| Scenario | Leak rate | Duration | Film thickness | Absorption | Containment | Slope | Roughness | Impact area (approx.) |
|---|---|---|---|---|---|---|---|---|
| Minor valve seep | 5 L/min | 10 min | 3 mm | 10% | 20% | 1% | 1.00 | ~12 m2 |
| Hose rupture on slab | 40 L/min | 15 min | 2 mm | 5% | 10% | 3% | 1.10 | ~300 m2 |
| Tank overflow near gravel | 25 gpm | 8 min | 6 mm | 25% | 5% | 6% | 1.40 | ~230 m2 |
- Total leaked volume (L): V(L) = Q × t, where Q is leak rate (L/min) and t is duration (min).
- Convert to cubic meters: V(m3) = V(L) × 0.001.
- Effective spread volume: Veff = V(m3) × (1−A) × (1−C), where A is absorption fraction and C is containment fraction.
- Base impact area: Areabase = Veff / h, where h is assumed average film thickness (m).
- Adjusted impact area: Areaadj = Areabase × S × R, where S = 1 + 0.012×slope(%) and R is a roughness factor.
- Enter the leak rate and select the correct unit.
- Enter the leak duration from start to isolation.
- Choose a realistic film thickness for the surface.
- Set absorption and containment based on site conditions.
- Add slope and roughness to refine the footprint estimate.
- Press Calculate to view results above the form.
- Use CSV or PDF exports for reports and checklists.
Leak footprint as a planning metric
Leak footprint estimates translate flow and time into an area crews can manage. Use the adjusted impact area to size absorbents, boom length, and exclusion zones. Because liquids form thin films on smooth slabs, a small volume can travel far. Record assumptions alongside results so supervisors can compare incidents consistently and refine response kits. Use drain distance and risk index to prioritize protection of inlets.
Choosing realistic film thickness
Film thickness represents the average depth of spread, not the deepest puddle. For water on sealed concrete, 1–3 mm often matches a visible sheen; for viscous fluids or rough surfaces, use 3–8 mm. When uncertain, run two cases: a thin-film case for worst footprint and a thicker case for realistic pooling. Check weather and wind only when outdoor runoff is possible.
Accounting for absorption and containment
Absorption captures losses into soil, joints, or porous base layers. Containment reflects immediate controls such as berms, drain covers, or temporary bunds. Enter conservative values if controls are not confirmed. Document field observations, because a small containment improvement can reduce effective spread volume and shrink the footprint quickly. If spill reaches a drain, escalate response and notify environmental staff.
Slope and surface effects on spread
Slope influences how fast liquid migrates and how the footprint elongates downslope. The slope factor increases area as grade rises, while the roughness factor accounts for micro-texture that slows flow and traps pockets. Use higher roughness for gravel or broken surfaces, but validate with site walkdowns and drainage mapping. Confirm slope direction; a small grade change can redirect flow.
Reporting and improving site readiness
Exported CSV and PDF outputs support shift handovers, incident logs, and toolbox talks. Track repeated locations using the site note field, then review recurring causes such as hose wear, valve packing, or overfilling. Pair calculated footprint with isolation time targets and inspection frequency to reduce both leak duration and impact. Review quarterly to justify training drills.
1) What does the adjusted impact area represent?
It is the estimated footprint after accounting for absorption, containment, slope, and surface roughness. Use it to size response materials and define a practical exclusion zone.
2) How should I pick absorption and containment values?
Base them on observed conditions and confirmed controls. If you are unsure, choose conservative values and update after inspection of joints, soil exposure, berms, and drain covers.
3) Why does film thickness change the result so much?
Area is computed from effective volume divided by assumed film thickness. A thinner film spreads the same volume over a larger area, so thin-sheen scenarios often define the upper footprint.
4) Is the risk index a compliance rating?
No. It is a screening score to help prioritize response near drains and on steep grades. Always follow your spill plan, permit conditions, and local environmental requirements.
5) When should I use circular versus rectangular spreading?
Use circular for open slabs where spreading is uniform. Use rectangular when flow is constrained by curbs, corridors, or a downslope channel, and set an aspect ratio that matches site geometry.
6) Can I use this for non-water liquids?
Yes, as a planning estimate, but adjust film thickness and absorption to match viscosity and surface interaction. For hazardous liquids, apply your safety data guidance and confirm containment capacity.