Since we do not have all of the facts pertaining to your requirement, solicitation/contract or contractor(s), the following answer is based solely on the background and question provided. As we do not have access to the contract folder or particulars that apply to this situation, we highly recommend you consult the Contracting Officer and possibly the Legal Office.
The reference the requester is seeking is the DoDM 4715.20, March 9, 2012, ENVIRONMENTAL RESTORATION DOCUMENTATION. The following is an excerpt:
"Pursuant to section 9613(k) of Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) and subparts 300.800-300.825 of NCP, the DoD Component shall establish and maintain administrative records and make them available to the public at or near the facility at issue. The administrative record contains the documents that form the basis for the selection of a CERCLA response action.
The administrative record shall be retained for a minimum of 50 years after the last site achieves RC, pursuant to section 9603(d)(2) of CERCLA. A DoD Component may choose to retain the administrative record for a longer period of time at its discretion."
As the legislation is quite complex, your local legal office and environmental component is the best source for a determination of whether the contract information is included in an administrative record.