After Sept. 11, the folks in the White House found a favorite tune — the need to decrease U.S. reliance on foreign oil any which way but through conservation — and it seems they just can’t stop singing it. First it was used to promote drilling in the Arctic National Wildlife Refuge; now, in a variation in a miner key, the Bush administration says our national security depends on increased coal-bed methane development in the Rockies. Yesterday afternoon, Interior Assistant Secretary Rebecca Watson said the Bureau of Land Management, which she oversees, is studying potential coal-bed methane development in five areas to help meet the goals of President Bush’s energy plan. Methane gas is collected by pumping groundwater to relieve the pressure trapping the gas in coal seams. Because it harms both crops and other vegetation, the practice does not always go over well with landowners or environmentalists.