We know it will take more than a few months to clear up contaminated groundwater, typically between 1 year and 15+ years to complete and achieve desired water quality.
Why Timescales Vary So Widely
Many sites are different sizes and shapes, and the depth and duration of contamination can also affect overall timescales. In general, a small, shallow plume can be cleaned up more quickly than a large, deep or ‘diffuse’ plume.
Contaminant Type and Concentration
Some contaminants are easily broken down or dispersed whilst others such as dense non-aqueous phase liquids (DNAPLs) e.g. chlorinated solvents can bond strongly to soil and take years to treat. Furthermore higher concentrations of contaminants are likely to require more treatment cycles before water can be declared suitable before release from the site.
Geology and Groundwater Flow
Groundwater that flows slowly through a clay-rich aquifer may have little opportunity to dilute or to migrate. However, it will require a long time to be flushed through a treatment system. The British Geological Survey (BGS) publishes data on the saturated thickness and hydraulic conductivity for different aquifer types across the UK (see how UK aquifer geology affects contaminant movement).
The Treatment Method Sets the Pace
Pump-and-treat systems operate for several years, whilst in-situ chemical or biological remediation can operate within a shorter timescale. For Groundwater Remediation, see soilfix.co.uk/services/groundwater-remediation/.
Regulatory Sign-Off Takes Time
Verification data is required to be supplied by the site operator over multiple monitoring rounds before a site can be closed by the relevant authorities. The land and groundwater remediation deployment form is an example of an early reporting requirement and is submitted within the relevant time period specified within the site investigation and remediation planning stages from the outset.
Realistic Milestones to Expect
Typically investigation and design will be completed within 3-6 months and active treatment may then be operated for between 1-5 years prior to site closure and a post closure monitoring period of 6 months to 2 years.
By setting out the key stages of a remediation project from the outset, costly delays can be avoided.
