Rival soil tests put PFAS levels at a former Oxfordshire fuel depot about 58 times apart

Newcore's lower number leaves the residential question open. Llewelyn called his result roughly 98% lower than the campaigners' and "the accurate results of our professional testing" ^[19]. The first part checks out: 0.0641 is about 1.7% of 3.74325 ^[16].

Meeting the residential limit is a separate question. Gallos Brook put PFOS at 205 times the safe limit for residential land use ^[18]. If PFOS is counted within the group's total of 3.74325 micrograms per kilo, the limit it applied can be no higher than about 0.018 micrograms per kilo ^[13]. Newcore's total is roughly 3.5 times that ceiling ^[14]. That figure covers all PFAS together, so it cannot show how much of Newcore's sample is PFOS ^[19].

We would not rank either number until both lab reports, with sampling locations and depths, are public. Gallos Brook describes its result as "likely the highest level of soil contamination measured anywhere in the UK" ^[17]. The BBC said it had not been presented with the official lab results to verify the figures independently ^[12].

Llewelyn accepts that the sampled spot is likely to hold PFAS. "A 'pressure group' has trespassed unlawfully to obtain a questionable sample from this site," he said, describing the spot as "the secured area of the site that was purposefully designed to accommodate foam for firefighting purposes, which is likely to contain PFAS" ^[9]. "I'm not sure there is anything to be surprised about here," he said ^[2]. His case for the homes rests on whether the chemicals can move. He said that although firefighting foam containers were on site from the MOD's operation in the 20th century, the company did not believe the foam was ever deployed, the containers were sealed, and successive surveys had confirmed there was no pathway for it to cause pollution ^[1].

One site cannot show how contamination checks run on brownfield land in general, but the order of events on this one is clear. Newcore says a Phase 1 assessment last year identified the potential for contamination, and that "the specification for the Phase 2 investigation has therefore been designed to specifically address this potential risk and any contamination identified will be cleaned up immediately" ^[10]. Llewelyn also said the company was made aware of the barrels "in recent weeks" and had them removed in a "responsible and professional manner" ^[8].

Gallos Brook tests for PFAS regularly in the area ^[17]. The depot once supplied fuel to the former RAF Upper Heyford, about five miles north, which is suspected to be a source of PFAS contamination from firefighting foam ^[6]. Images of the drums show they were made by Angus Fire Armour, which settled out of court with Yorkshire residents who claimed they had been exposed to PFAS near its foam plant ^[7]. The site has outline planning permission for residential and affordable homes ^[4]. Llewelyn, who took over the site in 2012, said Newcore plans for half of the housing to be affordable ^[8].