Waking up every morning thinking about how to move us beyond coal always comes with its share of highs and lows. But last week was an exceptionally wild roller coaster, and it left my brain spinning

Last week started with an adrenaline rush as the City of Alexandria, Virginia and GenOn Energy announced plans to phase out the Potomac River Generating Station just outside Washington, D.C. This symbolic, dirty coal plant started operating in 1949 and still lacks modern pollution controls. The Sierra Club and many local activists and coalition partners had targeted this coal plant for more than a decade. And just six weeks ago, New York City Mayor Michael R. Bloomberg stood with me in front of that plant to announce our $50 million partnership with Bloomberg Philanthropies to phase out one third of the coal plants in the U.S. by 2020.

I figured that the GenOn victory would lead to others, but I couldn’t imagine how quickly that would happen.

Then last Thursday we learned that Dominion Resources, Inc. planned to retire two dirty, old coal burners in coastal Virginia – Yorktown and Chesapeake. The Sierra Club had advocated for these plants’ retirement, and if the plans are approved, that is an impressive 1,025 megawatts of coal energy taken off line. The Chesapeake plant alone pumps more than 3 million tons of carbon a year, so this is a huge victory for the environment and for public health.

But this is not a total victory yet, as Dominion missed the opportunity to make any major commitment to wind, solar or energy efficiency. The Virginia Chapter of the Sierra Club has an aggressive campaign to convince Dominion to invest in offshore wind power, and with the announced retirement of these two coal plants, they will ramp up advocacy efforts to replace coal with wind power.

How big a deal are these coal plant retirements? Well, they bring the Beyond Coal Campaign’s tally up to 97 coal plants retired or committed to phasing out since the beginning of 2010 – and I’m sure number 100 will be just around the corner. Those 97 coal plants represent 33,000 megawatts of dirty energy, or almost 10% of the coal power in the country. Big Coal executives aren’t sleeping very soundly these days. These three coal plants represent the same pollution emitted by 25 million cars, and many are fueled with mountaintop removal coal. My beloved mountains of Appalachia are also singing from last week’s news.

The momentum was building into the Labor Day weekend so aggressively that I almost forgot that I was on this roller coaster – and that’s a dangerous thing to forget. Friday morning began with a nauseating plunge, as the Obama administration announced that it would direct the Environmental Protection Agency to withdraw draft smog protections that would have protected millions of Americans from air pollution.

The Sierra Club had been working for years – including aggressively this summer – to help administration officials like Cass Sunstein and Bill Daley see that Americans care about clean air and want tougher protections against smog pollution. But President Obama apparently caved in to coal and oil polluters, backing down on a commitment that he had made to put science and public health first.

Labor Day, the unofficial end of summer, may have passed, but let’s keep the heat on President Obama to get the clean air standards that our families deserve.