Step 9: Sampling

When do the 2015 - 2020 sampling requirements begin? What if a facility has to continue sampling?

Within the 2015-2020 general permit, sampling begins quarterly July 1, 2015, for a minimum of a year for those who applied and received permit coverage by June 30, 2015.

Permittees are required to sample quarterly until results from four separate quarters average below the permit benchmark value(s).

  • Quarter 1: July, August, September 2015 (form due no later than October 21, 2015)
  • Quarter 2: October, November, December 2015 (form due no later than January 21, 2016)
  • Quarter 3: January, February, March 2016 (form due no later than April 21, 2016)
  • Quarter 4: April, May, June 2016 (form due no later than July 21, 2016)

If you were you unable to collect samples during Quarters 1-4, continue sampling:

If you have collected samples but the averaged results are above the permit benchmark value(s), continue sampling:

  • Quarter 5: July, August, September 2016 (form due no later than October 21, 2016)
  • Quarter 6: October, November, December 2016 (form due no later than January 21, 2017)
  • Quarter 7: January, February, March 2017 (form due no later than April 21, 2017)
  • Quarter 8: April, May, June 2017 (form due no later than July 21, 2017)
  • Quarter 9: July, August, September 2017 (form due no later than October 21, 2017)
  • Quarter 10: October, November, December 2017 (form due no later than January 21, 2018)
  • Quarter 11: January, February, March 2018 (form due no later than April 21, 2018)
  • Quarter 12: April, May, June 2018 (form due no later than July 21, 2018)

New applicants will start sampling the first full calendar quarter after receiving permit coverage.

Step 9a View guidance materials

For answers to commonly asked questions about industrial stormwater sampling requirements, read and download the PDF icon Industrial Stormwater Sampling FAQ or view the PDF icon 2015-2020 Industrial Stormwater Sampling Worksheet.

View the Industrial Stormwater Sampling Videos

Check out the PDF icon Monitoring Guidance Manual For Minnesota’s Industrial Stormwater Multi-Sector General Permit (6/2015) to learn the answers to these questions:

  • Who needs to collect stormwater samples?
  • What do I need to sample for?
  • When do I take my sample?
  • Where do I take my samples?
  • How do I sample?
  • How do I report my sampling results?

Step 9b: Work with a testing laboratory

Permittees may use any Minn. Department of Health Certified Testing Laboratory to conduct analyses required by the permit:

Questions for the lab

  • Is the lab certified for the analyses that need to be sampled for?
  • Can this lab analyze the pollutant parameters I am sampling for?
  • What is the price of analyzing my samples?
  • What are the bottle delivery responsibilities?
  • What are the holding time/turnaround times?
  • What is the reporting methodology?
  • Can the laboratory help me with questions, such as how to take samples or help in getting sample bottles to me?
  • Where is the lab located and are they available to help me with my sampling needs?

Steps for working with a lab

  1. If you have never ordered bottles from a lab before, contact the lab before you are planning on conducting the stormwater sampling event. Be sure to have:
    • Your name, company/organization name, address, phone number and email address
    • Additional contacts that you want the final report and/or Invoice sent to
    • Number of samples/monitoring locations for your facility. 
    • Your subsector(s), including the parameters you have to monitor for
  2. Once the bottle order has been set up, bottles will arrive in a few days.
  3. Once the bottles arrive and a qualifying storm event occurs:
    • Fill the bottles according to the lab instructions
    • Place bottles in the cooler
    • Complete any remaining required sections of the Chain of Custody
  4. After packing the cooler:
    • Arrange for the delivery to the lab if you haven’t already.
    • Consider courier services such as Speedee, Elite Transportation,  FedEx or UPS, or drop off the cooler(s) in person
  5. Once samples are received by the laboratory:
    • Allow up to 10 business days for sample results
    • Results are required to be sent to the permittee
    • Permittee needs to fill out and send in the SWMR to the MPCA

Information about these steps was adapted from Pace Analytical “Steps for Placing a New or First Time Bottle Order” document.

Step 9c: Read the overview to stormwater sampling requirements

Benchmark monitoring information

Benchmark Monitoring is required by all permittees and the first sampling interval begins one quarter after receiving 2015 permit coverage.  For existing (renewing) applicants, this means quarterly sampling starts July 1, 2015. For any applicant who receives coverage after June 30, 2015, that means quarterly sampling starts the next full calendar quarter after receiving permit coverage. Need to know what you have to sample for? View the 2015-2020 benchmark monitoring requirements page.

Effluent limit monitoring information

Permittees with effluent limit monitoring requirements must conduct an additional, separate stormwater sample.

Step 9d: Determine whether you have effluent monitoring requirements

Two-and-a-half percent of Permittees also have industrial stormwater Effluent Monitoring Requirements. Is this you? This is a once-per-year, every year of the permit cycle. If you had no off-site surface water discharges, you are still required to submit the sampling form with a "no flow" explanation. Need to know what you have to sample for? View the 2015-2020 benchmark monitoring requirements page.

NOTE: Permittees who do not pass their effluent monitoring limits, it is a violation. Permittees who fail to submit results or a "no flow" form, it is a violation.

Step 9e: Determine when to sample

Permittees can take a stormwater sample anytime there is a measurable runoff event, which means any volume flowing past/through their monitoring location that allows you to collect a sample. You should take samples within 30 minutes of the start of a measurable discharge. If you aren't able to collect a sample within 30 minutes of flowing stormwater, still collect a sample and record on the SWMR why a sample could not be collected within the first 30 minutes of a measurable runoff event. Be sure it's been dry for at least 72 hours (3 days) since the last time you collected a sample.

Tip: If faced with collecting a sample after 30 minutes of discharge leaving your monitoring location or trying to sample another day, do not wait another day. Collect the sample now.

Winter thaw storm event

Because you are required to collect four benchmark samples in four separate quarters, winter thaw or winter rains will occur and collecting stormwater samples in the winter is often obtainable state-wide. Snow melt has the potential to carry significant accumulations of pollutants offsite.

Step 9f: Obtain equipment required for sampling

  • Flashlight (non-sparking)          
  • Hard Hat
  • Safety Goggles
  • Reflective Vests
  • Gloves (Latex or Nitrile)
  • Rain Gear
  • Safety Shoes
  • Traffic Cones
  • Rain Gauge
  • Eye Wash Bottle
  • Paper Towels  
  • Ice Cooler/Shipping Cooler
  • Field Sampling Notebook
  • Waterproof Pens
  • pH meter
  • Sampling Bottles
  • Preservatives   
  • Waterproof Labels      
  • First Aid Kit

Step 9g: Read other sampling manuals

Note: other states’ requirements may differ from Minnesota’s, so be sure to verify Minnesota’s regulations if you utilize another state’s guidance information.


Step 9h: Averaged results exceeded? Modify/add new BMPs

If you collected four samples over four separate quarters and your averaged results were above the permit benchmark values, you are required to immediately continue quarterly sampling until four results in a row average below the benchmark values.

First, determine which parameters you will be required to re-sample.  Second, identify the significant material or industrial activity that the exceedance is connected to. Consider:

  • What BMPs you can modify and change at your facility?
  • Can you move that material or conduct that activity indoors or within a permanent, storm-resistant shelter?
  • If not, are there other BMPs you can add to minimize or eliminate the contaminants of concern?

Example: If a facility has a stockpile of rusted metal, and the previous BMP of routine sweeping of rusted metal parts didn’t allow the facility to pass their benchmarks because of this material and this BMP, they could consider putting the rusted metal into a covered dumpster or other container so that run-on of stormwater does not come into contact with these materials. If precipitation still falls into an open dumpster; be sure to keep the dumpster closed and holes plugged.

What other areas may be causing you to exceed? What different structural and/or non-structural BMPs may help pass your benchmark monitoring requirements? Consider the following:

Step 9i:  Sector/pollutant-specific BMP ideas

The following BMPs have helped many permittees and may be applicable to your facility, even if you are within a different sector or managing different pollutants.

NOTE: These suggestions are facility specific and may not work for all permittees with similar problems. Consider non-structural or simple structural BMPs first, or contact MPCA staff for facility-specific ideas.


Pollutant-specific- exceedance

Guidance & Suggestions



  Solids, Total Suspended (gravel parking lots) You currently have Class 5 gravel. Options include:
  • Replace it with a swath of rip rap
  • Replace it with washed gravel
  • Pave even part of the area
  • Berm the area before the discharges go offsite
  • Install/manage a pond and an infiltration system to allow the water to filter/settle before discharging offsite
  • Lower the grade to that area so the stormwater ponds before discharging off-site
  • Install/maintain a 4-6’ vegetative buffer strip. A prairie mix of vegetation is preferred though even sod will help
Sector A, Timber Products Chemical Oxygen Demand
  • Address any decaying wood pallets, sawdust and other wood products/waste, look for other decaying materials. Watch this area to determine whether this is a one-time or longer-term problem
  • Create buffers/berms before stormwater is discharged. Tarp/cover wood ash. Address any off-site tracking of ash/wood waste. Increase or start sweeping and other general good housekeeping practices.
Sector E, Concrete Manufacturing Iron
  • Dust suppression/management
  • Product/cutting management
  • Slurry management
  • If you cut concrete, manage the spray wastewater appropriately (contaminated wastewater cannot be discharged to surface or ground waters)
EPA offers sector-specific fact sheets with BMP options. Sector E’s fact sheet highlights:
  • In general, incorporate better housekeeping techniques - Truck wheel contribution to offsite loss? Dry pond characteristics – may be able to tweak operations by deepening or increasing outlet. Dry ponds generally don’t treat particulates very well – easier to re-suspend.
  • Sketch on aerial photos to help identify key site operations, truck traffic and bulk handling areas, covered piles, washout zones, etc.
  • Move monitoring location, slope the land, or divert stormwater to an area where small structural BMPs can be installed. Monitor before stormwater moves into a culvert if the concern is that the culvert is leading to the higher TSS. Make pond/sedimentation system (2-celled system).
Sector L: Landfills Multiple
  • EPA Sector L Guidance: See the section dedicated to runoff/erosion issues, as well as “uncontrolled leachate.”
  • Consider hydrodynamic separators, these can be expensive and require changing filters often (likely not worth the money)
  • Make sure that spray sites have the required buffer area (50-200ft) around the facility. This allows containment of the liquid sprayed.
  • Don’t overspray treated leachate.
  • Stay within the property boundary
  • Don’t allow leachate to run off from the spray field
  • Spray only enough liquid that the cover crop and soil can handle.
Sector L: Landfills Zinc
Sector L: Landfills Iron
Sector M: Auto Salvage Yards Aluminum/Iron
  • EPA Auto Salvage (specifically the “heavy metals” references)
  • Presuming the parking lots are paved, utilizing a street sweeper for the parking lot areas may help. Of the two generic types of street sweepers; one pushes debris away, and the other has some sort of filter (that can capture and filter out pollutants).
  • The MPCA PDF icon Vehicle dismantling and salvage (w-hw4-63)
  • The manual provides some BMP ideas to manage industrial activities related to failing parking lots, such as car hulls/parts storage, crushing and/or, sand-blasting activities, or other industry-specific reasons.
  • The Wisconsin DNR guidance suggests that to control high levels of iron and aluminum, solutions might include proprietary filters, bioretention, and sand filters. A large BMP, such as a wet pond, might need the addition of a polymer to attain a high level of iron control.
  • Other contacts include Dave Kendziorski with StormTech, 414-549-1578, or Peter Hughes with the USGS at 608-821-3833.
Sector AA Aluminum/Iron
  • Look at the suggestions for the Sector M: Auto Salvage Yard sector.
Sector AB Solids, Total Suspended
  • Look at the general suggestions for all sectors above, including those for “gravel parking lot.”

Step 9j: Review other guidance materials 

The following additional resources may help provide information on different BMPs for your facility:

Helpful aspect of resource
EPA Industry Sector Notebooks
Most Industrial Stormwater Sectors are listed; each notebook provides detailed information about processes, pollution prevention opportunities, and more.
Stormwater Best Management Practices in an Ultra-Urban Setting: Selection and Monitoring (US Department of Transportation)
Many structural BMP ideas with diagrams, pollutant removal rates and design and cost considerations.
Portland Industrial Stormwater Best Management Practices
Fact sheet series for more than a dozen specific industrial activities.

Step 9k: Contact the MPCA for assistance

If you have reviewed Steps 9a-9k and still need guidance on types of BMPs to implement, you may contact the Program, which can provide you facility-specific suggestions. Contact

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