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Modified Discharge Permit for Kendall Station Power Plant in Cambridge, Mass. Significantly Advances Protections for Charles River

Release Date: 02/02/2011
Contact Information: David Deegan, EPA New England, (617) 918-1017

(Boston, Mass. – Feb. 2, 2011) – A new water discharge permit for the Kendall Cogeneration Station power plant in Cambridge, Mass. will significantly increase protections for ecological health and recreational water uses of the lower Charles River and Boston Harbor by requiring the plant to reduce its heat discharge and water withdrawal by approximately 95 percent, and closely monitoring river temperatures to ensure that even its reduced heat discharge does not warm the river excessively.

A final permit modification, issued jointly by the EPA’s New England regional office and the Massachusetts Dept. of Environmental Protection (MassDEP), modifies wastewater requirements for the 256-megawatt Kendall Cogeneration Station power plant, which is the largest industrial discharger on the Charles River. Kendall Station is owned and operated by GenOn (formerly Mirant).

The modified permit addresses adverse impacts to sustainable fish populations due to heat and the intake of cooling water, and ends longstanding litigation between EPA, MassDEP, GenOn, the Conservation Law Foundation (CLF), and the Charles River Watershed Association (CRWA), which have withdrawn their appeals of an earlier water permit.

Kendall Station’s existing “once-through” cooling system withdraws an average of 70 million gallons a day from the Charles River and discharges it back into the river at temperatures increased by 20 degrees Fahrenheit, up to a maximum discharge temperature of 105 degrees Fahrenheit. EPA and MassDEP issued a final permit to Kendall Station in 2006 to address adverse impacts to the balanced indigenous fish population due to Kendall Station's withdrawal of cooling water (which kills fish, fish eggs and fish larvae) and its discharge of heated water (which can make large parts of the Lower Charles River Basin unsuitable for fish passage or habitat). However, the 2006 permit was appealed by GenOn, CLF and CRWA. While the appeal was pending, the 2006 permit did not go into effect.

The modified permit (which was developed after discussions between EPA, MassDEP, GenOn, CLF, and CRWA) will require Kendall Station to make a significant facility upgrade that, in combination with a new steam pipeline to be built across the Longfellow Bridge in the next few years, will enable the plant to sell up to twice as much steam into Boston as is currently possible. These changes will result in major environmental benefits, including a reduction in Kendall Station's heat discharge and cooling water withdrawals of about 95 percent.

Furthermore, these changes may also result in indirect air quality benefits (potentially including reductions in greenhouse gas emissions) as local steam generation shifts to Kendall Station while other steam generation sources with relatively higher air emissions run less often. Additional air quality benefits may occur as customers with access to the additional steam source choose to replace older, less efficient boilers with relatively high air emissions with locally generated steam.

“We are taking another major step towards the recovery of the lower Charles River and Boston Harbor,” said Curt Spalding, regional administrator of EPA’s New England Office. “The lower Charles River Basin is an active, valuable urban river ecosystem which historically was home to abundant populations of migratory and fresh water fish. With this action, EPA and the Commonwealth are further advancing the ecological restoration of the River as sustainable fish habitat, so that it can be a healthy and resilient ecosystem and a treasured recreational resource. We commend GenOn for moving to a constructive, problem-solving approach and working with EPA and MassDEP to develop a solution that will dramatically reduce its heat discharge and water withdrawals while allowing the power plant to remain an ongoing source of electric power and steam for the greater Boston area. We also appreciate the positive contributions provided by CLF and CRWA during this process.”

The modified permit requires Kendall Station to install and operate a back pressure steam turbine and an air-cooled condenser, which together will enable the plant to reduce its water flow to 3.2 million gallons a day. The modified permit also requires Kendall Station to closely monitor river flows and temperatures to ensure that the plant’s heat discharge does not warm the river to levels that are no longer protective of fish populations and the aquatic habitat in the river.

“The volume of the power plant’s cooling water intake and the temperature of its discharge has definitely contributed to the degraded habitat for fish in the Charles River Basin over the years,” said MassDEP Commissioner Kenneth L. Kimmell. “The modification to the plant’s operation combined with innovative, real-time measurement of water temperature allows the facility to continue to efficiently respond to the area’s energy demands while substantially improving the river basin’s aquatic environment. This solution would not have been possible without the work of our partners, CLF and CRWA.”

EPA, MassDEP and many other state and local agencies have worked steadily for many years to improve ecological conditions in the lower Charles River, with a goal that the lower Charles should be fishable and swimmable. The modified permit is designed to help achieve that goal by protecting fish that live and spawn in the river, including its most sensitive fish populations – in particular, resident fish such as yellow perch and migrating fish such as alewife.

The modified permit requires Kendall Station to:
- Reduce its cooling water and discharge flow by approximately 95 percent;
- Monitor river temperatures whenever a predictive model indicates that the river may approach or exceed temperatures that are no longer protective of fish populations;
- Ensure that the Station's heat discharge does not warm the river basin above protective temperature levels;
- Stop discharging heat entirely after two consecutive days of high river temperatures.

The modified permit supersedes the 2006 permit, and GenOn, CLF, and CRWA have all withdrawn their appeals of the 2006 permit.

The modified permit took effect on February 1, 2011 and will be in effect for five years. However, because Kendall Station will need some time to comply with the revised permit conditions, EPA and MassDEP have imposed a compliance schedule, including interim limits, through federal and state administrative compliance orders. These orders require that GenOn proceed expeditiously with a construction schedule that will closely parallel the Longfellow Bridge construction schedule, and require interim effluent limitations that will include interim heat load reductions before the new technology is fully operational.

More information: Detailed information about the new final permit modification (

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