Construction & estimating · Site operations
Excavation dewatering estimate calculator
Inflow to a dewatered excavation treated as an equivalent large-diameter well in an unconfined aquifer, with pump power.
Standard: Dupuit–Forchheimer equivalent well · Sichardt radius
Open the live calculator → All construction & estimating calculators
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Excavation plan area | 600 | m² |
| Saturated aquifer thickness | 12 | m |
| Required drawdown | 4 | m |
| Permeability k | 0.0001 | m/s |
| Factor on flow | 1.5 | |
| Total pump head | 18 | m |
| Pump efficiency | 0.6 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Equivalent radius re | 13.82 | m |
| Sichardt R0 = 3000 s√k | 120.0 | m |
| Q (Dupuit) | 11.07 | L/s |
| Design flow | 16.60 | L/s |
| Daily volume | 1,435 | m³/day |
| Pump power | 4.9 | kW |
Method, formulas and assumptions
- Q = πk(H² − h²)/ln(R/re), h = H − s, R = R0 + re
- Order-of-magnitude estimate. Confirm k by pump test and design wellpoints or bores to suit.
Related construction & estimating calculators
- Concrete pour planner — Number of agitator trucks, trucks needed in rotation, pour duration, finish time and cost for a concrete pour.
- Rebar cutting length and laps — Cutting length for straight, L, U or closed-link bars with bend deductions and hooks, the laps needed for…
- Aggregate and base-course tonnage — Tonnes of road base, crushed rock or sand for an area and compacted thickness, with loose volume, truck…
- Compaction production and lifts — Number of lifts, roller output and days to place and compact a fill platform.
- Trench shoring take-off — Panels, strut rows and struts for a strutted trench, with excavation volume and hire cost.
- Truck and loader fleet balance — Truck cycle time, trucks needed to keep the loader busy, fleet production and hours to move a volume.
- Plant fuel and CO₂ — Diesel use, cost and CO₂ for a plant fleet from rated power, load factor and specific fuel consumption.
- Scaffold take-off (modular) — Component count for a single-run modular scaffold, with tie count and hire cost.
- Concrete maturity (strength in place) — Temperature–time factor and equivalent age from logged temperatures, and estimated in-place strength from a…
- Concrete mix design (ACI 211.1) — Batch quantities per m³ (water, cement, coarse and fine aggregate) by the ACI absolute-volume method.
For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.