BASIC DESIGN STUDY REPORT

Transcription

1 BASIC DESIGN STUDY REPORT ON THE PROJECT FOR URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBLIC OF INDONESIA DECEMBER 2001 JAPAN INTERNATIONAL COOPERATION AGENCY NIPPON KOEI CO., LTD. GR3 CR(1)

2 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, 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

3 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, 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, Motoyoshi Kawashima Project manager, Basic design study team on the Project for Urgent Countermeasures for Sedimentation in Wonogiri Multipurpose Dam Reservoir Nippon Koei Co., Ltd.

4 N N SUMATRA KALIMANTAN Jakarta JAWA SEA INDIAN OCEAN JAWA PROJECT AREA Mt. Merbabu 3142 Mt. Merapi 2914 KEY MAP K. Cemara Boyolali K. Gawe K K. Bram ba ng Klaten. Dengkeng SURAKARTA Bengawan Solo K. Semin K. Jlantah K. Mungkung Sragen K. Sragen K. Sawur Mt. Lawu o K. Ketongg Ngawi K. Gandon g K. Gonggang n K. Madiu K. Jerowan MADIUN K. Catur Mt. Buntung Mt. Pandan Wonogiri K. Asin Mt. Wilis 2000 Wonogiri Multipurpose Dam K. Ked uwan g K. Tempura n Ponorogo K. Mungkungan 2563 K. Manti K. Tirtomoyo K.Any ar K. Keyang B. Solo Legend Watershed River Wonogiri Dam Railway Road Mountain SCALE km Indian Ocean Pacitan Location Map City Town Provincial Boundary

5 ABBREVIATIONS APBN BAPPENAS CEP CDMP D/D DGPS EIA E/N FRP F/S GBHN GOI GOJ GPS H.P. JBIC JICA KIMPRASWIL LWL O&M OECF OTCA PBS PDAM PJT PKSA PLN PROPENAS SAPS WATSAL Central Government Resources and Expenditure Budget (Anggaran Pendapatan dan Belanja Negara) National Development Planning Agency (Badan Perencanaan Pembangan Nasional) Circle Error Possibility Comprehensive Development and Management Plan Study for Bengawan Solo River Basin Detailed Design Differential Global Positioning System Environmental Impact Assessment Exchange Note Fiber Reinfored Plastcs Feasibility Study Guideline for National Economic Development (Garis-Garis Besar Haluan Negara) Government of Indonesia Government of Japan Global Positioning System Hose Power Japan Bank for International Cooperation Japan International Cooperation Agency Ministry of settlement and regional development (Departemen Permukiman & Prasarana Wilayah) Low water level Operation and Maintenance Overseas Economic Cooperation Fund Overseas Technical Cooperation Agency Project Bengawan Solo Regional Drinking Water Supply Company (Perusahaan Daerah Air Minum) Jasa Terta Public Cooperation, Public Water Service Cooperation (Perum Jasa Terta) Water Resources Development and Conservation Section (Pengembangan Konservasi umber Sumber daya Air) National Electric Company (Perusahaan Listrik Negara) Five-year National Development Program (Program Pembangunan Nasional) Special Assistance for Project Sustainability Water Resources Sector Adjustment Loan iv

6 SUMMARY The Wonogiri Multipurpose Dam located in up-stream of the Solo River in the Central Java province was constructed in 1982 under the technical and the financial assistance of Japan. The principal features of the dam and the related structures including the power-house are shown in Fig It has been reported that routine operation of the Wonogiri dam, especially for water release for irrigation water supply and power generation has been disturbed due to a huge amount of sedimentation deposited in front of the intake facility. To clarity this problem, sediment deposit survey has been carried out by the agency concerned. Judging from the full record of sediment measurements including the results of a survey conducted on August/September, 2001 by the JICA Team, the sediment level has risen by 1.1 m in front of the trashrack and 3.8 m at the deepest point in less than two (2) years between December 1999 and August If the present rate of sedimentation in front of the intake facility continues without any countermeasures, the inlet portion of the intake is anticipated to be completely blocked 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 the reservoir is estimated to be 5.4 million m 3 in total. The plan of the Wonogiri dam reservoir and the profiles of tributaries are shown in Figs and 1.2.3, respectively. The maximum water discharge for the Wonogiri hydro-power generation has been determined at 75 m 3 /s to generate the annual power energy of 50,000 MWh in the design stage. The annual power energy has been generated on schedule until 1999, but power energy for the rainy season from December to April appears to have decreased since then. The main reason for reductions of power energy is that the lowest reservoir water level is now limited to EL m due to the sedimentation in front of the intake facility and the maximum intake discharge is restricted to 60.0 m 3 /s due to for the same reason at present. Serious problems in 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 for taking in the irrigation water have been reported. However, as the reservoir water level is operated above EL m, the utilizable volume between EL to m in the reservoir could not be used for the irrigation water supply. To cope with this water supply deficit, the reservoir water level is raised to a higher than normal water level (EL 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, the Government of the Republic of Indonesia (GOI) submitted an application for Japan Grant Aid for the following three components to the Government of Japan (GOJ); 1) Construction of two check dams (sand storage volume in total: about 550,000 m 3 ) on the Keduwang River to mitigate sediment entering the reservoir of the Wonogiri multipurpose dam. 2) Urgently dredging about 100,000 m 3 of sediment from in front of the intake facility S-1

7 of the dam to assure the intake function of the water, and 3) Providing a dredging system to assure the sustainable dredging of sediment continuously 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 JICA Team 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 implementing agency and the Project Bengawan Solo (PBS) belonging to KIMPRASWIL. Consequently, JICA and KIMPRASWIL agreed that the construction of the check dams should be excluded from the above request of GOI due to the technical problems. It was also agreed that other components proposed by GOI in their meeting should be examined in Tokyo, as shown in the minutes of meeting dated on 4 September, The JICA Team examined the contents of the above minutes of meeting in detail in Japan, and after careful consideration, it was determined to delete the dredging system requested by GOI, due to the present budgetary situation in Indonesia. The JICA Team accepted the urgent dredging from in front of the intake and associated projects proposed by GOI under GOJ s finantial assistance. The Basic Design Study Report (Draft) incorporated these conclusions. The GOJ dispatched the JICA Team to explain and discuss with GOI about the above report to Indonesia from October 28 to November 6, As a result, GOI agreed with the conclusions of the report in principle as shown in the minutes of meeting dated on 2 November, The five-year National Development Program (PROPENAS, ) was issued in August 2000 as a high level program of the government of Indonesia (GOI). The objectives of good maintenance and administration of industrial infrastructure (including those of water resources development), assurance of stable food supply, and increasing farmers income are set down in Chapter 4 of PROPENAS. In line with this policy, the target of this project was set at solving the sedimentation problems in the Wonogiri multipurpose dam reservoir to continuously maintain the functions of the dam for irrigation, power generation, 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 the following basic concepts: (1) Implementation of urgent measures to remedy the function of the Wonogiri reservoir by means of structural measures, and (2) Implementation of mid- and long term sediment mitigation measures by means of structural and nonstructural measures including basin reservation and management. To meet the concept (1), a basic study to meet the urgent requirements of removing sediment from in front of the intake is needed. For the concept (2), an overall master plan for alleviation of sediment delivery to the Wonogiri reservoir will be contemplated. From the above concepts, the principles of the Urgent Countermeasures for Sedimentation in the S-2

8 Wonogiri multipurpose dam reservoir under the requested Japanese assistance (hereinafter called as the Assistance Project) are determined as follows: Dredging near the intake channel and portal portions to secure the water intake function of the dam for 5 years (the project life time). Inspections and repairing of gates and relevant facilities, emergency release valve and spillway gates to assure water release during the dredging work at the intake channel 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 the Wonogiri reservoir is estimated at about 1,280,000 m 3 (refer to Appendix 7.1). Assuming that the bed load is about 15% of all sediment (as there are no actual measurement data, this assumption is based on data from the Brantus river basin), the suspended load volume is estimated to be about 1,090,000 m 3. It can be judged that most of the suspended load produced in the Keduwang River is entering the Wonogiri dam directly due to the following reasons that majority of the sediment deposited in the existing check dams 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 the suspended load entering the Wonogiri dam. (2) Possible methods of dredging to be provided to PBS are compared in terms of their potential sustainability in Table 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 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 m 3 ) 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 10 6 as shown in Table 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 by washing out water together with sediment by use of a siphon. Hence, the annual O&M cost is estimated at Rp. 210 x 10 6 as shown in Table 2.2.4, about 12 % of the cost of using a sand dredge. But this type has few examples actually utilized in projects and has unknown reliability. S-3

9 In conclusion, it is judged to be unjustified to provide either system from the viewpoints of O&M cost and 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 following gates and valve may need to be operated, and if so, they will need to be working reliably. Hence, prior to the commencement of the urgent dredging works, they should be inspected and, if necessary, repaired (refer to Fig ): 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 into the intake facility when the reservoir water level is equal to or below EL (i.e.lwl) m. iii) Construction of flat yards of EL m, being lower by 1.0 m than the LWL of the reservoir. Elevation of EL m is applied for fore-bay for the spillway in original design. The flat yards are to prevent the large quantities of sediment from entering the intake 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 m 3. (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 (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 after completion of the urgent dredging work as one of the O&M activities which should be made by the PJT I Bengawan Solo (PJT-IBS). The composition of the system is shown in Fig The Project would be implemented on the following conditions in consideration of application for S-4

10 Japan s Grant Aid system. (1) Director General of Rural Development, Ministry of Settlement and Regional Infrastructure (KIMPRASWIL) in Indonesia would be the executing agency for the Project implementation. (2) Immediately after the Exchange of Note (E/N) between GOJ and GOI regarding the stages of the detailed design and the construction works is signed, the KIMPRASWIL should commence the necessary actions for the implementation of the Project. (3) 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 tender documents for the selection of the Japanese Contractor for the civil works. Immediately after the completion of the preparation, the Japanese Consultant should start the tendering works. (4) GOI should commence the arrangement for the land acquisition in parallel with the detailed design, if necessary. (5) A Japanese Contractor immediately after signing the contract for the construction works with the KIMPRASWIL shall commence to undertake the construction works and the Japanese Consultant shall execute the construction supervision. The dredging work volume for the Assistance Project has been estimated at around 251,000 m 3, including 72,000 m 3 of garbage, and one (1) barge with grab bucket (3.5 m 3 ) shall be adopted as the dredging equipment. As the working area is limited, one set of dredging equipment is applied. The construction 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 m 3 (Daily dredging rate) x 30 days x 0.82 (Efficiency) = 24,919 m 3 /month 250,000 m 3 (Dredging volume in total) / 24,919 m 3 (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 the spoil banks (44 ha in total for the two (2) spoil banks), land for temporary offices, S-5

11 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 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 services based 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 in the Government of Indonesia and prompt internal transportation therein of the materials and equipment for the Assistance Project purchased under the Japan Grant Aid. (7) To exempt Japanese juridical and physical nationals engaged in the Assistance Project from customs duties, internal taxes and other fiscal levies which may be imposed in Indonesia with 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 the products and services under the Verified Contract such facilities as may be necessary for their entry into Indonesia and stay therein for the performance of their works (9) To provide necessary permissions, licenses and other authorizations for implementing the Assistance Project, if necessary. (10) To maintain and use properly and effectively the facilities constructed and equipment provided 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 of income of beneficiary farmers in the down-stream of the Wonogiri multipurpose dam and contributing to the stable electricity supply to the central Java province. It will hopefully contribute to stable food supply and social stabilization, the primary political strategies in Indonesia as described in of the report. S-6

12 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 is estimated at 45,200 households. By implementation of the Assistance Project, the direct effect will be annually Rp. 187 x 10 9 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 is estimated that the annual power generation energy of the Wonogiri power station (50,000 MWh) will contribute to power consumer of 61,000 households. By implementation of the Assistance Project, the direct effect will be annually Rp. 10x10 9, estimated by multiplying the electricity sale price of 200 Rp./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 the Wonogiri multipurpose dam reservoir to assure the water intake function of the dam for a period of about five (5) years from the completion of the Project (refer to 2.2.2(2)2)(d) of this report). In order to sustain 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, no serious defects to the power generation equipment (only one set of turbine and generator were inspected) were found. However, it is more than twenty (20) years since the hydropower station commenced operation. Therefore, in order to continue the power generation smoothly in the future, the prompt execution of an overall 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 intake facility and installation of a mechanical raking system on the screen 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 the long term, mid- and long term countermeasures such as water-shed conservation and sediment management of the Wonogiri dam reservoir, and structural measures in the reservoir against sediment flowing into the reservoir should be studied. In particular, new construction of another intake facility or of an inlet shaft at the inlet portion of the existing intake would 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 the Assistance Project shown in the attached figure in (7) of this report and the life time of the Assistance Project (around 5 years after completion). S-7

13 The Basic Design Study Report on the Project for Urgent Countermeasures for Sedimentation in Wonogiri Multipurpose Dam Reservoir in the Republic of Indonesia Preface Letter of Transmittal Location Map Abbreviations Summary Table of Contents Page CHAPTER 1 BACKGROUND OF THE PROJECT Introduction Sedimentation in the Wonogiri Multipurpose Dam Reservoir Present Situation of the Wonogiri Power Station and the Wonogiri Irrigation System Requested Japanese Assistance CHAPTER 2 CONTENTS OF THE PROJECT Basic Concept of the Project Government s Target and Target of the Project Basic Concept of the Project Basic Design of the Requested Japanese Assistance (the Assistance Project) Design Policy Basic Plan Basic Design Drawing Implementation Plan Obligations of Recipient Country Project Operation Plan Required Maintenance and Management Issues Operation and Maintenance Organization Other Relevant Issue CHAPTER 3 PROJECT EVALUATION AND RECOMMENDATION Project Effect Direct Effect Indirect Effect Recommendations i

14 List of Tables Table Monthly Power Output by Wonogiri Power Station... T- 1 Table Cropping Area and Cropping Intensity of Wonogiri Irrigation System... T- 2 Table Monthly Rainfall in Wonogiri Dam Watershed Area... T- 3 Table Comparison for Providing Dredging System... T- 4 Table Preliminary Estimation for Annual O&M Cost by Sand Pump Dredger... T- 5 Table Preliminary Estimation for Annual O&M Cost by Hydro-type Dredging System... T- 6 Table Comparison of Dredging Method for Urgent Dredging Works... T- 7 Table Profit and Loss Projection of Bengawan Solo Branch Office... T- 8 Table Project Effect and Extent of Improvement on Present Situation by Implementation of the Assistance Project... T- 9 List of Figures Fig Existing and on-going Projects by Japan s Grant Aid and JBIC Loan... F- 1 Fig Wonogiri Multipurpose Dam... F- 2 Fig Sediment Condition in front of Intake Structure... F- 3 Fig Anticipation of blockade in front of Intake Structure... F- 4 Fig Wonogiri Dam Reservoir... F- 5 Fig Wonogiri Dam Reservoir Profile... F- 6 Fig Variations of Power Generation from 1983 to F- 7 Fig Dredging Plan... F- 8 Fig Locations of Gate and Valve Inspection... F- 9 Fig Locations of Spoil Bank (1/2)-(2/2)... F-10 Fig Layout of Floating Log Boom... F-12 Fig Digital Echo Sounding System with GPS... F-13 Fig Locations of Wonogiri Irrigation System... F-14 Appendices 1. Member List of the Study Team... A Study Schedule... A List of Parties concerned in the Recipient Country... A Minutes of Discussions... A4-1 ii

15 5. Cost Estimation born by the Recipient Country... A Other Relevant Data... A Wonogiri Multipurpose Dam Reservoir Water Level Outflow Rainfall ( )... A Designed Cross Sections for Urgent Dredging Works for Wonogiri Multipurpose Dam... A Guide Line for Environmental Conservation in Indonesia... A Other Relevant Data... A References... A Estimation of Annual Sedimentation into the Wonogiri Dam Reservoir... A Middle and Long Term Countermeasure for Sedimentation Problem in the Wonogiri Multipurpose Dam (Draft)... A Hydro-Type Dredging System... A7-8 iii

16 CHAPTER 1 BACKGROUND OF THE PROJECT 1.1 Introduction The overall water resource development projects in the Bengawan Solo River basin, where the Wonogiri multipurpose 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 was formulated 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),. In accordance with this Master Plan, a series of high priority river basin development projects has been implemented under the technical cooperation and financial assistance of JICA and the Overseas Economic Cooperation Fund (OECF), which is the predecessor of the present Japan Bank for International Cooperation (JBIC). As shown in the below table and Fig , many projects have been completed under the financial assistance of Japan and it can be said that the Solo river has had close relationship with Japan. Bengawan Solo River Development Projects under JICA and JBIC Name of Projects Implementation Period Wonogiri Multipurpose Dam Project Wonogiri Irrigation Development Project Upper Solo River Improvement Project Madiun River Improvement Project Lower Solo Pumped Irrigation Project (JICA Grant) Lower Solo River Improvement Project 1996 (on-going) Among these, top priority was given to the Wonogiri Multipurpose Dam Project and the Wonogiri Irrigation Development Project and those were completed in 1982 and 1987, respectively. The principal features of the dam are shown in Fig 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 and 1993 by PBS. The survey results pointed out a decrease in the reservoir capacity. In addition, an echo sounding survey near the intake and in the Keuduwang River was carried out in 2000 by PBS. The decrement in capacity is shown below. Decrease of Reservoir Capacity Decrement of Capacity Sediment 53% 63% Water utilization 30% 36% Flood control 30% 33% 1-1

17 The results of the echo sounding survey revealed obstruction of the mouth of the intake. The profile of the upstream of the intake is shown in Fig Judging from the full record of sediment measurements including the results of a survey conducted on August/September, 2001 by the JICA Team, the sediment level has risen by 1.1 m in front of the trashrack and 3.8 m at the deepest point in less than two (2) years between December 1999 and August If the present rate of sedimentation in front of the intake facility continues without any countermeasures, the inlet portion 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 its junction with the reservoir to the intake is the shortest among the main tributaries. The other tributaries are the Tertomoyo River, Tenom River, Aran River and Wliyantoro River. The riverbed elevation in the reservoir 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 the reservoir is estimated to be 5.4 million m 3 in total. The plan of the Wonogiri dam reservoir and the profiles of tributaries are shown in Figs and 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 m 3 /s and the annual power generation energy 32,600 MWh in the design stage. However, the design figures have been revised in accordance with the actual reservoir operation adopted until now, and the planned annual power generation energy 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 in Table and Fig.1.3.1, respectively. Regarding the annual power generation energy, no major reductions are seen until 2000, however power energy for the rainy season from December to April appears to have decreased since The lowest reservoir water level is limited down to EL m due to the sedimentation in front of the intake facility and the maximum intake discharge is restricted to 60.0 m 3 /s for the 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 been investigated by the feed back study in the Water Resources Sector Adjustment Loan (WATSAL). Since the cropping area in 1999/00 was increased compared with those of 1997/98 and 1998/99, serious problems in 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 intake have been noticed. However, as the reservoir water level is operated above EL m because of the sedimentation problem, the utilizable volume between EL to m in the reservoir could not be used for the irrigation 1-2

18 water supply. To cope with this water supply deficit, the reservoir water level is raised to a higher than normal water level (EL m) at the end of the rainy season and the reservoir water then released to meet the water demand. 1.4 Requirement to Japanese Assistance In order to remedy the sedimentation problem in the Wonogiri multipurpose dam reservoir, the Government of the Republic of Indonesia (GOI) submitted an application for Japan Grant Aid to the Government of Japan (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 m 3 ) on the Keduwang River to mitigate sediment entering the reservoir of the Wonogiri multipurpose dam. 2) Urgently dredging about 100,000m 3 of sediment from in front of the intake facility of the dam to assure the intake function of the water, and 3) Providing a dredging system to assure the sustainable dredging of sediment continuously entering the reservoir. In response to the above request, GOJ dispatched the Basic Design Survey Team through JICA (hereinafter called as JICA Team) from August 13 to September 20, 2001 to Indonesia. The JICA Team conducted the field survey and discussed with the Director General of Rural Development, the Ministry of Settlement and Regional Development (KIMPRASWIL) being the implementing agency and the Project Bengawan Solo (PBS) belonging to KIMPRASWIL. Consequently, both parties agreed that the construction of the check dams should be excluded from the above request of GOI due to the technical considerations explained below in section 2.2.2(1) 1) of this report. It was also agreed that other components proposed by GOI in their request should be examined in Tokyo, as shown in the minutes of meeting dated on 4 September, The JICA Team examined the contents of the above minutes of meeting in detail in Japan, and he in conclusion, after careful consideration, not to provide the dredging system requested by GOI due to the present 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, as explained in of this report, as projects to be funded by Japan s grant aid. The Basic Design Study Report (Draft) incorporated these conclusions. The GOJ dispatched the JICA Team to explain and discuss with GOI about the above report to Indonesia from October 28 to November 6, As a result, GOI agreed the conclusions of the report in principle as shown in the minutes of meeting dated on 2 November,

19 CHAPTER 2 CONTENTS OF THE PROJECT 2.1 Basic Concept of the Project Government s Target and Target of the Project The five-year National Development Program (PROPENAS, ) was released in August 2000 as a high level program of the government of Indonesia (GOI). The objectives of good maintenance and administration of industrial infrastructure (including those of water resources development), assurance of stable food supply, and increasing farmers income are set in Chapter 4 of PROPENAS. Under such circumstances, in line with this policy, the target of this project was set at solving the sedimentation problems in the Wonogiri multipurpose dam reservoir to continuously maintain the functions of the dam for irrigation, power generation, and flood control, being the original purposes of the dam (hereinafter called as the Project) 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 following basic concepts: 1) Implementation of urgent measures to remedy the function of the Wonogiri reservoir by means of structural measures, and 2) Implementation of mid- and long term sediment mitigation measures by means of structural and nonstructural measures including basin reservation and management. To meet the concept (1), a basic study to meet the urgent requirements of removing sediment from in front of the intake is needed. For the concept (2), an overall master plan for alleviation of sediment delivery to the Wonogiri reservoir will be contemplated. From the above concepts, the principles of the Urgent Countermeasures for Sedimentation in the Wonogiri multipurpose dam reservoir as the requested Japanese assistance (hereinafter called as the Assistance Project) are determined as follows: Dredging near the intake channel and portal portions to secure the water intake function of the dam for 5 years (the project life time). Inspections and repairing of gates and relevant facilities, emergency release valve and spillway gates 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 2-1

20 (a) Intake gate Type : Coaster gate Nos. of gates : 1 Size : 5.5 m x 5.5 m (b) Emergency release valve Type : Hollow jet valve Nos. of valves : 1 Size : 1,950 mm diameter (c) Spillway gates Type : Radial gates Nos. of valves : 4 Size : 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 and Appendix 6.2) Restoration of the portion in front of the intake facility and the approach channel to the inlet portion 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 the reservoir water level falls below EL m, and Flat yards in right side of intake facility and in the fore-bay of the spillway to prevent sediment from the Keduwang River and from deposits in front of the spillway directly entering the portion in front of the intake facility. (b) Dredging volume (including garbage) Around 251,000 m 3 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 m 3 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 m 3 ) Dredging machine : Barge + crane with grab bucket (3.5 m 3 ) 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 of the dam The secondary spoil bank (40 ha); An area located about 1,000 m downstream of the dam and on the right bank of the Bengawan Solo River 2-2

21 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 m 3 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) 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 project area where the Wonogiri multipurpose dam is located is very distinct. The annual rainfall is 1,900 mm and the rainy season and dry season rainfalls are about 1,400 mm and 500 mm respectively, as shown in Table According to Appendix 7.1, the annual sediment input in the Keduwang River basin is estimated to be 1.28 m 3. About 1.09 x 10 6 m 3 of this sediment is judged to flow into the reservoir as suspended load in the rainy season. Hence, in order to prevent large amounts of new sediment entering the portion in front of the intake facility and the approach channel after dredging, a flat yard of EL m, being lower by 1.0 m than the LWL (EL m) of the reservoir, is to be designed on the right hand side of the approach channel to the intake facility. After the completion of the dredging works, the sediment flowing into the reservoir from the Keduwang River should be stopped in the stretch between the 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 enter smoothly into the portion in front of the intake facility. Therefore, for the smooth intake of water, the approach 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. 2-3

22 3) The maximum wind velocity is 30 m/s, so this value is to be adopted for the design of the floating log boom. 4) According to the Design Report of the Wonogiri Multipurpose Dam, in the stability analysis of the dam itself 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 the Wonogiri multipurpose dam to the irrigation area of about 30,000 ha in the downstream and to keep the restricted water level of EL m during the rainy season. 2) It is necessary that operation of the dam intake facility for the Wonogiri power station shall be stopped for 3-4 months, although this period should be kept as short as possible. 3) As the operation, maintenance and administration for the countermeasures on sedimentation of the Wonogiri 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 provided system 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 be constructed 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 and system provided, the operation and maintenance section of PJT-IBS had better participate in the Assistance 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 considering construction materials available in Indonesia such as cement, reinforcement bar, concrete pipe, etc.. Local contractors will be involved within technically allowable limits to activate the societies of the local contractors 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 as possible and to consider the environmental impact. 2) The floating log boom should be designed with adequate strength because floating log booms made in Indonesia 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 exemption procedures in Indonesia. Besides, it is considered that the requirement for materials, equipment, and labor should not fluctuate greatly throughout the construction period. In addition, the periods required for the preparation before the works and clearing away after the works should be determined in consideration of the period required for the various components of the works, the period required for installation and 2-4

23 removal of the temporary facilities, and the period required for procurement of the major materials and equipment to be used 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 only one of these was accepted. The reasons for rejecting the check dams and provision of a dredging system are 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 dams contains a high proportion of sand and gravel. Therefore, even if the check dams are constructed on the Keduwang River, it can be said that the dams will trap only sand and gravel (bed load) which are being deposited as the river deposit material. At the moment, the annual sediment input from the Keduwang River is estimated at about 1,280,000 m 3, (refer to Appendix 7.1). Assuming that the bed load is about 15% of all sediment (as there are no actual measurement data, this assumption is based on data from the Brantus river basin, being the eastern neighboring basin of the Solo River), the suspended load volume is estimated to be about 1,090,000 m 3. It can be judged that most of the suspended load produced in the Keduwang River is entering the Wonogiri dam 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 the check dams in the Keduwang River and at the Keduwang bridge were also conducted and the results are shown below. 2-5

24 Name of sample (sampling location) Keduwang bridge Results of Physical Tests Check dam No.1 Site Check dam No.2 Site About 5 km up-stream of Check dam No.2 (Existing test) (1) Near Wonogiri dam (Existing test) (2) up-stream edge of the Wonogiri reservoir Sampling Date of test Sep.2001 Sep Sep.2001 Sep.2001 About 1975 About 1993 Distance from the Wonogiri multipurpose dam(km) About 6 8 Sampling depth GL m Density of soil particle s(g/cm 3 ) Natural water content Wn( ) Gravel ( ) Sand( ) Gradation Silt( ) (0.3) (0.1) (<0.2) 0 5 Clay( ) 39 Uniformity coeff. Uc Curvat. Coeff. Uc Liquid limit w L ( ) Consistency Plastic limit wp ( ) Plastic index Ip Consistency index Ic Classification Well Well Well Well Silt gradate-d Gradate-d gradate-d gradate-d High liquid limit gravel Gravel gravel gravel Fine 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 reservoir is composed of 2% gravel, 19% sand and 79% silt and clay. It is indicated that the suspended load is deposited 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 and 1% 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 of the sediment trapped by them will be bed load (sand and gravel) and the volume will be only 190,000 m 3, 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 are made, it would be critical that the above suspended load of silt and clay be trapped and controlled in the Keduwang River basin. The conceivable countermeasures on these are as follows: 2-6

25 (a) To reduce sediment production volume by restraint of soil erosion through improvement of agricultural activities, (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 river structures to slow the velocity of the river flow, (d) To reduce the suspended load entering the Wonogiri multipurpose dam by constructing middle-scaled dams 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 the suspended load through a sand flushing tunnel and canal to be constructed between the Keduwang River and 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 the description of urgent countermeasures. Therefore, even if the two check dams are constructed in compliance with the request, their usefulness as urgent countermeasures against sedimentation in the Wonogiri multipurpose dam reservoir (the Assistance Project) could not be agreed because the reduction of the suspended load entering the Wonogiri dam would be minimal. 2) Providing dredging system Possible methods of dredging to be provided to PBS are compared in terms of their potential sustainability in Table 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 in Norway 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 by sediment, dredging work (about 40,000 m 3 ) 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 10 6 as shown in Table Further, if a grab bucket were used, the efficiency for dredging fine sediment is low, so the annual O&M cost would be 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 Cooperation Bengawan Solo Branch Office (PJT-IBS), which is not scheduled to be commence operation until January, 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 budget into the future, so if a sand pump dredge was provided under Japanese grant aid there is too much risk that it would go unused through lack of GOI funding. 2-7

26 (b) Hydro-type sand flushing system The hydro-type sand flushing system has been designed to remove sedimentation to the downstream by washing out water together with sediment by use of a siphon. Hence, the annual O&M cost is estimated at Rp. 210 x 10 6 as shown in Table , 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 sea using Hydro-J Type and another is Jhimruk hydropower project (12 MW) in Nepal using Hydro-Pipe System. In Japan, a test of this Hydro-type dredging system is scheduled to be made in the Sakuma dam in November, 2001, but this type has few examples actually utilized in projects and has unknown reliability. (c) Application to Japan s Grant Aid The applicability of different dredging systems for the sediment removal works in the Wonogiri reservoir are examined above. However, it is judged to be unjustified at the moment to provide either system from the 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 large O&M cost required for sustainable dredging of the Wonogiri reservoir under the present economic conditions in Indonesia (refer to 2.4.2(6) of the report). Therefore, the hydro-type dredging system, which is lower in O&M cost, is one alternative for sustainable sediment removal that could be applied in the future. (d) The requested components from GOI and selected components are tabulated below. Requested Components and Selected Components Requested component 1) Construction of two check dams on the Keduwang River (rejected) 2) Provision of a dredging system (rejected) Selected component 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 the intake (251,000m 3 ) 3) Installation of floating log boom 4) Providing echo sounding survey equipment together 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 following gates and valve may need to be operated, and if so, they will need to be working reliably. Hence, prior to the commencement of the urgent dredging works, they should be inspected and, if necessary, repaired due to the following reasons (refer to Fig ): 2-8

27 Intake coaster gate Emergency releasing hollow jet valve Spillway gates (a) (b) (c) (d) During the removal of garbage plugging the trashrack of the intake facility, the surrounding sediment will need to be flushed by operation of the hollow jet valve at the downstream. If this flushing works will be made through the power station, there will be a possibility that the casing and draft tube of the turbine may be abraded and damaged, then the operation of the hollow jet valve for this flushing works should be made. Therefore, prior to the commencement of this flushing works, the possibility of this hollow jet valve operation should be confirmed. During the above flushing works, and the dredging works in front of the intake facility, there will be 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 by closing the intake coaster gate. Therefore, prior to the commencement of this dredging works, the operability of this coaster gate should be confirmed. If irrigation water needs to be released during the garbage removal and dredging works, which require the closing of the intake facility,, then it can be released through the spillway. Hence, the removal works of the garbage and the dredging works are likely to frequently be made conducted while irrigation water is being released through the spillway. Any of the four spillway gates can be operated as required depending on the location of the dredges, sand draining pipes and associated equipment. According to the interviews conducted during the Field Works, during the rainy season, PBS frequently operates the spillway gates to control the water level in the reservoir. However, to guarantee safety during the construction, inspection, and if necessary repair, of the spillway gates is 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 required man-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. 2-9

28 ii) New construction of a waterway channel to take water from the Bengawan Solo River into the intake facility at times when the reservoir water level is equal to or below EL (i.e. LWL) m. In the upstream portion of the existing intake facility, the width of the waterway channel should be 3.0 m equal 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 conducted during 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 is the same as the low water level (LWL) of EL m, taking into account the accuracy of the echo sounding survey. The slope of the upstream end should be 1:10 gentler than the angle of repose. iii) Construction of flat yards of EL m, being lower by 1.0 m than the LWL of the reservoir. This also considers that EL m is the original design elevation of the fore-bay for the spillway. The flat yards are to prevent the large quantities of sediment from continuing to enter the portion in front of the intake 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 m, and the embankment for the railway remain on the right bank of the intake facility. Using the surrounding area of these structures, the flat yard of EL m that is the same elevation as these structures and is lower than the LWL by 1.0 m will be constructed. At portions lower than EL m, the dredging will be made to achieve the original topography. Out of the flat yard of EL m, the dredging works will be made following the angle of repose of the sediment material. At the above portion of the main dam higher than EL m, the sediment will be removed up to the dam body. In accordance with the original design, a fore bay of EL m has been constructed on the left bank of the intake facility. Therefore, the dredging works will be made up to EL 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 in Fig (refer to Appendix 6.2) and as below. Dredging Quantities (Unit:m 3 ) 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 and new sediment inflow to the dredging area is expected to occur between then and the completion of the dredging works (about 2 years). The sediment inflow amount is estimated from the following: 2-10

29 The sedimentation level in front of the intake facility has risen by m in the 2 years from December, 1999 to August, PBS is to dredge about 96,000 m 3 of sediment from the stretch in front of the intake facility to the Keduwang River in the two years of 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 rainy seasons) 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 by PBS) = ((300 m x 130 m x (1.1 m m) / 2) /2) x 3 96,000 m 3 = 47,000 m 3 Accordingly, the sediment volume to be actually dredged is 251,000 m 3. (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 the contractor as this will greatly affect the dredging works because of the construction conditions such as weather, reservoir water level and river flow discharge being varied due to the seasons. The sedimentation of about 250,000 m 3 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 the original topography/geology, the shape of the sediment deposited at moment, characteristics of the sediment, and the reservoir water level a) Condition of construction The construction method is restricted by the procurement of the construction equipment, locations of the spoil 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 such equipment would be adopted in the construction plan. Only equipment usually available in the market will 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 of the river water has increased. Hence, to allow their use throughout the year, the spoil banks should be proposed on the land without washing out the dredged sediment to the downstream by the river. 2-11

30 iii) Depth of dredging works The reservoir water level varies in the range from EL m in the rainy season to EL m in the dry season. Further, as the deepest elevation of the dredged area is EL m, the depth of dredging will be 20.0 m (EL m EL m = 20.0 m). This will be considered in the selection of available dredging 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 waterway was originally constructed by open cut excavation to rock. The bottom elevation is at EL m, the width 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, two berms of EL m and EL 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 overflow crest with a height of 1.5 m and crest elevation of 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 work carried out by PJT-I. This is mainly silt material composed of fine particles in which lumps of hard clay are 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 was completed. For the period of some years after 1983, the floating log boom had been repaired and maintained, however it has not been in place since Accordingly, during every rainy season, much garbage 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 has accumulated near the intake facility of the dam. This garbage has been plugging the screen of the intake facility and has accelerated the sedimentation in front of the intake facility. According to the inspection through the gate slot for the intake gate conducted during the Field Works, sedimentation of the sediment material and the garbage was not apparent in the head-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 estimated as follows: Annual accumulation; 100 m x 100 m x 0.6 m = 6,000 m 3 Period for the garbage to gather; 2000 year 1988 year = 12 years Accumulated garbage; 6,000 m 3 x 12 years = 72,000 m

31 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 system for urgent dredging work is shown in Table The barge and crane with grab bucket, which can remove all kinds of soil and garbage is the most suitable dredging system for this project for the following reasons: It can easily cope with the variation in water level and dredging work can be carried out in deep water. (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 garbage can not be identified near the intake facility. This system has the advantage of being able to dredge garbage 2-13

32 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 by compressed 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 5.3 m x 1.5 m; Total 42 pieces). A 160 ton crane is used for assembling the Uni-float ton crane is installed on the barge and 3.5 m 3 -grab bucket will be attached to the 80 ton crane, and the dredging work is carried out by using this 3.5 m 3 grab bucket. - The dredged sediment (including the silty-sand or silty-clay and the garbage) will be thrown to the vibration screen. - The dredged sedimentation will be separated into garbage and silty-sand or silty-clay by the vibration screen. - The garbage separated by the vibration screen will be transported to the bank by barge. After transportation to the bank, the garbage will be loaded onto a 4 ton truck with 2 ton crane by 40 ton crane 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 by compressed 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 be transported to the secondary spoil bank by 10-ton dump truck. The drained water generated from the dredged silty-sand or silty-clay at the primary spoil bank is returned to the reservoir through φ 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 the downstream Bengawan Solo River cannot be decided until the environmental impact assessment survey is finished. The selected primary spoil bank location, which is owned by PBS, is downstream of the sub dam incorporates the present spoil bank area for dredging work performed by the PJT-I (refer to Fig.2.2.2). However, a secondary spoil bank is needed because the capacity of the primary location is too small for the anticipated sediment volume. It is necessary that dredged material is transported and dumped at a secondary spoil bank after temporarily storage at the primary spoil bank. A secondary spoil bank location of about 40 ha is available about 1 km downstream of the right bank of the Bengawan Solo River, and it s the land is owned by PBS. Therefore, land acquisition for the spoil bank is not necessary. (Refer to Fig ) The pipe length for sediment transportation is about 2.0 km, and the distance of transportation by dump truck is about 1 km from the primary to secondary spoil bank. Construction of a dykes and drainage system is necessary at the primary spoil bank. 2-14

33 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 equipment Grab bucket 3.5 m 3 80 t class crawler crane Compressed air sediment transportation equipment (120 m 3 /h) 2. Tug Boat 200 PS 1 3. Anchor Barge 5.0 t 1 4. Earth Carrying Barge Capacity 80 m Commuter ship 30 PS 1 6. Pipe for dredging the sand 350 mm, about 1,500 m 1 [Garbage Transfer] (From barge to Secondary spoil bank with transfer from barge to truck at a temporary embayment and dock) 7. Crawler crane 40 t 1 8. Dump truck 4 t 1 [Compiling soil] At primary spoil bank 9. Bulldozer (for swamp) t Backhoe (flat loading) 1.0 m 3 2 [Transportation of soil] (From primary spoil bank to 2 nd spoil bank) 11. Dump truck 10 t 6 [Compiling soil] At secondary spoil bank 12 Bulldozer (c) Dredging period The working area consists of the intake area, fore bay of the spillway, new intake waterway, and the flat plane at the right side of the intake. The dredging work will be able to be carried out throughout the year in principle, but will need to be executed at different times for the different areas depending on the water level 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 carried out at the intake area. During the dredging works of this area, it will be necessary to close the water intake and supply water for irrigation and power generation through the spillway. Therefore, the dredging work in this area has to be carried out when the reservoir water level is higher than the spillway crest level of EL.131 m. 2-15

34 b) Fore-bay of spillway The dredging work in this area has to be carried out during the dry season because the spillway gates are sometimes operated during the rainy season. If the spillway gates are operated to release the flood discharge, 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 at any time. However, it is desirable that this work is carried out when the water level is as low as possible because 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 urgent works 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 point over a period of twenty one (21) months from December 1999 to August It is assumed that obstruction of the intake began to occur around The sediment level when intake obstruction began is assumed to be EL m based on the results of echo sounding survey in 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 smaller just in front of the intake facility and greater in the middle portion of the approach channel to the inlet of the intake facility. Estimation of the rate of sediment accumulation in front of the intake facility is made based on the average sedimentation rate. Hence, the rate of sediment accumulation in front of the intake facility is as follows: (3.8 m 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 m EL 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 from entering the intake. The layout of the floating log boom is shown in Fig In the design, the ratio of maximum deflection against the span length should be about 1/5 so that the diameter of the wire cable may become as small as possible. 2-16

35 A-line : B-line : C-line : D-line : Main purpose of this line is protection against the garbage from the Keduwang river. Both ends of the floating log boom are fixed by a concrete anchor block. The span length is about 100 m Main purpose of this line is protection against the garbage from the Bengawan Solo river. The left and right side anchor blocks are used together with A-line and C-line, respectively. The span length is about 105 m. This line is set parallel to the left side slope of the flat excavation area (EL m) in the forebay of the spillway. This line will direct the garbage from the Bengawan Solo river to the downstream through the spillway. Therefore, the garbage is judged not to be trapped along this line during flood occurring in the rainy season. The span length is about 110 m. This line will not trap much garbage. However, it would be set to prevent garbage that may accumulate in front of the spillway from moving to the inlet portion of the intake due to lowering of the water level in the reservoir or by wind and waves. The span length is about 105 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 to be within 1m by circle error probability (CEP). When a single GPS navigation unit is used on the survey boat, the accuracy of the measurement is usually estimated to be m. This positioning measurement would be meaningless for the echo sounding survey in front of the intake. Therefore, one fixed base station to enable differential GPS (DGPS) would be set at an unobstructed location near the intake facility, then the error correction of GPS on the survey boat could be made by using the DGPS at the fixed station. Then the positioning measurement of the survey boat could be made within the error of 1 m by CEP. (b) The echo sounding survey shall have the accuracy of less than 10 cm. In this survey, sound wave would be shot to the bottom of the reservoir by the echo sounder, the reflected sound wave would be captured by the echo sounder on the survey boat, the reflecting time would be measured and the water depth would be estimated. The important thing is that the reflection layer of the sound wave depends on the characteristics of the sediment layer deposited in the reservoir. At the moment, the PBS s survey using an old echo sounder, a sound wave of Hz is used. (c) The measured data are those of the positioning of the survey boat and of the echo sounding survey at the survey boat, and in order to collect these data, a portable computer would be required. Also, the computer program for the prompt data process and preparation of the contour map of water depth in the reservoir 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 for providing 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 (the Assistance Project) are shown in Fig and below: 2-17

36 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 boat 1) Two (2) wave frequency type, geodesic receiver 1 set 2) Two (2) wave frequency antenna 1 set 3) Wireless receiver 1 set (4) Stationary GPS station 1) Two (2) wave frequency type, geodesic receiver 1 set 2) Two (2) wave frequency antenna 1 set 3) Terminal for geodesic receiver in Item 4.1) 1 set 4) Large scale battery 1 set 5) 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 Basic Design Drawing Design drawings of the urgent dredging works and layout of the floating log booms are shown in Figs and Appendices 6.2, and Fig Further, the composition of the water depth survey system is shown in Fig 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 s Grant Aid system. (a) (b) (c) Director General of Rural Development, Ministry of Settlement and Regional Infrastructure (KIMPRASWIL) in Indonesia would be the executing agency for the Project implementation. Immediately after the Exchange of Note (E/N) between GOJ and GOI regarding the stages of the detailed design and the construction works is signed, the KIMPRASWIL should commence the necessary actions for the implementation of the Project. 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 tender documents for the selection of the Japanese Contractor for the civil works. Immediately after the completion of the preparation, the Japanese Consultant should start the tendering works. 2-18

37 (d) (e) GOI should commence the arrangement for the land acquisition in parallel with the detailed design, if necessary. A Japanese Contractor immediately after signing the contract for the construction works with the KIMPRASWIL shall commence to undertake the construction works and the Japanese Consultant shall 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 under Japan s Grant Aid Program. These contractors have employed local contractors as subcontractors, mostly for 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 Japanese contractor arranges construction equipment and material by itself and also uses the manpower supplied from 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 as the rainy and dry seasons, and the water intake function for irrigation having to be maintained during the construction 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 intake function from the reservoir be maintained to supply irrigation water to the 30,000 ha in the downstream irrigation area. Also, the dam operating rule of the restricting the water level to EL m for flood control in the rainy season must be strictly followed. The present situation of the Wonogiri power station and 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 for dredging work in front of the intake to be carried out because during this period water will not be able to be taken through the intake. 2-19

38 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 of noise and vibration provide serious affect to, the consideration of the impact to the people living in and around 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 heavy equipment. 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 is recorded 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 The safety countermeasures during construction should be strictly made, especially in the rainy season because the construction in the rainy season is very dangerous. (3) Scope of Works 1) Scope of works to be executed by Japanese side (a) (b) Detailed design and preparation of the tender documents Undertaking the construction supervision and provision of equipment, described in of the report (excluding the works to be executed by the Indonesian side shown below) 2) Undertaking by the Government of Indonesia (GOI) (a) (b) (c) (d) (e) Preparation of an FRP boat with outboard motor for echo sounding survey Land acquisition (if necessary) Budget arrangement and payment for import tax, internal tax, and other levies under implementation of Japan Grant Aid project (the Assistance Project) Coordination with other relevant agencies and issue consent(s) necessary for implementation of the Assistance Project Improvement of operation and maintenance for the Wonogiri multipurpose dam and the Wonogiri water power station 2-20

39 (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 and preparation of tender documents will be required. Immediately after signing the E/N between GOJ and GOI for the detailed design and the construction works, the contract for the consulting services will be concluded between the KIMPRASWIL and the Japanese Consultant. The detailed design and tender documents will then be prepared in collaboration with the KIMPRASWIL. The Consultant will discuss the design and implementation schedule of the works with the KIMPRASWIL during 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 Japanese Consultant 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 construction equipment, 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 the construction works and necessary inspection of the construction works 2-21

40 (c) Approval for the payment to the contractor Checking and evaluation of the performance of the works necessary for issuing payment certificates and completion 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 by a suitable method and equipment proposed by the Japanese Contractor. All costs shall be borne by the Contractor. (b) Effect liability period The effect liability period shall be one (1) year after the issuing of the certificate regarding the handing over to 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. In addition, the ready mixed concrete will be available near the construction site (the Wonogiri multipurpose dam). The dredging work and earthwork are of a major scale. Considering the condition that most of the required construction equipment for the construction works can be rented from lease companies in Indonesia, and the construction period is short (18.5 months), the required construction equipment will be leased for this construction works in principle. The compressed air sediment transportation equipment (120 m 3 /h) is very special and the rent is impossible in Indonesia. So this equipment will be imported from 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 2-22

41 As mentioned in 2.2.2(2)2) of this report, the dredging work volume for the Assistance Project is estimated to be around 251,000 m 3, including 72,000 m 3 of garbage, and one (1) barge with grab bucket (3.5 m 3 ) shall be adopted as the dredging equipment. As the working area is limited, more than two (2) sets of dredging equipment could not be efficiently workable. The construction period is estimated in the following manner 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 m 3 (Daily dredging rate) x 30 days x 0.82 (Efficiency) = 24,919 m 3 /month 250,000 m 3 (Dredging volume in total) / 24,919 m 3 (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 Detail Design Stage Construction Stage (Detail Design) (Preparation of Tender Document) (Tender) (Construction) 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 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 services based 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 in the Government of Indonesia and prompt internal transportation therein of the materials and equipment for the Assistance Project purchased under the Japan Grant Aid. (7) To exempt Japanese juridical and physical nationals engaged in the Assistance Project from customs duties, internal taxes and other fiscal levies which may be imposed in Indonesia with 2-23

42 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 the products and services under the Verified Contract such facilities as may be necessary for their entry into Indonesia and stay therein for the performance of their works (9) To provide necessary permissions, licenses and other authorizations for implementing the Assistance Project, if necessary. (10) To maintain and use properly and effectively the facilities constructed and equipment provided under the Assistance Project 2.4 Project Operation Plan 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 intake facilities, and the additional survey shall be carried out along the Keduwang river in the reservoir area at the start of dry season. The sedimentation situation near the intake facility and along the Keduwang river should be well-described and understood. The sedimentation into the reservoir from the Keduwang river can be considered to have the worst affect, badly obstructing the intake facilities. It is strongly recommended that the survey results be informed to the Japanese side (JICA Tokyo or the Consultant) after every 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 flow into the reservoir from all the tributaries. If the Wonogiri multipurpose dam had not been constructed, the garbage from all the tributaries would flow down to the downstream. Therefore, the garbage are recommended to be released to the downstream together with overflow water through the spillway as much as possible. The volume of such overflow water will be minor compared to the volume of water stored in the 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 log boom and in the reservoir. Of the garbage that is not discharged, that trapped by the floating log booms and the screen of the intake should be collected manually by boat, unloaded and transported to the designated incinerator in the same manner that PLN does at present. 2-24

43 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 with presidential decree (No.129/2000), and this was scheduled to occur in January However, it has not been realized so far and the PJT I Bengawan Solo (PJT-IBS) will be established in January, 2002 according to the hearing survey. Therefore, O&M works of the Wonogiri multipurpose dam after the construction completion will be executed by PJT-IBS, and the equipment provided by the Assistance Project will also be transferred to PJT-IBS. The principal responsibilities, target river, personnel and O&M works of PJT-IBS are mentioned below based 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 to the 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 East Java 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 water tariffs at the moment are shown below. Electricity (PLN) Rp /kwh Drinking water (PDAM) Rp /m 3 Industrial water Rp /m 3 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 Wonogiri multipurpose 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&M works 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 the CDMP Study, the required O&M costs, excluding those of the Assistance Project, are shown below. 2-25

44 (7) Available O&M budget Required O&M Cost (unit: million Rp.) Item Dam Wonogiri Colo Others (13 dams) Sub-total ,001 1,102 1,212 River B. Solo Madiun R Tributaries (2 nd ) Tributaries (3 rd ) Sub-total 1,245 1,370 1,507 1,658 1,824 Telemeter Office Total 2,332 2,610 2,886 3,190 3,527 Source: CDMP Study Report The five-year financial statement is shown in Table based on the CDMP Study and SAPS reports. It is assumed that the required O&M cost of Rp. 23,700,000 /year for the Assistance Project (refer to Appendix 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, the repairing the intake coaster gate, spillway radial gates and the emergency hollow jet valve should be made by 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 GPS base 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 the Wonogiri multipurpose dam reservoir which is now under way and is scheduled to be completed in February 2002, the possibility of the dredged material being disposed down-stream in the Solo river should 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. 2-26

45 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-power generation) and flood control. The requested Japanese assistance (hereinafter called as the Assistance Project) is the first steps to conquer the sedimentation problem in the Wonogiri multipurpose dam reservoir to assure the water intake function of the dam for a period of about five (5) years from the completion of the Project (refer to 2.2.2(2)2)(d) of this report). The Assistance Project is not designed to recover the flood control function as originally planned. For this, effective countermeasures shall be contemplated and implemented as mid to long term countermeasures for the entire sedimentation problem in the Wonogiri multipurpose dam reservoir. The beneficiaries of the Assistance Project are, therefore, the water users for irrigation and hydropower generation. The effect of implementing the Assistance Project and the extent to which the present situation will be improved are shown in Table The Assistance Project creates the direct benefit stated below. In summary, this is the maintenance of income of beneficiary farmers in the down-stream of the Wonogiri multipurpose dam and contributing to the stable electricity supply to the central Java province. In so doing it will hopefully contribute to stable food supply and social stabilization, the primary political strategies in Indonesia as described in of the report 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 ), which is the beneficial area of the Assistance Project. The number of beneficiaries is estimated 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 shown in the following table. However, if the Assistance Project is not implemented, the intake of the dam will be completely blocked and the cropping area and yield will reduce as shown in the below table. The loss due to the reduced harvest will be annually Rp. 187 x 10 9 at the present market price of 1,220 Rp./kg. This is considered to be the direct effect of the Assistance Project. 3-1

46 Comparison between Situation of the Present and the Intake of the Dam being Plugged Index The Present The Intake of the Dam being Plugged Land use Paddy field (Irrigation) 27,356 ha 21,100 ha Sugarcane field 2,100 ha Paddy field (Rain-fed) 2,233 ha Upland field Project area 29,589 ha 23,200 ha Paddy Area (Irrigation) Rainy Season 26,523 ha 19,000 ha Dry season-i 26,360 ha 19,000 ha Dry season-ii 23,142 ha 11,600 ha Annually irrigated area 76,025 ha 49,600 ha Cropping area Paddy rainy season 28,756 ha 19,000 ha Paddy dry season-i 26,360 ha 19,000 ha Paddy dry season-ii 23,142 ha 11,600 ha Palawijia & Others 1,444 ha 2,100 ha Annual cropping area 79,702 ha 51,700 ha Cropping intensity Paddy 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/ha Annual rice production 425,950 t 272,800 t Source: WATSAL Feed back study Further, as an index to assess the effect of the implementation of the Assistance Project, the cropping area by each cropping season will be adopted. As to the yield of irrigated paddy, there are variations between cropping seasons and large differences between official yields and those based on direct reports from farmers. 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 power supply system) and all electricity is supplied through the united power supply market. So strictly speaking, there is no specific beneficiary area of the Wonogiri hydropower station. However, the longer the power transmission line, the bigger the transmission loss, so the beneficiary area is mainly considered to be central Java province. Also, dividing the annual power generation energy of the Wonogiri power station (50,000 MWh) by the annual power consumption of an average household (820 kwh), the number of beneficiaries is estimated at 61,000 households. 3-2

47 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 about five (5) year after the completion of the Assistance Project. However, if the Assistance Project is not implemented, the intake of the dam will be fully blocked with power generation becoming impossible. The loss will be annually Rp. 10x10 9, estimated by multiplying the electricity sale price of 200 Rp./kWh at September in 2001 by the annual power generation energy of 50,000 MWh. This is considered to be the direct effect of the Assistance Project. Further, the indices adopted to assess the effect of the Assistance Project are the annual power generation energy by month, the maximum intake of water, and the number of stoppage days of power generation each month 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 serious defects to the power generation equipment (only one set of turbine and generator were 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 generation smoothly in the future, the prompt execution of an overall inspection of both the civil structures and the power generation equipment in the Wonogiri hydropower 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 intake facility and installation of a mechanical raking system on the screen of the intake are strongly recommended 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 flood control for the long term, mid- and long term countermeasures such as water-shed conservation and sediment management of the Wonogiri dam reservoir, and structural measures in the reservoir against sediment flowing into the reservoir should be studied. In particular, new construction of another intake facility or of an inlet shaft at the inlet portion of the existing intake and so on proposed in 7.2.3(5)3) of the Appendix 7.2 could be judged to be the most realistic and most effective. The completion of these midand long term countermeasures shall be made in time considering the planned completion of the Assistance Project shown in the attached figure in (7) of this report and the effective period of the Assistance Project (around 5 years after completion). 3-3

48 Basic Design Study Report on the Project for Urgent Countermeasures for Sedimentation in Wonogiri Multipurpose Dam Reservoir in the Republic of Indonesia Tables

49 Table Monthly Power Output by Wonogiri Power Station (Unit: kwh) Year Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Total ,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, ,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, ,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, ,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, ,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, ,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, ,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, ,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, ,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, ,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, ,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, ,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, ,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, ,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, ,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, , ,900 29,168, , ,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, ,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, ,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, ,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

50 Table Cropping Area and Croping Intensity of Wonogiri Irrigation System Whole 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 Annual 1995/96 Irrigated Paddy 20,307 20,025 15,816 56, Paddy Field Sugarcane ,121 ha Palawija ,374 2, Total 21,121 20,333 18,190 59, /97 Irrigated Paddy 20,616 20,369 18,990 59, Paddy Field Sugarcane ,121 ha Palawija , Total 21,121 20,740 19,810 61, /98 Irrigated Paddy 21,343 21,286 20,522 63, Paddy Field Sugarcane ,793 ha Palawija Total 21,793 21,493 20,854 64, /99 Irrigated Paddy 20,969 20,907 18,907 60, Paddy Field Sugarcane ,793 ha Palawija Total 21,793 21,080 19,567 62, /00 Irrigated Paddy 21,347 21,350 20,997 63, Paddy Field Sugarcane ,793 ha Palawija Total 21,730 21,621 21,418 64, Average of 3 years Irrigated Paddy 21,220 21,181 20,142 62, / /00 Sugarcane Paddy Field: 21,793 ha Palawija Total 21,772 21,398 20,613 63, / Including area classified as pumping irrigation area of 1,700 ha Source: Cabang Bundungan Wonogiri, Bengawan Solo Karanganyar & Sragen Whole Left 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 Annual 1997/98 Irrigated Paddy 4,947 4,899 1,893 11, Paddy Field Sugarcane 0 0 7,796 ha Palawija Rainfed Paddy 2,233 2, Total 7,180 4,899 2,097 14, /99 Irrigated Paddy 5,544 5,219 1,893 12, Paddy Field Sugarcane 0 0 7,796 ha Palawija Rainfed Paddy 2,233 2, Total 7,777 5,219 2,097 15, /00 Irrigated Paddy 5,419 5,419 5,215 16, Paddy Field Sugarcane 0 0 7,796 ha Palawija Rainfed Paddy 2,233 2, Total 7,652 5,419 5,419 18, Average of 3 years Irrigated Paddy 5,303 5,179 3,000 13, / /00 Sugarcane 0 0 Paddy Field: 7,796 ha Palawija Rainfed Paddy 2,233 2, Total 7,536 5,179 3,204 15, / Including area classified as pumping irrigation area of 450 ha Source: Cabang Bundungan Wonogiri, Bengawan Solo Wonogiri & Klaten Whole Wonogiri Irrigation Project 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 Annual 1997/98 Irrigated Paddy 26,290 26,185 22,415 74, Paddy Field Sugarcane ,589 ha Palawija Rainfed Paddy 2,233 2, Total 28,973 26,392 22,951 78, /99 Irrigated Paddy 26,513 26,126 20,800 73, Paddy Field Sugarcane ,589 ha Palawija , Rainfed Paddy 2,233 2, Total 29,570 26,299 21,664 77, /00 Irrigated Paddy 26,766 26,769 26,212 79, Paddy Field Sugarcane ,589 ha Palawija , Rainfed Paddy 2,233 2, Total 29,382 27,040 26,837 83, Average of 3 years Irrigated Paddy 26,523 26,360 23,142 76, / /00 Sugarcane Paddy Field: 29,589 ha Palawija Rainfed Paddy 2,233 2, Total 29,308 26,516 23,817 79, / Including area classified as pumping irrigation area of 2,150 ha Source: Cabang Bundungan Wonogiri, Bengawan Solo Karanganyar, Sragen, Wonogiri & Klaten

51 Table 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 Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total 1,942 1,706 1,684 2,046 1,908 1,744 2,131 1,880 Note: Operation Agency PBS: Proyek Bengawan Solo CJIS: Central Java Irrigation Service

52 Table Comparison for Providing Dredging System Dredging System Transportation Adaptability to geography The dredging depth Soil Property Adaptability to this project 1 Drag Suction Dredger (Large) The depth of dredging will be 30m at maximum. 2 Drag Suction Dredger (Small) The depth of dredging will be only 15m at maximum. 3 Cutter Dredger (Un-self mobile type) (Large) 4 Cutter Dredger (Un-self mobile type) (Small) The depth of dredging will be only 15m at 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 not suitable 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 against sediment with fine particles being inferior to those of by sand pump dredger. 17 Hydro Type including Crane Hydro-J Pipe Remarks

53 Table 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. Labor 1) Senior mariner(4) *1 Man-day 1,264 95, ,080 1,334 2) Common mariner(8) *2 Man-day 2,528 30,000 75, ) Common labor(2) *3 Man-day ,000 11, Material 1) Heavy oil *4 Liter 150,000 2, ,000 3,500 2) Lubricant Liter 4,500 22, ,250 1, Equipment 1) Repair. cost of Dredger *5 Year 1 929,070 10,323 2) Repair. cost of Tag boat *6 Year 1 150,102 1,668 3) Repair. cost of Pipe line *7 Year 1 37, Total 1,740,742 19,342 Remarks; 1) Time of cost estimate: June in ) 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.

54 Table 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, Material *2 Heavy oil *4 Liter 87,620 2, ,002 2,044 Total 213,002 2,367 Remarks; 1) Time of cost estimate: June in ) 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/h Annual consumed quantities of heavy oil (liter) = liter/hr x 10 hr/day x 200 day = 87,620

55 Table Comparison of Dredging Method for Urgent Dredging Works Dredging System 1 Drag Suction Dredger (Large) 2 Drag Suction Dredger (Small) Easiness for supply Transport ation Adaptability to geography The dredging depth Soil Property Garbage Adaptability to this project 3 Cutter Dredger (Un-self mobile type) 4 Cutter Dredger (Un-self mobile type) (Small) 5Broad Pump Dredger (Un-self-mobile type) 6 Cutterless Pump Dredger (Un-self-mobile 7 Ejector Dredger Remarks The depth of dredging will be 30m at maximum. The depth of dredging will be only 15m at maximum. The depth of dredging will be only 15m at maximum. This is for the deep dredging and not suitable for the continuous 8Micro-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 15 Barge+Crane with Sand-pump 16 Barge +Crane(Grab Bucket) Efficiency of dredging works against sediment with fine particles being inferior to those of by sand pump 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 sand from 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 few dredging works achievements in dam reservoir and it is taken long time for design and production.

56 Table Profit and Loss Projection of Bengawan Solo Branch Office No. Item Unit I. REVENUES 10 6 Rp. 3,925 4,294 5,239 5,733 7, Revenues of Water Services 10 6 Rp. 3,080 3,353 4,191 4,565 5,757 a. Production - Electricity 10 3 kwh 57,365 57,365 57,365 57,365 57,365 - Raw water for drinking water 10 3 m 3 5,632 6,420 7,208 7,997 8,785 - Raw water for Industries 10 3 m 3 30,945 34,040 37,444 41,188 45,307 b. Tariffs - Electricity Rp/kWh Raw water for drinking water Rp/m Raw water for Industries Rp/m c. Revenues of Water Service - Electricity 10 6 Rp ,046 - Raw water for drinking water 10 6 Rp Raw water for Industries 10 6 Rp. 1,993 2,192 2,894 3,183 4, Revenues of Non Water Service 10 6 Rp ,048 1,168 1,304 - Tourism 10 6 Rp Equipment rental 10 6 Rp Construction 10 6 Rp Consultant 10 6 Rp Land rental 10 6 Rp II. COSTS 10 6 Rp. 4,480 4,989 5,519 6,086 6,724 - O&M 10 6 Rp. 2,332 2,610 2,886 3,190 3,527 - Personnel 10 6 Rp. 1,288 1,417 1,559 1,715 1,886 - Travelling 10 6 Rp General 10 6 Rp Marketing 10 6 Rp Depreciation 10 6 Rp Socialization 10 6 Rp Service Fee 10 6 Rp Human Resources Development 10 6 Rp Watershed conservation 10 6 Rp III. Profit & Loss 10 6 Rp IV. Other Revenues 10 6 Rp ,083 1,206 - Bank Interest etc Rp PGPS (public servant salary) 10 6 Rp ,065 V. Other Costs 10 6 Rp Bank fee etc Rp VI. Profit and Loss from others sourc 10 6 Rp ,080 1,204 VII. Profit & Loss before Taxes 10 6 Rp ,541 VIII. Taxes 10 6 Rp IX. Profit & Loss after Taxes 10 6 Rp ,087 Source: CDMP Study Report, April 2001, SAPS Report, July 2001

57 Table Project Effect and Extent of Improvement on Present Situation by Implementation of the Assistance Project Present Situation and Problems Countermeasures by the Assistance Project 1. Because of the water intake trouble -Inspection and repairing of due to the sedimentation near the gates and valve intake of the Wonogiri multipurpose -Execution of the urgently dam, reservoir below EL.130m can dredging works in front of the not be operated. intake facility (250,000 m 3 ) If no any countermeasures are made, the intake will be plugged perfectly within about 2.8 years and stoppage of the power generation of the Wonogiri Power station and reducing of rice production in the Wonogiri irrigation system will be occurred. In particular, the reducing of rice production is big problem from the view point of security assurance of stable food supply as one of the national strategies. 2. During the rainy season, much garbage (stems or twigs of agricultural products) are flowing into the reservoir and being settled. Further, in front of the intake, the garbage is likely to be plugging the screen of the intake then much sedimentation are remaining in front of the intake without entering into the intake tunnel. In case due to the unbalanced earth pressure from the up-stream, the screen being destroyed, water turbine in the power-house may be damaged greatly, and the intake tunnel will be plugged due for the much sedimentation to enter into the tunnel which will cause the difficulty of water supply from the dam to the down-stream. 3. The Assistance Project is to provide only the urgent countermeasures on the sedimentation problems of the Wonogiri multipurpose dam reservoir then succeeding this, the permanent countermeasures (mid- and long term) should be made. If not, the same problems at moment will occur in future. Installation of the floating log boom Providing the water depth survey system with GPS Project Effect and Extent of Improvement By the dredging works in front of the intake, the water intake function will be extended by about 5 years after the construction completion. The planned annual production of power generation energy and rice production could be maintained as they are at moment. By the removal of garbage by using the spilled out water and also by the manual removal of garbage near the floating log boom, the plugging the screen of the intake will be prevented. Then the smooth water intake will be possibly made without plugging the intake. By execution of continuous monitoring, the sedimentation situation of the reservoir could be obtained year by year, and such data could be utilized usefully to prepare the permanent countermeasures. T-9

58 Basic Design Study Report on the Project for Urgent Countermeasures for Sedimentation in Wonogiri Multipurpose Dam Reservoir in the Republic of Indonesia Figures

59 R.. JAV A SEA Floodway Jatirogo Sidayulawas T uban Bengawan Solo River K N B lawi R. ening R B ojonegoro Gresik B abat L amongan Lower Solo River Improvement Project*) SURABAY A Semarmendem R. T. l R idu R. Pundang R. B esuki R. ca Pa Mt. B untung Mt. Pandan Madiun River Urgent Flood Control Project 500 LEGEND Mt. Wilis 2563 Watershed River Objective Strches of River Improvement Project Wonogiri Dam Remarks*):on-going project Colo Intake Weir L asem Project Area Mountain SCA L E km City Town Bo B lora Irrigation Pumping Station Project loke n R. Cepu ulung R. W. T inggeng R Bengawan Solo River Sragen Ngawi MA DIUN S awur R. Cemoro R Jerowan R. K etonggo R Sragen R. 500 Mu ngkung R Mt. Merbabu 3142 Mt. Merapi 2914 Wonogiri Irrigation Project Mt. L awu Boyolali SURAK ARTA B rambang R G awe R.. Gandong R C atur S emin R R Madiun R. Jlantah R. K laten D engk eng R. Gonggang R. A sin R. emer Wonogiri Upper Solo River Improvement Project Wonogiri Multipurpose Dam Project. C M ungkungan R Ponorogo Te mpuran R. du wang R K e irtomoyo R. ey ang R. K T. R A nyar M anti R. Pacitan INDIA N OCE A N BASIC DESIGN STUDY ON URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBRIC OF INDONESIA JAPAN INTERNATIONAL COOPERATION AGENCY Fig Existing and on-going Projects by Japan's Grant Aid and JBIC Loan

60 Flood Period Flood Period Flood Control Storage during Flood Period 220x10 6 m 3 Flood Control Space during Non-flood Period 175x10 6 m 3 Dam Crest EL m PMFWL EL m NHWL CWL FWL EL m Water Utilization 440 x 10 6 m 3 Flood Control Storage 220 x 10 6 m 3 LWL EL m EL m EL m Sediment Storage 120 x 10 6 m 3 Water Utilization during Flood Period 395x10 6 m 3 Water Utilization during Non-flood Period 440x10 6 m 3 Jan. Dec. Allocation of Storage Capacity Reservoir Water Level Dimension of Wonogiri Multipurpose Dam Dam type Center core type rockfill dam Normal water level EL m Dam height 40.0 m Designed flood water level EL m Dam crest length m Abnormal flood water level EL m Dam volume 1,223,300 m 3 Spillway (Radial gates) 7.5 m(h) x 7.8 m(w) x 4 nos. Catchment area 1,350 km 2 Spillway Crest elevation EL m Reservoir submerged area 73.6 km 2 Design outflow discharge from dam 400 m 3 /s Gross volume 735 x 106 m 3 Design flood discharge 5,100 m 3 /s Effective volume 615 x 106 m 3 Abnormal design flood discharge 9,600 m 3 /s Flood control volume 220 x 106 m 3 Power generation facilities Water utilization volume 440 x 106 m 3 Installed capacity 12.4 MW Sediment volume 120 x 106 m 3 Design head 20.4 m Sediment level EL m Maximum utilization water discharge 75 m 3 /s Restricted water level EL m Annual power generation energy 50,000 MWh/year BASIC DESIGN STUDY ON URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBRIC OF INDONESIA JAPAN INTERNATIONAL COOPERATION AGENCY Fig Wonogiri Multipurpose Dam

61 Aug./Sep SCALE Dec BASIC DESIGN STUDY ON URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBRIC OF INDONESIA JAPAN INTERNATIONAL COOPERATION AGENCY Fig Sediment Condition in front of Intake Structure

62 SCALE May 2004 (Forecast) EL Aug./Sep Dec Sep EL BASIC DESIGN STUDY ON URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBRIC OF INDONESIA JAPAN INTERNATIONAL COOPERATION AGENCY Fig Anticipation of blockade in front of Intake Structure

63 B engawan Solo R iver N WONOGIR I DA M L 3R L 4R L 5R L 3L L 4L K 2R 15L K 3R L 1R L 2R L eber R iv er L 1L L 2L 3L 2L 2R K 1L K 2L K 3L K 4L K 5L K 5R K 6R K 7R K 6L K 7L W7R W7L 3R W6R 4/5L 4R G 2R W3L W1L W2L W5R W4R G 1R G 1L G 2L T 2R T 3R W3R W2R W1R N8L N9L T 2L T 4R N2L N7R N3L N4/5L N5R N8R N7L N9R N4R N3R N6L N6R 7L N1L N2R 9L N1L 7R B 0R B 0L B 1L 9R B 6R B 7R B 7L B 1R B 2R T 3L T 4L T 5L T 5R T 6R T 7R T 6L T 7L T 8L T 8R T 9R T 9L K e duang R iv e T irtomoyo R iver 10L B 2L 10R B 5L B 5R B 4R B 5R 11L 11R B 8R B 4L B 5L T emon R iver B 8L A lang R i v e A 4L 12L A 1L A 2L A 3L A 4R A 1R 13L A 2R A 3R 14L 12R 13R 14R 15R 15L B e nga wan S olo R iver Legend Sections Rivers Contour El. 140 m Road SCALE km BASIC DESIGN STUDY ON URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBRIC OF INDONESIA JAPAN INTERNATIONAL COOPERATION AGENCY Fig Wonogiri Dam Reservoir

64 Keduwang -Original River Bed Keduwang -River Bed (1993) Keduwang -River Bed (2000) Solo -Original River Bed Solo -River Bed (1993) Tirtomoyo -Original River Bed Tirtomoyo -River Bed (1993) Distance Upstream of Dam (km) River Bed Elevation (EL. m) BASIC DESIGN STUDY ON URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBRIC OF INDONESIA JAPAN INTERNATIONAL COOPERATION AGENCY Fig Wonogiri Dam Reservoir Profile

65 80,000,000 70,000,000 Annual Dec. to Apr. 60,000,000 Power Generation (kwh) 50,000,000 40,000,000 30,000,000 20,000,000 10,000, Year Annual Power Generation from 1983 to ,000,000 9,000,000 8,000,000 Power Generation (kwh) 7,000,000 6,000,000 5,000,000 4,000,000 3,000,000 2,000,000 1,000, Month Monthly Power Generation past 4 year BASIC DESIGN STUDY ON URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBRIC OF INDONESIA JAPAN INTERNATIONAL COOPERATION AGENCY Fig Variations of Power Generation from 1983 to 2001

66 New waterway Approach channel EL.128.0m Access Road EL.126.0m Fore bay (in front of spillway) 126 1:10 1:4.0 EL.116.0m 1:4.0 Varies. Varies. 1:4.0 EL.128.0m 1:3.1 Intake Gate Shaft EL.142.0m 1:2.2 Bengawan Solo River : EL.126.0m Flat yard in the right bank :4.0 Varies :3.1 1: EL.126.0m EL.126.0m 28 New waterway Approach channel 1: SCALE 0 100(M) THE BASIC DESIGN STUDY ON URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBLIC OF INDONESIA Fig Dredging Plan JAPAN INTERNATIONAL COOPERATION AGENCY

67 BASIC DESIGN STUDY ON URGENT COUNTERMEASURES FOR SEDIMENTATION IN WONOGIRI MULTIPURPOSE DAM RESERVOIR IN THE REPUBRIC OF INDONESIA JAPAN INTERNATIONAL COOPERATION AGENCY Fig Locations of Gate and Valve Inspection