Municipal operation inspections

Staff collecting water data

Municipal operation inspections

Municipal operation inspections help reduce the impacts to stormwater from municipally owned or operated facilities, areas, or stormwater best management practices (BMPs). Staff conducting these inspections can stop pollution before it reaches stormwater, or minimize the impacts if your BMPs have failed or need maintenance.

The municipal separate storm sewer system (MS4) General Permit requires inspections of the following: (MS4 General Permit Part III.D.6.e)

• Annual inspections of structural stormwater BMPs to determine structural integrity, function, and maintenance needs.
• At least one inspection every permit term of stormwater ponds and outfalls to determine structural integrity, function, and maintenance needs.
• Quarterly inspections of stockpiles, and storage and material handling areas identified in the Facility Inventory to determine function and maintenance needs.

During each of these inspections, inspectors must look for evidence of illicit discharges (MS4 General Permit Part III.D.3.c.). All inspections must be documented (MS4 General Permit Part III.D.6.h.(1)), so save any checklists that you are using.

Municipal Operations inspections required by the MS4 General Permit
Link to this table

What to inspect	When to inspect	Why inspect	Examples of how-to inspect	What to document
Structural stormwater best management practices (BMPs) including green roofs, permeable pavement, infiltration basins or trenches, raingardens, filtration devices, sand filters, stormwater ponds or wetlands, hydrodynamic devices, infiltration trenches, etc. [Part III.D.6.e.(1)]	Annually	To determine structural integrity, proper function, and maintenance needs	Identify clogged, overloaded, and full devices, inlets, or outlets Identify misaligned inlets or outlets/overflow devices Identify materials that are deteriorating and releasing pollution Identify erosion/channelization, sedimentation, soil slides, animal burrows, undercutting, displaced riprap, or other problems For infiltration practices that should be dry (e.g. infiltration basins, filter strips/swales) identify standing water or wet spots If standing water is present, determine if the device is functioning as designed and meeting the 48 hour draw down requirement Identify excess or unwanted vegetation (e.g. long-grass, tree growth) If vegetation is designed to be present (e.g. bioretention basins, filter strips/swales), determine if the vegetation is healthy, is of appropriate size/density, and free of weeds and invasive species	Inspection findings and date [Part III.D.6.h.(1)] Dates & description of maintenance [Part III.D.6.h.(3)]
Outfalls where an MS4 discharges to a receiving water, or the discharge permanently leaves the MS4 [Part III.D.6.e.(2)]	Once per each permit term	To determine structural integrity, proper function, and maintenance needs	Identify erosion/channelization, scour, or other problems Identify displaced, damaged, missing, or clogged riprap Identify missing or damaged grates or guards, if applicable Identify cracked, undercut, or spalled aprons, if applicable Identify unwanted vegetation growth or decay, litter or debris, sediment buildup, or animal dens that may obstruct flow of water	Inspection findings and date [Part III.D.6.h.(1)] Dates & description of maintenance [Part III.D.6.h.(3)]
Stormwater ponds [Part III.D.6.e.(2)]	Once per each permit term	To determine structural integrity, proper function, and maintenance needs	Identify scour, erosion/channelization, sedimentation, litter, animals burrows, undercutting, displaced riprap or other problems at/around the banks, inlets, or outlets Identify clogged or overloaded inlets or outlets Identify excess or unwanted vegetation (e.g. long-grass, new trees) Identify and record materials within the device that are deteriorating and releasing pollution into the stormwater system Determine if the vegetation looks healthy, is of appropriate size/density, and free of weeds and invasive species Determine if there is evidence of sedimentation or erosion downstream of the outlet	Inspection findings and date [Part III.D.6.h.(1)] Dates & description of maintenance [Part III.D.6.h.(3)]
Stockpiles, and storage and material handling areas that are inventoried in the Facilities Inventory [Part III.D.6.e.(3)]	Quarterly	To determine maintenance needs and proper function	Identify leaking, leachate, or runoff Identify undercut, full, clogged, ripped, broken, misplaced, askew, or other BMP maintenance needs Install additional BMPs, such as secondary containment, impervious cover, runoff collection areas as needed	Inspection findings and date [Part III.D.6.h.(3)] Dates & description of maintenance [Part III.D.6.h.(3)]
Illicit discharges (Part III.D.3.c.&f.)	During the structural stormwater BMP; outfall; pond; and stockpile and storage and materials handing inspections	To identify and eliminate illicit discharges to the MS4	Identify and characterize any dry weather flow Describe the material (color, odor, sheen, froth, etc.), its effects (e.g. corrosion, pipe etching), or, if appropriate, analyze chemically Investigate potential upstream sources that may be contributing non-stormwater flow Record clear, unpolluted dry weather flows. If present, the discharge may be coming from unregulated sources Inspect areas that you've identified as priority areas likely to have illicit discharges (e.g. business/industrial areas, where illicit discharges have been identified in the past)	Date(s) and location(s) of IDDE inspections conducted [Part III.D.3.h.(1)]
Construction activity	At the frequency identified in the Construction Site Inspection procedure for your MS4	To prevent and minimize erosion to reduce the amount of sediment from entering your MS4	Inspect for items required by the MPCA construction stormwater permit and your regulatory mechanism, some examples include: Are erosion and sediment control and vehicle tracking BMPs effective, in good working condition, and able to perform their intended function? Are soils stabilized where needed? Do pipe outlets have energy dissipation? Are inlets protected? Are solid and hazardous wastes contained, stored, and properly disposed of? Is the contractor conducting the required site inspections? Is the permanent stormwater BMP designed appropriately and protected? Are temporary sedimentation basins used and with BMPs? Is dewatering discharging to a sediment basin or preventing nuisance conditions? Identify any potential pollution problems related to stormwater runoff or infiltration into the groundwater Determine if any additional BMPs, such as silt fence, temporary ponds or other BMPs may be appropriate	Checklist or other written means to document what was inspected for [Part III.D.4.h.(1)]

Resources

Fact sheets and guidance documents

• MPCA Managing Stormwater Sediment BMPs guidance - Guide for properly managing sediment from stormwater systems, such as ponds
• Documentation that MS4 staff should retain - List of all the documentation requirements (what information to keep, how long to keep it, level of detail to keep, etc.) for compliance with the MS4 permit

Checklists and templates

BMP inspection checklists

• Rain garden/bioretention basin inspection checklist - University of Minnesota's (U of M) checklist for inspecting bioretention systems, such as rain gardens
• Constructed wetland inspection checklist - U of M's checklist for inspecting constructed wetlands
• Filter strips and swales inspection checklist - U of M's checklist for inspecting filter strips and swales
• Filtration system inspection checklist - U of M's checklist for inspecting filtration systems
• Infiltration system inspection checklist - U of M's checklist for inspecting infiltration systems
• Underground sedimentation inspection checklist - U of M's checklist for inspecting underground sedimentation devices
• Permeable pavements inspection checklist - U of M's checklist for inspecting permeable pavers

Pond inspection checklists

• Wet pond inspection checklist - U of M's checklist for inspecting wet ponds
• Dry pond inspection checklist - U of M's checklist for inspecting dry ponds

Outfall inspection checklists

• Outfall inspection checklist - City of Rochester's checklist for inspecting outfalls
• Outfall inspection checklist - City of Arden Hills' checklist for inspecting outfalls