A PAPER PRESENTED BY ENGR BEN EFEKARURHOBO AT THE 4TH NIGERIAN DREDGING SUMMIT AND EXHIBITION HELD AT AMBER TINAPA HOTEL ADIABO CALABAR ON SEPT 22-24, 2010.

ORGANISED BY DREDGE SKILLS AND MARINE TRAINING CENTRE LTD.

DREDGING PROJECT: Engineering and Practice

Dredging as we know it, is the science of using different types of machines to excavate and deliver dredge spoils in the form of silts, mud, clay, sand and other material to a designated point from the river, creek or and sea. The idea of dredging any of these waterways is principally to improve the waterways or provide for land reclamation or create new channels or re-channel existing waterways.
 
The importance of dredging is greatly showcased in the Netherlands where the entire country is almost below sea level and the dredging science has kept the country going. There is a Dutch saying the “God created the heavens and the earth, but the Dutch created the Netherlands”. Hither to now this industry was a no go area for Nigerian. Only the likes of Westminster Dredging, Dredging International, Ballast Ham and other multinational companies carried out dredging works. The reason for their monopoly is not far fetched. They had a monopoly of dredging knowledge; they had the prerequisite funds or access to fund as dredging could be expensive. Nigerian companies were handicapped in dredging knowledge and where the knowledge was attained the funding was not there as we had to build a sound financial backing to acquire the needed equipment (dredgers). To begin with some Nigerian procured used dredgers from the multinationals to attempt a competition in the industry but ended up poorly as these used machines were far from sea worthiness. 
 
Dredging has a great future in Nigeria and for indigenous firm. The country is only about 5% dredged. There exists a great need for dredging works. The oil companies, the Niger Delta Development Commission, construction companies and indeed private individuals need the services of Nigerian content dredging companies. A recent Central Bank of Nigeria publication put the dredging need of the country for the next five years at over three and a half billion cubic meters (3.5billion m3) of sand for construction. It could therefore be claimed that dredging plays second fiddle on to oil in our economy. Many Nigerians are now very adept in dredging technology and could stand anywhere in the world and be held in high esteem. Let’s examine the different types of dredging operations

TYPES OF DREGERS 
 There are different types of dredgers for different types and needs in dredging works. Prominent among them are the following:-

Grab bucket or clamp shell dredgers
•	Cutter/Suction Dredgers  
o	Suction Dredgers
o	Wheel Dredgers
o	Hopper (Stick & Trailing) Dredgers
o	 
o	GRAB BUCKET OR CLAMP SHELL DREDGERS
o	 
o	These categories of dredgers are mainly used for front end activities of dredging works particularly in fresh canalization or capital dredging works. They are made up of a barge mounted with a crane. The crane is fitted with a grab bucket in form of a clamp shell. The bucket or clamp shell ranges in size from 1m3 – 15m3 depending on the size of the barge on which it is mounted and the power of the crane which ranges from 25hp to 250hp. Another factor to be considered in rigging a grab bucket dredger is the length of the crane’s boom vis-à-vis the width of the intended canal. 
o	 
o	CUTTER/SUCTION DREDGERS
o	  
o	These are the most popular types of dredgers in use the country today. They are usually built on five (5) pontoons. One pontoon which is the main pontoon houses the main engine, the auxiliary engine, the pump housing and a lot of components. Two pontoons are then place on either sides of the main pontoon which serves as diesel tanks for the use of various engines that constitute the dredger. The remaining two pontoons are mainly for flotation and dry storage. The ladder which is fitted at the front of the pontoons and carrying the cutter head, also acts as the stabiliser to the pontoon. 

o	The cutter/suction dredgers are of various sizes. They range from 10” to above 36”. Modern technology in dredging has made a great impact on recently produced dredgers.  With high yield in mind, dredge manufacturers especially in Europe (The Netherlands) have as a result of continuous research made dredgers with submerged dredge pumps there increasing output and reducing to zero the vacuum problems associated with the older versions. 
o	 
o	The cutter/suction dredger is a versatile machine that dredges from a lake, river or creek. With its cutter fitted with strong steel teeth cuts the bed of the borrow pit, sucks in the material thus cut with her centrifugal pump and transports the load of sand, mud or any other material hydrographically to an already prepared dump site. The rate of production depends on the size of dredger and the availability of materials in the borrow pit. With all variables in place, the following production output could be achieved in different dredgers as shown in the matrix below:-
o	 
o	Attached are brochures of different dredgers cutter/suction and wheel.
o	 
o	SUCTION DREDGERS
o	Suction dredgers are very much like their cutter/suction cousins. The difference between the two is the cutter. In most cases the suction dredgers carries a longer ladder and are equipped with powerful jets which assist in breaking the sea bed before suction is affected for hydrographical transportation of dredged materials to the sand fill bed area. Depending on the size of the suction pump, commensurate water or jet pump is powered by a separate auxiliary engine. 
o	 

o	WHEEL DREDGERS
o	Very much like the cutter/suction dredger, the wheel dredgers also cuts and sucks before discharging the spoil to the dumpsite. The wheel dredger however is a precision machine and enhances greater production. It is however more expensive and highly technical in make.
o	 
o	HOPPER DREDGERS (STICK AND TRAILING)
o	 
o	Hopper dredgers are huge dredging ship. Like their cutter/suction types they are equipped with suction ladders that are very long. Some reach as much as 60m. The length of the ladder is to enable them reach the bed of the sea or ocean where they are designed to mine from. These types of dredger takes its product onto its self in a cargo hold and travel to a designated spot where the sand is required and offload the stuff by blowing the cargo onshore or simply opening the cargo compartment and discharge the sand into the river near the final place of usage.
o	 
o	There are two  mainly used types of hopper dredgers. There is the trailing hopper and the stick hopper. 
o	 

TYPES OF DREDGING OPERATIONS

•	There are various types of dredging. We shall now discuss the various dredging operations;-
•	Capital Dredging
•	Sweeping or maintenance dredging
•	Canalization
•	Channelisation
•	Land reclamation
•	Sand winning or stockpiling
•	 
•	CAPITAL DREDGING
•	 
•	This type of dredging is mainly required by the oil companies. This entails deployment of almost all dredge types and equipment. It involves the construction of a fresh swamp oil location. After de-bushing of the oil well location with the use of swamp excavators (swamp buggies and swamp dozers), the next in line is the clamp-shell or grab bucket dredger which apart from de-stumping the wellhead and access area to the slot, will excavate to a depth of about 1 meter or dredge buoyancy. The essence of this type of dredge work is to create the required depth for the main equipment (the cutter/suction dredger) to access the location and dredge to the required depth.
•	 
•	SWEEPING OR MAINTENANCE DREDGING
•	 
•	Sweeping or maintenance dredging as the title implies, is using cutter/suction to remove silts from a waterway. Examples of these type of dredging works  are the maintenance dredging of oil companies’ 		 wellhead (slot) and access.
•	 
•	Due to constant movement on our rivers and creek (human vehicular movement and the regular current) the accesses and slots become silted thereby depriving the oil companies from accessing the wellheads for routine maintenance work. The need to smoothly 

o	deepen these location become apparent hence the services of a dredging company is sought by the oil companies. With an array of dredging plants, including clamp shells, swamp buggies and cutter/suction dredgers the dredging company moves in and carry out sweeping job. The usual maximum depth required at these locations is 2.65m + tolerance of about 20cm.
o	 
o	Sweeping can also be done in normal canals, creeks and rivers should the depth be compromised by silts.
o	 
o	CANALIZATION & CHANNELISATION
o	 
o	Canalization is the opening up of fresh grounds to form a waterway. This involves cutting the grounds to a specified depth, width an slope gradient. The initial dredging plants for this operation are :-
o	Swamp Buggies
o	Bucket or Grab dredgers
o	Cutter/Suction dredgers
o	 
o	The buggies and the grab will remove the top soil up to floatation and the cutter/suction will then dredge to required depth and with.
o	 
o	Channelisation however entails sweeping and re directing the flow of existing waterway. Like canalisation, because of the usual high level of siltation of the waterways, most of the listed dredge equipment is required in this operation.
o	 
o	LAND RECLAMATION
o	This type of dredging work entails using either a suction, or cutter/suction dredger or a wheel dredger to mine sand from a borrow pit and discharge unto a marshy swamp land until a solid ground is created. The purpose of this type of dredging is basically constructional. The reclamation could either be for housing, industry or road construction.
o	SAND WINNING OR S

o	SAND WINNING OR STOCKPILING
o	This is the most popular of dredging works. This entails mining sand and stockpiling same for sale to the construction industries or to private estate developers. There are a lot of works involved in this operation. 
o	 
o	To begin a profitable sand winning operation, the following must be considered:-
o	The dredging industry is plague with a lot of challenges which are surmountable depending on your approach. Some of these challenges are self inflicted by the practitioners knowingly or ignorantly. 
o	Let us examine some of the known challenges:
o	Communities’ disturbances
o	Slow or low output
o	Crewing the dredge
o	Government levies
o	Security
o	 
o	CUMMUNITIES DISTURBANCES
o	This comes in different shapes and styles but they quite surmountable if adequate attention is paid to them in time Community disturbances occur if what should be done is either neglected or taken for granted.
o	To avoid clashes with host communities, efforts should be made prior to dredging works the following steps must be taken.
o	The entire process will begin with site visitation. 
o	This will entail visiting the host community and sensitizing them about the job to be done in their area. Carry out reconnaissance survey of the borrow pit and sand-fill area. During the visit the survey team in consonance with the project engineer/consultant together with the host communities, shall among other things agree on the approach to execute the project. 
o	 
o	 
o	 

o	Community Courtesy Visit
o	 
o	A team of our Community Relation Officers will accompany the survey personnel to have preliminary talks with the communities. At the talk, the CROs will inform the communities of the project and detail the advantages of the project to them. They will among other things negotiate employment opportunities regarding the project and the issues of royalties. The talks shall be held at a public venue where everyone will partake and decisions reach will be known to all.
o	 
o	Youths Employment.
o	The fact that most youths living in the creeks of the Niger Delta are unemployed cannot be wished away. The project from the design stage should take notice of this perennial problem and provide reasonably for the youth who in most cases are the architect of trouble.
o	 
o	Mobilization of Equipment and Men.
o	 
o	Equipment
o	 
o	This shall include:
o	 
o	Various survey equipment
o	Machetes
o	Flagging ribbons
o	G. P. S. (Hand held)
o	Two Nos Swamp Buggies
o	Tug Boat (Twin screw 350 x 350 hp)
o	700 ton barge
o	20” cutter/suction dredger
o	Anchor boat (Multi c at 150 x 150 hp) or anchor booms
o	Jet Pontoon
o	Speed boat (2units 75hp fibre type and 2units 40hp)
o	1 unit survey dinghy 
o	 

o	Work force
o	 
o	This shall consist of:
o	 
o	2 Nos. Surveyors
o	2 Nos. Survey Assistants
o	6 Nos. lines men (to be engaged from local employees) 
o	2 Nos. Community Relation Officers
o	4 Nos. Plant Operators
o	4 Nos. Plant Mechanics
o	3 Nos. Dredging Masters
o	3 Nos. Assistant Dredging Masters
o	2 Nos. 3rd Class Marine Engineers
o	3 Nos. Marine Engineer Assistants
o	6 Nos. Deck Hands 
o	8 Nos. Securities (to be engaged from local employees)
o	2 Nos. Radio Operators
o	2 Nos. First Aiders
o	1 No. Safety Officer
o	1 No. QA/QC Officer
o	5 Nos. Boat Drivers
o	1 No. Quarter Master
o	Community workers
o	

o	Pre Dredge Surveys
o	 After settling all issues at the community visit, the survey team together with the consultants shall proceed to peg out and carry out the pre survey of the entire work area. The pre dredge survey shall among other things establish the existing levels at the site. All surveys shall be jointly conducted (client and the consultant).
o	 
o	While the pre dredge survey is continuing, the swamp Buggies or suitable earth moving machines shall be mobilised for bush clearing and minor excavation works. They shall remove or destump the sand-fill area and level same before the survey team will establish height for the stockpile. 
o	Land Transportation
o	 
o	Every care shall be taken to load the buggies or other plants on two 30tons low Bedded trailers. The trailers after loading shall begin the first leg of the journey to site. During this journey, the trailers shall be escorted by a pick-up van which shall carry armed policemen who shall ensure that the trip is incident-free. The policemen shall maintain a free flow of traffic and scare away any intruder throughout the journey. The pickup van shall also carry two wire boys whose duty shall be lifting of cables and wires from the course of the buggies while on transit. They shall use poles of dry wood to effect clearing wires along the way to prevent any electrocution. If the wires are crossing the route in such a manner that the wire boys are incapable of clearing them without causing any damage to electric power, efforts must be made to contact NEPA to switch off power on the line before crossing same.
o	 
o	Loading and offloading the buggies or other earth moving plants must be done during the day.

o	Water Transportation
o	 
o	Only pre-mobbed barges should be used for water towage of the buggies.
o	 
o	Before venturing on the water aspect of the journey, permission should be taken from the military authorities (Army and Navy). In particular, the men of Operation Restore Hope stationed at Warri. At least five soldiers should be taken to escort the spread to the site. In addition local militia should join the escort to avoid any mishap. Experience has shown that the local militias are greatly against the use of military personnel. 
o	 
o	 There should be no night sailing.
o	 
o	Adequate food and water should be provided for the estimated number of days the spread shall be on tow and the return trip of the tug boat. The first aid box should always be kitted with routine medicine for the journey.
o	 
o	Every sailor on board shall be kitted with life saving apparatus which must be worn at all times. The policy of ‘No life vests no boarding’ must strictly apply.
o	 

The job

o	The job
o	 
o	The buggies and or the earth moving plants shall have a head start of 14 days before the cutter/suction dredger shall join the spread. The buggies shall clear the proposed sand fill to an appropriate width and length depending on your space requirement. The pegged out area should be rid of all vegetations and stumps. All excavated material shall be used in to form the containment bund walls for actual dredging works. The buggies or earth moving plants shall create various basins at various points to receive dredging material (sand). The earth moving plants shall construct the channel for the run-off water at the end of which a water box shall be fitted. Apart from the earth moving equipment that will be required during dredging works for the purpose of stockpiling the sand so dredged, the swamp buggy should be demobilised having completed their work.
o	 
o	Cutter/Suction Dredger
o	 
o	The cutter/suction dredger shall join the dredging spread on the 12th day after the buggies had started bush clearing, Destumping minor excavation works and dressing the sand-fill area. It shall commence sand winning. 
o	Depending on the size of the cutter/suction dredge used, production will vary from 150m3 over 2,000m3 per production hour.
o	Demobilization
o	Demobilization of plants and equipment shall be in phases just like mobilization. The buggies will be the first set of equipment to be removed from site at the completion of their prescribed role. This will be followed by the dredger which will be removed from site after the final post dredge surveys and receipt of completion certificate for the entire dredging works.
o	

o	LOW OUTPUT
o	 
o	Any successful dredging venture begins with the choice of the dredge machine. It will be ridiculous to attempt to stockpile 1,000,000m3 of sand using 12” x10” dredge machine knowing that such machine has the capability of delivering 150m3 per production hour. When choosing or making the decision to deploy a dredge one must consider the quantum of work and the distance from the borrow pit to the sand-fill area. Another area that requires professional touch is the elevation from the river or lake.
o	 
o	In most cases low output are experienced when these factor are neglected and or not considered in planning your sand winning venture. Every dredge has its installed production limit under specific conditions.
o	 
o	CREWING YOUR DREDGE
o	 
o	 Effort should be made to crew your dredge with only well trained personnel. The crew of an average dredge shall include:
o	Two Dredge Masters (Certificated).
o	Two Marine/Dredge Engineers 
o	Two Marine Engineer’s Assistants (M.E.A.)
o	Two Greasers
o	Two Electronic/Electrical Engineers
o	One Safety Officer
o	One Medic
o	Four Deck Hands
o	3 Security personnel ( from your host community)
o	Two Sand-fill Masters
o	Two Quarter Masters
o	The number of the crew will depend on the size of your machine and your operating hours.

o	Effort should be made to regularly send the crew for on the job training in other to acquire new techniques of their trade and profession.
o	GOVERNMENT LEVIES
o	There are quite a number of government taxes on the industry. Chiefly among the lot are;
o	National Inland Water ways levy
o	Solid mineral levy
o	Local Government levy
o	No dredging outfit should ignore these guys as this may result in sanctions that will militate against your production targets.
o	 
o	SECURITY
o	 
o	Adequate security should be in place at any dredge work site preferably armed policemen.
o	 
o	OPPORTUNITIES
o	In the Niger Delta area there various areas you can source to get handsome contracts, Some of the companies wanting the use of dredgers are 
o	The Niger Delta Development Commission
o	The Shell Petroleum Development Company of Nigeria Eastern and Western Division
o	Nigerian Agip Company
o	Deawoo
o	Notore
o	Chevron Texaco
o	State Governments
o	 
o	 

o	COSTING SAND WINNING OPERATION 

o	THANK YOU FOR ATTENDING THIS FOURTH EDITION OF THE NIGERIAN DREDGING SUMMIT.