PHMSA letter of interpretation

Allowance to Fill IM Portable Tanks to Less than 80% of their Capacity

Pipeline and Hazardous Materials Safety Administration · Oct 17, 1995 · Reference No. 95-0189

PHMSA says to use caution with this letter. As proposed in the NPRM, we are revising § 173.32 to provide requirements for all portable tanks by consolidating the requirements for the use of IM portable tanks currently in § 173.32c into a single section and moving them to part 180, subpart G, with the qualification and maintenance requirements for IBCs, cargo tanks and tank cars. See HM-215D (66 FR 33315)

Interprets: 49 CFR § 173.32c

Reggie’s quick take

Someone asked whether IM portable tanks built to ADR standards and split into sections of up to 7,500 liters could be filled to less than 80% of capacity. PHMSA said no. Under § 173.32c(j), an IM portable tank, or any compartment of one, with a volume over 5,000 liters must be filled to at least 80% by volume, so loading those 7,500-liter tanks or sections below that level would violate the rule.

Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.

This is in response to your facsimile requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Part 173.32c). You state that you are planning to build tanks to the European Agreement for the International Carriage of Dangerous Goods by Road (ADR) requirements and fit them with partitions or surge plates into sections of not more than 7500 litre capacity. You ask if loading these tanks to less than 80% of their capacity would violate the requirements specified in § 173.32c(j).

The answer is yes. Section 173.32c(j) specifies that an intermodal (IM) portable tank or compartment thereof having a volume greater than 5,000 litre (1,900 gallons) may not be loaded to a filling density less than 80% by volume. Therefore, if these 7500 litre capacity tanks or sections are loaded to less than 80%, transportation of the IM portable tank would be in violation of the requirements in § 173.32c(j).

I hope this information is helpful. If we can be of further assistance, please contact us.

A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.