Between July 2009 and December 2010 Risk Engineering Ltd. implemented a contract for the development of technical certificates according to the requirements of Regulation No.5 of the Ministry of Regional Development and Public Works dated 28.12.2006 concerning the technical certificates of construction sites, thus elaborating the technical certificates of 15 (fifteen) major dam lakes and hydrotechnical facilities existing in the Republic of Bulgaria.
NEK EAD – Dams and Cascades Enterprise was the Customer under this contract, in its capacity of organization which takes charge of the hydraulic facilities which were the subject of the above contract. The scope of the contract included most of the existing major dam lakes and hydraulic structures in Bulgaria, all being first category construction sites as per the Spatial Planning Act (SPA) and Regulation No.1 of the Ministry of Regional Development and Public Works dated 30.07.2003 regarding the nomenclature of construction sites.The following fifteen dam lakes and hydraulic structures were the subject of the above mentioned contract:
- Chaira Dam Lake;
- Belmeken Dam Lake;
- Krichim Dam Lake;
- Studen Kladenets Dam Lake;
- Dospat Dam Lake;
- drainage systems for removal of Ovcharitsa river waters outside of “Troyanovo – North” mine’s supporting pillar – left and right affluents;
- Rozov Kladenets Dam Lake;
- Service Water System of TPP Maritsa East 2 EAD (Ovcharitsa Dam Lake);
- Vacha Dam Lake;
- Al. Stamboliyski Dam Lake;
- Ivaylovgrad Dam Lake;
- Iskar Dam Lake;
- Batak Dam Lake;
- Koprinka Dam Lake;
- Kardjali Dam Lake;
In compliance with the requirements of the Spatial Development Act and of Regulation No.5 of the Ministry of Regional Development and Public Works dated 28.12.2006, detailed site survey must be performed prior to the substantial development of the technical certificates of the existing facilities. The survey shall be summarized in a report on the results thereof and construction site as-built drawings shall be elaborated. Risk Engineering Ltd. experts implemented a large scale survey of each of the above mentioned hydraulic structures, including:
- Examination of the available design and as-built documentation, as well as of the documents concerning the commissioning of the objects, documents on the repairs during operation, additionally built facilities, and records of the dam lake operation;
- Walkdowns to determine the actual status of the site, taking photographic pictures of the defects and the problematic sections;
- geodetic survey of the area and survey of the actual geometric dimensions;
- Material tests of walls concrete (at the dam lakes with concrete walls) to determine the actual parameters of concrete;
- Engineering-geological survey (mainly for the dam lakes and structures with earth fill or stone fill dam walls with central clay core);
- Cadastral documents and documents to clarifying the property on the facilities were required and obtained from the state and municipal authorities;
- Strength and seismic analyses and seismic stability analysis of the surveyed dam lakes and hydrotechnical facilities were carried out in compliance with the regulatory documents;
- The respective conclusions on the safety of facilities were drawn up on the basis of the performed survey and analyses.
For each object, a Report was prepared based on the survey results. For each structure a Technical Certificate was elaborated after obtaining the approval of the reports by the Customer. The as-built documentation for the respective hydrotechnical facility, which was developed by Risk Engineering Ltd’s experts, was attached to each such certificate.
Recommendations for rehabilitation of the damaged areas, for recovery of the defective and improperly operating systems (electrical, mechanical, I&C) were provided as part of the certificates. Specific instructions were provided to enhance the operation and to improve the action plans in case of accident conditions.
All reports on the survey results and all certificates of the above mentioned hydrotechnical facilities were accepted on a Technical Council meeting of the Customer.
According to the regulatory requirements, the technical certificates and the attachments thereto (including the Reports with the survey results and the as-built documentation) were registered at the Ministry of Regional Development and Public Works and the respective municipalities, depending on the regulatory provisions settling these issues.