The short answer
EPA Rules and Their Control System Implications
The environmental agency sets the drinking water and wastewater rules that the states administer, and the rules reach into the control system through what they require to be measured continuously, recorded at set intervals, retained for years, and reported. The surface water treatment rules require turbidity on every filter and on the combined effluent with recording at fifteen-minute intervals and defined trigger values, and disinfection contact time computed from residual, flow, and volume; the residual rules require continuous disinfectant residual monitoring on larger systems and set maximum residual levels; the groundwater rule requires treatment demonstration and monitoring where triggered; the lead and copper rule shapes corrosion control monitoring; the coliform rule drives sampling; the discharge permit program sets effluent limits, monitoring frequencies, and the monthly report, with overflow and bypass reporting; the record rules set retention of five years for turbidity and microbiological records and ten for chemical; electronic reporting rules govern how reports are submitted; and the water infrastructure act requires the risk assessment and the emergency plan. A control system that is designed with those rules in view produces the compliance record as a byproduct of operation.
Key points
- The rules decide what is measured continuously, how often it is recorded, how long it is kept, and how it is reported.
- Filter turbidity every fifteen minutes with trigger values; contact time from residual, flow, and volume: the surface water rules are written into the SCADA.
- Continuous residual monitoring, maximum residual levels, and the byproduct sampling schedule shape disinfection control.
- The discharge permit sets the effluent monitoring, the monthly report, and the overflow reporting clock.
- Turbidity and microbiological records five years, chemical records ten: the historian retention policy starts here.
- The state primacy agency administers the rules and may add to them; it is the first call on any compliance question.
Drinking water rules
| Rule | What it requires | Control system implication |
|---|---|---|
| Surface water treatment rules, including the interim and long-term enhanced rules | Filtration and disinfection for surface water and groundwater under its influence; combined filter effluent turbidity limits with monitoring at least every four hours; individual filter turbidity monitored continuously and recorded at least every fifteen minutes; trigger values that require profiles and assessments; disinfection contact time credit; disinfection profiling and benchmarking | A turbidimeter per filter with sample flow monitoring; historian records at fifteen minutes with retention; alarms at the trigger values; the contact time calculation from residual, flow, level, temperature, and pH; reports of exceedances with times |
| Disinfectants and disinfection byproducts rules | Maximum residual disinfectant levels; byproduct limits with sampling by location and quarter; continuous residual monitoring where required; minimum residual entering distribution | Residual analyzers at the entry point and where required with alarms high and low; sampling schedules and the data for the byproduct calculations; residual records |
| Groundwater rule | Sanitary surveys; triggered source monitoring; corrective action including treatment with demonstration of virus inactivation where required; compliance monitoring of that treatment | Continuous residual monitoring at wells providing treatment credit; contact time demonstration; alarms on loss of treatment; records |
| Lead and copper rule and its revisions | Corrosion control treatment with water quality parameter monitoring; sampling; service line inventory; public notification | pH, alkalinity, and inhibitor residual monitoring at the entry and in distribution with limits; treatment control for the parameters; records |
| Revised total coliform rule | Sampling plans; assessments triggered by results | Sample point locations and records; the assessment may implicate storage and residual data |
| Consumer confidence and public notification rules | Annual reports; tiered notification with timelines by severity | The data behind the report; the notification templates in the emergency plan |
| Water infrastructure act assessment and plan | Risk and resilience assessment and emergency response plan for systems above a size, every five years, including cybersecurity | The security program and the manual operation procedures; certification on the schedule |
Wastewater
| Program | What it requires | Control system implication |
|---|---|---|
| Discharge permit program under the clean water law | Effluent limits by parameter; monitoring frequencies and methods; a monthly discharge report; sampling locations | Effluent flow, and where continuous, pH, dissolved oxygen, chlorine residual and other analyzers with records; totals for the report; sample event records |
| Overflow and bypass reporting | Notice of sanitary sewer overflows and bypasses, commonly within 24 hours by phone and in writing within days, per the permit and state rules | Lift station high level and overflow detection with alarms and time-stamped records; the reporting clock starts at awareness |
| Pretreatment program | Industrial user limits and monitoring | Flow and sampling at industrial points where the utility monitors them |
| Biosolids rules | Treatment standards, monitoring, and records for land application | Process records that demonstrate the treatment: time, temperature, feed rates |
| Electronic reporting rule | Discharge reports submitted electronically through the agency system | The data assembled from the historian and the laboratory in the required format |
Records and methods
The drinking water record rule sets minimum retention: turbidity and microbiological analysis records for five years, chemical analysis records for ten, records of actions taken to correct violations for three, sanitary survey reports for ten, and variance and exemption records for five. Discharge permit records are typically kept for at least three years and longer where the permit says. Those numbers are the floor of the historian retention policy for the tags that back the records. Compliance measurements are made by approved methods: online turbidimeters and residual analyzers used for compliance are of types the agency has approved, calibrated and verified as the method requires, with the records to show it. A control system that uses an unapproved instrument or an uncalibrated one for a compliance value has a compliance problem regardless of the reading.
Electronic records and reporting
Reports are increasingly submitted electronically, and the agency rule on electronic reporting and its cross-media electronic reporting regulation govern how an electronic submission is signed and kept. For the control system the implication is that the data behind a report has to be traceable: the historian value, its quality, its time, and the calculation, with an audit trail, so that a report can be defended. Utilities that generate the monthly report from the historian through a reporting database keep the query and the source data with the report.
The state
Nearly every state has primacy: it administers the federal rules, may adopt stricter or additional ones, inspects through sanitary surveys, and receives the reports. The state rule is the operative one, and the state primacy agency is the first call on any question about what must be monitored, how, and what to do when a monitor fails. The control system design references the state requirements for the plant, and the alarm response procedures name the state contact for the events that must be reported.
Designing to the rules
- 1
List the compliance measurements
From the state rules and the permit: each parameter, the location, the method, the frequency, the recording interval, and the retention.
- 2
Specify the instruments
Approved types where the rule requires; sample systems with flow monitoring; calibration provisions; redundancy where a failure would breach the rule.
- 3
Configure the historian
Tags at the recording interval or faster, no compression on compliance tags, retention per the record rule, quality stored with the value.
- 4
Configure the alarms
Trigger values from the rules with the required durations; loss of monitor alarms; the operator response and the reporting contact in the alarm description.
- 5
Build the reports
The monthly and periodic reports from the historian and the laboratory system, with the audit trail, in the format the state and the electronic system require.
- 6
Document
The compliance monitoring plan, the instrument list annotations, and the record retention policy, cross-referenced to the rules.
Frequently asked questions
- Does the SCADA historian count as the official record?
- It can, if the data is complete at the required interval, retained for the required period, protected from alteration, and producible on request. Many states accept electronic records; some require specific formats or certifications. Ask the primacy agency, and keep the exported compliance records as a backstop.
- What happens if the historian loses fifteen minutes of turbidity data?
- It is a monitoring gap. The rule and the state say how much gap is tolerable and what replaces it; a brief gap with grab sample data may be acceptable, a long one is a violation to report. The turbidimeter local memory, where the instrument has one, may fill the gap; that is a reason to buy instruments that log.
- Which turbidity values trigger action?
- The rules define combined filter effluent limits and individual filter values with durations that trigger reporting, a filter profile, a self-assessment, or a comprehensive performance evaluation. The values and durations are in the rule and the state version of it, and the control system alarms at them; the alarm description tells the operator what the trigger requires.
- How do wastewater plants meet the reporting clock for an overflow?
- With alarms that reach a person immediately, a time-stamped record of the high level and the overflow indication, and a procedure that names who calls the state and when. The clock starts when the utility knows, and the SCADA record is when the utility knew.
Related topics
- EPA GuidanceWhat the federal environmental agency provides to water and wastewater utilities on cybersecurity and what it expects: the free assessment, the checklist aligned with federal goals, joint incident response guidance, the enforcement position, and how to use it.
- AWIA RequirementsWhat the 2018 water infrastructure act requires of community water systems: a risk and resilience assessment and an emergency response plan, certified on a schedule by size and repeated every five years, with cybersecurity named in both, and who is covered.
- FiltrationControlling gravity and pressure filters: effluent rate and level control, head loss and turbidity on every filter, the backwash triggers and sequence, filter-to-waste and ripening, the turbidity rules that filter monitoring answers to, and the operator view.
- Disinfection ControlControlling chlorine and chloramine dosing at a water plant: the CT concept and how contact time is credited, flow-paced and residual-trimmed feed, gas, hypochlorite, and on-site generation systems, the point-of-entry residual as the compliance measurement, and the interlocks that stop a feed system from over- or under-dosing.
- Long-Term StorageKeeping historian data for years: a retention policy by data class that follows the record rules, tiered storage from online to offline copies, downsampling, archive management, exports that outlive the historian, and the annual proof that old data reads.
- Turbidity MeasurementNephelometric turbidimeters for filter effluent and raw water: how 90-degree scattering is measured, the methods and the NTU, low-range versus high-range instruments, bubbles and the debubbler, formazin calibration and verification standards, and the compliance record the instrument exists to produce.
Direct contact
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