A five-stories high, five-acre pile of broken concrete slabs has been spreading dust over a Huntington Park neighborhood since shortly after the 1994 Northridge earthquake. The debris, called La Montaña by residents, was dumped during repairs of the Santa Monica Freeway section that collapsed in the quake. On Tuesday, a state agency finally ordered the rubble cleared. "If there has ever been a poster child for environmental justice, this is it," said Linda Moulton-Patterson, chairwoman of the Integrated Waste Management Board.