The guiding principles underlying AECI’s land remediation activities are the protection of human health and the environment and the use of good science, proven concepts and the best available appropriate technologies. Human health and environmental risk assessments are undertaken and these influence subsequent activities. Stakeholder communication in the remediation process is vital and AECI cooperates with regulatory authorities and shares information with interested and affected parties on a regular basis. As part of the Group’s ongoing commitment to environmental best practice, the environmental status and baseline of a site is required to be verified prior to redevelopment.
An enhanced in-situ bioremediation programme has been implemented in response to impacts associated with operations that commenced in the first half of the previous century. This programme involves the creation of bio-barrier zones which degrade contaminants present in the groundwater down gradient of the contamination source areas. The growth of naturally occurring microbes in the bio-barrier zones is enhanced significantly through the injection of a nutrient source (vegetable oil), known as substrate, into the subsurface area. Active monitoring indicates that conditions are becoming increasingly favourable: the substrate is fermenting, microbial growth rates are being enhanced and there is evidence of increased contaminant degradation in most areas. An Intelligent Injection System (IIS) that facilitates continuous injection of substrate and chase water was commissioned during 2018. Benefits of the IIS include enhanced establishment of robust microbial populations within the subsurface and lower long-term operational costs. Also at the UIC, a 4 700m2 portion of land (known as Site 17) that was historically impacted by 70 years of pesticide manufacture was remediated through chemical fixation, stabilisation and capping, with regulatory approval. This site has since been redeveloped and leased to a customer that compresses natural gas.
Soil remediation at Site 17
At the UIC, 15 sites have been assessed over the past two years and assistance has been provided to facilitate redevelopment that is protective of human health and the environment; this approach is aligned with regulatory requirements. Furthermore, the establishment of baseline conditions protects the Group from acquiring liabilities that are rightfully those of another party.
A comprehensive remediation strategy for operations at Modderfontein was developed and presented at the AECI/Authorities Remediation Forum. It was pleasing that the strategy was adopted by these key stakeholders and implementation that commenced in 2018 has continued in 2019, with an update of the action plan appended to the strategy. Although the largest part of Modderfontein remains an active manufacturing site, sizeable areas have been identified for improvement projects to be executed within the framework of AECI’s Remediation Action Plan.
AECI applied for and received remediation authorisations for ImproChem’s sites in Pietermaritzburg and Chloorkop as well as for a site formerly occupied by Vynide (a plastics converter) in Somerset West. At the latter site, demolition of the buildings was completed in March. Remediation work comprised mainly characterisation to ensure that the land could be used safely for residential development. Some relatively small pockets of slightly contaminated soil (arsenic, lead and phthalates) were identified during the course of the year and a total of 340 tonnes of soil was excavated and disposed of at the Vissershok waste management facility. Clean-up of the site was almost complete at year-end. The Department of Environmental Affairs Remediation Order issued for this site was complied with at all time. Remediation of this site was virtually complete by year end.
Vynide plant demolition
Remediation and construction
Redevelopment in progress
At ImproChem’s Pietermaritzburg site, treatability studies indicated that soil at two source areas of contamination could be treated through stalibilisation and fixation technology. Remediation activities were completed without a single (safety or environmental) incident and without production interruptions, despite the confined space in which these projects were undertaken.
Risk assessment prior
to soil sampling
Treatment of contaminated
soil in a mixer
Installation of cut-off drain
between neighbouring properties
Covering of backfilled
materials on rainy days
Curring of treated
soil on site
After remediation (area re-used for
Remediation work at ImproChem’s Chloorkop site is nearing completion. This clean-up was necessitated by the effects of sump leaks over time, resulting in a preferential flow path of contaminants through a driveway. The impact was contained on site. Following treatment, the soil was restored and compacted to engineering requirement and the driveway was reinstated thereafter. A ground water extraction system will be installed to pump and treat residual contamination under the sumps and a monitoring well is re-installed down gradient of the remediated area to measure the effectiveness of the system.
Excavation of driveway - contaminated
at the base of old sumps
Hard surfaced driveway after soil
remediation and backfilling
From 1974, AECI operated the largest coal-based ammonia plant in the world, at Modderfontein. A by-product of the coal gasification process was large quantities of comparatively high calorific-value ash. Serious efforts were made to re-use this in a specially designed and built steam boiler but this proved to be unfeasible with the technology available at the time. As a result, the ash was deposited in slimes dams on site and more than 6 million tonnes had been accumulated by the time the ammonia plant shut down in the late 1990s. Leaving the ash in place was not an attractive proposition because a significant area of land is kept out of productive use and because slimes dams require maintenance and pose potential threats to the environment in the long term.
The ash from these historical gasifier operations at Modderfontein continues to be reclaimed by third parties. It is used by them as an energy source in the manufacture of various types of clay bricks, ranging from clay stock to high quality face bricks.
Extensive engagements with officials from the Department of Environmental Affairs and the Department of Water and Sanitation took place regarding Group sites in the Western Cape, KwaZulu-Natal and Gauteng to reconfirm that the authorities are in agreement with AECI’s approach to land remediation. Extensive engagement with communities neighbouring the Group’s larger sites, with respect to surface and water monitoring and remediation project progress.
Stakeholder engagement session