Chromium (total)

Castle Rock

Chromium is a naturally occurring metal, but industrial uses can elevate its levels in water. One form, hexavalent chromium, causes cancer. Total chromium is not a good indicator of the amount of hexavalent chromium in drinking water.

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Samples

Samples exceeding legal limit (MCL)

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2014	0.228 ppb	17	6	ND - 1.000 ppb
2015	0.333 ppb	11	8	ND - 1.000 ppb
2016	ND	2	0	ND
2017	ND	7	0	ND
2018	0.571 ppb	7	2	ND - 3.00 ppb
2019	1.50 ppb	6	5	ND - 2.00 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EPA Maximum Contaminant
Level (MCL) 100 ppb

The legal limit for total chromium, established in 1991, was based on a 1958 toxicity study in laboratory animals, and applies to both the less-toxic trivalent chromium and the more-toxic hexavalent chromium forms of this compound. This limit does not protect against the risk of cancer from ingestion of hexavalent chromium.

ppb = parts per billion

All test results

Date	Result
2014-02-20	ND
2014-04-29	ND
2014-07-21	ND
2014-07-21	ND
2014-07-22	ND
2014-07-22	ND
2014-08-13	ND
2014-08-13	0.810 ppb
2014-08-14	ND
2014-08-14	ND
2014-08-14	ND
2014-08-14	0.280 ppb
2014-09-02	0.990 ppb
2014-09-02	0.460 ppb
2014-11-19	ND
2014-12-16	1.000 ppb
2014-12-16	0.330 ppb
2015-02-11	0.680 ppb
2015-02-11	0.260 ppb
2015-02-11	0.570 ppb
2015-02-11	ND
2015-03-24	ND
2015-05-19	0.340 ppb
2015-05-19	1.000 ppb
2015-08-18	0.250 ppb
2015-08-18	0.350 ppb
2015-08-18	ND
2015-08-18	0.210 ppb
2016-05-23	ND
2016-11-14	ND
2017-02-21	ND
2017-02-21	ND
2017-03-22	ND
2017-04-18	ND
2017-05-16	ND
2017-07-17	ND
2017-10-18	ND
2018-03-19	ND
2018-05-21	ND
2018-08-30	ND
2018-09-13	ND
2018-11-16	1.000 ppb
2018-12-12	3.00 ppb
2018-12-12	ND
2019-02-07	2.00 ppb
2019-04-17	ND
2019-09-16	2.00 ppb
2019-09-16	2.00 ppb
2019-11-05	2.00 ppb
2019-11-25	1.000 ppb