Notice of Application for State Water Quality Certification

Public Notice (PN) Date: August 5, 2026                          PN Reference Number: POA-2026-00208 v1.0
PN Expiration Date: September 4, 2026                           Waterway: Miluveach River

Any applicant for a federal license or permit to conduct an activity that might result in a discharge into waters of the United States, in accordance with Section 401 of the Clean Water Act (CWA), must also apply for and obtain certification from the Alaska Department of Environmental Conservation that the discharge will comply with the CWA and the Alaska Water Quality Standards (18 AAC 70). The scope of certification is limited to the water quality-related impacts of the activity subject to the Federal license or permit (40 CFR 121.3, 18 AAC 15.180).

Notice is hereby given that a request for a CWA §401 Water Quality Certification of a Department of the Army Permit application, Corps of Engineers’ PN Reference Number indicated above, has been received[1] for the discharge of dredged and/or fill materials into waters of the United States (WOTUS), including wetlands, as described below, and shown on the project figures/drawings. The public notice and related project figures/drawings are accessible from the DEC website at https://dec.alaska.gov/water/wastewater/.

To comment on the project or request a public hearing with respect to water quality, submit comments via (preferred method) DEC website https://dec.alaska.gov/commish/public-notices/ or email to the DEC email address: DEC-401Cert@alaska.gov with the subject line referencing Public Notice Reference Number: POA-2026-00208 v1.0 or on or before the public notice expiration date listed above.

Applicant: Oil Search (Alaska), LLC, a subsidiary of Santos Limited, Alan Johnson, 501 West 5th Ave, Anchorage, AK 99501, (907) 375-4600; Alan.Johnson@santos.com

Agent: Oil Search (Alaska), LLC, a subsidiary of Santos Limited, Sofia Laughland, 501 West 5th Ave Anchorage, AK 99501; (907) 268-0788; Sonia.Laughland@santos.com.

Project Name: Quokka Development Project

Dates of the proposed activity are planned to begin and end: 11/01/2027 to 10/01/2031

Location: The proposed activity is located within Section 3,4,5,6,9,10,11,16,19,21,23,24,28-33,T.10N, 11N 13N R. 6E, 7E, 9E.  Umiat Meridian, in North Slope Borough, Alaska - Project Site (Latitude, Longitude): 70.295233, -150.37268.

Purpose: The purpose of the proposed Project is to enable Santos to safely and economically produce commercial quantities of liquid hydrocarbons from its Quokka Unit leasehold on the North Slope of Alaska. This includes developing infrastructure to access and extract hydrocarbons, processing them near the production areas, and transporting sales-quality oil by pipeline to the Trans-Alaska Pipeline System (TAPS). A secondary purpose is to facilitate further delineation of hydrocarbon-bearing formations within the leasehold using infrastructure developed to support the Project. The Project is needed to allow Santos to exercise its lease rights to develop subsurface resources. The Project would support the economic interests of the lessee and the State of Alaska, while also contributing to regional and national energy supply. Additionally, the Project is expected to generate workforce and business development opportunities at local, state, national, and international levels.

Description of Proposed Work: Oil Search (Alaska), LLC, a subsidiary of Santos Limited (Santos), is proposing development of hydrocarbon deposits from its oil and gas leaseholds on the North Slope of Alaska. The Quokka Project (Project) targets oil deposits in the Quokka reservoir. Santos would drill wells and construct and operate infrastructure and facilities to produce and transport sale-quality oil to the Trans-Alaska Pipeline System (TAPS). The Quokka Project would include two drill sites, a central processing facility, infield and import/export pipelines, infield roads and screeding at Oliktok Dock. The Project would also involve construction activities for supporting infrastructure, such as powerlines and fiber optic lines.

The Project would result in unavoidable temporary and permanent discharges into wetlands and other waters located within the project area. Permanent discharges would affect a total of 129.2 acres of wetlands and other waters, including 128.9 acres of gravel infrastructure and 0.3 acre of pipeline VSMs. Project development would require 1.62 million cubic yards (MCY) of clean gravel fill and 57,430 cy of sand slurry. The Project would also affect a total of 0.2 acres of uplands.

Gravel Pads: Santos would construct gravel pads with a minimum gravel thickness of 6 feet and 2H:1V side slopes. None of the pads would be within a mapped floodplain.

Quokka Drill Site A (QDA) and Quokka Drill Site B (QDB): The QDA drill site and the QDB drill site would accommodate up to 50 production and injection wells with 20-foot spacing between wellheads. Each drill site would also accommodate drilling equipment and drilling support facilities including hydraulic fracturing equipment, drilling mud and cement tanks, gathering facilities, diesel storage tanks, pipeline pigging and metering facilities, a communication tower, cold storage, emergency response equipment and drilling laydown areas. A service road at least 30 feet wide would be constructed around the perimeter of each pad to facilitate safe and efficient access to pad infrastructure. Routine well testing and process fluid heating would occur at the drill sites, with the majority of processing equipment located at the QPF.

Quokka Processing Facility (QPF): The QPF pad, located near QDB, would accommodate the processing and utilities modules that would process multiphase product (mixture of crude oil, natural gas and water) from the two drill sites (Sheets 8 and 9). Water separated from the oil would be re-injected back into the subsurface formation to help maintain pressure or disposed of via underground injection. Separated gas would be transported back to the drill sites via pipelines for gas lift and gas injection into the subsurface formation to help maintain pressure. Sales-quality oil would be transported via pipeline from the QPF to a tie-in with the existing Pikka sales oil pipeline. The QPF would be sized to process approximately 80,000 barrels of oil per day.

Processing facilities at the QPF would be comprised of a combination of truckable and sealift modules. These include equipment designed for phase separation, heating and cooling, pumping, gas treatment and compression for gas lift, gas injection and water treatment for water injection. The QPF would also include metering and pigging facilities; a communication tower; generating facilities; a tank farm consisting of crude oil, produced water, production chemical and methanol storage tanks; two underground injection control (UIC) wells for disposal of Resource Conservation and Recovery Act

(RCRA)-exempt and nonhazardous waste, such as produced water; construction material and equipment staging areas; and a high pressure/low pressure flare stack.

Quokka Tie-in Pad (QTP): The tie-in pad, QTP, would provide space for tie-in of the Quokka import/export pipelines (sales-oil, fuel gas, and seawater pipelines) to the Pikka import/export pipelines (Sheets 14 and 15). QTP infrastructure would include a pig launcher and receiver, a metering skid, pipe rack, power generation module, laydown area, and a communications tower. The pad would be connected to the existing Pikka road by a gravel access road.

Valve Pads: Two valve pads would be built on the QDA road, one on each side of the Miluveach River crossing. Valve pads provide space for the inclusion of shut-off valves on either side of the river crossing. The valve pad to the south of the Miluveach River would include a tundra access ramp for maintenance, spill response, or other purposes.

New Gravel Roads: Santos would construct two in-field roads to connect the Project with the existing Pikka road system:

• A road from the existing Pikka road system south to the QPF that would then continue to drill site QDB (Sheets 20 and 21).

• A road from the existing Pikka road system north to drill site QDA (Sheets 17-20).

Infield roads would be a minimum of 32 feet wide at the crown (minimum 52 feet at the base) to accommodate drill rig movement (Sheet 23). The roads would have a gravel thickness of at least 5 feet and 2H:1V side slopes. The road from the QPF to QDB would have one subsistence access ramp, and the road to QDA would have two subsistence access ramps to facilitate access and road crossings for off-road travelers. Each ramp would have a slope of approximately 15 percent.

Santos would site and design (both size and number) culverts at streams and other primary conveyance paths. Santos would also install cross-drainage culverts based upon local drainage patterns and field observations to accommodate meltwater during spring break up. An engineer would field-verify final culvert locations to confirm that natural drainage patterns are maintained. Culverts at fish-bearing streams would be built to accommodate fish passage.

In addition to culverts, the QDA access road would include three bridge crossings: two at waterways and one over the Pikka import/export pipelines. There would be a multi-span bridge across the Miluveach River consisting of steel girders with precast concrete decks and a 32-foot clear width between the faces of removable steel railings. The bridge would include 42-inch diameter pipe pile foundations and sheet pile abutments. Twelve piles would be placed below ordinary high water (OHW) and would have a footprint of 115 square feet.

There would be a single-span crossing of Trouble Creek just south of the QDA pad. The bridge would include 42-inch diameter pipe pile foundations; placement of piles will be avoided within the active channel to the extent practicable.

Additionally, an existing pipeline overpass would be required where the QDA access road crosses over the existing Pikka import/export pipelines. The existing pipeline overpass would use 42-inch diameter pipe pile foundations and would be designed to allow a drill rig to access QDA.

Pipelines: The Project would include construction of import/export and interconnecting (infield) pipelines. All pipelines would rest on pipeline supports. Each pipeline support would be made up of a horizontal support member (HSM) supported by vertical support members (VSMs) constructed from one or two 8- to 24-inch-diameter pipe piles (with an up to 36-inch diameter casing) spaced approximately 55 to 65 feet apart. These pipeline supports (referred to as pipe racks) would also carry power and fiber optic cables, as discussed further in Section 3.2.2.2. Where feasible, pipelines would be located parallel to gravel roads at a distance between 500 and 1,000 feet to minimize caribou disturbance and excessive snow drift accumulation while facilitating access for pipeline inspection, monitoring, repairs, modifications and testing. All pipelines and suspended cables would be a minimum of 7 feet above the summer ground surface except where pipelines intersect a road or pad. Where pipelines cross road embankments, pipelines would be encased in structural steel casings buried within the roadway section.

Santos would coat the external surface of insulated pipelines with fusion-bonded epoxy to prevent underinsulation corrosion. Pipelines containing temperature-controlled fluids and multiphase product would include an insulation system consisting of polyurethane foam insulation covered with an interlocked sheet metal jacket having a nonreflective finish. Santos would hydrostatically test the integrity of the pipelines before operation.

Infield Pipelines: Infield pipelines would connect the drill sites to the QPF (Sheets 38 through 41). The infield pipe rack would include:

• A 24-inch-diameter pipeline to transport multiphase product from each drill site to the QPF,

• An 8-inch-diameter gas-lift pipeline to transport treated gas from the QPF to the drill sites,

• A 6-inch-diameter gas injection pipeline to transport treated gas from the QPF to the drill sites,

• A 10-inch diameter pipeline to transport seawater from the QPF to the drill sites for injection,

• A 10-inch-diameter pipeline to transport produced water from the QPF to the drill sites for reinjection.

The QDA infield pipeline would include pipeline crossings of the Miluveach River and Trouble Creek. The Miluveach River pipeline crossing would include 36-inch diameter pipe pile foundations, of which two would be located below OHW for a footprint of 14 square feet (Sheet 46). The Trouble Creek pipeline crossing would include 36-inch diameter pipe pile foundations; the VSMs for the pipeline crossing would span Trouble Creek and no piles would be located below OHW (Sheet 46). Two valve pads would be built on the QDA road, one on each side of the Miluveach River crossing (Sheets 25 and 26).

Import/Export Pipelines: Import/export pipelines would connect the QPF to the QTP (see Figure 1; Sheets 34 and 35) and would include:

• a 16-inch-diameter pipeline to transport sales oil export to the tie-in with the Pikka sales oil pipeline north of the QPF,

• a 16-inch pipeline to transport seawater from the existing Pikka pipelines at the QTP to the QPF,

• an 8-inch pipeline to transport fuel gas from the existing Pikka pipelines at the QTP to the QPF.

The import/export pipelines would be built on the same pipe racks as the infield pipelines to QDA from the QPF to QTP.

Santos would also construct a utility pipeline to move fluids between the QPF and NPF. The utility pipeline would be on the same pipe rack as the Quokka QDA infield pipelines from the QPF north to the point at which the utility pipeline would turn northwest towards the NPF. The utility pipeline would then be constructed on new pipeline supports that parallel the existing Pikka pipelines to the NPF.

Applicant Proposed Mitigation: The applicant proposes the following mitigation measures to avoid, minimize, and compensate for impacts to waters of the United States from activities involving discharges of dredged or fill material.

1. Avoidance:

   • The Project would use existing infrastructure to the maximum extent practicable, thereby avoiding impacts to wetlands and other waters caused by the construction of additional, duplicative facilities.

   • The proposed project facilities have been sited adjacent to existing infrastructure on the North Slope, where practicable.

   • The processing of production fluids from all drill sites will primarily occur at the QPF, eliminating the need for additional on-pad facilities and a larger pad footprint at the drill sites.

   • Seasonal ice pads and roads would be used to support winter pipeline and gravel infrastructure construction, avoiding the need for additional fill and other temporary impacts to support construction.

   • Drilling for vertical support members (VSMs) would occur from an ice road, and drill cuttings would be sidecast onto the ice around each VSM, and the drill cuttings would be removed once VSM installation is complete, avoiding unnecessary discharges into wetlands and other waters. The sidecasting would not change the bottom elevation of wetlands or other waters or replace any portion with dry ground.

   • Where pipelines crossroad embankments, pipelines would be encased in structural steel pipe casings buried within the roadway section. Casings for pipeline-road crossings would extend beyond the road embankment toe. The power and fiber optic cables would cross under the road prism via a trench located parallel to each pipeline-road crossing or would be strapped to the pipeline. Trenching would occur during winter to the extent practicable. Trenched materials would be temporarily sidecast onto an ice pad adjacent to the trench. This would avoid a discharge of fill material into wetlands or other waters. Trenched materials would be taken off the ice pad and backfilled into the excavation once trenching is complete.

   • No gravel would be stockpiled in wetlands or other waters outside of the permitted footprint boundary.

   • External corrosion inspections of pipelines would be conducted during winter to the extent feasible and would be supported by approved tundra travel vehicles to avoid impacts associated with summer tundra travel.

   • Power cables and fiber optic cables would be installed on the HSMs using messenger cables, avoiding the need for power poles and associated fill.

   • At pipeline-river crossings, all pipelines and suspended cables would be elevated to maintain adequate freeboard.

2. Minimization:

   • All drill sites are sized to minimize overall gravel requirements while maintaining space for a sufficient number of wellheads to meet the overall project purpose.

   • Gravel roads would be constructed to be 32 feet wide at the surface but may be wider at curves to accommodate larger module transport. Gravel road footprints are further minimized by using 2H:1V side slopes to the extent practicable.

    

   • Existing water access points would be used to the extent practicable; no additional gravel roads for water access would be constructed.

   • Gravel infrastructure would be constructed during the winter months, when possible. All authorized fill area boundaries shall be surveyed and be clearly delineated (staked, flagged, or posted) prior to the discharge. After the gravel footprint is surveyed and staked, all snow and ice in excess of 4 inches would be removed from the tundra surface in the work area; the tundra surface would not be otherwise disturbed. Pit-run gravel would be placed in lifts using large-capacity dump trucks and would be spread out with bulldozers or similar heavy earthmoving equipment. Each lift would be compacted by a heavy roller. During summer months, ice that is present in the gravel would melt, leading to further consolidation and settlement. To enhance this process, the gravel would be farmed and re-compacted during the summer months. No infrastructure would be placed on gravel pads and roads until re-grading and compaction is completed.

   • To reduce impacts from equipment, Quokka Project construction methods would use machinery and techniques to minimize wetland impacts. This includes using machines with specially designed wheels or tracks and placing mats under heavy machines to reduce surface compaction and rutting for tundra travel. All required permits would be obtained for ice road/pad construction and operation.

   • If placement of the access road fill material is not completed within any winter season, sufficient openings shall be provided in the roadbed to maintain natural drainage flows and overland cross drainage at areas where overland flow is expected. Road opening widths shall be of sufficient size to prevent scouring of the adjacent tundra wetlands.

   • All disturbed, stockpile and fill areas shall be immediately stabilized to prevent erosion and sediment transport outside the project footprint. Active sloughing of fill material, increased water turbidity, accumulation of sediment in waters and wetlands, and erosion on slopes or around culverts shall be indicators fill slope stabilization is not adequate.

   • Snow removal management measures would be implemented to reduce the potential for gravel fill or other contaminants to be pushed off pads during snow removal.

   • Dust control measures would be implemented to reduce the incidence of dust on vegetation and snow, protect insulating vegetation, and minimize dust settlement on vegetation or snow, which could increase thermal conductivity and promote earlier spring thaw in affected areas.

   • Ice road and pad construction would begin after ADNR approves tundra travel and soil is considered sufficiently frozen to support the weight of equipment without damaging the underlying tundra. The ice roads would be a minimum of 6 inches thick and average approximately 12 inches thick due to terrain features. The ice roads would be constructed to support expected loads and protect the vegetation and organic soil beneath. The ice roads would be constructed to avoid sensitive vegetation, such as willows, that extend above the snow level, to the extent practicable. Ice roads would be wide enough (minimum of 20 feet) to safely accommodate two-way vehicular traffic and other traffic, as required.

   • Gravel roads provide all-season access to parallel pipelines for visual inspection and for routine and emergency maintenance and repairs. This also reduces the need for tundra travel associated with these activities. Roads and pipelines would be located within 1,000 feet of each other where feasible.

   • All on- and off-pad pipelines would be elevated above grade on VSMs to reduce impacts to permafrost.

   • Bridge abutments would be designed using sheet piles to minimize the gravel fill footprint, road embankment erosion, and stream scour.

3. Mitigation: The extremely low proportional disturbance (=0.31 percent within any watershed), the retention of intact watershed-scale functions, and the absence of practicable and ecologically meaningful compensatory mitigation opportunities within the watersheds indicate that compensatory mitigation would not provide environmental benefit for the Project. Consistent with the 2018 USACE/EPA Alaska MOA and the Section 404(b)(1) Guidelines, compensatory mitigation is not anticipated to be required for this Project. Avoidance and minimization measures incorporated into Project design are sufficient to satisfy mitigation sequencing requirements under the Clean Water Act.

After reviewing the application, the Department will evaluate whether the activity will comply with applicable water quality requirements (any limitation, standard, or other requirement under sections 301, 302, 306, and 307 of the CWA, any Federal and state laws or regulations implementing those sections, and any other water quality-related requirement of state law). The Department may certify (or certify with conditions) with reasonable assurance the activity and any discharge that might result will comply with water quality requirements. The Department also may deny or waive certification.

The permit application and associated documents are available for review. To inquire about or request copies of the documents, contact dec-401cert@alaska.gov or call 907-269-6285.

Disability Reasonable Accommodation Notice:  The State of Alaska, Department of Environmental Conservation, complies with Title II of the Americans with Disabilities Act (ADA) of 1990. If you are a person with a disability who may need special accommodation in order to participate in this public process, please contact ADA Coordinator Kristin Mabry, kristin.mabry@alaska.gov, 1-907-334-0884; or TDD Relay Service 1-800-770-8973/TTY or dial 711 at least 3 days prior to the expiration/closure date of this public notice to ensure that any necessary accommodations can be provided.

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