Environmental contamination has been an increasing concern over the past few decades as it poses a risk to both human health and the environment. Two major categories of environmental contamination are Water and Soil pollutants, which are often derived from anthropogenic sources such as household waste, manufacturing and agricultural wastes, fertilizers used by farmers, seepage from landfill, radioactive materials, and the rupture of underground storage tanks. To evaluate the potential and extent of environmental contamination, contamination assessments are carried out.
What is a contamination assessment?
Contamination assessments are used to evaluate the potential for a pollution linkage and consider whether actions are required to manage or mitigate the risk. This incorporates a number of strategies and methods to determine the nature or extent of contamination on or offsite, including the source of contamination and the potential risk posed to human and environmental health.
Why is it important to do a contamination assessment?
Soil and waste contamination can become a serious health risk to humans as it can result in acute toxicity, mutagenesis, carcinogenesis, and teratogenesis for humans and other organisms. Additionally, contamination can result in pollution of drinking water sources and can cause reduced soil fertility, crop yield and vegetation.
Illegal discharge or disposal of waste that results in contaminated land can cause significant regulatory, financial and reputation risks e.g., receiving a directive from the relevant national or provincial government which is accompanied by a fine and remediation activities.
Types of contamination assessments
Previous contamination assessments conducted by Umvoto include:
- Soil and Water Quality Assessments; and
- Waste Classification and Assessments.
Soil Screening and Monitoring
Soil testing and monitoring is a means to assess contamination by substances with the potential to have an adverse effect on the soil, surface water or groundwater. Soil testing identifies contaminants in the soil and provides an indication of whether the specific material can be re-used in site re-development. Soil assessments are governed by South African legislation whereby the South African Framework for the Management of Contaminated Land developed in line with NEM:WA (Act No. 59 of 2008) outlines the methodology for the screening of potentially contaminated sites to provide a risk-based decision support assessment protocol. In addition, the Department of Environmental Affairs has gazetted the GN 331: National Norms and Standards for the Remediation of Contaminated Land and Soil Quality (02 May 2014). GN 331 provides Soil Screening Values (SSVs), a tiered system for priority soil contaminants, to facilitate the sensitivity of the relevant receptor which may be subject to exposure. These are defined as:
- SSV1: Protective of both human health and aquatic ecosystem health, and not land-use specific; and
- SSV2: Protective of human health where protection of water resources is not an applicable pathway for consideration and are land-use specific: including informal residential, standard residential and commercial/industrial land uses.
Waste classification
Waste classification allows for the identification of waste types for the separation of materials, which may need to be sent off to different landfill types based on risk. Waste assessments and classifications are guided by various South African legislation including:
- NEM:WA (Act No. 59 of 2008) Government Notices (23 August 2013):
- R.634 Waste classification and Management Regulations;
- R.635 National norms and standards for the assessment of waste for landfill disposal; and
- R.636 National norms and standards for disposal of waste to landfill.
- NEM:WA Act No. 59 of 2008 GN R.715 Regulations Regarding the Exclusion of a Waste Stream or a Portion of a Waste Stream from the Definition of Waste (18 July 2018); and
- NEM:WA Act No. 59 of 2008 GN 85 of 2020, Notice Indicating the Exclusion of Certain Waste Streams or Portions of Waste Streams from the Definition of Waste for Beneficial Use (03 February 2020).
Modelling
Numerical groundwater transport models are important tools when undertaking contamination assessments as they can aid in predicting the temporal and spatial migration of the contaminant plume. This allows for the determination of contaminant impacts (high, medium or low) based on the current and future plume migration and contaminant dispersion. Understanding the behaviour of the contaminant migration allows for effective remedial design and implementation, which are important tools when undertaking contamination assessments as they can predict the temporal and spatial migration of the contaminant plume.
Numerical groundwater models are capable of making predictions about the transport of contaminants in non-homogenous and anisotropic media under stress conditions including well abstractions, well injections, and drought etc. Umvoto utilises sophisticated numerical models (finite difference and/or finite element) models using various software packages (Feflow and Groundwater Vistas) to solve both flow and solute transport differential equations. Solute/contaminant transport models are based on the convective-dispersive (or advective-dispersive) solute transport theory (Fick’s first law). In addition, the migration mechanisms of solutes/contaminants are subject to various physical processes such as: advection, dispersion, diffusion, decay and degradation. Understanding the physical and chemical properties of a groundwater system (aquifer and solute) will enable the prediction of groundwater flow patterns and contaminant concentrations both spatially and temporally.
If you would like to learn more about contamination assessments or determine the extent of a proposed / existing contaminant plume, please feel free to contact us on amazi@umvoto.com or 021 709 6700.
