# The Surface Waters (Shellfish) (Classification) Regulations (Northern Ireland) 1997, Schedule 1: Criteria for classification of waters as shellfish waters

Extent: N.I.
Status: prospective

No in Annex 1 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/1
A discharge affecting shell- fish waters must not cause the colour of the waters after filtration to deviate by more than 10 mg Pt/1 from the colour of waters not so affected.
— Filter through a 0.45 um membrane
Photometric method, using the platinum/cobalt scale
Quarterly
4.
Suspended solids
mg/1
A discharge affecting shell- fish waters must not cause the suspended solids 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 5 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
Conductivity
Monthly
6.
Dissolved oxygen
saturation %
≥70% (average value) Should an individual measurement indicate 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 1 sample represent- ative of low oxygen conditions on the day of sampling. However, where major daily variations are suspected, a minimum of 2 samples in 1 day shall be taken
7.
Petroleum hydrocarbons
Hydrocarbons must not be present in the shellfish water 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 shellfish
Visual examination
Quarterly
8.
Organohalo- genated 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 exceed a level which gives rise to 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 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/nisr/1997/489/schedule/1 (the official version)
Page: https://openlegislation.uk/surface-waters-shellfish-classification-regulations-northern-ireland-1997/schedule-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.