47 of 74  Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 3: Plant Description  return sludge pumping station shall be 1.5 m lower than the secondary clarifier tank hopper  bottom level.  For all valve and instrument chambers, pumping stations and pipe galleries;  3.3.4.36 Valve Chambers, Pumping Stations and Pipe galleries   Treated water supply system shall be designed and installed with all required equipment,  valve, pipe, fittings, etc. for washing and cleaning purposes.   The floor of these chambers, pumps rooms and these galleries shall be designed and  constructed with appropriate slope. There shall be drainage channel at the lowest edge of the  chambers and the side of the gallery. At the end of this channel, there shall be the permanent  drainage pump readily for use at drainage pit. This drainage pit shall be constructed  considering the installation of the drainage pump.  Foul air shall be collected from the buildings/rooms/galleries and shall be sent to the odor  treatment unit. For foul air collection; the collection piping network system with appropriate  material shall be designed and installed in the buildings/rooms/galleries. This network shall be  designed and installed to collect the foul air from the top and floor part of the areas. The main  collection line shall be installed at the top of the rooms with appropriate distance to the ceiling  and the foul air at the bottom part shall be collected with the pipe branches (drop legs)  connected to this top main collection line network. H$_{2}$S and CH$_{4}$ monitoring and warning  system shall be installed for the buildings/rooms/galleries. Minimum recycle rate and  locations foul air to be collected are given in Section 2.6.2.   If the pumping station shall be designed and constructed as buried, a lifting system shall be  provided to carry out the maintenance works.  3_Vol3_d4.3_Section 3_Plant Description_GIR_rev08 