# The Surface Waters (Shellfish) (Classification) 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 Coloration (after filtration) mg Pt/l A discharge affecting shellfish waters must not cause the colour of the waters after filtration to deviate by more than 10 mg Pt/l 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/l A discharge affecting shellfish waters must not cause the suspended solid content of the waters 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 Conductimetry 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 lower 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 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 waters and/or a deposit on the shellfish, have harmful effects on the shellfish Visual examination Quarterly 8 Organo-halogenated 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 Arsenic Cadmium Chromium Copper Mercury Nickel Lead Zinc mg/l Ag As Cd Cr Cu Hg Ni Pb Zn 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 --- Source: https://www.legislation.gov.uk/uksi/1997/1332/schedule (the official version) Page: https://openlegislation.uk/surface-waters-shellfish-classification-regulations-1997/schedule Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.