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The proposed design offered two alternative solutions: the first incorporated two new pumping stations with a total sewer length of 810 m; and the second had three pumping stations and total sewer length of 700 m. Budgetary considerations determined that the second solution was chosen. |
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The low-cost sewerage network that was finally constructed has the following characteristics: |
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1. House connections. All household wastewater and sullage flows directly to the street sewer. Connection is achieved by collars attached to the pipe. The PVC connections have a diameter of 75 mm. |
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2. Inspection chambers. Inspection chambers with heavy-duty lids were constructed at maximum distances of 50 m to provide access for sewer cleaning. They have been installed at very shallow depths (average 0.35 m) with internal dimensions of 0.30 ´ 0.40 m. |
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3. Drop connections. At particularly steep gradients, a number of drop connections have been constructed. These comprise a vertical pipe (200 mm diameter) with a plastic inspection cover. To keep the pipes vertical, cement rings were placed at their highest and lowest points. |
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4. Pumping stations. Four pumping stations were finally constructed, each containing two submersible pumps. They are fully equipped with all the necessary facilities (floating switches, non-return valves, alarm) and were constructed below ground for aesthetic reasons. |
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5. Overflow tanks. Because power cuts are frequent in Santorini, overflow tanks were considered necessary for the proper operation of the network. These have been incorporated into the network at the four pumping stations. Whenever the electricity supply is interrupted, wastewater accumulates at each pumping station and overflows into the tanks. The tanks were |
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