1 systems serving 3,294,305 people
  This drinking water quality report shows results of tests conducted by water utilities in Colorado, provided to the Environmental Working Group (EWG) by the State water agency. It is part of EWG's national database that includes 47,667 drinking water utilities and 20 million test results from 45 states and the District of Columbia. Water utilities nationwide detected more than 300 pollutants between 2004 and 2009. More than half of these chemicals are unregulated, legal in any amount. Despite this widespread contamination, the federal government invests few resources in protecting rivers, reservoirs, and groundwater from pollution in the first place. The information below summarizes drinking water quality for this state.

The state water agency did not respond to requests for water quality test data. Contact your water utility for the latest water quality report
  Violation Summary for Colorado

Data from the U.S. Environmental Protection Agency includes the following violations of federal standards in Colorado since 2004.

Violation Type Number of Violations
Failure to monitor regularly 11,060
Monitoring and Reporting Disinfection Byproduct Rule 1,034
Failure to monitor, Routine Major (Coliform bacteria) 678
Over maximum contaminant level, Average 420
Follow-up and Routine Tap Sampling 376
Failure to report information to the public or state agency in the Consumer Confidence Report 373
Failure to monitor, Routine Minor (Coliform bacteria) 131
Treatment Technique (Surface Water Treatment Rule) 124
Maximum contaminant level, Monthly (Coliform bacteria) 112
Failure to monitor or report, Routine/Repeat (Indicators of microbial or virus contamination) 110
Failure to monitor: Check/Repeat/Confirmation sampling 94
Initial Tap Sampling for Lead and Copper 62
Filter Turbidity Reporting 59
Excess Turbidity at 0.3 NTU 55
Failure to monitor, Repeat Major (Coliform bacteria) 44
Treatment Technique Precursor Removal 31
Failure to monitor, Repeat Minor (Coliform bacteria) 18
Excess Turbidity at 1 NTU 17
Over maximum contaminant level, Single Sample 16
Initial Water Quality Parameter Monitoring and Reporting 9
Public Notification Violation for National Primary Drinking Water Regulations 8
Optimal Corrosion Control Treatment Study Recommendation 8
Initial, Follow-up, or Routine Source Water Treatment Monitoring and Reporting 7
Maximum contaminant level, Acute (Coliform bacteria) 6
Public Education 5
Failure to Filter (Surface Water Treatment Rule) 5
Other Non-National Primary Drinking Water Regulations Potential Health Risks 1
Inadequate reporting of information to the public 1

Sources : EWG (Environmental Working Group)