BASIC DESIGN STUDY REPORTON

THE PROJECTFOR

URGENT COUNTERMEASURESFOR

SEDIMENTATIONIN

WONOGIRI MULTIPURPOSE DAM RESERVOIRIN

THE REPUBLIC OF INDONESIA

DECEMBER 2001

JAPAN INTERNATIONAL COOPERATION AGENCY

NIPPON KOEI CO., LTD.

No.

GR3CR(1)01-229

PREFACE

In response to a request from the Government of the Republic of Indonesia, the

Government of Japan decided to conduct a basic design study on the Project for Urgent

Countermeasure for Sedimentation in Wonogiri Multipurpose Dam Reservoir and entrusted

the study to the Japan International Cooperation Agency (JICA).

JICA sent to Indonesia a study team from August 13 to September 20, 2001.

The team held discussions with the officials concerned of the Government of Indonesia,

and conducted a field study at the study area. After the team returned to Japan, further

studies were made. Then, a mission was sent to Indonesia in order to discuss a draft basic

design, and as this result, the present report was finalized.

I hope that this report will contribute to the promotion of the project and to the

enhancement of friendly relations between our two countries.

I wish to express my sincere appreciation to the officials concerned of the Government

of the Republic of Indonesia for their close cooperation extended to the teams

December, 2001

Takao Kawakami President

Japan International Cooperation Agency

December, 2001

Letter of Transmittal

We are pleased to submit to you the basic design study report on the Project for Urgent

Countermeasure for Sedimentation in Wonogiri Multipurpose Dam Reservoir in the Republic

of Indonesia.

This study was conducted by Nippon Koei Co., Ltd., under a contract to JICA, during

the period from June, 2001 to December, 2001. In conducting the study, we have examined

the feasibility and rationale of the project with due consideration to the present situation of

Indonesia and formulated the most appropriate basic design for the project under Japan’s

grant aid scheme.

Finally, we hope that this report will contribute to further promotion of the project.

Very truly yours,

Project manager,Basic design study team on the Project forUrgent Countermeasures for Sedimentationin Wonogiri Multipurpose Dam ReservoirNippon Koei Co., Ltd.

Motoyoshi Kawashima

10001500

500

1000

2000

2000

500

20001500

K. Ked uwan g

Mt. Merbabu3142

Mt. Merapi2914

Mt. Lawu3265

Mt. Wilis2563

897Mt. Pandan

Mt. Buntung742

BoyolaliSURAKARTA

Klaten

Sragen

Wonogiri

Ngawi

MADIUN

Ponorogo

Indian Ocean

Wonogiri Multipurpose Dam

Pacitan

K. Cemara

K. Bram ba ng

K . Gawe

K

. D

engkeng

K. JlantahK. Semin

K. Mungkung

K. Sragen

K. Sawur

K.

Ketongg o

K. Gandon g

K. Manti

B. Solo

K. Tirtomoyo

K. Gonggang

K. Tempura n K. Mungkungan

K.A

nyar

K. M

adiu

n

K . Keyang

K. Asin

K. Catur

K . Jerowan

Beng

aw

an Solo

2298

KEY MAP

JAWA SEA

INDIAN OCEAN

SUMATRA

KALIMANTAN

Jakarta

PROJECT AREA

JAWA

N

N

SCALE

0 5 10 15 20 25 30 km

Legend

Watershed

River

Wonogiri Dam

Railway

Road

Mountain

City

Town

Provincial Boundary

Location Map

iv

ABBREVIATIONS

APBN Central Government Resources and Expenditure Budget(Anggaran Pendapatan dan Belanja Negara)

BAPPENAS National Development Planning Agency(Badan Perencanaan Pembangan Nasional)

CEP Circle Error PossibilityCDMP Comprehensive Development and Management Plan Study for Bengawan Solo River BasinD/D Detailed DesignDGPS Differential Global Positioning SystemEIA Environmental Impact AssessmentE/N Exchange NoteFRP Fiber Reinfored PlastcsF/S Feasibility StudyGBHN Guideline for National Economic Development

(Garis-Garis Besar Haluan Negara)GOI Government of IndonesiaGOJ Government of JapanGPS Global Positioning SystemH.P. Hose PowerJBIC Japan Bank for International CooperationJICA Japan International Cooperation AgencyKIMPRASWIL Ministry of settlement and regional development

(Departemen Permukiman & Prasarana Wilayah)LWL Low water levelO&M Operation and MaintenanceOECF Overseas Economic Cooperation FundOTCA Overseas Technical Cooperation AgencyPBS Project Bengawan SoloPDAM Regional Drinking Water Supply Company

(Perusahaan Daerah Air Minum)PJT Jasa Terta Public Cooperation, Public Water Service Cooperation

(Perum Jasa Terta)PKSA Water Resources Development and Conservation Section

(Pengembangan Konservasi umber Sumber daya Air)PLN National Electric Company

(Perusahaan Listrik Negara)PROPENAS Five-year National Development Program

(Program Pembangunan Nasional)SAPS Special Assistance for Project SustainabilityWATSAL Water Resources Sector Adjustment Loan

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SUMMARY

The Wonogiri Multipurpose Dam located in up-stream of the Solo River in the Central Java provincewas constructed in 1982 under the technical and the financial assistance of Japan. The principal featuresof the dam and the related structures including the power-house are shown in Fig. 1.1.2.

It has been reported that routine operation of the Wonogiri dam, especially for water release forirrigation water supply and power generation has been disturbed due to a huge amount of sedimentationdeposited in front of the intake facility. To clarity this problem, sediment deposit survey has beencarried out by the agency concerned. Judging from the full record of sediment measurements includingthe results of a survey conducted on August/September, 2001 by the JICA Team, the sediment level hasrisen by 1.1 m in front of the trashrack and 3.8 m at the deepest point in less than two (2) years betweenDecember 1999 and August 2001. If the present rate of sedimentation in front of the intake facilitycontinues without any countermeasures, the inlet portion of the intake is anticipated to be completelyblocked within about 2.8 years from now.

According to the estimation of the JICA Team as shown in Appendix 7.1, annual sediment inflow to thereservoir is estimated to be 5.4 million m3 in total. The plan of the Wonogiri dam reservoir and theprofiles of tributaries are shown in Figs. 1.2.2 and 1.2.3, respectively.

The maximum water discharge for the Wonogiri hydro-power generation has been determined at 75 m3/sto generate the annual power energy of 50,000 MWh in the design stage. The annual power energy hasbeen generated on schedule until 1999, but power energy for the rainy season from December to Aprilappears to have decreased since then. The main reason for reductions of power energy is that the lowestreservoir water level is now limited to EL. 130.0 m due to the sedimentation in front of the intake facilityand the maximum intake discharge is restricted to 60.0 m3/s due to for the same reason at present.

Serious problems in the Wonogiri irrigation could not be identified from the technical view point ofirrigation water supply (refer to Table 1.3.2). Further, even in the dry season, no major variations fortaking in the irrigation water have been reported.

However, as the reservoir water level is operated above EL. 130.0 m, the utilizable volume between EL.127.0 to 130.0 m in the reservoir could not be used for the irrigation water supply. To cope with thiswater supply deficit, the reservoir water level is raised to a higher than normal water level (EL. 136.0 m)at the end of the rainy season and the reservoir water then released to meet the water demand.

In order to remedy the sedimentation problem in the Wonogiri multipurpose dam reservoir, theGovernment of the Republic of Indonesia (GOI) submitted an application for Japan Grant Aid for thefollowing three components to the Government of Japan (GOJ);

1) Construction of two check dams (sand storage volume in total: about 550,000 m3) onthe Keduwang River to mitigate sediment entering the reservoir of the Wonogirimultipurpose dam.

2) Urgently dredging about 100,000 m3 of sediment from in front of the intake facility

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of the dam to assure the intake function of the water, and

3) Providing a dredging system to assure the sustainable dredging of sedimentcontinuously entering the reservoir.

In response to the above request, GOJ dispatched the Basic Design Survey Team through JICA(hereinafter called as the JICA Team) from August 13 to September 20, 2001 to Indonesia. The JICATeam conducted the field survey and held discussions with the Director General of Rural Development,the Ministry of Settlement and Regional Development (KIMPRASWIL) which is the implementingagency and the Project Bengawan Solo (PBS) belonging to KIMPRASWIL. Consequently, JICA andKIMPRASWIL agreed that the construction of the check dams should be excluded from the aboverequest of GOI due to the technical problems. It was also agreed that other components proposed byGOI in their meeting should be examined in Tokyo, as shown in the minutes of meeting dated on 4September, 2001.

The JICA Team examined the contents of the above minutes of meeting in detail in Japan, and aftercareful consideration, it was determined to delete the dredging system requested by GOI, due to thepresent budgetary situation in Indonesia. The JICA Team accepted the urgent dredging from in front ofthe intake and associated projects proposed by GOI under GOJ’s finantial assistance. The Basic DesignStudy Report (Draft) incorporated these conclusions.

The GOJ dispatched the JICA Team to explain and discuss with GOI about the above report to Indonesiafrom October 28 to November 6, 2001. As a result, GOI agreed with the conclusions of the report inprinciple as shown in the minutes of meeting dated on 2 November, 2001.

The five-year National Development Program (PROPENAS, 1999-2004) was issued in August 2000 asa high level program of the government of Indonesia (GOI). The objectives of good maintenance andadministration of industrial infrastructure (including those of water resources development), assurance ofstable food supply, and increasing farmers’ income are set down in Chapter 4 of PROPENAS. In line withthis policy, the target of this project was set at solving the sedimentation problems in the Wonogirimultipurpose dam reservoir to continuously maintain the functions of the dam for irrigation, powergeneration, and flood control, being the original purposes of the dam (hereinafter called as the Project).

The Project is needed to alleviate the sedimentation problems of the Wonogiri reservoir under thefollowing basic concepts:

(1) Implementation of urgent measures to remedy the function of the Wonogiri reservoir by means ofstructural measures, and

(2) Implementation of mid- and long term sediment mitigation measures by means of structural and non-structural measures including basin reservation and management.

To meet the concept (1), a basic study to meet the urgent requirements of removing sediment from infront of the intake is needed. For the concept (2), an overall master plan for alleviation of sedimentdelivery to the Wonogiri reservoir will be contemplated.

From the above concepts, the principles of the Urgent Countermeasures for Sedimentation in the

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Wonogiri multipurpose dam reservoir under the requested Japanese assistance (hereinafter called as theAssistance Project) are determined as follows:

· Dredging near the intake channel and portal portions to secure the water intakefunction of the dam for 5 years (the project life time).

· Inspections and repairing of gates and relevant facilities, emergency release valveand spillway gates to assure water release during the dredging work at the intakechannel and portal portions.

The scope of work for the Assistance Project was studied as follows;.

(1) The annual sediment input from the Keduwang River, which brings about much sediment to theWonogiri reservoir is estimated at about 1,280,000 m3 (refer to Appendix 7.1). Assuming that the bedload is about 15% of all sediment (as there are no actual measurement data, this assumption is based ondata from the Brantus river basin), the suspended load volume is estimated to be about 1,090,000 m3. Itcan be judged that most of the suspended load produced in the Keduwang River is entering the Wonogiridam directly due to the following reasons that majority of the sediment deposited in the existing checkdams comprises sand and gravel.

Therefore it was judged that, even if the two check dams are constructed in compliance with the request,it will not be effective for trapping the sediment load, resulting in no function for minimization of thesuspended load entering the Wonogiri dam.

(2) Possible methods of dredging to be provided to PBS are compared in terms of their potentialsustainability in Table 2.2.2. According to this table, the following are identified as applicable:

· Ordinary type sand pump dredger or grab bucket, and

· Hydro-type dredging system, which is recently being utilized by GTO Sediment AsCompany in Norway consists of Hydro-J System and Hydro-Pipe System.

In order to protect the inlet portion in front of the intake facility of the Wonogiri dam being from sediment

deposit, dredging work (about 40,000 m3) shall be made annually in front of the intake facility. For this

dredging works excluding the existing garbage, a sand pump dredge of more than 1,000 horse power

(H.P.) would be required and the annual cost is estimated to be Rp. 1,740 x 106 as shown in Table 2.2.3.

Further, if a grab bucket were used, the efficiency for dredging fine sediment is decreased and, the annual

O&M cost would be more than for a sand pump dredge. It is judged difficult for the central government

to assure this new budget into the future. Even if a sand pump dredge was provided under Japanese

grant aid, there is too much risk that it would be remained unused due to lack of GOI funding for its

O&M.

The hydro-type sand flushing system has been designed to remove sedimentation to the downstream bywashing out water together with sediment by use of a siphon. Hence, the annual O&M cost is estimatedat Rp. 210 x 106 as shown in Table 2.2.4, about 12 % of the cost of using a sand dredge. But this type hasfew examples actually utilized in projects and has unknown reliability.

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In conclusion, it is judged to be unjustified to provide either system from the viewpoints of O&M costand technical reliability.

Thus, the scope of works for the Assistance Project was determind as follows:

(1) Inspection and repairing of gates and valve

In order to conduct the urgent dredging works and secure the safety during the dredging, the followinggates and valve may need to be operated, and if so, they will need to be working reliably. Hence, priorto the commencement of the urgent dredging works, they should be inspected and, if necessary, repaired(refer to Fig. 2.2.1):

· Intake coaster gate (1 no., Size: 5.5 m x 5.5 m)

· Emergency releasing hollow jet valve (1 no., Diameter: 1,950 mm)

· Spillway gates (4 nos., 7.5 m(Width) x 8.1 m(Height))

(2) Urgent dredging and removal of garbage

1) Rational of dredging works and areas are as follows:

i) Restoration of the approach channel to the intake facility.

The approach channel should be restored to the original design.

ii) New construction of a waterway channel to take water from the Bengawan Solo River intothe intake facility when the reservoir water level is equal to or below EL. 127.0 (i.e.LWL)-130.0 m.

iii) Construction of flat yards of EL. 126.0 m, being lower by 1.0 m than the LWL of thereservoir. Elevation of EL. 128.0 m is applied for fore-bay for the spillway in originaldesign. The flat yards are to prevent the large quantities of sediment from entering theintake facility and the approach channel after they are dredged.

2) Dredging volume

The dredging volume comprises dredging volume estimated based on the result of echo sounding

survey and sediment volume flow up in the reservoir during dredging work period. The

estimated dredging volume is 251,000 m3.

(3) Setting of floating log boom

The floating log boom to be placed around the intake facility will effectively prevent garbage from

entering the intake. The layout of the floating log boom is shown in Fig. 2.2.3.

(4) Provision of Echo Sounding Survey System with GPS Navigation Equipment

The Facility will be used for the water depth survey to be carried out in front of the intake aftercompletion of the urgent dredging work as one of the O&M activities which should be made by the PJT IBengawan Solo (PJT-IBS). The composition of the system is shown in Fig. 2.2.4.

The Project would be implemented on the following conditions in consideration of application for

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Japan’s Grant Aid system.

(1) Director General of Rural Development, Ministry of Settlement and RegionalInfrastructure (KIMPRASWIL) in Indonesia would be the executing agency for theProject implementation.

(2) Immediately after the Exchange of Note (E/N) between GOJ and GOI regarding thestages of the detailed design and the construction works is signed, theKIMPRASWIL should commence the necessary actions for the implementation ofthe Project.

(3) A Japanese Consultant firm, recommended by the Japan International CooperationAgency (JICA) should be entrusted by the KIMPRASWIL and should prepare thedetailed design and tender documents for the selection of the Japanese Contractor forthe civil works. Immediately after the completion of the preparation, the JapaneseConsultant should start the tendering works.

(4) GOI should commence the arrangement for the land acquisition in parallel with thedetailed design, if necessary.

(5) A Japanese Contractor immediately after signing the contract for the constructionworks with the KIMPRASWIL shall commence to undertake the construction worksand the Japanese Consultant shall execute the construction supervision.

The dredging work volume for the Assistance Project has been estimated at around 251,000 m3,including 72,000 m3 of garbage, and one (1) barge with grab bucket (3.5 m3) shall be adopted as thedredging equipment. As the working area is limited, one set of dredging equipment is applied. Theconstruction period is estimated 18.5 months, which includes;

- Preparatory works　:　1.0 month

- Transportation, embarkation and erection of the main equipment　:　4.0 months

- Dredging works　: 10.0 months

1,013 m3 (Daily dredging rate) x 30 days x 0.82 (Efficiency) = 24,919 m3/month

250,000 m3 (Dredging volume in total) / 24,919 m3 (Monthly dredging rate)

= Around 10.0 months

- Setting floating log boom　:　1.0 month

- Disassembling dredging equipment and clearing the construction site　:　2.5 months

Obligation of recipient country (GOI) for the implementation of the Assistance Project are as follows:

(1) To secure the land necessary for the execution of the Assistance Project, such as thespoil banks (44 ha in total for the two (2) spoil banks), land for temporary offices,

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storage yards and others

(2) To carry out environmental impact assessment (EIA) for the Assistance Project

(3) To guarantee 3 - 4 month’s suspension of the Wonogiri power station operationduring the dredging work at the intake

(4) To arrange the staff of PBS and the budget for the implementation

(5) To bear commission of the Japanese foreign exchange bank for its banking servicesbased upon the banking arrangement, namely the advising commission of the“ Authorization to Pay” and payment commissions

(6) To ensure prompt unloading and customs clearance for ports of disembarkation inthe Government of Indonesia and prompt internal transportation therein of thematerials and equipment for the Assistance Project purchased under the Japan GrantAid.

(7) To exempt Japanese juridical and physical nationals engaged in the AssistanceProject from customs duties, internal taxes and other fiscal levies which may beimposed in Indonesia with respect to the supply of the products and services underthe Verified Contractor

(8) To accord Japanese nationals whose services may be required in connection with thesupply of the products and services under the Verified Contract such facilities as maybe necessary for their entry into Indonesia and stay therein for the performance oftheir works

(9) To provide necessary permissions, licenses and other authorizations forimplementing the Assistance Project, if necessary.

(10) To maintain and use properly and effectively the facilities constructed and equipmentprovided under the Assistance Project

After completion of the Assistance Project, following routine O&M issues are required:

· Water depth survey near the intake facility by the echo sounding survey equipment

· Removal of garbage from near the intake facility including the screen

It is noted that the O&M cost of Rp. 23,700,000 /year for the Assistance Project (refer to Appendix 5)will be provided by GOI.

The Assistance Project creates the direct benefit stated below. In summary, this is the maintenance ofincome of beneficiary farmers in the down-stream of the Wonogiri multipurpose dam and contributing tothe stable electricity supply to the central Java province. It will hopefully contribute to stable foodsupply and social stabilization, the primary political strategies in Indonesia as described in 2.1.1 of thereport.

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The Wonogiri multipurpose dam supplies irrigation water to the 29,590 ha Wonogiri irrigation system(refer to Fig.3.1.1), which is the beneficial area of the Assistance Project. The number of beneficiariesis estimated at 45,200 households. By implementation of the Assistance Project, the direct effect will beannually Rp. 187 x 109 at the present market price of 1,220 Rp./kg.

The beneficiary area for the Wonogiri hydro-power station is located in central Java province. It isestimated that the annual power generation energy of the Wonogiri power station (50,000 MWh) willcontribute to power consumer of 61,000 households. By implementation of the Assistance Project, thedirect effect will be annually Rp. 10x109, estimated by multiplying the electricity sale price of 200Rp./kWh at September in 2001 by the annual power generation energy of 50,000 MWh.

The Assistance Project represents the first steps needed to conquer the sedimentation problem in theWonogiri multipurpose dam reservoir to assure the water intake function of the dam for a period of aboutfive (5) years from the completion of the Project (refer to 2.2.2(2)2)(d) of this report). In order tosustain the existing facilities of the Wonogiri dam, the followings will be recommended;

(1) According to the visual inspection conducted on 11 September, 2001 by the JICA Team, noserious defects to the power generation equipment (only one set of turbine and generatorwere inspected) were found. However, it is more than twenty (20) years since the hydro-power station commenced operation. Therefore, in order to continue the power generationsmoothly in the future, the prompt execution of an overall inspection of both the civilstructures and the power generation equipment in the Wonogiri hydro-power station isstrongly recommended.

(2) In order to maintain the water intake function of the dam for the mid- or long term periodafter about five (5) years, the introduction of a dredging system to continue the dredgingworks in front of the intake facility and installation of a mechanical raking system on thescreen of the intake are strongly recommended after the Assistance Project is completed.

(3) In order to secure the dam reservoir space for water utilization and flood control for thelong term, mid- and long term countermeasures such as water-shed conservation andsediment management of the Wonogiri dam reservoir, and structural measures in thereservoir against sediment flowing into the reservoir should be studied. In particular, newconstruction of another intake facility or of an inlet shaft at the inlet portion of the existingintake would be the most realistic and most effective. The completion of these mid- andlong term countermeasures shall be made in time considering the planned completion of theAssistance Project shown in the attached figure in 2.2.4 (7) of this report and the life time ofthe Assistance Project (around 5 years after completion).

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The Basic Design Study Report on the Projectfor Urgent Countermeasures for Sedimentation

in Wonogiri Multipurpose Dam Reservoirin the Republic of Indonesia

PrefaceLetter of TransmittalLocation MapAbbreviationsSummary

Table of Contents

Page

CHAPTER 1 BACKGROUND OF THE PROJECT　......................................................................................... 1-1

1.1 Introduction　.................................................................................................................................. 1-1

1.2 Sedimentation in the Wonogiri Multipurpose Dam Reservoir　 .............................................................. 1-1

1.3 Present Situation of the Wonogiri Power Station and the Wonogiri Irrigation System　 ......................... 1-2

1.4 Requested Japanese Assistance　............................................................................................................. 1-3

CHAPTER 2 CONTENTS OF THE PROJECT　 ................................................................................................ 2-1

2.1 Basic Concept of the Project　 ................................................................................................................. 2-1

2.1.1 Government’s Target and Target of the Project　 ........................................................................... 2-1

2.1.2 Basic Concept of the Project　......................................................................................................... 2-1

2.2 Basic Design of the Requested Japanese Assistance (the Assistance Project)　 ...................................... 2-3

2.2.1 Design Policy　................................................................................................................................ 2-3

2.2.2 Basic Plan　 ..................................................................................................................................... 2-5

2.2.3 Basic Design Drawing　 .................................................................................................................. 2-18

2.2.4 Implementation Plan　 ..................................................................................................................... 2-18

2.3 Obligations of Recipient Country　 ......................................................................................................... 2-23

2.4 Project Operation Plan　 .......................................................................................................................... 2-24

2.4.1 Required Maintenance and Management Issues　 ........................................................................... 2-24

2.4.2 Operation and Maintenance Organization　 .................................................................................... 2-25

2.5 Other Relevant Issue　 ............................................................................................................................. 2-26

CHAPTER 3 PROJECT EVALUATION AND RECOMMENDATION　 .......................................................... 3-1

3.1 Project Effect　 ........................................................................................................................................ 3-1

3.1.1 Direct Effect　 ................................................................................................................................. 3-1

3.1.2 Indirect Effect　 ............................................................................................................................... 3-3

3.2 Recommendations　................................................................................................................................. 3-3

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List of Tables

Table 1.3.1 Monthly Power Output by Wonogiri Power Station　 .................................................................... T- 1

Table 1.3.2 Cropping Area and Cropping Intensity of Wonogiri Irrigation System　 ....................................... T- 2

Table 2.2.1 Monthly Rainfall in Wonogiri Dam Watershed Area　................................................................... T- 3

Table 2.2.2 Comparison for Providing Dredging System　............................................................................... T- 4

Table 2.2.3 Preliminary Estimation for Annual O&M Cost by Sand Pump Dredger　 ..................................... T- 5

Table 2.2.4 Preliminary Estimation for Annual O&M Cost by Hydro-type Dredging System　 ...................... T- 6

Table 2.2.5 Comparison of Dredging Method for Urgent Dredging Works　 ................................................ T- 7

Table 2.4.1 Profit and Loss Projection of Bengawan Solo Branch Office　...................................................... T- 8

Table 3.1.1 Project Effect and Extent of Improvement on Present Situation by Implementation

of the Assistance Project　.............................................................................................................. T- 9

List of Figures

Fig. 1.1.1 Existing and on-going Projects by Japan’s Grant Aid and JBIC Loan　 ........................................ F- 1

Fig. 1.1.2 Wonogiri Multipurpose Dam　 ....................................................................................................... F- 2

Fig. 1.2.1 Sediment Condition in front of Intake Structure　.......................................................................... F- 3

Fig. 1.2.2 Anticipation of blockade in front of Intake Structure　 .................................................................. F- 4

Fig. 1.2.3 Wonogiri Dam Reservoir　 ............................................................................................................. F- 5

Fig. 1.2.4 Wonogiri Dam Reservoir Profile　 ................................................................................................. F- 6

Fig. 1.3.1 Variations of Power Generation from 1983 to 2001　 .................................................................... F- 7

Fig. 2.1.1 Dredging Plan　 .............................................................................................................................. F- 8

Fig. 2.2.1 Locations of Gate and Valve Inspection　 ...................................................................................... F- 9

Fig. 2.2.2 Locations of Spoil Bank (1/2)-(2/2)　............................................................................................. F-10

Fig. 2.2.3 Layout of Floating Log Boom　 ..................................................................................................... F-12

Fig. 2.2.4 Digital Echo Sounding System with GPS　.................................................................................... F-13

Fig. 3.1.1 Locations of Wonogiri Irrigation System......................................................................................... F-14

Appendices

1. Member List of the Study Team　 ................................................................................................................. A1- 1

2. Study Schedule　........................................................................................................................................... A2- 1

3. List of Parties concerned in the Recipient Country　 .................................................................................... A3- 1

4. Minutes of Discussions　 .............................................................................................................................. A4- 1

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5. Cost Estimation born by the Recipient Country　 ......................................................................................... A5- 1

6. Other Relevant Data　 ................................................................................................................................... A6- 1

6.1 Wonogiri Multipurpose Dam Reservoir Water Level –Outflow – Rainfall (1986-2000)　....................... A6- 1

6.2 Designed Cross Sections for Urgent Dredging Works for Wonogiri Multipurpose Dam　....................... A6-19

6.3 Guide Line for Environmental Conservation in Indonesia　..................................................................... A6-25

6.4 Other Relevant Data　............................................................................................................................... A6-28

7. References　 .................................................................................................................................................. A7- 1

7.1 Estimation of Annual Sedimentation into the Wonogiri Dam Reservoir　 ............................................... A7- 1

7.2 Middle and Long Term Countermeasure for Sedimentation Problem

in the Wonogiri Multipurpose Dam (Draft)　............................................................................................ A7- 3

7.3 Hydro-Type Dredging System　 ............................................................................................................... A7- 8

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CHAPTER 1 BACKGROUND OF THE PROJECT

1.1 Introduction

The overall water resource development projects in the Bengawan Solo River basin, where the Wonogirimultipurpose dam is located, was formally commenced when the Solo river basin development office(Proyek Bengawan Solo: PBS) was established in 1969 in Surakarta city in Central Java province.

Subsequently, the Master Plan for water resources development in the Bengawan Solo River basin wasformulated in 1974 under the technical cooperation of the Overseas Technical Cooperation Agency(OTCA), which was the predecessor of the present Japan International Cooperation Agency (JICA),. Inaccordance with this Master Plan, a series of high priority river basin development projects has beenimplemented under the technical cooperation and financial assistance of JICA and the Overseas EconomicCooperation Fund (OECF), which is the predecessor of the present Japan Bank for InternationalCooperation (JBIC). As shown in the below table and Fig. 1.1.1, many projects have been completedunder the financial assistance of Japan and it can be said that the Solo river has had close relationship withJapan.

Bengawan Solo River Development Projects under JICA and JBIC

Name of Projects Implementation Period

Wonogiri Multipurpose Dam Project 1977 – 1982

Wonogiri Irrigation Development Project 1980 – 1988

Upper Solo River Improvement Project 1987 – 1994

Madiun River Improvement Project 1987 – 1995

Lower Solo Pumped Irrigation Project (JICA Grant) 1991 – 1992

Lower Solo River Improvement Project 1996 – (on-going)

Among these, top priority was given to the Wonogiri Multipurpose Dam Project and the WonogiriIrrigation Development Project and those were completed in 1982 and 1987, respectively.

The principal features of the dam are shown in Fig. 1.1.2.

1.2 Sedimentation in the Wonogiri Multipurpose Dam Reservoir

As part of monitoring for the Wonogiri reservoir, echo sounding surveys were carried out in the 1980’s and1993 by PBS. The survey results pointed out a decrease in the reservoir capacity. In addition, an echosounding survey near the intake and in the Keuduwang River was carried out in 2000 by PBS. Thedecrement in capacity is shown below.

Decrease of Reservoir Capacity

Decrement of Capacity1993 2000

Sediment 53% 63%Water utilization 30% 36%Flood control 30% 33%

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The results of the echo sounding survey revealed obstruction of the mouth of the intake. The profile of theupstream of the intake is shown in Fig. 1.2.1.

Judging from the full record of sediment measurements including the results of a survey conducted onAugust/September, 2001 by the JICA Team, the sediment level has risen by 1.1 m in front of the trashrackand 3.8 m at the deepest point in less than two (2) years between December 1999 and August 2001. If thepresent rate of sedimentation in front of the intake facility continues without any countermeasures, the inletportion of the intake is anticipated to be completely blocked within about 2.8 years from now.

The Keduwang river greatly affects the rate of sedimentation in front of the intake because distance from itsjunction with the reservoir to the intake is the shortest among the main tributaries. The other tributariesare the Tertomoyo River, Tenom River, Aran River and Wliyantoro River. The riverbed elevation in thereservoir at the outlet of the Keduwang river is already higher than the low water level.

According to the estimation of the JICA Team as shown in Appendix 7.1, annual sediment inflow to thereservoir is estimated to be 5.4 million m3 in total. The plan of the Wonogiri dam reservoir and theprofiles of tributaries are shown in Figs. 1.2.2 and 1.2.3.

1.3 Present Situation of the Wonogiri Hydro-power Station and the Wonogiri Irrigation

System

(1) Present situation of power generation of the Wonogiri hydro-power station

The maximum water discharge for power generation was determined at 75 m3/s and the annual powergeneration energy 32,600 MWh in the design stage. However, the design figures have been revised inaccordance with the actual reservoir operation adopted until now, and the planned annual power generationenergy has been set at 50,000 MWh.

Actual power generation energy for the period from 1983 to July in 2001 and the variation are shown inTable 1.3.1 and Fig.1.3.1, respectively. Regarding the annual power generation energy, no majorreductions are seen until 2000, however power energy for the rainy season from December to April appearsto have decreased since 1999. The lowest reservoir water level is limited down to EL. 130.0 m due to thesedimentation in front of the intake facility and the maximum intake discharge is restricted to 60.0 m3/s forthe same reason at present.

(2) Recent situation of the Wonogiri irrigation system

The recent situation of the Wonogiri irrigation system for the period from 1997 to 2000 has beeninvestigated by the feed back study in the Water Resources Sector Adjustment Loan (WATSAL). Sincethe cropping area in 1999/00 was increased compared with those of 1997/98 and 1998/99, serious problemsin the Wonogiri irrigation could not be identified from the technical view point of irrigation water supply(refer to Table 1.3.2). Further, even in the dry season, no major variations in the irrigation water intakehave been noticed.

However, as the reservoir water level is operated above EL.130.0 m because of the sedimentation problem,the utilizable volume between EL.127.0 to 130.0 m in the reservoir could not be used for the irrigation

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water supply. To cope with this water supply deficit, the reservoir water level is raised to a higher thannormal water level (EL.136.0 m) at the end of the rainy season and the reservoir water then released tomeet the water demand.

1.4 Requirement to Japanese Assistance

In order to remedy the sedimentation problem in the Wonogiri multipurpose dam reservoir, the Governmentof the Republic of Indonesia (GOI) submitted an application for Japan Grant Aid to the Government ofJapan (GOJ), and requested following three components from the Government of Japan (GOJ) ;

1) Construction of two check dams (sand storage volume in total: about 550,000 m3) on theKeduwang River to mitigate sediment entering the reservoir of the Wonogiri multipurpose dam.

2) Urgently dredging about 100,000m3 of sediment from in front of the intake facility of the dam toassure the intake function of the water, and

3) Providing a dredging system to assure the sustainable dredging of sediment continuously enteringthe reservoir.

In response to the above request, GOJ dispatched the Basic Design Survey Team through JICA (hereinaftercalled as JICA Team) from August 13 to September 20, 2001 to Indonesia. The JICA Team conducted thefield survey and discussed with the Director General of Rural Development, the Ministry of Settlement andRegional Development (KIMPRASWIL) being the implementing agency and the Project Bengawan Solo(PBS) belonging to KIMPRASWIL. Consequently, both parties agreed that the construction of the checkdams should be excluded from the above request of GOI due to the technical considerations explainedbelow in section 2.2.2(1) 1) of this report. It was also agreed that other components proposed by GOI intheir request should be examined in Tokyo, as shown in the minutes of meeting dated on 4 September,2001.

The JICA Team examined the contents of the above minutes of meeting in detail in Japan, and he inconclusion, after careful consideration, not to provide the dredging system requested by GOI due to thepresent budgetary situation in Indonesia as explained in 2.2.2(1) 2) of this report. The JICA Team did,however, accept the urgent dredging from in front of the intake and associated projects proposed by GOI, asexplained in 2.2.2 of this report, as projects to be funded by Japan’s grant aid. The Basic Design StudyReport (Draft) incorporated these conclusions.

The GOJ dispatched the JICA Team to explain and discuss with GOI about the above report to Indonesiafrom October 28 to November 6, 2001. As a result, GOI agreed the conclusions of the report in principleas shown in the minutes of meeting dated on 2 November, 2001.

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CHAPTER 2 CONTENTS OF THE PROJECT

2.1 Basic Concept of the Project

2.1.1 Government’s Target and Target of the Project

The five-year National Development Program (PROPENAS, 1999-2004) was released in August 2000 as ahigh level program of the government of Indonesia (GOI). The objectives of good maintenance andadministration of industrial infrastructure (including those of water resources development), assurance ofstable food supply, and increasing farmers’ income are set in Chapter 4 of PROPENAS. Under suchcircumstances, in line with this policy, the target of this project was set at solving the sedimentationproblems in the Wonogiri multipurpose dam reservoir to continuously maintain the functions of the dam forirrigation, power generation, and flood control, being the original purposes of the dam (hereinafter called asthe Project).

2.1.2 Basic Concept of the Project

(1) Principle of the Japanese Assistance

The Project is needed to alleviate the sedimentation problems of the Wonogiri reservoir under the followingbasic concepts:

1) Implementation of urgent measures to remedy the function of the Wonogiri reservoir by means ofstructural measures, and

2) Implementation of mid- and long term sediment mitigation measures by means of structural and non-structural measures including basin reservation and management.

To meet the concept (1), a basic study to meet the urgent requirements of removing sediment from in frontof the intake is needed. For the concept (2), an overall master plan for alleviation of sediment delivery tothe Wonogiri reservoir will be contemplated.

From the above concepts, the principles of the Urgent Countermeasures for Sedimentation in the Wonogirimultipurpose dam reservoir as the requested Japanese assistance (hereinafter called as the AssistanceProject) are determined as follows:

· Dredging near the intake channel and portal portions to secure the water intake function of the damfor 5 years (the project life time).

· Inspections and repairing of gates and relevant facilities, emergency release valve and spillwaygates to assure water release during the dredging work at the intake channel and portal portions.

(2) Outline of the Assistance Project

Details of the Assistance project are as follows:

1) Inspection and repairing of gates and valve

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(a) Intake gate

Type : Coaster gateNos. of gates : 1Size : 5.5 m x 5.5 m

(b) Emergency release valve

Type : Hollow jet valveNos. of valves : 1Size : 1,950 mm diameter

(c) Spillway gates

Type : Radial gatesNos. of valves : 4Size : 7.5 m (width) x 8.1 m (height)

2) Urgent dredging works and removal works of garbage

(a) Boundary of urgent dredging works (refer to Fig. 2.1.1 and Appendix 6.2)

· Restoration of the portion in front of the intake facility and the approach channel to the inletportion of the intake facility to the original design conditions,

· A channel to take water from the Bengawan Solo River to the reservoir intake facility in case thereservoir water level falls below EL. 130.0 m, and

· Flat yards in right side of intake facility and in the fore-bay of the spillway to prevent sedimentfrom the Keduwang River and from deposits in front of the spillway directly entering the portion infront of the intake facility.

(b) Dredging volume (including garbage)

Around 251,000 m3 in the above boundary area based on the echo sounding survey conducted in September,2001 plus predicted future sediment entering the dredged area until the completion of dredging works.

Note; This volume includes estimated garbage of 72,000 m3 such as wreck of agricultural product and domestic

waste, and so on (refer to 2.2.2(2)2)(b)a)vi of this report) .

(c) Dredging system (Daily dredging rate: 1,013 m3)

Dredging machine : Barge + crane with grab bucket (3.5 m3)Nos. of dredging machine : 1 set

(d) Location of Spoil banks

· The primary spoil bank (4.0 ha); An area located downstream of the sub-dam on the right bank ofthe dam

· The secondary spoil bank (40 ha); An area located about 1,000 m downstream of the dam and onthe right bank of the Bengawan Solo River

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3) Installation of a floating log boom

· Location : Area in front of the intake facility· Type : Floating type· Length : 452 m· Volume of anchor block made of concrete : 106 m3

4) Providing a water depth survey system

· Echo sounder (1 set)· Portable personal computer for data collection with software for preparation of the contour map in

the reservoir installed (1 set)· Portable GPS station on the survey boat (1 set)· Stationary GPS station (1 set)· FRP boat with outboard motor (Obligations of GOI as existing boat for the echo sounding survey

being available)Note ; To maintain the accuracy of the GPS positional data to within 1.0 m CEP (circular error probability),

construction of a stationary GPS base station is required. Without a base station to perform differential

correction, an error of about 20 to 30 m is associated with a portable GPS unit alone.

2.2 Basic Design of the Requested Japanese Assistance (the Assistance Project)

2.2.1 Principles of the basic Design

(1) Natural conditions

1) The separation of the rainy season (December to April) and dry season (May to November) in the projectarea where the Wonogiri multipurpose dam is located is very distinct. The annual rainfall is 1,900 mmand the rainy season and dry season rainfalls are about 1,400 mm and 500 mm respectively, as shown inTable 2.2.1. According to Appendix 7.1, the annual sediment input in the Keduwang River basin isestimated to be 1.28 m3. About 1.09 x 106 m3 of this sediment is judged to flow into the reservoir assuspended load in the rainy season. Hence, in order to prevent large amounts of new sediment enteringthe portion in front of the intake facility and the approach channel after dredging, a flat yard of EL. 126.0m, being lower by 1.0 m than the LWL (EL. 127.0 m) of the reservoir, is to be designed on the right handside of the approach channel to the intake facility. After the completion of the dredging works, thesediment flowing into the reservoir from the Keduwang River should be stopped in the stretch betweenthe flat yard and the outlet of the Keduwang River as much as possible.

In the above case, a hillock will be possibly formed due to the sedimentation from the Keduwang River,then in the dry season, there will be a possibility that river water from the Keduwang River can not entersmoothly into the portion in front of the intake facility. Therefore, for the smooth intake of water, theapproach channel to the intake facility should be extended toward the Bengawan Solo River.

2) The slope angle for the dredging works should be the angle of repose of the sediment material (1:4.0)which was obtained by the simple model test conducted during the Field Works by the JICA Team.

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3) The maximum wind velocity is 30 m/s, so this value is to be adopted for the design of the floating logboom.

4) According to the Design Report of the Wonogiri Multipurpose Dam, in the stability analysis of the damitself and the appurtenant structures, the seismic coefficients are Kh = 0.12 (horizontal) and Kv = 0.06(vertical). Hence, these values are to be adopted for the design of concrete structures.

(2) Social conditions

1) It is necessary that the urgent dredging works shall be made to secure the irrigation water supply from theWonogiri multipurpose dam to the irrigation area of about 30,000 ha in the downstream and to keep therestricted water level of EL. 135.3 m during the rainy season.

2) It is necessary that operation of the dam intake facility for the Wonogiri power station shall be stopped for3-4 months, although this period should be kept as short as possible.

3) As the operation, maintenance and administration for the countermeasures on sedimentation of theWonogiri dam reservoir is to be made in future by PJT-IBS, the basic design shall consider the followings:

· Maintenance and administration shall be kept simple by using construction material and providedsystem to be procured in the surrounding area of the Wonogiri dam or in Indonesia.

· Facilities and equipment that have easy operation, maintenance and administration shall beconstructed or provided and complicated structures or equipment shall be avoided.

· As PJT-IBS is scheduled to do the operation, maintenance and administration of the facilities andsystem provided, the operation and maintenance section of PJT-IBS had better participate in theAssistance Project from the construction stage.

(3) Local contractors and materials

The relevant facilities and system to be provided by Japan’s grant aid would be designed consideringconstruction materials available in Indonesia such as cement, reinforcement bar, concrete pipe, etc.. Localcontractors will be involved within technically allowable limits to activate the societies of the localcontractors and the construction materials suppliers.

(4) Standards of the facilities and system

1) The spoil banks should be designed so as to mitigate the negative impact to the surroundings as much aspossible and to consider the environmental impact.

2) The floating log boom should be designed with adequate strength because floating log booms made inIndonesia have broken in the past due to low strength.

(5) Design policy for implementation schedule

In formulation of the construction schedule, consideration is given to the number of annual workable days,location of the works, quantities of the works, consistency with the Japanese fiscal year, and tax exemptionprocedures in Indonesia. Besides, it is considered that the requirement for materials, equipment, and laborshould not fluctuate greatly throughout the construction period. In addition, the periods required for thepreparation before the works and clearing away after the works should be determined in consideration ofthe period required for the various components of the works, the period required for installation and

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removal of the temporary facilities, and the period required for procurement of the major materials andequipment to be used.

2.2.2 Basic Plan

(1) Selection of the composition of Japanese assistance (the Assistance Project)

As mentioned previously, the application for JICA’s Grant Aid included three components, although onlyone of these was accepted. The reasons for rejecting the check dams and provision of a dredging systemare discussed below.

1) Construction of Two Check Dams on the Keduwang River

Most of the river deposits in the Keduwang River consist of sand and gravel. On the other hand,suspended load material is very limited. Also, the river deposit material in the existing check damscontains a high proportion of sand and gravel. Therefore, even if the check dams are constructed on theKeduwang River, it can be said that the dams will trap only sand and gravel (bed load) which are beingdeposited as the river deposit material.

At the moment, the annual sediment input from the Keduwang River is estimated at about 1,280,000 m3,(refer to Appendix 7.1). Assuming that the bed load is about 15% of all sediment (as there are no actualmeasurement data, this assumption is based on data from the Brantus river basin, being the easternneighboring basin of the Solo River), the suspended load volume is estimated to be about 1,090,000 m3. Itcan be judged that most of the suspended load produced in the Keduwang River is entering the Wonogiridam for the following reasons.

· Situation of sedimentation in the existing check dams are as mentioned above

· Most of sediment material in meandering parts of the river is sand and gravel

· The river profile is rather steep (1/360)

During the field works, field investigation for the river bed material near the candidate locations of thecheck dams in the Keduwang River and at the Keduwang bridge were also conducted and the results areshown below.

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Results of Physical Tests

Name of sample(sampling location) Keduwang bridge Check dam

No.1 SiteCheck damNo.2 Site

About 5 kmup-stream ofCheck dam

No.2

(Existing test)(1)

NearWonogiri dam

(Existing test)(2)

up-stream edge ofthe Wonogiri

reservoir？Sampling・Date of test Sep.2001 Sep. 2001 Sep.2001 Sep.2001 About 1975 About 1993

Distance from the Wonogirimultipurpose dam(km) 8 12 19 24 0.5～2 About 6～8

Sampling depth GL－（m） 0.5 0.5 0.5 0.5 1.0 -Density of soil particleρs(g/cm3) 2.507 2.735 2.649 2.611 2.74～3.30 -Natural water content Wn(％) 52.2 13.1 10.8 22.7 - -

Gravel (％) 2 92 78 82 80～97 0Sand(％) 18 6 23 11 3～15 5Silt(％) 56Clay(％)

80 (0.3) (0.1) (<0.2) 0～539

Uniformity coeff. Uc 1.7 2.3 5.2 5.9 - -

Gradation

Curvat. Coeff . Uc’ - 1.3 2.0 1.8 - -Liquid limit wL(％) 64.5 - - - - -Plastic limit wp (％) 28.4 - - - - -

Plastic index Ip 36.1 - - - - -Consistency

Consistency index Ic 0.3 - - - - -

Classification Silt（High liquid limit）

Wellgradate-d

gravel

WellGradate-d

Gravel

Wellgradate-d

gravel

Wellgradate-d

gravelFine particle soil

Symbol of classification (MH) (GW) (GW) (GW) (GW) F

Sources of the existing tests(1):Engineering Report : Soil and Rock Material Investigation for Consulting Engineering Services

on Wonogiri Multipurpose Dam Project

(2):PEKERJAAN MONITORING SEDIMENTASI WADUK WONOGIRI DAN BENDUNGAN COLO

The riverbed material at Keduwang bridge which is located on the upstream edge of the Wonogiri reservoiris composed of 2% gravel, 19% sand and 79% silt and clay. It is indicated that the suspended load isdeposited on the upstream edge of the reservoir.

On the other hand, the riverbed material on the Keduwang River is composed of 99% sand and gravel and1% silt and clay. It is indicated that most of bed load is deposited in the Keduwang River.

Consequently, even if the check dams are constructed on the Keduwang River, it can be said that most ofthe sediment trapped by them will be bed load (sand and gravel) and the volume will be only 190,000 m3,and most of the suspended load will enter the Wonogiri reservoir.

On the other hand, sediment material in front of the intake facility of the dam is silt or fine particles of clay.If the urgent countermeasures for sedimentation in the reservoir of the Wonogiri multipurpose dam aremade, it would be critical that the above suspended load of silt and clay be trapped and controlled in theKeduwang River basin. The conceivable countermeasures on these are as follows:

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(a) To reduce sediment production volume by restraint of soil erosion through improvement of agriculturalactivities,

(b) To prevent the delivery of sediment from tributaries by construction of hillside works, gully plug works,and small-scaled earth dams to store the sediment,

(c) To expedite the deposition of fine sediment particles by reducing the slope of the river bed with riverstructures to slow the velocity of the river flow,

(d) To reduce the suspended load entering the Wonogiri multipurpose dam by constructing middle-scaleddams in the upstream part and stopping the fine particle soil, and

(e) To reduce the suspended load entering the Wonogiri multipurpose dam by means of by-passing thesuspended load through a sand flushing tunnel and canal to be constructed between the Keduwang Riverand the Baran River located down-stream of the Wonogiri dam.

However, these countermeasures are regarded as middle and the long term ones and do not meet thedescription of urgent countermeasures.

Therefore, even if the two check dams are constructed in compliance with the request, their usefulness asurgent countermeasures against sedimentation in the Wonogiri multipurpose dam reservoir (the AssistanceProject) could not be agreed because the reduction of the suspended load entering the Wonogiri dam wouldbe minimal.

2) Providing dredging system

Possible methods of dredging to be provided to PBS are compared in terms of their potential sustainabilityin Table 2.2.2. According to this table, the following are identified as applicable:

· Ordinary type sand pump dredger or grab bucket, and

· Hydro-type dredging system, which is recently being utilized by GTO Sediment As Company inNorway consists of Hydro-J System and Hydro-Pipe System.

(a) Sand pump dredger

In order to prevent the inlet portion in front of the intake facility of the Wonogiri dam being buried bysediment, dredging work (about 40,000 m3) shall be made annually in front of the intake facility. For thisdredging works, excluding the existing garbage, a sand pump dredge of more than 1,000 horse power (H.P.)would be required and the annual cost is estimated to be Rp. 1,740 x 106 as shown in Table 2.2.3. Further,if a grab bucket were used, the efficiency for dredging fine sediment is low, so the annual O&M cost wouldbe more than for a sand pump dredge.

It will be difficult for this cost to be financed from the O&M budget of Jasa Terta I Public CooperationBengawan Solo Branch Office (PJT-IBS), which is not scheduled to be commence operation until January,2002. The central government will need to subsidize the cost and make the necessary budget provisions..However, it is judged to be difficult at the moment for the central government to assure this new budgetinto the future, so if a sand pump dredge was provided under Japanese grant aid there is too much riskthat it would go unused through lack of GOI funding.

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(b) Hydro-type sand flushing system

The hydro-type sand flushing system has been designed to remove sedimentation to the downstream bywashing out water together with sediment by use of a siphon. Hence, the annual O&M cost is estimated atRp. 210 x 106 as shown in Table 2.2.4., about 12% of the cost of using a sand dredge.

However, this system has been applied to only two projects in the past; one is an oil well in the North seausing Hydro-J Type and another is Jhimruk hydropower project (12 MW) in Nepal using Hydro-PipeSystem. In Japan, a test of this Hydro-type dredging system is scheduled to be made in the Sakuma damin November, 2001, but this type has few examples actually utilized in projects and has unknownreliability.

(c) Application to Japan’s Grant Aid

The applicability of different dredging systems for the sediment removal works in the Wonogiri reservoirare examined above. However, it is judged to be unjustified at the moment to provide either system fromthe viewpoints of O&M cost and technical reliability.

Further, it is judged that it will continue to be difficult in the future to procure the budget for the largeO&M cost required for sustainable dredging of the Wonogiri reservoir under the present economicconditions in Indonesia (refer to 2.4.2(6) of the report). Therefore, the hydro-type dredging system, whichis lower in O&M cost, is one alternative for sustainable sediment removal that could be applied in thefuture.

(d) The requested components from GOI and selected components are tabulated below.

Requested Components and Selected Components

Requested component Selected component1) Construction of two check dams on the

Keduwang River (rejected)

2) Provision of a dredging system (rejected)

3) Urgent dredging work in front of the intake 1) Inspection and repairing of intake gate,emergency release valve and spillway

2) Urgent dredging works in front of theintake (251,000m3)

3) Installation of floating log boom

4) Providing echo sounding survey equipmenttogether with GPS navigation equipment

(2) Requirement to Japanese assistance (the Assistance Project )

1) Inspection and repairing of gates and valve

In order to conduct the urgent dredging works and secure the safety during the dredging, the followinggates and valve may need to be operated, and if so, they will need to be working reliably. Hence, prior tothe commencement of the urgent dredging works, they should be inspected and, if necessary, repaired dueto the following reasons (refer to Fig. 2.2.1):

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· Intake coaster gate· Emergency releasing hollow jet valve· Spillway gates

(a) During the removal of garbage plugging the trashrack of the intake facility, the surroundingsediment will need to be flushed by operation of the hollow jet valve at the downstream. If thisflushing works will be made through the power station, there will be a possibility that the casingand draft tube of the turbine may be abraded and damaged, then the operation of the hollow jetvalve for this flushing works should be made. Therefore, prior to the commencement of thisflushing works, the possibility of this hollow jet valve operation should be confirmed.

(b) During the above flushing works, and the dredging works in front of the intake facility, there willbe a strong possibility that garbage, sediment and other obstacles may enter the headrace tunnel.If this occurs, the inner portion of the head-race tunnel should be cleaned after first emptying it byclosing the intake coaster gate. Therefore, prior to the commencement of this dredging works, theoperability of this coaster gate should be confirmed.

(c) If irrigation water needs to be released during the garbage removal and dredging works, whichrequire the closing of the intake facility, , then it can be released through the spillway. Hence, theremoval works of the garbage and the dredging works are likely to frequently be made conductedwhile irrigation water is being released through the spillway. Any of the four spillway gates canbe operated as required depending on the location of the dredges, sand draining pipes andassociated equipment.

(d) According to the interviews conducted during the Field Works, during the rainy season, PBSfrequently operates the spillway gates to control the water level in the reservoir. However, toguarantee safety during the construction, inspection, and if necessary repair, of the spillway gatesis necessaryas a part of the Assistance Project.

Timing and period of inspection and repair are as follows:

Inspection of these gates and valve shall be made during the period of the Detailed Design stage by two (2)mechanical engineers, one (1) control device engineer and one (1) hydraulic jack engineer. The requiredman-months for the home works and the field works are estimated at 3.0 M/M in total

Timing and period of any repair works are to be decided based on the inspection results.

2) Urgent dredging and removal of garbage

(a) Area and work quantities of the dredging works

a) Area of dredging works

The area to be subjected to dredging is to be decided in consideration of the following:

i) Restoration of the approach channel to the intake facility.

The approach channel should be restored to the original design.

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ii) New construction of a waterway channel to take water from the Bengawan Solo River into the intakefacility at times when the reservoir water level is equal to or below EL.127.0 (i.e. LWL)-130.0 m.

In the upstream portion of the existing intake facility, the width of the waterway channel should be 3.0 mequal to that of the approach channel to the intake facility taking into consideration the ease of dredging.The side slope of the waterway channel should be 1:4.0. According to the simple model test conductedduring the Field Works, the angle of repose of the sediment material was 15 degrees.

The waterway should be extended upstream by 10 m from the location where the present sediment level isthe same as the low water level (LWL) of EL. 127.0 m, taking into account the accuracy of the echosounding survey. The slope of the upstream end should be 1:10 gentler than the angle of repose.

iii) Construction of flat yards of EL. 126.0 m, being lower by 1.0 m than the LWL of the reservoir. This alsoconsiders that EL. 128.0 m is the original design elevation of the fore-bay for the spillway. The flatyards are to prevent the large quantities of sediment from continuing to enter the portion in front of theintake facility and the approach channel after they are dredged.

The temporary coffer dam used for the intake construction, which has a crest elevation of EL. 126.0 m, andthe embankment for the railway remain on the right bank of the intake facility. Using the surroundingarea of these structures, the flat yard of EL. 126.0 m that is the same elevation as these structures and islower than the LWL by 1.0 m will be constructed. At portions lower than EL.126.0 m, the dredging willbe made to achieve the original topography.

Out of the flat yard of EL. 126.0 m, the dredging works will be made following the angle of repose of thesediment material. At the above portion of the main dam higher than EL. 126.0 m, the sediment will beremoved up to the dam body.

In accordance with the original design, a fore bay of EL. 128.0 m has been constructed on the left bank ofthe intake facility. Therefore, the dredging works will be made up to EL. 128.0 m in this area

b) Work quantities for the dredging

The work quantities for the dredging have been estimated based on the cross sections for dredging shown inFig. 2.1.1 (refer to Appendix 6.2) and as below.

Dredging Quantities

(Unit:m3)

Locations Work Quantities

Approach channel + Flat yard in the right bank 103,000

Fore bay（in front of spillway） 26,000

New waterway portion 75,000

Total 204,000

However, the above has been estimated based on the echo sounding survey results in September, 2001 andnew sediment inflow to the dredging area is expected to occur between then and the completion of thedredging works (about 2 years). The sediment inflow amount is estimated from the following:

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· The sedimentation level in front of the intake facility has risen by 1.1-3.8 m in the 2 years fromDecember, 1999 to August, 2001.

· PBS is to dredge about 96,000 m3 of sediment from the stretch in front of the intake facility to theKeduwang River in the two years of 2001-2002.

· The area of dredging work is approximately assumed to be 300 m x 130 m.

· The expected sediment inflow to the urgent dredging area for three (3) years (three times rainyseasons) from now (QI)

QI = (Sedimentation inflow from the Keduwang River to the portion in front of the intake facility) –(dredging amount to be made for two years of 2001-2002 by PBS)

= ((300 m x 130 m x (1.1 m + 3.8 m) / 2) /2) x 3 – 96,000 m3

= 47,000 m3

Accordingly, the sediment volume to be actually dredged is 251,000 m3.

(b) Construction method

The construction method should be decided taking into consideration the following:

· Dredging equipment that can be easily procured should be selected due to the urgency of the work.

· The construction method should be selected in consideration of the timing of the contract with thecontractor as this will greatly affect the dredging works because of the construction conditionssuch as weather, reservoir water level and river flow discharge being varied due to the seasons.

· The sedimentation of about 250,000 m3 in front of the intake facility should be dredged urgently.

· The dredging works in front of the intake facility should be made considering the affects of theoriginal topography/geology, the shape of the sediment deposited at moment, characteristics of thesediment, and the reservoir water level

a) Condition of construction

The construction method is restricted by the procurement of the construction equipment, locations of thespoil bank, and depth of the dredging works. Regarding these issues, the following should be considered:

i) Procurement of the construction equipment

To have equipment order-made requires much time for the design and the manufacturing, so no suchequipment would be adopted in the construction plan. Only equipment usually available in the marketwill be used for the construction.

ii) Locations of spoil bank

The dredged sediment is possibly washed out to the Bengawan Solo River in the downstream, however,from an environmental viewpoint, this will be preferably adopted in the rainy season when the discharge ofthe river water has increased. Hence, to allow their use throughout the year, the spoil banks should beproposed on the land without washing out the dredged sediment to the downstream by the river.

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iii) Depth of dredging works

The reservoir water level varies in the range from EL. 136.0 m in the rainy season to EL. 127.0 m in the dryseason. Further, as the deepest elevation of the dredged area is EL. 116.0 m, the depth of dredging will be20.0 m (EL. 136.0 m – EL. 116.0 m = 20.0 m). This will be considered in the selection of availabledredging equipment.

iv) Topography in front of the intake facility

In the stretch of about 130 m length in front of the intake facility, the approach channel for the waterwaywas originally constructed by open cut excavation to rock. The bottom elevation is at EL. 116.0 m, thewidth is 3.0 m at the bottom, the side slope is 1:0.5, and the height is 12.0 to 0.0 m. On the slope, twoberms of EL. 122.0 m and EL. 125.0 m have been constructed and the widths are 3.0 m and 1.0 m,respectively.

At the location just in front of the intake facility, at the start of the approach channel, a concrete overflowcrest with a height of 1.5 m and crest elevation of 117.5 m has been constructed.

v) Properties of sediment

Properties of the sediment can be judged to be the same or similar to the material of the dredging workcarried out by PJT-I. This is mainly silt material composed of fine particles in which lumps of hard clayare sometimes found. Very little sand and gravel is included.

vi) Existence of garbage

The floating log boom had been damaged for the first time in 1983 two (2) years after the dam wascompleted. For the period of some years after 1983, the floating log boom had been repaired andmaintained, however it has not been in place since 1988. Accordingly, during every rainy season, muchgarbage has accumulated in front of the intake facility of the dam.

This garbage has not been washed out through the spillway, and although PLN tried to remove it manually,the annual amount has ranged from tens to hundreds of cubic meters. Much of this remaining rubbish hasaccumulated near the intake facility of the dam.

This garbage has been plugging the screen of the intake facility and has accelerated the sedimentation infront of the intake facility. According to the inspection through the gate slot for the intake gate conductedduring the Field Works, sedimentation of the sediment material and the garbage was not apparent in thehead-race tunnel after the screen of the intake facility.

According to interviews with PLN staff, the accumulated garbage in front of the intake facility is estimatedas follows:

· Annual accumulation; 100 m x 100 m x 0.6 m = 6,000 m3

· Period for the garbage to gather; 2000 year – 1988 year = 12 years

· Accumulated garbage; 6,000 m3 x 12 years = 72,000 m3

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b) Dredging method

i) Selection of dredging system

Dredging systems are generally classified as follows based on the type of dredging machines used.

The dredging system for this project has to be selected from the following point of view.

· Ease for procurement due to urgent work of this dredging· Possibility of transportation· Topography· Dredging depth· Condition of sediment material· Garbage

There are few sets of dredging equipment that are either available or not too large to apply to this project,which is urgent dredging work in an inland reservoir. The comparative study result of dredging systemfor urgent dredging work is shown in Table 2.2.5. The barge and crane with grab bucket, which canremove all kinds of soil and garbage is the most suitable dredging system for this project for the followingreasons:

· It can easily cope with the variation in water level and dredging work can be carried out in deepwater. (Maximum water depth to dredging work at site is 20 m.)

· It is supposed that garbage makes up about 30% of the sedimentation, and the location of garbagecan not be identified near the intake facility.

· This system has the advantage of being able to dredge garbage

D redgingSystem

D redger

B arge

D rug suction dredger

Pum p dredger

C utter dredger(un-self-m obile, Large)

Loading pum p dredger(U n-self-m obile)

C utterless pum p dredger(U n-self-m obile)

Ejector dredger

M icro pum p dredger

B ucket dredger

D ipper dredger

B ackhoe dredger

G rab dredger

B arge + B ackhoe

B arge + D rag-crane

B arge + C rane(w ith sand pum p)

B arge + C rane(w ith grab bucket)

B arge + C rane(w ith H ydro-pipe)

C utter dredger(un-self-m obile, Sm all)

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ii) Air compressing sediment transportation work and removal method of garbage

The construction method for the dredging work and the transportation work of the dredged material bycompressed air sediment transportation equipment, and the removal of garbage are as follows:

- The barge (18.4 m x 31.6 m) is built by assembling the Uni-float (Size of one piece is 2.6 m x 5.3m x 1.5 m; Total 42 pieces). A 160 ton crane is used for assembling the Uni-float.

- 80 ton crane is installed on the barge and 3.5 m3-grab bucket will be attached to the 80 ton crane,and the dredging work is carried out by using this 3.5 m3 grab bucket.

- The dredged sediment (including the silty-sand or silty-clay and the garbage) will be thrown to thevibration screen.

- The dredged sedimentation will be separated into garbage and silty-sand or silty-clay by thevibration screen.

- The garbage separated by the vibration screen will be transported to the bank by barge. Aftertransportation to the bank, the garbage will be loaded onto a 4 ton truck with 2 ton crane by 40 toncrane and transported to the second spoil bank by 4 ton truck with 2 ton crane.

- The separated silty-sand or silty-clay, which passes through the vibration screen, is transported bycompressed air sediment transportation equipment to primary spoil bank (About 2 km).

- After the draining of water and drying the dredged sand, the dredged silty-sand or silty-clay will betransported to the secondary spoil bank by 10-ton dump truck. The drained water generated fromthe dredged silty-sand or silty-clay at the primary spoil bank is returned to the reservoir throughφ 600 mm concrete pipe.

c) Spoil bank

Spoil bank is designed to consider the following items.

· The dredged sediment is dumped in a spoil bank because the possibility of disposing them into thedownstream Bengawan Solo River cannot be decided until the environmental impact assessmentsurvey is finished.

· The selected primary spoil bank location, which is owned by PBS, is downstream of the sub damincorporates the present spoil bank area for dredging work performed by the PJT-I (refer toFig.2.2.2). However, a secondary spoil bank is needed because the capacity of the primarylocation is too small for the anticipated sediment volume. It is necessary that dredged material istransported and dumped at a secondary spoil bank after temporarily storage at the primary spoilbank.

· A secondary spoil bank location of about 40 ha is available about 1 km downstream of the rightbank of the Bengawan Solo River, and it’s the land is owned by PBS. Therefore, land acquisitionfor the spoil bank is not necessary. (Refer to Fig. 2.2.2)

· The pipe length for sediment transportation is about 2.0 km, and the distance of transportation bydump truck is about 1 km from the primary to secondary spoil bank. Construction of a dykes anddrainage system is necessary at the primary spoil bank.

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d) Construction equipment

Major construction equipment for this dredging work is shown below.

Equipment used for the dredging work

Construction Equipment Specification Number[Dredging Work]1. Barge with grab bucket

+ Compressed air sediment transfer equipmentGrab bucket 3.5 m3

80 t class crawler craneCompressed air sediment transportation

equipment (120 m3/h)

111

2. Tug Boat 200 PS 13. Anchor Barge 5.0 t 14. Earth Carrying Barge Capacity 80 m3 15. Commuter ship 30 PS 16. Pipe for dredging the sand 350 mm, about 1,500 m 1

[Garbage Transfer](From barge to Secondary spoil bank with transfer frombarge to truck at a temporary embayment and dock)7. Crawler crane 40 t 18. Dump truck 4 t 1

[Compiling soil]（At primary spoil bank）9. Bulldozer (for swamp) 19-20 t 2

10. Backhoe (flat loading) 1.0 m3 2[Transportation of soil](From primary spoil bank to 2nd spoil bank)11. Dump truck 10 t 6

[Compiling soil]（At secondary spoil bank）

12 Bulldozer 1

(c) Dredging period

The working area consists of the intake area, fore bay of the spillway, new intake waterway, and the flatplane at the right side of the intake. The dredging work will be able to be carried out throughout the yearin principle, but will need to be executed at different times for the different areas depending on the waterlevel of the reservoir as follows:

a) Intake area

Removal of garbage by divers and dredging of garbage and sediment by the grab dredger shall be carriedout at the intake area. During the dredging works of this area, it will be necessary to close the waterintake and supply water for irrigation and power generation through the spillway. Therefore, the dredgingwork in this area has to be carried out when the reservoir water level is higher than the spillway crest levelof EL.131 m.

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b) Fore-bay of spillway

The dredging work in this area has to be carried out during the dry season because the spillway gates aresometimes operated during the rainy season. If the spillway gates are operated to release the flooddischarge, it will be dangerous to execute the dredging work near the spillway.

c) New approach channel to the intake

The dredging of the new approach channel to the intake from the Bengawan Solo River can be executed atany time. However, it is desirable that this work is carried out when the water level is as low as possiblebecause this area has to be dredged down to EL.116 m which is 11m lower than the low water level (LWL)of the reservoir.

d) Flat yard on the right bank of the intake

The dredging work of the flat yard can be executed at any time.

(d) Effective period of the urgent dredging works

If no countermeasures are made after the urgent dredging works, the period of effectiveness of the urgentworks is estimated to be about five (5) years for the following reasons:

a) Sedimentation level in front of the intake facility

The sediment level has increased by 1.1 m in front of the intake screen and by 3.8 m at the greatest pointover a period of twenty one (21) months from December 1999 to August 2001. It is assumed thatobstruction of the intake began to occur around 1999. The sediment level when intake obstruction beganis assumed to be EL.123.0 m based on the results of echo sounding survey in 1999.

b) Rate of sediment accumulation in front of the intake facility

According to the results of the echo sounding survey in 2001, sediment accumulation is likely to be smallerjust in front of the intake facility and greater in the middle portion of the approach channel to the inlet ofthe intake facility. Estimation of the rate of sediment accumulation in front of the intake facility is madebased on the average sedimentation rate. Hence, the rate of sediment accumulation in front of the intakefacility is as follows:

(3.8 m + 1.1 m)/ 2/ 21 months x 12 months = 1.4 m/year

c) The expected duration of effectiveness of urgent dredging and garbage removal

The effective period is assumed as follows:

(EL. 123.0 m – EL. 116.0 m)/1.4 m/year = 5 years

3) Setting of floating log boom

The floating log booms to be placed around the intake facility will effectively prevent garbage fromentering the intake. The layout of the floating log boom is shown in Fig. 2.2.3. In the design, the ratio ofmaximum deflection against the span length should be about 1/5 so that the diameter of the wire cable maybecome as small as possible.

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A-line : Main purpose of this line is protection against the garbage from the Keduwang river. Bothends of the floating log boom are fixed by a concrete anchor block. The span length is about100 m

B-line : Main purpose of this line is protection against the garbage from the Bengawan Solo river. Theleft and right side anchor blocks are used together with A-line and C-line, respectively. Thespan length is about 105 m.

C-line : This line is set parallel to the left side slope of the flat excavation area (EL. 128.0 m) in the fore-bay of the spillway. This line will direct the garbage from the Bengawan Solo river to thedownstream through the spillway. Therefore, the garbage is judged not to be trapped along thisline during flood occurring in the rainy season. The span length is about 110 m.

D-line : This line will not trap much garbage. However, it would be set to prevent garbage that mayaccumulate in front of the spillway from moving to the inlet portion of the intake due tolowering of the water level in the reservoir or by wind and waves. The span length is about105 m.

4) Provision of Echo Sounding Survey System with GPS Navigation Equipment

Regarding the provision of the system, the followings should be key points:

(a) Position of the survey boat is measured by using global positioning system (GPS) and the accuracy is tobe within 1m by circle error probability (CEP). When a single GPS navigation unit is used on the surveyboat, the accuracy of the measurement is usually estimated to be 20-30 m. This positioningmeasurement would be meaningless for the echo sounding survey in front of the intake. Therefore, onefixed base station to enable differential GPS (DGPS) would be set at an unobstructed location near theintake facility, then the error correction of GPS on the survey boat could be made by using the DGPS atthe fixed station. Then the positioning measurement of the survey boat could be made within the error of1 m by CEP.

(b) The echo sounding survey shall have the accuracy of less than 10 cm. In this survey, sound wave wouldbe shot to the bottom of the reservoir by the echo sounder, the reflected sound wave would be captured bythe echo sounder on the survey boat, the reflecting time would be measured and the water depth would beestimated. The important thing is that the reflection layer of the sound wave depends on thecharacteristics of the sediment layer deposited in the reservoir. At the moment, the PBS’s survey usingan old echo sounder, a sound wave of 50-60 Hz is used.

(c) The measured data are those of the positioning of the survey boat and of the echo sounding survey at thesurvey boat, and in order to collect these data, a portable computer would be required. Also, thecomputer program for the prompt data process and preparation of the contour map of water depth in thereservoir would be installed into the computer.

(d) The survey boat, presently being used for the echo sounding survey by PBS is judged to be available forproviding this echo sounding survey system. (Obligation of Indonesian side)

The principal composition of the above echo sounding survey system provided by Japan’s Grant Aid (theAssistance Project) are shown in Fig. 2.2.4 and below:

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Echo Sounding Survey Equipment

Items Quantities(1) Echo sounder 1 set(2) Portable computer for data collection（computer program for preparation of the contour map in the reservoir installed） 1 set

(3) Movable GPS station on the survey boat1) Two (2) wave frequency type, geodesic receiver 1 set2) Two (2) wave frequency antenna 1 set3) Wireless receiver 1 set

(4) Stationary GPS station1) Two (2) wave frequency type, geodesic receiver 1 set2) Two (2) wave frequency antenna 1 set3) Terminal for geodesic receiver in Item 4.1) 1 set4) Large scale battery 1 set5) Wireless transmitter 1 set

Note; If a beacon radio wave similar to that transmitted from airports or harbors in Japan is available at the

Wonogiri dam site, the stationary GPS station can be omitted.

2.2.3 Basic Design Drawing

Design drawings of the urgent dredging works and layout of the floating log booms are shown in Figs.2.1.1 and Appendices 6.2, and Fig. 2.2.3. Further, the composition of the water depth survey system isshown in Fig. 2.2.4.

2.2.4 Implementation Plan

(1) Principle for implementation

1) Principle for implementation

The Project would be implemented on the following conditions in consideration of application for Japan’sGrant Aid system.

(a) Director General of Rural Development, Ministry of Settlement and Regional Infrastructure(KIMPRASWIL) in Indonesia would be the executing agency for the Project implementation.

(b) Immediately after the Exchange of Note (E/N) between GOJ and GOI regarding the stages of thedetailed design and the construction works is signed, the KIMPRASWIL should commence thenecessary actions for the implementation of the Project.

(c) A Japanese Consultant firm, recommended by the Japan International Cooperation Agency (JICA)should be entrusted by the KIMPRASWIL and should prepare the detailed design and tenderdocuments for the selection of the Japanese Contractor for the civil works. Immediately after thecompletion of the preparation, the Japanese Consultant should start the tendering works.

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(d) GOI should commence the arrangement for the land acquisition in parallel with the detailed design,if necessary.

(e) A Japanese Contractor immediately after signing the contract for the construction works with theKIMPRASWIL shall commence to undertake the construction works and the Japanese Consultantshall execute the construction supervision.

2) Formation of construction and provision of equipment

In Indonesia, several Japanese Contractors have been engaged in the construction works of projects underJapan’s Grant Aid Program. These contractors have employed local contractors as subcontractors, mostlyfor the purpose of manpower supply and rent of construction equipment.

In the Assistance Project, the construction works are planned to be performed on the basis that the Japanesecontractor arranges construction equipment and material by itself and also uses the manpower suppliedfrom the subcontractors.

3) Necessity of Japanese engineers in the contractor

The construction works and provision of equipment would consist of the following construction works:

· Repairing of gates and valve if required· Urgent Dredging Work and Removal of Garbage· Setting Works of Floating Log Boom· Provision of Echo Sounding equipment with GPS navigation equipment

Taking into account the quantities of construction materials, construction period and site conditions such asthe rainy and dry seasons, and the water intake function for irrigation having to be maintained during theconstruction works, the following Japanese engineers should be assigned to the Assistance Project.

· Manager· Civil Engineer (Dredging Work)· Mechanical Engineers (Repairing Gates and Valve if required, and Dredging Work)· Civil Engineer (Floating Log Boom）

(2) Conditions for implementation

1) Maintaining the water intake function from the reservoir of the dam to the down-stream

The dredging work for the Assistance Project shall be carried out on the conditions that the water intakefunction from the reservoir be maintained to supply irrigation water to the 30,000 ha in the downstreamirrigation area. Also, the dam operating rule of the restricting the water level to EL. 135.3 m for floodcontrol in the rainy season must be strictly followed. The present situation of the Wonogiri power stationand the Wonogiri irrigation system are described in 1.3 of the report.

It is unavoidable that the operation of the Wonogiri hydro-power station be stopped for 3-4 months fordredging work in front of the intake to be carried out because during this period water will not be able to betaken through the intake.

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2) Environmental impact caused by construction

Generally the following issues will be assumed as the environmental negative impact.

· Impact of noise· Impact of dust· Impact of vibration by heavy Equipment· Impact by traffic accident

Even though there are few facilities in the construction site of the Assistance Project to which the impact ofnoise and vibration provide serious affect to, the consideration of the impact to the people living in andaround the site will be very necessary. Thus, nighttime construction work should be prohibited.

The spread of water on the road should be carried out for dust protection caused by truck and heavyequipment.

As the protection of traffic accident, the following countermeasures should be carried out:

· Installation of instruments to limit the vehicle speed· Safety training of drivers,· Regular safety meetings· Putting safety control persons in the field to prevent traffic accidents

3) Security for construction

Considering the construction period, the construction should be carried out even in the rainy season. It isrecorded that the spillway gates are operated on average 30 times in the rainy season (December to April)for the flood control, and the frequency of the operation has increased year by year since 1998. The safetycountermeasures during construction should be strictly made, especially in the rainy season because theconstruction in the rainy season is very dangerous.

(3) Scope of Works

1) Scope of works to be executed by Japanese side

(a) Detailed design and preparation of the tender documents

(b) Undertaking the construction supervision and provision of equipment, described in 2.2.2 of thereport (excluding the works to be executed by the Indonesian side shown below)

2) Undertaking by the Government of Indonesia (GOI)

(a) Preparation of an FRP boat with outboard motor for echo sounding survey

(b) Land acquisition (if necessary)

(c) Budget arrangement and payment for import tax, internal tax, and other levies underimplementation of Japan Grant Aid project (the Assistance Project)

(d) Coordination with other relevant agencies and issue consent(s) necessary for implementation of theAssistance Project

(e) Improvement of operation and maintenance for the Wonogiri multipurpose dam and the Wonogiriwater power station

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(4) Plan of the detailed design and the construction supervision

1) Preparation of the detailed design and the tender documents

Prior to the commencement of the implementation of construction work, the detailed design andpreparation of tender documents will be required.

Immediately after signing the E/N between GOJ and GOI for the detailed design and the constructionworks, the contract for the consulting services will be concluded between the KIMPRASWIL and theJapanese Consultant. The detailed design and tender documents will then be prepared in collaborationwith the KIMPRASWIL.

The Consultant will discuss the design and implementation schedule of the works with the KIMPRASWILduring the first field investigation. At the detailed design stage, the following works will be done:

(a) Additional investigation based on the basic design

· Inspection of gates and valve· Re-check of sedimentation volume to be dredged· Investigation of sediment property to be dredged by conducting four (4) corings· Survey of land utilization, topography and access road in the candidate spoil bank yard· Investigation on availability of the navigational beacon radio signal at the Wonogiri damsite, which

may be used in place of the stationary GPS station for the water depth survey

(b) Preparation of the detailed design

· Detailed design based on the basic design and the additional investigation/ survey results· Review of the implementation cost of the Assistance Project through the detailed design

(c) Preparation of the tender documents

· Preparation of the tender drawings· Preparation of the tender documents for the construction works

2) Tendering and construction supervision

After the completion of the detailed design and the preparation of tender documents, the JapaneseConsultant will start the tendering works in collaboration with the KIMPRASWIL at first.

The scopes of the construction supervision are summarized as follows:

(a) Evaluation and approval of construction drawings

Evaluation and approval of construction drawings, sample of materials, specifications of the constructionequipment, etc. submitted by the contractor.

(b) Guidance of the construction works

Checking and guidance on the construction plan and time schedule, quality control and progress of theconstruction works and necessary inspection of the construction works

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(c) Approval for the payment to the contractor

Checking and evaluation of the performance of the works necessary for issuing payment certificates andcompletion certificate to the Contractor.

(5) Plan of the quality control

(a) Measurement for payment for the dredging works

The Contractor shall make measurement for the dredging works in presence of the Japanese Consultants bya suitable method and equipment proposed by the Japanese Contractor. All costs shall be borne by theContractor.

(b) Effect liability period

The effect liability period shall be one (1) year after the issuing of the certificate regarding the handing overto the KIMPRASWIL by the Consultant.

(6) Plan of procurement for the construction material and equipment

The major construction materials required are cement, aggregates, crushed stones and plywood form.These materials are available in Indonesia and the quality and procurement are usually satisfactory. Inaddition, the ready mixed concrete will be available near the construction site (the Wonogiri multipurposedam).

The dredging work and earthwork are of a major scale. Considering the condition that most of therequired construction equipment for the construction works can be rented from lease companies inIndonesia, and the construction period is short (18.5 months), the required construction equipment will beleased for this construction works in principle. The compressed air sediment transportation equipment(120 m3/h) is very special and the rent is impossible in Indonesia. So this equipment will be importedfrom Japan.

(7) Implementation Schedule

(a) Stage of the detailed design

FY 2001 FY 2002 FY 2003

・Detailed design 3.0 months － －

・Preparation of tender document 3.0 months － －

(b) Stage of the construction

FY 2001 FY 2002 FY 2003

・Tendering 2.0 months － －

・Main construction works － 7.0 months 11.5months

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As mentioned in 2.2.2(2)2) of this report, the dredging work volume for the Assistance Project is estimatedto be around 251,000 m3, including 72,000 m3 of garbage, and one (1) barge with grab bucket (3.5 m3) shallbe adopted as the dredging equipment. As the working area is limited, more than two (2) sets of dredgingequipment could not be efficiently workable. The construction period is estimated in the followingmanner and will take 18.5 months in total:

- Preparatory works :　1.0 month- Transportation, embarkation and erection of the main equipment　:　4.0 months- Dredging works :　10.0 months

1,013 m3 (Daily dredging rate) x 30 days x 0.82 (Efficiency) = 24,919 m3/month250,000 m3 (Dredging volume in total) / 24,919 m3 (Monthly dredging rate) = Around 10.0 months

- Setting floating log boom　:　1.0 month- Disassembling dredging equipment and clearing the construction site　:　2.5 months

The construction schedule is shown below.

month 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Detail Design

Stage

Construction

Stage

2.3 Obligations of Recipient Country

Obligation of recipient country (GOI) for the implementation of the Assistance Project are as follows:

(1) To secure the land necessary for the execution of the Assistance Project, such as the spoil banks(44 ha in total for the two (2) spoil banks), land for temporary offices, storage yards and others

(2) To carry out environmental impact assessment (EIA) for the Assistance Project

(3) To guarantee 3 - 4 month’s suspension of the Wonogiri power station operation during thedredging work at the intake

(4) To arrange the staff of PBS and the budget for the implementation

(5) To bear commission of the Japanese foreign exchange bank for its banking services based upon thebanking arrangement, namely the advising commission of the “ Authorization to Pay” and paymentcommissions

(6) To ensure prompt unloading and customs clearance for ports of disembarkation in the Governmentof Indonesia and prompt internal transportation therein of the materials and equipment for theAssistance Project purchased under the Japan Grant Aid.

(7) To exempt Japanese juridical and physical nationals engaged in the Assistance Project fromcustoms duties, internal taxes and other fiscal levies which may be imposed in Indonesia with

(Detail Design)

(Preparation of Tender Document)

(Tender)

(Construction)

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respect to the supply of the products and services under the Verified Contractor

(8) To accord Japanese nationals whose services may be required in connection with the supply of theproducts and services under the Verified Contract such facilities as may be necessary for their entryinto Indonesia and stay therein for the performance of their works

(9) To provide necessary permissions, licenses and other authorizations for implementing theAssistance Project, if necessary.

(10) To maintain and use properly and effectively the facilities constructed and equipment providedunder the Assistance Project

2.4 Project Operation Plan

2.4.1 Required Maintenance and Management Issues

After completion of the Assistance Project, following main O&M issues are required:

· Water depth survey near the intake facility by the echo sounding survey equipment

· Removal of garbage from near the intake facility including the screen

(1) Water depth survey

The echo sounding survey will need to be carried out once a year at the end of rainy season near the intakefacilities, and the additional survey shall be carried out along the Keduwang river in the reservoir area atthe start of dry season. The sedimentation situation near the intake facility and along the Keduwang rivershould be well-described and understood. The sedimentation into the reservoir from the Keduwang rivercan be considered to have the worst affect, badly obstructing the intake facilities. It is stronglyrecommended that the survey results be informed to the Japanese side (JICA Tokyo or the Consultant) afterevery survey.

(2) Removal works of garbage near the intake facilities

During the flood at the start of the rainy season, a huge amount of garbage together with the flood will flowinto the reservoir from all the tributaries. If the Wonogiri multipurpose dam had not been constructed, thegarbage from all the tributaries would flow down to the downstream. Therefore, the garbage arerecommended to be released to the downstream together with overflow water through the spillway as muchas possible. The volume of such overflow water will be minor compared to the volume of water stored inthe reservoir, so the loss for operation can be regarded as insignificant.

However, as not all the garbage could be put down-stream, some garbage will remain at the floating logboom and in the reservoir. Of the garbage that is not discharged, that trapped by the floating log boomsand the screen of the intake should be collected manually by boat, unloaded and transported to thedesignated incinerator in the same manner that PLN does at present.

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2.4.2 Operation and Maintenance Organization

A part of PBS is to be incorporated into the Jasa Tirta I Public Corporation (PJT-I) in accordance withpresidential decree (No.129/2000), and this was scheduled to occur in January 2001. However, it has notbeen realized so far and the PJT I Bengawan Solo (PJT-IBS) will be established in January, 2002 accordingto the hearing survey. Therefore, O&M works of the Wonogiri multipurpose dam after the constructioncompletion will be executed by PJT-IBS, and the equipment provided by the Assistance Project will also betransferred to PJT-IBS.

The principal responsibilities, target river, personnel and O&M works of PJT-IBS are mentioned belowbased on CDMP Study and SAPS reports.

(1) Principal responsibilities

· O&M of infrastructure for water resources development, and· Conducting the small scale rehabilitation of the above structures.

To gain proper profit through the above O&M with due regard for the necessity for a stable water supply tothe public by the public utilities.

(2) Target river

Twenty five (25) rivers including the Bengawan Solo river in the Solo river basin for the time being

(3) Number of personnel

About one hundred sixty (160) to one hundred ninety (190) persons

(The number of personnel will be decided in the official meeting among KIMPRASWIL, Central and EastJava province, PBS, PJT and so on.)

(4) Revenue

Main revenue of the PJT-IBS will be gained by selling the water to PLN, PDAM and factories. The watertariffs at the moment are shown below.

· Electricity (PLN) Rp. 15.66 /kwh· Drinking water (PDAM) Rp. 40.0 /m3

· Industrial water Rp. 52.0 /m3

Source　:　SAPS for 24 Infrastructure Rehabilitation Projects July, 2001

(5) Implementation organization for O&M

PJT-I carries out the O&M works with its own staff. Therefore, the O&M works of the Wonogirimultipurpose dam will be also carried out by PJT-I staff.

PJT-I can technically support PJT-IBS because it has enough knowledge and experience through the O&Mworks of dredging works so far in Wlingi dam and Sengguruh dam located in the Brantas river.

(6) Required O&M cost

A five-year financial statement was prepared in the CDMP Study and SAPS reports. According to theCDMP Study, the required O&M costs, excluding those of the Assistance Project, are shown below.

2-26

Required O&M Cost

(unit: million Rp.)Item 2001 2002 2003 2004 2005Dam· Wonogiri 523 575 632 696 765· Colo 190 209 230 253 279· Others (13 dams) 115 126 139 153 168Sub-total 828 910 1,001 1,102 1,212River· B. Solo 523 575 633 696 766· Madiun R. 261 288 316 348 383· Tributaries (2nd) 426 468 515 567 623· Tributaries (3rd) 35 39 43 47 52Sub-total 1,245 1,370 1,507 1,658 1,824Telemeter 80 120 132 145 160Office 179 210 245 286 332Total 2,332 2,610 2,886 3,190 3,527Source: CDMP Study Report

(7) Available O&M budget

The five-year financial statement is shown in Table 2.4.1 based on the CDMP Study and SAPS reports. Itis assumed that the required O&M cost of Rp. 23,700,000 /year for the Assistance Project (refer toAppendix 5) will be procured without problems from the above financial point of view.

The rejection of providing a dredging system to PBS was based upon the above financial point of view.According to the financial analysis, the required O&M cost of the hydro-type dredging system(Rp. 210,000,000 /year) could probably be arranged, but not the sand pump dredging system(Rp. 1,740,000,000 /year) (refer to 2.2.2(1)2) of the report).

2.5 Other Relevant Issue

In the course of the execution of the Assistance Project, the followings should be repeatedly pointed out:

(1) Based on the inspection results to be conducted by the Consultant during the detailed design stage, therepairing the intake coaster gate, spillway radial gates and the emergency hollow jet valve should be madeby the Contractor as required prior to the commencement of the dredging works.

(2) Investigation of the availability of a navigational beacon radio at the Wonogiri dam-site to serve as GPSbase station for the water depth survey should be made by the Consultant during the detailed design stage.If the navigational beacon wave is found to be available, the stationary GPS station could be omitted.

(3) Based on the results of the Environmental Impact Assessment study on the Dredging Works in theWonogiri multipurpose dam reservoir which is now under way and is scheduled to be completed inFebruary 2002, the possibility of the dredged material being disposed down-stream in the Solo rivershould be studied during the detailed design stage. If disposal in such a manner is found to be possible,the construction method of the dredging works in the Assistance Project should be modified.

3-1

CHAPTER 3 PROJECT EVALUATION AND RECOMMENDATION

3.1 Project Effect

The main purposes of the Wonogiri multipurpose dam are water supply (for irrigation and hydro-powergeneration) and flood control. The requested Japanese assistance (hereinafter called as the AssistanceProject) is the first steps to conquer the sedimentation problem in the Wonogiri multipurpose dam reservoirto assure the water intake function of the dam for a period of about five (5) years from the completion ofthe Project (refer to 2.2.2(2)2)(d) of this report). The Assistance Project is not designed to recover theflood control function as originally planned. For this, effective countermeasures shall be contemplatedand implemented as mid to long term countermeasures for the entire sedimentation problem in theWonogiri multipurpose dam reservoir. The beneficiaries of the Assistance Project are, therefore, the waterusers for irrigation and hydropower generation.

The effect of implementing the Assistance Project and the extent to which the present situation will beimproved are shown in Table 3.1.1.

The Assistance Project creates the direct benefit stated below. In summary, this is the maintenance ofincome of beneficiary farmers in the down-stream of the Wonogiri multipurpose dam and contributing tothe stable electricity supply to the central Java province. In so doing it will hopefully contribute to stablefood supply and social stabilization, the primary political strategies in Indonesia as described in 2.1.1 of thereport.

3.1.1 Direct Effect

(1) Irrigation water supply

1) Beneficial area and beneficiaries

The Wonogiri multipurpose dam supplies irrigation water to the 29,590 ha Wonogiri irrigation system(refer to Fig. 3.1.1), which is the beneficial area of the Assistance Project. The number of beneficiaries isestimated at 45,200 households.

2) Effect of the assistance

By implementation of the Assistance Project, it is possible to maintain the cropping area and harvest shownin the following table. However, if the Assistance Project is not implemented, the intake of the dam willbe completely blocked and the cropping area and yield will reduce as shown in the below table. The lossdue to the reduced harvest will be annually Rp. 187 x 109 at the present market price of 1,220 Rp./kg. Thisis considered to be the direct effect of the Assistance Project.

3-2

Comparison between Situation of the Present and the Intake of the Dam being Plugged

Index The Present The Intake of theDam being Plugged

Land usePaddy field (Irrigation) 27,356 ha 21,100 haSugarcane field 2,100 haPaddy field (Rain-fed) 2,233 haUpland fieldProject area 29,589 ha 23,200 haPaddy Area (Irrigation)Rainy Season 26,523 ha 19,000 haDry season-I 26,360 ha 19,000 haDry season-II 23,142 ha 11,600 haAnnually irrigated area 76,025 ha 49,600 haCropping areaPaddy（rainy season） 28,756 ha 19,000 haPaddy（dry season-I） 26,360 ha 19,000 haPaddy（dry season-II） 23,142 ha 11,600 haPalawijia & Others 1,444 ha 2,100 haAnnual cropping area 79,702 ha 51,700 haCropping intensityPaddy（rainy season） 97 % 82 %Paddy（dry season-I） 89 % 82 %Paddy（dry season-II） 78 % 50 %Palawijia & Others 5 % 9 %Annual cropping intensity 269 % 223 %Yield of irrigated paddy 5.5 t/ha 5.5 t/haAnnual rice production 425,950 t 272,800 tSource: WATSAL Feed back study

Further, as an index to assess the effect of the implementation of the Assistance Project, the cropping areaby each cropping season will be adopted. As to the yield of irrigated paddy, there are variations betweencropping seasons and large differences between official yields and those based on direct reports fromfarmers. Therefore, the yield of irrigated paddy will not be used as an index.

(2) Water supply for power generation

1) Beneficial area and beneficiaries

Power stations in the islands of Java and Bali are connected by one power supply system (Java-Bali powersupply system) and all electricity is supplied through the united power supply market. So strictlyspeaking, there is no specific beneficiary area of the Wonogiri hydropower station. However, the longerthe power transmission line, the bigger the transmission loss, so the beneficiary area is mainly consideredto be central Java province. Also, dividing the annual power generation energy of the Wonogiri powerstation (50,000 MWh) by the annual power consumption of an average household (820 kWh), the numberof beneficiaries is estimated at 61,000 households.

3-3

2) Effect of the Assistance Project

It will be possible to maintain to generate the annual power energy of 50,000 MWh as planned for aboutfive (5) year after the completion of the Assistance Project. However, if the Assistance Project is notimplemented, the intake of the dam will be fully blocked with power generation becoming impossible.The loss will be annually Rp. 10x109, estimated by multiplying the electricity sale price of 200 Rp./kWh atSeptember in 2001 by the annual power generation energy of 50,000 MWh. This is considered to be thedirect effect of the Assistance Project.

Further, the indices adopted to assess the effect of the Assistance Project are the annual power generationenergy by month, the maximum intake of water, and the number of stoppage days of power generation eachmonth.

3.1.2 Indirect Effect

There is no significant indirect effect of implementing the Assistance Project.

3.2 Recommendations

(1) According to the visual inspection conducted on 11 September, 2001 by the JICA Team, no seriousdefects to the power generation equipment (only one set of turbine and generator were inspected) werefound. However, it is more than twenty (20) years since the hydro-power station commenced operation.Therefore, in order to continue the power generation smoothly in the future, the prompt execution of anoverall inspection of both the civil structures and the power generation equipment in the Wonogiri hydro-power station is strongly recommended.

(2) In order to maintain the water intake function of the dam for the mid- or long term period after about five(5) years, the introduction of a dredging system to continue the dredging works in front of the intakefacility and installation of a mechanical raking system on the screen of the intake are stronglyrecommended after the Assistance Project is completed.

(3) As mentioned in Appendix 7.2, in order to secure the dam reservoir space for water utilization and floodcontrol for the long term, mid- and long term countermeasures such as water-shed conservation andsediment management of the Wonogiri dam reservoir, and structural measures in the reservoir againstsediment flowing into the reservoir should be studied. In particular, new construction of another intakefacility or of an inlet shaft at the inlet portion of the existing intake and so on proposed in 7.2.3(5)3) of theAppendix 7.2 could be judged to be the most realistic and most effective. The completion of these mid-and long term countermeasures shall be made in time considering the planned completion of theAssistance Project shown in the attached figure in 2.2.4 (7) of this report and the effective period of theAssistance Project (around 5 years after completion).

Tables

Basic Design Study Reporton the Project

for Urgent Countermeasuresfor Sedimentation

in Wonogiri Multipurpose Dam Reservoirin the Republic of Indonesia

Table 1.3.1 Monthly Power Output by Wonogiri Power Station

(Unit: kWh)Year Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Total1983 944,300 3,441,700 3,359,600 5,845,700 7,571,600 4,622,100 4,643,700 3,801,200 3,489,500 3,705,100 4,329,500 4,933,500 50,687,5001984 6,963,500 6,720,700 7,202,300 6,936,100 7,030,300 4,773,800 4,391,100 4,058,100 4,825,700 6,448,100 2,213,300 7,978,300 69,541,3001985 8,166,100 7,970,500 9,020,600 6,877,400 5,098,600 3,230,100 3,538,600 3,494,800 3,223,900 3,315,100 3,039,800 7,903,400 64,878,9001986 7,068,900 7,636,100 9,080,800 8,760,400 3,331,100 3,120,200 3,441,100 3,153,300 2,985,800 2,861,100 3,688,600 2,799,400 57,926,8001987 8,743,600 8,250,100 9,115,200 3,394,900 2,673,300 3,176,500 2,415,000 1,852,800 2,230,500 1,502,500 1,234,900 5,860,400 50,449,7001988 6,660,500 8,120,400 4,072,400 2,768,600 3,022,600 3,297,200 4,032,800 3,812,800 3,828,100 3,187,300 5,495,500 7,373,300 55,671,5001989 6,393,600 4,020,600 9,101,600 5,700,600 4,306,700 3,759,800 3,142,700 3,232,300 3,751,100 3,736,500 4,437,800 4,549,300 56,132,6001990 4,609,900 4,636,000 7,905,800 3,289,900 2,825,700 2,730,600 2,843,100 3,328,600 2,576,400 2,609,600 2,428,300 1,937,900 41,721,8001991 3,615,800 7,615,100 6,025,700 4,699,400 5,269,600 4,253,900 3,514,100 3,204,500 3,110,200 3,068,000 2,624,100 3,243,700 50,244,1001992 4,198,300 5,782,500 9,098,400 8,076,700 3,748,200 3,253,800 3,394,900 3,391,400 5,222,500 4,524,100 3,748,100 8,877,400 63,316,3001993 9,153,600 8,282,000 9,187,000 8,906,200 3,821,400 3,674,800 3,765,400 4,332,900 4,268,100 4,560,100 3,807,400 4,448,900 68,207,8001994 6,060,800 7,775,300 8,389,300 5,587,000 3,854,800 3,440,200 3,169,000 2,879,600 3,619,500 3,378,100 2,731,600 1,370,600 52,255,8001995 1,524,900 6,936,400 9,170,000 7,356,300 3,665,900 3,557,000 3,741,900 3,806,400 4,471,400 4,455,900 3,711,200 8,530,500 60,927,8001996 7,476,800 8,220,800 6,530,900 3,491,400 3,208,000 2,908,600 2,842,400 2,506,900 3,446,500 4,488,000 4,070,500 5,200,400 54,391,2001997 4,798,400 5,464,900 4,056,400 2,712,500 2,978,100 1,940,700 1,165,200 1,739,800 1,909,800 1,949,700 171,100 281,900 29,168,5001998 517,900 427,300 2,402,400 6,407,600 5,488,900 3,868,800 7,288,900 4,512,200 6,065,400 6,603,500 6,448,100 5,100,400 55,131,4001999 7,863,540 8,135,800 8,895,800 5,610,000 4,214,800 3,884,500 3,495,800 4,060,400 4,315,000 2,577,900 2,118,396 1,383,100 56,555,0362000 6,083,500 8,303,400 6,194,300 5,680,500 3,671,200 3,773,900 3,773,900 5,403,800 4,174,700 2,292,000 2,043,800 3,283,900 54,678,9002001 2,339,100 4,414,000 4,745,300 8,371,400 4,207,300 4,441,700 4,666,400 33,185,200

Average 5,430,686 6,429,137 7,029,147 5,814,347 4,209,900 3,563,589 3,645,579 3,476,211 3,750,783 3,625,700 3,241,222 4,725,350 55,104,830

Table 1.3.2 Cropping Area and Croping Intensity of Wonogiri Irrigation SystemWhole Right Bank Area 1/

Cropped Area (ha) Cropping Intensity (%)Wet Dry Dry Wet Dry Dry

Year Crops Season Season I Season II Annual Season Season I Season II Annual1995/96 Irrigated Paddy 20,307 20,025 15,816 56,148 96 95 75 266

Paddy Field Sugarcane 788 788 4 421,121 ha Palawija 26 308 2,374 2,708 0.1 1 11 13

Total 21,121 20,333 18,190 59,644 100 96 86 282

1996/97 Irrigated Paddy 20,616 20,369 18,990 59,975 98 96 90 284Paddy Field Sugarcane 381 381 2 221,121 ha Palawija 124 371 820 1,315 1 2 4 6

Total 21,121 20,740 19,810 61,671 100 98 94 292

1997/98 Irrigated Paddy 21,343 21,286 20,522 63,151 98 98 94 290Paddy Field Sugarcane 300 300 1 121,793 ha Palawija 150 207 332 689 1 1 2 3

Total 21,793 21,493 20,854 64,140 100 99 96 294

1998/99 Irrigated Paddy 20,969 20,907 18,907 60,783 96 96 87 279Paddy Field Sugarcane 713 101 814 3 0.5 421,793 ha Palawija 111 72 660 843 1 0.3 3 4

Total 21,793 21,080 19,567 62,440 100 97 90 287

1999/00 Irrigated Paddy 21,347 21,350 20,997 63,694 98 98 96 292Paddy Field Sugarcane 172 83 255 1 0.4 121,793 ha Palawija 211 188 421 820 1 1 2 4

Total 21,730 21,621 21,418 64,769 100 99 98 297

Average of 3 years Irrigated Paddy 21,220 21,181 20,142 62,543 97 97 92 2871997/98 - 1999/00 Sugarcane 395 61 456 2 0.3 2

Paddy Field: 21,793 ha Palawija 157 156 471 784 1 1 2 4Total 21,772 21,398 20,613 63,783 100 98 95 293

1/ Including area classified as pumping irrigation area of 1,700 ha Source: Cabang Bundungan Wonogiri, Bengawan Solo Karanganyar & Sragen

Whole Left Bank Area 1/

Wet Dry Dry Wet Dry DryYear Crops Season Season I Season II Annual Season Season I Season II Annual

1997/98 Irrigated Paddy 4,947 4,899 1,893 11,739 63 63 24 151Paddy Field Sugarcane 0 0

7,796 ha Palawija 204 204 3 3Rainfed Paddy 2,233 2,233 29 29

Total 7,180 4,899 2,097 14,176 92 63 27 182

1998/99 Irrigated Paddy 5,544 5,219 1,893 12,656 71 67 24 162Paddy Field Sugarcane 0 0

7,796 ha Palawija 204 204 3 3Rainfed Paddy 2,233 2,233 29 29

Total 7,777 5,219 2,097 15,093 100 67 27 194

1999/00 Irrigated Paddy 5,419 5,419 5,215 16,053 70 70 67 206Paddy Field Sugarcane 0 0

7,796 ha Palawija 204 204 3 3Rainfed Paddy 2,233 2,233 29 29

Total 7,652 5,419 5,419 18,490 98 70 70 237

Average of 3 years Irrigated Paddy 5,303 5,179 3,000 13,483 68 66 38 1731997/98 - 1999/00 Sugarcane 0 0

Paddy Field: 7,796 ha Palawija 204 204 3 3Rainfed Paddy 2,233 2,233 29 29

Total 7,536 5,179 3,204 15,920 97 66 41 2041/ Including area classified as pumping irrigation area of 450 ha Source: Cabang Bundungan Wonogiri, Bengawan Solo Wonogiri & Klaten

Whole Wonogiri Irrigation Project 1/

Wet Dry Dry Wet Dry DryYear Crops Season Season I Season II Annual Season Season I Season II Annual

1997/98 Irrigated Paddy 26,290 26,185 22,415 74,890 89 88 76 253Paddy Field Sugarcane 300 300 1 129,589 ha Palawija 150 207 536 893 1 1 2 3

Rainfed Paddy 2,233 2,233 8 8Total 28,973 26,392 22,951 78,316 98 89 78 265

1998/99 Irrigated Paddy 26,513 26,126 20,800 73,439 90 88 70 248Paddy Field Sugarcane 713 101 814 2 0.3 329,589 ha Palawija 111 72 864 1,047 0.4 0.2 3 4

Rainfed Paddy 2,233 2,233 8 8Total 29,570 26,299 21,664 77,533 100 89 73 262

1999/00 Irrigated Paddy 26,766 26,769 26,212 79,747 90 90 89 270Paddy Field Sugarcane 172 83 255 1 0.3 129,589 ha Palawija 211 188 625 1,024 1 1 2 3

Rainfed Paddy 2,233 2,233 8 8Total 29,382 27,040 26,837 83,259 99 91 91 281

Average of 3 years Irrigated Paddy 26,523 26,360 23,142 76,025 90 89 78 2571997/98 - 1999/00 Sugarcane 395 456 1 0.0 2

Paddy Field: 29,589 ha Palawija 157 156 675 988 1 1 2 3Rainfed Paddy 2,233 2,233 8 8

Total 29,308 26,516 23,817 79,703 99 90 80 2691/ Including area classified as pumping irrigation area of 2,150 haSource: Cabang Bundungan Wonogiri, Bengawan Solo Karanganyar, Sragen, Wonogiri & Klaten

Cropped Area (ha) Cropping Intensity (%)

Cropped Area (ha) Cropping Intensity (%)

Table 2.2.1 Monthly Rainfall in Wonogiri Dam Watershed Area(Unit:mm)

Station Song Putri Nawangan Paranjoho Ngancar WonogiriIrrigatio WonogiriDam Jatisrono Average(PBS) (PBS) (PBS) (CJIS) (CJIS) (PBS) (PBS)

Jan. 385 323 293 362 343 325 358 341Feb. 302 301 253 367 325 296 337 312Mar. 264 262 252 314 299 269 318 283Apr. 206 164 185 204 173 176 199 187May 105 74 76 92 117 97 95 94Jun. 59 59 58 70 63 56 64 61Jul. 36 26 38 26 31 24 29 30

Aug. 20 16 19 17 21 21 28 20Sep. 30 28 27 31 20 20 49 29Oct. 74 71 82 88 115 92 147 96Nov. 180 154 168 174 179 159 231 178Dec. 281 229 234 300 222 210 277 250Total 1,942 1,706 1,684 2,046 1,908 1,744 2,131 1,880

Note: Operation Agency PBS: Proyek Bengawan SoloCJIS: Central Java Irrigation Service

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Table 2.2.2 Comparison for Providing Dredging System

Dredging System Transportation Adaptability togeography

The dredgingdepth Soil Property Adaptability to

this project Remarks

1 Drag Suction Dredger (Large)× × ○ ○ ×

The depth of dredging will be 30m atmaximum.

2 Drag Suction Dredger (Small)○ × × ○ ×

The depth of dredging will be only 15mat maximum.

3 Cutter Dredger (Un-self mobile type) (Large) × × ○ ○ ×4 Cutter Dredger (Un-self mobile type) (Small)

○ × × ○ ×The depth of dredging will be only 15mat maximum.

5 Broad Pump Dredger (Un-self-mobile type) × × ○ ○ ×6 Cutterless Pump Dredger (Un-self-mobile type) ○ × ○ ○ ×7 Ejector Dredger

△ × ○ ○ ×This is for the deep dredging and notsuitable for the continuous dredging.

8 Micro-pump Dredger ○ × × ○ ×9 Bucket Dredger × △ ○ × ×

10 Dipper Dredger × △ △ △ ×11 Backhoe Dredger △ △ × △ ×12 Grab Dredger × △ ○ × ×13 Barge ＋Backhoe ○ △ × × ×14 Barge＋Dragline ○ × ○ △ × This is not suitable for the small scale.15 Barge＋Crane with Sand-pump ○ △ ○ ○ △16 Barge ＋Crane（Grab Bucket）

○ ○ ○ △ △

Efficiency of dredging works againstsediment with fine particles being inferiorto those of by sand pump dredger.

17 Hydro Type（including Crane＋Hydro-J Pipe） ○ ○ ○ ○ ○

Table 2.2.3 Preliminary Estimation for Annual O&M Cost by Sand Pump Dredger

Items Unit Quantities Unit Price Amount Equiv. Yen(Rp.) (1,000Rp.) (1,000Yen)

1. Labor1) Senior mariner(4) *1 Man-day 1,264 95,000 120,080 1,3342) Common mariner(8) *2 Man-day 2,528 30,000 75,840 8433) Common labor(2) *3 Man-day 400 29,000 11,600 129

2. Material1) Heavy oil *4 Liter 150,000 2,100 315,000 3,5002) Lubricant Liter 4,500 22,500 101,250 1,125

3. Equipment1) Repair. cost of Dredger *5 Year 1 929,070 10,3232) Repair. cost of Tag boat *6 Year 1 150,102 1,6683) Repair. cost of Pipe line *7 Year 1 37,800 420Total 1,740,742 19,342

Remarks; 1) Time of cost estimate: June in 20012) Exchange rate: 1Yen =90 Rp.3) Explanation;

*1: Man-days of senior mariners= 4 person x (200 day + 11 day/month x 10 month) + 2 person x 12 day = 1,264 man-days*2: Man-days of common mariners = 8 person x (200 day + 11 day/month x 10 month) + 4 person x 12 day = 2,528 man-days*3: Man-days of common labor = 2 person x 200 day = 400 man-days、(for inspection and maintenance for sand drain pipe)*4: Annually consumed quantities of heavy oil (liter) = 75 liter/hr x 10 hr/day x 200 day = 150,000*5: Annual repair cost of dredger = 222,000,000 yen x 135 % / 18 year = 16,650,000 yen (by Japanese)

Annual repair cost of dredger = 16,650,000 yen - 6,327,000 yen = 10,323,000 yen = 929,070,000 Rp. (by Indonesian)Note; Regarding this conversion, refer to the corresponding table of Japanese version report.

*6: Annual repair cost of tag boat = 26,900,000 yen x 220 % / 22year = 2,690,000 yen (by Japanese)Annual repair cost of tag boat = 2,690,000 yen - 1,022,200 yen = 1,667,800 yen = 150,102,000 Rp. (by Indonesian)Note; Regarding this conversion, refer to the corresponding table of Japanese version report.

*7: Annual repair cost of pipe line = 84,000 yen x 200 x 15 % / 6 year = 420,000 yen = 37,800,000 Rp.

Table 2.2.4 Preliminary Estimation for Annual O&M Cost by Hydro-type Dredging System

Items Unit Quantities Unit Price Amount Equiv. Yen(Rp.) (1,000Rp.) (1,000Yen)

1. Labor*1 Common labor *1 Man-day 1,000 29,000 29,000 322

2. Material*2 Heavy oil *4 Liter 87,620 2,100 184,002 2,044Total 213,002 2,367

Remarks; 1) Time of cost estimate: June in 20012) Exchange rate: 1Yen = 90 Rp.3) Explanation;

*1: Man-days of connon labor = 5 person x 200 day = 1,000 man-days、(for inspection and maintenance for sand drain pipe)

*2: 0.584l/kWh x 75 kW = 43.8l/hAnnual consumed quantities of heavy oil (liter) = 43.81 liter/hr x 10 hr/day x 200 day = 87,620

Table 2.2.5 Comparison of Dredging Method for Urgent Dredging Works

Dredging SystemEasiness for

supplyTransport

ationAdaptabilityto geography

The dredgingdepth

SoilProperty

GarbageAdaptability to

this projectRemarks

1 Drag Suction Dredger (Large)× × × ○ ○ × ×

The depth of dredging will be 30mat maximum.

2 Drag Suction Dredger (Small)× ○ × × ○ × ×

The depth of dredging will be only15m at maximum.

3 Cutter Dredger (Un-self mobile type) ○ × × ○ ○ × ×4 Cutter Dredger (Un-self mobile type)

(Small)○ ○ × × ○ × △

The depth of dredging will be only15m at maximum.

5 Broad Pump Dredger (Un-self-mobile type) △ × × ○ ○ × ×6 Cutterless Pump Dredger (Un-self-mobile × ○ × ○ ○ × ×7 Ejector Dredger

△ △ × ○ ○ × ×This is for the deep dredging andnot suitable for the continuous

8 Micro-pump Dredger ○ ○ × × ○ × ×9 Bucket Dredger △ × △ ○ × × ×

10 Dipper Dredger × × △ △ △ × ×11 Backhoe Dredger △ △ △ × △ × ×12 Grab Dredger ○ × △ ○ × ○ ×13 Barge ＋Backhoe ○ ○ △ × × ○ ×14 Barge＋Dragline △ ○ × ○ △ × × This is not suitable for the small15 Barge＋Crane with Sand-pump ○ ○ △ ○ ○ × △16 Barge ＋Crane（Grab Bucket）

○ ○ ○ ○ △ ○ ○

Efficiency of dredging worksagainst sediment with fine particlesbeing inferior to those of by sandpump dredger.

17 Hydro Type（including Crane＋Hydro-J × ○ ○ ○ ○ × × There are only a few achievements.

*) ○ : easy or possible, △ : a little difficult or narrowly possible, × : difficulty or impossibility. "Adaptability to this project" column was taken ○ or ×.

Hydro-J pipe is the patent method of construction developed in Norway. The tip part of pipe which set up slot hole in the bottom was bent in the "J" letter, and suction sandfrom the slot by the pump or the siphon system. Kowa Engineering Co., Ltd. purchases a limited area (in Japanese) patent to use. Aside from the removal works of garbage,technically it is possible enough and the operation cost becomes small too, as a dredging system. However, adaptability to this project isn't feasible, because it has a fewdredging works achievements in dam reservoir and it is taken long time for design and production.

Table 2.4.1 Profit and Loss Projection of Bengawan Solo Branch Office

No. Item Unit 2001 2002 2003 2004 2005

I. REVENUES 106 Rp. 3,925 4,294 5,239 5,733 7,061

1.1 Revenues of Water Services 106 Rp. 3,080 3,353 4,191 4,565 5,757

a. Production- Electricity 103 kWh 57,365 57,365 57,365 57,365 57,365

- Raw water for drinking water 103 m3 5,632 6,420 7,208 7,997 8,785

- Raw water for Industries 103 m3 30,945 34,040 37,444 41,188 45,307

b. Tariffs- Electricity Rp/kWh 15.00 15.75 16.54 17.36 18.23

- Raw water for drinking water Rp/m3 40.25 40.25 48.30 48.30 57.96

- Raw water for Industries Rp/m3 64.40 64.40 77.28 77.28 92.74

c. Revenues of Water Service- Electricity 106 Rp. 860 903 949 996 1,046

- Raw water for drinking water 106 Rp. 227 258 348 386 509

- Raw water for Industries 106 Rp. 1,993 2,192 2,894 3,183 4,202

1.2 Revenues of Non Water Service 106 Rp. 845 941 1,048 1,168 1,304

- Tourism 106 Rp. 108 130 156 187 225

- Equipment rental 106 Rp. 145 160 176 194 213

- Construction 106 Rp. - - - - -

- Consultant 106 Rp. 58 64 70 77 85

- Land rental 106 Rp. 534 587 646 711 782

II. COSTS 106 Rp. 4,480 4,989 5,519 6,086 6,724

- O&M 106 Rp. 2,332 2,610 2,886 3,190 3,527

- Personnel 106 Rp. 1,288 1,417 1,559 1,715 1,886

- Travelling 106 Rp. 242 266 293 322 354

- General 106 Rp. 175 193 212 233 256

- Marketing 106 Rp. 27 30 33 36 40

- Depreciation 106 Rp. 101 120 142 147 163

- Socialization 106 Rp. 50 55 61 67 73

- Service Fee 106 Rp. 139 160 183 209 241

- Human Resources Development 106 Rp. 50 55 61 67 73

- Watershed conservation 106 Rp. 75 83 91 100 110

III. Profit & Loss 106 Rp. -555 -695 -280 -352 337

IV. Other Revenues 106 Rp. 806 886 985 1,083 1,206

- Bank Interest etc. 106 Rp. 79 86 105 115 141

- PGPS (public servant salary) 106 Rp. 728 800 880 968 1,065

V. Other Costs 106 Rp. 2 2 2 3 3

- Bank fee etc. 106 Rp. 2 2 2 3 3

VI. Profit and Loss from others sourc 106 Rp. 804 884 983 1,080 1,204

VII. Profit & Loss before Taxes 106 Rp. 249 190 703 728 1,541

VIII. Taxes 106 Rp. 66 48 202 210 454

IX. Profit & Loss after Taxes 106 Rp. 183 141 501 519 1,087

Source: CDMP Study Report, April 2001, SAPS Report, July 2001

T-9

Table 3.1.1 Project Effect and Extent of Improvement on Present Situation

by Implementation of the Assistance Project

Present Situation and Problems Countermeasures by theAssistance Project

Project Effect and Extent ofImprovement

1. Because of the water intake troubledue to the sedimentation near theintake of the Wonogiri multipurposedam, reservoir below EL.130m cannot be operated.If no any countermeasures are made,the intake will be plugged perfectlywithin about 2.8 years and stoppage ofthe power generation of the WonogiriPower station and reducing of riceproduction in the Wonogiri irrigationsystem will be occurred.In particular, the reducing of riceproduction is big problem from theview point of security assurance ofstable food supply as one of thenational strategies.

-Inspection and repairing ofgates and valve-Execution of the urgentlydredging works in front of theintake facility (250,000 m3)

By the dredging works in front of theintake, the water intake function will beextended by about 5 years after theconstruction completion. The plannedannual production of power generationenergy and rice production could bemaintained as they are at moment.

2. During the rainy season, muchgarbage (stems or twigs of agriculturalproducts) are flowing into thereservoir and being settled. Further, infront of the intake, the garbage islikely to be plugging the screen of theintake then much sedimentation areremaining in front of the intakewithout entering into the intaketunnel.In case due to the unbalanced earthpressure from the up-stream, thescreen being destroyed, water turbinein the power-house may be damagedgreatly, and the intake tunnel will beplugged due for the muchsedimentation to enter into the tunnelwhich will cause the difficulty ofwater supply from the dam to thedown-stream.

Installation of the floating logboom

By the removal of garbage by using thespilled out water and also by the manualremoval of garbage near the floating logboom, the plugging the screen of theintake will be prevented. Then thesmooth water intake will be possiblymade without plugging the intake.

3. The Assistance Project is to provideonly the urgent countermeasures onthe sedimentation problems of theWonogiri multipurpose dam reservoirthen succeeding this, the permanentcountermeasures (mid- and long term)should be made. If not, the sameproblems at moment will occur infuture.

Providing the water depthsurvey system with GPS

By execution of continuous monitoring,the sedimentation situation of thereservoir could be obtained year by year,and such data could be utilized usefullyto prepare the permanentcountermeasures.

Figures

Basic Design Study Reporton the Project

for Urgent Countermeasuresfor Sedimentation

in Wonogiri Multipurpose Dam Reservoirin the Republic of Indonesia

2000

1000

500

1500

2000

500

1000

2000

1500

Mt.

Mer

babu

3142

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api

2914

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Tow

n

BASIC DESIGN STUDY ONURGENT COUNTERMEASURES FOR SEDIMENTATION

IN WONOGIRI MULTIPURPOSE DAM RESERVOIRIN THE REPUBRIC OF INDONESIA

JAPAN INTERNATIONAL COOPERATION AGENCY

Fig. 1.1.1

Existing and on-going Projects by Japan's Grant Aid and JBIC Loan

Dam

type

Cen

ter

core

type

roc

kfil

l dam

Nor

mal

wat

er le

vel

EL

. 136

.0 m

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8.3

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FW

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9.1 m

Water Utilization 440 x 106 m3

Flood ControlStorage

220 x 106 m3

Dam

Cre

st

LW

L

Jan.

Dec

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od P

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Water Utilization duringFlood Period395x10

6m

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Water Utilization duringNon-flood Period440x106m3F

lood

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trol Spa

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Dim

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ono

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ultipu

rpose

Dam

Allo

cat

ion

of

Sto

rage

Cap

acity

Rese

rvoir W

ater

Leve

l

BASIC DESIGN STUDY ONURGENT COUNTERMEASURES FOR SEDIMENTATION

IN WONOGIRI MULTIPURPOSE DAM RESERVOIRIN THE REPUBRIC OF INDONESIA

JAPAN INTERNATIONAL COOPERATION AGENCY

Fig. 1.1.2

Wonogiri Multipurpose Dam

Dec

. 199

9

Aug.

/Sep

. 200

1

128

129

129

126

129

127

128

124

125

130

130

Fig. 1.2.1

Sediment Condition in front of Intake Structure

SCA

LE

BASIC DESIGN STUDY ONURGENT COUNTERMEASURES FOR SEDIMENTATION

IN WONOGIRI MULTIPURPOSE DAM RESERVOIRIN THE REPUBRIC OF INDONESIA

JAPAN INTERNATIONAL COOPERATION AGENCY

Dec

. 199

9

EL.1

16.0

Sep.

199

6

May

200

4 (F

orec

ast)

Aug.

/Sep

. 200

1EL

.128

.0

SCA

LE

129

128

129

128 12

7

129

130

125

126

124

130

Fig. 1.2.2BASIC DESIGN STUDY ON

URGENT COUNTERMEASURES FOR SEDIMENTATIONIN WONOGIRI MULTIPURPOSE DAM RESERVOIR

IN THE REPUBRIC OF INDONESIA

JAPAN INTERNATIONAL COOPERATION AGENCY

Anticipation of blockade in front of Intake Structure

BASIC DESIGN STUDY ONURGENT COUNTERMEASURES FOR SEDIMENTATION

IN WONOGIRI MULTIPURPOSE DAM RESERVOIRIN THE REPUBRIC OF INDONESIA

JAPAN INTERNATIONAL COOPERATION AGENCY

Fig. 1.2.3

Wonogiri Dam Reservoir

Be nga wan S olo R iver

T irtomoyo R iver

K e duang R ive

L eber R iv er

A lang R i v e

T emon

R iver

WONOG IR IDA M

B engawan S olo R iver

Legend

SectionsRiversContour El. 140 mRoad

7RB 0R

7LN6R

N7R

N1L

N3R

N2L

N4/5L

N5R

N3L

N2R

N1L

N7LN9R

N6L

N8L

N8R

N9L

W1R

B 7R

B 7L

B 6R

B 1RB 0L

B 1L

9R

9LN4R

10L

11L

10R

11R

B 8L

12L 12R

13R

13L

A 1L

A 1R

14L

14R

15L

15R

A 3L

A 3R

A 4L

A 4R

A 2L

A 2R

B 8R

B 5L

B 5R

B 4R

B 4LB 5L

B 5R

B 2R

B 2L

T 2L

T 2R

T 3L

T 3R

T 4R

T 4L

T 5R

T 5L

T 6R

T 6L

T 7R

T 7L

T 8R

T 8L

T 9R

T 9L

G 2R

G 2LG 1L

G 1R

4R

4/5L

W1LW4R

W5R

W7RW7L

W6R

W3L

W3R

W2L

W2R

2L

2R

K 2L

K 2R

K 3L

K 3R

K 4L

L 1L

L 1R

L 2L

L 2R

K 5L

K 5R

K 6L

K 6R

K 7L

K 7R

L 5R

15L

L 4R

L 4L

L 3R

L 3L

3L

3R

K 1L

SCALE

0 1 2 3 4 km

N

Dist

ance

Ups

tream

of D

am (

km)

River Bed Elevation (EL. m)

110

115

120

125

130

135

140

05

10

15

20

25

Ked

uwan

g -O

rigin

al R

iver

Bed

Ked

uwan

g -R

iver

Bed

(199

3)

Ked

uwan

g -R

iver

Bed

(200

0)

Solo

-Orig

inal

Riv

er B

ed

Solo

-Riv

er B

ed (1

993)

Tirto

moy

o -O

rigin

al R

iver

Bed

Tirto

moy

o -R

iver

Bed

(199

3)

BASIC DESIGN STUDY ONURGENT COUNTERMEASURES FOR SEDIMENTATION

IN WONOGIRI MULTIPURPOSE DAM RESERVOIRIN THE REPUBRIC OF INDONESIA

JAPAN INTERNATIONAL COOPERATION AGENCY

Fig. 1.2.4

Wonogiri Dam Reservoir Profile

Annual Power Generation from 1983 to 2001

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,000

9,000,000

10,000,000

1 2 3 4 5 6 7 8 9 10 11 12Month

Pow

er G

ener

atio

n (k

Wh)

1998 1999 2000 2001 1998-2001

0

10,000,000

20,000,000

30,000,000

40,000,000

50,000,000

60,000,000

70,000,000

80,000,000

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Year

Pow

er G

ener

atio

n (k

wh)

AnnualDec. to Apr.

BASIC DESIGN STUDY ONURGENT COUNTERMEASURES FOR SEDIMENTATION

IN WONOGIRI MULTIPURPOSE DAM RESERVOIRIN THE REPUBRIC OF INDONESIA

JAPAN INTERNATIONAL COOPERATION AGENCY

Fig. 1.3.1

Variations of Power Generation from 1983 to 2001

Monthly Power Generation past 4 year

Dredging Plan

Fig. 2.1.1

128127

129 130

1:3.6

EL.128.0m

Varie

s.Bengawan Solo River

1:4.0

1:4.

0

1:4.

0

EL.126.0m

1:4.

0

Varies.

126

1:10

EL.126.0m

1:4.

0

EL.116.0m

Varies.

EL.128.0m

126

129

128127

1:3.1 EL.142.0m

EL.126.0mEL.126.0m

1:3.1

1:3.1

Intake Gate Shaft 1:2.2

Access Road

SCALE0 100(M)

28

28

27 26 25 24 23 22 21

20

19 17 15 13 11 9 7 5 3 1

18 16 14 12 10 8 6 4 2

252627 24 23 22 21

20

19

18

17 15

16 14

13

12

11 9

10 8

7 5

6 4 2

3 1

URGENT COUNTERMEASURES FOR SEDIMENTATIONIN WONOGIRI MULTIPURPOSE DAM RESERVOIR

IN THE REPUBLIC OF INDONESIA

JAPAN INTERNATIONAL COOPERATION AGENCY

THE BASIC DESIGN STUDY ON

New waterway Approach channel

Fore bay

Flat yard

in the right bank

(in front of spillway)

New waterway Approach channel

BASIC DESIGN STUDY ONURGENT COUNTERMEASURES FOR SEDIMENTATION

IN WONOGIRI MULTIPURPOSE DAM RESERVOIRIN THE REPUBRIC OF INDONESIA

JAPAN INTERNATIONAL COOPERATION AGENCY

Fig. 2.2.1

Locations of Gate and Valve Inspection