Secondary Containment Capacity Calculator

This tool compares a required containment target against the estimated available containment volume. Volumes are converted to liters internally for consistent math.

• Total stored volume: V_total = Σ V_i
• Largest container: V_max = max(V_i)
• Rule options:
  • 110% of largest: V_req = 1.10 × V_max
  • 10% of total: V_req = 0.10 × V_total
  • Greater-of rule: V_req = max(1.10×V_max, 0.10×V_total)
  • Custom percent: V_req = (p/100) × V_max
• Rainfall allowance (optional): V_rain = A × d
• Effective height: h_eff = h − h_freeboard
• Available volume: V_avail = A × h_eff − V_displacement
• Compliance margin: Margin = V_avail − (V_req + V_rain)

Always check local requirements and site-specific constraints.

1. Add each container and its stored volume.
2. Select the rule basis used by your project.
3. Choose geometry and enter inside dimensions and wall height.
4. Enter freeboard height to reserve storm space.
5. Add displacement if equipment occupies containment volume.
6. Optionally include rainfall depth for your design storm.
7. Press Calculate and review required, available, and margin.
8. Download CSV or PDF for documentation and reviews.

Accurate containment sizing reduces spills, fines, and downtime significantly.

1. Purpose of secondary containment

Secondary containment is the engineered space that captures leaks and spills from tanks, drums, IBCs, and fueling equipment. In construction yards it protects soil, storm drains, and adjacent work areas, while also reducing cleanup time and operational interruptions.

2. Common sizing targets

Many sites adopt a conservative target based on the largest single container (often 110% of that volume) and/or a fraction of the total stored volume (often 10%). This calculator lets you compare these approaches and apply a custom percentage when a project specification calls for it.

3. Geometry and effective height

Available capacity depends on the containment footprint area and the usable height. If a berm or wall is 0.45 m high but you reserve 0.05 m as freeboard, the effective height becomes 0.40 m. This simple adjustment can materially change the final margin.

4. Rainfall allowance in outdoor areas

Outdoor containment may collect rainwater. A practical method is to add a rainfall volume equal to area multiplied by the design rainfall depth. For example, a 20 m² pad with 25 mm of rainfall adds 0.50 m³ (500 L) to the required capacity.

5. Displacement from stored items

Stored pallets, pumps, ramps, and even partially submerged drums occupy space that cannot hold liquid. When you know the obstructed volume, enter it as displacement. If you only have dimensions, approximate each item as a box or cylinder and sum the volumes for a better field estimate.

6. Unit consistency and reporting

Construction projects often mix liters, gallons, and cubic meters. The calculator converts everything to liters internally and reports in both liters and gallons, helping teams document compliance, compare options, and export results for inspections or HSE reviews.

7. Interpreting the compliance margin

The most useful output is the margin: available volume minus required target and rainfall. A positive margin indicates theoretical compliance; a negative margin signals resizing is needed. In practice, add operational buffer for uneven grades, settlement, and measurement uncertainty.

8. Practical design improvements

If the margin is tight, increase berm height, expand the footprint, reduce stored volumes, or relocate bulky items outside the containment area. Pair capacity checks with good housekeeping, routine inspections, and a clear drainage plan for rainwater management. For lined systems, confirm chemical compatibility, seams, and penetrations. Record container inventory regularly and keep spill kits nearby. A well-sized bund performs best with disciplined procedures.

1) What is secondary containment capacity?

It is the volume a berm, sump, tray, or bund can hold to capture spills from stored liquids, after accounting for usable height, freeboard, rainfall, and obstructions.

2) Which sizing rule should I use?

Use the rule required by your site plan, client, or local authority. If uncertain, comparing 110% of the largest container and 10% of total stored volume is a common conservative starting point.

3) Why does freeboard matter?

Freeboard reserves height to prevent overtopping from waves, splash, uneven surfaces, or measurement error. It improves reliability, especially in high-traffic construction yards and outdoor pads.

4) How do I include rainfall?

Enable rainfall and enter the expected depth and unit. The calculator converts depth to meters and multiplies by containment area to estimate added volume that reduces available spill capacity.

5) What counts as displacement volume?

Any item inside the containment that occupies space: ramps, pallets, pumps, dunnage, or raised platforms. Estimate volumes using simple shapes, then sum them to approximate total displacement.

6) Can I use this for circular berms or tanks?

Yes. Select circular geometry and enter diameter and height. The tool computes the footprint area and capacity using cylinder formulas, then applies freeboard, rainfall, and displacement.

7) Does a positive margin guarantee compliance?

It indicates capacity based on inputs, but field conditions still matter. Verify dimensions, confirm target criteria, and consider extra buffer for slope, settlement, and equipment movement.