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When is it the right time to collect a sample? How long do I have to collect a sample? How many samples do I have to collect? Our customers ask us these questions often and almost every time it rains. Knowing when it is the right time to sample and what the true definition of a Qualifying Storm Event (QSE) is incredibly important. Sampling the required amount at the right time can keep you in compliance and out of litigation. So what is a QSE?

Definition of a QSE:

  • A storm event that produces a discharge from at least one discharge location.
  • This discharge must be proceeded by 48 hours (two days) of no discharge from any location at the site.
  • You have four hours from the start of discharge (stormwater runoff) at each location to collect your sample.
    • Example: If discharge from SP1 begins at 11 am you have until 3 pm to collect your sample at SP1. If SP2 then begins to discharge at 12 pm you have until 4 pm to collect your sample at SP2.
  • If stormwater begins to discharge when the facility is closed, you have four hours from when the facility opens to sample if; (a) it is still discharging and (b) it has not been discharging for more than 12 hours before opening.
    • Example: If facility operating hours are from 9 am – 5 pm and discharge begins at 11 pm, it will have been discharging for 10 hours before the facility opens so you have until 1 pm (four hours from 9 am to 1 pm) to collect a sample. If this same facility begins to discharge at 7 pm they cannot sample in the morning because it has been more than 12 hours of discharge. The facility will have to wait another 48 hours with no discharge for an event to be a QSE.
  • Once discharge stops, the next 48 hour (two day) period of no discharge begins for the next QSE.
Want someone to come out and train your staff? Let our experts help by teaching you and your staff what a QSE is and how to correctly collect a sample! Schedule Training

Required Amount of Samples:

  • Samples are required to be taken during operating hours and when it is safe to sample.
  • A total of four (4) samples must be taken in a reporting year (July 1st – June 30th).
  • Two (2) samples from July 1st – December 31st, and two (2) samples from January 1st – June 30th.
  • If you are in a compliance group you only need to collect two (2) samples for the reporting year. One from July 1st – December 31st and one from January 1st – June 30th.

What Parameters to Sample for:

  • All facilities have to sample for; TSS, pH and Oil & Grease
  • Additional parameters are based on your SIC Code

Facilities That Do Not Discharge:

Some facilities are designed to capture and retain stormwater discharge (unless there is a Noah’s Arch flood, in which case sampling will be the least of everyone’s worries). For these kinds of sites, they are not required to sample unless their containment/retention overflows and stormwater discharges from their site. For our monitoring program participants that have containment/retention BMPs at their site, we highly recommend for them to keep a Rain Log. A Rain Log is a record of all the days that it has rained, with documentation such as pictures, demonstrating that there was no discharge from the facility. It can be a pain in the neck to have to look up the weather everyday! This is why Mapistry has made it as easy as taking a picture and uploading it to our software. Our Rain Log automatically logs the days it rains from your closest weather station! Something as simple as this can help save you as much as $37,500/day in litigation costs (just think of what you could do with all that $)!

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