President Barack Obama has denied Transcanada's application for the construction of the Keystone XL Pipeline that would have carried oil from the Canadian tar sands to refineries on the Gulf Coast...Environmentalists on both sides of the border are claiming victory, saying that the pipeline would have allowed some of the world's dirtiest oil to travel from the tar sands in northern Alberta through America's heartland, putting air, water, land and climate at risk...[Obama said the United States] "...will continue to look for new ways to partner with the oil and gas industry to increase our energy security..."..."And we will do so in a way that benefits American workers and businesses without risking the health and safety of the American people and the environment," he said...TransCanada Corporation immediately announced that it would submit a new permit application.