Code of Federal Regulations Title 40. Protection of Environment § 40.704.11 Recordkeeping

(a) A copy of each report submitted by the person in response to the requirements of this part.

(b) Materials and documentation sufficient to verify or reconstruct the values submitted in the report.

(c) A copy of each notice sent by the person, return receipt requested, to that person's customers for the purpose of notifying their customers of the customer's reporting obligations under this part.

(d) All return receipts signed by the person's customers who received the notice described in paragraph (c) of this section.