Directive 2006/7/EC of the European Parliament and of the CouncilShow full title

1. Poor quality U.K.

Bathing waters are to be classified as ‘poor’ if, in the set of bathing water quality data for the last assessment period(1), the percentile values(2) for microbiological enumerations are worse(3) than the ‘sufficient’ values set out in Annex I, column D.

(1)

‘Last assessment period’ means the last four bathing seasons or, when applicable, the period specified in Article 4(2) or (4).

(2)

Based upon percentile evaluation of the log₁₀ normal probability density function of microbiological data acquired from the particular bathing water, the percentile value is derived as follows:

(i)

Take the log₁₀ value of all bacterial enumerations in the data sequence to be evaluated. (If a zero value is obtained, take the log₁₀ value of the minimum detection limit of the analytical method used instead.)

(ii)

Calculate the arithmetic mean of the log₁₀ values (μ).

(iii)

Calculate the standard deviation of the log₁₀ values (σ).

The upper 90‐percentile point of the data probability density function is derived from the following equation: upper 90‐percentile = antilog (μ + 1,282 σ).

The upper 95‐percentile point of the data probability density function is derived from the following equation: upper 95‐percentile = antilog (μ + 1,65 σ).

(3)

‘Worse’ means with higher concentration values expressed in cfu/100 ml.