Drinking Water Regulations and Public Health Protection
Drinking Water Regulations and Public Health Protection
This domain tests the federal Safe Drinking Water Act as implemented by the New York State Department of Health under 10 NYCRR Subpart 5-1. Expect questions on MCLs, treatment techniques, monitoring, public notification, and the Consumer Confidence Report (CCR).
Core rules and concepts
- MCLs include nitrate 10 mg/L as nitrogen, nitrite 1 mg/L, arsenic 0.010 mg/L, and total coliform rules under the RTCR. Lead and copper use action levels, not MCLs: lead 0.015 mg/L and copper 1.3 mg/L at the 90th percentile.
- Stage 2 DBPR compliance uses a locational running annual average (LRAA) for TTHM (80 µg/L) and HAA5 (60 µg/L).
- Public notification tiers: Tier 1 for acute risks (24 hours), Tier 2 for other violations (30 days), Tier 3 for monitoring/reporting issues (annual).
- The CCR must be delivered by July 1 each year and summarize source water, detected contaminants, and compliance.
Worked example
A system collects 20 lead samples. Results are ordered lowest to highest. The 90th percentile is the 18th value in that ordered list. If the 18th value is 0.018 mg/L, it exceeds the 0.015 mg/L action level, even if most individual samples are below 0.015. The system must conduct public education, corrosion-control treatment evaluation, and increased monitoring-not simply resample until the number falls.
Traps
Treating an action level as an MCL is the most common error. Another is using a single sample or a simple average for lead and copper instead of the 90th percentile. For TTHM/HAA5, a single high sample does not establish violation; the LRAA does. Tier 1 notification is not a 30-day task.