Demolition, Erosion and Sediment Control: Protect Your NSW Site

The riskiest weeks of a building project, from an environmental compliance perspective, are the ones people think of as “just clearing the site”. Demolition strips the roof and paving that were shedding water in an orderly way; the excavator opens bare earth; and the next storm turns your block into a sediment source pointed at the street drain – which flows, untreated, to the nearest creek. One muddy driveway track onto the road is all a council inspector needs to issue a fine.

Erosion and sediment control is not paperwork theatre. It is a legal obligation under the Protection of the Environment Operations Act 1997, a standard condition of every consent and complying development certificate, and one of the most actively enforced areas of council compliance – inspection blitzes across Sydney’s catchments target exactly this. The good news: on a typical residential site, doing it properly is cheap, quick and mostly a matter of sequencing. Here is how to protect your site, your neighbours’ drains and your wallet from demolition day to slab.

The legal framework in brief

• The POEO Act 1997 makes it an offence to pollute waters – and sediment-laden runoff leaving your site for a gutter, stormwater pit or creek is water pollution. Councils and the EPA can issue on-the-spot penalty notices to builders, owner-builders and trades, serve clean-up and prevention notices (with costs), and prosecute serious or repeat cases, where penalties escalate dramatically. Responsibility sits with whoever occupies and controls the site – you cannot outsource it to the tipper driver.
• Your consent or CDC conditions will require erosion and sediment controls to be installed before works commence and maintained until the site is stabilised. For most residential projects this means an Erosion and Sediment Control Plan (ESCP); larger disturbances trigger a more detailed Soil and Water Management Plan.
• The technical benchmark is Managing Urban Stormwater: Soils and Construction – universally known as the Blue Book – together with the NSW guidelines for erosion and sediment control on building sites, which councils reference in their conditions and DCPs. Design to these and you are speaking the inspector’s language.

The ESCP: your site’s water plan for the ugly phase

An ESCP for a house, duplex or small subdivision is a straightforward drawing – usually prepared by the civil engineer with the stormwater design – showing how water moves through the site while it is disturbed, and what stops soil moving with it. A competent plan covers:

• What stays – vegetation and ground cover retained wherever possible; the cheapest erosion control is the grass you don’t strip;
• Where water comes from – upslope (“clean”) water diverted around the disturbed area so it never picks up sediment;
• Where water goes – the site’s discharge points, and the sediment controls protecting each: sediment fences below disturbed areas, protection around inlets and pits, controlled outlets;
• How vehicles enter and leave – a stabilised site access (typically an aggregate pad) so trucks don’t track mud onto the road, the single most visible and most fined failure;
• Where materials live – stockpiles located away from drains, gutters and overland flow paths, on the high side where possible, covered or bunded;
• Staging and maintenance – controls installed before disturbance, inspected and repaired (especially after storms), and kept until the surface is stabilised by turf, paving or landscaping.

Demolition: the phase everyone underestimates

Demolition has its own approval and safety regime – licensed demolishers, asbestos identification and clearance, notification requirements, and disconnection/sealing of services including capping the sewer and protecting the water meter. But it is also the moment your site’s drainage behaviour changes fundamentally, and the erosion controls need to be in place before the first wall comes down, not before the slab pour weeks later. Demolition-phase specifics:

• Install the perimeter controls first – sediment fence on the low side, inlet protection on nearby street pits, stabilised access pad where the trucks will run;
• Dust is sediment in the air – water suppression during knock-down protects neighbours and prevents deposited dust becoming the next storm’s sediment load;
• Concrete and masonry rubble – crushing or removing hardstand exposes soil that was sealed for decades; treat freshly exposed ground as disturbed area from that moment;
• Old stormwater connections – redundant downpipe connections and pits become open conduits from your site straight to the street system; seal or protect them;
• Waste classification and lawful disposal – demolition waste must go to lawful facilities with documentation; illegal dumping and asbestos mishandling attract far heavier penalties than sediment breaches.

The controls that do the real work

On a residential-scale site, five controls carry most of the load. Installed correctly, they are inexpensive; installed wrongly, they are decoration:

• Sediment fence – a geotextile fence trenched into the ground on the low side of disturbance. The trenching is the point: a fence sitting on the surface filters nothing. Follow the contour, return the ends upslope, and don’t ask one fence to treat concentrated flow – it treats sheet flow only.
• Stabilised access – an aggregate construction entry long enough to shake mud off tyres, positioned where all vehicles must use it. If there is mud on the road each afternoon, the pad is too short, too dirty or being bypassed – and it is the first thing an inspector photographs.
• Inlet protection – filter socks, bags or barriers on the street pits downhill of your site, maintained so they filter rather than dam the road.
• Clean water diversion – a simple bund or shallow drain steering upslope runoff around the works. Halving the water crossing bare soil halves everything else’s job.
• Stockpile management – soil heaps bunded or fenced, away from flow paths, covered if they will sit through a storm season. A tonne of topsoil on the nature strip above a gutter is a penalty notice waiting for rain.

Add site-specific measures as conditions demand: check dams in drainage lines, temporary sediment traps or basins on larger cuts, wheel-wash facilities on big excavations, and progressive stabilisation (turf, mulch, sealing) of finished areas.

Concrete, paint and washout: the other pollutants

Sediment is the headline pollutant, but the same POEO Act provisions catch the rest of a building site’s liquids. Concrete washout is strongly alkaline and lethal to aquatic life: washing the agitator chute or the pump line into the gutter is a pollution offence, so provide a lined washout area or container on-site. The same discipline applies to paint, render, brick-cutting slurry, plaster and mortar wash-water, and fuel or oil from plant. A single designated washout point, communicated to every trade at induction, prevents nearly all of it.

Making it stick on a real site

• Sequence it into the programme – controls installed before demolition mobilises; certifiers commonly inspect and photograph before allowing works;
• Assign ownership – one named person (site supervisor or owner-builder) checks controls weekly and after every storm, and reinstates what deliveries and excavation flatten;
• Brief the trades – most breaches are committed by a subcontractor who was never told where the washout or the access pad is;
• Photograph your compliance – dated photos of installed and maintained controls are your evidence if a complaint lands after a storm that overwhelmed everything;
• Stabilise early – the obligation only ends when exposed surfaces are stabilised; turfing the verge and batters promptly is compliance, not just presentation.

Frequently asked questions

Do I need an erosion and sediment control plan for a single house or duplex?

Yes – consents and CDCs for residential works routinely condition an ESCP, with controls in place before any works (including demolition) commence. For small sites it is a single drawing prepared with the stormwater design; larger disturbed areas trigger more detailed soil and water management planning per council conditions and the Blue Book framework.

Who gets fined if sediment leaves the site – the owner or the builder?

Whoever has control of the site can be liable – councils issue penalty notices to builders, owner-builders and individual trades, and can serve clean-up or prevention notices on the responsible parties. Contractual arrangements matter between you and your builder, but they do not immunise an owner-builder, and repeat or serious pollution can be prosecuted with much higher penalties. Confirm current penalty amounts if you want to be motivated: they have only ever gone up.

When can the sediment fence come down?

When the surfaces draining to it are stabilised – turfed, paved, sealed or landscaped so they no longer shed soil – not when the slab is poured or the frame is up. Removing controls early, while batters and trenches are still raw, is one of the classic late-project breaches.

Does demolition need its own approval?

Demolition is approved either within your DA/CDC or as standalone complying development under the Codes SEPP demolition provisions, and it carries its own regime: licensed demolition contractors where required, asbestos assessment and clearance, notifications, service disconnections and waste documentation – plus erosion and sediment controls installed before it starts. Treat it as a project phase with its own checklist, not a prelude.

Contrive Consultants prepares erosion and sediment control plans, stormwater management and civil documentation for demolition and construction across Greater Sydney – designed to Blue Book principles and your council’s conditions. Review our services, call +61 497 848 111, email info@contriveconsultants.com.au or contact us before the excavator – or the inspector – arrives.