REVIEW OF DESIGN AND TENDER DOSSIERS FOR THE CONSTRUCTION OF PROVIDENCE II SANITARY LANDFILL IN MAHE – SEYCHELLES 1. BACKGROUND 1.1 Country background information The Republic of the Seychelles is an archipelago of more than 100 islands covering a land area of only 455 sq km and with a population of about 84,000 concentrated on the three main islands of Mahé, Praslin and La Digue (see map in Annex I). The majority of the population lives on the principal island of Mahé (144 sq km; 75,000inhabts), while the second and third biggest islands in the Seychelles in terms of population are Praslin and La Digue (7,500 and 2,200 respectively). Seychelles’ pristine environment has turned the country into one of the top tourist destinations. Since independence in 1976, the per capita output has grown significantly with the tourist sector being the backbone of the economy contributing more than 20% to the GDP in 2006. The high density of population on the three islands, around 468 inhabitants/ km2, as well as the main economic activities tourism and fishing impact on the islands fragile environment and natural resources. The economic and social welfare of the Seychelles population is thus largely dependent on the country’s environment integrity, and as a result the need for a well preserved environment is vital for the Seychelles. The land and coastal environment is increasingly under threat of pollution brought about by rapid developments, notably hotels and housing construction schemes. Coupled with scarce land resources and changes in consumers habits, it is clear that efficient collection, treatment and disposal of solid waste contribute significantly towards the conservation of the environment, and that sound environmental management and performance are crucial to the Seychelles. 1.2 Current State of affairs in the relevant sector The Seychelles generate about 550Kg/cap which are comparable to some affluent industrialised countries (EU 400, US 800). With an economy still in transition, a significant increase in waste is foreseen during the next decade which will put more pressure on limited land and resources being allocated to waste management. Solid waste collection and disposal services are currently contracted to the private company “Société de Transport et d’Assainissement de La Réunion”- STAR (Seychelles). STAR contract caters for the main waste management services on Mahé, directly supervised by the Department of Environment. These include collection, treatment and disposal of waste including hazardous waste, as well as Road and Beach cleaning. STAR also operates on the island of La Digue, but under separate agreements. TOR_framework Providence 2_ – final Page 2 / 10 On the main island of Mahé, solid waste is disposed of at the Providence landfill set on reclaimed land, with some green waste being composted and a small inert fraction being diverted to an unused landfill at Anse Royale (crushed glass). The landfill is located at Providence, close to the airport. It is unlined and surrounded on three sides by seawaters, being located on land reclaimed from the sea. Landfilling involves partial initial void infill with subsequent land raise. No leachate collection and control systems are installed. Sampling in July 2005 of groundwater under the proposed extension site near Providence 1 showed leachate contamination, including light hydrocarbons. Currently some 42,000 tonnes per year of waste are being disposed at Providence, representing more than 85% of Seychelles’ wastes. STAR installed a Materials Recovery Facility with backend composting unit but it is being used primarily for composting. To address the limitations of the current landfill disposal site, feasibility studies for an “Integrated Solid waste Management Programme” were carried out by the consortium Carl Bro / DCDM (Mauritius) in 2005/06, and subsequent detailed design and tender dossier were produced for the construction of a new landfill on Mahé at Providence, adjacent to the current landfill site, and of new landfills on Praslin and La Digue smaller island. The studies addressed institutional, environmental, technical, economical, financial and social aspects, as well as Environmental Impact Assessments of the new landfills, proposals for a better use of the existing landfill site at Anse Royale on Mahé, a cost-recovery system following the “polluter-pays” approach, and improvements of the STAR contract. Further to the approval in 2006 of the “Integrated Solid Waste management programme” financed by the EC under the 9th EDF, Technical assistance and capacity building were started in 2007, but the works for the new landfill on Mahé were unsuccessfully tendered, and are expected to be retendered in 2008 after some redesign has been carried out. The “Integrated Solid Waste management programme” is expected to reinforce Government strategy in the sector, notably in terms of policy, promotion of reuse and recycling, operational and environmental monitoring. Noticeable advances have been made in 2007 (recycling schemes for paper and plastic bottles; “environment police”, environment tax..), which are expected to be developed further in 2008 and beyond. 1.3 Related programmes and other donor activities The projects financed by EU in Seychelles related to the environmental sector are: Projects Description Status Updating of the Solid Waste Master Plan Funded under the 8th EDF outlines the Solid waste strategy from 2003 to 2010 Completed in 2004 Feasibility/design studies for the Solid waste integrated management programme Funded under the 9th EDF; includes feasibility, design, tender documents, assistance for evaluation of bids for construction of new landfills Completed in 2007 Integrated Solid waste Management Programme Funded by the 9th EDF, includes waste disposal works and supervision services, technical assistance, capacity building incl. trainings. Total cost: € of which E.C € 3M, GoS € , French € . On going (T.A and capacity started) Complementary studies for solid waste disposal on Praslin and La Digue Funded by the 9th EDF, under FWC, includes feasibility, and outline design for waste disposal on Praslin and La Digue Started in Melon Fruit Fly Eradication Programme To reduce and eradicate the melon fruit fly population in the Seychelles, through the installation of the facilities (incinerators) required to prevent the reintroduction of this and other fruit flies. (8th EDF) Completed in 2006 TOR_framework Providence 2_ – final Page 3 / 10 ARPEGE This is an environmental education programme financed under the 8th EDF in the frame of regional cooperation programme. Completed Decentralised Cooperation Programme Funded under the 9th EDF; This programme aims at implementing capacity building for Seychelles human resource development planning and training, and for NSA as partners’ development. Ongoing Regional Programme for the sustainable management of the coastal zones This programme is a regional cooperation programme funded under the 9th EDF;: a feasibility study of a regional programme for the sustainable management of the coastal zones and resources is under preparation. Ongoing Institutions presently involved in funding the environmental sector are: • UNDP/GEF: capacity building in the sector, water management, biodiversity conservation, and climate change and energy efficiency; • French Cooperation: in 2005, technical assistance to the Division of Pollution Control & Environmental Impacts; currently one technical adviser in the Division of Nature Conservation (Dept of Environment) and another at the Ministry of Land Use & Habitat; also funding partner of the “Solid Waste Programme under the 9th EDF” (training, study tours, partly AFVP volunteers) • UK cooperation: activities with NGOS in the environment sector (biodiversity conservation) • The World Bank – UNDP (coastal zone Management) • The Dutch Trust Fund (Bio diversity conservation) • Coopération Réunion – Seychelles (Marine pollution) Documentation The existing reports prepared that are useful to consult are as follows: • Detailed Studies and Technical Assistance for the Solid Waste Management Programme in Seychelles – Final Feasibility Report, Carl Bro a/s DCDM (Mauritius) January 2006 • Tender Dossier (Preparatory works) for construction of Providence 2 sanitary landfill (2006) • Tender Dossier (Main Works) for construction of Providence 2 sanitary landfill (2006) • Tender Evaluation Report for construction of Providence 2 sanitary landfill – Carl Bro Grontmij July 07 2.0 DESCRIPTION OF THE ASSIGNMENT The construction of Providence II sanitary landfill on Mahé is a component of the “Integrated Solid Waste Management Programme” started in January 2007, and was tendered as two separate contracts in March 2007, in a co-financing arrangement between the Government of Seychelles and the European Union. The two tenders comprised of: • The Preparatory works contract; which relate to the main earthworks, fencing, access road, staff building, etc.; Financed by the Seychelles Government • The Main works contract; which relate to installation of the composite liner, pumping station and leachate pre-treatment plant. Financed by the EC Tender evaluation was conducted in June 07 and although the preparatory works tender was successful, the tender for the main works had to be cancelled, as all administratively compliant tenders were significantly above budget. TOR_framework Providence 2_ – final Page 4 / 10 A quick review was undertaken by the Contracting Authority (MFA, Ministry of Foreign Affairs and International Cooperation, also EDF National Authorizing Officer), the Programme Supervisor (Department of Environment, Ministry of Environment and natural Resources) in association with the E.C to re-evaluate the technical requirements of the works in order to ensure that the planned infrastructure fit within the available budget of € 2 million, while still affording a high level of environmental protection. In view of the limited human resources and expertise available in the country, it was however finally decided to procure (under the present TORs) the services of a Consultant in order to carry out an in-depth review of the design and tender dossier(s) for the construction of Providence II sanitary landfill, and assist the Government during works tendering and evaluation. 2.1 Global objective The global objective of this assignment is to contribute to the sustainable development and the protection of the environment and public health on Mahé, in the framework of the “Integrated Solid Waste Management Programme in Seychelles” funded under the 9th EDF. 2.2 Specific objective The specific objective of the services is the review of Providence 2 sanitary landfill design and scope within available funding in view of successful tendering, whilst ensuring a suitably high level of environmental protection and reduced operation costs. 2.3 Requested services, including suggested methodology The assignment will be carried out in three phases: i) phase1 – Review of the design of the landfill and leachate treatment facilities and detailed cost estimates; ii) phase 2 – Production of new tender dossiers, and iii) phase 3 – Assistance for works tendering and evaluation. Phase 1 – Review of design and cost estimate i) Review of Parameters, in particular: • Review of leachate characteristics assumptions, based on previous studies and available data (notably sampling and analysis of leachate collected at the current landfill site at Providence, data from the landfill operator available from Reunion, Mauritius, …); • Assess the Greater Victoria Sewage Treatment Plant (GVSTP) capacity and current workload and operation, and existing sewerage regulations, in view of determining acceptable max. level and characteristics of leachate effluents that could technically be accommodated at the entrance of GVSTP (operating now at 25-30% capacity); • Work out, in close collaboration with the PUC (Authority for water & sewerage, and GVSTP operator) and under the auspice of the Ministry of Environment and natural Resources (responsible for both solid waste and water/sewerage) an agreement on the discharge of pre-treated leachate effluents into PUC sewerage system (max. characteristics, monitoring system, conditions, derogations, phasing in accordance to load variations, review mechanism,..); ii) Review the landfill design, in particular: • Review cells dimensions, phasing, membranes, pump system…. • Review landfill operation mode so that to optimise capital and operation costs, in consultation with the present operator; TOR_framework Providence 2_ – final Page 5 / 10 • Review the design of the double membrane system by assessing in details 2 options: a bentonite/PEHD membrane initially proposed, and a red-soil/PEHD membrane according to available data (soils analysis); propose the best economical solution; • Review the phasing of cells, pump system over the life time of the whole landfill • Produce the design review and cost estimate of the proposed solution iii) Review leachate treatment design, in particular: • Assess the applicability and suitability of modular treatment processes and other alternative technologies to SBR which can be adapted in the context of Providence II sanitary landfill and to the level of treatment required, in consultation with the present operator; • Investigate solutions to minimise the amount of leachate to be treated and reduce capital and operation cost • Consider other capital or operational issues which may lead to cost savings • Identify and select suitable treatment solutions, and carry out a multi-criteria comparison (efficiency, reliability, capital and O&M costs, flexibility…). Propose the best suitable solution for the pre-treatment. • Produce the design review and cost estimate of the proposed solution iv) New design of the works: • The consultant shall assess the overall feasibility and sustainability of the proposed reviewed solution for the landfill, pumping system and pre-treatment, estimate the capital and operational costs, and determine suitability to available funds; • The consultant shall produce preliminary design and drawings of the proposed solution, and a detailed confidential cost estimate; • The full detailed design and any optimization as required to ensure optimum benefits (capital and O&M gains) may be brought in parallel to phase 2 (tender dossiers). v) Others • The consultant shall work under the supervision of the Department of Environment, who will be assisted by the key expert who is currently providing Technical Assistance to the Department of Environment with regards to the implementation of the “Integrated Solid waste management programme” • He shall work in very close collaboration with the PUC and the present operator of the landfill on Mahé in design • Two work cessions will be conducted by the consultant for decision-makers: first cession after submission of the preliminary design review (review of parameters, best options; comparison, proposed solution, preliminary design and costing); and the second cession for the presentation of the draft design review report (together with the draft tender dossiers). Phase 2 – Preparation of new tender documentation • The Consultant shall review the tender dossiers for the construction of the landfill and associated leachate treatment facilities. • In the light of the proposed new design, the consultant will assess the need for separate contracts viz; preparatory and main works, for meeting the overall infrastructure cost. The separation of works in several lots as necessary will be reviewed, and a new definition of the scope of works of the different lots be proposed as may be advisable. • The new tender dossiers shall be prepared according to the Seychelles regulations for works to be funded by the GoS, and to EU regulations for works to be funded by the EC. TOR_framework Providence 2_ – final Page 6 / 10 • The tender dossiers shall contain all administrative and technical information required for tendering and shall be of a high standard. • The revised specifications, drawings and bill of quantities for the works and equipments will offer a sufficient level of details and a clear and precise identification of the works to be carried out, so that to allow contractors to make their bid and price the works in a straightforward manner. • Specifications for the treatment plant will include the leachate parameters within which the specified outflow characteristics shall be guaranteed, and the performance indicators for monitoring. • Particular attention will be given to scope of works limits between works lots, to the provision of public utilities and to the connection to the PUC sewerage infrastructures where pre-treated leachate is aimed to be rejected. Attention will also be given to monitoring equipment at landfill (infiltrations, gas) and treatment (inlet and outlet). Phase 3 -Assistance for works tendering and evaluation • The Consultant shall be present for the clarification meeting to be held in Seychelles with bidders during the works tender phase; • He shall assist, from home, the Department of Environment during the tender phase notably by providing any clarifications relating to bidder’s requests on the technical design and the specifications, drawings, BOQ and administrative provisions of the tender dossiers. • Prior to the tender closing date, the consultant shall compile all queries received and corresponding clarifications provided to the bidders in view of tenders’ evaluation. • After tender opening, he shall assist the Department of Environment in the evaluation process, by analysing all tenders received, preparing any necessary clarification requests to bidders and analysing bidders’ replies, and finally submit complete tender evaluation reporting with his recommendations in view of contract(s) awarding. 2.4 Required outputs The experts will work under close guidance from the E.C Delegation in Mauritius, the (MFA, Ministry of Foreign Affairs and International Cooperation (EDF National Authorizing Officer) and the Department of Environment in the Ministry of Environment and Natural Resources, to produce the services described here above and the deliverables hereunder: • Phase 1: - Preliminary design review report including parameters/criteria review, comparison of options, proposed solution, preliminary design and cost estimate: after four weeks max., to be presented to the main stakeholders in a work cession; (‘on principle” approval within 2 weeks); the proposed agreement on pre-treatment leachate discharges in PUC sewerage system shall be attached in appendix • Phase 2: - Draft design review report and draft tender dossiers including detailed specifications, drawings, BOQ and detailed cost estimate: within four weeks after “on principle approval” of the preliminary design review report, to be presented to the main stakeholders in a work cession (approval within 2 weeks) - Final design review report and tender dossiers: within two weeks after approval of the draft documents TOR_framework Providence 2_ – final Page 7 / 10 • Phase 3: - Clarifications related to bidder’s queries: within 48h maximum after any bidders’ query is forwarded to the Consultant - Works tenders’ evaluation report(s): ten days after the tenders’ opening. It is the responsibility of the Framework Consultant to ensure that these deliverables meet the quality standards before they are submitted to the E.C Delegation in Mauritius and the Government of Seychelles. 3 EXPERTS PROFILE 3.1 Number of requested experts per category and number of man-days per expert Indicatively, it is estimated that the services of two experts will be necessary for this assignment for a max. of 100 days worked (60 days worked on site, and 40 days home). The team leader expert should be of Category 1, and the other expert(s) of category 2. 3.2 Profile required (education, experience, references and category as appropriate) Fields of expertise to be covered by the Consultant team include: technical design and operation and maintenance of waste disposal sanitary landfills and leachate collection & pumping systems; process and technical design, operation and maintenance of leachate treatment plants; financial costing of above works; and works contract procurement (tender dossiers and evaluation for these works). The services are expected to be provided by a team of experts indicatively composed of a Team Leader / Waste Landfill Expert and a leachate treatment plant expert. The experts and other staff of the Consultant team shall be qualified and experienced in solid waste projects. The team leader expert should be of Category 1 and the other expert(s) of category 2. All experts must be fluent in English. Excellent writing and presentation skills are expected for the team leader; if he proves unable to meet the level of quality required for drafting the reports, the framework consultant will provide at no additional cost, immediate technical support to meet the desired standards. During the assignment, a high level of communication by the experts is expected with the E.C Delegation in Mauritius, and more importantly with the National Authorities so that to ensure maximum ownership. All stages of the drafting process will be done in close consultation with these stakeholders. They will interact with various stakeholders notably, but not limited to: The Department of Environment within the Ministry of Environment and Natural Resources, in particular the Division in charge of Pollution Control and Environmental Impacts; the Pollution and Waste Management Section (PWM); the Public Utilities Corporation (PUC); Mahé waste operator STAR Seychelles,…. The experts will be required to demonstrate professional sensitivity to the needs and concerns of the Seychelles beneficiaries (MFA, Department of environment, populations….). They will be expected to conduct themselves with high professionalism and diplomacy. The Consultant shall provide with his offer a synthetic methodological note describing the approach proposed for the assignment, and the competence, means, organization and complementarities of the team proposed for the assignment. TOR_framework Providence 2_ – final Page 8 / 10 3.3 Working language The working language will be English. 4 LOCATION AND DURATION 4.1 Starting period The commencement date is scheduled tentatively during the third week of February 2007. 4.2 Foreseen finishing period or duration The Consultant is expected to complete the assignment in a seven month’s duration maximum. 4.3 Planning The consultant will give, one week after the date of signing the contract, a detailed time schedule for implementing the various tasks of the assignment on the basis of the number of man-months. The following tables give an indication of the calendar for the assignment and the distribution of man-days. The assignment is expected to be completed by end of September 2008 at latest. Calendar of activities/milestones Tentative date Start of assignment 25 February 08 Phase 1 Field work March 08 Submission of the preliminary design review report, and work cession with the main stakeholders 31 March – 01 April 08 Approval of preliminary design review report (end of phase 1) 15 April 08 Phase 2 Field and home work 15 April- 15 May 08 Submission of the draft design review report and draft tender dossiers, and work cession with main stakeholders 15-16 May 08 Stakeholders comments on draft design review report and draft tender dossiers 30 May 08 Submission and approval of final design review report and final tender dossiers (end of phase 2) 13 June 08 Phase 3 Assistance during the works tender period, and for Bids analysis and evaluation reporting 16 June – 25 Indicative distribution of man-days per activity Man-days Phase 1: Field work and preparation/submission of preliminary design review report, incl. stakeholder work cession 45 Phase 2: Field and home work; preparation/submission of draft design review report and draft tender dossiers, incl. stakeholder work cession; Revision of draft documents / submission of final document 45 Phase 3: Assistance during works tender and for bids analysis and evaluation 10 Total man-days for all activities 100 TOR_framework Providence 2_ – final Page 9 / 10 4.4 Location of assignment The assignment will be composed of missions in Seychelles and work from the Consultant home office. Experts on mission will be required to work on the main island of Mahé. 5 REPORTING 5.1 Content, submission / comments timing The Consultant shall produce the following reports (details in 2.4 above): • Preliminary design review report: max. 04 weeks from mobilisation of experts on site • Draft design review report and draft tender dossiers: 04 weeks after “on principle approval” of the preliminary design review report • Final design review report and tender dossiers : 02 weeks after comments from main stakeholders on the drafts of these documents • Works tenders evaluation report(s): 10 days after tenders’ opening. All reports will be submitted in paper and electronic support. 5.2 Language The reports will be prepared in English. 5.3 Number of report(s) copies All the above reports and documents shall be submitted as per the General Terms of Reference for Framework contracts, plus the electronic copies, complete with all annexes / drawings by email and courier to the EC Delegation in Mauritius. The following “hard” copies will be dispatched: - 01 original and 01 copy to the head of the EC Delegation in Mauritius; - 01 original and 03 copies to the EDF National Authorizing Officer, the Ministry of Foreign affairs, Montfleuri, Mahé, Seychelles Email delivery will be made to the EC Delegation’s head of the Regional/Seychelles section and project officer namely: - - 6 ADMINISTRATIVE INFORMATION 6.1 Other authorized items to foresee under ‘Reimbursable’ N/A, the Contract will be a lump sum contract. 6.2 Tax and VAT arrangements The consultant will be exempted of VAT. 6.3 Interim payment(s) modalities, if any (only for a rider) N/A TOR_framework Providence 2_ – final Page 10 / 10 6.4 Others ?? Definition of Indicators The performance of the Consultant will be measured according to his ability to effectively implement the actions necessary to achieve the objectives of the assignment. The criteria below will be used: • Execution of each activity and their quality; • Submission of reports and their quality; • Compliance with approved time scheduled. • Performance and behaviour of each expert Criteria shall be rated as ‘Excellent’, ‘Very Good’, ‘Good’, ‘Satisfactory’, and ‘Poor’. General comments, qualitative suggestions or remarks could be made whenever required. ?? Facilities to be provided to the Consultant The Government of Seychelles will facilitate, wherever possible, access to all key documents and assist where necessary with arrangements of meetings with key stakeholders. Temporary office will be provided to the Consultant. TOR_framework Providence 2_ – final Annex 1 – p.1 ANNEX I MAP OF MAHE ISLAND – SEYCHELLES TOR_framework Providence 2_ – final Annex 2 – p.1 ANNEX II TABLE OF CONTENT OF FEASIBILITY REPORT – JANUARY 2006 Published : 09January 2006 Project : Prepared : The Project Team Checked : Carsten Skov Approved : Jørgen Bygvraa Hansen TABLE OF CONTENTS PAGE 1 INTRODUCTION…............................................................................................................................... 1.1 ACKNOWLEDGEMENTS…........................................................................... 1.2 THE PROJECT TEAM…................................................................................. 1.3 INTRODUCTION TO THE PROJECT …...................................................... 1.3.1 Project Context 1.3.2 The Terms of Reference for the Project 1.3.3 Phasing and Main Activities 1.3.4 Layout of the Feasibility Report 1.3.5 Related Reports 1.3.6 Currencies and Price Level 1.4 INTRODUCTION TO THE PROPOSED LANDFILLSERROR! BOOKMARK NOT DEFIN 1.4.1 Proposed Landfill Providence 2 1.4.2 Proposed Landfill Amitié 2 1.4.3 Proposed Landfill La Digue 2 1.5 INTRODUCTION TO SEYCHELLES…........................................................ 1.5.1 Historical and Political Background 1.5.2 Climate 1.5.3 Demography 1.5.4 The Economy 1.5.5 Analysis of the Country Background 2 EXECUTIVE SUMMARY AND CONCLUSIONS…............................................................................ 2.1 DEMARCATION OF THE PROPOSED SITES…........................................ 2.2 SUMMARY…..................................................................................................... 2.2.1 The Current Situation 2.2.2 Waste Quantities and Forecast 2.2.3 The Proposed New Landfill Sites 2.2.4 Birdstrike Risk Assessments 2.2.5 Government-STAR Contract 2.2.6 Institutional Issues 2.2.7 Project Costs 2.2.8 Cost Recovery 2.2.9 Better Use of the Sanitary Landfill at Anse Royale Composting Hazardous Waste Management 2.3 CONCLUSIONS…............................................................................................. TOR_framework Providence 2_ – final Annex 2 – p.2 2.4 PROJECT RISKS ….......................................................................................... 3 OVERVIEW OF THE EXISTING SITUATION AND REVIEW OF WASTE GENERATION FORECAST …........................................................................................................................................ 3.1 OVERVIEW OF THE EXISTING SITUATION IN WASTE MANAGEMENT….............................................................................................................. 3.1.1 The Existing Waste Generation 3.2 THE SOLID WASTE MASTER PLAN 2003-2010 ….................................... 3.3 REVIEW OF WASTE GENERATION FORECAST …................................ 3.3.1 Discussion 4 DESIGN STANDARDS AND ASSUMPTIONS FOR LANDFILL PROJECTS …............................... 4.1 BOTTOM-LINING…........................................................................................ 4.2 LEACHATE TREATMENT…......................................................................... 4.2.1 Compounds of Leachate for Treatment 4.2.2 Leachate Treatment Concepts 5 THE PROPOSED LANDFILL PROJECT PROVIDENCE 2 …............................................................. 5.1 THE SETTING OF THE SITE…..................................................................... 5.1.1 Description of the Location and the Surroundings 5.1.2 The Geology and Hydrology 5.2 THE ENVIRONMENTAL IMPACT ASSESSMENT OF THE PROPOSED LANDFILL PROJECT…............................................................................. 5.2.1 Conclusions on the Environmental Impact Assessment Study 5.2.2 Recommendations 5.2.3 Bird-Strike Risk Assessment 5.3 THE PROPOSED TECHNICAL DESIGN …................................................. 5.3.1 Layout of the Site and Phasing 5.3.2 Main Elements of the Landfill 5.3.3 Leachate Management 5.3.4 Landfill Gas Collection System 5.3.5 Mobile Equipment 5.4 THE INVESTMENTS AND THE COSTS OF OPERATION AND MAINTENANCE …............................................................................................................. 5.4.1 Investments 5.4.2 Indicative Annual Operation and Maintenance Costs 5.5 FINAL TERRAIN AND END USE ….............................................................. 5.6 THE MANUAL FOR OPERATION AND MAINTENANCE…................... 5.7 OVERALL ASSESSMENT OF THE FEASIBILITY OF THE PROPOSED PROJECT…................................................................................................... 6 THE PROPOSED LANDFILL PROJECT AMITIÉ 2…......................................................................... 6.1 THE SETTING OF THE SITE…..................................................................... 6.1.1 Description of the Location and the Surroundings 6.1.2 The Geology and Hydrology 6.2 THE ENVIRONMENTAL IMPACT ASSESSMENT OF THE PROPOSED LANDFILL PROJECT…............................................................................. TOR_framework Providence 2_ – final Annex 2 – p.3 6.2.1 Conclusions on the Environmental Impact Assessment Study 6.2.2 Recommendations 6.2.3 Bird Strike Risk Assessment 6.3 THE PROPOSED TECHNICAL DESIGNERROR! BOOKMARK NOT DEFINED. 6.3.1 Layout of the Site and Phasing 6.3.2 Main Elements of the Landfill 6.3.3 Leachate Management 6.3.4 Landfill Gas Collection System 6.3.5 Mobile Equipment 6.4 THE INVESTMENTS AND THE COSTS OF OPERATION AND MAINTENANCE …............................................................................................................. 6.4.1 Investments 6.4.2 Indicative Annual Operation and Maintenance Costs 6.5 FINAL TERRAIN AND END USE ….............................................................. 6.6 THE MANUAL FOR OPERATION AND MAINTENANCE…................... 6.7 OVERALL ASSESSMENT OF THE FEASIBILITY OF THE PROPOSED PROJECT…................................................................................................... 7 THE PROPOSED LANDFILL PROJECT LA DIGUE 2….................................................................... 7.1 THE SETTING OF THE SITE…..................................................................... 7.1.1 Description of the Location and the Surroundings 7.1.2 The Geology and Hydrology 7.2 THE EXPECTED ENVIRONMENTAL IMPACT OF THE PROPOSED LANDFILL PROJECT…............................................................................. 7.2.1 Conclusions of the Environmental Impact Assessment Study 7.2.2 Recommendations 7.3 THE PROPOSED TECHNICAL DESIGN …................................................. 7.3.1 Design Standards and Assumptions 7.3.2 Layout of the Site and Phasing 7.3.3 Main Elements of the Landfill 7.3.4 Leachate Management 7.4 THE INVESTMENTS AND THE COSTS OF OPERATION AND MAINTENANCE …............................................................................................................. 7.4.1 Investments 7.4.2 Indicative Annual Operation and Maintenance Costs 7.5 FINAL TERRAIN AND END USE ….............................................................. 7.6 THE MANUAL FOR OPERATION AND MAINTENANCE…................... 7.7 OVERALL ASSESSMENT OF THE FEASIBILITY OF THE PROPOSED PROJECT…................................................................................................... 8 FINANCIAL ANALYSIS AND COST RECOVERY…......................................................................... 8.1 FINANCIAL ANALYSIS….............................................................................. 8.1.1 Investment and Operating Costs 8.1.2 Financing 8.1.3 Results 8.1.4 Sensitivity Analysis 8.1.5 Conclusions on the Financial Analysis 8.2 COST RECOVERY…....................................................................................... TOR_framework Providence 2_ – final Annex 2 – p.4 8.2.1 Approach 8.2.2 Development in SWAC Fiscal Budgeting and Spending 8.2.3 Analysis of the Existing Cost Recovery Mechanisms and Instruments, Mahé 8.2.4 Analysis of Class 1 – Municipal Waste 8.2.5 Analysis of Classes 2 to 11 8.2.6 Synthesis and Results 8.2.7 Praslin and La Digue 8.2.8 The Current Unit Costs of Waste Management 8.2.9 Conclusions 8.3 CHARGES FOR COLLECTION AND DISPOSAL OF HOUSEHOLD WASTE…................................................................................................... 8.3.1 General on Economic Instruments 8.3.2 Charges for Household Waste Collection and Disposal 8.3.3 Eco-Tax and Import Levies 8.3.4 Gate Fees at Landfills 8.4 SOCIAL IMPACT AND AFFORDABILITY …............................................. 8.5 FUTURE WASTE MANAGEMENT CHARGES…...................................... 8.6 RECOMMENDATIONS…............................................................................... 8.6.1 Social Considerations 9 IMPLEMENTATION AND PROCUREMENT….................................................................................. 9.1 THE EUROPEAN DEVELOPMENT FUND….............................................. 9.2 IMPLEMENTATION PLAN…........................................................................ 9.2.1 Site Supervisor 9.3 PROCUREMENT UNDER EDF….................................................................. 9.3.1 Practical Guide to Contract Procedures financed from the 9th European Development Fund 9.4 ASSESSMENT OF THE MARKETPLACE…............................................... 9.5 PUBLIC-PRIVATE PARTNERSHIP….......................................................... 10 INTEGRATED WASTE MANAGEMENT ISSUES….......................................................................... 10.1 THE GOVERNMENT-STAR CONTRACT…............................................... 10.1.1 Overview of the Contract 10.1.2 Proposals 10.1.3 Conclusions 10.2 THE INSTITUTIONAL CAPACITY OF SWAC…....................................... 10.2.1 Situation Analysis 10.2.2 Institutional Strengthening 10.2.3 Conclusions 10.3 ANSE ROYALE SANITARY LANDFILL….................................................. 10.3.1 Introduction 10.3.2 Background 10.3.3 Diagnosis of the Actual Situation 10.3.4 Assessment of the Options Proposed by HYDROPLAN and the Master Plan 10.3.5 Assessment of other Options 10.3.6 Conclusions 10.4 BETTER UTILISATION OF COMPOST ….................................................. 10.4.1 The Current Situation TOR_framework Providence 2_ – final Annex 2 – p.5 10.4.2 Assessment of the Compost Quality 10.4.3 The Existing Compost Market 10.4.4 Proposal for Improved Production of Compost in Seychelles 10.4.5 Proposal for Incentives in the Government – STAR Contract 10.5 HAZARDOUS WASTE MANAGEMENT….................................................. 10.5.1 Legislation and Codes of Practice 10.5.2 Current Procedures for Management of Hazardous Waste 10.5.3 Estimated Quantities and Composition of Hazardous Waste 10.5.4 Discussion of the Needs of the Future and Applicable Options 10.5.5 Hazardous Waste Management Master Plan APPENDICES: Appendix 1: List of References. Appendix 2: Waste Forecast Review. Appendix 3: Bird-Strike Risk Assessment for the Proposed Landfills Providence 2 and Amitié 2. Appendix 4: Cost Recovery. Appendix 5: Technical Note. Options for Leachate Treatment. Appendix 6: Financial Analysis. Full Cost Recovery before Financing. Appendix 7: Drawings (attached in a separate drawings binder). LIST OF TABLES: Table Title Page Table 1.1: The Project Team. 2 Table 1.2: Strategic Objectives of the Government Adopted Master Plan 2003-2010. 3 Table 1.3 Strategy of Master Plan 2003-2010. 4 Table 2.1: Assumptions for Waste Minimisation, Reuse/ Recycling and Utilisation of Waste. 14 Table 2.2: Master Plan Scenario. Assumptions for Waste Minimisation, Reuse/ Recycling and Utilisation of Waste (%). 15 Table 2.3: Master Plan Minus Incineration Scenario. Assumptions for Waste Minimisation, Reuse/ Recycling and Utilisation of Waste (%). 15 Table 2.4: Status Quo Scenario. Assumptions for Waste Minimisation, Reuse/ Recycling and Utilisation of Waste (%). 15 Table 2.5: Summary Breakdown of the Estimated Investment and Costs of Operation and Maintenance of the Proposed Landfills. 19 Table 3.1: Recorded Waste Quantities 1997-2005 for Mahé. 25 Table 3.2: Waste Flow 2004 and 2005. 26 Table 3.3: Generation of Municipal Waste at Mahé, Praslin and La Digue for 2005. 27 Table 3.4: Master Plan Scenario. Assumptions for Waste Minimisation, Reuse/ Recycling and Utilisation of Waste (%). 30 Table 3.5: Master Plan Minus Incineration Scenario. Assumptions for Waste Minimisation, Reuse/ Recycling and Utilisation of Waste (%). 30 Table 3.6: Status Quo Scenario. Assumptions for Waste Minimisation, Reuse/ Recycling and Utilisation of Waste (%). 31 Table 3.7: Master Plan Scenario. The Waste Forecast and the Resulting Quantities for Landfills at Mahé, Praslin and La Digue (tonnes). 31 Table 3.8: Master Plan Minus Incineration Scenario. The Waste Forecast and the Resulting Quantities for Landfills at Mahé, Praslin and La Digue (tonnes). 32 Table 3.9: Status Quo Scenario. The Waste Forecast and the Resulting Quantities for Landfills at Mahé, Praslin and La Digue (tonnes). 32 Table 4.1: The Main Leachate Treatment Options. 38 Table 4.2: The Main Advantages and Disadvantages of the Leachate Treatment Concepts. 39 Table 5.1: List of Design Drawings, Providence. 46 TOR_framework Providence 2_ – final Annex 2 – p.6 Table Title Page Table 5.2: Estimate on Types and Quantities of Soil Materials Used at Providence 2. 48 Table 5.3: Main Landfill Elements. 48 Table 5.4: Comparison of Landfill Liner Costs for the First Disposal Unit at Providence 2. 51 Table 5.5: Leachate Quality. 53 Table 5.6: Leachate Design Data, Providence 2. 54 Table 5.7: Effluent Requirements, Providence 2. 54 Table 5.8: Initial Landfill Investments at Providence 2 including the First Disposal Unit at Providence 2. 56 Table 5.9: Total Landfill Investments at Providence 2. 57 Table : Estimated Annual Operation and Maintenance Costs at Providence 2. 58 Table : Staffing Levels and Costs, Providence 2. 58 Table 6.1: List of Design Drawings, Amitié. 66 Table 6.2: Estimate on Types and Quantities of Soil Materials Used at Amitié 2. 68 Table 6.3: Leachate Design Data. 70 Table 6.4: Effluent Requirements, Amitié. 70 Table 6.5: Initial Landfill Investments at Amitié 2. 72 Table 6.6: Total Landfill Investments at Amitié 2. 73 Table 6.7: Estimated Annual Operation and Maintenance Costs at Amitié 2. 74 Table 7.1: List of Design Drawings, La Digue 2. 82 Table 7.2: Estimate on Types and Quantities of Soil Materials Used at La Digue 2. 83 Table 7.3: Leachate Design Data, La Digue. 85 Table 7.4: Effluent Requirements, La Digue. 85 Table 7.5: Initial Landfill Investments at La Digue 2. 88 Table 7.6: Total Landfill Investments at La Digue 2. 89 Table 7.7: Estimated Annual Operation and Maintenance Costs at La Digue 2. 89 Table 8.1: Investment Cost Summary. 92 Table 8.2: Annual Operating Cost Summary. 93 Table 8.3: Proposed Investment Financing Option. 93 Table 8.4 Unit Project Costs before Financing. 95 Table 8.5 Unit Project Costs including Financing. 96 Table 8.6: Sensitivity Analysis on Unit Project Cost. 97 Table 8.7: Analysis of Budget Estimates and Actual Result for SWAC (2001-2005). 98 Table 8.8: Breakdown of Receipts and Expenses for SWAC for 2005 (Projected). 99 Table 8.9: Distribution of SWAC Expenses 2005. 100 Table : Summary of Cost Recovery Analysis for Waste Classes (Mahé only). 103 Table : Unit Costs for Waste Management 2005. 105 Table : Average Monthly Adjusted Expenditure per Household 1999/2000. 110 Table : Mean and Minimum Expenditure of Households. 110 Table : Households by Monthly Expenditure Groups. 111 Table : Income & Expenditure Statement Estimates for SWAC with Cost Recovery. 114 Table 9.1: Procurement Procedures Required under 9th EDF. 120 Table 10.1: Comparison of STARS’ Proposed and Actual Service Costs 128 Table 10.2: Staff Qualifications and Experience in SWAC. 135 Table 10.3: Summary of the Consultants’ Institutional Recommendations. 139 Table 10.4: Quantities of Waste Input for Composting as per Waste Forecast Review. 151 Table 10.5: Summary of Available Past Records of Hazardous Waste Disposal. 158 Table 10.6: Hazardous Waste Generation according to European Waste Catalogue Codes. 159 Table 10.7: Treatment and Disposal Methods in the EU and Estimated for Mauritius. 160 Table 10.8: The Forecast for Hazardous Waste Generation and the Capture Rate for Hazardous Waste Management System, Mauritius. 161 TOR_framework Providence 2_ – final Annex 2 – p.7 LIST OF ABBREVIATIONS (ABBREVIATIONS USED MORE THAN ONCE): ACP African, Caribbean and Pacific (countries) AIC Average Incremental Cost EDF European Development Fund EEA European Environment Agency EIA Environmental Impact Assessment EU European Union EUR Euro GDP Gross Domestic Product GM General Manager GVWTP Greater Victoria Wastewater Treatment Plant HDPE High Density Polyethylene HW Hazardous Waste ICAO International Civil Aviation Organisation LTD Land Transport Division MENR Ministry of Environment and Natural Resources MLUH Ministry of Land Use and Habitat MNA Member of the National Assembly MRF Material Recycling Facility msl Mean Sea Level (above) MSW Municipal Solid Waste PPP Polluter Pays Principle PS Principal Secretary (of MENR) PUC Public Utilities Corporation PV Present Value STAR Société de Transport et d’Assainissement de La Réunion SBR Sequencing Batch Reactor SCR Seychellois Rupee SW Scott Wilson SWAC Solid Waste and Cleaning Section TA Technical Assistance TOR Terms of Reference UCPS United Concrete Products Seychelles USD United States of America Dollar TOR_framework Providence 2_ – final Annex 3 – p 1 ANNEX III PROVIDENCE II SANITARY LANDFILL PRELIMINARY DESIGN (Extract from Feasibility report-January 2006) 4. Design Standards and Assumptions for landfill projects This Chapter of the Feasibility Report provides a discussion of standards and assumptions for the design of landfills under the Project. The main issues for discussion are the bottom-liner design and the leachate management system. The current environmental legislation in Seychelles does not set standards for the design, construction and operation of landfill. With the European Union as Project financier European Union standards logically would be the starting point recognising that these standards may not necessarily be adequate standards under Seychellois conditions. The European Union standard for planning, design and operation of landfills for municipal waste and hazardous waste is defined in the EU Directive for Landfill of Waste (99/31/EC) issued in 1999. Whereas the directive implies a vast strengthening of landfill practices in the EU (and the directive is still under implementation for existing landfills), the underlying philosophy and principles of the Directive are today industrial standard. 4.1 Bottom-Lining An example of the stricter requirements of the directive is the prescribed composite bottom-lining of landfills with a combination of a synthetic liner and a geological barrier. Although landfills with composite lining were seen in the EU in 1999 most “modern” landfills were mono-lined landfills at that time. Today, mono-lined landfills are not seen as adequate and the extra costs of a composite liner vis-à-vis the greater protection of soil and groundwater is seen as a good and necessary investment. The fundamentals of the composite liner as described by the Directive are that seepage of leachate through the synthetic liner will be stopped by the underlying geological liner. A synthetic liner will consist of welded or otherwise assembled fabrics and there will irrespective of the best installation practice be tiny small holes. Seeping leachate will, however, be stopped by the underlying geological liner. A composite liner made of two synthetic liners does not provide the same protection as percolating leachate could move horizontally in the liner construction and escape the second liner as well. The existing sanitary landfill at La Digue and the underutilised landfill at Anse Royale are both financed by the EU, but the design was done before the EU Directive was issued. The adopted design standards of the two mentioned landfills are in fact not very well documented, but it seems likely that the sites should be characterised technically as mono-lined landfills. Both sites are equipped with a high-density polyethylene (HDPE) membrane in combination with compacted red soil, but the soil falls short of the permeability requirement for the geological liner adopted in the Directive. The standard of the two landfills can therefore be characterised as “a typical mono-landfill applied in the EU prior to Directive 99/31/EC”. One could propose that a mono-lining should be the standard for the proposed three landfill sites, however, this would not seem advisable considering that the composite liner is by far superior to the mono-liner and the cost saving is (based on the estimates for Providence landfill in Chapter 5) approximately 25% calculated for a disposal unit and less than 15% for the entire landfill construction. The composite liner is prescribed as a HDPE liner in combination with a geological liner, primarily clay with a permeability K = 1.0 × 10- 9 m/s; thickness = 1m. Such clay properties are not available in Seychelles and an alternative must be found either through enhancement of red soil with bentonite or a replacement bentonite liner. Bentonite is a geosynthetic clay, which comes either as a granular product that enhances soil or as a thin reinforced liner composed of two carrier geotextiles needle-punched together to encapsulate a layer of bentonite. Bentonite is marked by many suppliers Worldwide and it is a well known product in landfill construction. Bentonite has excellent properties in terms of permeability (approximately 1.0 × 10-10 m/s- 1.0 × 10-11 m/s depending on the make) and swelling (bentonite soil sealants swell 10-15 times their dry volume TOR_framework Providence 2_ – final Annex 3 – p.2 when wetted, filling soil voids and impeding water flow), but questions remain for the durability of the material for certain hazardous materials. Leachate with waste oils seems to penetrate bentonite liners must faster than clay liners made to specification. Landfill experts are debating if the combination of HDPE and a bentonite-reinforced liner fulfils the Directive as this liner combination has no geological liner. This debate could seem theoretical, as the total permeability requirement has not been compromised, and there are landfill projects underway in Candidate Countries of the EU with this liner specification. Enhancement of Seychellois red soil with bentonite granulate is an alternative which could meet the wording of the Directive for the geological liner, but the Consultants recommend against this solution as substantial quantities of red soil would be required (33,000m3 for Providence 2 landfill) and this could in itself create complications in terms of the logistics (traffic, noise, etc. of the substantial number of truck loads of soil to be supplied) and ecological damage in borrow pits. Also, the cost of this solution is higher as documented in Section 0. Furthermore, it must be kept in mind that the Directive’s requirements on landfill bottom lining are set in order to prevent groundwater contamination. Thus, the Directive also states that “If, on the basis of an assessment of environmental risks, the competent authority has decided that collection and treatment of leachate is not necessary or it has been established that the landfill poses no potential hazard to soil, groundwater or surface water, the landfill bottom liner requirements may be reduced accordingly”. At the three sites in question, there is limited potential hazard to the surrounding soil and groundwater. Therefore, the Consultants consider the replacement of a natural geological barrier (which does not exist at the Seychelles) by a bentonite liner to be fully acceptable. The HDPE liner is recommended as this is the most common synthetic liner in sanitary landfill design. Alternatives such as asphalt can be found, but specifically asphalt has proven problematic in the aggressive environment created by leachate and the liner is sensitive to settlements. The Consultants recommend a composite bottom-lining for all proposed three landfills with a synthetic liner of HDPE in combination with a 3mm bentonite (K = 3.0 × 10-11 m/s) reinforced liner. It could be considered to allow for variations from bidders in the procurement phase of the Project, but this is likely to entail more work in review and rejection of liner proposals than work in comparing competitive proposals. Whenever variations are allowed, these tends to be used by manufactures of new products for marketing and the variations usually fail to meet the requirements. 4.2 Leachate Treatment An essential feature of the sanitary landfill is that wastewater created by the decomposition of waste (leachate) is collected to provide for treatment and controlled discharge rather than uncontrolled seepage to the environment. The pollution load of leachate is usually relatively heavy. This can be best illustrated by the estimated leachate generation at Providence 2, where the organic load of the leachate corresponds to wastewater from approximately 10,000 person equivalents. Thus, leachate treatment is critical and costly. There is no single best choice for all leachate compositions and the selection of a treatment process is site specific. The choice should be based on treatment efficiency required, capital cost, operation and maintenance cost, operation complexity, availability of skilled personnel and other issues. Investment in a costly, unproven system that may not meet the required treatment objectives is imprudent. The most important aspect in the selection of leachate treatment facilities is that an appropriate and costeffective solution is adopted. Although leachate can be treated to very high standards indeed, it is rare for this to be necessary. What is much more usual, is for a combined solution to be required, that will reliably meet a less stringent consent for discharge, as cost effective as possible. For example, combined systems with leachate pre-treatment before discharge into the public sewerage system, where effluent can receive final treatment in combination with domestic wastewaters, are often the BPEO (Best Practicable Environmental Option) solution, if available. This may be the best and least expensive option. Care must be taken to avoid “overloading” the plant. Studies have shown that a 5% loading of a sewage treatment plant with leachate will not disrupt its operations. This option offers the benefit of transferring wastewater treatment to the experts and offering the landfill owner a turnkey disposal option. For Providence (and Amitié in the near future) where TOR_framework Providence 2_ – final Annex 3 – p.3 such option exists the Public Utilities Corporation (PUC) has however discarded the option of discharging any raw leachate at its treatment plant. The majority of leachate treatment schemes that have been successfully installed on landfill sites have at their heart an aerobic biological treatment process. In the context of Seychelles, it is advisable to use a robust treatment system that is simple to operate and that provides some level of treatment even in case of operational problems. 4.2.1 Compounds of Leachate for Treatment The main compounds to be treated in leachate deriving from landfill of municipal solid waste are organic matters, ammonia and (if treated leachate will be discharged to freshwaters) chlorides. The degree and type of treatment varies greatly, depending on the standards for discharge, climatic conditions and the quality and quantity of leachate generated. A combination of treatment methods may therefore be required. Table 4.1 includes the range of treatment options for treatment of leachate. TOR_framework Providence 2_ – final Annex 3 – p.4 Table 4.1: The Main Leachate Treatment Options. Treatment Objectives Main Treatment Options Aerobic biological Activated sludge Sequencing batch reactor Rotating biological reactor Aerated lagoon/extended aeration Anaerobic biological Upflow sludge blanket Removal of degradable organic substances Aerobic nitrification Activated sludge Sequencing batch reactor Rotating biological reactor Aerated lagoon/extended aeration Constructed wetlands Air stripping Removal of ammonia Anoxic biological Sequencing batch reactor Constructed wetlands Denitrification Lime /coagulant addition Activated carbon Reverse osmosis Chemical oxidation Removal of non-degradable organics and toxics Activated carbon Reverse osmosis Chemical oxidation Removal of hazardous trace organic Hydrogen peroxide Odour removal Lime/coagulant addition, aeration and sedimentation Removal of dissolved iron , heavy metals and suspended solids Constructed wetlands Final polishing Sand filters Hypochlorite Disinfection Reverse osmosis Volume reduction/ pre concentration Evaporation TOR_framework Providence 2_ – final Annex 3 – p.5 4.2.2 Leachate Treatment Concepts The most appropriate options for the actual landfills are assessed to be: • Waste Stabilisation Ponds; • Aerated Lagoons; • Rotating Biological Contractors; • Sequencing Batch Reactor (SBR). The main advantages and disadvantages of the four concepts are summarised in Table 4.2. Table 4.2: The Main Advantages and Disadvantages of the Leachate Treatment Concepts. Treatment Concept Advantages Disadvantages Waste Stabilisation Ponds ? Easy to construct and operate ? Limited mechanical equipment ? Limited operational costs ? No need for highly qualified staff ? Large area demand ? No control possibilities ? Limited possibilities for nutrient removal Aerated lagoons ? Fairly easy to operate ? Limited control possibilities ? Limited possibilities for nutrient removal ? Need for clarifier Rotating Biological Contractors ? Fairly easy to operate ? Limited control possibilities ? Limited possibilities for nutrient removal ? Risk for mechanical failures ? Need for clarifier Sequencing Batch Reactors ? Good control possibilities ? Good possibilities for nutrient removal ? No need for additional clarifier ? Need fairly qualified technical staff Taking all conditions into account, hereunder the very limited areas available for treatment facilities, the Sequencing Batch Reactor (SBR) concept, alternatively the Rotating Biological Contractor concept, is deemed the most favourable concept. Due to the importance of robustness, control possibilities and flexibility, the SBR concept has been selected as the most attractive. However, when the works shall be tendered, it is recommended also to invite for alternative treatment concepts. The SBR concept has been selected as a basic concept for leachate treatment at all three proposed landfills. TOR_framework Providence 2_ – final Annex 3 – p 6 5. The Proposed Landfill Project Providence 2 5.1 The Setting of the Site 5.1.1 Description of the Location and the Surroundings The proposed Providence 2 sanitary landfill site is located on reclaimed land next to the existing Providence 1 landfill approximately 5km southeast of Victoria and west of the International Airport. The reclaimed land provides a levelled platform at approximately 2-3m above sea level, constructed from dredged coral sand and extends to approximately 600m out from the original coastline. The site has an infill of coral with embankments up to a level of 8m. The nearest neighbours to the site are STAR (composting plant and waste collection headquarter), United Concrete Products Seychelles (UCPS) (concrete production), SAMLO (scrap metal recycling) and other medium to small industries located in the Providence Industrial Estate. The Public Utilities Corporation (PUC) operates a 7,000m3/day sewage treatment plant and a 5,000m3/day reverse osmosis desalination plant both found to the northwest of the existing landfill. Residential buildings can be found on the old coastline in Petit Paris-Cascade with the nearest buildings located approximately 300m away (and beyond). Figures 5.1 and 5.2 overleaf show the proposed location of the Sanitary Landfill on Mahé and the location at Providence. 5.1.2 The Geology and Hydrology The proposed site is a reclaimed area, originally made up of 2-3m of dredged fill material deposited over reef structure and sediments. Grain size analyses show that the fill material consists of a well graded mixture of sand, gravel and some cobbles. The in-filled coral sand is underlain by Pre-Cambrain rock in a depth of between 15 and 30m. The groundwater is approximately 1m below ground and varying up to +/- with tide. Four test excavations were made in July 2005, showing that the coral sand in the excavations is mostly rather coarse, with a median diameter ranging from to . The permeability is ranging within a factor of 6, from 0.5 to 3.1×10-4 m/s, the highest value found near the existing landfill. The permeability may vary more, both horizontally and vertically, probably within a factor of 10, as finer grained and coarser grained areas may exist, determined by variations in the way it was filled in and natural variations in the composition of the bottom sediments which were used for the reclamation. Generally the material under the whole area of the site can be said to be rather uniform sand and gravel. It is rather well compacted (by the hydraulic action at the time of reclamation), but excavation under the groundwater table causes the sand to collapse immediately. A very low content of clay is present, only around 1-2%, and there is very little organic material in the sand, around 0.1-0.5%. The optimal water content for compaction is in the range 6-15%, which is less than the natural moisture content. However, the permeability of the sand cannot be reduced notably by compaction. TOR_framework Providence 2_ – final Annex 3 – p 7 Figure 5.1 TOR_framework Providence 2_ – final Annex 3 – p 8 Figure 5.2 TOR_framework Providence 2_ – final Annex 3 – p 9 The proposed site is surrounded on three sides by seawaters. A lagoon situated adjacent, west of the landfill, was created when the land was extended by reclaiming in 1985. The lagoon is subject to tidal fluctuations which provide good flushing in combination with the discharge of Trois Freres and Cascade Rivers that directly flow into it. The existing Providence 1 landfill to the west is an unlined facility reportedly involving partial initial void infill with subsequent land raise. No leachate collection and control systems are installed. The risk of leachate being generated and migrating off site is therefore high. Sampling in July 2005 of groundwater under the proposed site near Providence 1 showed leachate contamination, including light hydrocarbons. Surface water quality monitoring data show good water quality and no sign of heavy metal contamination in the area. This is explained by the significant level of dilution and mixing by the action of tide and currents within the zone. The geology and hydrogeology of the proposed site is “simple” in that the site has no impermeable soils that may form part of a landfill liner, the coral fill stocked on the site is a valuable construction material and the groundwater is hydraulically connected to the seawater around and below the site, causing tidal fluctuations in the groundwater. The hydraulic gradient and thus the flow velocity will vary with time, but the natural flow direction will constantly be away from the site, i.e. towards the sea and the lagoon across the boundary of the site. Towards the existing landfill the flow direction will be opposite, across the boundary from the old landfill towards the new site. 5.2 The Environmental Impact Assessment of the Proposed Landfill Project An Environmental Impact Assessment (EIA) Study is presented in a separate report and reference is made to this report for the detailed presentation of the EIA. 5.2.1 Conclusions on the Environmental Impact Assessment Study The existing municipal waste landfill in Providence does not meet international environmental standards. The landfill is an un-engineered site but with a reasonable level of organised operation. The site is unlined and leachate migrates to the surrounding environment. Good dilution and dispersion in the sea prevents direct, noticeable nuisances and impacts presently. The dilution caused by current and tide movements is high both on the seaside and the lagoon-side. The covering of waste at the existing landfill is irregular and the practice for landfill of putrescent waste is deficient, causing odour and attracting crowds of birds. The scoping exercise and public consultation meeting conducted as part of the EIA-process revealed that foul odour is a major concern with a wide range of stakeholders. Although the odour problem reportedly has decreased in recent years, nearly all stakeholders stressed the need to control odour emissions. The population of birds sustained by the food supply at the existing landfill and the impact on aviation safety was another important concern raised by several stakeholders including the Seychelles Civil Aviation Authority. The new sanitary landfill development will result in improved operation with smaller working area and less waste that will be openly exposed; improved daily and final covering of waste; new methods for landfill of putrescent waste; rigorous controls of pest, rodent and bird populations. The proposed landfill will be engineered to an international landfill standard, which means that the site will be equipped with bottom-lining to collect leachate and prevent leaching to the environment. Treatment of the collected leachate is another main feature for the proposed landfill. Overall there will therefore be a significant reduction of nuisances to neighbouring communities. The environmental impacts of construction and operation of the proposed landfill in Providence are, in general, not significant and most impacts can be mitigated to a high degree. The effectiveness of mitigation proposals will be highly dependent on both the quality of the landfill construction and the efficiency of site operation. The nearest residential buildings are located outside of the potential impact area for noise and odour. The water quality in the lagoon and sea will not be impacted. The visual impact will be similar to the present situation and with a good screening. A strict operational regime of the landfill with minimal open tipping front, frequent covering of operational sections and temporary covering of sections left for later completion will be prescribed TOR_framework Providence 2_ – final Annex 3 – to minimise odour emissions. Also a procedure for landfill of putrescent waste in trenches instead of an open pit will be proposed. This type of waste seems the main source of odour emissions and landfill of the waste in excavated trenches offer a better possibility for immediate covering. The trenches should be located towards the north of the disposal cell to increase the distance to odour sensitive areas such as the residential areas and the Providence Highway. An active system for collection and disposal of landfill gas from completed landfill sections will be another requirement to the operation to minimise the release of harmful greenhouse gasses and minimise the risk of fires and odour releases. The proposed landfill location is adjacent to the existing main landfill for Mahé and from this perspective the proposed utilisation of the location for landfill of waste will not drastically change the general surroundings of the location. The waste types and waste quantities for landfill will remain the same and so will the types and intensity of traffic to the site. The proposed location in Providence industrial estate is acceptable from a physical planning perspective and no major change will be incurred by the proposed landfill extension. The proposed landfill will not pose significant constraints for the planned development of light industry on the same reclamation to the southeast except on limitations on the use of the area for food industry. It is important to note that the existing landfill (Providence 1) needs proper closure measures in order for the proposed investment in a new engineered landfill to provide maximum effect in terms of the protection of the environment. The existing landfill will remain active in terms of generating leachate and producing landfill gas for many years to come and it would seem necessary to restore the landfill with a cover of impermeable soil and topsoil (possibly compost) and provide an installation for gas collection and flaring. The following conclusions are made in the EIA: • There will be beneficial impacts due to reduction in overall pollutant emissions in the project area; • Monitoring of the principal pollutant by-products (gas and leachate) is necessary; and • Consultation and dialogue is required with the public, particularly the nearest residential population to allay any concerns with respect to site development and operation. 5.2.2 Recommendations The development of a sanitary landfill at Providence will represent a considerable improvement on existing waste disposal options for Mahé. Most of the potential adverse environmental impacts can be, or have been, mitigated by a combination of site location, adequate design, high quality construction and high standards of site operation and restoration. It is concluded that, provided the proposed mitigation measures are incorporated, and the environmental, social, health and safety management of the facilities is addressed in the ways described within this report, then associated environmental, social and health impacts can be maintained within acceptable levels. 5.2.3 Bird-Strike Risk Assessment A separate assessment of the situation with respect to bird populations and aviation safety at the existing landfill at Providence and Seychelles International Airport (SIA) has been made. The assessment is presented in Appendix 3. The distance between the existing Providence landfill and SIA is approximately 1,500m measured from the centre of the landfill to the boundary of the airport (1,800m from the landfill to the runway). These distances will be reduced to 1,300 and 1,600m respectively with the proposed extension. Thus, the existing and the proposed landfills are within distances of an airport, which in accordance with international practices would require consent from the aviation authorities for operation1. 1 The International Civil Aviation Organisation (ICAO), of which Seychelles is a member, in amendment 51 to Annex 14 Volume 1 states that: “Garbage disposal dumps or any such source of bird attracting activity on or in the vicinity of an aerodrome shall be eliminated or their establishment prevented, unless an appropriate study indicates that they are unlikely to create conditions conducive to a bird hazard problem.” Any new developments within a 13 km radius zone of an airport, which might endanger the safety of aircraft by attracting birds, require consultation with the Airport authorities. It is stated by ICAO in Amendment 5 of Annex 14 Volume 1, and in the ICAO Airport Services Manual (ICAO Doc. 9137-AN/898/2) Volume 1 Part 3 ‘Bird Control and Reduction’, the purpose of which is ‘to provide assistance to states in ensuring that measures are taken to overcome potential bird hazards’. In Chapter 6 of the Airport Services Manual it is stated that, although a distance of 13km between an aerodrome and a waste disposal site is recommended, this general rule must be carefully examined since a number of measures may overcome the bird hazard problem even if the waste site is located nearer to the aerodrome. At the National level the US Federal Aviation Authority recommends in AC 150/5200-33 “Hazardous Wildlife TOR_framework Providence 2_ – final Annex 3 – The study concludes that significant populations of birds and in particular Cattle Egret and Common Mynah are attracted by the waste disposal, feed at the landfill and live in its vicinity. Currently, SIA does not file birdstrikes, but data for bird-strikes in 2003-2004 exist totalling 9 strikes over a period of 15 months including two strikes by Cattle Egret and Mynah out of 5 strikes where the specie of bird was known. There exists no guidance acceptance level for bird-strikes or any total risk factor to be met, but it is the views of the Consultants that the combination of a landfill with abundant supply of food for birds and an adjacent airport with no bird control is untenable. Aviation safety is paramount and maximum effort to preserve this is required at any time as the aviation industry is fundamental for Seychelles in general. The aircraft capacity of the national carrier Air Seychelles is limited so even a small interruption in service caused by unscheduled maintenance as a result of a minor bird-strike will result in sizeable losses in revenue for the company and the society as a whole. The recommendations for the proposed landfill are: • A Landfill Bird Hazard Management Plan including monitoring and enforcement of the plan should be drawn up between SWAC, the landfill operator and SIA; • Investigation of inclusion netting to prevent birds from feeding on the landfill; • • Removal of colonies of Cattle Egret; • Culling of birds. from e.g. household waste. The recommendations for SIA are: • Effective bird control on airside should be initiated immediately/upgraded. As the highest risk for birdstrikes is at the airport itself bird control should be exercised during any time of the day with flight operations; • Detailed documentation of birdstrikes and bird control activities towards reducing the risk is essential in all international airports. Thus an effective system of registration of bird activities and control measures using standardised forms should be set up and implemented; • Increase grass length to 20 – 30 cm. Cattle Egrets and Mynas (and several other relevant bird species relevant for SIA such as e.g. waders and feral Feral pigeonPigeon) generally prefer shortprefer short vegetation for feeding and airside By modifying the maintenance regime to allow the grass (vegetation) to grow taller to 20 to 30cm the attraction is largely eliminated. Attractions On or Near Airports” against locating municipal solid waste landfills within five statute miles of an airport if the landfill may cause hazardous wildlife to move into or through the airport’s approach or departure airspace. TOR_framework Providence 2_ – final Annex 3 – 5.3 The Proposed Technical Design Reference is made to location plans and design drawings for Providence Sanitary Landfill included in the separate Appendix 7 “Drawings”. The following drawings are available: Table 5.1: List of Design Drawings, Providence. No. Title Items Scale P1 General Site Plan and Setting Out Existing conditions, topography, and contours of landfill. Coordinates, etc. 1:1,000 P2 Overall Landfill Layout. Total Landfill Disposal units, embankments, leachate collection system, etc. 1:1,000 1:100 1:25 P3 Overall Landfill Layout. Disposal Unit 1 Disposal units, embankments, leachate collection system, etc. 1:1,000 1:100 1:25 P4 Inspection Chamber Details Inspection chamber. 1:50 1:25 P5 Restoration Plan Final covered landfill (plan and details). 1:1,000 1:100 5.3.1 Layout of the Site and Phasing The general appearance of a landfill is an important signal to neighbours and the surrounding communities and therefore it will be important to design the area with good traffic access and screening plantations. Where buildings and facilities are visible, these should be adapted to the environment through good architecture and landscaping. Area Requirement for the Landfill The proposed site for the new landfill takes up an approximate total area of 78,000m2. After deduction of area for surrounding embankments, buffer zone etc., an area of 65,000m2 is left for establishment of the waste disposal unit(s). Landscaping and Landfill Capacity The landfill has been designed to adapt into the surrounding landscape. It is assumed acceptable to establish the landfill as a hill with a maximum level of +25m (msl) with gentle slopes towards the borders of the reclaimed land, where the current level of approximately +8m will be reduced to a level of +6m in order to gain fill material for the landfill construction and additional landfill volume. Thus, at the landfill perimeter, there will be gentle slopes (slope 1v:5h) to provide for sufficient landfill volume. For practical and cost reasons it is proposed to build the landfill in two phases, covering two disposal units. The total landfill disposal capacity will amount to 710,000m3, which corresponds to 640,000 tonnes of waste, and which could last 21 years until year 2026 when applying the assumptions on waste forecast presented in Section Error! Reference source not found.. Soil and Fill Requirements Considerable amounts of different qualities of soil, sand and filling materials must be made available for the landfill construction and operation. The level of the landfill bottom is determined by the actual topographical, geotechnical and hydrogeological conditions. The bottom level at the existing depression at the new landfill TOR_framework Providence 2_ – final Annex 3 – area is just about +1m above sea level. Thus, no excess material can be gained from excavation and the landfill liner must be placed as low as practically possible in order to minimise soil works. The inner slopes of the existing depression are quite steep and must be levelled in order to establish a proper basis for the landfill liner to be installed along the landfill border. This levelling will provide some excess material which can be used for other landfill construction purposes (drainage layer etc.). Estimated quantities of soil, sand and filling materials needed for construction and operation of the landfill at Providence 2 are presented in Table 5.2. Table 5.2: Estimate on Types and Quantities of Soil Materials Used at Providence 2. Purpose Preferred Type of Material Estimated Amounts Comments Levelling of the landfill bottom + embankments Coral fill and soil 100,000m3 Drainage layers Coral fill, drainage sand (k > 10-3 m/s) 33,000m3 Internal roads etc. Gravel, sand or coral fill 2,000m3 These materials are partly excavated within the landfill area itself and partly within the nearby area to the south. Daily cover material Soil, crushed demolition waste etc. 70,000m3 Such secondary fill material is supposed to be supplied from various construction sites etc. during the landfill operation period. Final cover material Soil, clay, coral fill and topsoil 70,000m3 Partly on-site coral fill material and partly external soil material supplied during the operation period. 5.3.2 Main Elements of the Landfill When designing and constructing a new sanitary landfill, such landfill would usually include a number of typical main elements. These elements are described in Table 5.3 and their relevance for the new site at Providence 2 is discussed. Table 5.3: Main Landfill Elements. Landfill Element Comments on Relevance at Providence 2 Perimeter embankment A perimeter embankment of +6m above sea level is maintained around the site to screen the site and limit the visual impact. Thus, the existing dykes/ embankments will be lowered and levelled in order to allow for excess fill material to be used for landfill construction purposes and in order to increase the landfill volume. The dyke (or embankment) will be shaped so it fits into the future landscape and erosion is prevented. With the proceeding infilling of the landfill, the embankment is to be made higher, so it always fulfils its screening function. Fence The fence should be 2m high and placed in the site boundary. The fence shall be made of steel wires with upper part of barbed wire type. The fence shall have a lockable gate at the access road. A fence between the existing and new landfills would complete the fencing of the site, however, over time the landforms of the two sites should be joined and a fence would therefore need regular replacement as the void between the two sites may be utilised. TOR_framework Providence 2_ – final Annex 3 – Landfill Element Comments on Relevance at Providence 2 Planting In order to achieve a sheltering effect and to make the landfill appear aesthetically acceptable, planting along the surrounding embankments should be established. The planting should be of a type native to the Seychelles, fast growing, preferably impenetrable and with low maintenance. The Providence site already contains threes, which form a natural screening of the site. The completeness of the existing screening shall be accessed after the construction has been completed and supplementary planting made if necessary. Surface water drainage channels A surrounding surface water drainage channel is assumed established in order to prevent infiltration of surface water from the surroundings, and to collect and transport surface water from the future final landfill cover. Surrounding service road A surrounding service gravel road will be established for access to leachate wells etc. Waste reception area with weighbridge, office and staff buildings, maintenance workshop, parking area etc. It is assumed that the facilities operated by STAR and used for the operation of the existing landfill can also be used at the operation of the new landfill. Access road and internal roads and road for compactor and/or bulldozer. A new access road will be constructed from the STAR premises along the border of the existing landfill (approximately 300m long). A separate compactor/ bulldozer road is not considered necessary. A first disposal unit with capacity for at least 5 years, complete with bottom liner, leachate drainage layer, drains and wells for leachate collection. Additional disposal units must be constructed when there is a need for additional disposal capacity. Due to the considerable large size and the long active lifetime of the new landfill, the waste disposal area should be divided into two units. Only the first unit will be constructed from the beginning. Leachate collection Leachate collection wells shall be established in the lower end of each disposal unit. The collection well shall be equipped with a submersible pump. The leachate shall be conveyed to a main pumping station in the service area. From here the leachate shall be pumped to pre-treatment and final treatment at the nearby Greater Victoria Wastewater Treatment Plant (GVWTP). Leachate treatment. Leachate shall be pre-treated at GVWTP. After pre-treatment, secondary and tertiary treatment will be accomplished together with the domestic sewage in the GVWTP. Sludge from the pre-treatment plant shall be thickened and transported back to the landfill. Landfill gas treatment Vertical gas collection drains shall be installed in parallel with the waste filling. At the time for final covering it will be assessed if it is favourable to collect and utilise alternatively flare the gas. Groundwater monitoring wells. Two groundwater monitoring wells will be established for monitoring of groundwater. Mobile equipment Mobile equipment (e.g. bulldozer, dump trucks etc.) is assumed be provided by the landfill operation contractor on a lease basis (similar to the current arrangement for Providence 1 landfill). The main landfill elements to be included at Providence 2 are described in further details below. TOR_framework Providence 2_ – final Annex 3 – Access Road and Internal Roads The access road to the new disposal area shall be a 6m wide gravel road (or coral fill), and designed to heavy load. The internal service roads at the landfill shall be 3m wide, made of gravel/coral fill, and designed for medium loads. The First Disposal Unit The waste disposal area of the landfill is assumed divided into 2 disposal units. Only the first disposal unit will be constructed initially. The second unit should be constructed during the operation period in accordance with the disposal needs. This will reduce early investments and improve the overall cash flow for the landfill. Each disposal unit must be designed with environmental protection systems such as: • Liner; • Leachate collection systems; • Drains and ditches for surface water run-off; • Embankments. Liner In general, it is recommended to establish a landfill bottom liner in accordance with the EU-Landfill Directive 1999/31/EC. The Directive prescribes that the landfill base and sides shall consist of a mineral layer with a permeability value, K < 1.0×10-9 m/s and a thickness of at least . As there is no such geological barrier at Providence 2, the liner must be completed artificially and reinforced by other means giving equivalent protection. The geological barrier is assumed compensated for by means of installation of bentonite liner directly on top of levelled and compacted coral fill layers. In line with the EU-Landfill Directive, it is recommended to establish a second artificial and impermeable high-density polyethylene (HDPE) liner in addition to and directly on top of the geological barrier. The design of the landfill bottom liner in Figure 5.3 is proposed. Figure 5.3: Proposed Bottom Liner Design for the Landfill at Providence 2. Leachate drainage layer on top of the liner 50cm HDPE-liner () Bentonite liner (3mm) Compacted coral fill An alternative liner design has been considered, where the 3mm bentonite liner is replaced by a 50cm geological liner of enhanced red soil. In this case, large amounts of red soil would be imported from different borrow pits at the island of Mahé. Furthermore, since the permeability value of the red soil is too high (K > 1.0 x 10-8 m/s), it is necessary to improve the red soil material by mixing bentonite powder into it prior to installation and compaction of the liner. Minor cost savings would be obtained due to 50cm less coral fill needed below the liner. However, as shown in Table 5.4, this saving is more than eliminated by the significant additional costs for the construction of the red soil liner. Thus, the additional costs for a red soil bottom liner TOR_framework Providence 2_ – final Annex 3 – for the first disposal unit at Providence 2 amounts to approximately EUR 380,000 excluding project management and contingency. Table 5.4: Comparison of Landfill Liner Costs for the First Disposal Unit at Providence 2. Total (EUR) Pos. Item Proposed Liner Alternative Enhanced Red Soil Liner 1 Selective excavation/installation of fill material for liner basis 72,000 36,000 2 Final levelling and compaction of base layer for landfill liner 36,000 36,000 3.a Supply and installation of bentonite liner 306,000 - 3.b-1 Selective excavation of 20,000m3 red soil from borrow pits 140,000 3.b-2 Transport of red soil to the site at Providence – 300,000 3.b-3 Improvement of red soil permeability by means of mixing with bentonite powder - 200,000 3.b-4 Installation and compaction of a 50cm thick, improved red soil geological liner - 80,000 4 Supply and installation of HDPE liner 234,000 234,000 Landfill Liner Costs, excl. project management & contingency 648,000 1,026,000 5.3.3 Leachate Management Leachate Collection The bottom of the disposal unit shall be equipped with three slotted drains, 250mm HDPE pipes, that transport the leachate by gravity to a collection well established in the lowest end of the unit. The drain pipes are surrounded by a drainage layer of gravel to increase the drainage efficiency. The size of gravel will be specified to match the slots of the drain pipes to reduce the risk of clogging of the pipes. The upstream end of the drains shall end at the top of the embankment, giving access for flushing the drains. A leachate collection well shall be placed within the disposal unit and the top of the well shall be on level with the final level of the landfill. The well shall be equipped with one automatically controlled, submersible pump. From the collection well the leachate shall be lifted to a shallow gravity pipe placed in the service road. The gravity pipe shall convey the leachate to a main pumping station placed in the service area. The service area is located in the western section of the landfill near the entry of the access road to the landfill. Main Pumping Station The main pumping station shall pump leachate from the landfill area to the nearby Greater Victoria Wastewater Treatment Plant (GVWTP) operated by the Public Utilities Corporation (PUC). The distance from the service area to GVWTP is about 500m. The pumping station shall be equipped with two automatically controlled submersible pumps of which one pump shall be a spare pump. A location of the pumping station at the northern section of the landfill will provide a shorter leachate pipeline to GVWTP and provide a wider buffer zone towards the Providence Highway, but there are three main arguments that favour the proposed location: • The easy access to the pumping station in the Service Area will be maintained; • The area for the pumping station will not result in a reduction in the void space available; • The leachate pipeline will run along the access road and existing boundaries instead of along the coastline on the outside of the scrap metal yard to avoid waste deposits. TOR_framework Providence 2_ – final Annex 3 – Leachate Treatment Leachate belongs to the more “difficult” wastewaters with respect to treatment. The flow varies significantly within a year and the quality varies significantly over the years. Opposite common domestic wastewater loads, the highest pollution loads emerge during the first years and the influence of pollutant load variation can be managed only by establishing a treatment plant that is robust and flexible. The influence of waste age versus leachate quality is shown in Table 5.5. The values are derived by the Consultants from numerous sources and from actual analyses of the leachate produced at the existing Providence landfill. During the first phase (the acid phase), very high concentrations of the pollutants (primarily COD, BOD and Ammonia) emerge. These high concentrations decrease rapidly over the years since the acid conditions rapidly convert to methane conditions. Table 5.5: Leachate Quality. The general approach for assessment of leachate production at Providence 2, together with a presentation of technical options for treatment, is included in Appendix 5. Appendix 5 was prepared early in the Project and formed the foundation for the discussions between the PUC and the Consultants leading to the agreed recommended proposal to locate a leachate pre-treatment plant at the future expansion area of GVWTP and use GVWTP for final treatment and discharge of effluents to the sea outfall is good. This opens for PUC to manage the leachate pre-treatment plant, which would seem an optimal solution considering the expertise in PUC. The agreed and preferable solution for leachate treatment at Providence 2 includes the following elements: • Pumping of the leachate from the landfill site to GVWTP; Acid phase (0-2 years) Methane Phase (>2 years) Component Unit Typical Variation Design value Design value pH 5.0 – 6.5 6.0 7.5 COD mg/l 20,000 – 40,000 24,000 2,200 BOD5 mg/l 10,000 – 30,000 14,000 400 Ammonia-N mg/l 900 – 1,500 900 1,000 Chloride 1,000 – 3,000 1,900 2,000 PO4 –P mg/l 5-100 30 8 SS (suspended solids) mg/l 200-2000 500 250 Sulphate (mg/l) mg/l 200 – 1,000 500 200 Iron (mg/l) mg/l 5 – 1,000 400 10 Manganese (mg/l) mg/l 20 – 30 20 1 Zinc (mg/l) mg/l 1 – 5 3 0.5 Copper (mg/l) mg/l 0.2 – 5 1 0.2 Nickel (mg/l) mg/l 0.2 – 5 1 0.2 Chromium (mg/l) mg/l 0.2 – 2 1 0.1 Lead (µg/l) µg/l 50 – 1,000 100 100 Cadmium (µg/l) µg/l 1 – 100 10 5 Mercury (Hg) µg/l 0.2-50 10 10 TOR_framework Providence 2_ – final Annex 3 – • Pre-treatment of the leachate at the GVWTP site. The pre-treatment plant shall be established in the reserved area adjacent to the WTP (area reserved for extension of the WTP); • Conveying the effluent from the pre-treatment plant to the inlet works at the GVWTP; • Accomplish complete treatment of the leachate together with the domestic sewage at the GVWTP; • Collect and moderate thicken the excess sludge from the pre-treatment plant; • Transport (by vacuum trucks) the thickened sludge to the landfill for final disposal. The design data for leachate to be pre-treated at GVWTP is shown in Table 5.6. Table 5.6: Leachate Design Data, Providence 2. Parameter Unit Maximum Average Minimum Design Value Flow Q m3/day 720 266 ~0 412* COD kg/day 3,627 1,005 104 1,460 BOD5 kg/day 2,117 493 19 764 SS kg/day 90 NH3 kg/day 208 134 47 145 : Due to a design value lower than maximum generation, the annual peak generation is levelled, ensuring a less and more stable discharge to the GVWTP. During the rainy season, the peak leachate generation will be stored within the landfill unit itself, resulting in a temporarily leachate level of approximately above the landfill bottom. The maximum flow to the treatment plant will be controlled by inlet pumps to the treatment plant. The effluent standards for the pre-treatment shall comply with permissible values shown in Table 5.7. Table 5.7: Effluent Requirements, Providence 2. Parameter Unit Maximum Permissible Value Suspended solids (SS) mg/l 300 BOD5 at 20oC mg/l 300 Phenols mg/l 0.5 Chromium (total) Cr mg/l 10 Arsenic (total) As mg/l 0.5 Mercury (total) Hg mg/l 0.3 Cadmium (total) Cd mg/l Lead (total) Pb mg/l 0.6 Copper (total) Cu mg/l 0.5 Zinc (total) Zn mg/l 1 Iron (total) Fe mg/l 0.6 Nickel (total) Ni mg/l 3 Note: The permissible values are identical to PUC’s requirements for connection to the sewer system. In the present study a Sequencing Batch Reactor (SBR) concept has been selected as the most favourable technical concept. However, when the works shall be tendered it could be considered to invite alternative treatment solutions alongside the SBR concept. The SBR plant will include: • Inlet construction (splitting chamber); • Two reactor tanks; TOR_framework Providence 2_ – final Annex 3 – • Blowers and a fine bubble bottom aeration system; • Decanter; • Mixer; • Chemical dosing station; • Outlet chamber; • Pumping station for lifting the effluent to the inlet works at the WTP; • Sludge pumps; • Sludge collection and thickening tank. It should be noted that during landfill operation the leachate can be partly treated by recirculation through the waste layers by means of pumps and infiltration drainpipes in the disposal unit. Recirculation can also be used as creating a buffer for the leachate treatment plant in periods of heavy rainfall. Sprinkling of leachate onto the landfill surface during dry periods can provide a significant reduction of the leachate volume due to evaporation. This method is applied at the landfill at La Digue, but seemingly cannot eliminate leachate production. The practice of surface sprinkling provides drawbacks in terms of aerosols detrimental to human health and the method is not recommended. 5.3.4 Landfill Gas Collection System Vertical gas collection wells shall be established in parallel with the infilling of waste. The vertical drain wells shall be established with an internal distance of about 50m. At a later stage it will be decided if it is favourable to connect the wells with a piped system and transport the gas to a central gas treatment/ utilisation facility or to a gas flare (gas flaring is the minimum solution). 5.3.5 Mobile Equipment For the operation of the landfill, the following main vehicles and mechanical equipment is needed: • Landfill compactor: A large landfill compactor (approximately 30 tonnes) would be preferred for crushing of large waste items and for appropriate compaction of the waste layers; • Bulldozer: A 20 tonnes (200hp) bulldozer is feasible for spreading of waste and application of daily cover layers on top of the compacted waste; • Wheel loader: A wheel loader is needed for loading of soil and gravel materials; • Dump truck: A dump truck is needed for internal transportation of soil and gravel materials; • Water tanker: A water tanker truck is needed for watering of internal roads and squares in order to prevent dust problems; • Road sweeper (tractor): A road sweeper is needed for sweeping of roads and squares. As mentioned earlier, mobile equipment is assumed be provided by the landfill operation contractor. 5.4 The Investments and the Costs of Operation and Maintenance The Consultants have collected unit costs from the construction sector in Seychelles in order to establish reliable cost estimates. In many cases, however, these included unexplainable differences and variations and the Consultants have in most cased adopted prices from experience from other projects. As discussed in Section Error! Reference source not found. the local construction market is small and local costs on materials and supplies are often relatively high due to the general supply situation and the situation with shortage and parallel market of foreign exchange. The Consultants would recommend Thus, the Consultants have adopted a general contingency on the estimated investments of 20% for this reason, however, has been instructed to use maximum 10%. , which usually would be 5-10 percentage points too much at this stage of cost estimation and design. The contingency on operation costs has been set at 15% reflecting greater certainty about the unit costs. TOR_framework Providence 2_ – final Annex 3 – Generally, the costs have been made in “rounded” Euros and then converted to Seychellois Rupees. This gives very precise Rupees prices and possibly rounding errors in totals. Staff costs have been calculated in SCR and converted to EUR. 5.4.1 Investments An estimate of the initial landfill investments is presented in Table 5.8. This estimate includes the first disposal unit. Table 5.8: Initial Landfill Investments at Providence 2 including the First Disposal Unit. Pos. Item Total (SCR) Total (EUR) 1 General Infrastructure 1,768,583 265,000 1.1 Access road (6 m wide) 100,109 15,000 1.2 General utilities (power supply, sewage discharge) 200,217 30,000 1.3 Embankment, fence, gates, planting 1,468,258 220,000 2 Initial Landfill Infrastructure and Equipment (including Monitoring Equipment) 6,507,053 975,000 2.1 Site preparation 533,912 80,000 2.2 Leachate Treatment Plant 5,973,141 895,000 3 First Landfill Disposal Unit 7,661,637 1,148,000 3.1 Selective excavation/installation of fill material for liner basis 480,521 72,000 3.2 Final levelling and compaction of base layer for landfill liner 240,260 36,000 3.3 Supply and installation of bentonite liner 2,042,213 306,000 3.4 Supply and installation of 1.5 mm HDPE liner 1,561,692 234,000 3.5 Geo-textile for protection of HDPE-liner 480,521 72,000 3.6 Leachate collection wells 66,739 10,000 3.7 Leachate pump station 66,739 10,000 3.8 Leachate collection drains 153,500 23,000 3.9 Leachate drainage layer 2,402,604 360,000 Leachate recirculation system 166,848 25,000 Sub-total, excluding project management & contingency 15,937,273 2,388,000 Project management costs including supervision and commissioning (10%) 1,593,727 239,000 Total initial investments, excluding contingency 17,531,000 2,627,000 Contingency (120%) 1,753,100 262,700 Total Initial Landfill Investments 19,284,100 2,889,700 After completion of in-filling of the first disposal unit, a second unit can be realised at the site. Inclusive of the second disposal unit and the final cover, the total investments (in 2005 prices) amount to approximately EUR 5.8 million as presented in Table 5.9. TOR_framework Providence 2_ – final Annex 3 – p 21 Table 5.9: Total Landfill Investments at Providence 2. Pos. Item Total (SCR) Total (EUR) 1 Initial Landfill Investments (from Table 4.7 above) 15,937,273 2,388,000 2 A Second Disposal Unit 6,013,183 901,000 3 Landfill Gas Management 4,004,340 600,000 3.1 Gas collection drains, pumps and network 1,001,085 150,000 3.2 Flares, incl. monitoring system 3,003,255 450,000 4 Landfill Closure and Restoration 2,002,170 300,000 4.1 Fill layer (0.8 m coral) 1,087,845 163,000 4.2 Top soil layer () 567,282 85,000 4.3 Planting 347,043 52,000 Sub-total, excluding project management contingency 27,956,967 4,189,000 Additional project development including design 1,334,780 200,000 Project management costs including supervision and commissioning (10%) 2,796,364 419,000 Total landfill investments, excluding contingency 32,088,111 4,808,000 Contingency (10%) 3,208,811 480,800 Total Landfill Investments 35,296,922 5,288,800 With a total disposal capacity of 640,000 tonnes of waste, the simple average investment cost amounts to EUR 8.3 per tonne. 5.4.2 Indicative Annual Operation and Maintenance Costs It is assumed that landfill operation is carried out by a contractor who provides all rolling stock (vehicles and mechanical equipment) needed for the operation on a lease basis. Landfill operating costs can be divided into the following main items: • Staffing costs (exclusive of machine operators); • Hire of rolling stock, incl. machine operators, maintenance, fuel etc.; • Maintenance of infrastructure; • Operation of leachate and gas treatment plants; • Other consumables. An estimate of the total annual operation and maintenance costs has been prepared on the basis of the Consultants’ experience from similar projects. The estimate is presented in Table . TOR_framework Providence 2_ – final Annex 3 – Table : Estimated Annual Operation and Maintenance Costs at Providence 2. Item Calculation/ Estimate Total Costs (SCR) Total Costs (EUR) Staffing costs See Table below 467,173 70,000 30 Tonnes Compactor (full time) 1,101,193 165,000 20 Tonnes Bulldozer (50% of the year) 467,173 70,000 Rolling stock Wheel loader, Dump truck etc. (part time) 333,695 50,000 Infrastructure maintenance ×2,388,000 EUR/year (5% of initial landfill infrastructure cost) 794,194 119,000 Leachate treatment 734,129 110,000 Landfill gas treatment Estimate 533,912 80,000 Other consumables Including water, electricity, office plus staff facilities etc. (estimate) 500,543 75,000 Environmental monitoring 133,478 20,000 Subtotal 5,065,490 759,000 Contingency (10%) 506,549 75,900 Total Annual Landfill Operation and Maintenance Costs 5,572,039 834,900 The expected staffing levels and costs are presented in Table . Table : Staffing Levels and Costs at Providence 2. Total Annual Cost Staff Number Unit cost (SCR per Year) SCR EUR Landfill Manager 1 150,000 150,000 22,476 Weighbridge operator 2 (one paid by landfill) 65,000 65,000 9,739 Machine operator 2 Included in equipment lease 0 0 Electrician and mechanics 90,000 22,500 3,371 Leachate plant operator 1,000 hours Included in Leachate plant costs 0 0 Unskilled labour 2 65,000 130,000 19,479 Security guards 2 (one paid by landfill) 65,000 65,000 9,739 Administrative staff 0.5 70,000 35,000 5,244 Total 467,500 70,048 The Costs of Operation and Maintenance depend on the received waste quantity and the costs will decrease if the decline in waste for landfill will occur as a result of implementation of incineration. The assumptions for the Financial Model are stated in Section Error! Reference source not found.. After landfill closure, leachate and landfill gas will continue to be generated. Therefore, leachate and gas collection and treatment facilities must be operated for an estimated 20-30 years of aftercare period until leachate and gas amounts and concentrations have reached acceptable levels for direct release/ discharge into the environment. Aftercare costs during this 20-years passive operation period are expected to correspond to approximately EUR 1 (SCR 6.7) per tonne of waste received for disposal at the landfill over its active life. A total reservation for aftercare of EUR 600,000 (SCR 4,004,340) is recommended. TOR_framework Providence 2_ – final Annex 3 – 5.5 Final Terrain and End Use The Providence 2 landfill will continue to settle and generate landfill gas for the foreseeable future after closure and restoration. Thus, there is no possibility to use the site for construction purposes for a long period of time. Public access may be prohibited for a period of time after closure due to the landfill gas installations on the site, but in time the site could be opened for public access and furnished as a recreational area. The location is beautiful between the sea and the mountain range of Mahé and the site could be developed into a major attraction. 5.6 The Manual for Operation and Maintenance Reference is made to the report Landfill Operation and Management which includes the draft operation and maintenance manual for Providence landfill. The manual shall be completed by the landfill contractor and operator based on operating instructions for supplied plant and equipment. 5.7 Overall Assessment of the Feasibility of the Proposed Project The Consultants assess the overall feasibility of Providence landfill as good: • The capacity and lifetime of the site is reasonable and provides a medium investment for each void space created; • The incorporation of leachate treatment within the Greater Victoria Wastewater Treatment Plant is good and this optimises the leachate treatment; • The environmental setting is acceptable provided the bird population on site is controlled and maximum care is exercised in the landfill of odorous waste types; • The main risks to the Project are deemed to be i) careless operation of the landfill leading to sustained bird populations and increased risks for the aviation safety and ii) the projected reduction in waste quantities for landfill fails to materialise due to lack of investments in recycling, composting and incineration technologies. Annex 4 ANNEX IV APPENDIX 5 TO FEASIBILITY REPORT JANUARY 2006 : APPROACH TO LEACHATE PRODUCTION AND TREATMENT Republic of Seychelles The Ministry of Environment and Natural Resources Detailed Studies and Technical Assistance for the Solid Waste Management Programme in Seychelles EUROPE AID/120339/D/SV/SC Appendix 5 Approach for Assessment of Leachate Production and Leachate Treatment at the Planned Landfills at Providence 2, Amitié 2 and La Digue 2. Second Revised edition 09 January 2006 TOR_framework Providence 2_ – final Annex 4 – p.1 Table of Contents 1. GENERAL APPROACH ….........................................................................................3 1.1 THE WASTE CHARACTERISTICS…......................................................................3 1.1.1 The Waste Amount 3 1.1.2 The Waste Age 4 1.1.3 The Waste Types 4 1.2 LEACHATE CHARACTERISTICS ….......................................................................4 1.2.1 Leachate Production 4 1.2.2 Leachate Quality 6 1.3 TREATMENT METHODS …......................................................................................7 1.3.1 Range of Options 7 1.3.2 The Main Options 9 1.3.2 The Preferred Technical Concept 11 1.4 EFFLUENT REQUIREMENTS … 2. PROVIDENCE 2… 2.1 MAIN OPTIONS … 2.2 BRIEF DESCRIPTION OF “GREATER VICTORIA WWTP”… 2.2 LEACHATE PRODUCTION- DESIGN LOAD… 2.3 OPTION1A: DIRECT CONNECTION TO “GREATER VICTORIA WWTP”. NO PRE-TREATMENT PLANT ESTABLISHED… 2.3.1 Concept Description 15 2.3.2 Investments 16 2.3.3 Operation and Maintenance Costs 16 2.4 OPTION1B: DIRECT CONNECTION TO “GREATER VICTORIA WWTP”. PRE-TREATMENT PLANT ESTABLISHED AT THE WWTP SITE… 2.4.1 Concept Description 16 Option 1B includes the following elements: 17 2.4.2 Pre-Treatment Requirements 17 2.4.3 Construction Data, SBR-Plant 17 2.4.4 Investments 18 2.4.5 Operation and Maintenance Costs 18 2.5 OPTION1C: DIRECT CONNECTION TO “GREATER VICTORIA WWTP” SEA OUTFALL PIPE. PRE-TREATMENT ESTABLISHED AT LANDFILL SITE. 18 2.5.1 Concept description 18 2.5.2 Pre-Treatment Requirements 19 2.5.3 Construction Data, SBR-Plant 19 2.5.4 Investments 19 2.5.5 Operation and Maintenance Costs 20 2.6 OPTION2: COMPLETE TREATMENT AT THE LANDFILL SITE … 2.6.1 Effluent Requirements 20 2.6.2 Concept description 20 2.6.3 Construction Data, SBR-Plant 21 2.6.4 Investments 21 2.6.5 Operational Costs 22 TOR_framework Providence 2_ – final Annex 4 – p.2 3. AMITIÉ 2… 3.1 OPTIONS … 3.2 ASSUMPTIONS FOR INTERNAL TREATMENT ON SITE … 3.2.1 Effluent Requirements 23 3.2.2 Dimensioning Data 23 3.3 SBR CONCEPT FOR INTERNAL TREATMENT ON SITE… 3.4 INVESTMENTS … 3.5 OPERATION AND MAINTENANCE COSTS… 4. LA DIGUE 2… 4.1 OPTIONS … 4.2 ASSUMPTIONS FOR INTERNAL TREATMENT ON SITE … 4.2.1 Effluent Requirements 25 4.2.2 Dimensioning Data 25 4.3 SBR CONCEPT FOR INTERNAL TREATMENT ON SITE… 4.4 INVESTMENTS … 4.5 OPERATION AND MAINTENANCE COSTS… 5. SUMMARY … 5.1 INVESTMENTS … 5.2 OPERATION AND MAINTENANCE COSTS… 5.3 RECOMMENDATIONS… 5.4 PUC DECISION… TOR_framework Providence 2_ – final Annex 4 – p.3 1. General Approach The present Chapter 1 aims to present the general approach for assessment of the development in leachate production and leachate quality within the planning period at the planned landfills Providence 2, Amitié 2 and La Digue 2. The presentation is illustrated by tables and graphs related to the actual conditions for Providence 2. The same calculation procedures have been practised for the remaining two sites, Amitié 2 and La Digue 2. It is found relevant not to include the similar tables and graphs related to these to landfills, but mainly to include the main dimensioning data. Chapter 1 also includes a general description of methods for treatment of leachate and preferences for the actual sites. Chapters 2, 3 and 4 cover a presentation of technical options for leachate treatment at the three actual sites including estimates of investments and operation/ maintenance costs. Chapter 5 provides a summary of the presentation including recommendations for implementation. 1.1 The Waste Characteristics 1.1.1 The Waste Amount The foreseen amount of waste that is aimed to be disposed of over the planning period is a key parameter for assessment of both landfill arrangements and development in leachate production. Starting with the conditions for Providence 2, Figure 1.1 shows the foreseen waste disposal over the planning period (2006-2030). Accumulated waste disposal (t) 0 100000 200000 300000 400000 500000 600000 700000 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 2026 2028 2030 Year tonnes Figure 1.1: Waste Accumulation at Providence 2. TOR_framework Providence 2_ – final Annex 4 – p.4 1.1.2 The Waste Age The age of the waste plays an important role for the character of the chemical substances in the leachate. “Fresh” Municipal Solid Waste (MSW) (younger than about 2 years) generates leachate with qualities significantly different from older waste. Figure 1.2 shows the amount of waste that is younger than 2 years and the amount that is older than 2 years. It appears from Figure 1.2 that already after a few years the “more than 2-year old” waste dominates. Age of disposed waste 0 20 40 60 80 100 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 2026 2028 Year percent <2y >2y Figure 1.2: Age of Disposed Waste at Providence 2. 1.1.3 The Waste Types Obviously, the type of waste that is aimed to be disposed of is important for the leachate quality. It is presumed that all three sites will only receive “municipal solid waste” (MSW). 1.2 Leachate Characteristics 1.2.1 Leachate Production The amount of leachate from a landfill site highly depends on the precipitation/ evaporation and the state of landfill operation (open units, units under operation, closed and recovered units etc). Rainwater collected in unpolluted open units should preferably not be discharged to the leachate collection system but to the surface water system. The following figures for precipitation / evaporation are used in the models for leachate generation: Average rain 2,358mm/year Potential evaporation 1,402mm/year Actual evaporation 841mm/year (60% of potential evaporation) Surface run off from closed cells 60% Not surprisingly, the leachate production will vary significantly during the year due to the precipitation. TOR_framework Providence 2_ – final Annex 4 – p.5 The development of leachate production for Providence 2 during a year is presented in Figure 1.3. Leachate production Providence 2 0 100 200 300 400 500 600 700 800 J anuary Februar y March April May June July Aug ust September Octobe r November December Month m3/day Figure 1.3: Leachate Production during the Design Year (the Year with the Highest Leachate Production). It appears from Figure 1.3 that the flow varies from about 700m3 /day in January to about zero in July. Obviously, this is far from desirable when it comes to operation of a treatment plant. Using the landfill itself as a buffer, the flow from the landfill can be more or less equalised. By allowing the water height in the landfill to elevate 1m as a maximum, the design flow for the leachate treatment plant can be equalised to about 400m3 /day for Providence 2. The equalised flow will last for the main part of the year. The effect of equalising the flow in Providence 2 is shown in Figure 1.4 and 1.5. Leachate storage in landfill 0 5000 10000 15000 20000 25000 1 2 3 4 5 6 7 8 9 10 11 12 month 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Leachate height, m Storage m3 Out m3/month Leachate m3/month Leachate height, m Figure 1.4: Leachate Production utilising the Landfill as a Buffer at Providence 2. TOR_framework Providence 2_ – final Annex 4 – p.6 Leachate production with buffering Providence 2 0 50 100 150 200 250 300 350 400 450 Janua ry Febr uary March April May June July August September Octo ber No vember December Month m3/hour Figure 1.5: Leachate Production utilising the Landfill as a buffer at Providence 2. For all three planned landfills, the same approach for assessment of leachate production has been used. The equalised flows have been used as the dimensioning flow for treatment facilities. 1.2.2 Leachate Quality As mentioned earlier, the quality of MSW leachate depends significantly on the waste age. During the first years the leachate is “acetogenic” and for the later years “methanogenic”. Table 1.1 shows the typical concentrations of major components in leachate from these two phases. The values are derived from Word Bank, German and English sources and from actual analyses of the leachate produced at the existing Providence landfill. Table 1.1: Typical Concentrations of Pollutant Substances in Municipal Solid Waste. Based on the design values shown in Table 1.1 and the waste disposal forecast, projections for pollutant concentrations and loads can be calculated. Figure 1.6 illustrates the variation in COD, BOD Acid phase (0-2 years) Methane Phase (>2 years) Component Unit Typical Variation Design value Design value pH 5.0 – 6.5 6.0 7.5 COD mg/l 20,000 – 40,000 24,000 2,200 BOD5 mg/l 10,000 – 30,000 14,000 400 Ammonia-N mg/l 900 – 1,500 900 1,000 Chloride 1,000 – 3,000 1,900 2,000 PO4 -P mg/l 5-100 30 8 SS (suspended solids) mg/l 200-2000 500 250 Sulphate (mg/l) mg/l 200 – 1,000 500 200 Iron (mg/l) mg/l 5 – 1,000 400 10 Manganese (mg/l) mg/l 20 – 30 20 1 Zinc (mg/l) mg/l 1 – 5 3 0.5 Copper (mg/l) mg/l 0.2 – 5 1 0.2 Nickel (mg/l) mg/l 0.2 – 5 1 0.2 Chromium (mg/l) mg/l 0.2 – 2 1 0.1 Lead (µg/l) µg/l 50 – 1,000 100 100 Cadmium (µg/l) µg/l 1 – 100 10 5 Mercury (Hg µg/l 0.2-50 10 10 TOR_framework Providence 2_ – final Annex 4 – p.7 and NH4 concentrations expressed in mg/l and Figure 1.7 the correspondent variation in load expressed in tonnes/year. COD, BOD and NH4 concentrations 0 5000 10000 15000 20000 25000 30000 1 3 5 7 9 11 13 15 17 19 21 23 25 Year mg/l Figure 1.6: COD, BOD and NH4 Concentrations within the Planning Period at Providence 2. COD, BOD and NH4 load 0 200 400 600 800 1000 1200 1400 1 3 5 7 9 11 13 15 17 19 21 23 25 Year tonnes/year Figure 1.7: COD, BOD and NH4 Loads within the Planning Period. Figure 1.6 and 1.7 clearly illustrate the influence of the waste age. During the first years, the leachate concentrations and loads are significantly high. In contrast, the younger leachate is far more easily degradable and easier to treat than the older leachate. 1.3 Treatment Methods 1.3.1 Range of Options The main components to be treated in MSW leachate are organic matters, ammonia and (where the leachate will be discharged to fresh waters) chlorides. The degree and type of treatment varies greatly, depending on the standards for discharge, climatic conditions and the quality and quantity of leachate generated. A combination of treatment methods may therefore be required. COD BOD NH4 COD BOD NH4 TOR_framework Providence 2_ – final Annex 4 – p.8 Table 1.2 includes the range of treatment options for treatment of leachate. Treatment Objectives Main Treatment Options Aerobic biological Activated sludge Sequencing batch reactor (SBR) Rotating Biological Contactor (RCB) Aerated lagoon/extended aeration Anaerobic biological Upflow sludge blanket (USB) Removal of degradable organic substances (BOD) Aerobic nitrification Activated sludge Sequencing batch reactor (SBR) Rotating Biological Contactor (RCB) Aerated lagoon/extended aeration Constructed wetlands Air stripping Removal of ammonia Anoxic biological Sequencing batch reactor (SBR) Constructed wetlands Denitrification Lime /coagulant addition Activated carbon Reverse osmosis Chemical oxidation Removal of non-degradable organics and toxic Activated carbon Reverse osmosis Chemical oxidation Removal of hazardous trace organic Hydrogen peroxide Odour removal Lime/coagulant addition, aeration and sedimentation Removal of dissolved iron , heavy metals and suspended solids Constructed wetlands Final polishing Sandfilters Hypochlorite Disinfection Reverse osmosis Volume reduction/ pre concentration Evaporation Table 1.2: The Main Leachate Treatment Options. TOR_framework Providence 2_ – final Annex 4 – p.9 1.3.2 The Main Options The most appropriate options for the actual landfills are assessed to be: • Waste Stabilisation Ponds; • Aerated Lagoons; • Rotating Biological Contractors (RBC); • Sequencing Batch Reactor (SBR). The characteristics of these concepts are illustrated in Figures 1.8, 1.9, and . The informed pond volumes are roughly estimated and relates to a hypothetical treatment of the leachate produced at Providence 2. The correspondent design load is: Q= 412 m3 /day COD=1,460 kg/day BOD= 764 kg/day NH3 = 145 kg/day Figure 1.8 Waste Stabilisation Ponds. Sreen Anaerobic Cascade Facultative Maturation Landfill Outlet Pond volumes about 20,000 m3 Waste Stabilisation Ponds Inlet zone Landfill Outlet Pond volumes about 6,000m3 Aerated lagoons Clarifier Aerated lagoons TOR_framework Providence 2_ – final Annex 4 – Figure 1.9 Aerated Lagoons. Figure Rotating Biological Contractor (RBC). Figure Sequencing Batch Reactor (SBR). The main qualities in the four concepts are summarised in Table 1.3. Treatment Concept Main Design Parameters Advantages Disadvantages Waste Stabilisation Ponds Anaerobic ponds Volume load: 100g/m3 d Facultative ponds Surface load: 250 kg/ha d ? Easy to construct and operate ? Limited mechanical equipment ? Limited operational costs ? No need for highly qualified staff ? Large area demand ? No control possibilities ? Limited possibilities for nutrient removal Aerated lagoons F/M ratio: kg VSS Sludge concentration: 200mg/l Clarifier: 1-2 d retention time ? Fairly easy to operate ? Limited control possibilities ? Limited possibilities for nutrient removal ? Need for clarifier Inlet zone Landfill Outlet Pond volumes about 5,000 m3 RBC shafts Clarifier Rotating Biological Contractor (RBC) Inlet zone Landfill Pond volumes about 4,000 m3 SBR tanks Outlet Sequencing Batch Reactor (RBC) TOR_framework Providence 2_ – final Annex 4 – Treatment Concept Main Design Parameters Advantages Disadvantages Rotating Biological Contractors (RBC) Hydraulic load: - m3 /m2 d Surface load: kgBOD/m2 d ? Fairly easy to operate ? Limited control possibilities ? Limited possibilities for nutrient removal ? Risk for mechanical failures ? Need for clarifier Sequencing Batch Reactors (SBR) F/M ratio: kg VSS Sludge concentration: 5,000mg/l ? Good control possibilities ? Good possibilities for nutrient removal ? No need for additional clarifier ? Need for fairly qualified technical staff Table 1.3: The Main Qualities of the Four Treatment Concepts. 1.3.2 The Preferred Technical Concept Taking all conditions into account, hereunder the very limited areas available for treatment facilities, the Sequencing Batch Reactor (SBR) concept, alternatively the Rotating Biological Contactor (RBC) concept, seem to be the most favourable concepts. Due to importance of robustness, control possibilities and flexibility, the SBR concept has been selected as the most attractive. However, when the works shall be tendered, it is recommended also to invite for alternative treatment concepts. The main components in a SBR plant are illustrated in Figure . Figure : The SBR Concept. Splitting chamber Decanter Main pumping station Excess sludge to disposal unit Effluent to: ? Domestic WWTP(if pretreated) ? Stream ? Infiltration SBR 1 SBR- concept as a basis for comparison in investments etc SBR 2 Mixer Possible polishing: ? Wetland ? Sand filter Air blowers Chemicals Mixer Decanter TOR_framework Providence 2_ – final Annex 4 – 1.4 Effluent Requirements The effluent requirements influence highly on the size and complexity of a wastewater treatment plant. As examples, the effluent standards in the EU countries and Mauritius are shown in Table 1.4. EU Legislation 91/271/EEC Parameter Unit 2-10,000 pe 10-100,000 pe > 100,000 pe Mauritius BOD mg/l 25 25 25 40 COD mg/l 125 125 125 120 SS mg/l 60 35 35 35 Tot-P mg/l – 2 1* 25 Tot-N – 15* 10* - Table 1.4: Comparison of Effluent Standards. For discharge to sea, more easy terms are declared in certain countries. As an example, the permissible values for sea outfalls in Mauritius are shown in Table 1.5. Parameter Unit Value BOD mg/l 250 COD mg/l 750 SS mg/l 300 Tot-P mg/l - Tot-N mg/l - Table 1.5: Permissible Values for Sea Outfall Discharges in Mauritius. For the Seychelles, two sets of effluent requirements are relevant for the actual landfill projects. 1. The general effluent quality standards included in “Environmental Protection Act” issued in 1994. These standards will be relevant for leachate treatment at Amitié 2 and La Digue 2 2. The PUC requirements for connection to the sewer included in the “PUC Act”. These standards will be relevant in case the leachate from Providence 2 is transported to and co-treated at the existing treatment plant “Greater Victoria WWTP”. The two sets of standards are shown in Table 1.6. Parameter Unit Providence 2) Amitié 2 and La Digue 2) Temperature o C – 30 pH – - 5.5-6.5 Suspended solids (SS) 300 30 BOD5 at 200C mg/l 300 30 COD mg/l – 80 Phosphorous (as PO4) mg/l – 5 Nitrate (as NO3) mg/l – 15 Nitrite (as NO2) mg/l – 1.0 Phenols mg/l 0.5 0.1 Chromium (total) Cr mg/l 10 10 Arsenic (total) As mg/l 0.5 0.1 Mercury (total) Hg mg/l 0.3 Cadmium (total) Cd mg/l 0.2 Lead (total) Pb mg/l 0.6 0.9 Copper (total) Cu mg/l 0.5 1 Zinc (total) Zn mg/l 1 2 TOR_framework Providence 2_ – final Annex 4 – Parameter Unit Providence 2) Amitié 2 and La Digue 2) Iron (total) Fe mg/l 0.6 5 Nickel (total) Ni mg/l 3 1 Aluminium (total) Al mg/l – 1 Tin (total) Sn mg/l – 0.1 Manganese (total) Mn mg/l – 2 Oil and grease mg/l – 10 Total coliforms Nos/100 ml – 500 Faecal coliforms Nos/100 ml – 100 Faecal streptococci Nos/100 ml – 100 Salmonella Pesticides – - Must not be detected Pesticides – According to laws relating to pesticides in force Explosive and/ or combustible materials According to laws relating to pesticides in force - ) For pre-treatment and connection to Greater Victoria WWTP. Values according to PUC Act for connection to the sewer system. ) For full treatment. Values according to the Environmental Protection Act issued 1994. Table 1.6: Effluent Standards for Treatment of Leachate at Providence 2, Amitié 2 and La Digue 2. TOR_framework Providence 2_ – final Annex 4 – 2. Providence 2 2.1 Main Options There are two obvious options for treatment and disposal of leachate from Providence 2: Option 1: Connection to the nearby treatment plant for domestic wastewater “Greater Victoria WWTP” Option 2: Complete treatment of leachate at the landfill site and disposal of treated water by infiltration Depending on the degree of required pre-treatment before connection to “Greater Victoria WWTP” a number of alternatives occur for Option1. The following three sub-options are assessed to be the most obvious: • Option 1A: Raw leachate is transported from the landfill site to “Greater Victoria WWTP” and directly connected to the plant’s inlet works and mixed with the domestic wastewater. • Option 1B: Raw leachate is transported from the landfill site to “Greater Victoria WWTP” where pre-treatment (type SBR or similar) takes place at the WWTP premises. After pre-treatment the wastewater is connected to the plant’s inlet works and mixed with the domestic wastewater • Option 1C: Pre-treatment (type SBR or similar) takes place at the landfill site. After pre-treatment the leachate is transported to “Greater Victoria WWTP” and directly connected to the sea outfall via the existing outlet pumping station. 2.2 Brief Description of “Greater Victoria WWTP” Greater Victoria WWT was commissioned in 2001. It is informed that the plant is designed for 7,000m3 /day. However, only half of the design capacity is utilised today. It is likely to believe that the plant is designed for about 60,000 person equivalents (PE) based on BOD equivalents. The treatment plant is designed as an activated sludge plant including advanced nitrogen and phosphorous removal. The phosphorous removal takes place both biologically and by adding participation chemicals. Surface aerators provide the oxygen for the process. Disinfection takes place by UV radiation. The discharge from the plant takes place via an outlet pumping station located within the WWTP premises and a 1 km long sea outfall pipe equipped with diffusers at the pipe end. The sludge is dewatered in a belt press and the dewatered sludge is transported to the existing landfill site. The treatment plant is assessed to represent the state of art today for advanced treatment of domestic wastewater. TOR_framework Providence 2_ – final Annex 4 – 2.2 Leachate Production- Design load The foreseen future leachate production for Providence 2 is shown in Table 2.3. The data are derived according to the approach that is described in Chapter 1. Parameter Unit Maximum Average Minimum Design load Q m3/day 720 266 ~0 412 COD kg/day 3,627 1,005 104 1,460) BOD5 kg/day 2,117 493 19 764) SS kg/day 90) NH3 kg/day 208 134 47 145) PE 80% fractile pe – - – 12,733 PE average pe – 8,233 – - *) Assumed to represent 80% fractile of the daily leachate production. Use of the 80 % fractile for design purpose represents common design practise for treatment plants. Table 2.1: Foreseen Future Leachate Production. Design Load for Providence 2. 2.3 Option1A: Direct Connection to “Greater Victoria WWTP”. No Pre-Treatment Plant Established 2.3.1 Concept Description The elements in Option 1A is illustrated in Figure 2.1. Figure 2.1 Option 1A. In this option a complete co-treatment with the domestic sewage takes place at Greater Victoria WWTP. Consequently, the produced sludge includes solids and other substances from both the domestic sewage and the leachate. Greater Victoria WWTP Providence 2 Landfill Sea outfall New pumping main 150 mm Disposal Unit 1 Disposal Unit 2 Option 1A: Connection to Greater Victoria WWTP, no pre-treatment (SBR or similar) at Greater Victoria WWTP New Pumping station Inlet works Outlet pumping station Processing plant TOR_framework Providence 2_ – final Annex 4 – 2.3.2 Investments The investments for Option1A are shown in Table 2.2. Investment Component SCR EUR Transport to Greater Victoria WWTP Pumping station at the disposal unit 220,239 33,000 Pipe to Greater Victoria WWTP 213,564 32,000 Subtotal Transport to Greater Victoria WWTP 403,803 65,000 Arrangements at Greater Victoria WWTP Connection to inlet works etc. 266,800 40,000 Subtotal arrangements at Greater Victoria WWTP 266,800 40,000 Sub-total construction 700,760 105,000 Design, supervision 10% 70,076 11,000 Total construction 774,172 116,000 Contingencies 20% 153,500 23,000 Grand total ( rounded) 927,672 139,000 Table 2.2: Investments Option 1A. 2.3.3 Operation and Maintenance Costs The operation and maintenance (O&M) costs are shown in Table 2.3 O&M cost Component SCR/year EUR/year Operation 1. Power consumption 39,154 6,101 2. Chemicals 40,043 6,000 3. Staff operation ( supervision) 33,370 5,000 4. Others 10% 11,413 1,710 Subtotal operation 125,546 18,811 Maintenance (3% of investment) 3,766 564 Total( rounded) 133,478 20,000 Table 2.3: O&M Costs Option 1A. 2.4 Option1B: Direct Connection to “Greater Victoria WWTP”. Pre-Treatment Plant Established at the WWTP Site 2.4.1 Concept Description The elements in Option 1A is illustrated in Figure 2.2. TOR_framework Providence 2_ – final Annex 4 – Figure 2.2: Option 1B. Option 1B includes the following elements: • Pumping of the leachate from the landfill site to GVWTP; • Pre-treatment of the leachate at the GVWTP site. The pre-treatment plant shall be established in the reserved area adjacent to the WTP (area reserved for extension of the WTP); • Conveying the effluent from the pre-treatment plant to the inlet works at the GVWTP; • Accomplish complete treatment of the leachate together with the domestic sewage at the GVWTP; • Collect and moderate thicken the excess sludge from the pre-treatment plant; • Transport (by vacuum trucks) the thickened sludge to the landfill for final disposal. 2.4.2 Pre-Treatment Requirements The purpose of the pre-treatment is to achieve a quality of the effluent that observes PUC’s requirements for connection to the sewer network. Please see previous Table 1.5. 2.4.3 Construction Data, SBR-Plant The construction data for the SBR ent plant is shown in Table 2.4. Component Unit Quantity Total volume in SBR tanks m3 2,500 Number of SBR tanks Nos 2 Volume of each tank m3 1,250 Height of each tank m 5 Area of ach tank m2 250 Diameter of each tank m 17.8 Table 2.4: Option 1B, Construction Data. Sludge return by trucks Providence 2 Landfill Existing sea outfall New pumping main 150 mm Greater Victoria WWTP Disposal Unit 1 Disposal Unit 2 Sub-option 1B: Connection to Greater Victoria WWTP, pre-treatment (SBR) at Greater Victoria Pumping station Pretreat ment TOR_framework Providence 2_ – final Annex 4 – 2.4.4 Investments The investments for Option1A are shown in Table 2.5. Investment Component SCR EUR Transport to Greater Victoria WWTP 1. Pumping station at the disposal unit 220,239 33,000 2. Pipe to Greater Victoria WWTP 213,564 32,000 Subtotal Transport to Greater Victoria WWTP 433,804 65,000 Pre-treatment at Greater Victoria WWTP Mobilisation 93,435 14,000 Earthwork 113,456 17,000 Constructions, inclusive of SBR tanks 1,094,520 164,000 Mechanical installations 2,048,887 307,000 Electrical installations 153,500 23,000 Sludge thickening 553,994 83,000 Subtotal pre- treatment plant 4,091,101 613,000 Sub-total construction 4,524,904 678,000 Design, supervision 10% 452,490 67,800 Total construction 4,997,395 745,800 Contingencies 20% 995,479 149,200 Grand total ( rounded) 5,973,141 895,000 Table 2.5: Investments Option 1B 2.4.5 Operation and Maintenance Costs The correspondent operation and maintenance (O&M) costs is shown in Table 2.6. O&M cost Component SCR/year EUR/year consumption 229,369 34,368 2. Chemicals 137,927 20,667 3. Staff operation 133,478 20,000 4. Others 10% 50,077 7,503 Subtotal operation 550,851 82,538 Maintenance (3% of investment) 16,526 2,476 Total 573,955 86,000 Table 2.6: O&M Costs Option 1B 2.5 Option1C: Direct connection to “Greater Victoria WWTP” Sea Outfall Pipe. Pre- Treatment established at Landfill Site. 2.5.1 Concept description The elements in Option 1A is illustrated in Figure 23. TOR_framework Providence 2_ – final Annex 4 – Figure 2.3: Sub-Option 1C. The concept is similar to Option 1B with the following differences: • Pre-treatment takes place at the landfill site; • The pre-treated water is discharged directly to the sea outfall pipe at Greater Victoria WWTP. 2.5.2 Pre-Treatment Requirements It is assumed that the d water, if treated as in Option 1B, can be discharged directly to the sea without any co-treatment at Greater Victoria WWTP. 2.5.3 Construction Data, SBR-Plant The construction data for the SBR ent plant is shown in Table 2.7. Component Unit Total volume in SBR tanks m3 2,500 Number of SBR tanks Nos 2 Volume of each tank m3 1,250 Height of each tank m 5 Area of ach tank m2 250 Diameter of each tank m 17.8 Table 2.7: Option 1C, Construction Data. 2.5.4 Investments The investments for Option1A are shown in Table 2.8. New pumping main 150 mm Existing outfall to ocean Providence 2 Landfill Pumping Station Greater Victoria WWTP Disposal Unit 1 Disposal Unit 2 Sub-option 1C: Pre-treatment at Providence 2 and directly connection to the sea outfall at Greater Victoria WWTP Pretreat ment Pumping Station Outlet pumping station TOR_framework Providence 2_ – final Annex 4 – Investment Component SCR EUR Transport to Greater Victoria WWTP 1. Pumping station at the disposal unit 220,239 33,000 2. Pipe to Greater Victoria WWTP 249,159 37,333 3. Arrangements at Greater Victoria WWTP 133,478 20,000 Subtotal Transport to Greater Victoria WWTP 602,876 90,333 Pre-treatment at landfill site Mobilisation 93,435 14,000 Earthwork 146,826 22,000 Constructions, inclusive of SBR tanks 1,094,520 164,000 Mechanical installations 2,048,887 307,000 Electrical installations 153,500 23,000 Sludge thickening 168,848 25,000 Subtotal pre- treatment plant 3,704,015 555,000 Sub-total construction 4,540,477 680,333 Design, supervision 10% 454,048 68,033 Total construction 4,994,524 748,367 Contingencies 20% 998,905 149,200 Grand total ( rounded) 5,993,162 898,000 Table 2.8: Investments Option 1c. 2.5.5 Operation and Maintenance Costs The correspondent operation and maintenance (O&M) costs is shown in Table 2.9. O&M cost Component SCR/year EUR/year 1. Power consumption 245,030 36,715 2. Chemicals 137,927 20,667 3. Staff operation 133,478 20,000 4. Others 10% 51,644 7,738 Subtotal operation 568,079 85,119 Maintenance (3% of investment) 17,042 2,554 Total(rounded) 587,303 88,000 Table 2.9: O&M Costs Option 1C 2.6 Option2: Complete Treatment at the Landfill Site 2.6.1 Effluent Requirements The effluent shall comply with the standards included in “Environmental Protection Act” issued in 1994. See previous Table 1.5. 2.6.2 Concept description The elements in Option 1A is illustrated in Figure 2.4. TOR_framework Providence 2_ – final Annex 4 – Figure 2.4: Complete Treatment at the Landfill site. The discharge of the effluent in from the treatment plant located at the landfill site gives causes for concern. It is here assumed that the only realistic option is direct infiltration at the site. 2.6.3 Construction Data, SBR-Plant A SBR plant for achievement of complete treatment will include reactor volumes according to Table . Component Unit Total volume in SBR tanks m3 3,820 Number of SBR tanks Nos 2 Volume of each tank m3 1,910 Height of each tank M 5 Area of ach tank m2 382 Diameter of each tank M 22.1 Table : SBR Plant at Landfill Site for Complete Treatment. 2.6.4 Investments The investments for Option1A are shown in Table . Infiltration Option 2: Internal treatment at Providence 2 Existing outfall to ocean Providence 2 Landfill Pumping Station Greater Victoria WWTP Disposal Unit 2 New Leachate WWTP TOR_framework Providence 2_ – final Annex 4 – Investment Component SCR EUR Arrangements at landfill site Pumping station 177,970 26,666 Pumping mains 17,797 2,667 Subtotal pumping station 195,768 29,333 Treatment Plant at landfill site Mobilisation 88,985 13,333 Earthwork 222,463 33,333 Constructions, inclusive of SBR tanks 1,575,040 236,000 Mechanical installations 2,589,473 388,000 Electrical installations 266,956 40,000 Subtotal arrangements and treatment plant 4,742,918 710,667 Design, supervision 10% 441,091 66,092 Total 6,455,733 806,092 Contungency20% 1,075,955 161,218 Grand total 6,453,661 967,000 Table : Investments Option 2. Complete Treatment at the Landfill Site. 2.6.5 Operational Costs The correspondent operation and maintenance (O&M) costs is shown in Table . O&M cost Component SCR/year EUR/year Operation consumption 340,956 51,088 2. Chemicals 169,072 25,333 3. Staff operation 133,478 20,000 4. Others 10% 64,351 9,642 Subtotal operation 707,857 106,063 Maintenance (3% of investment) 21,236 3,182 Total 727,455 109,000 Table : O&M Costs Option 2. Complete Treatment at the Landfill Site. TOR_framework Providence 2_ – final Annex 4 – 3. Amitié 2 3.1 Options It is informed that planning for establishment of a new domestic wastewater treatment for Praslin, located close to the planned landfill site, is underway. This creates a situation for leachate treatment similar to Providence 2. In the absence of information about the planned domestic treatment plant it has been assumed that treatment of leachate has to take place at the landfill site. 3.2 Assumptions for Internal Treatment on Site 3.2.1 Effluent Requirements The effluent shall comply with the standards included in “Environmental Protection Act” issued in 1994. See previous Table 1.5. 3.2.2 Dimensioning Data The leachate characteristics for Amitié 2 are shown in Table 3.1. Parameter Unit Maximum Average Minimum Design Value Q m3/day 337 124 ~0 193 COD kg/day 479 263 49 328 BOD5 kg/day 241 107 8 147 SS kg/day 17 NH3 kg/day 126 60 22 77 PE PE – - – 2,450 PE PE – 1,700 – - Table 3.1: Design Data for Internal Treatment at Amitié 2. 3.3 SBR Concept for Internal Treatment on Site As for Providence 2, a sequencing batch reactor (SBR) concept has been selected as a basic concept for leachate treatment at Amitié 2. A SBR plant at Amitié 2 will included reactor volumes according to Table 3.2. Component Unit Design value Total volume in SBR tanks m3 640 Number of SBR tanks Nos 2 Volume of each tank m3 320 Height of each tank m 5 Area of ach tank m2 64 Diameter of each tank m 9.0 Table 3.2: SBR Plant at Amitié 2. A principle layout of the plant is shown in Figure far it is assumed that the effluent is allowed to be disposed of by direct infiltration at the treatment plant site. TOR_framework Providence 2_ – final Annex 4 – Figure 3.1: The Concept Solution for Leachate Treatment at Amitié 2. 3.4 Investments The investments related to a SBR concept are shown in Table 3.3. Investment Component SCR EUR Arrangements at landfill site Pumping station 133,478 20,000 Pumping mains 17,797 2,667 Subtotal pumping station 151,275 22,667 Treatment Plant at landfill site Mobilisation 44,493 6,667 Earthwork 20,912 3,133 Constructions, inclusive of SBR tanks 557,048 83,467 Mechanical installations 1,468,258 220,000 Electrical installations 222,463 20,000 Subtotal arrangements and treatment plant 2,313,174 346,600 Design, supervision 10% 242,884 36,393 Total 2,707,332 405,660 Contungency20% 541,466 81,132 Grand total 3,250,189 487,000 Table 3.3: Investments. 3.5 Operation and Maintenance Costs The O&M costs related to a SBR concept are shown in Table 3.4. O&M cost Component SCR/year EUR/year consumption 114,578 17,168 2. Chemicals 21,356 3,200 3. Staff operation 133,478 20,000 4. Others 10% 26,941 4,037 Subtotal operation 296,412 44,405 Maintenance (3% of investment) 8,891 1,332 Total (rounded) 307,000 46,000 Table 3.4: O&M Costs. Internal treatment at Amitié 2 Disposal Unit 1 Leachate WWTP Infiltration Disposal Unit 2 TOR_framework Providence 2_ – final Annex 4 – 4. La Digue 2 4.1 Options The existing landfill at La Digue is an “engineered” landfill equipped with bottom liner and collection of leachate. However, there are no treatment facilities for the collected leachate. The leachate is just recycled back to the landfill. It is assessed appropriate to integrate the produced leachate from the existing landfill with the produced leachate at the new bordering landfill unit. 4.2 Assumptions for Internal Treatment on Site 4.2.1 Effluent Requirements The effluent shall comply with the standards included in “Environmental Protection Act” issued 1994. See previous Table 2.1. 4.2.2 Dimensioning Data The dimensioning data for La Digue 2 are shown in Table 4.1. Parameter Unit Maximum Average Minimum Design value Q M3/day 63 23 ~0 48 COD kg/day 137 74 8 96 BOD5 kg/day 71 30 3 44 SS kg/day 3 NH3 kg/day 25 16 3 25 PE PE – - – 733 PE PE – 500 – - Table 4.1: Design Data for Internal Treatment at La Digue 2. 4.3 SBR Concept for Internal Treatment on Site As for Providence 2, a sequencing batch reactor (SBR) concept has been selected as a basic concept for leachate treatment at La Digue 2. A SBR plant at La Digueb2 will included reactor volumes according to Table 4.2. Component Unit Design value Total volume in SBR tanks m3 191 Number of SBR tanks No 2 Volume of each tank m3 96 Height of each tank m 5 Area of ach tank m2 19 Diameter of each tank m 4.9 Table 4.2: SBR Plant at La Digue. The concept of the plant is shown in Figure 4.1. So far it is assumed that the effluent is allowed to be disposed of by direct infiltration after flowing through a constructed wetland. TOR_framework Providence 2_ – final Annex 4 – Figure 4.1: The Concept for Leachate Treatment at La Digue 2. 4.4 Investments The investments related to a SBR concept are shown in Table 4.3. Investment Component SCR EUR Arrangements at landfill site Pumping station 133,478 20,000 Pumping mains 17,797 2,667 Subtotal pumping station 151,275 22,667 Treatment Plant at landfill site Mobilisation 44,493 6,667 Earthwork 20,912 3,133 Constructions, inclusive of SBR tanks 418,231 62,667 Mechanical installations 1,156,809 173,333 Electrical installations 222,463 33,333 Subtotal arrangements and treatment plant 1,862,908 279,133 Design, supervision 10% 195,605 29,309 Total 2,209,788 331,109 Contungency20% 441,958 66,222 Grand total (rounded) 2,625,212 398,000 Table 4.3: Investments. 4.5 Operation and Maintenance Costs The O&M costs related to a SBR concept are shown in Table 4.4. O&M cost Component SCR/year EUR/year consumption 91,263 13,675 2. Chemicals 12,457 1,867 3. Staff operation 133,478 20,000 4. Others 10% 23,720 3,554 Subtotal operation 260,919 39,095 Maintenance (3% of investment) 7,828 1,173 Total (rounded) 273,630 41,000 Table 4.4: O&M Costs. Wetland La Digue 2 Landfill Internal treatment at La Digue 2 Pumping Station Disposal Unit 2 Disposal Unit 1(Existing) New Leachate WWTP Existing collection Infiltartion TOR_framework Providence 2_ – final Annex 4 – 5. Summary The following summary includes all three landfill sites under consideration. 5.1 Investments The investments for the three landfills are shown in Table 5.1. The investment figures include 20% contingencies. The total investment for the three sites comprises EUR 1.0-1.9 million depending on the final solution for Providence 2. Providence 2 Amitié 2 La Digue 2 Option 1A: To Greater Victoria WWTP No pretreatment Option 1B: To Greater Victoria WWTP Pre-treatment at WWTP Option 1C: To Greater Victoria WWTP Pre-treatment at landfill Option 2: Pre- treatment at landfill and connection to Greater Victoria WWTP sea outfall Complete treatment at landfill Complete treatment at landfill 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 928 139 5,973 895 1,198 898 6,454 967 3,251 487 2,625 398 Table 5.1: Investments 5.2 Operation and Maintenance Costs The correspondent total O&M costs comprise EUR 100,000-200,000 per year, again dependent on the final solution for Providence 2. Providence 2 Amitié 2 La Digue 2 Option 1A: To Greater Victoria WWTP No pretreatment Option 1B: To Greater Victoria WWTP Pre-treatment at WWTP Option 1C: To Greater Victoria WWTP Pre-treatment at landfill Option 2: Pre- treatment at landfill and connection to Greater Victoria WWTP sea outfall Complete treatment at landfill Complete treatment at landfill 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 1,000 SCR 1,000 EUR 134 20 574 86 587 88 727 109 307 46 274 41 Table 5.2: O&M Costs. TOR_framework Providence 2_ – final Annex 4 – 5.3 Recommendations The following recommendations can be made: Site Recommendation Providence 2 From all aspects, an integration of the leachate treatment with the existing Greater Victoria WWTP will represent the most attractive solution. Obviously the leachate load from the landfill has to be carefully compared to the existing and planned load at the Greater Victoria WWTP. Internal treatment at the landfill site will most likely suffer from: ? Lack of staff familiar with wastewater treatment ? Lack of skilled staff with respect to wastewater treatment ? Difficulties to dispose the effluent in an acceptable way ? Possible nuisance to the nearby highway, sea territory and residential areas Amitié 2 From all aspects, an integration of the leachate treatment with the planned new domestic treatment plant for Praslin WWTP will represent the most attractive solution. Obviously the leachate load from the landfill has to be carefully compared to the existing and planned load at the new WWTP. Awaiting the finalisation of the planning of the new WWTP it is recommended: ? Accomplish complete treatment on landfill site ? Discharge the effluent via an infiltration plant La Digue 2 It is recommended: ? Accomplish complete treatment on landfill site ? Discharge the effluent via a constructed wetland followed by infiltration 5.4 PUC Decision The present paper concerning treatment options was presented for the Public Utilities Corporation (PUC) in July 2005 for the basis of a discussion on coordination and possible involvement of the PUC in use of existing and planned wastewater treatment facilities and involvement of PUC in operation and maintenance of possible treatment units at the landfills. PUC principally agreed to the solutions recommended by Carl Bro. Specifically for Providence 2, PUC will not accept to receive raw leachate for treatment in Greater Victoria WWTP, but PUC will accept to treat and discharge pre-treated leachate. The PUC confirmed its acceptance of providing land for the leachate pre-treatment facility at Greater Victoria WWTP (Option 1B) and this option is in many ways optimum as it opens for the leachate pre-treatment plant being operated by PUC. TOR_framework Providence 2_ – final Annex 5 – p.1 ANNEX V (A) LEACHATE CHARACTERISATION AT PROVIDENCE I () Parameter Unit Actual Values at Providence PUC acceptance Value Design Values - Construction of Providence 2 (Carl Bro) BOD5 mg/l 10,400 < 300 14,000 COD mg/l 34,100 90% removal 24,000 TSS mg/l 1825 < 300 500 pH 7-9 6 NH4-N mg/l 240 Not specified 900 NO2-N mg/l 2.8 < 2* - NO3-N mg/l 65 < 5* - Total Kjeldahl Nitrogen(TKN) mg/l 970 Not specified - Phosphorus mg/l 15 < 5* Fat, oil & grease – Not detectable Arsenic mg/l < 0.5 Cadmium Chloride mg/l 18,000 Not specified 1900 Copper mg/l < 0.5 - Cyanide mg/l < 1.5— Chromium (Hexavalent) mg/l – < 5 - Chromium (Total) mg/l < 10 - Iron mg/l < 15 400 Lead mg/l < 0.1 Manganese Mg/l – 20 Mercury mg/l ND (<) < 0.3 - Nickel mg/l < 3 1 Phenol mg/l – < 0.5 - Sodium mg/l Not specified - Sulfide mg/l 5.4 < 10 - Sulfate mg/l – 500 Zinc mg/l < 1 3 TOR_framework Providence 2_ – final Annex 5 – p.2 ANNEX V (B): EFFLUENT CRITERIA FOR DISCHARGE AT THE GREATER VICTORIA WASTEWATER TREATMENT PLANT Parameter Unit Value BOD5 mg/l < 300 COD mg/l 90% removal* TSS mg/l < 300 pH 7-9 NH4-N mg/l Not specified NO2-N mg/l < 2* NO3-N mg/l < 5* Total Kjeldahl Nitrogen(TKN) mg/l Not specified Phosphorus mg/l < 5* Fat, oil & grease Not detectable Arsenic mg/l < 0.5 Chloride mg/l Not specified Copper mg/l < 0.5 Cyanide mg/l < 1.5 Chromium (Hexavalent) mg/l < 5 Chromium (Total) mg/l < 10 Iron mg/l < 15 Lead mg/l < Mercury mg/l < 0.3 Nickel mg/l < 3 Phenol mg/l < 0.5 Sodium mg/l Not specified Sulfide mg/l < 10 Zinc mg/l < 1 TOR_framework Providence 2_ – final Annex 6 – p.1 ANNEX VI: PROVIDENCE II SANITARY LANDFILL DRAWINGS (Feasibility report – January 2006)
