Key issues of the method
- surface receptors
What and Why for Thresholds
• WFD requires Status assessment at start of each RBMP cycle
• Aim to achieve Good Status by 2015
• Status assessed against Threshold Values (TV)
• TV needed for pollutants which cause “at risk” characterisation
Development of the method
• Workshops of WP3
– Feb 05 & Nov 05
– Jan 06, Jun 06 and Sep 06
• Draft method delivered Feb 06
• WP4 case study examples
• Comments from the Advisory Board
• GWDD evolved considerably during the project - groundwater receptor
Guidance on Thresholds - Annex 2
• “the extent of interactions between
groundwater and associated aquatic and dependent terrestrial ecosystems”
• “hydrogeological characteristics…”
• “origins of pollutants, natural occurrence, toxicology and dispersion, persistence and bioaccumulation”
• All adds up to having a sound conceptual understanding of the system
A tiered approach
• Common in risk based methods
• Allows risk management in a balance between costs and (un)certainty
• Increasing certainty allows less
conservatism but at greater cost in time, effort and data. Data requirements
work, costs Conservatism
Uncertainty
Protection of Environmental resources
Tiers
• Tier 1 Natural background
• Tier 2 A receptor based quality standard, (existing relevant standards e.g. EQS)
• Tier 3 Dilution. This allows account to be taken of the proportion of the pollutant that is due to the groundwater.
• Tier 4 Attenuation. This allows
consideration of any attenuating processes that may occur
T ie r 2 Is [po llut an t] > QS?
C he ck for tr ends
C he ck for tr ends MONITOR ED DAT A
Is [po llut an t] > NBL ? T ier 1
Yes Set t hresh old = QS (o r
NBL if e xceed ing QS)
Se t th resho ld= QS/ DF St atu s = GOOD
St atu s = GOOD No
No
Is [po llut an t] > (QS/DF )*AF ? Se t thresho ld= (QS/DF )*AF Is [po llut an t] > (QS/DF )?
Tie r 3
Tie r 4
Stat us = GOOD
St atu s = POOR
Check for trends Yes
Yes N o
Rule s
1. U se the ap prop riate q ual ity stan dard , QS.
If ecol ogi cal ris k u se EQS.
If huma n hea lth risk use DWS.
2. If dil ution factor, DF, n ot kn own a ssume = 1 .0 3. If atte nua ti on factor, AF, not know n assum e =
1 .0
4. In ch eck fo r Tren ds use AL L tri gge rs-consi der n eed fo r tren d reversa l if crossin g each trig ger Do es ap pro priat e
Investigat ion sh ow th at co nd ition s for g oo d ch emic al
st atu s are n ot met ?
D efine Objective s a nd Mea sures Yes
N o Derive NBL
(a ccord ing to Ann ex I)
De rive TV (ac cord ing to
An nex II) T ie r 2a
Is [p ollu tan t] > T V?
OR No
Set t hresh old = NB L C he ck for tr ends Status = GOOD
Finding the natural background
• National data
• Local data
• Aquifer typology
Suggested reference standards
• See Annex I
Receptor Likely Substance Suggested reference standards Surface Water Ecological & Chemical Status
Aquatic ecosystem Any pollutant which causes risk to a surface water body
Surface water EQS (and ecotox data for aquatic organisms)
Dependent Terrestrial Ecosystems terrestrial ecosystems
(plants, vegetation)
Any pollutant which causes significant damage to a groundwater dependent ecosystem
To be determined specifically
(surface water EQS might be used as screening values)
Receptor Likely Substance Suggested reference standards Drinking Water Protected Areas
drinking water Any pollutant which causes risk to a groundwater body
Operational performance limit for existing or regionally usual
treatment infrastructure
Note: For many locations no treat- ments are used and hence Drinking water standards should apply.
Other legitimate uses
e.g. irrigation, crop washing Any pollutant which causes risk to a groundwater body
Dependent on use. Food-related use Drinking Water Standards (DWS), for non-food use suggest process operational needs
determined on case-by-case Saline or other Intrusions
groundwater chloride, sulphate and electrical conductivity
NBL
Widespread pollutants
groundwater nitrate, pesticides see WFD and GWDD:
- Nitrate 50 mg/l - Pesticides 0,1 µg/l General Chemical Assessment (pollution significantly impairing the resource)
groundwater Any pollutant which causes risk to a groundwater body
Relevant use related standard (or NBL)
Dilution estimates from…
• Age analysis
• Tracer analysis
• Temperature profiles
• Hydrograph separation
• See D10 Ch7
Attenuation
• Processes
– Diffusion/Dispersion – Volatilisation
– Sorption (or precipitation)
– Reaction (e.g.chemical oxidation/reduction) – Biological degradation
• The last step of Threshold setting
• An early step of further investigation ?
Key issues for surface receptors
• Attention - how far does interest extend beyond “groundwater itself” ?
• Definition (lack of) of suitable standards - existing EQS, proposed list from July
• Increasingly data hungry requirements as Tiers increase
• Increasingly demanding of expert understanding
Key issues too
• Needs may be more stringent than for groundwater receptor in some cases
• Prediction of future effects
• Factorial relationship for attenuation (and dilution) should it be additive ?
• Method means that we allow existing level of attenuation but no more
Thanks to
Anne-Marie, Dietmar,
Jan, Cath,
Andreas, Johannes,
Rudiger, Frank, Ariane, Teresa, Helene, Ralf, Kim, Mette, Klaus,
Stanslaw, Hilde, Jasper, Kristine...
Groundwater ? Who cares ? I need Airwater !
