E863Volume 2

FEDERAL REPUBLIC OF NIGERIAFEDERAL MINISTRY OF WATER RESOURCES

NATIONAL URBAN WATER SECTOR REFORMPROJECT (NUWSRP)

DAM SAFETY MEASURES REPORTMARCH 2004

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Table of Contents

Paae No.

1.0 Introduction 3

2.0 Record of findings from Dam Inspection of a Sample of the Dams. A

3.0 Recommendations ..14

4.0 Cost Estimates ..17

Appendices:

Annex A: Gantt Chart ..18

Annex B: Reservoir Survey Equipment ..19

Annex C: TORs for Assessment of Sedimentation Strategies for Reserviors ..22

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1.0 INTRODUCTiON

1.1 Scope of this Report

It is beyond the scope of this report to present details of the existing structural and safety statusof each dam, together with details of the engineering and technical solutions for addressing anyissues of safety. This requirement is part of the recommendations of this report. However, thescope of this report is to develop a set of actions that are to be implemented as part of theNigeria Urban Sector Water Reform Project (NUSWRP) to ensure that the existing damssupplying raw water to the participating State Water Boards operate safety.

Therefore, the methodology used to determine what these actions should be was based onreviewing existing Dam Safety literature and other available technical reports from theparticipating state water agencies and river basin authorities, interviews of their key technicalstaff, followed by site inspections of a representative sample of the Dams in the list contained inSection 1.8 of this report, viz-a-viz, the Dam Safety Operational Policy 4.37 of the World Bankand the specific objectives and limitations of the proposed NUWSRP.

The environmental issues associated with these dams and this project is also beyond the scopeof this report and is addressed separately in the Environment and Social ManagementFramework (ESMF) for this project.

1.2 Brief Background of the Water Sector In Nigeria

The problems facing the water supply sector in Nigeria are many, characterized by acuteshortage of supply, even though Nigeria is blessed with abundant water resources estimated at226 billion m3 of surface water and about 40 billion m3 of ground water. One projection ofNigeria's population estimates that it will reach the level of 338 million by the year 2050. If thisestimate and other country estimates are correct, Nigeria would move from 10th most populouscountry in the world to the 4' most populous country in a short span of just under 50 years.

For example, out of the 85 million people living in urban and peri-urban areas, less than halfhave reasonable water supply. Many households, often the poorest, end up purchasing waterfrom private vendors at a much higher charge than from the public supply. Moreover, watersupply services where they exist are unreliable and of low quality and are not sustainablebecause of difficulties in management, operation and pricing, and failure to recover costs. Also,many water supply systems show extensive deterioration and poor utilization of existingcapacities, due to under-maintenance and lack of funds for operations. Additionally, the highcost of imported equipment especially in terms of a depreciating currency, and inadequate costrecovery policies have contributed to large financial deficits in many State Water Agencies(SWA's). This has left most SWA's dependent upon state subventions to finance operations andmaintenance of their water systems, to service debt and to finance new investments.

The Federal Govemment of Nigeria and the states are totally committed to address thisproblem. Water has a top priority in the govemment's development agenda, mainly due to thecross-cutting impact of safe water on health, productivity, and quality of life, with seriousimplications for poor and vulnerable communities.

Therefore, the govemment of the Federal Republic of Nigeria is working to address theseproblems by recognizing the need to manage the water sector in an integrated and sustainable

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circumstances fund the construction of new dams, large or small. However, the operationsof the State Water Agencies (SWA's) depend either on the use of existing dams run, operatedand owned by themselves, as in some states or as in other states by the River BasinDevelopment Authority (RBDA) of that state, for one or a combination of the following functions:

i) as a reservoirii) to manage water flow and levels in riversiii) provision of raw water to SWA'siv) Generation of Hydro-Electric power.

1.7 Applicability of the Banks Operational Policy OP 4.37, Safety of Dams

The Bank may finance types of projects that do not include a new dam but will rely on theperformance of an existing dam such as water supply systems that draw directly from areservoir controlled by an existing dam, diversion dams or hydraulic structures downstream froman existing dam, where failure of the upstream dam could cause extensive damage to or failureof a new Bank-funded structure; and or irrigation or water supply projects that will depend on thestorage and operation of an existing dam. Projects in this category also include operations thatrequire increases in the capacity of an existing dam, or changes in the characteristics of theimpounded materials, where failure of the existing dam could cause extensive damage to orfailure of the Bank-funded facilities.

Therefore, for participating SWA's that involve the use of existing dams as described above, theBank requires that the FMWR arrange for one or more independent dam specialists to:

(a) inspect and evaluate the safety status of the existing dams or theirappurtenances, and its performance history;

(b) review and evaluate the owner's operation and maintenance procedures;and

(c) provide a written report of findings and recommendations for any remedialwork or safety-related measures necessary to upgrade the existing damsto an acceptable standard of safety.

The Bank may accept previous assessments of dam safety or recommendations orimprovements needed in the existing dam if the FMWR provides evidence that;

(a) an effective dam safety program is already in operation, and(b) full-level inspections and dam safety assessments of the existing dam,

which are satisfactory to the Bank, have already been conducted anddocumented.

As the state water agencies of the participating states rely on the provision of raw water fromthe management of several dams that either supply water directly to their water treatment plantand/or through controlled releases of water from the dams into the rivers upstream of raw waterintake at the treatment plant, the Banks OP4.37, Safety of Dams, applies to this project.

OP 4.37 Dam Safety requires the Federal Govemment of Nigeria (FRN) to prepare a DamSafety Measures Report (i.e. this report) to address safe and sustainable management andoperations of the Dams that will be supplying raw water to the participating state water boards.OP 4.37 also requires the FRN to include in the Dam Safety Measures report; other Dams

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supplying raw water to the states that are not being financed in this project by the Bank directly,but are included in the project anyway, even though they are financed from other (non-bank)sources.

This report and the Environmental and Social Management Framework (ESMF) will bedisclosed as separate and stand alone documents at the World Bank's infoshop and in Nigeria.The ESMF was disclosed before the project was appraised by the bank and this report will bedisclosed before this project is presented to the Board of the Bank for approval.

1.8 List of Dams in Participating States

KANO STATE

Name of Dam Year Built Height (m) Reservoir (Mm ) SpillwayTAdo BayeroAudu Bako -Baguada 1970 21 22.14 UncontrolledBirmin Kudu - 8 2Bunga - -Challawa Gorge 1977 40 969 UncontrolledDogwalaDudurun Gaya -GarangaGari 1980 22 214 UncontrolledGulka ._ _ _Guzuguzu 1979 17 24.6 Box CulvertHajiya Ladi Bako - _ __Ibrahim Adamu 1974 9 8 Controlled

_ggi - -_

Jakara 1976 14 65.2 UncontrolledKafia - -_Kafin Chari 1977 16 31.1 Ogee CrestKango - 15 8.73 Box CulvertKara Chada - _Kara Duwa - - _

Karaye 1971 15 17.2 UncontrolledKatini - - .Keffin GanaKiwia _Kiyako -KoreyelKunza -

Lower Mareshi -

Magaga 1980 19 t19.7 UncontrolledMareshi 1980 _1 1 6.77_B. UncontrolledMarke - -Misau

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Mahammadu 1975 16 5.53 Box CulvertAyubaPada 1980 14 12 UncontrolledRuwan Kanya 1976 22 UncontrolledShimar - ___Tiga 1975 47 1968 UncontrolledTomas 1976 14 60.3 Box CulvertTudun Wada 1977 21 20.8 UncontrolledTukurua - -Warwade - 10 12.3 Box CulvertWatari 1980 20 104 UncontrolledYakubu Gowon - ___

Kaduna State

Birnin-Gwari 1975 14 4 Uncontrolled(Bogoma) _Kangimi 1977 20 58 UncontrolledZaria 1975 14 15.3 Uncontrolled

Ogun State

Oyan 1183130 = =270 | GatedIkere Gorge 1991 50 -|630 |Uncontolled

Plateau State

Yakubu Gowon 1982 35 30 UncontrolledPankshin 1982 29.5 4 UncontrolledLangtang 1982 21 4.6 UncontrolledShendam 1984 13 4.5 UncontrolledBokkos 1985 - 0.1 UncontrolledLiberty 1972 27 20 UncontrolledKogingiri 1934 8.23 0.1 UncontrolledLamingo 1935 11.28 0.1 UncontrolledTollemarch 1961 7.64 0.1 Uncontrolled

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2.0 RECORD OF FINDINGS FROM DAM INSPECTION OF A SAMPLE OF THE DAMS.

These dams are water supply earthfill embankmenta dams. The review of the safety of thesedams looked at the following areas;

* Availability of reliable records of Dam operations, rainfall data, as-built drawings, etc.* Existence of Dam Operational Manuals, and its implementation.- River Hydrology.* Factors contributing to release schedule.* QualHfications and Experience of staff with key technical responsibilities.

Past performance and history of Dams in terms of over- topping, flooding, major andminor rehabilitation work, particular concems of staff, etc.

* Adequacy of installed instrumentation in terms of reliability, state of disrepair, andrecordings and monitoring.

* Physical condition of the State of Dilapidation/Disrepair observed through visualinspection only and any remedial work undertaken to address critical concerns such aserosion, sedimentation, siltation, seepage, etc.

* Availability of an Emergency Preparedness and Response plan.* Existing status and adequacy of spillways viz-a-viz design assumptions.* Availability of allocated financial resources/budget.

For example:

* 2.1 In Kano State

Kano is the State with the highest number of dams, however most of the water comes from TigaDam, which is has got the largest storage capacity (about 2 billion m3).

The positive aspects in terms of dam safety are the following:a) the areas in which the dams are located is of a very low seismicity being part of the

crystalline rocks of the Basement Complex;b) dam foundations are in the great majority on sound and massive rock formations;c) most of the dams have uncontrolled, free crest, spillways.

The aspects that require attention and action are:d) several cases of dam overtopping have occurredb; extreme hydrological events,

maximum floods, need to be re-assessed using the most recent information andappropriate modifications made to commensurate the discharge capacities to theassessment's findings;

e) information on design details, including as-built drawings is very poor;f) instrumentation and monitoring is inadequate, both in terms of facilities, and in terms

of operation;

^ In the absence of design drawings it was not possible to confirm whether the dams were homogenous or contain acore.b A small dam d/s of Tiga was overtopped and triggered spillway enlargement at Tiga. Bimin-Gwari and Zaira damwere overtopped in Kaduna. Mareshi dam was overtopped twice in Kano.

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g) deferred maintenance problems are evident at most of the dams, especially thesmaller ones.

Given the above, attention should be given to safety aspects related to: overtopping duringfloods, and intemal erosion.

* 2.2 In Kaduna State

2.2.1 The Bogoma (Birnin Gwari) Dam

Bogoma Dam was overtopped in 1992 and in 1994. Following those events the spillway systemwas enlarged and completed in 1999. There is very large erosion in progress in the river course,where the two spillway channels come together. Erosion is progressing fast (5 to 1OnV year)towards the toe of the dam which is now only 20 m away from the crest of the erosion slope.

It appears that the phenomenon is to be attributed to the hydraulic performance of the waterwaysystems. A modification of the layout, based on hydraulic model tests, is critically needed.Meanwhile, short term measures should be taken to slow erosion down.

There is evidence of extensive sedimentation in the reservoir.

Area downstream of the dam densely populated. Classifying risk according to population d/s ismeaningless, because people are many in any case (certainly more than 1,000, most likely inexcess of 10,000).

2.2.2 Zarla Dam

The Zaria Dam inaugurated in 1975, is located on the Galma River, at a distance of about 1OkmNNE of Zaria town. The Dam consists of a 550m long earthfill embankment with a maximumheight of about 14m. The service spill way is located on the left abutment and is about 91.5mlong.

The upstream face of the dam is protected with riprap which is in reasonable good condition andshows no sign of instability. The downstream face is also protected by stone pitching until theberm which is at about 3m below the crest and below the berm the slope is protected by riprap.Open concrete drain has been constructed at the toe of the dam and weep holes at regularintervals allow seepage water to discharge into this drain.

Raw water from the reservoir is pumped from the intake pumping station to the treatment plant.

At the time of inspection the reservoir level was about 0.7 m below spillway level and strongwinds prevailed from the direction of reservoir. The spillway crest and dissipation areas appearto be in good condition. Hydraulic performance of the works is satisfactory.

Zaria dam was overtopped in 1994 (see Haskoning report of May 1994). That event promptedthe raising of the crest of the dam by 1 m and concrete lining of the spillway dissipation area.Design documents supporting how the decision to raise the Dam height by I m (and not 2m say)was made are not available.

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Lack of maintenance is evident. The drainage ditch along the toe of the dam is filled withvegetation and debris resulting in blockage of the drain and seepage pipes.

The Haskoning report (May 1994) reports seepage from two areas of the dam: near themaximum height section and close to the right abutment. That report attributes that seepage tothe foundations. The installation of a couple of piezometers, inside investigation boreholes withcore recovery in the foundation zone, would serve the double purpose of checking thegeotechnical characteristics of the foundation (supplemented by surface outcrop observations),and of controlling the intemal seepage line in the embankment.

A larger dam is planned upstream of Zaria Dam to supplement flow. That dam is at the designstage. It is important to make sure that safety standards (mainly design flood) are at least equalto those that will be adopted for the existing dams.

Catchment erosion is severe and reservoir sedimentation is a major concern of Kaduna SWA,however, no direct measurements of accumulated sediments are available.

2.2.3 Kangiml Dam

The Kangimi Dam is located on the Kangimi River, at a short distance upstream from itsconfluence with the Kaduna River, some 30km NE of Kaduna Town. The reservoir was built tosupplement discharges in the Kaduna River during periods of low flow in order to assuresufficient discharge at the intakes for the Kaduna North and Kaduna South treatment plants.Water is released through outlet works from the reservoir onto the Kangimi River.

The Dam consists of a 1,31 5m long earthfill embankment with a maximum height of about 20m.On the right abutment a 121 .5m long uncontrolled ogee crested service spillway is located.

The upstream face of the Dam is protected with riprap which is in reasonably good condition.The crest of the dam is about 4.5m wide. The downstream face has no protective covering andincludes an approximately 3m wide berm with an open drain, an embedded pipe drain forseepage control is located at the toe of the dam.

The Haskoning Report of May 1994 indicates that signs of seepage were observed alongcertain parts of the downstream slope. Seepage water was evacuated from those areas throughan open drain which is connected at regular distances with the toe pipe drain.

The spillway which operates every rainy season is in good condition, with minor erosion signsobserved along a couple of joints on the crest. Other than that, conditions of structures indicategood hydraulic performance of the waterway. Dam crest walked along full length. No signs ofconcentrated seepage along the down stream slope. Upstream slope protection in goodconditions.

Drainage system along the downstream toe needs complete rehabilitation. Pits along thealignment of drainage pipes are silted up, and the pipes themselves are occasionally full ofdebris. A longitudinal ditch, downstream of the drainage system, is obstructed by earthfill anddam seepage (quite minor extent observed at the date of inspection) back- waters inside thedrainage pipes and inside a couple of inspection pits.

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During the rehabilitation of the drainage system, measuring devices (V notches like thoseinstalled at Tiga Dam) should be installed. A few piezometers (at least 3) should be installed inselected areas to monitor the location of the internal seepage line. Poor drainage could havecaused that to raise with respect to design assumptions. Piezometers were never installed atthe dam.

2.3 Ogun State

2.3.1 Oyan Dam

Oyan Dam which is owned and operated by the Ogun-Osun River Basin Development Authoritywas completed in 1983. It is 30m high with a reservoir capacity of 27OMm3 and a catchmentarea of approx. 9,000km2 and an embankment length of 1044 m. The design free board at10,000 years flood is approx. 2.10m high. It supplies water for irrigation and for domestic usesto the cities of Abeokuta and Lagos.

It has a concrete overflow section, gated (radial gates) spillway, with four bays. The reliefdrainage holes hole are clogged and need to be re-activated, including installation of pressuregages for monitoring uplift pressures underneath the concrete structure. Two of the four gates(those at the right and left side) are out of service, with the hoisting cables of one of these twoneeding urgent replacement. The one to the left needs re-alignment because the load on thecables is very uneven and does not allow raising. Problems at the control panel are alsoreported. The two central gates operate satisfactorily. Operation of these gates is assisted byelectrical motors which are powered by diesel generators. At the time of the inspection, thegenerators were not working because of lack of fuel and therefore the gates remained closed.The operations of the Dam are not connected to the national grid and hence with the generatorsalso not function, opening of hence gates during a tlood would have to be done manually. Thiswould require importing the necessary manpower to sight during an emergency, a processwhich could take several hours. Once the adequate manpower is on site, it would takeapproximately 4-6hours to open each gate.

The dissipation area downstream of the spillway has never been inspected to check possibleerosion. There is a 9MW Hydroelectric Power plant at the toe of the dam, but it does not operatedue technical reasons, including not being connected to the grid.There is an emergency spillway located on a saddle area at elevation about 1.7m below thecrest level. It is necessary to check the topography of this emergency spillway are and toimplement suitable land regularization works to ensure, it provides this emergency relieffunctions. This is extremely important because the service spillway is gated and the gateoperation is extremely unreliable.

Three Howell-Bunger valves control releases in the river bed for downstream uses. All of themrequire replacement of the motor; they also need overhaul of the mechanical parts. Butterflyvalves are installed under side of the HB valves.

The installed instrumentafion is inadequate needs to be rehabilitated and used. There is an areaadjacent to the toe of the embankment where seepage is reported to have been observed(reportedly more than one year ago). There is no collection system in the form of drainagepipes. A concrete channel at the toe is full of debris and clogged by vegetation.

The site inspection did not reveal any seepage. There is urgent need to: a) clear vegetation andremove debris; b) identify the seepage area and closely monitor seepage rates and turbidity ofthe effluent, including correlation with reservoir levels.

2.3.2 Abeokuta Weir

The Abeokuta weir is located some 20km downstream of the Oyan Dam. The weir has fiveopenings, is about 1 1m wide and 9.8m high. There is an emergency spillway for unforeseenflood events located adjacent to the weir.

2.4 Plateau State

All dams in Plateau State are owned by the State Water Corporation (SWC). The SWC reportthat none of their dams have been overtopped.

2.4.1 Yakubu Gowon Dam

The Yakubu Gowon Dam is the largest dam in Plateau state. It is 35m high and has a reservoircapacity of 30Mm3. The dam was built tor water supply to the SWC only. There is a gravityintake tower through which water is pumped through a pipe that runs through the damembankment directly to the water treatment plant.

At the time of the inspection the reservoir level was low and there were no signs of seepageobserved. The water in the reservoir is brown and muddy. There is no monitoring ofsiltation/sedimentation. There are signs of erosion in certain areas on of the downstream slope.The toe drain was blocked with debris. There are three piezometers, but they are not beingused. There is no form of record keeping going on at the Dam site. There are no personnelbased at the dam site. There is no operations and maintenance plan and there are no as-builtdrawings.

There is an open crested concrete spillway to the left had side of the embankment. The spillwaystructures appear to be in good condition thereby indicating good hydraulic performance of thewaterway. There are signs of erosion at the end of the spillway channel.2.4.2 Lamingo Dam

Lamongo Dam serves as an inter-basin transfer reservoir. The embankment dam is about 11 mhigh and the reservoir capacity is 0.001 Mm3.

The Dam is in a desperately unsafe condition and its collapse if no remedial action is taken isimminent. The rap along the bottom end of the upstream slope has settled so much it haspractically sheared away from the face of the slope and offers no protection of the slope. Thereare fairly large nym trees growing on both sides of the dam. The dam crest has major signs ofsettlement dips and erosion in various locations along its length A dam break threatens a roadabout 300m downstream, some fields and power transmission lines.This Dam needs immediate rehabilitation, which should be taken immediately to ensure safeoperation of the dam.

2.4.3 Liberty Dam

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Uberty dam is 27m high with a reservoir capacity of 29MM3 . The liberty dam is similar in designand operation to the Yakubu Gown dam. The open crested concrete spillway is in goodcondition thereby indicating good hydraulic performance of the waterway.There is evidence of siltation in the reservoir which has the potential to significantly reduce itscapacity if it continues. There is evidence of vegetative and other organic material growth onboth the upstream and downstream slopes. There are also signs of erosion and settlement onthe downstream slope. No signs of seepage observed. The gradient of the downstream slope isconsiderably steeper than the upstream slope which suggests design stability and seepage flowpaths concems.

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3.0 RECOMMENDATIONS

Due to current uncertainties about and lack of reliable records and information on the extent ofthe maximum floods throughout the all the entire states visited, a prudent approach in theinterest of safety must be adopted because there are densely populated areas downstreammost of the dams. Dam break analysis and inundation studies should be carried out andEmergency Preparedness Plans prepared accordingly. Such studies should proceed in acoordinated way in the four states wnth mutual exchange of information and consultation onpriorities (which dams should be included).

The dams that supply water for urban uses should not only be safe, but they should be able toprovide that service for an adequate period of time in the future, in a reliable manner. Wateryield reliability can be severely affected by reservoir sedimentation if adequate reservoirconservation strategies are not in place. For example, the reservoirs in Kano state arehydrologically large, i.e. their active capacity is larger than the average long-term annual run-offc. This means that their sediment trapping efficiency is quite high and that water releases forsediment flushing are not feasible.

3.1 Dam Safety measures to be Implemented in each state:

1. Preparation of construction of drawings showing details of the works and records of pastbehavior (as-built drawings to be updated following each rehabilitation work).2. Carrying - out a hydrological review to determine the extent of the floods to be used forchecking dam safety, (e.g. capacity of spillways, size of reservoirs, release schedulesetc.)3. Preparation or updating of Operation and Maintenance, and Surveillance Manuals andtraining of staff accordingly.4. Preparation or update Emergency Preparedness Plans making sure that no weak linksexist in the detection> decision> notification> warning> response chain.5. Installation or rehabilitation of instrumentation and monitoring devices and training ofsurveillance staff accordingly (Instrumentation Manual).6. Catch-up with deferred maintenance activities such as: debris along spillway crests, fuseplugs should be real fuses, drainage systems full of debris and vegetation, excessivevegetation on embankment slopes, etc.

3.2 Dam specific measures of a structural nature (repair and rehabilitation works)7. Adequate spillway capacities (both service and emergency) to updated floodassessments.8. Bogoma Dam (Kaduna) requires major modification to spillway and dissipation zonelayout.9. Marashi Dam (Kano) needs either provision of a controlled overtopping area on thecrest, or crest raising and new spillway (currently undersized box culvert).10. Other 9 dams in Kano (Guzuguzu, Jakara, Kango, Karaye, Magaga, Pada, Tomas,Tudun Wada, Warwade) most likely require spillway modification/ upgrading measures.11. Oyan Dam (Ogun State) requires urgent rehabilation works to get all four radial gatesoperating again and servicing of mechanical valves.

'Average capacity I run-off ratio is in excess of 1.3; it is 1.65 for Challawa Gorge and 1. 86 for Tiga Dams.

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12. Lamingo Dam (Plateau State) requires immediate rehabilitation of the upstream slope toprevent a catastrophic failure of the dam embankment.13. Fixing localized erosions on the embankment slopes.

3.3 Storage Conservation

The following actions need to be made to address these issues:14. Reservoir Sedimentation Surveys: staff training and equipment procurement (see Termsof Reference in annex)15. Carry out study on Sedimentation trends and preferred sedimentation managementstrategies16. Elaborate a Storage Conservation Action Plan (preliminary ToRs in Annex C)

3.4 Recommended actions

Step 1: Individual Dam SpecialistDuring meetings and site visits it has been noticed that dam operators have a goodunderstanding of the actions required to improve reliability of the headworks. Therefore that thefirst step should be that of facilitating preparation of terms of reference and technicalspecifications for further actions that will be undertaken by a consulting firm and contractors. Forthis purpose, the services of an individual dam specialist (IDS) should be obtained. The IDS willaddress all points (1 to 12) listed above, together with the dam operators, and assist them inpreparing terms of reference and tender documents for the procurement of consulting andcontractor services necessary to implement the corresponding activities. The IDS will assistnational staff in organizing a workshop (see step 2) in the very early stages of projectimplementation. The IDS will also perform on the job training of dam staff.

Step 2: Launch WorkshopThis workshop wOI have the following objectives: a) share issues and possible solutions amongthe technical staff of the four states; b) disclose project information to national consultants/contractors potentially interested in the tuture bid contracts; c) identify priorities and basiccriteria for the next steps.

Step 3: Consulting ServicesIt is understood that several consulting engineering firms operate in Nigeria. A consulting firm(probably a national one) will:

a) carry out activities from 1 to 4 and 14 to 16 (see list above);b) prepare design and tender documents for the execution of activities 5 to 13d;c) supervise construction activities related to b).

Steo 4: Rehabilitation WorksA contractor, preferably in association with an instrumentation equipment supplier, will beselected ior executing the works associated with activities 5 to 1is.

d Activities 6 (Deferred maintenance) and 13 (Erosion zones on embankment slopes) will probably be carried outdirectly by the SWA.' Activities 6 (Deferred maintenance) and 11 (Erosion zones on embankment slopes) will probably be carried outdirectly by the SWA.

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It must be pointed out that no provision has been made for implementing any sedimentationmanagement measures that would be recommended in 16 (Storage Conservation Action Plan).Any action thereof should be contemplated in a separate operation or re-considered during midterm review of the project.

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4.0 COSTS ESTIMATE

Table 1: Cost Estimate of Dam Safety-related measures

CostDescripUon Assumptions (US$)

International consultant to complete dam Fees 30k; travel andsafety surveys, estimate costs, and prepare accomodation 10kToRs. 40,000Launch workshop Sum 35,000Consulting firm (national?) to reconstruct as- National consulting firm;built dwgs, train staff (O&M, surveillance, 400k$ fees; 50k$instrumentation & monitoring, EPPs, investigations and lab testssedimentation surveys), prepare tenderdocuments of rehabilitation works, proposestorage conservation action plans, assistGON in contractor selection. 450,000Equipment for bathymetric surveys of ToRs in Annex Breservoirs 15,000Contractor, in joint venture with an Equipment supplyequipment supplier, implements (instruments, electricalrehabilitation works, instrument installation. control panels, valves, etc.)

at several dams 1,000,000Bogoma Dam, modification to spillway anddissipation zone layout. 2,000,000Marashi Dam (Kano) either provision of acontroDled overtopping area on the crest, orcrest raising and new spillway. 500,000Other 9 dams in Kano (Guzuguzu, Jakara, 2,000,000Kango, Karaye, Magaga, Pada, Tomas, toTudun Wada, Warwade) most likely require 4,000,000spillway modification/ upgrading measures.Lamingo Dam, urgent rehabilitation of 300,000upstream slope.

Consulting firm supervises construction 3 person @ 3k$/m for 3activities and carries out further staff training years; plus expenses(O&M manuals, and EPPs finalization) 560,000

Total 6.9 to 8.9 MUS$

B. Sedimentation survey equipment - ToRsC. Storage conservation study - ToRs

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Annex A:

The following Gantt diagram provides an overview of the activities and the expected durations.Nigera Urban Water Reform PrOject -Dam Managenwfnt Aspects -Action Plan

duration preparation year 1 2 3 4 5 6Action Descriptin (montihs)GON recrmits iterational consultant (indwa) 11

1 Launch Workshop2 Irternatiowal consultant to complete dam safety surveys,

estimate costs, and prepare ToRs. 2 CjGON procures consutng servicas (natina/?) for acffons 3.4,5and6 4

3 Consulting firm to reconstruct as-built dwgs, Irain staff (O&M.suIvelIlance, instrunentation & monitoring, EPPs,sedinentation surveys), prepare tender documents ofrehablitation works, propoe storage conservation acHonplans, assist GON In contractor selection 9GON procures contractor (national?) for action 3 4

4 Contractor, In joint venture with an International equipmentsupplier, Implements rehabilitation works. instrumentinstallaon; 24

5 Contsultng finm supervses constructon works and carriesout further staff training (O&M manuals, and EPPsfinallation). 24

A cost estimate of the activities that are necessary to address the dam safety aspects of theproject is contained in table 1 below. The estimates will have to be refined during steps 1, 2 and3, but are considered adequate for preliminary budget purposes. The largest uncertainty isrelated to the construction works for which a range is provided. A provision of US$7.5 millionshould be included in the project budget to address dam safety related measures.

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Annex B:

Description of Goods: Reservoir survey equipment (Sample for Information only)

Technical Details

1. General Requirements

Equipment should be certified and conform to intemational standards. Equipment should be lowpower consumption, portability, ease to use, rugged construction, built-in communicationinterfaces for navigation/data logging devices. Logging of bathymetric and navigation data maybe done with a separate computer and a software program.

- The GPS (General Positioning System) shall be with the high accuracy, dual station GPS(base station and field station) capable of providing X,Y,Z coordinates with an error ofposition not exceeding +/- 0.5 meters.- The echosounders shall be capable of providing depth reading in the range of 0 to 550 m, ifnecessary two echosounders can be proposed covering the 0-1 Om and 100-550 m range;- The full integration of the GPS and Echosounding equipment;- The Supplier shall be able to provide training.

Equipment will be used for reservoir bed surveys to determine the volume and disposition ofsediments within the reservoir, which can have a major bearing on the both dam safety andreservoir management. The GPS equipment will be also used for terrestrial survey.

Sediment volumes will be calculated from the bathymetric data, on the basis of previousbathymetric or topographic survey data of the site under investigation. Should previoustopographic surveys be inadequate, the sub-bottom profiling (SBP) technique will be used toprovide the necessary data to calculate sediment volurne without having prior information on thereservoir.The SBP system for mapping sediment thickness should be relatively small, simple to operateand well built. Depending on the nature of the sediment the system should be able to achieve 5to 30 meters of subsurface penetration. A data acquisitlon system for acquiring navigation andSBP data should also be considered.

19

2. Technical Specifications (Sample for information only)

DESCRIPTION Unit Price Totalamount

Quantity CIP

-~ 1 2 _ _ )3 4 5

I. GPS receiver, including: 1

1.2 12 channel base station

1.3 Field station

1.4 Controls, through display unit processor

1.5 Antenna, integral in display unit

1.6 Data output, NMEA through the port

1.7 Differcntial, FM broadcast decoder

1.8 Display, status and position on LCD panel

1.9 Frequency up to 40 kHz

1.10 AU necessary accessories and software for the above 2

2. Echosounder with carrying case, induding:

2.1 Dual frequency, 200 kHz

2.2 Transducer, 200 kHz

2.3 Depth range, 0.0 to 50 metres

2.4 Depth range, 50 to 100 metres (optional)

2.5 Accuracy, +/- 2% of total water depth

2.6 Sounding rate

2.7 Controls, Draftt Sound velocity

2.8 Gain control, fully automatic

2.9 Output, NMEA or ODOM format

2.10 All necessary accessories (including mounting bars), software,

20

etc.

3. Spare Parts Required

The Supplier is requested to provide a priced list of spare parts, which will be included in the bid price.The list should be comprehensive and cover a contingency requirement for at least the three five years ofoperation following installing and start up of equipment. The Purchaser will select spare parts from thislist for inclusion in an eventual Contract.

In this document the term spare parts refers to those items that require replacing due to excessive

wear and/or damage of some kind.

4. Manuals

The Supplier is requested to furnish a detailed operations and maintenance manual for each appropriateunit of Supplied Goods in English;

5. Warranty Oblieations

The warranty period shall be 12 months after the Goods have been delivered to and accepted bythe Purchase at the final destination indicated in the Contract. The period for correction ofdefects in the warranty period is three (3) months. The Goods for which warranty repairs orreplacements have been made shall remain under warranty for a period of one (1) year, but notmore than six (6) months beyond the expiry of the contractual warranty period.

6. Manufacturer's Authorization

Agents are requested to subrnit Manufacturer's Authorization for Goods to be supplied.

Photos

, ~ ~ ~ .. .~ . ..

21Staff training on use of reservoir | Data processing and storage equipmentsurvey equipment l

Annex C:

TERMS OF REFERENCE FOR ASSESSMENT OF SEDIMENTATION STRATEGIES FORRESERVOIRS

Objective

The objective of the project is to assess the feasibility of implementing a life-cycle managementapproach to manage the reservoir (system of reservoirs) identified in the Appendix. The lifecycle management approach aims at identifying and implementing management strategies thatwill ensure the sustainable long-term use of the developed resource(s). The basic concept isillustrated in the figure below, and is expanded on in Palmieri et al. (2003).

Extenal EXernal-Envlranmentel- Promj Focus- - SocletalConcers Ccvcenm

Mm-~~--

4, A4_ ,

a tibcFh_ c wSa,Ntim

U =_p "

_ [ .u2

MW - - .... .i, wI s,. + teeabo4K' - mmua X~~~D= Id 1 0_ d IM

Imp..Im B

CIO >," u Fllb

[*wlli_ b IW^II ~ ~ ~ ~ ~ ~ ~ ~ ~~2

Data Collection. Hydrology - Hydrologic data required include mean annual inflow into the reservoir,variation of the annual inflow, and a representative average water temperature in thereservoir. This data can be obtained from hydrology records and operating records for thereservoir and catchment.

* Sediment - Sediment inflow data required include annual sediment inflow and grain sizedistributions of suspended sediment and bedload. If sediment discharge / yield data has notbeen collected historically bathymetric re-surveys of the reservoirs can be used to estimatethese values. When following this approach the consultant should establish reasonablevalues for deposited sediment density and reservoir trap efficiency and use these to makedefensible estimates of sediment yield from the catchment.* Volume of Deposited Sediment - obtain records of re-surveys previously conducted at thereservoir to determine the volume of deposited sediment in existing reservoirs. If such datadoes not exist, make estimates of what the potential reservoir loss could be by making useof sediment transport data, if available. Altematively the volume of sediment in the reservoircan be surveyed by making use of modem echo-sounding and DGPS equipment.

ReportPrepare a report describing the approach, reservoir setting, data collected, analysis andanalysis results, and conclusions. Make recommendations as to whether the reservoir(s) canbe managed in a sustainable manner and what additional investigative work is required toaccomplish this. Terms of reference of such additional investigative works, and thecorresponding cost estimate, should be enclosed to the report.The report should provide the decision making entity with a clear, concise picture of the currentstorage loss trends and of the improvements that the proposed sedimentation managementstrategy can introduce. Costs associated with the proposed strategy, along with its benefitsshould be shown in the form of an action plan using a format similar to the one below.

RESERVOIR CONSERVATION ACTION PLAN tylAcal formatTime (vears)|5 | 10 I tI5 20 | 25 30 1 35 i 40 | 45 | 50100

§ 70 I|Past loss rate I 0[edwntManawment,Acjon anA

,6 30 tStatus guo "'-*10 |forecast troenjd

i 5 | t0 | 1S 20 | 25 | 30 35 |40 | 45 1 50Financial Plan for Profile A T

23

Financial Plan for Profile B -