1. a) Representative Samples

   A representative sample must be taken from locations as specified in Section 620.505.

2. b) Sampling and Analytical Procedures

   1. 1) Samples must be collected in compliance with the procedures specified in the documents pertaining to groundwater monitoring and analysis incorporated by reference in Section 620.125 or other procedures adopted by the appropriate regulatory agency.
   2. 2) Groundwater elevation in a groundwater monitoring well must be determined and recorded when necessary to determine the gradient.
   3. 3) Except as specified in other regulations, statistical methods used to determine naturally occurring groundwater quality background concentrations of contaminants must be conducted in compliance with "Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities, (March 2009 Unified Guidance)", incorporated by reference in Section 620.125, for use with prediction limits and all other statistical tests, including confidence limits and control charts.

   4. 4) The analytical methodology used for analyzing constituents specified in Subparts C and D must comply with the following:

      1. A) The methodology must have an LLOQ or LCMRL at or below the preventive response level of Subpart C or the groundwater standard of Subpart D, whichever applies; and
      2. B) "Methods for Chemical Analysis of Water and Wastes", "Methods for the Determination of Inorganic Substances in Environmental Samples", "Methods for the Determination of Metals in Environmental Samples", "Methods for the Determination of Organic Compounds in Drinking Water", "Methods for the Determination of Organic Compounds in Drinking Water, Supplement I", "Methods for the Determination of Organic Compounds in Drinking Water, Supplement II", "Methods for the Determination of Organic Compounds in Drinking Water, Supplement III", "Methods for the Determination of Organic and Inorganic Compounds in Drinking Water", "Prescribed Procedures for Measurement of Radioactivity in Drinking Water", "Procedures for Radiochemical Analysis of Nuclear Reactor Aqueous Solutions", "Radiochemical Analytical Procedures for Analysis of Environmental Samples", "Radiochemistry Procedures Manual", "Practical Guide for Ground Water Sampling", "Test Methods for Evaluating Solid Wastes, Physical/Chemical Methods" (SW-846), 40 CFR 136, appendix B, 40 CFR 141.80, 40 CFR 141.61, and 40 CFR 141.62, "Techniques of Water Resources Investigations of the United States Geological Survey, Guidelines for Collection and Field Analysis of Ground Water Samples for Selected Unstable Constituents", "Practical Guide for Ground-Water Sampling", "Techniques of Water Resources Investigations of the United States Geological Survey, Guidelines for Collection and Field Analysis of Ground-Water Samples for Selected Unstable Constituents", or other procedures incorporated by reference in Section 620.125.

      3. C) When sampling for Hexafluoropropylene oxide dimer acid (HFPO-DA), Perfluorobutanesulfonic acid (PFBS), Perfluorohexanesulfonic acid (PFHxS), Perfluorononanoic acid (PFNA), Perfluorooctanoic acid (PFOA), or Perfluorooctanesulfonic acid (PFOS), the incorporations by reference in Section 620.125 that apply for sample collection, preservation, storage, and analysis are:

         "Standard Test Method for Determination of Per- and Polyfluoroalkyl Substances in Water, Sludge, Influent, Effluent, and Wastewater by Liquid Chromatography Tandem Mass Spectrometry (LC/MS/MS) ASTM D7979-20;

         U.S. EPA, Office of Ground Water and Drinking Water, Standards and Risk Management Division. "Method 533: Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry," November 2019. https://www.epa.gov/sites/default/files/2019-12/documents/method-533-815b19020.pdf; and

         U.S. EPA, Office of Research and Development, Center for Environmental Solutions & Emergency Response. Shoemaker, J. and Dan Tettenhorst, Method 537.1: Determination of selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass spectrometry (LC/MS/MS). U.S. Environmental Protection Agency, Office of Research and Development, Center for Environmental Assessment, Washington, DC. Version 2.0, March 2020.

3. c) Reporting Requirements

   1. 1) Sample collection (including name of sample collector, time and date of the sample, method of collection, and identification of the monitoring location);
   2. 2) Sample preservation and shipment (including field quality control);
   3. 3) Analytical procedures (including the MDL, LLOQ, or LCMRL); and
   4. 4) Chain of custody control.

   Groundwater monitoring analytical results must include information, procedures, and techniques for:

(Source: Amended at 49 Ill. Reg. 4488, effective March 28, 2025)