City of Cape Town finally launches project to restore heavily polluted Milnerton Lagoon environment

Milnerton Lagoon, arguably the City of Cape Town’s most polluted water body, empties into Table Bay.(Photo: Jean Tresfon)

By Kristin Engel

A multibillion-rand rehabilitation project is being launched to finally address the Milnerton Lagoon’s long-standing pollution issues.

The Milnerton Lagoon is perhaps Cape Town’s most polluted waterways with multiple fish die-offs, sewage spills, a persisting stench in the area and health risks affecting residents as a result of the ongoing pollution of the Diep River and lagoon. 

Now a multibillion-rand rehabilitation project spearheaded by the City of Cape Town appears to finally be making headway to address urban pollution in the water body with short-, medium- and long-term solutions.

The short-term solutions are aimed at improving lagoon water quality and odour, including options to potentially aerate or bio-remediate the lagoon. The medium and long-term solutions address the restoration of the lagoon and cutting off sources of pollution.

This is after years of complaints over lack of transparency on water testing, appeals by residents for urgent assistance, and directives ordering the city to take action to contain the pollution at the lagoon where raw sewage and masses of litter sometimes flowed.

milnerton lagoon

Ongoing pollution into the Milnerton lagoon and the Diep River has made the lagoon and its surrounding environment effectively dead, largely as a result of non-compliant discharges from the Potsdam Wastewater Treatment Works. (Photo: Kristin Engel)

The lagoon’s ecological degradation is due to multiple pollution sources, but is largely affected by years of non-compliant discharges from the Potsdam Wastewater Treatment Works.

On Tuesday, 2 August 2023, Mayor Geordin Hill-Lewis will officially open the R5.2-billion construction upgrade of the wastewater treatment works, which will result in better treatment of effluent received from homes, businesses and industry to ensure high-quality treatment standards. The upgrade will double the plant capacity of treated wastewater from 47 million litres to 100 million litres.

Zahid Badroodien, the city’s Mayco member for Water and Sanitation, said they aim to finalise the Potsdam Wastewater Treatment Works upgrade in 2027, with the operational trial starting in 2026.

Potsdam upgrades have been delayed for more than 10 years due to appeals by bidders, which were dismissed earlier this year and allowed construction of the civil works to finally begin.

However, this is just one source of pollution affecting the lagoon. There are many others, including contaminated stormwater flow near Milnerton High School, which was pumped into the sewer system. As rehabilitation gets under way, other unknown sources of pollution may be discovered.

For years, the pollution has been harming not only the lagoon environment, but residents as well. In March 2022, a massive fish die-off was observed at the mouth of the lagoon where about 500 fish (Liza richardsoni), had washed up.

milnerton lagoon fish

A 2022 fish die-off in the sewage-polluted Milnerton Lagoon was probably the result of growth of algae which depleted the oxygen in the water, says the City of Cape Town. (Photo: Supplied by GroundUp)

In October 2022, amid the nauseating stench at the Milnerton Lagoon, another round of dead fish, unable to survive the toxic water, began washing up again.

How environmental degradation of the lagoon affects residents in the area

Besides discomfort from the stench wafting through the area, residents also expressed concern that this odour contains highly toxic hydrogen sulphide (H2S) and said that they were experiencing health impacts. This issue was highlighted at the Milnerton Lagoon quarterly stakeholder engagement meeting in March this year.

Residents in and around the area complained about health effects they were suffering including recurring eye and skin irritations, frequent sinusitis and asthma flare-ups.

Dr Michelle Maartens, a health practitioner and resident in Milnerton, confirmed that many of the residents that came to her at the time had persistent sinusitis and nasal irritation because of the foul odour.

At the last quarterly stakeholder engagement meeting on 24 July, the city brought in Haithum Wingrove, its senior air quality specialist, to share inputs from an investigation under way.

Wingrove said the main source of the odour was likely H2S, which he explained was a colourless, flammable and poisonous gas with a strong pungent odour, resembling rotten eggs.

The data collected through this monitoring indicated the existence of an odour problem, either through natural or anthropogenic sources in the area and “further investigation is needed to determine source”, said Wingrove.

He concluded that the current levels of H2S in ambient air indicated exposure might pose a nuisance and that there was a need for long-term air quality monitoring in the area to determine seasonal ambient H2S levels.

The director of NPO Rethink The Stink and environmental head of Milnerton Central Residents Association, Caroline Marx, has been extensively involved in holding the city accountable for its inaction on the Milnerton Lagoon. She has worked closely with the city to ensure transparency with residents, especially when it comes to discrepancies in water testing.

“I’m very pleased to hear that the city has started air quality monitoring because the smells around the lagoon are caused by toxic gases like methane and H2S, which have [a] health impact. They can cause allergic rhinitis, irritated eyes, they can perhaps precipitate breathing problems and people who have a predisposition to asthma or chronic lung disease… So it’s very encouraging to see that air monitoring is going to start so we can actually measure it and prove that there is a problem,” she said.

Marx said she felt that the city’s health department had been missing from this problem for a long while.

Despite pollution warnings that the Milnerton Lagoon, Milnerton Estuary Mouth and Lagoon Beach remain closed for swimming, playing and recreation as a result of ongoing pollution within the Diep River, during peak holiday months residents and visitors (especially children) continue to use these areas.

“Every year we see small children swimming in the lagoon despite the signs. Now there’s no monitoring if they later go to a clinic in another part of Cape Town, there’s no follow-up if they get any disease – there’s no tracking. City Health doesn’t seem to have been part of this conversation at all, and the same with air monitoring. We previously invited them to meetings but they are very absent,” Marx said.

At the moment, Marx said there was a definite improvement in water quality and they were even seeing some birds and fish swimming into the sea after the recent heavy rains which effectively flushed out the lagoon.

“But if they don’t find the sources of pollution and stop them, then we’re going to end up right back where we were with a highly polluted lagoon which smells and is devoid of any life. This is why it’s so important that the city follows up and finds the so-called unknown major sources of pollution,” she said.

The plan to restore the Milnerton Lagoon environment

Deputy Mayor and the city’s Mayco Member for Spatial Planning and Environment, Eddie Andrews, explained the strategy: “The city aims to steadily close off pollution sources to the lagoon, so that we can dredge and remove the sediment at the bottom, along with decades of pollution build-up. We are committed to addressing these challenges in partnership with all who care about restoring the health of the lagoon environment, which is non-negotiable for the city.”

Andrews said the intervention of various stakeholders was required to successfully rehabilitate the ecological condition of the lagoon – from the government to the public and industries within the Diep River Catchment area.

A key component of the action plan includes bioremediation to see if it could help break down organic materials in a lagoon environment.

Then there are short-term water quality and odour mitigation strategies.

They include: installing waste interceptors in the Diep, Black, and Salt rivers as well as the Jakkalsvlei Canal; constructing the Erica Road Outfall Low-flow diversion; investigating and correcting cross connections created by residents from stormwater and sewer pipes; cleaning ponds and refurbishing settlement tanks at Potsdam Wastewater Treatment Works; and installing screens and generators at sewer pump stations.

Long-term projects involve the upgrade of Potsdam Wastewater Treatment Works, Montague Gardens Bulk Sewer Rehabilitation, Koeberg Pump Station Upgrade, and the long-term pump station and pipe replacement programme in the region.

This could very well be the biggest and most expensive rehabilitation in the country.

Another key aspect is community involvement, as with the Milnerton Lagoon quarterly stakeholder engagement meetings, which began in December last year to keep the community updated on the implementation of the plan and to provide them with a space to ask questions and provide insights related to the lagoon pollution.

Speaking to Daily Maverick after the last quarterly stakeholder meeting, Badroodien said: “The Milnerton Lagoon is one of those issues that has plagued the city for a number of years. Pollution from all sources – informality, businesses, just blatant dumping across the riverbed, but then also majorly is our wastewater treatment works that hasn’t been discharging effluent to an acceptable standard. This resulted in a lot of frustration from residents who simply wanted to be taken on board as equal partners in what it is that the city is trying to do.”

Unknown source of pollution and intervention by the Green Scorpions

A meeting was held on Monday, 31 July between the city, RethinkTheStink and the Department of Water and Sanitation to discuss possible sources of sewage pollution in the Diep River, adjacent to the Potsdam Wastewater Treatment Works, which Marx said might be responsible for the high E. coli counts below the plant.

“Water samples were taken at eight points along the river to identify the point at which the pollution is entering the river,” she said.

Western Cape Department of Environmental Affairs and Development Planning spokesperson Rudolf van Jaarsveldt said the environmental degradation within the Milnerton Lagoon was being investigated by the Green Scorpions from the national Department of Forestry, Fisheries and Environment, due to the coastal estuary falling within the department’s jurisdiction and mandate.

The Western Cape Department of Environmental Affairs and Development Planning are investigating the sources of pollution within the lower Diep River catchment, in conjunction with the City of Cape Town and the Department of Water and Sanitation.

The intervention by the Green Scorpions comes after the Organisation Undoing Tax Abuse (Outa) called on them in 2022 to exercise an oversight role and hold the city accountable for ongoing failure to comply with the anti-pollution directive against it. DM


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