Water quality objectives can be set based on quality standards (threshold values) and compliance regime building entirely on technical expertise. Both require considering the spatial and temporal variability of pollution and the water quality measurement strategy (e.g.
the design of the monitoring network and the information made available for characterizing water quality).
The section of the report discusses the current situation with monitoring information for the selected groundwater body and approaches for establishing quality standards for groundwater in Latvia. It ends with discussing water quality objectives for the selected water body.
5.1 Monitoring information for water quality and status assessment
State monitoring is the main source of regular and representative monitoring data on groundwater chemical quality in Latvia. Other information sources might (1) include only single data (from irregular measurements - e.g. bore-holes database) and/or (2) characterize groundwater quality in separate local sites, usually highly polluted or potentially at risk - e.g.
monitoring of officially registered contaminated sites).
The State monitoring program provides information on the following quality parameters and polluting substances: pH, Eh, oxygen content and conductivity, Fe2+, Fe3+ ion content, Na+, K+, Ca2+, Mg2+, Cl-, SO42-, total nitrogen and its mineral forms (N/NH4+, N/NO2-, N/NO3), alkalinity, total organic carbon and total organic halogen. Depending on monitoring sites and parameters, information is available from 1960 onwards.
The parameters monitored as part of the programme reflect the aim of this program, i.e. to characterize natural chemical quality of groundwater and to indicate the presence of anthropogenic (mainly organic) pollution in groundwater. In the case of high concentrations for particular parameters (e.g. total organic carbon, Cl), investigative monitoring shall be carried out.
Due to financial constraints, the network has been reduced year by year. Currently, there is only one monitoring site in the case study area where groundwater quality is monitored (at the Imanta in the city of Riga) but petroleum products are not monitored there. Thus, other sources of information were used to characterize groundwater pollution with petroleum products:
• Self-monitoring of operators of fuel filling and petroleum stations. This is the only source providing regular monitoring information on concentration with petroleum products in the selected groundwater body (or for Latvia as a whole). This monitoring is mandatory for all operators (prescribed by the Regulation No 32 from 22.01.2002).
It shall be carried out once or twice a year by using accredited laboratories. At minimum, total petroleum products shall be monitored. Overall, there are around 145 operators of fuel filling and petroleum stations in the city of Riga (out of 156) who carry out such monitoring. In 46 sites, concentrations of petroleum products exceed current quality standards (mostly because of historical pollution).
• Monitoring for the officially registered “contaminated sites”. There are around 80 sites in the city of Riga that are registered in the official register of “contaminated sites” and where shallow groundwater is contaminated with petroleum products. Monitoring data are available for some of these sites (where investigative monitoring has been carried out).
It is important to stress that both information sources mentioned above aim at characterizing pressures and impacts of pollution sources. These data cannot be directly used for risk
assessment for the water body status as they do not provide a representative picture about the water body quality as a whole.
In conclusion there is no regular monitoring data available that can be used for assessing the petroleum concentration in the water body status. In practice, it means that the status assessment could be based either on the analysis of pressures followed by an assessment made by expert (as it was done as part of the characterization work in 2004) or based on modelling pollution in the groundwater body. Models are however not available.
5.2 Current approaches for setting quality objectives for groundwater in Latvia
This sub-section discusses the approaches for setting quality objectives for groundwater prescribed by the current national legislation.
The Regulation No 857 of 19.10.2004 prescribes that all groundwater bodies has to be classified into two quality classes – “good” or “poor”. It also prescribes that:
“18 The Chemical quality of groundwater is good if it corresponds to the following criteria:
18.1 Chemical composition of groundwater corresponds to the natural chemical composition that is typical for the respective water body and concentrations of polluting substances do not exceed environmental quality standards;
18.3 The chemical quality of groundwater does not bother achieving quality standards in connected surface waters, does not deteriorate ecological and chemical quality of the connected surface waters, as well as does not affect significantly terrestrial ecosystems directly connected to the water body.”
Accordingly to the explanation of “good” quality provided by this Regulation, it corresponds to the natural quality of the water body. On the other hand the article 19 of the Regulation says:
“The chemical quality of groundwater body is poor if due to the pollution or other anthropogenic pressure the concentrations of natural and polluting substances fixed in water exceed environmental quality standards or values of parameters characterizing chemical quality of water.” (The standards or values are not set by this Regulation.)
The Regulation 118 of 12.03.2002 amended by the Regulation No 752 of 04.10.2005 provides two quality standards for assessing groundwater quality – depending on whether groundwater is or not used for drinking water abstraction. Taking that groundwater in the case study area (shallow groundwater “under” the city of Riga) is rarely used for drinking water, the second standard might be applied.
This second standard is based on using A, B, and C threshold values Table 3 below gives explanation on these thresholds. The assumptions for linking given thresholds (A, B, C) with quality classes in the WFD context are also presented in the table. It should be noted that the threshold A for total petroleum products is not provided at all. As explained by experts, this results from the fact that the threshold B already corresponds to the detection limits of monitoring devices used to monitor this parameter.
Based on the information presented in Table 3, the threshold B has been taken as the threshold of “good” quality for the analysis, i.e. 0.2 mg/l for total petroleum products.
Table 3. Groundwater quality classes and standards set by the current legislation (for groundwater that is not used for drinking water abstraction)
Explanation of the quality classes from the
Regulation No 752
Thresholds of classes provided in the Regulation
Assumed corresponding classes
in the WFD terms Target value A
(The threshold A for the total petroleum products is not provided)
High
Slightly polluted water or water of low natural quality
between A and B*
(The threshold B for the total petroleum products is 0.2 mg/l)
Good
Polluted water between B and C (Critical threshold)
threshold of highly polluted water
C
(The threshold C for the total petroleum products is 1 mg/l)
* As assessed by experts the threshold B for petroleum products is a detection limit of monitoring devices used to monitor this parameter
Source: the Regulation No 752 of 04.10.2005
The Regulation No 752 also prescribes that, if the pollution level in groundwater reaches or exceeds threshold C, restoration shall be carried out.
It has to be noted that no direct reference to compliance regimes to be applied is made in legal documents.
5.3 Defining water quality objective for the selected groundwater body
The question “Which receptors should be considered when setting quality objectives for groundwater?” was discussed when defining the case study, i.e. only connected ecosystems or also other receptors including groundwater as such.
Different policy documents reviewed refer to different policy priorities, perspectives and objectives concerning groundwater protection and restoration, e.g. objectives aimed to prevent health risks (setting different threshold values for groundwater used for drinking water abstraction, specifying priorities for municipalities to restore polluted districts falling in residential areas) or specific policy objectives aiming to prevent groundwater deterioration and to restore historically contaminated sites. Such diversity of policy perspectives arises from the diversity of functions and values of groundwater supplied to society and to the environment. And these different aspects should be considered when setting quality objectives for a water body.
The WFD and the proposal for the new Groundwater Directive explicitly refers to a receptor-based approach for setting threshold values for groundwater (although it can be attributed also to the setting of quality objectives overall) aiming to protect significant receptors such as connected surface waters and terrestrial ecosystems. The question of whether other (socio-economic) receptors should be considered when establishing threshold values for groundwater is still in the process of discussions.
Considering the two receptors mentioned above only may appear as a narrow approach to groundwater protection. However, to prevent pollution risk for connected ecosystems, a minimum standard should be proposed when establishing quality objectives for groundwater.
Including other (socio-economic) receptors5 would be relevant only in situations when water quality objectives relevant to these sectors are more stringent than those obtained when considering connected ecosystems as receptors.
In light of above discussion and taking into account the specific situation of the selected water body (e.g. monitoring information provision, spatial variability of pollution), the following quality objectives for the groundwater body were used for the purpose of the analysis:
• Two alternative water quality objectives were selected: based on (1) considering only surface waters as a receptor, (2) considering all receptors identified. In case of the first objective, “good” quality is ensured when any damage to connected surface waters is prevented. In case of the second objective, “good” quality means that there is no damage to all receptors identified (including shallow groundwater itself and urban and socio-economic development).
• The objectives were built based on a constant “good” quality threshold value (0.2 mg/l for total petroleum products) and by different criteria for assessing compliance with this threshold value.
• In practical terms, each objective means meeting the given threshold for a given number of sites that have specific characteristics.
• In the case of the first objective, the threshold shall be met (additionally to the area of the water body currently complying with “good” quality) in all polluted groundwater sites with very high pollution level (floating layer of petroleum products in shallow groundwater) causing damage to surface waters and located in the current or future residential areas of the city. In practice, it means that the given threshold still can be failed in 62 groundwater sites out of the total of 97.
• In the case of the second objective, the given threshold shall be met everywhere in the groundwater body, as no impact is allowed (implying all sites being cleaned).
5 The most common socio-economic receptors are expected to be activities using groundwater (e.g.
groundwater abstraction for drinking needs) and groundwater itself (groundwater as a value itself). As concluded, the main socio-economic receptors for the groundwater body D-2/D4 are groundwater itself and urban and socio-economic development.