Yesterday, today and tomorrow
The Egyptian civilization by the Nile, the Mesopotamian civilization by the Euphrates and the Tigris, the Indus civilization by the Indus, the Chinese civilization by the Hwang Ho and the Yangtze_ all these civilizations of the ancient world originated beside rivers. These mighty flow of water bodies, are closely connected to the human soul. Population grew, business flourished and civilization expanded by and around the rivers. Nonetheless, these civilizations in course of time have managed to turn into a menacing threat for these rivers. The perfect flow of the stream has been marred by our senseless schemes like, building dams and bridges, unplanned housing development nearby them besides throwing off our noxious waste into the life-giving rivers. In addition, reckless timbering also resulted in decaying of the earth initiating disastrous landslides. In this age of industrialization most of the rivers have gone excessively silted at the cost of its navigability. Nevertheless, the gift a river makes to human life has not changed a bit since the remote past. Sea routes have been playing crucial role in trade growth since the birth of civilization. Hence we need to govern these rivers from time to time and regularly extracting the sludge and the silt out of it. This process of refreshening and revitalizing the rivers is known to us as dredging.
Dredging, revitalizing the rivers
Dredging brings back the life to the rivers by dredging the riverbed. This gives us three kinds of benefits, first, ensures safety of the river banks from erosion; second, guarantees the growth of landmass, and third, makes sure that big vessels can navigate well through the rivers.
Dredging can be of many different types. Depending on their method, we call them capital dredging, maintenance dredging and land reclamation dredging. Primary excavation known as capital dredging facilitates easy entry of huge ships into the harbor, the river channel and the berth or the port. This requires heavy powered machineries. The technique also requires cutter suction dredger, trailing suction hopper dredger, bucket dredger, grab-dredger and excavator. Sometimes drilling of the earth and blasting of the rocky soil is also a part of job for this type of dredging.
In addition to carrying out excavation works, dredging is also done for laying the foundation before the construction of bridges, the jetties and the wharfs.
Navigability of the channel regularly deteriorates due to the continuous collection of silts in it. To mitigate this, we need maintenance dredging. Most of the dredging works actually deal with this kind of crisis with trailing suction hopper dredgers which is quite costly. However, on a busy river route one does have an effortless alternative to it either.
In land reclamation dredging, sand, sludge and rocks are carried away to a different location for the formation of new land bodies. Cutter suction dredger and trailing suction dredger are needed for performing this job.
The Karnaphuli and the port
Rivers lie at the chore of the heart of the people of Bangladesh, the largest delta on this planet. About 700 rivers have crisscrossed the surface area of this land creating a huge network of water flow over it. In terms of economic importance, Karnaphuli is the most crucial among them which has given birth to the Port of Chittagong. This port is one of those naturally gifted ports in the world where cargoes are handled on jetties that lie straight beside the river channel not like many other ports, where they had to build artificial basins before facilitating the jetties. Port functions at Chittagong totally depend upon the tide and ebb of the mighty Karnaphuli. Naturally dredging is only obvious here. To maintain navigability, Karnaphuli have got to undergo the regular dredging, no getting away from it.
Olden times of dredging in Karnaphuli
Sea trade went through massive transformation by the start of the 20th century with the flourishing of science and new technology. Conventional sailing ships obliterated from the scenario and vessels metamorphosed into new shapes and sizes simultaneously necessitating ports to undergo relevant changes in its physical structure as well as its operational management. Chittagong port was no exception to this trend. The Authority prompted a number of surveys calling on the Chief Engineer of Kolkata port as the surveyor. In the report, he mentioned that a consolidated amount of 10 lac rupees would suffice for the maintenance of navigability in Karnaphuli, in turn enabling much bigger ships to anchor at Chittagong. However the Authority could not but refuse owing to shortage of fund in its treasury.
In 1928, three decades after the first initiative, Chittagong port was able to procure a trailing suction dredger, S D Patenga, having a capacity of 1,250 cubic meter hopper. This dredger was later scrapped in 1982. Another grab dredger with 375 cubic meter hopper capacity was procured in 1954 which got scrapped in 1992. The next dredger for the port was procured in 1964 which sank during the terrible cyclone in 1991 and part of it was scrapped after the salvage. N D Al-Amanat, the trailing suction dredger had a capacity of 1,250 cubic meter hopper. M V Khanak, the state-of-the-art trailing suction hopper dredger with a capacity of 2,500 cubic meter hopper joined the fleet of Chittagong port in 1991. Currently the regular maintenance dredging in the Karnaphuli is being done by this dredger.
After the dreadful cyclone the navigability of the channel drastically reduced due to collection of silts around the jetties of the port. The Authority had no dredger at that time capable of dredging this silt. As an alternative the silt was cleared off in 1992 using the pipe line dredger borrowed from the Water Development Board. The result however failed to meet up the mark. Later, an open tender was called in to assign the job to a service provider from the private sector. This process is still in place. Recently, a feasibility study conducted for the purchase of a grab dredger from Germany. However, the plan was dismissed later as the current process proves to be cost effective comparing to the pricey purchase.
First capital dredging operation in Karnaphuli was undertaken in 1981-82. Normally the dredging spots are separated by three bars, first, the outer bar at the estuary, second, the inner bar with a minimum draft of 7.2 meters located 2.26 kilometers from the outer bar, and third, the Gupta bar having a minimum draft of 6.9 meters located 6.55 kilometers from the outer bar. The Department of Hydrograph cites, draft at the outer bar area increased up to 8.5 meters after the capital dredging of 32,22,861 cubic meters in 1982. Later, in 1988, another dredging work of 17,80,000 cubic meters of area was undertaken for the restoration of navigability. Moreover, dredging work of 1,10,000 cubic meters of around the jetties and 15,00,000 cubic meters of area in the outer bar and the channel is being conducted as part of the maintenance dredging. Besides running dredging operation with its own dredger, the Port Authority also conducts 10 lac cubic meters of maintenance dredging round the year in its various modes and capacities.
Since 2001, maintenance dredging by the contractor has become a regular feature at the main jetty and the turning basin area standing before it. From 2008, the 12 blocks stretching from the Sadar Ghat to the port limit upstream the channel are being leased out to the private operators for a restricted period of one year. This decision has brought back new discipline in the dredging operation scenario. On the other hand, it was also decided that people who had been allotted lands for the building of jetties and slipways along the shoreline of Karnaphuli shall be liable for the dredging of their respective areas at their own cost.
In 2009, the Authority kicked off the capital dredging project from Sadar Ghat to the third Karnaphuli Bridge. Excess siltation during the construction of the third Karnaphuli Bridge in 2010 resulted in deterioration of navigability to an alarming extent. As such, the project rescheduled its implementation to May of 2012. It had then three segments in it, construction of the jetty, construction of the riverbank protective walls, and capital dredging. A jetty with a length of 400 meters and a width of 15 meters was constructed as part of the project for the anchorage of lighterage ships. By January of 2013, 80 percent of the river bank protection work and 42 percent of the channel dredging got completed. In addition, 4 canals had also been revitalized to mitigate the water logging of Chittagong city. Sadly, at such a crucial hour, the capital dredging work had to postpone for long four years thanks to a legal scuffle between the designated contractor and the Authority. As a result, Karnaphuli lost the normal navigability once again exposing out its sickly façade, especially, when it has a low tide.
New façade of capital dredging
In 2016, BUET submitted a report after conducting a feasibility study on the navigability of the Karnaphuli channel. By January 2017, a project proposal was finalized and duly submitted for approval by the ministry. Accordingly, the government decided to reinforce the life line of the Chittagong port through the Direct Procurement Method (DPM). The project got the green signal of the ministry under the banner of `Sadarghat to Char Bakalia Navigability Protection Project.’ Eventually, 42 lac cubic meters of earth would be excavated from an area with the length of 3.9 kilometers and breadth of 250 meters. Excavation for each cubic meter of earth would cost more than BDT 400. BUET in its report also suggested for at least a three-year maintenance dredging for its long term sustainability.
Implementation of the `Sadar Ghat to Char Bakalia Navigability Protection Project’ would ensure 4 meter draft for the movement of seagoing and inland ships, besides easing the operation at the newly built 400 meter jetty. This will also decrease naval mishaps through disciplining the berthing/mooring of the lighterage ships in that area plus facilitating cargo handling of the coastal and lighterage ships at the Sadar Ghat and the newly built jetty. Traders of Khatunganj and Asadganj would also benefit a lot by expanding their business through the waterways. Dredging of the canals that fall in to the river would relief the Chittagong city off its continuous water logging nuisance.
The project at the cost of BDT 258.52 crores covers the key canals and facilities including the third Karnaphuli Bridge, Raja Khal, Chaktai Khal, newly built 400 meter jetty and Sadar Ghat Jetty.
Stepping Stones
A dredging project begins with the hydrographic survey that defines the extent of need of the dredging. A pre-dredging hydrographic survey is conducted even before the signing and commencing of the actual dredging work. A body comprising the engineer of the assigned concern, the port authority and the consultancy firm would run the various surveys with sonograms and other equipment and decide on the range of the work and the procedures. As per the international rule, the dredging work must begin within 30 days from the day of the completion of the survey.
Actual dredging or excavation of the river bed begins in the next phase. Progress of the dredging depends on a number of factors, like, land properties of the area, target range of the dredging, depth of dredging, distance between the dredging area and the relocation area as well as the natural state of the area between these two points, hazard level of the waste ingredients and also on the transferring system. According to the project, dredging will cover an area of 42,79,000 cubic meters in those parts of the river by December of 2018, followed by three years of maintenance dredging.
In this, Authority also decided on applying two different types of dredgers, grab dredger and cutter suction dredger, taking into account the earth properties of the river bed. Grab dredger is the most commonly used dredger in the world that runs its operation from a fixed up position. It is comparatively easy to use and has no propulsion. Its capacity depends on its power of digging the amount earth in its one grab, which actually varies from 1 to 20 cubic meters. On the other hand, cutter suction dredger has a chamber in it where it can store the earth excavated. This earth then can be transferred to a separate location using a barge and a pipeline. Cutter suction dredger also works in a fixed up position and digs into the earth with a device in it called the cutter head. This can be used for digging of any types of earth. Considering the properties of the soil, these are the two types of dredgers that suit us best. The number of dredgers and their capacity should be such that can dig out 4.28 million cubic meters of earth within just 30 weeks. Once the project completes, hydrograph department of the port will take over the task and continue the routine maintenance dredging with its own manpower.
Transferring of the excavated earth and the sludge is a prime duty in all dredging works. The earth dredged out from the Karnaphuli would be carried away to Nazir Char through pipelines. Although the port can allocate a piece of land for a temporary storing of the earth, however, for fear of pollution it would not move in that direction, instead, actually depositing them in Nazir Char. Since, it needs to be dumped somewhere so as not get washed away into the river again posing further threat to the water besides causing air pollution.
In the next phase, the dredging firm in presence of the joint reps from the relevant concerns shall run hydrographic surveys on a regular basis that should report on the progress and procedure of the work. This would also provide ideas on solving any untoward hindrance or, if any, need for new changes to be introduced in the procedure.
The concluding phase is the post-hydrographic survey. Run by the dredging firm, this survey shall check out if all the targets have been achieved in realty. The joint authority will then decide on the outcome and the concerned firm shall be liable to run additional dredging and another post-hydrographic survey, all on its own cost, if asked by the supervising body. Before handing over the project, fulfilling the target of the dredging area is an imperative.
No hindrance in port functioning
The dredging firm shall take care of things keeping away from causing any type of hindrance in the day to day port functions. Bangladesh Inland Water Transport Authority (BIWTA), Bangladesh Inland Water Transport Corporation (BIWTC), Bangladesh Fisheries Development Corporation (BFDC), Chittagong City Corporation and Department of the Roads and Bridges shall provide the necessary cooperation in this.
Dredging firm shall operate in the Karnaphuli channel without creating any obstruction in the regular movement of vessels on its water. The indicator light must be on day and night on all floating dredgers and pontoons including alarm indicator light on all the tugboats and the vessels and the buoys.
For safety of our national asset, the third Karnaphuli Bridge, one representative from the Karnaphuli Bridge Authority and a second from the consultancy firm assigned by the port authority for the previous dredging project shall stand by when dredging work is underway anywhere within 200 meters of the bridge. An engineer from Karnaphuli Bridge Authority will also be there to assist in the inspection. During the dredging operation, special security measures will be in place for the safety of the newly built 400 meter Jetty near the Sadar Ghat area.
Let the river flow on for ever
Since the origin of the earth, the rivers have persistently enlivened it with life and health, wealth and enrichment. Nevertheless, at odd times they have also washed away thousands of communities, sometimes drying out and transforming the lands around it into deserts. For this, taking great care of the rivers is a binding duty for us.
Dredging is a continuous job and so, obliged to run on a regular basis for the maintenance of the navigability of the channel.
It must be kept in mind that Bangladesh is standing at the threshold of achieving its Vision 2021 and facing on to the challenge of achieving Vision 2041. It is obvious that the port also needs to comply with this pace and energy of the development spree of our economy.
Successful implementation of the dredging project shall result in a better quality of service by the port opening up great potentials of benefits and drive the country on its way towards a bright golden future.
