Modderfontein Stream – Modderfonteinspruit

Modderfontein Stream description and issues *

  • Run-off and flooding, leading to erosion, deep channels and habitat loss
  • Pollution of the water from sewage spills and industrial sources
  • Increasing encroachment of invasive plant species and conversion from grassland to bush
  • Lack of a management plan for the Illiondale Wetland, leaving metro departments without coordination and stakeholders with differing views about the wetland.

The Modderfontein Stream arises in the Isandovale area in Ekurhuleni. Two streams known as the Kevin Stream and the Sebenza Stream flow through the industrial area of Sebenza meet at the Cecil Awret Road Bridge in Illiondale. The Illiondale Wetland extends from there to the R25 Modderfontein Road bridge. The stream then enters Johannesburg and flows through Modderfontein Golf Course and the suburb of Modderfontein.

Map of the Modderfontein River catchment with main features and border between City of Johannesburg and City of Ekurhuleni
Map of the Modderfontein Stream catchment in Ekurhuleni and Johannesburg

RiverWatch Vision for the Modderfontein Stream is a continuous healthy riparian corridor providing habitat for biodiversity, recreation for people and floodwater attenuation. To this end Edenvale RiverWatch monitors changes in the course of the stream and related wetlands, and retains information on water quality and developments that is frequently lost or inaccessible to the public.

Run-off, flood and erosion management *

Development of the residential suburb of Illiondale and the industrial area of Sebenza encroached into buffer zone, wetland, flood plain and hillside seeps. Problems with flooding, erosion and pollution arose. Different metro departments intervened at times, but the projects have often been poorly conceived, badly or incompletely carried out, or allowed to languish unresolved. The main issues that challenge the stream and Illiondale Wetland are:

In 2010 the metro implemented the Isandovale Soil Erosion Management Project (Gaut 002/07-08/NO946) to address run-off, erosion and flooding. The capacity of four bridges between Driefontein Road and Cecil Awret Road were increased. Six or more concrete/gabion combination structures were built in the wetland between Cecil Awret and Margaret Roads to slow the flow and reduce erosion. The structures in the wetland all failed, in the first wet season according to residents. These concrete structures remain in the river channel causing obstruction, erosion and interfering with later projects.

Modderfontein Stream in Illiondale showing failed gabion and side erosion
Failed 2010 gabion and erosion in Illiondale Wetland

In 2013 gabions were constructed both upstream and downstream of the Cecil Awret Road and the Margaret Road Bridges to improve the stability of the channels. But the contractor abandoned the site without completing the work, leaving the upper gabion at the Margaret Road Bridge unbuilt even though he had excavated the channel in preparation for the work. The bridge was left in this vulnerable position. Only in 2019 was a minor fix done to address undermining of the bridge.

In addition, the gabion on the east bank below Cecil Awret Road Bridge collapsed within three months of construction. An investigation into this failure exonerated both the gabion design and the contractor, and was attributed as “purely caused by high volumes of water in the stream and the nature in which the water acts in the stream”.

In July 2015 a sewage spill collapsed an upstream wing of the bridge, which was then seriously at risk. The following year a new contractor replaced the missing bridge wing and gabions and enlarged the channel still further. The next three images show three stages of development of the channel downstream from the Cecil Awret Road bridge to cope with increasing volumes of run-off. In 2009 after the original development and after the projects in 2013 and 2016 described here. The video give a more detailed view of the changes

Illiondale stream channel at Cecil Awret Rd bridge in 2009
Illiondale stream channel at Cecil Awret Rd bridge in 2014
Illiondale stream channel at Cecil Awret Rd bridge in 2016

The channel at the end of Crawford Road had been eroding and threatening the Cedars residential complex for some years. In 2016 the contractor working at Cecil Awret Road Bridge installed a gabions to stabilize the east bank. But problems remained. The contractors departed leaving the west bank already side cut by the flow, and the stream flow completely bypassed the gabion structure. In addition one of the derelict concrete constructions from 2010 obstructs the exit of the new stabilized channel. Obtaining approval to remove existing infrastructure proved too daunting.

New gabion channel near Crawford Rd partly blocked by derelict 2010 structure

Modderfontein Outfall Sewer Project 2009 – 2019 *

Modderfontein Outfall Sewer Project: In the early development of this valley, two pump stations in Illiondale pumped waste water back over the ridge to an Ekurhuleni waste water treatment plant. This system became overloaded and unreliable resulting in frequents spills into the river. The new Modderfontein Outfall Sewer approved in 2009 (GAUT:002/08-09/N0584) was to overcome this by feeding the wastewater downhill by gravity to the Johannesburg waste water system. In 2011 a contractor started work but abandoned it in 2012. A new contractor took over in 2018. The pump houses were demolished in May 2019 and it appears the contractor and the Metro deem the project complete.

But there are major shortfalls. The contractor left building rubble at the site of the demolished pump house between Margaret Road and Modderfontein Road and slabs of concrete are in the channel of the stream. Unused pipes lie abandoned together with piles of rubble. This has become a signal for others to dump at the site.

Abandoned Modderfontein Outfall Sewer construction site with concrete slabs, rubble and discarded pipes

The track opened up by the sewer construction remains, giving access for illegal dumping in a number of places. Further upstream the contractors filled the Kelvin Stream channel with rocks to make a causeway. They did not restore the stream and now run-off spills out and floods Dunbar Road when it rains. It seems common sense that a contractor makes good at completion of a project, but there is more. The environmental authorization lists the rehabilitation required and includes an Environmental Management Plan (EMP) that lays out these obligations in detail. The EMP includes instructions for rehabilitation of the site and removal of temporary access roads, with follow up and environmental monitoring for up to 18 months. The conditions in the authorization and the EMP become part of the contract. It appears both contractor and owner (Ekurhuleni) ignored this.

The new sewer has not reduced the incidents of sewage spill. The next graph shows the number of known spills of sewage into the Modderfontein Stream from October 2018 to December 2019. The Outfall Sewer was commissioned in May 2019, so this is the transition point this gives a before and after comparison. There is no improvement seen.

Graph showing the number of sewage spills into the stream in Illiondale - Sebenza from October 2018 to December 2019
Sewage spills into the stream in Illiondale – Sebenza from October 2018 to December 2019
Stream channel filled with rocks for construction vehicle access, now diverting floodwaters out of the channel
Access road along the Modderfontein Outfall Sewer, covered with invasive weeds and not rehabilitated

Illiondale Wetland Restoration Project *

The Department of Environmental Resource Management of City of Ekurhuleni appointed Land Resources International in 2014 to assess the wetland from Cecil Awret Road to Modderfontein Road Bridge. They produced their report and proposed plan of rehabilitation in September 2014. Environmental Authorization was granted in April 2016 (Gaut 002/15-16/E0043). The plan had two phases. Phase 1 was to repair or build new gabions to stabilize the banks (but not the failed 2010 concrete/gabion structures) and remove the major stands of invasive plants. Phase 2 would slow the flow through the wetland and raise the water table, reversing the effects of erosion and channel deepening.

The first phase listed 26 interventions or tasks. A proposed fence around the area made up ten of these interventions, but the environmental authorization excluded the fence and these fell away. While this project was in the approval process the Department of Roads and Stormwater rebuilt the gabions at Cecil Awret Road Bridge in 2016, eliminating a further two interventions. So in 2017 when the work started 14 interventions remained. Six were gabion repairs and eight were alien plant removals. The map shows the position of the 14 interventions.

Map showing Illiondale Wetland Rehabilitation Project priorities at start of work in 2017
Illiondale Wetland Rehabilitation Project priorities at start of work in 2017

Phase 1  Started  first half of 2017 but with only with token effort. Of the the six stream bank priority interventions, only three were completed. The alien invader plant removal was so ineffective that it is puzzling why it was even done. The contractor cut down four of the six infestations of gray poplar and giant reed and removed the material. There was no attempt to eradicate by addressing the underground roots and stems. In spring new growth started as normal, continued through the 2017/18 summer season. The photo below shows regrowth of gray poplar, giant reed and bugweed one year after clearing. 

Phase 1 appears abandoned and there is no indication as to whether Phase 2 will take place.

Photo showing growth of invasive plants in Illiondale June 2018, one year after clearing
Regrowth of invasive plants in Illiondale June 2018, one year after clearing

Water Quality and Pollution *

Edenvale RiverWatch tracks water quality, pollution and the health of the Modderfontein Stream using four sets of measurements:

  • Quarterly Water Quality Reports by the two local authorities (Ekurhuleni and Johannesburg Metros)
  • Pollution tracking by RiverWatch and other volunteers
  • Bio-assessment of River Health using MiniSASS
  • Photo monitoring of specific sites to record change

Ekurhuleni Water Quality Reports: Counts for fecal coliforms per 100 ml taken from the quarterly reports show sewage pollution trend over the last 6 years. From a low base in 2013 pollution increased rapidly and then moved between about 10 000 and 400 000 counts per 100 mL to March 2019. 

Graph showing trend in coliform counts per 100 ml for Modderfontein Stream 2013 to March 2019 from Ekurhuleni Water Quality Reports, showing high level sewage contamination.
High level sewage pollution in Modderfontein Stream for six years to March 2019

The three major pollution risks for the Modderfontein Stream in Illiondale are: sewage spills, industrial discharges and ash silt from Kelvin Power.

First, sewage pollution from blockages and broken infrastructure is the overwhelming problem. The Modderfontein Outfall Sewer project completed in 2019 should have reduced the number of spills but there seems to be no improvement. See the report on this project.

Second, industrial pollution from a number of sources: Founder’s Hill South, although in Johannesburg, run-off and pollution flow into the Modderfontein Stream in Illiondale. This problem was taken up by Edenvale RiverWatch in May 2015.  A time lapse video was taken on 8 February 2016 showing at least 14 discharges took place in 12 hours. In spite of repeated intervention by officials from Johannesburg and Ekurhuleni metros the problem is not fully resolved to the end of 2019.

Modderfontein Stream industrial discharge
Industrial discharge Modderfontein Stream 6 July 26 July 2015

Industrial pollution also comes from the industrial area of Sebenza. Foaming has long been a problem, but in December 2019 Edenvale RiverWatch found a chemical factory in the area releasing the foaming agent.

Photo of foam pollution in Kelvin Stream near Dunbar Road 10 Dec 2019
Foam Kelvin Stream near Dunbar Road 10 Dec 2019

Third, the risk of silt pollution from Kelvin Power. In coal powered power stations fly-ash is managed with water and pumped into dams on top of the dumps. The ash is a grey-white colour. Over the weekend of 29 August 2014 Kelvin power released a fly ash suspension that covered the Modderfontein Stream bed from Sebenza to the Modderfontein Golf Course. The silt was removed from the stream bed manually, a massive undertaking, with a serious impact on the ecology of the area.

Pollution from bottom ash, which is black, is far more frequent. Bottom ash flows downstream from Kelvin Power in the run-off from every rainstorm.

Modderfontein Stream Kelvin silt Alpine Road
Fly ash pollution from Kelvin Power in the Modderfontein Stream September 2014
Photo of black water in the Kelvin stream 7 December 2019
Black water from bottom ash pollution in the Kelvin Stream 7 December 2019

River Health Bio-assessment: Modderfontein Stream has been assessed for river health by SASS methodology since 2007. The sites are Margaret Road Bridge, shown here, and the Sebenza and kelvin Streams at Cecil Awret Road Bridge. The results show the river health to be in the lowest ecological category “Very Poor” at all sites.

Graph showing River Health trend for Modderfontein Stream at Margaret Rd Bridge from 2007 to 2018, with a sharp decline in the last year
River Health Modderfontein Stream at Margaret Rd Bridge 2007 to 2018

Habitat and Wildlife *

Wildlife recorded by camera trap along the Upper Modderfontein Stream in Illiondale, Sebenza and Isandovale includes other signs, and verified by the University of Cape town Animal Demography Unit, includes water mongoose, slender mongoose and greater cane rat. Gerbil burrows and signs of small rodents occur in places.

Further downstream in the Westlake Wetland Duiker, Large Spotted Genet, Blacked Backed Jackal, Water Mongoose, Slender Mongoose and Serval are found. In addition the Modderfontein Reserve itself reports steenbok, reedbuck, duiker, black-backed jackals, Cape clawless otter, Spotted-necked Otter, hedgehogs, and four varieties of mongoose.

Wildlife Gallery – Modderfontein, Illiondale *

Water mongoose at headwaters of Modderfontein Stream December 2019

Illiondale Wetland and streams in Sebenza and Isandovale support water mongoose, slender mongoose, large spotted genet, greater cane rat, gerbils and grassland birds. Numbers have declined in the last few years due to vegetation cutting and removal and water pollution.

The Lower Modderfontein Stream

The course of the Modderfontein Stream continues through the Modderfontein Golf Course where there are a number of small dams, the Modderfontein Estate with the Modderfontein No 1 Dam, and the Modderfontein Reserve where there are two further dams. This was the original property of the AECI dynamite factory. Modderfontein Reserve is a private nature reserve managed by Endangered Wildlife Trust for the owners, and much time and expense has been invested in restoration and eliminating invader plants. There are many wetlands in this area. Finally the stream flows through undeveloped open grassland in Buccleuch to join the Jukskei River.