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sanjen (upper) hydroelectric project:

Sanjen Hydroelectric Project (SHEP) is located on the Sanjen River in Rasuwa District, Bagmati Zone of the Central Development Region.
SHEP is a cascade run-of-river hydropower development that utilizes the water from the tailrace of SUHEP powerhouse. Additionally, SHEP utilizes 0.5 m3/s water from ChhupchhungKhola. SHEP is one of the attractive projects due to its low specific investment costs and its limited environmental impacts. SHEP has major structures viz. forebay, headrace tunnel, underground surge tank, inclined and horizontal pressure shaft, powerhouse and tail race structures. Project utilizes design flow of 11.57 m3/s at 40 percentile flow exceedance of long term available river discharge and 442 m gross head to produce 42.5 MW power and 251.94 GWh gross energy per annum. Generation voltage of 11kV is stepped up at the switchyard by 11/132 kV transformer and 1.1 km 132 kV transsmission line connected at Chilime hub will be constructed for power evacuation.

Location and accessibility:

Geographically, the project area lies between longitudes from 850 16' 30' E to 850  18' 15" E and latitudes from 280 11'  00" N to 280  13'  00"  N.
Site is considered as remote area. The project is accessible via Kathmandu-Trisuli road (72 km), Trisuli-Somdang Highway (Pasang Lhamu Highway 72 km) and 6 km long access road up to existing headworks of Chilime Hydroelectric Project. The access road to the power house and headwork is constructed by the company.

Climate:

The Site is situated in high altitude and sometimes snowfall occurs in winter. Concreting during this period might be required to do in frosty condition. Construction works at forebay will have to be carried out in high altitudes above 2100 m above mean sea level and sometimes snowfall occurs in winter. In this elevation works may have to be executed in cold condition and Concreting during this period might be required to do in frosty condition in the winter season. Construction at powerhouse area is expected to be slightly more comfortable since this area lies about 400 m lower from the level of forebay area.

Hydrology:

The Sanjen Hydroelectric Project (SHEP) is a cascade run-of-river scheme which diverts the tail water coming from the powerhouse of Sanjen (Upper) Hydroelectric Project and the additional water (0.50m3/sec) from the Chhupchhung Khola. The major headworks structure of the SHEP will be a forebay cum intake structure. Water discharged from tailrace of SUHEP powerhouse and the water from the Chhupchhung Khola through feeder canal system will be collected in this forebay. There will be a simple intake structure, desander and a feeder canal to feed water from Chhupchhung Khola which is designed to convey 0.5m3/s of water from the intake and discharge to the forebay of the interconnection system. Adding this flow, the design discharge adopted for SHEP is 11.57 m3/s. The forebay is provided with side channel spillway.

Geology:

The project area is situated in the Higher Himalaya and the Lesser Himalaya, Central Nepal separated by the Main Central Thrust (MCT). Chhupchhung weir lies in recent alluvial deposits consisting of predominately coarse gravel toboulder derived from gneiss, schist, quartzite and slate in sand matrix with large boulders ofaugen gneiss. Forebay/Intake of SHEP is in a gently sloping terrain consisting of about 25-30mthick deposits with angular gravel to boulder sized rock fragments of powerhouse lies on a flat alluvium terrace consisting of a thick accumulation of alluvial deposits having sharp-textured, angular to sub-rounded, coarse-grained soil with gravels.

Brief description of project components:

Headworks:

The Sanjen Hydroelectric Project (SHEP) is a cascade run-of-river scheme which diverts the tail water coming from the powerhouse of Sanjen (Upper) Hydroelectric Project and the additional water (0.50m3/sec) from the ChhupchhungKhola. The major headworks structure of the SHEP will be a forebay cum intake structure. Water discharged from tailrace of SUHEP powerhouse and the water from the Chhupchhung Khola through feeder canal system will be collected in this forebay. There will be a simple intake structure, desander and a feeder canal to feed water from Chhupchhung Khola which is designed to convey 0.5m3/s of water from the intake and discharge to the forebay of the interconnection system. Adding this flow, the design discharge adopted for SHEP is 11.57 m3/s. The forebay is provided with side channel spillway.

Waterway:

The waterway consists of a low pressure steel pipe (216m long) of 2.4m diameter from Forebay to Tunnel inlet with siphon crossing across Chhupchhung Khola, followed by a 3635 m long, 3.5 x 3.75m (excavation section) sized D-shaped headrace tunnel and a steel lined penstock shaft of 1018m length and 106m to 2.5m finished internal diameter. A surge shaft of diameter 5.5 m with total height 55 m is situated at the end of Headrace tunnel.

Powerhouse and tailrace:

The powerhouse of surface area 57.5m length, 30m breadth and 15m height is located in the vicinity of existing Chilime HEP headworks at the right bank of Chilime River. The powerhouse is semi surface type. The powerhouse will be equipped with three units of Vertical Pelton turbines, 15 MW each and three synchronous generators of 16.85 MVA each.

Transsimission line:

About 1.1 km long single circuit 132 kV Transmission line is required to be constructed to evacuate power from this project up to Chilime hub.