In the backdrop of the looming water scarcity and energy security, Pakistan Water and Power Development Authority (WAPDA) has recently embarked upon implementing various multipurpose water and hydropower projects. These include Mohmand Dam, Dasu Dam and Hydropower and Diamer-Basha Dam projects.
On May 13, 2020 WAPDA has awarded contract for construction of only the main dam (excluding powerhouse and related infrastructure) to the joint venture of PowerChina (Power Construction Corporation of China) and the Frontier Works Organization (FWO) of Pakistan at Rs442 billion. Construction of dam, scheduled for completion by 2028, is expected to start as the contractor has already mobilised. Interestingly, FWO has no experience of constructing large dams, whereas PowerChina, primarily a power plant machinery business, was founded in China on September 29, 2011. The 21MW capacity Tangir hydropower station, within the scope of this contract, is being developed on the Tangir River to meet power requirements of Diamer-Basha project during construction. Financing details of the contract are not available to assess how much is the foreign exchange portion and how it is being financed by the Chinese contractor; as supplier’s credit or funded by the Chinese government – and on what terms. It is reported that the project has not yet achieved financial-close either.
WAPDA has appointed project consultants, namely Diamer Basha Consultants Group (DBCG), at a cost of Rs27.18 billion. The DBCG has a staggering team of twelve national and foreign consultants – perhaps a global first in dam construction industry. The list includes National Engineering Services Pakistan-- NESPAK (lead), Associated Consulting Engineers (Pakistan), Mott MacDonald International (UK), AFRY (Poyry) of Switzerland, MWH Global-Stantec (USA), Dolsar Engineering (Turkey), China Water Resources Beifang Investigation, Design and Research Co (China), Mirza Associates Engineering Services (Pakistan), Al-Kasib Group of Engineering Services, Development Management Consultants (Pakistan), MWH Pakistan and Mott MacDonald Pakistan. None of the Pakistani consultants, including the lead, has any recent experience of supervision of such large projects.
From its very inception the Diamer-Basha Dam project has been mired in controversy, criticism, concerns and divergent views it attracted on the aspects of its location, land acquisition, resettlement, compensation, environmental and ecological issues, appointment of international consultants in the past, and now award of contract for consultancy and construction. These issues have obscured the significance of this critical project of national importance, besides causing an incredible delay of decades.
The mega project is located on River Indus in the seismically active mountainous region of Diamer District (Gilgit-Baltistan) and Basha in Kohistan District (Khyber Pakhtunkhwa). This will become one of the most challenging dam and hydropower project ever undertaken, given the difficult geological and topographic site conditions. The project already enjoys global distinctions, though not very flattering. On completion, it would be the largest, highest dam in the world, and the most expensive dam and hydropower project too. It is the only project ever undertaken in the world in two phases---main dam is being constructed now, whereas phase two; power infrastructure and its electromechanical equipment has been postponed for an indefinite period. There will be two underground powerhouses, one on each abutment, of cumulative capacity 4,500MW. For dispersal of power to the national grid, two circuits of 500kV transmission lines over 450km long and difficult stretches of seismically active hilly region are planned.
Initially, the Diamer Dam project was to have gross storage capacity 7,030 million cubic meters (MCM) with a height of 200 meters, and power generation capacity 3,360MW. Total cost of the project was $6.60 billion. Feasibility was completed in 2001. But then the project location was revised to Diamer-Basha, allegedly so that the Khyber Pakhtunkhwa province could also claim “hydel royalty”. The project studies were revised accordingly by the German consultants who were appointed at a time when the firm was blacklisted by the World Bank. The project was approved in 2006 and finally by the ECNEC in 2008 with the revised cost of $12.6 billion, which was further revised to $13.68 billion in July 2012. However, there was no headway on the construction of main project due to non-availability of financing from the international donors like the World Bank and Asian Development Bank (ADB), considered essential for a project of this nature and magnitude.
Recently, serious questions have been raised by some engineers in the two articles that appeared in The News about the suitability of the RCC construction for the Diamer-Basha Dam project. The dam is proposed to be of roller compacted concrete (RCC), which is known as state-of-the art technology, but a new method for large dam construction. It has advantages of being cost-effective, high construction speed and more economical compared to conventional embankment type (rock-fill or earth-fill). RCC dams are further classified as gravity, arch and buttress type. Diamer-Basha Dam will be gravity type.
WAPDA had engaged various international independent consultants and panel of experts in the past, who confirmed suitability of an RCC dam. China is experienced in the construction of large RCC dams, and has recently completed constructing the over 216 metre RCC gravity Longtan Dam on Hongshui River, south China. Nonetheless, according to a study conducted in Sweden in 2018, “All RCC dams that have been built, usually face challenges both during construction and after construction, and it includes everything from temperature variations, cracks to leakage.”
Dams are considered critical infrastructure for any country and every dam project is unique as the site conditions determine its safety and sustainability. Planning and construction of large dams and hydropower projects have fundamental requirements of carrying out detailed geological, geophysical, seismological, topographic, hydrological and environmental studies, ensuring safety and security of dams.
Best practices for these investigations are adapted, and necessary measures are essentially put in place. It is however disturbing that experts on seismic aspects of large dams have recently raised serious questions about the design of Diamer-Basha dam.
A report published in a national newspaper on April 7, 2019 (Special report: how safe will Diamer Basha dam be?), while recognising that “as a concrete gravity high dam located in one of the most intense tectonic regions of the world, the Diamer-Basha Dam project represents a tremendous opportunity for Pakistan to achieve something that is unprecedented in the world”, these two international experts have opined that “from the information gathered, it seems that the maximum seismic acceleration proposed for the dam design is less than half of the actual value experienced during the 2005 Kashmir Earthquake!”
This however may not be factual, as many international consultants, over a span of a decade or more, have carried out detailed studies of the regional seismic zone, based on which seismic parameters for the project design were adopted. The dam has a seismic safety factor to withstand an earthquake of magnitude 8.0, according to information available from WAPDA sources. On the other hand, international experts who have been studying the Himalayan Tectonic Interface belt for decades are predicting future earthquakes of magnitude 8.7 in the region.
Dam disasters can happen due to a variety of factors, including design error, earthquake, landslides, rock-falls and glaciers into the reservoir, extreme inflow of water as a result of heavy unusual rains, use of substandard construction material, geological instability etc. All these aspects need in-depth investigations at the planning, design and construction stage. Dam failure can have disastrous consequences not limited to loss of lives and property. There have been many dam failures in countries including the US, Canada, Italy, Russia, Indonesia, Vietnam, China and India.
The Banqiao Dam burst in China in August 1975, caused 171,000 deaths. The large dam of 492-MCM reservoir capacity and hydropower station was constructed in 1952. An irrigation dam in Pakistan, Shakidor Dam near Pasni (Balochistan) collapsed in 2005 after two years of its construction resulting in loss of at least 70 lives. In 1979, Machchu-2 Dam incident in India caused about 10,000 deaths, while in 1961 their Panshet Dam collapsed after eleven years of its construction, claiming over 1,000 casualties.
One of the objectives of the Diamer-Basha Dam (272-meter high, to impound a 100km long reservoir), which is located 74km upstream Dasu Dam, currently under construction, and 315km upstream Tarbela Dam and Ghazi Barotha hydropower station, is to control floods downstream. On completion, the Diamer-Basha reservoir will have total storage capacity of 10,000-MCM (or ten billion metric tons in mass) and live storage capacity of 7,900-MCM (or 7.9 billion metric tons in mass) of water. This is a significant volume and mass of water coupled with a huge concrete volume of some 17-MCM (or 40.9 million tons in mass). One can imagine the catastrophe of a failure or accident. Hence, there must be no compromise on the safety of the dam.
It is therefore imperative for WAPDA to undertake detailed design review in consideration of recent and predicted seismic changes in the region before commencement of dam construction by engaging international independent seismic experts, particularly in view of inadequate experience of the existing contractors. This will ensure minimising the risk of Diamer-Basha Dam failure due to technical mistakes which can potentially create a disaster.
The writer is retired Chairman of the State Engineering Corporation