Brown Materials Silver Refining, Inc. (Brown) is engaged in the business of silver recovery from waste photographic and radiographic film stock. The silver recovery process uses a sodium cyanide solution to strip silver from film, which is electroplated out of the solution. EPA has determined that Brown has contributed or is contributing to the past or present handling, storage, treatment, transportation or disposal of solid and hazardous waste or constituents of such wastes that may present an imminent and substantial endangerment to health or the environment.