An abnormal increase in water leakage was observed on July 4 in the powerhouse of the 969-MW power plant, located in Muzaffarabad area in Azad Jammu & Kashmir (AJ&K), when it was generating electricity at its full capacity. This was controlled through continuous use of drainage pumps, whereas plant operators noted high water-pressure in the tailrace tunnel -- the tunnel that releases used water from the power plant to the river. The fault was investigated by the foreign consultant stationed at site, and next day it was concluded that abnormal increase in water-pressure in the tailrace tunnel was due to blockage -- about 42-meters in length -- in the 3.55-km long tunnel.
An abnormal increase in water leakage was observed on July 4 in the powerhouse of the 969-MW power plant, located in Muzaffarabad area in Azad Jammu & Kashmir (AJ&K), when it was generating electricity at its full capacity. This was controlled through continuous use of drainage pumps, whereas plant operators noted high water-pressure in the tailrace tunnel -- the tunnel that releases used water from the power plant to the river. The fault was investigated by the foreign consultant stationed at site, and next day it was concluded that abnormal increase in water-pressure in the tailrace tunnel was due to blockage -- about 42-meters in length -- in the 3.55-km long tunnel.
The management therefore decided, on July 6, closure of complete power plant to avoid further possible damage to power generation facilities, and it is dysfunctional since then. The shut-down of power plant is costing massive Rs10 billion to the government each month till the plant recommences its operations fully. Currently, the rehabilitation and restoration work at the tunnel is ongoing with full speed, which is expected to be completed by June 2023, at an estimated cost of Rs2.3 billion, by the Chinese contractor who was responsible for construction of this mega project.
Repair and restoration of damaged tailrace tunnel is one aspect of the issue. The other, and more critical, is to determine the causes of its failure; keeping in view the totality of safety and security of the complete power plant that has a total of 68.29-km of tunnels, and taking remedial actions, on priority, to avoid such incidents in future. Therefore, simultaneously, a team of independent international experts has undertaken, in September, inspection of the tunnel with the mandate to study in detail the serious damage to the tunnel.
The incident occurred within a short period of even less than four years of project achieving commercial operations as its last generating unit was commissioned in August 2018. Corrective measures are to be adopted on investigating the fault, for which no timeline can be given at this stage. However, a preliminary report has already been prepared by the international experts, having outlined a number of possible causes of blockage to the tailrace tunnel.
This run-of-the-river type hydropower complex is designed to divert water from the Neelum River to a power station on the Jhelum River. It mainly consists of a concrete gravity & rock-fill diversion dam, a waterway system involving 68.29-km long tunnels including river diversion tunnel, headrace tunnel and tailrace tunnel, and the underground powerhouse having four turbo-generator units installed each of 242.25-MW capacity, generating total 5,254 GWh energy annually.
Neelum-Jhelum hydropower is considered the world’s most expensive hydropower project -- in terms of cost and time overrun. Project cost accelerated from about Rs15 billion in 1989 to Rs507 billion on completion. Project, which started in 2003 as a priority project, was completed in 2018. The turnkey project was to be completed by the contractor in 93 months but it could go online only after 11 years. Indeed, the project is a typical example of poor planning, ineffective supervision & monitoring, lack of transparency, high-level mismanagement, and, above all, absence of political will. Ironically, this is the only project in the global history of hydropower schemes the construction was awarded to the contractor before appointment of its consultants.
On November 22, the chairman of National Electric Power Regulatory Authority (NEPRA) made a shocking statement to the Senate tanding Committee on Power that the damaged tailrace tunnel of NeelumJhelum hydropower project might collapse, at any time, causing disastrous consequences. Seemingly, the government has not taken a serious view of this alarming situation as yet.
Construction contract was given in March 2007, to a consortium of Chinese companies namely China Gezhouba Group Co (CGGC) and China Machinery Engineering Co (CMEC) on a single-bid basis. However, consultants to provide project detailed design & engineering and construction supervision were engaged in May 2008. This contract was awarded to a consortium of international and Pakistani consultants led by MWH Global (now Stantec) of the USA. The single contract for construction, valued at Chinese Yuan 21 billion, or Rs90.90 billion, covered all project activities by the Chinese contractors on turnkey basis including civil construction, electrical & mechanical power generation equipment, hydraulic steel equipment etc. But the actual cost increased exponentially during construction. Likewise, the consultancy contract, originally valuing Rs4 billion, was later revised to Rs16 billion.
There may be a number of causes for increased pressure in tailrace tunnel such as impact of higher seismic load than designed parameter, cracks in mountain from frequent rock sliding and adverse rock conditions that were not envisaged. This is a vitally important factor that construction contract was awarded on original design of 1997, which was obviously based on seismic conditions before the devastating October 2005 earthquake in AJ&K that severely hit the project site too.
The consultants were therefore entrusted to review and upgrade seismic design parameters ensuring safety and stability of the project. These design changes and subsequent revisions in construction resulted in giving as many as 101 variation (additional) orders to contractor valuing Rs86 billion until 2017 when project had achieved 87 percent physical progress, and variation orders continued till completion of project. According to the Performance Audit Report on the project conducted by the Auditor General of Pakistan in July 2018, “due to the earthquake of 2005 a fundamental change in design was needed to be approved before the award of construction contract”, which was not done.
The Audit Report also mentions that the consultants “failed to carry out a comprehensive review of design and specifications”. At a much later stage when most of the tunneling work was already done, it was decided to use TBM (tunnel boring machine) methodology instead of conventional drill & blast method deployed at site. This also resulted in some additional and vital design changes, besides risks involved for using new technology for tunnel boring. There was a rock burst at the tunnel on May 31, 2015, resulting in death of three workers and serious injuries to another14 workers, while the machine (TBM) was also damaged.
Another possible cause could be substandard construction such as improper concrete lining, insufficient ground support installation, poor construction procedures etc. Tunnels are supported by a sequential concrete lining over its entire length, instead of using steel-fiber reinforced shotcrete technology, which is considered a better solution for long and deep hydro tunnels. The Audit Report highlights that ‘consultants did not take vigilant and appropriate actions’ against contractor. Thus, consultants’ laxity shown to contractor and unsatisfactory supervision by them resulted in poor performance of contractor, besides long delays, and possibility of substandard construction cannot be ruled out.
Changes in water pressure in the tunnel could also be due to unexpected abnormal variations in hydraulic conditions that were not taken care of during the design stage. There were unprecedented high-water flows in rivers in June/July 2022. Also, a power plant, which is said to be operating at its full capacity at the time of accident, might be put into operation at more than its rated capacity though within the design capability of power generation, which is normal. Earlier, in April 2019 the power plant generated up to 1,040-MW beyond its installed capacity of 969-MW.
Meanwhile, international experts’ report is keenly awaited, so that actual cause, or a combination of causes, for tunnel blockage and damage could be known, and remedial measures be initiated by the management without loss of time.
The writer is retired chairman of the State Engineering Corporation
