Case study 1: Kelp Bay



Assessment of likely significant effect


The purpose of this scenario is to introduce the use of the guidance manual and the issues to be considered in a simple situation with a single proposed new discharge consent against a background of good water quality and condition of the interest feature.


There is a proposal for the construction of a food processing factory which will discharge an effluent having a high BOD and containing high concentrations of nitrogen, phosphorus and suspended solids. It is proposed to discharge the effluent into a sheltered coastal embayment via an outfall. The bay has been selected as a candidate SAC with shallow inlet and bay as the qualifying interest feature. The kelp forest which currently occupies 70% of the seabed in the bay has been identified as a key sub-feature contributing to the maintenance of the ecological integrity of the site. The condition of the kelp forest will be used as a baseline from which to judge the favourable condition of the interest feature. This feature is in good condition and water quality in the bay is considered to be very good, compared to similar types of site elsewhere.

Assessment of likely significant effect


The construction of a new food processing factory would have already gone through the planning process and the conservation and environment agencies would have been consulted at that stage. Likely water quality issues should have been identified at that early stage during the planning process and staff should encourage an appraisal of such factors as far as is possible during the initial planning stage. To be considering the likely significant effects of the proposed application for consent to discharge, we will assume that planning permission will already have been granted. Food processing is not a prescribed process under IPC (see Section 2) and consequently application for a consent to discharge will be made under the Water Resources Act in England and Wales (NB: food processing is to be brought under the control of the forthcoming Integrated Pollution Prevention and Control Regulations.) The principal components of the discharge are non-toxic but can have primary and secondary effects on interest features (see Section 4). There are no formal standards for the principal polluting substances (see Section 5) and consent conditions for these substances will have to be set such that the concentrations in the receiving water do not have an adverse effect on the integrity of the site.

In considering a consent for this new discharge, the competent authority will have come to a view on the appropriate location for the discharge (in consultation with the conservation agency). Avoiding damage during construction, as well as selecting a location which causes least risk to interest features locally, will be key considerations. This example considers only operational issues, not those arising during construction. The discharge point will be below Mean Low Water Springs (MLWS) and the design of outfall will be suitable to achieve the design guidance for initial dilution. The volume of the discharge under all flow conditions will have been specified and the components of the discharge identified. Consent conditions for polluting substances will also need to be set (as an absolute limit for a non-sewage discharge) such that all other appropriate EC Directives, international obligations, environmental, conservation and aesthetic considerations are met.

In parallel with these considerations, the proposed consent is subject to the Regulation 48 process to establish whether it is likely to have a significant effect on the interest features of the site.

The steps set out in this example are based on forthcoming joint EA/EN/CCW guidance Applying the Habitats Regulations to New Agency Authorisations and Activities (EAS/3100/4/2). The initial steps in the process: (a) is the plan or project directly connected with the management of the site for nature conservation, and (b) identify the interest features of the site, have already been completed. The steps below are those now used to determine whether the plan or project is likely to have a significant effect. Three general criteria have been identified:

I. Is there a hazard?

II. Is there a risk of exposure to the hazard?

III. What is the likely scale of any effect?

These are considered below.

Existing Guidance for the Review of Agency Permissions (English Nature, Countryside Council for Wales and Environment Agency 1999), sets out four steps in determining whether a discharge is likely to have a significant effect during the process of reviewing consents. These are adapted here to the process for considering new proposals, but more definitive advice on the steps involved is being developed.

Step I: Are the interest features sensitive to any hazard arising from this process?

Kelp Bay is a large shallow inlet or bay with a submerged reef comprising a kelp bed. The kelp bed is the vulnerable sub-feature present on site because of its sensitivity to light and nutrient regimes.

Step II: Is there a mechanism by which the consented discharge(s) is likely to affect the designated features of the site?

In this case, the discharge is directly onto the interest feature.

Step III: Is the potential scale of any effect likely to be significant?

Since the judgement of 'likely significance' is intended as a coarse filter to ensure that all relevant situations are appropriately assessed, any impact which is likely to have a measurable effect on the feature of interest should be considered potentially of significance (in a similar way a de minimis judgement is applied to the area of an interest feature potentially affected by a development, for example).

In helping to reach a judgement over whether the scale of any effect of a change in water quality due to a consented activity is likely to be significant, the following factors should be taken into account:

  • Is the area affected likely to be highly localised or more extensive?
  • Is the affected area likely to coincide with or impact on the designated feature?
  • Is the effect likely to be readily or rapidly reversible during the operation of the consented activity?
  • What is the likely contribution from the consented activity relative to other sources (and background levels)?
  • Is the designated feature particularly sensitive to the particular water quality change?
  • Are cumulative effects likely in association with other consented activities?

A table of this guidance manual lists 16 principal activities and the mechanisms by which water quality might be affected. With new discharges, it is important to ascertain what the polluting substances are in the discharge. This information will be contained in the proposed discharge consent. For many polluting substances, there is a profile held elsewhere under this topic in the website describing the behaviour of that substance, or group of substances, in the environment and the effects on groups of aquatic organisms. This information can be used to determine whether a mechanism exists which links the discharge and the designated features, and also to indicate whether the mechanism is likely to operate in this situation.

In situations such as this, where there are no clearly applicable standards, an understanding of any risks involved may be assisted by a comparison of the predicted state, with the current status of the site.

The guidance manual contains a summary of the water quality monitoring undertaken by the competent authorities in the UK which is co-ordinated at a national level within each country. The sources of information listed should be consulted for available information on a site by site basis. There may be local operational monitoring programmes undertaken by the regions of the competent authority and this information may be obtained from regional offices. Alternatively, Conservation Officers may have other (including anecdotal) information from a range of sources which suggest that water quality maybe an ongoing issue.

Water quality in Kelp Bay is believed to be good and there are no other discharges likely to affect the bay (although it is worth noting that inputs from the surrounding marine environment are known to be important for several shallow inlet situations in the UK, e.g. Lindisfarne, Budle Bay, Chichester/Langstone Harbours). Available monitoring data were, however, sparse because there has been no history of water quality problems and these areas tend to be monitored less frequently. In this case, therefore, available water quality information is likely to be of little help in determining whether a significant effect is likely, but we can therefore assume that background nutrient levels are unlikely to be affecting the feature adversely.

The conservation agencies may be consulted at this stage to provide information on whether features are in favourable condition. In the case of new discharges etc, this information may help to judge whether an additional pollution load is likely to stress the system such that it is unable to maintain its condition. This guidance manual can provide no information on the definition of favourable condition for individual features but can provide some guidance as to what aspects of water quality should be a component of the favourable condition table for each feature.

For the situation in Kelp Bay, the most appropriate response is that the designated feature is in favourable condition and current consents do not appear to be having a significant effect.

For the situation in Kelp Bay, the polluting substances are organic particulates (leading to elevated BOD), nitrogen, phosphorus and suspended solids. The kelp bed (with its associated fauna of invertebrates and fish) is used as the sub-feature for helping to judge the site condition. The profiles for the polluting substances are located in the appendix of the guidance manual.


Elevated BOD arises from the organic substances in the effluent that undergo aerobic degradation and, therefore, exert an oxygen demand on the water column or the sediments. Much of the organic matter is likely to be in particulate form and, depending on the particulate size distribution and the water movements around the outfall, the larger particles would be expected to settle out early in the secondary mixing process and the smaller particles may be carried further afield (see 'suspended solids' below). The oxygen demand on the water column may often be restricted to a small area around the discharge point and probably within the mixing zone. Making such a judgement in a specific case such as this cannot be based on information in this guidance document, instead specialist advice should be sought on the likely behaviour of oxygen demand in the particular circumstances being considered. This effectively will identify a condition where any impact of this factor may be considered trivial and needs not be considered further.

A mechanism exists for BOD lowering the oxygen status of the water column which in turn affects the fauna associated with the interest feature. Providing the water is well mixed (and it may be in this case - considering the tidal range and relatively shallow depth of the bay - although this would need to be confirmed by modelling), there will probably be sufficient transfer of oxygen from the atmosphere not to affect any pelagic fauna. However, in the absence of such modelling information, it would be reasonable to conclude that a significant effect is likely in this case due to BOD, and an appropriate assessment is required.

Suspended solids

Larger particles settling out of the water column will be used by filter feeding organisms as a food source and will accumulate initially on the substrate surface if hydrodynamic conditions allow. Water movements within the kelp bed will be reduced compared to the open bay and any particles transported to the kelp bed may be more likely to settle either on the sediment or on the kelp itself. Accumulation of organic particles may result in an oxygen demand on the sediment which can result in a change in the composition of the benthic fauna which could affect associated benthic feeding fish communities.

A mechanism therefore exists whereby suspended solids (comprised principally of organic matter) settle out of suspension and increase the sediment oxygen demand, thereby lowering the oxygen status of lower waters and of the sediment itself. Reduced sediment oxygen status is acknowledged as a major factor determining the infaunal community composition (and to some extent the surface-dwelling faunal community). The BENOSS model predicts the effects of organic suspended solids on the sediment faunal community and would be an appropriate tool to predict effects during an appropriate assessment. In this case, the existence of a mechanism whereby the interest feature is affected, together with the likely coincidence between area affected and the interest feature lead to a judgement of "likely significant effect" due to change in oxygen status.

Suspended solids also contribute to turbidity and so would decrease light penetration of the water column. The relationship between the lower depth limit of macrophyte colonisation (and thus the total area colonised by macrophytes) and water clarity is well established. Since macrophytes (in this case the kelp beds) form an important sub feature of this site, since also a mechanism exists whereby suspended solids (via effects on light penetration) can affect this sub-feature and since, although we have no information on the area likely to be affected or whether the kelp is in fact light limited in this case, there is likely to be coincidence between the area affected by change in suspended solid levels and the interest feature, a "likely significant effect" due to the effect of suspended solids on light penetration is a reasonable conclusion in this case.


The effects of nutrients on macroalgal communities are extremely difficult to determine. There is some evidence that elevated nutrient levels, up to a maximum concentration, stimulate the rate of growth of macroalgae. However, this maximum concentration is not known. For microalgae (phytoplankton) again there is evidence for N or P limiting growth in certain estuarine situations but the thresholds for this site would probably not be known.

Kelp forests are known to thrive at the nutrient concentrations which typically are likely to occur outside the mixing zone. However, increased nutrient availability could increase the standing crop of epiphytic algae, further reducing light availability to the kelp and thereby reducing the area colonised by the kelp, assuming that light availability is a limiting factor in this case.

For each of the polluting substances, there is a potential mechanism affecting the kelp bed or its associated fauna. For nutrients (this could be nitrogen and/or phosphorus) and suspended solids, there is sufficient evidence to suggest that there may be an effect on the kelp bed or its associated fauna and, without further information, an effect of BOD cannot be ruled out at this stage.

The conclusion for the situation in Kelp Bay is that the proposed consent for the discharge is likely to have a significant effect on the interest feature.

Step IV: Internal and external consultation

The conclusions of Steps I to III are subject to internal (within the competent authority) and external (with the country conservation agency) consultation to confirm, or otherwise, the judgement of likely significance. The reasons for the judgement of a likely significant effect in this case are:

  • The consent will cause an increase in BOD, suspended solids, turbidity and nutrients, all of which are factors to which the interest feature is considered sensitive.
  • There is insufficient evidence to be able to conclude that these effects are not likely to have a significant effect, specifically.
  • Insufficient evidence that BOD will not be raised locally such as to adversely affect an unacceptably large area of kelp-dominated habitat. Insufficient evidence that the nutrient regime will not adversely affect macro-or planktonic algal development.
  • Insufficient information available to determine where the suspended solids will settle, or to determine whether the sediment will become organically enriched, thereby affecting the sediment oxygen status, altering the particle size composition and potentially changing the infaunal community status.
  • Insufficient information to determine the effect of the discharge on the light climate within the bay (as a result of increased turbidity through the effects of increased suspended solids loading or in response to increased nutrient loading) and light availability to the kelp (as a result of settled particulate matter and potentially increased epiphyte standing crops.

Since the requirement is to establish a likely effect at this stage for the situation in Kelp Bay, the conclusion is up held through the consultation steps and the judgement of likely significant effect is confirmed. An "appropriate assessment" is therefore required. An important principle here is that we have erred on the side of caution, in the absence of further information in reaching this judgement. The process of delivering the appropriate assessment is considered briefly below, but more detailed forthcoming guidance (EAS/3100/4/2) should be referred to. Appropriate assessment

The purpose of an appropriate assessment is to gather and assess additional information to demonstrate adequately that a discharge will not affect the integrity of the site. This may involve a range of different activities, including those listed below, although it is important that the assessment remains appropriate, the level of assessment needs not be as comprehensive as indicated for all cases. The appropriate assessment may therefore involve:

* A more thorough assessment of available data in terms of compliance with statutory standards (particularly in relation to determining the existing status of the water body).

* Modelling dispersion of the discharge and the concentrations of pollutants within it; then comparing these concentrations with statutory standards (none relevant to this case study).

* Further investigation to determine the concentrations of pollutants within the water column and/or sediment (again relevant to determining current status of the water body).

* Gathering more information on the toxicity of pollutants contained in the discharge (no toxic substances in this case study).

* Undertaking comparative assessments of biotopes within the European marine site with otherwise similar biotopes from tidal water exposed to a range of concentrations of the same pollutants (possibly a useful approach in this case study).

* Ecological modelling to determine the likely effects (short, medium and/or long-term) of non-toxic pollutants contained in the discharge (in this case the BENOSS model would be appropriate for predicting organic carbon impacts).

* Laboratory studies to determine how different pollutants react with each other to affect their potential toxicity in the environment (not relevant to current scenario).

* Investigations of the potential for accumulation of pollutants within the sediment (in this case nutrient dynamics should be assessed).

* Studies to determine bioconcentration factors of discharged chemicals and the potential for bioaccumulation through the food chain (not relevant in this case).

* Collection of hydrodynamic data. Any hydrodynamic models must be validated against real measurements.

The level of assessment, and nature of information required will need to be discussed and agreed in advance with the competent authority and the developers. In this case study, the key issues for the assessment to address (based on the factors previously identified as likely to have a significant effect) are:

1. To assess likely effect of BOD:

* What is predicted size of dilution zone for BOD?

* What is its location in relation to the interest features?

* What is the duration/timing of maximum BOD loads and their relationship with existing BOD standards (e.g. for dissolved O2)?

2. What area is affected by increased suspended solids?

* Suspended solids deposition model needed.

* Suspended solids water column (light attenuation) model needed.

                            This should be compared with background levels (may require sampling) and their variation.

                    * Effect on benthos - location affected and sensitivity of benthos.

                    * Effect on macro-algal growth/distribution.

3.  Modelling of predicted N and P concentrations at 'worst case' situations (time of year, state of tide/wind).

* Area affected (timing and duration) by nutrients in relation to sensitivity of features. Must take account of relevant variables: tide, wind, stratification, freshwater flow.

* Background nutrient levels and variation.

* Relationship of nutrient concentrations with concentrations known to be likely to lead to elevated chlorophyll .

* Risk of accumulation in and release from sediments.

If, for example, nutrient concentration elevation is minimal relative to background levels and variation, and there is no other evidence of nutrient disturbance to the site (i.e. the site is not likely to be approaching an irreversible change in nutrient status) then it may be possible to ask for a time-limited consent to enable monitoring of the activity in order to determine:

* how accurate are any model predictions?

* are any (reversible) changes detectable in the most sensitive indicator species?

As with the initial assessment of likely significance, the competent authority is responsible for making the final judgement on whether current or proposed consent conditions will affect the integrity of a European marine site. However, there is a statutory requirement to consult the statutory nature conservation bodies over the results of the appropriate assessment and the conclusions over any effect on the integrity of the site.

It is possible that the results of an appropriate assessment investigation may still leave substantial doubt as to the medium or long-term impact of a discharge on the integrity of a site. The Habitats Regulations require there to be no adverse effect on integrity, so where this is the case, staff should employ the precautionary principle and require the proposal to be amended or rejected. In certain cases, e.g. where an adverse effect is clearly going to be reversible (in the short term) it may be acceptable to agree limited consent whilst further monitoring data are collected in order to test model predictions with the scheme in operation. However, even where an appropriate assessment suggests that the integrity of the site will be damaged by current or proposed consent conditions, those consent conditions may still be granted if there are overriding reasons of public interest and alternative solutions are not possible, ultimately a decision on this will be determined by the Secretary of State, and compensatory measures will then be required.

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