2018 CEQ Annual Report

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Rivers + Reservoirs

Rivers, Streams & Rain                Bald Eagles                 Drinking Water

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Public Drinking Water

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The presence of chloride is the largest contaminant detected in public water systems in 2018


Every public water system submits monthly quality reports to the Department of Public Health (DPH). This indicator shows the percentage of monthly reports that demonstrate full compliance, after weighting the reports to account for the number of people served by each system. Though long-term problems occur, they are rare in large systems. This indicator would show greater fluctuations if the larger utilities failed to deliver good water. 

The list of systems with violations includes several chronic or repeat offenders that serve relatively small numbers -- usually dozens, sometimes hundreds -- of customers.

By far, the most common problem during 2018 in systems with violations was excessive levels of chloride,** which is typical of most years. Other violations included excessive byproducts of disinfection and other chemicals. One system showed an unacceptable level of uranium, a naturally occurring contaminant. When a system has a violation, it can be required to provide additional monitoring and corrective action. The public must be notified of systems that are in violation. A 2019 report by the Auditors of Public Accounts for calendar year 2017 recommended that DPH strengthen oversight and enforcement. Data show a reliance on informal enforcement and an increase in 2017 and 2018 on informal enforcement over formal enforcement.  

The modest decline of 2014 reflects the discovery of water-treatment byproducts following new rules that became effective for small and medium-sized drinking water systems. New requirements for measuring and reporting total trihalomethanes (TTHM), four chemicals that are byproducts of using chlorine for disinfection during the treatment process were implemented in late 2013. The changes resulted in more violations being reported in subsequent years. Not all of the downward trend depicted in the chart above necessarily reflects changes in the quality of the drinking water; some of it could reflect post-2013 reporting of TTHM that had been present in the water in prior years when such a presence was not required to be reported as a violation. TTHMs are regulated because they have been determined to pose risks to human health.)

A Note About Lead

Lead contamination in Flint, Michigan gained national attention in 2015 and 2016. Usually, as in Michigan, large-scale lead contamination is a result of mismanagement. The lead normally is not found in the water source (such as reservoir, river or well). The problem occurs when corrosive water enters homes and schools through pipes that contain lead. The Connecticut DPH oversees the monitoring for lead by public water supplies, and also requires public water to be tested for corrosive properties (including pH). Lead contamination is an uncommon problem here, generally affecting only very small systems. Lead is not included in the chart above. 

Data are not completely comparable across all states, but federal reports suggest that Connecticut is among the very best in delivery of safe water from public supplies. This excellent record can be attributed to many factors, including Connecticut's policy of not permitting direct discharges of pollution into streams that flow to drinking water reservoirs.

About 80 percent of people in Connecticut are supplied by the public water systems included in the chart above. The remainder of the population relies on private wells, which are not monitored by any government agency and are not counted in this indicator. An unknown but significant number of private wells are contaminated by pollution or naturally-occurring toxins such as arsenic and uranium. Residents who drink from private wells are not required to test their water routinely, so the number of people who drink contaminated water from private wells cannot be measured.

*The term "detailed view" on the chart refers to the fact that the vertical axis has been shortened, beginning at 90 percent rather than the customary zero. This allows the reader to see year-to-year differences, which would be nearly imperceptible if the chart ran from zero to 100 percent.

**The standard for chloride is set by state regulation. Violations are reported to the Department of Public Health but are not included in the Department's annual compliance reports that are submitted to the federal government.