Regulation 8

[F1SCHEDULEN.I.Groundwater Threshold Values

[F2Table 1

Threshold values for assessing groundwater chemical status

ParameterUnitTo examine if groundwater abstraction is causing saline or other intrusionsTo examine if groundwater is providing a significant contribution to the failure of the environmental objectives of associated surface water bodiesTo examine if the quality of groundwater that is abstracted for potable use is deteriorating, possibly resulting in a need for increased purificationTo examine the spatial extent of a groundwater body or group of bodies that are exceeding an EU Standard or threshold value
(1)

The surface water environmental standards are set out in Schedule 1 to The Water Framework Directive (Classification, Priority Substances and Shellfish Waters) Regulations (Northern Ireland) 2015(S.R. 2015 No. 351).

(2)

The “dilution factor” is taken to be the fraction of the average annual river flow derived from groundwater inflows. It can be estimated from established hydrological indices such as the baseflow index, or from the ratio of catchment groundwater recharge to effective precipitation.]

Ammoniummg/l0.29
Arsenicμg/l7.5
Atrazineμg/l0.075
Cadmiumμg/l3.75
Chloridemg/l25
Electrical ConductivityμS/cm8001875
Leadμg/l7.5
MCPAμg/l0.075
Mecopropμg/l0.075
Mercuryμg/l0.75
Nitrate (as NO3)mg/l37.537.5
Nitriteμg/l375375
Simazineμg/l0.075
Sulphatemg/l187.5
Tetrachloroethyleneμg/l7.57.5
Trichloroethyleneμg/l7.57.5
Any pollutant in relation to which a surface water environmental standard has been set(1)0.5 x (surface water standard divided by dilution factor)(2)

Table 2

Threshold values for assessing the risk to wetlands

Column headerAnnual mean nitrate concentration (mg/l NO3)
Altitude Above Ordnance Datum
Wetland typeup to 175 metresmore than 175 metresany
Quaking bog184
Wet dune13
Fen (mesotrophic) and Fen Meadow229
Fen (oligotrophic and wetlands at tufa forming springs)204
Wet grassland269
Wet heath139
Peatbog and woodland on peatbog9
Wetland directly irrigated by spring or seepage9
Swamp (mesotrophic) and reedbed22
Swamp (oligotrophic)18
Wet woodland229]