Marimaca Signs Its Seawater Supply, Leaves Sulfuric Acid to the Market

• Marimaca Copper received environmental approval for the Marimaca Oxide Deposit (MOD) in November 2025, and the sectorial permits that authorize construction are still in progress.
• The project holds a signed option for recycled seawater from the Bay of Mejillones, with the intake already permitted and no continental or fresh water used.
• Conveyance is one pipeline of about 32 kilometers (km) with a capacity of 208 liters per second, and one pumping station is required.
• Certified renewable electricity is available to the site, with no supply agreement, contracted volume, or tariff disclosed.
• Sulfuric acid feeds both the agglomeration cure and the irrigation solution, and Marimaca names an owner-operated acid plant as an opportunity to lower operating costs.

Environmental Approval & the Permits Still Outstanding

Marimaca Copper (TSX: MARI | ASX: MC2) received environmental approval for the Marimaca Oxide Deposit (MOD) in November 2025 and has not yet obtained the sectorial permits that authorize physical construction. Chile grants the first as a Resolución de Calificación Ambiental (RCA), the resolution that qualifies a project on environmental grounds, and it covers the environmental impact declaration the company lodged in December 2024. That declaration route fast-tracked the permitting process. That closes the approval that an investor cannot price around, because a project without it has no development path. 

Multiple years of environmental baseline studies and voluntary stakeholder engagement sessions preceded the submission, and technical and engineering studies were presented alongside the declaration itself. Community engagement sessions were held in Mejillones, the coastal town whose bay supplies the project's process water and whose port handles its cathode. The site lies within 40 kilometers (km) of Antofagasta, so the project draws on a regional labor pool and requires no accommodation camp on site. There is no community land overlap at the site, and the project has access to a skilled local workforce. 

The next phase is the sectorial permits, the auxiliary approvals required for individual stages of construction and operation. The company is well advanced in that phase, with the permits progressing according to the master schedule. Land across the project area is predominantly government-owned or controlled, which narrows the surface-access counterparties involved. The environmental approval is a step toward being construction-ready at the deposit. These approvals gate physical work on the ground, so the date they land, and not the environmental approval already held, sets when earthmoving can begin at scale.

Seawater Supply & the Pipeline Design

Water is the input Marimaca has taken furthest, and in this project, it is a process reagent as well as a site utility. The company holds a signed option over recycled seawater drawn from the Bay of Mejillones, and the intake that feeds it is already permitted. The design uses no continental or fresh water at any stage. Conveyance is a single pipeline of about 32 km with a capacity of 208 liters per second to the site, and one pumping station is required to move it. The line shares its corridor with the power spur that feeds the site, and both run inland from the coastal strip, which places the port of Mejillones 25 km from the plant. 

The difference between a utility and a reagent decides what a water interruption costs. Crushed ore is irrigated with a sulfuric acid solution made up in seawater, and salt is added at the agglomeration stage, so seawater is the medium that carries copper out of the ore. A single seawater pond takes the incoming supply and feeds the mine itself, the agglomeration stage and the pond holding raffinate, the copper-stripped leach solution that returns from the plant. A supply failure would stop copper production and not merely site services. The permitted intake and the signed option stand between that outcome and the mine plan.

Chief Executive Officer of Marimaca Copper, Hayden Locke, ties the project's utilities to the same short coastal distance that carries its cathode to port: 

"It also means that all the infrastructure that we need to build and operate this mine is literally on our doorstep, which materially reduces your execution risk."

The corridor design is already fixed, and the water leg is the part backed by a signed agreement. The pipeline, the pumping station, and the flow rate are all specified. The electricity that runs alongside them is not.

Power Supply & Emissions Positioning

A certified renewable electricity supply is available to the project, and a power spur and line run to the site alongside water, transport, and communications. No supply agreement, contracted volume, tariff, or counterparty is disclosed. Availability describes the market the company would buy in, not a position it has fixed, so the electricity leg is the one an investor treats as open until a contract is announced. 

The emissions case attached to that power is a set of targets, not measured performance. The company is targeting the first quartile of global copper mine-site emissions intensity, and heap leaching is 38% less carbon intensive than traditional processing, a figure it has published since November 2021. Both are targets across all aspects of operations, and no measured intensity exists for a plant that has not yet been built. Limited impacts on flora and fauna are expected across the coastal Atacama Desert site.

An uncontracted electricity supply is a cost line without a fixed price. Nothing in the disclosure attaches a volume or a term to the renewable supply, so the electricity cost cannot be modeled from company figures. That is a smaller exposure than an unpermitted one, because the supply is available, and a larger one than water, which is documented down to its flow capacity and the number of pumping stations required.

Acid Consumption & the Owner-Operated Plant Option

Sulfuric acid enters the flowsheet twice and is consumed for as long as the plant runs. Crushing runs in 3 stages to a product in which 80% passes 12.5 millimeters, prior to agglomeration. Crushed ore is agglomerated, or bound into coarse pellets with acid and salt, at a dose that varies by ore type, then stacked on 4-meter dynamic heap leach pads across 12 heap leach cells at initial construction. The irrigation solution carries 10 grams per liter of sulfuric acid at a maximum rate of 10 liters per hour per square meter over a 2-phase cycle lasting 62 to 83 days, depending on the ore type. Copper is then recovered through a solvent extraction and electrowinning (SX-EW) circuit designed for a nominal 50,000 metric tons a year of cathode, with a 3-stage extraction configuration and a 142-cell electrowinning plant. 

Consumption therefore tracks tonnage through the plant, which averages 12.4 million metric tons a year across the first 5 years of steady state and 14.1 million metric tons a year over the life of mine, at a head grade of 0.52% copper in that first window and 0.42% over the full life, and at copper recoveries of 77% and 72% across those same periods. Total operating costs are US$12.3 per metric ton processed across the first window and US$11.9 per metric ton over the life of mine. C1 cash costs, covering mining, processing, general and administrative, marketing and sales, and royalty costs, are US$1.45 per pound of copper in the first 5 years of steady state and US$1.84 per pound over the life of mine at a long-term copper price of US$4.30 per pound, a second-quartile position. At the same copper price, all-in sustaining costs including sustaining capital, closure capital, and salvage value are US$1.97 per pound in the first window and US$2.29 per pound over the life of mine, and the earnings before interest, taxes, depreciation, and amortization (EBITDA) margin is 58%. Marimaca identifies an owner-operated sulfuric acid plant as an opportunity to lower operating costs, but provides no capital figure or savings estimate for it.

Locke groups acid supply with market sentiment among the exposures management cannot settle from inside the project:

"I think there is quite a lot of uncertainty that's coming out of what Mr. Trump is doing in the Middle East and what's going on with Iran and it keeps flaring up, and that does create quite a lot of uncertainty in terms of the global supply chain and certainly oil supply, but also other commodities that got into the mining industry, particularly for us, acid supply."

Management has named the exposure without sizing it, so the acid plant is an identified opportunity and not a costed decision. The cost base it would act on was built with Ausenco and NCL, engineering consultants whose regional copper work includes Mantoverde and Santo Domingo. Those figures are the reference against which any acid-plant decision would be measured. 

The Input Position Ahead of a Final Investment Decision

Three workstreams stand between the current input position and the start of construction. Detailed design and engineering are underway, with the execution strategy still to be defined. Site early works are proceeding ahead of a final investment decision (FID), and long-lead items with delivery beyond 50 weeks are still to be secured. Project financing workstreams are underway, and market conditions support a competitive process. The plant site is at 1,100 meters above sea level, part of the project's low execution risk position.

Marimaca held US$140.0 million in cash as of June 30, 2026, with no debt. Initial capital for the project is US$587 million, and life-of-mine capital is US$1,198 million, so project financing is the workstream standing between that balance sheet and a build. At a long-term copper price of US$4.30 per pound, the post-tax net present value at an 8% discount rate (NPV8%) is US$709 million, with a 31% post-tax internal rate of return (IRR) and a 2.5-year payback. At the COMEX 3-month average of US$5.05 per pound for copper as of August 25, 2025, the equivalent figures are US$1.1 billion and a 39% IRR. Management said in July 2026 that it was targeting a project financing announcement before the end of that year, and those workstreams remained underway at the start of September 2026.

Locke gives the build a date and attaches a condition to it:

"We'll be going into construction in 2027, and then it's a 24-month timeline to our first cathode, and we're targeting 2029. There is a world where we can bring that forward, but right now we're saying 2029." 

That date depends on a financing close the company has not announced, on the sectorial permits that gate ground work, and on equipment orders that have yet to be placed. First cathode in 2029 stands two steps beyond the current input position: a financing close, and then the build itself. The inputs settled so far govern what the plant consumes once it runs, not when the first spade goes in.

The Investment Thesis for Marimaca Copper Corp.

• Environmental approval already held means the project has cleared the approval required to determine whether it can be built at all, which leaves the auxiliary construction permits as the only permitting item still open.
• A signed seawater option provides the project with a permitted intake and a single pipeline route from the Bay of Mejillones, with no continental or fresh water drawn at any stage.
• Electricity that is available but not contracted leaves the power supply the least documented of the project's main inputs.
• Sulfuric acid consumed throughout the entire leach cycle falls inside a second-quartile operating cost whose price is set outside the company.
• An owner-operated acid plant is identified as an opportunity to lower operating costs, with no capital figure or savings attached.
• Cash of US$140.0 million and no debt fund the pre-construction workstreams, while project financing remains the step between the current balance sheet and the start of construction.

Water, electricity, and acid stand at different stages of settlement. Water is contracted and permitted down to the pumping station, and the design removes fresh water from the question entirely. Availability is all the company has disclosed for electricity, which converts a supply risk into a price risk without eliminating either. Sulfuric acid is consumed continuously, priced by a market the company does not control, and, so far, addressed as an opportunity with no numbers against it. For an investor weighing a 2029 first-cathode target, water is the only settled input, and both the power contract and the acid decision are still outstanding.

TL;DR 

The MOD is a permitted Chilean copper project whose water supply is contracted and whose acid supply is not. A signed recycled-seawater option with an already-permitted intake feeds a 32 km pipeline at 208 liters per second, and the design uses no continental or fresh water, while certified renewable electricity is available with no agreement disclosed. Sulfuric acid enters both the agglomeration cure and the irrigation solution, so consumption tracks the 12.4 million metric tons per year processed in the early steady state. Marimaca names an owner-operated acid plant as an opportunity, with no capital figure associated with it. Ahead of FID, the open items are project financing, sectorial permits, and long-lead equipment orders, against US$140.0 million in cash and US$587 million in initial capital.

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