| Scenario | Area (m²) | Existing depth (m) | Target depth (m) | Overdredge (m) | Bulking | Contingency | In-situ (m³) | Loose (m³) |
|---|---|---|---|---|---|---|---|---|
| Berth pocket touch-up | 12,000 | 11.0 | 12.0 | 0.2 | 1.20 | 5% | 15,120 | 18,144 |
| Approach widening | 32,500 | 9.5 | 11.0 | 0.3 | 1.30 | 7% | 58,052.5 | 75,468.3 |
| Turning basin deepening | 48,000 | 12.2 | 14.0 | 0.25 | 1.25 | 5% | 96,600 | 120,750 |
| Maintenance pocket | 8,700 | 10.0 | 10.8 | 0.15 | 1.15 | 3% | 8,278.5 | 9,520.3 |
| Small jetty basin | 6,200 | 6.0 | 7.2 | 0.20 | 1.35 | 5% | 9,114 | 12,303.9 |
- Area = (Length × Width) or entered directly.
- Depth increase = Target depth − Existing depth.
- Cut depth = Depth increase + Overdredge.
- In-situ volume = Area × Cut depth.
- With contingency = In-situ × (1 + %/100).
- Loose volume = With contingency × Bulking factor.
- For each row: Δdᵢ = Targetᵢ − Existingᵢ.
- Weighted base volume: Σ(Aᵢ × Δdᵢ).
- Overdredge added uniformly: Σ(Aᵢ) × Overdredge.
- Total in-situ = base + overdredge volume.
- Then apply contingency and bulking as above.
- Side slope ratio: m = H/V.
- Dredged cross-section area: A = d × (b + m × d).
- Volume: V = A × L.
- Then apply contingency and bulking factors.
- Select your unit system and calculation method.
- Enter plan dimensions or a direct plan area.
- Provide existing and target depths for the cut.
- Add overdredge, contingency, and bulking as needed.
- Press Calculate to show results above the form.
- Use the download buttons to export CSV or PDF.
Port dredging quantities are typically defined as in-situ excavation volumes referenced to a survey datum. This calculator converts simple geometry or area-weighted survey inputs into an in-situ quantity, then applies contingency and bulking to support haulage and disposal planning. For tendering, keep the assumed datum, cut limits, and tolerances consistent across drawings, surveys, and payment items.
The cut depth is the design depth increase plus an overdredge allowance. Overdredge is used to manage operational variability, soft material rebound, and verification uncertainty. In maintenance programs, a small allowance can reduce rework risk, but it should be justified against environmental controls and contract criteria.
Bulking factor converts in-situ volume to loose volume after excavation and handling. Fine sediments and saturated sands often bulk modestly, while stiff clays or mixed materials can bulk more depending on dredge method and dewatering. Use bulking to size barges, pipelines, stockpiles, and containment cells, then reconcile with measured water content and placement density.
When depths vary across a footprint, the survey method uses area-weighted depth differences: each row contributes A×Δd. This mirrors common takeoff practices where a basin is split into cells, each with a representative existing and target depth. Add more rows where slopes, pockets, or shoals change rapidly to reduce averaging error.
If density is enabled, the tool estimates dredged mass from loose volume. Mass is useful for disposal permits, trucking limits, and estimating treatment additives. Select density consistent with your unit system and material state (loose vs placed). Always document assumptions, and validate results using post-dredge surveys and production records.
1) What is the difference between in-situ and loose volume?
In-situ is the excavated quantity in place. Loose volume accounts for bulking after dredging, transport, and handling, and is better for barge, stockpile, and containment sizing.
2) When should I use the survey weighted grid method?
Use it when existing depths vary across the dredge area. Dividing the footprint into cells and applying area-weighted depth increases reduces error versus a single average depth.
3) How do I choose an overdredge allowance?
Base it on equipment tolerance, sediment behavior, and verification requirements. Keep it modest, justify it in notes, and align with contract limits and environmental controls.
4) What bulking factor is typical?
Common planning ranges are about 1.10–1.40, but it depends on material type, dredge method, and dewatering. Use project-specific data whenever available.
5) How does the trapezoidal channel option work?
It computes dredged cross-section area using bottom width and side slopes, then multiplies by channel length. It is useful for approach channels and fairways with consistent side slopes.
6) Does this replace a detailed surface-to-surface takeoff?
No. It is a planning and checking tool. Final quantities should be verified with survey surfaces, design templates, tolerances, and measurement rules required by your project.