Yeywa Dam

Yeywa Dam
River Myitnge at Shwe Sar Yan
Location of Yeywa Dam
Location	Kyaukse Township Burma
Coordinates	21°41′20″N 96°25′17″E / 21.68889°N 96.42139°E / 21.68889; 96.42139Coordinates: 21°41′20″N 96°25′17″E / 21.68889°N 96.42139°E / 21.68889; 96.42139
Construction began	2004
Construction cost	US$700 million
Designer	Colenco Power Engineering Ltd. (Switzerland)
Nearest city	Mandalay (52 km (32 mi))
Dam and spillways
Type of dam	RCC Dam
Impounds	Myitnge River, a tributary of the Ayeyarwady River
Length	690 m (2,263.8 ft)
Height	134 m (439.6 ft)
Spillway type	ungated spillway 157 m (515 ft) crest width 136 m (446 ft) net width
Spillway capacity	design flood: 6,600 m3 (5.4 acre·ft)/s
Reservoir
Creates	reservoir
Total capacity	2.6×109 m3 (9.82 Tmcft) gross storage 1.6×109 m3 (56.5 Tmcft) active storage
Catchment area	10,890 sq mi (28,200 km2)
Surface area	14,580 acres (59.0 km2)[1]
Max. water depth	>180 m (590.6 ft)
Power station
Commission date	2010 est.[2]
Turbines	four Francis Turbines @ 197.5 MW [3]
Installed capacity	800 MW
Annual generation	3,550 Gigawatt hours per year
Website Yeywa Dam

The Yeywa Hydropower Dam (Burmese: ရဲရွာ တာတမံ), located on the Myitnge River, 52 km (32 mi) southeast of Mandalay city, at Yeywa village in Kyaukse Township, Mandalay Division in central Myanmar, is the country's first roller-compacted concrete (RCC) dam,^[4] and the site of a 790-MW hydroelectric power plant, the largest in the country.^[5][6]

Background

The plant feasibility study was done in 1999. In May 2001, agreement of consulting service between MEPE and COLENCO Power Engineering, Ltd. had signed. In 2003 agreement part 2 for Detail Design, preparation of tender documents and guidance services for construction supervision was signed. The river diversion was completed on December 12, 2004 and RCC placement began on February 8, 2006.^[7] The Burmese government announced plans for the Yeywa Dam in late 2001. In 2004, Burma’s Ministry of Electric Power (MEPE) signed a MOU with a consortium of Chinese companies created by China International Trust & Investment Co. (CITIC) and Sinohydro Corporation for implementation of the project. On September 2, 2005, a ceremony to mark the signing of contract between the Hydroelectric Power Department under the Ministry of Electric Power and the China National Heavy Machinery Corporation (CHMC) for the Yeywa Hydroelectric Power Project was held in Yangon [Rangoon], Site work began in 2004 and is expected to be complete by the end of 2010.^[8]

Design

The dam design comprises a 197 m (646 ft) high RCC embankment gravity dam, built of 2,800,000 cubic metres (3,700,000 cu yd) of concrete. The dam includes an ungated spillway of reinforced conventional concrete cast after RCC placement, located in the central section of the dam for a design flood water discharge of 6,600 m³ (5.4 acre·ft)/s. The 448 ft (136.6 m) wide spillway consists of eight 56 ft (17.1 m) wide and 39 ft (11.9 m) high outlets.^[1]

There is a 790 MW (4 × 197.5 MW) powerhouse at the toe of the dam on the south bank of the river.^[5] The power house containing the turbines and generators is 510 ft (160 m) long, 148 ft (45 m) wide and 197 ft (60 m) high. The power house and dam structures are designed to withstand earthquakes of up to eight on the Richter scale.^[9]

The power generation facilities consist of four water intakes, each consisting of 22 ft (6.7 m) diameter and 492 ft (150.0 m) long high tensile steel pipe penstocks and 4 vertical axis Francis turbines and generator units and associated electro-mechanical and auxiliary equipment installed in an open air powerhouse. Four water intake towers were built as conventional reinforced concrete structures abutting the upstream (east) face of the RCC dam. This enabled the contractor to build the towers above the penstock inlets before the start of RCC construction in order to minimise interference with the RCC construction activity.^[4]

There is one permanent 10 m (33 ft) diameter, 450 m (1,480 ft) long, diversion tunnel in the north river bank serving as a bottom outlet. This outlet tunnel enables reservoir drawdown and control during reservoir filling, maintenance of downstream riparian river flow during the impounding period and, together with the spillway, erves to redirect flood waters of the Myitnge river and maintain river flow during an emergency when all turbines are closed down.^[5]

Two double circuit 230 kV transmission lines connect the main transformers located on the downstream side of the powerhouse to an open-air switchyard, located on the south river bank 550 m (1,800 ft) downstream of the powerhouse. The Yeywa Dam will supply electric power to the Meiktila Sub-Power Station through the 110 km (68 mi) long Yeywa-Meiktila 230 kV double power line link to the southwest and to the Bellin Substation through another 50 km long 230 kV double power line link in the west. The Bellin and the Meiktila Sub-Power Stations will be linked to each other with 100 km long 23 kV double power lines. US$ 45.8 million worth of 230 KVA cables and equipment were used for construction and linking of these sub- power stations.^[10][11]

Construction

Several construction companies from China, Switzerland, and Britain and Myanmar have been involved in various stages of the Yeywa Dam, including the Chinese companies: Export-Import Bank of China (China Exim Bank), China Gezhouba Group Co. (CGGC), China National Electric Equipment Co., Hunan Savoo Overseas Water & Electric Engineering Co. and China National Heavy Machinery Co. The Swiss company COLENCO Power Engineering, Ltd., the Germany based company Voith Siemens and the British Malcolm Dunstan & Associates.^[8]

A key aspect in the successful construction of the Yeywa RCC dam was comprehensive training of the local staff during preparative for and initial stages of the construction.High-Tech Concrete Technologies(HTCT)which is a member of Shwe Taung Group, was the one who has been succeeding the knowledge from local perspective.^[12] Up to 5,000 workers were employed on this large construction project. Equipment selected for the concreting operations include Putzmeister’s MX 32 stationary boom, an M 38 truck-mounted concrete pump and two BSA 2,109 HP stationary pumps.^[13]

A bridge was built across the river, just downstream of the dam, to replace the ferry system, which previously was the only means for transport across the river.^[5]

Impact

3,550 Gigawatt hours of electricity per year will be supplied to the Mandalay Division regional power grid for public and private consumption.

In 2005 the Myanmar Times reported that three villages near the dam had been relocated. The villagers had depended on the Myitnge River for their fishing, farming and logging livelihoods, the sources of which will be flooded by the dam. Ancient cultural sites like the Sappa Sukha Htattaw Temple will also be flooded and forever lost.^[3][14]

References

External sources

External images

Earlier works at Yeywa showing overtopping of Stage 1 and 2 (July 2006), photo

Earlier works at Yeywa before completion of integrated cofferdam (April 2007), photo

Yeywa RCC dam under construction (January 2008), photo

Yeywa Hydro Power Project, video 6:03