EVALUATION OF MUD FLOW DISASTER ALTERNATIVES IN SIDOARJO

John Mclachlan Karr I Putu Artama Wiguna Amien Widodo

ns lnstitut Teknologl Sep\lluh Nopember EVALUATION OF MUD FLOW DISASTER ALTERNATIVES IN , EAST , INDONESIA

ITS 628.92.. -1 l

December 2012 Xvafuation of3vt:ru{ :Ffow 'Disaster J'tfternatives in Sitfoarjo 'R.eEJe1lCy, Xast Java. IndOnesia.

ISBN 978-602-17652-0-3 II IIIII 1111 9 786021 765203

Written by: John Mclachlan Karr, I Putu Artama Wiguna, Amien Widodo

Setting and lay-out : Amien Widodo

Cover Designer: Sueb

Published by : This ·Pusat Studi Kebumian dan Bencana (PSKB) edu Lembaga Penelitian dan Pengabdian Masyarakat (LPPM) hoi lnstitut Teknologi Sepuluh Nopember {ITS)

Website: http://pskb .its.ac.id/ This publication may be reproduced in whole or in part and in any form for educational or not-for-profit purposes without special permission from the copyright holder, provided acknowledgement is made of the source.

Cover photo: John McLachlan Karr TABLE OF CONTENTS Page

PREFACE EXECUTIVE SUMMARY...... 2 CHAPTER I INTRODUCTION...... 9 1.1. Background...... 9 1.2. Aims and Objectives...... 11 1.3 Review of Existing Data...... 12 1.4 Brief Chronology ofEvents...... 13 1.5. hnpacts...... 14 1.6. Historical Setting of the Study Area ...... 20 1.8. Demography of the Study Area...... 22 CHAPTER II CONCEPTS...... 23 2.1. Energy ...... 24 2.2. Principles of Energy Systems...... 25 2.2.1. 1st Law ...... 25 2.2.2. 2nd La\V...... 26 2.2.3. 3rd Law...... 26 2.2.4. Emergy...... 27 2.2.5. Maximum Empower Principle (4th Law)...... 27 2.2.6. 5th Law ... All Systems Are Organized Hierarchically...... 28 2.2.7. The Principle ofUniversal Material Distribution And Processing...... 30 2.3 E1ndollars...... 31 CHAPTER III METHODOLOGY...... 33 3.1 Emergy Analysis and Other Energy Methods...... 33 3.2 Steps in the Method...... 34 CHAPTER IV RESULTS...... 43 4.1 Energy Systems Diagram Of Overview Model of Sidoatjo Regency...... 45 4.2. Economic Impact Evaluation in Emdollars...... 46 4.3. Emdollar Evaluation Tables...... 47

11 4.4. Disaster Impact Evaluation ...... 49 4.5. Impacts on Environment...... 52 4.5.1 Econon1ic System ...... 52 4.5.2. In1ports ...... 53 4.5.3. Petformance Indicators ...... 54 Figm 4.6. Evaluation of Altematives ...... 55 Figm 4.6.1. Potential Mud Diversion Site ...... 57 Figur 4.6.2. Preliminary Costing ...... 59 Figur 4.6.3. Costing Table of Altematives ...... 60 Figm 4.6.4. Impacts of Altematives to River and Coastal Area ... .. 66 4.7 Ecosystems ...... 69 Figw· 4. 7 .1. Mangrove System ...... 69 Figur 4. 7 .2. Other Species Survey ...... 71 4.7.3. Engineering A Mud Lay Down Area ...... 72 Figur 4.8. Modeling ...... 72 Figur 4.8.1. Mangrove Succession Model for Alternative ...... 72 4.8.2. Model of Water Diversion into the Deposition Area ...... 75 Figur CHAPTER V DISCUSSION ...... 79 Figm 5.1. Incorporation of Specialist Knowledge ...... 79 Figm Genetic Information and Nationally Shared Information ...... 80 Figur 1\ ,: 5.2. 'i)l 5.3. Geologic Cycle and Solar Hydrological Cycle ...... 80 l1 1 1 5.4. Cultural Systems ...... 82 Figur 5.5. Economic Systems ...... 83

5.6. Ecosy stetns ...... 84 Fi'=~ 5.6.1. Coastal Wetlands ...... 84 F".;,...: 85 'C' 5.6.2 Wetland-Aquaculture Production Model...... = 86 5.7 Organisms ...... = 89 CHAPTER VI CONCLUSION ...... = 6.1 Conclusion ...... 89 6.2 Further Research ...... 90 REFERENCES ...... 93

111 TABLE OF FIGURES

Page

Figure l. l Location of the Lusi Disaster in (red anow)...... 9 Figure I. 2 Model of Adaptive Response to the Lusi disaster...... 11 Figure l. 3 The first months of the Mud disaster...... 14 Figure 1. 4 Photo: site before mud mudflow (from CRISP, 2005) 15 Figure l. 5 Photos of the affected area by National Team ofMudflow Management March, 2007...... 15 Figure l. 6 Gas explosion in Porong (National Team Repmt, 2007)...... 16 Figure 1. 7 Flooding in Porong after a dam embankment failure in Febn1ruy 2008...... 19 Figure 1. 8 Impacttrom Subsidence ofLusi mud volcano in May 2008...... 20 Figure 2. 1 Sidorujo Regency is a sub-set of the yearly global energy material cycle...... 25 Figure 2. 2 Second law & matter transtonnity process...... 26 Figure 2. 3 Systems maximize power ...... 28 Figure 2. 4 Atl systems are organized as hierarchies ...... 29 Figure 2. 5 Spatial convergences of materials to centres because of their coupling to the convergence of energy ...... 30 Figure 2: 6 Coupling of energy flows and the dependant economic system with money circulating only on the Right...... 31 Figure 2.7 Overview showing relationship of money to energy flows in US$..... 32 Figure 3. 1 The energy flux of any area varies over time...... 35 Figure 3. 2 Arrangement of symbols in systems diagram...... 36 Figure 3. 3 Energy System symbols...... 36 Figure 3. 4 The preliminary overview model from the Team member inputs..... 37 Figure 3. 5 Emergy evaluation table...... 38 Figure 3. 6 All systems have a unique energy signature...... 38 Figure 3. 7 Transformity of a flow producing a new product of higher quality but with less energy...... 39 Figure 3. 8 Diagram used for evaluation of alternatives...... 39

iv Figw·e 3. 9 Evaluation of performance diagram ...... 40 Figu Figure 3.10 Modelling procedure used in the Study...... 41

Figure 4.1 GIS of Study area ...... 43 Figu Figure 4. 2 Over-view model of the main flows and processes in Sidoarjo Figu Regency...... 45

Figure 4. 3 Overview showing evaluation of natural capital in Sidorujo as Figu a fhnction of its contribution to GDP with 3 arm diagram below ...... 46 Figu Figure 4. 4 Emdollar signature of Sidomjo Regency (2006-7) in Logatithmic Figu Scale...... 49 Figu

Figure 4. 5 Magnitude of the Mud Volcru10 disaster as a pulse compared Figu1 to average inputs from the geological and hydrological cycle...... 50 Figure 4. 6 The sedimentary pulse from the mud volcano seen as a dramatic increase in energy 51 Figure 4. 7 Former urban area in Porong, Sidoarjo 52 Figure 4. 8 Value of main Internal Services in Sidoarjo Regency...... 53 Figure 4. 9 Performance indicators from diagram above...... 54 Figure 4. 10 Evaluation of Altematives Systems Diagram...... 56 Figure 4. II Inter-tidal Dynamics in the Coastal Area ...... 57 Figure 4. 12 Intertidal Dynamics in the Coastal Area ...... 58 'I Figure 4.13 River Diversion ...... 49 li:!i I Figure 4. I4 A synthesis ofresults of biological surveys ofthe lower Poroug River and inner Coastal Area from 2006 to 2007...... 66 Figure 4.15 Plankton Diversity Index for lower Porong and Aquaculture ponds (Tmnbak)...... 68 Figure 4. 16 Pattern of mangrove zonation in Porong Estuary...... 70 Figure 4. 17 Top Avicenna seedlings in understorey. Photo mangroves colonizing recent mud deposition in Outer Delta...... 7I Figure 4. 18 Mangrove Forest Model...... 73 Figure 4. 19 Nuhient up-take in wetland area...... 74

Figure 4. 20 Biomass growth in ma11grove wetland in Porong Delta. .__...... u. 74 Figure 4. 21 Sedimentary organic storage in Porong Delta...... 75 Figure 4. 22 Eco-hydrological model for water flows in the Porong delta...... 75 Figure 4. 23 Renewable inputs...... 76 Figure 4 24 Groundwater storage...... 76 Figure 4. 25 Average annual Stream to Sea discharge from Poron:g delta (time in years)...... 77 Figure 5. 1 Figure Energy Systems Hierarchy for Sidoatjo Regency...... 79 Figure 5. 2 Sediment from pumping partially blocking the in the dry season (2008)...... 81 Figure 5.3 High flow rates in: the Porong River during the wet season...... 81 Figure 5.4 Systems diagram of the Retrofitted Wetland Area...... 85 Figure 5. 5 Model mn for optimal mangrove area for maximum total yield...... 86 Figure 5. 6 Species of Sesarmid crab on the bank of the Porong River...... 86 Figure 6.1 People at the convergence of three essential energy flows...... 91

vi LIST OF TABLES

Page

Table 4. 1 The Results of the GIS evaluation...... 44 Table 4. 2 Accounting Table...... 48 Table 4. 3 Cost Benefit of Alternatives in Emdollars (converted back to Rupiahs) using land use values from the table below...... 61 Table 4.4 Macro fauna-benthic Species...... 67 Table 4.5 Macro-benthic species diversity (Shatmon-Weaver) index 'Tren' is trend and 'twun' is down...... 67

vii PREFACE

This collaborative project is supported by UNEP and AUSAID (Australian Embassy, Jakarta, Indonesia). AUSAID, through its Indonesia office, has committed its support for a multidisciplinary, international study to assist in the mitigation of impacts from the Lusi mud volcano disaster in Sidoa~o Regency, Java Timur. It is understood by AUSAID/UNEP that the response to the emergency is led by the Government of Indonesia (BPLS) with the Ministries of Environment, Public Works and Mines and Energy. The Ministry of Environment specifically requested UN assistance on environmental aspects of the emergency and the response. The UN has formed a working group (UNTWG) to coordinate UNEP assistance on this issue.

Steering Team: Representative from UNEP (Muralee Thummarukudy), Jon Borrough (AUSAID), Drs. Rasia Ridho Sani, MKom, MPM (Ministry of Environment), lr. Sucahyono, S. (BPLS).

Project Team: John McLachlan-Karr (UNEP Consultant); Dr. Putu Artama (Project Manager ITS,-Risk Management); lr. Amien Widodo, MSi (Geology-Disaster Management), Dr. Wahyudi (Marine Geology); Dr. Teguh Ha~anto (GIS Specialist); Prof. Perry Burhan (Organic Geochemistry); Prof. lndrasurya B. Mochtar (Geotechnical), Prof. Noor Endah (Geotechnical), lr. Anggrahini, MSc (Senior Hydrolic Engineer), Ora. R. Agnes Tuti, MSc (Statistic), lr. Lily Pudjiastuti MS (Chemistry); Drs. Dian Saptarini, MSc (Biology) and Dr. Eddy Soedjono (Environmental Engineer).

Acknowledgements: Special thanks are given to the Australian Embassy staff who contributed to this study, especially Jon Burrough and Prisca · Seridanta for support in the field and Ambassador Bill Farmer who agreed to provide funding at the request of the Indonesian Government. In Surabaya, thanks are given to all staff at ITS especially the Department of Civil Engineering for many hours of assistance and support. At UNEP, special thanks are given to Muralee Thummarukudy for technical input and Dawit Yared for administrative support and to John Carstensen (former UNEP Project Manager) for much initial encouragement and advice. mag EXECUTIVE SUMMARY at ~ SUb! wou imp< This Report is part of the UNEP/AUSAID response for a request from very the Government of Indonesia, Ministry of Environment, to fully evaluate alternatives for mitigation of the mud volcano disaster (known as 'Lusi', the abbreviation from Lumpur Sidoarjo) in East Java, Indonesia. The eruption of ener the Lusi mud volcano can be traced to May 29th 2006. By May 2008, there stre< are thirteen recorded fatalities directly related to the disaster and over 75,000 28 n persons impacted from 17,002 households. The total number of dwellings lost cyclt or damaged by the mud flow is about 14,000. The latest loss estimate of 18 r Sidoarjo Regency assets is around 26 trillion Rupiah (Tuti, 2008). sedi1 The current management option taken by BPLS, ( valu1 Mitigation Agency) is to contain the mud material around the extrusion zone Sus1 with a primary objective to protect main infrastructure and urban assets. This cam strategy seems reasonable if the mud flow ceased or a technical solution to stem the flow is found. The current approach also reflects complex issues Reg1 surrounding responsibility for the mudflow and relief efforts, land tenure and pure technical feasibility of alternative proposals. abOl In October 2006, as the mud flow threatened to overwhelm containment cons dams and costs mounted, some limited pumping of mud to the Porong River mak' Canal (Presidential Directive October 2006) was initiated. As the Porong River is the main flood water conduit for Sidoarjo Regency and City of impc Surabaya, this option carries with it increased risk of flooding in the Brantas voice River floodplain. of r In 2008, as economic and environmental impacts, risks and costs cont• associated with the current system of retention dams and river pumping Rive continue to increase and no end in sight to the mud flow, other alternatives river are being considered. A UNDP Mud Volcano Report, Oct. 20061 suggested that the mud flow~ volcano material was suitable for retrofitting wetland areas at the mouth of the large Porong River. This was seen as a way of mitigating impacts of the mud flow disaster in a heavily urbanized area of Sidoarjo Regency by working with hydro-sedimentary processes to 'match' the material with its productive potential in the delta/coastal wetland zone at lower capital costs than containment. This generated interest with Authorities in Indonesia and elsewhere as it seemed to have the potential to provide an economically beneficial use while mitigating some physical impacts from the mud disaster (mainly flooding and burial of assets/infrastructure and also groundwater contamination, land and primary production losses). The objective of this report is to assist the Indonesian Government to evaluate alternatives focusing on ways to mitigate and minimize the impacts from the on-going mud volcano disaster in Sidoarjo Regency. This may be considered part of efforts to alleviate mud disaster impacts and risk of flooding in the Porong River. Based on evaluation of the source and energy of the mud volcano, it showed the huge value of earth loss, mainly from subsidence to Sidoarjo Regency ($Em US 2.83 billion in 2007). This value over 1.7 orders of

2 magnitude greater than the next largest impact, the mud material, estimated at $Em US 166 million per year. The results suggested that in time, subsidence rather than the direct impact of the mud volcano flows energy would have an overall greater impact on Sidoarjo Regency. The economic impact of subsidence of the development corridor infrastructure is already very high. The disaster also impacts the most important hydrological system of the Regency, mostly the Porong River. Total stream chemical potential energy contributes 29 million emdollars per year to the Regency. These stream flows also carry much of the sedimentary load valued at an additional 28 million emdollars per year. The sedimentary load is a product of the Earth cycle that help support soils, ground water and ecosystems and contributes 18 million emdollars per year to Sidoa~o Regency. Stream flows carrying sediment and exported to the (not used within the study area) is valued at over 3 million emdollars per year. This Porong River Total Suspended Solid (TSS load) is greatly increased as part of the mud pumping campaign and negatively impacts the coastal area. Purchased inputs into the industry and service sectors of Sidoarjo Regency are about 109 million emdollars in 2006. Of this amount, the purchased fuel inputs alone make up 72 million emdollars in real wealth or about 40% of the total purchased emergy use in the Regency. This result is consistent with the high net yield of fossil fuels and the large contribution they make to the economy that use them. As part of mitigating impacts from the mud volcano in Sidoarjo, two important considerations are given: How can relief efforts mitigate mud volcano impacts and contribute to Sidoarjo Regency's more sustainable use of natural capital? Alternatives for mud volcano mitigation include: containment in situ (current mitigation efforts), pumping all the mud to the River via pipe, an open channel or pumping to a constructed wetland with river diversion. For natural disaster mitigation alternatives, it is necessity to compare flows from the human economy and flows of environmental resources at the larger scale. This problem is typified by land use diversions that require mud pumping to coastal areas as well as the restoration of some river flows to deltaic wetlands compared with containing the mud under the current dam retention systems. Both efforts require considerable economic investments including labour, goods and services and fuels. The question asked is: Do the anticipated benefits derived from such a project, including stabilizing and re­ creating deltaic mangrove wetlands using pumped mud material, merit the required economic investments? Based on the concept of energy matching, a high transformity resource (the mud) should be with a high energy system (wetland) where it can make a long term contribution to the sustainability of the Regency with minimum loss to established productive systems. Previous evaluations show the risk of environmental contamination from hydrogen sulphide -17 mg/1 (UNEP/OCHA, 2006), (Rumbudi et a/, 2007). The mud flow also contains low concentrations of hydrocarbons such as CH4 (methane) and aromatic carbons (Benzene, Toluene) (UNEP/OCHA, 2006), ITS (2007). Ongoing monitoring of the mud volcano shows no heavy metal or other high-risk potential contaminants from the mud extrusion ((UNEP/OCHA, 2006) (Rumbudi eta/, 2007), (Mazzini et al

3 2007), ITS (2007, 2008). Surveys in 2008 shows mangrove seedlings readily colonizing recent mud depositions near the Porong delta. In the long term, self-organization tends to retain systems where the effect of a flow is commensurate with inputs requirements that contributed to that flow. The best use of an emergy flow for maximizing production comes when the emergy few back to production matches the inputs emergy i.e. balancing potentially limiting factors. In the short term, this alternative may reduce risk of failure of retention systems, flooding, alleviate environmental health issues and long term operational maintenance costs. The project quantitatively evaluates the risks and benefits of a constructed wetland. The cost/benefit of 3 alternatives for moving the mud material to a constructed wetland area on the Porong River delta are compared with the current strategy (see Figure below).

The alternatives are: 1. Alternative 1 Current Strategy, using mud containment dams and baSI pumping mud to Porong River mainly in the wet season. the: 2. Alternative 2 Pump all mud to Porong River in wet season with River Diversion to Wetland Area and other flood risk reduction works. trillic 3. Alternative 3 Flow mud down an open channel wetland towards the coni coastal area. to tl 4. Alternative 4 Pumping mud by pipe year round directly to coastal som wetland area. geo· as I stre; reco fil l high

tot~ The inciL mos widE com loss grou proo loWE

- = Alternative 1-Currcnt = Al tematlvc 4- Plpe to coastal - = Alternative 2- River diversion · - ~ Alternative 3- Open cha

4 Net Present Value for each AJtematlve

40.0 - 35.0 t 30.0 > ~ 25.0 a.~ 20.0 z ~ 15.0 ~ 10.0 c 5.0

Attematives

Alternative 1 is the current containment strategy. The evaluation is based on the current budget and includes impacts and risk assessments to the surrounding area. Alternative 1 was found to be the second most expensive option (29 trillion IDR over the estimated 30 life of the project). It includes the cost of continued containment of the mud around the mud volcano and pumping mud to the Porong River, mainly during the wet season. During these months, some of this material (as suspended load) flows to the coastal area by river gee-potential energy. However, the heavier (sand/gravel fraction) has built up as bed load along a 5.2 km reach of the Porong River constricting flood stream flow and requires dredging. As a result, mud pumping is only recommended during the wet season when river gee-potential energy is highest. During the 2008 dry season, however, there is ongoing mud pumping to the Porong River and a River dredging campaign is still in its early stages. The costs of dredging some of this mud to remove River constrictions are included in this evaluation. The cost benefit evaluation of this Alternative is most sensitive the increased flood risk (estimated 10% probability) over a wide area. The main costs associated with Alternative 1 include: dam construction/maintenance, acquisition of additional assets (urban areas) and loss productive agricultural areas as well as contamination from loss of groundwater (well water) used by many local residents. This strategy also has productivity costs associated with TSS (suspended load) and shoaling of the lower Porong River. Alternative 2 Pump all mud to Porong River with lower River Diversion to a Wetland Area and associated flood risk reduction works. Alternative 2 has the lowest cost (NPV 14.5 trillion IRP per year). This alternative uses higher volume pumps to move most of the mud to the Porong River in the wet season. This alternative incorporates as much of the mud material as possible into a suitable mangrove wetland area via a river diversion. A possible wetland area was surveyed to the North of the Porong delta. It is proposed that mud material may be moved to this area using the Star pump but the Star pump technology is yet unproven, this Alternative considers flowing using River gee-potential energy to the proposed mangrove wetland area with a stream diversion (using about 50% of Porong Stream flow). In this Alternative, the cost benefit evaluation is most sensitive to the assessment of flood risk and works associated in flood risk mitigation.

5 Because of the river diversion and other flood control measures, flood risk is lower at 5%. efta To improve hydrologic functioning of the lower Porong River and fol"'v\ reduce flood risk some dam construction plant will need to be redeployed for thar river dredging, diversion construction and other flood control measures. This flood control campaign has the highest cost. Losses to stream and coastal con1 production are also included. COffl One long term benefit is increased coastal production and stability by limit mangrove forest restoration, but the evaluation is not very sensitive to its r because of the time required to re-grow the mangrove system (estimate 40 stru1 years) is less than the project evaluation time. (sub Alternative 3, Flowing the mud along an open channel across the go in flood plain towards the sea. This is most expensive option at (NRV 35.5 ben trillion lOR over 30 years). It requires moving the mud material from the disaster site along an open channel towards the sea. This option was this originally favoured by some Team members because of the unstable impr geotechnical situation with Alternative 1 (current strategy) and the increased and flood risk from the reduction of Porong River flow capacity. tech This option, however, involves high costs in a diversion structure and risk other works plus production losses to farming, groundwater and aquaculture unde areas. Some are the costs involve pumping water from the Porong River to equ help flow the viscous mud material down the open channel. It is anticipated cape: that any attempt to implement this alternative would invoke contentious land e F tenure issues and price speculation. This is reflected in the high costs associated with Alternative 3. me Alternative 4 is to pump the mud material directly to the coastal area g a wetland site (NRV 15.6 trillion lOR over 30 years) year round. A similar option was originally proposed and some plant (pipe and pumps) were installed to the mouth of the Porong River soon after the start of the disaster. At that time, however, technical feasibility of pumping the viscous material negated its usefulness . . This option is re-evaluated using recent data from trials of the "Star effec pump" technology specifically developed for this task. It is estimated that 7 pumps would be needed to work most of the time to move all the mud flow. Although the locally developed Star pump technology has some promise in overcoming some of the technical difficultly of moving mud, some UNEP/AUSAIO Team members as well as BPLS express concern about the full scale implementation of Star pump technology as it is yet to be proven in the field. The risks of not achieving its objectives are taken into account (using 40% risk of failure of full implementation). Thus, evaluation of this alternative is most sensitive to this risk and the cost of installing the trail system. Benefits of trialling this system include decreased flood risk as pumping can be done year round without using the Porong River, lower costs and reduced environmental impacts if the mud material is incorporated into a mangrove wetland area. The main impacts of this strategy are the increased TSS load in the coastal area reducing fisheries production. Additional works will be required to remove constrictions already along the Porong River as well as shoaling of the mouth of the Porong River.

6 This evaluation provides insights into the scale of the disaster, relief efforts and alternatives. It should be clear that no alternative is straight forward. In this disaster, capital costs and economic losses are much greater than impacts to environmental systems. Because of the high cost of containment in dam retention systems, continued pumping to the Porong River is considered inevitable. The double coffer dam system used by BPLS has to contend with confined area (this limits the capacity of the containment structure) and budget available (under its regulatory requirements) and engineering limitations of the earthen dam structure itself in an environment of increasing geotechnical instability (subsidence of the general area). In mid 2008, it appears that even with on­ going River mud pumping during the dry season, additional lay down area will be required. It is considered that Alternatives 2 and 4 may offer feasible options to this disaster by using the largest 'free' energy flows (river geo-potential) and improved pump technology to move the mud to the interface between land and sea where wetlands occur and can provide long term benefits. Pump technology failure and flood risks are estimated for these Alternatives. The risk of failure of a retrofitted wetland area can be minimized with understanding of (1) wetland function, especially the hydrology (2) the time required for wetlands to develop: and (3) by working with the self organization capacity of nature. Results of the modelling of these variables are included in the Report. Finally, energy systems modelling of the mud volcano flow mechanism and evaluation of the gee-potential energy (energy stored against gravity) in the containment structure as opposed to dispersing the mud suggests that higher geo-potential energy on the overlying geology of the underground mud storage is a factor in the rate of ground subsidence and therefore in self maintaining the mud flow. This, however, was not possible to quantify so is not included in the evaluations. Inevitably, the alternative chosen will be the most practical and cost effective as part of the adaptive response by BPLS to an on-going and novel disaster. Part of this flexibility will likely involve using a combination of the above alternatives e.g. pumping mud to the river during the wet season, continued improvement of the coffer dam containment structure, trailing and implementing Star pump technology if feasible, and a river dredging/diversion campaign to reduce flood risk. Alternatives 2 & 4 require that some of the budget currently used in Dam containment construction and maintenance is redeployed for dredging the Porong River. If successful and is able to reduce costs, is hoped that greater disaster victim relief may follow.

7