WGGW Amersfoort – 11 April 2016 Threshold Values: Report and Next Steps Tony Marsland (Amec Foster Wheeler) Tim Besien (Environment Agency – England)

DRIVER – Blueprint concerns about lack of clarity in TV methods. PURPOSE OF REPORT To understand Why the TVs used in the first RBMPs vary so much, by looking at methods and associated compliance regimes; To determine if and how MS are revising their approach for RBMP2; To gather evidence On which to base any proposals for rationalising the methods by which TVs are derived. The purpose of this work was to identify further why TVs in the first RBMP cycle varied so much – and to work out how much things were going to change in the next cycle. The work would gather evidence – and from this evidence we could propose ways of rationalising the methods by which MS calculated TVs.

CONCLUSIONS (1) “What are the key factors leading to variations in TVs? Natural Background Levels or Methods?” No single factor responsible for the wide ranges in TVs: Dilution factors, high NBLs and use of contaminated land criteria give rise to high TVs; Different methods of taking account of NBLs, safety factors/differences in summary statistics give rise to variability in the mid and lower range of TVs.

CONCLUSIONS (2) “ “Do the TV methods protect the different types of receptor noted in the WFD?” Unclear how only one status test can reflect range of receptors/CVs noted in WFD objectives unless very precautionary (low) TVs are used; Note: report not looking at risk assessment but assessing methods of deriving TVs when required i.e. risk from a pollutant has been identified In many cases existing TVs are less stringent than Drinking Water Standards e.g. due to differences in summary statistics (mean/MAC).

CONCLUSIONS (3) “Do the TV methods follow the approach(es) set out in CIS guidance?” Low uptake of CIS GD18 tests other than GQA and DWPA tests.

CONCLUSIONS (4) “Are there any major differences in RBMP2?” Relatively minor changes in RBMP2 noted from the 20 MS that provided RBMP2 data; Variability in TVs is to be expected if TVs are to reflect all receptors/uses of groundwater but there should be comparability once the effects of high NBLs are excluded and TVs are subdivided by component status test.

REPORT - POSSIBLE MEASURES (1) To increase transparency and comparability: Reporting of TVs by component status test; Clear indication of summary statistics and any dilution factors used; Indication of which method is used to take account of NBLs and whether NBL is > or < CV; Separation of TVs derived from contaminated land criteria.

REPORT - POSSIBLE MEASURES (2) Reduction in the number of methods used to take account of NBLs where NBL<CV; More widespread adoption of CIS GD18 status tests; Clarification of objectives behind the setting of TVs: when there is a significant risk from a pollutant; at a level reflecting risk to not meeting good status (close to good/poor status boundary); used at groundwater body level to assess status. Guidance on the use of summary statistics/safety factors.

OTHER ISSUES Link between TVs and trend assessment work; TVs are basis for starting point for trend reversal; WFD Art 7.3 implies deterioration (i.e. trends) should be assessed and GWD Art 4.2 indicates TVs to be set to contribute to assessment of this element of gw chemical status; Consistency of approach – failure of both status and trend objectives will drive measures.

CONTACT DETAILS Tim Besien Susie Roy and Tony Marsland; by email tim.besien@environment-agency.gov.uk Susie Roy and Tony Marsland; by telephone on +44 743 362000 or +44 7532 277599; by email susie.roy@amecfw.com or tonymarsland0@gmail.com

NEXT STEPS This meeting – brief discussion on report recommendations or issues raised; Set up voluntary group to look at these in more detail and come up with proposals for change; At this stage major revision of GD 18 not envisaged – possible supplementary note; Volunteers? Timescales.

DISCUSSION POINTS Are the TV methods used by MS sufficiently focused on the groundwater receptors/uses noted in the WFD/GWD? Are the implications of using differing summary statistics clear? When is a safety factor needed to take account of these differences? Where only the GQA test is used and there is no safety factor, is there a risk of under-reporting of poor status? Would wider use of the GD18 tests improve comparability of TVs and what are the barriers to such wider use? Are TVs based on NBLs appropriate as criteria for setting the good/poor status boundary?

NEXT STEPS This meeting – brief discussion on report recommendations or issues raised; Set up voluntary group to look at these in more detail and come up with proposals for change; At this stage major revision of GD 18 not envisaged – possible supplementary note; Volunteers? Timescales.