Construction World December 2016

Winner

The AfriSam Innovation Award for Sustainable Construction E REHABILITATION OF BRUMA LAKE

The key objectives of the remedial work were to address community problems, in particular the bad odour and aesthetics which characterised the lake. The remedial work aimed to reduce the public health risks and to restore the aesthetics and amenity of the area for the public and the surrounding business community. Initial land-based surveys were conducted in an attempt to quantify the amount of material that had ultimately silted up the entire lake but these were found to be impractical. The contractor employed the use of Lidar Survey, once draining the lake of surface water, to gain a clearer picture of just how much silt had collected over the years. This technology also allowed for intermittent aerial photography to judge progress over the duration of the project. The contractor subsequently procured a drone-mounted camera with which aerial photography and videography could be carried out on an ad hoc basis. Being a public space, the rehabilitation of Bruma Lake affected both the social aspects of the area as well as public and private business in the area and immediate surrounds. The architectural design incorporated existing elements of the lake and surrounds into the design of new elements with natural rock components to soften the harsh look and feel existing concrete basin and dam wall. Mounds and soft-rounded slopes ensured attractive flowing greens inviting people into the public space from outside. Wetlands and hydraulics expert Chris Brooker (cba Expert Engineers) executed the engineering design for the Bruma is a 30 year-old suburb of Johannesburg, South Africa. It is noted for a small (5 hectares) man-made lake which, until the commencement of this project, was being treated to reduce water- borne pollution. The pedestrian bridge crossing the original lake has also played an integral part in facilitating ease of access to the business district, recreational and retail facilities.

project and also acted as principal agent for the client. The proposed river bed was intended to replace the existing lake and the meticulous design was specified based on necessary environmental factors and shear forces experienced during worst- case conditions. The recovered silt was used for backfilling the remainder of the lake basin to create a recreational park. Immediately upstream the Queens Wetland area was rehabilitated. Over and above the wetland rehabilitation, stringent controls were put in place to monitor river conditions both upstream and downstream. This enabled the environmental control officer to determine the impact, if any, that the construction works may have on the quality of water being released downstream. The start of the project also saw the successful rescue of birds’ nests by the contractor with numerous eggs reportedly hatching at a local conservancy. Inoculation/prophylactic measures were taken for all persons who entered the site due to the initial potential for exposure to hazardous materials. This was a strict prerequisite to anyone who wished to gain entry into the lake basin. The in-situ soil was treated with limestone lime to aid in the natural breakdown of hazardous inorganics as well as balance the soil PH. The main scope of the project was completed within time (June 2015), save for the bridge works which were determined to be greater than expected and therefore collected a separate programme due to progressive design and adaptations as well as long lead items, completing March 2016. Through constant interaction between the contractor, principal agent and the project team numerous cost-saving initiatives were explored to prevent the project from exceeding budget. Treatment of hazardous material rather than spoiling off site meant that the risk of exposure to same would be limited to the confines of the site. The construction had a very low impact on surroundings/ environment and the end results has proved to have a high impact on public perception and improved quality of life with an equally positive long term impact on environment (treatment of hazardous material, protection of birdlife). Through the rebuilding of the pedestrian bridge the project was able to reinstate safe access to area for the public and local business community. The project may have a direct impact on the revival of Bruma business hub.

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Project information • Company entering: Basil Read • Client: Johannesburg Development Agency (for City of Johannesburg)

• Start date: June 2014 • End date: March 2016 • Main contractor: Basil Read • Architect: JDLEA

• Principal agent: cba Specialist Engineers • Project manager: LDM Project Management • Quantity surveyor: Walker Mare Quantity Survey • Consulting engineer: cba Specialist Engineers • Subcontractor: ARQ

• Subcontractor: AfriSam • Project value: R75-million

Construction WORLD

DECEMBER • 2016