Name: Consultancy Services for Preparation of Prefeasibility study for Chamkharchhu-II and III and Dangchhu HPP, Bhutan
Name of the client: Department of Hydropower & Power System (Lahmeyer International (India) Private Limited)
Project description: Social Studies, Environmental Studies, Topographical Survey, Geotechnical Investigation as
a) Core Drilling 450m
b) Permeability Test
c) Seismic Refraction Test for 5440 m
Scope of work:
Survey and Mapping
The Consultant shall organize and carry out all necessary survey work in the field to locate site investigation works needed for the prefeasibility studies. Based on the field survey and mapping, the Consultant shall prepare topographical maps of the overall project layout with relevant project areas such as reservoir area, dam & appurtenance structures like intake, river diversion and energy dissipation arrangements, HRT alignment, power house and other components like switch yard/pothead yard, TRT etc at scale of 1:10,000 with 10 m contour interval. The field survey and mapping for major project components such as dam, reservoir, surge shaft, pressure shaft, Power house, Tail Race Tunnel, etc at scale of 1:5000 with 5 m contour interval.
The Consultant shall also arrange for cross-sections of the river to be carried out at intervals of 100m for 1 km upstream and 2 km downstream of the dam/weir centerline and shall record observations of the water surface gradient for use in hydraulic calculations. A longitudinal profile of the river from at least 5 km upstream of the dam axis to at least 2 km downstream of the tailrace outlet will also be surveyed and prepared by the Consultants.
Geology and Geo-techniques
It is necessary to obtain a reliable indication of the geological and geotechnical conditions at the selected dam site and powerhouse area. Consequently, in addition to normal prefeasibility level geological investigations, the following work shall be carried out:
1. Seismic refraction measurements to determine the depth of overburden, fault zones and rock quality at the dam site, power house area and along parts of the head race tunnel. The tentative seismic refraction profiling for Dangchhu and Chamkharchhu (II & III) Integrated has been estimated at about 2500m and 5000m respectively. However, the above quantity may vary depending on the site conditions. The Consultant shall submit the work program to the Client for approval before implementation.
2. Exploration of the overall geometry and quality of the bedrock by carrying out at least 3 borehole as specified in the Bill of Quantities (BoQ) in each project and taking out core samples and its appraisal. However, the above quantity may vary depending on the site condition. The Consultant shall submit the work program to the Client for approval before implementation. Assessment of the bedrock conditions at main project structures, provisional appraisal of its geotechnical characteristics;
• Preliminary assessment of the seismic risk at the Project sites.
• Identification and quantification of quarry and potential areas for construction materials (including
• the identification and avoidance of environmental impacts due to borrowing and mining);
• Preliminary assessment of suitability of available materials and design parameters.
Social & Environment al & Social Impacts
The Consultant/Sub-consultants shall assess the social & environmental implications of the Hydropower Projects through field investigations, surveys & interviews with selected stakeholders within and adjoining the project. Data collected must be gender disaggregated whenever applicable and appropriate. Based on the available information, the initial ESIA-pre-feasibility will determine whether the impacts of the proposed project are likely to be significant and identify compensation and mitigation measures according to the national & international standard.
