Investigations into the condition of the dam at The Sanctuary shopping centre in Somerset West have taken a significant turn, with joint inspections revealing a sewer overflow discharging into a stormwater channel hydraulically connected to the waterbody.

The finding may account for distress among hundreds of fish in recent weeks.

DistrictMail & Helderberg Gazette reported on the matter after community members raised alarm on social media, alleging hundreds of carp were gasping at the surface of the shopping centre’s dam, with the water described as stagnant and oxygen-depleted (“Multi-agency probe into ‘gasping’ carp,” 10 June).

The Cape of Good Hope SPCA logged a case on 28 May, assigned an inspector within 24 hours, and closed the case on 3 June after concluding its investigation.

Wildlife supervisor Trevor Rodney contacted the Department of Forestry, Fisheries and the Environment, which sent a fish expert from the Shark Spotters Unit.

The expert visited twice, found no signs of distress and noted oxygen was being pumped into the water. Muddied water observed during a follow-up was attributed to grass cutting.

The City of Cape Town’s Biodiversity Management staff from the Helderberg Nature Reserve visited the dam on 1 June, alerted centre management and referred the matter to the City’s Water Pollution Control for further investigation.

On enquiry last week Zahid Badroodien, Mayoral Committee member for Water and Sanitation, said the Water Pollution Control Inspectorate was informed of suspected pollution at the waterbody on Tuesday 9 June, following reports of fish mortalities.

“Joint inspections were done on the same day and a sewer overflow was found, which was running into a stormwater channel that is hydraulically connected to the dam,” he explained.

“A service request was logged and Water and Sanitation teams cleared the blockage. Foreign objects, including rags and garden refuse, were found in the sewer line. Grease-trap inspections at the centre also revealed one tenant was suspected of dumping oils and fats into the line, and they were issued a transgression notice.”

Follow-up inspections were conducted on Friday 12 and Monday 15 June. “Fat residue was observed in sections of the sewer system upstream of the centre and further investigations are planned to determine other potential sources of sewer blockages.”

He added preliminary water-quality results showed high concentrations of ammonia, confirming the identified sewage overflow.

Centre management indicated their disappointment at the negative attention the shopping centre has received, noting the matter has been prioritised and a resolution is being sought.

A local plumbing company enlisted by centre management shared the following: “When the community raised concerns about the fish at the pond, we were asked to assist with improving oxygen levels in the water. We built an aeration system to get more air into the pond. Aeration pumps are now operating on two sides of the pond and the fish have stopped gathering at the surface, returning to normal behaviour underwater. This isn’t about plumbing; it’s about a community that cared enough to bring attention to something that matters. We were happy to play our part.”