EPA Pretreatment Compliance: Requirements Guide [For POTWs]

An EPA audit letter arrives. You have 30 days to produce complete documentation for every permitted facility: permits, inspections, violations, enforcement actions, and proof that your program meets all seven federally-required elements. If your first thought is “where do I even start?”—your compliance program has a problem.

EPA pretreatment compliance isn’t a single box to check. It’s a system of interconnected obligations that POTWs must satisfy simultaneously. Miss one element, and the whole program is at risk. Document everything but can’t connect the pieces, and auditors will find the gaps.

The regulations themselves—40 CFR 403—run dozens of pages. State requirements add more. But the core requirements aren’t actually complicated once you understand how they connect.

This guide explains what EPA pretreatment compliance actually requires, what triggers significant noncompliance, and how to build a program that holds up under audit.

What Is EPA Pretreatment Compliance?

EPA pretreatment compliance refers to a POTW’s adherence to the National Pretreatment Program requirements under 40 CFR 403. It requires POTWs to maintain approved programs with seven federally-mandated elements: legal authority, industrial user identification, adequate resources, local limits, control mechanisms for significant industrial users, annual inspections, and an enforcement response plan.

The National Pretreatment Program exists for a specific reason: to prevent industrial pollutants from passing through POTWs untreated or interfering with treatment processes. When industries discharge heavy metals, solvents, or other pollutants into the sewer system, those substances can damage treatment equipment, disrupt biological processes, contaminate biosolids, or pass through to receiving waters.

POTWs with approved pretreatment programs act as the control point. They identify industrial users, set discharge limits, monitor compliance, and enforce violations—all under EPA oversight (or delegated state authority).

Compliance isn’t optional. POTWs with approved programs must maintain all seven required elements. Failure to do so can result in enforcement actions against the POTW itself, not just against industrial users who violate their permits.

The 7 Required Elements of an Approved Program

Under 40 CFR 403.8(f), every approved pretreatment program must include seven specific elements. These aren’t suggestions—they’re federally mandated requirements that EPA or state auditors will verify.

1. Legal Authority

Your POTW must have the legal authority to control industrial discharges. This typically comes through a sewer use ordinance that grants power to: deny or condition discharge permits, require pretreatment where necessary, inspect facilities and sample effluent, require compliance schedules, and take enforcement action against violators.

Without adequate legal authority, nothing else in your program is enforceable.

2. Industrial User Identification and Notification

You must identify all industrial users discharging to your system and classify them correctly. Significant Industrial Users (SIUs) face the most stringent requirements. The regulation defines an SIU as any user subject to categorical standards, or any user discharging 25,000+ gallons per day of process wastewater, contributing 5%+ of POTW capacity, or designated by the POTW for potential adverse impact.

Once identified, industrial users must be notified of applicable requirements—categorical standards, local limits, and reporting obligations.

3. Adequate Resources

Your program needs sufficient funding and personnel to carry out pretreatment activities. This isn’t a vague requirement. Auditors will assess whether you have staff to conduct inspections, review self-monitoring reports, track violations, and prepare annual reports.

Programs that look good on paper but lack the resources to execute will be cited for deficiencies.

4. Local Limits

Beyond federal categorical standards, POTWs must develop local limits to protect their specific treatment process, receiving waters, and biosolids quality. Local limits address pollutants that categorical standards don’t cover and account for your POTW’s unique characteristics.

Developing and updating local limits requires technical analysis—a Maximum Allowable Headworks Loading (MAHL) study—that many programs neglect until auditors ask for it.

5. Control Mechanisms for SIUs

Every Significant Industrial User must have an individual control mechanism—typically a permit—specifying discharge limits, monitoring requirements, and reporting schedules. These permits must include:

• Effluent limits (categorical standards plus local limits)
• Self-monitoring requirements with specified parameters and frequencies
• Reporting requirements (typically semi-annual for SIUs)
• Standard conditions covering facility access, spill notification, and recordkeeping

Permits without enforceable conditions aren’t control mechanisms. If your permits lack specific limits or monitoring requirements, you have a compliance gap.

6. Annual Inspections and Sampling

Federal regulations require POTWs to inspect and sample each SIU at least once per year. Many programs conduct more frequent oversight based on facility risk or compliance history.

Inspections must verify that facilities are operating pretreatment equipment correctly, meeting permit conditions, and maintaining required records. Sampling provides independent verification of self-monitoring data.

This isn’t discretionary. An SIU that goes uninspected for a year is a program deficiency, regardless of whether the facility is actually in compliance.

7. Enforcement Response Plan (ERP)

Your program must have a documented plan for responding to violations. The ERP defines how violations are classified by severity and what response actions are required—from notices of violation through administrative orders to civil penalties and permit revocation.

The ERP must include escalating responses and timeframes. Auditors will check whether your actual enforcement actions match your documented procedures.

Program Element	40 CFR Reference	What Auditors Check
Legal authority	403.8(f)(1)	Sewer ordinance provisions, enforcement powers
IU identification	403.8(f)(2)(i-ii)	Complete inventory, correct classifications
Resources	403.8(f)(3)	Staffing levels, budget allocation
Local limits	403.8(f)(4)	Technical basis, current MAHL study
SIU control mechanisms	403.8(f)(2)(iii)	Permit content, enforceable conditions
Inspections/sampling	403.8(f)(2)(v)	Annual coverage, documentation
Enforcement response plan	403.8(f)(5)	Documented procedures, consistent application

What Triggers Significant Noncompliance (SNC)?

Not all violations are equal. Significant Noncompliance (SNC) is a specific designation under 40 CFR 403.8(f)(2)(viii) that identifies the most serious violations—the ones that must be published in your annual report and local newspaper.

An industrial user is in SNC if any of the following apply:

Chronic violations: Exceeding the same effluent limit in 66% or more of measurements taken during a six-month period. If a facility reports monthly and exceeds its copper limit four out of six months, that’s SNC.

Technical Review Criteria (TRC) violations: Exceeding an effluent limit by more than the TRC multiplier in 33% or more of measurements during a six-month period. TRC is 1.4 times the limit for conventional pollutants (BOD, TSS, fats/oils/grease) and 1.2 times the limit for toxic pollutants and metals.

Interference or pass-through: Any discharge that causes or contributes to a POTW violation or interferes with treatment operations.

Endangerment: Any discharge that endangers human health, the environment, or POTW personnel.

Failure to report: Not submitting required reports within 30 days of the deadline.

Failure to meet compliance schedules: Missing interim or final deadlines by more than 90 days.

Any other violation the POTW determines significant: This catch-all gives POTWs discretion to designate serious violations that don’t fit the specific criteria above.

SNC matters because it’s public. POTWs must publish a list of SNC facilities in the local newspaper annually. More importantly, a pattern of SNC across your program—or failure to properly identify and report SNC—signals to auditors that your program isn’t working.

How EPA Audits Pretreatment Programs

EPA (or the delegated state agency) conducts periodic audits of approved pretreatment programs. These aren’t surprise inspections—you’ll receive advance notice—but they are comprehensive reviews of program performance.

Auditors typically examine:

Program documentation. Your sewer use ordinance, approved program description, local limits technical basis, and enforcement response plan. These documents must exist, be current, and match what you’re actually doing.

Industrial user files. Auditors will pull files for a sample of permitted facilities and review permits, inspection reports, self-monitoring data, violation notices, and enforcement records. They’re checking for completeness, consistency, and appropriate follow-through.

Compliance rates. What percentage of SIUs are in compliance? How quickly do you identify and respond to violations? Are enforcement actions escalating appropriately for repeat violators?

Annual reports. Your pretreatment annual reports should accurately summarize program activities, SNC determinations, and enforcement actions. Auditors compare what you reported to what your files show.

Staff interviews. Auditors will talk to pretreatment staff about procedures, workload, and how the program actually operates day-to-day.

Common audit findings include:

• Incomplete or outdated permits lacking required conditions
• Missed annual inspections for one or more SIUs
• Inconsistent enforcement (similar violations receiving different responses)
• SNC determinations not made or not reported correctly
• Documentation gaps that make compliance history impossible to verify

The theme across most findings: disconnected information. Permits exist but aren’t linked to inspection schedules. Violations are documented but enforcement follow-through isn’t tracked. Annual reports don’t match the underlying data because compiling it required manual reconciliation from multiple sources.

Building an Audit-Ready Compliance Program

Passing an EPA audit isn’t about last-minute preparation. It’s about operating a program where compliance documentation is a byproduct of daily operations, not a separate project.

Connect Your Program Elements

The seven required elements aren’t independent. Your industrial user inventory drives your permit workload. Permits define inspection requirements. Inspections generate compliance data. Compliance data triggers enforcement. Enforcement outcomes feed your annual report.

If these workflows don’t connect in your tracking system, they won’t connect in your documentation. You’ll spend audit prep time manually assembling information that should flow automatically.

Maintain Complete Facility Records

For every SIU, you should be able to produce—immediately—the complete compliance history: current permit, all inspection reports, self-monitoring submissions, exceedance records, violation notices, and enforcement actions. If producing this requires searching multiple systems or asking colleagues what happened before they arrived, you have a documentation problem.

Track SNC Systematically

SNC determinations require comparing six months of monitoring data against permit limits and TRC thresholds. This analysis must happen systematically—not just when preparing the annual report. If you’re identifying SNC retroactively during annual report preparation, you’ve already missed required enforcement timelines.

Document Enforcement Consistently

Your ERP defines required responses for different violation types. Auditors will check whether actual enforcement matches documented procedures. Inconsistent enforcement—treating similar violations differently—is a common finding that suggests the ERP exists on paper but isn’t operationally integrated.

Use Your Annual Report as a Program Check

The pretreatment annual report required under 40 CFR 403.12(i) summarizes your program’s performance: SIU inventory changes, inspections conducted, SNC determinations, enforcement actions taken. If preparing this report requires weeks of data compilation and reconciliation, your tracking systems aren’t serving you.

Encina Wastewater Authority faced exactly this challenge with their legacy Linko system. After implementing Nexinite’s Pretreatment Information Management System, they integrated permits, inspections, sampling data, and enforcement into a single platform—reducing manual processes by over 50% while maintaining audit-ready documentation. See the full Encina case study for implementation details.

When Manual Tracking Puts Compliance at Risk

Many pretreatment programs still run on spreadsheets, Access databases, and paper files. These tools can store information, but they can’t connect it.

The compliance risk isn’t data loss—it’s data disconnection.

When inspection findings live in one system and violation tracking lives in another, enforcement follow-through falls through the cracks. When permit limits aren’t automatically compared against incoming monitoring data, exceedances go unnoticed until someone manually checks. When annual report preparation requires pulling data from five different sources, errors and omissions become inevitable.

Spreadsheets don’t flag overdue inspections. They don’t calculate SNC automatically. They don’t connect a permit modification to updated inspection requirements. Every connection that software should handle becomes a manual task that depends on staff memory and consistent processes.

For small programs with a handful of permitted facilities, this might be manageable. For programs with dozens of SIUs, thousands of monitoring results, and escalating enforcement timelines, manual tracking becomes the compliance risk itself.

The question isn’t whether your current approach stores the required information. It’s whether that information connects in ways that support compliance—or whether you’re managing seven separate systems that happen to address the same program.

EPA pretreatment compliance comes down to maintaining all seven program elements simultaneously while documenting everything in ways auditors can verify. That’s not a paperwork exercise—it’s an operational challenge that depends on whether your systems connect.

The POTWs that pass audits smoothly aren’t doing more work. They’re working with tools that connect industrial user inventory to permits to inspections to violations to enforcement to reporting. When those workflows integrate, compliance documentation becomes automatic. When they don’t, every audit becomes a scramble.

If your current approach leaves you uncertain about audit readiness, request a demo to see how Nexinite’s PIMS connects pretreatment workflows within your Microsoft environment. Or watch our PIMS webinar to see integration in action.

Related resources:

• Pretreatment Information Management System (PIMS)
• Encina Wastewater Authority Case Study
• Wastewater Pretreatment Software: Evaluation Guide
• Pretreatment Compliance Software: Evaluation Guide