Petrol Filling Stations – Contamination impacts and potential risks

From Affiliate member, Groundsure:

We often see former Petrol Filling Stations (PFSs) as the subject of our environmental searches in our day to day work stream. This is unsurprising when most contaminated land issues are the result of historic land uses. A 20121 report from The Department of Energy and Climate Change (DECC) identified the steep fall from 37,500 PFSs in the 1970s to less than 9,000 in 2011. The decline has slowed significantly with the UK Petroleum Industry Association2 figures identifying 8,406 sites in 2018 but it gives a sense of the scale of the number of former PFSs across the country.

This week, I was talking with a Contaminated Land Officer about ‘magic tanks’ which underlined the importance of understanding the risks from PFSs and service garages early in any project. The conversation also demonstrated to me how far we have travelled in the UK’s approach to pollution management over the decades. ‘Magic tanks’ were used in the 1960s, apparently under Government advice. They were underground storage tanks that had started to leak and given a new lease of life to slowly release waste oil into the ground in order to prevent it being poured down the drain. The impact of this to soils and groundwater can be extensive, even after this time. Pollution control improved in the 1980s when legislation was introduced ensuring new tanks were no longer single skin steel tanks but corrosion resistant double skinned epoxy-coated steel. This combined with stronger protection for our waste disposal and drainage processes has resulted in improving pollution management.

Groundsure’s experience of assessing former PFSs tells us that these and service garages have a range of issues associated with them. Gross contamination is perhaps the first consideration to spring to mind, found around the tanks, pipework, drains or other areas where waste liquids have been allowed to soak into the ground. This can also impact groundwater which can be expensive to remediate and be the source of a variety of noxious gases. However, we do, from time to time, find tanks which have continued to be used to store waste oils. Also there is the geotechnical issue of the stability of the tank and how it was decommissioned. If discovered later, these can have a significant impact on the viability of any transaction or development either through unexpected remedial costs or delays as concerns are assessed and addressed. As many of these properties are then put forward for residential development it is essential that the potential investment in investigation and remediation is identified and quantified early to ensure the financial viability of the project.

With the loss of around 30,000 PFSs in the last 50 years there are many properties that have a potential contamination legacy, despite no longer being in use for fuel storage. Our searches include the use of various data sources that assist in the identification of former PFS.

Historical mapping

We use historical Ordnance Survey (OS) mapping where there are certain layouts that indicate a PFS. Understanding the mapping is essential, so for example, in old OS terminology a ‘filling station’ was only used if the site had no other vehicle maintenance use, so it is necessary to look for other clues to potential petrol pumps at garage sites (site layout, canopies etc). These features have been captured in our Historical Land Use Database (HLUD) through the digitisation of our high detailed mapping collection and includes sites from the first PFSs in the 1920s to the late 1980s.

Permits

More modern filling stations are easier to find from other sources, for example, larger filling stations will require an environmental Part B permit for vapour recovery from the Local Authority. Our archive of Part B licences was started in the early 2000s so we can identify PFS sites long after they have ceased operation from this information. This data is not found as a matter of course in the open data sets.

Where we identify former PFSs and service garages in a sensitive location we may recommend a further phase of enquiry to allow a more informed decision as part of any transaction. This usually takes the form of a Phase 1 Preliminary Environmental Risk Assessment to gather more detailed site information, as well as a visit to the property to look for visual clues as to its past use. This can be satisfactory to resolve the outstanding uncertainties for the purposes of a transaction, although if the property is to be developed for residential purposes it is likely that a more detailed ground investigation will be required to demonstrate that it is suitable for its proposed use. As you can see, this is a common occurrence and the additional search is a case of better to be safe than sorry.

Further information is available on the most suitable searches that Groundsure provides and click here to find out more about the phase 1 preliminary environmental risk assessments for development purposes we offer, carried out by our own in house experts.

References

1. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/69760/7322-study-of-the-uk-petroleum-retail-market.pdf

2.  https://www.ukpia.com/media/2237/ukpia-statistical-review-2019.pdf

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