EWG's Tap Water Database



Public Wholesale WSD 5

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
20100.0550 ppm21ND - 0.110 ppm
20110.380 ppm220.310 ppm - 0.450 ppm
20120.195 ppm21ND - 0.390 ppm
20130.910 ppm220.850 ppm - 0.970 ppm
20140.375 ppm220.210 ppm - 0.540 ppm
20150.470 ppm220.140 ppm - 0.800 ppm

ppm = parts per million.

State and national drinking water standards and health guidelines

Health Guideline 0.14 ppm

The health guideline of 0.14 ppm for nitrate was defined in a peer-reviewed scientific study by EWG and corresponds to one-in-one-million annual cancer risk level.

ppm = parts per million.

EPA Maximum Contaminant
Level (MCL) 10 ppm

The enforceable federal standard that defines the highest level of a contaminant allowed in drinking water.

ppm = parts per million.

EPA Maximum Contaminant
Level Goal (MCLG)10 ppm

A non-enforceable federal health guideline. For cancer-causing chemicals, these health goals are typically set to zero.

ppm = parts per million.

All test results

Date Lab ID Result
2010-03-02542899WS0.110 ppm
2011-05-03561159WS0.310 ppm
2011-05-03561154BT0.450 ppm
2012-04-10577265BT0.390 ppm
2013-04-16594656BT0.850 ppm
2013-05-07595616WS0.970 ppm
2014-04-15967030.540 ppm
2014-04-221002090.210 ppm
2015-04-073090570.140 ppm
2015-04-213164650.800 ppm