Case study 1: Kelp Bay
Assessment of likely significant
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
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
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
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
- What is the likely contribution from the consented
activity relative to other sources (and background
- 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
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
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
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.
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
- 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
- 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.
18.104.22.168 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
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
What is its location in relation to the
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
Suspended solids deposition model needed.
Suspended solids water column (light attenuation)
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
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
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
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.