10.4 Safe Drinking Water Act Compliance & Public Notification
Key Takeaways
- A public water system serves at least 25 people or 15 service connections for at least 60 days a year, and is classified as community, nontransient noncommunity, or transient noncommunity.
- Maximum contaminant levels are enforceable while maximum contaminant level goals are non-enforceable health targets set at zero for carcinogens.
- A treatment technique is required where measuring a contaminant is not economically or technologically feasible, as with Giardia, viruses, and lead.
- Consumer Confidence Reports must be delivered to customers of community water systems by July 1 each year.
- South Carolina holds primacy for the drinking water program through SC DES, which may adopt requirements at least as stringent as the federal rules.
10.4 Safe Drinking Water Act Compliance & Public Notification
Section 10.3 covered the Clean Water Act and NPDES on the wastewater side. This is its drinking-water counterpart. Security, Safety and Administrative Procedures is worth 12 to 14 questions on the standardized water treatment exam, and the regulatory framework is the bulk of it. Compliance also reaches into Laboratory Analysis, where monitoring schedules and reporting triggers are tested directly.
1. What Counts as a Public Water System
A public water system (PWS) provides water for human consumption through pipes or other constructed conveyances to at least 15 service connections or serves an average of at least 25 people for at least 60 days a year.
| Type | Definition | Examples | Regulated for |
|---|---|---|---|
| Community (CWS) | Serves the same people year-round | Cities, towns, subdivisions, mobile home parks | All contaminants |
| Nontransient noncommunity (NTNCWS) | Serves the same 25+ people at least 6 months per year, but not year-round residence | Schools, factories, office parks with their own supply | Most contaminants, including those with chronic health effects |
| Transient noncommunity (TNCWS) | Serves transient populations | Highway rest stops, campgrounds, restaurants with own wells | Contaminants with acute effects: microbials, nitrate, nitrite |
Only community water systems must produce a Consumer Confidence Report.
2. MCLG, MCL, and Treatment Technique
| Term | Meaning |
|---|---|
| MCLG — Maximum Contaminant Level Goal | The level at which no known or anticipated adverse health effect occurs, with a margin of safety. Non-enforceable. Set at zero for known or probable human carcinogens and for microbial contaminants |
| MCL — Maximum Contaminant Level | The enforceable standard, set as close to the MCLG as is feasible considering treatment technology and cost |
| Treatment Technique (TT) | A required process, used where it is not economically or technologically feasible to measure the contaminant at the tap. Examples: Surface Water Treatment Rule for Giardia, viruses, and Cryptosporidium; the Lead and Copper Rule corrosion control requirement |
| MRDL / MRDLG | Maximum Residual Disinfectant Level and its goal — applied to chlorine, chloramine, and chlorine dioxide |
| SMCL — Secondary MCL | Non-enforceable federal aesthetic standards for taste, odor, color, and staining: iron 0.3, manganese 0.05, TDS 500, chloride 250, sulfate 250, zinc 5, pH 6.5–8.5, color 15 units, odor TON 3 |
Key MCLs to know
| Contaminant | MCL | Note |
|---|---|---|
| Total trihalomethanes (TTHM) | 0.080 mg/L | Locational running annual average |
| Haloacetic acids (HAA5) | 0.060 mg/L | Locational running annual average |
| Bromate | 0.010 mg/L | Ozone byproduct |
| Chlorite | 1.0 mg/L | Chlorine dioxide byproduct |
| Nitrate (as N) | 10 mg/L | Acute — methemoglobinemia; Tier 1 notice |
| Nitrite (as N) | 1 mg/L | Acute |
| Fluoride | 4.0 mg/L | SMCL 2.0 mg/L |
| Arsenic | 0.010 mg/L | |
| E. coli | Presence-based MCL | Acute; Tier 1 |
| Chlorine MRDL | 4.0 mg/L as Cl₂ | Chlorine dioxide MRDL 0.8 mg/L |
3. Primacy and South Carolina
EPA sets national minimums; a state with primacy enforces the program. South Carolina holds primacy through SC DES, which:
- Adopts requirements at least as stringent as the federal rules, and may be stricter;
- Conducts sanitary surveys on a regular cycle;
- Approves plans and specifications for new construction;
- Assigns the facility Group classification that determines the required operator class (Section 1.3);
- Takes enforcement action for violations.
Remember the split established in Section 1.1: SC DES regulates the system; SCLLR licenses the operator.
4. Monitoring and Reporting
Monitoring frequency scales with population served, source type, and history. Systems earn reduced monitoring through consistent compliance and lose it after a violation.
Reporting deadlines to remember:
| Requirement | Deadline |
|---|---|
| Report monitoring results to the state | Within 10 days after the end of the monitoring period |
| Report a violation to the state | Within 48 hours |
| Report an acute violation | As soon as practical, no later than 24 hours |
| Consumer Confidence Report delivery | July 1 each year, covering the prior calendar year |
5. Public Notification Tiers
This table is examined constantly and was introduced in Section 6.6. Learn it cold:
| Tier | Deadline | Delivery method | Triggers |
|---|---|---|---|
| Tier 1 | 24 hours | Broadcast media, hand delivery, posting — methods reaching everyone fast | E. coli MCL violation, nitrate/nitrite MCL, waterborne disease outbreak, failure of primary disinfection, chlorine dioxide MRDL exceedance in distribution, turbidity exceedance where the state determines a Tier 1 notice is needed |
| Tier 2 | 30 days | Mail or direct delivery, plus posting for noncommunity systems | Most other MCL and treatment technique violations, monitoring violations the state elevates |
| Tier 3 | 1 year | May be included in the CCR | Monitoring and reporting violations, operation under a variance or exemption |
Every public notice must contain ten required elements, including a description of the violation, when it occurred, the potential health effects using mandatory standard language, the population at risk, what the system is doing and when it expects resolution, what consumers should do, and contact information.
6. Consumer Confidence Report
Every community water system must deliver a CCR to its customers by July 1 each year covering the previous calendar year. Required contents include:
- Source of the water and a summary of the source water assessment
- Definitions of MCL, MCLG, treatment technique, and other terms used
- A table of detected contaminants with the MCL, MCLG, level detected, range, and likely source
- Information on any violations and their health effects
- Required educational statements on lead, Cryptosporidium where detected, nitrate, arsenic, and radon where applicable
- Language advising immunocompromised individuals to seek advice from health providers
- Contact information and notice of opportunities for public participation
7. Variances and Exemptions
| Variance | Exemption | |
|---|---|---|
| Basis | The system's raw water quality prevents compliance despite installing best available technology | The system cannot comply for compelling reasons, including cost, but is on a path to compliance |
| Requires | Installation of BAT and a compliance schedule | A compliance schedule with milestones |
| Not available for | Microbial contaminants under the SWTR or the coliform rules | Same |
| Retention of records | 5 years after expiration | Same |
Neither is available where public health would be unreasonably risked, and operation under either is a Tier 3 public notification trigger.
A community water system detects nitrate at 12 mg/L as nitrogen. What notification is required?
Why does the Lead and Copper Rule use a treatment technique rather than a maximum contaminant level?
Which type of public water system is NOT required to issue a Consumer Confidence Report?
What is the difference between an MCLG and an MCL?