A sewage spill into Silvermine Estuary has resulted in the death of juvenile fish and caused the beach near the estuary mouth to be closed to the public.
However, the City says it won’t affect the Blue Flag status of the beach this December.
Fish Hoek resident Lewis Walter noticed the sewage spill late last Monday afternoon, December 10, and the first report about it was sent to the City of Cape Town by 7pm.
The next morning at 10am he checked the area and sewage was still flowing from the pipe outlet on the Fish Hoek side, another resident he spoke with also reported the incident at 6.30am.
“A great many baby fish died, possibly a whole generation of fish has been lost,” he said.
Mr Walter feels that the council has abandoned its responsibility for preservation of the wetlands.
He provided photographs to the False Bay Echo to show the sewage still flowing full spate at 5.30pm on Tuesday December 11, 24 hours after it had first been reported.
Dr Zahid Badroodien, the City’s Mayoral committee member for community services and health, said the City’s Environmental Health Department has collected water samples for analysis in both the Silvermine River estuary, as well as the sea adjacent to the estuary, and is waiting for the results.
He said signage has been put up, warning the public not to enter the estuary and that the City’s life savers have also been instructed to keep the public away from the estuary and the sea in the vicinity of the estuary mouth.
The City’s Environmental Health Department will continue to take samples and monitor water quality closely, and the beach adjacent to the estuary will remain closed until the water quality improves.
Dr Badroodien said: “Regrettably, this has led to the die-off of primarily juvenile fishes.”
He confirmed that the sewage must have run for 24 hours before the source of the problem was found.
The estuary was, however, artificially breached on Thursday, December 13, to flush it.
The repair of the blockages, together with the flushing of the estuary through its artificial breaching, has prevented further die-off of fish, he said.
The Blue Flag bathing area is approximately a kilometre south of the estuary river mouth.
“Given this distance as well as wave energy and currents, it is anticipated that effluent that entered the sea via the estuary mouth will dissipate quickly and thereby not impact on the Blue Flag status,” he said.
It is a requirement of Blue Flag beaches that sea water samples are taken every 30 days. However, Dr Badroodien said the City conducted more frequent sampling in order to protect bathers and the environment.
“Should water samples fail the Blue Flag standards, the routine protocol will apply and the Blue Flag will be lowered until such time as the water quality improves,” he said.
He claimed this is a very infrequent occurrence, saying that the City has developed a sewage response protocol to enable a co-ordinated response between departments to effectively deal with such incidences.
Ward councillor Aimee Kuhl called on Andrew Taylor, Senior Professional Officer, Water and Sanitation about the sewage spill in the Silvermine Estuary, for details about the incident.
He said the initial assumption was that the spillage was as a result of a pump station failure but that was not the case.
He confirmed that the first report was made at 7pm on Monday December 10 but said it was only picked up by the depot early the next morning, Tuesday December 11, when the blockage team was dispatched.
He said tracing the actual location of the blockage proved to be problematic – the sewage was coming out of a storm water pipe and there were no above ground indications as to how it was getting into the system.
“Also, there are no known cross connections (overflows) between the sewer and storm water system in the area,” he said.
The issue was eventually found to have occurred 850 meters upstream of the discharge point into the river, at the circle on First Crescent / Disa Avenue.
Mr Taylor said there used to be a small “lifting” pump station on the First Crescent/Disa Avenue circle which was abandoned; the pumps and all electrics were removed.
The sump was however left in place. He said the pump station was then bypassed with conventional gravity sewer lines. It was this gravity line which was blocked.
“Somehow the sewage then flowed into the empty sump of the abandoned pump station, the sump filled up and the overflow took the sewage to the stormwater system. It was this stormwater pipe where the sewage was discharged into Silvermine River,” he said.
Mr Taylor said that after the source was found, the sump had to be emptied and cleaned up before the blockage could be cleared. This required the hiring of a tanker service, and the work was eventually completed on Wednesday morning December 12, after which the blockage was cleared.
Mr Taylor said that going forward, the overflow to storm water system was to be closed off, leakage from the sewage system to the abandoned sump was to be located and eliminated; and that sewer pipes in the area are going to be cleaned.
Xanthea Limberg, the City’s mayoral committee member for informal settlements, water and waste services; and energy, said: “The reason for the overflow is being addressed. It is very likely to be the misuse of the sewer by dumping inappropriate objects into it,” she said.
She confirmed the City’s plan for what she called a “mop up operation” and said sewer pipes in the area would be cleaned. She said the fact that it was a blockage and not a pump station problem would explain why no automatic warning signal was activated.