A greenbelt area is formed by the Rietvlei Game Reserve and the Historic Doornkloof Farm that encompasses the Olifantspruit and Hennops River valleys that lead into the Centurion Lake complex. The portions of the Farm Doornkloof that are located outside of the Centurion Town Council area come under the jurisdiction of the Eastern Services Council.

This area, located east of Centurion, is mostly a rural farming region with a water bearing dolomitic underlay. The area has been the home of the Smuts, van der Byl and Cullinan families for many generations and is of great historic value, with many fine old homes. The area, and the adjacent area, continues to support many new developments including the elite St George Conference Hotel, the Cornwall Hill Estate residential development as well as the Twin Rivers, Pheasant Hill Estate and the Irene Glen Estate residential developments. The Highway 21 Commercial Estate is now underway and plans for a number of other prestigious developments are under consideration.

The area has remained basically rural with concentrated residential areas becoming established in the northern segments and a number of concentrated commercial farming and 'rural' high technology / industrial activities are well established in the south-eastern sector. The large Eskom electrical distribution station Apollo is located in this south-eastern segment immediately south of the Rietvlei game reserve. The Salbu Experimental Radio Station is located between the R21 Freeway and the south-eastern boundary of the Rietvlei game reserve. The NuLaid, Valvita, Valcon, Civilcon and WKM offices together with their processing, distribution and maintenance depots are located to the south of the Salbu property. Whilst further commercial developments would be welcomed in this south-eastern segment, pollutant generating industries should not be encouraged as they would have a negative impact on the present activities in the area.

Both observations, and a number of scientific investigations, confirm the prevalence of intense atmospheric inversion layers in the Doornkloof Area. The area in question encompasses the Rietvlei Game Reserve, the Hennops River Valley, the Olifantspruit Valley and the area up to the east/west running "Apollo Road. Of particular concern is smoke and noise generating industries as both noise and smoke become 'trapped' under atmospheric inversion layer conditions and can have a serious negative impact of surrounding area. Atmospheric inversion leads to heavy winter night mists settling over the associated river valleys and dispersing into the surrounding residential areas shortly after sunset. Atmospheric sulphuric acid, formed from sulphur dioxide released from stationary or idling diesel engines and / or the burning of coal, combines with mist to form a smog comprising extremely small suspended particulates of sulphuric acid. These particulates not only cause eye irritation, but are most dangerous because they can penetrate deeply into human lungs. Acute effects include an increased mortality rate, especially among persons suffering from respiratory and coronary ailments. Statistical studies indicate that smog is a contributor to malignancies of many types. In addition, this smog can cause severe damage to many types of vegetation.

The area is characterised by heavy deposits of water bearing dolomites. Activities such as blasting, the bulk storage of fuel and / or the disposal of commercial sewage in the area would have a detrimental affect on the water and deep boreholes in the area. Dust and smoke particles, resulting from heavy industrial or mining operations would have a negative impact on the Apollo installation and the power line corridors radiating from this installation. In particular the DC apparatus at Apollo would attract dust particles onto the insulator strings and serious flashover could occur. Spark noise radiation from dusty insulators would cause electromagnetic noise radiation that would have a serious negative impact on the Salbu Experimental Radio Station located to the north-west of Apollo.