Stormwater management that matches the design
JMP Group constructs stormwater drainage across Brisbane, the Gold Coast and the Redlands: pit and pipe networks, on-site detention and retention storage, kerb adaptors, headwalls and subsoil drainage. Levels are set from the approved hydraulic and civil drawings so runoff reaches its lawful point of discharge at the rate the engineer nominated.
Scope of work
From roof water to the kerb, and everything buried between
Pit & pipe networks
Field inlet, grated and junction pits with RCP, PVC or PE pipe runs laid to design invert levels and surface grades.
On-site detention
Detention and retention tanks, underground storage, orifice plates and discharge control structures built to the certified volume.
Lawful point of discharge
Kerb adaptors, inter-allotment drainage and connections to council drainage, cut and reinstated to council specification.
Subsoil & agricultural drainage
Slotted subsoil lines, aggregate and geofabric surrounds behind retaining walls, under slabs and across saturated ground.
Water quality devices
Gross pollutant traps, sediment basins and bio-retention inlet works installed to the approved stormwater quality plan.
Flooding remediation
Investigation and rectification of ponding, undersized lines, blocked legacy pipes and overland flow hitting buildings.
Definitions
Stormwater terms that appear on your approval
Development approvals lean on a handful of terms that decide how much of a site gets dug up. Here is what each one means in practice.
- Lawful point of discharge
- The location council accepts stormwater leaving your property — typically a kerb, an inter-allotment drainage line or a council pipe. Discharging anywhere else is the single most common cause of neighbour disputes and enforcement notices.
- On-site detention (OSD)
- A tank or basin that holds part of a storm and releases it slowly, so a developed site discharges no faster than it did undeveloped. Volume and outlet size are certified, and building it undersized fails at inspection.
- Inter-allotment drainage
- A drainage line running through one or more lots under easement, used where a lot has no fall to the street. Access chambers and easement boundaries govern where it can be laid.
- Overland flow path
- The route water takes across the surface once the pipe network is at capacity. Filling or fencing across it moves flooding onto a building, so finished levels have to respect it.
- Subsoil drainage
- Perforated pipe in aggregate that removes groundwater rather than surface runoff. It protects retaining walls, slabs and pavements from hydrostatic pressure and saturation.
- Invert level
- The internal base level of a pipe or pit. Grades between inverts create the fall that makes a gravity system work, and a few millimetres of error across a long run removes it.
Diagnosing a wet site
Water pooling where it never used to
New flooding on an established property has a cause upstream, underground or next door. We survey levels, trace the existing network and identify what changed before recommending pipework.
- Upstream development — a neighbouring build has redirected runoff or raised surface levels.
- Blocked legacy pipe — an old terracotta or steel line has silted, cracked or filled with roots.
- Missing connection — downpipes and area drains discharge to the ground instead of a piped system.
- Undersized network — pipe capacity suits the original roof area, not the extension added later.
- Groundwater — the problem is subsoil water, and surface drainage alone will never fix it.
What we need to quote accurately
- Approved stormwater or civil drawings, including the OSD detail
- Site address and access constraints for plant and spoil removal
- Surface types along the alignment: turf, concrete, asphalt, pavers
- Any known services, easements or retaining structures nearby
Questions
Stormwater questions
Can I discharge stormwater onto my neighbour's land?
No. Stormwater has to reach the lawful point of discharge nominated by council, which is normally the kerb or a drainage easement. Where a lot has no fall to the street, inter-allotment drainage under easement is the approved solution.
Why does my development need on-site detention?
Roofs, driveways and paving shed water far faster than the ground they replaced. OSD holds the difference and releases it at the pre-development rate, protecting the downstream network. The requirement and volume come from the approval conditions.
Who designs the stormwater system?
A hydraulic or civil engineer produces the design and council approves it. We build to that documentation and flag any conflict between the drawing and site reality before construction rather than after.
How long does a kerb adaptor connection take?
Cutting the kerb, installing the adaptor and reinstating the concrete is short work compared with obtaining the council permit and arranging traffic control. We lodge the permit early so the machine does not sit waiting.
Will digging stormwater damage my driveway?
Where the alignment crosses concrete we saw-cut a defined section, excavate, then reinstate to matching thickness and finish. The quote states the area affected and the reinstatement standard, so there is no argument at completion.
Do you install stormwater for civil subdivisions?
Yes. Pit and pipe drainage, headwalls, subsoil lines and inter-allotment drainage are installed under head contract with ITPs, survey pick-ups and as-constructed records supplied for the council handover.
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