The Power of Information

National Drinking Water Database

City of Modesto Utilities - Modesto, CA

Serves 190,106 people

Selenium (total)

Selenium is a naturally occurring element that contaminates water due to mining or petrolum refining, fly-ash from coal-burning power plants, and irrigation of arid farmland soils high in selenium.
This Drinking Water System
Test Days Exceeding Health GuidelinesDefinition of what this is
0 days
Test Days Exceeding Legal LimitsNumber of days in which the samples taken in that day exceed the Maximum Contaminant Level (Depending on the contaminant and its MCL, that may or may not trigger an MCL violation. Some MCLs are based on averages spanning several months to a year)
0 days
Test DaysNumber of days in which this chemical has reported results in the data we received from the State
114 days
Tests ConductedNumber of individual tests done for this contaminant
160 tests

Testing Summary

Health Limit
Legal Limit

Testing History

-Tested      -Detected      -Over Health Guidelines      -Over Legal Limit*
Selenium (total)Selenium is a naturally occurring element that contaminates water due to mining or petrolum refining, fly-ash from coal-burning power plants, and irrigation of arid farmland soils high in selenium.0.93 ppb
10 ppb
50 ppb
50 ppb
NOTE: Each dot in the above graph represents one month.
* Water utilities are noted as exceeding the legal limit if any test is above the maximum contaminant level (MCL). Most MCLs are based on annual averages so exceeding the MCL for one test does not necessarily indicate that the system is out of compliance.

Health Based and Legal Limits for Selenium (total)

Health Based Limits for Selenium (total)

Maximum Contaminant Limit (MCL)The enforceable standard which defines the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to health-based limits (Maximum Contaminant Level Goals, or MCLGs) as feasible using the best available analytical and treatment technologies and taking cost into consideration. Source: U.S. Environmental Protection Agency.50 ppb
Maximum Contaminant Limit Goal (MCLG)A non-enforceable health goal that is set at a level at which no known or anticipated adverse effect on the health of persons occurs and which allows an adequate margin of safety. Source: U.S. Environmental Protection Agency.50 ppb
Lifetime health-based limit, non-cancer riskConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for a lifetime of exposure. The Lifetime health-based limit (or Health Advisory, HA) is based on exposure for a a 70-kg adult consuming 2 liters of water per day. Source: U.S. Environmental Protection Agency.50 ppb
EPA Human Health Water Quality CriteriaWater quality criteria set by the US EPA provide guidance for states and tribes authorized to establish water quality standards under the Clean Water Act (CWA) to protect human health. These are non-enforceable standards based upon exposure by both drinking water and the contribution of water contamination to other consumed foods. Source: U.S. Environmental Protection Agency.170 ppb
Drinking Water Equivalent LevelA lifetime exposure concentration protective of adverse, noncarcinogenic health effects, that assumes all of the exposure to a contaminant is from drinking water. Source: U.S. Environmental Protection Agency.200 ppb

Testing Results

Testing DateAverage
Samples taken that dayNumber of Non-DetectsRange of Results
2009-03-244 ppb210 to 8 ppb
2009-03-170 ppb220 ppb
2009-03-100 ppb110 ppb
2009-03-032.85 ppb210 to 5.7 ppb
2009-02-190 ppb110 ppb
2009-02-100 ppb330 ppb
2008-12-180 ppb110 ppb
2008-11-126.5 ppb106.5 ppb
2008-08-120 ppb110 ppb
2008-06-245.8 ppb105.8 ppb
2008-06-170 ppb110 ppb
2008-06-120 ppb110 ppb
2008-06-100 ppb110 ppb
2008-06-030 ppb110 ppb
2008-05-229.4 ppb109.4 ppb
2008-05-130 ppb110 ppb
2008-05-066 ppb106 ppb
2008-04-290 ppb220 ppb
2008-04-230 ppb110 ppb
2008-04-220 ppb110 ppb
2008-04-080 ppb110 ppb
2008-03-270 ppb220 ppb
2008-03-180 ppb110 ppb
2008-03-060 ppb110 ppb
2008-02-140 ppb110 ppb
2008-01-290 ppb110 ppb
2008-01-223.55 ppb210 to 7.1 ppb
2008-01-150 ppb440 ppb
2007-12-180 ppb110 ppb
2007-11-280 ppb110 ppb
2007-11-150 ppb110 ppb
2007-10-165.1 ppb105.1 ppb
2007-07-240 ppb110 ppb
2007-06-180 ppb110 ppb
2007-05-240 ppb110 ppb
2007-05-154.6 ppb210 to 9.2 ppb
2007-04-170 ppb330 ppb
2007-04-160 ppb110 ppb
2007-04-100 ppb110 ppb
2007-04-040 ppb110 ppb
2007-04-020 ppb110 ppb
2007-03-150 ppb110 ppb
2007-03-147.1 ppb107.1 ppb
2007-03-070 ppb110 ppb
2007-02-140 ppb110 ppb
2007-02-070 ppb110 ppb
2007-02-060 ppb110 ppb
2006-12-200 ppb110 ppb
2006-12-190 ppb110 ppb
2006-12-070 ppb110 ppb
2006-11-210 ppb110 ppb
2006-11-150 ppb220 ppb
2006-07-250 ppb110 ppb
2006-07-180 ppb110 ppb
2006-06-280 ppb110 ppb
2006-06-210 ppb110 ppb
2006-05-170 ppb110 ppb
2006-05-038 ppb108 ppb
2006-04-048.7 ppb108.7 ppb
2006-03-283.45 ppb210 to 6.9 ppb
2006-03-220 ppb110 ppb
2006-03-080 ppb110 ppb
2006-02-280 ppb110 ppb
2006-02-210 ppb220 ppb
2006-02-150 ppb220 ppb
2006-02-140 ppb110 ppb
2006-02-070 ppb220 ppb
2005-11-2210 ppb1010 ppb
2005-11-080 ppb220 ppb
2005-10-190 ppb110 ppb
2005-09-010 ppb110 ppb
2005-08-250 ppb110 ppb
2005-07-270 ppb220 ppb
2005-07-260 ppb110 ppb
2005-07-130 ppb110 ppb
2005-07-060 ppb110 ppb
2005-06-280 ppb110 ppb
2005-06-160 ppb110 ppb
2005-06-150 ppb110 ppb
2005-06-080 ppb110 ppb
2005-05-250 ppb220 ppb
2005-05-248 ppb108 ppb
2005-05-190 ppb110 ppb
2005-05-100 ppb220 ppb
2005-04-260 ppb110 ppb
2005-04-190 ppb110 ppb
2005-04-130 ppb110 ppb
2005-04-120 ppb110 ppb
2005-03-170 ppb110 ppb
2005-03-100 ppb220 ppb
2005-02-173 ppb320 to 9 ppb
2005-02-030 ppb330 ppb
2005-01-270 ppb220 ppb
2005-01-201.5 ppb430 to 6 ppb
2005-01-130 ppb220 ppb
2005-01-060 ppb330 ppb
2004-12-300 ppb110 ppb
2004-12-090 ppb110 ppb
2004-11-180 ppb110 ppb
2004-11-040 ppb330 ppb
2004-10-147 ppb107 ppb
2004-10-070 ppb110 ppb
2004-09-160 ppb110 ppb
2004-09-090 ppb110 ppb
2004-08-120 ppb330 ppb
2004-06-070 ppb110 ppb
2004-04-150 ppb220 ppb
2004-04-080 ppb440 ppb
2004-03-110 ppb220 ppb
2004-03-040 ppb110 ppb
2004-02-120 ppb110 ppb
2004-02-052 ppb320 to 6 ppb
2004-01-150 ppb110 ppb
2004-01-080 ppb110 ppb