Mining Tanks: Process Water and Leachate
Bolted steel tanks for mining: process water, leach solution and leachate containment, with corrosion-resistant coatings and fast, relocatable assembly.
Mining uses tanks for two critical functions: storing process water (fresh, recycled and thickener water) and containing leach solutions and leachate (pregnant leach solution, raffinate, acid mine drainage). For both, the bolted steel tank with a corrosion-resistant coating is the most practical option: it is erected in weeks at remote, high-altitude sites, withstands aggressive solutions with the right coating, and can be relocated when the mining front moves. This article covers the sector challenge, the Tech Tank solution and how to choose the coating.
The sector challenge: aggressive chemistry, remote logistics
Water in mining is rarely clean. Typical streams include:
- Process and recycled water: with suspended solids, flotation reagents and pH swings.
- Leach solution (PLS/raffinate): copper heap leaching uses dilute sulfuric acid; gold uses alkaline cyanide solutions. Both are chemically demanding.
- Leachate and acid mine drainage (AMD): low-pH drainage with dissolved metals that corrode bare steel quickly.
On top of the chemistry comes logistics: projects sit in remote, high-altitude locations with difficult access. Shipping a finished welded tank is unfeasible; building in concrete is slow and expensive. And the operation is dynamic: pads, ponds and plants relocate over the mine's life.
In Paraguay, handling process solutions and leachate falls under Law 294/93 on Environmental Impact Assessment and Law 3239/07 on Water Resources; containment and leak control are defined in the environmental license. Verify the current requirements with MADES.
The Tech Tank solution: bolted tanks with tailored coatings
Tech Tank builds bolted steel tanks to AWWA D103, selecting the coating by the aggressiveness of each stream:
- Glass-fused-to-steel (GFS) tank, enamel fused per ISO 28765: the best barrier against acidic, cyanide and leachate streams, because the glass is chemically inert, does not corrode and needs no repainting.
- Epoxy tank: for moderately aggressive process water, with a coating selected for chemical compatibility.
- Stainless steel tank: for very demanding streams or elevated temperatures.
Delivery is turnkey: engineering, foundation, on-site bolted assembly and commissioning, with panels shipped in containers to hard-to-reach sites. Being bolted, the tank is erected in weeks and can be dismantled and relocated as the mine plan advances, which concrete cannot. To compare construction technologies, see bolted vs welded vs concrete tanks and the pillar on what a bolted steel tank is.
Choosing the coating by stream
The key decision in mining is not the tank but its internal coating, because that defines service life against the chemistry. As a guide:
| Stream | Aggressiveness | Suggested coating | Note |
|---|---|---|---|
| Fresh / recycled water | Low-medium | Epoxy or GFS | Solids and variable pH |
| Thickener water / tailings | Medium-abrasive | GFS | Abrasion from solids |
| PLS / raffinate (Cu leaching) | High (acidic) | GFS | Dilute sulfuric acid |
| Cyanide solution (Au leaching) | High (alkaline) | GFS or stainless | Strict leak control |
| Acid mine drainage (AMD) / leachate | Very high (low pH) | GFS or stainless | Dissolved metals |
Final selection is confirmed against the real chemical composition of each stream (pH, chlorides, solids, temperature); these ranges are indicative.
Benefits over concrete and field-welded tanks
Against concrete, bolted steel with GFS offers a continuous chemical barrier with no seams that leak and a construction time of weeks instead of months. Against a field-welded tank, it avoids welding at height in a corrosive atmosphere and can be dismantled. Reference figures:
- Erection time: on the order of weeks for capacities of thousands of m³, depending on access and weather.
- GFS coating service life: typically 30-50 years with no repainting, versus periodic maintenance of field-applied coatings.
- Relocation: the tank moves to a new front while preserving the investment, key in finite-life operations.
| Criterion | Bolted steel (GFS/stainless) | Concrete | Field-welded |
|---|---|---|---|
| Construction time | Weeks | Months | Weeks-months |
| Chemical barrier | High (GFS/stainless) | Medium (needs liner) | Depends on coating |
| Remote/high-altitude access | High (panels in container) | Low | Medium |
| Relocatable | Yes | No | No |
| Coating maintenance | Minimal (GFS) | Crack repair | Periodic repainting |
If your operation needs to store process water or contain leachate, Tech Tank can select the coating, size the capacity and deliver the system turnkey on site. Request a technical quote with your stream composition and required capacity.
Frequently Asked Questions
Which coating best resists acidic leachate?
The glass-fused-to-steel coating (per ISO 28765) is the best barrier against acidic solutions and low-pH leachate, because the fused glass is chemically inert, does not corrode and needs no repainting. For extreme or high-temperature cases, stainless steel is evaluated.
Can a bolted tank hold cyanide solution for gold leaching?
Yes, with the right coating (GFS or stainless) and strict containment per the environmental license. Final selection is based on the chemical composition and pH of the solution and on the project's leak-detection requirements.
Can it be installed at remote, high-altitude sites?
Yes. Panels ship in containers and the tank is bolted on site, with no field welding and no cranes for large pieces. That is why it is a common solution for mining projects with difficult access.
Is it relocatable as the mine plan advances?
Yes. Being bolted, the tank can be dismantled and reassembled at a new front, preserving the investment. That is an advantage over concrete, which is fixed, in finite-life operations.
What regulations apply in Paraguay?
Handling process solutions and leachate falls under Law 294/93 on Environmental Impact Assessment and Law 3239/07 on Water Resources. Containment and leak control are defined in the environmental license; verify the current requirements with MADES.