(7) Compliance checking with environmental quality standards

1. (7) Compliance checking with environmental quality standards WG E (5), Brussels, 18 March 2009

2. Aim • To give a very broad overview of the issues that should be tackled in order to achieve the appropriate level of confidence and precision when compliance with EQS is checked. Preliminary questions intended to trigger discussion among the Members States on the proposed approach and the way foreward

3. The general approach to achieve compliance checking • The evaluation of the chemical status of a water body passes through the following subsequent operational steps: • Determining, at the level of the monitoring station and for EACH priority substance: • annual average concentration • maximum concentration (or percentile) • Determining, at the level of the monitoring station and for ALL priority substances : • compliance with AA-EQS, • compliance with MAC-EQS • Evaluating the chemical status for whole water body . • For each of these steps rules need to be applied in order to ensure a common approach for compliance within and between MSs.

4. Annual average concentration for each PS • Number of sampling sites and sampling frequency for an adequate level of confidence and precision • What should be defined as the “acceptable level of confidence and precision” for the purpose of assessing the chemical status of a water body? How should it be defined? • What is the acceptable number of samples for the calculation of the mean for each Priority Substance? • How to deal with ‘missing data’, i.e. stations for which the number of samples is below the minimum level for “acceptable level of confidence and precision” (ex. unusual weather conditions (drought, floods, etc.) or laboratory problems)? • To what extent is it possible to replace measured data with calculated data in order to compensate for ‘missing data’ and achieve the required “acceptable level of confidence”?

5. Annual average concentration for each PS (2) • Taking into account measurement uncertainty • Background : future QA/QC Directive • Article 4 : Minimum performance criteria for methods of analysis • 1. Member States shall ensure that the minimum performance criteria for all methods of analysis applied are based on an uncertainty of measurement of 50% or below (k = 2) estimated at the level of relevant environmental quality standards and a limit of quantification equal or below a value of 30% of the relevant environmental quality standards. • Provided that measurement data are accompanied by the associated measurement uncertainty, how should individualuncertainties be combined to assess the uncertainty of the calculated annual average concentration ? • How to deal with data when uncertainty is higher than 50 % at the level of EQS ? • How to deal with data without uncertainty ?

6. Annual average concentration for each PS (3) • Dealing with quantification limits • Initial requirement : LQ ≤1/3 EQS • LQ set to LQ/2 • But what happens when the quantification limit is between 1/3 EQS and the EQS? • How to deal with LQs above the EQS? • Is it acceptable to discard all these data, taking into account that today there are still several priority substances for which analytical techniques do not satisfy these performance requirements? • “Final” uncertainty will impact the confidence of the annual average concentration when LQs is taken into account (depending on the rules taken for LQs) and therefore the decision about LQs will be crucial for the final judgment.

7. Maximum concentration for each PS • Background • DIRECTIVE 2008/105/EC on environmental quality standards in its annex I part B allows that, “in accordance with section 1.3.4 of Annex V to Directive 2000/60/EC : • Member States may introduce statistical methods, such as a percentile calculation, to ensure an acceptable level of confidence and precision for determining compliance with the MAC-EQS. • UK proposal on percentile approach • It is necessary to express an absolute limit as a percentile, in order to calculate correctly the action needed to meet standards. • What is the highest individual concentration to be considered for compliance with MAC-EQS?

8. MAC EQS Max value Max value Max value AA EQS Mean value Mean value Mean value

9. Compliance with AA EQS or MAC EQS • How to integrate uncertainty • Background : • CIS Monitoring Guidance N°7 there are three possible approaches to assess the risk of failing the objectives (EQS, in this case): • Benefit of doubt approach: it passes even when the estimate has marginally failed • Fail safe approach: it fails even when the estimate has marginally passed • Face value approach: uncertainty is ignored and the pass/fail rule depends solely on the value. • Is there a need to define common rules on the approach to be used for compliance checking for chemical status? (i.e. what of these three approaches should be used)

10. Doubtful AA EQS

11. Determining compliance EQS at the monitoring station for all PS • How to deal with missing information on certain priority substances (for example, where a decision has been made to reject datasets when LQ is too high (i.e. >1/3 EQS or above EQS)? • Is there a minimum number of priority substances to assess the chemical status at the monitoring station ? • Is it possible to admit temporarily that some substances are missing ?

12. Compliance checking : chemical status for the “water body” • No station • Background • Monitoring Guidance N°7: “The Directive requires that sufficient water bodies should be included in the surveillance monitoring programme to provide an assessment of the overall surface water status • A good example of representative sub sampling is in some Nordic lake monitoring programmes where only relatively few of the many thousands of lakes are monitored and directly assessed. The results from the ‘few’ lakes are then extrapolated to the whole ‘population’ of lakes being assessed.” • Do we need to define more specific common rules on how to extrapolate and use monitoring data (or modelling data) for assessing compliance with EQS when no monitoring station is present in a water body ?

13. Compliance checking : chemical status for the “water body” (2) • More than one station • Citation from Monitoring Guidance N°7: “A requirement that is implicit in the WFD is that the purpose of identifying “water bodies” is to enable the status of surface waters and groundwaters to be accurately described.” • As a result, “A discrete element of surface water should not contain significant elements of different status. A “water body” must be capable of being assigned to a single status class with sufficient confidence and precision through the Directive’s monitoring programmes.” • Is the issue on how to aggregate and use monitoring data from multiple stations in the same water body, for the purpose of compliance checking, a real one  ?

14. Conclusion • These issues may be discussed at different levels and in particular at the national level in order to assess properly compliance checking with environmental quality standards. • Is it worthwhile to address these issues and probably other missing issues through • Ad-hoc working group at European level • Drafting group to establish a technical guidance • To adopt common rules at European level or at least to exchange in order to minimize the differences between MS’s.