Environmental laws provide a pathway to protection when pollutants exceed established safe limits, but they don't provide a way to predict when a community may be at risk of being served unhealthy water before it happens. In our effort to ensure Arizonans receive healthy drinking water, it is critical we are on the leading edge of environmental protection and implement innovative approaches to help public water systems (PWSs) proactively prevent exceedances. 

Small water systems, in particular, may  lack the technical, managerial and financial resources to address an unexpected exceedance or to implement operational changes to treatment necessary to address water quality changes in their source water.

To assist in filling this gap, ADEQ developed a model that predicts when a water system may exceed a maximum contaminant limit (MCL). Working cooperatively with PWSs, ADEQ has been piloting this first-of-its-kind predictive model to help identify and provide assistance to systems likely to exceed the arsenic MCL.

How does it work?

This proactive program features several key elements that are helping PWS be better prepared financially, react faster and create smarter, long-term solutions for healthy drinking water.

Forecasting Model

ADEQ developed a forecasting model to identify when a system is at risk of providing drinking water exceeding the arsenic federal safe drinking water standard. This model prioritizes vulnerable populations based on degree of magnitude, historic concentrations, likelihood of exceedance, and other factors.

Compliance Consultation

After a system is identified, ADEQ performs a site visit to evaluate conditions causing changes to water quality. This includes assessing demand changes, the sources and collecting interference samples for treatment evaluation (e.g., metals, inorganics, arsenic speciation, etc.). Site visits provide insight into how the water systems can avoid a future exceedance of the safe drinking water standard for arsenic.

Roadmap to Compliance

After the site visit, ADEQ works with the system to discuss feasible and sustainable options available to them to proactively address this concern and protect their consumers’ welfare.