URBAN WATER SUPPLY IN PEMBA
At the beginning of March 2015 Lotti Ingegneria successfully completed the second phase of “Consulting services for Design, tender documents preparation and construction supervision of Pemba Urban Water Supply and sanitation LOT3”.
The goal of the project is to improve the water services provision in the three town of Pemba: Chake-Chake, Wete and Mkoani.
Pemba is an island forming part of the Zanzibar Archipelago (Tanzania) with a land area of about one thousand square kilometres. It is situated about 50 kilometres to the north of Zanzibar, the largest island of the archipelago.
The project concerns both the water sources and the supply network. The sources are ground water from well fields.
The island is formed of calcareous and ancient alluvial material containing abundant aquifers. The high amount of annual rainfall and good permeability of the soil guarantees the annual borehole recharge. However the limited size of the island necessitates a careful study of hydro-geological conditions to avoid contaminating the aquifers themselves through seawater seepage.
The scope of works in the three towns has included: 18 production boreholes (110 meters deep) and 10 observation boreholes, conveyance networks, 4 ground tanks and 2 elevated tanks for 7600 m3 of water storage and 4500 m3 of reinforced concrete, about 80 km of distribution networks with variable diameter from 50 to 400 mm in HDPE and PVC, 2 pumping stations and 4 chlorination buildings.
Lotti has succesfully carried out the project in two phase:
- Design of source works and water scheme, preparation of tender documents;
- Supervision during construction and during the defect liability period.
During phase 1, Lotti executed the hydrogeological surveys and investigations to confirm the exact locations of the water sources and prepared the detailed design for water sources and observation boreholes.
Lotti discussed and agreed with the Client ZAWA (Zanzibar Water Authority) the design criteria, taking into consideration the local situation, the trend and the economic and financial feasibility of the project. Lotti prepared the tender documents in accordance with rules and procedures for procurement of AfDB funded projects.
The preparation of tender documents for boreholes and water schemes has included Cost Estimates, Bill of Quantities, Drawings and Techinical Specifications.
The construcion supervision activities included the supervision of contractor mobilization, the drilling activities and boreholes equipment, administration of the contracts, preparation of monthly and quarterly reports for the Client, evaluation of any claims and variations of works, inspection and approval of each work to ensure the compliance with the specifications, including site and factory tests.
The amount of the proposed works is approximately 6.5 million euro.