Republic of Senegal THIRD WATER PROJECT "INTERIM PHASE" DRINKING WATER COMPONENT. Environmental Impact Study

Transcription

1 Public Disclosure Authorized Republic of Senegal 687 Public Disclosure Authorized THIRD WATER PROJECT "INTERIM PHASE" DRINKING WATER COMPONENT Environmental Impact Study Public Disclosure Authorized Patrick LAURAS/Jean-Luc PIGEON Consulting Engineers SETUDE 11, boulevard Pershing PARIS E9440 (M) March 1995 Public Disclosure Authorized

2 TABLE OF CONTENTS 1. SCOPE OF SURVEY SUMMARY AND RECOMMENDATIONS REGULATION AND ADMINISTRATION FRAMEWORK For the management of water resources and the supply of drinking water For the protection of the environment DESCRIPTION OF THE PROJECTED INVESTMENTS Resource immobilization investments Investments for water transport Investments conceming the functional structure of the networks Investments into distribution Tailoring of needs and resources Technical summary of installation production conditions STATE OF THE ENVIRONMENT AND PROJECT IMPACTS General data concerning survey area Underground water resources: current situation and project impacts Impacts due to layout of piping and construction Sanitary impacts connected to water and drainage ALTERNATIVE ANALYSIS OF PROJECT Absence of overall altematives Individual or technical altematives MEASURES OF COMPENSATION TO THE BENEFIT OF THE ENVIRONMENT Compensatory measures and recommendations conceming the use of water resources mobilized by the project Compensatory measures and recommendations concerning the sanitary impacts of the project Compensatory measures and recommendations conceming impacts due to the piping layout 35 APPENDICES APPENDIX 1 Memos drafted at DAKAR subsequent to the 1st mission (June 1994) APPENDIX 2 Memos drafted at DAKAR subsequento the 2nd mission (February 1995) APPENDIX 3 Synthetic evaluation of ground water table APPENDIX 4 Maps of neighboring effects APPENDIX 5 Reproduced documents 97 REPUBLIC OF SENEGAL Environmental Impact SWdy Patrick LAURAS J Jean Luc PIGEON THIRD WATER PROJECT SETUDE - 11, bd Pershing PARIS INTERIM PHASE T (1) Fax. 16 (1)

3 2.SUMMARY AND RECOMMENDATIONS The survey of the impacts of the 3rd water project upon the environment was carried in the frame of the 2 missions to DAKAR from June 13 to and from February 8 to inclusive during which the main departments concerned by the CAP VERT water supply project were encountered, with the Ministry of Hydraulics, with SONEES, with the Cayor Canal survey mission. In the field, all the installations of the installations and the layout of the new pipes have been reconnoitred entirely Potential impacts of the project on the underground-wateresources are acceptable as long as a careful follow-up policy is applied 0 Impact of the new drawing off considered in the North Coastal ground-water is moderate. Potential drawing-off from the ground-water table and its piezometric evolution have been evaluated by BRGM in 1992 thanks to modelling of the ground-water table behavior and demonstrating that: * water exports by evaporation are in the great majority: 300,000 m 3 /day in 1992 with only 70,000 m 3 /day drawn off; * the loss induced by the new bore holes (35,000 m 3 /day) will not be felt on the north-south piezometric dome which protects the North Coastal ground-water table against the invasion of salt water; the effect of the bore holes will only be felt on the GUEOUL-THIES line i.e. near the layout zone: the induced drop should be around 2.5 to 5 meters over 15 years, acceptable considering the depth of the aquifer. However, it should be pointed out that under the current climatic conditions, the resource of the North coast is not perennial and the implementation of a long-term supply project, like the Cayor canal, should make it possible to reduce the water drawn off. O On the other hand, the resources in the CAP VERT region are a justified subject of concern. A considerable drop in the level of some of the aquifers have been observed. However, these drops are not a consequence of the project but result from the current drawing off of the ground-water table on the peninsula and the limestone ground-water table of POUT and SEBIKOTANE. It will be possible to maintain this amount of drawing off in the interim phase as long as piezometric evolutions are followed up regularly and critically together with the chlorine contents, sign of a possible intrusion by salt water. The amounts of water taken for WS at CAP VERT are from ground-water which, in some cases, is barely being refilled at the present time. Therefore, we have to insist upon the fact that the supply scheme for water to CAP VERT, in the interim phase is necessarily provisional. It would be very inadvisable to count on maintaining this amount of drawing off beyond a period of 10 or 20 years. REPUBLIC OF SENEGAL Environmental Impact Study Patrick LAURAS J Jean Luc PIGEON THIRD WATER PROJECT SETUDE -11, bd Pershing PARIS INTERIM PHASE Tel. 16 (1) Fax. 16 (1)

4 1.SCOPE OF SURVEY The "3rd water project" is an overall development project for the water sector on the CAP VERT peninsula. It has been divided into two major phases, the first 'urgent" phase which, in 1992, already made it possible to increase the available resources by 40,000 m3 per day thanks to 10 ne bore holes in the POUT region, into the Maestrichtian deep table, and a 'interim" phase which should be started during the forthcoming months. This interim phase will include: * considerable investments to reinforce the CAP VERT drinking water supply (estimate 116 billion francs CFA - see figure 1A, * an institutional reform of the water sector; * complementary surveys concerning the water sector (reuse of water by market gardeners, drainage studies, etc.); - if necessary, complementary investments such as, for instance, the drainage of R This survey is designed to evaluate the impacts of the investments provided f( water supply to Cap Vert and the environmental follow-up measures accompaw the project, while taking into consideration the perspectives of institutional re A number of investments which originally formed part of the "3rd water project' pro already underway or will be financed in another framework: * the 'WS Small Coast' project is underway, with CFD financing; - the "WS eight centers" project is underway with JICA financing; * the "WS six river centers' project is being surveyed (with financing by KFW); I * the "WS eleven towns' project should also be financed by KFW; the feasibilil Pi underway. cc Therefore, these projects were not examined during this impact survey. Th cas fac nec arnc REPUB REPUBLIC OF SENEGAL Environmental Impact Study Patrick LAURAS Jea_ THIRD V THIRD WATER PROJECT SETUDE - 11, bd Pers INTER,W INTERIM PHASE Tdl. 16 (1) (

5 O The report recommends a number of accompanying measures for the project. To some extent, this concerns arrangements for following up the evolution of the ground water used for WS in CAP VERT: * creation of 21 supplementary piezometers (already provided for in the GERSAR/BETURE draft project); * requirement to confirm the organization already set up by the Hydraulics Management (Direction de l'hydraulique)and SONEES so as to follow up on a monthly basis 88 piezometers (to which the 21 piezometers to be created must be added); * need to establish a forecast frame of reference for the piezometry of the North Coastal ground-water table so as to react in the event of the real piezometry drifting with respect to the forecasts of the BRGM model under the responsibility of the water resources management and planning department; * need to stipulate a regulation for checking the water drawn off by a decree applying to the water code law. 3 and, to some extent, the recommendations and compensatory measures: * regular cleaning of the PANTHIOR dam to improve the refilling of the SEBIKOTANE ground-water table; - preliminary survey to create other water refilling retainments; - establishing of a budget provision in order to be able to compensate for the drying up (or more probably the drop in the flow-rate) of several village wells near the new bore holes on the North Coast (deepening of the wells or connection to SONEES pipes) at the expense of the owner Impacts upon the environment and neighborhood of the installations are generally very limited Ol There are three potential impacts that are worth mentioning at this stage: - the crossing of the PIKINE - DAGOUDANE - THIAROYE built-up area will require particular attention conceming the work on the site in order to minimize the effects of nuisance upon the populations; * the construction of the MAMELLES reservoir is in a sensitive area; * crossing a number of the gardens will have a temporary effect upon the "market gardening" process. REPUBLIC OF SENEGAL Environmental Impact Study Patrick LAURAS I Jean Luc PIGEON THIRD WATER PROJECT SETUDE - 11, bd Pershing PARIS INTERIM PHASE Tel. 16 (1) Fax. 16 (1)

6 O The main recommendations made in this study concern: * the need to establish particular technical arrangements on the site for contractor consulting when crossing dense urban zones is involved (sheet piled excavations, rapid covering of trenches, maintained access to homes, etc.) and for the safety of the people concerned; * the need to pay attention to how the Mamelles reservoir is inserted while complying with the natural topology of the site; * the need to provide for financial compensation in the event of temporary market garden produce loss; * the need to ensure repair of the sites for crossing the listed forest of PoOt and the rewooding perimeter of Mbaw The sanitary impacts of the project are rather positive O The project will serve districts where inhabitants do not have running water in their home: at the present time (43,000 social connections are scheduled). This impact will be positive on the populations concerned. O However, i is certain that the water shortage will continue and that there will still be cuts, less numerous than at the present time, during the first years of the interim phase. It is important to underscore the fact that to attenuate this shortage, SONEES is committed to a water savings policy by searching for leaks and locating outdated networks, by anti-waste communication, etc. In 1994, using its own capital, it will refurbish a 40 km line (out of a total line length of 1600 km). This considerable effort have to be maintained for several years and it would be worth reinforcing it with a tertiary network renewal program forming part of the distribution section of the 3rd water project. O From another standpoint, fears about the risks of reinforced pollution caused by dumping into the sea are unjustified. O However, pollution by nitrates from the THIAROYE sand layer could lead to a problem of drainage connected to high urbanization and is liable to become increased. The current contents are already very high (150 to 300 mg/i) and therefore, it is advisable to: * maintain the current device to dilute this water more before putting it into distribution (connection to ALG1); * carefully monitor the nitrate contents and their bacteriological levels; REPUBLIC OF SENEGAL Environmenta Impact Sudy PatrIck LAURAS I Jean Luc PIGEON THIRD WATER PROJECT SETUDE - 11, bd Pershing PARIS INTERIM PHASE Tel 16 (1 u Fax. 16 (1)

7 3.REGULATION AND ADMINISTRATION FRAMEWORK Before going on to analyze the project and its impact, we have to briefly outline the regulatior and administrative framework of the water and environmental sectors in Senegal For the management of water resources and the drinking water supply O The government is the authority as concerns water in Senegal, on the basis of the following principles: * water production, transport and distribution are public and governmental services (law of July 19, 1965); * hydraulic resources are part of the public domain. Their use comes under government control (law of March 4, 1981 concerning the Water Code), as is water dumping. At the present time, the Hydraulics Department at the Ministry of Hydraulics is responsible fo these skills, with three different departments: * one department in charge of following up the rural WS (DEM); * one water resources management and planning department; * one drainage division. 0 The production and dilution of drinking water in the urban environment has been delegated t SONEES, a national company under govemment authority. This "delegation is comparable to a concession i.e. the government assets required by WS have been transferred to SONEES (law of July 5, 1983 and decree of August 1, 1983). Accordingly, investments in the drinking water supply field are made by SONEES, the owner As far as drainage is concerned, mdelegation" is more like licensing because the government is owner of the networks and equipment managed by SONEES. REPUBLIC OF SENEGAL Environmental Impact Sbtdy Patrick LAURAS I Jean Luc PIGEON THIRD WATER PROJECT SETUDE - 11, bd Pershing PARIS INTERIM PHASE T (1) Fax. 16 (1)

8 6 O An institutional reform should be taking place in the framework of the "3rd water project". The general outline of the reform has been sketched out by consultant HSD ERNST and YOUNG: they will be the subject of negotiations in the near future. In the following, we only point out the highlights conceming the "environmental management" section of our survey, considering them as working hypotheses: * the ownership of the equipment and prime contracting of the work will be covered by a national company; * the management of the equipment, water distribution and relations with clientele will be handled by an operating company via a licensing contract; * governmental facilities for exercising its authority and control may be improved by establishing a go-between organization between govemment and users (Higher Water Council) and a technical organization having the necessary personnel and a budget (Higher Water Commission). Refer to appendix 5.1 for more details For the protection of the environment Three documents can be mentioned with respect to this impact study: * the decree of January 1, 1950 for the protection of green areas and forestry reserves: the MBAW forestry reserve is concemed by the project; * the decree of June 27, 1978 for the protection of traditional villages (the project avoids them); * a decree regarding the protection of monuments, historical and archaeological locations. The MAMELLES location is protected in this way. REPUBLIC OF SENEGAL Environmental Impact Study Patrick LAURAS / Jean Luc PIGEON THIRD WATER PROJECT SETUDE -11, bd Pershing PARIS INTERIM PHASE Tel. 16 (1) Fax. 16 (1)

9 4.DESCRIPTION OF THE PROJECTED INVESTMENTS The investments projected for the interim phase to reinforce the WS of CAP VERT can be described by four main sub-systems: * investments to mobilize additional resources; * water transport investments; * investments concerning the functional structure of the networks; * investments into the distribution networks. The total cost of the investments comes to 116 billion francs to which must be added approximately 5 billion for prime contracting. Figure 1 identifies the main investments in a schematic diagram Resource mobilization investments During the interim phase, it should be possible to increase the resources available to CAP VERT from 191,000 to 262,000 m3/day. To do this, it is intended to raise the capacity of the NGNITH water treatment station from 39,000 to 64,000 m3/day and to sink 11 bore holes int the ground-water table of the North Coast for a capacity of 35,000 m3/day. 0 Bringing the NGNITH station up to level The NGNITH works was commissioned in It was designed to handle 64,000 m3/day (some civil engineering sections were even designed for 132,000 m3/day: exhaust station). Installing several electromechanical equipment items was, however, deferred to the point thz the effective capacity never exceeded 39,000 m3/day. Bringing the works up to level so that the capacity reaches 64,000 m3/day means carrying out a series of local operations: * reinforcing the pumping and discharge capacities; * bringing some equipment up to level; * making some major civil engineering repairs (filter bases, decanting devices); * partial automation (dosing, washing of filters, extraction of sludge from the decanter); * creation of a 3000 m3 reservoir. The cost of these investments is estimated at billion F.CFA (SONEES estimation after devaluation). REPUBUC OF SENEGAL Environmental Impact Sbudy Patrick LAURAS I Jean Luc PIGEON THIRD WATER PROJECT SETUDE - 11, bd Pershing PARIS INTERIM PHASE T4l. 16 (1) Fax. 16 (1)

10 8 O Creation of 11 bore holes operating at 125 to 150 m3/hour in the North Coastal ground-water table Subsequent to the BRGM study and to the water resources of the North Coastal groundwater table (results given in section "impact analysis"), it was decided to reinforce the drawing-off capacities from 27,000 to 62,000 m3/day. The holes will be located near the centerline of national highway 2, spread out over forty or so kilometers between GUEOUL and KELLE. They will be connected to the new conduit by discharge pipes having a diameter of 300 mm. They will be identical in design to the existing SONEES holes. The cost of the bore holes is estimated at billion F.CFA (SONEES estimation after devaluation). O To accompany these investments, the piezometer network will be densified: 21 new piezometers will be installed, added to the 140 existing piezometers. The estimation amounts to 706 million F.CFA. O In the THIES region, it is also intended to install 2 supplementary bore holes to supply the city, estimated at 838 million F.CFA Investments for water transport The transport of the new resources from NGNITH and the North Coast area to CAP VERT wvill be by the partial doubling of the existing "ALG" conduit: 103 km piping between GUEOUL and THIES and 54 km piping between THIES and DAKAR. In general, the new supply pipes will follow the ALG pipe. They will depart from it over a distance of several kilometers to cross inhabited or built-up areas. The cost of the pipe is estimated at billion F.CFA and that of the pipe at billion F.CFA Investments conceming the functional structure of the networks O The project provides for the implementation of a remote management system installed at point B (arrival and dispatching point for the water resources). This will be a complete monitoring, alarm, control and measurement system working on the networks with 6 secondary plants and 49 satellites. The installation cost is evaluated at 2.9 billion F.CFA. 0 A large 25,000 m3 reservoir has to be installed alongside the existing reserves of MAMELLES. It will practically double the capacity of the total current reserves at DAKAR- PIKINE (35,000 m3). Costs are estimated at 2.4 billion francs CFA. REPUBLIC OF SENEGAL Environmental Impact Study Patrick LAURAS I Jean Luc PIGEON THIRD WATER PROJECT SETUDE- 11, bd Pershing PARIS INTERIM PHASE T61. 16(1) Fax. 16(1)

11 Investments of the distribution section This concerns all the investments related to the CAP VERT distribution networks: * restructuring of the primary networks and interconnections (approximately 105 km); * renewal of any old leaky pipes (approximately 45 km); * extension of the distribution networks to new districts (approximately 400 km); * continuance of the social connections" policy (approximately 43,000 new connections); * equipping of the distribution networks with meters, analyzers and pressure gauges to be incorporated into the remote management system outlined above. The distribution investments are estimated at 27 billion francs CFA of which 2.5 billion went to prime contracting Tailoring of needs and water resources The CAP VERT population represents approximately 2,000,000 inhabitants today. It should continue to increase at a rate of approximately 5% per annum. This extremely fast development among the DAKAR population explains the outstanding water requirement upsurge (although forecasts are based on constant requirements per subscriber): - the average theoretical requirements work out to 280,000 m3/d in 1992 i.e. the deficit regarding average requirements was around 30%; - for the 1999 horizon, the average theoretical requirements will be around 380,000 m3/day; the deficit will still be around 35% in spite of recourse to new resources during the interim phase. Accordingly, the goal ot the interim phase may not be to re-establish balance between needs and resources but simply to preserve the water supply situation awaiting a large-scale structuring project such as the CAYOR CANAL which should resolve the problems at DAKAR to the year 2020 at the least. This provisional nature of the drawing-off from underground resources in the interim phase is essential in analyzing impacts as proposed in the following paragraph. REPU8LIC OF SENEGAL Environmental Impact Stdy Patrick LAURAS I Jean Luc PIGEON THIRD WATER PROJECT SETUDE - II, bd Pershing PARIS INTERIM PHASE T4l. 16(1) Fax, 16(1)

12 ..O, iagi6 > FIGURE 1 _ Mise A niveau de I' usine ms M - de NGNITH + reservoir300m3j I _4>v A I, I /tbedgn.e B,as~di lp-_ Sch6nia d'ensemble des investissements projetes O CEA N~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~N -ffillitillill lititlilii ill Li - Cana.istonslnuvelle P / eoint B > Ngutuhe DacOUR.,, 1 o Magnan Omar /.. - ;N_,,... / ~Gotoyt Mbtut,,-_' O. C~ E N ' /-oundt Maleye.? 9 / K Bassi _-,a/. p. J,,Mboul 1. TiougounA ' I * 87/ r ~~~~~~~~~~~~~~~~~~~Zone dl lnnplarlfmot. > / / ; ~~~~~ *me~r ( t25a io:3h I /0 m o QIII)WD~~~~~~~~Thb '- Q-r~~, ~ e lie des Madelemnes \ ( Aon~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Rd30 n t GUEOUL- $ THIES + Beye gdande ( -. ;2 lmki N ~~~~~~T 0Yoro Pezl i~ W-t secondalres~~~~~~~~~~~~~~~~~~~~~~4 brnheet / I." i.etutrto Polceta Veeeeto. {ojabut 0 I,!, a } 4, I. }~~~~~~~~~~~~~~~~~~~~~0ur w:~ ~~~~~~~~~~~~~~H ~ ~ ~ r our, iunou;ok ' 1 j X ' s 11 * t~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ t

13 4.6. Technical summary of the work production conditions The layouts of the large pipelines have been defined generally by GERSAR/BETURE (modified "mission 0" reports), far more accurately than before with engineering studies concerning the detailed pre-production project: only minor changes are liable to be made tc these layouts that we have checked through from end to end as part of assignments in DAKAR for the impact survey. More generally, impacts on the neighborhood are small compared to the amount of investment. This is due to the fact that the pipes are laid underground and that ground equipment is almost all located on sites that have already devoted to WS. TJ7engineering studies in terms of the detailed 2re-production project lead to the following indications: An expected work duration of 2 years from 1996 to The implementing of the Cayo Canal is to take place between the years 2000 and 2005 and the operation of the interim phase will take between 3 and 8 years, better establishing the provisional drawing-off device regarding the underground resources (as a reference, in 2002 and according to mission 0, the deficit of the needs with respect to the resources was 41%). A soil survey campaign was started in July 1994 to distinguish between five types of soils: laterites, limestone marnes, plastic and sandy clays, clayey or silty sands and sands whose physical, mechanical and chemical characteristics have been determined. A detailed topographic survey was engaged on the Thies-Dakar section beginning in July 1994 with the survey of study bands of 30, 50 or 100 m and the marking out of the control axis. This topographic surveys led to the underpinnings of maps to 1 :1000th and to lengthwise detailed profiles down to 1 :100th in elevation in urban areas so as to define the constraints of the layout accurately. From Thies to Dakar, the layout will run parallel to the existing pipe (ALG1) except in two places: - the descent from the Thies plateau to allow for the right of way of the Cayor canal, - the crossing of the Thiaroye-Pikine urban area, characterized by fast and uncontrolled development of urbanization and by a group of constructions that it would be difficult to penetrate. The layout in the Thiaroye-Pikine urban area was retained, after land surveys and acknowledgement of restructuring projects provided for on the site. Accordingly, the layout follows that of the Bonna pipe in the crossing of the Mbaw wooded perimeter, runs along thc perimeter via the North, follows the future layout of the motorway to the South in the unconstructed area (North of the police station), crosses a dense dwelling area, followinc the streets so that the machinery can pass without the homes being demolished, run, along the North motorway layout in the unbuilt parts of the Faidherbe camp, follows the maii tracks of the Guinaw Rails to avoid any damage to the existing constructions and meets bac on the layout of the existing ALG to the North at the intersection with the SNCS track at Pikine. At this level, two homes will have to be destroyed as they fall within the right of wa~ of the existing pipeline. REPUBLIC OF SENEGAL Envronmental Impact Study Patrick LAURAS J Jean Luc PIGEON THIRD WATER PROJECT SETUDE - 11, bd Pershing PARIS INTERIM PHASE Tl. 16 (1) Fax. 16 (1) '

14 Between Thies and Dakar, the technical characteristics of the works will take into consideration passages of infrastructures (SNCS track) to enable one of the two ALG pipes to be used in the event of maintenance or repairs while maintaining most of the flow, and integrate the future reinforcing constraints in the Cayor Canal phase. Finally, the part of the development chosen gives privilege to the visual and landscaped impact while using a totally buried layout between Thies and Dakar. The production construction conditions are as follows: - minimum right of way of 20 m during work on site outside of the urban areas (10 to 12 m after construction), - excavation material placed on the existing pipe but limited to a height of 3 m, or evacuated for sites in the urban areas, - the possibility of setting slight deviation angles on the pipes to avoid the main baobab trees in the line of the layout, - maintained water services during the work, - sheet piled excavations for the crossing of urban areas, - work carried out in the dry season in areas sensitive to erosion (e.g.: the Thies plateau). Acknowledgement of pipe laying constraints will require the following of the contractor: - servicing and maintenance of all the tracks to be used, - setting up signposting and prcviding the necessary information, - maintaining all the passages providing access to the land lots and the circulation of livestock, - minimizing impact upon the surrounding crops by avoiding destruction of hedges and tall standing trees, - the setting-up of all necessary arrangements to prevent the run-off of site water, - reduction to 15 m of the right of way in crossing the Mbaw perimeter. REPUBLIC OF SENEGAL Environmental Impact Study Patick LAURAS / Joan Luc PIGEON THIRD WATER PROJECT SElUDE - 11, bd Pershing PARIS INTERIM PHASE T4l. 16 (1) Fax. 16 (1)

15 13 Suivi du BONNA dans la trovers6e du p6rimetre de MBAW F~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Aperqu de /a piste d'exploitation de la conduite existante REPUBLIQUE DU SENEGAL Etude des impacts sur 1'environnement PATRICK LAURAS/ JEAN LUC i TROISIEME PROJET EAU SETUDE -11, bd Pershing 7501 PHASE INTERIMAIRE T61.16 (1) Fax.16 (1) 4'

16 5.STATE OF THE ENVIRONMENT AND PROJECT IMPACTS Analyses of the initial state of the environment and the impacts of the project have been grouped together here to make for easier reading regarding problems resulting from the project General data concerning the survey area The population of the DAKAR built-up area is estimated at 1.58 million inhabitants in 1993 and it is expected to reach 3 million inhabitants in 2010 (i.e. 25% of the country's total population) with an annual growth rate of 5 to 6%/o/annum (directorate of forecasts and statistics). The climate is sub-desert tropical with a dry season and a wet season from July to September when 90% of rainfall occurs. The rainfall in the project area is 400 mm/annur with heavy showers sometimes exceeding 150 mm in 24 hours and above all, 50 mm in on( hour. The mean annual temperature between 1955 and 1989 was approximately 240C with maximum in October (31.80C) and a minimum in January (15.30C). The drinking water supply in the survey zone is by the SONEES system drawing water from the ground water at CAP VERT (cf. appendix 3) with a supply pipe from the Guiers lak Volumes are 191,000 m3/d; 60% is distributed by domestic connections and 40% by founta points. Drainage in the DAKAR area is essentially by individual systems concerning 870,000 inhabitants. There is a drainage network in DAKAR for 646,000 inhabitants but only 454,00 are connected to it (a connection factor of 70%). The total waste water flow is estimated at 180,000 m3/day of which 37% (66,000 m3/day) is collected in the drainage system Underground-wateresources: current system and impacts of projects The project is based upon an increase in the amount of water drawn off from the North Coastal ground-water table, from 27,000 to 62,000 m3/day; in addition to the resources currently being exploited. This drawing-off from underground resources will have extensive potential impact, by far the most significant of the project. That is why the data and the surveys regarding the potential of these resources and their evolution have been examined with the greatest of care. Accordingly, a synthetic data sheet per aquifer has been established from the database compiled during the mission (appendix 3). REPUBLIC OF SENEGAL Enwironmental Impact Study Patrkck LAURAS / Jean Luc PIGEON THIRD WATER PROJECT SETUDE - 11, bd Pershing PARIS INTERIM PHASE T6l. 16 (1) Fax. 16 (1) :

17 5 THE NORTH COASTAL GROUND-WATER TABLE The amount of water now drawn off the North Coastal ground-water table has been reevaluated by BRGM in 1992 subsequent to a field survey. The survey also made it possibl4 to update the hydrodynamic data and work out the current ground-water table inlet/output balance. The results are as follows: * The most important demands resut from evaporation which has barely been compensated for by rainfall since For the year 1991, it is estimated at 300,000 m3/day (depending on sectors, corresponding to an evaporated water head included between 3 and 45 mm/year). To this evaporation balance we must add the drawn off water, amounting to 70,000 m3/day in 1991 (see detail in appendix 3). * Accordingly, the level of the ground-water table has dropped 50 cm per year between 1975 and 1991 in the piezometric dome region. On the RN2 line, it dropped 10 cm per year outside of the perimeters of influence of the SONEES bore holes. * It is expected that over-exploitation amounting to 35,000 m3/day will occur during the interir phase. The BRGM survey has made it possible to evaluate the evolution of the ground-wag table piezometry up to the year 2010, thanks to a hydrodynamic model which was appropriately set on the period (1052 grid sections measuring 3 km times 3 km) In appendix 5.2 we have added conclusions concerning the modelling and the two more significant schematic charts: - the first refers to the expected drops in the ground-water table without over-exploitation (this is the "reference state* without a project) for the horizon 2010; - the second gives the expected drops, taking the project into consideration, for the 2010 horizon. * Modelling demonstrates: - that the North Coastal ground-water table will drop, in any case, from 5 to 15 m by the 2010 horizon, even without the project (assuming that the weather conditions of the last 15 years prevail); - that the supplemental drops caused by new drawing off will be negligible regarding the North-South piezometric dome which it is essential to maintain to protect the groundwater table from the influx of salt water; - that the additional drops induced by new drawing-off on the GUEOUL-KEBEMER line w be around 2.5 to 5 m; - that the drop induced in the new bore holes themselves will be 14 m. Finally, BRGM observes that the new drawing-off will not induce any risk of the intrusion of the salt water in the North (LOUGA region). REPUBLIC OF SENEGAL Envronmental Impact Study Patrick LAURAS I Jean Luc PIGEON THIRD WATER PROJECT INTERIM PHASE SETUDE - 11, bd Pershing PARIS T4l. 16(1) Fax. 16(1) t

18 There are three conclusions resulting from the above: 1/ The impact of the new bore holes has to be put into proportion regarding the depletion of the resources that are not renewed in the current context of the rainfall deficit: on the scale of the North Coastal ground-water table, the new drawing-off onl represents 10% of the total evaporation recovery, approximately 300,000 m3/day. The drops are negligible at 20 km from the bore holes. 2/ The local impact of the holes could be considerable. In particular, it is probable that some wells or village holes near the new bore holes will dry up. However, this also has to be put into proportion: at the present time, SONEES is supplying water to 240 villages near the RN2 highway via taps from the existing WS pipe. The number of wells and bore holes along RN2 that are In activity is unknown but it is probably not very high. Whatever the case, this problem has to be taken into consideration and we will refer t it when dealing with compensatory measures. 3/ We must insist upon the fact that under the current weather conditions, the North Coastal resource is not perennial and the implementation of a long-term water supply project like the Cayor Canal should reduce the amount of water drawn off. REPUBLIC OF SENEGAL Environmental Impact Study Patrick LAURAS I Joan Luc PIGEON THIRD WATER PROJECT SETUDE - I 1, bd Pershing PARIS INTERIM PHASE T (1) Fax. 16 (1)

19 O THE CAP VERT REGION GROUND-WATER TABLE The first remark to be made is that we should take into consideration the fact that the evolution of the ground-water table in the CAP VERT region is not in actual fact an impact c the project because bore-holes already exist there and there will be no more in the future. However, impacts of the DAKAR WS system are too considerable to omit describing the m environmental state" of this ground-water table. In the following, we refer only to the more salient facts (see the synthetic data sheets per aquifer in appendix 3). * The infrabasaltic sandy ground-water table The infrabasaltic sandy ground-water table under the Cap Vert peninsula has been overexploited at certain times (between 1970 and 1985). This has resulted in some encroachment of salt water. The situation has been stabilized for the last ten years or so. Maintaining the current level of drawing-off (19,000 m3/day) is possible as long as the rainfs is sufficient because the ground-water supply appears to be connected to it. Section 7 deal with the question of following up piezometry and salinity which are essential because of this risk of salt water encroachment. * The THIAROYE Quatemary sandy ground-water table The operation of this layer has been reduced and the actual level has stabilized generally since The objective of drawing off 8,000 m3/day during the interim phase, corresponding to the volumes drawn off over the last few years is therefore not a problem regarding the resource (as long as the rainfall is sufficient). However, we should observe that the quality of the water has degraded over the last few years with a considerable increase in nitrate content: contents closeto 300 mg/i have been measured while the WHO recommends 50 mg/l as a limit for drinking water supply. This pollution results from the infiltration of waste water from PIKINE-THIAROYE, a built-up area covering the entire peninsula area where there is no drainage. * The SEBIKOTANE Palaeocene limestone ground-water table First and foremost, the ground-water we are about to refer to now is a single but complex aquifer system (SEBIKOTANE and POUT limestones and POUT Maestrichtian). The SEBIKOTANE ground-water was exploited enormously in the beginning of the 60's causing salt water to invade its southern part. Drawing-off was cut down to some extent an now amounts from 25,000 to 27,000 m3/day. It appears that the encroachment of the salt water is continuing, quite slowly, in the southemmost tip. The chloride contents of some piezometers have increased considerably since 1985 (increasing from 35 to 300 mg/i). Therefore, the ground-water is still slightly over-exploited and maintaining the current level c drawing off is only possible with close supervision and as part of an overall project for the DAKAR WS in a relatively short time. REPUBLIC OF SENEGAL THIRD WATER PROJECT INTERIM PHASE Environmentbd Impact Shtdy Patrick LAURAS I Jean Luc PIGEON SETUDE - 11, bd Pershing PARIS T (1) Fax. 16 (1) '-

20 * The POUT Palaeocene limestone ground-water table The ground-water here-is in a similar state to the SEBIKOTANE system: over-exploitation during the 60's leading to salt water invasion; at the present time, the drop is 60 cm per annum; chloride has increased in the south (120 to 275 mg/l between 1985 and 1993). For the interim phase it is intended to draw off 20,000 m3/day in all. This is a little more thal in 1992 but nevertheless down with respect to the years before 1991: the commissioning o the emergency phase bore holes in the Maestrichtian areas was accompanied by a deliberate reduction in the amount of water drawn off the Pout limestone layer because of tu connection between the two aquifers. In the same way as for the SEBIKOTANE ground-water, the scheduled volume is only acceptable if piezometry and salinity are monitored very carefully and if the perspective of a overall project for the DAKAR WS is confirmed within a reasonable period of time. * The POUT Maestrichtian ground-water table The Cap Vert WS urgent phase involves a major increase in the amount of water drawn off by SONEES in this deep-lying aquifer: from 37,000 m3/day in 1991 to 74,000 m3/day in During the interim phase, the drawing-off from the ground water will remain at this level of 74,000 m3/day, reached during the emergency phase. Other amounts drawn off will be considerable. They were estimated at 50,000 ms/day (in 1985). Therefore, total drawing-off will be around 120,000 m3/day (see appendix 3). With this amount of drawing off, the ground-water will drop by 1 m to 1.5 m per annum, acceptable without difficulty for 10 or 20 years considering the great depth of the aquifer. To summarize the above, there is more to be concerned about regarding the groundwater near DAKAR and the Pout and Sebikotane limestone ground-water than the increase in exploitation of the Maestrichtian and North Coastal ground-water. However, we must bear in mind that the water being drawn off here will come from quasi-fossil resources (not renewed in the current context of rainfall deficit) which wi not settle the problem of the long-term water supply for DAKAR. O IMPACT OF DRAWING-OFF IN THE GUIERS LAKE The MANANTALI and DIAMA dams will ensure that the Guiers lake is supplied with flowrates of around 40 to 50 m3/s, even during the dry season. The water drawn off at NGNITH 0.7 m3/s is negligible. However, we have to face the facts concerning the ecological problems that could confront the Guiers lake in the next few years: increase in the pesticide factor, loss of capacity due t sedimentation. However, none of these would be the result of drawing off water from NGNITH. REPUBLIC OF SENEGAL Environmental Impact Study Patrick LAURAS / Jean Luc PIGEON THIRD WATER PROJECT SETUDE - 11, bd Pershing PARIS INTERIM PHASE T (1) Fax. 16 (1)

21 5.3. Impacts due to the layout of the pipe and the constructions: Appendix 4 is a series of maps to a scale of 1:50,000 showing the main points of impact tha we describe below: O On the GUEOULUTHIES line, there is very little impact if we take care to place the pipe on the western side of the existing ALG pipe and to skirt around ten or so hamlets or villages s that we do not interfere with the fencing. In particular these are: N'DIAYE TIORO, BEUD FORAGE, DAKAR NGOGNE, PALMEO, GUEOUL NDANDE (sacred tree), etc. Almost everywhere, in fact, the ground is used for traditional millet and manioc crops. There are also two large swamp crossings where the pipe must be laid overhead on concre posts (and where the landscaping impact is of no consequence). O On the THIES-POINT K section, the sensitive areas through which the layout passes comprise market garden areas and orchards (Niayes area), the listed forest at PoOt and many talwegs with temporary flow conditions. * In the crop-growing areas, consisting of traditional family market gardens and large market gardening ventures, the passage of the pipe will lead to a temporary loss of operation. * In the PoOt forest, the 8.5 km of layout will lead to the elimination of vegetal elements (hedges) but, in theory, no tree felling. * In the talwegs, passage of the pipe will lead to the cut-off of flow and risks of erosion. O On the POINT K-POINT B section, we note three types of impact, in increasing order of importance: * the crossing of the rewooded perimeter of MBAO following the existing layout of the BONNA, * the crossing of many gardens, more often than not used for vegetable farming. The impact will be transient; * the crossing of dense built-up area between THIAROYE and PIKINE. The different solutions we have considered are analyzed in paragraph 6.2 below. O The construction of the MAMELLES reservoir (25,000 m3) is the most significant individua impact of the project. The Mamelles site is listed as regards the protection of historical and archaeological areas but this classification does not correspond to the precise criteria of the environment: the sit is agreeable but nothing exceptional and the environment will soon be urbanized. REPUBLIC OF SENEGAL THIRD WATER PROJECT INTERIM PHASE Environmental Impact Study Patrick LAURAS I Jean Luc PIGEON SETUDE - 11, bd Pershing PARIS Thl. 16 (1) Fax. 16 (1) E

22 In paragraph 6.1, we will see that there is no possible alternative to install a large-volume reservoir (which is indispensable for the continuity of distribution in the MAMELLES sector (i.e. the entire North of the peninsula) and for the safe distribution to DAKAR center. Careful insertion of the reservoir is recommended as regards compensatory measures (see paragraph 7.3). 0 Finally, we have to deal with problems of impacts connected to the site. More particularly, these include: * the hindrance to nearby residents in all the streets where pipes will be replaced (distribution section). This is temporary and conventional for all road works; * risks of accidents involving people living near the villages and in the built-up areas, connected to the opening of a trench approximately 3 m deep in highly frequented areas (see compensatory measures). REPUBLIC OF SENEGAL Environmental Impact Sty Patrick LAURAS I Jean Luc PIGEON THIRD WATER PROJECT SETUDE- 11, bd Pershing PARIS INTERIM PHASE Tdl. 16 (1) Fax. 16 (1) :

23 5.4. Sanitary aspects connected to water and drainage 2 Increasing the volumes available for drinking water supply will lead to the possibility of distributing water to a wider population and the probable increase of individual consumption. This will have sanitary impacts and consequences upon the purification of waste water. 0 SANITARY IMPACTS The first sanitary impact of the project is positive: it will extend service to the home thus considerably improving the sanitary state of the dwellings. The 'social connections" lot of the "distribution section" is essential on this point: it is intended to create 43,000 connections, meaning that the total number will be increased by around 30% from 122,000 to 165,000 subscribers (from 1990 to 1993, 41,000 social connections will already have been made - see appendix 5.6). Note that the extension of the water networks is not a factor of incitation to urban immigratior because the new districts are developing well ahead of the supply of water services. * In areas where there are drainage networks, there could be a considerable sanitary effect related to the increased flows to be evacuated. Will the hydraulic capacity of the used water networks be sufficient and are there not risks of waste water overflows? According to all the people questioned on the subject, the current problem is rather one of flow insufficiency in the networks and the considerable depots resulting therefrom. Accordingly, there is no risk of overflow of used waters in the interim phase. O DRAINAGE AND POLLUTION OF THE NATURAL ENVIRONMENT Several people raised the problems of the effects of the increased volumes of water consumed regarding the pollution of the natural environment. Distinctions must be made between several different cases: i in areas where there is no drainage, waste water is often evacuated by infiltration into the so by means of pits or infiltration wells (this is the case in the entire PIKINE - THIAROYE - GUEDIAWAYE built-in area where the soil is sandy). The fact that running water is available near the home means that people consume more, probably favoring the phenomenon of infiltration and accelerating the transfer of pollutants towards the underlying aquifers. This mechanism is a problem regarding the drinkability of water in the THIAROYE sandy ground-water used by SONEES at a rate of 8,000 m3/day: the nitrates have already reache( levels of around 150 to 300 mg/liter and it is probable that the increase will continue because of the urban planning itself and subsequently as a consequence of the acceleration in infiftrations (see recommendations in paragraph 7.2). * Conversely, the reinforced drinking water supply has barely any immediately incidence upon the pollution flows dumped into the sea via the used water networks. REPUBLIC OF SENEGAL Environmental Impact Std Patrick LAURAS I Jean Luc PIGEON THIRD WATER PROJECT SETUDE - 11, bd Pershing PARIS INTERIM PHASE T4l. 16(1) Fax. 16 (1)

24 The pollutants dumped by a population depend relatively little upon the amount of water consumed. The fact that water cuts are limited does not really modify the lifestyle of a household and its "production" of polluting matter: dumping simply becomes less concentrated. 22 Accordingly, the polluting impact of direct dumping into the sea will not be modified. However, it could have an effect upon the treatment stations: their hydraulic load could increase because of the dilution of the waste meaning that it would be necessary to limit the amount of pollution accepted for treatment. However, in our opinion, this effect will be very small during the interim phase (there is still a water shortage and drain-off will therefore be highly concentrated) and in any case will only concern pollution currently being treated (the main station, CAMBERENE, has a capacity of 100,000 equivalent inhabitants only while the population provided with drainage is estimated at 470,000 inhabitants). Obviously, it is indispensable that these drainage schemes, currently under study, take into consideration the future water volumes. On this point, the study of the DAKAR drainage scheme carried out by JICA, is a considerable anticipation because the retained volumes correspond to the "CAYOR CANAL" phase. Nevertheless, we should bear in mind that this survey does not mention the need that it will be eventually be necessary to increase the hydraulic capacity of the CAMBERENE treatment station: it has been designed to handle highly concentrated waste (9,600 m3/day for 6000 kg of DBO5). When the effluent is more diluted, because of the increased water consumption, the biological capacity may no longer be possible because of hydraulic insufficiency. REPUBLIC OF SENEGAL Environmenta Impact Sbady Patrick LAURAS I Jean Luc PIGEON THiRD WATER PROJECT SETUDE - 1t, bd Pershing PARIS INTERIM PHASE Tel. 16 (1) Fax. 16 (1)

25 23 6.ANALYSIS OF ALTERNATIVES There is no general altemative for the water supply to Cap Vert in the short term but there are a number of technical alternatives concerning the definition of the installations The absence of an overall altemative The idea of doubling the ALG pipe dates back to the beginning of the 80's. The feasibility study was by RHEIN-RHUR but the project did not go through because the CAYOR CANAL at the time, was seen to be a far more "structuring" alternative by the Senegalese authorities. The difficulty and lengthy nature of the CAYOR CANAL surveys soon came to the forefront, so that in 1985, the studies were restarted for a transient phase of water supply to Cap Vert while the perspective of creating the CAYOR CANAL was maintained for the medium term. This strategy is still current: a major long-term project is essential. But the production delays justify, considering the situation of the WS (in some districts, cut-offs are repetitive and last from moming to midnight), an interim phase" to be implemented more quickly. Therefore, the CAYOR CANAL should not be analyzed as an alternative to the interim phase project but as a medium-term perspective. What is more, there is no overall alternative making It possible to increase the DAKAR water resources by 60,000 m3/day in a three-year deadline Individual or technical altematives However, there are some technical alternatives concerning the definition of the installations, mainly already analyzed by BETURE as part of the modified mission 0": Oi The first major altemative concems the over-exploitation of the North Coastal ground-water. The modelled survey of the ground-water by BRGM in 1992 considered three over-exploitation hypotheses with respect to the current situation: +25,000 m3/day, +35,000 m3/day, and +50,000 m3/day. Although the level of 50,000 m3/day could have been considered, the Senegalese authorities wisely chose a 35,000 m3/day level. The impact of this drawing-off is submitted in paragraph 5 above. REPUBLIC OF SENEGAL Environmenta Impact Sudy Patrick LAURAS I Jean Luc PIGEON THIRD WATER PROJECT SETUDE- 11, bd Pershing PARIS INTERIM PHASE T4l. 16 (1) Fax. 16 (1)