Incatema awarded a new contract to build a marine outfall in Cambèréne (Senegal)

7 July, 2021

Incatema Consulting & Engineering has been awarded a new contract to build a marine outfall to discharge wastewater from the treatment plant that the company is remodelling and extending in Cambèréne district, city of Dakar, Senegal. The project involves construction of a connecting shaft to the land segment of the emissary pipe, which will serve as a working shaft for construction of a micro tunnel under the sea.

This tunnel will have length of 1,200 metres with a 2,200 mm-diameter and will be executed by means of a sophisticated tunnel boring machine with a “closed tunnel shield” which, as it perforates the soil, will lay a reinforced concrete pipe with an internal diameter of 1,600 mm, in segments of 2.5 m. On the end of the 1,200 linear metres of pipe a segment of HDPE pipe will be connected, with a length of 100 m and an internal diameter of 1,200 mm, installed with a series of nozzles for discharging the effluent.

In this regard, “construction of the emissary pipe is an additional element of the ambitious environmental plan to reduce pollution in Senegal’s capital city. According to the study presented by the Pasteur Institute of Dakar and the Senegalese Ministry of the Environment, among other bodies, the city of Dakar presents variable quantities of pollutant waste that not only has an impact on health, but also on fishing and other sector resources”, notes the Incatema Consulting & Engineering’s Director of Infrastructures, Fernando Díaz.

Marine outfalls, natural remedies for combating pollution

Marine outfalls comprise a series of submarine infrastructures with a large diameter and extension that facilitate the transportation of wastewater through a pipeline (generally made of polyethylene) buried in the seabed.

Marine currents and natural sea conditions of temperature, salinity, pressure and ultraviolet radiation favour a chemical, physical and biological process that purifies the wastewater and reduces, in this way, its impact on the environment. The outcome is that seawater and seabed conditions facilitate the water’s disinfection. “Therefore, its a process in which nature itself removes the waste cleanly and efficiently”, adds Díaz.

In this case, the material discharged into the sea is an effluent that has been previously treated with the most modern purification systems at the WWTP of Camberene, the extension of which is nearing completion.

 Sea and terrain conditions, decontamination allies

Dilution of the effluent occurs with the marine currents generated by the wind on the water’s surface layers. It is affected by the direction and intensity of the wind, morphology of the coastline and seabed and tides.

The urban perimeter of Dakar city “registers a systematic violation of people’s right to water and sanitation, with most residents living in poverty, in recent settlements emerging with internal migration from rural areas to the city provoking a rapid and disorderly urban growth in Dakar’s surrounding districts, particularly in Sangalkam, Yéne and Bambilor”, as reflected in the document Promoción del Derecho Humano al Agua y Saneamiento en la zona periurbana de Dakar, mejorando las políticas climáticas locales, financed by Madrid City Hall.

“In this regard,” adds Díaz, “Incatema continues with its commitment to promote the achievement of Sustainable Development Goal 6, to promote the right to clean water and sanitation in the countries where it operates”.

The project to build the marine outfall of Cambérène is the continuation of the project to refurbish and extend the WWTP of the district mentioned above, where assembly of the electromechanical equipment of the Waste Water Treatment Plant continues, an installation that will service more than 1,685,000 inhabitants, with an average treatment capacity of 92,000 cubic metres per day, capable of withstanding treatment peaks of up to 101,000 cubic metres daily.