--- title: "Pre-feasibility site-specific investigations" subject: "Hydropower Engineering" chapter: 2 key: "semester_7/hydropower_engineering:prefeasibility-site-investigations" source: https://www.bctengineer.com/q/semester_7/hydropower_engineering/prefeasibility-site-investigations site: BCT Engineering --- # Pre-feasibility site-specific investigations Hydropower Engineering · Chapter 2: Planning of Hydropower Projects - Asked in: 2070 Chaitra, 5 marks - Video: [#5 PRE-FEASIBILITY & FEASIBILITY STUDY IN HINDI | PROJECT MANAGEMENT](https://www.youtube.com/watch?v=N5F37nvcBbs) — Sonu Singh - PPT wale - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/hydropower_engineering/prefeasibility-site-investigations - Whole chapter: https://www.bctengineer.com/md/semester_7/hydropower_engineering/chapter-2 ## Question Explain site specific hydrological, geological and topographical investigations to be carried out during the pre-feasibility study level of a hydropower project. ## Answer Site-specific investigations in the pre-feasibility study are done only at a moderate level to select the best layout. #### Hydrological investigations - Collect rainfall, flow, and climate data from DHM stations in or near the basin. - Set up a gauge at the headworks and measure discharge across seasons (current meter, floats, salt dilution). - Estimate mean monthly flows and the flow duration curve by regional methods (WECS/DHM, MIP) and correlation with a nearby station. - Estimate flood flows of different return periods (frequency analysis, regional formula), and check for GLOF and landslide dam outburst. - Sample suspended sediment to estimate load and plan the desander. #### Geological investigations - Review regional geology maps and satellite images; do detailed surface mapping of the sites for the weir, intake, tunnel alignment, powerhouse and slope stability. - Find structures: faults, folds, shear zones, joint sets, and landslides. - Geophysical survey (seismic refraction, resistivity) to find overburden thickness and rock quality. - A few boreholes and test pits at the headworks and powerhouse; identify construction materials (quarry, borrow, sand). - Seismic hazard check. #### Topographical investigations - Topographic map (1:5,000 to 1:2,000) with contours of the project area. - River cross-sections and profile at the weir and powerhouse. - Alignment of the waterway and access road options. - Benchmarks and control points for later detailed survey. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. At what depth are site investigations done in the pre-feasibility study? A. Very detailed with drilling at every structure B. None C. Only at the end of construction D. Moderate, just enough to select the best layout Answer: D. Detailed work is delayed until feasibility, so pre-feasibility is moderate. (Key point: Pre-feasibility level) 2. Why is suspended sediment sampled in the hydrological investigation? A. To estimate load and plan the desander B. To calculate the tariff C. To set the turbine speed D. To measure rainfall Answer: A. Sediment load and size guide the design of the desander. (Key point: Purpose of sediment sampling) 3. What is the purpose of seismic refraction and resistivity surveys? A. To measure the river flow B. To find overburden thickness and rock quality C. To count the population D. To estimate the energy price Answer: B. Geophysics gives overburden depth and rock quality without many boreholes. (Key point: Geophysical survey) 4. Besides flood flows of different return periods, what should be checked in hydrology? A. Wind speed B. Soil colour C. GLOF and landslide dam outburst D. Fish species only Answer: C. Outburst events can exceed normal floods and threaten the project. (Key point: Flood hazards) 5. What is the extent of drilling at pre-feasibility? A. Drilling at all structures B. A few boreholes and test pits at the headworks and powerhouse C. None and no test pits D. One hundred boreholes along the tunnel Answer: B. Only a few holes are drilled; extensive drilling comes in feasibility. 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