Which Pretoria and Centurion Suburbs Sit on Dolomite? What It Means for Drilling

Dolomite is one of those geological facts that Centurion and southern Pretoria homeowners encounter sooner or later — usually when they apply for building plans or start asking about boreholes. The rock itself is not dangerous, but its behaviour under certain conditions is. Water dissolves dolomite over time, creating voids that can collapse without warning, a process called sinkhole or crown-hole formation. Understanding which areas carry this risk, and what it means in practice for a borehole project, is straightforward once you know where to look.

Which suburbs are on dolomitic land?

The dolomite belt runs roughly along the Magaliesberg geological formation, cutting through the southern and western parts of Tshwane. In practical terms for homeowners, the suburbs most commonly associated with dolomite include Irene, Eldoraigne, Lyttelton Manor, Hennopspark, Centurion CBD surrounds, Doringkloof and parts of Highveld. Portions of Pretoria West, Pretoria North and the southern Pretoria suburbs can also fall within or adjacent to dolomitic areas, though the risk classification varies erf by erf.

This is the critical point: dolomite risk is not uniform across a suburb. Two neighbouring properties can carry different risk classifications. The Council for Geoscience (Geoscience South Africa) maintains national dolomite hazard maps, and Tshwane Municipality holds local dolomite risk reports that inform building plan approvals. Neither WaterQuotes nor any driller can tell you your erf’s status from a map alone — you need to check the official records.

How to check your erf’s dolomite status

Start with two sources:

1. Council for Geoscience (www.geoscience.org.za) — The national geoscience body publishes dolomite hazard maps and can be approached for site-specific information. Their records cover the geological classification of land across South Africa.
2. City of Tshwane (www.tshwane.gov.za) — The municipality holds dolomite risk reports used in building plan assessments. The town planning or building development management department is your contact point. When you apply for building or borehole permits, the municipality will check these records as part of the approval process.

Your title deed and the Surveyor-General’s records may also reference dolomite conditions. A conveyancer or property lawyer familiar with the area can help interpret what is attached to your title.

What dolomite risk classes actually mean

South African dolomite risk is classified into classes D1 through D4 (lowest to highest inherent hazard), with a separate category for areas where active sinkhole or subsidence has occurred. The class assigned to your erf determines what engineering and geotechnical requirements apply to any construction or excavation on the site — including the drilling of a borehole.

In practical terms:

Risk class	General implication for borehole drilling
D1	Lower precaution level; standard dolomite protocols still apply
D2	Site-specific geotechnical input required before drilling
D3	Comprehensive risk assessment; design adaptations likely needed
D4	Highly restricted; specialist engineering required; some sites effectively not viable
Active features	Drilling typically not permitted until specialist assessment clears the site

These implications are general guidance. A registered geotechnical engineer or engineering geologist must make the site-specific determination for your erf. Do not rely on a neighbour’s class as a proxy for your own.

What it means for borehole drilling specifically

Boreholes introduce water into the ground and, in some cases, change groundwater flow patterns. On dolomitic land, excess water infiltration around the borehole casing or a poorly sealed annulus can accelerate dissolution of the rock, increasing sinkhole risk. For this reason, dolomite-area drilling carries specific obligations beyond standard practice.

Drillers operating in these suburbs should:

• Obtain the relevant municipal and geotechnical approvals before mobilising a rig
• Seal the borehole annulus (the gap between the casing and the borehole wall) properly to prevent surface water ingress
• Avoid unnecessary dewatering or large drawdowns that could destabilise voids
• Provide a completion report that documents casing depth, grouting and geological observations during drilling

Our article on drilling on dolomite: the risks and requirements covers the technical and regulatory detail in full, and is worth reading before you approach any driller. For a broader overview of what borehole projects in this part of Gauteng involve, the Centurion borehole drilling guide and the Pretoria borehole drilling overview provide useful context.

The Irene borehole drilling page is specifically relevant to homeowners in and around Irene, where dolomite is a common site condition and local groundwater yields vary considerably.

If you are on dolomitic land, getting quotes from drillers who have documented experience in your suburb matters more than anywhere else. Compare 3 free quotes — vetted installers, no obligation.

Costs: what dolomite adds to a borehole project

Dolomite compliance adds cost. As a Johannesburg reference point (which is broadly applicable to neighbouring Tshwane for planning purposes), complete borehole systems typically run R40,000–R150,000, with most projects falling between R60,000 and R100,000. On dolomitic land, a geotechnical risk assessment — which is a separate professional fee — and enhanced casing and grouting requirements can add meaningfully to that range. Get this confirmed in writing from any installer you engage, because the compliance scope varies by risk class and individual site.

Ask every driller you approach to confirm in writing whether they:

• Have experience drilling in your specific suburb
• Will arrange or assist with the geotechnical sign-off
• Include compliant casing and annulus sealing in their quote

A driller who dismisses the dolomite question or says it is not a concern in your area is a red flag.

Water quality on dolomitic ground

Dolomite geology influences groundwater chemistry. Water drawn from boreholes in these areas can have elevated hardness (calcium and magnesium carbonate), and occasionally higher fluoride levels, depending on the specific formation. None of this is predictable without testing. SANS 241 (2024 edition) is the South African standard for drinking water quality, and any borehole water intended for drinking or food preparation should be tested against it by an accredited laboratory before use. The principle here is straightforward: test first, treat second. A qualified water treatment professional can recommend a treatment approach once you have actual test results in hand.

Dolomite compliance, casing specs and water testing requirements differ from driller to driller — comparing quotes is the quickest way to see who takes it seriously. Get 3 no-obligation quotes from vetted installers and ask each one directly.

Before you commission a driller: a short checklist

For homeowners in Centurion and Pretoria suburbs where dolomite is a possibility, run through these steps before signing anything:

1. Check your erf status — contact the Council for Geoscience and the City of Tshwane to establish your risk class
2. Confirm permit requirements — ask Tshwane’s building development management office what approvals a borehole requires on your property
3. Require dolomite-specific experience — ask each driller for examples of completed work in your risk class or suburb (without expecting guarantees of outcomes)
4. Get a geotechnical assessment if required — your risk class or municipality may mandate this; budget for it separately
5. Insist on a full sealed casing specification — ask for the grouting method and depth in the written quote
6. Plan for water testing — before the water goes into your home for drinking, get a SANS 241 panel test done

Dolomite is a manageable constraint, not an automatic barrier. The suburbs affected by it have thousands of functioning boreholes. The difference between a problem-free installation and a costly one is usually the groundwork done before the drill rig arrives.