1.1 MoDNR Regulatory Framework & Operator Classification

The protection of Missouri's water resources and public health relies on a strict legal and administrative framework. The Missouri Department of Natural Resources (MoDNR) serves as the primary environmental regulatory agency in the state. Operating through its Division of Environmental Quality, MoDNR oversees the permitting, compliance monitoring, and operator licensing programs across thousands of public water supply systems and wastewater treatment works.

Two citizen commissions establish environmental policy, adopt formal rules, and adjudicate appeals in Missouri:

• The Missouri Safe Drinking Water Commission, authorized under Revised Statutes of Missouri (RSMo Chapter 640), establishes drinking water standards and rules codified in Title 10 of the Missouri Code of State Regulations, Division 60 (10 CSR 60).
• The Missouri Clean Water Commission, authorized under RSMo Chapter 644 (the Missouri Clean Water Law), establishes water quality standards, wastewater discharge limits, and operating regulations codified in Title 10, Division 20 (10 CSR 20).

Within this administrative code, 10 CSR 60-14 governs the certification and classification of drinking water operators, while 10 CSR 20-9 establishes the certification and classification requirements for wastewater operators.

+-----------------------------------------------------------------------------------------+
|                               MISSOURI REGULATORY GOVERNANCE                            |
+-----------------------------------------------------------------------------------------+
|  RSMo Chapter 640 (Drinking Water Law)        |  RSMo Chapter 644 (Clean Water Law)     |
|  -> Safe Drinking Water Commission            |  -> Clean Water Commission              |
|  -> 10 CSR 60-14 (Drinking Water Operators)   |  -> 10 CSR 20-9 (Wastewater Operators)  |
+-----------------------------------------------+-----------------------------------------+
|                                 MoDNR Water Protection Program                          |
|                     (Permitting, Compliance, Inspections & Certification)               |
+-----------------------------------------------------------------------------------------+

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Drinking Water Facility Classification (10 CSR 60-14.010, Table 1)

Under 10 CSR 60-14, a drinking water treatment facility is classified by its source water and the treatment processes it operates — not by the population it serves. The rule works as a checklist: you find every row in Table 1 that applies to the plant, and the highest level applicable to the system is the classification of the system. The operator certificate required for the chief operator matches that classification, with Level A highest and Level D lowest.

The single numeric threshold in the treatment table is a capacity figure, and it applies only to surface water:

Two rules catch candidates out repeatedly:

• Ion exchange for softening is included in all treatment and distribution certifications. It never sets the level by itself; the level is determined by the plant's other treatment or distribution characteristics.
• A system using only chlorination or ion exchange softening on ground water (not GWUDI) or purchased water, or using no treatment at all, is classified from the distribution table (Table 2) instead of the treatment table.

Worked example. A plant draws from a reservoir, runs coagulation, flocculation, sedimentation and dual-media filtration, and treats 6 MGD. Surface water above 1.5 MGD is a Level A row, so the plant is Level A and needs a Level A chief operator — the answer comes from the source and capacity, not from the 40,000 people it happens to serve.

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Distribution System Classification (10 CSR 60-14.010, Table 2)

Distribution systems are classified DS I through DS III, with DS III highest. Here population is a criterion, and the same "highest applicable row wins" logic applies:

Note the asymmetry the exam likes to test: gas chlorination in the distribution system pushes you to DS II, while hypochlorite only reaches DS I — the hazard of the chemical, not the disinfection itself, drives the level.

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Wastewater Facility Classification: The Point System (10 CSR 20-9.010)

Missouri classifies wastewater treatment facilities completely differently from drinking water plants. Instead of a "highest row wins" table, 10 CSR 20-9 assigns points for every item that applies and totals them. The point total sets the classification:

Selected point values operators are expected to recognise:

Worked example. A 2 MGD plant serving 18,000 P.E. discharging to an ordinary stream, with screening (3), grit removal (3), primary clarifiers (5), activated sludge (15), aerobic digestion (6), mechanical dewatering (8), chlorination (5) and BOD/DO/titration lab work (5): size 2 + 2 = 4, discharge 1, unit processes 45, lab 5 → 55 points → Level B. Adding anaerobic digestion (10) instead of aerobic (6) would push the total to 59 — still B; adding incineration (12) would carry it past 71 into Level A.

The rule also gives the department discretion: if unique treatment plant conditions distort the point total, the department may adjust the facility classification.

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Staffing Mandates: Chief Operator and Process Control Decisions

Missouri requires clear lines of operational responsibility. Every permitted drinking water system and wastewater treatment facility must designate a qualified chief operator.

• Certification rule: the chief operator must hold an active certificate of the appropriate type at a level equal to or higher than the facility's classification. A Level A surface water plant needs a Level A drinking water treatment operator as chief operator.
• Vacancy notification: under 10 CSR 60-14.010(4), the system owner shall notify the department in writing within fifteen (15) calendar days after the chief operator is replaced. This deadline is a favourite exam item — it is fifteen calendar days, not thirty, and not "the next monthly report".
• Contract operators: a water system that hires a contract operator must have a written agreement setting out the operator's responsibilities, containing at minimum the information required by 10 CSR 60-14.010(4)(F).
• Responsibilities: establishing standard operating procedures, supervising staff, reviewing and signing Monthly Operating Reports (MORs) and Discharge Monitoring Reports (DMRs), coordinating with MoDNR inspectors, and directing process optimisation.

Process control decisions and uncertified personnel

A process control decision is a judgement that directly changes water quality or effluent quality — adjusting coagulant or disinfectant dosing, changing filter backwash intervals, altering return activated sludge (RAS) or waste activated sludge (WAS) rates, or shifting hydraulic flows between unit processes. Missouri's experience rules define qualifying experience in exactly these terms: making or acting upon day-to-day process control and system integrity decisions, including the subsequent adjustment of chemical feeders.

Non-certified personnel — labourers, maintenance technicians, clerks, operators-in-training — may perform mechanical maintenance, read meters, pull samples and log data. They may not independently make process control decisions or alter chemical feed rates without the direction of a certified operator.