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Sampling Requirements for Used Oil Underground Storage Tank Systems

1. What are the indicator contaminants for a used oil release, and how are they determined?

When a release of used oil has occurred, the indicator contaminants shall be determined by the results of a used oil soil-screening sample. The sample shall be analyzed for all volatile, base/neutral, polynuclear aromatic (PNA), and metal parameters listed at Appendix B of 35 Illinois Administrative Code (35 Ill. Adm. Code) 732 or 734 (also listed after the last question of this fact sheet) and any other parameters the Licensed Professional Engineer or Licensed Professional Geologist suspects may be present based on underground storage tank (UST) system usage. The Illinois EPA may add degradation products or mixtures of any of the pollutants listed above. The used oil indicator contaminants shall be those parameters listed above that exceed their most stringent remediation objective at 35 Ill. Adm. Code 742 in addition to benzene, ethylbenzene, toluene, total xylenes (BETX) and the PNAs listed in Appendix B. If none of the parameters exceed their remediation objective, then the used oil indicator contaminants shall be BETX and the PNAs listed in Appendix B.

2. Where and when is the soil-screening sample collected to determine indicator contaminants?

Of the samples collected during Early Action activities, the soil sample that appears to be the most contaminated as a result of the release from the used oil UST system must be used to determine indicator contaminants. If none of the samples appear to be contaminated, then a floor sample collected from below the used oil UST must be used. This sample is to be used as a screening tool and should be collected and analyzed during Early Action. It must be collected and analyzed prior to the submittal of a site classification plan or site investigation plan.


Please be advised that sampling the tank contents is not an acceptable method to establish indicator contaminants.

3. How can metals be excluded from further consideration as indicator contaminants?

For used oil UST systems, metals may be excluded from further consideration by:


  • Utilizing the background concentrations located at 35 Ill. Adm. Code 742.Appendix A.Table G. The values listed in this table are based upon total metal concentrations. If the total metal concentration of the soil-screening sample is less than or equal to the background concentration listed in Table G, then that metal may be excluded as an indicator contaminant; or
  • Comparing TCLP or SPLP concentrations to the Tier 1 look-up soil remediation objectives table for residential properties at 35 Ill. Adm. Code 742.Appendix B.Table A. If the TCLP or SPLP metal concentration of the soil-screening sample is less than or equal to the remediation objective for the soil component of the groundwater ingestion exposure route listed in Table A, then that metal may be excluded as an indicator contaminant; or
  • Performing a pH analysis of a soil sample collected from an uncontaminated location on site and comparing the total metal concentration to the pH-specific soil remediation objective located at 35 Ill. Adm. Code 742.Appendix B.Table C or Table D. If the total metal concentration of the soil-screening sample is less than or equal to the remediation objective listed in Table C or D, then that metal may be excluded as an indicator contaminant.


For this reason, it is recommended that the soil-screening sample be analyzed for both total and soluble (TCLP or SPLP) metals and pH analysis be performed on a soil sample from an uncontaminated area.


For your information, the use of area background concentrations to exclude metals from consideration as used oil indicator contaminants does not result in a land use restriction.

4. What sampling is required after the soil-screening sampling?

After the indicator contaminants have been identified from the soil-screening sample, further sampling for the indicator contaminants is required in accordance with Early Action provisions.


Alternatively—and possibly the simplest course to follow—all Early Action samples, including the soil-screening sample, may be collected at the same time. Then, with a request to the laboratory for quick turnaround time, the soil-screening sample must be analyzed for all parameters noted above (in response to the first question of this fact sheet). At this time, too, all Early Action samples should be analyzed for BETX and PNAs (since these parameters are always required for used oil UST systems). Please note that a sufficient amount of soil should be collected per sample location for later testing of other indicator contaminants, if any.


Upon completion of Early Action activities, if compliance with applicable remediation objectives is not demonstrated, further sampling will be required pursuant to regulations governing site classification, site investigation, and/or corrective action.

5. What remediation objectives are used as a comparison to the analytical results?

The most stringent Tier 1 remediation objectives listed at 35 Ill. Adm. Code 742.Appendix B must be used for the established indicator contaminants. While the Tier 1 soil remediation objectives for residential properties are generally the most stringent, other remediation objectives (for example, the construction worker inhalation remediation objectives found at 35 Ill. Adm. Code 742.Appendix B.Table B) may be more stringent for some parameters.


In order to make the comparison between Tier 1 remediation objectives and the analytical results, the laboratory analytical reports must include a practical quantitation limit (PQL) or reporting limit that is less than or equal to the most stringent remediation objective for each parameter in compliance with 35 Ill. Adm. Code Section 734.415(b). The only exceptions are those parameters whose acceptable detection limits (ADL), as listed at 35 Ill. Adm. Code 742.Appendix B.Tables A and B, are higher than the remediation objectives. Namely, the parameters with higher ADLs are:


  • aldrin
  • bis(2-chloroethyl)ether
  • 1,2-dibromoethane (ethylene dibromide)
  • 3,3’-dichlorobenzidine
  • 1,3-dichloropropene (1,3-dichloropropylene, cis + trans)
  • dieldrin
  • 2,4-dinitrotoluene
  • 2,6-dinitrotoluene
  • heptachlor
  • heptachlor epoxidealpha-HCH ( alpha-BHC)
  • nitrobenzene
  • n-nitrosodi- n-propylamine
  • 2,4-dinitrophenol
  • 2,4,6-trichlorophenol

Further, the analytical results must be reported on a dry weight basis, and all sample analyses must be performed by a laboratory accredited for the analyzed parameters. Analytical results that do not meet these criteria will not be accepted as a demonstration of compliance.

6. Where can I get more information on this subject?

For more information, please contact the project manager on call for the Leaking Underground Storage Tank Section at 217-524-3300.

7. Minimum Soil-Screening Sampling Parameters for Used Oil UST Systems (from 35 Ill. Adm. Code 732/734.Appendix B)



  1. Benzene
  2. Bromoform
  3. Carbon tetrachloride
  4. Chlorobenzene
  5. Chloroform
  6. Dichlorobromomethane
  7. 1,2-Dichloroethane
  8. 1,1-Dichloroethene
  9. cis-1,2-Dichloroethylene
  10. trans-1,2-Dichloroethylene
  11. Dichloromethane (Methylene chloride)
  12. 1,2-Dichloropropane
  13. 1,3-Dichloropropylene (cis + trans)
  14. Ethylbenzene
  15. Styrene
  16. Tetrachloroethylene
  17. Toluene
  18. 1,1,1-Trichloroethane
  19. 1,1,2-Trichloroethane
  20. Trichloroethylene
  21. Vinyl chloride
  22. Xylenes (total)



  1. Bis(2-chloroethyl)ether
  2. Bis(2-ethylhexyl)phthalate
  3. 1,2-Dichlorobenzene
  4. 1,4-Dichlorobenzene
  5. Hexachlorobenzene
  6. Hexachlorocyclopentadiene
  7. n-Nitrosodi- n-propylamine
  8. n-Nitrosodiphenylamine
  9. 1,2,4-Trichlorobenzene


Polynuclear Aromatics


  1. Acenaphthene
  2. Anthracene
  3. Benzo(a)anthracene
  4. Benzo(a)pyrene
  5. Benzo(b)fluoranthene
  6. Benzo(k)fluoranthene
  7. Chrysene
  8. Dibenzo(a,h)anthracene
  9. Fluoranthene
  10. Fluorene
  11. Indeno(1,2,3-c,d)pyrene
  12. Naphthalene
  13. Pyrene
  14. Acenaphthylene
  15. Benzo(g,h,i)perylene
  16. Phenanthrene


Metals (total inorganic and organic forms)

  1. Arsenic
  2. Barium
  3. Cadmium
  4. Chromium (total)
  5. Lead
  6. Mercury
  7. Selenium


This fact sheet is for general information only and is not intended to replace, interpret, or modify laws, rules or regulations.

Revised August 2007