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A geomembrane lining a hazardous waste tank area must hold 100 percent of the largest tank inside it. That is the federal rule at 40 CFR 264.193, and the same paragraph says the liner must be free of cracks or gaps, surround the tank completely, and cover all surrounding earth likely to contact the waste if it is released.
That rule covers waste. The sodium hypochlorite tank at a water plant and the sulfuric acid tank at a leach operation hold product, and a different rulebook usually reaches them first. Sorting out which rule governs is the first step in sizing and lining chemical containment.
Product or waste: which rule applies
Oil storage answers to the federal SPCC rule, covered in our SPCC secondary containment guide. Chemicals split two ways.
- Chemical product in storage: the fire code. Section 5004.2.2 of the International Fire Code, as adopted by states and cities, requires secondary containment where its table calls for it and a single vessel holds more than 55 gallons or several vessels together hold more than 1,000 gallons. Whether the table calls for it depends on the hazard class of the material.
- Hazardous waste in tanks: RCRA, at 40 CFR 264.193 for permitted facilities. Part 265 carries parallel language that reaches interim status facilities and many generator accumulation tanks.
- Hazardous waste in drums and totes: 40 CFR 264.175, the container storage rule.
- State and local programs: many states add their own chemical storage rules, and water plants answer to the design standards their state drinking water program adopts.
One plant can carry all four. A wastewater facility may store ferric chloride and caustic as product, keep spent solvent drums as waste, and run a diesel generator under SPCC, each in its own containment with its own sizing rule.
How much volume the containment has to hold
The rules count capacity differently, and the difference shows up in wall height and floor area.
- RCRA tank systems: 100 percent of the largest tank. If the area is open to rain, run-on and precipitation must be kept out unless the system has spare capacity sized for a 25-year, 24-hour storm.
- RCRA container storage: 10 percent of the total container volume or the volume of the largest container, whichever is greater. Containers holding no free liquids are left out of the count.
- Fire code, indoor storage: the largest vessel, plus fire protection water from the sprinkler system for 20 minutes over the design area or the room, whichever is smaller.
Outdoor fire code provisions and state rules vary by edition and jurisdiction, so the design engineer and the fire marshal set the final number. The liner contractor builds to that number. The geometry still matters on the ground: tank displacement inside the berm, the lowest point of the wall, and the volume lost to pump pads and sumps all come out of the usable capacity.
Compatibility is written into the rule
RCRA does not leave material choice to preference. Section 264.193 requires the containment to be constructed of or lined with materials compatible with the waste, with enough strength and thickness to prevent failure. The fire code asks the same question of drainage systems, and it adds a second one: incompatible materials in open systems have to be separated from each other within the containment.
That second rule shapes layout at a water plant. Sodium hypochlorite and acid release chlorine gas when they mix, so a plant that stores both cannot share one lined bay between them. Each chemical gets its own cell, its own sump, and its own drain path.
For the liner itself, the reference test is EPA Method 9090. Samples of the geomembrane are immersed in the actual liquid for at least 120 days at 23 and 50 degrees Celsius, and their physical properties are measured against unexposed sheet. HDPE carries broad chemical resistance and is the default in many chemical services. XR-type alloy geomembranes are common where hydrocarbons are present. The right call depends on the chemical, its concentration, and its temperature at the site.
The 24-hour clock
Section 264.193 gives the containment two deadlines. Leak detection has to find a failure of the primary or secondary containment within 24 hours, or at the earliest practicable time. Waste that reaches the secondary system generally has to be removed within 24 hours, or as promptly as possible.
Both deadlines are design requirements for the liner. The floor has to slope to a sump so a release collects where someone will see it. The sump has to be reachable by a pump. The liner has to stay visible and clean enough to inspect.
What makes chemical containment hard to install
Chemical containment areas are small and crowded. A treatment plant chemical building or a mine reagent area is a few thousand square feet of tank ring walls, pipe supports, pump pads, and the transfer piping that connects them. Every boot and every termination to concrete is a hand weld, and every hand weld is a place a liquid could find its way under the sheet.
Most of this work happens next to tanks that stay in service. Hot work is controlled, access is tight, and the plant cannot stop feeding chemical while the containment is rebuilt. Prefabrication moves much of the welding indoors. EC Applications fabricates panels up to 25,000 square feet along with custom boots and fittings, so a drop-in liner arrives sized to the berm and the field crew concentrates on tie-ins and terminations.
Testing follows the project QA plan. Fusion seams are air pressure tested per ASTM D5820, and extrusion welds around boots and battens are vacuum box tested. In a small containment area, much of the welding is extrusion work around details, which puts the weight of the job on the welders.
Where EC Applications fits
EC Applications lines secondary containment for water and wastewater plants and for mines, working from offices in Anaheim, California, Midland, Texas, and Sparks, Nevada. The scope runs from new containment to relining an existing berm around in-service tanks. Our crews are the most experienced in the industry. They consistently deliver high quality installations with unparalleled customer service.
To scope a containment project, send the tank list with stored chemicals and concentrations, the containment dimensions, any existing drawings, and the governing permit or code basis.
