Amsterdam Bulk Water Supply Scheme - Phase 4

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Project Overview

The Amsterdam Bulk Water Supply Scheme - Phase 4 forms part of a critical municipal infrastructure programme aimed at strengthening long-term water security through major civil and earthworks construction.
As with many bulk water and municipal infrastructure projects in South Africa, construction activities were required to proceed over variable and locally weak subgrade soils, presenting challenges related to load support, constructability, and material efficiency.

To address these challenges, Tensar® Biaxial Geogrid TGSG 20 was deployed as a soil stabilisation and ground improvement solution, enabling improved subgrade performance while optimising the use of imported aggregates.

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Engineering Challenge: Weak Subgrades & Material Efficiency

Bulk water infrastructure projects typically involve:

• Extensive earthworks and platform construction

• Heavy construction traffic and plant movement

• Access roads, working platforms, and structural layers built over marginal soils

On this project, untreated subgrade conditions presented a risk of:

• Excessive rutting and deformation

• Reduced bearing capacity under construction loads

• Increased dependence on thick aggregate layers to achieve stability

Traditional “dig-and-replace” approaches would have resulted in higher aggregate volumes, increased haulage, extended construction timeframes, and elevated project costs.

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Geotechnical Solution: Tensar® Biaxial Geogrid TGSG 20

To mitigate these risks, Tensar® Biaxial Geogrid TGSG 20 was incorporated into the pavement and working platform build-up to form a Mechanically Stabilised Layer (MSL).

Why Tensar TGSG 20

Tensar TGSG 20 is a biaxial polypropylene geogrid engineered to stabilise soils and aggregates by:

• Promoting mechanical interlock between aggregate particles

• Restricting lateral movement under applied loads

• Increasing the effective stiffness of the composite soil-aggregate layer

• Improving load distribution across weaker subgrades

This performance mechanism is well documented by Tensar International for roads, working platforms, access routes, and infrastructure foundations.

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Application & Installation Overview

The geogrid was installed directly over prepared subgrade surfaces, followed by placement and compaction of engineered aggregate layers in accordance with recognised geosynthetics installation practices.

Typical installation methodology included:

1. Subgrade preparation to line and level

2. Placement of Tensar TGSG 20 biaxial geogrid over weak soils

3. Correct overlap and alignment to ensure continuity of reinforcement

4. Placement of aggregate cover layer

5. Compaction to specification to activate interlock

This approach allowed the formation of a stable working platform capable of supporting construction loads while limiting deformation.

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Performance Outcomes

Improved Soil Stability

The use of Tensar TGSG 20 significantly enhanced subgrade performance by creating a reinforced composite layer that improved bearing capacity and resistance to deformation.

Optimised Aggregate Usage

Consistent with Tensar International design guidance, the stabilised layer enabled reduced reliance on excessive aggregate thicknesses when compared to unreinforced construction over weak soils.
This translated into material efficiency benefits without compromising performance.

Tensar International documentation confirms that biaxial geogrids are routinely used to reduce aggregate demand and improve pavement efficiency on weak subgrades; however, achievable reductions are project-specific and design-dependent.

Enhanced Constructability

Stable working platforms improved site trafficability, reduced construction delays, and supported efficient progress of civil works.

Long-Term Infrastructure Performance

Improved load distribution and confinement contribute to the durability and serviceability of infrastructure layers over the design life of the asset.

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Role of Geosynthetics Africa

Geosynthetics Africa supplied Tensar® Biaxial Geogrid TGSG 20 as part of its broader capability to support soil stabilisation, ground improvement, and civil infrastructure projects across South Africa and the African continent.

With extensive experience in geogrids, geomembranes, geotextiles, and engineered geosynthetic systems, Geosynthetics Africa supports projects from design alignment through to material supply and technical support, ensuring solutions are aligned with international best practice.

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Conclusion

This project demonstrates the proven effectiveness of Tensar® Biaxial Geogrid TGSG 20 for soil stabilisation in municipal bulk water infrastructure applications.
By reinforcing weak subgrades and optimising aggregate usage, the geogrid solution delivered improved constructability, material efficiency, and long-term performance.

Geogrid-based stabilisation remains a cost-effective, technically robust solution for civil, municipal, mining, and infrastructure projects across Southern Africa.

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Products Supplied

 📄 Download Full Case Study (PDF)

Scope: Potable water Lining of leaking concrete water reservoir

Location: Rustenburg, North West Province, South Africa

Client: Rustenburg Municipality

Project: Concrete Potable Water Reservoir Tank Lining
Installer & Supplier: Geosynthetics Africa (Pty) Ltd
Completion: On Time & Within Budget

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The Problem: Aging Concrete and Water Contamination Risks

Municipalities across South Africa are facing a critical need to extend the lifespan of aging infrastructure while maintaining the integrity of potable water supply systems. Rustenburg Municipality faced similar challenges with a concrete reservoir tank that had begun showing signs of deterioration - including micro-cracking, water seepage, and increased risk of contamination. Traditional waterproofing methods were proving unsustainable, and compliance with potable water safety standards became a top priority.

The tank needed a permanent, hygienic, and certified lining solution that could withstand the internal hydraulic pressure, bond securely to vertical concrete walls, and meet South African drinking water regulations.

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The Solution: Certified PVC Lining System by Geosynthetics Africa

Geosynthetics Africa was selected as the preferred contractor due to our unmatched technical expertise, rapid deployment capacity, and proven track record in potable water containment systems across Africa. We designed and implemented a full lining system that delivered both long-term performance and compliance with SANS potable water standards.

Our approach ensured:

• • Full tank encapsulation using a certified potable water liner

• • Protection of the liner from concrete abrasion

• • Reinforcement on vertical surfaces for mechanical security

• • Dual sealing through glue application and thermal welding

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Scope of Work Included:

• • Surface preparation of internal concrete walls and floor

• • Installation of Mirafi Liner Protection Geotextile to prevent abrasion and punctures

• • Custom-fit lining using PVC 720gsm Potable Water Grade Liner

• • Application of Vertical Concrete Wall Reinforcement Anchors to secure vertical liner placement

• • Use of Geosynthetics Africa’s proprietary PVC Glue for high bond strength adhesion

• • Hot Air Welding and Testing of seams to ensure leak-proof connections

• • Final QA/QC inspections in line with municipal and SANS 1731 standards

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Products Used on This Project

Product	Description
PVC 720gsm Potable Water Grade Liner	Certified for direct contact with drinking water; UV-stabilised and chemically inert
Mirafi 400gsm Geotextile Underlay	High-strength, needle-punched protection layer beneath the liner to prevent mechanical damage
Vertical Wall Liner Reinforcement System	Secure anchoring detail for vertical surfaces to resist delamination and liner displacement
Geosynthetics Africa’s PVC Glue	Engineered for water tank applications with enhanced adhesion properties on concrete substrates
Heat Welding Equipment	Precision thermal welding to create seamless, leak-proof joints across liner panels

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Why choose Geosynthetics South Africa?

Geosynthetics Africa (Pty) Ltd has become the go-to partner for reservoir lining and geomembrane systems across Southern, Central, East, and West Africa. With experience spanning mining, municipal infrastructure, agriculture, and industrial containment, we are Africa’s leading supplier and installer of high-performance water containment systems.

We don’t just install liners - we provide engineered containment solutions, backed by decades of geosynthetics expertise, quality assurance, and after-sales support.

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Looking to Line Your Water Tank or Reservoir?

Whether it’s a concrete tank refurbishment, dam lining, or pond sealing - Geosynthetics Africa is your first choice across Africa.

📩 Email: sales@geosynthetics.co.za
🌍 Visit: www.geosynthetics.co.za
📍 Locations: South Africa | Ghana | Tanzania | Namibia | Ivory Coast | Mozambique and more