Nothing, but nothing can stand in the way of corporations' pursuit of the almighty dollar. It's the only way to Make America Great Again™, believe me. "The Trump administration is ramping up its war on clean water" "The Environmental Protection Agency and Army Corps of Engineers’ proposal to undo the Clean Water Rule has been published in the Federal Register, meaning that the plan to review and redefine an Obama-era water pollution rule is officially public. "The proposal is a two-step effort aimed at undoing the Clean Water Rule, which was finalized in 2015 and sought to clarify the legal jurisdiction for the federal government under the Clean Water Act. And while publishing the proposal is merely the first step in rolling back the Clean Water Rule, environmental groups fear that it signals an escalation of the Trump administration’s larger effort to prioritize industry over the protection of America’s streams, rivers, and drinking water. "Under the Clean Water Act, the government has the ability to regulate pollution throughout the “waters of the United States,” which the 1972 law defined as being “navigable waters.” Certain waters clearly fall under the definition of navigable — rivers like the Mississippi, for instance — but other kinds of waters, like wetlands or Western rivers that flow for only part of the year, are less clear. The vagueness of the Clean Water Act lead to years of litigation, and courts had to decide largely on a case-by-case basis if a particular body of water qualified for protection under the Clean Water Act. "In 2015, the Obama administration, after years of consultation with scientists, environmental groups, industry, and other stakeholders, finalized the Clean Water Rule, which used a 2008 opinion from Supreme Court Justice Anthony Kennedy defining the jurisdiction of the Clean Water Act as any body of water with a “significant nexus” to navigable waters. In doing so, the administration protected 2 million miles of streams, 20 million acres of wetlands, and the drinking water of 1 in 3 Americans that otherwise would not have been clearly covered by federal law. "The Clean Water Rule was widely criticized by both Republican lawmakers and industry, which argued the rule was a prime example of government overreach. In February, President Donald Trump signed an executive order directing the EPA to review and reconsider the rule; now, with the proposal published in the Federal Register, that effort can begin in earnest."
That is one area where trump's administration is being extremely successful... repealing Obama-era policies, initiatives, standards, etc. It's alarming, but reversible, in time. He may have won brownie points with his supporters and some conservatives with these actions, but the damage he is causing is only temporary. Still, these action are going to harm a large percentage of people, and most won't even think twice about it.