Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 1 : Introduction and Existing Condition  8 of 11  driest month with 68 mm precipitation. With a mean of 163.4 precipitation, the maximum rainfall is  observed in October. Due to topography, Giresun Municipality wastewater collection system is composed of main collector  line parallel to coast and sub collectors connected to this main collector. As the area is plain at the  coast, wastewater reaches to sea outfalls via 7 different pumping stations. Currently, there is no wastewater treatment plant in Giresun. In the existing situation, wastewater of  Giresun (Centre) is discharged to sea from 2 different points. The construction of the existing wastewater collection system of Giresun Municipality was  commissioned by IlBank in the years between 1985 and 1990. Wastewater collection system was built  using concrete pipes to serve city center located at the coast of lower altitudes.  Throughout the years, the Municipality has built street-based wastewater collection network lines in  required areas in parallel to the growth of the city. Those additions to wastewater network have not  been shown on those plans. There is no information about the ages of the network lines added to the  existing network.  By the end of 2012, the rate of population served by sewerage system to total population is stated as  90% by municipal authorities.  In Giresun, there are a lot of creeks discharging to Black Sea. Each stream collects surface waters from  city center and urban area in its own basin. They are working as natural stormwater drainage system.  The existing stormwater system constructed by the Municipality covers especially problematic area of  the city. The collected stormwater by the existing lines is discharged to the creeks. There are lots of creeks in the region with continuous north-south direction flow during summer- winter seasons. Aksu, Batlama, Boğacık, Büyükküre, Küçükküre, Veran and Gökgöz are some of  them. Aksu has the highest flowrate among them and discharges to Black Sea from the east of city  center. The catchment area is 752 km$^{2}$ wide and the length is 61 km. Besides, there are several creeks  feeding these creeks which are dry in summer time.  1_Vol3_d4 3_Section 1_IntroExisting Condition_GIR_rev8   Emniyet (Centre) Deep Sea Outfall: Wastewater collected between Güre locality and  Gemilerçekeği at the west and the centre of the city are pretreated and discharged to Black  Sea. Construction of Emniyet Deep Sea Outfall and pretreatment plant was commissioned by  Ilbank on 2009. Wastewater is collected by sewerage system and entered to discharge  pumping station and then it passes through the coarse screen, submersible pumps, fine screens,  grit removal, pumping station pumps, wastewater transfer pipeline (land-sea transfer pipeline)  and diffusers.  Aksu Deep Sea Outfall: Wastewater collected between Gemilerçekeği District and Aksu  District at the east of the city are pretreated and discharged to Black Sea. Aksu Deep Sea  Outfall was built by IlBank in the year of 1996. Before the wastewater is discharged, it passes  through the coarse screen, grit removal, submersible wastewater pumps, land pumping station,  valve chamber, sea discharge pumping line and diffusers.  1.3.5 Existing Wastewater Collection System 