DEFRA has recently estimated that £210 million per annum is spent unnecessarily on UK remediation due to poor site investigations. There are several reasons for this, but the high uncertainty created when constructing the conceptual site model by using the analytical results from a very small number of samples relative to the size of the site is a major contributory factor. During the soil excavation process on average 30% of the soil removed and taken to landfill is not contaminated and could have been re-used or sent to an inert landfill.
The On-Site methods used by QROS produce analytical results within minutes of taking a sample. The speed and low cost at which results are generated from samples provide huge advantages when investigating contaminated land. Investigators can react to data as it is generated. If an area is identified as being contaminated the sampling pattern can be adjusted to accurately follow the contamination plume and completely delineate the extent of the contamination. This removes the expensive requirement for multiple returns to the site to undertake further investigation to effectively complete the investigation.
On Site analysis techniques can analyse more than 50 samples a day, allowing more samples to be taken and so producing a robust site conceptual model that minimises the unexpected. This reduces the risk associated with uncertainty and inevitably leads to a lower overall remediation cost.
The cost to do this is also much lower than using just laboratory analysis alone. On Site analysis is typically 4 - 5 times lower in cost than laboratory analysis. The net result is that the nature and amount of contamination present can be more accurately estimated, allowing for more cost effective remediations to be carried out.
The QED is the only analyser, either on or off site, which positively identifies and quantifies the hydrocarbon in a single analysis. The much larger sampling density allowed by the low cost and rapid turnaround of this method gives a far truer picture of the Conceptual Site Model than can be achieved by laboratory methods alone. Typically in laboratory based methods very few samples are taken, perhaps 10 or fewer on a small project.
As Crumbling et al demonstrated in 2003, the overall quality of the data package and therefore the overall understanding of the site conceptual model is not particularly reliable with so few sampling points. The much larger number of samples that can be analysed with rapid measurement techniques significantly improves the reliability and accuracy of the site conceptual model.
Excavation and /or disposal
QROS has undertaken numerous projects where remediation of the soil was required, with rapid results allowing the contractor to fine tune their equipment/techniques and be confident that the treatment process was working to its full potential. In the case of hydrocarbons the information that QROS provides can also be used to indicate the suitability of the material for the remediation process. It was this approach conducted by QROS that primarily allowed the Olympics Groundworks Enabling Scheme to be completed three months ahead of schedule.
The old way of stockpiling potentially contaminated material on site or, if space is limited, sending the spoil off as contaminated can increase cost significantly. Waiting for laboratory results, even for 24 hours, means plant can remain idle, excavations left open or even temporarily refilled requiring re-excavation. Using QROS allows decisions be made within 10 minutes of the soil sample being taken.
The rapid nature of the testing provided by QROS also allows the contractor/consultant to decide if spoil can be sent off site or to an on site treatment process as it is excavated and/or loaded. Many landfill operators accept QROS data provided some laboratory analysis has been previously carried out to confirm the QROS results are accurate. If being sent off site, the soil can be correctly designated as hazardous, contaminated or inert and directed to the appropriate landfill.
With landfill costs running at up to £500 per lorry load for polluted soil and £3,000 per lorry for hazardous waste, it pays to make sure that each lorry load is what you think it is before it goes off site.
The validation of a remediation can also benefit from on-site analysis. On Site results can show that the area previously identified as contaminated has been removed and give confidence that the laboratory testing will also confirm that the area has been cleaned. Backfilling or concrete pouring can continue immediately minimising down-time for plant machinery or workforce. Soil going through an on site treatment process can be checked and used immediately, removing the need for more stockpiling.
Bioremediation or thermal treatment for hydrocarbon contamination can be more effectively managed, increasing throughput of soil. This reduces the time needed to process the soil and reduces the operating costs.
The Benefits of
On Site Analysis
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