Total Number of Violations
Data extracted from the US EPA’s ECHO database, which stores all drinking water violations for all systems in the United States. Only Community Water Systems and Maximum Contaminant Level violations are considered in this study. A Community Water System is an EPA-defined classification for water systems which serve the same population year-round. A maximum contaminant level violation indicates that a system had unacceptably high levels of a contaminant in the drinking water distribution system. The 2015 data represent violations which occurred in the EPA’s fiscal year 2015, ranging from October 1, 2014 to September 30, 2015. The 2016 data represents violations which occurred from October 1, 2015 to June 30, 2016 – so 9 months.
Population Affected
Population affected is determined using population data in the ECHO database. In the database, each water utility records a “population served” metric, which identifies the number of people who access the utility for drinking water. If a system has incurred a maximum contaminant level violation for one of the five contaminants considered in this study, it’s population is added to a running total which defines the number of people affected by violations. This total is then divided against the total number of people served by water systems in the state, which is also determined from ECHO data. The resulting ratio is multiplied by 100 to produce a percentage.
Average Duration
The duration of a violation is determined in two ways. The first method for determining duration is applied when a violation has a known resolved date. In these cases, the duration is the length of time between the violation being incurred and the violation being resolved. The date a violation is incurred is defined by the last day of the violation’s compliance period. In some cases, violations are resolved within their compliance period; when this occurs, violations are classified as having a duration of 0 days. In some cases, compliance period data cannot be determined; when this occurs, the duration cannot be defined and these violations are excluded from the average calculations. The second method for determining duration is applied when a violation has an unknown resolved date. In these cases, the duration is the length of time between the violation being incurred and the final date of the fiscal year. In the 2015 data, this is September 30, 2015. In the 2016 data, this is June 30, 2016. In some cases, the violation is incurred on the final day of the year; when this occurs, violations are classified as having a duration of 0 days. In other cases, the compliance period end date extends beyond the final day of the year; when this occurs, the duration cannot be defined and these violations are excluded from the average calculations. The average duration in each state is calculated as the total number of days with unresolved violations divided by the number of applicable violations. An “n.a” entry for average duration indicates that a state had one violation and the compliance period end date of this violation extended beyond the final day of the year.
