# Groundwater Regulations (Northern Ireland) 2009, Schedule 1: Groundwater Threshold Values

Extent: N.I.

Table 1
Threshold values for assessing groundwater chemical status
Parameter
Unit
To examine if groundwater abstraction is causing saline or other intrusions
To examine if groundwater is providing a significant contribution to the failure of the environmental objectives of associated surface water bodies
To examine if the quality of groundwater that is abstracted for potable use is deteriorating, possibly resulting in a need for increased purification
To 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.
Ammonium
mg/l
0.29
Arsenic
μg/l
7.5
Atrazine
μg/l
0.075
Cadmium
μg/l
3.75
Chloride
mg/l
25
Electrical Conductivity
μS/cm
800
1875
Lead
μg/l
7.5
MCPA
μg/l
0.075
Mecoprop
μg/l
0.075
Mercury
μg/l
0.75
Nitrate (as NO3)
mg/l
37.5
37.5
Nitrite
μg/l
375
375
Simazine
μg/l
0.075
Sulphate
mg/l
187.5
Tetrachloroethylene
μg/l
7.5
7.5
Trichloroethylene
μg/l
7.5
7.5
Any pollutant in relation to which a surface water environmental standard has been set
0.5 x (surface water standard divided by dilution factor)
Table 2
Threshold values for assessing the risk to wetlands
Column header
Annual mean nitrate concentration (mg/l NO3)
Altitude Above Ordnance Datum
Wetland type
up to 175 metres
more than 175 metres
any
Quaking bog
18
4
Wet dune
13
Fen (mesotrophic) and Fen Meadow
22
9
Fen (oligotrophic and wetlands at tufa forming springs)
20
4
Wet grassland
26
9
Wet heath
13
9
Peatbog and woodland on peatbog
9
Wetland directly irrigated by spring or seepage
9
Swamp (mesotrophic) and reedbed
22
Swamp (oligotrophic)
18
Wet woodland
22
9

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Source: https://www.legislation.gov.uk/nisr/2009/254/schedule (the official version)
Page: https://openlegislation.uk/groundwater-regulations-northern-ireland-2009/schedule
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.