I202501 NOPV Response

EXECUTIVE OFFICES
INTERMOUNTAIN GAS COMPANY
555 SOUTH COLE ROAD-P.O. BOX 7608• BOISE,IDAHO 83707• [phone]• FAX:[phone]
October 9,2025
Mr.Jeff Brooks,Programs Manager
Idaho Public Utility Commission
PO Box 83720
Boise,ID 83720-0074
Subject:Response to the Notice of Probable Violation received October 6,2025,dated March 6,2025
(Report#1202501)
Dear Mr.Brooks,
This letter is intended to address one(1)notice of probable violation stemming from a compliance follow up
inspection conducted by the Idaho Public Utilities Commission(IPUC)on February 4 ,2025,of Intermountain Gas
Company's(IGC)Rexburg LNG Plant pursuant of Chapter 601 Title,49,United States Code.
PROBABLE V10LA1iON
L 49 CFR $193.2603 General.
(a)Each component in service, including its support system, must be maintained in a condition
that is compatible with its operational or safety purpose by repair, replacement, or other
means.
(b) An operator may not place, return, or continue in service any component which is not
maintained in accordance with this subpart.
(c) Each component taken out of service must be identified in the records kept under §193.2639.
(d) If a safety device is taken our of service for maintenance,the component being served by the
device must be taken out of service unless the same safety function is provided by an alternate
means.
(e) If the advertent operation of a component taken out of service could cause a hazardous
condition,that component must have a tag attached to the controls bearing the words "do not
operate"or words of comparable meaning.
Finding(s)•
On October 18,2023,the IPUC conducted a field audit and the LNG tank saddles/supports were showing signs
of cracking. It was also discovered that IGC personnel has identified cracking in the concrete of the tank
foundation on May 5,2025, and again on October 5,2023.No corrective action had been taken by IGC until
IPUC personnel issued a Letter of Concern#I202310 on October 19,2023.
Intermountain Gas Res n� nse
On November 15,2023, IGC issued a response to Letter of Concern 41202310 stating"IGC acknowledges the
finding brought forth by the IPUC. IGC has contacted a third-party engineering company to discuss repair and
maintenance plan for tank saddles and supports."The IPUC accepted this response in good faith and closed out
the concern on November 15,2023.
Follow Up
On May 15,2024 a Concrete Cracking Investigation was performed by Forsgren Associates Inc. ("Forsgren")at
the facility to identify and present the findings of a structural condition assessment for the concrete cracking at
the piers of the LNG tank and for the containment structure walls.
On June 28,2024,Forsgren sent a Concrete Cracking Investigation letter(signed by two Professional Engineers)
to IGC regarding the Concrete Cracking Investigation at the facility. The investigation included site visit
observations, the concrete analysis results, a report from a petrographer, and contained recommendations for
mitigative steps to address the alkali silica reactivity("ASR"),water intrusion,and to allow concrete to dry out.

EXECUTIVE OFFICES
INTERMOUNTAIN GAS COMPANY
555 SOUTH COLE ROAD-P.O. BOX 7608• BOISE,IDAHO 83707•[phone]• FAX:[phone]
Intermountain Gas Resnonse
On January 9,2025,IGC provided another follow up response stating"IGC contracted a third-party engineering
company,Forsgren,to discuss a repair and maintenance plan for tank saddles and support. Forsgren complete
a site observation on May 15,2024.IGC is evaluating the recommendations and will coordinate necessary repairs
with Forsgren.A remediation plan will be developed by July 31,2025.
Findin¢(s)•
February 4,2025,IPUC inspectors conducted an on-site compliance follow-up inspection at the Rexburg LNG
Facility. During the inspection, the tank saddles/supports were exhibiting signs of crack propagation and
additional foundation spalling. The containment structure walls showed signs of increased cracking and
degradation.When compared to the(2024)Forsgren documentation,the cracking and spalling have worsened.
To date, no measures to prevent further deterioration have been implemented and no recommendations by
Forsgren have been followed.In the time since the concrete issues were originally identified(in May of 2023)
there have been multiple truck offloads,weather cycles,and personnel changes. IPUC staff believes the tank
foundation pedestals should be maintained in a condition that is compatible with its safety purpose by repair,
replacement,or other means.
Intermountain Gas Resnonse
The concrete work to mitigate the alkali silica reactivity (ASR) degradation was completed August 1, 2025.
IGC will internally inspect the concrete annually and perform third party engineering inspections every five
years.
Please contact Josh Sanders at(701)222-7773 with questions or comments.
Respectfully Submitted,
Pat Darras
Vice President,Engineering&Operations Services
Intermountain Gas Company