Southern Seawater Desalination Plant Performance Review Report

Transcription

1 Southern Seawater Desalination Plant 2018 Performance Review Report

2 Contents 1. Introduction Environmental Approval Report Objective 5 2. Environmental Factors, Risks and Impacts Key Environmental Factors Key Risks and Impacts 6 3. Environmental Monitoring Framework Environmental Quality Objectives Marine Environment Monitoring Programs Marine Environment Monitoring Program Dissolved Oxygen Monitoring Program Diffuser Performance Monitoring Program Whole Effluent Toxicity Monitoring Program Revegetation Management Plan 9 4. Environmental Performance Benthic Health Monitoring Discharge Water Quality Dilution, Whole Effluent Toxicity, Salinity, and Dissolved Oxygen Greenhouse Gas Emissions Benchmarking, Best Available Technology and Improvements in Environmental Management Seawater recirculation Lime waste recycling Research project - Effect of swell on brine discharge Risk mitigation Overflow collection header Seawater intake and effluent discharge monitoring Conclusion... 18

3 Glossary and Definition of Terms Actual Dilution The Actual Dilution achieved at the SSDP LEPA boundary is calculated from the results of the Diffuser Performance Monitoring Program. The method to calculate the Actual Dilution is provided in Section of the DPMP. Bottom Layer DER Saline The bottom saline layer is the whole bottom saline layer, a layer of higher salinity to that of the background salinity. The layer commences at the first salinity reading above the background salinity. Department of Environment Regulation (previously Department of Environment and Conservation) Desalination Effluent Desalination effluent consists of the brine stream from the RO system, neutralised clean-in-place (CIP) streams and wastewater originated from the backwash of the membrane filters and seawater strainers. The desalination effluent is discharged to the marine environment via a 320m diffuser array. DPMP Diffuser Performance Monitoring Program (Revision D, 2015) DO DoE DOMP DWER Environmental Quality Objectives EPA Dissolved Oxygen Department of the Environment (Commonwealth) Dissolved Oxygen Monitoring Program Department of Water and Environmental Regulation a department which combined the previous departments of DER, OEPA, and DoW (Department of Water). The Environmental Quality Objectives identified by the OEPA and specified in MS792 Schedule 1 for the marine environment surrounding the SSDP ocean diffuser. Environmental Protection Authority EPBC Act Environment Protection and Biodiversity Conservation Act 1999 Full Production GL IWSS LEPA Marine Environment Monitoring MEMP Full Production of the SSDP is the combined Stage 1 and Stage 2 operations, which produces 100GL of drinking water per year. Gigalitres Integrated Water Supply Scheme Low Ecological Protection Area Environmental monitoring undertaken in the marine environment as per the MEMP, DOMP, DPMP and WETMP. Marine Environmental Monitoring Program, including Discharge Water Quality Monitoring and Benthic Health Monitoring. MS792 Ministerial Statement 792 OEPA OEMF Office of the Environmental Protection Authority now OEPA section of DWER SSDP Operation Environmental Management Framework developed to address

4 MS792 requirements. ppt Recirculation RMP RO SSDP SSWA Parts per thousand Seawater entering through the seawater intake pipelines is recirculated directly back into the desalination effluent diffuser pipeline to increase on-shore dilution prior to diffusing into the marine environment. Revegetation Management Plan Reverse Osmosis Southern Seawater Desalination Plant Southern Seawater Alliance Target Dilution The minimum number of dilutions required to meet the ANZECC (2000) 99% species protection trigger at the boundary of the LEPA as per the latest valid WET testing results provided by the WET testing consultant. The 99% species protection trigger is theoretical or statistically inferred based on the results of sub-lethal toxicity testing and species sensitivity distributions. WET WETMP Worst Dilution Case Whole Effluent Toxicity Whole Effluent Toxicity Monitoring Program The Worst Case Dilution achieved at the SSDP LEPA boundary can be calculated from the Actual Dilution results of the Diffuser Performance Monitoring Program (salinity monitoring). If the number of marine salinity monitoring events (n) is less than 20, then the worst dilution result calculated for all of the salinity monitoring events in the reporting period will be used to represent the Worst Case Dilution. If the number of marine salinity monitoring events (n) is greater than 20 then the lower 5 th percentile of the dilution results calculated for all of the salinity monitoring events in the reporting period will be used to represent the Worst Case Dilution. 4

5 1. Introduction The Southern Seawater Desalination Plant (SSDP) consists of offshore marine infrastructure (intake and diffuser systems) and onshore infrastructure (treatment and storage infrastructure) on Taranto Road, Binningup, WA. Drinking water is supplied to Water Corporation s Integrated Water Supply Scheme (IWSS) via a storage tank facility near Harvey. The SSDP was designed and constructed in two stages, each capable of producing 50 GL of water annually. Stage 1 of the plant began commercial operations on the 12 March Stage 2 was commissioned on 17 January The combined has a nameplate capacity of producing 100 GL of drinking water annually. 1.1 Environmental Approval In July 2007 Water Corporation referred the proposal to construct and operate the SSDP to the Minister for Environment for assessment under Section 38 of the Environmental Protection Act It was formally assessed at the level of Public Environmental Review under the State process. The Proposal was approved by the Minister for Environment, with Ministerial Statement 792 (MS792) published on the 14 April 2009 (provided in Appendix 1 Ministerial Statement 792). The approval acknowledged that construction and operation of the desalination plant will have an impact on the marine environment. The project was referred to the Commonwealth Department of Environment, Water, Heritage and the Arts (now Department of the Environment and Energy) for assessment under the Environment Protection and Biodiversity Conservation Act The project was approved under conditions published in approval EPBC2008/4173 on 24 June Report Objective Water Corporation is required to submit a Performance Review Report (PRR) at the conclusion of the second, forth, and sixth year after commencement of operation in accordance with MS792 Condition 5-1. Condition 5-1 specifies that the PRR is required to address the following items: 1. The major environmental risks and impacts; the performance objectives, standards and criteria related to these; the success of risk reduction/impact mitigation measures and results of monitoring related to the management of the major risks and impacts; 2. The level of progress in the achievement of best practice environmental performance, including industry benchmarking, and the use of best available technology where practicable; and 3. Improvements gained in environmental management which could be applied to this and other similar projects. This PRR is the third and final PRR for the SSDP. The first PRR was submitted in 2014, and the second PRR was submitted in

6 2. Environmental Factors, Risks and Impacts 2.1 Key Environmental Factors The following Key Environmental Factors were identified as relevant to the construction and operation of the SSDP in the Report and recommendations of the Environmental Protection Authority (EPA) (Appendix 2 Report and recommendations of the EPA Report 1302): Water quality and Marine Biota impacts from construction and operation of the desalination plant, Terrestrial Fauna impacts from clearing of habitat, Terrestrial Vegetation and Wetlands impacts from clearing during infrastructure construction, and Greenhouse Gas Emissions proposed no net greenhouse gas emissions. 2.2 Key Risks and Impacts MS792 acknowledges that the discharge of desalination effluent will have an impact in the immediate vicinity of the discharge to the marine environment. A Low Ecological Protection Area (LEPA) has been established to limit the extent which the local marine ecosystem will be impacted. The LEPA is 100 metres by 600 metres (50 metres either side of the diffuser array), as required by MS792 Condition 6-1. A High Ecological Protection Area exists beyond the LEPA boundary, at which 99% protection of species must be met. The environmental risks and impacts for the construction and operation of the SSDP according to each key environmental factor are shown in Table 1. Table 1: SSDP Environmental Risks and Impacts EPA Key Environmental Factor Water Quality and Marine Biota - impacts from construction and operation of the desalination plant Environmental risk Discharge water quality Dissolved Oxygen (DO) Salinity Whole Effluent Toxicity (WET) Potential environmental impact Desalination effluent discharge quality exceeds trigger values (combination of 80 th percentile of baseline results and ANZECC 2000 triggers) at the LEPA boundary, causing a risk of adverse biological impacts. Desalination effluent discharge results in a DO concentration at the LEPA boundary below MS792 Condition 6 7 criteria of 60% saturation. DO is a key environmental quality indicator which may impact marine ecosystem integrity (structure biomass and biota abundance) if the concentration is below 60% saturation. Desalination effluent discharge results in salinity levels at the LEPA boundary of 1 ppt above background more than 5% of the time and/or salinity levels above 1.3 ppt above background on any occasion resulting in non-compliance with MS792 conditions. Note a salinity level of 1 ppt above background at the LEPA boundary equates to a dilution factor of The 2015 WET testing determined that the Target Dilution (the dilution required to meet 99% species protection at the LEPA boundary) for Full Production operations is 9.6. Therefore a salinity level of 1 ppt above background is protective of more than 99% species. The salinity of the bottom saline layer would need to be above 2.68 ppt above background to not meet 99% species protection at the LEPA boundary. N/A no risk of adverse impacts from WET testing WET Testing is required to establish the Target Dilution (the dilution required to protect 99% species at the LEPA boundary). The 2015 WET Testing results, representative of Full Production operations, determined that a dilution of 9.6 is required to meet 99% species protection. 6

7 Terrestrial Fauna impacts from clearing of habitat Dilution Benthic Health (construction and operation) Marine fauna & flora (construction phase) Terrestrial fauna The Worst Case Dilution does not achieve the Target Dilution (dilution required to achieve 99% species protection at the LEPA boundary) resulting in a risk of adverse impact to marine species. Construction of SSDP infrastructure has a long term adverse impact on benthic seagrass health. Discharge of desalination effluent during SSDP operation has an adverse impact on benthic seagrass health. Applicable for stage one construction only (i.e. dredging, blasting, construction) during the completion of all marine infrastructure works. Applicable for construction only. The revegetation of areas not required for above ground infrastructure according to MS792 and EPBC2008/4173 requirements will minimise the impact from clearing on terrestrial fauna. Terrestrial Vegetation and Wetlands- impacts from clearing during infrastructure construction Terrestrial flora & vegetation Applicable mainly to construction phase, with the exception of ongoing revegetation as part of the Revegetation Management Plan. Risk of revegetation not meeting regulatory requirements (MS792 and EBPC2008/4173 conditions) due to internal or external factors. Greenhouse Gas Emissions proposed no net greenhouse gas emissions Greenhouse gas emissions It is intended to purchase renewable energy or carbon offset credits to offset SSDP s electricity usage. Therefore there is no risk from greenhouse gas emissions. 3. Environmental Monitoring Framework 3.1 Environmental Quality Objectives The following Environmental Quality Objectives were identified by the OEPA and specified in MS792 Schedule 1 for the surrounding marine environment: Maintenance of ecosystem integrity at a low level of ecological protection within the Low Ecological Protection Area (LEPA) and at a high level of ecological protection at the designated LEPA boundary, Maintenance of aquatic life for human consumption assigned to all parts of the marine environment surrounding the ocean outlet, Maintenance of primary contact recreation values assigned to all parts of the marine environment surrounding the ocean outlet, Maintenance of secondary contact recreation values assigned to all parts of the marine environment surrounding the ocean outlet, Maintenance of aesthetic values assigned to all parts of the marine environment surrounding the ocean outlet, Maintenance of cultural and spiritual values assigned to all parts of the marine environment surrounding the ocean outlet, and Maintenance of Industrial Water Supply. 7

8 3.2 Marine Environment Monitoring Programs The following programs were designed to meet the Environmental Quality Objectives for the marine environment specified in MS792 Schedule 1: Marine Environment Monitoring Program (MEMP), including discharge water quality monitoring and benthic habitat monitoring, Diffuser Performance Monitoring Program (DPMP), Dissolved Oxygen Monitoring Program (DOMP), and Whole Effluent Toxicity Monitoring Program (WETMP). The Southern Seawater Alliance (SSWA) engaged an external contractor to undertake a review of the Marine Monitoring Programs (MEMP, DPMP, DOMP and WETMP) to assess the current requirements and determine which requirements have been met, which requirements are still to be completed and the anticipated completion dates. Water Corporation submitted the findings, including a new version of the MEMP to the OEPA on 7 October The MEMP is provided in Appendix 3 Marine Environment Monitoring Program. The OEPA approved the revisions of the monitoring plans via a letter dated 08 August In a letter dated 30 September 2016 the OEPA confirmed that monitoring programs associated with Condition 6 of MS792 had been completed satisfactorily (Appendix 12 Letter from OEPA acknowledging completion of monitoring required under Condition 6) Marine Environment Monitoring Program The MEMP was developed by Water Corporation and endorsed by the former Department of Environment and Conservation (now Department of Water and Environmental Regulation (DWER)). The MEMP outlines the monitoring commitments for the discharge of desalination effluent to the Indian Ocean via the marine outfall diffuser as per the requirements of MS792 Condition 6-2. Specifically the MEMP includes commitments for desalination effluent discharge quality monitoring and benthic habitat health monitoring. The MEMP is provided in Appendix 3 Marine Environment Monitoring Program Dissolved Oxygen Monitoring Program The Dissolved Oxygen Monitoring Program (DOMP) was developed: To address MS792 Condition 6-5 which requires Water corporation to monitor dissolved oxygen levels at least weekly, either by deploying data loggers or by hand, at sites agreed by the CEO of the Department of Environment and Conservation to determine whether the trigger values are being achieved, for a period of 12 months immediately following: o Completion of commissioning phase or six months from commencement of the commissioning phase, whichever is sooner; and o The initiation of full production (according to design specifications). To address MS792 Condition 6-7 which specifies a trigger of 60% DO saturation at the boundary of the LEPA. The DOMP is provided in Appendix 4 Dissolved Oxygen Monitoring Program Diffuser Performance Monitoring Program The Diffuser Performance Monitoring Program (DPMP) was developed: To determine compliance against the salinity trigger levels defined in MS792 Condition of 1 parts per thousand (ppt) salinity increase above background 95% of the time and not exceeding 8

9 an increase of 1.3 ppt above background at the boundary of the Low Ecological Protection Area; and To assess the diffuser performance in terms of number of dilutions achieved at the LEPA boundary required by MS792 Condition 6-8. The DPMP was revised in 2015 as recommended by a third party. The DPMP is provided in Appendix 5 Diffuser Performance Monitoring Program Whole Effluent Toxicity Monitoring Program The Whole Effluent Toxicity Monitoring Program (WETMP) was developed to meet MS792 Condition 6-9 which requires Water Corporation to conduct Whole Effluent Toxicity testing of wastewater consistent with the toxicity and testing protocol at the following intervals: One month following the initiation of the commissioning phase; 12 months following the completion of commissioning or 18 months following the initiation of commissioning (whichever occurs first); 12 months following the commencement of full production. The WETMP was revised in 2015 as recommended by a third party. The WETMP is provided in Appendix 6 Whole Effluent Toxicity Monitoring Program. 3.3 Revegetation Management Plan The SSDP Revegetation Management Plan (RMP) (Appendix 7 Revegetation Management Plan) was developed to guide revegetation on the SSDP site to meet MS792 Condition 9 and EPBC2008/4173 Condition 7 requirements. The plan was based on a flora and fauna survey conducted in 2008 (360 Environmental), the Public Environmental Review (Water Corporation 2008) and the Construction Environmental Management Framework (Water Corporation 2009). The RMP outlines the revegetation schedule and number of species that will be revegetated. Revegetation of the SSDP commenced in July 2009 with stockpiling of topsoil, mulch and branches and pre-planting weed spraying. Direct seeding and planting commenced in mid-2010 and the second seeding/planting campaign commenced in mid Planting of tubestocks and seedlings for 1.3 ha cleared at the northern area of the site was completed in The then DoE requested an amendment of the RMP to remove all references to the Harvey water tank site based on an audit conducted in February Water Corporation provided a revised plan to the DoE on 24 June 2015, which was subsequently approved on 4 January The 2015 Revegetation Program Monitoring Report was completed by a third party consultant and submitted to the OEPA along with a letter dated 15 July 2016 (Appendix 13 Letter to OEPA providing 2015 Revegetation Program Monitoring Report). The 2015 revegetation survey results demonstrated that the SSDP revegetation program is complete according to Ministerial Statement 792 requirements. The OEPA section of DWER confirmed the revegetation conditions had been met via communications dated on the 16 January 2018 (Appendix 11 Letter from OEPA acknowledging completion of Revegetation Conditions). 9

10 4. Environmental Performance Table 2 provides a summary of the status of each of the monitoring programs designed to meet the Key Environmental Factors and Environmental Quality Objectives during SSDP operations. The monitoring results indicate that the SSDP is operating effectively and that the Environmental Quality Objectives for the marine environment are being maintained. 10

11 Table 2: Status of SSDP Environmental Monitoring Programs EPA Key Environmental Factor Project risk (MS792) MS792 Criteria Status Description Water Quality and Marine Biota - impacts from construction and operation of the desalination plant Discharge water quality Dissolved Oxygen (DO) Compliant Table 5-1 within the MEMP states that in-pipe discharge water quality monitoring should take place with a frequency of two events annually for a period of five years. The five-year period ended in 2016; however the NATA accredited laboratory who conducted the first year of sampling in 2012 had limits of reporting (LOR) which were above the trigger level concentration for most of the parameters. This issue was resolved in the second year of sampling by changing to another NATA accredited laboratory that was able to achieve much lower LORs. A decision was made to complete one additional year of monitoring which was completed in Discharge water quality monitoring conducted between 2014 and 2017 demonstrates that the desalination effluent quality is within the anticipated range. During the discharge water quality monitoring program it was identified that the background (seawater) concentrations often exceed the water quality trigger levels, largely due to trigger levels being set as the 80th percentile of recorded background trigger levels. In the cases where background levels exceed trigger levels, it is impossible for the desalination effluent discharge to achieve a concentration less than the trigger value regardless of the dilution effect. In all cases where the calculated contaminant concentrations at the LEPA boundary were higher than the trigger levels; the calculated concentrations were within 5% of the seawater sample concentration Throughout the monitoring program there were only two occasions that the discharge concentration was calculated to be above trigger levels at the LEPA, when background concentrations were below the trigger level. On both occasions the calculated manganese concentrations at the LEPA were both below the maximum recorded baseline result of mg/l (Appendix 15 Discharge Water Quality Monitoring Completion Report). Water Corporation and the SSWA will continue to monitor in-pipe discharge effluent quality including conductivity (and calculated salinity), dissolved oxygen, ph, turbidity and oxidation reduction potential on a continuous basis for the duration of SSDP operations. 6 5, 6 6, 6 7 Completed OEPA acknowledged that Water Corporation met the requirements of MS792 Conditions 6-5 and 6-6 in a letter dated 21 October 2015 (Appendix 10 Letter from OEPA acknowledging completion of dissolved oxygen monitoring). The OEPA also noted that oxygen saturation never fell below 60% at the LEPA boundary and therefore Condition 6-7 was never triggered. Water Corporation ceased weekly DO monitoring on 21 October 2015 in response to OEPA s acknowledgement of the completion of MS792 Conditions 6-5 and 6-6. Salinity Compliant The SSDP has implemented strategies to ensure that the salinity trigger levels specified in MS792 Condition are met. This includes the optimisation of the seawater recirculation system to operate the recirculation pumps depending on the volume of RO brine produced. This

12 12 system has been shown to ensure that MS792 Condition salinity triggers are, and will continue to be met for future SSDP operations. The monthly salinity monitoring required for 12 months following the completion of Full Production on 17 January 2014 has been completed. Condition triggers for salinity were met during the monitoring period. Water Corporation provided the DPMP and WETMP Completion Report to the OEPA on 18 December The report advised that the salinity triggers specified in Condition have been met and that Water Corporation will be ceasing monthly salinity monitoring at the SSDP LEPA boundary based on compliance with Condition In a letter dated 30 September 2016 the OEPA confirmed that monitoring programs associated with Condition 6 of MS792 had been completed satisfactorily (Appendix 12 Letter from OEPA acknowledging completion of monitoring required under Condition 6). Water Corporation commenced the five-year annual salinity and diffuser assessment monitoring program in 2016 as per DPMP commitments. The results of the 2016 and 2017 salinity monitoring demonstrated the diffuser continues to be effective in maintaining salinity concentrations below the trigger levels. The five-year monitoring period will run until Whole Effluent Toxicity 6 9, 6 11 Completed WET testing has been undertaken at the following intervals to meet the requirements of MS792 Condition 6-9: One month following the initiation of the commissioning phase, on 14 December 2011; 12 months following the completion of commissioning, on 11 February 2013; An additional sample representative of commissioning of Full Production (100GL per year), on 14 January 2014; and A sample on 19 March 2015, 12 months following the commencement of Full Production. The 2015 WET Testing results, representative of Full Production operations, determined that a dilution of 9.6 is required to meet 99% species protection. Water Corporation provided the DPMP and WETMP Completion Report to the OEPA on 18 December The report advised that MS792 Conditions 6-9 and 6-11 have been adequately addressed and that no further WET testing will be undertaken unless there is a change to operations which alters the components of the desalination effluent discharge. Dilution 6-8 Compliant Monthly diffuser assessment required for 12 months following the completion of Full Production on 17 January 2014 as per MS792 Condition 6-8 has been completed. Water Corporation provided the DPMP and WETMP Completion Report to the OEPA on 18

13 13 December The report advised that MS792 Condition 6-8 has been adequately addressed and that Water Corporation will be ceasing monthly dilution assessment at the SSDP LEPA boundary based on compliance with Condition 6-8. In a letter dated 30 September 2016 the OEPA confirmed that monitoring programs associated with Condition 6 of MS792 had been completed satisfactorily (Appendix 12 Letter from OEPA acknowledging completion of monitoring required under Condition 6). Water Corporation commenced the five-year annual salinity monitoring program in 2016 as per DPMP commitments. The results of the 2016 and 2017 salinity monitoring demonstrated the diffuser continues to be effective in maintain salinity concentrations below the trigger levels. The five-year monitoring period will run until Benthic Health Compliant Condition states; Establish existing benthic community composition and health prior to marine construction and then monitor benthic composition and health annually after construction to determine impact and recovery. To meet the requirement of Condition a five-year annual Benthic Habitat Monitoring Program was conducted which comprised of recording seagrass shoot density at impact and reference locations. From 2012 when the program commenced to 2015 a general decline in seagrass shoot densities at the monitoring sites was recorded, particularly at the Impact and Southern Reference sites. The recorded decline in shoot density along with triggering of the Environmental Quality Standard (EQS) in 2015 resulted in a standalone investigation being conducted in The final year of the five-year Benthic Health Monitoring Program in 2016 again resulted in a trigger of the EQS however there were also early signs of a recovery of seagrass shoot densities, particularly at the Impact and Northern Reference sites. With respect to the results of the 2016 investigation and the final year of the five-year Benthic Health Monitoring Program it was decided to implement a further three-year Seagrass Health Monitoring Program. To date the results from the first two years (2017 and 2018) of the three-year annual Seagrass Health Monitoring Program have been promising and demonstrated a recovery and or stabilisation of seagrass shoot density at the Impact, Southern, and Northern Reference locations. However the EQS has been triggered at the Southern location in both 2017 and 2018.

14 14 Marine fauna & flora (construction phase) 7-1, 7-2, 7-3, 7-4, 7-5, 7-6 Completed Applicable for stage one construction phase only (i.e. dredging, blasting, construction) which saw completion of all marine infrastructure works. Terrestrial Fauna impacts from clearing of habitat Terrestrial Vegetation and Wetlands- impacts from clearing during infrastructure construction Terrestrial fauna Terrestrial flora & vegetation 8 1, 8 2 Completed Applicable for construction only. 9-7, 9-8, 9-9 Compliant The 2015 Revegetation Program Monitoring Report was completed by a third party consultant and submitted to the OEPA along with a letter dated 15 July 2016 (Appendix 13 Letter to OEPA providing 2015 Revegetation Program Monitoring Report). The 2015 revegetation survey results demonstrated that the SSDP revegetation program is complete according to Ministerial Statement 792 requirements. The OEPA section of DWER confirmed the revegetation conditions had been met via communications dated on the 16 January 2018 (Appendix 11 Letter from OEPA acknowledging completion of Revegetation Conditions). Greenhouse Gas Emissions proposed no net greenhouse gas emissions Greenhouse gas emissions 11 1, 11 2 Non-compliant Water Corporation was non-compliant with Conditions 11-1 and 11-2 during the reporting period. Water Corporation is in the process of developing a strategy for the purchase of renewable energy and/or carbon offsets for the SSDP.

15 4.1 Benthic Health Monitoring In response to the recorded decline in shoot density between 2012 and 2015, the Murdoch University Marine and Freshwater Research Laboratory (MAFRL) and BMT Oceanica were engaged to conduct an investigation into the shoot density declines in The investigation monitored a variety seawater quality parameters as well as seagrass shoot density to try and determine a cause of the observed seagrass shoot density decline. The investigation concluded; there was no conclusive relationship between salinity, light, turbidity, dissolved oxygen or any other stressor and the seagrass decline. As a result the specific cause of the seagrass density decline is unknown and may be due to a number of stressors (Appendix Seagrass Monitoring Review). Also in 2016 the final year of the five-year Benthic Seagrass Health Monitoring Program as required by the Ministerial Condition and the then Commonwealth Department of the Environment s Condition 16 was completed. The results showed that the impact and northern reference sites had an increase in shoot density while the southern reference site had a reduced rate of decline in shoot density (Appendix Benthic Health Monitoring Report). On conclusion of the five-year annual Benthic Seagrass Health Monitoring Program, it was decided to conduct an additional three-year annual Seagrass Health Monitoring Program commencing in To date the results from the first two years (2017 and 2018) of the threeyear program have been promising and demonstrated a recovery and or stabilisation of seagrass shoot density at the Impact, Southern, and Northern Reference locations. However EQS1 has been triggered at the Southern location in both 2017 and The 2017 and 2018 monitoring results were sent to the OEPA section of DWER with cover letters dated 20 April 2017 and 13 June 2018 respectively. Impact Mean shoot density (per m2 + SE) 1800 South Mean shoot density (per m2 + SE) Northern Reference Mean shoot density (per m2 + SE) Figure 1: Mean shoot density at monitoring locations (excerpt from the 2018 Seagrass Health Monitoring Report) 15

16 4.2 Discharge Water Quality Throughout the six monthly Discharge Water Quality Monitoring program conducted between 2012 and 2017 there were only two occasions that the discharge concentration was calculated to be above trigger levels at the LEPA, when background concentrations were below the trigger level. On both occasions the calculated manganese concentrations at the LEPA were both below the maximum recorded baseline result of mg/l (Appendix 15 Discharge Water Quality Monitoring Completion Report). Water Corporation and the SSJV will continue to monitor in-pipe discharge effluent quality including conductivity (and calculated salinity), dissolved oxygen, ph, turbidity and oxidation reduction potential on a continuous basis for the duration of SSDP operations. 4.3 Dilution, Whole Effluent Toxicity, Salinity, and Dissolved Oxygen Monitoring has demonstrated that MS792 conditions for salinity and dissolved oxygen in the marine environment have been met. In addition the SSDP is meeting the required diffuser performance to achieve 99% species protection at the LEPA boundary. In a letter dated 30 September 2016 the OEPA confirmed that monitoring programs associated with Condition 6 of MS792 had been completed satisfactorily (Appendix 12 Letter from OEPA acknowledging completion of monitoring required under Condition 6). 4.4 Greenhouse Gas Emissions Water Corporation was non-compliant with MS792 Conditions 11-1 and 11-2 during the reporting period. Water Corporation is in the process of developing a strategy for the purchase of renewable energy and/or carbon offsets for the SSDP. 16

17 5. Benchmarking, Best Available Technology and Improvements in Environmental Management SSWA and Water Corporation have implemented several initiatives at the SSDP based on industry benchmarking, best available technology and improving environmental management. These initiatives have improved the environmental performance of the SSDP. The initiatives include: Seawater recirculation, Lime waste recycling, Research project Effect of swell on brine discharge, Risk mitigation Overflow collection header, and Seawater intake and effluent discharge monitoring. 5.1 Seawater recirculation An investigation carried out with assistance from external parties in 2015 determined that seawater recirculation is required to ensure the salinity at the LEPA boundary is less than 1 ppt above background salinity for Reverse Osmosis (RO) brine flows of up to 300 ML/day. For RO brine flows above 300 ML/day no seawater recirculation is required to ensure the salinity at the LEPA boundary is less than 1 ppt above background. An equation was implemented in the continuous control system in October 2015 which turns the recirculation pumps on and off depending on the volume of RO brine produced. This system has been shown to ensure that MS792 Condition salinity triggers are, and will continue to be met for future SSDP operations. 5.2 Lime waste recycling During 2017 the Water Corporation and SSWA worked together with a local waste management company and DWER to set up a sustainable recycling option for a spent lime product in accordance with regulatory requirements. The local waste management company implemented the appropriate risk mitigation infrastructure and processes to treat the product and received approval to recycle the product via an amendment to their Part V licence (L7060/1997/13). The processed spent lime product is being used as a soil conditioner to improve acidic soils on agricultural lands. This has resulted in the largest solid waste stream from the SSDP being recycled, and resulted in a greater than 80% recycling rate of solid waste generated at SSDP. 5.3 Research project - Effect of swell on brine discharge The Water Corporation initiated a research project to further understand the effects of swell on the discharge velocity from the diffuser, and the secondary dilution effects of swell. This research will assist in incrementally progressing the science of brine discharge modelling and diffuser design. This work will be particularly useful when designing potential future plants which have discharge diffusers located in high energy coastal environments. 5.4 Risk mitigation Overflow collection header During plant risk assessments it was identified that under certain conditions the overflow collection header could be overloaded resulting in an unplanned discharge to secondary 17

18 containment. To mitigate the identified risk, controls were implemented including critical alarms and processes to further automate the shutting down of the plant to prevent overflow. 5.5 Seawater intake and effluent discharge monitoring The continuous control system has been updated to provide automated monitoring of key environmental parameters, such as flow and water quality parameters for seawater intake and effluent discharge. The monitoring process includes a regular report which is automatically generated and ed to appropriate personnel. 6. Conclusion Monitoring results indicate that the SSDP is operating effectively and that the Environmental Quality Objectives for the marine environment are being maintained. Water Corporation has demonstrated that the SSDP has met MS792 criteria for salinity and dissolved oxygen and is achieving the required diffuser performance to meet 99% species protection at the LEPA boundary. Seagrass Health Monitoring continues and while a decline in seagrass shoot density was recorded post construction we have seen a recovery and stabilisation of seagrass shoot density over the last three-years of monitoring. Water Corporation is in the process of developing a strategy for the purchase of renewable energy and/or carbon offsets for the SSDP. Water Corporation and SSWA plan to undertake the following; Continuous Seawater intake and effluent discharge water quality and flow monitoring, Annual in-situ salinity and diffuser performance monitoring, Complete the third year of the three-year Seagrass Health Monitoring Program, and Complete the Swell impact on diffuser performance research project. 18

19 Appendix 1 Ministerial Statement 792 Appendix 2 Report and recommendations of the EPA Report 1302 Appendix 3 Marine Environment Monitoring Program Appendix 4 Dissolved Oxygen Monitoring Program Appendix 5 Diffuser Performance Monitoring Program Appendix 6 Whole Effluent Toxicity Monitoring Program Appendix 7 Revegetation Management Plan Appendix Marine Environment Monitoring Annual Report Appendix Marine Environment Monitoring Annual Report Appendix 10 Letter from OEPA acknowledging completion of dissolved oxygen monitoring Appendix 11 Letter from OEPA acknowledging completion of Revegetation Conditions Appendix 12 Letter from OEPA acknowledging completion of monitoring required under Condition 6 Appendix Seagrass Monitoring Review Appendix Benthic Health Monitoring Report Appendix 15 Discharge Water Quality Monitoring Completion Report