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MD Water Operator: Source Water and Water Quality Monitoring

MD Water Operator · Work through your exam, one topic at a time.

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Source Water and Water Quality Monitoring

What this domain tests

This domain tests source-water protection and the monitoring program that proves compliance: sample collection, holding times, monitoring schedules, and contaminant limits. Maryland source waters include large surface supplies such as the Potomac and Patapsco, reservoirs, and groundwater-especially on the Eastern Shore-so nitrate, arsenic, and surface-water turbidity all appear in the exam.

Core rules and concepts

  • Source protection: Maryland's Source Water Assessment Program identifies susceptibility; wellhead protection and watershed controls reduce treatment burden. A susceptibility rating is not a violation, but it should shape monitoring and emergency planning.
  • Bacteriological monitoring: the Revised Total Coliform Rule uses routine and repeat samples. E. coli-positive samples trigger assessment and corrective action; they are not just a routine repeat.
  • Chemical monitoring: know the difference between an MCL (contaminant concentration) and an MRDL (disinfectant residual). Stage 2 DBPR limits are TTHM 80 µg/L and HAA5 60 µg/L as locational running annual averages.
  • Lead and copper: action levels are 0.015 mg/L for lead and 1.3 mg/L for copper at the 90th percentile; corrosion control and public education follow.
  • Sample integrity: use approved containers, preserve and hold samples correctly, and select representative taps. A bad sample is worse than no sample because it creates false compliance.

Worked example

Four quarterly TTHM results at one site are 42, 55, 68, and 55 µg/L. The running annual average is (42 + 55 + 68 + 55) ÷ 4 = 55 µg/L, below the 80 µg/L MCL. If the next quarter jumps to 120 µg/L, the new RAA is (55 + 68 + 55 + 120) ÷ 4 = 74.5 µg/L-still below 80, but one more high quarter could exceed it. Compliance is based on the locational running annual average, not a single sample.

Traps that cost marks

Missing holding times; sampling the wrong tap; treating a source-water susceptibility rating as an MCL violation; mixing up MCL and MRDL; and failing to follow repeat-sample rules after a coliform-positive result.