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Listing cover image

Cape Flats Aquifer Recharge Plant

  • Project Year
    2026

Project Type

  • Architecturally Exposed Steel
  • Industrial

Submitting Company (Non-SAISC Member)

BlueScope Steel Southern Africa (Pty) Ltd

Location

Project Team Interview Case Study

Project Overview

The Cape Flats Managed Aquifer Recharge (MAR) Plant is a pioneering water treatment facility located within the False Bay Nature Reserve, Cape Town. Developed in response to the city’s water crisis, the plant purifies treated effluent to potable standards and recharges the Cape Flats Aquifer, securing a sustainable future water supply. Designed by SALT Architects (architectural envelope) and Water & Wastewater Engineering (process design), the R341 million facility comprises four linear gravity-fed filtration buildings cascading along a slope, plus an administrative building. The structural system uses a concrete frame with steel roof rafters spanning column-free over open filtration tanks — enabling large clear spans at low pitch, and accommodating gantry cranes for equipment maintenance. Roofing in Klip-Tite 700 Colorbond Ultra (AZ200) was selected for its concealed-fix wind resistance and exceptional coastal corrosion durability. With 138.54 t of structural steelwork and approximately 27 t of cladding covering 6,700 m², steel was the critical material enabling the project’s complex geometry, rapid construction, and longevity in a highly corrosive coastal environment.

Steel Profiles Used

  • Date of Steelwork Completion
    2024-04-01
  • Tonnage
    139
  • Hot Rolled Structural Sections
    Steel Rafters
  • Plates
    Base Plates
  • Grating Hand Railing and Expanded Metal
    Hand Railings

Metal Cladding and Roofing Overview

  • Date of Cladding Completion
    2024-12-01
  • Material Used
    Colorbond Ultra AZ200
  • Cladding Profile
    Klip-Tite 700
  • Cladding Tonnage
    27
  • Cladding Area Coverage (m2)
    6700

Project Details

All structural steelwork was fabricated and pre-welded off-site at Madden Steel Projects’ workshop. Steel members were pre-assembled into complete structural bays — including rafters and associated bracings — to the maximum size permissible for road transport. The City of Cape Town enforced strict quality control throughout: welding inspections were conducted both in the workshop and again on site by resident engineers. Coating thicknesses were measured in the workshop and verified on site. The paint specification was a duplex system: hot-dip galvanizing followed by a two-part epoxy primer applied in the controlled workshop environment. Where any defects were identified, elements were returned to the workshop for rectification; no fabrication or coating work was carried out on site. This rigorous off-site approach ensured consistent quality and protected against the highly corrosive coastal conditions at the False Bay location.
Structural bays were pre-assembled on the ground at site, then lifted and positioned using a crawler crane — chosen due to the soft, sandy ground conditions that made conventional wheeled cranes impractical. Once positioned, steel rafters were chemically anchored and bolted to concrete upstand beams using moment-resisting base plate connections. Angle bracing in the plane of the roof provided lateral stability. The roof was designed in discrete bays with movement joints, allowing individual bays to be removed to install large mechanical and electrical equipment during the second contract phase. This modular erection strategy enabled the building envelope to be closed quickly, allowing interior work to proceed in parallel. Space constraints and multiple concurrent trades required careful demarcation of working areas on site, but no insurmountable technical challenges were encountered.
The primary environmental challenge was the highly corrosive coastal setting — strong southeasterly winds, shifting dune sands, and salt-laden air. This was addressed through rigorous material specification: Colorbond Ultra AZ200 cladding, hot-dip galvanizing plus duplex epoxy paint system on steelwork, and durable face brick and concrete for the building envelope. A key architectural challenge was admitting natural light to create humane operator workspaces while preventing algae growth in the open filtration tanks. The solution was a “gilled” facade with south-facing windows providing indirect light, eliminating direct sunlight. Structurally, achieving wide column-free spans at low pitch over the filtration tanks was solved by using steel rafters rather than deeper beam elements, minimising structural depth while providing sufficient clearance for gantry cranes. Soft ground conditions during erection required a crawler crane instead of standard overland cranes. The two-contract procurement structure (civil then M&E) was addressed by designing removable roof bays for equipment installation.

Benefits of Steel in this Application

Steel was selected for the Cape Flats MAR Plant for several critical reasons. Its high strength-to-weight ratio allowed wide-span, column-free roof structures over the filtration tanks — essential for the operational gantry cranes and process equipment. The relatively shallow, asymmetric roof geometry (achieving low pitch with large spans) was only practically achievable in steel. The Klip-Tite 700 concealed-fix profile provided superior wind uplift resistance against the site’s severe southeasterly winds, while Colorbond Ultra with AZ200 coating delivers long-term corrosion protection in the highly aggressive coastal environment — reducing maintenance frequency and lifecycle costs. Steel also enabled the roof to be fabricated off-site in bays, lifted into place by crane, and temporarily removed to install large mechanical-electrical equipment, significantly improving construction programming. The two-colour interior steel palette (green and red structure with complementary handrails) elevated the plant aesthetically, creating dignified, inspiring workspaces for operators. XPS insulation incorporated within the roofing system further improved thermal performance, reducing reliance on air conditioning.

Testimonials

“The outcome of the building is really something exceptional that achieved the client’s requirements of being a showcase building on international standards — especially for city utilities — showing that the city is really investing in all regards, prioritising excellence and a truly progressive stance towards development and advancements in all areas.” — Gustav Roberts, Architect, SALT Architects