40 CFR §60.5565a

1. (a)Your records must be in a form suitable and readily available for expeditious review.
2. (b)You must maintain each record for 5 years after the date of conclusion of each compliance period.
3. (c)You must maintain each record on site for at least 2 years after the date of each occurrence, measurement, maintenance, corrective action, report, or record, according to § 60.7. Records that are accessible from a central location by a computer or other means that instantly provide access at the site meet this requirement. You may maintain the records off site for the remaining year(s) as required by this subpart.