Between 1982 and 1990, B.J. Carney owned and operated a nonpressure wood pole treating facility subject to 40 C.F.R. § 429.75, a pretreatment requirement promulgated pursuant to Clean Water Act § 307(b), 33 U.S.C. § 1317(b). Section 429.75 provides that nonpressure woodpreserving facilities shall not discharge process wastewater pollutants into a publicly owned treatment works (POTW). B.J. Carney’s treatment tanks were situated in a depression below ground level.