Table 3.

Water quality classifications based on European Bathing Water Directive (BWD) criteria for Escherichia coli and confirmed intestinal enterococci (cIE) results from Swansea Bay designated sampling point during summer 2011 for two time period groupings and hourly time of day (EU, 2006: Annex I and II, Pages 46 to 48).

A. Two period classification (60 days):
Time of day (GMT)	BWD E. coli classification	BWD cIE classification	Number of observations
07:00–11:00	Sufficient	Poor	540
11:30–16:00	Good	Sufficient	600
B. Three period classification (24 days):
Time of day (GMT)	BWD E. coli classification	BWD cIE classification	Number of observations
07:00–11:00	Sufficient	Poor	216
11:30–15:00	Good	Sufficient	192
15:30–19:00	Sufficient	Poor	191
C. Hourly classification (07:00–16:00–60 days, 16:30–19:00–24 days)
Time of day (GMT)	BWD E. coli classification	BWD cIE classification	Number of observations
07:00	Sufficient	Poor	60
08:00	Sufficient	Poor	60
09:00	Sufficient	Poor	60
10:00	Good	Poor	60
11:00	Good	Sufficient	60
12:00	Good	Sufficient	60
13:00	Good	Sufficient	60
14:00	Good	Good	60
15:00	Good	Sufficient	60
16:00	Sufficient	Sufficient	60
17:00	Sufficient	Poor	24
18:00	Sufficient	Poor	24
19:00	Sufficient	Poor	24

Excellent: 95%ile E. coli ≤ 250 cfu/100 ml, 95%ile cIE ≤100 cfu/100 ml.

Good: 95%ile E. coli ≤ 500 cfu/100 ml, 95%ile cIE ≤200 cfu/100 ml.

Sufficient: 90%ile E. coli ≤ 500 cfu/100 ml, 90%ile IE ≤ 185 cfu/100 ml.

Poor: 90%ile E. coli > 500 cfu/100 ml, 90%ile cIE >185 cfu/100 ml.

Where: cfu = colony forming units and the limit values are geometric, calculated using the mean $\left(\overline{X}\right)$ and standard deviation (SD) of log₁₀ concentrations:

$90\%ile={10}^{(\overline{X}+1.282\times SD)}$

$95\%ile={10}^{(\overline{X}+1.65\times SD)}$