A routine total coliform sample comes back positive at a system that pumps from wells. For Drinking Water Operator Certification study, the practical question is what the federal Ground Water Rule (40 CFR Part 141, Subpart S) asks the system to do next. This explainer reads 141.400, 141.402(a), (c), (d) and (g), and 141.403(a), as they stand in the eCFR. It does not describe a rule change. In these sections "State" means, under 141.2, "the agency of the State or Tribal government which has jurisdiction over public water systems" (or the EPA Regional Administrator where the State or Tribe does not have primary enforcement responsibility). It makes several of the decisions below, so check its rules too.
Which systems does the Ground Water Rule cover?
141.400(b) says Subpart S "applies to all public water systems that use ground water except that it does not apply to public water systems that combine all of their ground water with surface water or with ground water under the direct influence of surface water prior to treatment under subpart H." It defines "ground water system" as any public water system meeting that statement, "including consecutive systems receiving finished ground water."
When is triggered source water monitoring required?
Under 141.402(a)(1), two conditions must both exist. First, the system "does not provide at least 4-log treatment of viruses (using inactivation, removal, or a State-approved combination of 4-log virus inactivation and removal) before or at the first customer for each ground water source." Second, since April 1, 2016, the system "is notified that a sample collected under §§ 141.854 through 141.857 is total coliform-positive and the sample is not invalidated under § 141.853(c)." (Those are the Revised Total Coliform Rule sections; the rule keeps the older 141.21 wording for samples up to March 31, 2016.)
141.402(a)(5) lists two exceptions: the State "determines, and documents in writing," that the positive sample "is caused by a distribution system deficiency," or the sample was collected at a location that "meets State criteria for distribution system conditions that will cause total coliform-positive samples."
How fast, and from where?
141.402(a)(2): the system "must collect, within 24 hours of notification of the total coliform-positive sample, at least one ground water source sample from each ground water source in use at the time the total coliform-positive sample was collected."
- The State "may extend the 24-hour time limit on a case-by-case basis if the system cannot collect the ground water source water sample within 24 hours due to circumstances beyond its control" (a)(2)(i).
- If approved by the State, a system with more than one ground water source may sample "a representative ground water source or sources" (a)(2)(ii).
- A system serving 1,000 or fewer people may use one repeat sample from the source for both the repeat monitoring and this source sample only if the State approves E. coli as the fecal indicator and approves the single-sample use (a)(2)(iv); if that sample is E. coli-positive, the system must collect the five additional samples under (a)(3).
What is the sample tested for?
141.402(c) requires "a standard sample volume of at least 100 mL for fecal indicator analysis" and analysis "for the presence of E. coli, enterococci, or coliphage" using a listed or approved alternative method.
What if the source sample is fecal indicator-positive?
Unless the State invalidates the result, public notice follows, then either five more samples or, if the State directs, corrective action; corrective action is also required if one of those five samples is positive. Under 141.402(d), the State may invalidate it only if the system provides "written notice from the laboratory that improper sample analysis occurred" or the State "determines and documents in writing that there is substantial evidence that a fecal indicator-positive ground water source sample is not related to source water quality"; the system must then collect another source sample within 24 hours of being notified of the State's decision (the State may extend this case by case) and have it analyzed for the same fecal indicator.
- Public notice. 141.402(g): the system, "including consecutive systems served by the ground water source, must conduct public notification under § 141.202."
- Five more samples, or corrective action. 141.402(a)(3): "If the State does not require corrective action under § 141.403(a)(2)" for the positive sample, "the system must collect five additional source water samples from the same source within 24 hours of being notified of the fecal indicator-positive sample."
- Corrective action if a follow-up sample is positive, or if the State directs. 141.403(a)(1) applies the treatment technique requirements "when a ground water source sample collected under § 141.402(a)(3) is fecal indicator-positive" (one of the five additional samples), and 141.403(a)(2) applies them to the first source sample "If directed by the State."
What does corrective action involve?
141.403(a)(4): unless the State directs a specific corrective action, the system "must consult with the State regarding the appropriate corrective action within 30 days" of receiving written notice from a laboratory that one of the five additional samples (141.402(a)(3)) was fecal indicator-positive, or direction from the State that the first positive sample requires corrective action. Under 141.403(a)(5), within 120 days of the same notice or direction ("or earlier if directed by the State"), the system must have completed corrective action or be in compliance with a State-approved corrective action plan and schedule. 141.403(a)(6): the system "must implement one or more of the following corrective action alternatives": "Correct all significant deficiencies"; "Provide an alternate source of water"; "Eliminate the source of contamination"; or "Provide treatment that reliably achieves at least 4-log treatment of viruses (using inactivation, removal, or a State-approved combination of 4-log virus inactivation and removal) before or at the first customer for the ground water source."
What about consecutive and wholesale systems?
141.402(a)(4) adds steps with 24-hour limits: a consecutive ground water system with a total coliform-positive sample "must notify the wholesale system(s) within 24 hours," and a wholesale system that gets such a notice must, within 24 hours, sample its ground water sources and, if a sample is fecal indicator-positive, "notify all consecutive systems served by that ground water source" within 24 hours of being notified of the result, and must also collect the five additional samples under (a)(3). The wholesale system's source sample is analyzed for a fecal indicator under 141.402(c).
Where to practice
The Revised Total Coliform Rule side (repeat samples and assessments) is in our total coliform study guide, and public notice tiers are in the public notification study guide. goraedu does not certify water operators, and our questions are not a state operator certification exam.