The Method
Unglamorous steel, a service rota, and a weighbridge discipline.
There is no invention here and we make no claim to one. Outfall netting is proven technology. What is missing in South Africa is a funded, staffed, measured operating model around it — so that is what we specify, cost and publish.
The hardware
A capture net assembly is two parts: a rigid hub that mates to the pipe, and a flexible net that does the work.
| Component | Specification |
|---|---|
| Hub | 304 or 316 stainless steel, fabricated in South Africa. 316 where marine salt exposure is direct. |
| Standard sizes | 18″, 24″, 30″, 36″ and 60″ nominal; custom sizes and rectangular culvert adaptations fabricated to survey. |
| Net | Commercial-grade HDPE mesh, minimum 5 ft (1.5 m) length; longer nets for high-volume catchments. |
| Capture threshold | Gross pollutants down to 5 mm, including organic material. This is a gross-pollutant device: it does not address microplastics, and we do not claim that it does. |
| Mounting | Anchored into concrete headwall, or clamped to an existing pipe end or outfall structure. |
| Overflow | Overflow paths designed into both the hub and the weir, so that a full or blinded net bypasses rather than backs up. This is the non-negotiable safety feature. |
| Emptying | Net is released and lifted by truck-mounted crane or hiab where access allows; manual handling on smaller sizes. Nets are washed, inspected and reused. |
| Design life | Hub: measured in years. Net: a consumable — budget for replacement, and inspect every service for UV degradation and abrasion at the throat. |
The operating cycle
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Catchment survey and outfall ranking
Walk the drainage network and its discharge points. Score each outfall on observed litter load, catchment character, pipe diameter, service vehicle access, tidal or surf exposure, safety, and land ownership. Photograph every candidate with a GPS fix. The best time to do this is during and immediately after the first substantial rain of the wet season, when the difference between a benign outfall and an offending one is unmistakable.
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Permission, not funding, from the authority
Approach the relevant municipal department with a written proposal that asks only for permission and access — you bring the hardware, the labour, the insurance and the disposal. Include the overflow design, the service schedule, a public liability certificate and an undertaking to report data back to them. Asking for permission is a vastly easier conversation than asking for budget, and the data you hand back is what eventually creates the budget.
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Survey, fabricate, install
Measure the pipe end precisely — nominal sizes lie, and old outfalls are rarely round. Fabricate the hub to the survey. Install in dry conditions with the catchment forecast clear, and photograph the completed installation from fixed reference points that you will re-shoot at every service.
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Service on a rota, and after every event
A fixed baseline rotation, plus a triggered service after any rainfall event above a defined threshold. The single most common failure mode in this field is a net installed with enthusiasm and serviced for two months. Assume every net will be full when you least want to go and get it, and budget the labour accordingly.
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Weigh, sort, photograph, record
Each haul is weighed wet at the site and, where practicable, drained and re-weighed. A sub-sample is sorted by polymer, item category and legible brand. Every record carries: outfall ID, GPS, date and time, days since last service, rainfall in the interval, gross mass, and photographs of the full net and the sorted sample.
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Dispose responsibly and report
Recoverable fractions go to recyclers or to waste-picker cooperatives where that relationship exists; the residual goes to licensed disposal with a receipt. Data is published. If a sponsor's brand appears in the audit, they see it in their own report — we will not run a brand audit we are unwilling to show the brand.
The jobs are the point, not a side effect
Servicing is recurring, local, weather-driven, physically demanding work that cannot be outsourced or automated, in coastal communities with severe unemployment. Every funded outfall is a slice of a real wage. We are explicit that servicing labour is the largest line in our operating budget and we do not intend to compress it — a project that saves money on servicing is a project that stops working within a season.
Crew standards we hold ourselves to: personal protective equipment appropriate to contaminated water and sharps; inoculation and a hygiene protocol; no confined-space entry and no in-pipe work, ever; no servicing during or immediately after a storm event; two-person minimum at any water-adjacent site; and payment at or above the sector minimum, on time.
What this method does not do
Stating the limits is how you stay credible with the engineers and the scientists whose support you need:
- It does not capture microplastics, tyre wear particles or dissolved pollutants.
- It does not reduce plastic production or consumption. It is an end-of-pipe intervention and end-of-pipe interventions are, on their own, a treadmill.
- It does not work where servicing cannot be sustained. An abandoned net is worse than no net.
- It does not substitute for waste collection. Where collection is absent, outfall netting treats a symptom — usefully, visibly and measurably, but it is a symptom.
- It cannot be installed everywhere. Some outfalls are inaccessible, unsafe, tidally submerged or hydraulically unsuitable, and should be left alone.
What it does do is remove a large, weighable mass of plastic from the path to the sea, today, for a known cost per kilogram, while generating the evidence that makes the upstream arguments winnable.