Barrister for developer near contaminated RAF Upper Heyford
claims dry-weather testing shows higher PFAS levels
By Pat Elder
November 11, 2026
On 11 November 2026, the Planning Inspectorate, acting on behalf of the Secretary of State for Transport held a hearing on environmental matters related to Oxfordshire Railfreight Limited’s proposed Strategic Rail Freight Interchange east of the former RAF Upper Heyford airbase.
The hearing took place at the Bicester Hotel Golf and Spa and online via Microsoft Teams as part of the examination of the company’s application for development consent. Water and ground conditions were among the topics discussed, including concerns expressed by members of the public concerning PFAS levels in the environment.
The barrister representing Oxfordshire Railfreight Limited maintains that the testing results provided on their site, being from samples drawn in dry weather conditions, are likely to be higher than typical samples drawn under normal conditions.
Generally, the available science suggests otherwise. There are field studies finding that rain can raise PFAS in streams and rivers, although the effect depends on the watershed and the storm.
In a small river catchment, researchers sampled two rain events and found PFAS concentrations rose during rainfall. Their mass-balance analysis attributed 30–60% of PFAS loads to diffuse inputs; rain itself contributed an estimated 10–50% of the overall loads.
In the Rio Grande near Albuquerque, a stormflow pulse that passed through the urban area was followed by a 58% increase in average PFAS concentration.
https://pubs.usgs.gov/publication/70268901?utm_source
A study of urban streams found the highest PFAS concentrations downstream of urban areas and known sources during wet weather.
https://pubmed.ncbi.nlm.nih.gov/39700609/
But it doesn’t happen every time. In a Passaic River study in New Jersey, rain-event concentrations were elevated, while one site had increases. The USGS also found that PFAS loads rose with rain-driven flow, although concentrations did not rise uniformly. https://pubs.usgs.gov/publication/sir20265018/full?utm_source
Rain can wash PFAS into a stream, while also adding water that dilutes what is already there. Which effect dominates depends on what the rain drains across and how contaminated those sources are.
Examine the Muddy Branch reporting results here. (20 mi north of Washington) See the source at the fire training area and then see the curious two MB 4 and MB4_2 results. This may suggest the flow of groundwater leaching into the creek. https://www.militarypoisons.org/latest-news/newly-released-mde-data-reveal-much-broader-pfas-contamination-in-muddy-branch-than-initially-reported
Dry-weather samples alone cannot establish whether PFAS concentrations in Upper Heyford’s streams are higher or lower during wet weather. A fuller assessment should include sampling across seasons and during multiple rain events: rainfall can wash PFAS into streams, but it can also dilute existing contamination, so the effect depends on the watershed, the storm, and when and where samples are collected.