and spawning and development of larvae herring to juveniles and then adults from May to October each year. If river water is too hot during this time of year, fish will avoid heated portions of the river or may succumb altogether.

EPA and DEP also paid close attention to the facility's potential to cause or exacerbate eutrophication, a process in which excessively warm nutrient-rich water can cause excessive growth of algae which, in turn, can lead to oxygen depletion and aesthetic impacts such an increased green and brown color in the water.

To address these various environmental issues, the draft permit includes the following requirements and conditions:

    • In-stream temperatures: Maximum seasonal allowable in-stream temperatures are established for specific locations in the Lower River Basin so that at least half of the basin maintains temperatures that support a balanced indigenous population of fish and so that the overall temperature does not contribute to excessive algae growth.
    • Discharge Temperature and Location: An annual average of 70 million gallons a day of cooling water can be discharged at temperatures of up to 105 degrees Fahrenheit from the present discharge pipes as long as these in-stream temperatures are not exceeded. If they are exceeded, the power plant will need to modify their operations to reduce overall heat inputs into the river.
    • Barrier Net: A barrier net or similar device must be installed over the facility's cooling water intake structure to achieve specific goals in reducing the number of fish that are trapped on or pulled into the cooling water intake structure. The intake structure, located just below the Longfellow Bridge, trapped about 2,400 fish during portions of 1999 and 2000, according to sampling done by the plant owners. Tens of millions of fish eggs and larvae were drawn into the plant during the same time period.
    • Monitoring: Kendall station will be required to undertake continuous water quality monitoring in the Lower Basin, including temperature readings and eutrophication-related measurements, to ensure that the Charles River is being protected.
EPA is accepting written public comments on the draft permit from June 14 to July 28. Written comments should be postmarked no later than July 28. Before making a final permit decision, EPA will review all written comments. If you wish to submit written comments or request a public hearing on this draft permit, please contact:
      George Papadopoulos, US EPA, Suite 1100 (CMA), 1 Congress St., Boston, MA 02114. Email address is and fax is 617-918-1505.
For more detailed information, including any updates during the public comment period, and copies of the draft permit and key supporting documents, visit the agency's web site at Documents can be downloaded and printed using Adobe Acrobat Reader.