# The Surface Waters (River Ecosystem) (Classification) Regulations 1994, Schedule: RIVER ECOSYSTEM CLASSIFICATIONS


(1) Class
(2) Dissolved Oxygen % saturation 10 percentile
(3) BOD(ATU) mg/l 90 percentile
(4) Total Ammonia mg N/l 90 percentile
(5) Un-ionised Ammonia mg N/l 95 percentile
(6) pH lower limit as 5 percentile; upper limit as 95 percentile
(7) Hardness mg/l CaCO3
(8) Dissolved Copper μg/l 95 percentile
(9) Total Zinc μg/l 95 percentile
RE1
80
2.5
0.25
0.021
6.0-9.0
≤ 10
> 10 and ≤ 50
> 50 and ≤ 100
> 100
5
22
40
112
30
200
300
500
RE2
70
4.0
0.6
0.021
6.0-9.0
≤ 10
> 10 and ≤ 50
> 50 and ≤ 100
> 100
5
22
40
112
30
200
300
500
RE3
60
6.0
1.3
0.021
6.0-9.0 ≤ 10
> 10 and ≤ 50
> 50 and ≤ 100
> 100
5
22
40
112
300
700
1000
2000
RE4
50
8.0
2.5
—
6.0-9.0
≤ 10
> 10 and ≤ 50
> 50 and ≤ 100
> 100
5
22
40
112
300
700
1000
2000
RE5
20
15.0
9.0
—
—
—
—
—

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Source: https://www.legislation.gov.uk/uksi/1994/1057/schedule (the official version)
Page: https://openlegislation.uk/surface-waters-river-ecosystem-classification-regulations-1994/schedule
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.