Calculator Inputs
Example Data Table
| Scenario | Inputs (summary) | Key outputs (summary) |
|---|---|---|
| Rectangular berm | 6 m × 4 m, height 0.35 m, freeboard 15%, obstruction 5%, runoff 0 mm | Gross ≈ 0.678 m³ (678 L), net spill ≈ 0.678 m³ |
| Circular containment | Diameter 5 m, height 0.30 m, freeboard 20%, obstruction 10%, runoff 10 mm | Gross ≈ 4.241 m³, runoff ≈ 0.196 m³, net spill ≈ 4.045 m³ |
| Compliance check | Area 30 m², height 0.25 m, spill 1200 L, safety 1.2, runoff 5 mm | PASS/FAIL depends on net spill ≥ 1.44 m³ |
Formula Used
1) Containment area
- Rectangle: Area = Length × Width
- Circle: Area = π × (Diameter ÷ 2)²
- Known area: Use the area you enter.
2) Usable height
- EffectiveHeight = BermHeight × (1 − Freeboard%)
3) Gross capacity with obstructions
- GrossCapacity = Area × EffectiveHeight × (1 − Obstruction%)
4) Runoff allowance
- RunoffVolume = Area × RunoffDepth
- NetAvailable = max(GrossCapacity − RunoffVolume, 0)
5) Compliance check
- Required = SpillVolume × SafetyFactor
- Pass when: NetAvailable ≥ Required
- Berm sizing solves for the minimum BermHeight that satisfies the rule.
How to Use This Calculator
- Select your unit system and calculation mode.
- Choose a shape and enter dimensions, or enter a known area.
- Enter berm height for capacity or compliance modes.
- Set freeboard and obstruction loss to reflect field conditions.
- Add a runoff depth allowance if rainfall may enter containment.
- For compliance or sizing, enter the spill volume and safety factor.
- Click Calculate to see results above the form.
- Use the export buttons to download CSV or PDF records.
Secondary Containment Sizing Benchmarks
On construction sites, temporary containment is often sized using benchmarks tied to stored liquids. A widely used rule is 110% of the largest container or 10% of total stored volume, whichever is greater, then adjusted for transfer activities. For five 200 L drums (1,000 L total), the benchmark minimum becomes 220 L, before considering rainfall, obstructions, and freeboard. Typical contents include diesel, hydraulic oil, form-release agents, and curing chemicals, so identify the largest credible release during storage or pumping, including sudden hose failures.
Geometry Converts Bermed Area Into Capacity
The calculator converts plan area into volume using berm height, then applies reductions and allowances. A 4.0 m × 3.0 m pad has 12.0 m² area; with a 0.30 m berm, gross capacity is 3.60 m³. If items inside displace 15% of the space, net geometric capacity drops to 3.06 m³. Circular pads change quickly because area scales with radius squared.
Freeboard and Runoff Allowance Preserve Headroom
Freeboard reserves headroom to reduce overtopping risk from uneven ground, settlement, or surging flow. Using 10% freeboard makes the effective height 90% of berm height. Rainfall can also consume capacity: a 25 mm runoff allowance equals 0.025 m × Area. On 12.0 m², that reserves 0.30 m³ (300 L) before any spill volume is stored.
Obstructions and Grade Are Common Failure Points
Real capacity is rarely the same as simple geometry. Skids, pumps, and bracing displace volume, while low spots overflow first on sloped bases. Treat obstruction loss as a measured estimate (often 5–25%), and use the lowest effective height unless the pad is regraded or lined to level.
Document Assumptions for Audits and Toolbox Talks
Compliance mode compares net available volume against a spill scenario multiplied by a safety factor (often 1.10–1.50). Record assumptions (containers present, runoff depth, freeboard, losses) and export CSV/PDF for inspection records. Recalculate after layout changes, repairs, or new materials arrive.
FAQs
1) What units does the calculator support?
Use metric (m, m², m³, L) or imperial (ft, ft², ft³, gal). Results show both primary and secondary units to help you verify entries quickly and avoid conversion mistakes.
2) Why include freeboard?
Freeboard keeps a buffer so small surges, settlement, or uneven ground do not overtop the berm. It reduces effective height, which makes the calculated usable volume closer to field performance.
3) How should I estimate obstruction loss?
Estimate how much containment space is occupied by skids, pumps, pallets, and bracing. Start with 5–10% for lightly loaded pads and 15–25% for crowded setups, then refine using measurements.
4) What does runoff depth allowance mean?
It reserves capacity for rainfall or washdown that can enter containment. The tool converts depth to volume by multiplying depth by area and subtracts it from the spill capacity you can safely store.
5) What is the difference between capacity and compliance?
Capacity calculates net available volume from geometry and allowances. Compliance compares that net volume to a defined spill volume multiplied by your safety factor and reports whether the setup passes.
6) Can I rely on this for permanent engineered containment?
It supports scoping and documentation, but permanent designs must follow your governing code, loading assumptions, and drainage details. Confirm requirements with your EHS lead or a qualified engineer before building.