DWQ-2025-002231

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DRAFT FACT SHEET AND STATEMENT OF BASIS
UNDERGROUND INJECTION CONTROL (UIC) CLASS V AREA PERMIT MODIFICATION
UTU-27-AP-BDCCF0C
MARCH 2025

Location:
Millard County, Utah

Operator:
Advanced Clean Energy Storage I (ACES I), LLC


Facility Contact:
William Myers
ACES I, LLC
3165 E. Millrock Dr. Suite 330
Holladay, UT 84121
[e-mail]
Tel. [phone]
Regulatory Contact:
Porter Henze
Utah Division of Water Quality
195 North 1950 West
Salt Lake City, UT 84116
[e-mail]
Tel. [phone]


Purpose of the Fact Sheet
Pursuant to section §144.39 of the Underground Injection Control (UIC) regulations in Title 40 of the Code of Federal Regulations (CFR) which is incorporated by reference in the Utah
UIC Administrative Rules (R317-7), the purpose of this fact sheet is to briefly describe the principal facts and considerations that went into preparing a permit modification for the
ACES Clean Energy Storage Class V Permit (“Permit”) by the Division of Water Quality (“Division”), the UIC permitting authority. To meet these objectives, this fact sheet contains a
description of the permitted facility, a description of the injectate, information on the permitting process, and a statement of basis for the major modification. This Permit was drafted
under UIC permit regulations for Class V injection wells associated with the production of electric power (R317-7-3.5.M and 40 CFR §146.5(e)(12)) by Utah UIC Director authority per Utah
Admin. Code R317-7-1.8.
Brief Description of the Facility
ACES I plans to inject, store, and withdraw hydrogen from underground storage caverns constructed in a tectonically thickened salt body located approximately 9 miles north of Delta,
Utah in Millard County and at depths greater than 3,000 feet below ground surface. The construction of these caverns is permitted by the ACES I solution mining UIC Class III Permit UTU-27AP-718D759.
The operation of the storage caverns is permited by UIC Class V Permit UTU-27-AP-BDCCF0C.
Description of Injectate
The storage caverns are created by solution mining with fresh water under the UIC Class III Permit which limits cavern capacity by imposing strict cavern diameter to pillar width (salt
mass between caverns) ratios and standoff distances to the edge of the salt formation itself. Brine created by the solution mining process is stored in nearby surface solar evaporation
ponds which are regulated by Ground Water Discharge Permit UGW270010. The completed caverns are then used to store and recover gaseous hydrogen by injection and recovery under pressure
as regulated by this UIC Class V permit. The hydrogen is generated on site by electrolysis of water and is used to generate electricity by combustion. The total storage volume in the
two caverns (CW-2 and CW-23) that will be constructed for this project is 11 million barrels. The limits of total hydrogen capacity and injection and withdrawal rates by mass and volume
are constrained by the total cavern volume, the maximum allowable hydrogen gas pressure (Specified in the Storage Cavern Field Operating, Monitoring and Reporting Plan (SCFOMRP) which
is Permit Attachment C).
Information on the Permitting Process
The Class V Permit Major Modification was prepared by the Division for public notice and public comment according to 40 CFR §144.39 which is incorporated by reference in Utah Admin.
Code R317-7-1. Public comments will be accepted by the Division for 30 days following the first day of public notice in the local newspaper that serves the affected community. Only conditions
subject to the modification are reopened (40 CFR §144.39(c)).
Statement of Basis for Establishing Permit Conditions
The basis for permitting for the UIC Class III & V permits for hydrogen storage is to ensure compliance with the Utah UIC administrative rules for Class V injection well activities,
Rule R317-7. Updated data from the geomechanical analyses will update proposed limits in the Storage Cavern Field Operating Plan (SCFOP). A Permit modification is being requested to
update the Maximum Operating Pressure Gradient (MaxAOPG) from geomechanical data and modify the subsidence monitoring plan.

Summary of Conditions of the Permit for Hydrogen Storage
Permit Modifications
Class V Cavern Operation Requirements
The Modification alters the permit under the operating requirements found in Part III.D.4.b of the Class V Permit UTU-27-AP-BDCCF0C. The MaxAOPG has been updated from 0.85 psi/ft to
0.80 psi/ft based on the latest geomechanical data. “Typical” operating pressure has been removed in favor of a maximum and minimum operating range (0.30 to 0.80 psi/ft).
Update Operating, Monitoring, and Reporting Plan
The Modification alters Section 1.5 and 2.2 of the Operating, Monitoring, and Reporting Plan. The cavern diameter has been given a range of 220 to 350 feet based on site-specific geological
conditions. The test pressure limit has been removed as it now exceeds the updated MaxAOPG limit. Naming conventions have also been updated.
Update Subsidence Monitoring Plan
The Modification alters the Subsidence Monitoring. The cavern diameter has been given a range of 220 to 350 feet based on site-specific geological conditions. The maximum range of the
subsidence monuments have been updated to match what is installed. The number of subsidence reference monuments have been reduced to reflect existing infrastructure. Reduced reference
points will not impact subsidence monitoring. Specified technology for monitoring requirements has been adjusted to allow for determination by a licensed surveyor.
Update Permit Language
The Modification updates permit language to current Division standards and corrects the Northing and Easting Coordinates in Section I.