A federal judge has rejected a lawsuit saying that the Merrimack Station coal-fired power plant in Bow was releasing too much hot water into the Merrimack River, violating its operating permit.

The ruling by Judge Joseph Laplante is very long – 86 pages – and dives deep into the question of how best to measure the effect on an ecosystem of an intermittent pollutant, examining issues of statistical analysis and sampling techniques. That’s a complicated issue that lies at the heart of a lot of environmental debates. The ruling is online here.

Like most power plants, Merrimack Station uses water to cool equipment as needed – that’s why so many power plants are built on rivers or coastlines. It releases heated water into the Hooksett Pool, a 5.8-mile long section of the river between Garvins Fall Dam and the Hooksett Dam. The question is whether too much water or water that is too hot has been released at times, harming fish and river’s ecosystem. 

Laplante emphasizes in the suit that the burden of proof lay with the plaintiffs, The Sierra Club and Conservation Law Foundation, not with the EPA or the power plant, but that their evidence “falls far short of a preponderance” needed.

To a certain extent, circumstances have bypassed this suit. There’s a feeling that Merrimack Station’s days are numbered because it won’t get any capacity payments after 2025. It operates these days as a peaker plant, running only when power prices are very high because of demand spikes, and that’s a tough way to make a living if you’re a big, slow-to-fire-up coal plant.

The two small kerosene-fired “jet engine” turbines on site, which can power up very quickly in emergencies, did win payments from the capacity auction and are in much better financial shape.

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