Trusted to serve Scotland KY11 8GG

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1 o Scottish Scottish Water Water Trusted to serve Scotland Trusted to serve Scotland Achiltibuie Achiltibuie Water Water Treatment Treatment Works Works Scottish Scottish Water Water Application Application for for Technical Technical Variation Variation to to Water Water Use Use Licence Licence CAR/ CAR/ L/ L/ Supporting Supporting Document Document October October Submitted Submitted by: by: Scottish Scottish Water Water Castle Castle House House 66 Castle Castle Drive Drive Carnegie Carnegie Campus Campus Dunfermline Dunfermline Fife Fife KY11 8GG

2 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CAR/ L/ ) Achiltibuie Water Treatment Works Scottish Water Application for Technical Variation to Water Use Licence CAR/ L/ Supporting Document Issue and revision record Revision Date Originator Checker Approver Description Draft September! i i 1 Final October 1

3 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CAR/ L/ ) Executive Summary Achiltibuie WRZ is a small rural zone situated in the North West Highlands on the shore of Loch Broom, 35 km North West of Ullapool. The existing water supply system extends approximately 23 km along the coastline, from Achvraie in the south to Reiff in the north, and feeds a household population of 314 in the villages of Achiltibuie, Polbain, Dornie, Altandhu, Reiff, Blarbuie and Achnahaird. Raw water is abstracted from a river intake on the Alit Ach a' Braighe, which gravitates 700 m to the Achiltibuie New WTW via a raw water holding tank. Raw water is treated using a tubular membrane plant then pumped to a CWT from which it gravitates into supply. Achiltibuie WTW has an existing Water Use Licence ( CAR Licence), CAR/ L/ , issued under the Water Environment ( Controlled Activities) ( Scotland) Regulations 2011 ( CAR). The CAR Licence was issued in 2008 and varied in 2009 and permits Scottish Water to abstract water from Alit Ach a' Braighe at a maximum rate of 309 m3/ day ( MI/ d) or 84, OOm3/ year ( 84 MI/ year). Following verification of the abstraction monitoring equipment in December 2016, analysis of licence compliance indicates current demand and operation of the works results in breaches of the allowable abstraction. The forecast raw water demand plus headroom) for the WRZ by the end of the current investment period in 2021 has been calculated as 456 m3/ day. Consequently there is a supply demand deficit in the Achiltibuie WRZ due to constraints under the current CAR licence. We are progressing this application with funding obtained to vary licences where the licence conditions are no longer appropriate. The 1 in 40 year Level of Service ( LOS) yield is MI/ d and the proposed new abstraction volume does not cause a deterioration of the relevant Environmental Standards. It is proposed that, in order for Scottish Water to meet its responsibilities in relation to delivering a sustainable public water supply for the local community, the abstraction from Alit Ach a' Braighe is increased from 309 m3/ day to 456 m3/day. As there is an existing annual limit condition it is proposed that the annual limit is increased to 121, 395 m3, comprised of 3 months ( 92 days) at maximum abstraction plus 9 months ( 273 days) at average abstraction. This is the supporting document for Licence Application Form G Application for Variation, applying for a technical variation to the existing licence ( CAR/ L/ ) under the Water Environment Controlled Activities) ( Scotland) Regulations 2011 ( as amended) ( CAR). The required CAR maximum allowable abstraction licence limit for Alit Ach a' Braighe is 456 m3/ day, with an annual limit of 121, 395 m3/ year. 4

4 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CAR/ L/ ) Table of contents 1. Introduction... 4 Achiltibuie Water Resource Zone Raw Water Sourcing and WTW Description Catchment Description Summary of Q& S IV investment Statement of need Current Supply Demand Balance Assessment Adequacy of current source Ecological Assessments Archaeological Assessments Water Resources Assessment CAR Licence Demand and Supply Demand Balance General Approach Supply Demand Balance Approach Analysis of current water demand Raw Water Demand Demand Forecast Current leakage Distribution leakage Conclusions & Proposals

5 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CARL/ ) 1. Introduction Achiltibuie WRZ is a small rural zone situated in the North West Highlands on the shore of Loch Broom, 35 km North West of Ullapool. The existing water supply system extends approximately 23 km along the coastline, from Achvraie in the south to Reiff in the north, and feeds the villages of Achiltibuie, Polbain, Dornie, Altandhu, Reiff, Blarbuie and Achnahaird. Raw water is abstracted from a river intake on the Allt Ach a' Braighe, which gravitates 700 m to the Achiltibuie New WTW via a raw water holding tank. Raw water is treated using a tubular membrane plant then pumped to a CWT from which it gravitates into supply. The estimated current residential population is

6 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CARL/ ) Achiltibuie Water Resource Zone 2. 1 Raw Water Sourcing and WTW Description Raw water is abstracted from Alit Ach a' Braighe burn. The water gravitates through a rough bar screen in a chamber below ground where course solids, vegetation etc, are screened. The raw water passes to a Break Pressure Tank ( BPT) approximately 300m from the abstraction point. The BPT volume is 68 m3. From here water gravitates to the WTW. At the WTW the raw water passes through 2 No. strainers to remove coarse debris. The water is then pumped through a PCI Membrane Filter made up of 2 No. membrane stacks. The permeate from the membrane filter is dosed with Sodium Hypochlorite solution before passing to a Limestone Contactor tank for ph adjustment, and on to an Instrumentation Tank. Finally the water is pumped to a twin compartment service reservoir, before gravitating to distribution. The treatment works operates automatically, based on the water level in the Service Reservoir which is situated adjacent to the BPT. 5

7 Technical Variation to CAR licence: Supporting Document 2. 2 Catchment Description At the point of abstraction, the Alit Ach a' Braighe drains a catchment area of km2, draining west from the peaks of Beinn nan Caorach and Conmheall. The highest headwater stream originates high on the upper slopes at around 550m with a stream length of approximately 3. 4 km in length from its headwaters to the abstraction intake. 9

8 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CAR/ L/ ) The catchment is entirely underlain by sandstone geology ( Applecross Formation - sedimentary bedrock formed approximately 541 to 1000 million years ago). The majority of the catchment is also characterised by superficial deposits ( Till and Morainic deposits ( undifferentiated) - Diamicton, Sand And Gravel). Soil coverage in the lower catchment is dominated by peaty gleys which cover 53% of the catchment, with the upper slopes characterised by Apline Podzols ( 47%). Land use is mostly heather moorland ( 75%) with areas of bare rock / scree on the upper peaks. As is typical with many upland Scottish catchments, the combination of impermeable soils and bedrock generates rapid runoff with no subsurface movement or storage of groundwater. Consequently the hydrological response can be classified as flashy with characteristic periods of rapid runoff during rainfall events and fast recession ( as suggested by the HOST -BFI for the catchment of 0. 15). The Ben More hydro scheme is located within the Alit Ach a' Braighe catchment. The abstraction intake is approx. 1. 2km upstream of the SW abstraction point, with water then being returned to river downstream of the SW intake. Agreement was made in 2013 that the Hydro abstraction would be limited by a hands- off flow ( HoF) of 1. 9 MI/ d ( m3/ s) which is equivalent to the LFE Q90 flow, plus the SW licence abstraction volume at the time ( MI/ d). ( Note that these are the figures from pre - application consultation with SW but would be useful for these to be confirmed from the CAR licence issued for the Hydro scheme). 7

9 Technical Variation to CAR licence: Supporting Document 2. 3 Summary of Q& S IV investment No SR15 investment or hydrological studies are planned for the Achiltibuie WRZ. 9

10 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CARL/ ) 3 Statement of need This section summarises the need for the proposal Current Supply Demand Balance Assessment The corporate reported dry year critical ( peak) period raw water demand plus headroom ( 2015/ 16) from the Supply Demand Balance ( SDB) for the WRZ is MI/ d. This assessment is based on metering at the outlet to the works during 2015/ early 2016 and includes an assessment of WTW losses, raw water mains losses and an uplift factor for a dry year and peak demand. WTW losses have been estimated at 18%. A review of the peak factors has been carried out and reduced the peak from 41% to 27%. This can clearly be seen from 2016/ 17 onwards. Some leakage investigation has been carried out which has brought about some reduction in overall demand, most notably in late Demand has been increasing again. There is no defined leakage project in the zone and it is acknowledged that relatively small leaks can have a significant impact in small zones with limited abstractions Adequacy of current source The WFD has set out standards associated with achieving good ecological status and these need to be assessed against current and future operational practice. UKTAG have developed standards which underpin the WFD and SEPA have advised SW to use these standards. The UKTAG standards provide a basis for assessing the level of abstraction associated with good ecological status, and SEPA have provided further guidance on the application of these standards Ecological Assessments Since this proposal is effectively formalising the current abstraction arrangement, then it is not anticipated that there will be any adverse effect on the surrounding ecology Archaeological Assessments The proposed variation to the CAR licence will not affect any archaeology in the area, therefore no archaeological assessment is proposed in relation to the abstraction. 9

11 m3 / M3 / Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CAR/ L/ ) 4 Water Resources Assessment The water resource component of this application will consider: The current and proposed CAR licenced abstraction The current assessment of source yield The application of Environmental Standards to the proposed abstraction. This information will be used to provide evidence to support Scottish Water' s request to formalise the current abstraction regime at Achiltibuie CAR Licence Raw water is abstracted from Alit Ach a' Braighe through a screened intake chamber from a small inlet channel from the burn From here, water is piped under gravity to supply Achiltibuie WTW. Supply from Alit Ach a' Braighe is currently regulated by a CAR licence which permits a maximum daily abstraction of 309 day There are no hands off flow conditions attached to this licence. It is proposed that the licenced maximum daily abstraction be increased to 456 day to permit increased supply of raw water to the treatment works to address supply demand balance constraints. As there is an existing annual limit condition it is proposed that the annual limit is increased to 121, 395 m3, comprised of 3 months ( 92 days) at maximum abstraction plus 9 months ( 273 days) at average abstraction Yield Assessment Current Yield Assessment The yield of Alit Ach a' Braighe has been assessed using a simple Hysim- Aquator model in order to provide an update to the previously used Report 108 methodology. Hysim model flows for the period have been derived based on a model calibrated against the SEPA gauged catchment at Polloch ( Alit Coire nan Con). Although there is a general lack of suitable gauged analogues for the Alit Ach a' Braighe catchment, Polloch was deemed to be the most appropriate donor model other models for Creed Bridge and Glenmeanie catchments were also assessed but produced unrealistic results). Further details on the Hysim model and analogue selection process are available on request to SEPA if required. The flow duration curve from the Hysim flows series is presented below in Figure 4. 1 and Table 4. 2 to allow comparison against the equivalent LFE model flows. This shows that Hysim and LFE are in agreement across the majority of the flow range down to Q80, below which Hysim flows show a greater drop off in flows compared to LFE. 10

12 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW - CAR licence ( Ref: CARL/ ) v g LL Percentile Figure 4. 1: Alit Ach a' Braighe - comparison of Hysim vs LFE flow duration curves Table 4. 2: Alit Ach a' Braighe - comparison of HYSIM vs LFE flow duration statistics Percentile Hysim Q ( Mild) LFE Q ( Mild) Difference Q % Q % Q % Q % Q % Q % Q % Q % Q % Q % Q % Q % Qmean % Q95/ Qmean 5. 3% 8. 0% 2. 7% Unfortunately there is no reliable flow gauging for the Alit Ach a' Braighe to allow any further validation of the Hysim or LFE flow estimates. Flow gauging was undertaken at the site historically by MNV over the period However, this data was subject to significant equipment issues and insufficient range / quality of gaugings. It has therefore been deemed to be of insufficient quality to allow any reliable assessment against the modelled flows. ( Data available to SEPA on request if required). 11

13 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CAR/ L/ ) In the absence of any reliable flow data for verification of the LFE model, the more conservative Hysim flow series has been used for the purposes of yield assessment for the Allt Ach a' Braighe catchment. The yield of the system was modelled within a simple Aquator model for the the Allt Ach a' Braighe catchment. The impact of upstream Hydro abstraction has not been included in the yield assessment. Given that there is a Q90 hands off flow condition, flows below Q90 should remain natural and therefore there should be no impact on the downstream yield which is defined by the lowest 1 - day flow in the 2-3 driest years in the modelled flow record. Table 4. 3: Allt Ach a' Braighe - Yield summary Method Reuel of " "" Servi+e:( Years) Yield ( MI/ d)" Hysim- Aquator 1 in Application of Environmental Standards The relevant river flow standards criteria are presented in table 4. 4 and the results of the environmental standards assessment presented in subsequent tables 4. 5 to The assessment is based on the LFE flow estimate for the Alit Ach a' Braighe catchment, rather than the SW Hysim model. The assessment is also based on natural flows only, with no attempt to account for the impact of the upstream Hydro scheme abstraction which is expected to have an additional impact on flows above Q90 ( flows below Q90 should remain natural due to the Hands off Flow condition on the Hydro licence). It is considered more appropriate for SEPA to undertake this assessment if required. Table 4. 4 Environmental Standards Criteria for Alit Ach a' Braighe Environmental Standard Good River Typology D2 Table for Good Standards B1. 2 Abstraction Limits Q60 25% Q60 -Q70 20% Q70 -Q95 15% 5Q95 10%* 12

14 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW - CAR licence ( Ref: CARL/ ) Calculated as % of Q95 for flows below Q95 The results in Table 4. 5 based on the current CAR licence limit of MI/ d show that High and Good ecological status is maintained down to Q80 flows, but below this the status drops down to Moderate at Q90 and below. Table 4. 5: River flow standards assessment for Allt Ach a' Braighe - existing CAR licence limit of Mild ( LFE non loch -adjusted flows in MI/ d) Percentile Natural Impacted Abstraction Standard Q % High Q % High Q % High Q % High Q % High Q % High Q % High Q % High Q % Good Q % Moderate Q % Moderate Q % Moderate Q % Moderate Table 4. 6: River flow standards assessment for Alit Ach a' Braighe - proposed CAR licence limit of Mild ( LFE non loch -adjusted flows in MI/ d) Percentile Natural Impacted Abstraction Standard Q % High Q % High Q % High Q % High Q % High Q % High Q % High Q % Good Q % Moderate Q % Moderate Q % Moderate Q % Poor Q % Poor Although the results shown above show a downgrading to Poor for the maximum proposed licence volume of MI/ d, it should be noted this is only by an extremely small margin of MI/ d ( i. e. abstraction of MI/ d maintains Moderate status at lowest flows). Furthermore, it should be acknowledged that the figure of MI/ d is the peak raw water abstraction including Headroom. Headroom is used as part of the SDB 13

15 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW - CAR licence ( Ref: CAR/ L/ ) calculations to account for uncertainty and therefore it is unrealistic to include this in an environmental standards assessment. For comparison purposes, Table 4. 7 below shows the environmental standards assessment for the maximum observed raw water demand from the period between Dec 2016 and Aug 2017 ( as shown later in Figure 5. 1). This shows that based on the most recent observed peak raw water abstraction ( MI/ d), the environmental standards status remains at Moderate at low flows Q80 and below. Table 4. 7: River flow standards assessment for Allt Ach a' Braighe - maximum observed daily abstraction ( Dec16- Aug 17) of MI/ d ( LFE non loch -adjusted flows in MI/ d) Percentile Natural Impacted Abstraction Standard Q % High Q % High Q % High Q % High Q % High Q % High Q % High Q % Good Q % Moderate Q % Moderate Q % Moderate Q % Moderate Q % Moderate 14

16 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CARL/ ) 5 Demand and Supply Demand Balance 5. 1 General Approach The purpose of this section is to consider, discuss and validate all relevant current and historic demand data available for the zone, and to report the most representative demands in support of the abstraction volume applied for. For CAR licencing purposes, an estimate of the raw water demand plus an allowance for headroom is required. The corporate SDB tables calculate a component based approach, where raw water demand is built up of treated water demand plus raw water mains losses and WTW losses. Treated water demand is dry year peak demand. ( See Table 5. 1 below for a list of the definitions). Where an independent estimate of raw water demand is available, either metered at the abstraction point or at the inlet to the WTW, this data will be presented and can be used to verify the assumptions in the SDB tables. The demand forecast is calculated by independently estimating the components of raw water demand and combining them together to provide a raw water demand position across the 25 year planning horizon. Scottish Water corporate data has been used to support the SDB assessment, unless additional specific analysis has been undertaken as described below Supply Demand Balance Approach This section explains the detailed component build- up of the corporate SDB which is Scottish Water' s planning tool for ensuring a resilient supply of water for the planning horizon. The table below provides an explanation of these components. Table 5. 1 Terms in relation to Supply Demand Balance Term Definition i Critical Period The critical period defines the length of the most sensitive period for the water resource zone during a drought year may be average or peak depending on amount of storage available. Demand AA (Water Balance) Annual average demand for the zone taken from the corporate water balance model. Demand DYAA Dry year annual average demand which allows for the effects of dry weather. Currently a 3% uplift factor is applied. Demand DYP Dry year peak demand with a zone specific percentage uplift factor to represent the extra seasonal demand. PCC Unmeasured household per capita consumption expressed as litres per head i per day ( 1/ h/ d). Target Headroom Defined as the minimum buffer that a prudent water company should allow between supply and demand to cater for specified uncertainties ( except for those due to outages) in the overall SDB. TD Leakage Top down leakage. Calculation of leakage based on an estimation of the other water demand components which, when deducted from the distribution input, provides an estimate of leakage. 15

17 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CAR/ L/ ) Bottom Up Leakage Leakage calculated using district metered areas ( DMAs) to establish the minimum night use and allowable night usage. WTW Losses 1 Based on a % of WTW output dependant on treatment type. Raw Water Mains An allowance for leakage on the raw water main. This is a calculation based jlosses on the age and length of the pipe. Potable Water Daily amount of water required to be produced at a WTW Produced Raw Water Demand Dry year peak demand + raw water mains losses + WTW losses Surplus Deficit i Minimum of: WTW capacity Yield compared with raw water demand + headroom CAR licence_ SDB Supply demand balance WTW Water treatment works IN

18 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW - CAR licence ( Ref: CARL/ ) Table 5. 2 CAR Summary Table of Supply Demand e a 9 B B@ D Demand - AA ( Water Balance) MI/ d Demand - DYAA MI/ d Demand - DYP MI/ d Total Population 000' s Total Properties 000' s PCC I/ h/ d Household Consumption MI/ d Non -Household Consumption MI/ d Other Water Use MI/ d TD Leakage ( including USPL) MI/ d Bottom Up Leakage MI/ d Zonal Transfers MI/ d Target Headroom 9. 7% 9. 6% 9. 7% 9. 9% 10. 0% 10. 0% Target Headroom MI/ d Dry Year Peak DI + Headroom MI/ d WTW Losses 18. 0% 18. 0% 18. 0% 18. 0% 18. 0% 18. 0% WTW Losses MI/ d Raw Water Mains Losses MI/ d Other Raw Water Factors MI/ d Potable Water Produced MI/ d Raw Water Demand MI/ d Raw Water Demand + Headroom MI/ d Surplus Deficit MI/ d Supply Constraint CAR CAR CAR CAR CAR CAR WTW Losses ( Max) MI/ d Raw Water Demand (Max) MI/ d Raw Water Demand + Headroom ( Max) MI/ d Analysis of current water demand Raw Water Demand Component based raw water demand from the Table above comprises the following: Potable water produced ( dry year peak) WTW process losses Raw water mains losses Using the WTW capacity as the constraint, the raw water demand has been estimated as MI/ d ( 422 m3/ day) by 2020/ 21. With an allowance for headroom, the estimated abstraction volume is MI/ d. The WTW runs at 82% recovery, and WTW losses have been confirmed at 18%. 17

19 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CAR/ L/ ) Annual abstraction data provided to SEPA for compliance assessment has led to CAS assessment scores of Very Poor in 2015 and 2016, due to the number of breaches of licence limits, however there were doubts about reliability of the monitoring equipment. The abstraction monitoring equipment was verified on 6 December 2016 and we are now confident of the data provided. The raw water abstraction data from 7 December 2016 to 25 September 2017 is provided below as the basis for this application. The average daily abstraction over this period was 291 m3/ d Figure 5-1 Achiltibuie Abstraction and Distribution Flows 5. 4 Demand Forecast As part of the Q& S IV development constraints submission, a growth model was produced to assess population changes based on all proposed development in Scotland to the end of the Q& S IV investment period In - migration, demographic movement and build out rates were considered and modelled to produce a more realistic estimate of new demand expected rather than local council projections. Based on the Scottish Water growth model, population and properties are estimated to maintain the current population of Current leakage Distribution leakage The Economic Level of Leakage ( ELL) is MI/ d however this must be viewed as an indicative figure only as it was calculated using the small zones approach and is not zone specific. 18

20 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW CAR licence ( Ref: CAR/ L/ ) The Table below shows the historic reported leakage figures for the zone. There are three DMAs in the zone covering 100% of properties. Table 5. 1 Reported Leakage Figures I i 1 Leakage / / / / / 16 Methodology Mild) ( Mild) MI/ d) MI/ d) ( MI/ d) Top- down Bottom- up j MLE Conclusions & Proposals On- going analysis of licence compliance for Achiltibuie and abstraction from Alit Ach a' Braighe indicates operation of the works results in occasional breaches of the allowable abstraction under licence. Consequently there is a supply demand deficit in Achiltibuie WRZ due to constraints under the current CAR licence. We are progressing this application with funding obtained to vary licences where the licence conditions are no longer appropriate. The 1 in 40 year yield of Alit Ach a' Braighe is calculated to be MI/ d based on LFE derived natural flows upstream of the abstraction point. The proposed increase in abstraction does not cause deterioration in environmental standards. Peak historic raw water demand for the zone based on the raw water metered data indicates raw water demands in excess of the licenced, 309 m3/ day have been experienced in the past. Therefore in order to ensure a sustainable supply of raw water for the Achiltibuie Community we propose an increase in the allowable abstraction from 309 m3/ day to 456 m3/ day with an annual limit of 121, 395m3. This will provide an allowance for uncertainty across the planning horizon. 19