Does my site need secondary containment?

Start with how much oil you can store, not how much you do store

The federal SPCC rule — Spill Prevention, Control, and Countermeasure, at 40 CFR Part 112 — keys off aggregate aboveground storage capacity, not the volume you happen to be holding today. A site sitting well under its limit on any given day can still be over the threshold on paper, because the rule measures what the tanks could hold.

The second half of the test is whether a discharge could reasonably reach navigable waters or adjoining shorelines. That is broader than it sounds. Dry washes, arroyos and drainage ditches that only run after rain routinely qualify, which catches out a lot of West Texas sites where there is no visible water for miles.

What counts as containment, and what does not

Containment has to hold the volume and hold it long enough for someone to respond. In practice that means the system is sized to the largest single container plus freeboard for precipitation, it is built of a material compatible with what it is holding, and it is sufficiently impervious that the release does not simply soak through.

• Compacted native soil is not impervious. Caliche is not impervious.
• A berm with a drain valve left open is not containment while that valve is open.
• A liner with seam separation, UV cracking or rodent damage is not containment.
• Containment that has silted up has lost the freeboard it was designed with.

The failure mode nobody plans for

The common finding is not an absent system. It is a system that was correct when installed and stopped being correct afterwards — equipment added inside the berm that displaces capacity, a liner that has taken years of UV, or a site that was regraded and now drains the wrong way.

What this costs if it is missed A containment system that has lost capacity gives you the confidence of protection without the protection. Sites with degraded containment often respond more slowly to a release than sites with none, because the berm is assumed to be holding.

Matching the system to the site

Modular drive-over containment suits locations where traffic has to keep crossing and where the layout may change. Primary containment pads suit fixed production equipment where the footprint is settled. High-wall systems are for large volumes or sloped ground, where a conventional berm would need an impractical footprint to hold the same volume.

The material specification matters as much as the geometry. HDPE liners are specified by thickness and seam method for the chemistry and the service life expected, not chosen from a catalog by area alone.