Joint Reply Comments

CERTIFICATE OF ATTORNEY

ASSERTION THAT INFORMATION CONTAINED IN AN IDAHO PUBLIC UTILITIES
COMMISSION FILING IS PROTECTED FROM PUBLIC INSPECTION

CASE NOS. IPC-E-26-09 & PAC-E-26-06

Application of Idaho Power Company and PacifiCorp D/B/A Rocky Mountain
Power for Certificates of Public Convenience and Necessity for Segment E-8 of
the Gateway West 500-kV Transmission Line

The undersigned attorney, in accordance with Commission Rules of Procedure 67,
believes that the attachment to Idaho Power Company and PacifiCorp’s Joint Reply
Comments, dated September 11, 2026, contains information that Idaho Power Company
and a third party claims are trade secrets, business records of a private enterprise require
by law to be submitted to or inspected by a public agency, and/or public records exempt
from disclosure by state or federal law (material nonpublic information under U.S.
Securities and Exchange Commission Regulation FD) as described in Idaho Code § 74-
101, et seq., and/or § 48-801, et seq. As such, it is protected from public disclosure and
exempt from public inspection, examination, or copying.

DATED this 11th day of September 2026.

Lisa C. Lance
Attorney for Idaho Power Company

JOINT REPLY COMMENTS - 1
LISA C. LANCE (ISB No. 6241)
DONOVAN E. WALKER (ISB No. 5921)
Idaho Power Company
1221 West Idaho Street (83702)
P.O. Box 70
Boise, Idaho 83707
Telephone: [phone]
Facsimile: [phone]
[e-mail]
[e-mail]

Attorneys for Idaho Power Company

JOSEPH DALLAS (ISB No. 10330)
Assistant General Counsel
PacifiCorp
825 NE Multnomah Street, Suite 2000
Portland, Oregon 97232
Telephone: [phone]
[e-mail]

Attorney for PacifiCorp

BEFORE THE IDAHO PUBLIC UTILITIES COMMISSION

IN THE MATTER OF THE APPLICATION
OF IDAHO POWER COMPANY AND
PACIFICORP D/B/A ROCKY MOUNTAIN
POWER FOR CERTIFICATES OF PUBLIC
CONVENIENCE AND NECESSITY FOR
SEGMENT E-8 OF THE GATEWAY WEST
500-KV TRANSMISSION LINE.

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CASE NO. IPC-E-26-09

CASE NO. PAC-E-26-06

IDAHO POWER COMPANY AND
PACIFICORP’S JOINT REPLY
COMMENTS

COMES NOW, Idaho Power Company (“Idaho Power” or “Company”) and
PacifiCorp d/b/a Rocky Mountain Power (collectively referred to as PacifiCorp) (together,
the “Parties” or “each Party”), and, pursuant to Idaho Public Utilities Commission’s
(“Commission”) Rules of Procedure 201-204 and the Notice of Modified Procedure, Order
JOINT REPLY COMMENTS - 2
No. 37069, hereby respectfully submit the following Reply Comments in response to
Comments filed by Commission Staff (“Staff”) and the Idaho Irrigation Pumpers
Association, Inc. (“IIPA”) on August 14, 2026, and public comments submitted by the NW
Energy Coalition and Renewable Northwest (together, “Joint Advocates”) and members
of the public.
The Gateway West project includes the addition of approximately 1,000 miles of
transmission lines planned to run from Wyoming to southwest Idaho. Gateway West was
first identified through the regional transmission planning process as far back as 2007 to
mitigate forecasted thermal overload violations primarily identified for east-to-west
transfer hours across Southern Idaho. Segment E-8 specifically was selected to create
more Midpoint West capacity, and was determined to be more cost-effective or would
more efficiently meet the needs of southern Idaho within this regional footprint.
Subsequently, Idaho Power’s Integrated Resource Planning (“IRP”) process indicated the
Gateway West segments in which Idaho Power retained ownership remained a key future
project, promoting continued grid reliability in a time of expanding energy resources.
By the 2025 IRP, which identified the inclusion of nearly 3,000 MW of generation
resource additions, it became clear that a portfolio without Segment E-8 was not a
possibility. Segment E-8 of Gateway West will create up to 2,000 MW of additional
transmission capacity, allowing continued adequate system reliability and providing the
ability to interconnect new generation resources across Idaho. While the construction of
Segment E-8 will create additional transmission capacity in the near-term, a 500-kilovolt
(“kV”) line is lower cost than a multi 230-kV transmission line alternative and provides for
additional operational benefits.
JOINT REPLY COMMENTS - 3
I. BACKGROUND
1. PacifiCorp’s Gateway Transmission Expansion Program, a plan to build
over 2,300 miles of new high-voltage transmission lines, primarily in Wyoming, Utah,
Idaho and Oregon, includes transmission lines in the Gateway Central, Gateway West,
Gateway South, and West of Hemingway regions, with routes within the regions identified
as Segments A through H. The Gateway West project includes the addition of
approximately 1,000 miles of transmission lines, identified as Segments D and E and
further categorized into Segments 1 through 10. As part of this proceeding, the Parties
are each requesting a Certificate of Public Convenience and Necessity (“CPCN”) for
Segment E-8 only.
2. Segment E-8 is an approximately 133-mile 500-kilovolt (“kV”) line that will
run from the Midpoint substation, near Jerome, Idaho, to the Hemingway Substation, near
Melba, Idaho. The Segment E-8 line will connect to Idaho Power’s proposed 500-kV
Mayfield substation, located near Mayfield, Idaho, resulting in two sections of the
Segment E-8 line, the approximately 40-mile Hemingway to Mayfield 500-kV line and the
approximately 90-mile Mayfield to Midpoint 500-kV line. The addition of Segment E-8 will
create approximately 2,000 MW of additional needed transmission capacity on Idaho
Power’s Midpoint West and Boise East transmission paths, supporting bidirectional
transfers between the Magic and Treasure Valleys and the delivery of energy to the
Treasure Valley from planned new resource interconnections in the Mountain Home and
Magic Valley areas. Idaho Power will have 99 percent ownership interest in the capacity
of Segment E-8 and PacifiCorp will have the remaining one percent ownership interest.
JOINT REPLY COMMENTS - 4
3. Gateway West was first identified through the regional transmission
planning process conducted in 2007, along with the 2008-2009 biennial planning process,
and components of the Gateway West project have been consistently selected in each
biennial regional transmission plan since. Following identification in the regional
transmission plans, Gateway West was first considered as part of Idaho Power’s 2009
IRP, where, in the latter half of the planning horizon, 2020-2029, the project was included
in every portfolio because then-current constraints would require the addition of new
transmission capacity for resources to be added in southern Idaho, east of the Treasure
Valley load center. Ultimately, beginning with the 2015 IRP, Idaho Power began modeling
Segment E-8 separately from other segments of Gateway West and the results indicated
the segments in which the Company had ownership remained a key future project,
promoting continued grid reliability in a time of expanding energy resources.
4. Benefits associated with the addition of Segment E-8 include the bolstering
of transmission capabilities to support load growth and the improved ability to interconnect
new generation resources between the Magic Valley and the Treasure Valley areas.
Recent studies indicate that the pre-Segment E-8 Idaho Power transmission system can
only accommodate approximately 250 MW of additional Treasure Valley load above
late-2020s levels. System imports from the east and south, as well as generation from
existing resources, must all cross the Midpoint West path to reach the Treasure Valley
load. Therefore, to meet any growth on the system, Idaho Power must either build new
generation close to the Treasure Valley or must increase transmission capability into the
region. It is infeasible from both a permitting and land perspective to site the magnitude
of resources in, or adjacent to, the Treasure Valley. With the transmission capabilities to
JOINT REPLY COMMENTS - 5
serve incremental demand currently limited, Segment E-8 will provide additional
transmission capability, both east-to-west and west-to-east.
5. Segment E-8 will also provide additional operational flexibility for
transmission outages and reduce the risk of automated generation curtailment that exists
on today’s transmission system. Because Idaho Power’s Midpoint West path is currently
congested, any sustained outages on the path reduce Idaho Power’s ability to transmit
generation to serve load. Should the Midpoint to Hemingway 500-kV line be out of service,
Idaho Power must restrict actual flows east-to-west on the Midpoint West path to maintain
compliance, resulting in a reduction of approximately 2,500 MW of east-to-west capacity
across Idaho Power’s transmission system. Segment E-8 will provide a second 500-kV
path for transfers between the Magic Valley and Treasure Valley, allowing for the
redistribution of flow during an outage, noticeably increasing the expected transfer
capability under outage conditions, and reducing the likelihood that transmission related
curtailments will be severe, and allowing Idaho Power to continue to serve customer load
effectively and economically.
6. The Gateway West project does not individually provide access to a liquid
market hub, additional transmission is needed to do so and therefore does not act as a
stand-alone resource. However, without Gateway West, the number of incremental
resources that can be added to Idaho Power’s system is constrained. As such, as part of
the 2023 IRP, the Gateway West project was modeled as an enabling project to allow the
incremental resource additions to be interconnected on the Idaho Power transmission
system east of the Treasure Valley. The Company again modeled the Gateway West
project as part of the 2025 IRP, however, when developing the portfolios, it had become
JOINT REPLY COMMENTS - 6
clear that developing a portfolio without Segment E-8 was not a possibility. Therefore,
Idaho Power modeled the addition of Segment E-8 as a baseline assumption to enable
the incremental resource additions. Gateway West Segment E-8 was a key component
of Idaho Power’s 2025 IRP Preferred Portfolio.
7. Pre-construction activities have occurred to support the Segment E-8
project since 2018, when the right-of-way was granted by the Bureau of Land
Management (“BLM”). Segment E-8 will be located on federal land managed by the BLM
and the Bureau of Reclamation, state lands managed by the Idaho Department of Lands,
and private lands. The Gateway West Segment E-8 transmission project is progressing
through required permitting and right-of-way activities, working with the Idaho Department
of State Lands to acquire appropriate easements across state lands for permanent
facilities prior to construction, as well as with private landowners to obtain the necessary
easements.
8. In 2023, the bulk of pre-construction activities began to move forward
including environmental, cultural and paleontological surveys, obtaining the necessary
easements, and engineering design. Construction of Segment E-8 is expected to
commence in October 2027 and will be performed in three phases, though the scope of
work is consistent across each phase. In January 2026, Idaho Power began the
competitive solicitation process to secure a contractor for material procurement and
construction of Segment E-8 and a formal Request for Proposal event occurred during
the summer of 2026.
9. On April 3, 2026, the Parties submitted an Application to the Commission
for an order granting Idaho Power and PacifiCorp each a CPCN for Segment E-8 of the
JOINT REPLY COMMENTS - 7
Gateway West 500-kV line, finding Segment E-8 is in the public interest and allowing for
the commencement of construction of the line. To allow for the commencement of
construction in October 2027, the Parties are requesting the Commission issue the
CPCNs no later than October 31, 2026, prior to the Parties entering into any contracts
associated with material procurement and construction of Segment E-8. A final
Commission decision in October 2026 will allow for commencement of construction of the
project in time to meet the November 2028 in-service date.
10. On August 14, 2026, Comments were filed by Staff and IIPA. In addition, as
of August 27, 2026, the Joint Advocates and three members of the public commented in
support of the issuance of the CPCNs (“Public Commentors”). In their Comments, Staff
recommends the Commission (1) approve CPCNs for Segment E-8 for both Idaho Power
and PacifiCorp, (2) direct Idaho Power to ensure all costs associated with Segment E-8
are fully captured and tracked in the Company’s records, (3) direct Idaho Power to provide
a detailed plan explaining how it will resolve system capacity deficits caused by additional
new large loads whenever Idaho Power proposes to enroll additional new large loads,
and (4) direct the Parties, through compliance filings, to submit: (a) the current budget for
each phase of the project, broken down by cost category, within 60 days of the final order,
and (b) monthly budget forecasts within 30 days after each forecast is finalized.1 The IIPA
does not contest the issuance of CPCNs for both Parties but requests the Commission
preserve issues relating to cost causation, allocation of regional transmission benefits and
future ratemaking treatment associated with Segment E-8 and related facilities.2 The Joint

1 Staff Comments, page 12.
2 IIPA Comments, page 5.
JOINT REPLY COMMENTS - 8
Advocates and Public Commentors recommend the Commission approve the CPCNs for
both Idaho Power and PacifiCorp.3
11. In these Reply Comments, the Parties reply to Staff and the Joint
Advocates’ support of the CPCNs, respond to the recommendations offered by Staff, and
acknowledge IIPA’s request for preservation of future cost allocation, prudence, and
ratemaking treatment concerns raised. The Parties respectfully request the Commission
(1) accept Staff and the Joint Advocate’s recommendation to issue CPCNs to both Idaho
Power and PacifiCorp for Gateway West Segment E-8, and (2) reject Staff’s proposed
unnecessary and administratively burdensome compliance filings for both Idaho Power
and PacifiCorp.
II. REPLY COMMENTS
A. The Commission should adopt Staff and the Joint Advocate’s
recommendation to issue CPCNs to both Idaho Power and PacifiCorp for
Segment E-8.

12. Idaho Power’s 2025 IRP portfolios included 2,965 MW of new gas, wind,
and solar generation resource additions to support load growth during the 20-year
planning horizon, focused heavily on the Treasure Valley area. As a result, absent the
addition of Segment E-8, new resources would need to be sited within the Treasure Valley
area, which has proven to be challenging. In addition, the limited capacity available
between the Magic Valley and Treasure Valley area necessitates a transmission capacity
upgrade east of the Treasure Valley to support the increased generation. The addition of
Segment E-8 will enable the incremental resource additions and therefore was a key
component of Idaho Power’s 2025 IRP Preferred Portfolio. Staff agreed with Idaho

3 Joint Advocates, page 3.
JOINT REPLY COMMENTS - 9
Power’s evaluation, indicating “strong evidence that additional transmission between the
Magic Valley and Treasure Valley is necessary.”4
13. Segment E-8 is necessary for PacifiCorp to meet its customers’ short- and
long-term energy demand and will strengthen the overall reliability of the existing
transmission system, long having been recognized as an integral component of
PacifiCorp’s long-term transmission planning. Staff highlighted PacifiCorp’s need for a
small ownership interest in Segment E-8 to maintain a “long-term strategic interest in the
entire Gateway West transmission line.”5 The Parties have an obligation to provide
adequate, efficient, just, and reasonable service on a nondiscriminatory basis to all those
that request it within their certificated service territory. Segment E-8 of Gateway West will
create up to 2,000 MW of additional transmission capacity, allowing continued adequate
system reliability and providing the ability to interconnect new generation resources
across Idaho.
14. The Parties appreciate Staff and the Joint Advocate’s review of the request
in this case and their recommended issuance of CPCNs for Segment E-8 for both
PacifiCorp and Idaho Power. Staff thoroughly evaluated the Application, supporting
documentation and discovery in this proceeding, finding that the Parties “met the
necessary regulatory requirements for a CPCN.”6 With respect to Idaho Power’s need for
Segment E-8, Staff believes that the Company has a legitimate need for the line, as it
supports regional objectives through identification in the Regional Transmission Plans,
provides economic benefits to customers as evidenced by the robust analysis performed

4 Staff Comments, page 4.
5 Id.
6 Id., page 3.
JOINT REPLY COMMENTS - 10
as part of the 2023 IRP, and creates another delivery path for sufficient new resources to
be sited east of the Treasure Valley.7 Finding PacifiCorp’s demonstration of “its ownership
commitment by taking the lead on permitting and easement acquisition,” Staff supports
PacifiCorp’s one percent ownership of Segment E-8 highlighting its ownership share “is
commensurate with its need for the project.”8 The Joint Advocates commend the Parties’
analyzing of transmission expansion as part of the IRP to maintain reliable and affordable
energy. With respect to Segment E-8, the Joint Advocates note the line will “decrease
overall risk by enabling access to new resources and enhancing the bulk transmission
system.”9 Both Staff and the Joint Advocates recommend the Commission approve the
Parties’ request and grant the CPCNs.10
B. Segment E-8 is the most cost-effective alternative for providing Idaho Power
with the necessary incremental capacity to enable generation resource
additions.

15. As part of the review of the Parties’ request in this proceeding, Staff
evaluated the cost-effectiveness of Segment E-8, finding that, while PacifiCorp’s need to
demonstrate the project was the least-cost, least-risk option is “irrelevant due to its need
being strategic in nature and its miniscule cost share of the project,” Idaho Power
presented “compelling evidence that alternatives to the project were severely limited.”11
Staff, however, cited difficulties determining whether Segment E-8 was the lowest cost
alternative due to what they have identified as three issues: (1) limited alternatives, (2)
the belief that the line is oversized, and (3) the complexity of quantifying potential

7 Id., pages 3-4.
8 Id., page 4.
9 Joint Advocates Comments, page 2.
10 Staff Comments, page 12 and Joint Advocates Comments, page 1 and 3.
11 Staff Comments, page 2.
JOINT REPLY COMMENTS - 11
additional benefits. Idaho Power understands Staff’s difficulties assessing the cost-
effectiveness of a project such as Segment E-8, which is unlike the Boardman to
Hemingway transmission line (“B2H”) or the Southwest Intertie Project-North
transmission lines, both of which individually provide access to a liquid market hub.
Gateway West, on the other hand, does not act as a standalone resource but rather,
enables incremental resource additions to be interconnected to Idaho Power’s
transmission system east of the Treasure Valley. However, Staff’s economic assessment
and associated concerns appear to be premised on flawed assumptions. As discussed in
greater detail below, though Segment E-8, as a 500-kV project, creates additional transfer
capability in excess of the immediate, forecasted need, the project is comparable in cost
to an alternative 230-kV solution, introduces substantially greater system benefits, and
provides long-term operational value, resulting in the most cost-effective solution to
customers.
i. Idaho Power has rightsized Segment E-8 as a 500-kV transmission line
based on current resource addition needs.
16. The identification of Segment E-8 as a least-cost alternative does not
“hinge[] on the presence of yet-undeclared new system load, presumably one or more”12
new large load customers, as suggested by Staff. With total new gas, wind, and solar
generation resource additions in the 2025 IRP Preferred Portfolio of 2,695 MW, there is
no question that Idaho Power is experiencing unprecedented load growth. But that
determination was made utilizing a load forecast based on current system load forecasts,
including Idaho Power’s largest customers along with other committed large load
customers who have entered into procurement or construction agreements. It was clear

13 Id., page 7.
JOINT REPLY COMMENTS - 12
that the forecasted system needs required additional transmission capacity between the
Magic Valley and the Treasure Valley to enable the necessary resource additions and
therefore Segment E-8 was modeled as a baseline assumption. Idaho Power’s
justification of the project was not based on “undeclared new load from one or more” new
large load customers, as assumed by Staff.13
17. Staff’s incorrect conclusion that Idaho Power has oversized Segment E-8
appears to be based on data presented in Figure 3 of Mr. Ellsworth’s Direct Testimony,
which identifies projected available transmission capacity along Midpoint West following
the addition of Segment E-8 in which Staff concluded that the available transmission
capacity is in excess.14 To understand the data presented in Figure 3, first note Figure 2
of Mr. Ellsworth’s Direct Testimony, which presents the forecasted available transmission
capacity on the existing Midpoint West transmission line, absent Segment E-8. The red
dots on the chart indicate hours that transfers across the line exceed the total transfer
capability and may cause facility overloads. The chart identifies minimum transfer
capability needed of approximately 200 MW in as early as 2029, approximately 500 MW
by 2033, and up to 600 MW by 2036. When reliability considerations are incorporated,
however, the minimum transfer capability needed grows even more. Because Segment
E-8 will provide Idaho Power up to 1,980 MW of additional capacity, resulting in up to
approximately 1,300 MW of available transmission capacity, Staff incorrectly suggests
that a 230-kV transmission line solution that provides less capacity would suffice and is a
more cost-effective alternative.

13 Id., page 7.
14 Id., pages 6-7.
JOINT REPLY COMMENTS - 13
ii. A 230-kV transmission line alternative is not lower cost.
18. Staff’s assumption that a 230-kV transmission line alternative would be
more cost-effective is mistaken. Staff suggests, without merit, that “one – or possibly two
– 230-kV lines should have been assumed as the alternative instead of multiple 230-kV
lines” and concludes that in “the case of only one new 230-kV line, Staff believes it would
be the least-cost solution.” It is possible to meet the projected 600 MW minimum transfer
capability with two 230-kV lines, as considered by Staff.15 However, it is important to note
that two, 230-kV lines would provide less than half of the capacity increase that the
Segment E-8 500-kV transmission line would provide, but at an equivalent cost of one,
500-kV transmission line. That is, Staff’s recommendation would result in less than 1,000
MW of additional capacity at nearly the same cost as Segment E-8. Furthermore, it does
not appear that Staff considered the right-of-way obtained for Segment E-8 is for the
infrastructure associated with a 500-kV transmission line and does not allow for the
construction instead of two 230-kV lines. In order to determine whether the two line
solution is even feasible, it would be necessary to reapply for permits. The use of 230-kV
transmission lines is simply not the least-cost solution in this circumstance.16
19. The two 230-kV transmission lines alternative would also limit the additional
operational benefits provided by a 500-kV transmission line. For example, Idaho Power
relies heavily on purchasing low-cost power from the Pacific Northwest and transmitting
it west-to-east on Path 14. However, most of that capacity is already allocated. While
there is a planned project that will potentially increase Path 14’s transmission capacity,
the next limiting element to import capacity from the west is the overload of the

15 Id., page 7.
16 Id.
JOINT REPLY COMMENTS - 14
Hemingway 500/230-kV transformer. Segment E-8 will provide that increase in import
capacity from the Idaho to Northwest west-to-east, mitigating overloads of the Hemingway
transformer and providing an additional 500-kV path out of the Hemingway substation. If,
however, Segment E-8 was constructed as two 230-kV lines as Staff suggests, the
minimum transfer capability would nearly fully utilize the additional capacity provided by
the lines, limiting the ability to import additional capacity west-to-east, and eliminating any
of the associated benefits that Staff agreed are valuable.17
20. Another benefit of Segment E-8 Staff acknowledged was advantageous, is
the east-to-west transfer conditions created with the addition of the 500-kV line and the
reduced reliance on the Midpoint-Hemingway-Summerlake remedial action scheme
(“RAS”). The Midpoint-Hemingway-Summer Lake RAS is an automatic scheme designed
to relieve overloads experienced when either the Midpoint to Hemingway or Hemingway
to Summer Lake 500-kV lines are lost with heavy east-to-west flows. With Segment E-8,
the rating of Midpoint West will increase dramatically creating a parallel 500-kV pathway
to facilitate energy transfers. While the construction of 230-kV lines rather than a 500-kV
line would also alleviate the need for RAS, the Midpoint West rating would not significantly
increase due to the higher impedance associated with 230-kV lines. If overloaded, the
new 230-kV lines would not allow for the offload of the existing Midpoint to Hemingway
or Hemingway to Summer Lake 500-kV lines. Rather, to move flows away from the
existing 500-kV line, without a new 500-kV line, the existing series compensation would
have to be bypassed and new series compensation needed for the new 230-kV lines. The
result is the requirement to build multiple 230-kV lines east of Midpoint, and additional

17 Id., page 8.
JOINT REPLY COMMENTS - 15
investments at the Midpoint station to increase the 345/230-kV transmission capacity to
source the 230-kV lines. In addition to being cost prohibitive, the Midpoint station does
not have spare bays or physical space to add the capacity, requiring a rebuild of the
station. A single 230-kV transmission line cannot provide the required transfer capability,
two 230-kV transmission lines are equivalent in cost but do not provide the same level of
operational benefits or require additional investments to achieve similar benefits,
increasing the cost of the 230-kV line alternative, clearly identifying Segment E-8 as the
least-cost alternative.
21. Staff’s assertion that Segment E-8 is being sized for “one or more
undeclared [new large load] customers” is premised on its conclusion that only one or two
230-kV lines should have been considered as the relevant alternative. However, as
discussed above, that comparison is flawed. The appropriate comparison is between
Segment E-8 and a solution that satisfies the identified transmission need and provides
commensurate system benefits, which is what the Parties presented in the Application.
When evaluated on that basis, Segment E-8 is the least-cost alternative, notwithstanding
the additional capacity it provides in the near term. The cost of a 500-kV transmission line
is equivalent to that of the required 230-kV transmission line alternative but provides
double the capacity, and operational benefits, affording customers added value over the
life of the line.
C. The Commission does not need to adopt Staff’s recommended compliance
filings of both Idaho Power and PacifiCorp.
22. Staff highlights two risks associated with Segment E-8, including the risk of
delay in bringing the line online and the risk of cost overrun and as a result proposes
certain compliance filings of Idaho Power and PacifiCorp. While potential delays or cost
JOINT REPLY COMMENTS - 16
overruns in the construction of a project of this magnitude could occur, it is premature to
implement any type of compliance requirement as the evaluation of customer associated
customer impacts is more appropriately addressed in a future rate proceeding.
i. It is not necessary to direct Idaho Power to submit a detailed system
capacity deficiency resolution plan.
23. Following their review of the status of the permitting and easement process,
though the Parties assessed potential risks and indicated delays are not expected as all
necessary permits and rights of way are secured or in process and on schedule, Staff
expressed continued concern about construction delays resulting from the permitting
process. Pointing to the construction delays of the B2H project, and their understanding
of the “frequent public resistance to transmission lines and environmental sensitivity,”18
Staff believes the “potential for delay is significant”19 and recommends Idaho Power delay
executing any Energy Service Agreements (“ESA”) associated with new large loads.20
24. The Parties disagree with Staff’s assessment. There are no current risks
associated with timely securing necessary permits and easements and Idaho Power does
not believe the B2H project is an appropriate comparison in this circumstance. In addition
to being nearly half the length of B2H, Segment E-8 will generally parallel the existing
Hemingway to Midpoint 500-kV transmission line through Owyhee, Canyon, Ada
Counties, and the majority of Elmore County, and will cross less than one-third the private
land that B2H does, resulting in fewer landowner easements needed.
25. Idaho Power appropriately plans for system capacity needs, first through
the IRP process, which develops the 20-year long-term resource plan based on

18 Id., pages 8-9.
19 Id., page 9.
20 Id., page 10.
JOINT REPLY COMMENTS - 17
forecasted peak loads, and again during the near-term resource decision-making phase,
as the annual capacity positions become very fluid, performing a system reliability
assessment using the most up-to-date load and resource inputs to determine near-term
annual capacity positions. The results of the IRP process and the refreshed system
reliability assessment are the foundation of the Company’s resource procurement
decisions and support each CPCN or contract approval request. The Commission should
reject Staff’s recommendation that Idaho Power “submit a detailed plan explaining how it
will resolve system capacity deficits”21 caused by any new ESAs it executes as the
Company already does so as part of all resource procurement proceedings.
ii. The Commission should reject Staff’s proposed current budget and
monthly budget forecast compliance filings.
26. With respect to the risk of cost overrun, Staff’s belief that because the
project “is a self-build,” there is a “high probability of cost overruns” is unfounded.22 In
addition to extensive budget approval processes in place, both Parties have and will
continue to utilize best practices to manage costs through the construction of Segment
E-8. Construction management will be executed primarily through service contracts,
including the construction contract, which will include typical protective provisions such
as change order validation, delay damages, and schedule obligations, akin to the
provisions present within a third-party construction contract, contrary to Staff’s assertion
that they will be absent. Though the project will be owned by the Parties, contractual
protective provisions will be utilized to manage project costs.

21 Id.
22 Id.
JOINT REPLY COMMENTS - 18
27. As explained in the Company’s Application, the Parties are not requesting
binding ratemaking treatment in this case, rather the Parties’ request in this case is that
the Commission find that both Idaho Power and PacifiCorp met the requirements of Idaho
Code § 61-526 and issue an order granting CPCNs for both Parties. The Parties agree
that ultimately a filing for cost recovery is when Staff will perform a prudence review of
the costs23 as the request in this proceeding is for a decisional prudence determination,
confirming that Segment E-8 is necessary for continued adequate system reliability and
to provide the ability to interconnect new generation resources across Idaho; evaluation
of operational prudence decisions would be undertaken in a future proceeding.
28. Though a full prudence determination will be necessary once Segment E-8
is placed in service and rate recovery is requested, the Parties included, as part of the
request in this case, the most recent forecast of the total project costs, incorporating costs
associated with permitting, pre-construction activities, construction of Segment E-8 and
substation work, as well as contingency, overheads and Allowance for Funds Used
During Construction (“AFUDC”), consistent with Idaho Power’s presentment of B2H costs
in Idaho Power’s CPCN proceeding for the transmission line. Staff however was critical
of the Parties, indicating that Staff wanted a more “detailed project budget to establish a
baseline for comparison when the Companies seek recovery of the project in future
proceedings”24 suggesting detailed budgets per project phase would be more appropriate
for a prudence review. Because the cost information provided by the Parties were not
what Staff envisioned, Staff recommends the Commission order the Parties to submit a
compliance filing within 60 days of the final order in this proceeding that includes a “project

23 Id.
24 Id., page 11.
JOINT REPLY COMMENTS - 19
budget broken down by cost category for each phase of the project.”25 The Parties do not
believe a compliance filing is necessary. Now that Staff has made the Parties aware of
the level of detail desired, the Parties have broken out the total cost estimate and have
included it as Confidential Attachment 1 to these Reply Comments. Specifically, included
in Confidential Attachment 1 is the summary of Segment E-8 costs, by phase, major work
within each phase, and cost category.
29. As well as requesting cost information broken down by phase and cost
category for review during future prudence requests, Staff recommends that the Parties
submit monthly budget forecasts26 citing a report provided in discovery.27 As an initial
clarification, the monthly budget forecasts referenced by Staff were not reflective of total
Segment E-8 budget forecasts and would not “allow Staff to compare initial and updated
budgets to actual project costs and identify budget changes and cost overruns.”28 Rather,
the monthly budget forecasts provided primarily included costs authorized under the
Project Development Agreement, or pre-construction and permitting activities, and do not
include a forecast of construction costs expected under the yet-to-be executed
Construction Funding Agreement. Further, the monthly budget forecast template is a
PacifiCorp-maintained document, that will continue to be managed for costs associated
with pre-construction and permitting activities following commencement of construction
activities and the point at which Idaho Power’s role as construction project manager of
Segment E-8 begins. Additionally, with the Parties in two different project management
roles simultaneously and utilizing two different budgeting systems to manage Segment

25 Id.
26 Id.
27 See Response to Staff’s Request for Production No. 21.
28 Staff Comments, page 11.
JOINT REPLY COMMENTS - 20
E-8 project costs, merging the differing processes for submittal to the Commission on a
monthly basis would be onerous.
30. In addition to being administratively burdensome and onerous to provide
monthly budget forecasts, because a construction contract has not been executed, and
material procurement has not begun, the Parties do not anticipate any significant changes
in the total project cost estimate and therefore do not believe the compliance requirement
would provide Staff value at this time. Rather, Idaho Power and PacifiCorp remain
committed to providing transparency and retaining any Segment E-8 budget reports to
make available to Staff during future prudence request proceedings, the point at which
Staff would have a more robust record of activities to review budget variances and the
appropriate vehicle for which any associated recommendations could occur. Therefore,
the Parties propose the Commission reject Staff’s recommended monthly compliance
filing requirement.
D. The Parties agree that cost causation and rate making treatment associated
with Segment E-8 are more appropriately contemplated in a future
proceeding.
31. As part of their assessment of the cost-effectiveness of Segment E-8, Staff
concludes that a portion of Segment E-8 is attributable to one or more undeclared new
large loads.29 Though the merits of Staff’s cost-effectiveness assessment were discussed
earlier, Idaho Power does not disagree with Staff’s recommendation that a portion of the
capacity Segment E-8 will allow for the integration of resources necessary to serve new
large loads. As clarified in previous CPCN requests, Idaho Power will ensure that all costs
associated with the Company’s ownership share in Segment E-8 are “fully captured and

29 Id., page 8.
JOINT REPLY COMMENTS - 21
distinctly tagged in its records for future allocation in accordance with the methodology
ultimately determined as part of the class cost-of-service proceeding, Case No. IPC-E-
26-07.30
32. The Parties will make future filings to address the cost recovery associated
with Segment E-8 and do not believe a cost cap is necessary, as suggested by the Joint
Advocates.31 It is in this future proceeding that the Parties will justify all costs associated
with the project, including cost overruns, if incurred, which will be presented for review
and determination, ensuring a complete record for a prudence decision.32 IIPA
acknowledged that their comments are intended to “preserve issues related to cost
causation, future cost allocation, and ratemaking treatment”33 that will occur in a future
proceeding. The Parties appreciate IIPA’s recognition of the request in this proceeding
and acknowledgement that cost allocation, a prudence review, benefits associated with
third-party utilization of Segment E-8, and ratemaking treatment will be addressed in the
future, and, if changes in the ownership structure occur, a request for approval will be
made.
III. CONCLUSION
33. The Parties acknowledge and appreciate IIPA, the Joint Advocates, and
Staff’s review of the request in this proceeding and respectfully request that the
Commission (1) accept Staff and the Joint Advocate’s recommendation to issue CPCNs
to both Idaho Power and PacifiCorp for Gateway West Segment E-8, and (2) reject Staff’s
proposed compliance filings for both Idaho Power and PacifiCorp. The evidentiary record

30 Id., page 5.
31 Joint Advocates Comments, page 3.
32 Staff Comments, page 11 and IIPA Comments, page 4.
33 IIPA Comments, page 1.
JOINT REPLY COMMENTS - 22
demonstrates that Segment E-8 meets the statutory standard of public convenience and
necessity because it will create up to 2,000 MW of additional transmission capacity,
allowing continued adequate system reliability and providing the ability to interconnect
new generation resources across Idaho.
DATED at Boise, Idaho this 11th day of September 2026.
LISA C. LANCE
Attorney for Idaho Power Company
JOSEPH DALLAS
Attorney for PacifiCorp
JOINT REPLY COMMENTS - 23
CERTIFICATE OF SERVICE

I HEREBY CERTIFY that on the 11th day of September, 2026, I served a true and
correct copy of Idaho Power Company and PacifiCorp’s Joint Reply Comments upon the
following named parties by the method indicated below, and addressed to the following:

Commission Staff
Kelsea E. Ross
Deputy Attorney General
Idaho Public Utilities Commission
11331 W. Chinden Blvd., Bldg No. 8
Suite 201-A (83714)
PO Box 83720
Boise, ID 83720-0074

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Idaho Irrigation Pumpers Association, Inc.
Eric L. Olsen
Echo Hawk & Olsen, PLLC
505 Pershing Avenue, Suite 100
P.O. Box 6119
Pocatello, ID 83205

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Lance Kaufman, Ph.D.
Deborah Glosser, Ph.D.
2623 NW Bluebell Place
Corvallis, OR 97330
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PacifiCorp
Joseph Dallas
825 NE Multnomah Street, Suite 2000
Portland, Oregon 97232

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Jana Saba
1407 West North Temple, Suite 330
Salt Lake City, UT 84116
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JOINT REPLY COMMENTS - 24

MICRON TECHNOLOGY, INC.
Austin Rueschhoff
Thorvald A. Nelson
Richard A. Arnett
Holland & Hart LLP
555 17th Street, Suite 3200
Denver, CO 80202
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Stacy Gust
Regulatory Administrative Assistant

BEFORE THE

IDAHO PUBLIC UTILITIES COMMISSION

CASE NOS. IPC-E-26-09 and PAC-E-26-06

IDAHO POWER COMPANY

CONFIDENTIAL

ATTACHMENT 1