Table 1.1 IOC Monitoring Requirements Monitoring type System type Source Sampling frequency Notes Initial Routine Sampling All CWSs & NTNCWs GW Once during initial 3 year compliance period. SW Annually during the initial 3 year compliance period. Reduced Sampling All CWSs & NTNCWs GW Same as initial. SW Repeat Sampling All CWSs & NTNCWs GW Once during subsequent 3 year compliance period. SW Annually during each subsequent 3 year compliance period. Increased Sampling All CWSs & NTNCWs GW Minimum of 2 quarters beginning next quarter to determine R&C <MCL. SW Minimum of 4 quarters beginning next quarter to determine R&C <MCL. Waivers All CWSs & NTNCWs Any SW systems must have monitored annually for 3 consecutive years and GW systems must have conducted 3 consecutive compliance periods without exceeding the MCL. Max waiver period is 9 years. One sample must be collected during the waiver period. Waivers must be renewed every 9 years. Waivers must be issued in writing. Code of Federal Regulation (§141.23(a)(1-3)); (§141.23(c)(1-4)) & (§141.23(c)(8))
Table 1.3 Nitrite Monitoring Requirements Monitoring type System type Source Sampling frequency Notes Initial Routine Sampling All Any All PWSs must take one sample in the first 3 year compliance period. Reduced Sampling All Any After the initial sample, systems where result is < ½ the MCL shall monitor once per nine year. Increased Sampling > ½ MCL All Any Must collect 4 consecutive quarterly samples following any one sample that is > ½ MCL State may allow a system to reduce to annual sampling after determining the system is R&C below the MCL. Increased Sampling >MCL All Any Compliance with the MCL is determined by averaging results of initial and confirmation samples. Confirmation sample must be collected within 24 hours of the systems receipt of the analytical results of first sample. Waivers All Any Waived for any systems that chlorinate. Waivers must be issued in writing. Code of Federal Regulation (§141.23(e)(1-3)); (§141.23(i)(3)) & (§141.23(f)(2))
Table 3.1 SOC Monitoring Requirements Monitoring type System type Source Pop. Sampling frequency Notes Initial Routine Sampling All CWSs & NTNCWs Any Any Four consecutive quarterly samples during initial compliance period. Sampling required unless waiver is granted. Reduced monitoring All CWSs & NTNCWs Any <3,300 May be reduced to 1 sample during each consecutive compliance period. May be reduced ONLY if system had no detects in the initial of routine sampling. >3,300 May be reduced to two quarterly samples in 1 year during each consecutive compliance period. Increased monitoring (If exceed detection limit or MCL) All CWSs & NTNCWs Any Any Must collect 1 sample per quarter until state determines sampling results are reliably and consistently (R&C) below MCL. Systems must take at least 4 quarterly samples. Reduced Monitoring (once state determines system is R&C below MCL) All CWSs & NTNCWs Any Any State may reduce sampling frequency to 1 sample annually, taken during the same quarter which previously yielded the highest analytical result. May be reduced ONLY if the state determines that sampling results fall R&C below the MCL. Waivers All CWSs & NTNCWs Any Any Systems granted waivers are not required to monitor. System may be granted waiver if contaminant is not detected in 3 consecutive annual samples. Systems also eligible for use waiver. Waivers must be renewed every 3 years. Waivers must be issued in writing. Code of Federal Regulation (§141.24(h)