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3.12 Stormwater Sampling
3.12.1 Storm Sampling
Checklist
Many stormwater runoff monitoring permits require a first-flush
grab sample within the first 30 minutes of the storm event and a
time- or flow-paced composite sample during the remainder of
the event. The 3700 Sampler's STORM pacing is ideal for moni-
toring storm events. Storm pacing allows you to:
• Divide the sampler's bottles into two groups. The first
bottle group receives the first flush grab sample. The
grab sample is always a time-paced sample. The second
bottle group receives either a flow-paced or time-paced
sample.
• Collect samples for the second bottle group after
collecting the first-flush samples or collect samples for
both groups at the same time. See Figures 3-16 and
3-17.
• Distribute sample volumes to both bottle groups sequen-
tially or in any of the three multiplexing schemes:
bottles-per-sample, samples-per-bottle, or
multiple-bottle compositing.
• Use an Isco 4200 Series Flow Meter or a 4100 Series
Flow Logger to enable or disable the sampler according
to the level or flow rate of the flow stream or to specific
amount of rainfall.
• Use a maximum flow interval setting to terminate a
STORM routine that uses flow-paced sampling.
The maximum-flow-interval setting affects routines that fill
the second bottle group with flow-paced samples. The maxi-
mum-flow-interval setting limits the amount of time between
flow-paced sample events. For example, if the flow rate
declines so that the amount of time between flow-paced sam-
ple events exceeds a maximum-flow-interval setting of two
hours, the sampler will terminate the routine when more than
two hours elapses between events.
The maximum-flow-interval setting allows the sampler to ter-
minate the routine when the flow rate falls below an accept-
able rate or drops off completely. This limits the sampling
routine to one storm event so that samples from multiple
storm events are not deposited into the bottle groups.
This section provides two checklists: a list of suggested storm
monitoring equipment and a brief installation checklist. Notes on
terminating a routine, manual sampling during a storm routine,
and a storm routine's run state displays follow the checklist.
Example Storm Sampling contains a STORM programming
example.
You can find additional information about storm monitoring
installations in the Teledyne Isco Storm Water Runoff Moni-
toring Pocket Guide. The pocket guide contains the following
information:
• How to connect the sampler and rain gauge to the flow
meter
• Programming examples for flow meters and samplers
3700 Portable Samplers
Section 3 Programming Guidelines
3-67
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