Public Water Systems 90th Percentile Lead Sampling Results

Lead and Copper Rule 90th percentile lead in drinking water sampling results.

The Lead and Copper Rule applies to all Community public water systems (COM) and Non-Transient Non-Community (NTNC) public water systems such as schools and office buildings. As of December 2018, there were approximately 763 COM and NTNC public water systems in Massachusetts. Although the Lead and Copper Rule does not establish a Maximum Contaminant Level (MCL), it does establish an Action Level (AL) which, when exceeded, requires certain actions to be taken by the Public Water System (PWS) to reduce lead concentration in the drinking water. The Action Level for lead is 0.015 milligrams per liter (mg/L) or 15 parts per billion (ppb), and is exceeded when the 90th percentile value of all sampling results collected during each monitoring period is greater than the Action Level. The number of samples that need to be collected depends on the population served. For example, a PWS that serves less than 100 people must collect 5 samples, whereas a PWS that serves over 100,000 people must collect 100 samples. All samples collected by the public water system that meet the proper site selection and sample collection procedures specified by the USEPA and the state are used to determine the 90th percentile calculation, even if the PWS collected samples from more sites than required. No more than 10% of samples collected should be over the action level. For more information on how to calculate the 90thpercentile see (pages 34-36).

When the 90th percentile lead level exceeds the Lead Action Level, the PWS is required to notify the public and perform other corrective actions.


90th Percentile Lead Sampling Results

Listed in the MS Excel (LCR - 90th Percentile Lead Sampling Results for Most Recent Sampling Round) file below are the 90th percentile values for the most recent round of sampling, including results over the lead action level.

For more information about a public water system that is listed in the MS Excel file below you should contact the public water system using the contact information listed in the MS Excel "MA Public Water Supplier contacts sorted by Town" spreadsheet below.

Additional Resources for 90th Percentile Lead Sampling Results