Heritage Cases

Pipe Replacement Projects are based on the collection of the extent of sewer failure experiences in certain networks and collector pipes within the entire City of Johannesburg. These projects therefore entail the replacement of this old infrastructure informed by asset management register, pipe replacement potential results, and hydraulic models to ensure that the oldest poor condition infrastructure is replaced and as a result, pollution to the environment due to overflows is avoided. Various Project Charters identify areas within the City which have the highest replacement potential. A Project Charter requesting the replacement of sewers in Davidsonville Ext. 2 was received from Johannesburg Water’s Infrastructure Planning and was assigned to the Design Section for further investigations, design and implementation as part of Johannesburg Water’s Upgrade and Replacement programme. Johannesburg Water’s Infrastructure Planning prepared the scope of work that was handed over to the Design Section. The sewer pipelines within the Davidsonville Ext. 2 area are predominantly made of Asbestos Cement (AC) and some are made of clay (vitrified clay pipe), situated mostly in mid-block position. The existing AC pipes have either reached or surpassed their useful life span thus Johannesburg Water has decided to replace the AC and clay pipes with a more suitable pipe material as part of their city-wide pipe replacement programme. The primary benefit of the replacement would ensure a reliable sewer system as well as improve future operational efforts to provide adequate accessibility for maintenance of the system. In some instances the community has encroached on the mid-block servitudes with various permanent structures or they are unavailable to provide access into their yards thereby making it difficult to access the sewers for maintenance. The main objectives of this project which were identified included: • Keeping the existing mid-block sewer infrastructure by using trenchless methods. • Replace all existing pipes as follows:  150mm diameter AC pipes with 200mm diameter HDPE PE 100 PN 8 pipes for sewers.  200mm diameter AC and 200mm diameter Clay pipes with 250mm diameter HDPE PE 100 PN 8 pipes. • Decommission all existing mid-block sewers. Existing Sewer Pipeline The existing sewers under consideration are as follows:  Approximately 3624m of mid-block 150mm diameter AC pipes which date back to 1988.