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Step 6 – Sampling Your Runoff

  • You must take a sample that is representative of your facility’s runoff. If you have more than one drainage area, you must take a sample from each.
  • Samples must be taken quarterly. In addition, you must take a “first fall storm event” sample during the first storm event after October 1st of each year.
  • Samples must be collected within the first 12 hours of discharge events – that’s when stormwater runs off your property at the identified discharge locations. If that is not possible, you must collect them as soon as you can and make sure to document why. You do not need to sample outside of regular business hours, during unsafe conditions or during quarters where there is no discharge.
  • You must report the results, even if there was no discharge, to the Department of Ecology by providing an electronic Discharge Monitoring Report or DMR. More on this in further steps.

For information on how to properly take a sample, visit our YouTube Channel or take a look at this guidance document from the Washington Dept. of Ecology



Find a Lab

Benchmarks and Sampling Requirements

Sampling Checklist

Stormwater Sampling Manual

Discharge Sample Point Update Form