Gisborne WWTP Stage 2 Upgrade Value Engineering

Transcription

1 Report Appendix 1 Report Gisborne WWTP Stage 2 Upgrade Value Engineering Prepared for Gisborne District Council (Client) By CH2M Beca Limited 2 November 2016

2 Revision History Revision Nº Prepared By Description Date A Sarah Burgess Draft for Client Review 21/10/2016 B Sarah Burgess Final 1/11/2016 Document Acceptance Action Name Signed Date Prepared by Sarah Burgess 2/11/2016 Reviewed by Rachael Shaw 2/11/2016 Approved by Garry Macdonald 2/11/2016 on behalf of CH2M Beca Limited CH2M Beca 2016 (unless CH2M Beca has expressly agreed otherwise with the Client in writing). This report has been prepared by CH2M Beca on the specific instructions of our Client. It is solely for our Client s use for the purpose for which it is intended in accordance with the agreed scope of work. Any use or reliance by any person contrary to the above, to which CH2M Beca has not given its prior written consent, is at that person's own risk CH2M Beca // 2 November 2016 // Page i

3 Executive Summary Background The Banks St WWTP s discharge consent requires GDC to establish the most appropriate longterm management option for Gisborne s wastewater by assessing the feasibility and level of community acceptance of upgrading the treatment plant with either a conventional solids removal and disinfection system or an alternative wastewater management system, which may involve a range of alternative use and disposal (AUD) options. As such GDC, in conjunction with NIWA, has been pilot trialling a series of enhanced pond and wetland stages to provide tertiary treatment of the effluent and solids streams following discharge from the existing Biological Trickling Filter plant (BTF). A Council decision as to how to proceed is required by December In order to initiate the community engagement process and inform the Council decision, Council requires that both options be developed into an engineering design to a level suitable to allow costing to +/- 30%. GDC has commissioned CH2M Beca Ltd (Beca) to develop these options into concept level engineering designs and prepare cost estimates to allow the feasibility of both options to be assessed by GDC and the WTAG. Two concept designs were developed and presented to the WTAG in October Option 1 was for a scaled up natural treatment system based on the processes that have been pilot trialled at the Banks St WWTP. Option 2 was for conventional clarification and solids handling at the Banks St WWTP. The capital cost estimate for Option 1 was significantly higher than Council or the WTAG had anticipated and as such the value engineering workshop undertaken with the WTAG identified a number of permutations of both the conventional treatment and natural treatment process for further development. Order of magnitude capital and whole of life estimates have been developed for each of the identified options, described as Options A through K with old Option 1 now Option J and old Option 2 now Option A. The options have not been developed to the same level of detail as the original two options presented in the concept design report and as such should be treated as comparative only. The WOL estimates consider both the capital cost of the option and the operational costs over a 20y period. Default Consent Requirements The consent variation granted in April 2015 stipulates that should the Alternative Use and Disposal (AUD) study conclude that it is not feasible to implement an alternative treatment process, Council is required to upgrade the Banks St treatment plant to provide a second BTF to reduce the BTF loading 1 to less than 0.4kg BOD/m³.d and install disinfection 2 to comply with less than 1000 cfu/100ml Enterococci in the domestic discharge. The requirement to install a clarification stage following the BTF will be dependent on whether the reduced BOD loading on the BTF can reliably and consistently achieve TSS in the discharge of less than 30mg/l. Compliance with the default consent requirements are addressed with Options B and C. 1 Clause 4A(g), Clauses 37 and Clause 4e, Clause 42 CH2M Beca // 2 November 2016 // Page 1

4 Technical Risks All the options described in this report are variations on the two main options set out in the Concept Design Report. As such, while the magnitude of some of them may change, the general risks associated with the options are substantially the same as those discussed in Section 9 of that report. The main risk area and ratings are summarised in table A1. Table A1 Technical Risk Summary from Concept Design Report Risk Natural Treatment: Risk Level with Mitigation Conventional Treatment: Risk Level with Mitigation Design Basis Low Low Process Performance Medium-high Low - Medium Noise Low Low Odour Medium Low Site Selection/Availability of suitable land Site Geotechnical Characteristics impacting on cost estimates High Medium-high Medium Low Biosolids Disposal Medium Medium Discharges to Land Medium-high Low Please refer to the Concept Design Report for the full discussion on risks. Basis of Estimates The purpose of these estimates is to provide Cost Estimate values to support the evaluation and selection of the optimal WWTP solution. Notably, the comparative values for the respective options are not necessarily the expected Total Cost of the option but more likely an indicative outturn cost. These estimates are to be read in conjunction with the basis of estimate summarised in Appendix A, which provides a summary of the level of design development supporting the estimate, the methodology in preparing the estimate, the source and general status of rates applied, assumptions, inclusions and exclusions and the expected level of accuracy associated with these inputs Options Comparison A comparison of the different unit cost breakdowns for each option are shown in Figure A along with the comparative capital cost estimate. Table A2 provides a summary of all Value Engineering options along with an assessment of expected effluent quality. The discharge has been colour coded using a traffic light system to indicate whether the quality of the discharge is considered suitable for discharge to a habitat wetland, to a river or stream, to groundwater via land or to the ocean. Where an option is coded Green, the effluent quality parameters are considered likely to be acceptable for the associated receiving environment, subject to confirmation of the specific nature/location of the receiving environment. Where an option is coded Orange, the effluent quality parameters may be suitable to discharge subject to the specific receiving environment. For example, solids and/or nutrients concentrations CH2M Beca // 2 November 2016 // Page 2

5 may not be considered suitable for discharge to an urban or small waterway but may be suitable for discharge to the confluence of the Waipaoa. Where an option is coded Red, the effluent quality parameters listed are considered likely to exceed the allowable levels for a discharge to the receiving environment. The traffic light assessment does not consider economic, social or cultural factors as this assessment will be undertaken by Council and the WTAG. Table A2 also provide a summary of the comparative capital and operating costs and an assessment of the Whole of Life (WOL) cost based on a 20year Net Present Value (NPV) assessment. Conclusions The value engineering workshop undertaken with the WTAG on the 5 and 6 October identified a number of permutations of the conventional treatment and natural treatment process. Order of magnitude capital and whole of life estimates have been developed for each of the identified options. The options have not been developed to the same level of detail as the original two options presented in the concept design report and as such should be treated as comparative only. Nominal conveyance distances have been included between the different treatment and final sites but these will change depending on the final locations of these. The cost of a habitat wetland has not been included in any of the options, nor has the cost for land purchase or any new outfall or disposal structure to river, stream or groundwater been included. These could be significant additional costs to the costs already presented. Option B(i) has the lowest comparative capex and WOL cost ($10M and $11.6M respectively). By constructing a second BTF, it provides a level of treatment redundancy which is currently missing at the Banks St Plant and is expected to increase the level of biotransformation of the wastewater and reduce the quantity of biosolids in line with what has been observed at Hastings. The operational costs are the lowest of all options as there is minimal additional pumping, no additional chemical consumption and there are no sludge handling or disposal costs. At $10.8M and $13.3M respectively Option B(ii) has the second lowest capex and WOL cost. It provides for the default requirements of the consent with regard to disinfection but may not meet the default TSS requirements of the consent. Staged implementation of the second BTF and then UV would enable Council to confirm whether the discharge could comply with the default TSS conditions without the need for the significant step up in capital and operating costs associated with solids separation, handling and disposal. Option A, previously Option 2 of the concept design report, provides for solids separation, handling and disposal at the Banks St Site and is estimated to have a capex and WOL cost of $17.7M and $35M respectively. However, it does not address the current issues with BTF redundancy at Banks St or provide any enhancement of the level of biotransformation. The high operational costs are associated with the biosolids dewatering and transport out of District to a landfill disposal site. The operational cost is highly sensitive to the level of dewatering achieved. This is common to all options with biosolids. Option C is a combination of Options A and B(ii). It allows for the default requirements of the consent to be met, including the TSS. The Capex and WOL cost is estimated at $28.5m and $47.8M respectively. Option D builds on Option C but provides further nitrogen and solids removal through the addition of a denitrifying sand filter. The capex costs step up from $28.5M for Option C to $38.6M. The WOL costs increase to $61.4M. Whilst denitrification is very unlikely to be required for an ocean CH2M Beca // 2 November 2016 // Page 3

6 discharge, it has been assessed as providing a comparable level of nitrogen removal with what may be achieved in some of the Natural Treatment systems options. The costs for disinfection are based on the ocean discharge requirements but equally could be specified to comply with standards suitable for discharge to recreational waterways. The incremental cost increase to provide a disinfection standard suitable for a river discharge has not been assessed. Options E through to K are configured as natural processes or conventional/natural treatment hybrids with the objective of treating the wastewater to a standard which is suitable for disposal to land or surface water rather than the ocean, in line with the goals of the WTAG and WMC. As they are based on natural processes it also contributes to the cultural restoration of the water s mauri or life-giving energy. Options E is a hybrid option which provides for solids separation and UV disinfection at Banks St followed by 6km conveyance to a 100ML storage pond, tertiary treatment in a woodchip filter and a further conveyance of 4km to the habitat wetland. It has capex and WOL costs of $55.0M and $77.1M respectively. The woodchip filter provides denitrification and some additional disinfection. The storage pond allows the flow to and the size of the WDF to be reduced but in doing so introduces a new high cost element. The cost of the storage pond is high ($4M) as it is assumed that due to elevated ground water levels the construction is primarily above ground requiring large quantities of imported material to construct the bunds. It is also likely to trigger the large dam consent requirements. Options F and G are hybrid options. Option F provide solids separation and UV disinfection at Banks St followed by 6km conveyance to tertiary wetlands and a woodchip filter and a further conveyance of 4km to the habitat wetland. It has capex and WOL costs of $55.1M and $78.7M respectively. Option G has settlement at Banks St and tertiary treatment in HRAPs with UV disinfection at the alternative treatment site and has a capex of $64.2M and the highest WOL cost of all options at $94.4M. Options H through to K are all natural treatment options. Each option includes 6km conveyance to the alternative treatment site and utilises earthen settlement ponds. Each option has two suboption associated with the Biosolids handling. Option (i) utilises earthen pond sludge digesters and Option (ii) utilises sludge treatment reed beds (STRB). Capital and operating costs for the STRBs options (ii) have been excluded as the conceptual design and cost estimates provided by Orbicon did not allow sufficient detail for a reasonable technical evaluation to be undertaken by Council. Option H is based on settlement followed by UV disinfection and a 30ha wetland and has capex and WOL costs of $40.1M and $55.7M respectively. The costs are based on the 16 parallel train wetland design from the concept design (Option 1) and potentially could be simplified to reduce the capital cost. Option I is based on settlement followed by 12 HRAPs and the associated algal harvesters and digesters and has capex and WOL costs of $51.9M and $72.3M respectively. UV is provided in order to meet a disinfection standard suitable for land or river/stream discharge. Option J is for the full natural treatment scheme (previously Option 1 of the concept design report) and utilises the full suite of sludge settling ponds and digesters, 16 HRAPs and associated Algal Harvesters and digesters, wetlands and wood chip filters. The capex and WOL costs are $68.1M and $88.5M respectively. The capital cost has increased from that presented in the concept design report due to the inclusion of the 4km conveyance from the alternative site to the habitat wetland. Option K is a cut down version of Option J and has capex and WOL costs of $64.2 and $84.6M respectively. A small saving is achieved through the reduced HRAP size. CH2M Beca // 2 November 2016 // Page 4

7 In general terms, it can be seen from the summary in Section 5 and the discussion above that for both the natural and conventional treatment systems proposed, improving treatment performance requires a significant increase in both capital investment and operational cost. Significant capital cost factors are the cost to convey the wastewater to and from the natural treatment site(s), the large area of the natural treatment processes required and the associated civil costs for forming the bunds, accessways and earth embankments for the deep settlement ponds and digesters. Operational costs for both natural and conventional treatment are heavily influenced by the power cost for pumping both to and from the sites, or inter-process pumping. In addition, there is a significant capital and operating cost associated with biosolids thickening, dewatering and disposal for both natural and conventional treatment options. This could be reduced through development of a local reuse market or local disposal site for the dewatered biosolids, however in the absence of a viable existing local disposal option, out of district trucking and landfilling has been assumed as the worst case. In the absence of specific sites for the natural treatment options and habitat wetland / discharge location, a number of assumptions have been made which have a significant bearing on the WOL costs. Some of the major assumptions which have significant bearing on the cost estimates for natural treatment options are summarised below: Conveyance: All of the natural treatment options include 2 stages of conveyance, 6km to the treatment site and then a further 4km to the habitat wetland/discharge location. This conveyance requirement adds approximately $14.5M capital cost to the options. If suitable sites were able to be secured closer to Banks St, this cost could be reduced. Site topography: A number of assumptions have been made regarding the site topography and degree of levelling required to construct the natural processes. Ground Conditions: Due to the shallow groundwater likely to be encountered in the study area, all processes using deep ponds have been designed to be built out of the ground. This introduces higher capital costs associated with structural stabilisation of the earthen bunds and the required quantity of imported materials to construct the walls. Liners: the options assume that the HRAPs and wetlands will be largely unlined, with sufficient lining only to protect and stabilise the earthen bunds. The deep ponds, digesters and woodchip filters are all assumed to be HDPE lined. This assumption carries a high cost risk as it assumes that the unlined HRAPs and wetlands will self-seal over time and any discharge to ground will be consentable. It may also be a condition in any new consents that lining of these facilities is required to minimise seepage to sensitive groundwaters (depending on the sites finally selected). CH2M Beca // 2 November 2016 // Page 5

8 A Lamella Clarifiers, Solids Thickening /Dewatering Cost $17.7M Bi Install a second BTF Cost $10M Bii Install a second BTF UV Disinfection Cost $10.8M C Install a second BTF Lamella Clarifiers, Solids Thickening /Dewatering UV Disinfection Cost $28.5M D Install a second BTF Lamella Clarifiers, Solids Thickening /Dewatering Denitrifying Sand Filtration UV Disinfection Cost $38.6M E Install a second BTF Lamella Clarifiers, Solids Thickening /Dewatering UV Disinfection Remote Site (6km) Peak Flow Buffer Storage Pond Woodchip Denitrifying Filters (4ha) Cost $55.1M F Lamella Clarifiers, Solids Thickening /Dewatering UV Disinfection Remote Site (6km) Surface Flow Constructed Wetlands (30ha) Woodchip Denitrifying Filters (2ha) Cost $55.0M G Lamella Clarifiers, Solids Thickening /Dewatering Remote Site (6km) HRAPs, with AHs and ADs (12 off) UV Disinfection Cost $64.2M H (i) Remote Site (6km) Sludge Settlers and Digesters UV Disinfection Surface Flow Constructed Wetlands (30ha) Cost $40.1M H (ii) Remote Site (6km) Sludge Settlers and STRBs UV Disinfection Surface Flow Constructed Wetlands (30ha) Cost $36.8M (excl STRB) I (i) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) UV Disinfection Cost $51.9M I (ii) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) UV Disinfection Cost $48.6M (excl STRB) J (i) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (16 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $68.1M J (ii) Remote Site (6km) Sludge Settlers and STRBs HRAPs, with AHs and ADs (16 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $64.8M (excl STRB) K (i) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $64.2M K (ii) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $60.9M (excl STRB) Figure A: Comparison of Options (All Options Exclude ) CH2M Beca // 2 November 2016 // Page 6

9 Table A2 Treatment Options (excl. ) No. Description BOD TSS NH4/NO3 Ent. E.Coli Habitat W/L River/Stream GW via land Sea OoM Cost ($M) Opex ($M) NPV ($M) A Solids Removal , Nutrients, disinfection, solids Nutrients, disinfection nutrients $17.7M Med-High 1.31M $35.0M B (i) BTF# <1, Nutrients, disinfection, solids Nutrients, disinfection, solids Nutrients, disinfection, solids $10M Very Low 0.12M $11.6M B (ii) Default Consent - BTF#2 + UV (Note 1) <1, Nutrients, solids Nutrients, solids Nutrients, solids $10.8M Very Low 0.19M $13.3M C BTF#2, Solids Removal + UV (Note 2) <1, Nutrients, disinfection $28.5M Med-High 1.46M $47.8M D BTF#2 + Solids Removal + DN Filter + UV (Note 2) to H/Wetland 5 5 <1, Phosphorus, disinfection $38.6M High 1.73M $61.4M E BTF#2 + Solids Removal + UV + buffer storage + WDF to H/Wetland (Note 5) <1, phosphorus $55.0M High 1.71M $77.1M F Solids Removal + UV to SFCW + WCF to H/Wetland <1, Nutrients Nutrients $55.1M High 1.64M $78.7M G Solids Removal to HRAPs + UV to H/Wetland 3 5 <1, Nutrients Nutrients $64.2M High 2.3M $94.4M No. Description BOD TSS NH4/NO3 DRP E.Coli Habitat W/L River/Stream Land - GW Sea OoM Cost ($M) Opex ($M) NPV ($M) H (i) (ii) Solids Removal + UV + SFCWs (Note 3) + H/Wetland - Sludge Digesters - STRBS (Note 4) <5 (as TN) Note 6 Phosphorus $40.1M $36.8M + STRB Med 1.15M $55.7M Note 4 I (i) (ii) Solids Removal + 12 HRAPs + UV to H/Wetland - Sludge Digesters - STRBS (Note 4) 3 10 <1, Note 6 Phosphorus $51.9M $48.6M + STRB High 1.55M $72.3M Note 4 J (i) (ii) Full Scheme: 16 HRAPs + SFCWs (Note 3) and WDFs to H/Wetland - Sludge Digesters - STRBS (Note 4) 5 10 <1,< $68.1M $64.8M + STRB High 1.53M $88.5M Note 4 K (i) (ii) Solids removal + 12 HRAPs + SFCWs (Note 3) and WDFs to H/Wetland - Sludge Digesters - STRBs (Note 4) 3 5 <1, $64.2M $60.9M + STRB High 1.53M $84.6M Note 4 CH2M Beca // 2 November 2016 // Page 7

10 Notes: 1. UV cost estimates for Options A, B,C,D based on compliance with the default Enterococci limits of the consent 2. Capital cost Options C and D is based on disinfection compliance with Consent Clause 42 i.e. Enterococci < 1000 cfu/100ml. For discharge to a river or stream a more stringent E.coli standard is likely. Cost of UV system for discharge to river or stream has not been evaluated at this stage. 3. Given time constraints the capital cost estimate for a simplified Big Foot Wetland has not been developed. Potential capital cost savings may be realised at the next stage of design. 4. Capital and WOL Estimates for STRBs not included. 5. Capital and WOL Estimates for Habitat wetland (H/wetland) not included 6. Disinfection as measured post UV CH2M Beca // 2 November 2016 // Page viii

11 Table of Contents 1 Introduction Background Domestic Default Consent Requirements Industrial Default Consent Requirements Original Concept Design Options Report Scope and Design Basis WTAG Value Engineering Workshop Outcomes System Objectives Key Outcomes Value Engineering Options Overview Technical Risks Full Conventional Treatment Options Combined Hybrid Options Full Natural Treatment System Options Basis of Estimates Scope and Basis of Estimates Options Comparison Discussion and Conclusion Appendices Appendix A Basis of Estimate Appendix B Process Flow Diagrams CH2M Beca // 2 November 2016 // Page ix

12 Glossary BOD BTF CFD DRP EWPS GBT HDPE HRAP NPV OoM SiD SFCW STRB TN TP TSS UV WDF WOL WTAG WWTP Biological Oxygen Demand Biological Trickling Filter Computational Fluid Dynamics Dissolved Reactive Phosphorus Enhanced Wetland and Pond System Gravity Belt Filter High-density polyethylene High Rate Algal Pond Net Present Value Order of magnitude Safety in Design Surface Flow Constructed Wetland Sludge Treatment Reed Beds Total Nitrogen Total Phosphorus Total Suspended Solids Ultra Violet Woodchip Denitrifying Filter Whole of Life Wastewater Technical Advisory Group Wastewater Treatment Plant CH2M Beca // 2 November 2016 // Page x

13 1 Introduction 1.1 Background The Banks St WWTP s discharge consent requires GDC to establish the most appropriate longterm management option for Gisborne s wastewater by assessing the feasibility and level of community acceptance of upgrading the treatment plant with either a conventional solids removal and disinfection system or an alternative wastewater management system, which may involve a range of alternative use and disposal (AUD) options. As such GDC, in conjunction with NIWA, has been pilot trialling a series of enhanced pond and wetland stages to provide tertiary treatment of the effluent and solids streams following discharge from the existing Biological Trickling Filter plant (BTF). A Council decision as to how to proceed is required by December In order to initiate the community engagement process and inform the Council decision, GDC commissioned CH2M Beca to develop both options to an engineering design level suitable for costing to +/- 30%. These options were then assessed by GDC and the WTAG in a value engineering workshop on 5 and 6 October 2016 which was attended by representatives from NIWA and CH2M Beca. 1.2 Domestic Default Consent Requirements The consent variation granted in April 2015 stipulates that should the Alternative Use and Disposal (AUD) study conclude that it is not feasible to implement an alternative treatment process, Council is required to upgrade the Banks St treatment plant to provide a second BTF to reduce the BTF loading 3 to less than 0.4kg BOD/m³.d and install disinfection 4 to comply with less than 1000 cfu/100ml Enterococci in the domestic discharge. The requirement to install a clarification stage following the BTF will be dependent on whether the reduced BOD loading on the BTF can reliably and consistently achieve TSS in the discharge of less than 30mg/l. New Zealand is unique in that there are a number of lowly-loaded BTF treatment plants in which solids are not separated from the treated effluent as part of the normal secondary or tertiary treatment process. This is not normal practice internationally so other than for similar BTF plants in Hastings, Napier, and Greymouth there are no other reference sites from which operating data on UV disinfection and TSS concentrations can be derived. There is some evidence to suggest that the quantity of solids generated in trickling filters reduces with reduced BOD loading 5. The Napier City BTF Pilot trial ( ), tested both random and structured media at different BOD loadings. The trial showed that the TSS from the BTF reduced with reduced BOD loading. When loaded at 0.4kg BOD/m³.d, as per the Gisborne default consent condition, the results were highly promising with TSS generally less than 30mg/l. However the data set was limited to just 3 days over 2 months and is considered too small to provide a definitive 3 Clause 4A(g), Clauses 37 and Clause 4e, Clause 42 5 Napier Pilot Trial Performance data, provided to CH2M Beca CH2M Beca // 2 November 2016 // Page 1

14 answer. The trial also showed better TSS performance from structure media (as installed at Gisborne) to random media (as installed at Hastings and Greymouth). The Hastings WWTP operates a lowly loaded BTF and discharges without solids separation or disinfection to the ocean. Published data 6 indicates that the effluent is unlikely to achieve compliance with the TSS requirements of the consent without a settlement process. The Greymouth WWTP also operates a lowly loaded BTF without settlement but with UV disinfection. Greymouth published data 7 indicates that the effluent could possibly comply with the Gisborne Enterococci disinfection standard but the data does not provide the TSS performance. Given the available New Zealand findings, we conclude that: a) It may be possible to comply with the Enterococci disinfection standard without implementing a solids separation stage b) It is less likely to comply with the TSS standard without implementing a solids separation stage c) The consent default options be developed for a second BTF, UV and with and without solids separation We recommend that Council seek feedback from Hastings District and Grey District regarding the long term performance of their BTFs. Should Council proceed with upgrading the Banks St site to comply with the default consent conditions, we recommend that the upgrade be staged to allow the performance of the BTF when operated at 0.4kg BOD/m³.d to be assessed as an input to sizing and specifying the UV treatment and confirming whether the solids separation stage is required. 1.3 Industrial Default Consent Requirements The 2015 Consent variation also stipulates that once Council implements the long term treatment strategy for the domestic wastewater, the separated Industrial wastewater will also have to comply with the enterococci standard of <1000 cfu/100ml. The development of the options to date does not allow for treatment of the separated Industrial flows. We understand that Council will engage directly with the Industrial traders to ensure compliance. 1.4 Original Concept Design Options The engineering design for the base treatment options discussed in the VE Workshop is set out in the Gisborne WWTP Stage 2 Upgrade Concept Design Report (CH2M Beca, September 2016). Briefly, the two options developed were: Option 1: Enhanced Wetland and Pond System (EWPS), based on process sizing and operational inputs from NIWA, which includes: Pump station and rising main from the Banks St WWTP to the EWPS site, assumed to be located at a distance of 4 to 8km, 6km used in cost estimates. Gravity settling of BTF solids (4 ponds) High-rate algal ponds (HRAPs) (16 off) 6 Hastings Wastewater. An update of this remarkable win-win No sludge wasterwater Treatment Solution that challenged conventional practice MWH, WaterNZ Paper Years In The Making Cleaning Up Greymouth, IPWEA 2015 CH2M Beca // 2 November 2016 // Page 2

15 Gravity settling of HRAP algal solids (16 off) Surface flow constructed wetlands (SFCWs) and woodchip denitrification filters (WDFs) (16 trains) BTF solids and Algal solids digestion (4 BTF, 8 Algal) OR sludge treatment reed beds and algal digestion (concept by Orbicon) Option 2: Conventional clarification and biosolids handling and disposal. These options were presented at the workshop on 5 October. The estimated capital cost for Option 1, which includes the transfer pumping station to a hypothetical site within 4 to 8km of the Banks St WWTP, as well as the construction of all elements of the EWPS but excluding conveyance to and construction of a habitat wetland and final outfall, was between $67.4M and $75.0M, depending on the length of the rising main (4 8 km). The capital cost estimate for Option 2 was $17.7M. A review workshop had been carried out by Beca, NIWA and Council on 23 September in order to review the Option 1 full scale concept design, review rates and quantities and identify opportunities to optimise the cost of the EWPS system, whilst still retaining the benefits of the natural treatment system such as keeping human wastewater out of the ocean outfall, and restoration of the wastewater s mauri. The outcomes of this review informed the discussion of the value engineering options developed in the WTAG workshop. In parallel, the Option 1 concept drawings and schedule of quantities were issued to a major civil contractor for the purpose of benchmarking the rates and assumptions and assessing constructability. The Beca comparative cost estimates presented in this report have been adjusted following the civil contractor feedback. 1.5 Report Scope and Design Basis This report presents descriptions, risks, advantages, comparative cost estimates, operational costs and NPVs for the potential options identified in the WTAG workshop. Where possible the original concept design cost estimates have been retained. Where this was not possible, i.e. for unit processes which were not included in the original two options, order-of-magnitude cost estimates have been developed in order to allow quantitative comparison of the options and identify a balance between capital cost and the overall objectives of the project. Not all options discussed at the VE workshop have been able to be developed in the time frame available. It All risks and advantages of the unit processes discussed in the Concept Design Report and in the WTAG workshop still apply unless noted otherwise. The flows and loads to be treated in these systems are still as set out in Section 3.1 of the Concept Design Report. The treatment levels provided vary between systems. This is discussed further in Section 4. CH2M Beca // 2 November 2016 // Page 3

16 2 WTAG Value Engineering Workshop Outcomes 2.1 System Objectives The resource consent for the Gisborne Wastewater Scheme stipulates various conditions for treatment including end-of-pipe discharge quality requirements and treatment process requirements to meet a number of treatment objectives for the Gisborne community. The original treatment objectives were categorised in Technical Memorandum 15 Mapping Treatment Options for the Gisborne Wastewater Scheme (CH2M Beca, August 2008) as Environmental, Social and Cultural objectives. The current upgrade design has the following objectives under these categories: Environmental: Social: Cultural: Economic Reducing the organic carbon (particulate and soluble BOD 5) and dissolved nutrients in the wastewater through biological processes, allowing it to meet ANZECC guidelines in its final receiving environment. Discharging wastewater with an acceptable quality to maintain public health (i.e. by adding a disinfection treatment step) Providing a treatment process that meets the cultural objectives for the community (i.e. biotransformation of human waste and potential alternative use of domestic wastewater), restoring the mauri of the treated water An affordable and robust asset with up to 50 years of design life and long term resource consent In general, achieving each objective in the order shown will require a greater level of wastewater treatment and therefore greater cost. 2.2 Key Outcomes The following were the key outcomes from the VE Workshop: There was agreement on the desired objectives for the long-term scheme against which options need to be tested with the addition of restoring of mauri to the wastewater under community values Robust asset with up to 50 year design life & long-term resource consent Limit nuisance effects such as odour and midges What outcomes does our community value? Biotransformation? Human waste out of the ocean? Beneficial re-use or surface water recharge? Reducing Emerging Contaminants of Concern? Amenity or Educational Value? What can our community afford? Capital costs Operating Costs There was a recognition that conveyance (pumping and pipelines) costs are a major component of the proposed alternative schemes because the very large land areas required for these are CH2M Beca // 2 November 2016 // Page 4

17 not close to Banks Street, and nor are possible locations of new habitat wetlands nor sites for disposal to freshwater rivers or streams Until such time as land areas and disposal locations are identified, realistic conveyance costs need to be added to the treatment schemes to reflect final disposal options and routes to give a more complete picture of the scheme costs Participants were interested in the different quality of effluent produced by various conventional and alternative schemes and how compatible these are with candidate disposal sites and water bodies (eg, habitat wetlands, rivers/streams, groundwater, ocean) Estimated effluent quality to be given for the different schemes and a traffic light coding assessed for different receiving environments Modified configurations of the alternative treatment processes [HRAPs, SFCWs, WNFs and sludge treatment (sludge digesters and STRBs)] were discussed, as were other possible conventional treatment processes at the Banks Street site [clarification plus a second BTF, UV disinfection and denitrifying sand filters] A suite of sub-options for both the Alternative and Conventional treatment schemes was developed including some hybrid options which combined conventional and alternative treatment components at the Banks Street and remote sites - which cover a range of costs and different final effluent qualities These are to be developed further by the technical experts and summarised in schematics and tabular form for presentation to the WTAG and elected members Order-of-magnitude comparative Capital and Operating costs estimates are to be produced for these different schemes to better demonstrate the cost to the community of achieving environmental, social and cultural objectives (as above). CH2M Beca // 2 November 2016 // Page 5

18 3 Value Engineering Options 3.1 Overview The options that have been identified as alternative options to achieve the treatment objectives for the Gisborne Wastewater Scheme can be divided into four categories as shown in Table 1. Table 1 - Alternative Treatment Options Categorisation Option General Overview Type of Treatment Option A Option 2 from the concept design. Improve the Banks St WWTP site by installing conventional solids removal, thickening and dewatering processes. Conventional Options B, C & D: Options E, F & G: Options H, I, J & K: Improve the Banks St WWTP site by installing a second BTF with or without additional treatment steps to improve BOD 5 reduction, solids removal and disinfection, improving the transformational /cultural objectives of the Scheme, and limiting the process risk through the use of conventional treatment processes Combine conventional treatment processes for solids removal and disinfection with elements of the EWPS to provide BOD and nutrient removal, spread across both the Banks St site and a remote site yet to be identified, with or without a second BTF. This allows for more fulfilment of the cultural objectives of the system through the use of additional natural treatment processes Provide all further wastewater treatment at a remote site using either the full EWPS system (as described in Option 1 from the Concept Design Report) or significant elements of it combined with conventional UV disinfection. This provides the most fulfilment of the cultural objectives of the system Conventional Hybrid Natural Brief descriptions of each option, including high level comparative cost estimates are provided below. The determination of what a habitat wetland is has yet to be developed by the WTAG and as such the cost associated with the construction of it has not been assessed by Beca or included in the scheme costs. Depending on the size and specification of the habitat wetland this could be a significant additional cost and should not be overlooked. A high level assessment of operational costs has been undertaken for each option. The operational cost assessment has considered the following: CH2M Beca // 2 November 2016 // Page 6

19 Table 2 - Operational costs Item Conventional Treatment Alternative Treatment Labour No additional staff required over current operation 1 new FTE to monitor remote site and undertake routine maintenance Power Inter-process Pumping, UV /from site, Inter-process Pumping, Maintenance % of mechanical and electrical Included in labour cost. Wetlands assume 20% replanting in first year due to bird predation, 5% in second and 2% thereafter. UV Chemical Consumption Solids Disposal Polymer for solids Carbon for Denitrifying filter Transport and Gate fees assessed on 16% DS Polymer for Algal Harvesters Temporary dewatering contract Transport and Gate fees assessed on 20% DS The operational cost for each option has been classified as shown in Table 3. Table 3 - Qualitative Opex Rankings (per annum) Opex Ranking Description Very Low Likely to have an annual operating cost of less than $250,000 Low Likely to have an annual operating cost between $250,000 and $750,000 Low Medium Likely to have an annual operating cost between $750,000 and $1M Medium Medium High High Likely to have an annual operating cost between $1M and $1.25M Likely to have an annual operating cost between $1.25M and $1.5M Likely to have an annual operating cost more than $1.5M The capital cost and operational costs have been used to provide a whole of life assessment using a 20y NPV. The NPV analysis uses the following factors: Period 20 years Discount 6.7% Inflation 3% Further analysis of the options is provided in Section 5 based on an assessment of treatment performance against capital and whole of life (NPV) costs and compliance with the objectives set out in Section 2.1. The upgrades required for each option are presented as blocks denoting the type of treatment process used. Process flow diagrams are included in Appendix B. The VE Workshop also recognised the high capital and operating costs involved in pumping wastewater from Banks Street to a remote site for treatment and then to a final disposal site such as a habitat wetland or a freshwater river or stream. In the Options presented below, two sets of conveyance costs, as shown in Figure 1, are included as an illustration of the order of costs for pumping effluent between the various sites which as yet have not been identified. It has been assumed that for all natural treatment processes the EWPS site will be located within 6km of Banks Street and that the habitat wetland will be within a further 4km conveyance distance from the EWPS site. The exception to this is Option D which assumes additional treatment at Bank St and conveyance to a habitat wetland site within 4km. For the conventional CH2M Beca // 2 November 2016 // Page 7

20 treatment options, conveyance costs to the existing ocean outfall from the Banks Street site are not included as this uses existing infrastructure and is an existing operational cost. Banks St WWTP EWPS PS 6 Km site PS 4 Km Habitat Wetland Figure 1 Conveyance Distance Assumptions used for WWTP Upgrade Estimates Should Gisborne District Council wish to pursue any of these options, further refinement of the design and cost estimating will be required. 3.2 Technical Risks All the system configurations set out in this section are variations on the two main options set out in the Concept Design Report. As such, while the magnitude of some of them may change, the general risks associated with the options are substantially the same as those discussed in Section 9 of that report. The main risk area and ratings are summarised in Table 4. Risk Table 4 Technical Risk Summary from Concept Design Report Natural Treatment: Risk Level with Mitigation Design Basis Low Low Conventional Treatment: Risk Level with Mitigation Process Performance Medium-high Low - Medium Noise Low Low Odour Medium Low Site Selection/Availability of suitable land Site Geotechnical Characteristics impacting on cost estimates High Medium-high Medium Biosolids Disposal Medium Medium Discharges to Land Medium-high Low Please refer to the Concept Design Report for the full discussion on risks. 3.3 Full Conventional Treatment Options Option A Solids removal and dewatering. (Previously Option 2 Concept Design) In this option compact footprint lamella clarifiers are added at the Banks St Site to remove solids from the BTF discharge. A new building to house biosolids thickening and dewatering processes is included. Low CH2M Beca // 2 November 2016 // Page 8

21 $17,700,000 Lamella Clarifiers, Solids Thickening /Dewatering Cost $17.7M Note: all costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 2 Block Diagram for Option B This option would not provide any further treatment or biotransformation. It would reduce the solids currently discharge to the ocean outfall. At present, it is assumed that the biosolids are disposed to landfill, resulting in significant ongoing operational costs. Option CAPEX ($M) OPEX ($M) NPV ($M) A $ (Medium High) $ Option B Second BTF & UV Options B(i) and B(ii) allow for the default conditions in the consent should AUD not proceed. With Option B(i) providing a second BTF at the Banks St WWTP and B(ii) providing a second BTF and UV disinfection. The second BTF would be designed to the same parameters as the existing BTF and the two would operate in parallel to treat up to 460l/s, allowing the overall organic loading on the BTFs to be reduced from the current 0.8 kg BOD/m³ filter media/day to 0.4 kg BOD/m³ filter media/day. Reducing the organic load on the BTFs will also improve nitrification across the system, and improve the biotransformation of human wastes into plant matter. Treated wastewater would be discharged, without solids removal or disinfection, via the existing ocean outfall as it is now. The requirement to install a clarification stage following the BTF will be dependent on whether the reduced BOD loading on the BTF can reliably and consistently achieve TSS in the discharge of less than 30mg/l (refer discussion in Section 1.2). Option C below makes provision for this. Disinfection is based on utilising Ultra Violet light (UV). We understand that alternative means of disinfecting such as chlorination or ozonation had previously been considered by the WTAG and discarded due to the use of additional chemicals. Disinfection can also be achieved through microfiltration. Microfiltration was considered during the concept design as an alternative means of achieving solids separation but was discarded on cost basis. $10,000,000 Install a second BTF Cost $10M Note: all costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 3 Block Diagram for Option B(i) CH2M Beca // 2 November 2016 // Page 9

22 $10,000,000 $840,000 Install a second BTF UV Disinfection Cost $10.8M Note: all costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included Figure 4 Block Diagram for Option B(ii) This option would improve BOD removal and nitrification and add to the the resilience of the existing WWTP by providing treatment redundancy. The BOD loading will reduce from the current 0.8kg BOD/m3 media to 0.4kg/m³. At these loadings BOD removal is expected to be approximately 88% and nitrification greater than 95% 8. At approximately $10M, Option B also has the lowest capital cost of all the options considered. These options have the lowest capital and operational cost as biosolids continue to be discharged with the treated effluent as currently. This eliminates biosolids handling and disposal costs, which are not insignificant. The addition of a second BTF will primarily result in some increased power costs (increased pumping to maintain wetting rates) and some increase in maintenance costs. Option CAPEX ($M) OPEX ($M) NPV ($M) B(i) $ M (Very Low) $11.6 B(ii) $ M (Very Low) $ Option C Second BTF, Solids Removal and UV This option combines the lamella clarification and solids thickening and dewatering from Option A with a second BTF and UV disinfection, all located at Banks St. Treated wastewater would continue to be discharged to the existing ocean outfall. $10,000,000 $17,700,000 $840,000 Install a second BTF Lamella Clarifiers, Solids Thickening /Dewatering UV Disinfection Cost $28.5M Note: all costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 5 Block Diagram for Option C This option, which comes to a total of approximately $28.54M, would improve BOD and nitrification, and introduces solids removal and disinfection. It should also be noted that with solids removal comes the need for solids treatment and disposal, which in this option is provided by conventional mechanical thickening and dewatering before transport off-site. The operational cost will be slightly higher than Option A due to the increased pumping and maintenance associated with the new BTF and the power demand of the UV system. 8 Based on Napier City BTF pilot trial performance data with structured cross flow media at 0.4kg/m³ loading. CH2M Beca // 2 November 2016 // Page 10

23 Option CAPEX ($M) OPEX ($M) NPV ($M) C $ M (Medium High) $ Option D Second BTF, Solids Removal, Denitrification and UV This option builds on that described in Option C by adding denitrifying sand filtration to further improve nutrient removal, in particular Nitrogen. This additional step could bring the wastewater quality to a level suitable for discharge to surface water via a habitat wetland as an alternative to continued discharge through the ocean outfall. The UV is based on the cost to comply with the ocean discharge. It should be noted that a further log reduction is likely to be required for a discharge to a river or stream. $10,000,000 $17,700,000 $4,000,000 $840,000 $6,060,000 Install a second BTF Lamella Clarifiers, Solids Thickening /Dewatering Denitrifying Sand Filtration UV Disinfection Cost $38.6M Note: all costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 6 Block Diagram for Option D The capital cost for this option comes to approximately $38.6M. A carbon source is required to complete the denitrification process. It is assumed that there is sufficient head to gravitate from the lamellas to the sand filters although this will need to be confirmed at the subsequent stage of design. Operating costs are higher than C due to the addition of a carbon source for the denitrification process, increased solids handling and disposal (filter backwash) and additional power required for conveyance to the habitat wetland site. Option CAPEX ($M) OPEX ($M) NPV ($M) D $ M (High) $ Combined Hybrid Options Option E Second BTF, Solids Removal, and UV at Banks St, Denitrification at Remote Site In this option a second BTF would still be constructed to improve biotransformation and treatment of organics and improve resilience, with solids removal and UV disinfection as described in Options C and D. However instead of using denitrifying sand filters the disinfected wastewater would be pumped to a remote site, for denitrification with WDFs as per the EWPS. The WDFs would be sized for average rather than peak flows to limit the area required, with an offline (nominal 75ML to 100ML) buffer pond provided to balance peak flows 9. 9 Buffer pond size to be optimised to provide approximately 2 to 3 days storage at peak flows. CH2M Beca // 2 November 2016 // Page 11

24 $10,000,000 $17,700,000 $840,000 $8,430,000 $4,000,000 $8,060,000 $6,060,000 Install a second BTF Lamella Clarifiers, Solids Thickening /Dewatering UV Disinfection Remote Site (6km) Peak Flow Buffer Storage Pond Woodchip Denitrifying Filters (4ha) Cost $55.1M Note: all costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 7 Block Diagram for Option E The capital cost for this option comes to approximately $55.09M. The additional operational cost of the WDF is not expected to be significant, but the power required to convey the wastewater to the remote site and then on to the habitat wetland will increase the opex from that in Option D. Option CAPEX ($M) OPEX ($M) NPV ($M) E $ M (High) $ Option F Solids Removal and UV at Banks St, Wetlands and Denitrification at Remote Site In this option additional organics removal is provided by two banks of SFCWs, with denitrification provided by a smaller area of WDFs than required in Option E. These processes will be located at the remote treatment site, with conventional settling and disinfection at Banks St. The use of SFCWs instead of the second BTF potentially further improves the biotransformation and hence the cultural acceptability of the final wastewater. The additional unit processes may also provide additional disinfection. $17,700,000 $840,000 $8,430,000 $14,980,000 $2,520,000 $6,060,000 Lamella Clarifiers, Solids Thickening /Dewatering UV Disinfection Remote Site (6km) Surface Flow Constructed Wetlands (30ha) Woodchip Denitrifying Filters (2ha) Cost $55.0M Note: Total cost includes $4.43M for EIC and Site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 8 Block Diagram for Option F The capital cost for this option comes to approximately $55M. These estimates assume that the SFCWs will be of the same size and configuration as those developed for Option 1 in the Concept Design Report. Some cost savings could potentially be made by changing this design to make the cells larger and the plantings less dense, but care would need to be taken in their design to limit the risk of short circuiting through the larger cells. Operational costs are likely to be similar to Option E. Option CAPEX ($M) OPEX ($M) NPV ($M) F $ M (High) $ Option G - Solids Removal at Banks St, HRAPs and UV at Remote Site CH2M Beca // 2 November 2016 // Page 12

25 Removal of organics and nutrients could also be provided by HRAPs rather than SFCWs. The HRAPs are likely to provide some additional disinfection, and the settled effluent from the HRAPs can be disinfected using UV light, unlike wetland effluent. The algae grown in the ponds must be removed and treated. It is assumed that this solids stream will be treated in ambient-temperature digesters as per the Concept Design Report. $17,700,000 $8,430,000 $27,250,000 $580,000 $6,060,000 Lamella Clarifiers, Solids Thickening /Dewatering Remote Site (6km) HRAPs, with AHs and ADs (12 off) UV Disinfection Cost $64.2M Note: Total cost includes $4.22M for EIC and site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 9 Block Diagram for Option G The capital cost for this option comes to approximately $64.24M. These estimates assume that the HRAPs will the same size and configuration as those developed for Option 1 in the Concept Design Report, but only 12 will be used. Operational costs are likely to be higher than for the wetland-only options, due to the additional power use by the algal harvester feed pumps and sludge pumps. Option CAPEX ($M) OPEX ($M) NPV ($M) G $ M (High) $ Full Natural Treatment System Options Option H Solids Removal, UV, Wetlands and UV Disinfection at Remote Site In this option effluent from the single BTF would be pumped straight to the remote site for treatment. BTF solids are removed using gravity settling ponds, with the collected solids pumped to either i. Ambient-temperature anaerobic digesters; or ii. Sludge Treatment Reed Beds (STRBs) Estimates have been prepared for both these sub-options, but the cost of the STRBs has been provided by a separate provider and is not included in the estimates developed in this report. The settled wastewater is UV disinfected, and further organics and nutrients are removed in SFCWs and WDFs as per Option 1 in the Concept Design Report, before conveyance to the Habitat Wetland. $8,430,000 $5,330,000 $840,000 $14,980,000 $6,060,000 Remote Site (6km) Sludge Settlers and Digesters UV Disinfection Surface Flow Constructed Wetlands (30ha) Cost $40.1M Note: Total cost includes $4.43M for EIC and site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 10 Block Diagram for Option H(i) CH2M Beca // 2 November 2016 // Page 13

26 $8,430,000 $2,040,000 $860,000 $14,980,000 $6,030,000 Remote Site (6km) Sludge Settlers (and STRBs) UV Disinfection Surface Flow Constructed Wetlands (30ha) Cost $36.8M Note: Total cost includes $4.43M for EIC and site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 11 Block Diagram for Option H(ii) The capital cost for option H(i) comes to approximately $40.1M. These estimates assume that the SFCWs will be of the same size and configuration as those developed for Option 1 in the Concept Design Report. Some cost savings could potentially be made by changing this design to make the cells larger and the plantings less dense, but care would need to be taken in their design to limit the risk of short circuiting through the larger cells. The capital cost for Option H(ii) comes to approximately $36.8M, but excludes capital and operating costs associated with the STRB. Option CAPEX ($M) OPEX ($M) NPV ($M) H(i) $40.1 $1.15 (medium) $55.7 H(ii) $36.8 (excl. STRB) Not assessed Not assessed Option I Solids Removal, HRAPs and UV at Remote Site In this option effluent from the single BTF would be pumped straight to the remote site for treatment. BTF solids are removed using gravity settling ponds, with the collected solids pumped to either i. Ambient-temperature anaerobic digesters; or ii. Sludge Treatment Reed Beds Estimates have been prepared for both these sub-options. The settled wastewater then undergoes further organics and nutrients removal in 12 HRAPs and is UV disinfected before conveyance to the. $8,430,000 $5,330,000 $27,250,000 $580,000 $6,030,000 Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) UV Disinfection Cost $51.9M Note: Total cost includes $4.22M for EIC and site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 12 Block Diagram for Option I(i) CH2M Beca // 2 November 2016 // Page 14

27 $8,430,000 $2,030,000 $27,250,000 $580,000 $6,030,000 Remote Site (6km) Sludge Settlers (and STRBs) HRAPs, with AHs and ADs (12 off) UV Disinfection Cost $48.6M Note: Total cost includes $4.22M for EIC and site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 13 Block Diagram for Option I(ii) The capital cost for Option I(i) comes to approximately $51.9M. The capital cost for I(ii) comes to approximately $48.6M but excludes capital and operating costs associated with the STRB. These estimates assume that the HRAPs will the same size and configuration as those developed for Option 1 in the Concept Design Report, but only 12 will be used. Option CAPEX ($M) OPEX ($M) NPV ($M) I(i) $51.9 $1.55 (high) $72.3 I(ii) $48.6 (excl. STRB) Not assessed Not assessed Option J Full EWPS Treatment System with Reduced SFCW Area This option is identical to Option 1 from the Concept Design Report, with the exception of the SFCWs which have a total of half the area assumed in that report. Effluent from the single BTF is pumped straight to the remote site for treatment. BTF solids are removed using gravity settling ponds, with the collected solids pumped to either i. Ambient-temperature anaerobic digesters; or ii. Sludge Treatment Reed Beds Estimates have been prepared for both these sub-options. The settled wastewater then undergoes further organics and nutrients removal in 16 HRAPs and 16 trains of SFCWs and WDFs before conveyance to the. The combination of different treatment systems will also provide disinfection of the wastewater. $8,430,000 $5,360,000 $31,160,000 $10,260,000 2,520,000 $6,030,000 Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (16 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $68.1M Note: Total cost includes $4.34M for EIC and site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 14 Block Diagram for Option J(i) CH2M Beca // 2 November 2016 // Page 15

28 $8,430,000 $2,030,000 $31,160,000 $10,260,000 2,520,000 $6,030,000 Remote Site (6km) Sludge Settlers (and STRBs) HRAPs, with AHs and ADs (16 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $64.8M Note: Total cost includes $4.34M for EIC and site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 15 Block Diagram for Option J(ii) The capital cost for option J(i) comes to approximately $68.1M. The capital cost for J(ii) comes to approximately $64.8M but excludes capital and operating costs associated with the STRB. These estimates assume that the SFCWs will have the same configuration as those developed for Option 1 in the Concept Design Report. Some cost savings could potentially be made by changing this design to make the cells larger and the plantings less dense, but care would need to be taken in their design to limit the risk of short circuiting through the larger cells. Option CAPEX ($M) OPEX ($M) NPV ($M) J(i) $68.1 $11.53 (high) $88.5 J(ii) $64.8 (excl. STRB) Not assessed Not assessed Option K Full EWPS Treatment System with Reduced HRAPs and SFCW Area In this option, effluent from the single BTF is pumped straight to the remote site for treatment. BTF solids are removed using gravity settling ponds, with the collected solids pumped to either i. Ambient-temperature anaerobic digesters; or ii. Sludge Treatment Reed Beds Estimates have been prepared for both these sub-options. The settled wastewater then undergoes further organics and nutrients removal in 12 HRAPs and 16 trains of SFCWs and WDFs before conveyance to the. The combination of different treatment systems will also provide disinfection of the wastewater. The treatment performance of this system may be slightly lower than Option J, due to the decreased residence time through the 12 HRAPs $8,430,000 $5,360,000 $27,250,000 $10,260,000 2,520,000 $6,030,000 Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $64.2M Note: Total cost includes $4.34M for EIC and site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 16 Block Diagram for Option K(i) CH2M Beca // 2 November 2016 // Page 16

29 $8,430,000 $2,030,000 $27,250,000 $10,260,000 2,520,000 $6,030,000 Remote Site (6km) Sludge Settlers and STRBs HRAPs, with AHs and ADs (12 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $60.9M Note: Total cost includes $4.34M for EIC and site works including roads and fencing. All costs indicated include percentage add-ons for P&G, design and construction monitoring, and contingency. Allowance for risk and escalation is not included. Figure 17 Block Diagram for Option K(ii) The capital cost for Option K(i) comes to approximately $64.2M. The capital cost for K(ii) comes to approximately $60.9M but excludes capital and operating costs associated with the STRB. These estimates assume that the SFCWs will have the same configuration as those developed for Option 1 in the Concept Design Report. Some cost savings could potentially be made by changing this design to make the cells larger and the plantings less dense, but care would need to be taken in their design to limit the risk of short circuiting through the larger cells. CH2M Beca // 2 November 2016 // Page 17

30 4 Basis of Estimates 4.1 Scope and Basis of Estimates The purpose of these estimates is to provide Cost Estimate values to support the evaluation and selection of the optimal WWTP solution. Notably, the comparative values for the respective options are not necessarily the expected Total Cost of the option but more likely an indicative outturn cost. These estimates are to be read in conjunction with the basis of estimate summarised in Appendix A, which provides a summary of the level of design development supporting the estimate, the methodology in preparing the estimate, the source and general status of rates applied, assumptions, inclusions and exclusions and the expected level of accuracy associated with these inputs. CH2M Beca // 2 November 2016 // Page 18

31 5 Options Comparison A comparison of the different unit cost breakdowns for each option are shown in Figure 16 along with the comparative capital cost estimate. Table 5 provides a summary of all Value Engineering options along with an assessment of expected effluent quality. The discharge has been colour coded using a traffic light system to indicate whether the quality of the discharge is considered suitable for discharge to a habitat wetland, to a river or stream, to groundwater via land or to the ocean. Where an option is coded Green, the effluent quality parameters are considered likely to be acceptable for the associated receiving environment, subject to confirmation of the specific nature/location of the receiving environment. Where an option is coded Orange, the effluent quality parameters may be suitable to discharge subject to the specific receiving environment. For example, solids and/or nutrients concentrations may not be considered suitable for discharge to an urban or small waterway but may be suitable for discharge to the confluence of the Waipaoa. Where an option is coded Red, the effluent quality parameters listed are considered likely to exceed the allowable levels for a discharge to the receiving environment. The traffic light assessment does not consider economic, social or cultural factors as this assessment will be undertaken by Council and the WTAG. Table 5 also provide a summary of the comparative capital and operating costs and an assessment of the 20year Net Present Value (NPV) or the options. CH2M Beca // 2 November 2016 // Page 19

32 A Lamella Clarifiers, Solids Thickening /Dewatering Cost $17.7M Bi Install a second BTF Cost $10M Bii Install a second BTF UV Disinfection Cost $10.8M C Install a second BTF Lamella Clarifiers, Solids Thickening /Dewatering UV Disinfection Cost $28.5M D Install a second BTF Lamella Clarifiers, Solids Thickening /Dewatering Denitrifying Sand Filtration UV Disinfection Cost $38.6M E Install a second BTF Lamella Clarifiers, Solids Thickening /Dewatering UV Disinfection Remote Site (6km) Peak Flow Buffer Storage Pond Woodchip Denitrifying Filters (4ha) Cost $55.1M F Lamella Clarifiers, Solids Thickening /Dewatering UV Disinfection Remote Site (6km) Surface Flow Constructed Wetlands (30ha) Woodchip Denitrifying Filters (2ha) Cost $55.0M G Lamella Clarifiers, Solids Thickening /Dewatering Remote Site (6km) HRAPs, with AHs and ADs (12 off) UV Disinfection Cost $64.2M H (i) Remote Site (6km) Sludge Settlers and Digesters UV Disinfection Surface Flow Constructed Wetlands (30ha) Cost $40.1M H (ii) Remote Site (6km) Sludge Settlers and STRBs UV Disinfection Surface Flow Constructed Wetlands (30ha) Cost $36.8M (excl STRB) I (i) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) UV Disinfection Cost $51.9M I (ii) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) UV Disinfection Cost $48.6M (excl STRB) J (i) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (16 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $68.1M J (ii) Remote Site (6km) Sludge Settlers and STRBs HRAPs, with AHs and ADs (16 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $64.8M (excl STRB) K (i) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $64.2M K (ii) Remote Site (6km) Sludge Settlers and Digesters HRAPs, with AHs and ADs (12 off) Surface Flow Constructed Wetlands (15ha) Woodchip Denitrifying Filters (2ha) Cost $60.9M (excl STRB) Figure 16: Comparison of Options (All Options Exclude ) CH2M Beca // 2 November 2016 // Page 20

33 Table 5 Treatment Options (excl. ) No. Description BOD TSS NH4/NO3 Ent. E.Coli Habitat W/L River/Stream GW via land Sea OoM Cost ($M) Opex ($M) NPV ($M) A Solids Removal , Nutrients, disinfection, solids Nutrients, disinfection nutrients $17.7M Med-High 1.31M $35.0M B (i) BTF# <1, Nutrients, disinfection, solids Nutrients, disinfection, solids Nutrients, disinfection, solids $10M Very Low 0.12M $11.6M B (ii) Default Consent - BTF#2 + UV (Note 1) <1, Nutrients, solids Nutrients, solids Nutrients, solids $10.8M Very Low 0.19M $13.3M C BTF#2, Solids Removal + UV (Note 2) <1, Nutrients, disinfection $28.5M Med-High 1.46M $47.8M D BTF#2 + Solids Removal + DN Filter + UV (Note 2) to H/Wetland 5 5 <1, Phosphorus, disinfection $38.6M High 1.73M $61.4M E BTF#2 + Solids Removal + UV + buffer storage + WDF to H/Wetland (Note 5) <1, phosphorus $55.0M High 1.71M $77.1M F Solids Removal + UV to SFCW + WCF to H/Wetland <1, Nutrients Nutrients $55.1M High 1.64M $78.7M G Solids Removal to HRAPs + UV to H/Wetland 3 5 <1, Nutrients Nutrients $64.2M High 2.3M $94.4M No. Description BOD TSS NH4/NO3 DRP E.Coli Habitat W/L River/Stream Land - GW Sea OoM Cost ($M) Opex ($M) NPV ($M) H (i) (ii) Solids Removal + UV + SFCWs (Note 3) + H/Wetland - Sludge Digesters - STRBS (Note 4) <5 (as TN) Note 6 Phosphorus $40.1M $36.8M + STRB Med 1.15M $55.7M Note 4 I (i) (ii) Solids Removal + 12 HRAPs + UV to H/Wetland - Sludge Digesters - STRBS (Note 4) 3 10 <1, Note 6 Phosphorus $51.9M $48.6M + STRB High 1.55M $72.3M Note 4 J (i) (ii) Full Scheme: 16 HRAPs + SFCWs (Note 3) and WDFs to H/Wetland - Sludge Digesters - STRBS (Note 4) 5 10 <1,< $68.1M $64.8M + STRB High 1.53M $88.5M Note 4 K (i) (ii) Solids removal + 12 HRAPs + SFCWs (Note 3) and WDFs to H/Wetland - Sludge Digesters - STRBs (Note 4) 3 5 <1, $64.2M $60.9M + STRB High 1.53M $84.6M Note 4 CH2M Beca // 2 November 2016 // Page 21

34 Notes: 1. UV cost estimates for Options A, B,C,D based on compliance with the default Enterococci limits of the consent. 2. Capital cost Options C and D is based on disinfection compliance with Consent Clause 42 i.e. Enterococci < 1000 cfu/100ml. For discharge to a river or stream a more stringent E.coli standard is likely. Cost of UV system for discharge to river or stream has not been evaluated at this stage. 3. Given time constraints the capital cost estimate for a simplified Big Foot Wetland has not been developed. Potential capital cost savings may be realised at the next stage of design. 4. Capital and WOL Estimates for STRBs not included. 5. Capital and WOL Estimates for Habitat wetland (H/wetland) not included 6. Disinfection as measured post UV CH2M Beca // 2 November 2016 // Page 22

35 6 Discussion and Conclusion The value engineering workshop undertaken with the WTAG on the 5 and 6 October identified a number of permutations of the conventional treatment and natural treatment process. Order of magnitude capital and whole of life estimates have been developed for each of the identified options. The options have not been developed to the same level of detail as the original two options presented in the concept design report and as such should be treated as comparative only. Nominal conveyance distances have been included between the different treatment and final sites but these will change depending on the final locations of these. The cost of a habitat wetland has not been included in any of the options, nor has the cost for land purchase or any new outfall or disposal structure to river, stream or groundwater been included. These could be significant additional costs to the costs already presented. Option B(i) has the lowest comparative capex and WOL cost ($10M and $11.6M respectively). By constructing a second BTF, it provides a level of treatment redundancy which is currently missing at the Banks St Plant and is expected to increase the level of biotransformation of the wastewater and reduce the quantity of biosolids in line with what has been observed at Hastings. The operational costs are the lowest of all options as there is minimal additional pumping, no additional chemical consumption and there are no sludge handling or disposal costs. At $10.8M and $13.3M respectively Option B(ii) has the second lowest capex and WOL cost. It provides for the default requirements of the consent with regard to disinfection but may not meet the default TSS requirements of the consent. Staged implementation of the second BTF and then UV would enable Council to confirm whether the discharge could comply with the default TSS conditions without the need for the significant step up in capital and operating costs associated with solids separation, handling and disposal. Option A, previously Option 2 of the concept design report, provides for solids separation, handling and disposal at the Banks St Site and is estimated to have a capex and WOL cost of $17.7M and $35M respectively. However, it does not address the current issues with BTF redundancy at Banks St or provide any enhancement of the level of biotransformation. The high operational costs are associated with the biosolids dewatering and transport out of District to a landfill disposal site. The operational cost is highly sensitive to the level of dewatering achieved. This is common to all options with biosolids. Option C is a combination of Options A and B(ii). It allows for the default requirements of the consent to be met, including the TSS. The capex and WOL cost is estimated at $28.5m and $47.8M respectively. Option D builds on Option C but provides further nitrogen and solids removal through the addition of a denitrifying sand filter. The capex costs step up from $28.5M for Option C to $38.6M. The WOL costs increase to $61.4M. Whilst denitrification is very unlikely to be required for an ocean discharge, it has been assessed as providing a comparable level of nitrogen removal with what may be achieved in some of the Natural Treatment systems options. The costs for disinfection are based on the ocean discharge requirements but equally could be specified to comply with standards suitable for discharge to recreational waterways. The incremental cost increase to provide a disinfection standard suitable for a river discharge has not been assessed. Options E through to K are configured as natural processes or conventional/natural treatment hybrids with the objective of treating the wastewater to a standard which is suitable for disposal to CH2M Beca // 2 November 2016 // Page 23

36 land or surface water rather than the ocean, in line with the goals of the WTAG and WMC. As they are based on natural processes it also contributes to the cultural restoration of the water s mauri or life-giving energy. Options E is a hybrid option which provides for solids separation and UV disinfection at Banks St followed by 6km conveyance to a 100ML storage pond, tertiary treatment in a woodchip filter and a further conveyance of 4km to the habitat wetland. It has capex and WOL costs of $55.0M and $77.1M respectively. The woodchip filter provides denitrification and some additional disinfection. The storage pond allows the flow to and the size of the WDF to be reduced but in doing so introduces a new high cost element. The cost of the storage pond is high ($4M) as it is assumed that due to elevated ground water levels the construction is primarily above ground requiring large quantities of imported material to construct the bunds. It is also likely to trigger the large dam consent requirements. Options F and G are hybrid options. Option F provide solids separation and UV disinfection at Banks St followed by 6km conveyance to tertiary wetlands and a woodchip filter and a further conveyance of 4km to the habitat wetland. It has capex and WOL costs of $55.1M and $78.7M respectively. Option G has settlement at Banks St and tertiary treatment in HRAPs with UV disinfection at the alternative treatment site and has a capex of $64.2M and the highest WOL cost of all options at $94.4M. Options H through to K are all natural treatment options. Each option includes 6km conveyance to the alternative treatment site and utilises earthen settlement ponds. Each option has two suboption associated with the Biosolids handling. Option (i) utilises earthen pond sludge digesters and Option (ii) utilises sludge treatment reed beds (STRB). Capital and operating costs for the STRBs options (ii) have been excluded as the conceptual design and cost estimates provided by Orbicon did not allow sufficient detail for a reasonable technical evaluation to be undertaken by Council. Option H is based on settlement followed by UV disinfection and a 30ha wetland and has capex and WOL costs of $40.1M and $55.7M respectively. The costs are based on the 16 parallel train wetland design from the concept design (Option 1) and potentially could be simplified to reduce the capital cost. Option I is based on settlement followed by 12 HRAPs and the associated algal harvesters and digesters and has capex and WOL costs of $51.9M and $72.3M respectively. UV is provided in order to meet a disinfection standard suitable for land or river/stream discharge. Option J is for the full natural treatment scheme (previously Option 1 of the concept design report) and utilises the full suite of sludge settling ponds and digesters, 16 HRAPs and associated Algal Harvesters and digesters, wetlands and wood chip filters. The capex and WOL costs are $68.1M and $88.5M respectively. The capital cost has increased from that presented in the concept design report due to the inclusion of the 4km conveyance from the alternative site to the habitat wetland. Option K is a cut down version of Option J and has capex and WOL costs of $64.2 and $84.6M respectively. A small saving is achieved through the reduced HRAP size. In general terms, it can be seen from the summary in Section 5 and the discussion above that for both the natural and conventional treatment systems proposed, improving treatment performance requires a significant increase in both capital investment and operational cost. Significant capital cost factors are the cost to convey the wastewater to and from the natural treatment site(s), the large area of the natural treatment processes required and the associated civil CH2M Beca // 2 November 2016 // Page 24

37 costs for forming the bunds, accessways and earth embankments for the deep settlement ponds and digesters. Operational costs for both natural and conventional treatment are heavily influenced by the power cost for pumping both to and from the sites, or inter-process pumping. In addition, there is a significant capital and operating cost associated with biosolids thickening, dewatering and disposal for both natural and conventional treatment options. This could be reduced through development of a local reuse market or local disposal site for the dewatered biosolids, however in the absence of a viable existing local disposal option, out of district trucking and landfilling has been assumed as the worst case. In the absence of specific sites for the natural treatment options and habitat wetland / discharge location, a number of assumptions have been made which have a significant bearing on the WOL costs. Some of the major assumptions which have significant bearing on the cost estimates for natural treatment options are summarised below: Conveyance: All of the natural treatment options include 2 stages of conveyance, 6km to the treatment site and then a further 4km to the habitat wetland/discharge location. This conveyance requirement adds approximately $14.5M capital cost to the options. If suitable sites were able to be secured closer to Banks St, this cost could be reduced. Site topography: A number of assumptions have been made regarding the site topography and degree of levelling required to construct the natural processes. Ground Conditions: Due to the shallow groundwater likely to be encountered in the study area, all processes using deep ponds have been designed to be built out of the ground. This introduces higher capital costs associated with structural stabilisation of the earthen bunds and the required quantity of imported materials to construct the walls. Liners: the options assume that the HRAPs and wetlands will be largely unlined, with sufficient lining only to protect and stabilise the earthen bunds. The deep ponds, digesters and woodchip filters are all assumed to be HDPE lined. This assumption carries a high cost risk as it assumes that the unlined HRAPs and wetlands will self-seal over time and any discharge to ground will be consentable. It may also be a condition in any new consents that lining of these facilities is required to minimise seepage to sensitive groundwaters (depending on the sites finally selected). CH2M Beca // 2 November 2016 // Page 25

38 Appendix A Basis of Estimates CH2M Beca // 2 November 2016 // Page 26

39 Basis of Estimates A1 Basis of Estimate and Expected Level of Accuracy These estimates are based on concept design drawings and the performance criteria outlined in the technical sections above. Depending on the level of information available, costs have been factored from previous estimates, calculated on an elemental basis, and where appropriate on bulk quantities or budget costs for individual items. The estimated costs have been prepared from a combination of concept and preliminary drawings and information, and the expected accuracy is in the order of minus 10% to plus 35% overall inclusive of the estimating contingency. Contingency An estimating contingency of 15% has been included in the estimate to cover items of unforeseen detail and design development. This allowance is expected to cover estimating growth and design development. It is likely that this allowance will be converted into scope and therefore should not be regarded as discretionary. Contingency has not been applied to implementation (design and project management) costs. Scope change and risk items are not covered by this allowance. Rates The rates used in these estimates are based on construction rates generally prevailing in the industry which have been benchmarked against Council held rates for local projects and adjusted for local differences. A benchmarking exercise was carried out in which rates adopted in the alternative treatment options were priced by a major civil works contractor based on a provisional schedule of quantities prepared by Beca. Taking cognisance of the fact that the location of the site was not divulged in the pricing exercise, some of these rates were adopted and the Beca estimates updated for this report. Indirect Costs Allowances of 9% and 6% were included for contractors on-site overheads and off-site overheads and profit respectively. Subsequent benchmarking exercise based on contractor rates has highlighted the possibility of 15% and 15% overheads and profit. Implementation costs Provision for the design and construction implementation percentages applied in these estimates are based on IPENZ/ACENZ fee guidelines for design and construction. Generally the percentages applied are: Civil underground pipework Rising mains 10% Civil - works Alternative treatment design 11% Structures and MES Pumpstations, lamella structures, etc. 14% Cost Escalation CH2M Beca // 2 November 2016 // Page 27

40 This estimate is based on current rates prevailing in the industry and does not make allowance for escalation in pre contract costs. In the current environment it is expected that the New Zealand based rates may come under pressure and it is recommended that a provision for escalation in costs and market conditions be included. Currency Variation and Rate of Exchange The estimate currency is NZ$ for all building and civil works and locally supplied mechanical services, etc. The cost of imported equipment is based on current exchange rates and no provision has been made in the estimate for fluctuations in exchange rates. A2 General Assumptions and Exclusions General Exclusions No provision has been made in the estimated costs for the following items: GST Legal and finance costs Legal and other costs associated with use of public or private land for pipelines, etc. Increased costs due to escalation (estimate based on 2016 rates) Currency fluctuations Pre Capex costs including consenting and legal Resource Consent (Pre-Capex) Lease termination costs Land purchase costs Establishment Insurances Capitalised Interest Staffing & training Testing & Commissioning Laboratory Equipment Pre Project expenditure Consents and Authorities Owner direct costs General Assumptions The following assumptions are made in the preparation of these estimates: The base date of this estimate is September 2016 and does not include any provision for escalation in costs prior to or during implementation of the works. A head contractor will be engaged to carry out the works including providing attendance to major equipment vendors and mechanical installation contracts. Contractors have unrestricted access to the site during construction. Contractors have access to site services such as temporary power and water during construction. CH2M Beca // 2 November 2016 // Page 28

41 A3 Options Specific Assumptions and Exclusions The following table summarises exclusions and assumptions made in the preparation of these capital cost estimates. These figures are to be read in conjunction with the basis of design and detailed estimates issued in previous reports. CH2M Beca // 2 November 2016 // Page 29

42 Table 6 - Option Specific Assumptions and Exclusions Cost Element Basis of Estimate/ Design Methodology Specific Exclusions Assumptions Conventional Treatment (Banks St) Lamella Clarifiers, Solids Thickening /Dewatering Concept design Based on typical structures or similar projects Rough quantities Elemental rates and factored allowances for piping, etc. Factored historical costs. Sludge Settlers Concept design Factored historical costs. Demolition of existing structures, foundations (other than those indicated) Work to existing plant outside battery limits. Contaminated materials Retaining structures Landscaping Modification of existing structures, siteworks or reticulation. Assumes concrete lattice ground substructure to 11m with reinforced earth raft over; extending 5m outside the foundation areas. Conventional footings on the lattice raft above. Second BTF/ Biofilter Based on construction drawings of existing Combination of derived unit rate and factored cost Contract rates escalated (as above) (as above) UV Disinfection Concept design of typical unit by vendor Rough quantities estimate based on similar structures (as above) (as above) Current industry unit rates Denitrifying Sand Filtration Concept design of typical unit by vendor Rough quantities estimate based on similar structures (as above) (as above) Current industry unit rates Buffer Storage Ponds Peak Flow Buffer Storage Pond Based on similar existing design. (dairy plant WWTP pond) adapted for Gisborne site Rough quantities takeoff. Combination of escalated contract rates and industry norms Land purchase Demolition of existing structures, rock etc. Ground improvement Assumed excavation below ground level maximum 1m of which 75% in suitable for fill and balance of wall construction from imported fill.

43 Cost Element Basis of Estimate/ Design Methodology Specific Exclusions Assumptions Pumpstation (PS) Pumpstation based on scaled down existing design Rough quantities estimate Combination of escalated contract rates and industry norms Based on 1.5m water table. Remote Site Concept based on indicative route to possible site options. Combination of escalated contract rates and industry norms Land costs Legal, easements Stream crossings / pipe bridges, directional drilling, etc. General route via rail reserve Land is available for pipe-route Assumes single pumpstation Alternative Treatment Wetlands (SFCW ) Concept layout Rough quantities Unit rates based on similar projects, recent local tender rates and benchmarked contractor rates. Land purchase costs Site investigation costs Excavation unsuitable material Digested sludge thickening and disposal Generally flat site No bulk earthworks. Nominal site clearance required No existing structures, rock, etc. All excavated materials are suitable for use as fill on site. All topsoil can be reused as the wetland media and reinstatement Liners to bunds for stabilization. Bases unlined. HRAPs Concept layout (as above) (as above) (as above) HRAP (12 No.) Concept layout (as above) (as above) Assumed deeper digesters offsets reduced piping costs Wood Chip Filters) (WDF) Digesters and settlers Concept layout (as above) (as above) (as above) but fully HDPE lined Concept layout (as above) Assumed roads not elevated EIC Concept layout Excludes power supply to site.

44 Cost Element Basis of Estimate/ Design Methodology Specific Exclusions Assumptions Siteworks Concept layout (as above) Assumes treatment facility is located on flat site. Concept based on Factored using conveyancing Pipeline exclusions as for conveyancing Pipeline length assumes the proposed indicative route to possible site options. pipeline rates Combination of escalated contract rates and industry norms pipelines (above) wetland located at existing golf course Habitat wetland (Excluded) Habitat wetland not priced

45 Appendix B Process Flow Diagrams

46 Option A Solids removal and dewatering BTF #1 existing Lamella Clarifiers Thickening Dewatering PS existing Ocean Outfall existing Cake to Disposal NZ Gisborne Wastewater Management Options

47 Option B(i) Install a second BTF BTF #1 existing BTF #2 PS existing Ocean Outfall existing NZ Gisborne Wastewater Management Options New price element

48 Option B(ii) Install a second BTF and UV disinfection BTF #1 460 l/s existing BTF #2 UV Disinfection PS existing Ocean Outfall existing NZ Gisborne Wastewater Management Options New price element

49 Option C Second BTF, solids removal, and UV BTF #1 460 l/s existing BTF #2 Lamella Clarifiers Thickening Dewatering UV Disinfection PS existing Ocean Outfall existing Cake to Disposal NZ Gisborne Wastewater Management Options New price element

50 Option D Second BTF, solids removal, denitrification and UV BTF #1 Carbon source 460 l/s existing Lamella Clarifiers Denit. sand filter UV Disinfection PS Habitat Wetland BTF #2 Thickening Dewatering Cake to Disposal 460 L/s Rising main 4 km NZ Gisborne Wastewater Management Options New price element

51 Option E Second BTF, solids removal and UV at Banks St, denitrification at remote site BTF #1 existing Lamella Clarifiers 460 l/s UV Disinfection PS Peak Flow Buffer Pond Larger WDF. (4ha) WDF PS Habitat Wetland BTF #2 Thickening Dewatering 460 L/s Rising main 6km 460 L/s Rising main 4km Cake to Disposal NZ Gisborne Wastewater Management Options New price element

52 Option F - Solids removal and UV at Banks St site, wetland treatment at remote site 15 ha 2 ha 15 ha BTF #1 Lamella Clarifiers UV Disinfection PS SFCW #1 WDF SFCW #2 PS Habitat Wetland existing Thickening Dewatering 460 L/s Rising main 6km 460 L/s Rising main 4km Cake to Disposal NZ Gisborne Wastewater Management Options New price element

53 Option G Solids removal at Banks St, 12 HRAPs and UV treatment at remote site Includes Ahs/ADs 12 HRAPs HRAP1 BTF #1 Lamella Clarifiers PS HRAP2 UV Disinfection PS Habitat Wetland existing Thickening Dewatering Cake to Disposal 460 L/s Rising main 6km 460 L/s Rising main 4km NZ Gisborne Wastewater Management Options New price element

54 Option H(i) Solids removal, UV and wetland treatment at remote site, solids digested BTF #1 PS Sludge Settlers UV Disinfection 15 ha 2 ha 15 ha SFCW1 SFCW2 PS Habitat Wetland 460 L/s Rising main 6km Sludge Digesters Reuse or Disposal Alternative bigfoot wetland Instead of 2 x 15ha wetlands. Not priced 30 ha SFCW1 460 L/s Rising main 4km NZ Gisborne Wastewater Management Options New price element

55 Option H(ii) Solids removal, UV and wetland treatment at remote site, solids in STRB 15 ha 2 ha 15 ha BTF #1 PS Sludge Settlers UV Disinfection SFCW1 SFCW2 PS Habitat Wetland existing 460 L/s Rising main 6km STRBs Reuse or Disposal Alternative bigfoot wetland Instead of 2 x 15ha wetlands. Not priced 30 ha SFCW1 460 L/s Rising main 4km Orbicon price element NZ Gisborne Wastewater Management Options New price element

56 Option I(i) Solids removal, 12 HRAP and UV treatment at remote site, solids digested 12 HRAPs HRAP1 BTF #1 PS Sludge Settlers HRAP2 UV Disinfection PS Habitat Wetland existing 460 L/s Rising main 6km Sludge Digesters Reuse or Disposal 460 L/s Rising main 4km NZ Gisborne Wastewater Management Options New price element

57 Option I(ii) Solids removal, 12 HRAP and UV treatment at remote site, solids in STRB 12 HRAPs HRAP1 BTF #1 PS Sludge Settlers HRAP2 UV Disinfection PS Habitat Wetland existing 460 L/s Rising main 6km STRBs Reuse or Disposal 460 L/s Rising main 4km Orbicon price element NZ Gisborne Wastewater Management Options New price element

58 Option J(i) Full EWPS design, with sludge digesters 16 HRAPs HRAP1 7.5 ha 2 ha 7.5ha BTF #1 existing PS Sludge Settlers HRAP ha SFCW1 SFCW2 PS Habitat Wetland 460 L/s Rising main 6km Sludge Digesters Reuse or Disposal Alternative bigfoot wetland Instead of 2 x 7.5ha wetlands. Not priced 15 ha 460 L/s Rising main 4km SFCW1 NZ Gisborne Wastewater Management Options New price element

59 Option J(ii) Full EWPS design, with sludge in STRBs 16 HRAPs HRAP1 7.5 ha 2 ha 7.5 ha BTF #1 existing PS Sludge Settlers HRAP ha SFCW1 SFCW2 PS Habitat Wetland 460 L/s Rising main 6km STRBs Reuse or Disposal Alternative bigfoot wetland Instead of 2 x 7.5ha wetlands. Not priced 15 ha 460 L/s Rising main 4km SFCW1 Orbicon price element NZ Gisborne Wastewater Management Options New price element

60 Option K(i) EWPS design with 12 HRAPs, sludge digesters 12 HRAPs Option 6 HRAP1 7.5 ha 2 ha 7.5 ha BTF #1 existing PS Sludge Settlers HRAP ha SFCW1 SFCW2 PS Habitat Wetland 460 L/s Rising main 6km Sludge Digesters Reuse or Disposal Alternative bigfoot wetland Instead of 2 x 7.5ha wetlands. Not priced 15 ha SFCW1 460 L/s Rising main 4km NZ Gisborne Wastewater Management Options New price element

61 Option K(ii) EWPS design with 12 HRAPs, sludge in STRBs 12 HRAPs Option 6 HRAP1 7.5 ha 7.5 ha BTF #1 existing PS Sludge Settlers HRAP ha SFCW1 SFCW2 PS Habitat Wetland 460 L/s Rising main 6km STRBs Reuse or Disposal Alternative bigfoot wetland Instead of 2 x 7.5ha wetlands. Not priced 15 ha 460 L/s Rising main 4km SFCW1 Orbicon price element NZ Gisborne Wastewater Management Options New price element

62 Perforated outlet collection pipe set in coarse gravel filter zone 0.6 m deep Inlet pipes at~ 20 m intervals into openwater inlet zone Open water zones m depth Islands and low bunds to direct flows Wetland planting 0.3 m depth Simplified Wetland Concept - Plan

63 Woodchip Rock wall/ gabion SFCW Simplified Wetland Concept - Section