Island of Seil Wastewater Treatment

Options Review

FINAL REPORT

May 2017

Document History

Version Comment V2.0 FINAL

Scottish Water FINAL 19 May 2017

Executive Summary

1. PURPOSE

The purpose of this report is to provide an overview of Scottish Water’s appraisal of the options available to deliver sustainable wastewater treatment solutions on the Isle of Seil.

2. BACKGROUND

a. Original Project

A project to provide a first time sewerage and treatment scheme for the Island of Seil (Argyll and Bute) was implemented in the 2006-2010 investment period (SR06), replacing private raw discharges and creating a treatment works serving a population of circa 300 at Balvicar, discharging to a shellfish water (Seil Sound).

The Shellfish Water designation ordinarily requires disinfection of the effluent and modelling of the bacterial loading to demonstrate quality. During this period, Scottish Water utilised a relatively new membrane technology in a number of communities where high standards/disinfection was required. This provides a barrier treatment, effectively removing bacteria to deliver a high quality effluent. SEPA therefore accepted a proposal for a membrane treatment plant and network designed to serve a community of up to 500 population with minimal spills. b. Community Experience - Project Delivery

The first time sewerage and treatment works was delivered through Scottish Water Solutions. During delivery there was a great deal of community disruption with the laying of a new sewer for the settlement adjacent to the coast. This involved significant intrusion into gardens and private property and extensive roadworks along the single track road that forms the main thoroughfare around the island.

The works constructed at Balvicar is directly in front of several properties, along the main tourist route, interrupting a scenic outlook across Seil Sound with a treatment works and unattractive security fencing.

There were a number of incidents where the community complained about the performance of contractors. Coupled with the extensive disruption and significant dissatisfaction with the works delivered, the community view of Scottish Water was very poor at the point when the works was commissioned in 2008-9.

Further community complaints were raised following the commissioning of the works. The operation of the works introduced noise nuisance to several of the properties nearby, with one resident particularly impacted, leading to extensive dialogue directly and with MSPs.

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c. Works Performance

The works has delivered a high quality effluent through its operation, but it has not been possible to sustain the required level of flow through the works. The membranes have clogged up quicker than was expected leading to extensive maintenance and resulting in spilling untreated screened discharges to the shellfish water more frequently than anticipated when it was designed and licensed.

These spills are reported to SEPA as part of the licence condition, and have been a key source of complaint from the community

3. DEVELOPMENT OF A NEW PROJECT

Scottish Water has two key drivers to satisfy within the 2015-2021 investment period:

1. a quality enhancement project to provide first time treatment to 8 properties at Seaview Terrace currently served by a raw public outfall; 2. a capital maintenance project to address the performance of the existing works.

Isle of Seil

Existing Works (Balvicar) Seaview Terrace

Seil Sound Shellfish Water Easdale Bay Special Area of Conservation

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a. Initial Optioneering

During 2014-15, initial optioneering indicated that the lowest whole life cost proposal would be to combine both drivers and deliver a single scheme. This would see the replacement of the existing works with a pumping station to pass forward flows for treatment at a community septic tank at Seaview Terrace. Discharging to Easdale Bay would remove the need to meet the shellfish disinfection driver at Seil Sound.

Early community engagement on this proposal led to very negative responses and significant escalations within the community. This was compounded by an exceptionally low level of trust due to the previous experience of Scottish Water. Specific objections centred on wildlife (it is designated a Special Area of Conservation) and amenity value (watersports and wildlife tourism) within Easdale Bay.

The MSPs Mike Russell and Mike Mackenzie (constituency and list MSPs respectively at the time) were engaged by the community. Dissatisfaction about the delivery and operation of the current works, together with concerns over the new proposals were raised during Scottish Water’s appearance at the Scottish Parliament’s Transport, Infrastructure and Climate Change Committee in December 2015.

b. Community Stakeholder Group

In June 2016 a Community Stakeholder Group, chaired by Mike Russell MSP, was created with the objective to engage the community in the development of a mutually acceptable option. This was supported by several community information events and the appointment of an independent technical expert (Chris Chubb, former head of Environmental Quality at the Environment Agency) to support community scrutiny.

The Group agreed to a process that would see a range of options developed (including those suggested by the community), and appraised through a common project evaluation system. This covered criteria such as customer experience, service and environmental outcomes and costs. Based on assurances given at the Scottish Parliament in December 2015, the community were assured that the ultimate decision making would rest with the SW Board, taking into account the importance of community endorsement.

c. Options Appraisal

A draft report covering 12 options (variations of 6 core options) was issued to the Stakeholder Group in December 2016 and discussed at the Stakeholder meeting in January 2017, and at a technical meeting with the community, project team and technical experts in March.

An appraisal based on cost, feasibility and acceptability grounds, led to two principal options being considered further to satisfy the drivers:

 Option 1A – creation of a new tertiary treatment works away from the immediate

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community to replace the existing works, still discharging to Seil Sound Shellfish Water and create a small septic tank to serve the Seaview Terrace residents

 Option 3 – single large septic tank and UV system located in the vicinity of Seaview Terrace to serve all properties currently connected to the public sewerage system, with disinfected effluent discharged to Easdale Bay

Option 1A is viable as it relies on proven technology and would be acceptable to Scottish Water, the community and to SEPA.

Option 3 is viable, and in Scottish Water’s view would satisfy the environmental needs, however this option is firmly rejected by the stakeholder group. It would face opposition, delay, technical challenges, legal escalation and further negative feeling in the community.

Option Capital Cost Comments

1A £5.6m No major objections anticipated, has stakeholder support

3 £5.5m Includes risk allowance for extensive community resistance and legal challenge, potential outfall extension requirements and project delays

Whilst Option 1A is more expensive, on balance it is believed to have the best opportunity to successfully deliver the outcomes and maintain community support. The capital cost of Option 3 relates to the likely augmented solution that would be required (e.g. 3B).

The key areas of risk to Option 1A that need to be locked down include securing the relevant regulatory licences, permissions to build (planning and land purchase) and final cost appraisal once the detailed design is completed.

4. CONCLUSION

The conclusion of the report is that Option 1A (tertiary treatment discharging to Seil Sound and separate small septic tank at Seaview Terrace) be progressed as the preferred option. This is subject to gaining planning and regulatory permissions and final cost appraisal.

This option is believed to have the best opportunity to successfully deliver the necessary regulatory outcomes and maintain community support.

5. PROGRESSING TO DELIVERY

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In developing this project, informed by a Community Stakeholder Group established with local community members and representatives, there is a need to ensure the wider community is further engaged. Scottish Water will hold an information event with the community to explain the process followed, the solutions identified as viable, and to provide further details of the preferred solution arising from the process. Feedback will be taken from the event to help us to understand and shape the way in which the project might be delivered.

The recommended option from this process for a two site solution (stand alone septic tank in the vicinity of Seaview Terrace, and a new treatment works located away from the current site) means they can potentially progress with a degree of independence. Regulatory and planning permissions for each site are currently being sought, which will enable a clearer scope to be finalised and delivery plans to be agreed. The expected timeline for delivering each site is being prepared for further engagement with the community and will be informed by feedback from the community, regulators and planning authorities.

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Contents

1. PURPOSE ...... 2 2. BACKGROUND ...... 2 a. Original Project ...... 2 b. Community Experience - Project Delivery ...... 2 c. Works Performance ...... 3 3. DEVELOPMENT OF A NEW PROJECT ...... 3 a. Initial Optioneering ...... 4 b. Community Stakeholder Group ...... 4 c. Options Appraisal ...... 4 4. CONCLUSION ...... 5 Glossary ...... 1 1. Introduction ...... 2 1.1 Background ...... 2 1.2 Current Drivers ...... 2 1.3 Current Wastewater System ...... 3 2. Project Needs ...... 8 2.1 Project Needs ...... 8 2.2 Environmental Regulation Requirements ...... 9 3. Investigation and analysis ...... 12 3.1 Sewerage Networks ...... 12 3.2 2011 Flow Survey ...... 13 3.3 Development of a new Network Model ...... 13 3.4 Further Network Investigation and Remedial Works ...... 14 3.5 Site Investigations – Soakaway ...... 14 3.6 Marine Modelling ...... 15 3.7 Growth ...... 15 ...... 15 3.8 Community Engagement ...... 15 3.9 SEPA Policy Requirements ...... 16 4. Decision Making Criteria ...... 17 5. Option Development ...... 20

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5.1 Defining Options ...... 20 5.2 Summary of Options ...... 21 5.3 Option Cost Summary ...... 23 6. Outcome of Option Appraisal ...... 25 7. Conclusion ...... 28 8. Appendix 1 – Overview of Each Option Considered ...... 29 8.1 The ‘Do Nothing’ Option (Zero Option) ...... 30 8.2 Zero Option A: Membrane Works with Storm and UV treatment at Balvicar and Septic Tank at Seaview ...... 31 8.3 Zero Option B: Membrane Works with parallel treatment system and UV Treatment at Balvicar and Septic Tank at Seaview ...... 33 8.4 Zero Option C: Membrane Works and UV Treatment at Balvicar and Surface Water Separation and Septic Tank at Seaview ...... 35 8.5 Summary of Zero Options A, B and C ...... 37 8.6 Option 1: Replace existing WWTW with Septic Tanks / Submerged Aerated Filter / UV at the existing site ...... 39 8.7 Option 1A: Replace existing WWTW with Septic Tank / Submerged Aerated Filter / UV Located Away from Existing Site ...... 42 8.8 Option 2: Replace existing WWTW with septic tank / reed bed / UV system ...... 48 8.9 Option 2A: Replace existing WWTW with septic tank / reed bed / UV system in alternative location ...... 51 8.10 Option 3: Transfer to Seaview ...... 54 8.11 Option 3A: Transfer to Seaview with additional UV treatment ...... 59 8.12 Option 3B: Transfer to Seaview with alternative outfall location ...... 62 8.13 Option 4: Disaggregation of treatment ...... 64 8.14 Option 5: Transfer discharge outwith SWPA ...... 65 9. Appendix 2: Network Investigations and Surface Water Removal ...... 67

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Glossary

CAR Controlled Activities Regulations

CSO Combined Sewer Overflow

DWF Dry Weather Flow

FFT Flow to Full Treatment

FST Final Settlement Tank

MPA Marine Protected Area

OSPAR Oslo and Paris Convention

PE Population Equivalent

RB Reed Bed

SAC Special Area of Conservation

SAF Submerged Aerated Filter

SEPA Scottish Environment Protection Agency

SIR Site Investigation Report

SNH Scottish Natural Heritage

ST Septic Tank

SW Scottish Water

SWPA Shellfish Waters Protected Area

UV Ultra Violet Disinfection

UWWTD Urban Waste Water Treatment Directive

WFD Water Framework Directive

WLC Whole Life Cost

WWTW Waste Water Treatment Works

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1. Introduction

1.1 Background

The Isle of Seil sits within the Firth of Lorn off the west coast of Scotland. It is bounded to the east by Seil Sound, a designated Shellfish Water Protected Area, and to the south and west by the Firth of Lorn Special Area of Conservation (Figure 1). There are also specific shellfish harvesting areas through Seil Sound and to the northern part of the island.

Figure 1: Isle of Seil and the local marine designated areas

1.2 Current Drivers

The EU Urban Waste Water Treatment Directive (UWWTD) stipulates that wastewater agglomerations receive an appropriate level of treatment prior to discharge.

Currently, raw sewage from Seaview Cottages is collected and discharged untreated via a short sea outfall directly into Easdale Bay. This has been the case for many years and, hence requires first time treatment provision. The project is included within Scottish Water’s 2015-21 Regulatory Business Plan.

Scottish Water operates a wastewater treatment works at a site in Balvicar on the east of the island, discharging to the shellfish water in Seil Sound. Serving customers predominantly along the eastern coast, this was installed in 2008-9 to replace a number of raw private discharges, but has struggled to deliver the expected performance. As a consequence of a significant risk of spills from the network it must be changed or modified to consistently capture and treat sufficient flows within the network to protect the quality of the shellfish water and the environment.

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1.3 Current Wastewater System

1.3.1 Sewerage Network

The wastewater flows on the island are almost exclusively domestic foul and surface water drainage. Recent studies and network models have demonstrated there is some infiltration into the network, but this is not atypical for this type of sewer network, where long lengths of sewer serve relatively few properties. In 2008-9 Scottish Water delivered a project to provide first time sewerage and treatment on the Island of Seil to address the problem of raw private discharges to the designated shellfish water.

The scheme was delivered as part of Scottish Water’s ‘First Time Provision’ programme within the regulatory investment period that ran from 2006-2010. Specifically, the project was promoted in agreement with regulators to address the problem of private raw sewage discharges into Seil Sound, which is designated as a Shellfish Waters Protected Area.

The specific objectives were to connect and treat the sewage from 159 properties which equates to a ‘population equivalent’ (PE – a design figure based on the occupancy in the area) of 350. The pre- existing raw private discharges were therefore removed as part of this work to address the risk to the shellfish water.

A sewerage network was installed to capture all flows within the connected agglomeration. Small networks such as the Isle of Seil need also to be sized to provide a minimum flushing rate to reduce the risk of blockages. The network was designed for a flow rate of up to 6 litres per second (beyond which, the network may spill) to support this, which exceeded the level of flow understood to be required at the time of installation.

In practice, actual flows have often approached this level – beyond what was used in designing for the works, however this has been accommodated within the network – evidenced in limited spills upstream of the treatment works.

The system is a combined surface water and foul sewerage network, meaning that it collects both the surface water runoff from properties (roofs and hard standing areas within the curtilage of a property) and the domestic wastewater from properties mainly in Clachan and Balvicar. This is conveyed via a series of pumping stations and sewers to a treatment works at Balvicar where it is treated and discharged to Seil Sound, with overflows at strategic locations (pumping stations). A schematic representation of a combined system is shown in Figure 2.

Figure 2: schematic of a combined system capturing surface water and foul drainage

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At Clachan Seil the overflows are located at the pumping stations which only operate in the event of pump failure (e.g. power or mechanical) or in extreme rainfall events. There is a final Combined Sewer Overflow (CSO) at the head of the treatment works which, as demonstrated in flow reports, is the main source of the excess spills from the network.

Figure 3 below shows a simple schematic of the sewerage system installed, with a chain of 4 pumping stations (PS) transferring flow from the northern end of the catchment at Atlantic Bridge (Clachan Bridge Pumping station) to the works at Balvicar Bay. The southern part of the network has two pumping stations taking flow from the main part of the village.

Seil Sound

Figure 3: Schematic of the pumping station and treatment works arrangement installed during the original first time sewerage provision project

1.3.2 Treatment Works

Under the EU Urban Wastewater Treatment Directive (UWWTD), a community of the size of Seil would require ‘Appropriate Treatment’, defined as a primary form of treatment, but also that the works must take account of other relevant designations.

For the works constructed at Balvicar and discharging to Seil Sound, appropriate treatment means that the bacteriological load discharged to the shellfish water would need to support the standards for discharge to Shellfish Waters Protected Areas.

The technology chosen to provide treatment at Balvicar in 2008-9 was a membrane bioreactor, a relatively innovative technology. This was selected as it provided a high level of treatment to the influent sewage to meet the needs of the shellfish water, and also benefitted from a relatively small land footprint. At that time, it was considered to be the most appropriate means to treat wastewater to a high standard in small communities, effectively providing both secondary and tertiary treatment to the effluent. Following primary settlement, the treatment is provided in two ways:

1. Barrier treatment – the very small pore size of the membranes prevents the pass through of material larger than the size of the pores, including bacterial components of wastewater 2. Biological treatment and breakdown of the organic load – provided by a biomass growing within the membrane system

In terms of design capacity, based on the understanding of the catchment at that time, the works was licensed and hence designed to meet a continuous flow of 3 litres per second.

The Water use Licence issued by SEPA under the Controlled Activities Regulations (hereafter ‘the licence’) is described as a ‘two-tier’ licence with standards set for the receiving water. Two tier refers to the different ways of assessing performance for parameters such as Biochemical Oxygen Demand

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(BOD). There is a lower level of performance that must be met throughout the year with performance measured against a look up table of permissible exceedences, and an upper tier which is effectively the backstop standard for the water body.

The standards set are:

 BOD – lower tier 20mg per litre, upper tier 50mg per litre  Total Suspended Solids – 100mg per litre  pH 5-9

There is no bacteriological standard; instead the works must be capable of treating up to 3 litres per second through the membrane barrier treatment. 1.3.3 Operation and Performance

The WWTW receives flows from within the network to the works inlet pump station. Flows are passed forward through 6mm and 1mm screens to remove gross solids and debris and into two banks of membranes. These operate as parallel treatment processes, with treated effluent being combined prior to discharge via outfall to Seil Sound. As noted above, it is designed to treat 3 litres per second (l/s) – the required Flow to Full Treatment (FFT) within the licence. Flows in excess of 3 litres per second are intended to be stored in the network up to a point where they are discharged upstream of the treatment plant having passed through a 6mm screen.

Since it was commissioned, operation of the system has proven to be challenging with a significant constraint at the works in being able to sustaining the designed Flow to Full Treatment, with intervention and maintenance far above what was previously anticipated.

The technology faces two principal challenges:

1. Sustaining the required wastewater flow (FFT) - through the membrane system, with the pores in the membrane clogging more quickly than in the specification and a risk of wastewater backing up and spilling upstream of the treatment works

2. Sustaining the biomass - the living biological media that provides treatment by breaking down organic matter. As the combined sewage inflows are relatively weak there is insufficient concentration of organic material to consistently ‘feed’ the biomass

In addition, as noted previously, the flows within the network can be higher than the 3 litres per second design of the works, compounding the problem of passing the required flow through the membranes. There is a further risk that the membrane material becomes damaged over time leading to a risk of breakthrough of bacteriological element into the final effluent. These are shown in Figures 4 and 5 below.

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4: The high level of fouling (dark matter) accumulating between the membrane plates within one of the racks (removed for maintenance)

Figure 5: Physical damage to a membrane plate

A detailed analysis of the performance issues of the current site has identified numerous factors contributing to this failure to perform. All of these have been considered and optimised as far as possible within the current works specification.

In terms of the impact to the community it is further understood that the current works may present a potential nuisance to the nearby neighbours in terms of the noise. The works operates on cleaning cycles with coarse air scourers, intended to keep the membranes clear of debris, acting as a potential source of noise nuisance.

1.3.4 Optimising the current system

In parallel with the development of investment options, Scottish Water is continuing with a programme of measures to improve the operability of the sewer network and WWTW. This seeks to make the existing system work better but cannot overcome the challenge of increasing the problem that flows greater than 3 litres per second can be conveyed by the network.

Work to optimise the site has included implementation of enhanced membrane cleaning processes to help to sustain the flow through the works, and the dosing of organic load (molasses) to sustain the biomass of the works.

The challenges noted above have been the subject of further work through the engagement of

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Cranfield University’s Professor Judd in 2016, an expert in membrane bioreactors. Specifically Professor Judd was asked to review the current measures and advise of any further actions that could be taken to optimise performance. Professor Judd concluded that the actions taken by the operating staff appear to be largely appropriate for the plant given the challenges faced. He noted that whilst these remedial steps could be taken, this technology was not compatible with the combined surface water / foul wastewater within this sewerage catchment. Separating surface water is considered further within options set out later in this report.

1.3.5 Membrane Technology – Lessons Learned

Membrane technology was developed and applied to wastewater systems at a number of sites during the 2000s on the basis that it was considered a suitable technology for small communities where there may be a need for an enhanced form of treatment. This has not proven to be the case in practice in Scotland.

Membranes may continue to have an important role in some wastewater applications, and remain a proven technology for water treatment. However, given the experiences above it is now Scottish Water’s policy to replace these types of wastewater treatment plants with more reliable processes at the appropriate points within the life cycle of the asset.

We have included an option of retaining the existing membrane treatment works in this report, but for the reasons outlined above this is not a technology that we wish to continue to operate.

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2. Project Needs

2.1 Project Needs

The review has considered both separate (dual site) and combined (single site) options to address the needs, and this report sets out the work undertaken to date to identify, understand and evaluate the available options. Within the development of these options, the intention is also to retain the existing sewerage infrastructure, including pumping stations, which represents the dominant element of the previous first time sewerage investment.

As outlined earlier, this project has two key needs:

1. Provide a first time treatment service for the residents of Seaview Terrace where raw sewage is currently discharged direct to sea 2. Address the performance issues and secure a compliant wastewater service for our existing customers served by the works at Balvicar

A supplementary opportunity (where appropriate) is to provide additional capacity to potentially connect properties in Ellenabeich at a point in the future.

Summary of performance issues to be addressed:

 The network passes flow forward at up to 6 litres per second, primarily based on the design specification for the pipework to ensure a minimum capacity for flushing.  Subsequent analysis of flow through surveys, infiltration studies, and a new network model (see below) indicate the actual flows in the network are larger than previously understood  The treatment works installed was designed to meet a Flow to Full Treatment of up to 3 litres per second based on the previous understanding of anticipated flows in the network.  This mismatch means that whilst higher flows can be buffered by network storage, there is a greater risk of spilling during high rainfall.  Additionally, the membrane plant has struggled to sustain the 3 litres per second flow rate, exacerbating the spill risk.  As a consequence, there are very limited spills from the network, but significant spills recorded at the treatment works as evidenced in flow reports to SEPA.

The project must therefore

Provide appropriate treatment for the flows within the network such that:

 The wastewater system complies with UWWTD requirements for capture, conveyance and appropriate treatment of flows under normal climatic conditions – equating to a capacity of circa 6 litres per second  There are fewer than 10 significant network spills to the shellfish water per annum  Treated discharges from the public system to the shellfish water do not constrain the ability of the shellfish water to meet the required quality objectives  Treated discharges support the required Environmental Quality Standards for the receiving water body, reflected in the conditions of the discharge licence

The project must also provide first time treatment to the properties at Seaview Terrace, in compliance with the above – either as discrete stand-alone works, or in combination with those properties currently within the public system.

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2.2 Environmental Regulation Requirements

The environmental regulatory requirements for the project are centred on European Union (EU) Directives for the environment. Whilst the UK as a whole has elected to leave the EU, these directives are transposed into Scots Law and therefore remain statutory instruments that are in force in Scotland.

In terms of discharges to the water environment, regulatory standards drawn from European and other relevant legislation are generally enforced through the Water Environment (Controlled Activities) (Scotland) Regulations 2011. The Scottish Environment Protection Agency (SEPA) implements the regulations through the issuing of appropriate licences which contain the standards that must be met.

2.2.1 Urban Wastewater Treatment Directive (UWWTD)

The Urban Waste Water Treatment Directive (UWWTD) as transposed into Scots Law by the Urban Waste Water Treatment (Scotland) Regulations 1994 sets the basic needs for the collection and treatment of urban wastewaters. The UWWTD specifies the provision of an appropriate collection system and the conveyance of waste water flows for appropriate treatment prior to discharge without spilling except during heavy rainfall.

The UWWTD sets requirements for treatment according to population size by the sewer catchment. For populations greater than 2000 (discharging to freshwater and estuaries), and 10,000 (discharging to coastal waters) the UWWTD requires the provision of ‘secondary’ or equivalent treatment systems. This would generally comprise a form of primary settlement followed by secondary biological or chemical treatment.

For populations below 10,000 (coastal) and 2000 (freshwater/estuarine) the UWWTD requires that ‘appropriate’ treatment is provided. This may be a form of primary treatment or septic tank system or any other treatment system provided it, “allows the receiving waters to meet the relevant quality objectives and the relevant provisions of the Directive and other Community Directives”.

The appropriate treatment requirements of the UWWTD also place obligations for more stringent treatment systems if the area is designated as sensitive to eutrophication. In such cases the directive requires nutrient removal to meet prescribed standards.

With an assessed ‘population equivalent’ of circa 500, the population currently served, and the wider population of the Isle of Seil is well below the thresholds set out in the UWWTD as requiring mandatory secondary treatment, with the Directive instead requiring ‘appropriate treatment’. This is determined as the level of treatment required to meet local water quality needs. No waters around the Isle of Seil carry any sensitive area designation in terms of UWWTD and there is consequently no requirement to deliver nutrient removal.

With respect to the network performance, the UWWTD also requires that the sewerage system conveys wastewater for treatment without spilling except during heavy rainfall. As noted above, the network capacity is able to support this up to 6 litres per second, but this is not matched by the treatment works capacity. Increased flows beyond what was anticipated and designed for at the works (3 litres per second) means there is a risk of excessive spills prior to treatment, exacerbated by the performance issues of the membranes.

This will need to be addressed by whichever solution is delivered through this project.

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2.2.2 Water Framework Directive

The Water Framework Directive (WFD) covers inland and inshore water bodies to distance from land of 3 nautical miles. It classifies water bodies in terms of the ecological and chemical status as assessed by the appropriate regulatory authority. In Scotland, the Scottish Environment Protection Agency (SEPA) classifies and reports the status of water bodies to Europe. The status of water bodies are described across a scale of ‘High’, ‘Good’, ‘Moderate’, ‘Poor’ and ‘Bad’ in terms of the ecological condition of the environment. In terms of chemical parameters, there are ‘Environmental Quality Standards’ (EQS) that underpin the ecological status and these are used in regulation to support the ecological status.

The marine waters around the Isle of Seil are already classed as ‘High Status’ and in such cases there are no further needs to improve quality. The directive instead sets the requirement for there to be no deterioration in status. To that end, any new activities which may lead to discharges to the environment need to demonstrate that they will not breach the relevant Environmental Quality Standards for the water bodies.

2.2.3 Shellfish Waters

The designation and regulation of Shellfish Growing Waters under the EC Shellfish Waters Directive has been subsumed into the Water Framework Directive (WFD). This sets the requirements for ensuring the management of water quality and, as for WFD is implemented through CAR licensing by SEPA. The intention is to provide appropriate water quality management for the growing of shellfish through the control of microbiological and chemical parameters.

There are a number of active leases for shellfish growing harvesting (pacific oysters and mussels) in Seil Sound which are further classified under the Shellfish Hygiene Directive. The Shellfish Hygiene Directive is implemented by Food Standards Scotland and centres on bacteria levels within shellfish flesh to protect consumers.

In practical terms this means that SEPA will consider the requirements of the shellfish growing waters and set CAR licences as appropriate. In the case of the current works at Balvicar, the nature of the treatment system (membrane barrier) coupled with the licence requirement for 3 litres per second was intended to cover this.

2.2.4 Marine Strategy Framework Directive

The Marine Strategy Framework Directive (MSFD) sets out to promote Good Environmental Status in EU waters by 2020. This applies at a scale of large water bodies that would be reported under the Oslo-Paris (OSPAR) convention – i.e. North Celtic Sea, North Atlantic etc. The Firth of Lorn to the south and west of the Isle of Seil is already at Good Environmental Status under this directive, further supporting the High Ecological Status of the inshore waters under the Water Framework Directive.

2.2.5 Birds and Habitats Directive

The Firth of Lorn is designated a Special Area of Conservation (SAC) for the qualifying features of the marine rocky reef and marine mammals. It does not identify a particular species as part of this designation – it principally centres on the habitat. There is a proposed further designation for the Inner Hebrides and Minches to be a SAC for the harbour porpoise, a European protected species. The Firth is currently considered to be in favourable status in terms of the Birds and Habitats Directive.

In order to continue to protect the status of the Firth, any new discharges into the area will be assessed in terms of the ability of the water body to continue to meet the Environmental Quality standards (EQS) as set in the Water Framework Directive (WFD). Scottish Natural Heritage (SNH)

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have the responsibility to advise on any particular requirements for SEPA to consider in setting appropriate discharge standards.

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3. Investigation and analysis

To support the development of options and the decision making process there has been extensive work to investigate various aspects that will need to be considered in identifying and evaluating the suitability of options. This includes the performance of the current sewerage network and site investigations on the island and of the marine environment.

3.1 Sewerage Networks

In combined sewer systems as on the Island of Seil, the components of flow are as follows:

 Domestic foul flows (dominant continuous drainage)  Trade effluent from non-domestic/industrial customers (practically zero)  Statutory surface water drained from the curtilage of properties (major component in this case)  Infiltration – groundwater ingress that will occur in the majority of networks (though is relatively small in this network)  Non statutory surface – roads and other drainage

The design of sewerage systems and treatment works is generally undertaken on the basis of standard calculations of flow and loads from the population to be served1. From this a value of the Dry Weather Flow (DWF) is determined; the average flow that might be expected during a dry period. The network is then sized based on typical rainfall for the area and the treatment works capacity set to meet a minimum Flow to Full Treatment (FFT), effectively the flow that the network and treatment works should be able to accommodate and fully treat during normal climatic conditions.

The ability to meet the FFT requirements can be compromised if there is excess flow in the system (e.g. through infiltration), or because of problems in sustaining the FFT through the works. The system was designed for surface water and foul wastewater, and in order to determine if the actual flows in the network are now presenting a problem a series of investigations are required to understand several potential sources.

3.1.1 Surface Water

Statutory surface water is rainfall and snow melt which enters the sewers through roof and road drainage. More modern developments have separate foul and surface water systems, however in older systems – including within individual properties - it was common to connect both to a combined sewerage system. This is the situation in the Island of Seil.

During the connection of new properties and extension of the sewerage scheme in 2008-9, it was deemed not practical or cost effective to retrospectively separate the properties that were being connected to the extended sewerage collection system. Most of these connections tied in the drainage from the properties being connected upstream of the raw outfall pipe or septic tank, hence the combined surface and foul flows were collected.

3.1.2 Infiltration and Saline Intrusion

Infiltration is ground water which can enter the sewerage system through cracks in pipes, joints, and chambers. Small volumes of infiltration at multiple points within the network can have a large

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cumulative effect on flows and influence the operation of sewer overflows. Infiltration can be costly to detect and rectify and is assessed by measuring the DWF and night flows in the system.

Saline intrusion is the infiltration of seawater into sewers in similar ways to groundwater at coastal edges. It may also cover high tides backing up through outfalls and overflows, and overtopping sea walls and entering the sewers through road drains and manhole/chamber covers.

Salinity testing has confirmed that saline intrusion is not present in the Clachan Seil and Balvicar sewerage network. The majority of the network sits above tidal ranges and much of the pipework sits in rock trenches which reduces the risk of saline intrusion into this network.

3.1.3 Non-Statutory Surface Water

Non-statutory surface water includes land drains and watercourses which may have been connected to sewers e.g. via culverts. Sewers are not designed to carry such flows and they can significantly affect sewer and treatment capacity and capability, and the premature operation of overflows.

These flows would be generally be highlighted by higher than expected dry weather and night time flows, which are not a characteristic of this network.

3.2 2011 Flow Survey

Given concerns raised at the risk of spills from the works, following installation the performance of the sewerage networks was explored through work to evaluate the flows in the system and the sources of potential ingress. This work (Clachan Seil and Balvicar Flow Survey Report, Mott MacDonald, 2011) involved the establishment of flow monitors to evaluate the flows and integrity of the network as part of investigations into the causes of spills at the treatment works.

This work concluded that there is not significant groundwater infiltration, and there are no indications that non-statutory surface waters (e.g. culverted watercourses) are a problem in the network.

The report did identify some small areas of ingress and sealing of manholes to be addressed, which was completed, however statutory surface water coupled with foul flows are the dominant flows in the network. The rainfall response of the system confirmed that significant roof and property curtilage drainage is connected within the network which. As a consequence, the flows can be greater than the current design Flow to Full Treatment capacity of the works (3 litres per second), exacerbated by the performance problems at the membrane plant and the inability to sustain this level of performance. This will need to be considered and accommodated in any future system.

3.3 Development of a new Network Model

In order to support outline design work for the option development, and as the existing sewerage network is being substantially retained, technical consultants were engaged to develop a new network model for Seil. A network model records the sewerage network as built, includes factors for all of the expected flows within the network and determines the range of hydraulic flow conditions that might be expected. This can then be used to determine the size of any treatment system required to capture and treat all of the flows under normal climatic conditions.

Once the model has been developed it needs to be verified using real data. Initial verification work used the flow monitoring undertaken during the 2011 survey noted above, however in 2016 Scottish Water constructed 7 additional flow monitoring chambers at key points within the network. The purpose of this is to refine the data and optimise the size of any storage or pumping required as part of a new solution.

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The review, calibration and model verification process is substantially complete and has largely addressed the flow discrepancies. Scottish Water is satisfied that the network model replicates the actual performance of the network, subject to some minor modifications. This has enabled design assumptions to be confirmed, however further work will increase confidence in the model outputs as they are used to progress the detailed design. Data continues to be gathered and this will support the re-calibration of the network model, and detailed design assurance of the scheme to be progressed following optioneering.

The key conclusion is that a revised Flow to Full Treatment is required greater than the 3 litres per second capacity of the existing works. It is estimated that the treatment capacity will need to be enhanced to 6 litres per second to deal with the range of surface and foul flows within the network to allow recovery of the storm storage capacity within the network as the measured storm induced flows as measured contribute to a larger flow than estimated at the time the original scheme was implemented. Coupled with additional storage of circa 75m3, the increased Flow to Full Treatment will minimise spill risks to fewer than 10 per annum in line with shellfish water requirements.

3.4 Further Network Investigation and Remedial Works

A survey undertaken following the installation of the 7 new network flow meters over summer 2016 has identified approximately 10 locations in two of the pumping station catchments that would benefit from remedial works to address low level infiltration visible in manhole chambers. This work will be completed over the next few months, but is not significant in the context of the range of surface water flows in the system.

Additional infiltration was identified in the network through the modelling and flow measurement work, however the level of infiltration is not atypical of rural networks where the length of sewer is relatively high compared with the number of properties served. It is concluded that the most cost-effective means to deal with this is to ensure that the network, storage and treatment works are appropriately sized to prevent spills, and this was presented to the community stakeholder group at the technical meeting on 21st March 2017.

3.5 Site Investigations – Soakaway

A land based discharge was explored as a potential option, associated particularly with the transfer of treatment to an inland site. In order to understand the opportunity and the development of any solutions, site and ground investigations were required to understand (among other things) the soil types, depth of bedrock and stability of the area. This indicates if the consideration of soakaways rather than discharge to watercourses is likely to be feasible.

Where appropriate, local ground conditions have been investigated and generally identified shallow soils, rock substrata and the risk of runoff for options involving soakaways.

Site Investigation Reports have been compiled to help understand any construction constraints as ground conditions can be a significant factor in the cost and difficulty of a particular option. This survey was consolidated as a single survey covering the numerous options and sites under consideration, and indicated a low probability that soakaways would be suitable.

During engagement with the community stakeholder group in January 2016, Scottish Water agreed to further work to assess the viability of a soakaway. Geotechnical experts from Amey were appointed to review the site geology. This concluded that the geology may be able to support a soakaway at several locations across the island based on the permeability of the strata, and outputs were presented at the technical meeting on 21st March 2017.

At the meeting it was recognised that development of any potential soakaway must ensure that any

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proposed location would not result in visual impact, effluent ponding, pollution of watercourses, or odour issues. During discussions it was recognised that, whilst geological data supported a number of possible locations across the island, it was likely that these would be hindered by a thin topsoil and rock formation, and hence be unsuitable.

An aerial survey of the potential locations relative to Option 1A (the preferred treatment solution for the community) has reinforced the impact of rock formations and land availability, presence of standing water and the potential for surface water pollution. In Scottish Water’s view (and by agreement with the Technical Expert) this makes the viability of a soakaway in the vicinity of Option 1A extremely difficult; not only in terms of addressing the concerns highlighted above but also in terms of meeting the requirements of SEPA Policy (WAT-RM-04).

Scottish Water will not therefore pursue a discharge soakaway solution for a site landward of the B844.

3.6 Marine Modelling

All new and modified discharges to sea are required to meet the provisions of SEPA Policy in relation to achieving a minimum number of dilutions (WAT-SG-11: Modelling discharges to coastal and transitional waters) and where the discharge may impact on other water users the discharge is required to meet the provisions of WAT-RM-13: Microbiological discharges.

Scottish Water engaged Anderson Marine to undertake studies at two locations in Easdale Bay to assess the length and depth of outfall required to meet the provisions of SEPA Policy. This report was submitted to SEPA for their review and comment, confirming that it meets their requirements and specifications for such work.

The dispersion modelling concluded that options to transfer flows to a septic tank type treatment and discharge to Easdale Bay through an outfall appropriately positioned to deliver the required dilution levels would meet the required environmental standards and could support compliance with ‘Excellent’ Bathing Water standards at the shoreline.

3.7 Growth

A further driver considered within some of the options in this report is the potential to support future growth on the island. Whilst a basic level of ‘future proofing’ will be built into all of the solutions to ensure that a reasonable level of future development is not constrained, options for a combined solution with a treatment system discharging to Easdale Bay could also be sized to accommodate a future connection for Ellenabeich.

Such provision of an expanded septic tank capacity at Seaview to accommodate the properties at Ellenabeich, which predominantly has private raw discharges, would require a larger treatment with the associated sewer connection and an extended outfall. Any future such plans would need to be agreed with SEPA and the Scottish Government as a new first time sewerage scheme.

3.8 Community Engagement

Scottish Water has sought to ensure that the opinions, view and feelings of the community have been captured through a variety of activities including two community information events, and the setting up of a community stakeholder group chaired by the constituency MSP Michael Russell. The group is made up of both community and elected representatives.

Community information events were held at Seil Island Hall on 21st June 2016 and a further session

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on 16th August. At these sessions Scottish Water canvassed the opinions of the community and on initial proposals.

In addition, community stakeholder meetings have taken place on 6th June 2016 and 16th August 2016, and a technical meeting involving the Technical Expert and representatives of the community stakeholder group on 21st March 2017. The latest community meeting took place on 24th April 2017.

3.9 SEPA Policy Requirements

Discussions with SEPA have enabled a presentation of their policy and licensing requirements for the options under discussion, and whilst not exhaustive these are summarised in the following text provided by SEPA below (WAT-RM refers to Regulatory Methods for water regulation, available on SEPA website, www.sepa.org.uk):

SEPA Policy Requirements:

For a discharge to Balvicar Bay:

 Any proposal to replace the existing MBR plant at Balvicar with an alternative treatment technology e.g. as per Option 1/1A would constitute a modification to the existing arrangements requiring an application to be submitted for a technical variation to the existing licence (WAT-RM-09 refers)  Any such application would require to be advertised (WAT-RM-20 refers)  Scottish Water would be required to demonstrate that any modification does not compromise the attainment of GOOD status in the SWPA (The Scotland River Basin District (Quality of Shellfish Water Protected Areas) (Scotland) Directions 2015 refers)  Scottish Water would be required to demonstrate a CSO spill frequency of no more than 10 significant spills pa into the SWPA unless it can be demonstrated that the relevant microbiological standard can be achieved via numeric modelling (WAT-RM-13 refers)  WAT-RM-03, WAT-RM-07, WAT-SG-11 also refer

For a discharge to Easdale Bay:

 Any proposal to replace the existing MBR plant at Balvicar with an alternative treatment technology discharging to Easdale Bay e.g. as per Option 3 would require Scottish Water to submit an application for a new discharge (WAT-RM-03, WAT-RM-13, WAT-RM-20 and WAT-SG-11 refer)  Any CSO/EO facility retained for a discharge to Balvicar Bay or other locations would require Scottish Water to submit new applications (WAT-RM-03 and WAT-RM-07 refer)  Any such applications would require to be advertised (WAT-RM-20 refers)  Scottish Water would be required to demonstrate compliance with “sufficient” bathing standards insofar as they apply to a non-designated waterbody (WAT-RM13, specifically App.3 refers)  Any discharge to Easdale Bay has the potential to impact on the Firth of Lorn SAC and consideration must be given to SEPA’s Natural Heritage obligations (Nature Conservation Procedure for Environmental Licensing refers)

For a discharge west of Ardencaple:  Any discharge to a new location west of Ardencaple would require Scottish Water to submit an application for a new discharge (WAT-RM-03, WAT-RM-13, WAT-RM-20 and WAT-SG- 11 refer)  Any CSO/EO facility retained for a discharge to Balvicar Bay or other locations would require Scottish Water to submit new applications (WAT-RM-03 and WAT-RM-07 refer)  Depending on the outfall location there may be a requirement to consider risk of impact to the SWPA and shellfish harvesting areas at the north end of Seil Island (WAT-RM-13 and WAT-SG-11 refer)

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4. Decision Making Criteria

Scottish Water has applied specific criteria across the options to determine the relative strength of the option against the following set of criteria.

These criteria had previously been presented to the community via the Stakeholder Group (16th August meeting), and were subsequently applied to evaluate the options.

The decision making criteria are contingent on two key factors; pre-requisites that must be met in order to progress or the option will be discarded and variable factors which may enable differentiation of the strengths and weaknesses of options.

Each option in the report considered and evaluated in terms of the following criteria:

 Customer Experience  Customer Service  Certainty of Performance  Construction and Timing  Future Flexibility, Resilience and Sustainability  Whole Life Cost

The intention is to demonstrate to stakeholders, the Scottish Water Board and any independent reviewer or other interested party that we have taken a reasonable and balanced approach to the selection of the most appropriate treatment solution for the Island of Seil.

1) Pre-requisites

These are elements that must be achieved to consider the option viable – we would not proceed if these are not met:

 Meet the Directions from Scottish Government as laid out in Appendix 1 of the Scottish Water Delivery Plan 2015 to 2021. o “Easdale Isle of Seil - provision of appropriate Ww Treatment”

 Deliver Compliance with Environmental Licence Conditions o We demonstrate this through appropriate evidence based science and meeting the Regulatory Framework as laid out by SEPA (and other statutory consultees)

 Fully comply with Scottish Water Health and Safety requirements

2) Variable Factors

Customer Experience ‘Customer Experience’ considers the disruption that options have on our customers’ lives or communities, over the short term (typically during the construction period) and in the longer term (by considering the level of input required to operate and maintain the solution).

Customer Service Customer service considers the additional benefits over and above project deliverables in relation to the services we provide customers.

Certainty of Performance Certainty considers the level of confidence that the option will definitely work (tried and tested) against an option that is expected to work (maybe considered innovative for this application) but may have

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some risk of failure.

Construction and Timing Construction and Timing considers the value to Scottish Water of the relative ease of construction and potential value to SW or customers of delivering the benefits of an investment ahead of the plan target dates.

Future Flexibility, Resilience and Sustainability Future flexibility and resilience considers how an option may allow ease of future extension to meet demand changes, or an option that creates increased service resilience within the asset base. Sustainability assesses the carbon impact, environmental impact and societal impacts of options

Whole Life Cost

As a public body, we must understand and demonstrate the Whole Life Cost of any decision we make – i.e. the combination of capital and operational costs over a 25 year planning horizon.

To provide some further insight into how the options will be assessed, the following table outlines the extremities of each of the variable criteria.

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Extremities of Assessment

Low Strength High Strength

Major customer disruption during construction. No customer disruption during construction.

Customer Experience On-going significant operational and maintenance activities necessitating high levels of site activity. Minimal or no operational / maintenance activities required

Customer Service Significant additional customer benefits affecting a very large number of No additional customer benefit customers

Certainty of High risk of not delivering the performance required. Brand new process / Certain to deliver the performance required. Process/technology known to SW. Performance technology for this application. Not yet adopted in any industry Considerably experienced in operation for this application

No significant construction activity required Large and complex solution with a number of demanding technical issues –

likely to include tunnelling and other specialist activities. Construction and Timing High confidence in meeting plan milestone dates

No confidence in meeting plan milestone dates Variable Criteria Variable

No potential to expand and constrains future options and ability to grow. Highly expandable or growth allowance already built in. Land available on SW Future Flexibility, owned site. No special licence required. No power required. Very low carbon Resilience and Very high carbon footprint. Relies on use of scarce resource. Single source footprint. Relies on use of abundant local resource. High number of suppliers Sustainability supplier resulting in potential unreliability in future. to provide future reliability.

Whole Life Cost (WLC) Significantly higher WLC than other viable options Lowest WLC

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5. Option Development

5.1 Defining Options

5.1.1 Appropriate Treatment

One of the statements often used in seeking to identify the correct solution is “Appropriate Treatment”. As noted earlier in this report, this is used in legislation such as the Urban Waste water Treatment Directive (UWWTD) to cover treatment systems that do not have to meet prescribed standards within the directive. The Isle of Seil is below the prescribed population thresholds for full secondary treatment, hence ‘appropriate treatment’ requirements apply.

To that end, the other water quality drivers must be taken into account – in this case the Water Framework Directive (which includes the Shellfish Waters Protected Areas) and Birds and Habitats Directive, which would require the water quality objectives to be met for any system.

5.1.2 Option Selection

Whilst option development has been underway for some time, the level of detailed design is reflective of the relatively early stage in optioneering. At this stage in a selection process Scottish Water would generally consider a range of options and outline costs to help identify a preferred option for more detailed design, specification and costing.

In selecting options to support the long term sustainable solution for the island, the technical objectives are to:

1. Capture and provide Flow to Full treatment (FFT) for all connected flows on the island – effectively enhancing the current 3 litres per second FFT at the existing works to a system that can treat up to 6 litres per second (>6 x Dry Weather Flow). This is based on current population equivalents and network model, and in line with regulatory expectations and Scottish Water design standards

2. Provide the appropriate level of treatment to support water quality objectives in any receiving water

3. Provide first time sewage treatment for Seaview Terrace

Options have therefore been selected to meet the objectives of these statutory drivers.

Feasibility

Scottish Water has primarily focussed on options that could support the statutory requirements, and appear feasible. However there are two other options that we considered that may not be practicable. These are a full surface water separation, and the disaggregation of treatment within the existing sewerage network. These are included as they have been a key point of interest for the community that we have been asked to explore further.

Additionally, the stakeholder group and community have specifically asked for further consideration of a ‘zero option’ centred on the objective to try and make the existing treatment solution work at Balvicar. Variants of this are therefore considered within the option appraisal.

Discharge to Soakaway/Land

There has also been consideration of whether a land discharge may be feasible via a soakaway for

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several of the options. Site investigations at the Seaview Terrace location do not support such an approach owing to the proximity of the bedrock. Similar challenges are faced outwith these areas from our understanding of the site investigations to date, and from our current information we do not believe this is feasible.

Following a stakeholder technical meeting at which the geological and practical issues were discussed, Scottish Water has determined that a soakaway discharge solution will not be progressed for any option located landward of the B844.

An explanation of the ‘’Do Nothing’ or Zero Option and potential scope, along with the other options considered is contained within Appendix 1. 5.2 Summary of Options

Table 1 below presents a summary of the options considered (noting the soakaway is still to be considered further). There are 12 options overall, spread across six principal types of option, with sub-options through some of them. These start with a ‘zero’ option based on retaining the existing works, of which there are 3 variants (A, B and C) and are summarised below.

Option Existing Clachan Balvicar STW Seaview Terrace

0A Retain existing works with additional treatment New 20m3 septic tank with existing outfall of storm discharges and UV disinfection

0B Retain existing WWTW and provide additional New 20m3 septic tank with existing outfall side stream treatment with UV disinfection

0C Retain existing WWTW, remove surface water, New 20m3 septic tank with existing outfall and provide additional UV treatment

1 Replace existing works with septic tank, New 20m3 septic tank with existing outfall submerged aerated filter, final settlement tank and UV disinfection, discharge via existing outfall

1A Variant on Option 1 with WWTW relocated to New 20m3 septic tank with existing outfall landward side of B844 to reduce the impact to the local community, discharge via existing outfall

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Option Existing Clachan Balvicar STW Seaview Terrace

2 Replace existing works with septic tank, reed New 20m3 septic tank with existing outfall bed and UV disinfection, discharging via existing outfall;

2A Variant on Option 2 – relocate reed bed to New 20m3 septic tank with existing outfall landward side of road to reduce the impact to the local community with discharge to existing outfall (with UV)

3 Transfer Option. Replace existing WwTW with Existing outfall removed and Seaview modified pumping station, storage and rising network connected to new septic tank main. Transfer flows to new septic tank capable of serving the island. (240m3) located at Seaview site. New outfall to meet environmental standards

3A As Option 3 Variant on Option 3 with provision of additional UV disinfection

3B Variant on Option 3 with relocation of As Option 3 outfall to a location to the south of the reef features

4 Disconnect the current agglomeration and New 20m3 septic tank with existing outfall provide multiple septic tanks in Clachan Balvicar network

5 Transfer Clachan / Balvicar flows to North or New 20m3 septic tank with existing outfall South of the current area via new (circa 4km) sewer, dependent on designations and further engagement

Each option is described in more detail in Appendix 1

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5.3 Option Cost Summary

During the earlier stages of engagement with the community, SW provided high level indicative costs associated with the initial options. As part of this phase of optioneering, we have undertaken a more detailed cost estimation of the options, which take account of ground conditions based on the site surveys, engineering challenges, and our supply chain prices, together with forecast maintenance demands. As such, the costs presented here are substantially higher than the indicative figures that may have been quoted to date, noting that it has previously been made clear that these were indicative costs that had not been through full cost estimation.

In finalising this options report, costs have been assessed by Scottish Water’s Costing Services function with the costing tools used to support Scottish Water’s capital delivery. These are current estimates and they are intended to enable options to be appropriately compared. The cost will be refined as we develop detailed designs.

The costs to date also need to be taken into account. At just over £0.5m, this includes the costs of site investigations, network modelling, dispersion studies, marine modelling and flow monitoring, as well as the project overhead. The level of investigation to date in this project is higher than would normally be incurred for other similar projects at this stage of development.

Key sources of cost increases in remaining options:

 Option 3 - original ST site was by the main road in the field opposite Seaview cottages. It has now been moved to the old quarry site out of view and has the benefit of improving this brown field area. This has added more sewer length and increased the length of the access track  Increased risk provision in the delivery of Option 3, noting the potential for extended outfall, timelines and management effort to support delivery. Option 3B now takes outfall into deeper water to ensure compliance within the 100m mixing zone edge boundary from the initial point of discharge and Option 3A has been modified to the southern outfall deep water location to ensure compliance within 15m from the initial discharge point.

 The removal of the existing exposed sea outfall at Seaview has been included within Option 3. It is also proposed to reduce the visual impact of the existing site (new small kiosk) and removal of redundant equipment plus infill and planting in the current membrane plant site

 The detailed site investigation has been used to make a better estimate of the pipeline route and the volume and hardness of any rock excavation required

 By directional drilling this outfall we have minimised the environmental impact on the reefs, over the original surface lay and concrete mattress option costing

 Indexation inflation on original costing

 Option 1A – increased detail on the design development of this option has highlighted a greater length of access track and site re-profiling work. There will be a need for detailed environmental screening to support planning applications (this option needs 3 separate applications), costs are based on less developed design than Options 3 variants. Utility information such as power supply availability and costs have not yet been confirmed.

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Summary of Cost Estimates

Cost summaries are presented in two ways; capital cost for construction and Whole Life cost, taking account of future capital maintenance demands. As noted above cost presented here are current estimates intended to support decision-making and will require further refinement in the development of the project.

Option Capital costs Whole Life Cost

0A £2.2m £3.1m

0B £2.7m £4.5m

0C £5.2m £5.4m

1 £4.6m £3.7m

1A £5.6m £5.9m

2 £4m £3.6m

2A £5.2m £5.4m

3 £4.6m £5.3m

3A £4.8m £5.5m

3B £4.8m £5.5m

4 £6.6m £7.1m

5 £4.9m £5.6m

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6. Outcome of Option Appraisal

Using the framework described in section 4 above, each of the options has been assessed based on the criteria set out. No weightings have been applied to any of the factors and the scores were assigned following debate and challenge within Scottish Water.

Option 0A Option 0B Option 0C Option 1 Option 1A Option 2 Option 2A Option 3 Option 3A Option 3B Option 4 Option 5

Score Score Score Score Score Score Score Score Score Score Score Score Criteria Customer Experience 2 2 1 2 3 2 3 4 4 4 1 4

Customer Service 1 2 2 3 3 3 3 3 5 4 1 4 Certainty of Performance 3 3 2 5 5 3 3 5 5 5 1 5 Construction and Timing 3 3 1 3 3 3 3 3 3 3 1 2 Future flexibility, Resilience and Sustainability 3 3 3 4 4 4 4 5 4 5 2 4

Whole Life Cost 1 3 1 4 4 4 4 5 4 5 3 3

Total Score 13 16 10 21 22 19 20 25 25 26 9 22

Table 1 –Outcomes from option scoring

The above table is translated into a ranking of options below, with the discarded options greyed out:

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Overall Option Existing Clachan Balvicar STW Seaview Terrace Ranking

3B Transfer option. Replace existing works Variant on Option 3 with relocation of 1 with modified pumping station and rising outfall to point to south of reef main, Transfer flows to new septic tank features (240m3) located at Seaview site. New outfall to meet environmental standards

3 Transfer option. Replace existing works Existing outfall removed and 1 with modified pumping station and rising Seaview network connected to new main, Transfer flows to new septic tank Septic Tank capable of serving the (240m3) located at Seaview site. New island. outfall to meet environmental standards

3A Transfer option. Replace existing works Variant on Option 3 with provision of 1 with modified pumping station and rising additional UV disinfection main, Transfer flows to new septic tank (240m3) located at Seaview site. New outfall to meet environmental standards

1A Variant on Option 1 with WWTW relocated New 20m3 septic tank with existing 2 to landward side of B844, discharge to outfall existing outfall

5 Transfer Clachan / Balvicar flows to North New 20m3 septic tank with existing 3 or South. outfall

1 Replace existing works with Septic Tank, New 20m3 septic tank with existing 4 Submerged Aerated Filter, Final outfall Settlement Tank and UV disinfection, discharge via existing outfall

2A Variant on option 2 – relocate reed bed to New 20m3 septic tank with existing 5 landward side of road with soakaway outfall adjacent to the reed bed or on the golf course (no UV) or with discharge to existing outfall (with UV)

2 Replace existing works with Septic Tank, New 20m3 septic tank with existing 6 Reed bed and UV disinfection outfall

0B Retain existing WWTW and provide New 20m3 septic tank with existing 7 additional side stream (SAF/ FST filter) outfall and additional UV treatment

0A Retain existing WWTW with additional New 20m3 septic tank with existing 8 treatment of storm discharges (Spruce outfall Filter) & UV

0C Retain existing WWTW, remove surface New 20m3 septic tank with existing 9 water, and provide additional UV outfall treatment

4 Disaggregated septic tanks in Clachan New 20m3 septic tank with existing 10 Balvicar network outfall

Table 2 –Ranking of options following scoring.

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The table is split into two parts. The first 4 options (technically 2 options as Option 3 has 3 sub- variants) are the options Scottish Water considers technically feasible, able to be delivered and would provide an acceptable level of service and environmental performance.

Options ranked below this are considered to be impractical, not feasible or to present cost challenges beyond what is reasonable, and these will not be considered further. The base Option 1 is also included in the discarded options as there is a reasonable expectation that the works could be located as set out in Option 1A, thereby addressing a key community acceptability element.

The discharge to the northwest is discarded owing to problems securing landowner agreement for the pipeline route.

Option 1A is viable as it relies on proven technology and would be acceptable to Scottish Water, the community and to SEPA.

Option 3 is viable, and in Scottish Water’s view would satisfy the environmental needs, however this option is firmly rejected by the community and the MSP. It would face fierce opposition, delay, technical challenges, legal escalation and further negative feeling in the community.

Whilst Option 1A is more expensive, on balance it is believed to have the best opportunity to successfully deliver the outcomes and maintain community support.

The key areas of risk to Option 1A that need to be locked down include securing the relevant regulatory licences, permissions to build (planning and land purchase) and final cost appraisal once the detailed design is completed.

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7. Conclusion

The most favourable option according to the decision making criteria set out within this document is likely to be a variant of option 3, namely the transfer scheme with a septic tank at Seaview.

However, recognising the importance of community acceptability, the conclusion of the report is that Option 1A (tertiary treatment relocated to landward side of B844 and discharging to Seil Sound and separate small septic tank at Seaview Terrace) be progressed as the preferred option. This is subject to gaining planning and regulatory permissions and final cost appraisal.

Option 3 would only be reconsidered in the event that there are unforeseen problems that prevent the delivery of Option 1A.

Option 1A is believed to have the best opportunity to successfully deliver the necessary regulatory outcomes and maintain community support.

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8. Appendix 1 – Overview of Each Option Considered

The following sections outline the options that have been considered, outlining the scope, site specific challenges, costs and pros and cons of the option as we understand it.

It should be noted that any figures contained within these options are indicative to help understand what the option might look like.

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8.1 The ‘Do Nothing’ Option (Zero Option)

The starting point for any project undertaken by Scottish Water is to determine whether there is a ‘Do Nothing’ solution (accept the current situation) or whether we could operate the system in a different way to achieve the necessary outcome without having to build anything new.

The ’Do Nothing’ option in this case does not exist. Even with the activities we have undertaken over the last year to optimise the performance of the works, the current treatment arrangement at Balvicar WwTW needs enhancing to treat a flow up to 6 litres per second. Therefore, whilst the performance of the works at lower flow levels is generally good, leaving the works in its current form is not a viable option.

We have considered options that retain the existing treatment works but look at what enhancements would be required to secure full and reliable compliance across the increased levels of flow up to 6 litres per second. We have called these the ‘Zero’ options.

The Zero options do not address the necessary first time treatment provision for Seaview Cottages and we would therefore require a separate localised treatment arrangement to provide treatment at Seaview.

Three sub options have been investigated within the ‘Zero’ option. Each option would retain the existing works on the existing site, but would require expansion to differing degrees.

The specific objectives the zero options seek to address are to either provide additional capacity to deal with the inability to pass the full flows from the network through the existing works, or to reduce the inflows to the existing works. In addition, full refurbishment of the membrane works and additional UV treatment will be required.

The Zero options are summarised as:

 Zero Option A Refurbish the existing membrane works, install additional storm treatment capacity with further UV system to treat flows beyond what the current works can support, and address problems of break through of microbes from the membrane plant.

Install a septic tank at Seaview Cottages serving only the existing properties.

 Zero Option B Refurbish the existing membrane works, install parallel sidestream treatment system through a traditional secondary treatment technology, provide additional UV disinfection to address the problems of microbial breakthrough.

Install a septic tank at Seaview Cottages serving only the existing properties.

 Zero Option C Refurbish the existing membrane works, deliver (up to 100%) surface water separation in several sub- catchments to seek to reduce the peak flows to 3 litres per second at the membrane works. Install UV disinfection to address the risk of microbial breakthrough from the membranes in the event of operational wear.

Install a septic tank at Seaview Cottages serving only the existing properties.

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8.2 Zero Option A: Membrane Works with Storm and UV treatment at Balvicar and Septic Tank at Seaview

Outline Scope

Refurbish the existing membrane works; install additional storm treatment capacity with further UV system to treat flows beyond what the current works can support, and address problems of break- through of microbes from the membrane plant. Install a septic tank at Seaview Cottages serving only the existing properties.

This option seeks to accommodate the current risk of bacterial input to the Seil sound Shellfish Water from the CSO spills as a consequence both of the inability to consistently pass the FFT, the higher flows being experienced in the network, and also addresses the risk of bacterial breakthrough from the existing membranes. It seeks to address this through a parallel storm treatment process and UV system. The main features of this option are:

 Retain existing works in the current configuration, refurbish the membranes with on-going capital replacement and future asset replacements  Separately, create a new ‘side stream’ storm treatment system to increase the overall FFT capacity at the works to 6 litres per second by capturing storm flows that cannot pass through the membrane rather than allowing them to spill  Provide further storm storage and pumping arrangements, with mechanical filtration (spruce or disc filter arrangement)  Install a new UV system downstream of the confluence of the membrane and the filtered storm outfalls to both disinfect the storm flows and guard against breakthrough from the membrane works to meet Shellfish water quality standards  Provide new 20m3 septic tank at Seaview Terrace for 10 properties discharging via either a new outfall to sea or soakaway to land

This is a novel approach – there are no other works like this in Scotland. In terms of impact, the associated works would require additional equipment to be placed on the site.

Costs

The current estimate of cost for this option is an upfront capital cost for construction of £2.2m, with a Whole Life Cost for this option (which includes the cost of future operation and maintenance) estimated as £3.1m

There are a number of pros and cons for this sub-option as follows:

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Pros – Balvicar Cons – Balvicar

o Retains the existing treatment works, o The existing membrane treatment system maximising the utilisation of the original has been shown to be inappropriate to investment this application, and retention is counter to Scottish Water’s policy of removing o Removes the need to install additional membrane works pipelines to transfer flows out with the catchment o Existing treatment process will require augmentation through side stream

treatment and UV, extending the scale of the site

o Existing nuisance concerns of the nearby community are not addressed

o Performance and maintenance challenges of the membrane system are retained

o Does not accommodate potential future inclusion of Ellenabeich

o This is the most costly option

Pros – Seaview Cons – Seaview

o Minimises impact on Seaview area o Seaview Terrace septic tank likely to be sited at current outfall on the foreshore

o Effluent discharge will still be adjacent to properties via existing outfall at Seaview

o Visible access for tanker and de-sludge with associated perception of odours at Seaview

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8.3 Zero Option B: Membrane Works with parallel treatment system and UV Treatment at Balvicar and Septic Tank at Seaview

Outline Scope

Refurbish the existing membrane works, install parallel side stream treatment system through a traditional secondary treatment technology; provide additional UV disinfection to address the problems of microbial breakthrough. Install a septic tank at Seaview Cottages serving only the existing properties.

As for Zero Option A this option would retain a refurbished membrane treatment plant, but in this case the capacity would be augmented to deal with up to 6 litres per second through the provision of a further treatment process to operate in parallel with the works. The specific features of this option are:

 Retain existing works in the current configuration, refurbish the membranes with on-going capital replacement and future asset replacements  Expand the treatment capacity of the current membrane plant, not through more membranes, but through provision of a 4.5 litres per second traditional secondary treatment plant ‘side stream’ to operate in parallel  The side stream treatment would comprise a septic tank/primary settlement stage, a submerged aerated filter (SAF) secondary treatment unit, and a final settlement tank (FST)  As for Zero Option A this would discharge to the same outfall at the membrane works, and a UV system would be constructed downstream of the confluence to provide disinfection for the side stream and address the risk of breakthrough of microbes from the membrane plant to meet Shellfish water quality standards  Provide new 20m3 septic tank at Seaview Terrace for 10 properties discharging via either a new outfall to sea or soakaway to land

This option would address the challenges in capturing all flows whilst minimising spills to fewer than 10 per annum and allow for membrane relaxation and chemical cleaning to support membrane optimisation.

However there is a risk that the option would exacerbate the current problems of retaining and feeding the biomass to support biological treatment in the membranes. It further complicates the operation of the plant which is essentially operating two parallel treatment plants on the same site.

The current estimate of cost for this option is an upfront capital cost of £2.7m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £4.5m.

An assessment of the pros and cons of this option are as follows:

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Pros – Balvicar Cons – Balvicar

o Retains the existing treatment works, o The existing membrane treatment system maximising the utilisation of the original has been shown to be inappropriate to investment this application, and retention is counter to Scottish Water’s policy of removing o Removes the need to install additional membrane works pipeline to transfer flows outwith the catchment o Existing treatment process will require augmentation through storm storage, settlement and treatment and UV, extending the scale of the site

o SAF type solution will increase the land footprint of the site and bring additional disruption in the vicinity

o Existing nuisance concerns of the nearby community are not addressed

o Performance and maintenance challenges of the membrane system are retained

o Does not accommodate potential future inclusion of Ellenabeich

Pros – Seaview Cons – Seaview

o Minimises impact on Seaview area o Seaview Terrace septic tank likely to be sited at current outfall on the foreshore

o Effluent discharge will still be adjacent to properties via existing outfall at Seaview

o Visible access for tanker and de-sludge with associated perception of odours at Seaview

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8.4 Zero Option C: Membrane Works and UV Treatment at Balvicar and Surface Water Separation and Septic Tank at Seaview

Refurbish the existing membrane works, deliver up to 100% surface water separation in several sub- catchments to seek to minimise spills at the terminal CSO and sustain the ability to treat 3 litres per second at the membrane works. Install UV disinfection to address the problems of microbial breakthrough. Install a septic tank at Seaview Cottages serving only the existing properties.

This option would retain the existing works configuration, but seek to significantly reduce the surface water flows into the system from within the curtilage of existing properties to the point where the existing membrane plant can reliably operate without the need for any further treatment capacity at the site and the ensure the spills from the network are limited to below 10 spills per year as required. This would need to be achieved through extensive surface water separation projects throughout the catchment.

The assessment of the level of surface water requiring to be removed is based on a determination of the flow arriving into the network during typical rainfall time series, and assessed against the 2011 data used to build and verify the network model. This model has identified the parts of the network that would require to be addressed in order to sustain the correct pass forward flow and the storage levels required to balance these flows within the network and limit spills at the various transfer Sewage Pumping Stations (SPS).

The specific aspects of this option centre on the management of the network in sections, with the catchment divided according to pumping station ‘sub-catchments’ and analysis of the required levels of flow to be sustained to prevent spills:

The key elements in developing a solution that will limit the spill risk to <10 per annum are:

 Retain existing works in the current configuration, refurbish the membranes with on-going capital replacement and future asset replacements  Build additional UV system to manage quality in the event of microbial breakthrough on the membranes  Develop and deliver scenarios for surface water removal projects based on assessment work completed following from further analysis of the network model  For surface water separation only option, this may require disconnection of the surface water element from the majority of properties currently connected to the system:

o 60% impermeable drainage removed from the Clachan North Pumping Station and CSO o 60% impermeable drainage removed from the Clachan Brookside Pumping Station and CSO o 100% impermeable drainage removed from the Balvicar Cottages Pumping Station and CSO o 80% impermeable drainage removed from the Clachan – Balvicar Pumping Station and CSO

in total our calculations indicate that we would have to disconnect the surface water element of greater than 130 of the properties that currently flow to the Balvicar WwTW. There is a further option where the further use of storage to manage peak flows would reduce the need to remove as much surface water as follows:

 50% impermeable drainage removed from the Clachan North, Clachan Brookside, Balvicar Cottages, and Clachan – Balvicar Pumping Stations and CSOs. Further potential consideration of works capacity, to operate in tandem with the additional storage to minimise risk of spills to fewer than 10 per annum.

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 Provide new 20m3 septic tank at Seaview Terrace for 10 properties discharging via either a new outfall to sea or soakaway to land

The practicalities of delivering this need to be seriously considered as the scale of surface water removal that would be required is considerable.

This option will be very intrusive and disruptive for every property identified for surface water removal. For example, we would need to separate out the roof drainage at the downpipes and any hard standing gullies within the curtilage of the properties and create a new mini-drainage system for surface water only within the property owners land.

Where surface water is removed there will be a requirement for appropriate discharge locations; either to land (given site ground conditions this option will be limited on many properties), or to a nearby watercourse. The latter may result in multiple property boundary crossings and an assessment of the impact of surface water disposal on adjacent properties.

In legal terms Scottish Water has limited statutory powers to remove property curtilage surface water from its existing combined sewers, but it can be achieved in agreement with individual householders and on new developments by provision of separate public surface water sewers (to achieve SUDS objectives). Whilst we will be happy to engage in discussions with the community on the willingness to undergo this process, we believe it is unlikely that all surface water removal opportunities can be delivered.

There would also need to be further consideration of maintenance and management of individual surface water pipes and systems on third party land not vested with Scottish Water unless they are serving multiple properties. Modifications would also need Local Authority Building Control authorisation and approval.

Overall, whilst we strongly agree with the principle of surface water separation to reduce the volumes of combined sewage that we have to pump and treat, the practicalities of retrofitting this in existing drainage systems are very complicated and the scale of what we need to reduce to get close to the level of flow to minimise network spills and that could be reliably treated is extensive and may not be practicable.

For the purposes of cost estimation it is important to note that at this stage in development, the level of cost certainty with the development of surface water removal options is low as there are a significant number of site specific issues that require to be assessed for each of the properties.

Costs

The current estimate of cost for this option is an upfront capital cost of £5.2m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £5.4m.

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The pros and cons of this option are set out as follows:

Pros – Balvicar Cons – Balvicar

o Retains the existing treatment works, o The existing membrane treatment system maximising the utilisation of the original has been shown to be inappropriate to investment this application, and retention is counter to Scottish Water’s policy of removing o Removes the need to install additional membrane works sewers to transfer flows outwith the catchment o Existing treatment process will still require augmentation through UV system o Promotes a ‘sustainable drainage’ to guard against breakthrough, extending approach on the island the scale of the site o Potential significant customer impact o Seeks to address the core problem of the from the delivery of this solution, ability to sustain flows at the treatment uncertainty regarding future surface works through treatment of water system maintenance predominantly foul flows with limited wet weather impacts o Uncertainty that sufficient property owners would willingly agree to separation

o Existing nuisance concerns of the nearby community are not addressed

o Does not accommodate potential future inclusion of Ellenabeich

o Second most costly option

Pros – Seaview Cons – Seaview

o Minimises impact on Seaview area o Seaview Terrace septic tank likely to be sited at current outfall on the foreshore

o Effluent discharge will still be adjacent to properties via existing outfall at Seaview

o Visible access for tanker and de-sludge with associated perception of odours at Seaview

8.5 Summary of Zero Options A, B and C

Having considered these options, whilst they are taken forward for scoring against other options, Scottish Water has concerns that the retention of the existing works may not be practicable in certain cases, or would present a viable long term solution.

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Further, they do not address the concerns of some parts of the community regarding the existing site, and retain the high maintenance/operational demands of the existing membrane technology.

Zero Options A, B and C are therefore discarded.

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8.6 Option 1: Replace existing WWTW with Septic Tanks / Submerged Aerated Filter / UV at the existing site

Option 1 comprises two separate treatment elements:

1. Purchase additional land adjacent to the existing site and construct a new treatment process comprising septic tanks (ST), submerged aerated filter (SAF), final settlement tank and UV disinfection, discharging via the existing outfall. This arrangement is shown in figure 7 below.

2. Provide new 20m3 septic tank at Seaview Terrace for 10 properties discharging via the existing outfall

Figure 7 – schematic of the potential location of this option

Outline Scope

Existing Balvicar WWTW Site:

The basis of this option is to provide a replacement solution at the existing Balvicar site that would deliver the needs of reliability and certainty of outcome to minimise the risk that further interventions would be required.

The basis for the design of this works is centred on the need to provide an alternative to the current membrane works with a high confidence that all of the necessary standards could be achieved.

The proposed design is consistent with some other treatment works that Scottish Water operates in small communities, and in particular mirrors the installation at Kishorn to protect the Loch Kishorn Shellfish Water Protection Area, although local site constraints will dictate the final layout.

The capacity of the works would be increased to support 6l/s Flow to Full Treatment. The work undertaken to review the flows in the network and develop a new network model has given us confidence in this initial design figure and further refinement of the model will give increased confidence in the figures to be used for detailed design.

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The treatment system will comprise a septic tank to provide primary settlement, a submerged aerated filter to provide secondary biological treatment, and a UV disinfection unit to meet the requirements of the shellfish water, discharging via the existing outfall.

To support the increased capacity there will be an upgrade to the existing WWTW inlet pump station.

Collectively this will ensure sufficient flows are treated to the required standard and that the risk of spills is reduced to fewer than 10 per annum in keeping with shellfish water requirements.

Seaview Terrace

A stand-alone septic tank sized to 20 cubic metres to accommodate 10 properties at Seaview terrace would be installed locally to that site with a discharge to sea centred on existing outfall, pending further investigation.

Costs

The current estimate of cost for this option is an upfront capital cost of £3.7m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £4.6m.

The relative pros and cons of Option 1 are set out below:

Pros – Balvicar Cons – Balvicar

o Removes the need to install additional o Large site footprint 50m x 135m pipeline to transfer flows out with the approximately catchment o Visible elevated treatment units SAF, o Potential reduction in site noise blower kiosk, UV unit and control panels compared with the existing works o Site will require security fencing and screening with a risk of exacerbating negative customer feedback on the current site

o On-going risk of managing discharge compliance to Seil Sound SWPA

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Pros – Seaview Cons – Seaview

o Minimises impact on Seaview area o Seaview Terrace septic tank likely to be sited at current outfall on the foreshore

o Effluent discharge will still be adjacent to properties via existing outfall at Seaview

o Visible access for tanker and de-sludge with associated perception of odours at Seaview

o Does not accommodate potential future inclusion of Ellenabeich

Summary

Option 1 is feasible and lower cost, however a viable alternative site has been located and in view of the community acceptability of retaining a new works at the existing site, this option is discarded. In doing this, regard will be given to Argyll and Bute Council planning advice which advises this should be the least environmental sensitive solution taking regard to the sensitivities of the site and surrounding area, and provides guidance on greenfield and foreshore development. Details of this can be found in Scottish Government planning policy guidance and Argyll and Bute Council local development planning guidelines. This will further direct the appropriate level of impact assessment etc to be carried out in securing planning agreements.

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8.7 Option 1A: Replace existing WWTW with Septic Tank / Submerged Aerated Filter / UV Located Away from Existing Site

There is a variant to Option 1, which seeks to remove the works from the existing site and locate the new treatment works to the landward side of the B844 (see also Option 2a for the proposed location) away from the immediately visible site at Balvicar.

The existing site would be converted to a storm storage and pumping station, with the majority of the visible assets removed. The access gates and areas of hard standing for maintenance, tank cleaning and safe operation would be retained, along with a number of control kiosks.

Outline Scope

The new works would follow the same specification as for Option 1 above, and while this site has more complexities than other options these are not believed to be insurmountable. Additional needs for this option are:

 Excavation and construction of an access road to build, operate and service the new works, which may take the route identified above owing to our understanding of land access constraints. Up to 10,000 tonnes of imported material, with associated vehicle movements would be required to support this.  Levelling of the proposed site to address 12m level difference  Pumping station and storm tank conversion at the existing site would be sized to balance flows within the network (75m3) and to enable the appropriate flows (6l/s) to be passed to the treatment works  A new sewer would be constructed under the existing public roadway and via fields to the potential site of the works  A new final effluent pipe would be constructed in parallel with the new foul sewer, to take the UV disinfected effluent down to the current sea outfall for discharge

Land would require to be purchased and the site would be located in the hillside shown in figure 8. There was consideration of the opportunity to discharge to a soakaway, however following further investigation and engagement with the community and the Technical Expert, and in reference to SEPA policy, Scottish Water does not believe this is a reasonable option. The existing outfall is therefore proposed to be retained.

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Figure 8 – location and aspect of the potential SAF plant located on the hillside

Associated pipework would need to be created to carry the flow pumped from the modified pumping station at the existing Balvicar site. A potential route for this is shown in Figure 9.

Figure 9 – The pipework route to convey the discharge back via the existing outfall into Seil Sound is marked in red

Access to both construct the works and to support operation and maintenance would need to be

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created through the provision of a new access road. Based on our understanding of the land availability and topography this would be likely to follow the route shown in Figure 10.

Figure 10 as for the reed bed option (Option 2), the potential route of the access road.

Figure 11 – indicative location relative to Balvicar Post Office.

Figure 11 above represents the indicative location for the works. The height of the SAF plant would be circa 5m, and the overall site layout and size similar to that shown in Option 1 for the existing site at Balvicar, the visual aspects have been investigated using a drone to determine that there would not be an unacceptable visual impact, and this will form part of further design detail and planning if this option is to be progressed.

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For the construction of the access road, the route shown in Figure 10 takes account of our understanding of the potential land access difficulties in the area.

The appearance of the hillside site may be similar to another Scottish Water treatment works at Kishorn:

This option also requires a new septic tank (20m3) to be constructed at Seaview Cottages in a lay by that will be built in the location of the existing outfall which will be retained. It is likely it would be located in the following areas:

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Costs

The current estimate of cost for this option is an upfront capital cost of £5.6m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £5.9m.

The relative pros and cons of Option 1A are set out below:

Pros – Balvicar Cons – Balvicar

o Removes the need to install additional o Dual site operation with the retention of pipeline to transfer flows outwith the the existing site as a pumping station and catchment storm storage facility

o Remove the nuisance impact from the o Land purchase and a large site footprint existing site consistent with option 1 (circa 50m x 135m) o Minimises impact on Seaview area o Visible elevated treatment units SAF, o Reduced (compared with option 1) blower kiosk, UV unit and control panels visibility to the local community – albeit in more remote location

o Reduced visibility of desludging and o Site will require some security fencing maintenance activities and screening in an otherwise clear area

o Access road creation will increase local impact of the solution on landscape, and will result in significant local vehicle movements to import construction material

o On-going risk of managing discharge compliance to Seil Sound Shellfish Waters Protected Area

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Pros – Seaview Cons – Seaview

o Minimises impact on Seaview area o Seaview Terrace septic tank likely to be sited at current outfall on the foreshore

o Effluent discharge will still be adjacent to properties via existing outfall at Seaview

o Visible access for tanker and de-sludge with associated perception of odours at Seaview

o Does not accommodate potential future inclusion of Ellenabeich

Summary

Option 1A is retained as the preferred option for development on the basis of a discharge via the existing outfall at Balvicar.

This option also includes provision of a new 20m3 Septic Tank and Layby on the existing outfall in front of Seaview Cottages. This will retain the existing outfall at this location.

A soakaway is not considered viable at either site.

In addition, as noted in the summary for Option 1, regard will be given to Argyll and Bute Council planning advice which advises this should be the least environmental sensitive solution taking regard to the sensitivities of the site and surrounding area, and provides guidance on greenfield and foreshore development. Details of this can be found in Scottish Government planning policy guidance and Argyll and Bute Council local development planning guidelines. This will further direct the appropriate level of impact assessment etc to be carried out in securing planning agreements.

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8.8 Option 2: Replace existing WWTW with septic tank / reed bed / UV system

Whilst Option 1 provides a traditional WWTW to replace the existing membrane works, it has been recognised that this will require a larger footprint with process structures above ground which will be visually intrusive (circa 5m elevation). Option 2 was therefore proposed as a potentially less industrial-looking option through the deployment of reed beds which could be considered to have a more naturalised appearance.

Performance of such systems are less secure than conventional treatment, however Scottish Water has deployed this technology in several locations in Scotland, where they work well under the right circumstances.

Option 2 considers two separate treatment elements:

1. Retain the existing Clachan Balvicar WWTW site, purchase additional land and construct a new treatment process comprising a septic tank, reed bed and UV disinfection, discharging via the existing outfall.

2. Provide new 20m3 septic tank at Seaview Terrace for 10 properties discharging via existing outfall as per Option 1 above.

Outline Scope

As with Option 1 above, the basis of design is drawn from the approved Scottish Water Standards and Specifications for the purpose of providing wastewater treatment. However it should be noted that Scottish Water has not previously utilised the combination of technologies that would be employed here to discharge to a Shellfish Water Protected Area.

This option has been suggested and reviewed in response to community perception that this would provide a preferable, greener, and less visual treatment solution compared to other, more complex treatment options.

The operational intensity of this option may be less than for the SAF etc. option presented earlier as it is a largely passive system, however will still require primary treatment, pumping and disinfection stages. It is further anticipated that the rock excavation to create the base for the reed bed would increase the carbon intensity of construction.

Whilst there will need to be further engagement and agreement with SEPA on the discharge standards to be applied to any of the potential solutions, it is recognised that Reed Bed performance can be less certain than more traditional forms of treatment. Scottish Water has some experience of reed bed systems, however in order to progress this solution there would need to be a particular focus on the regulatory approach to licence and regulate to a suitable discharge standard. This would need to accommodate the year round performance of the system and ensure all parties are confident in the approach.

All remaining elements of Option 2 are as per Option 1 above.

The potential layout of this option is shown in Figure 12 below.

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Figure 12 – potential layout of the reed bed and associated treatment processes at the existing site.

Costs

The current estimate of cost for this option is an upfront capital cost of £3.6m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £4m.

The relative pros and cons of Option 2 are set out below:

Pros - Balvicar Cons - Balvicar

 Further pipeline across the island is  Largest site footprint 40m x 200m avoided approximately, will need additional land and potential for significant rock  Passive treatment system (reed bed) excavation with reduced maintenance demands and operational intensity, but intervention and  SEPA agreement on final effluent licence maintenance still required for other condition to SWPA elements  Retains activity at current site in terms of  Potential to reduce extent and impact of tankering and maintenance security fencing

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Pros - Seaview Cons - Seaview

 Reduced disruption to Seaview residents  Seaview Terrace septic tank likely to be sited at current outfall on the foreshore

 Effluent discharge will still be adjacent to properties via existing outfall at Seaview

 Visible access for tanker and de- sludge with associated perception of odours at Seaview

 Does not accommodate potential future inclusion of Ellenabeich

Summary

Option 2 is discarded as a reed bed is not considered viable for this site.

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8.9 Option 2A: Replace existing WWTW with septic tank / reed bed / UV system in alternative location

As for Option 1, there is a variant to Option 2, which seeks to remove the works from the existing site and locate the reed bed system to the landward side of the B844, away from the immediately visible site at Balvicar.

Outline Scope

In terms of an outfall, as for option 1A, Scottish Water has reviewed this option in the context of both a soakaway and a gravity discharge leading back to the existing Clachan Balvicar WWTW outfall.

The viability of a soakaway solution is believed to be low based on the Site Investigation Report as the area is waterlogged and initial borehole surveys have identified the strata as being peat and broken rock overlying impermeable bedrock. The lack of suitable drainage may lead to pollution, significant further waterlogging and odour risks.

Through discussion with the community, and on the basis of site and geological reports, Scottish Water has concluded that a soakaway solution will not be progressed for this option based on the limitations presented by land availability, impact of rock formations and potential for environmental impact. As such, the existing outfall would be retained.

All remaining elements of Option 2A are as per Option 2 above. The existing site would be converted to a storm storage and pumping station, with the majority of the above ground assets removed. The access gates and areas of hard standing for maintenance, cleaning of storm tanks and safe operation would be retained, along with some control kiosks.

Land would require to be purchased and the site would likely be located in the hillside area shown in Figure 13 below:

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Figure 13 – Potential location and route of access road for the hillside option

The pipework to carry pumped flows from the modified pumping station that would be created at the existing Balvicar site, and to gravity feed the treated effluent to the current outfall into Seil Sound is shown in Figure 14.

Figure 14 – pipe tracks to carry flow to and from the works.

Costs

The current estimate of cost for this option is an upfront capital cost of £5.4m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £5.2m.

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The relative pros and cons of Option 2A are set out below:

Pros - Balvicar Cons - Balvicar

 Further pipeline across the island is  Two site operation – pumping station avoided and treatment works

 Removal of principal source of  Largest footprint (circa 40m x 200m) nuisance at Balvicar, reduce extent with further access roads. of fencing at existing Balvicar site  Constructed reed bed will need  More remote site – reduced impact significant rock excavation

 Reduced disruption to Seaview  Additional site and access (including residents road) infrastructure to maintain

 Further SEPA engagement required on licence condition to shellfish water if direct discharge (with UV)



Pros - Seaview Cons - Seaview

 Reduced disruption to Seaview  Seaview Terrace septic tank likely to residents be sited at current outfall on the foreshore

 Effluent discharge will still be adjacent to properties via existing outfall at Seaview

 Visible access for tanker and de- sludge with associated perception of odours at Seaview

 Does not accommodate potential future inclusion of Ellenabeich

Summary

Option 2A is discarded as it is not considered viable for this site and is less attractive than the SAF solution in 1A.

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8.10 Option 3: Transfer to Seaview

Option 3 takes a very different approach with the combining of the treatment for the Island of Seil to a single site located in the abandoned quarry across from Seaview Terrace. This would discharge via a new tunnelled outfall into Easdale Bay to a depth that will achieve the necessary environmental standards.

The existing site at Balvicar would be converted to a pumping station and storm storage tank and a new transfer sewer constructed to pass flows to the new works at Seaview. The new works at Seaview would be designed as a Septic Tank solution with the configuration and outfall location designed to meet the appropriate standards.

Outline Scope

The specific elements contained within Option 3 are as follows:

 Construct new pumping station at Clachan Balvicar WWTW operating at 6 litres per second, and remove redundant above ground assets; provide appropriate storm storage to limit risk of spills to fewer than 10 per annum.  Retain existing Balvicar discharge outfall as a CSO operating per shellfish water needs  Construct new pumped sewer rising main from the existing site (as converted to a pumping station) across to the south of Seaview Terrace to transfer flows  Construct a new 240m3 Septic Tank (ST), sized for the maximum flow from the current connected properties with the addition of Seaview Terrace. We would also size the tank arrangements to be able to accommodate Ellenabeich if required at some point in the future.  Connect Seaview Terrace drainage to new ST via new small pumping station and rising main.  Outfall to Easdale Bay to be constructed through directional drilling to an appropriate point in Easdale Bay to meet requirements of receiving water

The potential site of the septic tank and the pipe route from the existing site is shown in Figure 15.

Why a Septic Tank?

In terms of the requirement to provide ‘Appropriate Treatment’ in the context of the needs set out in legislation, and to meet SEPA policy, a population the size of Seil discharging to coastal areas would require primary (septic tank) treatment as a minimum standard. Treatment would normally be enhanced to meet further water quality and environmental needs as appropriate.

In relation to preventing pollution and adverse environmental impact and classification of water bodies a number of environmental quality parameter limits are set in SEPA policy and regulatory requirements. These limits are impacted by the available initial dilutions (which are a function of the water depth above the outfall) and secondary mixing in the vicinity of the outfall. The design of outfalls seeks to remove visual appearance of any new outfalls (in terms of surface boil and the wider fresh water/ salt water mixing plume).

Secondary treatment is aimed at principally reducing biological oxygen demand, where there is a lack of available dilution or at sensitive sites where elevated ammonia / phosphate may harm fish or lead to issues such as algae and excessive aquatic plant growth. In this case environmental quality limits can easily be achieved well within the allowable 100m mixing zone edge.

Tertiary treatment (UV or chemical disinfection) is provided where there is recognised activity and water usage – in particular designated bathing waters and shellfish waters. RM13 recognises that where it can be designated as specific recreational usage (economically justified recreational water use in a specific unique area – ref to Appendix 3) it may be appropriate to assess the waters against the sufficient bathing water standard.

Marine modelling has shown that septic tank treatment with a discharge point located at a suitable

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point within Easdale Bay, and for the rate of flow from the works, would satisfy the required water quality and SEPA policy needs, subject to agreement. This includes consideration of the SEPA view that consideration be given to achieving the standards of the Bathing Waters Directive at the shoreline in front of Seaview Terrace. The removal of the raw discharge at Seaview Terrace and replacement with a septic tank treatment and seabed discharge to meet SEPA dilutions policy represent an enhancement to the existing situation, even with the flows from Balvicar.

Details have been provided on the base option 3, which is based on a 2.44m depth of outfall and pollutant load based on Dry Weather Flow. (Note at higher flows the pollutant load remains constant as the foul flow is mixed with freshwater from property roofs and hardstanding areas). So whilst being volumetrically higher the total final effluent pollutant load does not increase in proportion to the flow and essentially adds to the dilution and mixing arrangement. The Septic Tank sizing under all Option 3 variants have been sized at > 2 times the minimum sizing (100m3) required by Scottish Water to ensure adequate sludge storage and settlement well beyond the 6l/s base design flow. This treatment capacity provision allowed flexibility in the final detailed design to allow increased the pass forward flow from Balvicar to reduce spills at this location or the conversion of the overflow from a CSO to and EO.

Two further variants were looked at an outfall further to the south and into deeper water 5.09m water depth (one with no UV and one with UV treatment). Both show compliance with “good” bathing water quality standards within the 100m and 10m respectively. These options both fully address concerns raised by the stakeholder group should RM13 recreational sufficient bathing water requirements be applied to the new discharge at Easdale bay.

We would not generally consider a higher level of treatment, for example creation of a major secondary treatment works, for a coastal discharge that was not directly into a water designated for a bacterial standard. However options 3A and 3B consider supplementary treatment/disinfection, or alternative outfall location to provide more assurance.

The potential arrangements for the septic tank within the quarry, outfall and the route of the pumping main is shown in Figure 15 below.

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Figure 15 – potential layout at Seaview for the septic tank and outfall, and the potential route of the transfer pipeline.

A further option, instead of the outfall to Easdale Bay is the creation of a soakaway adjacent to the site.

The viability of a soakaway solution has been provisionally explored through Site Investigations, however initial borehole surveys have identified the ground conditions are not favourable owing to the shallow depth of soil above the bedrock.

A soakaway is therefore unlikely to be viable and hence discharge via a new outfall is the likely discharge solution for this option.

All other aspects of the Clachan Seil and Balvicar sewer network, including wastewater pumping stations, will remain unchanged.

The existing WWTW will be de-commissioned and process equipment removed from site. The MBR cells will be in-filled and planted; and the security fence replaced by simple post and wire fencing. A small kiosk will be installed for the new pump and screen control panel.

The former quarry site at Seaview will be levelled for the installation of a small pumping station with control kiosk to enable connection of flows to the new ST. New access will be created to allow maintenance activities (including tankering) and operational visits to be undertaken.

The new ST would be sized to enable further development; including the connection of the properties at Ellenabeich should this be viable or required at a point in the future.

Construct a new outfall, positioned such that a minimum of 50x initial dilutions in the receiving water are achieved as per SEPA policy. This can be achieved with an outfall 194m long (from the septic tank) discharging at a depth of 3.75m below Mean Low Water Springs, with an approximate distance of 100m from the shoreline. The initial Anderson Marine dispersion report was based on a 2.44m depth, supplementary modelling data is available to demonstrate the impact of flows on the visual plume modelling outcomes.

Marine Modelling has confirmed the situation with respect to the dispersion in Easdale Bay, especially in relation to coliform bacteria and achieving the requirements of SEPA’s relevant Regulatory Method document (RM-13, available on SEPA’s website). It would further support bathing water standards at the shoreline.

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Potential impact on the designated features of the Birds and Habitats Directive Special Area of Conservation and Marine Protected Area (SAC/MPA) would need to be accommodated and minimised by directionally drilling the outfall, and the specific seabed conditions would be taken into account to ensure the outfall would not emerge onto the sea bed in immediate proximity to reef features.

With respect to the water quality standards, SEPA will determine final effluent quality standards to be achieved to ensure that the water quality in the vicinity of the outfall is not adversely impacted by the new discharge. The SAC designation and any other relevant factors would be considered in setting this standard.

Costs

The current estimate of cost for this option is an upfront capital cost of £5.3m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £4.6m.

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The relative pros and cons of Option 3 are set out below:

Pros - Balvicar Cons - Balvicar

 Direct risk is removed from the Shellfish  Significant pipeline needs to be laid Water Protected area, noting the CSO across farmland retained at the site  Outfall from new ST is into SAC/ MPA  Removes the current noise nuisance risk leading to further scrutiny of the at the existing works, with most above appropriate discharge standards ground assets removed  Concern expressed by stakeholder group  Non-complex treatment with low that effluent is being treated to a lesser operational risk standard than at present, notwithstanding the enhanced dilution.  Intrusion and nuisance risk from desludging etc. is minimised  Perception that community benefit/ impact simply moved to a less populous area

Pros - Seaview Cons - Seaview

 Raw discharge removed, replaced with  Significant pipeline needs to be laid solution that supports bathing water across farmland standard  Outfall from new ST is into SAC/ MPA  ST is located in brownfield former quarry leading to further scrutiny of the site, away from properties and visually appropriate discharge standards well screened with a low visual footprint from any aspect  Directional drilling of outfall minimises impact on qualifying features, but  Removal of existing outfall discharge point will need to be carefully positioned  Non-complex treatment with low operational risk  Rock excavation will be required

 Concern expressed by stakeholder group that effluent is being treated to a lesser standard than at present, notwithstanding the enhanced dilution.

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8.11 Option 3A: Transfer to Seaview with additional UV treatment

A modification to Option 3 takes further account of the indication from SEPA that Bathing Water standards would require to be met at the shoreline. This retains all of the features of Option 3, but includes an additional secondary filter stage and UV disinfection of the effluent. Whilst the dispersion study indicates that bathing water standards could be met without this additional treatment stage, it is included here for further consideration.

This is a relatively novel treatment arrangement, but a full process guarantee is now available from Scottish Water’s suppliers for this treatment Option. This can present a problem with setting a numeric bacteriological discharge standard to be met at the outfall, and any progression of this would need to be based on the evidence of recreational water usage to enable areas of usage and the benefits of disinfection to be better identified.

Whilst Marine Modelling has demonstrated that the Bathing Waters standards could be met along the shoreline, UV disinfection will significantly reduce the extent of the mixing zone that would be required. It is anticipated that the removal of the raw outfall at Seaview Terrace and replacement with this option would eliminate the local bacterial impact from the raw outfall. The good bathing water boundary on the southern outfall with and without UV treatment is highlighted below;

Costs

The current estimate of cost for this option is an upfront capital cost of £5.4m, with a Whole Life Cost

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(which includes the cost of future maintenance) estimated as £4.8m.

The relative pros and cons of Option 3a (additional to the statements in Option 3) are set out below:

Pros - Balvicar Cons - Balvicar

 Direct risk is removed from the Shellfish  Significant pipeline needs to be laid Water Protected area, noting the CSO across farmland retained at the site  Outfall from new ST is into SAC/ MPA  Removes the current noise nuisance risk leading to further scrutiny of the at the existing works, with most above appropriate discharge standards ground assets removed  Concern expressed by stakeholder group  Non-complex treatment with low that effluent is being treated to a lesser operational risk standard than at present, notwithstanding the enhanced dilution.  Intrusion and nuisance risk from desludging etc. is minimised  Perception that Community benefit/ impact simply moved to a less populous area

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Pros - Seaview Cons - Seaview

 Raw discharge removed, replaced with  Significant pipeline needs to be laid solution that supports bathing water across farmland standard  Outfall from new septic tank is into SAC/  ST is located in brownfield former quarry MPA leading to further scrutiny of the site, away from properties and visually appropriate discharge standards well screened with a low visual footprint from any aspect  Directional drilling of outfall minimises impact on qualifying features, but  Removal of existing outfall discharge point will need to be carefully positioned  Non-complex treatment with low operational risk  Rock excavation will be required

 Further treatment of the ST effluent  Concern expressed by stakeholder group would enhance performance in terms of that effluent is being treated to a lesser bathing water standards beyond what will standard than at present, notwithstanding already be achieved through dispersion the enhanced dilution.

 Increased operational and maintenance impact

 Going beyond the standards that would normally be required for this type of discharge would increase carbon emissions and cost for limited benefit

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8.12 Option 3B: Transfer to Seaview with alternative outfall location

A further variant of Option 3, retaining all of the existing features, is to extend and site the outfall to the south of the immediate marine reef features. This would increase the dilution and dispersion, providing a level of further protection to the water body.

This Option could also be further revised to include spruce filter and UV disinfection per option 3A if necessary to further enhance bathing water level quality.

Costs

The current estimate of cost for this option is an upfront capital cost of £5.4m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £4.8m.

Additionally, if this were combined with option 3A through the inclusion of spruce filter and UV, the Whole Life Cost would increase by circa £300-400k

The relative pros and cons of Option 3 are set out below (additional to the statements associated with Option 3):

Pros - Balvicar Cons - Balvicar

 Direct risk is removed from the Shellfish  Significant pipeline needs to be laid Water Protected area, noting the CSO across farmland retained at the site  Outfall from new ST is into SAC/ MPA  Removes the current noise nuisance risk leading to further scrutiny of the at the existing works, with most above appropriate discharge standards ground assets removed  Concern expressed by stakeholder group  Non-complex treatment with low that effluent is being treated to a lesser operational risk standard than at present, notwithstanding the enhanced dilution.  Intrusion and nuisance risk from desludging etc. is minimised  Perception that Community benefit/ impact simply moved to a less populous area

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Pros - Seaview Cons - Seaview

 Raw discharge removed, replaced with  Significant pipeline needs to be laid solution that supports bathing water across farmland standard  Outfall from new ST is into SAC/ MPA  ST is located in brownfield former quarry leading to further scrutiny of the site, away from properties and visually appropriate discharge standards well screened with a low visual footprint from any aspect  Directional drilling of outfall minimises impact on qualifying features, but  Removal of existing outfall discharge point will need to be carefully positioned  Non-complex treatment with low operational risk  Rock excavation will be required

 Provides a further level of dispersion and  Concern expressed by stakeholder group dilution which may increase the that effluent is being treated to a lesser acceptability of solution locally standard than at present, notwithstanding the enhanced dilution.

 Potential to install discharge beyond the minimum requirements

Summary of Option 3/3A/3B

Scottish Water considers these schemes technically viable and able to deliver the required service and environmental standards. Despite scoring highest in the evaluation criteria, these options are considered second to the preferred option 1A on the basis of community acceptability.

These options will be retained only in the event that Option 1A is not able to be delivered.

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8.13 Option 4: Disaggregation of treatment

A major departure from the provision of treatment at either Balvicar or Seaview is to fully disaggregate the catchment and provide localised treatment at the property level.

Outline Scope

The specific elements required in this solution are:

1. Disaggregation of the Clachan Seil and Balvicar sewerage network to a number of discrete local solutions throughout the catchment

2. Installation of multiple septic tanks serving smaller parts of the community, potentially at the property level

3. Provide a new 20m3 septic tank at Seaview Terrace for 10 properties discharging via either a new outfall to sea or soakaway to land as per Option 1

Costs

The current estimate of cost for this option is an upfront capital cost of £7.1m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £6.6m.

Viability

There are a number of problems associated with this solution. Whilst ST treatment is a viable option at Seaview Terrace, it does not provide a sufficient level of treatment for discharge to the Seil Sound Shellfish Waters Protected Area. It would result in a deterioration of water quality, even taking into account the current inconsistent performance of the Balvicar WTW.

Disaggregation of the agglomeration without providing an equivalent level of treatment (e.g. tertiary disinfection) is also contrary to the requirements of the Urban Wastewater Treatment Directive and may present a risk of infraction proceedings.

We do not believe SEPA or the Scottish Government would give approval to this Option as it would not support the objectives for shellfish water quality.

For these reasons Option 4 is not considered to be a realistic and viable option.

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8.14 Option 5: Transfer discharge outwith SWPA

Given the challenge of achieving the appropriate quality standards within Seil Sound, Option 5 proposes that the discharge should be taken to a point for discharge out with the designated Shellfish Water Protected Area.

Specifically, Option 5 would:

1. Replace the existing Clachan Balvicar WWTW with new Septic Tank treatment on the existing site for discharge beyond either the northern or southern boundary of the Seil Sound SWPA. 2. Provide new 20m3 septic tank at Seaview Terrace for 10 properties discharging via either a new outfall to sea or soakaway to land as per Option 1 above.

This option would require the construction of approximately 4km of new pipeline and outfall whether to the north or south of the existing site.

The coastal waters to the north of Seil Sound are part of the same SAC as Easdale, while to the south the waters are part of a Marine Protected Area. Marine modelling would be required to assess compliance with SEPA’s discharge policy (WAT-RM-13), and ensure that the discharge would not impact at the boundary of the designated SWPA.

Construction of a pipeline to the south would present potential impacts that would need to be managed within the Ballachuan Hazel Wood Scottish Wildlife Trust Reserve. Further, discussions with a local landowner whose land the pipeline would have to cross, have generated a strong resistance to this proposal making the viability of this option increasingly unlikely.

Costs

Whilst there would need to be more refinement depending on the north or south route, the current estimate of cost for this option is an upfront capital cost of £5.6m, with a Whole Life Cost (which includes the cost of future maintenance) estimated as £4.9m.

The relative pros and cons of Option 5 are set out below:

Pros Cons

 Simplified treatment and removes direct  Two septic tank sites with additional and discharge from Seil sound shellfish higher head pumping requirement water, contingent on acceptable water quality conditions  Uncertain environmental acceptability

 Reduced visual impact at Balvicar  Increased on land environmental impact from extended pipelines

 High cost relative to other options

 Landowner acceptability low

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Summary

Option 5 is attractive in that it removes the discharge from areas of concern, however landowner acceptability and the significant costs associated with an alternative route mean this option is discarded.

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9. Appendix 2: Network Investigations and Surface Water Removal

While Scottish Water will seek to manage infiltration into its sewer network, industry specifications (CESWI) for pipework acknowledge a degree of infiltration is normal. A survey of Balvicar sewers was undertaken in 2011 and confirmed that dry weather flow (DWF) was < 1 l/s. On-going investigation of flows received at the WWTW also confirms normal flow to the works is at a level which would suggest leakage within the system is minimal.

However, in order to better understand the hydraulic nature of the system, identify opportunities to reduce infiltration, and inform the detailed designed of the finalised preferred Option, Scottish Water is undertaking a number of interventions. These measures include:

 Installation of flow meters on the rising main from each wastewater pumping station (WWPS) to validate rainfall induced flows, flows transferred to the WWTW, and inform infiltration studies  Installation of a flow meter on the CSO at the WWTW to validate the frequency, duration, and volume of storm overflows  Sewer network studies to identify sources of infiltration and non-statutory surface water (land drains and culverted watercourses) which will subsequently drive sewer rehabilitation measures

A sewer model has been built and calibrated with information gathered from a rainfall gauge and from the flow meters. Validation of the model using time series rainfall simulations to ascertain how much surface water will enter the network for a given rainfall event have shown a good correlation between modelled and actual events. Flow meters will remain in place to monitor long term flows.

This data will be used to confirm storm storage requirements to ensure that there are no more than 10 significant spills each year.

The FFT in all options will be increased from 3 l/s to 6 l/s and any removal of infiltration or non- statutory surface water will only impact on the size of the storage being provided to limit spills at the Balvicar CSO. All other overflows are Emergency Overflows and do not operate as a result of normal rainfall in the catchment.

The ongoing refinement of the sewer network model gives us confidence that the proposed DWF and 6l/s FFT is appropriate and this will be used to progress the initial designs. The further refinements outlined above will be built in to the detailed design process.

It should be noted that Scottish Water has no powers to disconnect statutory surface water (roof and property curtilage drainage) and any disconnections would require the agreement of individual property owners. Work of this nature can be highly disruptive and cost between £6,000– £15,000k per property, making sure that all reinstatements are to the property owner’s satisfaction.

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