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Interpretation Response #PI-20-0005

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date:

Company Name: Commonwealth LNG

Individual Name: Mr. Scott Ray

Location State: TX Country: US

View the Interpretation Document

Response text:

Mr. Scott Ray
Senior VP Engineering and Permitting
Commonwealth LNG
1 Riverway, Suite 500
Houston, TX 77056

Dear Mr. Ray:

In a letter to the Pipeline and Hazardous Materials Safety Administration (PHMSA), dated January 6, 2020, you requested an interpretation of 49 Code of Federal Regulations (CFR) Part 193. Specifically, you requested an interpretation regarding §§ 193.2161 and 193.2167.

You stated that Commonwealth LNG, LLC, proposes to construct and operate a natural gas liquefaction and export facility in Cameron Parish, Louisiana. You stated the liquefied natural gas (LNG) facility would have six 40,000 cubic meter full containment LNG tanks with parameters of: nominally 165 feet high, nominally 131 feet diameter, primary (internal liquid container) tank wall of 9 percent Nickel (9 % Ni) steel, and secondary (outer liquid container) tank wall of 9 % Ni steel. You stated that the design Standards and Codes would be per American Petroleum Institute and National Fire Protection Association (NFPA) 59A.

You state that the 2019 edition of NFPA 59A Standard (NFPA 59A-2019) allows for a full containment tank system with the secondary (i.e. outer) liquid container and roof to be constructed either from metal or of pre-stressed concrete. Also, you stated that the secondary metal 9 % Ni container wall is suitable for exposure to cryogenic temperatures, and the preliminary design of the secondary LNG container considers missile impact criteria per the Nuclear Regulatory Commission Regulatory Guide 1.221.

You stated that currently 49 CFR Part 193 incorporates by reference the 2001 edition of NFPA 59A (NFPA 59A-2001), whereas your proposed design is based on the NFPA 59A-2019. You further stated that §§ 193.2161 and 193.2167 prescribe a requirement that the secondary container be of concrete - in apparent conflict with NFPA 59A-2019. You believe that the proposed LNG storage tank design fulfills the safety objectives of NFPA 59A-2019. Therefore, you request PHMSA's interpretation of whether your secondary container design material would comply with the intent of §§ 193.2161 and 193.2167.

Section 193.2161, Dikes general, requires that, "An outer wall of a component served by an impounding system may not be used as a dike unless the outer wall is constructed of concrete." Likewise, § 193.2167, Covered Systems, requires that "A covered impounding system is prohibited except for concrete wall designed tanks where the concrete wall is an outer wall serving as a dike." Therefore, the outer wall of an LNG storage tank must be concrete. Otherwise, the outer wall may not be used as a dike.

Because your secondary containment is made of 9 % Ni steel, it does not comply with the current requirements of §§ 193.2161 and 193.2167. Please note that while your design may comply with NFPA 59A-2019, Part 193 incorporates NFPA 59A-2001, therefore you must comply with the requirements in NFPA 59A-2001. Likewise, where there is a conflict between the requirements of Part 193 and NFPA 59A-2001, the regulations in Part 193 apply.

PHMSA provides written clarifications of the Federal pipeline safety regulations in the form of interpretation letters. These letters reflect the agency's current application of the regulations to the specific facts presented by the person requesting the clarification. Interpretations are not generally applicable, do not create legally-enforceable rights or obligations, and are provided to help the specific requestor understand how to comply with the regulations.

If we can be of further assistance, please contact Tewabe Asebe at 202-366-5523.


John A. Gale
Director, Office of Standards
and Rulemaking

Regulation Sections

Section Subject
193.2161 Dikes, general
193.2167 Covered systems