Horse Island, Fada and Tanera Ece Estimates 2018
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SSF SUMMER ISLES ECE ESTIMATES 2018 SCOTTISH SEA FARMS SSF) SUMMER ISLES: HORSE ISLAND, FADA AND TANERA ECE ESTIMATES 2018 REPORT SUMMER ISLES 002.DOCX For: Scottish Sea Farms Ltd Laurel House Laurel Hill Business Park Stirling FK7 9JQ REPORT 1 SUMMER ISLES 002. DOCX SSF SUMMER ISLES ECE ESTIMATES 2018 SUMMARY This report outlines the hydrography of the area around the Summer Isles, to estimate the effect of existing fish farms at Fada and Tanera, and of a potential fish farm at Horse Island, on local nutrient concentrations via the ' Equilibrium Concentration Enhancement' ( ECE) approach. Tidal and residual flows near the Summer Isles sites have been estimated to be sufficient to dilute the nitrogen released from existing consented sites at Fada and Tanera, and from the potential site at Horse Island, such that the likely ECE of nitrogen in waters local to the sites and in the surrounding waterbodies is less than about 20 µgN.litre-1. The estimated values of ECE compare favourably with various relevant or regulatory standards that relate to: typical background concentrations a previous Environmental Quality Standard for available nitrogen of 168 gN.litre-1 OSPAR & Water Framework Directive Reference Conditions: in offshore waters such as these (salinity above 34), the DIN (Dissolved Inorganic Nitrogen) reference value is 10M and the threshold 15M. Increases are therefore limited to 5 M (70 gN.l-1). In the circumstances examined here, the predicted ECE values are therefore insignificant within the Summer Isles water bodies. REPORT 2 SUMMER ISLES 002. DOCX SSF SUMMER ISLES ECE ESTIMATES 2018 CONTENTS 1 INTRODUCTION ........................................................................................................... 6 1.1 SUMMER ISLES REGULATORY ISSUES ............................................................................... 6 1.2 THE ECE APPROACH....................................................................................................... 7 2 PHYSICAL BACKGROUND ......................................................................................... 8 2.1 NON-TIDAL CIRCULATION ON THE WEST COAST OF SCOTLAND ............................................ 8 2.2 THE SCOTTISH SHELF MODEL .......................................................................................... 9 2.3 TIDAL RANGE ................................................................................................................ 10 2.3.1 THE TIDAL STREAM ATLAS ................................................................................................. 11 3 FARM SITES .............................................................................................................. 12 3.1 SITE DETAILS ................................................................................................................ 12 3.2 HORSE ISLAND .............................................................................................................. 13 3.2.1 HORSE ISLAND: CURRENTS ............................................................................................... 13 3.2.2 HORSE ISLAND: INFLUENCE OF WIND ................................................................................. 13 3.2.3 HORSE ISLAND: SPREADING AND DISPLACEMENT ............................................................... 14 3.3 FADA ............................................................................................................................ 15 3.3.1 FADA: CURRENTS .............................................................................................................. 15 3.3.2 FADA: INFLUENCE OF WIND ............................................................................................... 15 3.3.3 FADA: SPREADING AND DISPLACEMENT .............................................................................. 16 3.4 TANERA ONE ................................................................................................................. 17 3.4.1 TANERA ONE: CURRENTS .................................................................................................. 17 3.4.2 TANERA ONE: SPREADING AND DISPLACEMENT .................................................................. 17 3.5 LOCAL RESIDUAL FLOW AT HORSE ISLAND ...................................................................... 18 3.5.1 SCALE OF DILUTING FLOW .................................................................................................. 19 3.5.2 DISPERSION ...................................................................................................................... 19 3.5.3 SITE FLUSHING AND ECE ..................................................................................................20 3.6 SUMMARY ..................................................................................................................... 21 4 CONCLUSIONS .......................................................................................................... 22 5 REFERENCES ............................................................................................................ 23 REPORT 3 SUMMER ISLES 002. DOCX SSF SUMMER ISLES ECE ESTIMATES 2018 TABLES TABLE 1: TIDES AT ULLAPOOL ............................................................................................... 10 TABLE 2: EXISTING AND PROPOSED SITES .............................................................................. 12 TABLE 3: HORSE ISLAND SUMMARY HYDROGRAPHIC STATISTICS ( 3-8-2012 TO 9-9-2012) .......13 TABLE 4: STATISTICS OF 6-HOUR NEAR- SURFACE AND CAGE BOTTOM DISPLACEMENTS ............ 14 TABLE 5: FADA SUMMARY HYDROGRAPHIC STATISTICS ( 3-8-2012 TO 9-9-2012) .....................15 TABLE 6: STATISTICS OF 6-HOUR NEAR- SURFACE AND CAGE BOTTOM DISPLACEMENTS ............ 16 TABLE 7: TANERA ONE SUMMARY HYDROGRAPHIC STATISTICS ( 3-8-2012 TO 9-9-2012) .........17 TABLE 8: STATISTICS OF 6-HOUR NEAR- SURFACE AND CAGE BOTTOM DISPLACEMENTS ............ 18 TABLE 9: ENHANCEMENT IN DISPERSED RESIDUALS OVER ONE DAY ( TANERA 1 & 2 COMBINED) 20 REPORT 4 SUMMER ISLES 002. DOCX SSF SUMMER ISLES ECE ESTIMATES 2018 FIGURES FIGURE 1: TWO WATER BODIES AROUND THE SUMMER ISLES.................................................... 6 FIGURE 2: CATEGORY 3 AREAS ( YELLOW) IN THE SUMMER ISLES REGION .................................. 6 FIGURE 3: SUMMER ISLES SITES AT TANERA, FADA AND HORSE ISLAND .................................... 7 FIGURE 4: CURRENT PATHS WEST OF SCOTLAND (AFTER ELLETT, 1994) ..................................8 FIGURE 5: FLOW PARTITIONS WEST OF SCOTLAND (AFTER ELLETT, 1994) ................................9 FIGURE 6: SURFACE RESIDUALS MAY TO OCTOBER, SSM SUB DOMAIN MODEL, M.S-1 .............. 10 FIGURE 7: TIDAL STREAMS 4 HOURS BEFORE HW DOVER; NEAP & SPRING ( TENTHS OF KNOT) . 11 FIGURE 8: EXISTING AND PROPOSED SITES ............................................................................ 12 FIGURE 9: HORSE ISLAND, ALL 6-HOUR NEAR- SURFACE DISPLACEMENTS ................................ 14 FIGURE 10: FADA, 6-HOUR DISPLACEMENTS: NEAR- SURFACE & MID DEPTH ( INSET) ................. 16 FIGURE 11: TANERA ONE, 6-HOUR DISPLACEMENTS: NEAR- SURFACE & MID DEPTH ( INSET) ...... 18 FIGURE 12: PROPOSED LAYOUT AT HORSE ISLAND, SHOWING THE MAIN CURRENT DIRECTION .. 19 FIGURE 13: SPREADING OF A PLUME FROM A FARM SITE IN A RESIDUAL CURRENT AT TIME T ..... 19 REPORT 5 SUMMER ISLES 002. DOCX SSF SUMMER ISLES ECE ESTIMATES 2018 1 INTRODUCTION 1.1 SUMMER ISLES REGULATORY ISSUES The Summer Isles aquaculture sites are positioned within two water bodies Summer Isles and Minch East, Figure 1, from http://map.sepa.org.uk/rbmp/) with an overall status of Good with High confidence in 2012, overall ecological status of Good and overall chemical status of Pass. These are not categorised areas as defined within the Locational Guidelines for the Authorisation of Marine Fish Farms in Scottish Waters (http://www.gov.scot/Resource/ 0052/00529751. pdf). Figure 1: Two water bodies around the Summer Isles Nor are there categorised areas listed nearby. Figure 2 is taken from https://marinescotland. atkinsgeospatial. com/nmpi/default.aspx?layers=530 , as the Scottish Government 2018 map of categorised areas. The three areas shown Lochs Broom and Ewe) are low impact risk category 3. An estimate of nutrient enhancement for planning purposes or environmental impact assessment and an assessment of the cumulative effect of nutrients released from the Summer Isles sites is nevertheless appropriate and required. Figure 2: Category 3 areas (yellow) in the Summer Isles region REPORT 6 SUMMER ISLES 002. DOCX SSF SUMMER ISLES ECE ESTIMATES 2018 This report estimates the increase in nitrogen concentration near the Summer Isles resulting from the sites shown in Figure 3. Figure 3: Summer Isles sites at Tanera, Fada and Horse Island 1.2 THE ECE APPROACH The ECE equation was developed by SEERAD Marine Laboratory for the Locational Guidelines. The ECE model is a simply derived mass balance and dilution relation see www.gov.scot/Topics/marine/Fish-Shellfish/18716/environmentalimpact/ models) that considers dissolved nitrogen, particulate nitrogen and nitrogen that may have re- dissolved from the seabed, all in relation to water flows through a region. The model takes no direct account of biological or chemical processes. The equation estimates the enhancement of nitrogen from aquaculture above background levels, on the assumption that released nitrogen is conserved and only removed by water flows. The Equilibrium Concentration Enhancement