2.5 The Federal Drinking Water Rule Framework Operators Are Tested On
Key Takeaways
- The Surface Water Treatment Rule family requires filtered surface water and GWUDI systems to achieve at least 3-log removal or inactivation of Giardia lamblia and 4-log of viruses, with Cryptosporidium addressed by the Interim Enhanced and Long Term 2 rules.
- The Revised Total Coliform Rule replaced the old MCL-based approach with a treatment technique: a total coliform positive triggers repeat sampling, and Level 1 or Level 2 assessments are required when assessment triggers are exceeded.
- An E. coli MCL violation is acute and requires Tier 1 public notice — broadcast or hand delivery as soon as practical but within 24 hours.
- The Ground Water Rule requires sanitary surveys, triggered source water monitoring after a total coliform positive, and 4-log virus treatment for systems that elect or are directed to provide it.
- Public notification is tiered: Tier 1 within 24 hours for acute risks, Tier 2 within 30 days for most MCL and treatment technique violations, and Tier 3 within one year for monitoring and reporting violations, with an annual Consumer Confidence Report due to customers of community systems by July 1.
2.5 The Federal Drinking Water Rule Framework Operators Are Tested On
North Carolina has primacy for the Safe Drinking Water Act: the Commission for Public Health adopts the federal National Primary Drinking Water Regulations into 15A NCAC 18C, and the DEQ Public Water Supply Section enforces them. The Board's Needs to Know documents list "Rules – PWS" as a scored category on every surface and well examination, so operators need the federal architecture, not just the state citation.
The Surface Water Treatment Rule family
| Rule | What it added |
|---|---|
| SWTR (1989) | Filtration and disinfection requirements for surface water and GWUDI; 3-log Giardia and 4-log virus removal/inactivation; disinfectant residual entering and maintained in the distribution system |
| Interim Enhanced SWTR (IESWTR) | Applies to systems serving ≥ 10,000; tightened filtration performance to ≤ 0.3 NTU in 95 percent of monthly combined filter effluent readings, never > 1 NTU; individual filter effluent monitoring; 2-log Cryptosporidium removal; sanitary surveys; disinfection profiling and benchmarking |
| Long Term 1 (LT1ESWTR) | Extended the IESWTR turbidity and Cryptosporidium requirements to systems serving fewer than 10,000 |
| Long Term 2 (LT2ESWTR) | Source water Cryptosporidium monitoring, bin classification, and additional treatment from the microbial toolbox; covered finished water storage and uncovered reservoir requirements |
| Filter Backwash Recycling Rule | Recycle streams must be returned prior to the point of primary coagulant addition unless the State approves an alternate location, with plant schematics and recycle records kept |
Log credit arithmetic. A conventional plant meeting the turbidity standards is credited 2.5-log Giardia, 2-log virus, and 2-log Cryptosporidium removal, leaving 0.5-log Giardia and 2-log virus inactivation to be demonstrated by disinfection CT. Free chlorine is not credited against Cryptosporidium, which is why UV and ozone dominate the LT2 toolbox.
The Revised Total Coliform Rule (RTCR)
The RTCR replaced the total coliform MCL with a treatment technique:
- Systems sample according to a written sample siting plan at the frequency set by population.
- Any total coliform positive triggers repeat samples (normally three) at, upstream of, and downstream of the original site, plus E. coli analysis of the positive sample.
- Assessment triggers — for example, more than 5.0 percent of monthly samples total coliform positive for systems collecting 40 or more samples, or two or more positives for systems collecting fewer than 40 — require a Level 1 assessment by the system.
- An E. coli MCL violation or repeated Level 1 triggers require a Level 2 assessment conducted by an approved party, and sanitary defects found in either assessment must be corrected.
The E. coli MCL is violated when, for example, a routine sample is E. coli positive and a repeat is total coliform positive, or a routine is total coliform positive and a repeat is E. coli positive. That is an acute violation requiring Tier 1 notice.
The Ground Water Rule
The Ground Water Rule protects against fecal contamination in groundwater systems through sanitary surveys, triggered source water monitoring after a distribution total coliform positive, assessment monitoring where the State directs, corrective action for significant deficiencies or fecal contamination, and compliance monitoring for systems that provide 4-log treatment of viruses by disinfection.
Lead and copper: LCR, LCRR, and LCRI
- The original Lead and Copper Rule set an action level of 0.015 mg/L for lead and 1.3 mg/L for copper at the 90th percentile of first-draw tap samples from high-risk sites.
- The Lead and Copper Rule Revisions (LCRR) added a service line inventory, a 0.010 mg/L lead trigger level, sampling in schools and child care facilities, public notification of a lead action level exceedance within 24 hours, and find-and-fix requirements.
- The Lead and Copper Rule Improvements (LCRI), published October 2024 with a compliance date of November 1, 2027, lowers the lead action level to 0.010 mg/L, eliminates the trigger level, and requires systems to replace lead and galvanized-requiring-replacement service lines, generally within 10 years. Sampling changes include collecting first-liter and fifth-liter samples at sites served by a lead service line.
Public notification tiers (40 CFR Part 141 Subpart Q)
| Tier | Timing | Examples |
|---|---|---|
| Tier 1 | Within 24 hours, by broadcast media, hand delivery, posting, or another method approved by the State | E. coli MCL violation; waterborne disease outbreak; nitrate/nitrite MCL exceedance; turbidity above 5 NTU when the State consults and determines Tier 1 is warranted; chlorine dioxide MRDL exceedance in the distribution system |
| Tier 2 | Within 30 days | Most MCL and treatment technique violations, including TTHM and HAA5 exceedances and monthly turbidity violations |
| Tier 3 | Within one year | Monitoring and reporting violations, operation under a variance or exemption, and the fluoride secondary standard notice |
Community water systems must also deliver an annual Consumer Confidence Report to customers by July 1, covering the prior calendar year's source, detected contaminants, violations, and required educational language for lead, arsenic, nitrate, and Cryptosporidium where applicable.
[!NOTE] Why the federal citation matters on a state exam. The needs-to-know references "Rules Governing Public Water Systems (Green Book)" for these topics because 18C adopts the federal requirements. When a question gives you a state rule number and a federal rule number for the same requirement, both can be correct — read the stem for which body is being asked about.
A routine distribution sample is total coliform positive, and the repeat sample is E. coli positive. What is the required public notification?
Under the Lead and Copper Rule Improvements published in October 2024, what changes for systems on the November 1, 2027 compliance date?
A conventional surface water plant meets its turbidity standards. How much Giardia inactivation must its disinfection process still demonstrate through CT?