Industrial Stormwater: How to Collect a Sheet Flow Sample

Uploaded by TheMnPCA on 17.08.2011

Hi. My name is Melissa Wenzel and I'm an inspector with the Minnesota Pollution Control Agency's
Industrial Stormwater program.
As you know, the industrial stormwater multi-sector general permit requires all
permittees to conduct benchmark monitoring.
Today I'll be demonstrating how to collect the storm water sample using the
sheet flow sampling method.
The process for collecting and submitting results can be broken down into six parts.
I will be demonstrating part four - how to collect the storm water sample using
the sheet flow sampling method.
At the end of this video, we'll provide links to the other parts of the storm
water sampling process.
A sheet flow sample is a sample that's flowing over an impervious or gravel surface.
While there might be other ways to collect the sample,
I will demonstrate one that is low in cost, easy to collect,
and should be appropriate for most facilities.
Be sure to have these materials ready, ahead of time, right before you're going to
collect your sample.
What you need to be able to collect a sample for sheet for sampling is:
three two gallon zip lock bags
one, one quart sized zip lock bag
one pair of gloves
an item like a shovel handle or other device to create a dam
a small quantity of wet or dry sand
scissors, sampling jars
a cooler
and ice.
Be sure to choose a time and location where storm water is flowing.
And collect a sample within the first thirty minutes of a measurable runoff event.
Before you go outside write the name of the person collecting the sample
and the date.
Cut the top
and sides off one of the two gallon bags.
Unfold that bag.
Fill the other two gallon bags about a quarter full of sand.
squeeze all of the air and out of the bags and zip the bags shut.
Cut the top off the quart sized bag.
Now, let's go outside to collect a sample.
Find a flat, smooth area that is representative of the sheet flow runoff
from your industrial storm water discharges,
and lay the plastic sheet down on the ground
in the direction of storm water flow.
Place the sand bags on the sampling surface
so that it creates a funneling effect
for the sheet flow.
Place the shovel handle under the plastic
which will help you to collect your sample.
Place your fingers inside the bag to open the bags mouth.
Place it over the shovel handle or other device to allow the storm water to
flow inside the plastic bag.
Lift the top of the bag to transfer the sample to the bottom of the bag.
Continue until you have enough stormwater in the plastic bag.
Shake the plastic bag and pour the simple into your sample jar.
You'll notice that I'm not placing my fingers or hands over the top or inside
the bottle when collecting the sample.
Otherwise I might contaminate the sample.
Your lab should have instructed you how full the bottle should be.
Fill it to the level they instructed you to fill it.
If the sample bottles came with preservatives, add them now.
Be careful not to spill
as preservatives are most often acids. Cap the sample bottle.
Then, record the time the sample was collected.
Place the samples inside a resealable plastic bag and place the bottles into
the cooler.
Prepare the cooler according to lab instructions for pickup
or shipment to the lab.
Often, labs require that the samples be packed in ice
to help preserve the sample.
After you've taken your sample, make sure to take thorough notes on how the
sampling event went
and facility conditions. You might want to consider taking a photo of sampling
conditions after you take your sample.
This may help remind you of site conditions when filling out the
monitoring report.
That's it!
While I demonstrated how to collect a sheetful sample, you might be collecting from
another location such as a man-hole, ditch or swale.
Be sure to check-out our grab sample video if that's the case.
For more information about the best sampling methods, tips to sampling the
right way, visit the program's website
Go to the what's new section to find the sampling manual.
It is filled with more detailed information about all parts of the storm
water sampling process.