A first Pre-feasibility Study of the NamNgum2 Project was carriedout by Motor Columbus of Switzerland in 1987 with UNDP/IBR Dassistance,together with the pre-feasibility for two other hydropower projects,NamTheun2 and NamNgum3.In June 1987, a first phase report (" 1 st Phase Report ") was completed.This report ranked the Nam Ngum 2 Project (320 MW) best, the Nam Theun2 Project (800MW) second, and the Nam Ngum3 Project (400MW) third.
The 1st phase report was followed by an Interim Report in February 1988 covering the Nam Theun 2 and the Nam Ngum 2 projects.This report presented the studies made and compared two alternative dam types for Nam Ngum 2, a concrete arch dam and a rockfill dam with the original solution proposing a concrete gravity dam. The alternative with the concrete arch dam resulted in a 13% cost reduction,while the costs for a rockfill dam were calculated to be much higher atthattime .The report proposed a staged development with aninitial capacity of 140 MW for the first stage ( FSL at 340 masl ) followed by a second stage development with an increased capacity of 320 MW ( FSL at 360 masl).
In the year 1991, the Government of Laos (GoL) signed a Memorandum of Understanding with the Shlapak Development Co.Ltd ( with Bilfinger & Berger Ltd., Ch. Karnchang PCL and equipment suppliers ) for the development of the Nam Ngum 2 hydropower project.
In 1993 Nippon Koei Ltd. of Japan prepared an update of the Pre-Feasibility Study for the Ministry of Industry and Handicraft of the Lao PDR and in 1995/1996 a Feasibility Study has been carried out by Electrowatt Engineering Ltd. of Switzerland and Bechtel of USA for the Shlapak Group.
From the studies it was concluded that the foundation conditions were not favorable for the construction of an arch dam of the height envisaged. More detailed design studies compared two other dam types, a roller compacted concrete (RCC) and a concrete face rockfill (CFR) dam of which the RCC alternative was ranked most feasible. However, taking into account the disadvantages of an RCC dam ( longtransport distances and in particular the unreliability of fly as supply in sufficient quality and quantity from Thailand ) the development consortium decided to implement the CFRD concept.
In 1997/1998 Environmental and Social Impact Assessment swerecarried out by Electrowatt Engineering Ltd. of Switzerland.
Due to the Asian financial crisis which started in 1997 the project development was suspended at that time. In the year 2004 a changed development group, now led by Ch.Karnchang PCL, resumed the development of the project. Until the year 2005/2006 an update of the project studies and the Outline Design (TenderDesign) and Tender Documents were prepared by Electrowatt-EkonoLtd. In 2006 construction of the Nam Ngum2 project started with Ch.Karnchang(Lao)Ltd. being the EPC contractor.
II. Project Location
The Nam Ngum 2 Hydropower Project (HPP) is located approximately 90 km north of Vientiane in central Laos and approximately 35 km up stream of the existing Nam Ngum 1 dam just upstream of where Nam Ngum River flows into the Nam Ngum 1 reservoir.
III. Geological setting
The Project is located in an area dominated by terrigenous continental sedimentation of Mesozoicage and shallow marinese dimentation of Paleozoic age, characterized by reddish and gray colours. The fonner sediments are widespread in southern-central Laos and northeastern Thailand, where they have been mapped as the Khorat group.
Compression stresses led to the folding of the Paleozoic beds during the Late Carboniferous followed by post-orogenicde position of sandstones. Slight folding and faulting of the sediment cover started during the Late Mesozoic.The resulting anticlines and synclines are open folds with E-W striking axes.
The geomorphology is strongly controlled by the lithology. Dip slopes and scarps are common for the hards and stone and lime stone beds, while the weaker sand stone and mudstone units result into a more gentle to pography.
Entrenched gorges are common along the Nam Ngum, where mainly hard sand stoneis exposed.In the softer rocksa long the Nam Muay and partly along the Nam Song, open valleys are developed.
In the river valleys, debris deposits are common. They consis to flarge block sands labs, detached from the sands tone ridges on the upper slopes, as a result of stress relieve, parallel to the trace of the valley.
The stratigraphy of the Project area is summarized as follows:
- Jurassic-Cretaceous: red sandstone, siltstone and conglomerate
- Triassic: micaceous sandstone,siltstone and conglomerate
- Pennian-Upper Carboniferous
- 1calcareousseries: mainly limestone
- Argilliteseries:shale,fine sandstone and siltstone
- Lower Carboniferous-Devonian: low grade metamorphoseds and stone, shale, mudstone and limestone.
The predominant rocks in the project area are Mesozoics and stonesand siltstones.The Paleozoic limestones,shalesands chistsare limited to the northern part of the reservoir.
The dam site is located within an arrow section of the NamNgum valley, bordered by steep slopes. The river runs ahnost exactly from north to south. From two originally studied alternative dam sites, the upper one has been retained.
During the years 1994 and 1995 this dam site was geologically exploredto develop information for preliminary design purposes. An aerial reconnaissance of the quarry deposits was conducted. The reservoir area was checked by aerial reconnaissance to evaluate the potential for leak agethrough the limest one formations.
The geological for mationsat the proposed dam site consist of medium bedded to massive cliff-forming sandstone and conglomerate, interbedded, thin to thick bedded claystone, sandstone and siltstone of Jurassic-Cretaceous ageand Quaternary age deposits.
The quartz-rich sandstone forms prominent vertical cliffs through out the dam site area. It is typically tan to light gray, medium to coarse grained and hard to veryhard, particularly when cemented with silica. Near the base of the formation,the sandstone grades in to a well cemented conglomerate. The sandstone is tan to light-brown when weathered and commonly exhibitscross-bedding.
The interceded sandstone/claystone/siltstone units are moderately hard to very hard (excepttheclaystones), closely to moderately jointed and moderately weathered to decomposed where exposed. The interceded claystones and siltstones are less resistant to weathering than the hard sandstones within the interceded formation and form gentler slopes.
About 80% of the reservoir area consists of sandstone in the narrow river valleys and on the steep slopes and of siltstone or claystone in the upland areas of smoother topography. About 15% of the reservoir is under lain by Pennianto Upper Carboniferousage, gray limestone that occurs as isolated cliffs around the villages of Viengkeo (fonnerlyBanXon) and Ban Phapouk. The limestone cliffs are surrounded by the younger sandstones and claystone formation and it is thought that these fonnations overlay the limestone.
Further north in the reservoir, along the Nam Ngumriver, gray mica schist occurs, which is apparently one of the oldest rocks (Paleozoic) in the reservoir area. Another rock, of presumably Lower Carboniferous-Devonianage, isaredshale, cropping out along the NamHuay, atributary of the Nam Leuk. These Paleozoicrocks under layabout 5% of the reservolf.
IV. Environment and Social Development
The project is developed under the 30 years (2007-2037) Concession Agreement (CA) between the Government of Lao PDR (GoL) and Nam Ngum 2 Power Company Limited (NN2PC). To maximize the project benefit with sustainable social and environment condition and to comply with the GoL regulation for development projects, Environment Management Plan (EMP), Resettlement Action Plan (RAP), and Social Development Plan (SDP), and Ethnic Minority Development Plan (EMDP) were planned and implemented to mitigate and monitor the environment and social impacts from the construction and operation of theproject.
Implementation of EMP,RAP,SDP,and EMDP for NN2 HPP covers three main phases;
ü Construction Phase from 2006 to March 2010
ü Priorto Commercial Operation Date (Pre-COD) Phase from April 2010 to November 2010
ü Operation Phase from December 2010 to December 2037
1.1 Environment Management Plan (EMP)
ü Water quality monitoring has been conducted every year since 2006
ü Four times a year in the March, May, September, and November time frames
ü Monitor the·change of conservation or protection forest situation at NN2 watershed area
ü Watershed patrolling and monitoring in Ban Naxaysavang of NamMeuy, NamSieng, and Nam Kor
1.2 Resettlement Action Plan
ü Enable People Affected Persons (PAPs) and concerned parties to understand every step of the compensation and resettlement development.
ü Obtain feed back from PAPs in design and management of resettlement program.
ü The affected people are entitled to receive asdecreed by Laws of LaoPDR
ü To minimize social impact from the project development.
ü PAPs shall be compensated and resettled so as to improve their living standards.
ü Land acquisition and resettlement shall be planned and implemented in such a way as to cause least possible amount of social cultural and economic disruption.
ü Livelihoods shall be restored and be done so without detriment to the environment.
ü Existing cultural and religious practices shall be respected and to the maximum extent practical, preserved.
ü Special measures shall be incorporated on the resettlement plan to protect socially and economically vulnerable groups such as indigenous peoples, families headed by women, children and aged people without support structures, and people living in extreme poverty.
ü The previous level of community services and resources shall be improved after resettlement.
ü The resettlement programs shall be planned and implemented with the consent and agreement of the affected people and host population and shall be encouraged their active participation. A full participatory public involvement process shall be implemented.
ü Land acquisition for resettlement.
ü Detailed design and construction of infrastructures ands upporting facilities.
ü Relocation to new villages.
- 1.3 Social Development Plan (SDP)
ü Public Health
ü Community institute
ü Educationand Culture
- Income Generation program
ü Crop cultivation
ü Livestock raising
ü Forest plantation
ü Other occupational development
- Ethnic Minority Development Plan (EMDP)