Scottish Sanitary Survey Report Sanitary Survey Report Brindister Voe SI 023 February 2013 Report Distribution – Brindister Voe Date Name Agency Linda Galbraith Scottish Government Mike Watson Scottish Government David Denoon SEPA Douglas Sinclair SEPA Fiona Garner Scottish Water Alex Adrian Crown Estate Dawn Manson Shetland Island Council Angus Walterson Harvester Sandy Duncan HMMH Alice Mathewson SSQC Partner Organisations The hydrographic assessment and the shoreline survey and its associated report were undertaken by SSQC, Scalloway. i Table of Contents 1. General Description ................................................................ 4 2. Fishery .................................................................................... 6 3. Human Population ................................................................... 8 4. Sewage Discharges .............................................................. 10 5. Agriculture ............................................................................. 13 6. Wildlife .................................................................................. 16 7. Land Cover ........................................................................... 19 8. Watercourses ........................................................................ 21 9. Meteorological data ............................................................... 24 9.1 Rainfall ............................................................................................ 24 9.2 Wind ................................................................................................ 26 10. Classification Information ...................................................... 28 11. Historical E. coli data ............................................................. 29 11.1 Validation of historical data ............................................................. 29 11.2 Summary of microbiological results ................................................. 29 11.3 Overall geographical pattern of results ............................................ 30 11.4 Overall temporal pattern of results .................................................. 31 11.5 Seasonal pattern of results ............................................................. 31 11.6 Analysis of results against environmental factors............................ 33 11.6.1 Analysis of results by recent rainfall ........................................ 33 11.6.2 Analysis of results by tidal height ............................................ 34 11.6.3 Analysis of results by water temperature ................................ 36 11.6.4 Analysis of results by salinity .................................................. 37 11.7 Evaluation of results over 230 E. coli MPN/100 g ........................... 37 11.8 Summary and conclusions .............................................................. 38 12. Designated Shellfish Growing Water Data ............................ 39 13. Bathymetry and Hydrodynamic Assessment ......................... 41 13.1 Introduction ..................................................................................... 41 13.2 Bathymetry ...................................................................................... 42 13.3 Field Data ........................................................................................ 45 13.4 Tidal Information ............................................................................. 47 13.5 Currents .......................................................................................... 51 13.6 Salinity ............................................................................................ 65 13.7 Summary ......................................................................................... 68 14. Shoreline Survey Overview ................................................... 70 15. Overall Assessment .............................................................. 73 16. Recommendations ................................................................ 78 17. References ............................................................................ 80 18. List of Figures and Tables ..................................................... 82 ii Appendices 1. General Information on Wildlife Impacts 2. Tables of Typical Faecal Bacteria Concentrations 3. Statistical Data 4. Hydrographic Section Glossary 5. Shoreline Survey Report © Crown Copyright 2013. Food Standards Agency Scotland and Cefas. All rights reserved. iii I. Executive Summary The sanitary survey at Brindister Voe was undertaken due to the risk ranking the area received amongst areas that had not yet been surveyed. Brindister Voe is a narrow inlet on the western coast of Mainland Shetland opens to the Atlantic Ocean in the North and to the south meets the shallow, sheltered lagoons of The Vadills at Uni Firth. Brindister Voe production area contains one long-line mussel farm. At the time of survey it consisted of three long-lines near to the east shore of the voe, one set on the north end of the seabed lease and two set on the southern end. To the north of the production area boundary, a farm consisting of 6 sets of long-lines is used for collection of spat. A small salmon and mussel shore base is located on the northwest shore of the voe. Overall, the Brindister Voe production area is subject to relatively little faecal contamination. The main sources of contamination are varied diffuse sources along the western shoreline. Livestock, wildlife and a failing septic tank contribute to modest faecal contamination of watercourses discharging to the voe along much of the western shore and the head of the voe. A septic tank discharge from the shore base was the only direct discharge seen to the marine environment. There is a possibility of overboard discharges from boats, particular at the north end of the voe. A few watercourses also discharge to the east side of the voe. These drain steep, inaccessible terrain used for grazing sheep. Contamination observed in mussels appears to be rainfall associated which is consistent with the observed diffuse, land-based sources. Due to its association with freshwater sources, it is anticipated that faecal contaminants may be more concentrated in lower salinity water at or near the surface. Seasonal variation is seen in monitoring results, with lowest results are occurring from April to July. This corresponds with the trend in historical rainfall over the same period. A significant correlation was found between historical monitoring results and rainfall, although this was driven by the number of very low results rather than by high results. Results exceeding 230 E. coli MPN/100 g occurred at low as well as high rainfall values, indicating that rainfall is a poor predictor of high results at this location. Hydrographic analysis showed a consistent near surface flow from the head toward the mouth of the loch, which suggests that contamination carried into the loch via watercourses would move predominantly northward. Given this, it 1 is likely that sources arising in the north of the voe from the shore station and adjacent burn would be taken out of the voe and therefore would be less likely to impact the mussel farm and spat farm to the south. It is recommended that the production area boundaries be extended northward to cover the entire Brindister Voe waterbody and curtailed at the south end to exclude Uni Firth and the Vadills. The RMP should be relocated to a point on the southern end of the Brindister Voe site and bagged shellfish should be placed at that location to ensure consistency in sampling location. Further details on the sampling plan and recommended boundaries can be found in tabular form overleaf and on page 78. 2 II. Sampling Plan and Recommended Production Area Boundaries Production Area Brindister Voe Site Name Brindister Voe SIN SI 023 406 08 Species Common mussel Type of Fishery Long-line aquaculture NGR of RMP HU 2877 5649 East 428770 North 1156490 Tolerance (m) 40 Depth (M) 1 Method of sampling Hand Frequency of Sampling Monthly Local Authority Shetland Islands Sean Williamson Authorised Marion Slater Sampler(s) Daniel Stone Vicki Smith HMMH Sean Williamson Liaison Officer Area bounded by lines drawn between HU 2865 5630 and Production Area HU 2877 5640 and between Boundaries HU 2827 5770 and HU 2858 5782 and extending to MHWS. 3 III. Report 1. General Description Brindister Voe is an inlet on the western coast of Mainland Shetland. It is approximately 1.5 km long and 500 m wide. The voe opens to the Atlantic Ocean in the North and to the south meets The Vadills at Uni Firth. The area around the Voe is very sparsely populated, with road access to the western shore only. A small number of farms and a shore base with pier are located along the road, and cattle grids are identified on the OS map. The sanitary survey at Brindister Voe was undertaken due to the risk ranking the area received amongst areas that had not yet been surveyed. A map showing the location of the area is shown in Figure 1.1. 4 © Crown Copyright and Database 2013. All rights reserved. Ordnance Survey licence number [GD100035675] Figure 1.1 Location of survey area 5 2. Fishery The currently classified fishery at Brindister Voe is comprised of a single mussel (Mytilus edulis) farm at site Brindister Voe (SIN SI-023-406-08) in two adjoining legs running parallel to the east shore of the voe. As the site and production area have the same name, the mussel farm itself will be referred to as Brindister Voe site. At the time