Lead Action Level Exceeded in One Tier
A community water system serving 9,500 people conducts lead and copper tap monitoring under the Lead and Copper Rule. The 90th-percentile lead result is 0.018 mg/L, above the 0.015 mg/L action level. The exceedance is driven by samples from older homes with lead service lines; newer homes are well below. The system currently uses pH adjustment with lime to a target of 7.8 and reports a corrosion-control treatment that has been in place for years. The state has not yet been contacted. The utility board wants to know whether it must replace all lead service lines immediately and what public notification is required. The operator has a corrosion-control study from five years ago showing the water was marginally stable.
1. Explain the regulatory obligations triggered by the 90th-percentile exceedance and what is and is not required immediately.
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An action level exceedance triggers a defined sequence, not immediate full replacement of all lead service lines. Required steps typically include:
- Public education within the required timeframe (delivered to all bill-paying customers and to at-risk populations such as homes with lead service lines, schools, and pregnant women).
- Corrosion control treatment evaluation and, if optimal treatment is not in place, installation or re-optimization, with state approval.
- Source water and treatment monitoring to confirm corrosion control is working.
- A lead service line replacement program on a schedule set by the rule and the state, which may be phased and may allow partial replacement with conditions.
- Continued tap monitoring on the required schedule. Immediate full replacement of every lead service line is not the first obligation; the first obligations are public education, corrosion control, and a state-approved replacement plan. The state must be contacted promptly because the compliance timeline and any enforcement are state-driven.
2. Given the marginal corrosion-control study, what technical steps would you recommend before committing to a replacement-only strategy?
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Re-optimize corrosion control first, because replacement alone may not solve the problem if the water remains aggressive. Steps:
- Update the corrosion-control study with current water quality (pH, alkalinity, hardness, temperature, chloride-to-sulfate ratio, and any recent source changes).
- Evaluate whether the current lime target of 7.8 is actually achieving stability; consider raising pH within the optimal range or adding orthophosphate or silicate, with state approval.
- Run pilot or bench testing and monitor lead and copper at taps before and after any treatment change.
- Verify that the distribution system is not contributing (e.g., changes in source blend or disinfectant).
- Pair treatment optimization with a prioritized service line replacement plan targeting the homes driving the exceedance. The recommendation: treat corrosion control and replacement as complementary, not either/or; the five-year-old study is stale and should be redone.
3. Outline the public education and board communication you would deliver.
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Public education (within the rule's timeframe):
- Deliver required language to all bill-paying customers and to at-risk groups, explaining what lead is, health effects (especially for pregnant women and children), sources, and steps to reduce exposure (flushing, cold water for drinking and cooking, filters certified for lead removal).
- Provide the results and the actions the utility is taking. Board communication:
- State the exceedance plainly, the regulatory timeline, and the cost/options for corrosion control versus replacement.
- Clarify that full immediate replacement is not legally required on day one; the required path is public education, treatment optimization, and a state-approved replacement schedule.
- Present a phased plan with milestones and monitoring to show progress.
- Emphasize transparency: the board should not delay public education while debating replacement strategy.