Pneumatic Slug Testing: An New Approach for Hydraulic Conductivity Monitoring?

Conventional slug testing offers some major advantages over pump tests in site investigations but there are some issues associated with projecting slug test permability values to larger aquifer volumes. Could pneumatic slug testing provide an alternative?

Slug testing using a known volume of water or an item that displaces a measured volume has become a standard tool in the hydrogeologist's or engineer's kit bag in recent years. The approach offers a number of advantages over standard pump-based tests because it is easy to implement in the field, offers large cost savings, and it will work in low flow environments.

Conventional slug testing has improved our ability to determine hydraulic conductivity, and consequently made a major positive difference to site characterisation across a range of applications. However there are some drawbacks, particularly related to the need for the insertion of a water sample or a solid slug. For instance;

• The pressure wave caused by insertion may impact data accuracy.


• Slugs may not manoeuvre around well or borehole casings


• It may be difficult to deploy a slug large enough to create sufficient displacement for measurement.

Pneumatic slug testing offers an interesting new option to overcome these issues because, as the name suggests, no physical slug is used. Instead the well or borehole is sealed and air is used to pressurise the water column. When equilibrium is reached between the pressure in the water head and the well then de-pressurisation takes place and a data logger can measure the resulting changes in water level.

Apart from removing or reducing the problems associated with physical slug insertion, pneumatic slug testing also provides near instantaneous slugging events, which is very important in achieving the best possible accuracy.

Waterra In-Situ Technical Director, Peter Dumble, believes that pneumatic slug testing will in time become a preferred mechanism for monitoring hydraulic conductivity in monitoring wells and boreholes.

"This method of hydraulic conductivity testing has some clear advantages over both pump testing and conventional physical testing. In the short term I can see some important niche applications for the approach and over time we are likely to see it become the method of choice in the industry"

To find out more about pneumatic slug testing download our datasheet (PDF opens in new window) or call the Waterra-In-Situ's technical support team today on +44 (0)121 733 7743.



Waterra In-Situ - For a full range of oil water interface level meters

Monitoring water and DNAPL levels in real-time

Monitoring DNAPL levels in real-time has always been a challenge. Now with the help of the In-Situ Level TROLL® 500 instrument there is an effective way of keeping track.

DNAPL (dense non-aqueous phase liquid) contaminants have the unpleasant property of sinking below the water table and creating the potential for long term environmental problems.The difficulty for organisations who are engaged in the monitoring or remediation of brown field sites is that DNAPL materials such as chlorinated solvents, creosote or oils are simultaneously very common but have a slow migration profile. As such the impact on aquifers may take some time to show through.

The Level TROLL® 500 instrument provides an accurate method of providing data on the thickness of DNAPL levels in real-time and, if required, over the long term. The installation requires two devices; one for the DNAPL layer and the second in the water column. This allows the thickness of the DNAPL layer to be calculated by comparing the difference in density between the two liquids.

The Level TROLL® 500 has some very important features that allows it to cope with hostile conditions and remain operational for an extended period ;

• Titanium casing


• TROLL® Shield antifouling system


• A battery pack with typical life expectancy of up to 10 years

Waterra In-Situ Technical Director, Peter Dumble, believes that this use of the Level TROLL® 500 could have some important benefits in the remediation sector:

"Without a clear understanding of a site's DNAPL profile it is very difficult to choose the most appropriate remediation technique. What we have here is a mechanism that maximises the chance of getting it right first time."

To find out more about the DNAPL measurement procedure and the layer calculation equation download our datasheet (PDF opens in new window), take a look at the Level TROLL® 500 page on our website or call the Waterra-In-Situ's technical support team today on +44 (0)121 733 7743.


Waterra In-Situ - Experts in passive groundwater sampling techniques.