Lead Action Level Exceedance in a Mid-Size System
A community water system with 3,400 connections and 280 known lead service lines has no corrosion control treatment. Finished water pH is 7.1 and alkalinity is 35 mg/L as CaCO3. The latest six-month Lead and Copper Rule sampling round used 62 sites, including 38 lead-service-line homes. The 90th-percentile lead result is 0.019 mg/L and copper is 1.0 mg/L. One sample was collected after only one hour of stagnation, and two samples were taken from kitchen faucets with aerators that had been removed and rinsed the day before. The system has never exceeded the lead action level before. The superintendent proposes immediately replacing all 280 lead service lines within 12 months and doing no public education until the next round confirms the result.
1. Is this a lead action level exceedance? How should the sampling data be evaluated?
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The 90th-percentile lead result of 0.019 mg/L exceeds the lead action level of 0.015 mg/L, so this is an action-level exceedance, not a maximum contaminant level violation. But the sampling round must be validated first. LCR samples require at least six hours of stagnation; a one-hour sample does not meet the protocol and should be invalidated and replaced. The aerator issue should be checked against the approved sampling instructions; if the protocol was not followed, the site may also be questionable. If enough valid sites remain and the 90th percentile is still above 0.015 mg/L, the system has an exceedance. The system should not wait for the next round to act, but it should correct the sampling pool and resample invalid sites.
2. What response timeline and actions does a lead action level exceedance require?
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Required response: public education within 60 days of the exceedance, delivered to all customers and especially to lead-service-line homes, with language about lead health effects, sources, and steps to reduce exposure. The system must also continue lead and copper monitoring and submit a corrosion control treatment recommendation within six months. MDE will designate optimal CCT; the system must install it and then conduct follow-up monitoring. Source water monitoring may be required. Lead service line replacement is not automatically due immediately for a first exceedance unless the system continues to exceed after installing CCT. The system should also update its lead service line inventory and sampling pool.
3. Evaluate the superintendent's proposal to replace all lead service lines within 12 months and delay public education.
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The superintendent's plan is well intentioned but not compliant. Replacing all 280 lead service lines within 12 months without public education violates the 60-day education requirement and skips the corrosion control evaluation. Replacing lines is expensive and may not be necessary if optimized CCT lowers the 90th percentile. The correct sequence is: invalidate the bad sample, complete public education, recommend and install CCT (likely pH adjustment and orthophosphate, given pH 7.1 and alkalinity 35 mg/L), then monitor. If the action level is still exceeded after CCT, lead service line replacement begins, with customer notification and schedules. The system can proactively replace lines, but it still must meet the regulatory steps and coordinate with MDE.