What Can Utilities Expect from New Lead Fifth-Liter Sampling Based on Historic First-Draw Data?

Area of Science:

• Environmental Science
• Water Quality
• Public Health

Background:

• The US EPA revised the Lead and Copper Rule, a significant change after 30 years.
• A key change is the requirement for a fifth-liter (L5) sample instead of a first-liter (L1) sample for compliance monitoring.
• This impacts homes with lead service lines (LSLs) and water lead level (WLL) limit compliance.

Purpose of the Study:

• To evaluate if L5 WLLs better represent water in contact with LSLs.
• To explore the regulatory impacts of incorporating L5 samples into compliance monitoring.
• To assess the effectiveness of the new sampling method in identifying issues.

Main Methods:

• Analysis of sequential sampling data from three large water systems.
• Evaluation of compliance data from Michigan utilities using L1 and L5 samples for 90th percentile calculations.
• Retrospective analysis of historic L1 data to identify systems likely to exceed action levels with L5 sampling.

Main Results:

• Sequential sampling showed no single sample volume universally captures water in LSLs.
• L5 samples are more likely to originate from LSLs than L1 samples.
• Michigan data indicated L5 sampling could lead to higher 90th percentile WLLs and identify utilities needing better corrosion control.

Conclusions:

• The L5 sample, while not always perfect, is a better indicator of water in contact with LSLs than L1.
• L5 sampling is likely to increase the number of systems exceeding 90th percentile WLLs.
• A significant portion of systems likely to exceed action levels with L5 sampling could be identified using historical L1 data.