{
  "url": "https://openlegislation.uk/surface-waters-shellfish-classification-regulations-1997/schedule",
  "json_url": "https://openlegislation.uk/surface-waters-shellfish-classification-regulations-1997/schedule.json",
  "legislation": "uksi/1997/1332",
  "legislation_title": "The Surface Waters (Shellfish) (Classification) Regulations 1997",
  "legislation_url": "https://openlegislation.uk/surface-waters-shellfish-classification-regulations-1997",
  "path": "schedule",
  "kind": "schedule",
  "number": null,
  "heading": "CRITERIA FOR CLASSIFICATION OF WATERS AS SHELLFISH WATERS",
  "text": "No. in Annex to 79/923/EEC\nParameter\nUnits\nRequirements to be satisfied\nReference methods of analysis\nMinimum sampling and measuring frequency\n1\npH\npH unit\n≥7 and ≤9\nElectrometry\nMeasured in situ at the time of sampling\nQuarterly\n3\nColoration (after filtration)\nmg Pt/l\nA 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\nFilter through a 0.45 μm membrane\nPhotometric method, using the platinum/cobalt scale\nQuarterly\n4\nSuspended solids\nmg/l\nA 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\nFiltration through a 0.45 μm membrane, drying at 105°C and weighing\nCentrifuging (for at least five minutes, with mean acceleration 2,800 to 3,200g), drying at 105°C and weighing\nQuarterly\n5\nSalinity\n‰\n≤40‰\nA discharge affecting shellfish waters must not cause their salinity to exceed by more than 10% the salinity of waters not so affected\nConductimetry\nMonthly\n6\nDissolved oxygen\nSaturation %\n≥70% (average value)\nIf an individual measurement indicates a value lower than 70%, measurements shall be repeated\nAn individual measurement may not indicate a value lower than 60% unless there are no harmful consequences for the development of shellfish colonies\nWinkler’s method\nElectrochemical method\nMonthly, 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.\n7\nPetroleum hydrocarbons\nHydrocarbons must not be present in the shellfish waters in such quantities as to:\nproduce a visible film on the surface of the waters and/or a deposit on the shellfish,\nhave harmful effects on the shellfish\nVisual examination\nQuarterly\n8\nOrgano-halogenated substances\nThe 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\nGas chromatography after extraction with suitable solvents and purification\nHalf-yearly\n9\nMetals\nSilver\nArsenic\nCadmium\nChromium\nCopper\nMercury\nNickel\nLead\nZinc\nmg/l\nAg\nAs\nCd\nCr\nCu\nHg\nNi\nPb\nZn\nThe 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\nThe synergic effects of these metals must be taken into consideration\nSpectrometry of atomic absorption preceded, where appropriate, by concentration and/or extraction\nHalf-yearly\n11\nSubstances affecting the taste of the shellfish\nConcentration should be lower than that which is liable to impair the taste of the shellfish\nExamination of the shellfish by tasting where the presence of one of these substances is presumed",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/uksi/1997/1332/schedule",
    "retrieved_at": "2026-10-29T12:08:20.535744+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}