Poor quality

Poorbathing water quality Excellent Good Sufficient Poor Symbol according to Commission implementing decision of 27 May 2011 (2011/321/EU)

The European regulation DIRECTIVE 2006/7/EC defines poor quality as follows:

Bathing waters are to be classified as ‘poor’ if, in the set of bathing water quality data for the last assessment period (a), the percentile values (b) for microbiological enumerations are worse (c) than the ‘sufficient’ values set out in Annex I, column D.
NOTES
(a ‘Last assessment period’ means the last four bathing seasons or, when applicable, the period specified in Article 4(2) or (4).
(b) 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).
(c) ‘Worse’ means with higher concentration values expressed in cfu/100 ml.

Excerpt from Article 5(4)(a):
in respect of each bathing water classified as ‘poor’, the following measures shall be taken with effect from the bathing season that follows its classification:
  1. adequate management measures, including a bathing prohibition or advice against bathing, with a view to preventing bathers' exposure to pollution;