# The Surface Waters (Shellfish) (Classification) (Scotland) Regulations 1997, Schedule: CRITERIA FOR CLASSIFICATION OF WATERS AS SHELLFISH WATERS


No. in Annex to 79/923/EEC
Parameter
Units
Requirements to be satisfied
Reference methods of analysis
Minimum sampling and measuring frequency
1
pH
pH unit
≥7 and ≤9
Electrometry.
Measured in situ at the time of sampling.
Quarterly
3
Colouration (after filtration)
mg Pt/1
A discharge affecting shellfish waters must not cause the colour of the waters after filtration to deviate by more than 10mg Pt/1 from the colour of waters not so affected.
Filter through a 0.45 μm membrane
Photometric method, using the platinum/cobalt scale.
Quarterly
4
Suspended solids
mg/1
A discharge affecting shellfish waters must not cause the suspended solid content of the water to exceed by more than 30% the content of waters not so affected.
Filtration through a 0.45 μm membrane, drying at 105°C and weighing.
Centrifuging (for at least five minutes, with mean acceleration 2,800 to 3,200g), drying at 105°C and weighing.
Quarterly
5
Salinity
‰
≤40‰
A discharge affecting shellfish waters must not cause their salinity to exceed by more than 10% the salinity of waters not so affected.
Conductmetry.
Monthly
6
Dissolved oxygen
Saturation %
≥ 70% (average value)
If an individual measurement indicates a value lower than 70% measurements shall be repeated.
An individual measurement may not indicate a value of less than 60% unless there are no harmful consequences for the development of shellfish colonies.
Winkler’s method.
Electrochemical method.
Monthly, with a minimum of one sample representative of low oxygen conditions on the day of the sampling. However, where major daily variations are suspected, a minimum of two samples in one day shall be taken.
7
Petroleum hydrocarbons
Hydrocarbons must not be present in the shellfish waters in such quantities as to:
produce a visible film on the surface of the water and/or a deposit on the shellfish,
have harmful effects on the shellfish.
Visual examination.
Quarterly
8
Organohalogenated substances
The concentration of each substance in the shellfish waters or in shellfish flesh must not reach or exceed a level which has harmful effects on the shellfish and their larvae.
Gas chromatography after extraction with suitable solvents and purification.
Half-yearly
9
Metals
Silver Ag
Arsenic As
Cadmium Cd
Chromium Cr
Copper Cu
Mercury Hg
Nickel Ni
Lead Pb
Zinc Zn
mg/1
The concentration of each substance in the shellfish waters or in the shellfish flesh must not reach or exceed a level which has harmful effects on the shellfish and their larvae.
The synergic effects of these metals must be taken into consideration.
Spectrometry of atomic absorption preceded, where appropriate, by concentration and/or extraction.
Half-yearly
11
Substances affecting the taste of the shellfish
Concentration should be lower than that which is liable to impair the taste of the shellfish.
Examination of the shellfish by tasting where the presence of one of these substances is presumed.

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Source: https://www.legislation.gov.uk/uksi/1997/2470/schedule (the official version)
Page: https://openlegislation.uk/surface-waters-shellfish-classification-scotland-regulations-1997/schedule
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.