Lingza - Ministry of Power

Central Crystalline
Gneissic Complex
28
Preliminary Feasibility Report
Lingza HE Project (3 x 40 MW)
Banded gneiss with augen gneiss and quart-biotite gneiss.
Augen gneiss.
Rock types belonging to Central Crystallines of Higher Himalaya occupy the area.
4.3 TOPOGRAPHIC AND GEOTECHNICAL ASPECTS OF COMPONENT
STRUCTURES
The region is thickly vegetated and falls within Tolung Reserve Forest. From the peruse
of topographic sheet 78 A/6 Jumthul Chhu an E-W flowing nala originating from Jumthul
glacier meets Dwathang Chhu near Tolung and thus give rise to Ringpi Chhu. Beyond
this confluence Ringpi Chhu flows almost N-S with occasional easterly and westerly
swings. Upstream of Ishana the nala takes a southwesterly direction till it meets
Rangyong Chu. Beyond the confluence of jhumthul Chhu and Dwathang Chhu near
Tolung the nala is joined by few tributaries namely Ludul Chhu, Pegor Chhu, Kangcha
Chhu and Zong Chhu all left bank tributaries. The area is bound by ridges, which
generally trend NE-SW and follow the general strike of formations. The river flows in a
steep gradient. The project area is occupied by Central Crystallines of Higher Himalaya.
Ringpi Chhu almost flows along the strike of the formations. Entire area has a highly
rugged terrain with elevation in vicinity varying from 1600 M to 6000 M. Near Shobrung
and Ishana the topography is approximate as indicated in the topographic map.
The area is approachable by a fair weather road upto Lingza beyond which a foot track
reaches Tolung. In general the valley slopes are occupied by slope wash material, while
rock fromations are exposed as steep ridges.
4.3.1 Diversion Structure
The proposed diversion structure is located approximately 700m upstream of Ishana.
Here, Ringpi takes a westerly swing and flows southwesterly to southerly. The area was