MARINE ENVIRONMENTAL IMPACT ASSESSMENT FOR THE PROPOSED DESALINATION PLANTS AROUND THE CAPE PENINSULA, SOUTH AFRICA Marine Specialist Report October 2017 Anchor Environmental Consultants Report No. 1768/3 MARINE ENVIRONMENTAL IMPACT ASSESSMENT FOR THE PROPOSED DESALINATION PLANTS AROUND THE CAPE PENINSULA, SOUTH AFRICA Marine Specialist Report October 2017 Report prepared for Advisian: WorleyParsons Group 31 Allen Drive, Loevenstein Cape Town, South Africa www.advisian.com Report Prepared by: Anchor Environmental Consultants (Pty) Ltd Suite 8 Steenberg House, Silverwood Close, Tokai 7945, South Africa www.anchorenvironmental.co.za Authors: Megan Laird, Amy Wright, Vera Massie and Barry Clark Citation: Laird MC, Wright AG. Massie V and Clark BM. 2017. Marine Environmental Impact Assessment for the Proposed Desalination Plants around the Cape Peninsula, South Africa. Report no. 1768/3 prepared by Anchor Environmental Consultants for Advisian: WorleyParsons Group. Pp 128. © Anchor Environmental Consultants Use of material contained in this document by prior written permission of Anchor Environmental Consultants only. TABLE OF CONTENTS TABLE OF CONTENTS ...................................................................................................................................... IV EXECUTIVE SUMMARY ................................................................................................................................... VI GLOSSARY .................................................................................................................................................... XIII LIST OF ABBREVIATIONS ............................................................................................................................ XVIII 1 INTRODUCTION ....................................................................................................................................... 1 1.1 PROJECT BACKGROUND ............................................................................................................................... 1 1.2 TERMS OF REFERENCE ................................................................................................................................. 3 2 DESCRIPTION OF THE RECEIVING ENVIRONMENT .................................................................................... 4 2.1 REGIONAL OCEANOGRAPHY .......................................................................................................................... 4 2.2 REGIONAL WATER QUALITY, SEDIMENT, TURBIDITY AND OXYGEN .......................................................................... 5 2.2.1 West Coast ........................................................................................................................................ 5 2.2.2 False Bay ........................................................................................................................................... 6 2.3 MARINE PROTECTED AREAS ......................................................................................................................... 8 2.4 BLUE FLAG STATUS ..................................................................................................................................... 9 3 AVAILABLE DATA ON INDIVIDUAL SITES ................................................................................................ 10 3.1 SILWERSTROOMSTRAND ............................................................................................................................ 10 3.2 PORT OF CAPE TOWN AND TABLE BAY ......................................................................................................... 15 3.3 GRANGER BAY ......................................................................................................................................... 23 3.4 GLEN COUNTRY CLUB (CAMPS BAY) ............................................................................................................ 27 3.5 HOUT BAY .............................................................................................................................................. 30 3.6 DIDO VALLEY ........................................................................................................................................... 35 3.7 STRANDFONTEIN TIDAL POOL ..................................................................................................................... 42 3.8 MONWABISI TIDAL POOL ........................................................................................................................... 50 3.9 HARMONY PARK AND GORDON’S BAY .......................................................................................................... 57 4 IMPACT ASSESSMENT ............................................................................................................................ 63 4.1 CONSTRUCTION PHASE .............................................................................................................................. 70 4.1.1 Disturbance of intertidal habitat and associated biota .................................................................. 70 4.1.2 Disturbance of subtidal habitat and associated biota .................................................................... 71 4.1.3 Mobilisation of benthic sediment during laying of pipelines .......................................................... 72 4.1.4 Disposal of solid waste .................................................................................................................... 73 4.1.5 Hydrocarbon spills........................................................................................................................... 74 4.1.6 Noise and vibration management during construction .................................................................. 75 4.2 OPERATIONAL PHASE ................................................................................................................................ 76 4.2.1 Mortality of marine life due to the intake of seawater ................................................................... 78 4.2.2 Sediment scouring and shifts in sediment movement patterns ...................................................... 80 4.2.3 Increased salinity due to brine discharge ........................................................................................ 81 4.2.4 Elevated temperature ..................................................................................................................... 85 4.2.5 Decreased dissolved oxygen concentration .................................................................................... 86 4.2.6 Co-pollutants in backwash water.................................................................................................... 88 4.2.7 Reduced pH ..................................................................................................................................... 93 4.2.8 Impacts on recreational users ......................................................................................................... 94 4.3 DECOMMISSIONING PHASE ................................................................................................................ 95 iv 4.4 CUMULATIVE IMPACTS .............................................................................................................................. 96 5 MONITORING ...................................................................................................................................... 100 5.1 WATER QUALITY GUIDELINES ................................................................................................................... 100 5.2 EFFLUENT QUALITY MONITORING............................................................................................................... 102 5.2.1 End of pipe compliance monitoring .............................................................................................. 102 5.2.2 Water quality compliance at the edge of the RMZ ....................................................................... 103 5.3 ECOLOGICAL ASPECTS OF THE RECEIVING ENVIRONMENT ................................................................................ 104 5.3.1 Biological monitoring .................................................................................................................... 104 5.3.2 Water quality in the receiving environment ................................................................................. 105 5.4 PIPELINE INTEGRITY ................................................................................................................................ 106 5.5 CONTINGENCY PLAN ............................................................................................................................... 106 6 RECOMMENDATIONS .......................................................................................................................... 108 7 REFERENCES ........................................................................................................................................ 112 APPENDIX 1 – IMPACT RATING METHODOLOGY .......................................................................................... 125 v EXECUTIVE SUMMARY Advisian: WorlyParsons Group (WSP) was appointed by the City of Cape Town (CoCT) to prepare Coastal water Discharge Permit (CWDP) applications for eleven proposed Reverse Osmosis (RO) desalination plants on the West Coast, the Cape Peninsula