BAKUN Dam operator Sarawak Energy Bhd (SEB) said the dam was in good condition as per its last safety review conducted in October 2022.

The operator’s statement came after the Natural Resources, Environment and Climate Change Ministry’s (NRECC) dam safety flying squad reported that eight dams in the country, including Bakun, were “damaged and could pose a threat to residents and properties”.

SEB stated that the dam safety flying squad had later found the dam to be safe and in good condition.

The other seven dams are the Muda and Ahning in Kedah, Jor and Mahang in Perak, the Sultan Abu Bakar dam in Pahang, Babagon in Sabah, and Kenyir in Terengganu.

The NRECC said inspections found high sediment formation in reservoirs, damage to instrumentation and water control equipment, seepage, damage to the integrity of concrete structures, soil erosion, and signs of collapse.

Addressing issues in the report, SEB, in a statement, stated sediment formation in the Bakun reservoir, the second-tallest concrete-faced rockfill dam in the world with generative capacity of 2,400 megawatts of electricity, was “designed to withstand sedimentation up to 1,000 years”.

On damage to instrumentation, SEB stated that the auditors’ concerns had been addressed.

On seepage, SEB stated that the level was “normal and within tolerance” and “minor defects highlighted in the audits were not detrimental to the structure’s stability”.

Nevertheless, it stated that minor defects had been rectified.

On soil erosion of the dam’s downstream slopes, SEB stated that the slopes were assessed as “non-critical and have been resolved”. 

SEB added that its dam safety review audits were carried out by independent international hydropower consultants on all its hydro dams every five to seven years in accordance with the requirements established by the Malaysia Dam Safety Management and the International Committee on Large Dams’ guidelines.

“Sarawak Energy’s hydropower facilities have been designed according to the highest international technical standards for durability and safety,” the state power company said.

“Specifically, its hydropower projects are designed in accordance with guidelines established by the International Committee on Large Dams (Icold), an international body set up in 1928 to share knowledge and set standards and guidelines to ensure that dams are built and operated safely.

“These guidelines are also used to ensure dam safety worldwide including in seismically active regions of the world such as the Himalayas and Japan,” SEB stated. 

In addition to the independent consultants, the power company stated that it has two in-house certified dam inspectors, certified by the Malaysian National Committee on Large Dams (Mycold).

“The company’s dam safety division conducts biannual internal reviews, on top of the daily, weekly, and monthly routine inspections conducted by its onsite personnel.”

Earlier this year, Bakun’s seismicity system was refurbished, and instrumentation was automated.

Sarawak conservation group Save Rivers said high sediment formation in a dam’s reservoir is a common risk expected in high precipitation areas.

Save Rivers chairman Peter Kallang said a study by the University of Oxford’s Energy Policy – which examined 245 large dams built in 65 different countries between 1934 to 2007 – found that large dams negatively impacted human beings and the environment.

“One of the most commonly occurring natural hazards impacting hydropower facilities is landslides. The movement of large amounts of materials close to a site can lead to the burial of structures, weakening of foundations, and dumping of large volumes of materials into the reservoir,” Kallang said.

“Even if a single landslide impact isn’t disastrous, the cumulative effect of small-scale slides can significantly damage a site and reduce the productive water volume. Landslides, however, do not occur only as a consequence of earthquakes, but also as stand-alone events due to general slope instability.” 

Kallang said the 3,300mm-3,800mm annual rainfall in about 75% of Sarawak was an added risk to hydroelectric dams like Batang Ai, Bakun, Muru, and Baleh.

“Runoffs from heavy rainfall contribute to siltation which accumulates in the dams’ reservoirs, which then affects the strength of the dams’ structures.”

He pointed out that the recent catastrophe in Derna, Libya – reportedly due to upstream dam failure on the Derna river, “proved the risk posed by mega dams”.

More than 11,000 people were reported dead or missing in the disaster. – October 3, 2023.