Groundwater monitoring frequency

The concentrations of arsenic are usually, but not always, stable, Where concentrations are likely to be stable (i.e. deep groundwater), monitoring would normally only need to take place infrequently. Where water supplies for populations are subject to treatment to remove arsenic, samples are normally best taken at the treatment works, where the frequency of monitoring should be sufficient to ensure that the process is effective,... 

Groundwater and air quaHty monitoring ate requited for all faciHties that have the potential to generate emissions. There ate also requinements for contingency plans in the case of accidents, closure and post-closure plans, and financial requinements to ensure that closure plans can be foUowed. Permit appHcations must include an estimate of the composition, quantity, concentration, and frequency or rate of disposal, treatment, transport, or storage. 

Monitoring of the composition and levels of the shallow and deep groundwaters in the Otway Project area has provided a pre-injection baseline revealing both seasonal and non-seasonal changes. Continued monitoring is recommended at the same frequency for at least 2 years... 

Identification of sewers, discharge locations and inputs to the final effluent or ETP (if one exists). The main streams and inputs to the ETP (if present) should be identified, along with sub-component streams (information should already be available as part of a Toxicity Prevention/Response Plan described in Section 5.1). Inputs should include process, site-runoff, stormwater runoff and groundwater sources. A description of the process and operation at each location should also be provided (including operation frequency). Locations with existing monitoring equipment and flow control devices should also be identified. 

Monitor indicator parameters (pH, temperature, conductivity, ORP) in a flowthrough cell every 1-2 minute (min) during purging. At the same frequency, monitor dissolved oxygen and turbidity. Record all measurements in the Groundwater Sampling Form. 

Composite data from the Comprehensive Emergency Response, Compensation, and Liability Act (CERCLA) monitoring program indicate that benzene was detected at a frequency of 11.2% in groundwater in the vicinity of 178 inactive hazardous waste disposal sites (Plumb 1987). Data from a 1980 national survey by the Council on Environmental Quality on groundwater and surface water contamination showed benzene concentrations in contaminated drinking water wells in New York, New... 

Parameters for the classification of quantitative status, groundwater level monitoring network, including density of monitoring sites, frequency, and interpretation and presentation of results. 

The frequency of monitoring also needs to be adequate, especially to support trend assessment. The identification of trends will require the application of statistical methods and their data requirements will inform the frequency of monitoring. However, there are additional factors that will need to be considered, particularly those relating to the behaviour of groundwater systems and pollutants. The minimum frequency dictated by the WFD is once per year but it is widely acknowledged that this will be too low in many hydrogeological situations. The conceptual model, once again, has a very important role to play. 

Plasticizers have been detected in surface water (Table 18.4) at concentrations ranging from 0.002 to 86 pg/L, and in groundwater samples at concentrations of 8 ng/L to 200 pg/L (Table 18.5). Kohli et al generalized that the most commonly occurring phthalates in siuface water were di-(2-ethylhexyl) phthalate and di-n-butyl phthalate. However, some of the samples in these reports were biased in that the samples were collected from monitoring wells near waste sites and industrial areas. Plasticizers have also been reported in samples of drinking water (Table 18.6) at concentrations ranging from 0.03 to 470 pg/L (see HSDB for specific information on the location of the samples and frequency of... 

Water quality monitoring consists of frequent analysis of the main constituents. The required data input consists of (1) mean composition of the influent (2) mean composition of native groundwater in each layer of the target aquifer (3) native geochemistry of each layer of the target aquifer (4) the cumulative frequency curve of detention times in each model layer or flow path as derived from either separately run hydrological model or tracer breakthrough data and (5) specific information derived from the mass balance of the water phase (the reactions that are needed, how O2 and NO3" distribute over the various redox reactions, etc.). 

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