🕳️ Sampling of groundwaters according to PN-ISO 5667-11 — and the clauses that laboratories exclude

Physicochemistry PN-ISO 5667-11

Overview

STATUS (state of the PKN cards on 22.09.2026). PN-ISO 5667-11:2017-10 is in force, publication 16-10-2017, 38 pages, ICS 13.060.10 and 13.060.45, "Implements: ISO 5667-11:2009 [IDT]". The card has no withdrawal note — the standard is CURRENT. The previous edition PN-ISO 5667-11:2004 (which implemented ISO 5667-11:1993) was withdrawn on 16-10-2017 and replaced precisely by this edition.

THE STANDARD IS CURRENT ONLY IN THE ENGLISH VERSION — AND THIS IS NOT A TRIFLE. The 2004 edition was a POLISH version. The 2017 edition that replaced it was published by PKN in the ENGLISH version (card: "PN-ISO 5667-11:2017-10 - wersja angielska" [English version]). Since 16 October 2017 there has been no Polish text of this standard. A laboratory that applies it — and 94 laboratories apply it — works on the English text or on its own translation, for which it alone is responsible.

THE 2017 EDITION ABSORBED A SEPARATE PART OF THE STANDARD. In the "Replaces" field the PKN card lists TWO standards: PN-ISO 5667-11:2004 and PN-ISO 5667-18:2004. The ISO foreword says the same: the second edition cancels and replaces the first edition (ISO 5667-11:1993) AND ISO 5667-18:2001, i.e. the guidance on sampling of groundwater AT CONTAMINATED SITES. Anyone looking today for the "part 18" standard will not find it as a separate document — its content is inside part 11. This is where the clauses on trial pits and on free-phase liquids, which had no place in the 1993 edition, come from.

THESE ARE GUIDELINES, NOT A PROCEDURE — AND THE STANDARD SAYS SO ITSELF. The introduction contains a sentence that decides how the whole document is to be read: a prescriptive specification of methods and applications IS NOT POSSIBLE, so the standard gives information on the most commonly used and available techniques and lists their advantages, disadvantages and limitations. The document therefore does not say "do this", but "here are the techniques, here is how they differ". This is the cause of the phenomenon described below: a standard made up of variants cannot be accredited in full if the laboratory does not carry out half of the variants.

THE PHENOMENON OF EXCLUSIONS — MEASUREMENT ON THE ACCREDITATION SCOPES (reading of 23.09.2026; fields with the citation, matching covering BOTH forms of notation: the full word "wyłączeniem" [excluding] and the abbreviation "wył."). Out of 96 entries in the scopes (94 laboratories), 68 entries, i.e. 66 laboratories, cite this standard WITH clauses EXCLUDED. 28 entries cite it without any exclusion. THE NUMBER DEPENDS ON WHETHER THE EXCLUSION IS ATTRIBUTED TO THIS STANDARD OR TO THE ROW — and this is decisive here. One field of reference documents usually contains several standards of the 5667 series at once, each with its own list of exclusions. If one counts the rows in which the word "wyłączeniem" occurs ANYWHERE, the result is 72 entries at 70 laboratories — but in four of them the exclusion concerns PART 6 or PART 4 of the series, not part 11 (example: "PN-EN ISO 5667-6:2016-12 z wyłączeniem pkt. 7.2; 7.5; 7.6 | PN-ISO 5667-11:2017-10"). The numbers given in this entry take only the fragment of the notation belonging to THIS standard — from its number to the next "PN".) THE FORM OF NOTATION IS PART OF THE MEASUREMENT HERE, so we give it together with the number. Laboratories write the exclusion in two ways: "z wyłączeniem pkt 5.2" [excluding clause 5.2] (76 occurrences) and with the abbreviation "z wył. pkt. 5.2" (25 occurrences); once "wyłaczeniem" appears without the diacritic. Matching on the full word alone gives 54 entries at 52 laboratories — i.e. one fifth fewer, and not because those laboratories do not exclude clauses, but because they wrote it more briefly. Distribution of the most frequently excluded clauses: • clause 5.2 — 67 entries / 65 laboratories, • clause 6.2 — 54 entries / 52 laboratories, • clause 6.3 — 45 entries / 45 laboratories, • clause 6.1.2 — 35 entries / 33 laboratories. Exclusion is not an exception or an oversight here: it is the BASIC form of citing this standard.

WHAT LIES BEHIND THESE NUMBERS (table of contents of the ISO 5667-11:2009 edition): • 5.2 — "Unsaturated zone monitoring", monitoring of the UNSATURATED ZONE, i.e. the layer ABOVE the groundwater table (pp. 8–11 of the standard); • 6.2 — "Trial pits" (p. 19); • 6.3 — "Sampling of free-phase contaminants (DNAPLs and LNAPLs)", sampling of contaminants in the FREE PHASE — organic liquids with very low solubility in water and a density higher (DNAPL, e.g. chlorinated hydrocarbons) or lower (LNAPL, e.g. petroleum products) than that of water (p. 19); • 6.1 — "Purging", i.e. purging the borehole before taking the sample (pp. 15–19). The table of contents does not break down clause 6.1.2, and the available extract of the standard ends at clause 4.2.1 — WHAT EXACTLY 6.1.2 CONCERNS WE HAVE NOT ESTABLISHED, and we do not guess. The excluded clauses therefore form one pattern: laboratories keep sampling from the saturated zone, from piezometers and wells, and give up the techniques for contaminated land — those that entered the standard together with the former part 18.

THE SENTENCE FROM CLAUSE 4.1 THAT MUST BE PLACED NEXT TO THE NUMBER 65. In clause 4.1 the standard warns directly: sampling groundwater from the saturated zone alone usually DOES NOT ALLOW a full assessment of the level of subsurface contamination where an unsaturated zone of considerable thickness exists. A possible consequence of omitting the unsaturated zone is that the unsaturated zone and the groundwater system become EXTENSIVELY CONTAMINATED before any detectable trace of the leak appears in the samples taken from below the water table. Putting these two things together is not a reproach against the laboratories. Excluding clause 5.2 is an honest statement: "we do not carry out this technique". The matter concerns the CLIENT: a test carried out in accordance with PN-ISO 5667-11 with clause 5.2 excluded is a test of the saturated zone, and if the question is "is anything leaking from this landfill", the answer may come too late — and the report will be fully compliant with the standard and with the accreditation scope.

WHAT THE STANDARD DOES NOT COVER (from the scope, explicitly): it does not apply to sampling related to the ROUTINE day-to-day operational control of groundwater abstractions intended for drinking purposes. The standard does, however, cover sampling both from the saturated zone (below the water table) and from the unsaturated zone (above the water table).

TWO DEFECTS OF NOTATION VISIBLE IN THE SCOPES. First, 4 entries write this standard as "PN-EN ISO 5667-11" — but this standard is NOT a European standard: it implements ISO directly, without an EN element (unlike the sister part 6, which really is PN-EN ISO 5667-6). Second, 2 entries cite the withdrawn edition PN-ISO 5667-11:2004. Both numbers are small, but they show that with this standard even both things at once are confused — the designation and the year.

SCALE AND CONTEXT. The standard is one of the most frequently cited sampling methodologies: 96 entries at 94 laboratories, i.e. at roughly every fourteenth laboratory in the database of scopes (1281 laboratories). The methodology standing next to it is predominantly "Pobieranie próbek do badań chemicznych i fizycznych" [sampling for chemical and physical tests], often together with a measurement of the temperature of the sample taken. The test object is sometimes described simply as "Woda" [water] (63 entries), less often explicitly as "Woda podziemna" or "Wody podziemne" [groundwater] (28 entries) — i.e. from the test object in the scope alone it is NOT VISIBLE that groundwater is meant; this can only be seen from the standard number.

THE "LABORATORIES" TAB FOR THIS ENTRY WILL SHOW FEWER. Matching by the BEGINNING of the notation gives 89 entries and 87 laboratories — the difference from 96 and 94 is small here, because in most scopes this standard stands first in the citation. The seven entries that drop out are joint citations in which part 4 (lakes), part 5 (drinking water) or part 6 (rivers) stands before it.

Method principle

A groundwater sample is taken from a monitoring point (piezometer, well, nest of piezometers at different depths, multilevel sampler) after the borehole has first been purged, so that the sample comes from the aquifer and not from water stagnating in the pipe. The choice of point, frequency and determinands follows from the purpose of the test — from quality control of an abstraction to detection of contamination and assessment of the effectiveness of remediation. The standard gives variants of techniques with their advantages, disadvantages and limitations; the choice is made by the contractor, and the laboratory accredits only those variants that it actually carries out.

Applications

• Monitoring the quality of groundwater abstractions and assessing the suitability of water for supply
• Detecting and assessing groundwater contamination around waste landfills and industrial sites
• Investigations of contaminated land — after the former part 18 was incorporated into this standard
• Assessing the effectiveness of remediation and designing remedial measures
• Demonstrating compliance with permit conditions and collecting evidence for the authorities
• Reading an accreditation scope in which a list of excluded clauses stands next to this standard

Key parameters

Standard

Standard number

PN-ISO 5667-11:2017-10 (wersja ANGIELSKA; wprowadza ISO 5667-11:2009 [IDT])

Title (PL)

Jakość wody — Pobieranie próbek — Część 11: Wytyczne dotyczące pobierania próbek wód podziemnych

Title (EN)

Water quality — Sampling — Part 11: Guidance on sampling of groundwaters

Step-by-step procedure

1. Defining the purpose of the test — before choosing anything

   The standard sets this as a precondition: without a defined purpose it is not possible to indicate the principles for a specific task. The purpose may differ for assessing the suitability of water for drinking, for detecting contamination from a neighbouring site, and for assessing the effectiveness of remediation.

2. Choosing the location of the points (clause 4.2)

   Take into account the hydrogeological conditions of the site, the past and future use of the plot, the purpose of the test, the expected or known water quality and the nature and extent of possible contamination.

3. Deciding on the unsaturated zone

   A STEP FROM CLAUSE 4.1 OF THE STANDARD: if an unsaturated zone of considerable thickness lies above the water table, sampling only from below the water table will not allow a full assessment of contamination. If the contractor does not cover the unsaturated zone (clause 5.2 excluded in the scope), this must be agreed with the client BEFORE the test, not explained after the result.

4. Selecting determinands and frequency (clauses 4.3 and 4.4)

   The determinands and frequency follow from the purpose; in Annex A the standard gives a nomogram for determining the sampling frequency.

5. Choosing the installation and the sampling technique (clause 5)

   Unsaturated zone — clause 5.2; saturated zone — clause 5.3. The standard gives variants with their advantages, disadvantages and limitations; the choice belongs to the contractor and must fall within its accreditation scope.

6. Purging the borehole before sampling (clause 6.1)

   Removal of the water stagnating in the pipe, so that the sample comes from the aquifer. We have not established the details of subclause 6.1.2, which is sometimes excluded — check in the standard itself.

7. Techniques for contaminated land, if they are in the scope

   Trial pits (6.2) and sampling of free-phase liquids DNAPL and LNAPL (6.3) — these are the clauses brought into the standard together with the former part 18, and it is these that are most frequently excluded from accreditation scopes.

8. Equipment materials and preventing contamination of the sample (clauses 6.4 and 6.5)

   Selection of equipment materials with regard to the determinands and measures against secondary contamination of the sample.

9. Labelling, records and quality control (clauses 7–9)

   Safety rules (clause 7), sample identification and records (clause 8), quality assurance and quality control (clause 9). Annex B gives a model sampling report. The standard is read together with ISO 5667-1 and ISO 5667-3 (preservation and handling of samples).

10. Entering the exclusions in the report

    If the laboratory has the standard in its scope with clauses excluded, the report must give the citation in the same form as the accreditation scope — with the list of excluded clauses. The name of the standard alone, without exclusions, suggests a broader scope than is covered by accreditation.

Required equipment and apparatus

Health and safety (OHS)

• Excluding clause 5.2 means that the test does not cover the unsaturated zone — and in clause 4.1 the standard warns that with a thick unsaturated zone the contamination may already be extensive before it appears in samples from below the water table
• Citing the standard without the list of exclusions, when the accreditation scope contains them, suggests to the client a broader scope of testing than was carried out
• Since 2017 the standard has existed in the Polish collection only in English — a working translation used in the procedure is the responsibility of the laboratory, not of PKN
• The notation "PN-EN ISO 5667-11" is wrong: this part is not a European standard, unlike PN-EN ISO 5667-6 (the latter is current, but in the PKN catalogue only in the ENGLISH VERSION — reading of 22.09.2026)
• The 2004 edition has been withdrawn since 16-10-2017; it differs in its source (ISO 5667-11:1993) and does not contain the content of the former part 18
• The standard is not intended for routine operational control of drinking water abstractions — another part of the series serves that purpose

Frequently asked questions