Action Level List for Drinking Water
Groundwater in Connecticut can be affected by chemical contamination from recent or historic releases involving pesticides, industrial chemicals, fuel products, landfills and other sources. Depending on the volume spilled, local conditions, and nature of the substance, the result can be groundwater contamination. Such contamination may present a health risk to those who use contaminated water as a source of water for drinking, bathing, washing, or cooking.The Connecticut Department of Public Health (CT DPH) establishes drinking water Action Levels that are protective of public health and also feasible based upon analytical detection and treatment technology. If well contamination exceeds the value shown on the Action Level List (see below), the Connecticut Department of Energy and Environmental Protection (CT DEEP) is authorized under CT General Statutes Section 22a-471 to take further action in addressing groundwater contamination at the site. Additionally, the list provides guidance to local health departments and citizens when evaluating the potability of water. The Action Level list includes the most common groundwater contaminants. CT DPH is available to make determinations for additional chemicals if found in Connecticut groundwater.
The following list includes the Action Level value and recommended laboratory methods to detect the contaminant at the Action Level. If you have questions about the Action Level List call the Environmental and Occupational Health Section of CT DPH (860-509-7740). For questions about analytical methods call CT DPH’s Laboratory Certification Program (860-509-7389). If your well is contaminated with a chemical at a concentration above the Action Level, inform your local health department and CT DEEP (860-424-3705).
| Chemical Contaminant | CT Action Level (µg/L) | Analytical Method1 | Date of Revision |
| Arsenic | 10 | 200.5, 200.8, 200.9, SM 3113B, SM3114B |
2004 |
| Barium | 2000 | 200.7, 200.8, SM 3113B 200.5, SM3111D, SM3120B |
2004 |
| Benzene | 1 | 524.2, 524.3, 524.4 |
2004 |
| Carbon Tetrachloride | 0.5 | 524.2, 524.3, 524.4 |
2012 |
| Chlordane (technical) | 0.3 | 505, 508, 508.1 | 2004 |
| Chromium (total) | 15 | 200.7, 200.8, 200.9, SM 3113B 200.5, SM3111D, SM3120B |
2012 |
| 1,4-Dichlorobenzene | 5 | 524.2, 524.3, 524.4 |
2012 |
| 1,2-Dichloroethane | 0.5 | 524.2, 524.3, 524.4 |
2012 |
| Dichloromethane | 5 | 524.2, 524.3, 524.4 |
2004 |
| 2,4-Dichlorophenoxyacetic Acid (2,4 – D) | 70 | 515 (.1 - .4), 555 | 2004 |
| 1,2-Dichloropropane | 1 | 524.2, 524.3, 524.4 |
2012 |
| 1,1-Dichloroethane | 25 | 524.2, 524.3, 524.4 |
2004 |
| 1,1-Dichloroethylene | 7 | 524.2, 524.3, 524.4 |
2004 |
| Dieldrin | 0.03 | 505, 508, 508.1, 525.2, 525.3 |
2004 |
| 1,4-Dioxane | 3 | 8260D (modified), 522 |
2012 |
| Endrin | 2 | 505, 508, 508.1, 525.2, 525.3, 551.1 |
2004 |
| Ethylene Dibromide (EDB) | 0.052 | 504, 524.3, 551.1, 524.2, 524.4 |
2004 |
| Isopropanol | 2300 | 8260D | 2004 |
| Lead | 15 | 200.5, 200.8, 200.9, SM 3113B | 2004 |
| Manganese | 300 | 200.7, 200.8, 200.9, 200.5, SM3111D, SM3113B, SM3120B |
2019 |
| Mercury | 2 | 245.1, 245.2, 200.8, SM3112B |
2004 |
| Methoxychlor | 40 | 505, 508, 508.1, 525.2, 525.3, 551.1 |
2004 |
| Methyl T-butyl Ether (MTBE) | 70 | 524.2, 524.3, 524.4 |
2004 |
| Nitrate Nitrogen | 10,000 | 300.0, 353.3, 300.1, SM4500 NO3 (D-F) |
2004 |
| Nitrite Nitrogen | 1,000 | 300.0, 353.3, 300.1, SM4500 NO2B, SM4500 NO3 (E-F) |
2004 |
| per- and polyfluorinated alkyl substances (PFAS) |
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| 6:2 chloropolyfluoroether sulfonic acid (6:2 Cl-PFESA; F-53B major)3 |
0.002 |
533, 537.1 |
2023 |
| 8:2 chloropolyfluoroether sulfonic acid (8:2 Cl-PFESA; F-53B minor)3 |
0.005 |
533, 537.1 |
2023 |
| Hexafluoropropylene oxide-dimer acid (HFPO-DA; GenX) |
0.019 |
533, 537.1 |
2023 |
| Perfluorobutane sulfonic acid (PFBS) |
0.76 |
533, 537.1 |
2023 |
| Perfluorobutanoic acid (PFBA) |
1.8 | 533 | 2023 |
| Perfluorohexane sulfonic acid (PFHxS) | 0.049 | 533, 537.1 |
2022 |
| Perfluorohexanoic acid (PFHxA) |
0.24 | 533, 537.1 |
2023 |
| Perfluorooctane sulfonic acid (PFOS) | 0.01 | 533, 537.1 |
2022 |
| Perfluorooctanoic acid (PFOA) | 0.016 | 533, 537.1 |
2022 |
| Perfluorononanoic acid (PFNA) | 0.012 | 533, 537.1 |
2022 |
| Polychlorinated Biphenyls (PCBs) | 0.2 | 505, 508, 508.1, 525.2, 525.3 for Aroclors and 508A for decachlorobiphenyl upon any Aroclor detection |
2012 |
| Selenium | 50 | 200.5, 200.8, 200.9, SM 3113B, SM3114B |
2004 |
| Silvex | 50 | 515 (.1 – .4), 555 | 2004 |
| Tertiary-butyl Alcohol (TBA) (total oxygenates)4 | 100 | 524.2, 524.3, 524.4 |
2004 |
| Tetrachloroethylene | 5 | 524.2, 524.3, 524.4 |
2004 |
| Toluene | 150 | 524.2, 524.3, 524.4 |
2012 |
| Total Petroleum Hydrocarbon (TPH) | 2505 | EPH/VPH or ETPH6 | 2012 |
| 1,1,1-Trichloroethane | 200 | 524.2, 524.3, 524.4 |
2004 |
| Trichloroethylene | 1 | 524.2, 524.3, 524.4 |
2012 |
| 1,2,3-Trichloropropane | 0.05 | 504, 524.3, 551.1, 524.2, 524.3 |
2004 |
| Vinyl Chloride | 0.5 | 524.2, 524.3, 524.4 |
2012 |
1 The analytical methods listed are from US EPA, the SM designation indicates APHA/AWWA Standard Methods for the Examination of Water and Wastewater.
2 EDB Action Level is the same value as the federal MCL, based upon EDB detection limits established in the past. However, the current detection limit is 0.02 µg/L. Detections between 0.02 and 0.05 µg/L should receive follow-up monitoring, and can be referred to DPH for possible follow-up actions.
3 EPA METHODS 533 & 537.1 refer to 6:2 Cl-PFESA as 9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid (9Cl-PF3ONS) and 8:2 Cl-PFESA as 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)
4 If the TBA concentration alone, or the sum of all oxygenates in the sample equals 100 µg/L, additional action is recommended (e.g., follow-up monitoring, evaluation of sources and mitigation/treatment options, and possible provision of alternative water supply). List of oxygenates: TBA, MTBE, ethyl-t-butyl ether (ETBE), t-amyl-methyl ether (TAME), diisopropyl ether (DIPE).
5 Action Level pertains to TPH as detected by the CT DEEP’s ETPH method, Extractable Petroleum Hydrocarbon Fractions using the ETPH Analytical Method and Criteria Development.
6 If the EPH/VPH method is used instead, the Action Level for individual fractions is between 100 to 1000 µg/L, as described by the groundwater protection criteria for these fractions. See Table 5 of CTDEEP document, Petroleum Hydrocarbons using the EPH/VPH/APH Analytical Methods and Criteria Development.