Accredited testing and why laboratory choice matters
Regulators check the schedule of accreditation, not the logo. What accreditation covers, what it does not, and how sample handling and holding times decide whether data survives scrutiny.
An accredited laboratory for planning reports is not a laboratory with a certificate on the wall. Accreditation is granted test by test, matrix by matrix and method by method, so a laboratory can be accredited for metals in soil and not accredited for the same metals in water, or accredited for a determinand by one method and not by the method your consultant specified. Regulators check the schedule, not the logo.
That is why the laboratory question belongs in your scope of works rather than in your contractor's supply chain decisions. A Phase 2 report built on unaccredited data is a report the council's contaminated land officer can set aside, and by then the samples are gone.
Why accreditation gets checked
Two schemes matter in England. Accreditation to the international standard for testing and calibration laboratories, administered in the UK by the national accreditation body, establishes that the laboratory can perform a named test competently and reproducibly. The Environment Agency's own certification scheme sits on top of that for environmental monitoring, adding requirements specific to regulatory data.
Where analytical results will inform a regulatory decision, including the discharge of a contaminated land condition, the expectation is that the data comes from a laboratory accredited for those specific tests. Guidance on land affected by contamination pushes in the same direction, and the practical consequence is straightforward. Accredited data is accepted and argued about. Unaccredited data is returned.
The same logic reaches beyond soil chemistry. Sound level meters used for a Noise Impact Assessment need a valid calibration traceable to national standards, usually on a two year cycle, and an environmental health officer will ask for the certificate. Stack emissions monitoring has its own certification requirements. Materials testing feeding a Geotechnical Assessment is accredited by test in the same way as chemistry.
Reading a schedule of accreditation
Every accredited laboratory publishes a schedule listing what it is accredited for. Read it before you accept a quotation, and read it against the determinand list in the specification.
Four columns matter. The matrix, meaning soil, water, gas or air. The determinand or group. The method, usually referenced to a published standard or an in-house method number. And any stated limitations, such as a concentration range or a sample type exclusion.
The mismatches to look for are specific. A laboratory accredited for total petroleum hydrocarbons but not for the banded speciation your risk assessment needs. Accreditation for asbestos identification but not for quantification. Accreditation for a determinand in soil but not in leachate, when the assessment requires a leachate test. And a determinand absent from the schedule altogether, which is common for newer contaminants.
Where a test falls outside the schedule, the laboratory will normally say so on the certificate. It should also be flagged in the report, with an explanation of what weight the result can carry.
Sample handling and chain of custody
Accreditation covers what happens inside the laboratory. Most data is lost before the sample arrives.
Containers are determined by determinand. Volatile organic compounds need containers filled without headspace, semi-volatiles need amber glass with inert cap liners, and metals tolerate plastic. A single sample split across three containers is normal on a contaminated site, and a sampler working from a generic container kit will compromise something.
Temperature and transport matter next. Samples travel chilled, and the temperature on arrival is recorded. A cool box left in a van over a warm weekend produces results the laboratory will qualify.
Chain of custody documentation ties the sample to the location, the depth, the date, the time, the sampler and each transfer. It is the document a regulator uses to satisfy itself that the certificate relates to the borehole the report says it does. Incomplete chain of custody forms are the commonest reason otherwise good data is challenged, and the fix costs nothing at the time.
Holding times and what invalidates a result
Every determinand has a period within which analysis must start. Volatile compounds are measured in days. Some inorganic determinands and metals allow weeks. Asbestos identification has no practical limit.
The laboratory's own schedule states the holding time for each test, and results analysed outside it are reported with a qualification. That qualification is what a regulator seizes on.
Three consequences follow for programme. Sampling on a Friday afternoon wastes two days of the holding time for short-life determinands. Adding a test after the samples have been in storage for a fortnight may mean returning to site. And a phased investigation where Phase 2a results drive the Phase 2b suite needs the second round of sampling planned as a separate mobilisation rather than as an afterthought.
Reading a certificate of analysis
The certificate is a legal record and it repays five minutes of attention.
- Check which results are marked as accredited. Certificates distinguish accredited from unaccredited and subcontracted tests, usually by a symbol keyed in the footer.
- Check the units and the basis. Soil results are normally reported in milligrams per kilogram on a dry weight basis, and comparing a wet weight result against a dry weight assessment criterion produces a false pass.
- Check the limit of detection against the assessment criterion. A detection limit above the screening value tells you nothing useful, and it happens more often than people expect with some organic determinands.
- Check the sample descriptions against the field records. A transposed sample identifier is easy to spot on the certificate and almost impossible to spot in the report.
- Check for deviating sample notes. Broken containers, insufficient sample, high arrival temperature and exceeded holding times all appear here.
A Contaminated Land Assessment that reproduces the certificate as an appendix and addresses each qualification in the text is a document a regulator can sign off. One that presents a clean table with no reference to the underlying qualifications invites questions.
Where accreditation does not reach
Accreditation is about measurement, so several things you might assume it covers sit outside it.
Sampling in the field is usually not accredited, and the competence of the person taking the sample is a separate question from the competence of the laboratory. Interpretation is not accredited at all, which is why the land contamination regime expects reports prepared by suitably qualified and experienced persons rather than simply by an accredited laboratory's clients.
In-situ field measurements, including ground gas monitoring readings and field pH, are instrument readings rather than accredited analyses. They are still useful, and they need calibration records.
And a laboratory may subcontract a test it is not accredited for. That is legitimate where it is declared, and the certificate should identify the subcontractor and its accreditation status.
Specifying the suite before anyone samples
The determinand suite should come out of the conceptual site model, not out of a standard package.
Write the specification with four elements: the determinand list by matrix, the method or standard required for each, the accreditation requirement stated explicitly, and the detection limits needed to compare against the relevant assessment criteria. Then ask the laboratory to confirm, against its schedule, that it holds accreditation for each line.
That exchange takes one email and it prevents the expensive version of this problem, which is discovering at report stage that the determinand driving the risk assessment was analysed by an unaccredited method. The detail of what to look for in soil and water work specifically is covered in the guidance on accredited laboratories for soil and water analysis.
Land contamination reporting is a report type where a suitably qualified and experienced person is legally expected. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.
If you need a reviewer to check a draft before it goes to the council, the professional directory is the route.
Frequently asked questions
Is a laboratory accredited for everything it tests?
No. Accreditation is granted test by test, matrix by matrix and method by method. A laboratory can be accredited for metals in soil and not in water, or for a determinand by one method and not by the method your specification calls up. Read the published schedule of accreditation against your determinand list before accepting a quotation.
What happens if results come from an unaccredited method?
The laboratory will normally flag it on the certificate, and the report should explain what weight the result can carry. Where the data informs a regulatory decision such as discharging a contaminated land condition, unaccredited results are frequently set aside. By that point the samples are usually gone and a return visit is needed.
Why do holding times matter?
Every determinand has a period within which analysis must start, from days for volatile compounds to weeks for some metals. Results analysed outside that window are reported with a qualification, and regulators seize on qualifications. Sampling on a Friday afternoon wastes two days of a short holding time before anything reaches the bench.
What should I check on a certificate of analysis?
Which results are marked accredited, the units and whether results are on a dry weight basis, the limit of detection against the relevant assessment criterion, the sample descriptions against your field records, and any deviating sample notes covering broken containers, insufficient sample, arrival temperature or exceeded holding times.
Does accreditation cover the sampling itself?
Usually not. Accreditation addresses measurement in the laboratory. Field sampling competence, in-situ readings such as ground gas monitoring, and interpretation of the results all sit outside it. That is why the land contamination regime expects reports prepared by suitably qualified and experienced persons rather than simply by an accredited laboratory's client.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.