Transportation/Hazardous Materials: Pipeline and Hazardous Materials Safety Administration Interpretive Letter Addressing Agricultural Fertilizer
December 23, 2025
By:
Walter G. Wright
Category:
Arkansas Environmental, Energy, and Water Law
Arkansas Environmental, Energy, and Water Law
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The Pipeline and Hazardous Materials Safety Administration (“PHMSA”) sent a December 11th Interpretive Letter to DG Advisor addressing the application of the federal Hazardous Materials Regulations (“HMR”) to what is described as a new agricultural fertilizer compound.
PHMSA was responding to an August 4th Letter from DG Advisor.
The agricultural fertilizer compound is described as consisting of:
- 69.5% ammonium nitrate.
- 30.5% ammonium phosphate.
- No combustible substances.
DG Advisor is stated to have indicated an understanding that the mixture was not regulated as hazardous material because in accordance with the flowchart in Section 39.5 of the UN Manual of Tests & Criteria titled “Classification criteria” (which is incorporated by reference in the HMR), analysis of the fertilizer’s properties lead to box 26 which states it is “not classified.”
PHMSA states that in accordance with § 173.22 of the HMR, it is the shipper’s responsibility to properly classify a hazardous material. However, based on the information provided in DG Advisor’s letter, PHMSA states that the agricultural fertilizer described is not regulated as a hazardous material. This conclusion is stated to be based on understanding that the company:
- Classified its material in accordance with § 172.102, special provision 132.
- Followed the decision logic and required testing in the UN Manual of Tests and Criteria, 7th revised edition.
A copy of the Interpretive Letter and attachments can be found here.
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