Calculator Inputs
Formula Used
- Wet mass (t) = In-situ volume (m³) × Wet density (t/m³).
- Loose volume (m³) = In-situ volume × (1 + Swell% ÷ 100).
- Solids mass (t) = Wet mass × (1 − Initial moisture% ÷ 100).
- Dewatered mass (t) = Solids mass ÷ (1 − Target moisture% ÷ 100).
- Transport cost = (Dewatered mass × Distance × Rate) + Mobilization.
- Disposal cost = Dewatered mass × Disposal fee per ton.
- Dewatering cost = In-situ volume × Dewatering cost per m³.
- Total cost = (All direct costs) × (1 + Contingency% ÷ 100).
How to Use This Calculator
- Enter the dredged in-situ volume and a representative wet density.
- Choose a swell factor for handling and storage allowances.
- Set initial and target moisture to model dewatering benefits.
- Select a disposal method, then enter disposal fee per ton.
- Choose transport mode, distance, rate, and mobilization costs.
- Add dewatering, site preparation, monitoring, and contingency values.
- Press Submit to view results above the form and download files.
Example Data Table
| Material type | Wet density (t/m³) | Swell factor (%) | Typical moisture (%) | Notes |
|---|---|---|---|---|
| Silt | 1.25–1.45 | 20–35 | 40–60 | High water content, can benefit from dewatering. |
| Clay | 1.35–1.60 | 15–30 | 35–55 | May require longer drainage and handling time. |
| Sand | 1.55–1.90 | 10–25 | 15–35 | Often easier to dewater; may suit beneficial reuse. |
| Mixed sediments | 1.35–1.75 | 15–35 | 25–55 | Confirm with sampling and lab results where possible. |
Volume and Mass Basis
The calculator starts with in-situ dredged volume in cubic meters and converts it to wet mass using a user-selected wet density. For early estimates, fine silts often fall near 1.25–1.45 t/m³, clays around 1.35–1.60 t/m³, and sands commonly 1.55–1.90 t/m³. A swell factor then expands the handled volume to reflect bulking during dredging, stockpiling, and loading operations. Use verified survey quantities to align estimates with pay items.
Moisture Adjustment and Dewatering
Moisture content is treated as a weight fraction, letting you model how dewatering reduces payable tonnage for hauling and tipping. Solids mass equals wet mass × (1 − initial moisture). Dewatered mass equals solids mass ÷ (1 − target moisture). For example, moving from 45% to 30% moisture reduces payable mass by roughly 21% for the same solids, improving transport and disposal economics.
Transport Cost Drivers
Hauling cost is calculated with a ton-kilometer structure: dewatered tons × distance × rate, plus a fixed mobilization allowance. Use the rate field to capture mode differences—trucks suit short hauls and frequent trips, barges suit longer corridors and high volumes, and rail can be competitive where terminals exist. Sensitivity testing a ±10% rate change quickly shows which variable dominates your total.
Disposal Fees and Compliance Allowances
Disposal cost is computed as dewatered tons × disposal fee per ton, which can represent landfill tipping, confined disposal placement, or beneficial reuse processing. The separate site preparation and monitoring inputs let you capture liners, berms, access roads, sampling, reporting, and inspection requirements. These allowances keep budgets realistic when permit conditions add measurable labor and materials beyond basic hauling.
Interpreting Unit Rates for Bids
The output includes total cost, cost per in-situ cubic meter, and cost per disposed ton. Cost per m³ supports quantity-based bidding and change-order pricing, while cost per ton is useful when fees are weight-based. Apply contingency to reflect unknowns such as production variability, weather delays, or testing outcomes. Use exported CSV and PDF outputs to document assumptions during reviews.
FAQs
1) What volume should I enter for pricing?
Use the in-situ quantity from surveys or design drawings. The swell factor separately accounts for bulking during handling, so avoid inflating the base volume twice.
2) Why does moisture affect hauling and disposal costs?
Many transport rates and tipping fees are weight-based. Reducing moisture lowers payable tonnage for the same solids, which can reduce both hauling and disposal components.
3) How do I choose a wet density value?
Start with material type ranges, then refine using sampling results or past projects. If uncertain, run low, typical, and high densities to bracket costs.
4) What does the ton-kilometer rate represent?
It is an all-in variable transport cost per ton moved per kilometer. Enter a blended rate that reflects fuel, labor, payload, turn time, tolls, and subcontractor pricing.
5) When should I add site preparation and monitoring costs?
Include them when disposal requires containment works, access improvements, liners, or testing and reporting. These costs often grow with strict permit conditions and long-duration projects.
6) Is the contingency applied to all costs?
Yes. Contingency is applied to the direct-cost subtotal to cover uncertainty. Adjust it based on data quality, production risks, weather exposure, and regulatory review timelines.