14 of 74  Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 3: Plant Description  of this tender. According to the detailed design of the collector system, the invert elevation of pipe at  the connection point of the existing inlet structure is -1.94 masl. 3.3.4 Wastewater Treatment Plant Units  3.3.4.1 Inlet Structure and Stone Trap  The wastewater shall be discharged from the connection manhole of main collector with 1000 mm  diameter into the inlet structure. Inlet structure shall be designed, constructed and equipped regarding the requirements set in Table 2-1.  The maximum flow (Q$_{WW,h}$) of the related stage requirements shall be met for the unit.  Inlet structure shall have minimum two chambers. The first chamber consists of inlet section. The  other chamber shall have a stone trap unit. In this inlet chamber, there shall be one main inlet  penstock. The main inlet penstock shall be installed before the stone trap chamber. This penstock shall be wall  type with double spindle, fully watertight and with electrically driven actuators in accordance with the  specifications given in Section 7.8.8 and 7.8.18. The operation status of the penstocks should be  monitored and controlled by the SCADA system.  Operation of the penstocks in the inlet structure shall be controlled by the ultrasonic level or radar type  sensor.  In this unit, an automatic sampling equipment shall be installed.  The top of the inlet structure shall also be covered with removable covers and foul air shall be  collected from the structure and shall be sent to the odor treatment unit.  After the first chamber, a rock/stone trap should be constructed. This unit shall be designed and  constructed to provide the wastewater horizontal velocity should be maximum 0.3 m/s. Minimum  hydraulic retention time of the unit should be 15 second at maximum flow rate. Length/Width ratio of  the unit shall be minimum 4/1. The rock/stone trap shall contain all necessary equipment such as  clamshell scoop, container etc. The clamshell grab bucket shall be electrically operated to remove  large objects. A permanent monorail crane system shall be provided for the clamshell. The bucket of  clamshell shall be 80 cm width and perforated. The holes of bucket shall be determined at the design  stage according to the local conditions. Stone trap unit shall also be covered as per section 7.7.3 and  7.7.4.  From inlet structure, wastewater shall be transported to coarse screens. Minimum storage capacity and type container  : in accordance with 7.8.29.  Minimum number of the containers  : 2 items  3.3.4.2 Coarse Screens  Coarse screens shall remove solids that may be harmful to the inlet pumps. 3_Vol3_d4.3_Section 3_Plant Description_GIR_rev08 