Study areas – approach & descriptions

Case studies of groundwater contamination to test & refine assessment methods are an integral part of the projectTwo areas have been identified and access to historical data arranged – Secunda (Sasol) & the Cape Flats aquifer (iThemba labs nuclear facility, Coastal Park & Faure landfills)Theory & approach:

Case studies – theoryUnsaturated zone vulnerability

The ease with which groundwater may become contaminated – determined by the overlying strata & the contaminantThe relative predominance of preferential flow determines the relative importance of chemical buffering.

Saturated zone vulnerabilityThe spatial extent of contaminationThe lifetime of contaminationFactors: flow type, rate, chemical buffering & decomposition, recharge

Case studies – approachCareful analysis of the data to identify the weaknesses of the theoryThe first round of an iterative approach to refining vulnerability assessmentExamples

Observing the differences in vulnerability of the same unsaturated zone & aquifer to different contaminants (e.g. waste disposal sites, radio-isotopes)Observing the differences in vulnerability of different unsaturated zone profiles & aquifers to the same or similar contaminants, at the same site (e.g. Secunda)

Case studies – the roles of different institutions

US/ISCW – special purpose classification system to estimate the attenuation capacities of soils for contaminants – to be applied at the study areas

UWC – testing & refining approaches & models of contaminant transport through the unsaturated zone, with particular focus on preferential flow

CSIR – geochemical models to help identify likely chemical attenuation processes in the saturated zone (possibly also the unsaturated zone), and test the usefulness of groundwater flow and transport modellingfor assessing saturated zone vulnerability

Ithemba Labs – Location Map

IthembaLab

IthembaLab

Ithemba Labs – Site Photograph

iThemba Labs – Selection CriteriaImportant industrial/urban areaImportant groundwater contaminant source

Existing data setsThe site allows joint efforts and comparison of methodsApplicable to SA conditionsSupport & co-operation of managementBenefit to local communityRange of vulnerabilityFuture research value

Logistics and effort

YesPotentially high-profile source –radioactive contaminants and good groundwater tracers for study purposes. Special case of metal and salt contamination.AvailableYes

YesYesYesExtreme case of high vulnerabilityPotential for testing applicability of metal isotopes as groundwater tracers, looking at differential mobility of metals in Cape Flats aquifer and recharge studies.Minimal – site is close to most project team members

iThemba Labs – Data Availability

ClimateSoil descriptionsHydrogeologyContaminant typesContaminant loading historyGroundwater monitoring and sampling data

AvailableAvailableAvailableAvailableAvailable

Some data available. Further data to become available

Coastal Park Waste Disposal Site

Coastal Park Waste Disposal Site

Coastal Park - selection criteriaImportant industrial/urban area YesImportant groundwater contaminant source Well-studied site with a wealth of good data and an

important landfill site for the Cape Town metropolitan area. Of concern is the possible migration of contaminated groundwater towards the Zeekoeivlei Canal which runs into False Bay.

Existing data sets: GIS, soils, geology, groundwater & contaminants AvailableThe site allows joint efforts and comparison of methods YesApplicable to SA conditions YesSupport & co-operation of management YesBenefit to local community YesRange of vulnerability Extreme case of high vulnerabilityFuture research value Probably the most intensively studied landfill in terms of

groundwater in SA – this project can build on existing work and hopefully contribute new insights

Logistics and effort Minimal – site is close to most project team members & theAbundance of historical data means that the resources of this project can be directed to interpretation of existing data

Data availabilityClimate AvailableSoil descriptions AvailableHydrogeology AvailableContaminant types AvailableContaminant loading history AvailableGroundwater monitoring & sampling data Data from 1985

to present available, including borehole logs and numerous specialist studies.

Faure Waste Disposal Site

Faure Waste Disposal Site

Faure - selection criteriaImportant industrial/urban area YesImportant groundwater contaminant source The site needs to be closed urgently, so an improved

understanding of contaminant hydrogeology is important.Existing data sets: GIS, soils, geology, groundwater & contaminants AvailableThe site allows joint efforts and comparison of methods YesApplicable to SA conditions YesSupport & co-operation of management YesBenefit to local community YesRange of vulnerability Extreme case of high vulnerabilityFuture research value Useful case study of the comparative vulnerability of the upper

primary and deeper (fractured) aquifer, and close (< 1 km) to the iThemba labs site which makes it possible to compare the vulnerability of the same aquifer to different contaminant types.

Logistics and effort Minimal – site is close to most project team members’ institutions

Data availabilityClimate AvailableSoil descriptions AvailableHydrogeology AvailableContaminant types AvailableContaminant loading history AvailableGroundwater monitoring & sampling data 1990 to present &

several specialist studies.