{"id":3273,"date":"2026-05-29T12:04:10","date_gmt":"2026-05-29T11:04:10","guid":{"rendered":"https:\/\/tobelikethis.org\/?p=3273"},"modified":"2026-05-30T13:51:22","modified_gmt":"2026-05-30T12:51:22","slug":"how-pfas-chemicals-get-into-our-water-supply-draft","status":"publish","type":"post","link":"https:\/\/tobelikethis.org\/?p=3273","title":{"rendered":"How PFAS chemicals get into our water supply (DRAFT)"},"content":{"rendered":"\n

The water source for Upper and Lower Heyford is a groundwater source<\/strong> drawn from Jurassic limestone aquifers, rather than a river or reservoir. In plain terms, rain falls on higher land, sinks through cracks, joints and porous layers in the rock, then moves through limestone beds until it reaches a spring, stream, or borehole. Thames Water tell us that we are part of their Deddington water supply zone, that this is borehole water that goes through Heyford Hill. They say that they THINK that the treatment works are valve-fed off Duns Tew. Despite two lengthy exchanges, they still refuse to provide any further detail, so far.<\/p>\n\n\n\n

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The local geology sits within the Middle Jurassic limestone and clay sequence<\/strong> of north Oxfordshire. The key rocks include Cornbrash<\/strong>, Forest Marble Formation<\/strong>, and White Limestone Formation<\/strong>, which form part of the wider Great Oolite Group. The Cornbrash is a rubbly, fossil-rich limestone with clay-rich partings, and it often sits above the Forest Marble Formation (British Geological Survey, n.d.-a). The Forest Marble is not just marble; it includes limestone, mudstone and clay-rich beds (British Geological Survey, n.d.-b). This mix matters because limestone can carry water, while clay-rich beds can slow or divert it.<\/p>\n\n\n\n

The White Limestone Formation<\/strong> is especially important because it is classed locally as a “Principal Aquifer”<\/strong> and is used for local water supply in the Upper Heyford area (Cherwell District Council planning document, 2018). A principal aquifer is a rock unit that can store and yield enough water for public supply and can also feed rivers and wetlands. The British Geological Survey and Environment Agency classify aquifers in this way to show their value for drinking water and for the wider water system (British Geological Survey, n.d.-c).<\/p>\n\n\n\n

Water in these limestone aquifers may move through pores in the rock, but also through fractures, joints and solution-widened cracks. This means flow can be uneven. In some places water may move quite slowly through fine pores; in others it may pass faster through cracks or weathered zones. <\/p>\n\n\n\n

The British Geological Survey specifically notes that while the Great Oolite and Inferior Oolite aquifers are distinct, vertical leakage can occur where faults cut through lower-permeability layers (British Geological Survey, n.d.-d). In turn, this is particularly important near former air bases because pollution won’t always move as a neat plume. It can follow cracks, drains, made ground, ditches, old service trenches, and the line of least resistance.<\/p>\n\n\n\n

For Upper and Lower Heyford then, the likely pattern is this: the former airfield sits on limestone and clay-rich Jurassic strata. Rainwater can wash contaminants from soil or made ground into shallow groundwater. Some water may perch above clay layers, while some may descend into limestone aquifers. Boreholes used for public supply may draw from deeper or more productive parts of the aquifer. Springs, brooks and drainage channels may also receive groundwater. This is why PFAS contamination at a former fire-training site raises concern: PFAS can dissolve in water, resist natural breakdown, and travel with groundwater.<\/p>\n\n\n\n

This does not prove that a given tap supply is contaminated. It does mean the local geology creates plausible routes that should be mapped, tested and monitored. The key evidence that we need includes the borehole locations, depth, screened aquifer, source protection zone, groundwater flow direction, PFAS results in raw and treated water, and PFAS results in nearby surface water and sediments.<\/p>\n\n\n\n

References<\/h3>\n\n\n\n

British Geological Survey. (n.d.-a). Cornbrash Formation<\/em>. BGS Lexicon of Named Rock Units. https:\/\/webapps.bgs.ac.uk\/lexicon\/lexicon.cfm?pub=CB<\/a><\/p>\n\n\n\n

British Geological Survey. (n.d.-b). Forest Marble Formation<\/em>. BGS Lexicon of Named Rock Units. https:\/\/webapps.bgs.ac.uk\/lexicon\/lexicon.cfm?pub=FMB<\/a><\/p>\n\n\n\n

British Geological Survey. (n.d.-c). Aquifer designation data<\/em>. https:\/\/www.bgs.ac.uk\/datasets\/aquifer-designation-data\/<\/a><\/p>\n\n\n\n

British Geological Survey. (n.d.-d). Properties of the Great Oolite and Inferior Oolite aquifers<\/em>. https:\/\/www2.bgs.ac.uk\/groundwater\/waterResources\/thames\/limestones.html<\/a><\/p>\n\n\n\n

Cherwell District Council. (2018). Ground conditions and geology: Upper Heyford planning documentation<\/em>. https:\/\/planningregister.cherwell.gov.uk\/Document\/Download?fileName=9192714.pdf&imageId=102&isPlan=False&module=PLA&planId=107372&recordNumber=66077<\/a><\/p>\n\n\n\n

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(c) 2026 Graham Wilson. This work is licensed under CC BY-NC 4.0. To view a copy of this license, visit creativecommons.org<\/p>\n<\/div>\n<\/div>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

The water source for Upper and Lower Heyford is a groundwater source drawn from Jurassic limestone aquifers, rather than a river or reservoir. In plain terms, rain falls on higher land, sinks through cracks, joints and porous layers in the rock, then moves through limestone beds until it reaches a spring, stream, or borehole. Thames […]<\/p>\n","protected":false},"author":1,"featured_media":3261,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[42,32],"tags":[],"class_list":["post-3273","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-pfas","category-pure-blog"],"_links":{"self":[{"href":"https:\/\/tobelikethis.org\/index.php?rest_route=\/wp\/v2\/posts\/3273","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tobelikethis.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tobelikethis.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tobelikethis.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tobelikethis.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3273"}],"version-history":[{"count":3,"href":"https:\/\/tobelikethis.org\/index.php?rest_route=\/wp\/v2\/posts\/3273\/revisions"}],"predecessor-version":[{"id":3294,"href":"https:\/\/tobelikethis.org\/index.php?rest_route=\/wp\/v2\/posts\/3273\/revisions\/3294"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/tobelikethis.org\/index.php?rest_route=\/wp\/v2\/media\/3261"}],"wp:attachment":[{"href":"https:\/\/tobelikethis.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3273"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tobelikethis.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3273"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tobelikethis.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3273"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}