Milnerton Lagoon Woodbridge Island Pollution Report: October 2025 - December 2025
"The Milnerton Lagoon and adjacent Woodbridge Island are part of a systemic environmental challenge in Cape Town, South Africa, where chronic sewage pollution, degraded water quality and odour issues have persisted through late 2025. Between October and December 2025, key themes in environmental reporting and community experience include:
- Ongoing sewage contamination entering the Diep River and Milnerton Lagoon, reflected in elevated bacteriological indicators outside applicable health standards.
- Ambient air quality monitoring for hydrogen sulphide (H₂S) showing levels below international health guidelines but debated by activists for methodological limitations
- Infrastructure upgrades, notably the Potsdam Wastewater Treatment Works, progressing but not yet completed; extensions for compliance deadlines have been granted.
- Significant community concern and advocacy, with residents and groups questioning official responses, data transparency, and public health protection measures.
This report synthesises official data, recent news sources, scientific monitoring summaries, and community advocacy perspectives, with analysis of drivers, impacts, governance responses, and policy implications.
1. Geographic and Environmental Overview
1.1 Milnerton Lagoon and Woodbridge Island
The Milnerton Lagoon is an estuarine section of the lower Diep River system, opening into Table Bay near Lagoon Beach and lying adjacent to Woodbridge Island, a residential and recreational precinct in Cape Town’s northern suburbs. Water flows from inland catchments—including Montague Gardens, Joe Slovo and Dunoon—into the lagoon, with stormwater and riverine pathways linking upstream conditions to coastal water quality outcomes. Chronic pollution in this complex hydrological system directly affects local ecology, recreation, and community health perceptions.
2. Current Pollution Dynamics: Water Quality
2.1 Bacteriological Contamination
Recent coverage and water quality monitoring reports indicate enduring water quality challenges in the Milnerton Lagoon. In 2024–25 inland water reports, Milnerton Lagoon was categorised among sites with persistently high bacterial counts (e.g., Escherichia coli), linked to untreated sewage, dry-weather flows from informal settlements, and infrastructure faults. The inland water quality classification schemes found high proportions of samples in the “unacceptable” category for bacteriological risk (City of Cape Town Inland Water Quality Report 2024/25). (Cape Town Resources)
Independent reports underscore that stormwater channels and sewage treatment effluent contain elevated E. coli, often far exceeding safe thresholds (e.g., stormwater outfalls measuring hundreds of thousands of CFU/100 ml). These figures greatly exceed internationally recognised 1000 CFU/100 ml safety benchmarks for recreational contact, as indicated by independent water tests. (GroundUp News)
2.2 Regulatory Context and Enforcement
South African water quality regulation—under the National Water Act (No. 36 of 1998) and associated guidelines—mandates that water bodies should be assessed against microbiological and chemical safety criteria for their designated uses. Recreational waters are subject to stringent standards to protect human health. The available official data for inland waters continue to show Milnerton Lagoon at high risk for recreational use, triggering public health advisories and signage. (IOL)
2.3 Public Health Implications
High E. coli counts suggest persistent faecal contamination, posing a risk of gastrointestinal illnesses and other infections if ingested or contacted during recreational use. Multiple community observations and independent postings indicate that foul smells and scares about sewage contact persist, and there is concern that children still access the water despite warning signage. (EWN)
3. Ambient Air Quality: Hydrogen Sulphide MonitoringThe City of Cape Town maintains that signage and advisories are essential to keep the public informed that the lagoon is not suitable for swimming or other direct water contact. These warnings remain in place as a precautionary public health measure. (IOL)
3.1 Monitoring Programme
In response to public complaints about foul odours associated with sewage degradation in the lagoon, the City reinstated continuous ambient air quality monitoring for hydrogen sulphide (H₂S) at Woodbridge Island in February 2025. The monitoring station measures H₂S—an odour-causing gas associated with anaerobic decomposition of organic matter—and compares recorded levels against the World Health Organization’s (WHO) daily guideline of approximately 110 parts per billion (ppb) for acute health risk evaluation. (IOL)
City officials have reported that continuous H₂S levels have remained below the WHO health guidelines, and no formal health risk assessment has been declared necessary at present. They emphasise that data collected since commissioning the monitoring station show concentrations “well below” the threshold, reflecting no immediate health risk from air exposure. (IOL)
3.2 Community Debate on Monitoring Approaches
Despite official assurances, local community groups and environmental activists have challenged the adequacy and transparency of H₂S monitoring. Critics argue that:
- Peak exposures may be concealed by 24-hour averaging, even if daily averages are within limits;
- The monitor’s elevation (typically ~3.5 m) may not accurately reflect ground-level exposure for residents, especially vulnerable groups such as children and the elderly;
- No ground-level supplemental monitoring has been publicly disclosed to confirm whether breathing-zone exposures align with official measurements. (Cape Argus)
Activists also link short-term odour episodes with symptom reports of nasal irritation and respiratory discomfort that they attribute to localised air pollutant spikes. These concerns underscore the complexities of assessing nuisance odours vis-à-vis formal acute toxicity thresholds.
4.1 Potsdam Wastewater Treatment Works Upgrade
The Potsdam Wastewater Treatment Works (WWTW), a central component of Cape Town’s wastewater infrastructure serving much of the northern metropolitan area, is undergoing a major upgrade to expand capacity and improve effluent quality. As of late 2025, the project has reached approximately 60% completion and remains on track for full delivery by late 2027, according to municipal reporting. The upgrade aims to more than double treatment capacity—from 47 to 100 million litres per day—and incorporate modern ultrafiltration and disinfection systems. (Cape Argus)
Once complete, the upgraded WWTW is expected to significantly reduce untreated sewage spill volumes and improve the quality of effluent discharged into the Diep River, thereby reducing bacterial loads and other pollutants entering the Milnerton Lagoon over time. (Cape Argus)
4.2 Compliance Deadlines and Extensions
The Western Cape provincial government has granted extended deadlines to the City of Cape Town to comply with pollution remediation directives, a development that has drawn sharp criticism from environmental watchdog groups. RethinkTheStink and other advocates argue that granting up to three additional years to complete overdue upgrades may contravene original regulatory commitments and delay urgently needed improvements. Critics have called for transparent legal justification for the extensions under environmental legislation, citing high E. coli counts that continue to exceed safe levels. (IOL)
City officials contend that complex construction timelines, unforeseen delays, and dependencies on authorisations beyond municipal control justify the extended compliance periods while efforts continue to restore environmental conditions. (IOL)
4.3 Additional Remediation Measures
Beyond the Potsdam WWTW upgrade, municipal departments report ongoing actions to address sewer network leaks, pump station upgrades (e.g., at Koeberg), sewer line rehabilitation, enhanced vacuum tanker deployment, and low-flow stormwater diversions. These efforts aim to reduce unplanned discharges and improve the resilience of sanitation infrastructure that directly affects water quality in the Milnerton Lagoon catchment. (Table Talk)
5.1 Resident Experiences and Public Health Claims
Local representative councillors and activists have highlighted lived experiences of pollution impacts. Residents near the lagoon have reported persistent foul odours and adverse health symptoms, including respiratory irritation, nausea and headaches—conditions they associate with lagoon emissions and stagnant water, attributing these to toxic gases like H₂S and ammonia. These accounts have been raised in local council meetings and public forums as part of broader pressure on municipal authorities. (Cape Argus)
CAPEXIT and other political actors have emphasised that residents’ quality of life and property values have been negatively affected by long-term pollution and odour issues, framing the environmental condition as both a public health and socio-economic concern. (Table Talk)
5.2 Advocacy for Greater Transparency and Monitoring
Community groups continue to call for:
- Ground-level air quality monitoring in addition to elevated stations;
- Public disclosure of raw monitoring data to allow independent interpretation;
- Expanded water quality sampling points and more frequent reporting.
These advocacy positions reflect scepticism about official assurances and a desire for more participatory environmental governance.
6. Ecological and Recreational Impacts6.1 Ecosystem Function and Biodiversity
Chronic sewage pollution and high nutrient loads have contributed to hypereutrophic conditions in the lagoon, reducing dissolved oxygen levels and stressing estuarine ecosystems. High bacterial loads and organic matter accumulation can impair habitats critical for fish, birdlife and aquatic vegetation, eroding biodiversity and ecological resilience. (Cape Town Resources)
6.2 Recreational Restrictions
Due to ongoing contamination, the City maintains signage advising against recreational contact with lagoon water. Clubs and sports groups, such as the Milnerton Canoe Club, have curtailed activities in the lagoon and relocated programmes due to unsafe conditions, affecting community sport and leisure opportunities. (Table Talk)
7.1 Temporal and Spatial Data Coverage
While continuous ambient air quality monitoring and periodic water sampling occur, the data currently available to the public may not fully capture short-term pollutant spikes or fine-scale spatial variations—especially near informal settlements and stormwater outlets where pollution ingress is frequent.
7.2 Integrated Health Outcome Monitoring
There is limited publicly accessible epidemiological data linking documented environmental pollution to clinical health outcomes in the population, hindering formal public health risk assessments that integrate environmental monitoring with medical reporting.
8.1 Align Monitoring with Exposure Reality
Given community concerns about measurement protocols, authorities should consider:
- Supplemental ground-level air quality monitoring to assess real exposure conditions, especially during odour events.
- Enhanced temporal resolution in water quality reporting to detect short-term pollutant surges.
These enhancements would strengthen risk communication and improve confidence in environmental assessments.
8.2 Strengthen Transparency and Public Reporting
Public access to raw, real-time monitoring data (air and water) would bolster community trust and allow independent scientific analysis that can inform adaptive management strategies.
8.3 Accelerate Infrastructure Delivery and Interim Mitigation
While long-term infrastructure projects progress, interim measures—such as targeted sewer network repairs, increased stormwater treatment, and emergency overflow containment—could reduce ongoing pollutant inputs into waterways.
- Ongoing bacterial contamination of lagoon waters at levels unsafe for recreation.
- Ambient air quality readings remaining below formal health thresholds, yet contested by community stakeholders.
- Infrastructure upgrades making progress but not yet delivering full remediation outcomes, with extended timelines raising public frustration.
- Strong community advocacy and calls for increased monitoring transparency and protective measures.
Addressing these issues requires integrated policy action bridging environmental science, public health, infrastructure investment, and community engagement." (Source: ChatGPT 2025)
ReferencesCape Argus News. (2025, December 19). Milnerton Lagoon air quality remains safe, confirms City monitoring. iol.co.za. (IOL)
Environmental activists challenge Cape Town’s air quality claims around Milnerton Lagoon. (2025, December 23). Cape Argus News. (Cape Argus)
City of Cape Town. (2025). Inland water quality technical report summary 2024/25. resource.capetown.gov.za. (Cape Town Resources)
Milnerton’s R5.2 billion Potsdam wastewater treatment upgrade on track at 60% completion. (2025, September 30). Cape Argus News. (Cape Argus)
Extension granted to fix ‘stinky’ Milnerton Lagoon. (2025, May 19). Cape Argus News. (IOL)
Milnerton Lagoon gets air monitoring boost. (2025, July 14). TableTalk. (Table Talk)
Call to improve signs for lagoon ‘health hazard’. (2025, January 23). TableTalk. (Table Talk)
Polluted Milnerton Lagoon “particularly disgusting”. (2025). GroundUp. (GroundUp News)
City of Cape Town. (2025). State of the environment 2022 overview (water quality section). resource.capetown.gov.za. (Cape Town Resources)
CAPEXIT takes Milnerton Lagoon stench to City Council. (2025). TableTalk/Cape Town local news. (Table Talk)
Guardian coverage on historical Milnerton Lagoon pollution (contextual background). (theguardian.com)
Disclaimer
The 'Milnerton Lagoon / Woodbridge Island Pollution Status Report December 2025' was compiled by ChatGPT on the request of Vernon Chalmers Photography. Vernon Chalmers Photography was not instructed by any person, public / private organisation or 3rd party to request compilation and / or publication of the report on the Vernon Chalmers Photography website.
This independent status report is based on information available at the time of its preparation and is provided for informational purposes only. While every effort has been made to ensure accuracy and completeness, errors and omissions may occur. The compiler of this Pollution Report (ChatGPT 2025) and / or Vernon Chalmers Photography (in the capacity as report requester) disclaim any liability for any inaccuracies, errors, or omissions and will not be held responsible for any decisions made based on this information.
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