Response and damage assessment

The initial response to any such incident must be to identify the source of the problem and stop further leakage. This in itself is often problematic as affected pipework is usually buried and thus the point of leakage is not obvious.

Assessment of the extent and severity of the contamination caused is extremely complicated as subterranean conditions are different for every property. Properties come in all shapes, sizes and construction techniques, whilst soil types and strata are infinitely variable. Only when the subterranean conditions for the specific property affected have been determined can the true potential for problems be understood and assessment for actual contamination spread be undertaken. Assessment work is carried out in 2 Phases.

Phase 1
An initial visual inspection is carried out to look for physical evidence of contamination i.e. oil staining of walls/floors, die back of grass/ plants externally, evidence of oil in drains / septic tanks / local water courses etc. Air sampling inside the property for volatile organic compounds (VOC’s) using a photoionisation detector (PID) gives an instant indication as to whether the contamination within the property is significant and whether continued occupation is advised or not.

Phase 2
Where the Phase 1 assessment reveals very extensive contamination and / or complicated leak/ground conditions, a Phase 2 assessment is essential. Such an assessment involves the site / construction characterisation and hydrogeological surveying. Soil and where necessary groundwater samples are taken and analysed. From the results obtained the spread of the oil (plume) can be mapped.

With the local ground conditions and construction method fully understood the required contaminant concentration targets at the completion of the remediation work can be discussed and agreed with the appropriate governing body, usually with the local Environmental Health Department or the Environment Agency. Only when all of these factors have been considered can the appropriate remediation method be decided upon and a remediation programme proposed.

Remediation techniques

1.) Dig and dump – this is the traditional remediation technique whereby all of the affected soil and parts of the affected property are removed and disposed of. It is very invasive and increasingly costly as waste disposal costs are rising rapidly due to the reduction in licensed land-fill sites, however it is the only method that can guarantee 100% removal of the contamination

2.) Soil Vapour Extraction (SVE) – SVE is an in-situ remediation technology in which air is pumped into the affected soil through boreholes then a vacuum is applied adjacent to the boreholes to induce a controlled flow of air through the soil to remove volatile and semi-volatile contaminants. The gas leaving the soil may be treated to recover the contaminant or burnt to destroy the volatile gases. This is a useful technique where the contaminant is particularly volatile i.e. petrol

3.) Thermal treatment – thermal treatment entails injecting heat into the affected soil. It is sometimes performed in-situ outside of buildings where heating pipes are buried in the affected soil but most usually the soil is dug up and treated on-site. A soil temperature of between 200-500°C is required to volatilise water and organic contaminants which are carried in a gas stream to a treatment system either to recover the contaminant or to be burnt off

4.) Bio-remediation – Bio-remediation techniques rely on the ability of indigenous or inoculated micro-organisms (e.g. fungi, bacteria and other microbes) to degrade organic contaminants and ultimately convert them to carbon dioxide. In the absence of oxygen (anerobic conditions) the contaminants will be ultimately changed to methane. In-situ bio remediation of soil typically involves the injection of oxygenated water containing nutrients to stimulate indigenous micro-organisms or introduced micro-organisms plus appropriate nutrients.

Bio-remediation relies on ideal temperature, moisture and oxygen conditions being achieved in the affected soil to be successful. The benefits of bio-remediation are that it is relatively un-invasive however predicting remediation timescales are problematic as achieving optimum soil conditions are very difficult.

Heating oil contamination and insurance claims

Heating oil contamination insurance claims are fraught with complications. It is almost impossible to set an accurate reserve on anything but a simple spillage without undertaking a Phase 2 assessment. Exact quantification of the scale of the problem is usually only possible if the property is invasively inspected. Costs for remediation have risen dramatically in the last 3 years with the increase in disposal costs for contaminated soil. In-situ remediation whilst apparently attractive in cost terms is usually accompanied by negatives such as an indeterminate process timescales (leading potentially to increased alternative accommodation costs) and lack of acceptance from local governing bodies because of fears of contamination spreading during the process.

Recent refinement by insurers of policy wording now means that treatment disposal costs for contaminated soil may not be covered if not deemed part of the property reinstatement costs. As a general rule such claims are always much more expensive and complicated than that thought of at first glace

 

Case Studies: (click on text to open, please allow a few seconds for uploading)

1. Heating Oil Contamination Remediation - Adjoining properties, North Wales.

2. Heating Oil Contamination Remediation - Residential property Morayshire, Scotland.

This is the second of our Technical briefings: to view Issue #01 covering "Rope Access Solutions" please click the link below:

Technical Briefing #01 - 'Rope Access Solutions'

For further information on BELFOR’s 'Oil Contamination Remediation' or to unsubscribe contact us by clicking the link below:

Contact us