Q. Need PHMSA approval
The situation you have described would seem to be appropriate for a ruling or approval by the Pipeline and Hazardous Materials Safety Administration.
PHMSA's Approvals and Permits Division is responsible for the issuance of DOT Special Permits and Approvals. A Special Permit sets forth alternative requirements, or variances, to the requirements in the HMR. Federal hazardous materials transportation law authorizes PHMSA to issue such variances in a way that achieves a safety level that is at least equal to the safety level required under Federal hazmat law or is consistent with the public interest if a required safety level does not exist. An approval is written consent, including a competent authority approval, from the Associate Administrator or other designated Department official, to perform a function that requires prior consent under the HMR.
Please contact the Office of Hazardous Materials Safety Approvals and Permits Division with questions by going to http://www.phmsa.dot.gov/hazmat/regs/contact