A drainage set is spread over several sheets. The plan shows where the pipes go, the long sections show how deep, the pit schedule says what each structure is and the details show how it's built. We read them together, because each one leaves out something the others show.
What's included
Pipes and trenches
- Pipes by material, size and depth
- Excavation and trench support
- Bedding and backfill
- Connections to existing drainage
Pits and structures
- Precast and cast-in-situ pits
- Headwalls and scour protection
- Box and pipe culverts
- Gross pollutant traps
Detention and treatment
- On-site detention tanks
- Basins and bioretention
- Subsoil drainage
- Outlet structures
Finishing
- Reinstatement of roads, paths and turf
- CCTV and testing
- Work-as-executed survey
- Traffic control for road works
Depth is what costs money
A metre of pipe at four metres deep is a different job to a metre at one. Shoring, trench boxes and digging all climb steeply with depth, so we price every run in its depth band. Where the plan, the long section and the pit schedule disagree on lengths, we flag it rather than averaging it out.
Precast or cast in situ is the other big call on pits and tanks. It changes the price, the crane and the programme. We price what the drawings ask for, and if the other way looks cheaper we'll say so.
Water mains, sewer and pump stations on the same job are priced by our specialist practice, Water Sewer Estimating Sydney, with the same lead estimator.
Common questions
Do you price from the plan or the long sections?
Both, together with the pit schedule and details. The long sections set the depths and grades, which drive most of the cost.
Do you price on-site detention (OSD) tanks?
Yes, precast and cast in situ, including the dig, base, walls, access, outlets and backfill.