Mangdechhu Hydroelectric Project (720 MW)

720 MW Mangdechhu Hydroelectric project is one amongst the ten hydroelectric projects planned under the 10,000MW Hydropower Development Program, by the year 2020, of the Royal Government of Bhutan supported by the Indian government.
The bilateral agreement to execute the Mangdechhu Hydroelectric project was signed between Indian government and the Royal Government of Bhutan on 30th April 2010 at the approved cost of Rs. 28,963 million (March 2008 Price Level) with funding by Indian government as 30 per cent grant and 70 per cent loan at 10 per cent annual interest to be paid back in thirty equated semiannual installments.

The fund for the project is released by the Indian government in a timely manner based on the requirement of the project. The 1st Revised Cost Estimate (RCE) was approved by the Indian government for Nu./Rs. 40,206.30 million (March 2014 price level), an increase of Nu./Rs. 11,243.30 million from the initial approved cost of Nu./
Rs. 28,963.00 (March 2008 price level).

The 2nd Revised Cost Estimate for Nu./Rs. 46723.85 million (March 2016 price level) has been approved by the Indian government. As on 31st December 2017, the Mangdechhu Hydroelectric Project has received a total amount of Nu./Rs. 42,706.30 million of the total receipts, Nu./Rs. 41,237.46 million has been spent till 31st December 2017 including
advances for various activities, representing fund utilisation of 88.3 per cent against 2nd Revised Cost Estimate.
NHPC Limited, is the consultant to MHPA for design and engineering works. The project is environment friendly, run of the river scheme, located on river Mangdechhu, in Trongsa District of Central Bhutan.

STATUS OF DAM AND ASSOCIATED WORKS (PACKAGE: C-1) BY JAIPRAKASH ASSOCIATES LIMITED Achievement as on 31st December 2017 The overall physical progress of C-1 package is 97.98 per cent with an average progress of 0.61 per cent per month during the fourth quarter. The C-1 Package works consists of dam and associated Underground Works.

Surface Works
The construction of 114m high Concrete Gravity Dam is in progress. The total concrete placement in Dam is estimated to be 4.83 lakh cu.m. Up to the end of fourth quarter i.e. 31.12.2017, 4.42 lakh cu.m. concrete has been placed. The average monthly concrete placement achieved during the quarter was 10,294 cu.m. The balance quantity of 0.408 lakh cum is planned for completion by 30th June 2018. The Plunge Pool and Apron concreting has been completed. Concreting for Cladding walls in Apron, Plunge Pool and up stream of Dam area progressing as per the schedule and shall be completed by 30th June 2018.

Underground Works
Excavation for underground structures is completed. Concrete lining for all underground structures has been completed except an Adit plug which is under progress. Concreting of both SFT gates has also been completed.

Behavior of Instruments Installed in Dam The various instruments installed in the dam body and its appurtenant structures showed deformation in the early stage of installation. However, no significant deformation has been observed during the quarter. All the instruments are functioning properly and are providing the requisite data.

Status Of Head Race Tunnel Works (Package C-2) by Gammon Engineers and Contractors Private
Limited (Gepcl)
All the excavation works in HRT are completed. The status of balance works in

HRT is as below:
Problems Being Encountered in Completion of the Balance HRT
Works
The HRT is on Critical path and all out efforts are being made to complete the balance works as per the schedule. The main reasons for slow progress of works in HRT are as given below:
1. The financial condition of the contractor i.e. GECPL is not sound and the Contractor is facing severe liquidity crunch every month.
2. There had been a shortage of boulders for production of sand and aggregates since last one year as the private developers of the quarry could not supply the required quantity of boulders to the Contractor. However, the issue has now been resolved as the permission to mine the Waichchhu river shoal has been granted by the RGoB in December 2017.
3. Monthly salary offered by M/s GECPL to highly skilled/ skilled/ unskilled workforce is just at par with the wages offered in India. There is no extra incentive available to the above referred workforce to work in Bhutan under difficult conditions.

Measures initiated/ adopted by the MHPA Management for the Completion of the Balance HRT Works
1. To improve the liquidity of the Contractor, MHPA has provided interest free advance of Nu. 11 crore against submission of Bank Guarantees with the approval of the Competent Authority.
Due to the poor financial health of GECPL and stringent regulations adopted by the banking sector of India, the GECPL is finding it difficult to provide BG for the release of balance amount of additional advance of
Nu. 7 crore (Out of total Nu. 18 crore advance approved by the MHPA Authority). MHPA shall be seeking the approval in the next Authority meeting for the release of the balance Nu.7 crore to GECPL even without submission of BG to improve the liquidity and also to complete the balance concrete
lining works.
2. To maintain the continuity of Cement supply by DCCL to GECPL, MHPA has released Nu. 10.6 crore directly to the DCCL on behalf of the Contractor with the approval of the Chairman, MHPA, so that Concreting of HRT is not affected due to the shortage of cement. The endorsement for the same shall be obtained in the next Authority meeting. The above advances shall be recovered from the RA bills of the Contractor.
3. MHPA team is also vigorously pursuing with various Sub-Contractors to mobilise more manpower to expedite the balance works.
4. Since the Management of GECPL is unable to provide financial support to the Site Unit for the HRT works of the Mangdechhu project, MHPA is providing all possible support including interest free additional advance to the Contractor to complete the balance works.
After completion of works, the outstanding advances to the Contractor (if any) shall be recovered by encashing the BGs submitted by the Contractor to MHPA.

Status Of Underground Power House And Associated Works (Package C-3) By Jaiprakash Associates Limited
The excavation in the Machine and Transformer Hall Caverns has already been completed in all respects. The concreting in Transformer Hall has been completed. The Unit-1, 2, 3 and 4 concreting has been completed and generator barrels have been handed over for erection of Generators. All the excavation works in Pressure Shaft 1 and 2, Surge Shaft and Tail Race Tunnel is completed.
The Concrete lining of TRT is completed and lining of Pressure Shaft 1 and 2 is progressing with erection of ferrules. For Surge Shaft, out of 147.20 m, 142.60m concrete lining has been completed and the balance 4.60 m shall be completed by April 2018 along-with the interfacing works
for Gates.

Geotechnical Monitoring of Power House and Transformer Hall Cavern
Geotechnical instruments installed in and around the caverns are regularly being monitored. The recorded data, its evaluation, interpretation and graphical representation along with excavation sequences have been communicated regularly to the Consultant/NHPC Limited and NIRM, Bangalore. The actual deformations observed and recorded have been compared with the deformation as predicted/anticipated in the 3DECnumerical modeling studies. The maximum deformation as anticipated at Crown of Machine Hall was 25.5mm whereas maximum deformation observed was of the order of 13mm (as on 27.12.2017). Similarly the anticipated deformation at U/S and D/S wall of Machine Hall was 73.39mm and 55.05mm whereas maximum deformation observed was of the order of 28.6 mm and 42.8mm (as on 27.12.2017) respectively. Maximum Load observed in the Power house cavern is 211.2KN at EL 1045 m, RD 65m (Downstream side). As such no significant deformation is observed in these instruments in this quarter and all the instrument readings are indicating stable state.

Pothead Yard
1) Excavation of Pits for Gantry Tower and other Equipment Footing at Pothead yard is under Progress. Total 23 nos. of footing have been completed in this quarter including footings for LA, CVT, BPI, ISO, CT and LM. Consolidation grouting has also been done in the foundation rock. Geological logging of the foundation has been done before placing the cover concrete. Out of total 72 nos. of footings for equipment, 65 nos have been completed so far.
2) Monitoring of Pothead yard cut slope is being done with the help of 13 nos of MPBX, 1 no. of SPBX, 6 nos. of Load Cell and survey target points installed at different RDs and Elevations of Pothead yard cut slopes. As such no significant deformation is observed in these instrument readings indicating the stable state.

Status Of Hydro-Mechanical Works (Package: C-4) By Pes Engineers Pvt. Limited
• The works of HM Package is progressing smoothly and all the HM works are scheduled for completion by May 2018 with an acceleration measures except the 4th Radial Gate of Dam which shall be completed by July/ August 2018.
• Fabrication of Steel Liner completed: 10,372.7MT out of total 10492.43 MT (98.86 per cent).
• Erection Completed during the 4th Quarter (October to December 2017): 1357.72 MT.
• Total Erection completed : 8224.13MT (78.38 per cent) .
• Steel Liner erection for Crest & Glacis for S1, S2, S3 and S4 Blocks in Dam has been completed.
• Erection of Intake Service Gates and Intake Bulk Head Gates are completed and is ready for commissioning.
• Erection of Gates for De-silting Chamber are completed and is ready for commissioning.
• Erection of SFT -2 Gate is completed and SFT-1 Gate is under progress.
• Transportation of Surge Shaft Gates to site is completed and erection of rail guide is under progress.
• The erection of hoisting arran­gements for TRT Gates is under progress.
• The erection of Pressure Shaft Steel Liners and Gate Works shall be completed by May 2018. The execution of Radial Gates at Dam shall be completed by July/ August 2018.

DIVISION
Tests Conducted on Construction Materials QC/QA Division has conducted 8760 Nos. of suitability tests during the quarter on different construction materials as given in Table-1. These tests signifies that all the necessary tests as per the QA programme have been conducted and the use of specified materials only has been assured. In addition to this, 36 advanced tests (chemical and mechanical test which cannot be conducted in-house) were conducted at out-side laboratories.

Mix Proportion for M70A20 Grade Concrete
A mix design programme for designing M70 grade high performance concrete for use in Dam Spillway Glacis was undertaken in the QC Laboratory. For this purpose, specific materials like aggregate suitable for wearing surfaces and a good quality PC based admixture samples, cement OPC 43 and 53 grades and PPC were made available for various trials. A total of 50 numbers of laboratory trials were conducted with different combinations of materials and the most suitable optimised mix proportion was finalised and issued for implementation. The following specific processes/materials were recommended for achieving consistent good quality concrete:
1. Only crushed RBM material with abrasion resistance not more than 30 per cent shall be used for aggregate.
2. Silt content of crushed sand shall be within 3 per cent.
3. PC based admixture (Glenium ACE30UG, Make: BASF India Ltd. or equivalent) shall be used.
4. Micro silica: Elkem 920D (recommended)
5. Mixing Time: The minimum mixing time of 2 minutes shall be ensured for each concrete batch.

FIELD QC WORKS
The quality of work at site was maintained by supervision at batching plants, placement sites, checking of quality of materials and workmanship.
The concrete poured in different structures was tested in its fresh and hardened state at batching plants. Fresh concrete properties like slump value, air content, and temperature were determined before dispatch of concrete from batching plant. Hardened concrete was tested by casting cubes and tested at 7 and 28 days for compressive strength.
A total of 1723 sets of concrete cubes were cast and tested for compressive strength. The strength test results were statistically analyzed to assess their conformity with the acceptance criteria given in IS 456:2000. The average of four consecutive strength test results (28 days) were obtained for each grade of concrete used.It is found that the line representing the average of 4 consecutive results is above the minimum acceptance line indicating the conformity with the acceptance criteria as per IS 456:2000.

Long Term Strength Gain
Long term strength gain upto 90 days in concrete was also assessed. For this, mass concrete cubes of different grades cast at dam site were tested at 90 days and some cubes have been kept for 1 year testing also. The average strength at 7, 28 and 90 days for M15 and M25 grade concrete used in Dam.

The average increase in strength at 90 days with respect to 28 days strength is shown in the graph. It is found that the average compressive strength of M25 and M15 grade concrete is increased by 4.02 per cent and 6.53 per cent respectively at 90 days with respect to their 28 days strength. It is evident from the graph that the 90 days strength of M15 grade mass concrete rises upto 21.53 MPa and that of M25 grade, upto 31.59 MPa.

Hydro-meteorological Data
The atmospheric temperature (daily maximum and minimum), River Discharge (monthly minimum and maximum) and sediment (monthly maximum and minimum) at dam site were recorded during the quarter.

Activities of Social and Environment Division
The Mangdechhu Hydro-electric Project Authority (MHPA) is committed for the upliftment of the Socio-Economic conditions of the local communities surrounding the project area. Apart from the up gradation of the Basic Health Units (BHU), initiative for land management campaign, biogas project, rabies control programme, establishment of semi-commercial poultry farm, mass vaccination against Foot and Mouth diseases, Feed and Fodder development programme are being taken up for implementation. MHPA is also committed to protect the existing flora and fauna in and around the project area and the work for compensatory afforestation in the catchment area.

On the request of the community, at Beyling, the restoration and renovation of the dilapidated prayer wheel was carried out by SED and the Security personnel of MHPA. The water prayers were built earlier around fifteen years ago and needed immediate restoration works. The water wheel had stopped rotating at a constant speed and the water flow was also irregular and the roofs had also collapsed.

The structure was expanded and roof was repaired. The work was completed within two weeks. It is simply a prayer wheel that is turned by flowing water. “The water that is touched by the wheel is said to become blessed and carries its purifying power into all life forms in the oceans and lakes that it feeds into”.

Mass Cleaning Campaign
To commemorate the Anniversary of His Majesty the King’s accession to the Golden Throne, 9th of every month is declared as Nation Wide Cleaning Campaign day. MHPA has been actively participating in the Nation Wide Cleaning Campaign. On 9th December 2017, MHPA decided to clean the work place in the project site i.e the Underground Power House area and the Dam Complex. All the MHPA staffs took part in the cleaning campaign and collected solid garbage and debris to the tune of almost 2.5 tons from the Power House and Transformer Hall Cavern areas.

Wachichhu River Training and Reclamation Works To meet the aggregates requirements for HRT lining works and to facilitate the completion of the project in time, an additional 10.009 acres of GRF land was acquired by MHPA in continuation for development of Wachichhu River Shoal area with River Training and Reclamation Works. It was of paramount importance to acquire the additional area to collect the materials; sgravels and boulders as part of river training works and utilize the excess materials for concreting and developmental works. Clearances from Dzongkhag Administration, Trongsa (DAT), Jigme Singye Wangchuck National Park (JSWNP), Department of Forests and Park Services (DoFPS) have been availed including environment clearance from Ministry of Works and Human Settlement (MoWHS). The Land Lease Certificate from National Land Commission (NLC) has been acquired. The collection of materials has been started by M/s Gammon Engineers and Contractors Private Limited (GECPL) since December 2017.

Tashidingkha Drinking Water Supply
The Tashidingkha Water Supply Scheme was one of the commitments of MHPA agreed upon during the acquisition of land at the start/inception of the Mangdechhu Project. The works on the water supply began in March 2017 and the same has been completed in the last week of December 2017. The required materials were provided by the Project while the execution of the work was done by the beneficiaries. The works included; lying of 3.8 km of HDPE main supply pipe line, construction of five numbers of valve chambers, three numbers of air valve chambers and construction of reservoir tank. The scheme benefits 26 Households.MHPA contributed Nu. 2.7 million for drinking water supply at Tashidingkha.

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