Stormwater Inspection & Maintenance: NPDES, Checklists, and Best Practices

Stormwater inspections are an essential aspect of maintaining your property and protecting the environment. At a manufacturing site I worked with in Texas, clogged storm sewers after a storm nearly caused a shutdown. Only because routine inspections had flagged silt fence damage earlier were we able to avoid uncontrolled stormwater runoff. Experiences like this underline why consistent inspections protect both compliance and operations.

Key Takeaways

• Regular stormwater facility inspections prevent pollutants from reaching waterways, protect people and property, and support regulatory compliance.

• Under EPA’s 2021 MSGP, facilities typically conduct quarterly routine inspections, quarterly visual assessments during qualifying rain or snowmelt, and an annual comprehensive site inspection. 

• A stormwater inspection checklist should cover pre-planning, on-site observations, best management practices (BMPs), and airtight records.

• Pair inspections with timely stormwater maintenance so your stormwater management system performs as designed.

What Are Stormwater Inspections?

Stormwater inspections are structured, on-the-ground reviews of a property's stormwater management system. An inspector traces how water moves across the property, checks whether controls are installed correctly, and confirms that daily practices align with the Stormwater Pollution Prevention Plan (SWPPP). The purpose is to prevent polluted stormwater runoff from entering nearby waters, verify that permit requirements are being met, and confirm that best management practices (BMPs) are effective.

During an inspection, the team focuses on conditions that can be observed and corrected quickly. Common items include:

1. 1. Outdoor storage and handling areas

   2. Drainage pathways, outfalls, storm sewers, ditches, and swales

   3. Sediment basins, ponds, filters, and other treatment controls

   4. Housekeeping, chemical spill or leak prevention, and material transfer areas

   5. Documentation, training logs, and prior inspection findings

Understanding what’s inspected leads directly to why inspections matter. Stormwater systems, if neglected, can quickly fail. This leads to clogged drains, uncontrolled stormwater runoff, and possible contamination of nearby waterbodies.

Key Regulatory Requirements for Inspections

Under the Clean Water Act (CWA), stormwater is treated as a pollutant. This means that facilities discharging stormwater must have a plan in place and conduct inspections to verify that their systems are working properly and are maintaining regulatory compliance.

NPDES Permits and MSGP Rules

The National Pollutant Discharge Elimination System (NPDES) permit program, managed by the Environmental Protection Agency (EPA) and authorized states, regulates stormwater discharges. Facilities operating under the Multi-Sector General Permit (MSGP) must follow specific rules for inspections:

These inspections form a continuous cycle of review, corrective action, and documentation that helps keep a facility in compliance. In addition to scheduled inspections, there are some special cases where inspection rules change:

• • Inactive and Unstaffed Sites: Facilities that meet the definition of “inactive and unstaffed” may be eligible for reduced inspection requirements. For example, they can certify that no activities take place on site and reduce or waive routine inspections or visual assessments.

  • Sector-Specific Conditions: Some MSGP sectors (like landfills, metal mining, and chemical plants) have extra inspection requirements tied to their activities and pollutant risks.

  • Corrective Actions: If a visual assessment, routine inspection, or monitoring event shows a problem, the permit requires follow-up inspections to confirm that corrective measures were implemented.

  • Impaired Waters or TMDL Watersheds: Facilities discharging to impaired waters may have additional monitoring and inspection expectations depending on pollutant load concerns.

  • Adverse Weather Waivers: If unsafe conditions prevent inspections during a qualifying event (e.g., flooding, icy conditions), the missed inspection can be documented with justification instead of being performed.

💡 Permit Variations to Watch

"While the EPA’s MSGP applies in certain states and territories, many states issue and enforce their own industrial stormwater permits. These programs often differ in inspection frequency, documentation requirements, and sector-specific rules. Always review your state-issued permit carefully so you know the exact inspection duties that apply to your site."

These unscheduled inspections are considered best management practices under the MSGP framework. They help facilities respond to unexpected conditions while keeping the site in compliance and protecting water quality.

OSHA Safety Considerations

When conducting inspections, worker safety is still a priority. The Occupational Safety and Health Administration (OSHA) standards apply to many tasks inspectors face:

• • Personal Protective Equipment (PPE): Hard hats, safety boots, gloves, and eye protection are common, with hearing or respiratory protection added where needed.

  • Fall Protection Equipment: Required when inspecting elevated structures, open tanks, or headwalls.

  • Hazard Communication (HazCom): Inspectors and staff must be trained on chemical hazards, labeling, and spill response.

“During my first stormwater inspection at a chemical facility, I underestimated how quickly conditions could change near open tanks. A senior inspector reminded me, 'Your PPE is the first barrier between you and the unknown.' That advice has stuck with me for years.”

By blending regulatory compliance with safe inspection practices, facilities can protect both their workforce and the environment.

Stormwater Inspection Checklist

A well-prepared checklist keeps inspections consistent, thorough, and defensible. Instead of rushing through items, each step should be treated as a focused review of a specific aspect of the site.

Pre-Inspection Preparation

Before walking the site, make sure everything you need is in place. This includes assigning roles and confirming that staff have access to the most recent SWPPP. Inspectors should also gather prior inspection reports, maintenance logs, and site maps. Tools such as cameras, flashlights, sample jars, pH meters, and turbidity tubes should be ready, along with the appropriate PPE.

Visual Site Review

Once on-site, begin with a broad walkthrough. Follow drainage paths from where stormwater originates to where it leaves the site. Watch for stained soils, oily sheens, residue, or evidence of track-out from vehicles. Loading areas, above-ground tanks, and dumpsters should be checked for leaks or unsecured lids.

BMP Inspection

Catch basins and inlets should be inspected for sediment buildup, trash, or blockages that restrict flow. Silt fences must be upright, keyed-in, and free from undercutting. Swales, ditches, culverts, and storm sewers should be clear and functioning properly. Treatment systems such as sediment basins, ponds, or filters need to be evaluated for capacity, condition, and accessibility for maintenance. Source controls like covers, berms, and secondary containment should also be reviewed to verify they are intact and effective.

Documentation & Recordkeeping

An inspection is only as strong as its records. Inspectors should complete standardized logs that capture what was observed, when it was observed, and by whom. All visual assessment forms, sampling results, and maintenance logs should be stored together with the SWPPP so they are easy to locate during audits or regulatory reviews.

Stormwater Visual Inspection Explained

A stormwater visual inspection is a simple, high-value check of discharge quality. It involves collecting a grab sample of stormwater runoff during a qualifying rain or snowmelt event and examining it under good lighting conditions. The purpose is to spot obvious signs of pollution that may indicate failing controls or poor housekeeping.

Parameters to Observe

Color: Discharge should appear natural and not have unusual tints like bright green, red, or black, which could indicate contamination from chemicals or rust.

Clarity: Cloudiness or murkiness may signal sediment, erosion, or other pollutants being carried off site.

Odor: Fuel, chemical, or sewage-like odors are signs of possible contamination that require immediate follow-up.

Floating solids: The presence of trash, debris, oil sheen, or foam suggests that BMPs are not containing pollutants effectively and corrective action is needed.

Who Conducts Stormwater Inspections?

Stormwater inspections are conducted by qualified inspectors who are trained to assess the effectiveness of stormwater management practices. The inspector must have experience in stormwater management and environmental regulations. Some municipalities require that inspections be performed by a certified professional.

Typical Stormwater Inspectors

• • Site staff inspectors: Many facilities designate employees who have been trained in stormwater management to complete routine inspections and visual assessments.

  • Third-party professionals: Environmental consultants are often hired for annual comprehensive SWPPP inspections, independent audits, or when specialized expertise is needed.

  • Regulatory inspectors: Agencies such as the EPA or state environmental departments conduct compliance inspections to verify that permit conditions are being met.

💡Stormwater Inspections in Construction Sites

“For construction projects, stormwater inspection requirements differ from those for industrial facilities under the MSGP. Construction activities usually fall under the Construction General Permit (CGP), and the rules are stricter because soil disturbance and erosion risks are higher.”

Stormwater Management Systems Maintenance

Proper stormwater maintenance keeps your stormwater management system operating effectively over the long term. Each type of system has unique needs, and inspections often identify when maintenance is due. Below are some common systems and how they should be maintained:

Catch basins

Catch basins trap sediment and debris before it enters downstream pipes or treatment systems. Inspectors should measure sump depth and schedule cleanouts when sediment reaches one-third of the sump’s capacity. Grates, frames, and trash racks must remain secure and free of blockages.

Green infrastructure

Systems like rain gardens, bioswales, permeable pavement, and green roofs are designed to mimic natural filtration. Maintenance includes removing trash and invasive weeds, monitoring plant health, and checking infiltration rates. If water pools for more than 48 hours, it may indicate clogged media that needs replacement.

Wet ponds

Wet ponds provide storage and settling for sediment and pollutants. SWPPP inspections should cover embankment integrity, outlet structures, inlets, and access roads. Forebays must be dredged when sediment accumulation reaches design thresholds, and vegetation around the pond should be managed to prevent erosion and maintain aesthetics.

Wetlands

Constructed or enhanced wetlands use plants and soils to treat stormwater naturally. Maintenance focuses on keeping the hydrology balanced and vegetation zones intact. Inspectors should monitor for invasive species, mosquito issues, and sediment buildup at inlets and outlets. Periodic harvesting or replanting may be needed to maintain function.

By tailoring maintenance to each system, facilities extend the lifespan of their control measures and avoid costly failures. Regular attention also reinforces compliance and shows regulators that the site is actively managing its stormwater systems.

Common Issues Found During Stormwater Inspections

Even with good systems in place, inspectors frequently see recurring problems. These issues can lead to enforcement actions, costly fines, or environmental damage if not corrected quickly.

• • Missed Inspections: Facilities that skip required quarterly or annual checks risk being flagged for noncompliance. Repeated failures can result in formal notices of violation and escalating fines.

  • BMP Neglect: Clogged inlets, broken silt fences, and overgrown vegetation are common failures that reduce system effectiveness. Poor maintenance also shortens the lifespan of stormwater infrastructure and may cause flooding.

  • Housekeeping Lapses: Open dumpsters, uncovered materials, and track-out from vehicles are visible signs of poor control. These lapses often lead to oily sheen, debris, or sediment in outfalls that trigger corrective action orders.

  • Recordkeeping Gaps: Missing inspection logs or incomplete SWPPP updates make it hard to prove compliance. In an audit, a lack of documentation can be treated the same as not performing inspections at all.

  • Uncontrolled Runoff: Stockpiles or fueling areas often generate polluted flows if not contained or covered. This can directly contaminate nearby waterways and result in immediate enforcement or mandated cleanup.

According to the U.S. EPA, facilities that fail to maintain stormwater controls or records can face civil penalties of over $66,000 per day, per violation (adjusted annually for inflation). In a recent EPA enforcement alert, officials emphasized that inadequate inspections and poor documentation are among the most common causes of fines in stormwater compliance cases.

Preparing for Your Next Stormwater Inspection

Preparing well ahead of time helps inspections go smoothly and demonstrates a commitment to compliance. Start by reviewing your most recent drainage map and updating it to reflect current flow paths and outfalls. Look for small housekeeping fixes that can make a big difference in inspection outcomes. 

Service your BMPs by removing sediment from catch basins, repairing damaged controls, and refreshing filter media where needed. It’s also wise to practice the visual assessment steps with staff so they know exactly how to collect and record samples when the time comes. 

Keep a clear log of corrective actions, supported by photos and dates, to show progress over time. Finally, schedule refresher training so employees understand their roles and are ready to respond confidently during the inspection. These practical steps reduce surprises and keep both the site and documentation inspection-ready year-round.

Stormwater Inspection FAQs

What is required in a stormwater inspection checklist for industrial facilities?

A stormwater inspection checklist should cover every part of the stormwater management system. This includes pre-inspection preparation (forms, PPE, and tools), a visual site review for leaks, spills, or sediment, inspection of best management practices (BMPs) such as storm drains, silt fences, sediment basins, and swales, and proper documentation with logs, photos, and digital records.

How often must inspections be done under the NPDES industrial stormwater permit?

Inspection frequency depends on the specific permit and site conditions, but the NPDES industrial stormwater permit generally requires inspections on a quarterly basis. Some facilities may also need additional inspections after major rain events or as required by their individual SWPPP (Stormwater Pollution Prevention Plan).

What is a stormwater visual assessment and how do I conduct one correctly?

A stormwater visual assessment is a quick, hands-on evaluation of runoff samples to check for pollutants. Inspectors collect runoff from storm sewers or outfalls and evaluate simple parameters: color, clarity, odor, and floating solids. Conducting one correctly means using a clean container, observing the sample promptly, and documenting results as part of the facility’s compliance records.

Why is inspector certification important for stormwater compliance?

Stormwater inspector certification demonstrates that the individual is trained to recognize compliance issues, evaluate BMPs, and understand regulations.

How can facilities avoid common stormwater inspection violations?

Facilities can prevent violations by:

• • Keeping their stormwater inspection checklist up to date.

  • Performing routine maintenance on stormwater management systems.

  • Ensuring BMPs like silt fences and storm sewers are in good condition.

  • Training staff on spill prevention and documentation practices.

  • Maintaining clear, organized inspection records.

Most violations stem from poor documentation, lack of BMP upkeep, or missed inspections, all of which can be avoided with consistent stormwater maintenance and proper planning.

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