spoil bank
n.— «In the rolling hills just a few miles outside town, a forest of black locust, black cherry and young sugar maple grows from what the locals call spoil banks, mounds of dirt and rock tossed aside by years of strip-mining.» —“Quoth the raven: ‘I’m back’” by Kevin Mayhood in Wintersville, Ohio Columbus Dispatch (Ohio) May 20, 2008. (source: Double-Tongued Dictionary)