Introduction

Agriculture is one of the most important sectors of the Egyptian economy and occupies a large part of the country's workforce. Its output is limited by the lack of cultivable land and water resources.

The old Esna dam was the principal source of irrigation supply for the Governorate of Qena, supplying water to 125,000 hectares of agricultural land. Built in 1908 with the piers made of sandstone rubble masonry around a centre of hydraulic mortar and then repaired and reinforced in 1947, if has become obsolete and no longer has the necessary impounding capacity required for agricultural needs, nor is it able to efficiently manage the river traffic any longer. In addition, if did not exploit; the available head for electric generation.

History of the project

Starting in 1978, various international organizations and major consulting companies performed studies on the existing dam and on the  best solutions to be adopted, coming to the  conclusion that it was no longer advantageous to repair the old dam and that a new one downstream the present one should be constructed .

Based upon a design executed by the French company Sogreah, in 1986 the Egyptian Ministry of Public Works and Water Resources, in agreement with the Ministry of Energy, announced an international tender for the construction of the new dam, which also included a hydroelectric plant capable of exploiting the available head producing over 600 GWh of electrical energy a year.

The fundamental objectives of the project may be summarized as follows:

1) Ensuring better regulation and use of irrigation water, permitting irrigated areas to be maintained and expanded in future years;

2) Handling the expected future erosions of the river bed;

3) Producing electrical energy by using the available head;

4) Permitting better navigation conditions by constructing a lock with a boat passage capacity greater than that of the old one and sufficient to meet the expected needs of the river traffic;

5) Constructing an alternative road on top of the dam to connect the two banks.

The call for tenders for this project, which was of extremely high priority for the country, aroused the interest of various nations, including Italy, who expressed their willingness to contribute to the financing of the Project.

14 bids were submitted and publicly opened in December 1986 by groups leadered by companies from 10 different countries.

The offer of the Italian group, which consists of the Italian companies Impregilo, the group leader, and Cogefar (now merged in a single company known as Impregilo S.p.A.) for the civil works and GIE (now Ansaldo Energia) with the participation of the Rumanian Romenergo for the hydro-mechanical portion, was the best one.

The contract was signed in March 1989 and the construction began immediately.

The works

The works started on April 1, 1989, when the order to proceed was given. The residential camps for Employer's and Engineer's personnel, and the one for the foreign staff were built, as well as the workshops, warehouses, offices and plants necessary for the construction.

At the same time, a cofferdam was realized to separate the left zone of the Nile in which the concrete works were located: navigation lock, powerhouse, spillway.

A geologic campaign was performed in order to control and define certain basic data found in the tender documents, and the final design was developed, the civil engineering portion of which was assigned to the Italian company ELC - Electroconsult of Milan.

The embankment was waterproofed by means of a diaphragm wall 40 meters deep, and the entire area it enclosed was dewatered and kept dry by a special pump network, while the excavations and concrete works were performed.

As the entire foundation of the works is on sand, diaphragm walls up to 40 meters deep were constructed to prevent the passage of water. Both the diaphragm wall under the dam and that one in the temporary cofferdam were constructed by a group of specialized subcontractors, leadered by RODIO of Casalmaiocco (Milan).

All the concrete works, about 300,000 cu m, were constructed within 20 months, with production peaks of 25,000 cu m a month.

For concrete pouring, moving the forms and reinforcement steel placing, seven enormous tower cranes, sliding on rails were used so that they were able to serve the entire area involved in the works.

When the temporary cofferdam was removed, the navigation along the Nile was diverted from the right side of the river to the left, through the navigation lock; the right side was closed by a rock barrier which forced the entire flow of water to pass through the spillway, and then the closure dam was constructed in granular materials with protections in rockfill and a waterproofing diaphragm wall.

At the same time as the civil works, the electromechanical group supplied and erected the hydromechanical parts, the turbines, the auxiliary equipment and plants and the electrical parts.

General description of the project

The contract includes the construction design of the Project, the construction, training of personnel and maintenance of the plant for two years and includes the following works and machinery:

Civil Works

• A concrete powerhouse for No. 6-15MW bulb turbines.

• A concrete spillway with 11 openings, suitable for 12 m radial gates with the possibility of closure by means of stoplogs and the maximum discharge capacity of 7,000 m3/sec.

• A concrete navigation lock 160 m long, 17 m wide and of minimum 3 meters draught.

• A closure dam in loose materials.

• Canals, buildings, roads and additional works. .

• Employer's and Engineer's camp. .

• Waterproofing operations (permanent Diaphragm Wall more than 1 kilometer long and about 40 meters deep).

• Temporary works for river diversion; cofferdam to include the area with the concrete works; temporary diaphragm wall about 2 kilometers long and 40 meters deep; dewatering.

• Works and infrastructures for the construction:

  plants, quarries, camps and services for foreign and local personnel.

The main quantities of works are:

Electromechanical Works:

90 MW electric plant including:

• n.6 Kaplan type horizontal turbines 15 MW each, with 3 blades, rotor diameter 6.25 m, nominal head 5.7 m.
• n.6-15 MW generators, voltage 11 KV, power factor 0.85, brush less excitation.
• Control systems, medium and low voltage equipment, 60/30/30 MVA transformers, aerial lines.
• 132 KV elevating switchyard with aerial transmission lines.
• Auxiliary systems such as air compression, water treatment, drainage, fire prevention, air conditioning and ventilation, etc.
• n. 2   90 ton gantry cranes
• n. 2   15 ton cranes
• n.11   radial gates for spillway (12x12.9 ml
• n. 6   sets of stoplogs for maintenance
• n. 2   gates for the navigation lock
• n. 1   Bascule bridge, 17 m long and 12 m wide.

Value of contract and financing

The initial value of the contract for the civil works is 67 million Egyptian pound and a foreign currency component equivalent to 48 million dollars; that one for the electromechanical supply and erection is 18 million Egyptian pound and a foreign currency component equivalent to 77 million dollars.

The total amounts to 160 million dollars at 1989 exchange rates.

The foreign currency portions were mainly financed by the Italian Government through the Italian Agency for International Cooperation, with minor portions by Austrian and Rumanian loans.