Feasibility Study, Environmental Impact Assessment (EIA) Study, Detailed Design and Construction Supervision of Sardi Khola Hydroelectric Project

Project Description

Sardi Khola is a small tributary of Seti River with a total Catchment area at intake of 27 km2, maximum elevation within catchment 4070m, has occasional snow cover. The Project was designed as a run of the river project with steel pipe as the main water conveyance system. The design hydrological parameters were:
• Design discharge = Discharge with 40% exceedance probability (Q40) = 2.14 m3/s
• Design flood(Flood,Q100) = 131 m3/s at intake, 160 m3/s at Powerhouse
• Dominant mineral distribution in the suspended sediment is Mica (>40%) with presence of Quartz <20% Available Design Head: The gross design head available is 250.3m and the net design head is 230.3m after the total maximum head loss of 20.0m, which is 8.0%. Headworks: Weir: Total 26m long, 2.5m high divided into two sections: i) 20m overflow section and ii) 6m under-sluice section with 2 bays of 2.5m each with a 1.0m pier in between Intake: Two rectangular orifice of size 1.50m width x 1.0m height Gravel Trap: 3.0m wide x 1.0m deep Approach canal: 2.0m wide x 1.5m deep Settling Basin: Length 20m plus transition (4m at inlet and 3m at outlet), 2 bays of 2m width and 3m depth, designed for 90% removal of particles equal and larger than 0.2mm size. Forebay: Length 30m x width 4m x depth 3m, designed to retain inflow volume for 3 minutes. Water Conveyance System As a result of study of possible alternatives, the optimal water conveyance system for the project resulted in a steel pipe of diameter 1.0m. The total length of the pipe from settling basin to the turbine is 2975m which is divided into two nearly equal sections of low pressure headrace pipe and high pressure penstock by introducing a fore-bay at mid-length. Powerhouse A surface powerhouse is designed at the right bank of the river at ward no. 2 of Machapuchhre Rural Municipality. The area is the extension of flood plain privately owned and cultivated. Land acquision is required for this area only. Electro-mechanical Design Turbine: Two units of double jet horizontal axis Pelton turbines with axis at elevation 1298.00m. Nameplate capacity of each unit is 2 MW. Generator: The generator selected is a 3-phase horizontal shaft, ordinary type synchronous generator with a salient pole revolving field and AC brushless exciter. The cooling system shall be of the self-ventilating and recalculating type with water-cooled air coolers. The continuous rating of generators shall be 2400 kVA under following conditions: Rated Voltage 6.6 kV; Rated current ; Frequency 50 HZ; Rated power factor 0.85 lagging The rated speed of the Generator shall be 600 rpm. The generator shall be designed to withstand the maximum runaway speed of 1200 rpm for a period of 15 minutes. Direction of rotation shall be clockwise as viewed from end. Transformer Two nos of 2.7 MVA 6.6 kV three phase step up power transformers will be installed in the switchyard. Each of two generators will be directly connected to 2.7 MVA 6.6/33 kV three phase transformers. Each set of the two power transformers will be connected to 33 kV single bus bar systems through their individual 33 kV isolators and gas circuit breakers. Average annual energy generation is 22.106 GWh, out of which 3.553 GWh is dry season energy. Total Project Cost NRs. 800.114 million The study report was submitted to Department of Electricity Development (DOED).

Assignment Description

Feasibility and Detail Design Phase: The services provided included the following: • Feasibility study, Preparation and Approval of Environmental Impact Assessment (EIA) of Transmission line • Survey and Investigation : This included detailed topographical survey, hydrological survey, geological survey • Review of past study document • Capacity optimization • Social & environmental study with action plan • Detailed Design of the Project • Civil Design • Electromechanical Design • Hydro-mechanical Design • Tender and Contract Document Preparation Civil design consisted in hydraulic and structural design of facilities for diversion of water, exclusion of sediment and conveyance of water from intake to the turbine and the design of powerhouse to accommodate the electro-mechanical equipment for power production. The design philosophy has remained to design these structures as small and light as is just required to serve the purpose and keep functional all the time with minimum closure. Electromechanical design consisted in selection of the type of turbine and number of units and determining the specification for the current generator, transformer and all appurtenant equipment. The general scope of consulting services includes the technical support to project office. The services is advisory in nature but the consultant was fully responsible for qualify control, measurement and billing of the work as well as the responsibilities for the engineering design. Construction Supervision Phase: The major scope of services of consultant for construction supervision includes the following: • Provide the construction contractor with points, lines, and level of references established and check the contractors setting out; this included the accurate locations and levels of all structures, the lines and levels etc; • Checking contractor working schedule plan and make weekly, Monthly, Bi-monthly constructional schedule and submit to client's Project Manager for its approval. Prepare annual detail constructional plan by using necessary tools. • Supervision of all materials and equipments delivered and used in construction site, construction works and installation of equipments, laying and testing; • Responsible for maintaining the quality of construction works as per technical specifications, drawings, conditions of contract etc; • Develop and maintain detail record of work activities accomplished; • Review progress invoice submitted and claimed for payment by contractor and forward to the Project Manager with recommendations. • Advise construction contractor to follow activities as stipulated in the schedule. • Preparation of effective construction schedule and advice construction contractor to follow the work activities as stipulated in the schedule. • Periodic checking of contract quantities and a constant check on the cost estimate Including updating of monthly cash flow projections for project office recommendations; • Maintaining appropriate records, correspondence and dairy during construction for efficient supervision and post construction for sufficient period of time to assist the project office for processing the contractor’s claims; • Assessment, examination of the contractor’s claim and interpretation of related contract provisions and make suitable decisions with regards to the claims. • Negotiate with contractors to finalize rate of new work items not included in the bill of quantities on the basis of contract rates established on the basis of competitive bidding; • Check adequacy of contractor facilities at site and capability of their staffs to perform the contract; • Inspection including sample checking where required, of all materials and workmanship to ensure that they comply with specifications and design. Issuing of notices to the contractors for correction of any defects and their deficiencies observed during the inspection. • Suggest measures to overcome implementation difficulties to project office. • Recommend to project office regarding modifications/addition/deletion in design and specification during construction if necessary. • Assist project office in matters related to the project implementation. • Preparation of project completion report and as-built drawings and submitted to project office.