Lingza - Ministry of Power

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Preliminary Feasibility Report
Lingza HE Project (3 x 40 MW)
This water conductor system shall be housed within the rock types of gneisses with
occasional bands of augen gneisses. A thick band of quartzite was observed in vicinity of
place Be. This band appears to be 150-200m thick. Since the contact between the two is
under a debris its nature could not be ascertained. The gneisses and quartzites are strong
to very strong and are expected to offer a good tunneling media. The rock types trend
NE-SW dipping 40-65º towards NW (Plate-4.1). Sufficient superincumbent cover is
available above the tunnel. Prima-facie no major drainage appears to have deeply incised
the proposed tunnel alignment.
4.3.3 Powerhouse
The powerhouse location was fixed keeping in view the FRL of Panan Scheme.
Accordingly, it was proposed to keep the tail water above the FRL of Panan Scheme. A
foot track runs above the proposed powerhouse location and the present appraisal is
based on the observations made along this foot track. At the proposed powerhouse
location the formation are exposed as steep rocky escarpments. A thick pile of slope wash
material occupies the area along the foot track. An underground powerhouse has been
contemplated since steep ridges bind the area. The underground powerhouse area shall be
housed within gneisses, which occupy the area. These trend NE-SW dipping towards NW
(Plate-1). Fair to good rock media is expected during powerhouse excavation. Sufficient
superincumbent cover is available above the proposed powerhouse cavern. The
orientation of powerhouse shall be suitably aligned with respect to principal
discontinuity.
4.4 SEISMICITY
The site lies within Zone-IV of seismic zoning map of India IS 1893 (Part-I) 2002.
Technical report on seismic history and seismicity of the teesta basin of sikkim covering
proposed sites for hydroelectric schemes has been collected from IMD and enclosed as
annexure 4.2. The report contains a list of earthquake events that have occurred within