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ME Water Operator study materials
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ME Water Operator: Source water and regulatory compliance

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

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Source water and regulatory compliance

Source water and regulatory compliance covers where water comes from, what limits apply, and how results are reported. The exam expects you to read monitoring results, apply MCLs and treatment techniques, and know when public notice is required.

Core rules

  • The Safe Drinking Water Act sets MCLs, treatment techniques, monitoring, and public notification. Maine Drinking Water Program rules implement them for public water systems.
  • Key MCLs: nitrate 10 mg/L as N; nitrite 1 mg/L as N; arsenic 0.010 mg/L; TTHM 80 µg/L; HAA5 60 µg/L. Lead and copper use action levels: lead 0.015 mg/L and copper 1.3 mg/L at the 90th percentile.
  • The Revised Total Coliform Rule requires repeat samples within 24 hours of a total coliform-positive routine sample. E. coli positives trigger Tier 1 public notice.
  • The Ground Water Rule requires 4-log virus treatment or compliance monitoring for groundwater systems vulnerable to fecal contamination.
  • The Consumer Confidence Report is due by July 1 each year and covers the previous calendar year.
  • Source water assessments identify threats; they do not replace monitoring or treatment.

Worked example: nitrate

A lab reports nitrate as NO3 at 35 mg/L. The MCL is written as nitrogen, so convert: 35 × 0.226 = 7.9 mg/L as NO3-N. 7.9 is below the 10 mg/L MCL, so the result is not a violation. If the lab reported 50 mg/L as NO3, the converted value is 11.3 mg/L as N, which exceeds the MCL and requires Tier 1 public notice.

Traps

Reporting NO3 without converting to N; comparing a raw result to the wrong MCL; missing the 24-hour repeat window; late CCR; and treating a source water assessment as an enforceable limit.