Southwest Environmental Limited

Ground Water Risk Assessment

There are many types of Ground Water Risk Assessment, they may be required at planning, or in support of a environmental permit application. What ever the reason for you requiring a Ground Water Risk Assessment Southwest Environmental Limited ( Environmental Consultants) can help out.

Groundwater Risk Assessment Informational Requirements

• calculate the area of the drainage field; 
• calculate the average infiltration rate over the drainage field;
• determine attenuation within the drainage blanket and the unsaturated zone and calculate the concentration of the substance of concern at the water table;
• determine the dilution factor for non-hazardous pollutants and calculate their concentration in groundwater immediately down-gradient of the drainage field;
• determine attenuation within the saturated zone for non-hazardous pollutants and calculate their concentration at a point down-gradient of the drainage field; and
• determine provisional discharge limit values. 

In following the above steps it is possible to model impacts of you proposed activity on ground water.

Natural background (up-gradient) Quality

This might be used to assess the discernibility of hazardous substances where background concentrations are higher than detection limits or the MRV. Alternatively it might be used for non-hazardous pollutants where the natural background concentration exceeds the relevant standard such as a drinking water standard (DWS) or environmental quality standard (EQS).

Groundwater Risk Assessment and EQS

In some cases it will be appropriate to use lower concentrations than the DWS or EQS to provide satisfactory protection to a receptor. For example, it may be suitable to apply a safety factor to provide greater security to an existing drinking water supply (such as 0.75 x DWS). In other cases where the DWS or EQS represents a significantly higher concentration than the natural background quality, use of such values might represent a significant level of deterioration (for example, a DWS of 250 mg/l of chloride compared to a background concentration of for example, 30 mg/l). In these cases you may need to discuss this with us and derive a more suitable value between the MRV or background concentration and the EQS or DWS.

Site Investigations for Groundwater Risk Assessments

Investigations should include: field observations of the proposed landfill development, geological exposures and hydrogeological features such as springs installation and logging of geological boreholes and groundwater wells in-situ testing of the soil beneath the site to determine geotechnical properties laboratory testing of soil and rock materials to determine both the geotechnical and attenuating properties tracer tests and groundwater quality monitoring over time non-intrusive surface and down borehole geophysics You can find more guidance in the British Standards Institution’s code of practice for ground investigations (BS 5930:2015).

If you require SWEL to prepare a Groundwater Risk Assessment on your behalf then please contact us we would be happy to assist. We can prepare such reports on a very quick turnaround if required to do so.

Groundwater Risk Assessment Desktop Study

A desktop study you need to research how your activity may be a ‘source’ of pollution to groundwater, the ‘pathways’ that the pollution could take to reach groundwater from your site, and the potential groundwater ‘receptors’ that could be affected by that pollution.

Drinking Water

When groundwater is the source for public water supply, understanding the impacts of land use and aquifer vulnerability are fundamental to groundwater protection. The risks to groundwater are two-fold—adverse land use and over extraction—thus requiring a dual nature of protection . Therefore, it is important to identify which aquifer systems are at high risk in order to adopt appropriate risk management options.