E863 Volume 2

FEDERAL REPUBLIC OF FEDERAL MINISTRY OF WATER RESOURCES Public Disclosure Authorized NATIONAL URBAN WATER SECTOR REFORM PROJECT (NUWSRP) Public Disclosure Authorized Public Disclosure Authorized

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DAM SAFETY MEASURES REPORT MARCH 2004

Public Disclosure Authorized a-'''FLE COP 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

2 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 status of each dam, together with details of the engineering and technical solutions for addressing any issues of safety. This requirement is part of the recommendations of this report. However, the scope of this report is to develop a set of actions that are to be implemented as part of the Nigeria Urban Sector Water Reform Project (NUSWRP) to ensure that the existing dams supplying raw water to the participating State Water Boards operate safety.

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

The environmental issues associated with these dams and this project is also beyond the scope of this report and is addressed separately in the Environment and Social Management Framework (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 acute shortage of supply, even though Nigeria is blessed with abundant water resources estimated at 226 billion m3 of surface water and about 40 billion m3 of ground water. One projection of Nigeria's population estimates that it will reach the level of 338 million by the year 2050. If this estimate and other country estimates are correct, Nigeria would move from 10th most populous country 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 half have reasonable water supply. Many households, often the poorest, end up purchasing water from private vendors at a much higher charge than from the public supply. Moreover, water supply services where they exist are unreliable and of low quality and are not sustainable because of difficulties in management, operation and pricing, and failure to recover costs. Also, many water supply systems show extensive deterioration and poor utilization of existing capacities, due to under-maintenance and lack of funds for operations. Additionally, the high cost of imported equipment especially in terms of a depreciating currency, and inadequate cost recovery 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 and maintenance 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 this problem. Water has a top priority in the govemment's development agenda, mainly due to the cross-cutting impact of safe water on health, productivity, and quality of life, with serious implications for poor and vulnerable communities.

Therefore, the govemment of the Federal Republic of Nigeria is working to address these problems by recognizing the need to manage the water sector in an integrated and sustainable 3 circumstances fund the construction of new dams, large or small. However, the operations of the State Water Agencies (SWA's) depend either on the use of existing dams run, operated and owned by themselves, as in some states or as in other states by the River Basin Development Authority (RBDA) of that state, for one or a combination of the following functions: i) as a reservoir ii) to manage water flow and levels in rivers iii) provision of raw water to SWA's iv) 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 the performance of an existing dam such as water supply systems that draw directly from a reservoir controlled by an existing dam, diversion dams or hydraulic structures downstream from an existing dam, where failure of the upstream dam could cause extensive damage to or failure of a new Bank-funded structure; and or irrigation or water supply projects that will depend on the storage and operation of an existing dam. Projects in this category also include operations that require increases in the capacity of an existing dam, or changes in the characteristics of the impounded materials, where failure of the existing dam could cause extensive damage to or failure of the Bank-funded facilities.

Therefore, for participating SWA's that involve the use of existing dams as described above, the Bank 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 their appurtenances, 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 remedial work or safety-related measures necessary to upgrade the existing dams to an acceptable standard of safety.

The Bank may accept previous assessments of dam safety or recommendations or improvements 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 and documented.

As the state water agencies of the participating states rely on the provision of raw water from the management of several dams that either supply water directly to their water treatment plant and/or through controlled releases of water from the dams into the rivers upstream of raw water intake 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 Dam Safety Measures Report (i.e. this report) to address safe and sustainable management and operations 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 5 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 be disclosed 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 be disclosed 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 ) SpillwayT Ado Bayero - Baguada 1970 21 22.14 Uncontrolled Birmin Kudu - 8 2 Bunga - - Challawa Gorge 1977 40 969 Uncontrolled Dogwala Dudurun Gaya - Garanga Gari 1980 22 214 Uncontrolled Gulka _ _ ._ Guzuguzu 1979 17 24.6 Box Culvert Hajiya Ladi Bako - _ __ Ibrahim Adamu 1974 9 8 Controlled _ggi_ - - Jakara 1976 14 65.2 Uncontrolled Kafia - _ - Kafin Chari 1977 16 31.1 Ogee Crest Kango - 15 8.73 Box Culvert Kara Chada - _ Kara Duwa - - _ Karaye 1971 15 17.2 Uncontrolled Katini - - . Keffin Gana Kiwia _ Kiyako - Koreyel

Kunza - Lower Mareshi - Magaga 1980 19 t19.7 Uncontrolled Mareshi 1980 _1 1 6.77_B. Uncontrolled Marke - - Misau

6 Mahammadu 1975 16 5.53 Box Culvert Ayuba Pada 1980 14 12 Uncontrolled Ruwan Kanya 1976 22 Uncontrolled Shimar - ___ Tiga 1975 47 1968 Uncontrolled Tomas 1976 14 60.3 Box Culvert 1977 21 20.8 Uncontrolled Tukurua - - Warwade - 10 12.3 Box Culvert Watari 1980 20 104 Uncontrolled - ___

Birnin-Gwari 1975 14 4 Uncontrolled (Bogoma) _ Kangimi 1977 20 58 Uncontrolled Zaria 1975 14 15.3 Uncontrolled

Oyan 1183130 = =270 | Gated Ikere Gorge 1991 50 -|630 |Uncontolled Plateau State

Yakubu Gowon 1982 35 30 Uncontrolled Pankshin 1982 29.5 4 Uncontrolled Langtang 1982 21 4.6 Uncontrolled Shendam 1984 13 4.5 Bokkos Uncontrolled 1985 - 0.1 Uncontrolled Liberty 1972 27 20 Uncontrolled Kogingiri 1934 8.23 0.1 Uncontrolled Lamingo 1935 11.28 0.1 Uncontrolled Tollemarch 1961 7.64 0.1 Uncontrolled

7 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 these dams 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 and minor rehabilitation work, particular concems of staff, etc. * Adequacy of installed instrumentation in terms of reliability, state of disrepair, and recordings and monitoring. * Physical condition of the State of Dilapidation/Disrepair observed through visual inspection only and any remedial work undertaken to address critical concerns such as erosion, 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 State

Kano is the State with the highest number of dams, however most of the water comes from , 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 and appropriate modifications made to commensurate the discharge capacities to the assessment'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 a core. b A small dam d/s of Tiga was overtopped and triggered spillway enlargement at Tiga. Bimin-Gwari and Zaira dam were overtopped in Kaduna. Mareshi dam was overtopped twice in Kano. 8 g) deferred maintenance problems are evident at most of the dams, especially the smaller ones.

Given the above, attention should be given to safety aspects related to: overtopping during floods, 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 system was 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 waterway systems. 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 is meaningless, because people are many in any case (certainly more than 1,000, most likely in excess 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 1Okm NNE of Zaria town. The Dam consists of a 550m long earthfill embankment with a maximum height of about 14m. The service spill way is located on the left abutment and is about 91.5m long.

The upstream face of the dam is protected with riprap which is in reasonable good condition and shows no sign of instability. The downstream face is also protected by stone pitching until the berm 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 regular intervals 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 strong winds prevailed from the direction of reservoir. The spillway crest and dissipation areas appear to 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 prompted the raising of the crest of the dam by 1m 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.

9 Lack of maintenance is evident. The drainage ditch along the toe of the dam is filled with vegetation and debris resulting in blockage of the drain and seepage pipes. The Haskoning report (May 1994) reports seepage from two areas of the dam: maximum near the height section and close to the right abutment. That report attributes that seepage the to foundations. The installation of a couple of piezometers, inside investigation boreholes core with recovery in the foundation zone, would serve the double purpose of checking geotechnical the 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 design stage. It is important to make sure that safety standards (mainly design flood) are at least equal to 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 confluence from its with the Kaduna River, some 30km NE of Kaduna Town. The reservoir was supplement built to discharges in the Kaduna River during periods of low flow in order sufficient to assure 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 On 20m. 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 and includes an approximately 3m wide berm with an open drain, an embedded pipe drain for seepage control is located at the toe of the dam. The Haskoning Report of May 1994 indicates that signs of seepage were observed certain along parts of the downstream slope. Seepage water was evacuated from those areas through an 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 signs observed along a couple of joints on the crest. Other than that, conditions of structures good indicate hydraulic performance of the waterway. Dam crest walked along full length. No signs concentrated of seepage along the down stream slope. Upstream slope protection in conditions. good

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

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

2.3 Ogun State

2.3.1 Oyan Dam

Oyan Dam which is owned and operated by the Ogun-Osun River Basin was completed in 1983. It is Development Authority 30m high with a reservoir capacity of 27OMm3 area of approx. 9,000km2 and and a catchment an embankment length of 1044 m. The 10,000 years flood is approx. 2.10m design free board at high. It supplies water for irrigation and to the cities of Abeokuta and Lagos. for domestic uses It has a concrete overflow section, gated (radial gates) spillway, with drainage holes hole are clogged four bays. The relief and need to be re-activated, including installation gages for monitoring uplift pressures underneath of pressure (those the concrete structure. Two of the four at the right and left side) are out of service, gates needing with the hoisting cables of one of these urgent replacement. The one to the left two cables needs re-alignment because the load on is very uneven and does not allow raising. the reported. The Problems at the control panel are also two central gates operate satisfactorily. Operation electrical motors which of these gates is assisted by are powered by diesel generators. At the generators were not working time of the inspection, the because of lack of fuel and therefore the The operations of the Dam are gates remained closed. not connected to the national grid and hence also not function, opening of hence with the generators gates during a tlood would have to be would require importing the necessary done manually. This manpower to sight during an emergency, which could take several hours. Once a process the adequate manpower is on site, it approximately 4-6hours to open each gate. would take The dissipation area downstream of the spillway has never erosion. There is been inspected to check possible a 9MW Hydroelectric Power plant at the toe due technical reasons, of the dam, but it does not operate including not being connected to the grid. There is an emergency spillway located on a saddle area crest level. It is at elevation about 1.7m below the necessary to check the topography of implement suitable this emergency spillway are and to land regularization works to ensure, it functions. This is extremely provides this emergency relief important because the service spillway operation is extremely unreliable. is gated and the gate

Three Howell-Bunger valves control releases in the river bed for downstream require replacement of the motor; they uses. All of them also need overhaul of the mechanical parts. valves are installed under side of the HB valves. Butterfly The installed instrumentafion is inadequate needs adjacent to be rehabilitated and used. There is an to the toe of the embankment where area (reportedly seepage is reported to have been observed more than one year ago). There is no collection pipes. A concrete channel system in the form of drainage at the toe is full of debris and clogged by vegetation. The site inspection did not reveal any seepage. remove There is urgent need to: a) clear vegetation debris; b) identify the seepage area and and the effluent, closely monitor seepage rates and turbidity including correlation with reservoir levels. of 2.3.2 Abeokuta Weir

The Abeokuta weir is located some 20km downstream of the Oyan openings, is about 11m wide and Dam. The weir has five 9.8m high. There is an emergency spillway flood events located adjacent to the weir. for unforeseen 2.4 Plateau State All dams in Plateau State are owned by the State Water Corporation (SWC). The that none of their dams have been overtopped. SWC report 2.4.1 Yakubu Gowon Dam The Yakubu Gowon Dam is the largest dam 3 in Plateau state. It is 35m high capacity of 30Mm . The dam was built and has a reservoir intake tor water supply to the SWC only. There tower through which water is pumped is a gravity embankment through a pipe that runs through directly to the water treatment plant. the dam At the time of the inspection the reservoir level was low and there were observed. The water in the reservoir no signs of seepage siltation/sedimentation. is brown and muddy. There is no There are signs of erosion monitoring of The toe drain in certain areas on of the downstream was blocked with debris. There are slope. used. There is no three piezometers, but they are not form of record keeping going on at being based at the dam the Dam site. There are no personnel site. There is no operations and maintenance drawings. plan and there are no as-built

There is an open crested concrete spillway to the structures appear left had side of the embankment. The to be in good condition thereby indicating spillway waterway. There are signs good hydraulic performance of the of erosion at the end of the spillway channel. 2.4.2 Lamingo Dam Lamongo Dam serves as an inter-basin transfer high and reservoir. The embankment dam is the reservoir capacity is 0.001 Mm3. about 11 m The Dam is in a desperately unsafe condition and its imminent. The collapse if no remedial action is taken rap along the bottom end of the upstream is practically sheared slope has settled so much it away from the face of the slope and has are fairly large nym offers no protection of the slope. There trees growing on both sides of the dam. settlement dips and erosion The dam crest has major signs of in various locations along its length about 300m downstream, some A dam break threatens a road fields and power transmission lines. This Dam needs immediate rehabilitation, which should operation of the dam. be taken immediately to ensure safe

2.4.3 Liberty Dam

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

13 3.0 RECOMMENDATIONS

Due to current uncertainties about and lack of reliable records and information on the the maximum floods throughout extent of the all the entire states visited, a prudent approach interest of safety must be adopted in the because there are densely populated areas downstream most of the dams. Dam break analysis and inundation studies should be carried out Emergency Preparedness Plans prepared and accordingly. Such studies should proceed in a coordinated way in the four states wnth mutual exchange of information and consultation on priorities (which dams should be included). The dams that supply water for urban uses should not only be safe, but they should be provide that service for an adequate able to period of time in the future, in a reliable manner. Water yield reliability can be severely affected by reservoir conservation sedimentation if adequate reservoir strategies are not in place. For example, the reservoirs hydrologically large, in are i.e. their active capacity is larger than the average long-term offc. This means that their sediment annual run- trapping efficiency is quite high and that water releases sediment flushing are not feasible. for 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 past behavior (as-built drawings to be updated following each 2. Carrying rehabilitation work). - out a hydrological review to determine the extent checking of the floods to be used for dam safety, (e.g. capacity of spillways, size of reservoirs, etc.) release schedules 3. Preparation or updating of Operation and Maintenance, and Surveillance training of staff accordingly. Manuals and 4. Preparation or update Emergency Preparedness Plans making exist in the detection> sure that no weak links decision> notification> warning> response chain. 5. Installation or rehabilitation of instrumentation and monitoring devices and training of surveillance staff accordingly (Instrumentation Manual). 6. Catch-up with deferred maintenance activities such as: debris along spillway plugs should be real fuses, crests, fuse drainage systems full of debris and vegetation, excessive vegetation 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) assessments. to updated flood 8. Bogoma Dam (Kaduna) requires major modification to layout. spillway and dissipation zone 9. Marashi Dam (Kano) needs either provision of a controlled crest, or crest overtopping area on the raising and new spillway (currently undersized box culvert). 10. Other 9 dams in Kano (Guzuguzu, Jakara, Kango, Karaye, Magaga, Tudun Wada, Warwade) Pada, Tomas, most likely require spillway modification/ upgrading measures. 11. Oyan Dam (Ogun State) requires urgent rehabilation works to get all four radial gates operating 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. 14 12. Lamingo Dam (Plateau State) requires immediate rehabilitation of the upstream slope to prevent 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 of Reference in annex) (see Terms 15. Carry out study on Sedimentation trends and preferred strategies sedimentation management 16. Elaborate a Storage Conservation Action Plan (preliminary ToRs in Annex C) 3.4 Recommended actions

Step 1: Individual Dam Specialist During meetings and site visits it has been noticed understanding that dam operators have a good of the actions required to improve reliability of the headworks. first step should Therefore that the be that of facilitating preparation of terms of reference specifications for further actions and technical that will be undertaken by a consulting firm and contractors. this purpose, the services of an individual For dam specialist (IDS) should be obtained. The IDS address all points (1 to 12) listed above, will together with the dam operators, and assist them preparing terms of reference and tender in documents for the procurement of consulting and contractor services necessary to implement the corresponding national activities. The IDS will assist staff in organizing a workshop (see step 2) implementation. in the very early stages of project The IDS will also perform on the job training of dam staff. Step 2: Launch Workshop This workshop wOI have the following objectives: a) share issues the technical and possible solutions among staff of the four states; b) disclose project information contractors potentially to national consultants/ interested in the tuture bid contracts; c) identify criteria for the next steps. priorities and basic

Step 3: Consulting Services It is understood that several consulting engineering firms operate in Nigeria. A consulting (probably a national one) will: firm 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 Works A contractor, preferably in association with an instrumentation selected equipment supplier, will be ior executing the works associated with activities 5 to 1is.

d Activities 6 (Deferred maintenance) and 13 (Erosion zones on embankment directly by the SWA. slopes) will probably be carried out ' Activities 6 (Deferred maintenance) and 11 (Erosion zones on embankment slopes) directly by the SWA. will probably be carried out 15 It must be pointed out that no provision has been made for implementing any sedimentation management 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 mid term review of the project.

16 4.0 COSTS ESTIMATE

Table 1: Cost Estimate of Dam Safety-related measures

Cost DescripUon Assumptions (US$) International consultant to complete dam Fees 30k; travel and safety surveys, estimate costs, and prepare accomodation 10k ToRs. 40,000 Launch workshop Sum 35,000 Consulting firm (national?) to reconstruct as- National consulting firm; built dwgs, train staff (O&M, surveillance, 400k$ fees; 50k$ instrumentation & monitoring, EPPs, investigations and lab tests sedimentation surveys), prepare tender documents of rehabilitation works, propose storage conservation action plans, assist GON in contractor selection. 450,000 Equipment for bathymetric surveys of ToRs in Annex B reservoirs 15,000 Contractor, in joint venture with an Equipment supply equipment supplier, implements (instruments, electrical rehabilitation works, instrument installation. control panels, valves, etc.) at several dams 1,000,000 Bogoma Dam, modification to spillway and dissipation zone layout. 2,000,000 Marashi Dam (Kano) either provision of a controDled overtopping area on the crest, or crest raising and new spillway. 500,000 Other 9 dams in Kano (Guzuguzu, Jakara, 2,000,000 Kango, Karaye, Magaga, Pada, Tomas, to Tudun Wada, Warwade) most likely require 4,000,000 spillway modification/ upgrading measures. Lamingo Dam, urgent rehabilitation of 300,000 upstream slope.

Consulting firm supervises construction 3 person @ 3k$/m for 3 activities 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 - ToRs C. Storage conservation study - ToRs

17 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 6 Action Descriptin (montihs) GON recrmits iterational consultant (indwa) 11 1 Launch Workshop 2 Irternatiowal consultant to complete dam safety surveys, estimate costs, and prepare ToRs. 2 Cj GON 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 of rehablitation works, propoe storage conservation acHon plans, assist GON In contractor selection 9 GON procures contractor (national?) for action 3 4 4 Contractor, In joint venture with an International equipment supplier, Implements rehabilitation works. instrument installaon; 24 5 Contsultng finm supervses constructon works and carries out further staff training (O&M manuals, and EPPs finallation). 24

A cost estimate of the activities that are necessary to address the dam safety aspects project of the is contained in table 1 below. The estimates will have to be refined during steps 1, 2 and 3, but are considered adequate for preliminary budget purposes. The largest uncertainty related is to the construction works for which a range is provided. A provision of US$7.5 million should be included in the project budget to address dam safety related measures.

18 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 low power consumption, portability, ease to use, rugged construction, built-in interfaces communication for navigation/data logging devices. Logging of bathymetric and navigation data may be 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 of position not exceeding +/- 0.5 meters. - The echosounders shall be capable of providing depth reading in the range of 0 to 550 necessary m, if 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 sediments of within the reservoir, which can have a major bearing on the both dam safety and reservoir management. The GPS equipment will be also used for terrestrial survey. Sediment volumes will be calculated from the bathymetric data, on the basis of previous bathymetric or topographic survey data of the site under investigation. Should topographic previous surveys be inadequate, the sub-bottom profiling (SBP) technique will be used to provide the necessary data to calculate sediment volurne without having prior reservoir. information on the The SBP system for mapping sediment thickness should be relatively small, simple to operate and well built. Depending on the nature of the sediment the system should be able to achieve to 30 meters 5 of subsurface penetration. A data acquisitlon system for acquiring navigation and SBP data should also be considered.

19 2. Technical Specifications (Sample for information only)

DESCRIPTION Unit Price Total amount 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 of operation following installing and start up of equipment. The Purchaser will select spare parts from this list 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 appropriate unit of Supplied Goods in English;

5. Warranty Oblieations

The warranty period shall be 12 months after the Goods have been delivered to and accepted by the Purchase at the final destination indicated in the Contract. The period for correction of defects in the warranty period is three (3) months. The Goods for which warranty repairs or replacements have been made shall remain under warranty for a period of one (1) year, but not more 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

, ~ ~ .. .~. ..

21 Staff training on use of reservoir | Data processing and storage equipment survey equipment l Annex C:

TERMS OF REFERENCE FOR ASSESSMENT OF SEDIMENTATION RESERVOIRS STRATEGIES FOR

Objective

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

Extenal EXernal -Envlranmentel- Promj Focus- - Socletal Concers Ccvcenm

a tibcFh_ c wSa,Ntim Mm-~~--

4,UA4_ =_p" MW - - ....wI s,. .i, , + teeabo4K'_ - mmua X~~~D=Id 1 0_ u2[ .d IM Imp..Im B

CIO >," u Fllb

[*wlli_ b IW^II~ ~ ~ ~ ~ ~ ~ ~ ~~2 Data Collection . Hydrology - Hydrologic data required include variation mean annual inflow into the reservoir, of the annual inflow, and a representative reservoir. average water temperature This data can be obtained from hydrology in the reservoir and catchment. records and operating records for the

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

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

RESERVOIR CONSERVATION ACTION PLAN tylAcal format Time (vears) |5 | 10 I tI5 20 | 25 30 1 35 i 40 100 | 45 | 50

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 50 Financial Plan for Profile A T 23

Financial Plan for Profile B -