3. THE OKAPI PIPELINES PROJECT

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3.1. Project Data

• The Pipeline Number 1 (P1)will deliver 25 m ³/s from Moanda in DRC to Walvis Bay 1000 km away in Namibia, and later 100 m s in three phases spanning three years.
• The Pipeline Number 2 (P2) will supply Port Sudan in the Red Sea from Lisala in the DRC with first 25 m³/s, then later on, the discharge will be upgraded to 200 m³/s in 5 phases over 5 years.

 

3.2. Viability Study of the Pipelines Number 1 and Number 2

3.2.1. The hydrological concerns
At the light of the data provided in previous paragraphs, it can be confidently assessed that intakes of 200 m³/s at Lisala and 100 m³/s at Moanda (final phases) respectively will not have noticeable impact on the Congo River's regime or on the microclimate. Nevertheless, customary precautions will be taken in order to prevent the aquatic fauna from being enticed into the intake works and machinery. The intake works will be designed in such a manner as to ensure the required discharge at any time and to avoid their flooding. The elimination of solid materials will necessitate the following equipment:

• A grate system to retain drifting bodies.
• A threshold to remove the bed-load made of heavy sands and gravel.
• Reservoirs to deposit and remove the suspended-load of fine sands and contingent silt.

Practically, water will be diverted or pumped from the river into a channel or a big conduit equipped with a grate and a threshold, in order to retain both the drifting and the bed-load. Then, water will enter a clear pond where fine sand will settle. The clearing equipment will be cleaned regularly. A spillway system will be provided in order to ensure the restitution of excess water to the river.

 

3.2.2 Technical and technological issues

3.2.2.1 Electricity supply
At Moanda, it will be possible for the project to be connected to the national network of SNEL; but verifications should be done for the sufficiency and reliability of the supply. At Lisala, such possibility is discarded. The nearest source of energy is the Mobaye-Mbongo hydro-electrical plant. Thus, in order to have electricity in Lisala, the project has the options of:

• Financing the construction of a transmission line from the Mobayi plant.
• Construct a micro hydroelectric plant and provide emergency generators at Lisala.
• Install all thermal (diesel) capacity power plants, which will bring about theproblems of regularity of supply and the costs of maintenance.

For the maintenance of the pipeline and the power supply of the unavoidable boosting pumping stations along the route, there will be an incidental corridor along the pipeline comprised of the pipeline facility, the transmission line(s) and the indispensable road.

 

3.2.2.2 General Corridor Location and Design Parameters
The planning, design and locating of corridors involves many factors, such as: the facility terminal locations, the need for rights-of way, the type of transportation modes, environmental and social factors, engineering and design considerations, safety and security concerns, topography, geology, land-use plans, economics, politics, regulations and standards. The project being an international one, harmonization and co-ordination will be the key word!

3.2.3 Design of pumping stations and choice pump types

Once the exact and definitive pipelines routes are determined, the engineer will be able to choose the most suitable material pipes, compute their dimensions and calculate the head loss and the flow velocity, in function of the discharge, using the universally agreed-upon formulae, namely the Bemouilli, the Darcy-Weisbach and the Colebrook-White (a combination of the Karman-Prandtl formulae) equations. The linear head loss and the physical elevation (static head) will be added to local losses due to abrupt enlargement or contraction of the pipe's section, elbows and valves. The total head loss will serve to design the pumping system, as it will permit: Choose the type of pump type: Centrifugal (high head and small discharge), mixed flow (median values) or axial flow (low head and big discharges). Pump types may be more explicitly defined by the parameter called specific speed (N_s) expressed by:

N_s= NQ^0.5/ H^0.75

where Q is the discharge, H the total head and N the rotational speed (rev/mm). This expression is derived from dynamical similarity considerations and may be interpreted as the speed in rev/mm at which unit discharge (e.g. 1 1/s) when generating unit head (e.g. 1m). Given the length of the projected pipelines and the importance of the discharges involved, it may be necessary to combine pumps both in series (pressure boost) and in parallel (added discharges and operational flexibility) in order to reduce the number of booster pumping stations to a minimum. The initial pumping stations will thus be very important given the fact that the traversed areas are sparsely populated, covered by dense forests or bare deserts. Specially designed equipment will be preferred to standard. Nevertheless, a survey by the Water Power & Dam Construction Journal reveals that, in recent years the most used machinery systems for conveying huge discharges at high head are: the Reversible Francis combined or not with pumps and the reversible turbine. Other equipment comprise the reversible Kaplan bulb, the Pelton and pumps combination, the reversible Deriaz, and a pump only combination. In all cases, a life cycle cost (LCC) analysis of the complex made of the pumping system and the pipelines system must be undertaken. The main reasons being that the purchase cost can become insignificant compared with running costs over the life of the pump. In difficult applications, as is this, the costs of excessive wear, maintenance, spare parts, unplanned downtime, loss of productivity, seal replacements, and water lost by the pump can form a substantial proportion of the LCC, dwarfing the capital expenditure and routing operating costs.

If the option of pumping from the river, instead of diverting the effluent, to the purification plant and the intake basin: low head massive volume axial pumps similar to those used for rainwater removal in major cities. Nevertheless, we suggest that the solution of a diversion canal be preferred for two reasons:

• The topography of the proposed intake points in the Congo does not present any challenges to the drilling of such works.
• The reliability of the supplying system is assured and need only few periodical maintenance works. Whereas the maintenance and reliability of pumps may necessitate more qualified personnel. The cost of energy is also avoided.

With the chemical and physical contents of the Congo River's water in mind the purification issue is not of great concern; A treatment plant equipped with automatic process units will be built to ensure effective and controlled dosing of the various chemicals necessary for a preliminary purification process. Special attention will be paid to the removal of organic algae and to the reduction of the water hardness. Nevertheless, given the huge discharges involved and the variability of water utilization, the treatment of water will preferably be done at Port-Sudan, Walvis-Bay and the pumping stations respectively. At the intake points, at Moanda and Lisala. only a minimal treatment will be applied: that treatment will concentrate in removing the suspended load (sand) that can be a thread for the longevity of the pumps and cause accretions in the pipelines. The chemical treatment will be limited to the reduction of the aggressiveness of the effluent to the transporting system.

 

Given the quantities of water involved, it appears that a series of large diameter (3 to 4-m) concrete ducts between pump stations will be the transport system. Not only can they be manufactured locally, using materials produced and processed along the routes, their manufacturing will accommodate labor-intensive techniques to provide thousand of job and training pportunities to the riparian populations. Furthermore, in the wake of these projects, the very same corridors will host many others, namely:

• A series of spare pipelines will be laid down awaiting for the exploitation of the methane gas in the Kivu Lake and the petrol reserves in the equatorial forest.
• The corridor will be used as an information highway by laying optic fiber ducts crossing Africa from the Red Sea to Cape-Town through Egypt, Sudan, Centre-Afrique, Congo, Angola, Namibia and South Africa.
• The hydroelectric potential of the INGA and the MOBAYI-BONGO sites will be developed at the fullest to supply Africa with a clean, cheap and renewable energy to support its long awaited development. The Sahara as well as the Kalahari Desert regions will be not only irrigated but also industrialized.

 

3.2.4 Storage Facilities at the Final Destinations
As it can be observed from the data in TABLE 2 above, from the first stage of the projects and chiefly at later stages, the discharges involved are of such a magnitude that they are comparable to the minimum discharges of European rivers. Therefore, the issue of the storage of such huge quantities of water will be addressed. The storage facilities will be designed in such a way as to absorb any inadequacy between the supply and the consumption of water.

3.2.5 Environmental Considerations
A heightened sensitivity towards the impact of man's actions on the natural and social environment has characterized the last decades of this particularly industrious century. A great deal of time and money is spent studying the project environment, assessing impacts, evaluating alternatives and recommending the most environmentally appropriate facility location based on guidelines intended to mitigate impacts. The three basic questions the project developer should ask himself are:

• What are the anticipated environmental effects of the project on the nature, the landscape, the culture and the social life of the riparian populations (and how can they be mitigated)?
• Is there an alternative site/route that minimizes the negative effects?
• Does the society, at large, need this project?

 

The answers to these questions are not simple, as it have been proved that in most cases Early Environmental Impact Assessment Studies (EIS) were carried out long after fundamental decisions as to project location and design characteristics had been made; decisions which, in effect, predetermine certain environmental impacts. Coming so late in the development process, the EIS was rarely able to make significant changes in either location or design. Because considerable investment of time and money had already been made, there was undoubtedly considerable pressure to make the best of a possibly less-than-desirable situation. A more comprehensive and exhaustive procedure starts nowadays with siting a board of geographical analysis and progressively narrowing down in three phases:

• The first phase is a regional screening to exclude/or to include large areas from/or for further consideration.
• The second is the identification of alternate sites or corridors using more detailed criteria.
• The final phase is an evaluation and comparison of alternatives which leads to the optimal site/route.

Fortunately in the case of the OKAPI PIPELINES, no such pressure on environmental issue exists at present. The riparian populations on the site chosen and along the route (corridor) adopted will estimate themselves as favored. In these underdeveloped countries were job opportunities are quasi non-existent, this project will afford them with the new material and social opportunities. At the national level, the income from taxes and indirect sources will be welcomed given the political imbroglio most of the involved countries got strangled in. The electrification of the sites, the construction of the access roads and the supply of drinking water to the riparian populations will be considered as major contributions towards the development. Other contributions will be the erection of housing for the personnel and other facilities, such as, schools and hospitals. More technically, the low degrees of industrialization of these countries have left the natural environment almost intact. That makes it an opportunity for Westrac and SAC to apply the up-to-date technology that is the least harmful for the environment, having learnt from the experiences of previous similar projects elsewhere in the world.

In order to produce an environmental protection plan, the existing conditions at site and corridors will be assessed following the subsequent steps:

STEP 1: The physical environment: the report on the existing physical conditions relevant to the project is compiled. It will define: the bedrock geology, the surfacial geology, surface and subsurface drainage, topography and landforms, air quality, ambient noise levels, water quality and climatic features.

STEP 2: The natural environment will be concerned by factors related to the project area and the project itself including: vegetation, wildlife populations and habitat characteristics in quantity, quality and sensitivity, aquatic life and their habitat.

STEP 3: The socio-economic environment that describes the socio-economic conditions of the project area including such factors as existing land uses, cultural activities, proposed land uses and programs, community values and economic affordability.

STEP 4: The engineering conditions of the project area and the existing water system will be explained, including such factors as existing water condition of the water system, hydraulic capacity, water quality, operational problems, hydro-geological and drainage considerations, navigability and land area constraints.

While it is generally recognized that pipelines provide the safest mode of transportation, environmental damage during the construction stage is high and must therefore be accomplished utilizing the highest technical standards to maximize the opportunity for proper restorative measures to be instituted. The ideal routing will be the shortest distance between the source and terminal point. Factors such as pipeline material, pipeline pressure, topographic and soil conditions, surveillance and control procedures will be addressed in the initial planning and design stages in order that a full appreciation for the potential pipeline hazards can be realized. General design and location parameters to be addressed when locating the pipelines are:

• Straight-line alignments, where possible, represent a primary objective.
• Grades, although sensible, do not represent a major obstacle in pipeline construction.
• Given the environmental impact of constructing a pipeline, the design stage will recognize areas having suitable access roads, camp and storage areas, and those areas that are workable during the wet seasons.
• Environmentally sensitive areas, including those locations with high slide potential due to extreme slopes, saturated sands or silts, will be avoided.

In all cases, the legislation of the host countries (where they exist) will be consulted and applied with judgement.

 

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