late 80s and early 90s, i made a small fortune pulling old tanks, installing new tanks...soil remediation. bought 1/4 of land 4 miles from town that met all the state requirements for stockpiling/cleaning that soil. hired an old guy....like me now, to knock the piles down with an old champion grader, and he pulled a disc daily over the material with an old 4020 deere until the PPM met the state requirements. lot of that material as accepted by the state inspectors, was hauled back to town and used for fill.