Thoughts on economics and liberty

Two of Indrajit Barua’s many articles

Following on from my post here. I’d like to thank Pankaj Das for managing to collect a few articles from the late Indrajit Barua’s home.

I’ve OCRd two of them. I’m publishing the scanned image for all three + text (for two of them). These are specialist technical articles, not the ones that demonstrate his liberal credentials. I do recall many of his articles criticising the public sector and the waste created by socialism.

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Measures to protect Majuli, Indrajit Barua, Thursday, September 8, 2016

The world’s largest riverine island, Majuli, the seat of Assamese culture and a piece of real estate that occupies a very important position in our hearts and minds, which also happens to be the constituency of our present Chief Minister, and under serious threat of extinction due to soil erosion by the Brahmaputra, is hosting a Cabinet meeting of the Sarbananda Sonowal-led Government on September 8. 2016.

At care time, the Brahmaputra and the Dihing flowed close to each other in parallel courses. A flood that occurred around 1750 AD is said to have diverted a part of the flow of the Brahmaputra through the channel of the Dihing about 190 km upstream of its confluence. When the two rivers joined, the intervening land area became what is now called the Majuli island. In the later part of the 18th century, Mejuli was a duster of 15 large and numerous small islands.

In 1901 the island covered an area of 1255 sq km. By 1917. the island’s area had been reduced to 751 sq km; it gradually shrank to 564 sq km during 1966-19T2. to 454 sq km in 1996 and to 422 sq km in 2001; its present area would be around 400 sq km. From 1917 to 1972. the average annual rate of erosion was 1.77 sq km, 1.84 sq km per year from 1972 to 1996. and 6.42 sq km per year from 1996 to 2001. These figures clearly indicate a gradual increase in the rate of erosion progressively despite the very expensive efforts of the State and Central governments to control erosion.

The island is under the threat of extinction due to the extensive soil erosion of its banks, The reason for it is the large embankments built in the nearby towns upstream to pre vent erosion during the rainy season when the river overtops its banks. When the flood recedes, it carries away substantial chunks of Assam’s land mass. Because Majuli sits directly in the course of the flow of a turbulent Brahmaputra, the river vents its fury on the island, eroding whatever comes in its path whenever its waters develop “silt hunger”.

We therefore need to take a fresh look at our erosion control measures with the view to adopting technically viable schemes that will actually arrest erosion, because, clearly, the schemes undertaken by the State Water Resources Department and the Brahmaputra Board Wile have failed to protect Majuli from erosion despite hundreds of crores of public money having been expended in the name of erosion control.

Much of the upper reaches of the Brahmaputra and the entire island of Majuli consist of fine grained sand (technically, silt), which lacks cohesion (adhesive quality) and it is in such kind of soils that river bank erosion occurs easily. What is therefore needed is to change the soil properties to make the non-cohesive or sandy soils more resistant to erosion. This can be done by injection of a slurry of cement and water into the soil from the ground surface deep into the ground below the “low water lever” (LWL) wider pressure though a perforated steel pipe. The procedure is known as high pressure cement grouting and has been used elsewhere in the world to combat such problems.

A study at the Teheran University showed that non-cohesive soils grouted with cement slurry resisted erosion when exposed directly to a water jet with a velocity of three metres per second in a testing flume. There is no reason why such grouting should not work in Majuli or elsewhere in Assam wherever the riverbank consists of sandy soil lacking in cohesion.

After grouting, the steel pipe should be left undisturbed to act as a reinforcing bar to further strengthen the soil. Addition of ironite powder to cernent-water slurry may also be done. This will result in increased resistance to erosion. The grouting operation can be done in a number of rows around the periphery of the island to create an erosion resistant river bank 10-15 metres wide. No agricultural operation or any other activity involving disturbance of the treated soil should be permitted in this strip of land. Amarlata (Tinosporia cordfolia) can be planted in the erosion-prone riverbanks to increase their resistance to erosion. This plant thrives in water; its roots and leaves will prevent disturbance of the soil by water currents.

A river’s natural tendency is to scour its bed during high floods and to deposit silt during low water periods when the velocity reduces. It is when the velocity of the stream reduces and the water level ebbs that bank erosion occurs because the hydraulic gradient aids such erosion. At the same time, due to reduction of velocity, the water mass In energy and deposits solids carried by it on the riverbed further downstream. Such deposit of silt at selected locations can be encouraged by human intervention. This writer’s personal experience is that wherever an immovable obstruction is placed close to a riverbank, it causes silt deposit around the obstruction during the low water period. The site for water intake (on the Brahmaputra) of the Guwahati Refinery was chosen as it had never been silted till that time (1961-62). A barge was constructed and placed as near to the bank as practicable to act as a floating pumping station for the Refinery’s 130 million litres per day water treatment plant. It surprised everyone that right during the next low water season (winter), the river started silting up around the barge and such silting has continued ever since then, requiring dredging of the riverbed every year during the low water period to maintain the water supply to the refinery.

Therefore, to encourage silt deposit on the bed around the banks of the island suitable obstructions may have to be placed to impede the flow and to encourage silting during the periods of low water flow. Stone spurs placed in the bed of a turbulent river like the Brahrroputra may not work as such spurs tend to get moved around and dislodged during high flood periods as they are not firmly anchored into the riverbed. What needs to be done is to construct spurs or obstructions that will not get dislodged by the forte of water current during high flood conditions. This can be achieved by constructing rectangular or circular concrete wells (similar to bridge foundations) by sinking to the required depth into the riverbed to ensure their stability during high flood conditions, plugging the bottoms, providing sand fill inside, and finally sealing the tops with concrete well caps. However, as already noticed in Majuli, such river control exercises may have unpleasant side effects on the island’s environs and even further downstream. To gauge what may happen if such impediments to encourage silting around the island are constructed, the Central Water and Power Research Station at Pune may be requested to carry out a model study.

The model study may take some time, but the danger of erosion will continue unabated to further reduce the island in the meanwhile. Therefore, to control and arrest erosion and save the island from extinction, operations to inject cement-water-ironite powder slurry into the ground beyond the low water level and the planting of Arnarlata on the banks shoued be undertaken without any further loss of time.

 

Water-logging in Guwahati, Indrajit Barua

The citizens of Guwahati would not have had to suffer the miseries and woes caused by water  logging of their lands, homes and streets if the State Government had Implemented a proper storm water drainage scheme when the State’s capital was shifted from Shillong to Guwaliati in 1972. It is not that the Government was unaware of the problem of storm water drainage for Guwahati city in the past. As early as in 1969-70, even before Assam’s capital was shifted from Shillong to Guwahati, the Government of Assam had engaged the Calcutta Metropolitan Development Organization {later known as Calcutta Metropolitan Development Authority (CMDA)} to prepare a master plan for Guwahati. That master plan, inter alia, included the preparation of a comprehensive plan to provide solutions for the problems of water supply, sanitary sewerage and storm water drainage of Greater Guwahati, taking into account its future development, increase of population and other relevant parameters, The CMDA made a detailed physical survey of the city covering these aspects, and submitted a detailed master plan to the State Government in 1970. That master plan was approved by the Assam Legislative Assembly in 1971.

For the scheme of storm water drainage, the CMDA had furnished comprehensive details and data, including a topographical survey map of Greater Guwahati including the Deepor Beel, storm water (rainfall) run-off calculations, permanent benchmarks with supporting records for the purpose of establishing the correct bed levels and slopes of the storm water drainage system that was to be constructed in phases in the future and monograms (charts/graphs) for designing individual schemes.

Consequent to the shifting of the State’s capital from Shillong to Guwahati in 1972, the city witnessed mushroom growth of population and buildings without any control, and without the construction of the requisite, essential and supporting infrastructure. Thus, 43 years after the approval of the master plan for Greater Guwahati by the Assam Legislative assembly in 1971, the means to discharge the storm water into the natural outfalls remain more or less where they were back in 1971. This is the root cause of misery of the inhabitants of Guwahati city today.

The solution is to adopt the CMDA report of 1971 as the basic document for designing the storm water drainage scheme for Guwahati, with the following steps-in-aid thereof:

1) Update the storm water runoff calculation to account for increase due to urbanization. The storm water run-off – the quantity of water that reaches the drains after a storm – increases as the density of buildings, roads and other impermeable surfaces increases in a given area. The storm water run-off in 1971 would have been much less than what it is today. Therefore, in any urban habitat, in planning drainage systems, the planners have to take into account the increased run-off caused by increased urbanization. The mathematical models used for computing storm water run-offs have built in provisions for the needed adjustments in this respect.

2) Design and construct a storm water drainage network to cope with the run-off at any given time with margins for increased run-off over the years due to increased urbanization with the aid of established scientific and rational mathematical models of hydrology and hydraulics, taking into account the recommendations and the database provided by the CMDA.

3) Earmark or acquire land along the Bharalu (the only drainage channel for the Bharalu basin) for re-sectioning it to increase its holding capacity; also earmark or acquire land for accommodating reservoirs for storm water drainage in the future, so that nothing else can be constructed in such locations.

4) Design and construct a proper pumping station at Bharalumukh with a stand-by DG set to provide power to the pumps when the electricity grid is switched off. The duly ratings of the pumps, that are actually required from a consideration of appropriate hydrological factors need to be determined to ensure that the system performs property when pumping out of water from the Bharalu into the Brahmaputra when needed.

And this:

A slightly different version of tghe above article:

THE LOWER SUBANSIRI HYDROELECTRIC PROJECT

PROBLEMS & PROSPECTS

By: Indrajit Barua, Consulting Engineer, Guwahati

The hydroelectric power generation potential of the Subansiri Basin has been known for long. As long ago as 1955, the Brahmaputra  Flood Control Commission (BFCC) of the Government of Assam envisaged a 125 metre high dam at Gerukamukh in Lakhimpur District of Assam State for the express purpose of flood control. But nothing happened till 1983, when the Brahmaputra Board, the agency constituted by Government of India to plan, design, construct and operate multipurpose (flood control, power generation and irrigation) projects to utilize the waters of the mighty Brahmaputra for human welfare, prepared a Master Plan to harness the waters of the Subansiri River, one of the major tributaries of the Brahmaputra, to generate 4,800 megawatts (MW) of power, to bestow benefits of flood moderation and to make water available for irrigation downstream during the dry season by means of a single 257 metre high rock-fill dam located at Gerukamukh.  However, this proposal was strenuously opposed by the Government of Arunachal Pradesh for the reason that many human settlements including the district headquarter of Dapojiro would be submerged.  Due to this, in 1985, Brahmaputra Board formulated an alternative proposal of constructing three dams, the first on the upper reaches of the river at Menga upstream of Dapojiro (the Upper Subansiri Project), the second upstream of Tamen on Kamla River (a tributary of the Subansiri – the Middle Subansiri Project), and the third at Gerukamukh in Assam (the Lower Subansiri Project).

While the upper and middle projects with dams of heights of 213 m. and 265 m. would have installed capacities of 2,000 MW and 1,600 MW respectively, the lower and last project with a 116 m. high dam would have an installed capacity of 2,000 MW.

In the year 2000, the Government of India directed the Brahmputra Board to hand over the construction of projects on the Subansiri and the Siang basins to the National Hydroelectric Power Corporation (NHPC), which, in 2005, took up the construction of the dam for the Lower Subansiri H.E. Project after receiving the mandatory clearances from Government of India.

The ‘Detailed Project Report’ (DPR) envisaged the construction of a ‘concrete gravity dam’ with a storage height of 116 m. A gravity dam is one that resists overturning and sliding effects of horizontal forces from pressure of water stored upstream of the dam together with forces generated by earthquakes by means of it own weight (due to gravity).

In 2010-2011, while the construction work on the dam was in progress, two well known and respected public organizations, namely, the AASU and the Krishak Mukti Sangram Samiti (KMSS) started protesting against the ongoing construction on the mainly on the grounds that such a high dam should not be constructed in a seismic sensitive area that has witnessed the severe earthquakes of 1897 and 1950, and that the dam would greatly harm the ecology and environment of the downstream area.  The matter became an emotive issue, and public protests against the construction of the dam rose to such a pitch that NHPC was compelled to halt all construction work in December, 2011.

The public protests led by AASU and KMSS have some justification, as later developments have proved.

An ‘Expert Group’ constituted by the Government of Assam at the suggestion of AASU  opined that there were serious shortcomings in many critical areas like aseismic design, the depth of foundation of the structure, the poor engineering properties of the soil on which the foundation rested, the inadequacy of the proposed overflow section of the dam to pass the maximum anticipated flood, and a danger to the safety of the dam by sudden collapse of unstable obstructions caused by landslides upstream of the dam. The Expert Group found fault with the way NHPC had ignored the baneful effects that the project would have on the river basin immediately downstream of the proposed dam by restricting the lean period flow to just 6 cubic metres per second (6 cumecs) when the observed minimum flow in the river has been about 180 cumecs.

The Expert Group was of the view that the ‘Seismic Design Factor’ (SDF) based on a ‘Peak Ground Acceleration’ (PGA) of 0.38g for the given site adopted by NHPC for the aseismic design of the dam was too low and recommended a SDF based on a PGA value of 0.5g instead [‘g’ means acceleration due to gravity – 9.807 metres per second per second]. The adopted value for the PGA at the given site, namely, 0.38g, has been approved by the National Committee on Seismic Design Parameters. The site of the dam is 240 km south-west of the epicentre of the Great Assam Earthquake of 1950 and 330 km, to the north-east of the epicentre of the Shillong Earthquake of 1897, in tectonic provinces different from that of the project. Both these events originated at focal depths of more than 20 km. below ground.  The Expert Group constituted by the Govt. of Assam had recommended a PGA value of 0.5g assuming a focal depth of 10 km., but without mentioning the data source on which its conclusion is based.

On the refusal of the IIT-Guwahati to participate of a meeting of another group of experts, the NHPC approached Dr. A.S. Arya, Professor Emeritus, IIT-Roorkee, and an acknowledged international expert in the field of Earthquake Engineering, for his views in the matter of the ‘seismic design parameter’ for the dam. Prof. Arya was of the opinion that that a seismic design factor (SDF) based on a PGA of 0.38g was appropriate. Here, it may be mentioned that the Guwahati Refinery and the 1st Brahmaputra Bridge are both designed for a SDF of 0.1g corresponding to a PGA of 0.2g, the Koliabhomora Bridge at Tezpur for a SDF of 0.167g corresponding to a PGA of 0.334g, and the Numaligarh Refinery for a SDF of 0.19g corresponding to a PGA of 0.38g.

In January 2011, to look into various issues about the project, at the instance of the Prime Minister’s Office, the Planning Commission constituted a committee of two distinguished and very experienced engineers, namely, Dr. C.D. Thatte and Dr. M.S. Reddy, both former Secretaries to the Govt. of India in the Ministry of Water Resources, as a ‘Technical Expert Committee’ (TEC) to study the matter and to submit a report thereon to the Planning Commission.

This TEC submitted its report in July, 2012. The findings of the TEC Report, briefly, are as follows:

  • The sandstone on which the dam is founded, which really looks and behaves like a sand rock is very weak. Its adequacy and competence to support the concrete dam is not established satisfactorily. The foundation soil should be as strong and hard as the concrete with which the dam is built (the foundation soil at Gerukamukh has an ultimate strength of 630 tonnes per square metre while the concrete with which the dam is being built has an ultimate strength of over 2,000 tonnes per square metre). The sandstone is friable (easily broken into small pieces) and loses much of its strength under prolonged exposure to water and is porous to the point of being practically free-draining.  The Thatte Committee agrees with the views expressed by the Expert Group, the Geological Survey of India (GSI) and the Central Water Commission (CWC) in that the dam is founded on a weak stratum. It has expressed concern about the stability of the dam as planned and as under construction.
  • There is no danger to the safety of the ‘non-overflow block’ of the dam even for an earthquake with PGA of 0.5g. The higher value of the PGA advised by the Experts Group does not call for a thicker cross section, and the presently adopted triangular section is best suited for seismic conditions.
  • The design flood value of 37,500 cumecs approved by the CWC and adopted by NHPC is in order. This value is higher than the value of 21,230 cumecs recommended by the Experts Group of Govt. of Assam.
  • The slopes and large base width of 1.35 times the height of the dam are unusual for a gravity dam and have been adopted by NHPC by concerns for the stability of the dam under high seismic design parameter and the quality of the foundation rock (a larger base width transmits lower pressures to the foundation).
  • The concrete diaphragm (cut-off wall) extending well below the foundation and the extra-large base width are design innovations. Whether these innovations are good enough to increase the competence of the foundation and to ensure the safety of the dam are open to question. However, the poor soil characteristics do not preclude a gravity dam if duly validated by ‘Finite Element Analysis’.
  • The ‘Energy Dissipation Arrangement’ which is required to prevent damage to the downstream floor of the dam and the river banks when water is released through the sluice gates at high velocity as adopted by NHPC is not the right arrangement and needs substantial modification.
  • NHPC’s proposal to provide a cut-off wall only in the overflow section of the dam leaving the non-overflow sections unprotected is not enough to improve the safety of the foundation. The upstream cut-off wall should therefore be provided from end to end throughout the width of the dam.
  • Since the dam is of gravity type and is provided with a spillway or overflow section, a temporary overtopping, say by a landslide upstream, is unlikely to affect the safety of the dam.
  • The NHPC should constitute an independent ‘Dam Design Review Panel’ to take a final view on the ‘Energy Dissipation Arrangement’, aseismic design, foundation competence, and if there are any inadequacies, to advise remedial and strengthening measures for the dam, keeping in view the present status of construction.

Following the recommendations of the Thatte Committee, the Ministry of Power, Government of India, on the 2nd April 2012 constituted a ‘Dam Design Review Panel’ (DDRP) for the project, comprising of experts from the Central Water Commission, Central Electricity Authority, Geological Survey of India, Central Water & Power Research Station, IIT-Roorkee and NHPC to address the issues highlighted by the Thatte Committee.

The DDRP has agreed with the views of the Expert Group of the Govt. of Assam and the Thatte Committee that the dam is indeed founded on weak rock. The rock mass is soft, weak and friable but behaves satisfactorily in undisturbed /confined /in-situ conditions. However, the weak properties do not rule out the construction of a gravity dam if it is designed taking into account these properties and if the codal provisions on limits for stresses prescribed in Indian Standard 6512-1984 (Criteria for Design of Solid Gravity Dams) are complied with. The stresses transferred to the foundation would have to be validated by the ‘Finite Element Method’ (FEM) for static and dynamic loading conditions to ensure that the stresses are indeed within permissible limits. Weak soil properties demand that a wider base area should be provided, and this is what has been done from the very beginning. The high pressure cement grouting carried out by NHPC over the entire foundation area to seal joints and fissures in the rock mass will minimize chances of migration of sand particles from the foundation. The permeability parameter has improved vastly after grouting, from 42 Lugeon to 2-3 Lugeon. A good property of the foundation rock mass is that it is homogenous, which rules out distress from differential settlements.

The DDRP has recommended that the foundation of the dam should be confined to prevent migration of sand particles. Such confinement would also improve the compressive strength of the rock mass. (This writer has designed high speed machine foundations that are subject to continuous vibration on confined sand; these foundations have been performing satisfactorily over the last 38 years. The foundation of the storage tanks of Guwahati Refinery also rest on confined sand, and these have performed extremely well over the last 50 years.) NHPC had already agreed to provide confinement, albeit partially, by providing upstream and downstream cut-off walls in the overflow section and in some portions of the non-overflow section. However, to provide complete confinement, NHPC must provide cut off walls on the upstream face throughout the whole width of the dam to protect the foundation.  The DDRP further recommended provision of an additional cut-off wall on the downstream side to provide complete confinement and to act as a second line of defence to prevent any possible movement of the sand particles of the foundation. The downstream cut-off wall will also provide protection to the toe of the dam at the time of discharge of water from the dam spillway.

The DDRP also recommended some changes in the Energy Dissipation Arrangement suggested by the Thatte Committee to ensure that spillway outflow is thrown away at considerable distance from the toe of the dam. This would prevent any scour at the toe of the dam that might endanger its safety.

On the 23rd December 2013, a meeting was organized by the Government of Assam between the members of the Experts Group (EG) and the Dam Design Review Panel (DDRP) led by the Chairman, Central Water Commission. This writer was present at that meeting on the invitation of the Govt. of Assam. At that meeting, the EG mainly referred to the geology of the dam location stating that the site was very close to the Main Boundary Thrust of the Eastern Himalayas (MBT) which made it susceptible to severe earthquakes. The DDRP made an excellent presentation on the improvements made in the design of the dam to ensure its safety and serviceability. The DDRP pointed out that any proximity of the site to the MBT would have no impact on the safety of the dam, which, being a squat and rigid structure with a base width much more than its height, has such a large natural period of vibration that it is safe against an event with a PGA of 0.5g even though it is designed for an earthquake with a PGA of 0.38g (Explanation: Slender and flexible structures like multistoried buildings and top heavy water tower structures with small natural periods of vibration may suffer distress if subjected to a severe shaking of 0.50 g if these have designed for a lesser PGA of 0.38g, and not a squat and rigid structure like the Lower Subansiri Dam).

At the end of the meeting, a member of the EG opined that if the NHPC had arranged such a well thought out and well designed presentation of the design parameters earlier, then perhaps such protracted and long drawn-out discussions about the safety of the dam and related issues would not have been necessary.

The NHPC authorities have already declared that they would implement all the safety additional features recommended by the DDRP to ensure the safety of the dam.

The questions now arise: Will the Lower Subansiri Dam be safe in the event of a major earthquake in the North-Eastern Region? Will the dam be of service to the people of Assam?

In the humble opinion of this writer, the dam with all the additional features recommended by the Thatte Committee and the Dam Design Review Panel fully implemented in its construction is capable of withstanding an earthquake with up to 0.5 PGA that may originate in or near any of the known epicentres in the N.E. Region without significant distress. Of course, if any such mega-event really happens, then much of the State – the multistoried buildings of Guwahati, the three bridges over the Brahmaputra and other lesser bridges, the four oil refineries and other structures with comparatively shorter natural frequencies of vibration will suffer huge damage if not total collapse.

The dam will make much needed 533 megawatts of electric power available to Assam. At present, much of the State remains dark during the peak hours of 5 PM to 11 PM even with ‘peak load restrictions’ imposed on industrial consumers. The blessing of Light will come where the curse of Darkness prevails now.

 

Reduction of floods within 30 km. downstream of the dam will definitely be witnessed. Of course, significant flood moderation will only happen when the other two stages – the Upper and the Middle Subansiri Projects are constructed.  Without the Lower Subansiri Dam, at present there will be no relief whatsoever from the high waters of the Subansiri in the flood-ravaged area immediately downstream of the proposed dam.

At this time, there are practically no irrigation facilities in the Subansiri Basin. It will be possible for the State Government to provide much needed irrigation facilities to the farmers in the vicinity of the dam only if it is constructed, otherwise not. NHPC has already agreed to release 300-320 cumecs of water during the lean season by operating at least one turbine continuously so that the ecology and environment of the downstream area are protected. Despite what some ‘experts’ in Delhi think, Assam does need irrigation during the winter months to give us the benefits of multi-cropping. Of course, we have high rainfall compared to most parts the rest of the country, but this rainfall is distributed in such a way that causes floods in the monsoon months and water starvation in the winter months, and that is the reason why our farmers need irrigation.

The questions posed above therefore answer themselves. The Lower Subansiri Dam, of course designed and built as a safe dam, is needed for the good of the people of Assam.

Sanjeev Sabhlok

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