All dischargers subject to this chapter shall retain for no less than three years any records, books, documents, memoranda, reports, correspondence, and any summaries thereof relating to monitoring, sampling, and chemical analysis of its discharge, whether or not the records are required by this chapter. All the records shall be made available for inspection and copying by the DNR and the EPA, and the authority in the case of an industrial user. All records which pertain to matters which are the subject of administrative action, enforcement, or litigation shall be maintained and preserved until all enforcement limitation with respect to any and all appeals have expired.
