ABP Southampton. Environmental Statement for Port of Southampton: Berth 201/202 Works. Appendix K. Recommended Marine Conservation Zone Assessment

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1 ABP Southampton Environmental Statement for Port of Southampton: Berth 201/202 Works Appendix K Recommended Marine Conservation Zone Assessment

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3 Appendix K Berth 201/202 Works Potential Impact on Recommended Marine Conservation Zones

4 Appendix K. Potential Impact on Recommended Marine Conservation Zones Table of Contents Introduction... ii Draft Conservation Objectives and Interest Features... ii Previous Disposal Operations at the Nab... v Numerical Modelling... vi Impact Assessment... vi Physical Loss from Smothering... vii Potential Dispersion of Contaminants... vii Potential Effects of Changes in Suspended Sediment Concentrations...viii Summary... ix References... ix Tables Table 1 Interest features and conservation objectives for rmczs in study area P.1523 i R.1837

5 Introduction Since the Berth 201/202 Environmental Statement (ES) was submitted in December 2008, the UK has signed up to international agreements that aim to establish an ecologically coherent network of Marine Protected Areas (MPAs) by This network will be made up of current MPAs as well as a new type of MPA called a Marine Conservation Zone (MCZ). The Balanced Seas Project ( is tasked with designing the network of MPAs and MCZs, which in the southeast England area encompasses the Environmental Impact Assessment (EIA) study area for the Berth 201/202 development. A number of MCZs have been recommended by the Balanced Seas Project that occur within the wider EIA study area (Balanced Seas, 2011). Ministers will draft designation orders, and carry out formal public consultation which is expected to take place in early This appendix aims to provide an assessment of the impacts of Berth 201/202 works on the recommended (r) MCZs, in light of proposed conservation objectives that have been drafted for each of the supporting marine interest features. Supplementary data and interpretation is provided in this appendix, cross-referencing to the relevant sections of the main ES. Draft Conservation Objectives and Interest Features Based on the recommendations that were published in early June 2010, the nearest sites that could potentially be indirectly affected by the Berth 201/202 works, as a result of the disposal of capital and maintenance dredge material at the Nab disposal ground, are presented in Figure 1. These are as follows: Bembridge rmcz no 22; Utopia rmcz no 28; and Offshore Overfalls rmcz no 17. The interest features and preliminary draft conservation objectives that were developed by Natural England and Joint Nature Conservation Committee (JNCC) advisors for each of these rmczs are outlined in Table 1. The draft conservation objective maintain means that in general the current levels of activity in the area are considered acceptable, but they will be monitored and restrictions may have to be introduced if necessary. means that restrictions on certain activities may be necessary to allow the feature to recover to favourable condition. It does not necessarily mean that an activity will be prohibited, as other mitigation measures might be appropriate (e.g. change in fishing gear type, reduction in intensity, seasonal restrictions etc.). P.1523 ii R.1837

6 Table 1. Interest features and conservation objectives for rmczs in study area rmcz Feature Type Feature Name Draft Conservation Objectives A5.2 Subtidal sand Broad-scale habitat A5.3 Subtidal mud A5.4 Subtidal mixed sediments Maerl beds Mud habitats in deep water Habitat Features of Conservation Importance (FOCI) Rossworm (Sabellaria spinulosa) reef Seagrass beds Native oyster (Ostrea edulis) beds Bembridge rmcz no 22 Sea-pen and burrowing megafauna communities Tentacled lagoon worm (Alkmaria romijni) Lagoon sand shrimp (Gammarus insensibilis) Kaleidoscope stalked jellyfish (Haliclystus auricula) Long-snouted seahorse (Hippocampus guttulatus) Species FOCI Low mobility Short-snouted seahorse (Hippocampus hippocampus) Starlet sea anemone (Nematostella vectensis) Native oyster (O. edulis) Peacock s tail (Padina pavonica) Sea snail (Paludinella littorina) Utopia rmcz no 28 Habitat FOCI Fragile sponge and anthozoan communities Offshore Overalls rmcz no 17 Broad-scale habitat A5.1 Subtidal coarse sediments A5.2 Subtidal sand P.1523 iii R.1837

7 rmcz Feature Type Feature Name Draft Conservation Objectives A5.4 Subtidal mixed sediments Habitat FOCI Rossworm (S. spinulosa) reef Subtidal sands and gravels Species FOCI Undulate ray (Raja undulata) Geology English Channel outburst flood features P.1523 iv R.1837

8 Previous Disposal Operations at the Nab Both capital and maintenance dredging of the main navigation channel, dock approaches and berths have been undertaken in Southampton Water for over two centuries. Key details relating to past dredging are summarised in Table 8.2 of Chapter 8 in the main ES. A total of over 11 million m 3 of capital dredging was removed from Southampton Water during these operations, including 3 million m 3 in 1951 (Webber, 1980) and 6.6 million m 3 in 1996/7. The disposal of annual maintenance dredge arisings at the Nab Deposit Ground from all the estuaries and harbours in the Solent amounts to around 0.7 million m 3 per year. It should also be noted that until the ban on the disposal of sewage sludge at sea in 1998, the Nab Deposit Ground was used regularly for this purpose. The site has, therefore, had a history of high levels of bacteria, albeit this is likely to have recovered in recent years. During 1996 and early 1997, the entrance channel to the Port of Southampton was deepened by 2.4m. This resulted in the removal of 6.6 million m 3 of fine sand and silts, the majority of which was deposited at the Nab Deposit Ground. As a result of the possible environmental impacts that were identified during the EIA (ABP Research & Consultancy, 1995), a programme of monitoring was stipulated by the then Ministry of Agriculture, Fisheries and Food (MAFF) which is now the Department of Environment, Food and Rural Affairs (Defra). This included detailed monitoring at the Nab Deposit Ground, in response to concerns that were expressed about the potential effects of the increased suspended sediment concentrations and deposition on the local lobster and crab fisheries. Detailed bathymetric surveys of the deposit ground were undertaken before the capital dredge disposal, during and towards the end of disposal. Analysis of all surveys showed that the material was generally dispersed over the area of the deposit and reductions in water depth at the end of the deposit were generally less than 0.5m (ABP Research & Consultancy, 2000). Two side scan sonar surveys and Roxann bed description surveys with associated sampling and dive inspections were undertaken near the beginning of the dredge and during, when material had been deposited at the site. The initial area of coverage was based on the predicted distribution of dispersal of sediment remaining on the bed established from the numerical modelling (i.e. along a northeast to southwest axis). The main conclusions from inter-comparison of the surveys were that the particle size distribution of the bed sediments did not significantly change as a result of the dredged material deposits (ABP Research & Consultancy, 2000). In other words, the deposits did not change the physical nature of the bed sediments. With the aid of fishermen, pots were also placed adjacent to the Nab Deposit Ground along the northeast and southwest edges (i.e. the direction of the dispersion plume) and monitored before and throughout the dredge to determine whether any changes in numbers and health of the crabs and lobsters occurred as the dredge progressed. The results indicated that no significant changes occurred during the 8 months that dredge arisings from the capital works were being disposed of at the Nab Deposit Ground (ABP Research & Consultancy, 2000). P.1523 v R.1837

9 The conclusion made by the Fisheries Liaison Officer was that: From the information obtained during the above monitoring programme I can confirm that there appears to have been no detrimental effects to fisheries by the dumping operation at the Nab Deposit Ground or in the adjacent area. In summary, previous intensive disposal operations at the Nab Deposit Ground have shown that there is no significant effect on the bed sediment or adjacent local shellfisheries. The disposal of capital dredge material from the proposed Berth 201/202 is expected to result in a similar pattern of dispersion (i.e. along a northeast to southwest axis) but is of a far smaller scale, in terms of volume (less than 3% of the total volume deposited during the 1996/97 capital dredge) and duration (disposal will only occur over a period of around 4 weeks). Furthermore the amount to be deposited from the capital dredge of Berth 201/202 is in the order of 26% of annual maintenance deposits at the site from all the estuaries and harbours in the Solent, and such deposits have not raised concern in the past. Numerical Modelling A detailed description of the modelling scenario that was developed to simulate the disposal of the dredged material from Berth 201/202, dredge methods and frequencies of disposal has been set out in detail in Appendix C of the ES. The various materials to be dredged from Berth 201/202 and the method of dredging on which the modelling scenarios have been developed are characterised in detail in Appendix B of the ES. In general terms, the materials to be dredged from the berth pocket are consolidated greensand and very stiff sandy clay of the Bracklesham Beds. These consolidated materials will require some form of mechanical dredging. Preliminary discussions with dredging contractors indicate that the dredge is likely to be undertaken by backhoe dredger. The model scenario used to evaluate the dispersion characteristics that will arise from the deposits of the fine material dredged from Berths 201/202 at the Nab Deposit Ground has assumed that all material will break into its constituent particle sizes. This will tend to maximise the extent of dispersion and suspended sediment concentrations away from the deposit ground but underestimate the initial amount of deposition directly on the bed. The disposal scenario was modelled in total over a spring neap cycle. The model was then allowed to run on to determine the decay in suspended sediments following the end of disposal. Impact Assessment The potential for impact to the interest features of rmczs (Table 1) occurring in the wider study area arises from the indirect effects during the disposal of capital and maintenance dredge arisings. P.1523 vi R.1837

10 The key impact pathways identified and addressed in the following sections are as follows: Physical loss through smothering; Introduction of contaminants into the water column and to seabed sediments; and Physical damage by elevated suspended sediment levels. Physical Loss from Smothering It is estimated that around 182,000m 3 in situ of capital material will need to be disposed of as a result of the proposed dredge at the existing Nab Deposit Ground, subject to a beneficial use being identified. Simulation of the dispersal and deposition of sediments from the deposit ground indicates that the maximum bed accumulations outside of the disposal ground boundaries will be less than 1mm and only present for very short periods (maximum of around two hours at any time throughout the circa 4 week period of the disposal of capital dredge arisings). The magnitude of the impact on the Bembridge, Utopia and Offshore Overfall rmczs will be, therefore, negligible. In any case, the interest features of these rmczs are already characterised by any potential effects of regular disturbance through the disposal of maintenance dredge arisings at the disposal ground from all the estuaries and harbours in the Solent. The overall impact on these features is, therefore, considered to be insignificant. Potential Dispersion of Contaminants For the purpose of the Berth 201/202 proposal, a number of sediment samples were analysed within the berth pocket for a range of heavy metals, polychlorinated biphenyls (PCBs), total petroleum hydrocarbons (TPHs) and polyaromatic hydrocarbons (PAHs). The results are presented in Chapter 9 of the main ES. For the most part, contaminant levels are either below the UK Cefas action Level 1 or not sufficiently above to raise concerns about relocation of the material to the marine environment. ABP is currently consulting with Cefas, who will ultimately inform the marine licensing decision by undertaking their own sample analysis for the full suite of chemical contaminants, including tributyltin (TBT) and dibutyltin (DBT), to determine the suitability of the material for disposal at sea. With respect to the Bembridge, Utopia and Offshore Overfall rmczs, the modelling shows that only a very small proportion of the suspended sediment moves into these designated areas and no permanent deposits are likely to occur of any magnitude (see above). On the whole, there will be no change to general contamination levels arising from the capital dredge compared to those that occur from the existing maintenance dredge commitments from around the Solent. Overall, given the negligible to very low exposure to chemical contamination during disposal, together with the high dispersion of material outside the deposit ground and rapid dilution of any contaminants as soon as the dredge load is released into the water column, the impact on interest features comprising the nearby rmczs is considered to be insignificant. P.1523 vii R.1837

11 Potential Effects of Changes in Suspended Sediment Concentrations There will be short term elevations in suspended sediment concentrations in the water column during the disposal of capital dredge arisings at the Nab Deposit Ground. Increased suspended sediment concentrations will be greatest at the immediate site of the disposal and will reduce rapidly as the sediment remaining in the water column is dispersed, predominantly in the axis direction of the flood and ebb flows (northeast/east to southwest/west). Maximum suspended sediment concentrations near to the point of disposal will exceed 200mg/l during disposal, but rapidly reduce to around 25mg/l within about 30 minutes following each disposal and within about 2.6km downstream in the southwest/west direction on the ebb and less than 1km in the northeast/east direction on flood flows. Peak concentrations outside the immediate disposal plume of up to around 150mg/l will occur in the Bembridge rmcz albeit for very short periods of time (circa 15 minutes). For the most part, the average suspended sediment concentrations arising from the disposal are predicted to be about 25mg/l. In terms of the Utopia and Offshore Overfalls rmczs, the modelling shows that only a very small proportion of the suspended sediment will move into these designated areas. Peak concentrations, at any one time over the 4 week period of disposal, will be up to 50mg/, with a small proportion in the Offshore Overalls rmcz reaching a maximum of up to 100mg/l. Average suspended sediments concentrations in these areas, however, will be considerable less. The Nab Deposit Ground is a highly dispersive site that has been used for many years as a licensed disposal site. The dredge arisings from Berth 201/202 that will disperse from the site will be of a similar character to the existing deposits from maintenance dredging. The increase in suspended sediments and the overall extent of effect will be comparable to that normally experienced during maintenance dredge disposal operations, although, the total volume disposed will be considerably less (around 26% of annual maintenance deposits at the site). Taking all the above factors into account, the magnitude of change in suspended sediment concentrations is considered to be small. In terms of receptor sensitivity, apart from maerl beds, all of the habitat and species interest features comprising the Bembridge, Utopia and Offshore Overfalls rmczs are considered to have a negligible to low sensitivity to changes in suspended sediment concentration (MarLIN website). Maerl beds are considered to have a higher sensitivity to increases in suspended sediment because the key structural species within this habitat, either Lithothamnion glaciale or Phymatolithon calcareum, is photosynthetic and, thus, likely to be sensitive to increases in turbidity in the photic zone (Birkett et al., 1998). Many of the other characterising species in this biotope live between the maerl nodules. Some of these species may benefit by increases in siltation (e.g. suspension feeders, species that use particles in construction), whilst others will decline due to subsequent changes in the sediment grain size of the habitat. Any disposed sediment that settles over this habitat will be re-dispersed within up to two hours and is therefore not considered to be a significant impact pathway. In any case, all the interest features of the rmczs are already characterised by the effects of regular disturbance through the disposal of maintenance dredge arisings and the effects of the licensed aggregate dredging within the area, which combined comprise a greater change than the proposed disposal of arisings from Berth 201/202 when they occur. Therefore, the impact of the disposal to rmcz interest features in the study area is considered to be insignificant to the majority of rmcz P.1523 viii R.1837

12 interest features, apart from maerl beds where the impact is considered to be at worst minor adverse significant. Summary Overall the deposit of Berth 201/202 dredged material at the Nab Deposit Ground is considered to have insignificant effects on the majority of habitats and species interest features of the rmczs that occur in the study area. The impacts are considered to be at worst minor adverse significant to maerl beds, a habitat FOCI of the Bembridge rmcz, given their sensitivity to changes in suspended sediments and turbidity. All the rmcz interest features have already been subject to such changes over variable time periods for many years (by annual maintenance dredging, intermittent capital dredge campaigns, aggregate dredging and sewage sludge disposal); therefore, the communities have developed to be accustomed to these variable conditions above the natural background variability of what is a relatively dynamic area. Furthermore, the monitoring undertaken in connection with the disposal of dredge arisings from the channel deepening of 1996/7, which was of much greater scale than the current proposal, did not cause concern at the time. References Balanced Seas, Balanced Seas Marine Conservation Zone Project. Final Recommendations. September 7 th Birkett, D.A., Maggs, C.A. and Dring, M.J., Maerl. An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Natura 2000 report prepared by Scottish Association of Marine Science (SAMS) for the UK Marine SACs Project., Scottish Association for Marine Science. (UK Marine SACs Project, vol V.). MarLIN (The Marine Life Information Network) website, Last accessed 30 August P.1523 ix R.1837