Secondary Containment Linings

Secondary containment is the backup barrier around primary storage — tank dikes and bunds, curbed pads, trenches, sumps, drum storage areas and truck loading pads. Its job is to capture a release from a leaking tank, ruptured hose or overfilled container and prevent it from reaching soil, groundwater, drains or surface water. Most containment is built from reinforced concrete, sometimes from steel, and bare concrete is both porous and vulnerable to attack by acids, solvents and many other chemicals.

Protective linings turn that concrete or steel into a liquid-tight, chemically resistant, cleanable surface. The lining must survive weather and foot or vehicle traffic for years, yet perform when a spill finally occurs.

Regulatory context

Requirements vary by jurisdiction and stored material; in the United States, common drivers include:

• EPA Spill Prevention, Control, and Countermeasure (SPCC) rule, 40 CFR 112 — for facilities storing oil above threshold quantities. For bulk storage containers, secondary containment generally must hold the entire capacity of the largest single container plus sufficient freeboard for precipitation, and be sufficiently impervious to contain oil.
• RCRA hazardous waste tank systems (40 CFR 264.193 and related provisions) — require secondary containment that is compatible with the waste, free of cracks or gaps, and able to detect and collect releases.
• Fire codes, state programs and local permits — often add requirements for flammable and hazardous materials.

Containment designs, including lining selection, are frequently reviewed or certified by a professional engineer. Facility owners should confirm which requirements apply to their site; this article is a technical overview, not regulatory advice.

Choosing a lining

The first question is always: what will it contain? Gather the full chemical list with concentrations and temperatures, and estimate the likely contact time — containment usually sees intermittent exposure until a spill is cleaned up, which is less severe than continuous immersion but still demands genuine resistance.

Use the manufacturer’s chemical resistance chart as a starting point, and for critical chemicals ask for test data or run spot or immersion tests — for example per ASTM C868 for protective linings or ASTM D1308 for spot exposure. Chemistry background is in epoxy coatings and polyurea coatings.

Typical system configurations

• Thin-film epoxy — roughly 10–30 mils (250–750 µm) for mild exposures and oils.
• High-build novolac or vinyl ester — thicker, sometimes with fiberglass mat or flake reinforcement, for aggressive chemicals.
• Elastomeric polyurea or hybrid — commonly 40–80 mils (1–2 mm) or more, with excellent crack-bridging and impact resistance, sometimes topcoated with a chemical-resistant layer.
• Sheet or geomembrane liners — used particularly in earthen containment, outside the scope of coatings.

Surface preparation and detailing

Containment concrete is often older, oil-soaked, weathered and cracked, which makes preparation challenging. Grinding or shot blasting to the manufacturer’s CSP is standard, along with removal of laitance and contamination. Oil-impregnated concrete may need degreasing, hot water cleaning, or removal and replacement, since oil can migrate back to the surface and destroy adhesion. See concrete surface preparation.

Moisture matters too: containment areas are outdoors, collect rainwater and may be slabs on grade without vapor retarders. Test per ASTM F2170 or F1869, and consider moisture-tolerant primers where needed — see concrete moisture testing.

1. Evaluate. Survey the structure, confirm capacity, map cracks, joints and penetrations, and review chemical exposures.
2. Clean and prepare. Remove contamination and old coatings and profile the concrete; blast steel to SSPC-SP 10/NACE No. 2 or as specified.
3. Repair. Patch spalls, rout and fill static cracks, and treat moving cracks with flexible fillers and reinforcing fabric.
4. Detail. Treat joints, wall-to-floor transitions (often with a cove), pipe and anchor penetrations and tank supports with reinforcement before field coats.
5. Prime. Apply penetrating primer to seal the substrate and reduce outgassing.
6. Apply lining. Build the specified layers by spray, roller or trowel, including any reinforcement and topcoat.
7. Test and document. Measure thickness, holiday-test, repair and retest, then document the system for the facility’s plan.

Testing and inspection

Because containment must be liquid-tight, continuity testing is central to acceptance. On concrete, ASTM D4787 describes spark testing of linings, which may require a conductive primer layer or adequate substrate moisture for the test to work. On steel, NACE SP0188 applies. See holiday testing. Pull-off adhesion testing per ASTM D7234 (concrete) or ASTM D4541 (steel) verifies bond where specified.

In service, facilities typically include containment in routine inspections, looking for cracks, blisters, disbonding, chemical attack, damaged joints and accumulated stormwater. For aboveground storage tank facilities, industry inspection standards such as STI SP001 are commonly referenced in spill plans.

Common failures

• Reflective cracking through rigid linings as concrete cracks propagate.
• Debonding from oil-contaminated or weak concrete.
• Chemical attack — softening, swelling or discoloration from incompatible products.
• Blistering from moisture vapor drive or osmotic effects.
• UV degradation of aromatic epoxies and polyureas in exposed containment; a UV-stable topcoat helps where appearance or chalking matter.

Frequently asked questions

Is bare concrete acceptable for secondary containment?

Sometimes, for products like certain oils, but concrete is porous and cracks, and many chemicals attack it. Whether it is “sufficiently impervious” depends on the product, the regulation and the condition of the concrete; many facilities line containment to remove doubt.

Which is better for containment, epoxy or polyurea?

Polyurea excels at crack-bridging, impact and fast return to service; epoxies and novolacs typically offer broader resistance to aggressive chemicals. Combination systems — an elastomeric base under a chemical-resistant topcoat — are common.

How thick should a containment lining be?

It depends on the chemistry and exposure, from roughly 10–30 mils (250–750 µm) for thin-film epoxies to 40–80+ mils (1–2+ mm) for elastomeric or reinforced systems. Follow the manufacturer’s recommendation for the specific exposure.

Can containment be relined while tanks are in service?

Often, with careful planning: sections are isolated, temporary containment is provided, and safety controls address flammable vapors and confined areas. The approach should be agreed with the facility’s engineer and safety team.