Conventional Sustainable

FuelLabourExpertise Plant & Equipment Construction Materials

Architect - Engineer: Collis & AssociatesArchitects:

Structural Engineers: Civil/Geotechnical Engineers:

Contractors:

Collis/Walton/Irvine/McGiven/McDonald/de Bruyn/Curtis Collis/O’Neill Williams/Henry Fagan &Partners/van Gysen Collis/Du Plessis (Kantey&Templer)/Prof Alexander UCT Botes Kennedy & Manyana /Agmac Construction/ Consulmet

The Team

Koidu Diamond MineA sustainably built mine in Sierra Leone

Mining waste was used to make bricks & concrete for new buildings & roads

We used the mine as a catalyst for social transformation and economic growth

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Recreational Complex Lounge with mine housing on Monkey Hill behind.Truss detail of Roof Monitor bringing light and ventilation

Incinerator showing use of the expressed concrete structure frame

One of 10 managers houses built on Monkey Hill

East-west oriented Emulsion store. So cool that the contractors used it for recreation until handover

Main Dining Room of Recreation complex with rhythmic hammer beam trusses

Managers’ quarters entrance stoeps. After mine closure these houses will become a village.

Monkey Hill managers’ houses and club house under construction in the foreground

Mining is an extractive industry and the pressure is to mine as soon as possible. Supporting infrastructure is erected fast with little thought given to the environment, the life cycle of buildings or the community affected. Mining is an economic anomaly which functions for a period and is abandoned, leaving empty skeletons on scarred land. With this mine, the aim was to radically rethink this entire process.

The site is near the Guinean border, about 300km from Freetown, the only port for importing materials. After years of poor governing and civil war, Sierra Leone’s infrastructure is rudimentary and in a state of disrepair, with manufacturing and the availability of building materials limited. Almost everything, including diesel for generators would have to be trucked to site over shocking roads.

The project was to design and build the mine, including the processing plant and support buildings. The scope was limited to the buildings: a variety of scales and typologies from small switchrooms and large workshops capable of servicing 80-tonne machines to a clinic, houses and mine community facilities.

At the time of appointment, a number of decisions regarding the mine buildings had been made. The client wanted to maximise the materials and expertise coming from RSA. The client envisaged that

most components would be manufactured in RSA, shipped to Freetown then trucked 12-hours to the site & assembled by South Africans.

The main contractor was appointed on an area & rate per m² for each building based on steel, portal-framed structures and profiled sheet cladding with few windows. They would generally be very deep, wide buildings with no regard to climate, orientation or natural lighting. The planning was at best functional with little concern for the levels of comfort for occupants.

Following resource mapping, an alternative construction technology was proposed. This would

minimise the material importation, maximise local materials and labour, recycling mine waste wherever possible. UCT Engineering labs analysed the Kimberlite rock as potential building material which was suitable for aggregate in concrete, bricks, blocks, tiles and as base material for roads and building platforms.

The proposed imported steel portal-framed building plans were redesigned to be regionally specific appropriate buildings with a possibility for longevity. This included omitting steel. Local buildings, although limited in scale, were studied to understand a vernacular response to climate; hot tropical, heavy rains and a dry, cool period when the Harmattan wind blows across the Sahara from the northwest.

Our alternative building proposal was accepted by the client for being more economical. Additionally, well thought through sustainable solutions also reduced construction time, pressure and significantly reduced reliance on the global supply network; the implications for sustainability being far-reaching.

Thirty four building types were designed in 12 months and the building process took eighteen months. With this speed and the remoteness of the site, a number of design constraints and informants were necessary.

1. Minimise engineering complexity employing a structural grid. This reduced cost and increased ease and speed of construction. A masonry structural grid was employed on all smaller buildings and a reinforced concrete/block-work frame was used for the larger ones. RC pre-cast tilt-up 12m columns were used for the large workshop.

2. For ease and speed of construction, we adopted a repeated family of details and limited the material palette – bagged bricks/blocks, un-plastered RC columns and beams & timber trusses.

Above: Artisanal miners sell their diamonds to local traders.

Above: Money Flow map. Influence of the mine on the Sierra Leone economy.

Left: Sierra Leone is situated in West Africa. The country has a tropical climate, with a diverse environment ranging from savannah to rainforests. It has 6 million inhabitants and a violent history of colonisation, miliatery coups and dictatorships.

Above: Resource Flow map. Construction technology from the mine infrustructure is a lever for further social, economic and environmental growth in Sierra Leonne.

Right, from top: 1: There is limited protection of the remaining forests, so we avoided any use of local timber; 2: Local skills informed design of timber windows and trusses. We upskilled locals to make trusses; 3: No economic opportunities means many people crush granite aggregate by hand, a backbreaking task, something we avoided; 4: Artisanal mining in rich alluvial and once ‘blood diamond’ sands; 5 & 6: Mosque near Koidu and an old trading store on the road to Freetown. We looked at successful vernacular roof technologies to inform our design.

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Below: Much of the region we were working in was covered in primary tropical rain forest, straight from “Heart of Darkness”

Conventional Sustainable

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Above: Plan of courtyard clinic at the mines entrance to serve the local community and mine. In the future it is designed to extend into a hospital.

Eventually the mine will become a village

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We researched tropical passive climate control. The best buildings in this climate mimic the cooling system of large canopy trees.

Doors and windows on the managers’ buildings are made from sustainably managed pine and built using simple technology. Windows have internal shutters for night shift workers.

3. Labour and materials sourced locally redistributed resources back into Sierra Leone’s economy.

4. Maximise use of treated pine for roofs and windows. Aluminium windows and doors were changed to windows made from sustainably grown pine. All buildings to be oriented east-west with deep, double-pitched, vernacular roof overhangs shading buildings from the sun and rain.

Natural ventilation and light were maximised through narrow, single stacked buildings with perimeter circulation. Roof monitors on the large span roofs circulated cool air and brought natural daylighting. Indoor/outdoor living was facilitated using enclosed courtyards and shaded verandahs over entrances and living areas.

The client defined the position of most buildings according to mining process and functional requirements. We fine-tuned the positions in relation to roads and the orientation for solar thermal control. Housing and recreation employees were sited on Monkey Hill, with views over the countryside, removing the residential component from the 24-hour noisy mine activities.

Mining follows a strict hierarchy which was flattened by creating housing and community facilities which supported interaction. This was achieved deliberately creating uniformity across the hierarchical accommodation types. The material finishes for all houses were the same.

The lounges and eating spaces were scaled to allow general access to all employees and all buildings were designed so that, after the eventual closure of the mine, they would continue to be functional for the local community.

Resource Flow as found:

Resource Flow achieved:

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Before designing anything, we did extensive mapping of all natural, man-made and socio-economic resources, on a local, regional and global level. This became a critical design generator .

Through our designs and infrastructure we maximised on local resources, reduced carbon footprint and reduced environmental impact on many levels. A key outcome was to give the mining infrastructure a life way beyond the short term use typical of a mining concession of this type.

Above: Plan of the recreational area & clubhouse which overlooks the pool and small dam below. It has a countryside vista to south. It is designed for multiple use and can adapt in the future to become a community building. In this way the mine will benifit short term and the community long term.

Plan of workers mess complex around internal courtyard with connecting perimeter walkway. After mine closure this building can convert into a school or college.

Before designing anything, we do extensive research and resource mapping