EWG's Tap Water Database — 2021 UPDATE



Colchester Commons

Nitrate, a fertilizer chemical, frequently contaminates drinking water due to agricultural and urban runoff, and discharges from municipal wastewater treatment plants and septic tanks. Excessive nitrate in water can cause oxygen deprivation in infants and increase the risk of cancer. Click here to read more about nitrate.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20140.140 ppm32ND - 0.310 ppm
20150.227 ppm32ND - 0.590 ppm
20160.407 ppm32ND - 0.980 ppm
20170.113 ppm330.0200 ppm - 0.250 ppm
20180.557 ppm330.0300 ppm - 1.24 ppm
20190.222 ppm550.0700 ppm - 0.330 ppm

ppm = parts per million

State and national drinking water standards and health guidelines

EWG Health Guideline 0.14 ppm

The EWG Health Guideline of 0.14 ppm for nitrate was defined by EWG . This health guideline protects against cancer and harm to fetal growth and development.

EPA Maximum Contaminant
Level (MCL) 10 ppm

The legal limit for nitrate, established in 1962, was developed to protect infants from acute methemoglobinemia, a life-threatening disorder of oxygen transport in the body. This limit does not fully protect against the risk of cancer and harm to the developing fetus.

ppm = parts per million

All test results

Date Lab ID Result
2014-07-29BG83660NOX0.110 ppm
2014-07-29BG83661NOX0.310 ppm
2015-04-24BJ07684NOX0.0900 ppm
2015-04-24BJ07685NOX0.590 ppm
2016-03-24BK87905NOX0.240 ppm
2016-03-24BK87906NOX0.980 ppm
2017-01-12BX21457NOX0.0700 ppm
2017-04-07BY00694NOX0.0200 ppm
2017-10-10BZ18334NOX0.250 ppm
2018-04-27CA37955NOX0.0300 ppm
2018-04-27CA37956NOX0.400 ppm
2018-04-27CA37957NOX1.24 ppm
2019-10-21CE445540.0700 ppm
2019-10-21CE445550.190 ppm
2019-10-21CE445590.200 ppm
2019-10-21CE445600.320 ppm
2019-10-21CE445560.330 ppm