SHPP "Prokopanik”

The construction of the small HPP „Prokopanik“ - similar to the most channel HPPs - requires redirection of the river and execution of relatively deep excavations for the plant building and overflows. The site itself is located along a relatively wide section of the Iskar River, which in turn requires construction of two non-overflow dikes acting as a barrage on both sides of the plant. The geotechnical works are divided into two phases using the jet grouting technology. It allows construction of nearly vertical slopes, allowing both reliability and watertightness of the excavation and founding of the foundations. Due to the wide transverse profile of the river, the second phase of the construction has been considerably shorter.

First phase - shifting of the river bed only at the left part for construction of HPP building, overflow facilities, platform to the access road and one part of the non-overflow dike at the other part of the HPP:

• Jet grouting treatment of the dike longitudinal to the flow and the two transverse dikes closing the construction site at the right part of the river;
• Reinforcement of the HPP building area by means of jet grouting;
• Execution of a watertight diaphragm at the upper course below the inlet channel by means of jet grouting of the rock through the columns;
• Execution of a watertight diaphragm below the fields of the overflows;
• Execution of columns by means of jet grouting and injections in the area of the non-overflow wall, where the platform to the access road is located;
• Extension of the longitudinal redirection dike to the river by means of jet grouting columns of double fluid system using air and grouting for mixing of the soil with parallel execution of steel concrete diaphragm for the permanent non-overflow dike.

Second phase - letting the river flow through the overflow facilities and gradual closing of the left part of the river for construction of the non-overflow dike:

• Execution with double fluid system of  jet grouting columns and parallel construction of a steel concrete diaphragm for the the non-overflow dike;
• Tests of the watertight diaphragm and the non-overflow dike.

The construction began in June 2011 and the site was commissioned in July 2013.