How to Take a Stormwater Sample

Collecting a Stormwater Sample
Annual CMTA Marine Trades Exposition
October 5, 2010
• Sample at designated outfalls annually, before October 1st
• Storm event must be:
• > 0.1 inch in magnitude
• >72 hours from a previous storm of 0.1 inch or greater
No snow or ice runoff
Grab sample only
Collect sample within the first 30 minutes of discharge
Take all discharge samples during the same storm event, if
• You will need this information for the storm event:
the date
discharge temperature
time of the start of the discharge
time of sampling
magnitude (in inches) of the storm event sampled
pH of the uncontaminated rainfall (before it contacts the
– duration between the storm event sampled and the end of
the most recent storm event that produced a discharge.
• Sample bottles
– Get them from the lab at the beginning of the
sampling season
• Powder-free disposable nitrile or latex gloves.
– These are sold by medical and laboratory suppliers.
Do not use powdered gloves as the powder may
contain metals that could contaminate metals samples
such as zinc.
• Cooler(s) & ice
• Sharpie & paper
• Wear disposable powder-free gloves
when sampling.
• Grab samples with the stormwater
entering directly into bottles supplied
by your lab. Do not transfer the samples
from another container if possible.
Metal contamination of ordinary
containers is common and household
detergents often contain phosphorus.
• Keep your hands away from the
opening to prevent contaminating the
Do not rinse or overfill the bottles. The bottles
supplied by your lab for some parameters (ammonia
and phosphorus) will include small amounts of liquid
preservative (generally a few drops). Fill the bottle to
about ½ inch of the top to ensure that no preservative
is lost. Do not transfer this liquid to other bottles.
As soon as the sample is collected, cap the bottle and
label it. It is important that the bottles are labeled
correctly so that the lab will be able to identify samples
by sample site and ensure proper preservation for
each parameter. It is a good idea to place sample
bottles in reclosable bags.
Place the samples in a picnic cooler partially filled
with ice. Plan to maintain ice in the picnic cooler until
the samples arrive at the lab. Remember to make
certain that the samples will be delivered to the lab
soon enough for the lab to meet holding times.
Avoid Contamination
• Wear gloves
• Use only bottles
supplied by lab
• Don’t transfer
Lessons Learned
• Figure out how you are
going to get your sample
before you have to!
• Check with your lab-some
are open on Saturdays!
• Lab will tell you how long
you have to get the sample
to the lab (eg aquatic
toxicity test has to be done
within 36 hours of
collection-lab wants it
there within 24 hours)
Quarterly Visual Monitoring
required in the 2011 SWGP
• Once each quarter for the entire permit term, you must
collect a stormwater sample from each outfall and conduct a
visual assessment of each of these samples.
• For monitoring purposes, quarters will begin on January 1,
April 1, July 1 and October 1.
• The visual assessment must be made of a sample in a clean,
clear glass, or plastic container, and examined in a well-lit
Quarterly Visual Monitoring
• Visually inspect the sample for the presence of the following water quality
1. Color
2. Odor
3. Clarity
4. Floating solids
5. Settled solids
6. Suspended solids
7. Foam
8. Oil sheen
9. Other obvious indicators of stormwater pollution.
• You must keep records of your quarterly visual monitoring & take steps to
eliminate any potential problem.
All photo credits: Washington State Department of Ecology
Publication #02-10-071, revised March 2010

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