Headwall — Attenuation Outlet Quantity Calculator
Controlled attenuation outlet combining a precast headwall with orifice plate and optional flap valve, weir, or penstock to BS EN 12889. Computes headwall unit (Nr), outlet ironmongery, scour protection (rock armour to HD 78/16 or gabion mattress), and excavation.
Slug · headwall_attenuation_outlet · v1.0
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Paid assemblies surface their parameter forms, BoQ output, project save/reload, and full per-standard Excel + DXF + PDF deliverables once a CivilQuants subscription or 7-day pass is active. Per-standard bills across CESMM4, NRM2, SMM7, and MMHW; project-level recompute; watermark-free outputs.
Headwall — Attenuation Outlet — a worked example, measured four ways
The same assembly at default dimensions, rendered as a Bill of Quantities under each measurement standard. Switch the standard to see how the bill changes. Change the inputs in the calculator to compute your own.
CESMM4 · 7 items · units sum, nr, m³
| Code | Description | Unit | Quantity |
|---|---|---|---|
| A.4.1 | Provisional sum (Prime Cost): Orifice plate flow-control device to outfall, 150mm orifice ID, target discharge 5.00 l/s, generic | sum | 1 |
| A.4.1.fix | Fixing only: Orifice plate flow-control device to outfall, 150mm orifice ID, target discharge 5.00 l/s, generic | nr | 1 |
| E.4.3.4 | Excavation for foundations, maximum depth 1-2m | m³ | 18.93 |
| E.5.3 | Disposal of excavated material off-site | m³ | 18.93 |
| F.1.1.1 | In-situ concrete blinding, C8/10, thickness 150mm | m³ | 0.22 |
| H.7.1.2 | Precast concrete headwall to 600mm diameter outfall pipe, approximately 2.5t, set on bedding (catalogue size PHW_600) | nr | 1 |
| E.4.1 | Scour protection apron to precast outfall headwall, rock armour, nominal 200mm graded stone | m³ | 1.5 |
Procurement take-off: the total quantity to order of each material, from the same compute. Supplier-neutral, so you buy anywhere.
- Concrete Blinding0.22 m³
- Disposal18.93 m³
- Excavation Foundation18.93 m³
- Flap Valve1 nr
- Flap Valve1 sum
- Headwall1.5 m³
- Headwall1 nr
Illustrative example at default dimensions · engine ref a7f7d8 · not a tendered quantity