The Baltalimani (BL) and Üsküdar (Ü) Sea Outfalls are situated on two coasts of the Bosphorus and are 2×300 m and 270 m long with nominal diameter ⌈ 1727 mm and ø 1219 mm, respectively. These outfalls were constructed by the Alarko Company for ISKI in the years 1988-1993 to discharge the pretreated or treated waste waters to the bottom current of the Bosphorus.
The submarine pipelines have been installed by a) bottom pulling in the dredged trench, b) short launch-way (L/W) very close to the shore, c) pulling from the same coast via an anchored pulley in Ü, and d) pulling from the other coast of the Bosphorus in BL. Preparation of the pipes, comprising of corrosion coating, cathodic protection, assembly and concrete weight coating, was performed at the Kadìköy Site. Following dredging of the offshore trenches, bedding material was laid. Meanwhile the L/Ws were fabricated and erected. Installations of the pipelines were executed by placing the pipe sections on the L/Ws, making the field joints and pulling towards the sea into the trench. After testing, the submarine pipelines were covered; first with a layer of gravel then with a layer of armour stone and connected to the landline. Ü outfall was put into operation satisfactorily immediately upon completion.