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Nevada's design rule for mine tanks fits in two sentences. NAC 445A.436 says that vats, tanks, and other containers that confine process fluids and can be inspected for leaks visually do not need double liners if a secondary containment area equal to 110 percent of the largest container is provided. Containers that are partially buried and cannot be inspected visually must have a leak detection system.
That rule is why the process plant at a Nevada mine usually sits inside lined containment instead of on a double-lined floor. It is also one of several rules that can reach the tanks on a single mine site, and they do not all count capacity the same way.
Three rulebooks inside one fence
A working mine stores three broad classes of liquid: process solution, fuel, and reagents. Each one brings its own requirements.
- Process fluids: Nevada's mining facility rules in NAC Chapter 445A set the 110 percent containment standard for tanks, require process components to withstand runoff from a 24-hour, 100-year storm, and require synthetic liners rated to resist process fluids at a permeability of 1 x 10^-11 cm/sec.
- Fuel and oil: the federal SPCC rule, 40 CFR Part 112, generally applies once aboveground oil storage exceeds 1,320 gallons. Bulk storage containers need secondary containment for the entire capacity of the largest single container plus enough freeboard for precipitation, built of material sufficiently impervious to hold the oil.
- Cyanide: operations that sign the International Cyanide Management Code commit to Standard of Practice 3.1 for unloading, storage, and mixing facilities and Standard of Practice 4.7 for spill prevention or containment at process tanks and pipelines, verified by independent third-party audits.
The baselines differ. Nevada's rule starts from the largest container. SPCC adds freeboard for rain. Cyanide Code audits have checked containment against the largest tank, any piping that drains back to it, and the design storm. A containment area sized to one standard can come up short under another, so the volume calculation belongs at the start of design, before the stemwalls are formed.
What actually sits inside the containment
Nevada water pollution control permits for mills commonly list the equipment that must sit within secondary containment: tanks, thickeners, vessels, pumps, and piping, with spills reporting to sumps that pump back to primary containment. Reagent tanks, including cyanide and caustic solution tanks, get their own containment.
Around the plant sit the fuel farms that supply haul trucks and generators, and on acid leach operations, sulfuric acid storage. Each of these is a separate lined area with its own liquid, its own penetrations, and often its own regulator.
Matching the liner to the liquid
Chemistry decides the material. Cyanide solution is held at high pH so cyanide stays in solution instead of forming gas, and HDPE handles alkaline process solutions well, which is why it is the default sheet for process and reagent containment on most gold operations.
Fuel is different. Geomembranes that do well in water service can degrade under long hydrocarbon contact, and XR-type ethylene interpolymer alloy geomembranes are the common specification for long-term fuel exposure. For sulfuric acid, concentration and temperature both matter, so the manufacturer's chemical resistance data for the actual stored concentration should settle the choice.
Containment liners also live in the open. Unlike a pad liner buried under ore, a tank area liner sees sunlight, foot traffic, and maintenance equipment for its whole service life, so UV resistance and puncture performance weigh as heavily as chemical compatibility.
Why small containment areas are hard to line
A leach pad is acres of open sheet. A reagent containment area is a few thousand square feet of corners. Tank ring walls, pipe supports, pump pads, stemwalls, and sumps break the floor into short runs, and every pipe that passes through the liner needs a boot welded to the sheet. Every concrete edge needs a batten or embedment attachment that holds under thermal cycling.
Much of this work is retrofit. The plant keeps running, hot work near fuel and reagents is tightly controlled, and the liner goes in around equipment that cannot move. Nevada mine sites mostly sit between 4,500 and 7,000 feet, where wind, cold, and wide daily temperature swings narrow the welding window. Crews schedule seaming for workable temperatures and run trial welds under actual field conditions.
Prefabrication moves much of that welding indoors. EC Applications fabricates panels up to 25,000 square feet along with custom boots and fittings, so a drop-in liner arrives with corners and penetrations already built and fewer welds are made on site. Our crews are the most experienced in the industry. They consistently deliver high quality installations with unparalleled customer service.
Keeping the containment inspectable
Nevada's exemption from double liners depends on the tank being visually inspectable, and the same logic applies to the containment around it. A floor that drains to a sump, stays free of standing debris, and can be walked is one an operator can actually inspect. SPCC adds its own discipline: rainwater should not leave a diked area until it has been inspected, with bypass valves normally sealed closed.
Seam testing follows the project QA plan. Fusion seams are air pressure tested per ASTM D5820, and extrusion welds around boots and attachments are vacuum box tested per ASTM D5641 or spark tested. The panel logs, repair records, and test results become part of the record the operator relies on at permit renewal and Code recertification.
Where EC Applications fits
EC Applications works from its office at 150 Isidor Court in Sparks, on the I-80 corridor east of Reno, and installs the full containment scope a mine runs on: heap leach pad liners, solution ponds, tailings liners, and the secondary containment around fuel and reagent storage. The same crews that line pads and ponds line the tank areas, so the seam standards match across the site.
