Friends of Rietvlei
Member of the Wildlife & Environment Society of South Africa Western Cape Region
Newsletter November 2011
Evening Talk at Rietvlei:
“Overview of students projects for 2011” Five nature conservation students have spent this year working in Rietvlei, Blaauwberg and Atlantis conservation areas and have some interesting projects to share from their studies.
Speakers: North region nature conservation students
Where: Rietvlei Education Centre, off Grey Avenue Flamingo Vlei
When: Thursday 10 November @ 19h30 for 20h00. View the sunset over the vlei waters at Rietvlei!
Contact: Pat on 083 701 4318
This will be our end-of-year function so we would like to request all members to bring a plate of eats to share. We will have wine, juice, tea and coffee available.
Evening Talk at BCA:
“Understanding informal economy of illicit harvesting within City of Cape Town”
Speaker: Leif Petersen (University of Queensland, Australia)
Where: Log Cabin, Eerste Steen, Otto du Plessis Drive, between Big Bay and Melkbosstrand. View another sunset from the beach!
When: Tuesday 15 November @ 19h30 for 20h00
Contact: Roy on 071 671 9552
This promises to be a fascinating presentation by an overseas speaker.
On Friday 14 October numbers of fish were found dying in the Diep River just north of the Blaauwberg Road Bridge. Nearly 40 dead carp were counted in a stretch of about 150 meters. The water in the river was visibly polluted and it is suspected that the source is one or more of the stormwater drains into the river upstream of the bridge.
Diep River at Lookout Point Du Noon Stormwater Outfall
Diep River at Lookout Point Du Noon Stormwater Outfall
Needless to say, birds soon discovered the dead fish and a few hours later more than 55 pelicans were counted together with large numbers of ibis, herons, egrets, etc. A couple of days later most of the dead fish were gone and the birds had also moved on.
We have not received the water quality results for October, but the results for the end of September (sampled on 27 September) show high levels of pollutants at the Blaauwberg Road bridge. Total Nitrogen was 2.9 mg/l, this was about the average level measured in the river that day; the acceptable level is less than 2.5mg/l. Total Phosphate was 0.98 mg/l, the highest level in the river that day; the acceptable level is less than 0.25 mg/l. Dissolved oxygen was measured at 3.1 mg/l, about average for the river, excluding the estuary, on that day, this was about 30% saturation – not exceptionally low for periods of low water flow.What is disturbing is that the faecal coliform bacterial count was extremely high, at 45,000 /100ml it was more than 3 times the level measured downstream of the Potsdam discharge point. The water quality guideline for “intermediate contact (not swimming)” is a maximum of 1,000 /100ml. This means that the levels of bacteria were 45 times higher than it should be for safe human contact.
The level at the N7 bridge was only 320 /100ml; which clearly indicates that the source of the pollution was between the N7 bridge and Blaauwberg Road and thus most likely one of the stormwater outfalls in this section of the river.
The situation has been reported to the City’s stormwater department. We realize that polluted stormwater is a major problem in the City, and we hope that the recently completed study of the stormwater discharges on the eastern shore of the Diep River from the mouth to the N7 bridge will lead to a resolution of this particular problem.
Another concern we have following the fish deaths and the increase in stormwater pollutants is the pressure from Milnerton Estates and Aska Properties for the city to reduce the approved buffer along the Diep River on their Rivergate Development. This area is on the western side of the Diep River north of the railway bridge. The city has already built its portion of the M12 road from the N7 and across the Diep River. The developers are supposed to be completing the link road from Sandown road to the M12. The developers excuse for not building their portion appears to be aimed at getting more development rights out of the authorities. They wish to have the stormwater polishing undertaken within the river corridor. Based on the bad quality of stormwater entering the Diep River from the areas such as Killarney Gardens and Du Noon we do not want to see the new developments following the same methods. Stormwater needs to be polished by removing pollutants and litter before it gets to the river corridor. Unfortunately for developers this means setting aside land for dealing with stormwater. But for local residents and our wildlife such as fish and birds, this could mean a cleaner river system.
Mark Robinson saw a large otter – he says it was HUGE – running across the grass near the Toilet Block next to the Rietvlei Education Centre a couple of weeks ago. The otter was not too perturbed by the presence of people in the vicinity, but disappeared into the undergrowth before he could get to his camera out of his car. Nice to know that the otters feel at home at Rietvlei!
On a sadder note Gail MacDonald recently found a dead grysbok next to the R27 near the Otto Du Plessis Bridge and opposite Sunset Beach.
Our environmental education centre at Rietvlei is being refurbished, the roof needed urgent attention and some of the wooden slats on the outside are being replaced. The committee has approved expenditure of just over R7,000 for the job, but it may cost more as the contractors have discovered some hidden problems that were not visible before they started the job. Fortunately we have had some donations from environmental penalties that were issued to the contractors for non-compliance with the Construction Environmental Management Plan at both the Bayside and Makro sites. The independent Environmental Control Officers on these sites issued the penalties, following warnings that were not adhered to.
As always we are involved with several impact assessments of developments in the area. In the previous newsletter we reported on the response to our appeal against the expansion of Potsdam. We are still waiting to hear about the appeal against conditions for the development of the Gold Circle property next to the Milnerton Racecourse Nature Reserve.
Another study that has just been announced is a proposal to develop a Biosolids Beneficiation plant near the Vissershok Waste Management Facility. Biosolids is the product of the sludge from the biofilters at sewage works, this sludge is dried and currently used for making compost. Most of the drying happens at the City’s various waste water treatment works, but the City is now proposing a centralised facility as many of the treatment works do not have the capacity to handle large volumes of biosolids. It is interesting to note that the better technology in waste water treatment has resulted in more sludge being produced – this means a cleaner quality effluent that is discharged from the treatment works.
The Draft Scoping Report is now available for comment – several locations in the Vissershok vicinity have been identified as possible alternative sites. We are closely involved so that we can ensure that development and use of the site that is eventually chosen does not impact on the Diep River in any way. One of the interesting facets of the project is investigating the possibility of energy generation by gas production; as well as utilising it for composting and fertilisation, thus also using it as a source of nutrient energy.
Environmental Education Centre – 021 521 9900
Entrance Gate – 021 557 5900
Emergencies and standby number 071 268 9637
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