The Drinking Water List of Standards and Guidelines is a compilation of guidance values for evaluating contaminants in Massachusetts' drinking water.
- Standards are maximum contaminant levels (MCLs), set by the US Environmental Protection Agency and promulgated in the Massachusetts Drinking Water Regulations (310 CMR 22.00), plus a few MCLs set specifically by Massachusetts. State standards may be more stringent than those of EPA.
Note that private residential drinking-water wells are not subject to the requirements of 310 CMR 22.00; however, these standards are recommended for the evaluation of private drinking water supplies.
- Guidelines are issued by MassDEP's Office of Research & Standards for chemicals that do not have an established MCL or other federal standards or guidance. ORS uses methodology similar to that of US EPA when setting guidelines.
In addition to the Standards and Guidelines, MassDEP has also derived "Immediate Action Levels" for routinely-used water treatment chemicals, to enable water-treatment plant operators to identify and address serious incidents of chemical overfeed or misuse. These parameters are frequently and routinely monitored in the treatment plant.