The current Maximum Contaminant Level (MCL) for arsenic was lowered from 0.050 mg/l to 0.010 mg/l. All Community and Non-Transient Non-Community (NTNC) Public Water Systems (PWS) must comply with the new lower arsenic standard of 0.010 mg/l.

If results of routine Arsenic samples exceed the Arsenic MCL, then the monitoring frequency will be increased to quarterly. Compliance with the Arsenic MCL will be based on a running annual average (RAA) of quarterly results.