Mitchell’s Plain Hospital

Client: Western Cape Government, Department of Transport and Public Works

Completed: 2014

The Western Cape Government Department of Transport and Public Works’ Mitchells Plain Hospital is located adjacent to a nature reserve on the Cape Flats, a low-lying landscape.

The site is highly exposed to the prevailing winter and summer winds and is perched above a high water table with the Cape Flats Aquifer below. Remnants of the endangered Cape Flats Dune Strandveld covered the site and connected it to an adjacent biodiversity corridor that together, created a continuous system linking to the False Bay coast.

The primary design informant to the design is stormwater management. Consistent with water sensitive design, it is designed to recharge the aquifer via a system of swales, detention ponds and planting beds, with every opportunity taken to create permeable surfaces, including those that by function necessitate hardness such as pathways that are designed as loose calcrete pathways.

This approach is consistent with water sensitive design, but represents a radical departure from the engineer’s design which followed the traditional method of channelling stormwater into hard infrastructure pipes for disposal offsite.

Materials such as calcrete that was excavated during the construction of the hospital were incorporated in the hard landscaping and in the preparation of the soft landscape. It was crushed and used to line the drainage channels and swales to provide a porous, spongy drainage layer to filter and store stormwater. The stored water is ideally located for plants that draw on it over time eliminating the need for irrigation once established.

The volume of the swales and ponds, though calculated by engineers are integrated into the natural landscape forms. These basins assist to manage stormwater by holding it temporarily in detention ponds or in swales for infiltration to the storage layer or aquifer. They serve to prevent flooding and reduce runoff into the stormwater system thereby fulfilling an important role traditionally filled by hard infrastructure.

The swales are located in the large parking areas and in the building’s interstitial spaces created by the “wings”. In both areas they serve an infrastructure and spatial function. Whilst they provide visually interesting spaces for those using the parking area or in the hospital, they also break the larger area into smaller “rooms” that add as sense of scale to an otherwise large landscape.

Those swales closer to the building are used to collect and store the rainwater discharged from the roofs via downpipes to the ground surface below, whilst those located in parking areas rely on stormwater drained from the hard landscaping.

The rainwater from the roofs is channelled across the ground surface in calcrete-shaped “fins” into calcrete-lined stomwater channels towards planting beds and trees where it can be used immediately and also stored for future use, utilising a similar methodology to the swale. Because the design team had not implemented the system before, getting it right required experimentation and collaboration between the TKLA landscape Architecture team and the engineer, the success of which is apparent across the site.

Larger calcrete boulders were added to the landscape to add texture and scale to the swales and ponds and as bollards along the roadway edges. Whilst providing a protective edge, they also create cooler micro habitats where moisture can be trapped thereby enabling plant growth.

The plant material used in the landscape is grown from seeds and cuttings taken from the adjacent nature reserve as required by the Environmental Impact Assessment Record of Decision. Small plants were used throughout the project planted at a high density to offset the possible attrition rate. Fortunately most plants survived and the dense mat created acts as a kind of “growing mulch”. Over and above this benefit are those associated with the proliferation of endemic plant material that is waterwise and that builds the biodiversity of the area. It furthermore increases the footprint of the endangered Cape Flats Dune Strandveld and creates a habitat for endemic insects, reptiles, birds and mammals.

The soft landscape was established within the first year using borehole water via an automated irrigation system that by year three would be eliminated. This methodology has proven successful and there has been no irrigation for the past three years, despite the drought.

The success of the Mitchell’s Plain Hospital is manifold. Not only does it create an attractive, diverse landscape but it also integrates the landscape with the water cycle. Over and above the positive outcomes already discussed, the water sensitive design approach reprented a significant cost saving to the construction budget of R4.5 million and further savings were accumulated through the elimination of stormwater infrastructure upgrades downstream of the development. In addition, there are cost savings from reduced municipal water usage that have not been quantified, but will no doubt be substantial for the size of the facility.

This project is an exemplar of how designing with the natural water cycle as a system creates a sustainable landscape. It is not only an important, functional part of the hospital’s infrastructure, but it also a “healing landscape” that compliments and enhances the hospital’s work.

Mosaics by Lovell Friedmann