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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 itself 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 on the Action Level List, you should inform your local health department and CT DEEP (860-424-3705). 

Chemical Contaminant

CT Action Level (µg/L)

Analytical Method Date of Revision
 Arsenic 10 200.5, 200.8, 200.9, SM 3113B 2004
 Barium 2000  200.7, 200.8, SM 3113B 2004
 Benzene 1  524.2, 524.3 2004 
 Carbon Tetrachloride  0.5  524.2, 524.3 2012 
 Chlordane (technical)  0.3  505, 508, 508.1 2004 
 Chromium (total)  15  200.7, 200.8, 200.9, SM 3113B 2012
 1,4-Dichlorobenzene  5  524.2, 524.3  2012
 1,2-Dichloroethane  0.5  524.2, 524.3 2012 
 Dichloromethane  5  524.2, 524.3 2004 
 2,4-Dichlorophenoxyacetic Acid (2,4 – D)  70  515 (0.1-0.4), 555 2004
 1,2-Dichloropropane  1  524.2, 524.3 2012 
 1,1-Dichloroethane  25  524.2, 524.3 2004 
 1,1-Dichloroethylene  7  524.2, 524.3 2004
 Dieldrin  0.03  505, 508, 508.1 2004 
 1,4-Dioxane  3  524.3, 8260B (modified) 2012
 Endrin 2 505, 508, 508.1 2004
 Ethylene Dibromide (EDB)  0.052 504, 524.3, 551.1 2004
 Isopropanol  2300  524.3, 8260B 2004 
 Lead 15  200.5, 200.8, 200.9, SM 3113B 2004 
 Manganese 300  200.7, 200.8, 200.9  2019
 Mercury 2  245.1, 245.2, 200.8 2004 
 Methoxychlor 40  505, 508, 508.1 2004 
 Methyl T-butyl Ether (MTBE) 70  524.2, 524.3 2004 
 Nitrate Nitrogen 10,000  300.0, 353.3 2004 
 Nitrite Nitrogen 1,000  300.0, 353.3 2004 
 Perfluorinated alkyl substances (sum of PFOS, PFOA, PFNA, PFHxS, PFHpA)3 0.07 537 rev 1.1, 537.1 2016
 Polychlorinated Biphenyls (PCBs) 0.2 505, 508, 508.1 2012
 Selenium 50 200.5, 200.8, 200.9, SM 3113B 2004
 Silvex 50 515 (.1 – .4), 555 2004
 Tertiary-butyl Alcohol (TBA) (total oxygenates)4 100 524.2, 524.3  2004
 Tetrachloroethylene 5 524.2, 524.3  2004
 Toluene 150 524.2, 524.3 2012 
 Total Petroleum Hydrocarbon (TPH) 2505 EPH/VPH or ETPH5 2012
 1,1,1-Trichloroethane 200 524.2, 524.3 2004
 Trichloroethylene 1 524.2, 524.3 2012
 1,2,3-Trichloropropane 0.05 504, 524.3, 551.1 2004
 Vinyl Chloride 0.5 524.2, 524.3 2012

 

1 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.

3PFAS (perfluorinated alkyl substances) abbreviations: PFOS: perfluorooctanesulfonate; PFOA: perfluorooctanoic acid; PFNA: perfluorononanoic acid; PFHxS: perfluorohexanesulfonate; PFHpA: perfluoroheptanoic acid. 

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.  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