Skip to main content

Chemical Monitoring

All public water systems in Vermont must conduct required monitoring of their drinking water in accordance with state and federal regulations. Drinking water monitoring is necessary to ensure that public health is being adequately protected.

Terms to know:

  • Maximum Contaminant Level (MCL) – The maximum contaminant level is a legal limit set by the State or USEPA for the allowed amount of a substance to be present in public water systems. MCLs are based on a cost-benefit analysis and are legally enforceable standards.
  • Vermont Health Advisory (VHA) – The concentration level of a substance in drinking water below which does not pose a public health risk or public health hazard, and for which there is no MCL established. VHAs are non-enforceable standards.
  • Secondary Drinking Water Standard – A standard that is not a primary standard, but rather a guideline to assist public water systems in managing aesthetic concerns in their drinking water. This means in situations where the taste, odor or appearance of the water deters persons served to not consume or discontinue use of provided drinking water. These standards may be applied in order to protect public health and welfare.  

Refer to the Chemical Sampling Frequency Table for monitoring information.

For more information regarding health effects, please visit the Vermont Department of Health’s website.


All public drinking water systems must sample for nitrate annually. TNC systems may sample at any time during the year. Seasonal TNC systems are required to submit sample results while they are open and serving water to a public population. NTNC and Community systems must sample for nitrate according to the system's established monitoring schedule

Sources of nitrate in drinking water include runoff from fertilizer use, leaking septic tanks or sewage, and erosion of natural deposits. Health concerns from nitrate include "blue baby syndrome" or methemoglobinemia. Infants under six months of age are the most susceptible to this concern as elevated nitrate levels render the infant's blood less able to carry oxygen. Confirmed sample results above the nitrate MCL require a Do Not Drink notice.

Samples for nitrate must be taken at the entry point to the distribution system, following all treatment and storage, and at or before the first tap/user in distribution.


Manganese is a common mineral found in rocks, soil, groundwater, and some surface water in Vermont. It is a naturally-occurring component of most foods and is a trace mineral in our diets. Manganese is an essential metal required for many metabolic and cellular functions. Low amounts of manganese are essential to good health.   Elevated manganese exposure over a long time could harm the nervous system. The Health Advisory for manganese in drinking water is 0.3 mg/L, established by the Vermont Department of Health. Infants and children up to 1 year old should not be given water containing manganese over 0.3 mg/L because they could have greater difficulty processing manganese than older children and adults. Special care should be taken to avoid making infant formula with water with a manganese concentration exceeding 0.3 mg/L.  USEPA has helpful manganese health information available.

Manganese is regulated as a secondary contaminant due to aesthetic concerns. Manganese equal to or greater than 0.05 mg/L can lead to an unacceptable taste or staining of fixtures. Recent studies have shown potential health effects from consuming too much manganese. Because of these studies, VDH and the DWGWPD have worked together to establish a Health Advisory for manganese in drinking water of 0.3 mg/L (or 300 ppb).   Based on the system's sampling result history, systems may sample for Manganese once per quarter, once per year, or once every three years.  While manganese is often part of the entire IOC suite, it can be "broken" out from the full IOC suite and treated separate from those other contaminants in IOCs.  Samples for manganese must be taken at the entry point to the distribution system, following all treatment (if applicable).

Manganese Guidance for Public Water Systems


The term radionuclide refers to the following regulated drinking water contaminants in Vermont:

  • Uranium
  • Combined Radium -226 and -228
  • Gross Alpha Particle Activity

Certain rock types in Vermont have naturally-occurring radionuclides which can make their way into drinking water. Community Systems are required to routinely monitor for these contaminants. NTNC systems are required to perform some initial monitoring which will then dictate the need for future monitoring. The sampling frequency for radionuclides is based on the concentration of the contaminant present. 

Through work with the Department of Health, Vermont has established a Maximum Contaminant Level (MCL) for uranium which is more stringent than the federal MCL in drinking water in order to better protect public health. Vermont's Uranium MCL is 20 micrograms per liter, while the federal MCL is 30 micrograms per liter.  A confirmed finished water sample result above the Vermont MCL of 20 ug/L requires a Do Not Drink notice.

Compliance samples for radionuclides must be taken at the entry point to the distribution system, following all treatment and storage and at or before the first tap/user in distribution.

Inorganic Compounds (IOCs)

Community Systems and NTNCs and  are required to sample for IOCs.  Baseline monitoring for surface water systems is once per year and for groundwater systems is once every three years.  Based on the system's results, it may be possible to reduce IOC monitoring or to receive a sampling waiver for IOCs. IOCs can either be naturally-occurring in drinking water or can result from contamination of a drinking water source due to human activities. If not naturally-occurring, IOC contamination can result from industrial processes including metal manufacturing, metal refining and mining activity/runoff, explosives residues,  improper waste disposal, fertilizers, chemical manufacturing, and glass manufacturing.  

The full regulated list of IOCs (displayed as All Inorganic Chemicals on your schedule) includes 14 analytes:

  • Antimony
  • Arsenic
  • Barium
  • Beryllium
  • Cadmium
  • Chromium
  • Cyanide
  • Fluoride
  • Iron
  • Manganese
  • Mercury
  • Nickel
  • Selenium
  • Thallium

Compliance samples for IOCs must be taken at the entry point to the distribution system, following all treatment and storage and at or before the first tap/user in distribution.

Synthetic Organic Compounds (SOCs)

Community systems and NTNCs are required to sample for SOCs.  The frequency for monitoring is based on the system's previous sampling results, the size of the system, and whether the system has an updated Source Protection Plan.  Surface water systems utilizing Lake Champlain as a water source are not eligible for SOC monitoring waivers; however, other systems may qualify for a monitoring waiver to either reduce the sampling frequency or eliminate the need to sample for SOCs.  SOCs are not naturally occurring and while we rarely see contamination in Vermont, if we did- it would be the result of human activities.  Water sources can become contaminated by SOCs from agricultural runoff or commercial or industrial processes. SOCs are mainly used as herbicides, pesticides, and some fuel additives. 
The regulated list of SOCs includes 25 analytes:

  • 1,2-Dibromo-3-Chloropropane (Dibromochloropropane)
  • 2,4,5-TP (Silvex)
  • 2,4-D (Agent Orange)
  • Atrazine
  • Benzo[a]pyrene
  • BHC-Gamma (Lindane)
  • Carbofuran
  • Chlordane
  • Di(2-ethylhexyl) Adipate
  • Di(2-ethylhexyl) Phthalate
  • Dinoseb
  • Endrin
  • Ethylene Dibromide (EDB)
  • Heptachlor
  • Heptachlor Epoxide
  • Hexachlorobenzene
  • Hexachlorocyclopentadiene
  • Lasso (Alachlor)
  • Methoxychlor
  • Oxamyl (Vydate)
  • Pentachlorophenol
  • Picloram
  • Simazine
  • Total Polychlorinated Biphenyls (PCBs)
  • Toxaphene

Compliance samples for SOCs must be taken at the entry point to the distribution system, following all treatment and storage and at or before the first tap/user in distribution.

Volatile Organic Compounds (VOCs)  

Community systems and NTNCs are required to sample for VOCs.  Upon becoming a new system or permitting a new source, systems need to take four consecutive quarters of VOC samples.  Based on the results of the sampling, the required frequency for future sampling is established; most systems in Vermont sample for VOCs once every three years.  A water system that sees VOC detections will need to monitor more frequently. VOCs are in the form of either chlorinated solvents or fuel components.  Drinking water contamination may occur due to leaching from landfills, hazardous waste dumps or spills, industrial facilities, chemicals improperly cured or used during plumbing or storage tank work, fuel spills, or leaking fuel storage tanks.  
The regulated list of VOCs includes 21 analytes:

  • 1,1,1-Trichloroethane
  • 1,1,2-Trichloroethane
  • 1,1-Dichloroethylene
  • 1,2,4-Trichlorobenzene
  • 1,2-Dichloroethane
  • 1,2-Dichloropropane
  • Benzene
  • Carbon Tetrachloride
  • Chlorobenzene (Monochlorobenzene)
  • Cis-1,2-Dichloroethylene
  • Dichloromethane (Methylene Chloride)
  • Ethylbenzene
  • O-Dichlorobenzene
  • P-Dichlorobenzene
  • Styrene
  • Tetrachloroethylene
  • Toluene
  • Trans-1,2-Dichloroethylene
  • Trichloroethylene
  • Vinyl Chloride (Chloroethene)
  • Xylenes, Total

Compliance samples for VOCs must be taken at the entry point to the distribution system, following all treatment and storage and at or before the first tap/user in distribution.

Turbidity (surface water sources only)

In order to control of microbial contaminants, especially Cryptosporidium, all systems that utilize surface water or groundwater under the direct influence of surface water (GWUDI) are required to routinely monitor turbidity.  Turbidity monitoring helps to determine the adequacy of the treatment process and watershed control requirements; if a system suddenly experiences high finished water turbidity levels, it may mean a breakthrough in the treatment process, which could then allow viruses, bacteria and/or parasites into the water system.

Secondary Contaminants

Existing NTNC and Community systems may be required to monitor for and comply with the secondary standards at the discretion of the DWGWPD.  These contaminants may either be naturally-occuring or be the result of human activity.  The secondary contaminants include: Aluminum, Chloride,  Copper, Corrosivity, Fluoride, Foaming Agents, Iron, Manganese, Odor, pH, Silver, Sodium, Sulfate, Total Disolved Solids (TDS), and Zinc.  Some of these contaminants (such as Copper, and Fluoride) are also considered primary contaminants and are captured in the suites of sampling identified above.

Other Drinking Water Contaminants

Asbestos:  Asbestos contamination is the result of using asbestos cement (also known as "transite" or "ac") pipes whereby the fibers of asbestos in the pipes degrade and enter the flow of water.  Systems utilizing asbestos cement pipes are required to monitor for asbestos contamination in the distribution system at a point following the water's maximum residence time in the pipe in question.

Table of contaminant MCLs

For additional information about potential health effects for any of the contaminants listed above, visit the Vermont Department of Health’s website.

*Some water systems may be eligible for sampling waivers.  In order to be considered for a waiver, the system needs to start with the application

Search Form Logo

YouTube logo