Civil Engineering July 2021 | Vol 29 No 6

Civil Engineering July 2021 43 The first layer applied to the existing tank was a cementitious product. This was used to create a uniform surface for the application of subsequent layers. This was followed by a moisture bar- rier product, and finally, a chemical corrosion inhibitor. The existing tank had a footprint of 5 000 m 2 and is constantly exposed to the elements. The size had a significant im- pact on how rehabilitation activities were carried out. Arguably, the most critical factor in the application of the rehabilita- tion products was temperature, as it had to be considered for mixing water storage on site as well as during the application of products. During the day, the concrete reached temperatures above those allow- able for product specification, and given that conventional methods of cooling the substrate were unreasonable on a structure of this magnitude, nightwork was unavoidable. Curing methods also considered the effects of temperature. The preferred method of curing the tank floor was to place carpet felt on the saturated concrete while a combination of sprinkler systems and plastic sheeting was used on the walls. PIPELINE REPAIR AND TIE-IN The beach area downstream of the tanks presented a hyper-aggressive corrosive environment. One of the early challenges of working here was the deterioration of the existing pipeline, presumably a result of the prevalent conditions. This deterioration became apparent when multiple leaks were discovered along the pipe during excavation activities and the installation of sheet piles. Pipe wall thickness tests confirmed a reduction in width from 12 mm to 4 mm in several localised spots. The decision was made to temporarily repair these leaks to maintain operation of the original sea outfall and to inhibit further spillage. These repairs served as a valuable prepa- ration for the tie-in of the new pipelines into the existing sea outfall. The most critical part of the project works was the tie-in of the new HDPE pipelines. As the sea outfall would have to be decommissioned during the tie-in, the spillage of effluent onto the beach area and into the ocean was unavoidable. Early observations during the repair of the leaks showed that effluent appeared to be trapped within the surf zone and travelled along the coast instead of washing further out to sea. With this knowledge, the relevant authorities were approached to ensure the closure of the affected beaches during the tie-in and the Council for Scientific and Industrial Research (CSIR) was appointed to confirm when the beaches could be reopened safely. Following the development of an hourly programme for the works and a review of anticipated tidal conditions, a 72-hour window to undertake the tie-in activities was agreed upon. Demolition activities that could be completed prior to the 72-hour shutdown were undertaken and the large diameter pipes were assembled outside of the cradle in a dry run. During the shutdown, the team encountered a new challenge due to an unpredicted high tide. The team tried to insert an inflatable rubber bag to prohibit backflow from the sea outfall near the works, but the tide was higher than expected and made this impossible. An additional four hours were required to complete the works. SOCIAL IMPACT While the project focus was the design of the technical infrastructure, the associated construction logistics had several social impacts that needed to be considered. It was anticipated that Tanjore Drive – the main road to Cuttings Beach – would be handed over to the contractor, becoming unavailable to the public. At AECOM, understanding the social impact of a project is at the forefront of what we do, and we work with our clients to develop and ensure human-centred designs. With this in mind, and as agreed with the client, a gravel parking area and designated footpath was outlined in the contractor’s temporary works. In addition, as the con- tractor’s office occupied the entrance to the beach itself, further temporary works included alternative access to the shore via a timber boardwalk through the beach dunes. This assured safe passage for everyone, including young children and wheelchair users. The project did not comprise typical, everyday structures and we were fortunate to work alongside a proactive contractor who proposed innovative strategies for improved implementation. With intensive planning, significant tem- porary works and an ongoing community focus, the project reached completion in November 2020.  REFERENCE Brooks S, Sutherland C, Scott D, Guy H. Integrating qualitative methodologies into risk assessment: Insights from South Durban. S Afr J Sci. 2010;106(9/10), Art. #324, 10 pages. DOI: 10.4102/sajs.v106i9/10.324. Work in progress at the northern chamber of the sea outfall pipeline installation