o ScottishScottish Water Water Trusted Trusted toto serve serve Scotland Scotland AchiltibuieAchiltibuie WaterWater TreatmentTreatment WorksWorks ScottishScottish WaterWater ApplicationApplication forfor TechnicalTechnical VariationVariation toto WaterWater UseUse LicenceLicence CAR/CAR/ L/L/ 10127101012710 SupportingSupporting DocumentDocument October October 20172017 SubmittedSubmitted by:by: ScottishScottish WaterWater CastleCastle HouseHouse 66 Castle Castle Drive Drive CarnegieCarnegie CampusCampus Dunfermline Dunfermline FifeFife KY11 8GG Technical Variation to CAR licence: Supporting Document Achiltibuie WTW — CAR licence ( Ref: CAR/ L/ 1012710) Achiltibuie Water Treatment Works Scottish Water Application for Technical Variation to Water Use Licence CAR/ L/ 1012710 Supporting Document Issue and revision record Revision Date Originator Checker Approver Description Draft September ! i i 1 Final October 1 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW — CAR licence ( Ref: CAR/ L/ 1012710) 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/ 1012710, 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 ( 0. 309 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 0. 392 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/ 1012710) 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 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW — CAR licence ( Ref: CAR/ L/ 1012710) Table of contents 1. Introduction................................................................................................... 4 Achiltibuie Water Resource Zone.......................................................................... 5 2. 1 Raw Water Sourcing and WTW Description ................................................ 5 2. 2 Catchment Description................................................................................ 6 2. 3 Summary of Q& S IV investment.................................................................. 8 3 Statement of need............................................................................................. 9 3. 1 Current Supply Demand Balance Assessment ............................................ 9 3. 2 Adequacy of current source........................................................................ 9 3. 3 Ecological Assessments.............................................................................. 9 3. 4 Archaeological Assessments....................................................................... 9 4 Water Resources Assessment....................................................................... 10 4. 1 CAR Licence............................................................................................. 10 5 Demand and Supply Demand Balance.......................................................... 15 5. 1 General Approach..................................................................................... 15 5. 2 Supply Demand Balance Approach........................................................... 15 5. 3 Analysis of current water demand............................................................. 17 5. 3. 1 Raw Water Demand........................................................................... 17 5. 4 Demand Forecast...................................................................................... 18 5. 5 Current leakage......................................................................................... 18 5. 5. 1 Distribution leakage............................................................................ 18 6 Conclusions & Proposals............................................................................... 19 3 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW — CAR licence ( Ref: CARL/ 1012710) 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 314. 4 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW — CAR licence ( Ref: CARL/ 1012710) 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 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 3. 58 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 Technical Variation to CAR licence: Supporting Document Achiltibuie WTW — CAR licence ( Ref: CAR/ L/ 1012710) 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