20260930Tariff Advice No. INT-TAG-26-03.pdf

RECEIVED
September 30, 2026
IDAHO PUBLIC
INTERMOUNTAIN` UTILITIES COMMISSION
GAS COMPANY
A Subsidiary of MDU Resources Group,Inc. INT-TAG-� -O
In the Community to Serve®
September 30, 2026
Monica Barrios-Sanchez
Commission Secretary
Idaho Public Utilities Commission
P.O. Box 83720
Boise, ID 83720-0074
RE: Intermountain Gas Company, Case No. INT-TAG-26-03
Dear Ms. Barrios-Sanchez:
Enclosed for filing with this Commission is a copy of Intermountain Gas Company's ("Intermountain" or
"Company") proposed revisions to Section C of its General Service Provisions.The proposed edits to Section
C are presented in Attachment No. 1. The resulting proposed Section C is presented in Attachment No. 2.
The proposed revisions outlined below are in line with Commission Order No. 34735 in Case No. INT-G-20-
01 which authorizes the Company to "file an annual tariff advice to update the Allowable Investment
Factors, the Service Line Cost per Foot, and the construction overhead charge." (See Order No. 34735 at 9.)
1. The update to the Allowable Investment Factors in Section 4.3 includes a change in the compound
inflation factor, an update to the embedded costs on pages 2-3 of Attachment No. 3 to reflect the most
recent information from Case No. INT-G-25-02, and an update to the depreciation lives on page 2 of
Attachment No. 3 to reflect the most recent information from Case No. INT-G-26-01. The embedded
costs update follows the same methodology approved by the Commission in Order No. 34735. Please
note,that since the settlement exhibits in Case No. INT-G-25-02 did not provide all the amounts
required by the approved methodology,the Company derived the relevant amounts using the amounts
proposed in the Company's initial filing, reduced by a settlement reduction percentage. The calculation
of the derived amounts is clearly shown on pages 2-3 of Attachment No. 3.
The compound inflation factor is updated to include inflation data for January 2026 through August
2026.The Company adjusts for inflation of the embedded costs from its last general rate case (Case No.
INT-G-25-02)to ensure that new applicants are treated the same as existing customers in terms of the
amount of facilities for which their Allowable Investment will pay.
The calculation of the proposed Allowable Investment Factors, including the adjustments discussed
above, is shown in Attachment No. 3, pages 1-4.

Intermountain Gas Company Page 2 of 2
Case No. INT-TAG-25-03
2. The update to its service line cost per foot in Section 5.2 is based on a new three-year average of
service line costs divided by the feet installed during the same years.The proposed three-year average
service line cost per foot is shown in Attachment No. 3, page 5.
3. After the conclusion of Case No. INT-G-25-02,the Company and Commission Staff engaged in several
workshops regarding the Section C of the Company's General Service Provisions. One of the focuses of
those workshops related to reducing line extension cost variances. To help in this effort,the Company
proposes to remove the construction overhead rate stated in Section 5.3(c)to allow the Company to
use the most current construction overhead rate in its line extension cost estimates. In general,the
Company calculates the construction overhead rate at the beginning of the calendar year, however,the
construction overhead rate approved in this tariff update typically becomes effective towards the end
of the year. This proposed change will eliminate the lag and align the construction overhead rate
included line extension costs estimates with the currently calculated construction overhead rate.
The Company requests that the proposed revisions become effective one month after Commission approval
to give the Company enough time to implement the changes to its systems and forms.Therefore,the
Company proposes a Commission approval date of November 1, 2026, and an effective date of December
1, 2026.
If you have any questions or require additional information regarding the attached, please contact me at
[phone] or Jacob Darrington at [phone].
Sincerely,
/s/Michael Parvinen
Michael Parvinen
Director—Regulatory Affairs
Intermountain Gas Company
Enclosures