Environment Agency appropriate assessment: Pembroke Power Station Environmental Permit Report – Final v 2.5 - 1 - PROTECT - Environmental Permit EA/EPR/DP3333TA/A001 Executive summary Purpose An ‘Appropriate Assessment’ (AA) as required by Regulation 61 of the Conservation of Habitats and Species Regulations (in accordance with the Habitats Directive (92/43/EEC), has been carried out on the application for an environmental permit for a 2100 MW natural gas-fired combined cycle gas turbine (CCGT) power station, near Pembroke. This Appropriate Assessment is required before the Environment Agency can grant an Environmental Permit and consider the implications of the environmental permit on the Pembrokeshire Marine / Sir Benfro Forol Special Area of Conservation (SAC) and Afonydd Cleddau / Cleddau Rivers SAC. Approach The purpose of the AA is to ensure that the granting of an environmental permit does not result in damage to the natural habitats and species present on sites protected for their important wildlife. In this sense, the AA is similar to an environmental impact assessment with special focus on wildlife of international and national importance. In technical terms an, AA is a legal requirement to determine whether activities (not necessary for nature conservation) could adversely affect the integrity of the conservation site(s), either alone or in combination with other activities, and given the prevailing environmental conditions. It is required before the Agency, as a competent authority, can grant permission for the project. An adverse effect on integrity is one that undermines the coherence of a sites ecological structure and function, across its whole area, that enables the site to sustain the habitat, complex of habitats and/or levels of populations of the species for which the site is important. The AA was carried out in view of the conservation objectives for the sites, as determined by the Countryside Council for Wales (CCW), and having due regard to their advice. Particular attention was paid to: the current conservation status of designated ‘special interest’ habitats and species present on the sites; the physical, biological and chemical effects of potential hazards from the environmental permit; the scale and duration of effects; and the likely ecological response to the anticipated changes. The AA followed national procedures, explained in section 1c, which were devised in conjunction with CCW and Natural England (NE). These procedures have been reviewed annually (since 2003) and endorsed as fit-for-purpose by CCW and NE. The complexity of the Milford Haven ecosystem, the need to make certain reasonable assumptions in the mathematical models used to predict environmental changes and minor scientific uncertainties about the precise biological responses to environmental change, meant that we have used expert judgement to reach our conclusion about effects and impacts. Internal experts have confirmed that the models used have been judged to be fit for purpose and robust, having been developed over many years using measured information. The source data, assumptions and the approach we used in reaching conclusions have been internally and externally peer-reviewed, and endorsed, by international experts, with particular knowledge of Milford Haven. - 2 - We were advised by CCW that the main reasons for some of the habitats being in unfavourable conservation status are habitat loss and nutrient enrichment. Other factors of potential concern included toxic contamination, artificial changes in temperature, physical damage, siltation, turbidity and smothering. All of these factors have been assessed as part of the AA, but most scrutiny was focused on three major concerns of toxic contamination, nutrient enrichment and temperature effects, due to concerns from CCW. The conclusions below reflect our findings for both Pembrokeshire Marine / Sir Benfro Forol Special Area of Conservation (SAC) and Afonydd Cleddau / Cleddau Rivers SAC, due to the features overlapping between both designated sites. Toxic contamination The proposed power station intends to use sodium hypochlorite as a biocide in the cooling water to prevent fouling of the cooling water system. The effects of the use of sodium hypochlorite on the benthic and planktonic habitats and species were assessed using mathematical modelling that included reasonable assumptions about the size of the ’mixing zone’ in the Haven. A mixing zone is defined as ‘the ‘area of water within which we are prepared to accept Environmental Quality Standard (EQS) exceedance’, within the Environment Agency document ‘WQTAG160’ and is common practice for discharges to the marine environment. Evidence suggests that the effects of the residual biocide in the Haven would be small and not significant because: the decay rate is rapid (a few minutes); the bioaccumulation risk is minimal; the volume of water affected per tidal cycle would be small (0.26% of tidal volume of the Milford Haven at average equinox springs tide); and the mixing zone area would coincide with a very small proportion (<2%) of mudflat and sandflat habitat (the feature most predominantly found within the mixing zone). In our opinion the potential effects of the very localised influence of sodium hypochlorite on benthic communities and on planktonic life-stages of benthic fauna would not adversely affect the ecological functioning of the sites. The typical species found within the mixing zone are widely found within the rest of the protected site, outside of the mixing zone. Equally no acute effect is occurring which would adversely affect the site integrity of the protected features. Changes to the thermal regime The extent and impact of heated water discharged from the direct cooling process were assessed by detailed mathematical models using tidal cycle information to establish the mixing zone and the resulting thermal ‘footprint’ in the Haven. The thermal footprint is considered to be the area where water temperature is likely to be +2ºC above ambient (background). The extent of the thermal footprint will vary with the state of the tide and the tidal cycle. It is estimated that for 95% of the time, the footprint will coincide with 3.9% of the water surface and 1.6% of the sea-bed in the Haven. It is estimated that the volume of discharged water will be 0.26% of tidal volume of the Milford Haven at average equinox spring tide. - 3 - PROTECT - Environmental Permit EA/EPR/DP3333TA/A001 In our opinion migratory fish will not be inhibited by the thermal plume and will be able to pass through the Haven. Cefas (Centre for Environment, Fisheries and Aquaculture Science) agreed with this conclusion in their response to our consultation. We also believe that any changes in the benthic flora and fauna resulting from the thermal plume will be localised and that, overall, the communities will remain typical for the habitat which Pembroke Marine SAC is designated. Physical damage The risk of physical damage to the site has been assessed. Given that a channel has already been dredged (not part of this EPR permit) and that the velocity of the discharge water will reduce greatly in the vicinity of the discharge, due to the natural velocity of the tidal waters, the proposed flow from the discharge will cause no adverse effects. Siltation & Turbidity & Smothering The risks of siltation, turbidity and smothering have been assessed. We are confident that the levels of siltation and turbidity will remain within the wide range of natural parameters for this estuary. Intertidal organisms in the vicinity of the cooling water discharge are resilient and adaptable, and as a result can easily tolerate exposure to highly turbid and silty waters. Equally, the habitats and species concerned, are resilient and adaptable to smothering from sediment and detritus, as this is typical of the environment that they are adapted to live within. Nutrient enrichment and Habitat loss Nutrient enrichment Using the proposed emission data provided by the applicant, together with the latest Cefas information (Aldridge & Painting 2011) on nutrients in Pennar Gut, we have modelled the potential effects. As the addition or redistribution of nutrients has the potential to have adverse effects on habitats and species, in particular the eel grass beds found within Pennar Gut, suitable mitigation has been proposed by the applicant. The mitigation will be in the form of the removal of any process contribution of phosphate from the site discharge together with a reduction in phosphate from the discharge of a sewage treatment works close to the Pennar Gut. This will ensure that there is a net reduction in the amount of phosphate in the Pembrokeshire Marine SAC and enhance protection of the eel grass beds. As a result of the mitigation and using detailed modelling together with internal and expert opinion, we have ascertained that nutrient levels will not increase significantly and the re- distribution caused by the abstraction and discharge of cooling water will not cause a significant increase in algal growth. Habitat loss The proposed cooling water will discharge into an already dredged channel (not part of this EPR permit) and velocities will dissipate quickly over the adjacent mudflat shallows, therefore avoiding excessive erosion. Our external marine experts consider that the sediment and benthic fauna will quickly adapt to the new environmental conditions; any effect would be localised and not have an adverse effect on the integrity of the mudflats or of the site. In particular, we believe that the risk of smothering of eel-grass due to an increase in turbidity and siltation is not significant across the site. - 4 - In combination effects Another technical aspect of the AA is the assessment of ‘in combination’ effects. This is required to determine whether this activity could have additive or synergistic effects with other activities. The potential effects of these factors acting ‘in combination’ with each other and with other activities affecting the SACs were also taken into account, using the same national procedures, explained in section 1c, which were devised in conjunction with CCW and Natural England.