Geotechnical and
Environmental Services

Specialists in the investigation, assessment and reclamation
of development land.

Water Resources

Water quality is so precious and yet so often unappreciated, particularly the water that lies beneath our feet. BRD can assess the impact any contaminated soils may have on the water environment and identify what, if anything, needs to be done.

We tend to take it for granted, but water is vital for our lives.  Protecting the quality of our water resources is just plain common sense.

When assessing pollutants in soil we are often concerned with concentrations at parts per million (ppm), but with water even smaller amounts may be of concern at the parts per billion (ppb) level.  It is hard to imagine such small quantaties, but an example is that just a couple of tablespoons of petrol is enough to render a volume of water equvalent to an Olympic sized swimming pool  (50m by 25m by 2m deep) unfit to drink.

It is relatively easy to appreciate the impact of pollution on a river or stream with reports of fish kills and discoloured water featured in the news when such incidents occur.  Pollution of groundwater is a far harder concept to appreciate.  As the name suggests, this is water trapped in porous soil layers or rock known as aquifers.  The importance of groundwater is illustrated by the fact it supplies a third of drinking water in England and Wales.  Groundwater also supplies what is called baseflow to rivers and streams.  It therefore vital to protect groundwater as well as surface waters from pollution.

In order to asses the risk contaminated soils present to water resources multiple types of testing is required.  This includes  testing of total soil concentrations, concentrations in water that has been mixed with the soil (so called ‘leaching’ tests) and testing of the water itself whether it be surface water or groundwater.  For groundwater, samples are obtained from wells constructed in boreholes.

The assessment of the risk to water resources is a tiered approach.  This starts off with a good conceptual site model to identify whether or not water resources are of concern, progresses to simple conservative semi-quantative screening so low risk sites can be easily discounted and then the assessment gets progressively more complex.  The complex assessment employs the collected test data together with physical properties of the ground in a numerical model.  BRD employ the Environment Agency’s numerical model “Methodology for the derivation of remedial targets for soil and groundwater to protect water resources” (also known as a P20 assessment).  For more complex modelling, BRD have the Risk Assessment Model (RAM) software available for use.

As the risk assessment gets more complex the cost increases from both collecting the additional data required and interpretating the data.  So what is the benefit to the Client?  Quite simply it can save money.  As the modelling gets more complex it also gets more accurate and thereby less conservative.   It can be mean the difference between whether remediation works are necessary or not.

There is no easy way to explain in detail the technical complexities and intricacies of groundwater assessment, but you can be assured that BRD will present the findings in a manner that all Clients can understand.