32 of 40 Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 04: General Requirements for the Execution and Completion of the Works   A period of 1 week shall be allowed for stabilisation (intake of water into the concrete).   Water levels shall be measured by approved means at 24 hours intervals for a test period of  7 days.   During the test period the total permissible water level drop, after allowing for evaporation  and rainfall, shall not exceed 1/500 of the average water depth of the full tank or 10 mm,  whichever is the more.  The testing procedure shall be used also for small chambers (flow confluence or distribution  chambers) and for manholes of gravity pipelines.  Notwithstanding the satisfactory completion of the above test, any leakage or soaking visible on  the outside face of the tank walls shall be stopped, after allowing for self-sealing. Any caulking or  making good of cracks in the concerned wall section shall, where practicable, be carried out from  the inside face.  Adjacent internal chambers within a structure shall be tested sequentially in case the treatment  process allows for emptying of the respective chamber independently of the whole structure. Then  chambers adjacent to the chamber under test shall be empty during the test.  4.19.3 Trial operation (running-in and process proving)  Once the pre-commissioning and commissioning tests have been completed to the satisfaction of  the Engineer, wastewater shall be introduced into the plant according to the start-up programme. The Contractor shall operate and maintain the plant in accordance with the draft operation and  maintenance manuals for a trial period of approx. three months. During this period, the Engineer  shall have the opportunity to witness all operation and maintenance activities, the objectives of  which are to optimize the function and operation of the entire plant.  Before starting the trial operation the Contractor shall, at his own cost, ensure that all tanks are  filled with consumables and if necessary, provide seeding sludge to start-up the process.  Activated sludge shall be produced within this 3 months period as per the conditions explained in  the below paragraph.  The plant shall be operated under automatic and manual control as directed by the Engineer to  prove the functionality and reliability of the control systems.  The Contractor shall run the plant and monitor the performance during the trial operation. The  Contractor shall ensure that the treated effluent complies with the required effluent standards at  least for 7 consecutive running days. After that The Contractor informs the Engineer that the plant  is ready for the Test on Completion.  In order to demonstrate that the constructed wastewater treatment plant conforms to the herewith  Employer’s Requirements and the performance guarantees provided by the Contractor as a part of  the Contract, the Contractor shall carry out performance tests in accordance with the following  requirements:  General  4_Vol3_d4.3_Section 4 General Requirements_en_GIR_rev6 