IN-SITU INJECTION

Organic and inorganic contaminants in groundwater can be remediated “in-situ” by injecting the chemical or biological reagents directly into the groundwater.

 

In-situ injection approaches are well suited to scenarios where contaminants are difficult to access, for example contamination plumes beneath buildings or around building foundations, whilst minimising above-ground disturbance and disruptions to other site activities.

 

ERS has designed and implemented in-situ remediation schemes using both direct injection methods and bespoke injection wells:

 

• Direct injection consists of driving injection rods to the target treatment zone and injecting pre-calculated doses of reagent at relevant depths.  This technique is usually quick and leaves no trace, although its application can be limited by the geology.  

 

• Injection wells are installed within the treatment zone and of suitable construction to allow the injection of reagents.  This is an attractive method when the geology is not suited to direct injection, e.g. bedrock.  Injection wells can be cost effective when several rounds of injection are anticipated, as only one mobilisation of a drilling rig is necessary.  Well injection can also allow a lower injection rate and pressure to limit daylighting and prevent the uncontrolled fracturing of the treatment zone.

 

A successful in-situ groundwater remediation project requires the right type and dosage of reagents and an appropriate distribution of the reagents in the subsurface.  Distribution is particularly important for in-situ chemical oxidation (ISCO).  Therefore, the injection process itself is a very important step of in-situ remediation.

 

At ERS, in-situ injection projects always involve both our technical and drilling divisions to ensure that all relevant aspects are considered from the start: from the geology, hydrogeology and choice of method, to the expected radius of influence and the choice and dose of reagent supported by our in-house laboratory, to the health and safety aspects and daylighting risks.

 

We have our own specialist equipment, including rigs, pumps, mixing vessels and packers for the introduction of reagents in different scenarios.  We have designed and implemented in-situ remediation programmes using a range of drilling rigs to drive injection rods to depth or install injection wells: direct push rigs, more conventional percussive and rotary rigs and also sonic drilling rigs.

 

Our combined experience has allowed us to successfully treat contamination in some difficult environments.  For instance, we recently treated a confined aquifer impacted by chlorinated solvents in London, whilst minimising the upward flow of contaminated groundwater into previously treated shallow soils.

 

If you’d like to find out if in-situ injection is suitable for your site, contact us today to speak to one of our experts.