Features
Raising of the Kotmale dam – misconceptions and facts
By Asoka Herath
BSc (Geology Hons); MSc (Engineering Geology), CEng.
Over the past few months, there has been considerable interests among not only geoscientists and engineers but also ordinary people in the potential risks faced by two of the major hydropower projects constructed in the central highlands, namely the Victoria and Kotmale projects. These projects have come into the limelight owing to some minor seismic tremors felt in the Victoria area, together with the recent announcement of the intention to raise the Kotmale dam. Alarm bells are ringing that seismic activity may jeopardize the integrity of the Victoria dam and the raising of Kotmale may result in dam failure. Should these dams fail, they will be the biggest manmade disasters our country has ever faced. This risk has prompted suggestions from the people higher up that we should seek advice from foreign experts.
Various opinions from the leading geoscientists of the country, regarding the causes and effects of this unusual activity were aired through the media recently. Some have attributed the seismic tremors to limestone quarrying in the Victoria reservoir area, some as the result of neo-tectonic movements of the central highlands, yet some others said they are reservoir-induced earthquakes. Those who are interested in the fundamentals of such activity may find the presentation in this link useful (https://www.youtube.com/watch?v=7huzvuU9TEI).
The intention of this article is to provide an insight into the geotechnical issues that influence the Kotmale Project, the risks, and to address some misconceptions people may have regarding the project. I take the liberty of writing on these issues as a person who has an in-depth knowledge of the Project by working from the site investigation phase through to construction completion, the later years as the Senior Engineering Geologist, leading the project geoscientist team.
The Project
Kotmale was meant to be the main upstream storage reservoir under the Mahaweli development scheme launched in the 1960s. It will regulate the Mahaweli waters, while providing a substantial energy component. The capacity of the reservoir will be more than doubled by the proposed raising of the dam, approximately by 30 m. The project was inaugurated in 1979 and funded by Sweden. Sir William Halcrow and Partners of UK (Halcrow) with Central Engineering Consultancy Bureau of Sri Lanka (CECB) was the design engineer and Skanska of Sweden was the contractor.
Geology of the Project Area
To understand the project risks, it is essential to understand the geology and structure of the project area. The area is underlain by Pre-Cambrian age metamorphic rocks comprising predominantly of two rock types, charnokite (gneiss) and crystalline limestone (dolomite or marble) with minor quartzites. The limestone is sandwiched between layers of charnokite gneiss.
The rock units are folded into a gentle anticlinorium (an arch like structure-convex shape) which has a slight plunge downstream. The axis of the anticline trends northwest and falls on the right abutment in the dam area. As such the dam foundation rocks have a slight inclination (15°-25°) downstream and into the abutments.
Charnokite is a very strong resistant rock, which does not breakdown easily while limestone deteriorates and erodes more easily. The initial site investigation drilling in the Kotmale valley found limestone thickness varied from 20 m to 130 m within the project area.
The limestone consists mainly of calcium carbonate (CaCO3) and partly magnesian carbonate (MgCO3). Carbonates dissolves in acidic water (acid rain) and forms solution cavities. These cavities have the potential to create leaks from the reservoirs.
Formation of the Kotmale Valley
The Kotmale valley is an amphitheatre-like valley reshaped by the erosional activity of the Kotmale Oya for millennia. It is approximately 5 km wide at the widest point, is surrounded by high rock cliffs up to 300 m high on both flanks, which converge at the Kadadora village; the site of the dam construction. The valley forming process was a combination of differential weathering and erosion of the underlying limestone unit, resulting in the collapse of overlying more resistant rock units. The basal slopes of the cliffs consist of accumulated debris of rocks and soil derived from the cliffs (termed as scree or talus). Historically these talus slopes were in perpetual slow motion (creep) towards the river. They were subjected to numerous landslides, typically during or after heavy rain events. Generally, the Kotmale valley was infamous for landslide activity.
History of Kotmale Project investigations
The location of the dam site had been selected for the seemingly favourable topography formed by the converging valley flanks. One of the first jobs assigned to me when I joined the CECB in 1978 as a young engineering geologist, was to map four exploratory tunnels driven into the abutments of the proposed dam and report the rock conditions. Our evaluation indicated the left abutment had very poor rock conditions not suitable for a dam foundation.
In 1979, to evaluate the landslide risk to the project, Halcrow carried out a landslide survey of the project area. This survey was done due to the frequent landslide activity in the Kothmale area, and its similarities to the Vajont Dam disaster that occurred in Italy in 1963, which wiped out several downstream towns resulting about 2500 deaths.
This study identified the left abutment as a settled block (subsided en mass); limestone solution the likely cause. It strongly recommended to move the damsite downstream and monitor the impressive cliffs on the left flank of the valley for potential movements.
Evaluation by a panel of experts
As these findings were major issues impacting the viability of the Project, the Mahaweli Authority of Sri Lanka as the owner of the project, in early 1980 engaged a panel of foreign experts who were the leaders in the fields of rock and soil mechanics, to evaluate the potential issues and provide recommendations. This panel endorsed the relocation of the damsite.
Subsequently, the dam axis was moved approximately 200 m downstream from the original location.
Nature and distribution of the limestone
At the new location, the limestone was at a much greater depth below the dam foundation compared to the original site as shown in Figure 1. Even so, solution cavities were observed in the contact zone and within the limestone itself identified by drilling and close circuit television (CCTV) inspections carried out in the drillholes. Our best estimate indicated small cavities, however a drillhole represents only a small area, therefore the existence of larger cavities could not be ruled out.
Leakage through cavernous limestone is widespread from the reservoirs built in our hill country. The Samanalawewa Project is the best example where significant leakage had been occurring through a cavernous limestone under the right abutment since the impoundment, which could not be sealed.
Continuity of the Kotmale limestone
Investigations were carried out to establish the continuity of the Kotmale limestone to downstream areas in view of potential leakage which were inconclusive. The recent geological map for the Kandy-Nuwara-Eliya districts (GSMB), I am convinced that the Kotmale limestone continues to Gampola-Atabage Valley and further to the Victoria Reservoir as a major rock unit. The limestone quarrying in the Victoria Reservoir area occurs in the same unit, which caused the recent furore about seismic events allegedly caused by blasting. Whilst I do not believe there is (or will be) significant leakage from Kotmale Reservoir, future raising of the dam may enhance leakage if it exists which needs evaluation.
Water tightness of the dam foundation
To eliminate the risk of water leakage through the limestone under the dam foundation, it was extensively grouted from a grouting gallery constructed below the dam level (see Figure 1). Generally, the grout intakes were low. Nevertheless, few holes required significant amounts of grout before they could be sealed. Subsequent water pressure testing indicated the limestone unit was properly sealed and the foundation was watertight.
Monitoring of the cliffs and other landslides
During the initial impoundment, the cliffs were inspected by walkover surveys and by periodic monitoring with geodetic surveying. Movements of any significance, precursor of an impending major failure were not recorded during the early years after construction.
Reservoir Induced Seismicity (RIS)
One important consideration in the construction of large reservoirs is the potential for reservoir induced seismicity (RIS). RIS is the incidence of earthquakes triggered due to the impoundment of water behind a dam. A simplistic explanation is that reservoirs trigger earth tremors due to the load of water which could activate otherwise dormant faults, the energy released causing earth tremors.
Halcrow decided to investigate the risk of movement of some major structures present in the Kotmale reservoir area upon impoundment, which could potentially induce seismic events. Consequently, a micro-seismic monitoring network (MSMN) consisting of four monitoring stations was established around Kotmale project in 1981. The monitoring program was managed by the CECB and continued until the early 90s.
Published data (Fernando & Kulasinghe 1985) show that the maximum event recorded at Kotmale during the first two and half years of monitoring, was an event of 2.25 magnitude (Richter Scale), located far away from the project area. The monitoring led to the conclusion that the potential for RIS at Kotmale was extremely low or non-existent. However, in view of the recent seismic events recorded around Victoria, it will be prudent to revisit the monitoring records from the Kotmale network, presumably archived by the CECB.
Potential risks from future raising
The Kotmale project infrastructure, were designed and constructed for future raising. Theraised dam simply achieves the original vision of the project, as the main upstream storage reservoir and increases power output.
In my opinion the geotechnical risks arising from the raising of the Kotmale dam are as follows:
= The raised water level in the reservoir will fully inundate the scree slopes and reach the base of the left bank cliffs with potential to create major landslides. Cliff monitoring should be re-established using modern methods such as satellite based synthetic aperture radar interferometry (inSAR).
= There is potential for leakage through the limestone with raised water levels. All evidence suggests the limestone under the dam was properly sealed. Leakage from the reservoir flanks cannot be prevented, which is not a fatal flaw to the project. Requirement for abutment sealing should be revisited.
= It will be useful to re-establish the monitoring program of stream gauging in the Gampola-Atabage valley to investigate if any leakage will occur from Kotmale to Atabage valley. This should be initiated before the dam raising.
= All evidence points to reservoir induced seismicity is a non-issue for Kotmale Project.
Finally, I strongly advocate the raising of the dam for the following reasons:
= The original project infrastructure was developed with the intention of future raising.
= There are potential risks but not fatal flaws to the viability of the Project. These risks can be mitigated.
= People were evacuated from their ancestral lands going under the reservoir and if the project is not completed as originally intended, then this relocation of people was without merit and a grave injustice to them.
= The country unnecessarily lost approximately 30 MW of power for more than 35 years.
The potential risks with the raising of the Kotmale dam discussed here need to be evaluated, and if the need arise, they should be mitigated and managed using local expertise. In my opinion, what Sri Lanka lacks is good project managers vital in successful implementation of projects of such enormous national importance. In hindsight, the Kotmale reservoir should have been built to the full capacity at the first instance.
(The author currently works as a Principal Geotechnical Engineer with AMC Consultants Pty Ltd, Perth, Australia, and can be contacted at hma1904@gmail.com).
Features
The Division Bell Mystery
Tales of Mystery and Suspense 3
The murder, in a private dining room in the house, is of a financier with whom the government was negotiating a loan. When this seemed difficult the Minister of Home Affairs agreed to lead discussions, since he had known Mr Oissel the financier when they were young. Hence the private dinner, but when the Minister stepped out for a vote, Oissel was shot just as the Division Bell rang.
The Brahms and Simon detective novels, the first of which I wrote about last week, were amongst several books by the pair that Robert Scoble gave me when I was in Australia towards the end of last year. Amongst them was another thriller of a very different sort, though that too was written and set between the wars.
Called The Division Bell Mystery, it was set in the House of Commons, the first such book I believe, and was by Ellen Wilkinson, a Labour MP who became Minister of Education in Attlee’s government after the war, having served previously as Parliamentary Private Secretary to several ministers. Her hero Robert West is also a PPS, but a conservative, and his Minister, of Home Affairs, is an old style aristocrat, not much loved by the less orthodox Prime Minister, who nevertheless needs his support on many occasions.
The murder, in a private dining room in the house, is of a financier with whom the government was negotiating a loan. When this seemed difficult the Minister of Home Affairs agreed to lead discussions, since he had known Mr Oissel the financier when they were young. Hence the private dinner, but when the Minister stepped out for a vote, Oissel was shot just as the Division Bell rang.
West was just outside the door when the shot was heard, and when he opened it saw only the dead body with a revolver beside it. The assumption that this was suicide was however challenged by Oissel’s grand-daughter Annette, who was his heir, on the grounds that he would never have killed himself. But her view was given greater credence by the Inspector put in charge of the case who said there were no burn marks on the body which would have been the case had Oissel fired the pistol himself.
Matters are complicated by the fact that Oissel’s flat had been burgled while he was at dinner, and Jenks the policeman allocated to him, who had served the Home Secretary and seemed more acceptable to Oissel than someone from the Security Service, had been killed. Matters get even more complicated when Annette says her grand-father’s notebook in which he wrote his secrets in cipher was missing.
That was found in Jenks’ pocket, and then a photographer came to West to say he had been asked by Jenks to photograph this. More worryingly for West, he finds in the Home Secretary’s drawer a few pages from the notebook with what appears to be an interpretation of the cipher.
Overwhelmed by all this he confides in a recently created peer who knows all about the business world, who insists that they leave the house party at which they had met over dinner and discuss the matter with the Prime Minister who promptly summons the Home Secretary.
But the Home Secretary had gone to Scotland to launch a ship over the weekend, so the meeting could take place only on the morning of the Monday, when difficult questions were expected on the adjournment motion. He admits at the meeting that he had got Jenks to take the notebook, and also that he knew the code since it had been created by him and Oissel when they were young.
He thought he should resign, and even contemplated suicide, but the Prime Minister told him that that would be even worse for the government, and that he should go home to bed. The Prime Minister said that he himself would handle the question, which he did with aplomb, insisting that confidentiality was needed until the inquest. What had happened would be made clear then, he declared, leaving West and Inspector Blackit and Lord Dalbeattie what seemed the impossible task of solving the murder.
Dalbeattie had suggested that West ask a female Labour MP who was very fond of him to get what information she could from the staff. That there was some involvement there had become clear when West, going back late one night to collect a briefcase he had left in a dining room, found someone lurking in the dark in the corridor outside the private rooms. Room J, where the murder had happened, was meant to be guarded throughout by a policeman, but he had left the room having felt dizzy, and it seemed that his coffee had been drugged. West’s sudden appearance however had prevented anyone else getting into the room.
Dalbeattie decides to recreate the scene of the murder and has a dinner party in Room J on the Tuesday night, inviting West and Annette and the society hostess at whose house he had met, and also Patrick Kinnaird, an MP who was engaged to Annette, as well as the Permanent Secretary to the Home Ministry.
After coffee Inspector Blackit comes in with Grace, the Labour MP who had got the confidence of the staff, and a journalist who had also been helpful, and just as they say they think they are on the track the division bell rings. Grace jumps up and tells the Inspector that that provides the solution and they get a ladder, and sure enough find the revolver in the space where the bell is. Directed at the place where Oissel had sat, it had been primed to go off with the ringing of the bell. The waiter who had helped to set things up made clear who the murderer had been.
The reason for the murder and the confused motives of all those involved made for a fascinatingly intricate mix. But also impressive in the book were the descriptions of the isolation possible in the crowded premises of the house, the forceful characterization of the members – Grace based on the writer, the society hostess based on Nancy Astor, the first female MP – and the laid back nature of senior politicians which West realized had to change in the brave new world of high finance.
Features
The challenge of keeping value-based politics alive
The current outbreak of anti-immigrant protests in Durban, South Africa is bound to have taken many a subscriber to value-based politics or political idealism quite by surprise. After all, this is evidence that despite the historic accomplishments of nation-builders of the stature of the late President Nelson Mandela it cannot be taken for granted that identity politics, including racism in its worst forms, is no more in South Africa.
At the time of this writing details are scarce on the substantive root causes of the protests but it could very well be that economic grievances, particularly on the part of the majority community in South Africa, are contributing considerably to the disaffection. Shrinking employment and material prospects are likely to figure majorly among the factors igniting the unrest.
Fortunately, the local authorities in Durban are losing no time in calling for peaceful co-existence among the relevant communities and are pointing to the vital importance of stepping-up national integration processes. Apparently, immigrants in sizable numbers from neighbouring countries are present in Durban. However, international TV footage of the protests quoted some local authorities as saying that the majority of the immigrants in some centres that housed them were not illegal migrants and had the documents that entitle them to be in Durban.
In the Durban protests the world has fresh proof of the socially divisive consequences of the gathering globe-wide economic disaffection, touched off particularly by the continuing crisis in West Asia. Going ahead, the world would need to brace for increasing identity-based unrest of the kind it is just witnessing in South Africa.
Considering that the material lot of ordinary people everywhere could only aggravate progressively, with the US and Iran showing no signs of negotiating an end to their confrontation any time soon, it will be left to the more democratic and progressive sections of the world community to initiate positive measures collectively to bring a measure of relief to the discontented.
The swiftness with which such relief will be provided would depend crucially on the importance those sections taking up these undertakings attach to value-based politics as opposed to Realpolitik of power politics.
Going by these yardsticks, Italy could be considered to be moving in the right direction. Recently Italy came to the fore in initiating the collective named, ‘Rome Coalition for Food Security and Access to Fertilizer’, which has as one of its aims the swift provision of fertilizer to economically weak African countries.
In a recent statement Italian Minister of Foreign Affairs and International Cooperation, Antonio Tajani, said that a principal aim of the project was to ensure that the farmers of Africa gained easy access to fertilizer, considering that food security is a growing concern among some of Africa’s economically vulnerable countries.
The statement went on to mention that some 30 countries hailing from the Mediterranean region, the Middle East, the Balkans as well as the FAO had been invited to join the coalition. The venture is far-seeing in that food security is main among the reasons for social discontent which in turn could degenerate into endemic political turmoil and bloodshed. Separatist violence and geographical fragmentation of countries wouldn’t be too far behind these developments, as Africa itself has often proved.
It is hoped that more G7 countries would take the cue from Italy and do what they could to ease the hardships of economically distressed countries, particularly of the global South. In these efforts they would need to break rank with the US, which is today brutally indifferent to the consequences of its policy of making ‘America First’, come what may.
Going by current developments, the Trump administration seems to be blithely oblivious to the wider, deleterious effects of its policy course in West Asia. Besides rendering Iran militarily and otherwise impotent nothing else seems to matter to Washington, as regards West Asia. This is policy short-sightedness of an extreme kind. After all, right now West Asia could be said to be sitting on the proverbial powder keg.
On the other hand, Iran is not giving the world the impression that it is doing anything constructive to get out of the policy straitjacket that it wove for itself decades ago. Rather than enter into a policy of ‘live and let live’ in relation to Israel in particular and initiate a process of reconciliation with the latter, it has chosen to operate within policy parameters that continue to damn Israel. This has put Israel always on the ‘defensive’ so to speak and prevented the opening up of space for meaningful dialogue.
That said, Israel is obliged to explore the possibilities of entering into a negotiatory process with the Arab-Islamic world that could lead to a de-escalation of tensions and bloodshed. It cannot continue to look at its neighbours through lenses that distort them as archetypal enemies who should be ‘wiped off completely from the face of the earth.’
In other words, the need is urgent for Realpolitik to give way to value-based politicks. Italy is beginning to prove that the latter approach could be pursued with some success. May be the EU and the UK could throw their weight behind these initiatives as well and establish that international politics could be refashioned on the basis of humane, civilized norms. The UN would need to be fully supportive of these moves and prove an organizational nucleus of the operations that follow.
In fact the time is ripe for people of conscience to collectively stand up on the side of peace and say ‘No’ to war and violence. Organizations such as the ICRC, the WHO and Medicines Sans Frontiers have already taken up this call. Referring to the widespread destruction of health facilities and their dehumanizing results these organizations have said, among other things, that ‘This is not a failure of the law. It is a failure of political will.’
True, ‘failure of political will’ among those powers that matter accounts for the runaway, uncontrollable nature of war and destruction in contemporary times, but more fundamentally it is a failure of the human conscience. It could very well be that the phenomenal levels to which violence and war have been unleashed today have had the effect of deadening consciences. This is a matter for urgent study and wide discussion.
Features
Vesak celebrations … with Cuteefly
I would describe Indunil Kaushalya Dissanayaka as innovative and creative, and she operates under the name of Cuteefly.
Indunil always comes up with something novel to celebrate special occasions, and she does it with candles … and that’s her profession.
She was in the spotlight when she created a happening scene, with candles, for Christmas, Sinhala and Tamil New Year, and Valentine’s Day.
As lanterns light up Sri Lanka for Vesak, the Colombo-based candle maker is quietly turning wax and wick into little pieces of the festival.

Candles reflecting Vesak themes
Her candles reflect Vesak themes – light, peace, remembrance, giving, etc., to enable you to fill your Vesak celebration with devotion and beauty.
Among her Vesak creations is a lotus-shaped soy candle, scented with sandalwood, lavender, etc., meant to burn during this Vesak Poya Day.

Indunil Kaushalya Dissanayaka: Customers
praise her for her creativity
These handcrafted Vesak candles are perfect for offering at the temple, she says.
What makes her creations so novel is that they come in different shapes, scents, themes, and all are handmade.
What’s more, her customers have heaped praise on her for her creativity.
According to Indunil, her creations are perfect as a thoughtful gift … to bring beauty, unity, and light into every moment.
Says Indunil: “Our beautifully handcrafted Unity candles are designed with premium detail and love, making them perfect for celebrations, gifts, and meaningful occasions.”
Cuteefly, says Indunil, is available online.
Readers could contact Indunil on 0778506066 for more details.
He Facebook Page is: Cuteefly.

Handmade with love
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